Tue, 03 Mar 2020 12:57:23 +0000
Merge
1 /*
2 * Copyright (c) 2001, 2019, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
25 #if !defined(__clang_major__) && defined(__GNUC__)
26 #define ATTRIBUTE_PRINTF(x,y) // FIXME, formats are a mess.
27 #endif
29 #include "precompiled.hpp"
30 #include "classfile/metadataOnStackMark.hpp"
31 #include "code/codeCache.hpp"
32 #include "code/icBuffer.hpp"
33 #include "gc_implementation/g1/bufferingOopClosure.hpp"
34 #include "gc_implementation/g1/concurrentG1Refine.hpp"
35 #include "gc_implementation/g1/concurrentG1RefineThread.hpp"
36 #include "gc_implementation/g1/concurrentMarkThread.inline.hpp"
37 #include "gc_implementation/g1/g1AllocRegion.inline.hpp"
38 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
39 #include "gc_implementation/g1/g1CollectorPolicy.hpp"
40 #include "gc_implementation/g1/g1ErgoVerbose.hpp"
41 #include "gc_implementation/g1/g1EvacFailure.hpp"
42 #include "gc_implementation/g1/g1GCPhaseTimes.hpp"
43 #include "gc_implementation/g1/g1Log.hpp"
44 #include "gc_implementation/g1/g1MarkSweep.hpp"
45 #include "gc_implementation/g1/g1OopClosures.inline.hpp"
46 #include "gc_implementation/g1/g1ParScanThreadState.inline.hpp"
47 #include "gc_implementation/g1/g1RegionToSpaceMapper.hpp"
48 #include "gc_implementation/g1/g1RemSet.inline.hpp"
49 #include "gc_implementation/g1/g1RootProcessor.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/orderAccess.inline.hpp"
69 #include "runtime/vmThread.hpp"
71 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;
73 // turn it on so that the contents of the young list (scan-only /
74 // to-be-collected) are printed at "strategic" points before / during
75 // / after the collection --- this is useful for debugging
76 #define YOUNG_LIST_VERBOSE 0
77 // CURRENT STATUS
78 // This file is under construction. Search for "FIXME".
80 // INVARIANTS/NOTES
81 //
82 // All allocation activity covered by the G1CollectedHeap interface is
83 // serialized by acquiring the HeapLock. This happens in mem_allocate
84 // and allocate_new_tlab, which are the "entry" points to the
85 // allocation code from the rest of the JVM. (Note that this does not
86 // apply to TLAB allocation, which is not part of this interface: it
87 // is done by clients of this interface.)
89 // Local to this file.
91 class RefineCardTableEntryClosure: public CardTableEntryClosure {
92 bool _concurrent;
93 public:
94 RefineCardTableEntryClosure() : _concurrent(true) { }
96 bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
97 bool oops_into_cset = G1CollectedHeap::heap()->g1_rem_set()->refine_card(card_ptr, worker_i, false);
98 // This path is executed by the concurrent refine or mutator threads,
99 // concurrently, and so we do not care if card_ptr contains references
100 // that point into the collection set.
101 assert(!oops_into_cset, "should be");
103 if (_concurrent && SuspendibleThreadSet::should_yield()) {
104 // Caller will actually yield.
105 return false;
106 }
107 // Otherwise, we finished successfully; return true.
108 return true;
109 }
111 void set_concurrent(bool b) { _concurrent = b; }
112 };
115 class ClearLoggedCardTableEntryClosure: public CardTableEntryClosure {
116 size_t _num_processed;
117 CardTableModRefBS* _ctbs;
118 int _histo[256];
120 public:
121 ClearLoggedCardTableEntryClosure() :
122 _num_processed(0), _ctbs(G1CollectedHeap::heap()->g1_barrier_set())
123 {
124 for (int i = 0; i < 256; i++) _histo[i] = 0;
125 }
127 bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
128 unsigned char* ujb = (unsigned char*)card_ptr;
129 int ind = (int)(*ujb);
130 _histo[ind]++;
132 *card_ptr = (jbyte)CardTableModRefBS::clean_card_val();
133 _num_processed++;
135 return true;
136 }
138 size_t num_processed() { return _num_processed; }
140 void print_histo() {
141 gclog_or_tty->print_cr("Card table value histogram:");
142 for (int i = 0; i < 256; i++) {
143 if (_histo[i] != 0) {
144 gclog_or_tty->print_cr(" %d: %d", i, _histo[i]);
145 }
146 }
147 }
148 };
150 class RedirtyLoggedCardTableEntryClosure : public CardTableEntryClosure {
151 private:
152 size_t _num_processed;
154 public:
155 RedirtyLoggedCardTableEntryClosure() : CardTableEntryClosure(), _num_processed(0) { }
157 bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
158 *card_ptr = CardTableModRefBS::dirty_card_val();
159 _num_processed++;
160 return true;
161 }
163 size_t num_processed() const { return _num_processed; }
164 };
166 YoungList::YoungList(G1CollectedHeap* g1h) :
167 _g1h(g1h), _head(NULL), _length(0), _last_sampled_rs_lengths(0),
168 _survivor_head(NULL), _survivor_tail(NULL), _survivor_length(0) {
169 guarantee(check_list_empty(false), "just making sure...");
170 }
172 void YoungList::push_region(HeapRegion *hr) {
173 assert(!hr->is_young(), "should not already be young");
174 assert(hr->get_next_young_region() == NULL, "cause it should!");
176 hr->set_next_young_region(_head);
177 _head = hr;
179 _g1h->g1_policy()->set_region_eden(hr, (int) _length);
180 ++_length;
181 }
183 void YoungList::add_survivor_region(HeapRegion* hr) {
184 assert(hr->is_survivor(), "should be flagged as survivor region");
185 assert(hr->get_next_young_region() == NULL, "cause it should!");
187 hr->set_next_young_region(_survivor_head);
188 if (_survivor_head == NULL) {
189 _survivor_tail = hr;
190 }
191 _survivor_head = hr;
192 ++_survivor_length;
193 }
195 void YoungList::empty_list(HeapRegion* list) {
196 while (list != NULL) {
197 HeapRegion* next = list->get_next_young_region();
198 list->set_next_young_region(NULL);
199 list->uninstall_surv_rate_group();
200 // This is called before a Full GC and all the non-empty /
201 // non-humongous regions at the end of the Full GC will end up as
202 // old anyway.
203 list->set_old();
204 list = next;
205 }
206 }
208 void YoungList::empty_list() {
209 assert(check_list_well_formed(), "young list should be well formed");
211 empty_list(_head);
212 _head = NULL;
213 _length = 0;
215 empty_list(_survivor_head);
216 _survivor_head = NULL;
217 _survivor_tail = NULL;
218 _survivor_length = 0;
220 _last_sampled_rs_lengths = 0;
222 assert(check_list_empty(false), "just making sure...");
223 }
225 bool YoungList::check_list_well_formed() {
226 bool ret = true;
228 uint length = 0;
229 HeapRegion* curr = _head;
230 HeapRegion* last = NULL;
231 while (curr != NULL) {
232 if (!curr->is_young()) {
233 gclog_or_tty->print_cr("### YOUNG REGION " PTR_FORMAT "-" PTR_FORMAT " "
234 "incorrectly tagged (y: %d, surv: %d)",
235 curr->bottom(), curr->end(),
236 curr->is_young(), curr->is_survivor());
237 ret = false;
238 }
239 ++length;
240 last = curr;
241 curr = curr->get_next_young_region();
242 }
243 ret = ret && (length == _length);
245 if (!ret) {
246 gclog_or_tty->print_cr("### YOUNG LIST seems not well formed!");
247 gclog_or_tty->print_cr("### list has %u entries, _length is %u",
248 length, _length);
249 }
251 return ret;
252 }
254 bool YoungList::check_list_empty(bool check_sample) {
255 bool ret = true;
257 if (_length != 0) {
258 gclog_or_tty->print_cr("### YOUNG LIST should have 0 length, not %u",
259 _length);
260 ret = false;
261 }
262 if (check_sample && _last_sampled_rs_lengths != 0) {
263 gclog_or_tty->print_cr("### YOUNG LIST has non-zero last sampled RS lengths");
264 ret = false;
265 }
266 if (_head != NULL) {
267 gclog_or_tty->print_cr("### YOUNG LIST does not have a NULL head");
268 ret = false;
269 }
270 if (!ret) {
271 gclog_or_tty->print_cr("### YOUNG LIST does not seem empty");
272 }
274 return ret;
275 }
277 void
278 YoungList::rs_length_sampling_init() {
279 _sampled_rs_lengths = 0;
280 _curr = _head;
281 }
283 bool
284 YoungList::rs_length_sampling_more() {
285 return _curr != NULL;
286 }
288 void
289 YoungList::rs_length_sampling_next() {
290 assert( _curr != NULL, "invariant" );
291 size_t rs_length = _curr->rem_set()->occupied();
293 _sampled_rs_lengths += rs_length;
295 // The current region may not yet have been added to the
296 // incremental collection set (it gets added when it is
297 // retired as the current allocation region).
298 if (_curr->in_collection_set()) {
299 // Update the collection set policy information for this region
300 _g1h->g1_policy()->update_incremental_cset_info(_curr, rs_length);
301 }
303 _curr = _curr->get_next_young_region();
304 if (_curr == NULL) {
305 _last_sampled_rs_lengths = _sampled_rs_lengths;
306 // gclog_or_tty->print_cr("last sampled RS lengths = %d", _last_sampled_rs_lengths);
307 }
308 }
310 void
311 YoungList::reset_auxilary_lists() {
312 guarantee( is_empty(), "young list should be empty" );
313 assert(check_list_well_formed(), "young list should be well formed");
315 // Add survivor regions to SurvRateGroup.
316 _g1h->g1_policy()->note_start_adding_survivor_regions();
317 _g1h->g1_policy()->finished_recalculating_age_indexes(true /* is_survivors */);
319 int young_index_in_cset = 0;
320 for (HeapRegion* curr = _survivor_head;
321 curr != NULL;
322 curr = curr->get_next_young_region()) {
323 _g1h->g1_policy()->set_region_survivor(curr, young_index_in_cset);
325 // The region is a non-empty survivor so let's add it to
326 // the incremental collection set for the next evacuation
327 // pause.
328 _g1h->g1_policy()->add_region_to_incremental_cset_rhs(curr);
329 young_index_in_cset += 1;
330 }
331 assert((uint) young_index_in_cset == _survivor_length, "post-condition");
332 _g1h->g1_policy()->note_stop_adding_survivor_regions();
334 _head = _survivor_head;
335 _length = _survivor_length;
336 if (_survivor_head != NULL) {
337 assert(_survivor_tail != NULL, "cause it shouldn't be");
338 assert(_survivor_length > 0, "invariant");
339 _survivor_tail->set_next_young_region(NULL);
340 }
342 // Don't clear the survivor list handles until the start of
343 // the next evacuation pause - we need it in order to re-tag
344 // the survivor regions from this evacuation pause as 'young'
345 // at the start of the next.
347 _g1h->g1_policy()->finished_recalculating_age_indexes(false /* is_survivors */);
349 assert(check_list_well_formed(), "young list should be well formed");
350 }
352 void YoungList::print() {
353 HeapRegion* lists[] = {_head, _survivor_head};
354 const char* names[] = {"YOUNG", "SURVIVOR"};
356 for (uint list = 0; list < ARRAY_SIZE(lists); ++list) {
357 gclog_or_tty->print_cr("%s LIST CONTENTS", names[list]);
358 HeapRegion *curr = lists[list];
359 if (curr == NULL)
360 gclog_or_tty->print_cr(" empty");
361 while (curr != NULL) {
362 gclog_or_tty->print_cr(" " HR_FORMAT ", P: " PTR_FORMAT ", N: " PTR_FORMAT ", age: %4d",
363 HR_FORMAT_PARAMS(curr),
364 curr->prev_top_at_mark_start(),
365 curr->next_top_at_mark_start(),
366 curr->age_in_surv_rate_group_cond());
367 curr = curr->get_next_young_region();
368 }
369 }
371 gclog_or_tty->cr();
372 }
374 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) {
375 OtherRegionsTable::invalidate(start_idx, num_regions);
376 }
378 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) {
379 // The from card cache is not the memory that is actually committed. So we cannot
380 // take advantage of the zero_filled parameter.
381 reset_from_card_cache(start_idx, num_regions);
382 }
384 void G1CollectedHeap::push_dirty_cards_region(HeapRegion* hr)
385 {
386 // Claim the right to put the region on the dirty cards region list
387 // by installing a self pointer.
388 HeapRegion* next = hr->get_next_dirty_cards_region();
389 if (next == NULL) {
390 HeapRegion* res = (HeapRegion*)
391 Atomic::cmpxchg_ptr(hr, hr->next_dirty_cards_region_addr(),
392 NULL);
393 if (res == NULL) {
394 HeapRegion* head;
395 do {
396 // Put the region to the dirty cards region list.
397 head = _dirty_cards_region_list;
398 next = (HeapRegion*)
399 Atomic::cmpxchg_ptr(hr, &_dirty_cards_region_list, head);
400 if (next == head) {
401 assert(hr->get_next_dirty_cards_region() == hr,
402 "hr->get_next_dirty_cards_region() != hr");
403 if (next == NULL) {
404 // The last region in the list points to itself.
405 hr->set_next_dirty_cards_region(hr);
406 } else {
407 hr->set_next_dirty_cards_region(next);
408 }
409 }
410 } while (next != head);
411 }
412 }
413 }
415 HeapRegion* G1CollectedHeap::pop_dirty_cards_region()
416 {
417 HeapRegion* head;
418 HeapRegion* hr;
419 do {
420 head = _dirty_cards_region_list;
421 if (head == NULL) {
422 return NULL;
423 }
424 HeapRegion* new_head = head->get_next_dirty_cards_region();
425 if (head == new_head) {
426 // The last region.
427 new_head = NULL;
428 }
429 hr = (HeapRegion*)Atomic::cmpxchg_ptr(new_head, &_dirty_cards_region_list,
430 head);
431 } while (hr != head);
432 assert(hr != NULL, "invariant");
433 hr->set_next_dirty_cards_region(NULL);
434 return hr;
435 }
437 #ifdef ASSERT
438 // A region is added to the collection set as it is retired
439 // so an address p can point to a region which will be in the
440 // collection set but has not yet been retired. This method
441 // therefore is only accurate during a GC pause after all
442 // regions have been retired. It is used for debugging
443 // to check if an nmethod has references to objects that can
444 // be move during a partial collection. Though it can be
445 // inaccurate, it is sufficient for G1 because the conservative
446 // implementation of is_scavengable() for G1 will indicate that
447 // all nmethods must be scanned during a partial collection.
448 bool G1CollectedHeap::is_in_partial_collection(const void* p) {
449 if (p == NULL) {
450 return false;
451 }
452 return heap_region_containing(p)->in_collection_set();
453 }
454 #endif
456 // Returns true if the reference points to an object that
457 // can move in an incremental collection.
458 bool G1CollectedHeap::is_scavengable(const void* p) {
459 HeapRegion* hr = heap_region_containing(p);
460 return !hr->isHumongous();
461 }
463 void G1CollectedHeap::check_ct_logs_at_safepoint() {
464 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
465 CardTableModRefBS* ct_bs = g1_barrier_set();
467 // Count the dirty cards at the start.
468 CountNonCleanMemRegionClosure count1(this);
469 ct_bs->mod_card_iterate(&count1);
470 int orig_count = count1.n();
472 // First clear the logged cards.
473 ClearLoggedCardTableEntryClosure clear;
474 dcqs.apply_closure_to_all_completed_buffers(&clear);
475 dcqs.iterate_closure_all_threads(&clear, false);
476 clear.print_histo();
478 // Now ensure that there's no dirty cards.
479 CountNonCleanMemRegionClosure count2(this);
480 ct_bs->mod_card_iterate(&count2);
481 if (count2.n() != 0) {
482 gclog_or_tty->print_cr("Card table has %d entries; %d originally",
483 count2.n(), orig_count);
484 }
485 guarantee(count2.n() == 0, "Card table should be clean.");
487 RedirtyLoggedCardTableEntryClosure redirty;
488 dcqs.apply_closure_to_all_completed_buffers(&redirty);
489 dcqs.iterate_closure_all_threads(&redirty, false);
490 gclog_or_tty->print_cr("Log entries = %d, dirty cards = %d.",
491 clear.num_processed(), orig_count);
492 guarantee(redirty.num_processed() == clear.num_processed(),
493 err_msg("Redirtied " SIZE_FORMAT " cards, bug cleared " SIZE_FORMAT,
494 redirty.num_processed(), clear.num_processed()));
496 CountNonCleanMemRegionClosure count3(this);
497 ct_bs->mod_card_iterate(&count3);
498 if (count3.n() != orig_count) {
499 gclog_or_tty->print_cr("Should have restored them all: orig = %d, final = %d.",
500 orig_count, count3.n());
501 guarantee(count3.n() >= orig_count, "Should have restored them all.");
502 }
503 }
505 // Private class members.
507 G1CollectedHeap* G1CollectedHeap::_g1h;
509 // Private methods.
511 HeapRegion*
512 G1CollectedHeap::new_region_try_secondary_free_list(bool is_old) {
513 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
514 while (!_secondary_free_list.is_empty() || free_regions_coming()) {
515 if (!_secondary_free_list.is_empty()) {
516 if (G1ConcRegionFreeingVerbose) {
517 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
518 "secondary_free_list has %u entries",
519 _secondary_free_list.length());
520 }
521 // It looks as if there are free regions available on the
522 // secondary_free_list. Let's move them to the free_list and try
523 // again to allocate from it.
524 append_secondary_free_list();
526 assert(_hrm.num_free_regions() > 0, "if the secondary_free_list was not "
527 "empty we should have moved at least one entry to the free_list");
528 HeapRegion* res = _hrm.allocate_free_region(is_old);
529 if (G1ConcRegionFreeingVerbose) {
530 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
531 "allocated " HR_FORMAT " from secondary_free_list",
532 HR_FORMAT_PARAMS(res));
533 }
534 return res;
535 }
537 // Wait here until we get notified either when (a) there are no
538 // more free regions coming or (b) some regions have been moved on
539 // the secondary_free_list.
540 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
541 }
543 if (G1ConcRegionFreeingVerbose) {
544 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
545 "could not allocate from secondary_free_list");
546 }
547 return NULL;
548 }
550 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) {
551 assert(!isHumongous(word_size) || word_size <= HeapRegion::GrainWords,
552 "the only time we use this to allocate a humongous region is "
553 "when we are allocating a single humongous region");
555 HeapRegion* res;
556 if (G1StressConcRegionFreeing) {
557 if (!_secondary_free_list.is_empty()) {
558 if (G1ConcRegionFreeingVerbose) {
559 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
560 "forced to look at the secondary_free_list");
561 }
562 res = new_region_try_secondary_free_list(is_old);
563 if (res != NULL) {
564 return res;
565 }
566 }
567 }
569 res = _hrm.allocate_free_region(is_old);
571 if (res == NULL) {
572 if (G1ConcRegionFreeingVerbose) {
573 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
574 "res == NULL, trying the secondary_free_list");
575 }
576 res = new_region_try_secondary_free_list(is_old);
577 }
578 if (res == NULL && do_expand && _expand_heap_after_alloc_failure) {
579 // Currently, only attempts to allocate GC alloc regions set
580 // do_expand to true. So, we should only reach here during a
581 // safepoint. If this assumption changes we might have to
582 // reconsider the use of _expand_heap_after_alloc_failure.
583 assert(SafepointSynchronize::is_at_safepoint(), "invariant");
585 ergo_verbose1(ErgoHeapSizing,
586 "attempt heap expansion",
587 ergo_format_reason("region allocation request failed")
588 ergo_format_byte("allocation request"),
589 word_size * HeapWordSize);
590 if (expand(word_size * HeapWordSize)) {
591 // Given that expand() succeeded in expanding the heap, and we
592 // always expand the heap by an amount aligned to the heap
593 // region size, the free list should in theory not be empty.
594 // In either case allocate_free_region() will check for NULL.
595 res = _hrm.allocate_free_region(is_old);
596 } else {
597 _expand_heap_after_alloc_failure = false;
598 }
599 }
600 return res;
601 }
603 HeapWord*
604 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first,
605 uint num_regions,
606 size_t word_size,
607 AllocationContext_t context) {
608 assert(first != G1_NO_HRM_INDEX, "pre-condition");
609 assert(isHumongous(word_size), "word_size should be humongous");
610 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
612 // Index of last region in the series + 1.
613 uint last = first + num_regions;
615 // We need to initialize the region(s) we just discovered. This is
616 // a bit tricky given that it can happen concurrently with
617 // refinement threads refining cards on these regions and
618 // potentially wanting to refine the BOT as they are scanning
619 // those cards (this can happen shortly after a cleanup; see CR
620 // 6991377). So we have to set up the region(s) carefully and in
621 // a specific order.
623 // The word size sum of all the regions we will allocate.
624 size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords;
625 assert(word_size <= word_size_sum, "sanity");
627 // This will be the "starts humongous" region.
628 HeapRegion* first_hr = region_at(first);
629 // The header of the new object will be placed at the bottom of
630 // the first region.
631 HeapWord* new_obj = first_hr->bottom();
632 // This will be the new end of the first region in the series that
633 // should also match the end of the last region in the series.
634 HeapWord* new_end = new_obj + word_size_sum;
635 // This will be the new top of the first region that will reflect
636 // this allocation.
637 HeapWord* new_top = new_obj + word_size;
639 // First, we need to zero the header of the space that we will be
640 // allocating. When we update top further down, some refinement
641 // threads might try to scan the region. By zeroing the header we
642 // ensure that any thread that will try to scan the region will
643 // come across the zero klass word and bail out.
644 //
645 // NOTE: It would not have been correct to have used
646 // CollectedHeap::fill_with_object() and make the space look like
647 // an int array. The thread that is doing the allocation will
648 // later update the object header to a potentially different array
649 // type and, for a very short period of time, the klass and length
650 // fields will be inconsistent. This could cause a refinement
651 // thread to calculate the object size incorrectly.
652 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
654 // We will set up the first region as "starts humongous". This
655 // will also update the BOT covering all the regions to reflect
656 // that there is a single object that starts at the bottom of the
657 // first region.
658 first_hr->set_startsHumongous(new_top, new_end);
659 first_hr->set_allocation_context(context);
660 // Then, if there are any, we will set up the "continues
661 // humongous" regions.
662 HeapRegion* hr = NULL;
663 for (uint i = first + 1; i < last; ++i) {
664 hr = region_at(i);
665 hr->set_continuesHumongous(first_hr);
666 hr->set_allocation_context(context);
667 }
668 // If we have "continues humongous" regions (hr != NULL), then the
669 // end of the last one should match new_end.
670 assert(hr == NULL || hr->end() == new_end, "sanity");
672 // Up to this point no concurrent thread would have been able to
673 // do any scanning on any region in this series. All the top
674 // fields still point to bottom, so the intersection between
675 // [bottom,top] and [card_start,card_end] will be empty. Before we
676 // update the top fields, we'll do a storestore to make sure that
677 // no thread sees the update to top before the zeroing of the
678 // object header and the BOT initialization.
679 OrderAccess::storestore();
681 // Now that the BOT and the object header have been initialized,
682 // we can update top of the "starts humongous" region.
683 assert(first_hr->bottom() < new_top && new_top <= first_hr->end(),
684 "new_top should be in this region");
685 first_hr->set_top(new_top);
686 if (_hr_printer.is_active()) {
687 HeapWord* bottom = first_hr->bottom();
688 HeapWord* end = first_hr->orig_end();
689 if ((first + 1) == last) {
690 // the series has a single humongous region
691 _hr_printer.alloc(G1HRPrinter::SingleHumongous, first_hr, new_top);
692 } else {
693 // the series has more than one humongous regions
694 _hr_printer.alloc(G1HRPrinter::StartsHumongous, first_hr, end);
695 }
696 }
698 // Now, we will update the top fields of the "continues humongous"
699 // regions. The reason we need to do this is that, otherwise,
700 // these regions would look empty and this will confuse parts of
701 // G1. For example, the code that looks for a consecutive number
702 // of empty regions will consider them empty and try to
703 // re-allocate them. We can extend is_empty() to also include
704 // !continuesHumongous(), but it is easier to just update the top
705 // fields here. The way we set top for all regions (i.e., top ==
706 // end for all regions but the last one, top == new_top for the
707 // last one) is actually used when we will free up the humongous
708 // region in free_humongous_region().
709 hr = NULL;
710 for (uint i = first + 1; i < last; ++i) {
711 hr = region_at(i);
712 if ((i + 1) == last) {
713 // last continues humongous region
714 assert(hr->bottom() < new_top && new_top <= hr->end(),
715 "new_top should fall on this region");
716 hr->set_top(new_top);
717 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, new_top);
718 } else {
719 // not last one
720 assert(new_top > hr->end(), "new_top should be above this region");
721 hr->set_top(hr->end());
722 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, hr->end());
723 }
724 }
725 // If we have continues humongous regions (hr != NULL), then the
726 // end of the last one should match new_end and its top should
727 // match new_top.
728 assert(hr == NULL ||
729 (hr->end() == new_end && hr->top() == new_top), "sanity");
730 check_bitmaps("Humongous Region Allocation", first_hr);
732 assert(first_hr->used() == word_size * HeapWordSize, "invariant");
733 _allocator->increase_used(first_hr->used());
734 _humongous_set.add(first_hr);
736 return new_obj;
737 }
739 // If could fit into free regions w/o expansion, try.
740 // Otherwise, if can expand, do so.
741 // Otherwise, if using ex regions might help, try with ex given back.
742 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size, AllocationContext_t context) {
743 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
745 verify_region_sets_optional();
747 uint first = G1_NO_HRM_INDEX;
748 uint obj_regions = (uint)(align_size_up_(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords);
750 if (obj_regions == 1) {
751 // Only one region to allocate, try to use a fast path by directly allocating
752 // from the free lists. Do not try to expand here, we will potentially do that
753 // later.
754 HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */);
755 if (hr != NULL) {
756 first = hr->hrm_index();
757 }
758 } else {
759 // We can't allocate humongous regions spanning more than one region while
760 // cleanupComplete() is running, since some of the regions we find to be
761 // empty might not yet be added to the free list. It is not straightforward
762 // to know in which list they are on so that we can remove them. We only
763 // need to do this if we need to allocate more than one region to satisfy the
764 // current humongous allocation request. If we are only allocating one region
765 // we use the one-region region allocation code (see above), that already
766 // potentially waits for regions from the secondary free list.
767 wait_while_free_regions_coming();
768 append_secondary_free_list_if_not_empty_with_lock();
770 // Policy: Try only empty regions (i.e. already committed first). Maybe we
771 // are lucky enough to find some.
772 first = _hrm.find_contiguous_only_empty(obj_regions);
773 if (first != G1_NO_HRM_INDEX) {
774 _hrm.allocate_free_regions_starting_at(first, obj_regions);
775 }
776 }
778 if (first == G1_NO_HRM_INDEX) {
779 // Policy: We could not find enough regions for the humongous object in the
780 // free list. Look through the heap to find a mix of free and uncommitted regions.
781 // If so, try expansion.
782 first = _hrm.find_contiguous_empty_or_unavailable(obj_regions);
783 if (first != G1_NO_HRM_INDEX) {
784 // We found something. Make sure these regions are committed, i.e. expand
785 // the heap. Alternatively we could do a defragmentation GC.
786 ergo_verbose1(ErgoHeapSizing,
787 "attempt heap expansion",
788 ergo_format_reason("humongous allocation request failed")
789 ergo_format_byte("allocation request"),
790 word_size * HeapWordSize);
792 _hrm.expand_at(first, obj_regions);
793 g1_policy()->record_new_heap_size(num_regions());
795 #ifdef ASSERT
796 for (uint i = first; i < first + obj_regions; ++i) {
797 HeapRegion* hr = region_at(i);
798 assert(hr->is_free(), "sanity");
799 assert(hr->is_empty(), "sanity");
800 assert(is_on_master_free_list(hr), "sanity");
801 }
802 #endif
803 _hrm.allocate_free_regions_starting_at(first, obj_regions);
804 } else {
805 // Policy: Potentially trigger a defragmentation GC.
806 }
807 }
809 HeapWord* result = NULL;
810 if (first != G1_NO_HRM_INDEX) {
811 result = humongous_obj_allocate_initialize_regions(first, obj_regions,
812 word_size, context);
813 assert(result != NULL, "it should always return a valid result");
815 // A successful humongous object allocation changes the used space
816 // information of the old generation so we need to recalculate the
817 // sizes and update the jstat counters here.
818 g1mm()->update_sizes();
819 }
821 verify_region_sets_optional();
823 return result;
824 }
826 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) {
827 assert_heap_not_locked_and_not_at_safepoint();
828 assert(!isHumongous(word_size), "we do not allow humongous TLABs");
830 uint dummy_gc_count_before;
831 uint dummy_gclocker_retry_count = 0;
832 return attempt_allocation(word_size, &dummy_gc_count_before, &dummy_gclocker_retry_count);
833 }
835 HeapWord*
836 G1CollectedHeap::mem_allocate(size_t word_size,
837 bool* gc_overhead_limit_was_exceeded) {
838 assert_heap_not_locked_and_not_at_safepoint();
840 // Loop until the allocation is satisfied, or unsatisfied after GC.
841 for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
842 uint gc_count_before;
844 HeapWord* result = NULL;
845 if (!isHumongous(word_size)) {
846 result = attempt_allocation(word_size, &gc_count_before, &gclocker_retry_count);
847 } else {
848 result = attempt_allocation_humongous(word_size, &gc_count_before, &gclocker_retry_count);
849 }
850 if (result != NULL) {
851 return result;
852 }
854 // Create the garbage collection operation...
855 VM_G1CollectForAllocation op(gc_count_before, word_size);
856 op.set_allocation_context(AllocationContext::current());
858 // ...and get the VM thread to execute it.
859 VMThread::execute(&op);
861 if (op.prologue_succeeded() && op.pause_succeeded()) {
862 // If the operation was successful we'll return the result even
863 // if it is NULL. If the allocation attempt failed immediately
864 // after a Full GC, it's unlikely we'll be able to allocate now.
865 HeapWord* result = op.result();
866 if (result != NULL && !isHumongous(word_size)) {
867 // Allocations that take place on VM operations do not do any
868 // card dirtying and we have to do it here. We only have to do
869 // this for non-humongous allocations, though.
870 dirty_young_block(result, word_size);
871 }
872 return result;
873 } else {
874 if (gclocker_retry_count > GCLockerRetryAllocationCount) {
875 return NULL;
876 }
877 assert(op.result() == NULL,
878 "the result should be NULL if the VM op did not succeed");
879 }
881 // Give a warning if we seem to be looping forever.
882 if ((QueuedAllocationWarningCount > 0) &&
883 (try_count % QueuedAllocationWarningCount == 0)) {
884 warning("G1CollectedHeap::mem_allocate retries %d times", try_count);
885 }
886 }
888 ShouldNotReachHere();
889 return NULL;
890 }
892 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size,
893 AllocationContext_t context,
894 uint* gc_count_before_ret,
895 uint* gclocker_retry_count_ret) {
896 // Make sure you read the note in attempt_allocation_humongous().
898 assert_heap_not_locked_and_not_at_safepoint();
899 assert(!isHumongous(word_size), "attempt_allocation_slow() should not "
900 "be called for humongous allocation requests");
902 // We should only get here after the first-level allocation attempt
903 // (attempt_allocation()) failed to allocate.
905 // We will loop until a) we manage to successfully perform the
906 // allocation or b) we successfully schedule a collection which
907 // fails to perform the allocation. b) is the only case when we'll
908 // return NULL.
909 HeapWord* result = NULL;
910 for (int try_count = 1; /* we'll return */; try_count += 1) {
911 bool should_try_gc;
912 uint gc_count_before;
914 {
915 MutexLockerEx x(Heap_lock);
916 result = _allocator->mutator_alloc_region(context)->attempt_allocation_locked(word_size,
917 false /* bot_updates */);
918 if (result != NULL) {
919 return result;
920 }
922 // If we reach here, attempt_allocation_locked() above failed to
923 // allocate a new region. So the mutator alloc region should be NULL.
924 assert(_allocator->mutator_alloc_region(context)->get() == NULL, "only way to get here");
926 if (GC_locker::is_active_and_needs_gc()) {
927 if (g1_policy()->can_expand_young_list()) {
928 // No need for an ergo verbose message here,
929 // can_expand_young_list() does this when it returns true.
930 result = _allocator->mutator_alloc_region(context)->attempt_allocation_force(word_size,
931 false /* bot_updates */);
932 if (result != NULL) {
933 return result;
934 }
935 }
936 should_try_gc = false;
937 } else {
938 // The GCLocker may not be active but the GCLocker initiated
939 // GC may not yet have been performed (GCLocker::needs_gc()
940 // returns true). In this case we do not try this GC and
941 // wait until the GCLocker initiated GC is performed, and
942 // then retry the allocation.
943 if (GC_locker::needs_gc()) {
944 should_try_gc = false;
945 } else {
946 // Read the GC count while still holding the Heap_lock.
947 gc_count_before = total_collections();
948 should_try_gc = true;
949 }
950 }
951 }
953 if (should_try_gc) {
954 bool succeeded;
955 result = do_collection_pause(word_size, gc_count_before, &succeeded,
956 GCCause::_g1_inc_collection_pause);
957 if (result != NULL) {
958 assert(succeeded, "only way to get back a non-NULL result");
959 return result;
960 }
962 if (succeeded) {
963 // If we get here we successfully scheduled a collection which
964 // failed to allocate. No point in trying to allocate
965 // further. We'll just return NULL.
966 MutexLockerEx x(Heap_lock);
967 *gc_count_before_ret = total_collections();
968 return NULL;
969 }
970 } else {
971 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
972 MutexLockerEx x(Heap_lock);
973 *gc_count_before_ret = total_collections();
974 return NULL;
975 }
976 // The GCLocker is either active or the GCLocker initiated
977 // GC has not yet been performed. Stall until it is and
978 // then retry the allocation.
979 GC_locker::stall_until_clear();
980 (*gclocker_retry_count_ret) += 1;
981 }
983 // We can reach here if we were unsuccessful in scheduling a
984 // collection (because another thread beat us to it) or if we were
985 // stalled due to the GC locker. In either can we should retry the
986 // allocation attempt in case another thread successfully
987 // performed a collection and reclaimed enough space. We do the
988 // first attempt (without holding the Heap_lock) here and the
989 // follow-on attempt will be at the start of the next loop
990 // iteration (after taking the Heap_lock).
991 result = _allocator->mutator_alloc_region(context)->attempt_allocation(word_size,
992 false /* bot_updates */);
993 if (result != NULL) {
994 return result;
995 }
997 // Give a warning if we seem to be looping forever.
998 if ((QueuedAllocationWarningCount > 0) &&
999 (try_count % QueuedAllocationWarningCount == 0)) {
1000 warning("G1CollectedHeap::attempt_allocation_slow() "
1001 "retries %d times", try_count);
1002 }
1003 }
1005 ShouldNotReachHere();
1006 return NULL;
1007 }
1009 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size,
1010 uint* gc_count_before_ret,
1011 uint* gclocker_retry_count_ret) {
1012 // The structure of this method has a lot of similarities to
1013 // attempt_allocation_slow(). The reason these two were not merged
1014 // into a single one is that such a method would require several "if
1015 // allocation is not humongous do this, otherwise do that"
1016 // conditional paths which would obscure its flow. In fact, an early
1017 // version of this code did use a unified method which was harder to
1018 // follow and, as a result, it had subtle bugs that were hard to
1019 // track down. So keeping these two methods separate allows each to
1020 // be more readable. It will be good to keep these two in sync as
1021 // much as possible.
1023 assert_heap_not_locked_and_not_at_safepoint();
1024 assert(isHumongous(word_size), "attempt_allocation_humongous() "
1025 "should only be called for humongous allocations");
1027 // Humongous objects can exhaust the heap quickly, so we should check if we
1028 // need to start a marking cycle at each humongous object allocation. We do
1029 // the check before we do the actual allocation. The reason for doing it
1030 // before the allocation is that we avoid having to keep track of the newly
1031 // allocated memory while we do a GC.
1032 if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation",
1033 word_size)) {
1034 collect(GCCause::_g1_humongous_allocation);
1035 }
1037 // We will loop until a) we manage to successfully perform the
1038 // allocation or b) we successfully schedule a collection which
1039 // fails to perform the allocation. b) is the only case when we'll
1040 // return NULL.
1041 HeapWord* result = NULL;
1042 for (int try_count = 1; /* we'll return */; try_count += 1) {
1043 bool should_try_gc;
1044 uint gc_count_before;
1046 {
1047 MutexLockerEx x(Heap_lock);
1049 // Given that humongous objects are not allocated in young
1050 // regions, we'll first try to do the allocation without doing a
1051 // collection hoping that there's enough space in the heap.
1052 result = humongous_obj_allocate(word_size, AllocationContext::current());
1053 if (result != NULL) {
1054 return result;
1055 }
1057 if (GC_locker::is_active_and_needs_gc()) {
1058 should_try_gc = false;
1059 } else {
1060 // The GCLocker may not be active but the GCLocker initiated
1061 // GC may not yet have been performed (GCLocker::needs_gc()
1062 // returns true). In this case we do not try this GC and
1063 // wait until the GCLocker initiated GC is performed, and
1064 // then retry the allocation.
1065 if (GC_locker::needs_gc()) {
1066 should_try_gc = false;
1067 } else {
1068 // Read the GC count while still holding the Heap_lock.
1069 gc_count_before = total_collections();
1070 should_try_gc = true;
1071 }
1072 }
1073 }
1075 if (should_try_gc) {
1076 // If we failed to allocate the humongous object, we should try to
1077 // do a collection pause (if we're allowed) in case it reclaims
1078 // enough space for the allocation to succeed after the pause.
1080 bool succeeded;
1081 result = do_collection_pause(word_size, gc_count_before, &succeeded,
1082 GCCause::_g1_humongous_allocation);
1083 if (result != NULL) {
1084 assert(succeeded, "only way to get back a non-NULL result");
1085 return result;
1086 }
1088 if (succeeded) {
1089 // If we get here we successfully scheduled a collection which
1090 // failed to allocate. No point in trying to allocate
1091 // further. We'll just return NULL.
1092 MutexLockerEx x(Heap_lock);
1093 *gc_count_before_ret = total_collections();
1094 return NULL;
1095 }
1096 } else {
1097 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
1098 MutexLockerEx x(Heap_lock);
1099 *gc_count_before_ret = total_collections();
1100 return NULL;
1101 }
1102 // The GCLocker is either active or the GCLocker initiated
1103 // GC has not yet been performed. Stall until it is and
1104 // then retry the allocation.
1105 GC_locker::stall_until_clear();
1106 (*gclocker_retry_count_ret) += 1;
1107 }
1109 // We can reach here if we were unsuccessful in scheduling a
1110 // collection (because another thread beat us to it) or if we were
1111 // stalled due to the GC locker. In either can we should retry the
1112 // allocation attempt in case another thread successfully
1113 // performed a collection and reclaimed enough space. Give a
1114 // warning if we seem to be looping forever.
1116 if ((QueuedAllocationWarningCount > 0) &&
1117 (try_count % QueuedAllocationWarningCount == 0)) {
1118 warning("G1CollectedHeap::attempt_allocation_humongous() "
1119 "retries %d times", try_count);
1120 }
1121 }
1123 ShouldNotReachHere();
1124 return NULL;
1125 }
1127 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
1128 AllocationContext_t context,
1129 bool expect_null_mutator_alloc_region) {
1130 assert_at_safepoint(true /* should_be_vm_thread */);
1131 assert(_allocator->mutator_alloc_region(context)->get() == NULL ||
1132 !expect_null_mutator_alloc_region,
1133 "the current alloc region was unexpectedly found to be non-NULL");
1135 if (!isHumongous(word_size)) {
1136 return _allocator->mutator_alloc_region(context)->attempt_allocation_locked(word_size,
1137 false /* bot_updates */);
1138 } else {
1139 HeapWord* result = humongous_obj_allocate(word_size, context);
1140 if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) {
1141 g1_policy()->set_initiate_conc_mark_if_possible();
1142 }
1143 return result;
1144 }
1146 ShouldNotReachHere();
1147 }
1149 class PostMCRemSetClearClosure: public HeapRegionClosure {
1150 G1CollectedHeap* _g1h;
1151 ModRefBarrierSet* _mr_bs;
1152 public:
1153 PostMCRemSetClearClosure(G1CollectedHeap* g1h, ModRefBarrierSet* mr_bs) :
1154 _g1h(g1h), _mr_bs(mr_bs) {}
1156 bool doHeapRegion(HeapRegion* r) {
1157 HeapRegionRemSet* hrrs = r->rem_set();
1159 if (r->continuesHumongous()) {
1160 // We'll assert that the strong code root list and RSet is empty
1161 assert(hrrs->strong_code_roots_list_length() == 0, "sanity");
1162 assert(hrrs->occupied() == 0, "RSet should be empty");
1163 return false;
1164 }
1166 _g1h->reset_gc_time_stamps(r);
1167 hrrs->clear();
1168 // You might think here that we could clear just the cards
1169 // corresponding to the used region. But no: if we leave a dirty card
1170 // in a region we might allocate into, then it would prevent that card
1171 // from being enqueued, and cause it to be missed.
1172 // Re: the performance cost: we shouldn't be doing full GC anyway!
1173 _mr_bs->clear(MemRegion(r->bottom(), r->end()));
1175 return false;
1176 }
1177 };
1179 void G1CollectedHeap::clear_rsets_post_compaction() {
1180 PostMCRemSetClearClosure rs_clear(this, g1_barrier_set());
1181 heap_region_iterate(&rs_clear);
1182 }
1184 class RebuildRSOutOfRegionClosure: public HeapRegionClosure {
1185 G1CollectedHeap* _g1h;
1186 UpdateRSOopClosure _cl;
1187 int _worker_i;
1188 public:
1189 RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, int worker_i = 0) :
1190 _cl(g1->g1_rem_set(), worker_i),
1191 _worker_i(worker_i),
1192 _g1h(g1)
1193 { }
1195 bool doHeapRegion(HeapRegion* r) {
1196 if (!r->continuesHumongous()) {
1197 _cl.set_from(r);
1198 r->oop_iterate(&_cl);
1199 }
1200 return false;
1201 }
1202 };
1204 class ParRebuildRSTask: public AbstractGangTask {
1205 G1CollectedHeap* _g1;
1206 public:
1207 ParRebuildRSTask(G1CollectedHeap* g1)
1208 : AbstractGangTask("ParRebuildRSTask"),
1209 _g1(g1)
1210 { }
1212 void work(uint worker_id) {
1213 RebuildRSOutOfRegionClosure rebuild_rs(_g1, worker_id);
1214 _g1->heap_region_par_iterate_chunked(&rebuild_rs, worker_id,
1215 _g1->workers()->active_workers(),
1216 HeapRegion::RebuildRSClaimValue);
1217 }
1218 };
1220 class PostCompactionPrinterClosure: public HeapRegionClosure {
1221 private:
1222 G1HRPrinter* _hr_printer;
1223 public:
1224 bool doHeapRegion(HeapRegion* hr) {
1225 assert(!hr->is_young(), "not expecting to find young regions");
1226 if (hr->is_free()) {
1227 // We only generate output for non-empty regions.
1228 } else if (hr->startsHumongous()) {
1229 if (hr->region_num() == 1) {
1230 // single humongous region
1231 _hr_printer->post_compaction(hr, G1HRPrinter::SingleHumongous);
1232 } else {
1233 _hr_printer->post_compaction(hr, G1HRPrinter::StartsHumongous);
1234 }
1235 } else if (hr->continuesHumongous()) {
1236 _hr_printer->post_compaction(hr, G1HRPrinter::ContinuesHumongous);
1237 } else if (hr->is_old()) {
1238 _hr_printer->post_compaction(hr, G1HRPrinter::Old);
1239 } else {
1240 ShouldNotReachHere();
1241 }
1242 return false;
1243 }
1245 PostCompactionPrinterClosure(G1HRPrinter* hr_printer)
1246 : _hr_printer(hr_printer) { }
1247 };
1249 void G1CollectedHeap::print_hrm_post_compaction() {
1250 PostCompactionPrinterClosure cl(hr_printer());
1251 heap_region_iterate(&cl);
1252 }
1254 bool G1CollectedHeap::do_collection(bool explicit_gc,
1255 bool clear_all_soft_refs,
1256 size_t word_size) {
1257 assert_at_safepoint(true /* should_be_vm_thread */);
1259 if (GC_locker::check_active_before_gc()) {
1260 return false;
1261 }
1263 STWGCTimer* gc_timer = G1MarkSweep::gc_timer();
1264 gc_timer->register_gc_start();
1266 SerialOldTracer* gc_tracer = G1MarkSweep::gc_tracer();
1267 gc_tracer->report_gc_start(gc_cause(), gc_timer->gc_start());
1269 SvcGCMarker sgcm(SvcGCMarker::FULL);
1270 ResourceMark rm;
1272 print_heap_before_gc();
1273 trace_heap_before_gc(gc_tracer);
1275 size_t metadata_prev_used = MetaspaceAux::used_bytes();
1277 verify_region_sets_optional();
1279 const bool do_clear_all_soft_refs = clear_all_soft_refs ||
1280 collector_policy()->should_clear_all_soft_refs();
1282 ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy());
1284 {
1285 IsGCActiveMark x;
1287 // Timing
1288 assert(gc_cause() != GCCause::_java_lang_system_gc || explicit_gc, "invariant");
1289 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
1291 {
1292 GCTraceTime t(GCCauseString("Full GC", gc_cause()), G1Log::fine(), true, NULL, gc_tracer->gc_id());
1293 TraceCollectorStats tcs(g1mm()->full_collection_counters());
1294 TraceMemoryManagerStats tms(true /* fullGC */, gc_cause());
1296 double start = os::elapsedTime();
1297 g1_policy()->record_full_collection_start();
1299 // Note: When we have a more flexible GC logging framework that
1300 // allows us to add optional attributes to a GC log record we
1301 // could consider timing and reporting how long we wait in the
1302 // following two methods.
1303 wait_while_free_regions_coming();
1304 // If we start the compaction before the CM threads finish
1305 // scanning the root regions we might trip them over as we'll
1306 // be moving objects / updating references. So let's wait until
1307 // they are done. By telling them to abort, they should complete
1308 // early.
1309 _cm->root_regions()->abort();
1310 _cm->root_regions()->wait_until_scan_finished();
1311 append_secondary_free_list_if_not_empty_with_lock();
1313 gc_prologue(true);
1314 increment_total_collections(true /* full gc */);
1315 increment_old_marking_cycles_started();
1317 assert(used() == recalculate_used(), "Should be equal");
1319 verify_before_gc();
1321 check_bitmaps("Full GC Start");
1322 pre_full_gc_dump(gc_timer);
1324 COMPILER2_PRESENT(DerivedPointerTable::clear());
1326 // Disable discovery and empty the discovered lists
1327 // for the CM ref processor.
1328 ref_processor_cm()->disable_discovery();
1329 ref_processor_cm()->abandon_partial_discovery();
1330 ref_processor_cm()->verify_no_references_recorded();
1332 // Abandon current iterations of concurrent marking and concurrent
1333 // refinement, if any are in progress. We have to do this before
1334 // wait_until_scan_finished() below.
1335 concurrent_mark()->abort();
1337 // Make sure we'll choose a new allocation region afterwards.
1338 _allocator->release_mutator_alloc_region();
1339 _allocator->abandon_gc_alloc_regions();
1340 g1_rem_set()->cleanupHRRS();
1342 // We should call this after we retire any currently active alloc
1343 // regions so that all the ALLOC / RETIRE events are generated
1344 // before the start GC event.
1345 _hr_printer.start_gc(true /* full */, (size_t) total_collections());
1347 // We may have added regions to the current incremental collection
1348 // set between the last GC or pause and now. We need to clear the
1349 // incremental collection set and then start rebuilding it afresh
1350 // after this full GC.
1351 abandon_collection_set(g1_policy()->inc_cset_head());
1352 g1_policy()->clear_incremental_cset();
1353 g1_policy()->stop_incremental_cset_building();
1355 tear_down_region_sets(false /* free_list_only */);
1356 g1_policy()->set_gcs_are_young(true);
1358 // See the comments in g1CollectedHeap.hpp and
1359 // G1CollectedHeap::ref_processing_init() about
1360 // how reference processing currently works in G1.
1362 // Temporarily make discovery by the STW ref processor single threaded (non-MT).
1363 ReferenceProcessorMTDiscoveryMutator stw_rp_disc_ser(ref_processor_stw(), false);
1365 // Temporarily clear the STW ref processor's _is_alive_non_header field.
1366 ReferenceProcessorIsAliveMutator stw_rp_is_alive_null(ref_processor_stw(), NULL);
1368 ref_processor_stw()->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/);
1369 ref_processor_stw()->setup_policy(do_clear_all_soft_refs);
1371 // Do collection work
1372 {
1373 HandleMark hm; // Discard invalid handles created during gc
1374 G1MarkSweep::invoke_at_safepoint(ref_processor_stw(), do_clear_all_soft_refs);
1375 }
1377 assert(num_free_regions() == 0, "we should not have added any free regions");
1378 rebuild_region_sets(false /* free_list_only */);
1380 // Enqueue any discovered reference objects that have
1381 // not been removed from the discovered lists.
1382 ref_processor_stw()->enqueue_discovered_references();
1384 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
1386 MemoryService::track_memory_usage();
1388 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
1389 ref_processor_stw()->verify_no_references_recorded();
1391 // Delete metaspaces for unloaded class loaders and clean up loader_data graph
1392 ClassLoaderDataGraph::purge();
1393 MetaspaceAux::verify_metrics();
1395 // Note: since we've just done a full GC, concurrent
1396 // marking is no longer active. Therefore we need not
1397 // re-enable reference discovery for the CM ref processor.
1398 // That will be done at the start of the next marking cycle.
1399 assert(!ref_processor_cm()->discovery_enabled(), "Postcondition");
1400 ref_processor_cm()->verify_no_references_recorded();
1402 reset_gc_time_stamp();
1403 // Since everything potentially moved, we will clear all remembered
1404 // sets, and clear all cards. Later we will rebuild remembered
1405 // sets. We will also reset the GC time stamps of the regions.
1406 clear_rsets_post_compaction();
1407 check_gc_time_stamps();
1409 // Resize the heap if necessary.
1410 resize_if_necessary_after_full_collection(explicit_gc ? 0 : word_size);
1412 if (_hr_printer.is_active()) {
1413 // We should do this after we potentially resize the heap so
1414 // that all the COMMIT / UNCOMMIT events are generated before
1415 // the end GC event.
1417 print_hrm_post_compaction();
1418 _hr_printer.end_gc(true /* full */, (size_t) total_collections());
1419 }
1421 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
1422 if (hot_card_cache->use_cache()) {
1423 hot_card_cache->reset_card_counts();
1424 hot_card_cache->reset_hot_cache();
1425 }
1427 // Rebuild remembered sets of all regions.
1428 if (G1CollectedHeap::use_parallel_gc_threads()) {
1429 uint n_workers =
1430 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
1431 workers()->active_workers(),
1432 Threads::number_of_non_daemon_threads());
1433 assert(UseDynamicNumberOfGCThreads ||
1434 n_workers == workers()->total_workers(),
1435 "If not dynamic should be using all the workers");
1436 workers()->set_active_workers(n_workers);
1437 // Set parallel threads in the heap (_n_par_threads) only
1438 // before a parallel phase and always reset it to 0 after
1439 // the phase so that the number of parallel threads does
1440 // no get carried forward to a serial phase where there
1441 // may be code that is "possibly_parallel".
1442 set_par_threads(n_workers);
1444 ParRebuildRSTask rebuild_rs_task(this);
1445 assert(check_heap_region_claim_values(
1446 HeapRegion::InitialClaimValue), "sanity check");
1447 assert(UseDynamicNumberOfGCThreads ||
1448 workers()->active_workers() == workers()->total_workers(),
1449 "Unless dynamic should use total workers");
1450 // Use the most recent number of active workers
1451 assert(workers()->active_workers() > 0,
1452 "Active workers not properly set");
1453 set_par_threads(workers()->active_workers());
1454 workers()->run_task(&rebuild_rs_task);
1455 set_par_threads(0);
1456 assert(check_heap_region_claim_values(
1457 HeapRegion::RebuildRSClaimValue), "sanity check");
1458 reset_heap_region_claim_values();
1459 } else {
1460 RebuildRSOutOfRegionClosure rebuild_rs(this);
1461 heap_region_iterate(&rebuild_rs);
1462 }
1464 // Rebuild the strong code root lists for each region
1465 rebuild_strong_code_roots();
1467 // Purge code root memory
1468 purge_code_root_memory();
1470 if (true) { // FIXME
1471 MetaspaceGC::compute_new_size();
1472 }
1474 #ifdef TRACESPINNING
1475 ParallelTaskTerminator::print_termination_counts();
1476 #endif
1478 // Discard all rset updates
1479 JavaThread::dirty_card_queue_set().abandon_logs();
1480 assert(dirty_card_queue_set().completed_buffers_num() == 0, "DCQS should be empty");
1482 _young_list->reset_sampled_info();
1483 // At this point there should be no regions in the
1484 // entire heap tagged as young.
1485 assert(check_young_list_empty(true /* check_heap */),
1486 "young list should be empty at this point");
1488 // Update the number of full collections that have been completed.
1489 increment_old_marking_cycles_completed(false /* concurrent */);
1491 _hrm.verify_optional();
1492 verify_region_sets_optional();
1494 verify_after_gc();
1496 // Clear the previous marking bitmap, if needed for bitmap verification.
1497 // Note we cannot do this when we clear the next marking bitmap in
1498 // ConcurrentMark::abort() above since VerifyDuringGC verifies the
1499 // objects marked during a full GC against the previous bitmap.
1500 // But we need to clear it before calling check_bitmaps below since
1501 // the full GC has compacted objects and updated TAMS but not updated
1502 // the prev bitmap.
1503 if (G1VerifyBitmaps) {
1504 ((CMBitMap*) concurrent_mark()->prevMarkBitMap())->clearAll();
1505 }
1506 check_bitmaps("Full GC End");
1508 // Start a new incremental collection set for the next pause
1509 assert(g1_policy()->collection_set() == NULL, "must be");
1510 g1_policy()->start_incremental_cset_building();
1512 clear_cset_fast_test();
1514 _allocator->init_mutator_alloc_region();
1516 double end = os::elapsedTime();
1517 g1_policy()->record_full_collection_end();
1519 if (G1Log::fine()) {
1520 g1_policy()->print_heap_transition();
1521 }
1523 // We must call G1MonitoringSupport::update_sizes() in the same scoping level
1524 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
1525 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
1526 // before any GC notifications are raised.
1527 g1mm()->update_sizes();
1529 gc_epilogue(true);
1530 }
1532 if (G1Log::finer()) {
1533 g1_policy()->print_detailed_heap_transition(true /* full */);
1534 }
1536 print_heap_after_gc();
1537 trace_heap_after_gc(gc_tracer);
1539 post_full_gc_dump(gc_timer);
1541 gc_timer->register_gc_end();
1542 gc_tracer->report_gc_end(gc_timer->gc_end(), gc_timer->time_partitions());
1543 }
1545 return true;
1546 }
1548 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
1549 // do_collection() will return whether it succeeded in performing
1550 // the GC. Currently, there is no facility on the
1551 // do_full_collection() API to notify the caller than the collection
1552 // did not succeed (e.g., because it was locked out by the GC
1553 // locker). So, right now, we'll ignore the return value.
1554 bool dummy = do_collection(true, /* explicit_gc */
1555 clear_all_soft_refs,
1556 0 /* word_size */);
1557 }
1559 // This code is mostly copied from TenuredGeneration.
1560 void
1561 G1CollectedHeap::
1562 resize_if_necessary_after_full_collection(size_t word_size) {
1563 // Include the current allocation, if any, and bytes that will be
1564 // pre-allocated to support collections, as "used".
1565 const size_t used_after_gc = used();
1566 const size_t capacity_after_gc = capacity();
1567 const size_t free_after_gc = capacity_after_gc - used_after_gc;
1569 // This is enforced in arguments.cpp.
1570 assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
1571 "otherwise the code below doesn't make sense");
1573 // We don't have floating point command-line arguments
1574 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
1575 const double maximum_used_percentage = 1.0 - minimum_free_percentage;
1576 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
1577 const double minimum_used_percentage = 1.0 - maximum_free_percentage;
1579 const size_t min_heap_size = collector_policy()->min_heap_byte_size();
1580 const size_t max_heap_size = collector_policy()->max_heap_byte_size();
1582 // We have to be careful here as these two calculations can overflow
1583 // 32-bit size_t's.
1584 double used_after_gc_d = (double) used_after_gc;
1585 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
1586 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
1588 // Let's make sure that they are both under the max heap size, which
1589 // by default will make them fit into a size_t.
1590 double desired_capacity_upper_bound = (double) max_heap_size;
1591 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
1592 desired_capacity_upper_bound);
1593 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
1594 desired_capacity_upper_bound);
1596 // We can now safely turn them into size_t's.
1597 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
1598 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
1600 // This assert only makes sense here, before we adjust them
1601 // with respect to the min and max heap size.
1602 assert(minimum_desired_capacity <= maximum_desired_capacity,
1603 err_msg("minimum_desired_capacity = " SIZE_FORMAT ", "
1604 "maximum_desired_capacity = " SIZE_FORMAT,
1605 minimum_desired_capacity, maximum_desired_capacity));
1607 // Should not be greater than the heap max size. No need to adjust
1608 // it with respect to the heap min size as it's a lower bound (i.e.,
1609 // we'll try to make the capacity larger than it, not smaller).
1610 minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size);
1611 // Should not be less than the heap min size. No need to adjust it
1612 // with respect to the heap max size as it's an upper bound (i.e.,
1613 // we'll try to make the capacity smaller than it, not greater).
1614 maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size);
1616 if (capacity_after_gc < minimum_desired_capacity) {
1617 // Don't expand unless it's significant
1618 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
1619 ergo_verbose4(ErgoHeapSizing,
1620 "attempt heap expansion",
1621 ergo_format_reason("capacity lower than "
1622 "min desired capacity after Full GC")
1623 ergo_format_byte("capacity")
1624 ergo_format_byte("occupancy")
1625 ergo_format_byte_perc("min desired capacity"),
1626 capacity_after_gc, used_after_gc,
1627 minimum_desired_capacity, (double) MinHeapFreeRatio);
1628 expand(expand_bytes);
1630 // No expansion, now see if we want to shrink
1631 } else if (capacity_after_gc > maximum_desired_capacity) {
1632 // Capacity too large, compute shrinking size
1633 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
1634 ergo_verbose4(ErgoHeapSizing,
1635 "attempt heap shrinking",
1636 ergo_format_reason("capacity higher than "
1637 "max desired capacity after Full GC")
1638 ergo_format_byte("capacity")
1639 ergo_format_byte("occupancy")
1640 ergo_format_byte_perc("max desired capacity"),
1641 capacity_after_gc, used_after_gc,
1642 maximum_desired_capacity, (double) MaxHeapFreeRatio);
1643 shrink(shrink_bytes);
1644 }
1645 }
1648 HeapWord*
1649 G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
1650 AllocationContext_t context,
1651 bool* succeeded) {
1652 assert_at_safepoint(true /* should_be_vm_thread */);
1654 *succeeded = true;
1655 // Let's attempt the allocation first.
1656 HeapWord* result =
1657 attempt_allocation_at_safepoint(word_size,
1658 context,
1659 false /* expect_null_mutator_alloc_region */);
1660 if (result != NULL) {
1661 assert(*succeeded, "sanity");
1662 return result;
1663 }
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, context);
1670 if (result != NULL) {
1671 assert(*succeeded, "sanity");
1672 return result;
1673 }
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 }
1684 // Retry the allocation
1685 result = attempt_allocation_at_safepoint(word_size,
1686 context,
1687 true /* expect_null_mutator_alloc_region */);
1688 if (result != NULL) {
1689 assert(*succeeded, "sanity");
1690 return result;
1691 }
1693 // Then, try a Full GC that will collect all soft references.
1694 gc_succeeded = do_collection(false, /* explicit_gc */
1695 true, /* clear_all_soft_refs */
1696 word_size);
1697 if (!gc_succeeded) {
1698 *succeeded = false;
1699 return NULL;
1700 }
1702 // Retry the allocation once more
1703 result = attempt_allocation_at_safepoint(word_size,
1704 context,
1705 true /* expect_null_mutator_alloc_region */);
1706 if (result != NULL) {
1707 assert(*succeeded, "sanity");
1708 return result;
1709 }
1711 assert(!collector_policy()->should_clear_all_soft_refs(),
1712 "Flag should have been handled and cleared prior to this point");
1714 // What else? We might try synchronous finalization later. If the total
1715 // space available is large enough for the allocation, then a more
1716 // complete compaction phase than we've tried so far might be
1717 // appropriate.
1718 assert(*succeeded, "sanity");
1719 return NULL;
1720 }
1722 // Attempting to expand the heap sufficiently
1723 // to support an allocation of the given "word_size". If
1724 // successful, perform the allocation and return the address of the
1725 // allocated block, or else "NULL".
1727 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size, AllocationContext_t context) {
1728 assert_at_safepoint(true /* should_be_vm_thread */);
1730 verify_region_sets_optional();
1732 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
1733 ergo_verbose1(ErgoHeapSizing,
1734 "attempt heap expansion",
1735 ergo_format_reason("allocation request failed")
1736 ergo_format_byte("allocation request"),
1737 word_size * HeapWordSize);
1738 if (expand(expand_bytes)) {
1739 _hrm.verify_optional();
1740 verify_region_sets_optional();
1741 return attempt_allocation_at_safepoint(word_size,
1742 context,
1743 false /* expect_null_mutator_alloc_region */);
1744 }
1745 return NULL;
1746 }
1748 bool G1CollectedHeap::expand(size_t expand_bytes) {
1749 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
1750 aligned_expand_bytes = align_size_up(aligned_expand_bytes,
1751 HeapRegion::GrainBytes);
1752 ergo_verbose2(ErgoHeapSizing,
1753 "expand the heap",
1754 ergo_format_byte("requested expansion amount")
1755 ergo_format_byte("attempted expansion amount"),
1756 expand_bytes, aligned_expand_bytes);
1758 if (is_maximal_no_gc()) {
1759 ergo_verbose0(ErgoHeapSizing,
1760 "did not expand the heap",
1761 ergo_format_reason("heap already fully expanded"));
1762 return false;
1763 }
1765 uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes);
1766 assert(regions_to_expand > 0, "Must expand by at least one region");
1768 uint expanded_by = _hrm.expand_by(regions_to_expand);
1770 if (expanded_by > 0) {
1771 size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes;
1772 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
1773 g1_policy()->record_new_heap_size(num_regions());
1774 } else {
1775 ergo_verbose0(ErgoHeapSizing,
1776 "did not expand the heap",
1777 ergo_format_reason("heap expansion operation failed"));
1778 // The expansion of the virtual storage space was unsuccessful.
1779 // Let's see if it was because we ran out of swap.
1780 if (G1ExitOnExpansionFailure &&
1781 _hrm.available() >= regions_to_expand) {
1782 // We had head room...
1783 vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion");
1784 }
1785 }
1786 return regions_to_expand > 0;
1787 }
1789 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
1790 size_t aligned_shrink_bytes =
1791 ReservedSpace::page_align_size_down(shrink_bytes);
1792 aligned_shrink_bytes = align_size_down(aligned_shrink_bytes,
1793 HeapRegion::GrainBytes);
1794 uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes);
1796 uint num_regions_removed = _hrm.shrink_by(num_regions_to_remove);
1797 size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes;
1799 ergo_verbose3(ErgoHeapSizing,
1800 "shrink the heap",
1801 ergo_format_byte("requested shrinking amount")
1802 ergo_format_byte("aligned shrinking amount")
1803 ergo_format_byte("attempted shrinking amount"),
1804 shrink_bytes, aligned_shrink_bytes, shrunk_bytes);
1805 if (num_regions_removed > 0) {
1806 g1_policy()->record_new_heap_size(num_regions());
1807 } else {
1808 ergo_verbose0(ErgoHeapSizing,
1809 "did not shrink the heap",
1810 ergo_format_reason("heap shrinking operation failed"));
1811 }
1812 }
1814 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1815 verify_region_sets_optional();
1817 // We should only reach here at the end of a Full GC which means we
1818 // should not not be holding to any GC alloc regions. The method
1819 // below will make sure of that and do any remaining clean up.
1820 _allocator->abandon_gc_alloc_regions();
1822 // Instead of tearing down / rebuilding the free lists here, we
1823 // could instead use the remove_all_pending() method on free_list to
1824 // remove only the ones that we need to remove.
1825 tear_down_region_sets(true /* free_list_only */);
1826 shrink_helper(shrink_bytes);
1827 rebuild_region_sets(true /* free_list_only */);
1829 _hrm.verify_optional();
1830 verify_region_sets_optional();
1831 }
1833 // Public methods.
1835 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away
1836 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
1837 #endif // _MSC_VER
1840 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* policy_) :
1841 SharedHeap(policy_),
1842 _g1_policy(policy_),
1843 _dirty_card_queue_set(false),
1844 _into_cset_dirty_card_queue_set(false),
1845 _is_alive_closure_cm(this),
1846 _is_alive_closure_stw(this),
1847 _ref_processor_cm(NULL),
1848 _ref_processor_stw(NULL),
1849 _bot_shared(NULL),
1850 _evac_failure_scan_stack(NULL),
1851 _mark_in_progress(false),
1852 _cg1r(NULL),
1853 _g1mm(NULL),
1854 _refine_cte_cl(NULL),
1855 _full_collection(false),
1856 _secondary_free_list("Secondary Free List", new SecondaryFreeRegionListMtSafeChecker()),
1857 _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()),
1858 _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()),
1859 _humongous_reclaim_candidates(),
1860 _has_humongous_reclaim_candidates(false),
1861 _free_regions_coming(false),
1862 _young_list(new YoungList(this)),
1863 _gc_time_stamp(0),
1864 _survivor_plab_stats(YoungPLABSize, PLABWeight),
1865 _old_plab_stats(OldPLABSize, PLABWeight),
1866 _expand_heap_after_alloc_failure(true),
1867 _surviving_young_words(NULL),
1868 _old_marking_cycles_started(0),
1869 _old_marking_cycles_completed(0),
1870 _concurrent_cycle_started(false),
1871 _heap_summary_sent(false),
1872 _in_cset_fast_test(),
1873 _dirty_cards_region_list(NULL),
1874 _worker_cset_start_region(NULL),
1875 _worker_cset_start_region_time_stamp(NULL),
1876 _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()),
1877 _gc_timer_cm(new (ResourceObj::C_HEAP, mtGC) ConcurrentGCTimer()),
1878 _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()),
1879 _gc_tracer_cm(new (ResourceObj::C_HEAP, mtGC) G1OldTracer()) {
1881 _g1h = this;
1883 _allocator = G1Allocator::create_allocator(_g1h);
1884 _humongous_object_threshold_in_words = HeapRegion::GrainWords / 2;
1886 int n_queues = MAX2((int)ParallelGCThreads, 1);
1887 _task_queues = new RefToScanQueueSet(n_queues);
1889 uint n_rem_sets = HeapRegionRemSet::num_par_rem_sets();
1890 assert(n_rem_sets > 0, "Invariant.");
1892 _worker_cset_start_region = NEW_C_HEAP_ARRAY(HeapRegion*, n_queues, mtGC);
1893 _worker_cset_start_region_time_stamp = NEW_C_HEAP_ARRAY(uint, n_queues, mtGC);
1894 _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC);
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();
1904 // Initialize the G1EvacuationFailureALot counters and flags.
1905 NOT_PRODUCT(reset_evacuation_should_fail();)
1907 guarantee(_task_queues != NULL, "task_queues allocation failure.");
1908 }
1910 G1RegionToSpaceMapper* G1CollectedHeap::create_aux_memory_mapper(const char* description,
1911 size_t size,
1912 size_t translation_factor) {
1913 size_t preferred_page_size = os::page_size_for_region_unaligned(size, 1);
1914 // Allocate a new reserved space, preferring to use large pages.
1915 ReservedSpace rs(size, preferred_page_size);
1916 G1RegionToSpaceMapper* result =
1917 G1RegionToSpaceMapper::create_mapper(rs,
1918 size,
1919 rs.alignment(),
1920 HeapRegion::GrainBytes,
1921 translation_factor,
1922 mtGC);
1923 if (TracePageSizes) {
1924 gclog_or_tty->print_cr("G1 '%s': pg_sz=" SIZE_FORMAT " base=" PTR_FORMAT " size=" SIZE_FORMAT " alignment=" SIZE_FORMAT " reqsize=" SIZE_FORMAT,
1925 description, preferred_page_size, p2i(rs.base()), rs.size(), rs.alignment(), size);
1926 }
1927 return result;
1928 }
1930 jint G1CollectedHeap::initialize() {
1931 CollectedHeap::pre_initialize();
1932 os::enable_vtime();
1934 G1Log::init();
1936 // Necessary to satisfy locking discipline assertions.
1938 MutexLocker x(Heap_lock);
1940 // We have to initialize the printer before committing the heap, as
1941 // it will be used then.
1942 _hr_printer.set_active(G1PrintHeapRegions);
1944 // While there are no constraints in the GC code that HeapWordSize
1945 // be any particular value, there are multiple other areas in the
1946 // system which believe this to be true (e.g. oop->object_size in some
1947 // cases incorrectly returns the size in wordSize units rather than
1948 // HeapWordSize).
1949 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
1951 size_t init_byte_size = collector_policy()->initial_heap_byte_size();
1952 size_t max_byte_size = collector_policy()->max_heap_byte_size();
1953 size_t heap_alignment = collector_policy()->heap_alignment();
1955 // Ensure that the sizes are properly aligned.
1956 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
1957 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
1958 Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap");
1960 _refine_cte_cl = new RefineCardTableEntryClosure();
1962 _cg1r = new ConcurrentG1Refine(this, _refine_cte_cl);
1964 // Reserve the maximum.
1966 // When compressed oops are enabled, the preferred heap base
1967 // is calculated by subtracting the requested size from the
1968 // 32Gb boundary and using the result as the base address for
1969 // heap reservation. If the requested size is not aligned to
1970 // HeapRegion::GrainBytes (i.e. the alignment that is passed
1971 // into the ReservedHeapSpace constructor) then the actual
1972 // base of the reserved heap may end up differing from the
1973 // address that was requested (i.e. the preferred heap base).
1974 // If this happens then we could end up using a non-optimal
1975 // compressed oops mode.
1977 ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size,
1978 heap_alignment);
1980 // It is important to do this in a way such that concurrent readers can't
1981 // temporarily think something is in the heap. (I've actually seen this
1982 // happen in asserts: DLD.)
1983 _reserved.set_word_size(0);
1984 _reserved.set_start((HeapWord*)heap_rs.base());
1985 _reserved.set_end((HeapWord*)(heap_rs.base() + heap_rs.size()));
1987 // Create the gen rem set (and barrier set) for the entire reserved region.
1988 _rem_set = collector_policy()->create_rem_set(_reserved, 2);
1989 set_barrier_set(rem_set()->bs());
1990 if (!barrier_set()->is_a(BarrierSet::G1SATBCTLogging)) {
1991 vm_exit_during_initialization("G1 requires a G1SATBLoggingCardTableModRefBS");
1992 return JNI_ENOMEM;
1993 }
1995 // Also create a G1 rem set.
1996 _g1_rem_set = new G1RemSet(this, g1_barrier_set());
1998 // Carve out the G1 part of the heap.
2000 ReservedSpace g1_rs = heap_rs.first_part(max_byte_size);
2001 G1RegionToSpaceMapper* heap_storage =
2002 G1RegionToSpaceMapper::create_mapper(g1_rs,
2003 g1_rs.size(),
2004 UseLargePages ? os::large_page_size() : os::vm_page_size(),
2005 HeapRegion::GrainBytes,
2006 1,
2007 mtJavaHeap);
2008 heap_storage->set_mapping_changed_listener(&_listener);
2010 // Create storage for the BOT, card table, card counts table (hot card cache) and the bitmaps.
2011 G1RegionToSpaceMapper* bot_storage =
2012 create_aux_memory_mapper("Block offset table",
2013 G1BlockOffsetSharedArray::compute_size(g1_rs.size() / HeapWordSize),
2014 G1BlockOffsetSharedArray::N_bytes);
2016 ReservedSpace cardtable_rs(G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize));
2017 G1RegionToSpaceMapper* cardtable_storage =
2018 create_aux_memory_mapper("Card table",
2019 G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize),
2020 G1BlockOffsetSharedArray::N_bytes);
2022 G1RegionToSpaceMapper* card_counts_storage =
2023 create_aux_memory_mapper("Card counts table",
2024 G1BlockOffsetSharedArray::compute_size(g1_rs.size() / HeapWordSize),
2025 G1BlockOffsetSharedArray::N_bytes);
2027 size_t bitmap_size = CMBitMap::compute_size(g1_rs.size());
2028 G1RegionToSpaceMapper* prev_bitmap_storage =
2029 create_aux_memory_mapper("Prev Bitmap", bitmap_size, CMBitMap::mark_distance());
2030 G1RegionToSpaceMapper* next_bitmap_storage =
2031 create_aux_memory_mapper("Next Bitmap", bitmap_size, CMBitMap::mark_distance());
2033 _hrm.initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage);
2034 g1_barrier_set()->initialize(cardtable_storage);
2035 // Do later initialization work for concurrent refinement.
2036 _cg1r->init(card_counts_storage);
2038 // 6843694 - ensure that the maximum region index can fit
2039 // in the remembered set structures.
2040 const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
2041 guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
2043 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
2044 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
2045 guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
2046 "too many cards per region");
2048 FreeRegionList::set_unrealistically_long_length(max_regions() + 1);
2050 _bot_shared = new G1BlockOffsetSharedArray(_reserved, bot_storage);
2052 _g1h = this;
2054 {
2055 HeapWord* start = _hrm.reserved().start();
2056 HeapWord* end = _hrm.reserved().end();
2057 size_t granularity = HeapRegion::GrainBytes;
2059 _in_cset_fast_test.initialize(start, end, granularity);
2060 _humongous_reclaim_candidates.initialize(start, end, granularity);
2061 }
2063 // Create the ConcurrentMark data structure and thread.
2064 // (Must do this late, so that "max_regions" is defined.)
2065 _cm = new ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage);
2066 if (_cm == NULL || !_cm->completed_initialization()) {
2067 vm_shutdown_during_initialization("Could not create/initialize ConcurrentMark");
2068 return JNI_ENOMEM;
2069 }
2070 _cmThread = _cm->cmThread();
2072 // Initialize the from_card cache structure of HeapRegionRemSet.
2073 HeapRegionRemSet::init_heap(max_regions());
2075 // Now expand into the initial heap size.
2076 if (!expand(init_byte_size)) {
2077 vm_shutdown_during_initialization("Failed to allocate initial heap.");
2078 return JNI_ENOMEM;
2079 }
2081 // Perform any initialization actions delegated to the policy.
2082 g1_policy()->init();
2084 JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon,
2085 SATB_Q_FL_lock,
2086 G1SATBProcessCompletedThreshold,
2087 Shared_SATB_Q_lock);
2089 JavaThread::dirty_card_queue_set().initialize(_refine_cte_cl,
2090 DirtyCardQ_CBL_mon,
2091 DirtyCardQ_FL_lock,
2092 concurrent_g1_refine()->yellow_zone(),
2093 concurrent_g1_refine()->red_zone(),
2094 Shared_DirtyCardQ_lock);
2096 dirty_card_queue_set().initialize(NULL, // Should never be called by the Java code
2097 DirtyCardQ_CBL_mon,
2098 DirtyCardQ_FL_lock,
2099 -1, // never trigger processing
2100 -1, // no limit on length
2101 Shared_DirtyCardQ_lock,
2102 &JavaThread::dirty_card_queue_set());
2104 // Initialize the card queue set used to hold cards containing
2105 // references into the collection set.
2106 _into_cset_dirty_card_queue_set.initialize(NULL, // Should never be called by the Java code
2107 DirtyCardQ_CBL_mon,
2108 DirtyCardQ_FL_lock,
2109 -1, // never trigger processing
2110 -1, // no limit on length
2111 Shared_DirtyCardQ_lock,
2112 &JavaThread::dirty_card_queue_set());
2114 // In case we're keeping closure specialization stats, initialize those
2115 // counts and that mechanism.
2116 SpecializationStats::clear();
2118 // Here we allocate the dummy HeapRegion that is required by the
2119 // G1AllocRegion class.
2120 HeapRegion* dummy_region = _hrm.get_dummy_region();
2122 // We'll re-use the same region whether the alloc region will
2123 // require BOT updates or not and, if it doesn't, then a non-young
2124 // region will complain that it cannot support allocations without
2125 // BOT updates. So we'll tag the dummy region as eden to avoid that.
2126 dummy_region->set_eden();
2127 // Make sure it's full.
2128 dummy_region->set_top(dummy_region->end());
2129 G1AllocRegion::setup(this, dummy_region);
2131 _allocator->init_mutator_alloc_region();
2133 // Do create of the monitoring and management support so that
2134 // values in the heap have been properly initialized.
2135 _g1mm = new G1MonitoringSupport(this);
2137 G1StringDedup::initialize();
2139 return JNI_OK;
2140 }
2142 void G1CollectedHeap::stop() {
2143 // Stop all concurrent threads. We do this to make sure these threads
2144 // do not continue to execute and access resources (e.g. gclog_or_tty)
2145 // that are destroyed during shutdown.
2146 _cg1r->stop();
2147 _cmThread->stop();
2148 if (G1StringDedup::is_enabled()) {
2149 G1StringDedup::stop();
2150 }
2151 }
2153 size_t G1CollectedHeap::conservative_max_heap_alignment() {
2154 return HeapRegion::max_region_size();
2155 }
2157 void G1CollectedHeap::ref_processing_init() {
2158 // Reference processing in G1 currently works as follows:
2159 //
2160 // * There are two reference processor instances. One is
2161 // used to record and process discovered references
2162 // during concurrent marking; the other is used to
2163 // record and process references during STW pauses
2164 // (both full and incremental).
2165 // * Both ref processors need to 'span' the entire heap as
2166 // the regions in the collection set may be dotted around.
2167 //
2168 // * For the concurrent marking ref processor:
2169 // * Reference discovery is enabled at initial marking.
2170 // * Reference discovery is disabled and the discovered
2171 // references processed etc during remarking.
2172 // * Reference discovery is MT (see below).
2173 // * Reference discovery requires a barrier (see below).
2174 // * Reference processing may or may not be MT
2175 // (depending on the value of ParallelRefProcEnabled
2176 // and ParallelGCThreads).
2177 // * A full GC disables reference discovery by the CM
2178 // ref processor and abandons any entries on it's
2179 // discovered lists.
2180 //
2181 // * For the STW processor:
2182 // * Non MT discovery is enabled at the start of a full GC.
2183 // * Processing and enqueueing during a full GC is non-MT.
2184 // * During a full GC, references are processed after marking.
2185 //
2186 // * Discovery (may or may not be MT) is enabled at the start
2187 // of an incremental evacuation pause.
2188 // * References are processed near the end of a STW evacuation pause.
2189 // * For both types of GC:
2190 // * Discovery is atomic - i.e. not concurrent.
2191 // * Reference discovery will not need a barrier.
2193 SharedHeap::ref_processing_init();
2194 MemRegion mr = reserved_region();
2196 // Concurrent Mark ref processor
2197 _ref_processor_cm =
2198 new ReferenceProcessor(mr, // span
2199 ParallelRefProcEnabled && (ParallelGCThreads > 1),
2200 // mt processing
2201 (int) ParallelGCThreads,
2202 // degree of mt processing
2203 (ParallelGCThreads > 1) || (ConcGCThreads > 1),
2204 // mt discovery
2205 (int) MAX2(ParallelGCThreads, ConcGCThreads),
2206 // degree of mt discovery
2207 false,
2208 // Reference discovery is not atomic
2209 &_is_alive_closure_cm);
2210 // is alive closure
2211 // (for efficiency/performance)
2213 // STW ref processor
2214 _ref_processor_stw =
2215 new ReferenceProcessor(mr, // span
2216 ParallelRefProcEnabled && (ParallelGCThreads > 1),
2217 // mt processing
2218 MAX2((int)ParallelGCThreads, 1),
2219 // degree of mt processing
2220 (ParallelGCThreads > 1),
2221 // mt discovery
2222 MAX2((int)ParallelGCThreads, 1),
2223 // degree of mt discovery
2224 true,
2225 // Reference discovery is atomic
2226 &_is_alive_closure_stw);
2227 // is alive closure
2228 // (for efficiency/performance)
2229 }
2231 size_t G1CollectedHeap::capacity() const {
2232 return _hrm.length() * HeapRegion::GrainBytes;
2233 }
2235 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) {
2236 assert(!hr->continuesHumongous(), "pre-condition");
2237 hr->reset_gc_time_stamp();
2238 if (hr->startsHumongous()) {
2239 uint first_index = hr->hrm_index() + 1;
2240 uint last_index = hr->last_hc_index();
2241 for (uint i = first_index; i < last_index; i += 1) {
2242 HeapRegion* chr = region_at(i);
2243 assert(chr->continuesHumongous(), "sanity");
2244 chr->reset_gc_time_stamp();
2245 }
2246 }
2247 }
2249 #ifndef PRODUCT
2250 class CheckGCTimeStampsHRClosure : public HeapRegionClosure {
2251 private:
2252 unsigned _gc_time_stamp;
2253 bool _failures;
2255 public:
2256 CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) :
2257 _gc_time_stamp(gc_time_stamp), _failures(false) { }
2259 virtual bool doHeapRegion(HeapRegion* hr) {
2260 unsigned region_gc_time_stamp = hr->get_gc_time_stamp();
2261 if (_gc_time_stamp != region_gc_time_stamp) {
2262 gclog_or_tty->print_cr("Region " HR_FORMAT " has GC time stamp = %d, "
2263 "expected %d", HR_FORMAT_PARAMS(hr),
2264 region_gc_time_stamp, _gc_time_stamp);
2265 _failures = true;
2266 }
2267 return false;
2268 }
2270 bool failures() { return _failures; }
2271 };
2273 void G1CollectedHeap::check_gc_time_stamps() {
2274 CheckGCTimeStampsHRClosure cl(_gc_time_stamp);
2275 heap_region_iterate(&cl);
2276 guarantee(!cl.failures(), "all GC time stamps should have been reset");
2277 }
2278 #endif // PRODUCT
2280 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl,
2281 DirtyCardQueue* into_cset_dcq,
2282 bool concurrent,
2283 uint worker_i) {
2284 // Clean cards in the hot card cache
2285 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
2286 hot_card_cache->drain(worker_i, g1_rem_set(), into_cset_dcq);
2288 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2289 size_t n_completed_buffers = 0;
2290 while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) {
2291 n_completed_buffers++;
2292 }
2293 g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::UpdateRS, worker_i, n_completed_buffers);
2294 dcqs.clear_n_completed_buffers();
2295 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!");
2296 }
2299 // Computes the sum of the storage used by the various regions.
2300 size_t G1CollectedHeap::used() const {
2301 return _allocator->used();
2302 }
2304 size_t G1CollectedHeap::used_unlocked() const {
2305 return _allocator->used_unlocked();
2306 }
2308 class SumUsedClosure: public HeapRegionClosure {
2309 size_t _used;
2310 public:
2311 SumUsedClosure() : _used(0) {}
2312 bool doHeapRegion(HeapRegion* r) {
2313 if (!r->continuesHumongous()) {
2314 _used += r->used();
2315 }
2316 return false;
2317 }
2318 size_t result() { return _used; }
2319 };
2321 size_t G1CollectedHeap::recalculate_used() const {
2322 double recalculate_used_start = os::elapsedTime();
2324 SumUsedClosure blk;
2325 heap_region_iterate(&blk);
2327 g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0);
2328 return blk.result();
2329 }
2331 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
2332 switch (cause) {
2333 case GCCause::_gc_locker: return GCLockerInvokesConcurrent;
2334 case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent;
2335 case GCCause::_g1_humongous_allocation: return true;
2336 case GCCause::_update_allocation_context_stats_inc: return true;
2337 case GCCause::_wb_conc_mark: return true;
2338 default: return false;
2339 }
2340 }
2342 #ifndef PRODUCT
2343 void G1CollectedHeap::allocate_dummy_regions() {
2344 // Let's fill up most of the region
2345 size_t word_size = HeapRegion::GrainWords - 1024;
2346 // And as a result the region we'll allocate will be humongous.
2347 guarantee(isHumongous(word_size), "sanity");
2349 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
2350 // Let's use the existing mechanism for the allocation
2351 HeapWord* dummy_obj = humongous_obj_allocate(word_size,
2352 AllocationContext::system());
2353 if (dummy_obj != NULL) {
2354 MemRegion mr(dummy_obj, word_size);
2355 CollectedHeap::fill_with_object(mr);
2356 } else {
2357 // If we can't allocate once, we probably cannot allocate
2358 // again. Let's get out of the loop.
2359 break;
2360 }
2361 }
2362 }
2363 #endif // !PRODUCT
2365 void G1CollectedHeap::increment_old_marking_cycles_started() {
2366 assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
2367 _old_marking_cycles_started == _old_marking_cycles_completed + 1,
2368 err_msg("Wrong marking cycle count (started: %d, completed: %d)",
2369 _old_marking_cycles_started, _old_marking_cycles_completed));
2371 _old_marking_cycles_started++;
2372 }
2374 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) {
2375 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
2377 // We assume that if concurrent == true, then the caller is a
2378 // concurrent thread that was joined the Suspendible Thread
2379 // Set. If there's ever a cheap way to check this, we should add an
2380 // assert here.
2382 // Given that this method is called at the end of a Full GC or of a
2383 // concurrent cycle, and those can be nested (i.e., a Full GC can
2384 // interrupt a concurrent cycle), the number of full collections
2385 // completed should be either one (in the case where there was no
2386 // nesting) or two (when a Full GC interrupted a concurrent cycle)
2387 // behind the number of full collections started.
2389 // This is the case for the inner caller, i.e. a Full GC.
2390 assert(concurrent ||
2391 (_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
2392 (_old_marking_cycles_started == _old_marking_cycles_completed + 2),
2393 err_msg("for inner caller (Full GC): _old_marking_cycles_started = %u "
2394 "is inconsistent with _old_marking_cycles_completed = %u",
2395 _old_marking_cycles_started, _old_marking_cycles_completed));
2397 // This is the case for the outer caller, i.e. the concurrent cycle.
2398 assert(!concurrent ||
2399 (_old_marking_cycles_started == _old_marking_cycles_completed + 1),
2400 err_msg("for outer caller (concurrent cycle): "
2401 "_old_marking_cycles_started = %u "
2402 "is inconsistent with _old_marking_cycles_completed = %u",
2403 _old_marking_cycles_started, _old_marking_cycles_completed));
2405 _old_marking_cycles_completed += 1;
2407 // We need to clear the "in_progress" flag in the CM thread before
2408 // we wake up any waiters (especially when ExplicitInvokesConcurrent
2409 // is set) so that if a waiter requests another System.gc() it doesn't
2410 // incorrectly see that a marking cycle is still in progress.
2411 if (concurrent) {
2412 _cmThread->clear_in_progress();
2413 }
2415 // This notify_all() will ensure that a thread that called
2416 // System.gc() with (with ExplicitGCInvokesConcurrent set or not)
2417 // and it's waiting for a full GC to finish will be woken up. It is
2418 // waiting in VM_G1IncCollectionPause::doit_epilogue().
2419 FullGCCount_lock->notify_all();
2420 }
2422 void G1CollectedHeap::register_concurrent_cycle_start(const Ticks& start_time) {
2423 _concurrent_cycle_started = true;
2424 _gc_timer_cm->register_gc_start(start_time);
2426 _gc_tracer_cm->report_gc_start(gc_cause(), _gc_timer_cm->gc_start());
2427 trace_heap_before_gc(_gc_tracer_cm);
2428 }
2430 void G1CollectedHeap::register_concurrent_cycle_end() {
2431 if (_concurrent_cycle_started) {
2432 if (_cm->has_aborted()) {
2433 _gc_tracer_cm->report_concurrent_mode_failure();
2434 }
2436 _gc_timer_cm->register_gc_end();
2437 _gc_tracer_cm->report_gc_end(_gc_timer_cm->gc_end(), _gc_timer_cm->time_partitions());
2439 // Clear state variables to prepare for the next concurrent cycle.
2440 _concurrent_cycle_started = false;
2441 _heap_summary_sent = false;
2442 }
2443 }
2445 void G1CollectedHeap::trace_heap_after_concurrent_cycle() {
2446 if (_concurrent_cycle_started) {
2447 // This function can be called when:
2448 // the cleanup pause is run
2449 // the concurrent cycle is aborted before the cleanup pause.
2450 // the concurrent cycle is aborted after the cleanup pause,
2451 // but before the concurrent cycle end has been registered.
2452 // Make sure that we only send the heap information once.
2453 if (!_heap_summary_sent) {
2454 trace_heap_after_gc(_gc_tracer_cm);
2455 _heap_summary_sent = true;
2456 }
2457 }
2458 }
2460 G1YCType G1CollectedHeap::yc_type() {
2461 bool is_young = g1_policy()->gcs_are_young();
2462 bool is_initial_mark = g1_policy()->during_initial_mark_pause();
2463 bool is_during_mark = mark_in_progress();
2465 if (is_initial_mark) {
2466 return InitialMark;
2467 } else if (is_during_mark) {
2468 return DuringMark;
2469 } else if (is_young) {
2470 return Normal;
2471 } else {
2472 return Mixed;
2473 }
2474 }
2476 void G1CollectedHeap::collect(GCCause::Cause cause) {
2477 assert_heap_not_locked();
2479 uint gc_count_before;
2480 uint old_marking_count_before;
2481 uint full_gc_count_before;
2482 bool retry_gc;
2484 do {
2485 retry_gc = false;
2487 {
2488 MutexLocker ml(Heap_lock);
2490 // Read the GC count while holding the Heap_lock
2491 gc_count_before = total_collections();
2492 full_gc_count_before = total_full_collections();
2493 old_marking_count_before = _old_marking_cycles_started;
2494 }
2496 if (should_do_concurrent_full_gc(cause)) {
2497 // Schedule an initial-mark evacuation pause that will start a
2498 // concurrent cycle. We're setting word_size to 0 which means that
2499 // we are not requesting a post-GC allocation.
2500 VM_G1IncCollectionPause op(gc_count_before,
2501 0, /* word_size */
2502 true, /* should_initiate_conc_mark */
2503 g1_policy()->max_pause_time_ms(),
2504 cause);
2505 op.set_allocation_context(AllocationContext::current());
2507 VMThread::execute(&op);
2508 if (!op.pause_succeeded()) {
2509 if (old_marking_count_before == _old_marking_cycles_started) {
2510 retry_gc = op.should_retry_gc();
2511 } else {
2512 // A Full GC happened while we were trying to schedule the
2513 // initial-mark GC. No point in starting a new cycle given
2514 // that the whole heap was collected anyway.
2515 }
2517 if (retry_gc) {
2518 if (GC_locker::is_active_and_needs_gc()) {
2519 GC_locker::stall_until_clear();
2520 }
2521 }
2522 }
2523 } else if (GC_locker::should_discard(cause, gc_count_before)) {
2524 // Return to be consistent with VMOp failure due to another
2525 // collection slipping in after our gc_count but before our
2526 // request is processed. _gc_locker collections upgraded by
2527 // GCLockerInvokesConcurrent are handled above and never discarded.
2528 return;
2529 } else {
2530 if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc
2531 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2533 // Schedule a standard evacuation pause. We're setting word_size
2534 // to 0 which means that we are not requesting a post-GC allocation.
2535 VM_G1IncCollectionPause op(gc_count_before,
2536 0, /* word_size */
2537 false, /* should_initiate_conc_mark */
2538 g1_policy()->max_pause_time_ms(),
2539 cause);
2540 VMThread::execute(&op);
2541 } else {
2542 // Schedule a Full GC.
2543 VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause);
2544 VMThread::execute(&op);
2545 }
2546 }
2547 } while (retry_gc);
2548 }
2550 bool G1CollectedHeap::is_in(const void* p) const {
2551 if (_hrm.reserved().contains(p)) {
2552 // Given that we know that p is in the reserved space,
2553 // heap_region_containing_raw() should successfully
2554 // return the containing region.
2555 HeapRegion* hr = heap_region_containing_raw(p);
2556 return hr->is_in(p);
2557 } else {
2558 return false;
2559 }
2560 }
2562 #ifdef ASSERT
2563 bool G1CollectedHeap::is_in_exact(const void* p) const {
2564 bool contains = reserved_region().contains(p);
2565 bool available = _hrm.is_available(addr_to_region((HeapWord*)p));
2566 if (contains && available) {
2567 return true;
2568 } else {
2569 return false;
2570 }
2571 }
2572 #endif
2574 // Iteration functions.
2576 // Applies an ExtendedOopClosure onto all references of objects within a HeapRegion.
2578 class IterateOopClosureRegionClosure: public HeapRegionClosure {
2579 ExtendedOopClosure* _cl;
2580 public:
2581 IterateOopClosureRegionClosure(ExtendedOopClosure* cl) : _cl(cl) {}
2582 bool doHeapRegion(HeapRegion* r) {
2583 if (!r->continuesHumongous()) {
2584 r->oop_iterate(_cl);
2585 }
2586 return false;
2587 }
2588 };
2590 void G1CollectedHeap::oop_iterate(ExtendedOopClosure* cl) {
2591 IterateOopClosureRegionClosure blk(cl);
2592 heap_region_iterate(&blk);
2593 }
2595 // Iterates an ObjectClosure over all objects within a HeapRegion.
2597 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2598 ObjectClosure* _cl;
2599 public:
2600 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2601 bool doHeapRegion(HeapRegion* r) {
2602 if (! r->continuesHumongous()) {
2603 r->object_iterate(_cl);
2604 }
2605 return false;
2606 }
2607 };
2609 void G1CollectedHeap::object_iterate(ObjectClosure* cl) {
2610 IterateObjectClosureRegionClosure blk(cl);
2611 heap_region_iterate(&blk);
2612 }
2614 // Calls a SpaceClosure on a HeapRegion.
2616 class SpaceClosureRegionClosure: public HeapRegionClosure {
2617 SpaceClosure* _cl;
2618 public:
2619 SpaceClosureRegionClosure(SpaceClosure* cl) : _cl(cl) {}
2620 bool doHeapRegion(HeapRegion* r) {
2621 _cl->do_space(r);
2622 return false;
2623 }
2624 };
2626 void G1CollectedHeap::space_iterate(SpaceClosure* cl) {
2627 SpaceClosureRegionClosure blk(cl);
2628 heap_region_iterate(&blk);
2629 }
2631 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2632 _hrm.iterate(cl);
2633 }
2635 void
2636 G1CollectedHeap::heap_region_par_iterate_chunked(HeapRegionClosure* cl,
2637 uint worker_id,
2638 uint num_workers,
2639 jint claim_value) const {
2640 _hrm.par_iterate(cl, worker_id, num_workers, claim_value);
2641 }
2643 class ResetClaimValuesClosure: public HeapRegionClosure {
2644 public:
2645 bool doHeapRegion(HeapRegion* r) {
2646 r->set_claim_value(HeapRegion::InitialClaimValue);
2647 return false;
2648 }
2649 };
2651 void G1CollectedHeap::reset_heap_region_claim_values() {
2652 ResetClaimValuesClosure blk;
2653 heap_region_iterate(&blk);
2654 }
2656 void G1CollectedHeap::reset_cset_heap_region_claim_values() {
2657 ResetClaimValuesClosure blk;
2658 collection_set_iterate(&blk);
2659 }
2661 #ifdef ASSERT
2662 // This checks whether all regions in the heap have the correct claim
2663 // value. I also piggy-backed on this a check to ensure that the
2664 // humongous_start_region() information on "continues humongous"
2665 // regions is correct.
2667 class CheckClaimValuesClosure : public HeapRegionClosure {
2668 private:
2669 jint _claim_value;
2670 uint _failures;
2671 HeapRegion* _sh_region;
2673 public:
2674 CheckClaimValuesClosure(jint claim_value) :
2675 _claim_value(claim_value), _failures(0), _sh_region(NULL) { }
2676 bool doHeapRegion(HeapRegion* r) {
2677 if (r->claim_value() != _claim_value) {
2678 gclog_or_tty->print_cr("Region " HR_FORMAT ", "
2679 "claim value = %d, should be %d",
2680 HR_FORMAT_PARAMS(r),
2681 r->claim_value(), _claim_value);
2682 ++_failures;
2683 }
2684 if (!r->isHumongous()) {
2685 _sh_region = NULL;
2686 } else if (r->startsHumongous()) {
2687 _sh_region = r;
2688 } else if (r->continuesHumongous()) {
2689 if (r->humongous_start_region() != _sh_region) {
2690 gclog_or_tty->print_cr("Region " HR_FORMAT ", "
2691 "HS = " PTR_FORMAT ", should be " PTR_FORMAT,
2692 HR_FORMAT_PARAMS(r),
2693 r->humongous_start_region(),
2694 _sh_region);
2695 ++_failures;
2696 }
2697 }
2698 return false;
2699 }
2700 uint failures() { return _failures; }
2701 };
2703 bool G1CollectedHeap::check_heap_region_claim_values(jint claim_value) {
2704 CheckClaimValuesClosure cl(claim_value);
2705 heap_region_iterate(&cl);
2706 return cl.failures() == 0;
2707 }
2709 class CheckClaimValuesInCSetHRClosure: public HeapRegionClosure {
2710 private:
2711 jint _claim_value;
2712 uint _failures;
2714 public:
2715 CheckClaimValuesInCSetHRClosure(jint claim_value) :
2716 _claim_value(claim_value), _failures(0) { }
2718 uint failures() { return _failures; }
2720 bool doHeapRegion(HeapRegion* hr) {
2721 assert(hr->in_collection_set(), "how?");
2722 assert(!hr->isHumongous(), "H-region in CSet");
2723 if (hr->claim_value() != _claim_value) {
2724 gclog_or_tty->print_cr("CSet Region " HR_FORMAT ", "
2725 "claim value = %d, should be %d",
2726 HR_FORMAT_PARAMS(hr),
2727 hr->claim_value(), _claim_value);
2728 _failures += 1;
2729 }
2730 return false;
2731 }
2732 };
2734 bool G1CollectedHeap::check_cset_heap_region_claim_values(jint claim_value) {
2735 CheckClaimValuesInCSetHRClosure cl(claim_value);
2736 collection_set_iterate(&cl);
2737 return cl.failures() == 0;
2738 }
2739 #endif // ASSERT
2741 // Clear the cached CSet starting regions and (more importantly)
2742 // the time stamps. Called when we reset the GC time stamp.
2743 void G1CollectedHeap::clear_cset_start_regions() {
2744 assert(_worker_cset_start_region != NULL, "sanity");
2745 assert(_worker_cset_start_region_time_stamp != NULL, "sanity");
2747 int n_queues = MAX2((int)ParallelGCThreads, 1);
2748 for (int i = 0; i < n_queues; i++) {
2749 _worker_cset_start_region[i] = NULL;
2750 _worker_cset_start_region_time_stamp[i] = 0;
2751 }
2752 }
2754 // Given the id of a worker, obtain or calculate a suitable
2755 // starting region for iterating over the current collection set.
2756 HeapRegion* G1CollectedHeap::start_cset_region_for_worker(uint worker_i) {
2757 assert(get_gc_time_stamp() > 0, "should have been updated by now");
2759 HeapRegion* result = NULL;
2760 unsigned gc_time_stamp = get_gc_time_stamp();
2762 if (_worker_cset_start_region_time_stamp[worker_i] == gc_time_stamp) {
2763 // Cached starting region for current worker was set
2764 // during the current pause - so it's valid.
2765 // Note: the cached starting heap region may be NULL
2766 // (when the collection set is empty).
2767 result = _worker_cset_start_region[worker_i];
2768 assert(result == NULL || result->in_collection_set(), "sanity");
2769 return result;
2770 }
2772 // The cached entry was not valid so let's calculate
2773 // a suitable starting heap region for this worker.
2775 // We want the parallel threads to start their collection
2776 // set iteration at different collection set regions to
2777 // avoid contention.
2778 // If we have:
2779 // n collection set regions
2780 // p threads
2781 // Then thread t will start at region floor ((t * n) / p)
2783 result = g1_policy()->collection_set();
2784 if (G1CollectedHeap::use_parallel_gc_threads()) {
2785 uint cs_size = g1_policy()->cset_region_length();
2786 uint active_workers = workers()->active_workers();
2787 assert(UseDynamicNumberOfGCThreads ||
2788 active_workers == workers()->total_workers(),
2789 "Unless dynamic should use total workers");
2791 uint end_ind = (cs_size * worker_i) / active_workers;
2792 uint start_ind = 0;
2794 if (worker_i > 0 &&
2795 _worker_cset_start_region_time_stamp[worker_i - 1] == gc_time_stamp) {
2796 // Previous workers starting region is valid
2797 // so let's iterate from there
2798 start_ind = (cs_size * (worker_i - 1)) / active_workers;
2799 OrderAccess::loadload();
2800 result = _worker_cset_start_region[worker_i - 1];
2801 }
2803 for (uint i = start_ind; i < end_ind; i++) {
2804 result = result->next_in_collection_set();
2805 }
2806 }
2808 // Note: the calculated starting heap region may be NULL
2809 // (when the collection set is empty).
2810 assert(result == NULL || result->in_collection_set(), "sanity");
2811 assert(_worker_cset_start_region_time_stamp[worker_i] != gc_time_stamp,
2812 "should be updated only once per pause");
2813 _worker_cset_start_region[worker_i] = result;
2814 OrderAccess::storestore();
2815 _worker_cset_start_region_time_stamp[worker_i] = gc_time_stamp;
2816 return result;
2817 }
2819 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) {
2820 HeapRegion* r = g1_policy()->collection_set();
2821 while (r != NULL) {
2822 HeapRegion* next = r->next_in_collection_set();
2823 if (cl->doHeapRegion(r)) {
2824 cl->incomplete();
2825 return;
2826 }
2827 r = next;
2828 }
2829 }
2831 void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r,
2832 HeapRegionClosure *cl) {
2833 if (r == NULL) {
2834 // The CSet is empty so there's nothing to do.
2835 return;
2836 }
2838 assert(r->in_collection_set(),
2839 "Start region must be a member of the collection set.");
2840 HeapRegion* cur = r;
2841 while (cur != NULL) {
2842 HeapRegion* next = cur->next_in_collection_set();
2843 if (cl->doHeapRegion(cur) && false) {
2844 cl->incomplete();
2845 return;
2846 }
2847 cur = next;
2848 }
2849 cur = g1_policy()->collection_set();
2850 while (cur != r) {
2851 HeapRegion* next = cur->next_in_collection_set();
2852 if (cl->doHeapRegion(cur) && false) {
2853 cl->incomplete();
2854 return;
2855 }
2856 cur = next;
2857 }
2858 }
2860 HeapRegion* G1CollectedHeap::next_compaction_region(const HeapRegion* from) const {
2861 HeapRegion* result = _hrm.next_region_in_heap(from);
2862 while (result != NULL && result->isHumongous()) {
2863 result = _hrm.next_region_in_heap(result);
2864 }
2865 return result;
2866 }
2868 Space* G1CollectedHeap::space_containing(const void* addr) const {
2869 return heap_region_containing(addr);
2870 }
2872 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2873 Space* sp = space_containing(addr);
2874 return sp->block_start(addr);
2875 }
2877 size_t G1CollectedHeap::block_size(const HeapWord* addr) const {
2878 Space* sp = space_containing(addr);
2879 return sp->block_size(addr);
2880 }
2882 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2883 Space* sp = space_containing(addr);
2884 return sp->block_is_obj(addr);
2885 }
2887 bool G1CollectedHeap::supports_tlab_allocation() const {
2888 return true;
2889 }
2891 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
2892 return (_g1_policy->young_list_target_length() - young_list()->survivor_length()) * HeapRegion::GrainBytes;
2893 }
2895 size_t G1CollectedHeap::tlab_used(Thread* ignored) const {
2896 return young_list()->eden_used_bytes();
2897 }
2899 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size
2900 // must be smaller than the humongous object limit.
2901 size_t G1CollectedHeap::max_tlab_size() const {
2902 return align_size_down(_humongous_object_threshold_in_words - 1, MinObjAlignment);
2903 }
2905 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
2906 // Return the remaining space in the cur alloc region, but not less than
2907 // the min TLAB size.
2909 // Also, this value can be at most the humongous object threshold,
2910 // since we can't allow tlabs to grow big enough to accommodate
2911 // humongous objects.
2913 HeapRegion* hr = _allocator->mutator_alloc_region(AllocationContext::current())->get();
2914 size_t max_tlab = max_tlab_size() * wordSize;
2915 if (hr == NULL) {
2916 return max_tlab;
2917 } else {
2918 return MIN2(MAX2(hr->free(), (size_t) MinTLABSize), max_tlab);
2919 }
2920 }
2922 size_t G1CollectedHeap::max_capacity() const {
2923 return _hrm.reserved().byte_size();
2924 }
2926 jlong G1CollectedHeap::millis_since_last_gc() {
2927 // assert(false, "NYI");
2928 return 0;
2929 }
2931 void G1CollectedHeap::prepare_for_verify() {
2932 if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) {
2933 ensure_parsability(false);
2934 }
2935 g1_rem_set()->prepare_for_verify();
2936 }
2938 bool G1CollectedHeap::allocated_since_marking(oop obj, HeapRegion* hr,
2939 VerifyOption vo) {
2940 switch (vo) {
2941 case VerifyOption_G1UsePrevMarking:
2942 return hr->obj_allocated_since_prev_marking(obj);
2943 case VerifyOption_G1UseNextMarking:
2944 return hr->obj_allocated_since_next_marking(obj);
2945 case VerifyOption_G1UseMarkWord:
2946 return false;
2947 default:
2948 ShouldNotReachHere();
2949 }
2950 return false; // keep some compilers happy
2951 }
2953 HeapWord* G1CollectedHeap::top_at_mark_start(HeapRegion* hr, VerifyOption vo) {
2954 switch (vo) {
2955 case VerifyOption_G1UsePrevMarking: return hr->prev_top_at_mark_start();
2956 case VerifyOption_G1UseNextMarking: return hr->next_top_at_mark_start();
2957 case VerifyOption_G1UseMarkWord: return NULL;
2958 default: ShouldNotReachHere();
2959 }
2960 return NULL; // keep some compilers happy
2961 }
2963 bool G1CollectedHeap::is_marked(oop obj, VerifyOption vo) {
2964 switch (vo) {
2965 case VerifyOption_G1UsePrevMarking: return isMarkedPrev(obj);
2966 case VerifyOption_G1UseNextMarking: return isMarkedNext(obj);
2967 case VerifyOption_G1UseMarkWord: return obj->is_gc_marked();
2968 default: ShouldNotReachHere();
2969 }
2970 return false; // keep some compilers happy
2971 }
2973 const char* G1CollectedHeap::top_at_mark_start_str(VerifyOption vo) {
2974 switch (vo) {
2975 case VerifyOption_G1UsePrevMarking: return "PTAMS";
2976 case VerifyOption_G1UseNextMarking: return "NTAMS";
2977 case VerifyOption_G1UseMarkWord: return "NONE";
2978 default: ShouldNotReachHere();
2979 }
2980 return NULL; // keep some compilers happy
2981 }
2983 class VerifyRootsClosure: public OopClosure {
2984 private:
2985 G1CollectedHeap* _g1h;
2986 VerifyOption _vo;
2987 bool _failures;
2988 public:
2989 // _vo == UsePrevMarking -> use "prev" marking information,
2990 // _vo == UseNextMarking -> use "next" marking information,
2991 // _vo == UseMarkWord -> use mark word from object header.
2992 VerifyRootsClosure(VerifyOption vo) :
2993 _g1h(G1CollectedHeap::heap()),
2994 _vo(vo),
2995 _failures(false) { }
2997 bool failures() { return _failures; }
2999 template <class T> void do_oop_nv(T* p) {
3000 T heap_oop = oopDesc::load_heap_oop(p);
3001 if (!oopDesc::is_null(heap_oop)) {
3002 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
3003 if (_g1h->is_obj_dead_cond(obj, _vo)) {
3004 gclog_or_tty->print_cr("Root location " PTR_FORMAT " "
3005 "points to dead obj " PTR_FORMAT, p, (void*) obj);
3006 if (_vo == VerifyOption_G1UseMarkWord) {
3007 gclog_or_tty->print_cr(" Mark word: " PTR_FORMAT, (void*)(obj->mark()));
3008 }
3009 obj->print_on(gclog_or_tty);
3010 _failures = true;
3011 }
3012 }
3013 }
3015 void do_oop(oop* p) { do_oop_nv(p); }
3016 void do_oop(narrowOop* p) { do_oop_nv(p); }
3017 };
3019 class G1VerifyCodeRootOopClosure: public OopClosure {
3020 G1CollectedHeap* _g1h;
3021 OopClosure* _root_cl;
3022 nmethod* _nm;
3023 VerifyOption _vo;
3024 bool _failures;
3026 template <class T> void do_oop_work(T* p) {
3027 // First verify that this root is live
3028 _root_cl->do_oop(p);
3030 if (!G1VerifyHeapRegionCodeRoots) {
3031 // We're not verifying the code roots attached to heap region.
3032 return;
3033 }
3035 // Don't check the code roots during marking verification in a full GC
3036 if (_vo == VerifyOption_G1UseMarkWord) {
3037 return;
3038 }
3040 // Now verify that the current nmethod (which contains p) is
3041 // in the code root list of the heap region containing the
3042 // object referenced by p.
3044 T heap_oop = oopDesc::load_heap_oop(p);
3045 if (!oopDesc::is_null(heap_oop)) {
3046 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
3048 // Now fetch the region containing the object
3049 HeapRegion* hr = _g1h->heap_region_containing(obj);
3050 HeapRegionRemSet* hrrs = hr->rem_set();
3051 // Verify that the strong code root list for this region
3052 // contains the nmethod
3053 if (!hrrs->strong_code_roots_list_contains(_nm)) {
3054 gclog_or_tty->print_cr("Code root location " PTR_FORMAT " "
3055 "from nmethod " PTR_FORMAT " not in strong "
3056 "code roots for region [" PTR_FORMAT "," PTR_FORMAT ")",
3057 p, _nm, hr->bottom(), hr->end());
3058 _failures = true;
3059 }
3060 }
3061 }
3063 public:
3064 G1VerifyCodeRootOopClosure(G1CollectedHeap* g1h, OopClosure* root_cl, VerifyOption vo):
3065 _g1h(g1h), _root_cl(root_cl), _vo(vo), _nm(NULL), _failures(false) {}
3067 void do_oop(oop* p) { do_oop_work(p); }
3068 void do_oop(narrowOop* p) { do_oop_work(p); }
3070 void set_nmethod(nmethod* nm) { _nm = nm; }
3071 bool failures() { return _failures; }
3072 };
3074 class G1VerifyCodeRootBlobClosure: public CodeBlobClosure {
3075 G1VerifyCodeRootOopClosure* _oop_cl;
3077 public:
3078 G1VerifyCodeRootBlobClosure(G1VerifyCodeRootOopClosure* oop_cl):
3079 _oop_cl(oop_cl) {}
3081 void do_code_blob(CodeBlob* cb) {
3082 nmethod* nm = cb->as_nmethod_or_null();
3083 if (nm != NULL) {
3084 _oop_cl->set_nmethod(nm);
3085 nm->oops_do(_oop_cl);
3086 }
3087 }
3088 };
3090 class YoungRefCounterClosure : public OopClosure {
3091 G1CollectedHeap* _g1h;
3092 int _count;
3093 public:
3094 YoungRefCounterClosure(G1CollectedHeap* g1h) : _g1h(g1h), _count(0) {}
3095 void do_oop(oop* p) { if (_g1h->is_in_young(*p)) { _count++; } }
3096 void do_oop(narrowOop* p) { ShouldNotReachHere(); }
3098 int count() { return _count; }
3099 void reset_count() { _count = 0; };
3100 };
3102 class VerifyKlassClosure: public KlassClosure {
3103 YoungRefCounterClosure _young_ref_counter_closure;
3104 OopClosure *_oop_closure;
3105 public:
3106 VerifyKlassClosure(G1CollectedHeap* g1h, OopClosure* cl) : _young_ref_counter_closure(g1h), _oop_closure(cl) {}
3107 void do_klass(Klass* k) {
3108 k->oops_do(_oop_closure);
3110 _young_ref_counter_closure.reset_count();
3111 k->oops_do(&_young_ref_counter_closure);
3112 if (_young_ref_counter_closure.count() > 0) {
3113 guarantee(k->has_modified_oops(), err_msg("Klass %p, has young refs but is not dirty.", k));
3114 }
3115 }
3116 };
3118 class VerifyLivenessOopClosure: public OopClosure {
3119 G1CollectedHeap* _g1h;
3120 VerifyOption _vo;
3121 public:
3122 VerifyLivenessOopClosure(G1CollectedHeap* g1h, VerifyOption vo):
3123 _g1h(g1h), _vo(vo)
3124 { }
3125 void do_oop(narrowOop *p) { do_oop_work(p); }
3126 void do_oop( oop *p) { do_oop_work(p); }
3128 template <class T> void do_oop_work(T *p) {
3129 oop obj = oopDesc::load_decode_heap_oop(p);
3130 guarantee(obj == NULL || !_g1h->is_obj_dead_cond(obj, _vo),
3131 "Dead object referenced by a not dead object");
3132 }
3133 };
3135 class VerifyObjsInRegionClosure: public ObjectClosure {
3136 private:
3137 G1CollectedHeap* _g1h;
3138 size_t _live_bytes;
3139 HeapRegion *_hr;
3140 VerifyOption _vo;
3141 public:
3142 // _vo == UsePrevMarking -> use "prev" marking information,
3143 // _vo == UseNextMarking -> use "next" marking information,
3144 // _vo == UseMarkWord -> use mark word from object header.
3145 VerifyObjsInRegionClosure(HeapRegion *hr, VerifyOption vo)
3146 : _live_bytes(0), _hr(hr), _vo(vo) {
3147 _g1h = G1CollectedHeap::heap();
3148 }
3149 void do_object(oop o) {
3150 VerifyLivenessOopClosure isLive(_g1h, _vo);
3151 assert(o != NULL, "Huh?");
3152 if (!_g1h->is_obj_dead_cond(o, _vo)) {
3153 // If the object is alive according to the mark word,
3154 // then verify that the marking information agrees.
3155 // Note we can't verify the contra-positive of the
3156 // above: if the object is dead (according to the mark
3157 // word), it may not be marked, or may have been marked
3158 // but has since became dead, or may have been allocated
3159 // since the last marking.
3160 if (_vo == VerifyOption_G1UseMarkWord) {
3161 guarantee(!_g1h->is_obj_dead(o), "mark word and concurrent mark mismatch");
3162 }
3164 o->oop_iterate_no_header(&isLive);
3165 if (!_hr->obj_allocated_since_prev_marking(o)) {
3166 size_t obj_size = o->size(); // Make sure we don't overflow
3167 _live_bytes += (obj_size * HeapWordSize);
3168 }
3169 }
3170 }
3171 size_t live_bytes() { return _live_bytes; }
3172 };
3174 class PrintObjsInRegionClosure : public ObjectClosure {
3175 HeapRegion *_hr;
3176 G1CollectedHeap *_g1;
3177 public:
3178 PrintObjsInRegionClosure(HeapRegion *hr) : _hr(hr) {
3179 _g1 = G1CollectedHeap::heap();
3180 };
3182 void do_object(oop o) {
3183 if (o != NULL) {
3184 HeapWord *start = (HeapWord *) o;
3185 size_t word_sz = o->size();
3186 gclog_or_tty->print("\nPrinting obj " PTR_FORMAT " of size " SIZE_FORMAT
3187 " isMarkedPrev %d isMarkedNext %d isAllocSince %d\n",
3188 (void*) o, word_sz,
3189 _g1->isMarkedPrev(o),
3190 _g1->isMarkedNext(o),
3191 _hr->obj_allocated_since_prev_marking(o));
3192 HeapWord *end = start + word_sz;
3193 HeapWord *cur;
3194 int *val;
3195 for (cur = start; cur < end; cur++) {
3196 val = (int *) cur;
3197 gclog_or_tty->print("\t " PTR_FORMAT ":" PTR_FORMAT "\n", val, *val);
3198 }
3199 }
3200 }
3201 };
3203 class VerifyRegionClosure: public HeapRegionClosure {
3204 private:
3205 bool _par;
3206 VerifyOption _vo;
3207 bool _failures;
3208 public:
3209 // _vo == UsePrevMarking -> use "prev" marking information,
3210 // _vo == UseNextMarking -> use "next" marking information,
3211 // _vo == UseMarkWord -> use mark word from object header.
3212 VerifyRegionClosure(bool par, VerifyOption vo)
3213 : _par(par),
3214 _vo(vo),
3215 _failures(false) {}
3217 bool failures() {
3218 return _failures;
3219 }
3221 bool doHeapRegion(HeapRegion* r) {
3222 if (!r->continuesHumongous()) {
3223 bool failures = false;
3224 r->verify(_vo, &failures);
3225 if (failures) {
3226 _failures = true;
3227 } else {
3228 VerifyObjsInRegionClosure not_dead_yet_cl(r, _vo);
3229 r->object_iterate(¬_dead_yet_cl);
3230 if (_vo != VerifyOption_G1UseNextMarking) {
3231 if (r->max_live_bytes() < not_dead_yet_cl.live_bytes()) {
3232 gclog_or_tty->print_cr("[" PTR_FORMAT "," PTR_FORMAT "] "
3233 "max_live_bytes " SIZE_FORMAT " "
3234 "< calculated " SIZE_FORMAT,
3235 r->bottom(), r->end(),
3236 r->max_live_bytes(),
3237 not_dead_yet_cl.live_bytes());
3238 _failures = true;
3239 }
3240 } else {
3241 // When vo == UseNextMarking we cannot currently do a sanity
3242 // check on the live bytes as the calculation has not been
3243 // finalized yet.
3244 }
3245 }
3246 }
3247 return false; // stop the region iteration if we hit a failure
3248 }
3249 };
3251 // This is the task used for parallel verification of the heap regions
3253 class G1ParVerifyTask: public AbstractGangTask {
3254 private:
3255 G1CollectedHeap* _g1h;
3256 VerifyOption _vo;
3257 bool _failures;
3259 public:
3260 // _vo == UsePrevMarking -> use "prev" marking information,
3261 // _vo == UseNextMarking -> use "next" marking information,
3262 // _vo == UseMarkWord -> use mark word from object header.
3263 G1ParVerifyTask(G1CollectedHeap* g1h, VerifyOption vo) :
3264 AbstractGangTask("Parallel verify task"),
3265 _g1h(g1h),
3266 _vo(vo),
3267 _failures(false) { }
3269 bool failures() {
3270 return _failures;
3271 }
3273 void work(uint worker_id) {
3274 HandleMark hm;
3275 VerifyRegionClosure blk(true, _vo);
3276 _g1h->heap_region_par_iterate_chunked(&blk, worker_id,
3277 _g1h->workers()->active_workers(),
3278 HeapRegion::ParVerifyClaimValue);
3279 if (blk.failures()) {
3280 _failures = true;
3281 }
3282 }
3283 };
3285 void G1CollectedHeap::verify(bool silent, VerifyOption vo) {
3286 if (SafepointSynchronize::is_at_safepoint()) {
3287 assert(Thread::current()->is_VM_thread(),
3288 "Expected to be executed serially by the VM thread at this point");
3290 if (!silent) { gclog_or_tty->print("Roots "); }
3291 VerifyRootsClosure rootsCl(vo);
3292 VerifyKlassClosure klassCl(this, &rootsCl);
3293 CLDToKlassAndOopClosure cldCl(&klassCl, &rootsCl, false);
3295 // We apply the relevant closures to all the oops in the
3296 // system dictionary, class loader data graph, the string table
3297 // and the nmethods in the code cache.
3298 G1VerifyCodeRootOopClosure codeRootsCl(this, &rootsCl, vo);
3299 G1VerifyCodeRootBlobClosure blobsCl(&codeRootsCl);
3301 {
3302 G1RootProcessor root_processor(this);
3303 root_processor.process_all_roots(&rootsCl,
3304 &cldCl,
3305 &blobsCl);
3306 }
3308 bool failures = rootsCl.failures() || codeRootsCl.failures();
3310 if (vo != VerifyOption_G1UseMarkWord) {
3311 // If we're verifying during a full GC then the region sets
3312 // will have been torn down at the start of the GC. Therefore
3313 // verifying the region sets will fail. So we only verify
3314 // the region sets when not in a full GC.
3315 if (!silent) { gclog_or_tty->print("HeapRegionSets "); }
3316 verify_region_sets();
3317 }
3319 if (!silent) { gclog_or_tty->print("HeapRegions "); }
3320 if (GCParallelVerificationEnabled && ParallelGCThreads > 1) {
3321 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3322 "sanity check");
3324 G1ParVerifyTask task(this, vo);
3325 assert(UseDynamicNumberOfGCThreads ||
3326 workers()->active_workers() == workers()->total_workers(),
3327 "If not dynamic should be using all the workers");
3328 int n_workers = workers()->active_workers();
3329 set_par_threads(n_workers);
3330 workers()->run_task(&task);
3331 set_par_threads(0);
3332 if (task.failures()) {
3333 failures = true;
3334 }
3336 // Checks that the expected amount of parallel work was done.
3337 // The implication is that n_workers is > 0.
3338 assert(check_heap_region_claim_values(HeapRegion::ParVerifyClaimValue),
3339 "sanity check");
3341 reset_heap_region_claim_values();
3343 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3344 "sanity check");
3345 } else {
3346 VerifyRegionClosure blk(false, vo);
3347 heap_region_iterate(&blk);
3348 if (blk.failures()) {
3349 failures = true;
3350 }
3351 }
3352 if (!silent) gclog_or_tty->print("RemSet ");
3353 rem_set()->verify();
3355 if (G1StringDedup::is_enabled()) {
3356 if (!silent) gclog_or_tty->print("StrDedup ");
3357 G1StringDedup::verify();
3358 }
3360 if (failures) {
3361 gclog_or_tty->print_cr("Heap:");
3362 // It helps to have the per-region information in the output to
3363 // help us track down what went wrong. This is why we call
3364 // print_extended_on() instead of print_on().
3365 print_extended_on(gclog_or_tty);
3366 gclog_or_tty->cr();
3367 #ifndef PRODUCT
3368 if (VerifyDuringGC && G1VerifyDuringGCPrintReachable) {
3369 concurrent_mark()->print_reachable("at-verification-failure",
3370 vo, false /* all */);
3371 }
3372 #endif
3373 gclog_or_tty->flush();
3374 }
3375 guarantee(!failures, "there should not have been any failures");
3376 } else {
3377 if (!silent) {
3378 gclog_or_tty->print("(SKIPPING Roots, HeapRegionSets, HeapRegions, RemSet");
3379 if (G1StringDedup::is_enabled()) {
3380 gclog_or_tty->print(", StrDedup");
3381 }
3382 gclog_or_tty->print(") ");
3383 }
3384 }
3385 }
3387 void G1CollectedHeap::verify(bool silent) {
3388 verify(silent, VerifyOption_G1UsePrevMarking);
3389 }
3391 double G1CollectedHeap::verify(bool guard, const char* msg) {
3392 double verify_time_ms = 0.0;
3394 if (guard && total_collections() >= VerifyGCStartAt) {
3395 double verify_start = os::elapsedTime();
3396 HandleMark hm; // Discard invalid handles created during verification
3397 prepare_for_verify();
3398 Universe::verify(VerifyOption_G1UsePrevMarking, msg);
3399 verify_time_ms = (os::elapsedTime() - verify_start) * 1000;
3400 }
3402 return verify_time_ms;
3403 }
3405 void G1CollectedHeap::verify_before_gc() {
3406 double verify_time_ms = verify(VerifyBeforeGC, " VerifyBeforeGC:");
3407 g1_policy()->phase_times()->record_verify_before_time_ms(verify_time_ms);
3408 }
3410 void G1CollectedHeap::verify_after_gc() {
3411 double verify_time_ms = verify(VerifyAfterGC, " VerifyAfterGC:");
3412 g1_policy()->phase_times()->record_verify_after_time_ms(verify_time_ms);
3413 }
3415 class PrintRegionClosure: public HeapRegionClosure {
3416 outputStream* _st;
3417 public:
3418 PrintRegionClosure(outputStream* st) : _st(st) {}
3419 bool doHeapRegion(HeapRegion* r) {
3420 r->print_on(_st);
3421 return false;
3422 }
3423 };
3425 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
3426 const HeapRegion* hr,
3427 const VerifyOption vo) const {
3428 switch (vo) {
3429 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr);
3430 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr);
3431 case VerifyOption_G1UseMarkWord: return !obj->is_gc_marked();
3432 default: ShouldNotReachHere();
3433 }
3434 return false; // keep some compilers happy
3435 }
3437 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
3438 const VerifyOption vo) const {
3439 switch (vo) {
3440 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj);
3441 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj);
3442 case VerifyOption_G1UseMarkWord: return !obj->is_gc_marked();
3443 default: ShouldNotReachHere();
3444 }
3445 return false; // keep some compilers happy
3446 }
3448 void G1CollectedHeap::print_on(outputStream* st) const {
3449 st->print(" %-20s", "garbage-first heap");
3450 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
3451 capacity()/K, used_unlocked()/K);
3452 st->print(" [" INTPTR_FORMAT ", " INTPTR_FORMAT ", " INTPTR_FORMAT ")",
3453 _hrm.reserved().start(),
3454 _hrm.reserved().start() + _hrm.length() + HeapRegion::GrainWords,
3455 _hrm.reserved().end());
3456 st->cr();
3457 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
3458 uint young_regions = _young_list->length();
3459 st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
3460 (size_t) young_regions * HeapRegion::GrainBytes / K);
3461 uint survivor_regions = g1_policy()->recorded_survivor_regions();
3462 st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
3463 (size_t) survivor_regions * HeapRegion::GrainBytes / K);
3464 st->cr();
3465 MetaspaceAux::print_on(st);
3466 }
3468 void G1CollectedHeap::print_extended_on(outputStream* st) const {
3469 print_on(st);
3471 // Print the per-region information.
3472 st->cr();
3473 st->print_cr("Heap Regions: (Y=young(eden), SU=young(survivor), "
3474 "HS=humongous(starts), HC=humongous(continues), "
3475 "CS=collection set, F=free, TS=gc time stamp, "
3476 "PTAMS=previous top-at-mark-start, "
3477 "NTAMS=next top-at-mark-start)");
3478 PrintRegionClosure blk(st);
3479 heap_region_iterate(&blk);
3480 }
3482 void G1CollectedHeap::print_on_error(outputStream* st) const {
3483 this->CollectedHeap::print_on_error(st);
3485 if (_cm != NULL) {
3486 st->cr();
3487 _cm->print_on_error(st);
3488 }
3489 }
3491 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
3492 if (G1CollectedHeap::use_parallel_gc_threads()) {
3493 workers()->print_worker_threads_on(st);
3494 }
3495 _cmThread->print_on(st);
3496 st->cr();
3497 _cm->print_worker_threads_on(st);
3498 _cg1r->print_worker_threads_on(st);
3499 if (G1StringDedup::is_enabled()) {
3500 G1StringDedup::print_worker_threads_on(st);
3501 }
3502 }
3504 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
3505 if (G1CollectedHeap::use_parallel_gc_threads()) {
3506 workers()->threads_do(tc);
3507 }
3508 tc->do_thread(_cmThread);
3509 _cg1r->threads_do(tc);
3510 if (G1StringDedup::is_enabled()) {
3511 G1StringDedup::threads_do(tc);
3512 }
3513 }
3515 void G1CollectedHeap::print_tracing_info() const {
3516 // We'll overload this to mean "trace GC pause statistics."
3517 if (TraceGen0Time || TraceGen1Time) {
3518 // The "G1CollectorPolicy" is keeping track of these stats, so delegate
3519 // to that.
3520 g1_policy()->print_tracing_info();
3521 }
3522 if (G1SummarizeRSetStats) {
3523 g1_rem_set()->print_summary_info();
3524 }
3525 if (G1SummarizeConcMark) {
3526 concurrent_mark()->print_summary_info();
3527 }
3528 g1_policy()->print_yg_surv_rate_info();
3529 SpecializationStats::print();
3530 }
3532 #ifndef PRODUCT
3533 // Helpful for debugging RSet issues.
3535 class PrintRSetsClosure : public HeapRegionClosure {
3536 private:
3537 const char* _msg;
3538 size_t _occupied_sum;
3540 public:
3541 bool doHeapRegion(HeapRegion* r) {
3542 HeapRegionRemSet* hrrs = r->rem_set();
3543 size_t occupied = hrrs->occupied();
3544 _occupied_sum += occupied;
3546 gclog_or_tty->print_cr("Printing RSet for region " HR_FORMAT,
3547 HR_FORMAT_PARAMS(r));
3548 if (occupied == 0) {
3549 gclog_or_tty->print_cr(" RSet is empty");
3550 } else {
3551 hrrs->print();
3552 }
3553 gclog_or_tty->print_cr("----------");
3554 return false;
3555 }
3557 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
3558 gclog_or_tty->cr();
3559 gclog_or_tty->print_cr("========================================");
3560 gclog_or_tty->print_cr("%s", msg);
3561 gclog_or_tty->cr();
3562 }
3564 ~PrintRSetsClosure() {
3565 gclog_or_tty->print_cr("Occupied Sum: " SIZE_FORMAT, _occupied_sum);
3566 gclog_or_tty->print_cr("========================================");
3567 gclog_or_tty->cr();
3568 }
3569 };
3571 void G1CollectedHeap::print_cset_rsets() {
3572 PrintRSetsClosure cl("Printing CSet RSets");
3573 collection_set_iterate(&cl);
3574 }
3576 void G1CollectedHeap::print_all_rsets() {
3577 PrintRSetsClosure cl("Printing All RSets");;
3578 heap_region_iterate(&cl);
3579 }
3580 #endif // PRODUCT
3582 G1HeapSummary G1CollectedHeap::create_g1_heap_summary() {
3584 size_t eden_used_bytes = _young_list->eden_used_bytes();
3585 size_t survivor_used_bytes = _young_list->survivor_used_bytes();
3586 size_t heap_used = Heap_lock->owned_by_self() ? used() : used_unlocked();
3588 size_t eden_capacity_bytes =
3589 (g1_policy()->young_list_target_length() * HeapRegion::GrainBytes) - survivor_used_bytes;
3591 VirtualSpaceSummary heap_summary = create_heap_space_summary();
3592 return G1HeapSummary(heap_summary, heap_used, eden_used_bytes,
3593 eden_capacity_bytes, survivor_used_bytes, num_regions());
3594 }
3596 void G1CollectedHeap::trace_heap(GCWhen::Type when, GCTracer* gc_tracer) {
3597 const G1HeapSummary& heap_summary = create_g1_heap_summary();
3598 gc_tracer->report_gc_heap_summary(when, heap_summary);
3600 const MetaspaceSummary& metaspace_summary = create_metaspace_summary();
3601 gc_tracer->report_metaspace_summary(when, metaspace_summary);
3602 }
3604 G1CollectedHeap* G1CollectedHeap::heap() {
3605 assert(_sh->kind() == CollectedHeap::G1CollectedHeap,
3606 "not a garbage-first heap");
3607 return _g1h;
3608 }
3610 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) {
3611 // always_do_update_barrier = false;
3612 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
3613 // Fill TLAB's and such
3614 accumulate_statistics_all_tlabs();
3615 ensure_parsability(true);
3617 if (G1SummarizeRSetStats && (G1SummarizeRSetStatsPeriod > 0) &&
3618 (total_collections() % G1SummarizeRSetStatsPeriod == 0)) {
3619 g1_rem_set()->print_periodic_summary_info("Before GC RS summary");
3620 }
3621 }
3623 void G1CollectedHeap::gc_epilogue(bool full) {
3625 if (G1SummarizeRSetStats &&
3626 (G1SummarizeRSetStatsPeriod > 0) &&
3627 // we are at the end of the GC. Total collections has already been increased.
3628 ((total_collections() - 1) % G1SummarizeRSetStatsPeriod == 0)) {
3629 g1_rem_set()->print_periodic_summary_info("After GC RS summary");
3630 }
3632 // FIXME: what is this about?
3633 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
3634 // is set.
3635 COMPILER2_PRESENT(assert(DerivedPointerTable::is_empty(),
3636 "derived pointer present"));
3637 // always_do_update_barrier = true;
3639 resize_all_tlabs();
3640 allocation_context_stats().update(full);
3642 // We have just completed a GC. Update the soft reference
3643 // policy with the new heap occupancy
3644 Universe::update_heap_info_at_gc();
3645 }
3647 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
3648 uint gc_count_before,
3649 bool* succeeded,
3650 GCCause::Cause gc_cause) {
3651 assert_heap_not_locked_and_not_at_safepoint();
3652 g1_policy()->record_stop_world_start();
3653 VM_G1IncCollectionPause op(gc_count_before,
3654 word_size,
3655 false, /* should_initiate_conc_mark */
3656 g1_policy()->max_pause_time_ms(),
3657 gc_cause);
3659 op.set_allocation_context(AllocationContext::current());
3660 VMThread::execute(&op);
3662 HeapWord* result = op.result();
3663 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
3664 assert(result == NULL || ret_succeeded,
3665 "the result should be NULL if the VM did not succeed");
3666 *succeeded = ret_succeeded;
3668 assert_heap_not_locked();
3669 return result;
3670 }
3672 void
3673 G1CollectedHeap::doConcurrentMark() {
3674 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
3675 if (!_cmThread->in_progress()) {
3676 _cmThread->set_started();
3677 CGC_lock->notify();
3678 }
3679 }
3681 size_t G1CollectedHeap::pending_card_num() {
3682 size_t extra_cards = 0;
3683 JavaThread *curr = Threads::first();
3684 while (curr != NULL) {
3685 DirtyCardQueue& dcq = curr->dirty_card_queue();
3686 extra_cards += dcq.size();
3687 curr = curr->next();
3688 }
3689 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
3690 size_t buffer_size = dcqs.buffer_size();
3691 size_t buffer_num = dcqs.completed_buffers_num();
3693 // PtrQueueSet::buffer_size() and PtrQueue:size() return sizes
3694 // in bytes - not the number of 'entries'. We need to convert
3695 // into a number of cards.
3696 return (buffer_size * buffer_num + extra_cards) / oopSize;
3697 }
3699 size_t G1CollectedHeap::cards_scanned() {
3700 return g1_rem_set()->cardsScanned();
3701 }
3703 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure {
3704 private:
3705 size_t _total_humongous;
3706 size_t _candidate_humongous;
3708 DirtyCardQueue _dcq;
3710 // We don't nominate objects with many remembered set entries, on
3711 // the assumption that such objects are likely still live.
3712 bool is_remset_small(HeapRegion* region) const {
3713 HeapRegionRemSet* const rset = region->rem_set();
3714 return G1EagerReclaimHumongousObjectsWithStaleRefs
3715 ? rset->occupancy_less_or_equal_than(G1RSetSparseRegionEntries)
3716 : rset->is_empty();
3717 }
3719 bool is_typeArray_region(HeapRegion* region) const {
3720 return oop(region->bottom())->is_typeArray();
3721 }
3723 bool humongous_region_is_candidate(G1CollectedHeap* heap, HeapRegion* region) const {
3724 assert(region->startsHumongous(), "Must start a humongous object");
3726 // Candidate selection must satisfy the following constraints
3727 // while concurrent marking is in progress:
3728 //
3729 // * In order to maintain SATB invariants, an object must not be
3730 // reclaimed if it was allocated before the start of marking and
3731 // has not had its references scanned. Such an object must have
3732 // its references (including type metadata) scanned to ensure no
3733 // live objects are missed by the marking process. Objects
3734 // allocated after the start of concurrent marking don't need to
3735 // be scanned.
3736 //
3737 // * An object must not be reclaimed if it is on the concurrent
3738 // mark stack. Objects allocated after the start of concurrent
3739 // marking are never pushed on the mark stack.
3740 //
3741 // Nominating only objects allocated after the start of concurrent
3742 // marking is sufficient to meet both constraints. This may miss
3743 // some objects that satisfy the constraints, but the marking data
3744 // structures don't support efficiently performing the needed
3745 // additional tests or scrubbing of the mark stack.
3746 //
3747 // However, we presently only nominate is_typeArray() objects.
3748 // A humongous object containing references induces remembered
3749 // set entries on other regions. In order to reclaim such an
3750 // object, those remembered sets would need to be cleaned up.
3751 //
3752 // We also treat is_typeArray() objects specially, allowing them
3753 // to be reclaimed even if allocated before the start of
3754 // concurrent mark. For this we rely on mark stack insertion to
3755 // exclude is_typeArray() objects, preventing reclaiming an object
3756 // that is in the mark stack. We also rely on the metadata for
3757 // such objects to be built-in and so ensured to be kept live.
3758 // Frequent allocation and drop of large binary blobs is an
3759 // important use case for eager reclaim, and this special handling
3760 // may reduce needed headroom.
3762 return is_typeArray_region(region) && is_remset_small(region);
3763 }
3765 public:
3766 RegisterHumongousWithInCSetFastTestClosure()
3767 : _total_humongous(0),
3768 _candidate_humongous(0),
3769 _dcq(&JavaThread::dirty_card_queue_set()) {
3770 }
3772 virtual bool doHeapRegion(HeapRegion* r) {
3773 if (!r->startsHumongous()) {
3774 return false;
3775 }
3776 G1CollectedHeap* g1h = G1CollectedHeap::heap();
3778 bool is_candidate = humongous_region_is_candidate(g1h, r);
3779 uint rindex = r->hrm_index();
3780 g1h->set_humongous_reclaim_candidate(rindex, is_candidate);
3781 if (is_candidate) {
3782 _candidate_humongous++;
3783 g1h->register_humongous_region_with_in_cset_fast_test(rindex);
3784 // Is_candidate already filters out humongous object with large remembered sets.
3785 // If we have a humongous object with a few remembered sets, we simply flush these
3786 // remembered set entries into the DCQS. That will result in automatic
3787 // re-evaluation of their remembered set entries during the following evacuation
3788 // phase.
3789 if (!r->rem_set()->is_empty()) {
3790 guarantee(r->rem_set()->occupancy_less_or_equal_than(G1RSetSparseRegionEntries),
3791 "Found a not-small remembered set here. This is inconsistent with previous assumptions.");
3792 G1SATBCardTableLoggingModRefBS* bs = g1h->g1_barrier_set();
3793 HeapRegionRemSetIterator hrrs(r->rem_set());
3794 size_t card_index;
3795 while (hrrs.has_next(card_index)) {
3796 jbyte* card_ptr = (jbyte*)bs->byte_for_index(card_index);
3797 if (*card_ptr != CardTableModRefBS::dirty_card_val()) {
3798 *card_ptr = CardTableModRefBS::dirty_card_val();
3799 _dcq.enqueue(card_ptr);
3800 }
3801 }
3802 assert(hrrs.n_yielded() == r->rem_set()->occupied(),
3803 err_msg("Remembered set hash maps out of sync, cur: " SIZE_FORMAT " entries, next: " SIZE_FORMAT " entries",
3804 hrrs.n_yielded(), r->rem_set()->occupied()));
3805 r->rem_set()->clear_locked();
3806 }
3807 assert(r->rem_set()->is_empty(), "At this point any humongous candidate remembered set must be empty.");
3808 }
3809 _total_humongous++;
3811 return false;
3812 }
3814 size_t total_humongous() const { return _total_humongous; }
3815 size_t candidate_humongous() const { return _candidate_humongous; }
3817 void flush_rem_set_entries() { _dcq.flush(); }
3818 };
3820 void G1CollectedHeap::register_humongous_regions_with_in_cset_fast_test() {
3821 if (!G1EagerReclaimHumongousObjects) {
3822 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0.0, 0, 0);
3823 return;
3824 }
3825 double time = os::elapsed_counter();
3827 // Collect reclaim candidate information and register candidates with cset.
3828 RegisterHumongousWithInCSetFastTestClosure cl;
3829 heap_region_iterate(&cl);
3831 time = ((double)(os::elapsed_counter() - time) / os::elapsed_frequency()) * 1000.0;
3832 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(time,
3833 cl.total_humongous(),
3834 cl.candidate_humongous());
3835 _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0;
3837 // Finally flush all remembered set entries to re-check into the global DCQS.
3838 cl.flush_rem_set_entries();
3839 }
3841 void
3842 G1CollectedHeap::setup_surviving_young_words() {
3843 assert(_surviving_young_words == NULL, "pre-condition");
3844 uint array_length = g1_policy()->young_cset_region_length();
3845 _surviving_young_words = NEW_C_HEAP_ARRAY(size_t, (size_t) array_length, mtGC);
3846 if (_surviving_young_words == NULL) {
3847 vm_exit_out_of_memory(sizeof(size_t) * array_length, OOM_MALLOC_ERROR,
3848 "Not enough space for young surv words summary.");
3849 }
3850 memset(_surviving_young_words, 0, (size_t) array_length * sizeof(size_t));
3851 #ifdef ASSERT
3852 for (uint i = 0; i < array_length; ++i) {
3853 assert( _surviving_young_words[i] == 0, "memset above" );
3854 }
3855 #endif // !ASSERT
3856 }
3858 void
3859 G1CollectedHeap::update_surviving_young_words(size_t* surv_young_words) {
3860 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
3861 uint array_length = g1_policy()->young_cset_region_length();
3862 for (uint i = 0; i < array_length; ++i) {
3863 _surviving_young_words[i] += surv_young_words[i];
3864 }
3865 }
3867 void
3868 G1CollectedHeap::cleanup_surviving_young_words() {
3869 guarantee( _surviving_young_words != NULL, "pre-condition" );
3870 FREE_C_HEAP_ARRAY(size_t, _surviving_young_words, mtGC);
3871 _surviving_young_words = NULL;
3872 }
3874 class VerifyRegionRemSetClosure : public HeapRegionClosure {
3875 public:
3876 bool doHeapRegion(HeapRegion* hr) {
3877 if (!hr->continuesHumongous()) {
3878 hr->verify_rem_set();
3879 }
3880 return false;
3881 }
3882 };
3884 #ifdef ASSERT
3885 class VerifyCSetClosure: public HeapRegionClosure {
3886 public:
3887 bool doHeapRegion(HeapRegion* hr) {
3888 // Here we check that the CSet region's RSet is ready for parallel
3889 // iteration. The fields that we'll verify are only manipulated
3890 // when the region is part of a CSet and is collected. Afterwards,
3891 // we reset these fields when we clear the region's RSet (when the
3892 // region is freed) so they are ready when the region is
3893 // re-allocated. The only exception to this is if there's an
3894 // evacuation failure and instead of freeing the region we leave
3895 // it in the heap. In that case, we reset these fields during
3896 // evacuation failure handling.
3897 guarantee(hr->rem_set()->verify_ready_for_par_iteration(), "verification");
3899 // Here's a good place to add any other checks we'd like to
3900 // perform on CSet regions.
3901 return false;
3902 }
3903 };
3904 #endif // ASSERT
3906 #if TASKQUEUE_STATS
3907 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
3908 st->print_raw_cr("GC Task Stats");
3909 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
3910 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
3911 }
3913 void G1CollectedHeap::print_taskqueue_stats(outputStream* const st) const {
3914 print_taskqueue_stats_hdr(st);
3916 TaskQueueStats totals;
3917 const int n = workers() != NULL ? workers()->total_workers() : 1;
3918 for (int i = 0; i < n; ++i) {
3919 st->print("%3d ", i); task_queue(i)->stats.print(st); st->cr();
3920 totals += task_queue(i)->stats;
3921 }
3922 st->print_raw("tot "); totals.print(st); st->cr();
3924 DEBUG_ONLY(totals.verify());
3925 }
3927 void G1CollectedHeap::reset_taskqueue_stats() {
3928 const int n = workers() != NULL ? workers()->total_workers() : 1;
3929 for (int i = 0; i < n; ++i) {
3930 task_queue(i)->stats.reset();
3931 }
3932 }
3933 #endif // TASKQUEUE_STATS
3935 void G1CollectedHeap::log_gc_header() {
3936 if (!G1Log::fine()) {
3937 return;
3938 }
3940 gclog_or_tty->gclog_stamp(_gc_tracer_stw->gc_id());
3942 GCCauseString gc_cause_str = GCCauseString("GC pause", gc_cause())
3943 .append(g1_policy()->gcs_are_young() ? "(young)" : "(mixed)")
3944 .append(g1_policy()->during_initial_mark_pause() ? " (initial-mark)" : "");
3946 gclog_or_tty->print("[%s", (const char*)gc_cause_str);
3947 }
3949 void G1CollectedHeap::log_gc_footer(double pause_time_sec) {
3950 if (!G1Log::fine()) {
3951 return;
3952 }
3954 if (G1Log::finer()) {
3955 if (evacuation_failed()) {
3956 gclog_or_tty->print(" (to-space exhausted)");
3957 }
3958 gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec);
3959 g1_policy()->phase_times()->note_gc_end();
3960 g1_policy()->phase_times()->print(pause_time_sec);
3961 g1_policy()->print_detailed_heap_transition();
3962 } else {
3963 if (evacuation_failed()) {
3964 gclog_or_tty->print("--");
3965 }
3966 g1_policy()->print_heap_transition();
3967 gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec);
3968 }
3969 gclog_or_tty->flush();
3970 }
3972 bool
3973 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
3974 assert_at_safepoint(true /* should_be_vm_thread */);
3975 guarantee(!is_gc_active(), "collection is not reentrant");
3977 if (GC_locker::check_active_before_gc()) {
3978 return false;
3979 }
3981 _gc_timer_stw->register_gc_start();
3983 _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start());
3985 SvcGCMarker sgcm(SvcGCMarker::MINOR);
3986 ResourceMark rm;
3988 print_heap_before_gc();
3989 trace_heap_before_gc(_gc_tracer_stw);
3991 verify_region_sets_optional();
3992 verify_dirty_young_regions();
3994 // This call will decide whether this pause is an initial-mark
3995 // pause. If it is, during_initial_mark_pause() will return true
3996 // for the duration of this pause.
3997 g1_policy()->decide_on_conc_mark_initiation();
3999 // We do not allow initial-mark to be piggy-backed on a mixed GC.
4000 assert(!g1_policy()->during_initial_mark_pause() ||
4001 g1_policy()->gcs_are_young(), "sanity");
4003 // We also do not allow mixed GCs during marking.
4004 assert(!mark_in_progress() || g1_policy()->gcs_are_young(), "sanity");
4006 // Record whether this pause is an initial mark. When the current
4007 // thread has completed its logging output and it's safe to signal
4008 // the CM thread, the flag's value in the policy has been reset.
4009 bool should_start_conc_mark = g1_policy()->during_initial_mark_pause();
4011 // Inner scope for scope based logging, timers, and stats collection
4012 {
4013 EvacuationInfo evacuation_info;
4015 if (g1_policy()->during_initial_mark_pause()) {
4016 // We are about to start a marking cycle, so we increment the
4017 // full collection counter.
4018 increment_old_marking_cycles_started();
4019 register_concurrent_cycle_start(_gc_timer_stw->gc_start());
4020 }
4022 _gc_tracer_stw->report_yc_type(yc_type());
4024 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
4026 uint active_workers = AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
4027 workers()->active_workers(),
4028 Threads::number_of_non_daemon_threads());
4029 assert(UseDynamicNumberOfGCThreads ||
4030 active_workers == workers()->total_workers(),
4031 "If not dynamic should be using all the workers");
4032 workers()->set_active_workers(active_workers);
4035 double pause_start_sec = os::elapsedTime();
4036 g1_policy()->phase_times()->note_gc_start(active_workers, mark_in_progress());
4037 log_gc_header();
4039 TraceCollectorStats tcs(g1mm()->incremental_collection_counters());
4040 TraceMemoryManagerStats tms(false /* fullGC */, gc_cause(),
4041 yc_type() == Mixed /* allMemoryPoolsAffected */);
4043 // If the secondary_free_list is not empty, append it to the
4044 // free_list. No need to wait for the cleanup operation to finish;
4045 // the region allocation code will check the secondary_free_list
4046 // and wait if necessary. If the G1StressConcRegionFreeing flag is
4047 // set, skip this step so that the region allocation code has to
4048 // get entries from the secondary_free_list.
4049 if (!G1StressConcRegionFreeing) {
4050 append_secondary_free_list_if_not_empty_with_lock();
4051 }
4053 assert(check_young_list_well_formed(), "young list should be well formed");
4054 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
4055 "sanity check");
4057 // Don't dynamically change the number of GC threads this early. A value of
4058 // 0 is used to indicate serial work. When parallel work is done,
4059 // it will be set.
4061 { // Call to jvmpi::post_class_unload_events must occur outside of active GC
4062 IsGCActiveMark x;
4064 gc_prologue(false);
4065 increment_total_collections(false /* full gc */);
4066 increment_gc_time_stamp();
4068 if (VerifyRememberedSets) {
4069 if (!VerifySilently) {
4070 gclog_or_tty->print_cr("[Verifying RemSets before GC]");
4071 }
4072 VerifyRegionRemSetClosure v_cl;
4073 heap_region_iterate(&v_cl);
4074 }
4076 verify_before_gc();
4077 check_bitmaps("GC Start");
4079 COMPILER2_PRESENT(DerivedPointerTable::clear());
4081 // Please see comment in g1CollectedHeap.hpp and
4082 // G1CollectedHeap::ref_processing_init() to see how
4083 // reference processing currently works in G1.
4085 // Enable discovery in the STW reference processor
4086 ref_processor_stw()->enable_discovery(true /*verify_disabled*/,
4087 true /*verify_no_refs*/);
4089 {
4090 // We want to temporarily turn off discovery by the
4091 // CM ref processor, if necessary, and turn it back on
4092 // on again later if we do. Using a scoped
4093 // NoRefDiscovery object will do this.
4094 NoRefDiscovery no_cm_discovery(ref_processor_cm());
4096 // Forget the current alloc region (we might even choose it to be part
4097 // of the collection set!).
4098 _allocator->release_mutator_alloc_region();
4100 // We should call this after we retire the mutator alloc
4101 // region(s) so that all the ALLOC / RETIRE events are generated
4102 // before the start GC event.
4103 _hr_printer.start_gc(false /* full */, (size_t) total_collections());
4105 // This timing is only used by the ergonomics to handle our pause target.
4106 // It is unclear why this should not include the full pause. We will
4107 // investigate this in CR 7178365.
4108 //
4109 // Preserving the old comment here if that helps the investigation:
4110 //
4111 // The elapsed time induced by the start time below deliberately elides
4112 // the possible verification above.
4113 double sample_start_time_sec = os::elapsedTime();
4115 #if YOUNG_LIST_VERBOSE
4116 gclog_or_tty->print_cr("\nBefore recording pause start.\nYoung_list:");
4117 _young_list->print();
4118 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
4119 #endif // YOUNG_LIST_VERBOSE
4121 g1_policy()->record_collection_pause_start(sample_start_time_sec, *_gc_tracer_stw);
4123 double scan_wait_start = os::elapsedTime();
4124 // We have to wait until the CM threads finish scanning the
4125 // root regions as it's the only way to ensure that all the
4126 // objects on them have been correctly scanned before we start
4127 // moving them during the GC.
4128 bool waited = _cm->root_regions()->wait_until_scan_finished();
4129 double wait_time_ms = 0.0;
4130 if (waited) {
4131 double scan_wait_end = os::elapsedTime();
4132 wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
4133 }
4134 g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms);
4136 #if YOUNG_LIST_VERBOSE
4137 gclog_or_tty->print_cr("\nAfter recording pause start.\nYoung_list:");
4138 _young_list->print();
4139 #endif // YOUNG_LIST_VERBOSE
4141 if (g1_policy()->during_initial_mark_pause()) {
4142 concurrent_mark()->checkpointRootsInitialPre();
4143 }
4145 #if YOUNG_LIST_VERBOSE
4146 gclog_or_tty->print_cr("\nBefore choosing collection set.\nYoung_list:");
4147 _young_list->print();
4148 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
4149 #endif // YOUNG_LIST_VERBOSE
4151 g1_policy()->finalize_cset(target_pause_time_ms, evacuation_info);
4153 // Make sure the remembered sets are up to date. This needs to be
4154 // done before register_humongous_regions_with_cset(), because the
4155 // remembered sets are used there to choose eager reclaim candidates.
4156 // If the remembered sets are not up to date we might miss some
4157 // entries that need to be handled.
4158 g1_rem_set()->cleanupHRRS();
4160 register_humongous_regions_with_in_cset_fast_test();
4162 assert(check_cset_fast_test(), "Inconsistency in the InCSetState table.");
4164 _cm->note_start_of_gc();
4165 // We call this after finalize_cset() to
4166 // ensure that the CSet has been finalized.
4167 _cm->verify_no_cset_oops();
4169 if (_hr_printer.is_active()) {
4170 HeapRegion* hr = g1_policy()->collection_set();
4171 while (hr != NULL) {
4172 _hr_printer.cset(hr);
4173 hr = hr->next_in_collection_set();
4174 }
4175 }
4177 #ifdef ASSERT
4178 VerifyCSetClosure cl;
4179 collection_set_iterate(&cl);
4180 #endif // ASSERT
4182 setup_surviving_young_words();
4184 // Initialize the GC alloc regions.
4185 _allocator->init_gc_alloc_regions(evacuation_info);
4187 // Actually do the work...
4188 evacuate_collection_set(evacuation_info);
4190 free_collection_set(g1_policy()->collection_set(), evacuation_info);
4192 eagerly_reclaim_humongous_regions();
4194 g1_policy()->clear_collection_set();
4196 cleanup_surviving_young_words();
4198 // Start a new incremental collection set for the next pause.
4199 g1_policy()->start_incremental_cset_building();
4201 clear_cset_fast_test();
4203 _young_list->reset_sampled_info();
4205 // Don't check the whole heap at this point as the
4206 // GC alloc regions from this pause have been tagged
4207 // as survivors and moved on to the survivor list.
4208 // Survivor regions will fail the !is_young() check.
4209 assert(check_young_list_empty(false /* check_heap */),
4210 "young list should be empty");
4212 #if YOUNG_LIST_VERBOSE
4213 gclog_or_tty->print_cr("Before recording survivors.\nYoung List:");
4214 _young_list->print();
4215 #endif // YOUNG_LIST_VERBOSE
4217 g1_policy()->record_survivor_regions(_young_list->survivor_length(),
4218 _young_list->first_survivor_region(),
4219 _young_list->last_survivor_region());
4221 _young_list->reset_auxilary_lists();
4223 if (evacuation_failed()) {
4224 _allocator->set_used(recalculate_used());
4225 uint n_queues = MAX2((int)ParallelGCThreads, 1);
4226 for (uint i = 0; i < n_queues; i++) {
4227 if (_evacuation_failed_info_array[i].has_failed()) {
4228 _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]);
4229 }
4230 }
4231 } else {
4232 // The "used" of the the collection set have already been subtracted
4233 // when they were freed. Add in the bytes evacuated.
4234 _allocator->increase_used(g1_policy()->bytes_copied_during_gc());
4235 }
4237 if (g1_policy()->during_initial_mark_pause()) {
4238 // We have to do this before we notify the CM threads that
4239 // they can start working to make sure that all the
4240 // appropriate initialization is done on the CM object.
4241 concurrent_mark()->checkpointRootsInitialPost();
4242 set_marking_started();
4243 // Note that we don't actually trigger the CM thread at
4244 // this point. We do that later when we're sure that
4245 // the current thread has completed its logging output.
4246 }
4248 allocate_dummy_regions();
4250 #if YOUNG_LIST_VERBOSE
4251 gclog_or_tty->print_cr("\nEnd of the pause.\nYoung_list:");
4252 _young_list->print();
4253 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
4254 #endif // YOUNG_LIST_VERBOSE
4256 _allocator->init_mutator_alloc_region();
4258 {
4259 size_t expand_bytes = g1_policy()->expansion_amount();
4260 if (expand_bytes > 0) {
4261 size_t bytes_before = capacity();
4262 // No need for an ergo verbose message here,
4263 // expansion_amount() does this when it returns a value > 0.
4264 if (!expand(expand_bytes)) {
4265 // We failed to expand the heap. Cannot do anything about it.
4266 }
4267 }
4268 }
4270 // We redo the verification but now wrt to the new CSet which
4271 // has just got initialized after the previous CSet was freed.
4272 _cm->verify_no_cset_oops();
4273 _cm->note_end_of_gc();
4275 // This timing is only used by the ergonomics to handle our pause target.
4276 // It is unclear why this should not include the full pause. We will
4277 // investigate this in CR 7178365.
4278 double sample_end_time_sec = os::elapsedTime();
4279 double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
4280 g1_policy()->record_collection_pause_end(pause_time_ms, evacuation_info);
4282 MemoryService::track_memory_usage();
4284 // In prepare_for_verify() below we'll need to scan the deferred
4285 // update buffers to bring the RSets up-to-date if
4286 // G1HRRSFlushLogBuffersOnVerify has been set. While scanning
4287 // the update buffers we'll probably need to scan cards on the
4288 // regions we just allocated to (i.e., the GC alloc
4289 // regions). However, during the last GC we called
4290 // set_saved_mark() on all the GC alloc regions, so card
4291 // scanning might skip the [saved_mark_word()...top()] area of
4292 // those regions (i.e., the area we allocated objects into
4293 // during the last GC). But it shouldn't. Given that
4294 // saved_mark_word() is conditional on whether the GC time stamp
4295 // on the region is current or not, by incrementing the GC time
4296 // stamp here we invalidate all the GC time stamps on all the
4297 // regions and saved_mark_word() will simply return top() for
4298 // all the regions. This is a nicer way of ensuring this rather
4299 // than iterating over the regions and fixing them. In fact, the
4300 // GC time stamp increment here also ensures that
4301 // saved_mark_word() will return top() between pauses, i.e.,
4302 // during concurrent refinement. So we don't need the
4303 // is_gc_active() check to decided which top to use when
4304 // scanning cards (see CR 7039627).
4305 increment_gc_time_stamp();
4307 if (VerifyRememberedSets) {
4308 if (!VerifySilently) {
4309 gclog_or_tty->print_cr("[Verifying RemSets after GC]");
4310 }
4311 VerifyRegionRemSetClosure v_cl;
4312 heap_region_iterate(&v_cl);
4313 }
4315 verify_after_gc();
4316 check_bitmaps("GC End");
4318 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
4319 ref_processor_stw()->verify_no_references_recorded();
4321 // CM reference discovery will be re-enabled if necessary.
4322 }
4324 // We should do this after we potentially expand the heap so
4325 // that all the COMMIT events are generated before the end GC
4326 // event, and after we retire the GC alloc regions so that all
4327 // RETIRE events are generated before the end GC event.
4328 _hr_printer.end_gc(false /* full */, (size_t) total_collections());
4330 #ifdef TRACESPINNING
4331 ParallelTaskTerminator::print_termination_counts();
4332 #endif
4334 gc_epilogue(false);
4335 }
4337 // Print the remainder of the GC log output.
4338 log_gc_footer(os::elapsedTime() - pause_start_sec);
4340 // It is not yet to safe to tell the concurrent mark to
4341 // start as we have some optional output below. We don't want the
4342 // output from the concurrent mark thread interfering with this
4343 // logging output either.
4345 _hrm.verify_optional();
4346 verify_region_sets_optional();
4348 TASKQUEUE_STATS_ONLY(if (ParallelGCVerbose) print_taskqueue_stats());
4349 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
4351 print_heap_after_gc();
4352 trace_heap_after_gc(_gc_tracer_stw);
4354 // We must call G1MonitoringSupport::update_sizes() in the same scoping level
4355 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
4356 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
4357 // before any GC notifications are raised.
4358 g1mm()->update_sizes();
4360 _gc_tracer_stw->report_evacuation_info(&evacuation_info);
4361 _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold());
4362 _gc_timer_stw->register_gc_end();
4363 _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions());
4364 }
4365 // It should now be safe to tell the concurrent mark thread to start
4366 // without its logging output interfering with the logging output
4367 // that came from the pause.
4369 if (should_start_conc_mark) {
4370 // CAUTION: after the doConcurrentMark() call below,
4371 // the concurrent marking thread(s) could be running
4372 // concurrently with us. Make sure that anything after
4373 // this point does not assume that we are the only GC thread
4374 // running. Note: of course, the actual marking work will
4375 // not start until the safepoint itself is released in
4376 // SuspendibleThreadSet::desynchronize().
4377 doConcurrentMark();
4378 }
4380 return true;
4381 }
4383 void G1CollectedHeap::init_for_evac_failure(OopsInHeapRegionClosure* cl) {
4384 _drain_in_progress = false;
4385 set_evac_failure_closure(cl);
4386 _evac_failure_scan_stack = new (ResourceObj::C_HEAP, mtGC) GrowableArray<oop>(40, true);
4387 }
4389 void G1CollectedHeap::finalize_for_evac_failure() {
4390 assert(_evac_failure_scan_stack != NULL &&
4391 _evac_failure_scan_stack->length() == 0,
4392 "Postcondition");
4393 assert(!_drain_in_progress, "Postcondition");
4394 delete _evac_failure_scan_stack;
4395 _evac_failure_scan_stack = NULL;
4396 }
4398 void G1CollectedHeap::remove_self_forwarding_pointers() {
4399 assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity");
4401 double remove_self_forwards_start = os::elapsedTime();
4403 G1ParRemoveSelfForwardPtrsTask rsfp_task(this);
4405 if (G1CollectedHeap::use_parallel_gc_threads()) {
4406 set_par_threads();
4407 workers()->run_task(&rsfp_task);
4408 set_par_threads(0);
4409 } else {
4410 rsfp_task.work(0);
4411 }
4413 assert(check_cset_heap_region_claim_values(HeapRegion::ParEvacFailureClaimValue), "sanity");
4415 // Reset the claim values in the regions in the collection set.
4416 reset_cset_heap_region_claim_values();
4418 assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity");
4420 // Now restore saved marks, if any.
4421 assert(_objs_with_preserved_marks.size() ==
4422 _preserved_marks_of_objs.size(), "Both or none.");
4423 while (!_objs_with_preserved_marks.is_empty()) {
4424 oop obj = _objs_with_preserved_marks.pop();
4425 markOop m = _preserved_marks_of_objs.pop();
4426 obj->set_mark(m);
4427 }
4428 _objs_with_preserved_marks.clear(true);
4429 _preserved_marks_of_objs.clear(true);
4431 g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0);
4432 }
4434 void G1CollectedHeap::push_on_evac_failure_scan_stack(oop obj) {
4435 _evac_failure_scan_stack->push(obj);
4436 }
4438 void G1CollectedHeap::drain_evac_failure_scan_stack() {
4439 assert(_evac_failure_scan_stack != NULL, "precondition");
4441 while (_evac_failure_scan_stack->length() > 0) {
4442 oop obj = _evac_failure_scan_stack->pop();
4443 _evac_failure_closure->set_region(heap_region_containing(obj));
4444 obj->oop_iterate_backwards(_evac_failure_closure);
4445 }
4446 }
4448 oop
4449 G1CollectedHeap::handle_evacuation_failure_par(G1ParScanThreadState* _par_scan_state,
4450 oop old) {
4451 assert(obj_in_cs(old),
4452 err_msg("obj: " PTR_FORMAT " should still be in the CSet",
4453 (HeapWord*) old));
4454 markOop m = old->mark();
4455 oop forward_ptr = old->forward_to_atomic(old);
4456 if (forward_ptr == NULL) {
4457 // Forward-to-self succeeded.
4458 assert(_par_scan_state != NULL, "par scan state");
4459 OopsInHeapRegionClosure* cl = _par_scan_state->evac_failure_closure();
4460 uint queue_num = _par_scan_state->queue_num();
4462 _evacuation_failed = true;
4463 _evacuation_failed_info_array[queue_num].register_copy_failure(old->size());
4464 if (_evac_failure_closure != cl) {
4465 MutexLockerEx x(EvacFailureStack_lock, Mutex::_no_safepoint_check_flag);
4466 assert(!_drain_in_progress,
4467 "Should only be true while someone holds the lock.");
4468 // Set the global evac-failure closure to the current thread's.
4469 assert(_evac_failure_closure == NULL, "Or locking has failed.");
4470 set_evac_failure_closure(cl);
4471 // Now do the common part.
4472 handle_evacuation_failure_common(old, m);
4473 // Reset to NULL.
4474 set_evac_failure_closure(NULL);
4475 } else {
4476 // The lock is already held, and this is recursive.
4477 assert(_drain_in_progress, "This should only be the recursive case.");
4478 handle_evacuation_failure_common(old, m);
4479 }
4480 return old;
4481 } else {
4482 // Forward-to-self failed. Either someone else managed to allocate
4483 // space for this object (old != forward_ptr) or they beat us in
4484 // self-forwarding it (old == forward_ptr).
4485 assert(old == forward_ptr || !obj_in_cs(forward_ptr),
4486 err_msg("obj: " PTR_FORMAT " forwarded to: " PTR_FORMAT " "
4487 "should not be in the CSet",
4488 (HeapWord*) old, (HeapWord*) forward_ptr));
4489 return forward_ptr;
4490 }
4491 }
4493 void G1CollectedHeap::handle_evacuation_failure_common(oop old, markOop m) {
4494 preserve_mark_if_necessary(old, m);
4496 HeapRegion* r = heap_region_containing(old);
4497 if (!r->evacuation_failed()) {
4498 r->set_evacuation_failed(true);
4499 _hr_printer.evac_failure(r);
4500 }
4502 push_on_evac_failure_scan_stack(old);
4504 if (!_drain_in_progress) {
4505 // prevent recursion in copy_to_survivor_space()
4506 _drain_in_progress = true;
4507 drain_evac_failure_scan_stack();
4508 _drain_in_progress = false;
4509 }
4510 }
4512 void G1CollectedHeap::preserve_mark_if_necessary(oop obj, markOop m) {
4513 assert(evacuation_failed(), "Oversaving!");
4514 // We want to call the "for_promotion_failure" version only in the
4515 // case of a promotion failure.
4516 if (m->must_be_preserved_for_promotion_failure(obj)) {
4517 _objs_with_preserved_marks.push(obj);
4518 _preserved_marks_of_objs.push(m);
4519 }
4520 }
4522 void G1ParCopyHelper::mark_object(oop obj) {
4523 assert(!_g1->heap_region_containing(obj)->in_collection_set(), "should not mark objects in the CSet");
4525 // We know that the object is not moving so it's safe to read its size.
4526 _cm->grayRoot(obj, (size_t) obj->size(), _worker_id);
4527 }
4529 void G1ParCopyHelper::mark_forwarded_object(oop from_obj, oop to_obj) {
4530 assert(from_obj->is_forwarded(), "from obj should be forwarded");
4531 assert(from_obj->forwardee() == to_obj, "to obj should be the forwardee");
4532 assert(from_obj != to_obj, "should not be self-forwarded");
4534 assert(_g1->heap_region_containing(from_obj)->in_collection_set(), "from obj should be in the CSet");
4535 assert(!_g1->heap_region_containing(to_obj)->in_collection_set(), "should not mark objects in the CSet");
4537 // The object might be in the process of being copied by another
4538 // worker so we cannot trust that its to-space image is
4539 // well-formed. So we have to read its size from its from-space
4540 // image which we know should not be changing.
4541 _cm->grayRoot(to_obj, (size_t) from_obj->size(), _worker_id);
4542 }
4544 template <class T>
4545 void G1ParCopyHelper::do_klass_barrier(T* p, oop new_obj) {
4546 if (_g1->heap_region_containing_raw(new_obj)->is_young()) {
4547 _scanned_klass->record_modified_oops();
4548 }
4549 }
4551 template <G1Barrier barrier, G1Mark do_mark_object>
4552 template <class T>
4553 void G1ParCopyClosure<barrier, do_mark_object>::do_oop_work(T* p) {
4554 T heap_oop = oopDesc::load_heap_oop(p);
4556 if (oopDesc::is_null(heap_oop)) {
4557 return;
4558 }
4560 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
4562 assert(_worker_id == _par_scan_state->queue_num(), "sanity");
4564 const InCSetState state = _g1->in_cset_state(obj);
4565 if (state.is_in_cset()) {
4566 oop forwardee;
4567 markOop m = obj->mark();
4568 if (m->is_marked()) {
4569 forwardee = (oop) m->decode_pointer();
4570 } else {
4571 forwardee = _par_scan_state->copy_to_survivor_space(state, obj, m);
4572 }
4573 assert(forwardee != NULL, "forwardee should not be NULL");
4574 oopDesc::encode_store_heap_oop(p, forwardee);
4575 if (do_mark_object != G1MarkNone && forwardee != obj) {
4576 // If the object is self-forwarded we don't need to explicitly
4577 // mark it, the evacuation failure protocol will do so.
4578 mark_forwarded_object(obj, forwardee);
4579 }
4581 if (barrier == G1BarrierKlass) {
4582 do_klass_barrier(p, forwardee);
4583 }
4584 } else {
4585 if (state.is_humongous()) {
4586 _g1->set_humongous_is_live(obj);
4587 }
4588 // The object is not in collection set. If we're a root scanning
4589 // closure during an initial mark pause then attempt to mark the object.
4590 if (do_mark_object == G1MarkFromRoot) {
4591 mark_object(obj);
4592 }
4593 }
4595 if (barrier == G1BarrierEvac) {
4596 _par_scan_state->update_rs(_from, p, _worker_id);
4597 }
4598 }
4600 template void G1ParCopyClosure<G1BarrierEvac, G1MarkNone>::do_oop_work(oop* p);
4601 template void G1ParCopyClosure<G1BarrierEvac, G1MarkNone>::do_oop_work(narrowOop* p);
4603 class G1ParEvacuateFollowersClosure : public VoidClosure {
4604 protected:
4605 G1CollectedHeap* _g1h;
4606 G1ParScanThreadState* _par_scan_state;
4607 RefToScanQueueSet* _queues;
4608 ParallelTaskTerminator* _terminator;
4610 G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
4611 RefToScanQueueSet* queues() { return _queues; }
4612 ParallelTaskTerminator* terminator() { return _terminator; }
4614 public:
4615 G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h,
4616 G1ParScanThreadState* par_scan_state,
4617 RefToScanQueueSet* queues,
4618 ParallelTaskTerminator* terminator)
4619 : _g1h(g1h), _par_scan_state(par_scan_state),
4620 _queues(queues), _terminator(terminator) {}
4622 void do_void();
4624 private:
4625 inline bool offer_termination();
4626 };
4628 bool G1ParEvacuateFollowersClosure::offer_termination() {
4629 G1ParScanThreadState* const pss = par_scan_state();
4630 pss->start_term_time();
4631 const bool res = terminator()->offer_termination();
4632 pss->end_term_time();
4633 return res;
4634 }
4636 void G1ParEvacuateFollowersClosure::do_void() {
4637 G1ParScanThreadState* const pss = par_scan_state();
4638 pss->trim_queue();
4639 do {
4640 pss->steal_and_trim_queue(queues());
4641 } while (!offer_termination());
4642 }
4644 class G1KlassScanClosure : public KlassClosure {
4645 G1ParCopyHelper* _closure;
4646 bool _process_only_dirty;
4647 int _count;
4648 public:
4649 G1KlassScanClosure(G1ParCopyHelper* closure, bool process_only_dirty)
4650 : _process_only_dirty(process_only_dirty), _closure(closure), _count(0) {}
4651 void do_klass(Klass* klass) {
4652 // If the klass has not been dirtied we know that there's
4653 // no references into the young gen and we can skip it.
4654 if (!_process_only_dirty || klass->has_modified_oops()) {
4655 // Clean the klass since we're going to scavenge all the metadata.
4656 klass->clear_modified_oops();
4658 // Tell the closure that this klass is the Klass to scavenge
4659 // and is the one to dirty if oops are left pointing into the young gen.
4660 _closure->set_scanned_klass(klass);
4662 klass->oops_do(_closure);
4664 _closure->set_scanned_klass(NULL);
4665 }
4666 _count++;
4667 }
4668 };
4670 class G1ParTask : public AbstractGangTask {
4671 protected:
4672 G1CollectedHeap* _g1h;
4673 RefToScanQueueSet *_queues;
4674 G1RootProcessor* _root_processor;
4675 ParallelTaskTerminator _terminator;
4676 uint _n_workers;
4678 Mutex _stats_lock;
4679 Mutex* stats_lock() { return &_stats_lock; }
4681 public:
4682 G1ParTask(G1CollectedHeap* g1h, RefToScanQueueSet *task_queues, G1RootProcessor* root_processor)
4683 : AbstractGangTask("G1 collection"),
4684 _g1h(g1h),
4685 _queues(task_queues),
4686 _root_processor(root_processor),
4687 _terminator(0, _queues),
4688 _stats_lock(Mutex::leaf, "parallel G1 stats lock", true)
4689 {}
4691 RefToScanQueueSet* queues() { return _queues; }
4693 RefToScanQueue *work_queue(int i) {
4694 return queues()->queue(i);
4695 }
4697 ParallelTaskTerminator* terminator() { return &_terminator; }
4699 virtual void set_for_termination(int active_workers) {
4700 _root_processor->set_num_workers(active_workers);
4701 terminator()->reset_for_reuse(active_workers);
4702 _n_workers = active_workers;
4703 }
4705 // Helps out with CLD processing.
4706 //
4707 // During InitialMark we need to:
4708 // 1) Scavenge all CLDs for the young GC.
4709 // 2) Mark all objects directly reachable from strong CLDs.
4710 template <G1Mark do_mark_object>
4711 class G1CLDClosure : public CLDClosure {
4712 G1ParCopyClosure<G1BarrierNone, do_mark_object>* _oop_closure;
4713 G1ParCopyClosure<G1BarrierKlass, do_mark_object> _oop_in_klass_closure;
4714 G1KlassScanClosure _klass_in_cld_closure;
4715 bool _claim;
4717 public:
4718 G1CLDClosure(G1ParCopyClosure<G1BarrierNone, do_mark_object>* oop_closure,
4719 bool only_young, bool claim)
4720 : _oop_closure(oop_closure),
4721 _oop_in_klass_closure(oop_closure->g1(),
4722 oop_closure->pss(),
4723 oop_closure->rp()),
4724 _klass_in_cld_closure(&_oop_in_klass_closure, only_young),
4725 _claim(claim) {
4727 }
4729 void do_cld(ClassLoaderData* cld) {
4730 cld->oops_do(_oop_closure, &_klass_in_cld_closure, _claim);
4731 }
4732 };
4734 void work(uint worker_id) {
4735 if (worker_id >= _n_workers) return; // no work needed this round
4737 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerStart, worker_id, os::elapsedTime());
4739 {
4740 ResourceMark rm;
4741 HandleMark hm;
4743 ReferenceProcessor* rp = _g1h->ref_processor_stw();
4745 G1ParScanThreadState pss(_g1h, worker_id, rp);
4746 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, rp);
4748 pss.set_evac_failure_closure(&evac_failure_cl);
4750 bool only_young = _g1h->g1_policy()->gcs_are_young();
4752 // Non-IM young GC.
4753 G1ParCopyClosure<G1BarrierNone, G1MarkNone> scan_only_root_cl(_g1h, &pss, rp);
4754 G1CLDClosure<G1MarkNone> scan_only_cld_cl(&scan_only_root_cl,
4755 only_young, // Only process dirty klasses.
4756 false); // No need to claim CLDs.
4757 // IM young GC.
4758 // Strong roots closures.
4759 G1ParCopyClosure<G1BarrierNone, G1MarkFromRoot> scan_mark_root_cl(_g1h, &pss, rp);
4760 G1CLDClosure<G1MarkFromRoot> scan_mark_cld_cl(&scan_mark_root_cl,
4761 false, // Process all klasses.
4762 true); // Need to claim CLDs.
4763 // Weak roots closures.
4764 G1ParCopyClosure<G1BarrierNone, G1MarkPromotedFromRoot> scan_mark_weak_root_cl(_g1h, &pss, rp);
4765 G1CLDClosure<G1MarkPromotedFromRoot> scan_mark_weak_cld_cl(&scan_mark_weak_root_cl,
4766 false, // Process all klasses.
4767 true); // Need to claim CLDs.
4769 OopClosure* strong_root_cl;
4770 OopClosure* weak_root_cl;
4771 CLDClosure* strong_cld_cl;
4772 CLDClosure* weak_cld_cl;
4774 bool trace_metadata = false;
4776 if (_g1h->g1_policy()->during_initial_mark_pause()) {
4777 // We also need to mark copied objects.
4778 strong_root_cl = &scan_mark_root_cl;
4779 strong_cld_cl = &scan_mark_cld_cl;
4780 if (ClassUnloadingWithConcurrentMark) {
4781 weak_root_cl = &scan_mark_weak_root_cl;
4782 weak_cld_cl = &scan_mark_weak_cld_cl;
4783 trace_metadata = true;
4784 } else {
4785 weak_root_cl = &scan_mark_root_cl;
4786 weak_cld_cl = &scan_mark_cld_cl;
4787 }
4788 } else {
4789 strong_root_cl = &scan_only_root_cl;
4790 weak_root_cl = &scan_only_root_cl;
4791 strong_cld_cl = &scan_only_cld_cl;
4792 weak_cld_cl = &scan_only_cld_cl;
4793 }
4795 pss.start_strong_roots();
4797 _root_processor->evacuate_roots(strong_root_cl,
4798 weak_root_cl,
4799 strong_cld_cl,
4800 weak_cld_cl,
4801 trace_metadata,
4802 worker_id);
4804 G1ParPushHeapRSClosure push_heap_rs_cl(_g1h, &pss);
4805 _root_processor->scan_remembered_sets(&push_heap_rs_cl,
4806 weak_root_cl,
4807 worker_id);
4808 pss.end_strong_roots();
4810 {
4811 double start = os::elapsedTime();
4812 G1ParEvacuateFollowersClosure evac(_g1h, &pss, _queues, &_terminator);
4813 evac.do_void();
4814 double elapsed_sec = os::elapsedTime() - start;
4815 double term_sec = pss.term_time();
4816 _g1h->g1_policy()->phase_times()->add_time_secs(G1GCPhaseTimes::ObjCopy, worker_id, elapsed_sec - term_sec);
4817 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::Termination, worker_id, term_sec);
4818 _g1h->g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::Termination, worker_id, pss.term_attempts());
4819 }
4820 _g1h->g1_policy()->record_thread_age_table(pss.age_table());
4821 _g1h->update_surviving_young_words(pss.surviving_young_words()+1);
4823 if (ParallelGCVerbose) {
4824 MutexLocker x(stats_lock());
4825 pss.print_termination_stats(worker_id);
4826 }
4828 assert(pss.queue_is_empty(), "should be empty");
4830 // Close the inner scope so that the ResourceMark and HandleMark
4831 // destructors are executed here and are included as part of the
4832 // "GC Worker Time".
4833 }
4834 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerEnd, worker_id, os::elapsedTime());
4835 }
4836 };
4838 class G1StringSymbolTableUnlinkTask : public AbstractGangTask {
4839 private:
4840 BoolObjectClosure* _is_alive;
4841 int _initial_string_table_size;
4842 int _initial_symbol_table_size;
4844 bool _process_strings;
4845 int _strings_processed;
4846 int _strings_removed;
4848 bool _process_symbols;
4849 int _symbols_processed;
4850 int _symbols_removed;
4852 bool _do_in_parallel;
4853 public:
4854 G1StringSymbolTableUnlinkTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols) :
4855 AbstractGangTask("String/Symbol Unlinking"),
4856 _is_alive(is_alive),
4857 _do_in_parallel(G1CollectedHeap::use_parallel_gc_threads()),
4858 _process_strings(process_strings), _strings_processed(0), _strings_removed(0),
4859 _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0) {
4861 _initial_string_table_size = StringTable::the_table()->table_size();
4862 _initial_symbol_table_size = SymbolTable::the_table()->table_size();
4863 if (process_strings) {
4864 StringTable::clear_parallel_claimed_index();
4865 }
4866 if (process_symbols) {
4867 SymbolTable::clear_parallel_claimed_index();
4868 }
4869 }
4871 ~G1StringSymbolTableUnlinkTask() {
4872 guarantee(!_process_strings || !_do_in_parallel || StringTable::parallel_claimed_index() >= _initial_string_table_size,
4873 err_msg("claim value " INT32_FORMAT " after unlink less than initial string table size " INT32_FORMAT,
4874 StringTable::parallel_claimed_index(), _initial_string_table_size));
4875 guarantee(!_process_symbols || !_do_in_parallel || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size,
4876 err_msg("claim value " INT32_FORMAT " after unlink less than initial symbol table size " INT32_FORMAT,
4877 SymbolTable::parallel_claimed_index(), _initial_symbol_table_size));
4879 if (G1TraceStringSymbolTableScrubbing) {
4880 gclog_or_tty->print_cr("Cleaned string and symbol table, "
4881 "strings: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed, "
4882 "symbols: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed",
4883 strings_processed(), strings_removed(),
4884 symbols_processed(), symbols_removed());
4885 }
4886 }
4888 void work(uint worker_id) {
4889 if (_do_in_parallel) {
4890 int strings_processed = 0;
4891 int strings_removed = 0;
4892 int symbols_processed = 0;
4893 int symbols_removed = 0;
4894 if (_process_strings) {
4895 StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed);
4896 Atomic::add(strings_processed, &_strings_processed);
4897 Atomic::add(strings_removed, &_strings_removed);
4898 }
4899 if (_process_symbols) {
4900 SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed);
4901 Atomic::add(symbols_processed, &_symbols_processed);
4902 Atomic::add(symbols_removed, &_symbols_removed);
4903 }
4904 } else {
4905 if (_process_strings) {
4906 StringTable::unlink(_is_alive, &_strings_processed, &_strings_removed);
4907 }
4908 if (_process_symbols) {
4909 SymbolTable::unlink(&_symbols_processed, &_symbols_removed);
4910 }
4911 }
4912 }
4914 size_t strings_processed() const { return (size_t)_strings_processed; }
4915 size_t strings_removed() const { return (size_t)_strings_removed; }
4917 size_t symbols_processed() const { return (size_t)_symbols_processed; }
4918 size_t symbols_removed() const { return (size_t)_symbols_removed; }
4919 };
4921 class G1CodeCacheUnloadingTask VALUE_OBJ_CLASS_SPEC {
4922 private:
4923 static Monitor* _lock;
4925 BoolObjectClosure* const _is_alive;
4926 const bool _unloading_occurred;
4927 const uint _num_workers;
4929 // Variables used to claim nmethods.
4930 nmethod* _first_nmethod;
4931 volatile nmethod* _claimed_nmethod;
4933 // The list of nmethods that need to be processed by the second pass.
4934 volatile nmethod* _postponed_list;
4935 volatile uint _num_entered_barrier;
4937 public:
4938 G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) :
4939 _is_alive(is_alive),
4940 _unloading_occurred(unloading_occurred),
4941 _num_workers(num_workers),
4942 _first_nmethod(NULL),
4943 _claimed_nmethod(NULL),
4944 _postponed_list(NULL),
4945 _num_entered_barrier(0)
4946 {
4947 nmethod::increase_unloading_clock();
4948 _first_nmethod = CodeCache::alive_nmethod(CodeCache::first());
4949 _claimed_nmethod = (volatile nmethod*)_first_nmethod;
4950 }
4952 ~G1CodeCacheUnloadingTask() {
4953 CodeCache::verify_clean_inline_caches();
4955 CodeCache::set_needs_cache_clean(false);
4956 guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be");
4958 CodeCache::verify_icholder_relocations();
4959 }
4961 private:
4962 void add_to_postponed_list(nmethod* nm) {
4963 nmethod* old;
4964 do {
4965 old = (nmethod*)_postponed_list;
4966 nm->set_unloading_next(old);
4967 } while ((nmethod*)Atomic::cmpxchg_ptr(nm, &_postponed_list, old) != old);
4968 }
4970 void clean_nmethod(nmethod* nm) {
4971 bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred);
4973 if (postponed) {
4974 // This nmethod referred to an nmethod that has not been cleaned/unloaded yet.
4975 add_to_postponed_list(nm);
4976 }
4978 // Mark that this thread has been cleaned/unloaded.
4979 // After this call, it will be safe to ask if this nmethod was unloaded or not.
4980 nm->set_unloading_clock(nmethod::global_unloading_clock());
4981 }
4983 void clean_nmethod_postponed(nmethod* nm) {
4984 nm->do_unloading_parallel_postponed(_is_alive, _unloading_occurred);
4985 }
4987 static const int MaxClaimNmethods = 16;
4989 void claim_nmethods(nmethod** claimed_nmethods, int *num_claimed_nmethods) {
4990 nmethod* first;
4991 nmethod* last;
4993 do {
4994 *num_claimed_nmethods = 0;
4996 first = last = (nmethod*)_claimed_nmethod;
4998 if (first != NULL) {
4999 for (int i = 0; i < MaxClaimNmethods; i++) {
5000 last = CodeCache::alive_nmethod(CodeCache::next(last));
5002 if (last == NULL) {
5003 break;
5004 }
5006 claimed_nmethods[i] = last;
5007 (*num_claimed_nmethods)++;
5008 }
5009 }
5011 } while ((nmethod*)Atomic::cmpxchg_ptr(last, &_claimed_nmethod, first) != first);
5012 }
5014 nmethod* claim_postponed_nmethod() {
5015 nmethod* claim;
5016 nmethod* next;
5018 do {
5019 claim = (nmethod*)_postponed_list;
5020 if (claim == NULL) {
5021 return NULL;
5022 }
5024 next = claim->unloading_next();
5026 } while ((nmethod*)Atomic::cmpxchg_ptr(next, &_postponed_list, claim) != claim);
5028 return claim;
5029 }
5031 public:
5032 // Mark that we're done with the first pass of nmethod cleaning.
5033 void barrier_mark(uint worker_id) {
5034 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
5035 _num_entered_barrier++;
5036 if (_num_entered_barrier == _num_workers) {
5037 ml.notify_all();
5038 }
5039 }
5041 // See if we have to wait for the other workers to
5042 // finish their first-pass nmethod cleaning work.
5043 void barrier_wait(uint worker_id) {
5044 if (_num_entered_barrier < _num_workers) {
5045 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
5046 while (_num_entered_barrier < _num_workers) {
5047 ml.wait(Mutex::_no_safepoint_check_flag, 0, false);
5048 }
5049 }
5050 }
5052 // Cleaning and unloading of nmethods. Some work has to be postponed
5053 // to the second pass, when we know which nmethods survive.
5054 void work_first_pass(uint worker_id) {
5055 // The first nmethods is claimed by the first worker.
5056 if (worker_id == 0 && _first_nmethod != NULL) {
5057 clean_nmethod(_first_nmethod);
5058 _first_nmethod = NULL;
5059 }
5061 int num_claimed_nmethods;
5062 nmethod* claimed_nmethods[MaxClaimNmethods];
5064 while (true) {
5065 claim_nmethods(claimed_nmethods, &num_claimed_nmethods);
5067 if (num_claimed_nmethods == 0) {
5068 break;
5069 }
5071 for (int i = 0; i < num_claimed_nmethods; i++) {
5072 clean_nmethod(claimed_nmethods[i]);
5073 }
5074 }
5076 // The nmethod cleaning helps out and does the CodeCache part of MetadataOnStackMark.
5077 // Need to retire the buffers now that this thread has stopped cleaning nmethods.
5078 MetadataOnStackMark::retire_buffer_for_thread(Thread::current());
5079 }
5081 void work_second_pass(uint worker_id) {
5082 nmethod* nm;
5083 // Take care of postponed nmethods.
5084 while ((nm = claim_postponed_nmethod()) != NULL) {
5085 clean_nmethod_postponed(nm);
5086 }
5087 }
5088 };
5090 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock");
5092 class G1KlassCleaningTask : public StackObj {
5093 BoolObjectClosure* _is_alive;
5094 volatile jint _clean_klass_tree_claimed;
5095 ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator;
5097 public:
5098 G1KlassCleaningTask(BoolObjectClosure* is_alive) :
5099 _is_alive(is_alive),
5100 _clean_klass_tree_claimed(0),
5101 _klass_iterator() {
5102 }
5104 private:
5105 bool claim_clean_klass_tree_task() {
5106 if (_clean_klass_tree_claimed) {
5107 return false;
5108 }
5110 return Atomic::cmpxchg(1, (jint*)&_clean_klass_tree_claimed, 0) == 0;
5111 }
5113 InstanceKlass* claim_next_klass() {
5114 Klass* klass;
5115 do {
5116 klass =_klass_iterator.next_klass();
5117 } while (klass != NULL && !klass->oop_is_instance());
5119 return (InstanceKlass*)klass;
5120 }
5122 public:
5124 void clean_klass(InstanceKlass* ik) {
5125 ik->clean_weak_instanceklass_links(_is_alive);
5127 if (JvmtiExport::has_redefined_a_class()) {
5128 InstanceKlass::purge_previous_versions(ik);
5129 }
5130 }
5132 void work() {
5133 ResourceMark rm;
5135 // One worker will clean the subklass/sibling klass tree.
5136 if (claim_clean_klass_tree_task()) {
5137 Klass::clean_subklass_tree(_is_alive);
5138 }
5140 // All workers will help cleaning the classes,
5141 InstanceKlass* klass;
5142 while ((klass = claim_next_klass()) != NULL) {
5143 clean_klass(klass);
5144 }
5145 }
5146 };
5148 // To minimize the remark pause times, the tasks below are done in parallel.
5149 class G1ParallelCleaningTask : public AbstractGangTask {
5150 private:
5151 G1StringSymbolTableUnlinkTask _string_symbol_task;
5152 G1CodeCacheUnloadingTask _code_cache_task;
5153 G1KlassCleaningTask _klass_cleaning_task;
5155 public:
5156 // The constructor is run in the VMThread.
5157 G1ParallelCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, uint num_workers, bool unloading_occurred) :
5158 AbstractGangTask("Parallel Cleaning"),
5159 _string_symbol_task(is_alive, process_strings, process_symbols),
5160 _code_cache_task(num_workers, is_alive, unloading_occurred),
5161 _klass_cleaning_task(is_alive) {
5162 }
5164 void pre_work_verification() {
5165 // The VM Thread will have registered Metadata during the single-threaded phase of MetadataStackOnMark.
5166 assert(Thread::current()->is_VM_thread()
5167 || !MetadataOnStackMark::has_buffer_for_thread(Thread::current()), "Should be empty");
5168 }
5170 void post_work_verification() {
5171 assert(!MetadataOnStackMark::has_buffer_for_thread(Thread::current()), "Should be empty");
5172 }
5174 // The parallel work done by all worker threads.
5175 void work(uint worker_id) {
5176 pre_work_verification();
5178 // Do first pass of code cache cleaning.
5179 _code_cache_task.work_first_pass(worker_id);
5181 // Let the threads mark that the first pass is done.
5182 _code_cache_task.barrier_mark(worker_id);
5184 // Clean the Strings and Symbols.
5185 _string_symbol_task.work(worker_id);
5187 // Wait for all workers to finish the first code cache cleaning pass.
5188 _code_cache_task.barrier_wait(worker_id);
5190 // Do the second code cache cleaning work, which realize on
5191 // the liveness information gathered during the first pass.
5192 _code_cache_task.work_second_pass(worker_id);
5194 // Clean all klasses that were not unloaded.
5195 _klass_cleaning_task.work();
5197 post_work_verification();
5198 }
5199 };
5202 void G1CollectedHeap::parallel_cleaning(BoolObjectClosure* is_alive,
5203 bool process_strings,
5204 bool process_symbols,
5205 bool class_unloading_occurred) {
5206 uint n_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
5207 workers()->active_workers() : 1);
5209 G1ParallelCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols,
5210 n_workers, class_unloading_occurred);
5211 if (G1CollectedHeap::use_parallel_gc_threads()) {
5212 set_par_threads(n_workers);
5213 workers()->run_task(&g1_unlink_task);
5214 set_par_threads(0);
5215 } else {
5216 g1_unlink_task.work(0);
5217 }
5218 }
5220 void G1CollectedHeap::unlink_string_and_symbol_table(BoolObjectClosure* is_alive,
5221 bool process_strings, bool process_symbols) {
5222 {
5223 uint n_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
5224 _g1h->workers()->active_workers() : 1);
5225 G1StringSymbolTableUnlinkTask g1_unlink_task(is_alive, process_strings, process_symbols);
5226 if (G1CollectedHeap::use_parallel_gc_threads()) {
5227 set_par_threads(n_workers);
5228 workers()->run_task(&g1_unlink_task);
5229 set_par_threads(0);
5230 } else {
5231 g1_unlink_task.work(0);
5232 }
5233 }
5235 if (G1StringDedup::is_enabled()) {
5236 G1StringDedup::unlink(is_alive);
5237 }
5238 }
5240 class G1RedirtyLoggedCardsTask : public AbstractGangTask {
5241 private:
5242 DirtyCardQueueSet* _queue;
5243 public:
5244 G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue) : AbstractGangTask("Redirty Cards"), _queue(queue) { }
5246 virtual void work(uint worker_id) {
5247 G1GCPhaseTimes* phase_times = G1CollectedHeap::heap()->g1_policy()->phase_times();
5248 G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::RedirtyCards, worker_id);
5250 RedirtyLoggedCardTableEntryClosure cl;
5251 if (G1CollectedHeap::heap()->use_parallel_gc_threads()) {
5252 _queue->par_apply_closure_to_all_completed_buffers(&cl);
5253 } else {
5254 _queue->apply_closure_to_all_completed_buffers(&cl);
5255 }
5257 phase_times->record_thread_work_item(G1GCPhaseTimes::RedirtyCards, worker_id, cl.num_processed());
5258 }
5259 };
5261 void G1CollectedHeap::redirty_logged_cards() {
5262 double redirty_logged_cards_start = os::elapsedTime();
5264 uint n_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
5265 _g1h->workers()->active_workers() : 1);
5267 G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set());
5268 dirty_card_queue_set().reset_for_par_iteration();
5269 if (use_parallel_gc_threads()) {
5270 set_par_threads(n_workers);
5271 workers()->run_task(&redirty_task);
5272 set_par_threads(0);
5273 } else {
5274 redirty_task.work(0);
5275 }
5277 DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set();
5278 dcq.merge_bufferlists(&dirty_card_queue_set());
5279 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
5281 g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0);
5282 }
5284 // Weak Reference Processing support
5286 // An always "is_alive" closure that is used to preserve referents.
5287 // If the object is non-null then it's alive. Used in the preservation
5288 // of referent objects that are pointed to by reference objects
5289 // discovered by the CM ref processor.
5290 class G1AlwaysAliveClosure: public BoolObjectClosure {
5291 G1CollectedHeap* _g1;
5292 public:
5293 G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
5294 bool do_object_b(oop p) {
5295 if (p != NULL) {
5296 return true;
5297 }
5298 return false;
5299 }
5300 };
5302 bool G1STWIsAliveClosure::do_object_b(oop p) {
5303 // An object is reachable if it is outside the collection set,
5304 // or is inside and copied.
5305 return !_g1->obj_in_cs(p) || p->is_forwarded();
5306 }
5308 // Non Copying Keep Alive closure
5309 class G1KeepAliveClosure: public OopClosure {
5310 G1CollectedHeap* _g1;
5311 public:
5312 G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
5313 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
5314 void do_oop(oop* p) {
5315 oop obj = *p;
5316 assert(obj != NULL, "the caller should have filtered out NULL values");
5318 const InCSetState cset_state = _g1->in_cset_state(obj);
5319 if (!cset_state.is_in_cset_or_humongous()) {
5320 return;
5321 }
5322 if (cset_state.is_in_cset()) {
5323 assert( obj->is_forwarded(), "invariant" );
5324 *p = obj->forwardee();
5325 } else {
5326 assert(!obj->is_forwarded(), "invariant" );
5327 assert(cset_state.is_humongous(),
5328 err_msg("Only allowed InCSet state is IsHumongous, but is %d", cset_state.value()));
5329 _g1->set_humongous_is_live(obj);
5330 }
5331 }
5332 };
5334 // Copying Keep Alive closure - can be called from both
5335 // serial and parallel code as long as different worker
5336 // threads utilize different G1ParScanThreadState instances
5337 // and different queues.
5339 class G1CopyingKeepAliveClosure: public OopClosure {
5340 G1CollectedHeap* _g1h;
5341 OopClosure* _copy_non_heap_obj_cl;
5342 G1ParScanThreadState* _par_scan_state;
5344 public:
5345 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
5346 OopClosure* non_heap_obj_cl,
5347 G1ParScanThreadState* pss):
5348 _g1h(g1h),
5349 _copy_non_heap_obj_cl(non_heap_obj_cl),
5350 _par_scan_state(pss)
5351 {}
5353 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
5354 virtual void do_oop( oop* p) { do_oop_work(p); }
5356 template <class T> void do_oop_work(T* p) {
5357 oop obj = oopDesc::load_decode_heap_oop(p);
5359 if (_g1h->is_in_cset_or_humongous(obj)) {
5360 // If the referent object has been forwarded (either copied
5361 // to a new location or to itself in the event of an
5362 // evacuation failure) then we need to update the reference
5363 // field and, if both reference and referent are in the G1
5364 // heap, update the RSet for the referent.
5365 //
5366 // If the referent has not been forwarded then we have to keep
5367 // it alive by policy. Therefore we have copy the referent.
5368 //
5369 // If the reference field is in the G1 heap then we can push
5370 // on the PSS queue. When the queue is drained (after each
5371 // phase of reference processing) the object and it's followers
5372 // will be copied, the reference field set to point to the
5373 // new location, and the RSet updated. Otherwise we need to
5374 // use the the non-heap or metadata closures directly to copy
5375 // the referent object and update the pointer, while avoiding
5376 // updating the RSet.
5378 if (_g1h->is_in_g1_reserved(p)) {
5379 _par_scan_state->push_on_queue(p);
5380 } else {
5381 assert(!Metaspace::contains((const void*)p),
5382 err_msg("Unexpectedly found a pointer from metadata: "
5383 PTR_FORMAT, p));
5384 _copy_non_heap_obj_cl->do_oop(p);
5385 }
5386 }
5387 }
5388 };
5390 // Serial drain queue closure. Called as the 'complete_gc'
5391 // closure for each discovered list in some of the
5392 // reference processing phases.
5394 class G1STWDrainQueueClosure: public VoidClosure {
5395 protected:
5396 G1CollectedHeap* _g1h;
5397 G1ParScanThreadState* _par_scan_state;
5399 G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
5401 public:
5402 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
5403 _g1h(g1h),
5404 _par_scan_state(pss)
5405 { }
5407 void do_void() {
5408 G1ParScanThreadState* const pss = par_scan_state();
5409 pss->trim_queue();
5410 }
5411 };
5413 // Parallel Reference Processing closures
5415 // Implementation of AbstractRefProcTaskExecutor for parallel reference
5416 // processing during G1 evacuation pauses.
5418 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
5419 private:
5420 G1CollectedHeap* _g1h;
5421 RefToScanQueueSet* _queues;
5422 FlexibleWorkGang* _workers;
5423 int _active_workers;
5425 public:
5426 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
5427 FlexibleWorkGang* workers,
5428 RefToScanQueueSet *task_queues,
5429 int n_workers) :
5430 _g1h(g1h),
5431 _queues(task_queues),
5432 _workers(workers),
5433 _active_workers(n_workers)
5434 {
5435 assert(n_workers > 0, "shouldn't call this otherwise");
5436 }
5438 // Executes the given task using concurrent marking worker threads.
5439 virtual void execute(ProcessTask& task);
5440 virtual void execute(EnqueueTask& task);
5441 };
5443 // Gang task for possibly parallel reference processing
5445 class G1STWRefProcTaskProxy: public AbstractGangTask {
5446 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
5447 ProcessTask& _proc_task;
5448 G1CollectedHeap* _g1h;
5449 RefToScanQueueSet *_task_queues;
5450 ParallelTaskTerminator* _terminator;
5452 public:
5453 G1STWRefProcTaskProxy(ProcessTask& proc_task,
5454 G1CollectedHeap* g1h,
5455 RefToScanQueueSet *task_queues,
5456 ParallelTaskTerminator* terminator) :
5457 AbstractGangTask("Process reference objects in parallel"),
5458 _proc_task(proc_task),
5459 _g1h(g1h),
5460 _task_queues(task_queues),
5461 _terminator(terminator)
5462 {}
5464 virtual void work(uint worker_id) {
5465 // The reference processing task executed by a single worker.
5466 ResourceMark rm;
5467 HandleMark hm;
5469 G1STWIsAliveClosure is_alive(_g1h);
5471 G1ParScanThreadState pss(_g1h, worker_id, NULL);
5472 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5474 pss.set_evac_failure_closure(&evac_failure_cl);
5476 G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL);
5478 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5480 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5482 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5483 // We also need to mark copied objects.
5484 copy_non_heap_cl = ©_mark_non_heap_cl;
5485 }
5487 // Keep alive closure.
5488 G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, &pss);
5490 // Complete GC closure
5491 G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _task_queues, _terminator);
5493 // Call the reference processing task's work routine.
5494 _proc_task.work(worker_id, is_alive, keep_alive, drain_queue);
5496 // Note we cannot assert that the refs array is empty here as not all
5497 // of the processing tasks (specifically phase2 - pp2_work) execute
5498 // the complete_gc closure (which ordinarily would drain the queue) so
5499 // the queue may not be empty.
5500 }
5501 };
5503 // Driver routine for parallel reference processing.
5504 // Creates an instance of the ref processing gang
5505 // task and has the worker threads execute it.
5506 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) {
5507 assert(_workers != NULL, "Need parallel worker threads.");
5509 ParallelTaskTerminator terminator(_active_workers, _queues);
5510 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _queues, &terminator);
5512 _g1h->set_par_threads(_active_workers);
5513 _workers->run_task(&proc_task_proxy);
5514 _g1h->set_par_threads(0);
5515 }
5517 // Gang task for parallel reference enqueueing.
5519 class G1STWRefEnqueueTaskProxy: public AbstractGangTask {
5520 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
5521 EnqueueTask& _enq_task;
5523 public:
5524 G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) :
5525 AbstractGangTask("Enqueue reference objects in parallel"),
5526 _enq_task(enq_task)
5527 { }
5529 virtual void work(uint worker_id) {
5530 _enq_task.work(worker_id);
5531 }
5532 };
5534 // Driver routine for parallel reference enqueueing.
5535 // Creates an instance of the ref enqueueing gang
5536 // task and has the worker threads execute it.
5538 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
5539 assert(_workers != NULL, "Need parallel worker threads.");
5541 G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task);
5543 _g1h->set_par_threads(_active_workers);
5544 _workers->run_task(&enq_task_proxy);
5545 _g1h->set_par_threads(0);
5546 }
5548 // End of weak reference support closures
5550 // Abstract task used to preserve (i.e. copy) any referent objects
5551 // that are in the collection set and are pointed to by reference
5552 // objects discovered by the CM ref processor.
5554 class G1ParPreserveCMReferentsTask: public AbstractGangTask {
5555 protected:
5556 G1CollectedHeap* _g1h;
5557 RefToScanQueueSet *_queues;
5558 ParallelTaskTerminator _terminator;
5559 uint _n_workers;
5561 public:
5562 G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h,int workers, RefToScanQueueSet *task_queues) :
5563 AbstractGangTask("ParPreserveCMReferents"),
5564 _g1h(g1h),
5565 _queues(task_queues),
5566 _terminator(workers, _queues),
5567 _n_workers(workers)
5568 { }
5570 void work(uint worker_id) {
5571 ResourceMark rm;
5572 HandleMark hm;
5574 G1ParScanThreadState pss(_g1h, worker_id, NULL);
5575 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5577 pss.set_evac_failure_closure(&evac_failure_cl);
5579 assert(pss.queue_is_empty(), "both queue and overflow should be empty");
5581 G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL);
5583 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5585 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5587 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5588 // We also need to mark copied objects.
5589 copy_non_heap_cl = ©_mark_non_heap_cl;
5590 }
5592 // Is alive closure
5593 G1AlwaysAliveClosure always_alive(_g1h);
5595 // Copying keep alive closure. Applied to referent objects that need
5596 // to be copied.
5597 G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, &pss);
5599 ReferenceProcessor* rp = _g1h->ref_processor_cm();
5601 uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q();
5602 uint stride = MIN2(MAX2(_n_workers, 1U), limit);
5604 // limit is set using max_num_q() - which was set using ParallelGCThreads.
5605 // So this must be true - but assert just in case someone decides to
5606 // change the worker ids.
5607 assert(0 <= worker_id && worker_id < limit, "sanity");
5608 assert(!rp->discovery_is_atomic(), "check this code");
5610 // Select discovered lists [i, i+stride, i+2*stride,...,limit)
5611 for (uint idx = worker_id; idx < limit; idx += stride) {
5612 DiscoveredList& ref_list = rp->discovered_refs()[idx];
5614 DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive);
5615 while (iter.has_next()) {
5616 // Since discovery is not atomic for the CM ref processor, we
5617 // can see some null referent objects.
5618 iter.load_ptrs(DEBUG_ONLY(true));
5619 oop ref = iter.obj();
5621 // This will filter nulls.
5622 if (iter.is_referent_alive()) {
5623 iter.make_referent_alive();
5624 }
5625 iter.move_to_next();
5626 }
5627 }
5629 // Drain the queue - which may cause stealing
5630 G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _queues, &_terminator);
5631 drain_queue.do_void();
5632 // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure
5633 assert(pss.queue_is_empty(), "should be");
5634 }
5635 };
5637 // Weak Reference processing during an evacuation pause (part 1).
5638 void G1CollectedHeap::process_discovered_references(uint no_of_gc_workers) {
5639 double ref_proc_start = os::elapsedTime();
5641 ReferenceProcessor* rp = _ref_processor_stw;
5642 assert(rp->discovery_enabled(), "should have been enabled");
5644 // Any reference objects, in the collection set, that were 'discovered'
5645 // by the CM ref processor should have already been copied (either by
5646 // applying the external root copy closure to the discovered lists, or
5647 // by following an RSet entry).
5648 //
5649 // But some of the referents, that are in the collection set, that these
5650 // reference objects point to may not have been copied: the STW ref
5651 // processor would have seen that the reference object had already
5652 // been 'discovered' and would have skipped discovering the reference,
5653 // but would not have treated the reference object as a regular oop.
5654 // As a result the copy closure would not have been applied to the
5655 // referent object.
5656 //
5657 // We need to explicitly copy these referent objects - the references
5658 // will be processed at the end of remarking.
5659 //
5660 // We also need to do this copying before we process the reference
5661 // objects discovered by the STW ref processor in case one of these
5662 // referents points to another object which is also referenced by an
5663 // object discovered by the STW ref processor.
5665 assert(!G1CollectedHeap::use_parallel_gc_threads() ||
5666 no_of_gc_workers == workers()->active_workers(),
5667 "Need to reset active GC workers");
5669 set_par_threads(no_of_gc_workers);
5670 G1ParPreserveCMReferentsTask keep_cm_referents(this,
5671 no_of_gc_workers,
5672 _task_queues);
5674 if (G1CollectedHeap::use_parallel_gc_threads()) {
5675 workers()->run_task(&keep_cm_referents);
5676 } else {
5677 keep_cm_referents.work(0);
5678 }
5680 set_par_threads(0);
5682 // Closure to test whether a referent is alive.
5683 G1STWIsAliveClosure is_alive(this);
5685 // Even when parallel reference processing is enabled, the processing
5686 // of JNI refs is serial and performed serially by the current thread
5687 // rather than by a worker. The following PSS will be used for processing
5688 // JNI refs.
5690 // Use only a single queue for this PSS.
5691 G1ParScanThreadState pss(this, 0, NULL);
5693 // We do not embed a reference processor in the copying/scanning
5694 // closures while we're actually processing the discovered
5695 // reference objects.
5696 G1ParScanHeapEvacFailureClosure evac_failure_cl(this, &pss, NULL);
5698 pss.set_evac_failure_closure(&evac_failure_cl);
5700 assert(pss.queue_is_empty(), "pre-condition");
5702 G1ParScanExtRootClosure only_copy_non_heap_cl(this, &pss, NULL);
5704 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(this, &pss, NULL);
5706 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5708 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5709 // We also need to mark copied objects.
5710 copy_non_heap_cl = ©_mark_non_heap_cl;
5711 }
5713 // Keep alive closure.
5714 G1CopyingKeepAliveClosure keep_alive(this, copy_non_heap_cl, &pss);
5716 // Serial Complete GC closure
5717 G1STWDrainQueueClosure drain_queue(this, &pss);
5719 // Setup the soft refs policy...
5720 rp->setup_policy(false);
5722 ReferenceProcessorStats stats;
5723 if (!rp->processing_is_mt()) {
5724 // Serial reference processing...
5725 stats = rp->process_discovered_references(&is_alive,
5726 &keep_alive,
5727 &drain_queue,
5728 NULL,
5729 _gc_timer_stw,
5730 _gc_tracer_stw->gc_id());
5731 } else {
5732 // Parallel reference processing
5733 assert(rp->num_q() == no_of_gc_workers, "sanity");
5734 assert(no_of_gc_workers <= rp->max_num_q(), "sanity");
5736 G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers);
5737 stats = rp->process_discovered_references(&is_alive,
5738 &keep_alive,
5739 &drain_queue,
5740 &par_task_executor,
5741 _gc_timer_stw,
5742 _gc_tracer_stw->gc_id());
5743 }
5745 _gc_tracer_stw->report_gc_reference_stats(stats);
5747 // We have completed copying any necessary live referent objects.
5748 assert(pss.queue_is_empty(), "both queue and overflow should be empty");
5750 double ref_proc_time = os::elapsedTime() - ref_proc_start;
5751 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
5752 }
5754 // Weak Reference processing during an evacuation pause (part 2).
5755 void G1CollectedHeap::enqueue_discovered_references(uint no_of_gc_workers) {
5756 double ref_enq_start = os::elapsedTime();
5758 ReferenceProcessor* rp = _ref_processor_stw;
5759 assert(!rp->discovery_enabled(), "should have been disabled as part of processing");
5761 // Now enqueue any remaining on the discovered lists on to
5762 // the pending list.
5763 if (!rp->processing_is_mt()) {
5764 // Serial reference processing...
5765 rp->enqueue_discovered_references();
5766 } else {
5767 // Parallel reference enqueueing
5769 assert(no_of_gc_workers == workers()->active_workers(),
5770 "Need to reset active workers");
5771 assert(rp->num_q() == no_of_gc_workers, "sanity");
5772 assert(no_of_gc_workers <= rp->max_num_q(), "sanity");
5774 G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers);
5775 rp->enqueue_discovered_references(&par_task_executor);
5776 }
5778 rp->verify_no_references_recorded();
5779 assert(!rp->discovery_enabled(), "should have been disabled");
5781 // FIXME
5782 // CM's reference processing also cleans up the string and symbol tables.
5783 // Should we do that here also? We could, but it is a serial operation
5784 // and could significantly increase the pause time.
5786 double ref_enq_time = os::elapsedTime() - ref_enq_start;
5787 g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0);
5788 }
5790 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info) {
5791 _expand_heap_after_alloc_failure = true;
5792 _evacuation_failed = false;
5794 // Should G1EvacuationFailureALot be in effect for this GC?
5795 NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();)
5797 g1_rem_set()->prepare_for_oops_into_collection_set_do();
5799 // Disable the hot card cache.
5800 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
5801 hot_card_cache->reset_hot_cache_claimed_index();
5802 hot_card_cache->set_use_cache(false);
5804 const uint n_workers = workers()->active_workers();
5805 assert(UseDynamicNumberOfGCThreads ||
5806 n_workers == workers()->total_workers(),
5807 "If not dynamic should be using all the workers");
5808 set_par_threads(n_workers);
5810 init_for_evac_failure(NULL);
5812 rem_set()->prepare_for_younger_refs_iterate(true);
5814 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
5815 double start_par_time_sec = os::elapsedTime();
5816 double end_par_time_sec;
5818 {
5819 G1RootProcessor root_processor(this);
5820 G1ParTask g1_par_task(this, _task_queues, &root_processor);
5821 // InitialMark needs claim bits to keep track of the marked-through CLDs.
5822 if (g1_policy()->during_initial_mark_pause()) {
5823 ClassLoaderDataGraph::clear_claimed_marks();
5824 }
5826 if (G1CollectedHeap::use_parallel_gc_threads()) {
5827 // The individual threads will set their evac-failure closures.
5828 if (ParallelGCVerbose) G1ParScanThreadState::print_termination_stats_hdr();
5829 // These tasks use ShareHeap::_process_strong_tasks
5830 assert(UseDynamicNumberOfGCThreads ||
5831 workers()->active_workers() == workers()->total_workers(),
5832 "If not dynamic should be using all the workers");
5833 workers()->run_task(&g1_par_task);
5834 } else {
5835 g1_par_task.set_for_termination(n_workers);
5836 g1_par_task.work(0);
5837 }
5838 end_par_time_sec = os::elapsedTime();
5840 // Closing the inner scope will execute the destructor
5841 // for the G1RootProcessor object. We record the current
5842 // elapsed time before closing the scope so that time
5843 // taken for the destructor is NOT included in the
5844 // reported parallel time.
5845 }
5847 G1GCPhaseTimes* phase_times = g1_policy()->phase_times();
5849 double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0;
5850 phase_times->record_par_time(par_time_ms);
5852 double code_root_fixup_time_ms =
5853 (os::elapsedTime() - end_par_time_sec) * 1000.0;
5854 phase_times->record_code_root_fixup_time(code_root_fixup_time_ms);
5856 set_par_threads(0);
5858 // Process any discovered reference objects - we have
5859 // to do this _before_ we retire the GC alloc regions
5860 // as we may have to copy some 'reachable' referent
5861 // objects (and their reachable sub-graphs) that were
5862 // not copied during the pause.
5863 process_discovered_references(n_workers);
5865 if (G1StringDedup::is_enabled()) {
5866 double fixup_start = os::elapsedTime();
5868 G1STWIsAliveClosure is_alive(this);
5869 G1KeepAliveClosure keep_alive(this);
5870 G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive, true, phase_times);
5872 double fixup_time_ms = (os::elapsedTime() - fixup_start) * 1000.0;
5873 phase_times->record_string_dedup_fixup_time(fixup_time_ms);
5874 }
5876 _allocator->release_gc_alloc_regions(n_workers, evacuation_info);
5877 g1_rem_set()->cleanup_after_oops_into_collection_set_do();
5879 // Reset and re-enable the hot card cache.
5880 // Note the counts for the cards in the regions in the
5881 // collection set are reset when the collection set is freed.
5882 hot_card_cache->reset_hot_cache();
5883 hot_card_cache->set_use_cache(true);
5885 purge_code_root_memory();
5887 if (g1_policy()->during_initial_mark_pause()) {
5888 // Reset the claim values set during marking the strong code roots
5889 reset_heap_region_claim_values();
5890 }
5892 finalize_for_evac_failure();
5894 if (evacuation_failed()) {
5895 remove_self_forwarding_pointers();
5897 // Reset the G1EvacuationFailureALot counters and flags
5898 // Note: the values are reset only when an actual
5899 // evacuation failure occurs.
5900 NOT_PRODUCT(reset_evacuation_should_fail();)
5901 }
5903 // Enqueue any remaining references remaining on the STW
5904 // reference processor's discovered lists. We need to do
5905 // this after the card table is cleaned (and verified) as
5906 // the act of enqueueing entries on to the pending list
5907 // will log these updates (and dirty their associated
5908 // cards). We need these updates logged to update any
5909 // RSets.
5910 enqueue_discovered_references(n_workers);
5912 redirty_logged_cards();
5913 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
5914 }
5916 void G1CollectedHeap::free_region(HeapRegion* hr,
5917 FreeRegionList* free_list,
5918 bool par,
5919 bool locked) {
5920 assert(!hr->is_free(), "the region should not be free");
5921 assert(!hr->is_empty(), "the region should not be empty");
5922 assert(_hrm.is_available(hr->hrm_index()), "region should be committed");
5923 assert(free_list != NULL, "pre-condition");
5925 if (G1VerifyBitmaps) {
5926 MemRegion mr(hr->bottom(), hr->end());
5927 concurrent_mark()->clearRangePrevBitmap(mr);
5928 }
5930 // Clear the card counts for this region.
5931 // Note: we only need to do this if the region is not young
5932 // (since we don't refine cards in young regions).
5933 if (!hr->is_young()) {
5934 _cg1r->hot_card_cache()->reset_card_counts(hr);
5935 }
5936 hr->hr_clear(par, true /* clear_space */, locked /* locked */);
5937 free_list->add_ordered(hr);
5938 }
5940 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
5941 FreeRegionList* free_list,
5942 bool par) {
5943 assert(hr->startsHumongous(), "this is only for starts humongous regions");
5944 assert(free_list != NULL, "pre-condition");
5946 size_t hr_capacity = hr->capacity();
5947 // We need to read this before we make the region non-humongous,
5948 // otherwise the information will be gone.
5949 uint last_index = hr->last_hc_index();
5950 hr->clear_humongous();
5951 free_region(hr, free_list, par);
5953 uint i = hr->hrm_index() + 1;
5954 while (i < last_index) {
5955 HeapRegion* curr_hr = region_at(i);
5956 assert(curr_hr->continuesHumongous(), "invariant");
5957 curr_hr->clear_humongous();
5958 free_region(curr_hr, free_list, par);
5959 i += 1;
5960 }
5961 }
5963 void G1CollectedHeap::remove_from_old_sets(const HeapRegionSetCount& old_regions_removed,
5964 const HeapRegionSetCount& humongous_regions_removed) {
5965 if (old_regions_removed.length() > 0 || humongous_regions_removed.length() > 0) {
5966 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
5967 _old_set.bulk_remove(old_regions_removed);
5968 _humongous_set.bulk_remove(humongous_regions_removed);
5969 }
5971 }
5973 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) {
5974 assert(list != NULL, "list can't be null");
5975 if (!list->is_empty()) {
5976 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
5977 _hrm.insert_list_into_free_list(list);
5978 }
5979 }
5981 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) {
5982 _allocator->decrease_used(bytes);
5983 }
5985 class G1ParCleanupCTTask : public AbstractGangTask {
5986 G1SATBCardTableModRefBS* _ct_bs;
5987 G1CollectedHeap* _g1h;
5988 HeapRegion* volatile _su_head;
5989 public:
5990 G1ParCleanupCTTask(G1SATBCardTableModRefBS* ct_bs,
5991 G1CollectedHeap* g1h) :
5992 AbstractGangTask("G1 Par Cleanup CT Task"),
5993 _ct_bs(ct_bs), _g1h(g1h) { }
5995 void work(uint worker_id) {
5996 HeapRegion* r;
5997 while (r = _g1h->pop_dirty_cards_region()) {
5998 clear_cards(r);
5999 }
6000 }
6002 void clear_cards(HeapRegion* r) {
6003 // Cards of the survivors should have already been dirtied.
6004 if (!r->is_survivor()) {
6005 _ct_bs->clear(MemRegion(r->bottom(), r->end()));
6006 }
6007 }
6008 };
6010 #ifndef PRODUCT
6011 class G1VerifyCardTableCleanup: public HeapRegionClosure {
6012 G1CollectedHeap* _g1h;
6013 G1SATBCardTableModRefBS* _ct_bs;
6014 public:
6015 G1VerifyCardTableCleanup(G1CollectedHeap* g1h, G1SATBCardTableModRefBS* ct_bs)
6016 : _g1h(g1h), _ct_bs(ct_bs) { }
6017 virtual bool doHeapRegion(HeapRegion* r) {
6018 if (r->is_survivor()) {
6019 _g1h->verify_dirty_region(r);
6020 } else {
6021 _g1h->verify_not_dirty_region(r);
6022 }
6023 return false;
6024 }
6025 };
6027 void G1CollectedHeap::verify_not_dirty_region(HeapRegion* hr) {
6028 // All of the region should be clean.
6029 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
6030 MemRegion mr(hr->bottom(), hr->end());
6031 ct_bs->verify_not_dirty_region(mr);
6032 }
6034 void G1CollectedHeap::verify_dirty_region(HeapRegion* hr) {
6035 // We cannot guarantee that [bottom(),end()] is dirty. Threads
6036 // dirty allocated blocks as they allocate them. The thread that
6037 // retires each region and replaces it with a new one will do a
6038 // maximal allocation to fill in [pre_dummy_top(),end()] but will
6039 // not dirty that area (one less thing to have to do while holding
6040 // a lock). So we can only verify that [bottom(),pre_dummy_top()]
6041 // is dirty.
6042 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
6043 MemRegion mr(hr->bottom(), hr->pre_dummy_top());
6044 if (hr->is_young()) {
6045 ct_bs->verify_g1_young_region(mr);
6046 } else {
6047 ct_bs->verify_dirty_region(mr);
6048 }
6049 }
6051 void G1CollectedHeap::verify_dirty_young_list(HeapRegion* head) {
6052 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
6053 for (HeapRegion* hr = head; hr != NULL; hr = hr->get_next_young_region()) {
6054 verify_dirty_region(hr);
6055 }
6056 }
6058 void G1CollectedHeap::verify_dirty_young_regions() {
6059 verify_dirty_young_list(_young_list->first_region());
6060 }
6062 bool G1CollectedHeap::verify_no_bits_over_tams(const char* bitmap_name, CMBitMapRO* bitmap,
6063 HeapWord* tams, HeapWord* end) {
6064 guarantee(tams <= end,
6065 err_msg("tams: " PTR_FORMAT " end: " PTR_FORMAT, tams, end));
6066 HeapWord* result = bitmap->getNextMarkedWordAddress(tams, end);
6067 if (result < end) {
6068 gclog_or_tty->cr();
6069 gclog_or_tty->print_cr("## wrong marked address on %s bitmap: " PTR_FORMAT,
6070 bitmap_name, result);
6071 gclog_or_tty->print_cr("## %s tams: " PTR_FORMAT " end: " PTR_FORMAT,
6072 bitmap_name, tams, end);
6073 return false;
6074 }
6075 return true;
6076 }
6078 bool G1CollectedHeap::verify_bitmaps(const char* caller, HeapRegion* hr) {
6079 CMBitMapRO* prev_bitmap = concurrent_mark()->prevMarkBitMap();
6080 CMBitMapRO* next_bitmap = (CMBitMapRO*) concurrent_mark()->nextMarkBitMap();
6082 HeapWord* bottom = hr->bottom();
6083 HeapWord* ptams = hr->prev_top_at_mark_start();
6084 HeapWord* ntams = hr->next_top_at_mark_start();
6085 HeapWord* end = hr->end();
6087 bool res_p = verify_no_bits_over_tams("prev", prev_bitmap, ptams, end);
6089 bool res_n = true;
6090 // We reset mark_in_progress() before we reset _cmThread->in_progress() and in this window
6091 // we do the clearing of the next bitmap concurrently. Thus, we can not verify the bitmap
6092 // if we happen to be in that state.
6093 if (mark_in_progress() || !_cmThread->in_progress()) {
6094 res_n = verify_no_bits_over_tams("next", next_bitmap, ntams, end);
6095 }
6096 if (!res_p || !res_n) {
6097 gclog_or_tty->print_cr("#### Bitmap verification failed for " HR_FORMAT,
6098 HR_FORMAT_PARAMS(hr));
6099 gclog_or_tty->print_cr("#### Caller: %s", caller);
6100 return false;
6101 }
6102 return true;
6103 }
6105 void G1CollectedHeap::check_bitmaps(const char* caller, HeapRegion* hr) {
6106 if (!G1VerifyBitmaps) return;
6108 guarantee(verify_bitmaps(caller, hr), "bitmap verification");
6109 }
6111 class G1VerifyBitmapClosure : public HeapRegionClosure {
6112 private:
6113 const char* _caller;
6114 G1CollectedHeap* _g1h;
6115 bool _failures;
6117 public:
6118 G1VerifyBitmapClosure(const char* caller, G1CollectedHeap* g1h) :
6119 _caller(caller), _g1h(g1h), _failures(false) { }
6121 bool failures() { return _failures; }
6123 virtual bool doHeapRegion(HeapRegion* hr) {
6124 if (hr->continuesHumongous()) return false;
6126 bool result = _g1h->verify_bitmaps(_caller, hr);
6127 if (!result) {
6128 _failures = true;
6129 }
6130 return false;
6131 }
6132 };
6134 void G1CollectedHeap::check_bitmaps(const char* caller) {
6135 if (!G1VerifyBitmaps) return;
6137 G1VerifyBitmapClosure cl(caller, this);
6138 heap_region_iterate(&cl);
6139 guarantee(!cl.failures(), "bitmap verification");
6140 }
6142 class G1CheckCSetFastTableClosure : public HeapRegionClosure {
6143 private:
6144 bool _failures;
6145 public:
6146 G1CheckCSetFastTableClosure() : HeapRegionClosure(), _failures(false) { }
6148 virtual bool doHeapRegion(HeapRegion* hr) {
6149 uint i = hr->hrm_index();
6150 InCSetState cset_state = (InCSetState) G1CollectedHeap::heap()->_in_cset_fast_test.get_by_index(i);
6151 if (hr->isHumongous()) {
6152 if (hr->in_collection_set()) {
6153 gclog_or_tty->print_cr("\n## humongous region %u in CSet", i);
6154 _failures = true;
6155 return true;
6156 }
6157 if (cset_state.is_in_cset()) {
6158 gclog_or_tty->print_cr("\n## inconsistent cset state %d for humongous region %u", cset_state.value(), i);
6159 _failures = true;
6160 return true;
6161 }
6162 if (hr->continuesHumongous() && cset_state.is_humongous()) {
6163 gclog_or_tty->print_cr("\n## inconsistent cset state %d for continues humongous region %u", cset_state.value(), i);
6164 _failures = true;
6165 return true;
6166 }
6167 } else {
6168 if (cset_state.is_humongous()) {
6169 gclog_or_tty->print_cr("\n## inconsistent cset state %d for non-humongous region %u", cset_state.value(), i);
6170 _failures = true;
6171 return true;
6172 }
6173 if (hr->in_collection_set() != cset_state.is_in_cset()) {
6174 gclog_or_tty->print_cr("\n## in CSet %d / cset state %d inconsistency for region %u",
6175 hr->in_collection_set(), cset_state.value(), i);
6176 _failures = true;
6177 return true;
6178 }
6179 if (cset_state.is_in_cset()) {
6180 if (hr->is_young() != (cset_state.is_young())) {
6181 gclog_or_tty->print_cr("\n## is_young %d / cset state %d inconsistency for region %u",
6182 hr->is_young(), cset_state.value(), i);
6183 _failures = true;
6184 return true;
6185 }
6186 if (hr->is_old() != (cset_state.is_old())) {
6187 gclog_or_tty->print_cr("\n## is_old %d / cset state %d inconsistency for region %u",
6188 hr->is_old(), cset_state.value(), i);
6189 _failures = true;
6190 return true;
6191 }
6192 }
6193 }
6194 return false;
6195 }
6197 bool failures() const { return _failures; }
6198 };
6200 bool G1CollectedHeap::check_cset_fast_test() {
6201 G1CheckCSetFastTableClosure cl;
6202 _hrm.iterate(&cl);
6203 return !cl.failures();
6204 }
6205 #endif // PRODUCT
6207 void G1CollectedHeap::cleanUpCardTable() {
6208 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
6209 double start = os::elapsedTime();
6211 {
6212 // Iterate over the dirty cards region list.
6213 G1ParCleanupCTTask cleanup_task(ct_bs, this);
6215 if (G1CollectedHeap::use_parallel_gc_threads()) {
6216 set_par_threads();
6217 workers()->run_task(&cleanup_task);
6218 set_par_threads(0);
6219 } else {
6220 while (_dirty_cards_region_list) {
6221 HeapRegion* r = _dirty_cards_region_list;
6222 cleanup_task.clear_cards(r);
6223 _dirty_cards_region_list = r->get_next_dirty_cards_region();
6224 if (_dirty_cards_region_list == r) {
6225 // The last region.
6226 _dirty_cards_region_list = NULL;
6227 }
6228 r->set_next_dirty_cards_region(NULL);
6229 }
6230 }
6231 #ifndef PRODUCT
6232 if (G1VerifyCTCleanup || VerifyAfterGC) {
6233 G1VerifyCardTableCleanup cleanup_verifier(this, ct_bs);
6234 heap_region_iterate(&cleanup_verifier);
6235 }
6236 #endif
6237 }
6239 double elapsed = os::elapsedTime() - start;
6240 g1_policy()->phase_times()->record_clear_ct_time(elapsed * 1000.0);
6241 }
6243 void G1CollectedHeap::free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info) {
6244 size_t pre_used = 0;
6245 FreeRegionList local_free_list("Local List for CSet Freeing");
6247 double young_time_ms = 0.0;
6248 double non_young_time_ms = 0.0;
6250 // Since the collection set is a superset of the the young list,
6251 // all we need to do to clear the young list is clear its
6252 // head and length, and unlink any young regions in the code below
6253 _young_list->clear();
6255 G1CollectorPolicy* policy = g1_policy();
6257 double start_sec = os::elapsedTime();
6258 bool non_young = true;
6260 HeapRegion* cur = cs_head;
6261 int age_bound = -1;
6262 size_t rs_lengths = 0;
6264 while (cur != NULL) {
6265 assert(!is_on_master_free_list(cur), "sanity");
6266 if (non_young) {
6267 if (cur->is_young()) {
6268 double end_sec = os::elapsedTime();
6269 double elapsed_ms = (end_sec - start_sec) * 1000.0;
6270 non_young_time_ms += elapsed_ms;
6272 start_sec = os::elapsedTime();
6273 non_young = false;
6274 }
6275 } else {
6276 if (!cur->is_young()) {
6277 double end_sec = os::elapsedTime();
6278 double elapsed_ms = (end_sec - start_sec) * 1000.0;
6279 young_time_ms += elapsed_ms;
6281 start_sec = os::elapsedTime();
6282 non_young = true;
6283 }
6284 }
6286 rs_lengths += cur->rem_set()->occupied_locked();
6288 HeapRegion* next = cur->next_in_collection_set();
6289 assert(cur->in_collection_set(), "bad CS");
6290 cur->set_next_in_collection_set(NULL);
6291 cur->set_in_collection_set(false);
6293 if (cur->is_young()) {
6294 int index = cur->young_index_in_cset();
6295 assert(index != -1, "invariant");
6296 assert((uint) index < policy->young_cset_region_length(), "invariant");
6297 size_t words_survived = _surviving_young_words[index];
6298 cur->record_surv_words_in_group(words_survived);
6300 // At this point the we have 'popped' cur from the collection set
6301 // (linked via next_in_collection_set()) but it is still in the
6302 // young list (linked via next_young_region()). Clear the
6303 // _next_young_region field.
6304 cur->set_next_young_region(NULL);
6305 } else {
6306 int index = cur->young_index_in_cset();
6307 assert(index == -1, "invariant");
6308 }
6310 assert( (cur->is_young() && cur->young_index_in_cset() > -1) ||
6311 (!cur->is_young() && cur->young_index_in_cset() == -1),
6312 "invariant" );
6314 if (!cur->evacuation_failed()) {
6315 MemRegion used_mr = cur->used_region();
6317 // And the region is empty.
6318 assert(!used_mr.is_empty(), "Should not have empty regions in a CS.");
6319 pre_used += cur->used();
6320 free_region(cur, &local_free_list, false /* par */, true /* locked */);
6321 } else {
6322 cur->uninstall_surv_rate_group();
6323 if (cur->is_young()) {
6324 cur->set_young_index_in_cset(-1);
6325 }
6326 cur->set_evacuation_failed(false);
6327 // The region is now considered to be old.
6328 cur->set_old();
6329 _old_set.add(cur);
6330 evacuation_info.increment_collectionset_used_after(cur->used());
6331 }
6332 cur = next;
6333 }
6335 evacuation_info.set_regions_freed(local_free_list.length());
6336 policy->record_max_rs_lengths(rs_lengths);
6337 policy->cset_regions_freed();
6339 double end_sec = os::elapsedTime();
6340 double elapsed_ms = (end_sec - start_sec) * 1000.0;
6342 if (non_young) {
6343 non_young_time_ms += elapsed_ms;
6344 } else {
6345 young_time_ms += elapsed_ms;
6346 }
6348 prepend_to_freelist(&local_free_list);
6349 decrement_summary_bytes(pre_used);
6350 policy->phase_times()->record_young_free_cset_time_ms(young_time_ms);
6351 policy->phase_times()->record_non_young_free_cset_time_ms(non_young_time_ms);
6352 }
6354 class G1FreeHumongousRegionClosure : public HeapRegionClosure {
6355 private:
6356 FreeRegionList* _free_region_list;
6357 HeapRegionSet* _proxy_set;
6358 HeapRegionSetCount _humongous_regions_removed;
6359 size_t _freed_bytes;
6360 public:
6362 G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) :
6363 _free_region_list(free_region_list), _humongous_regions_removed(), _freed_bytes(0) {
6364 }
6366 virtual bool doHeapRegion(HeapRegion* r) {
6367 if (!r->startsHumongous()) {
6368 return false;
6369 }
6371 G1CollectedHeap* g1h = G1CollectedHeap::heap();
6373 oop obj = (oop)r->bottom();
6374 CMBitMap* next_bitmap = g1h->concurrent_mark()->nextMarkBitMap();
6376 // The following checks whether the humongous object is live are sufficient.
6377 // The main additional check (in addition to having a reference from the roots
6378 // or the young gen) is whether the humongous object has a remembered set entry.
6379 //
6380 // A humongous object cannot be live if there is no remembered set for it
6381 // because:
6382 // - there can be no references from within humongous starts regions referencing
6383 // the object because we never allocate other objects into them.
6384 // (I.e. there are no intra-region references that may be missed by the
6385 // remembered set)
6386 // - as soon there is a remembered set entry to the humongous starts region
6387 // (i.e. it has "escaped" to an old object) this remembered set entry will stay
6388 // until the end of a concurrent mark.
6389 //
6390 // It is not required to check whether the object has been found dead by marking
6391 // or not, in fact it would prevent reclamation within a concurrent cycle, as
6392 // all objects allocated during that time are considered live.
6393 // SATB marking is even more conservative than the remembered set.
6394 // So if at this point in the collection there is no remembered set entry,
6395 // nobody has a reference to it.
6396 // At the start of collection we flush all refinement logs, and remembered sets
6397 // are completely up-to-date wrt to references to the humongous object.
6398 //
6399 // Other implementation considerations:
6400 // - never consider object arrays at this time because they would pose
6401 // considerable effort for cleaning up the the remembered sets. This is
6402 // required because stale remembered sets might reference locations that
6403 // are currently allocated into.
6404 uint region_idx = r->hrm_index();
6405 if (!g1h->is_humongous_reclaim_candidate(region_idx) ||
6406 !r->rem_set()->is_empty()) {
6408 if (G1TraceEagerReclaimHumongousObjects) {
6409 gclog_or_tty->print_cr("Live humongous region %u size " SIZE_FORMAT " start " PTR_FORMAT " length " UINT32_FORMAT " with remset " SIZE_FORMAT " code roots " SIZE_FORMAT " is marked %d reclaim candidate %d type array %d",
6410 region_idx,
6411 obj->size()*HeapWordSize,
6412 r->bottom(),
6413 r->region_num(),
6414 r->rem_set()->occupied(),
6415 r->rem_set()->strong_code_roots_list_length(),
6416 next_bitmap->isMarked(r->bottom()),
6417 g1h->is_humongous_reclaim_candidate(region_idx),
6418 obj->is_typeArray()
6419 );
6420 }
6422 return false;
6423 }
6425 guarantee(obj->is_typeArray(),
6426 err_msg("Only eagerly reclaiming type arrays is supported, but the object "
6427 PTR_FORMAT " is not.",
6428 r->bottom()));
6430 if (G1TraceEagerReclaimHumongousObjects) {
6431 gclog_or_tty->print_cr("Dead humongous region %u size " SIZE_FORMAT " start " PTR_FORMAT " length " UINT32_FORMAT " with remset " SIZE_FORMAT " code roots " SIZE_FORMAT " is marked %d reclaim candidate %d type array %d",
6432 region_idx,
6433 obj->size()*HeapWordSize,
6434 r->bottom(),
6435 r->region_num(),
6436 r->rem_set()->occupied(),
6437 r->rem_set()->strong_code_roots_list_length(),
6438 next_bitmap->isMarked(r->bottom()),
6439 g1h->is_humongous_reclaim_candidate(region_idx),
6440 obj->is_typeArray()
6441 );
6442 }
6443 // Need to clear mark bit of the humongous object if already set.
6444 if (next_bitmap->isMarked(r->bottom())) {
6445 next_bitmap->clear(r->bottom());
6446 }
6447 _freed_bytes += r->used();
6448 r->set_containing_set(NULL);
6449 _humongous_regions_removed.increment(1u, r->capacity());
6450 g1h->free_humongous_region(r, _free_region_list, false);
6452 return false;
6453 }
6455 HeapRegionSetCount& humongous_free_count() {
6456 return _humongous_regions_removed;
6457 }
6459 size_t bytes_freed() const {
6460 return _freed_bytes;
6461 }
6463 size_t humongous_reclaimed() const {
6464 return _humongous_regions_removed.length();
6465 }
6466 };
6468 void G1CollectedHeap::eagerly_reclaim_humongous_regions() {
6469 assert_at_safepoint(true);
6471 if (!G1EagerReclaimHumongousObjects ||
6472 (!_has_humongous_reclaim_candidates && !G1TraceEagerReclaimHumongousObjects)) {
6473 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0);
6474 return;
6475 }
6477 double start_time = os::elapsedTime();
6479 FreeRegionList local_cleanup_list("Local Humongous Cleanup List");
6481 G1FreeHumongousRegionClosure cl(&local_cleanup_list);
6482 heap_region_iterate(&cl);
6484 HeapRegionSetCount empty_set;
6485 remove_from_old_sets(empty_set, cl.humongous_free_count());
6487 G1HRPrinter* hr_printer = _g1h->hr_printer();
6488 if (hr_printer->is_active()) {
6489 FreeRegionListIterator iter(&local_cleanup_list);
6490 while (iter.more_available()) {
6491 HeapRegion* hr = iter.get_next();
6492 hr_printer->cleanup(hr);
6493 }
6494 }
6496 prepend_to_freelist(&local_cleanup_list);
6497 decrement_summary_bytes(cl.bytes_freed());
6499 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0,
6500 cl.humongous_reclaimed());
6501 }
6503 // This routine is similar to the above but does not record
6504 // any policy statistics or update free lists; we are abandoning
6505 // the current incremental collection set in preparation of a
6506 // full collection. After the full GC we will start to build up
6507 // the incremental collection set again.
6508 // This is only called when we're doing a full collection
6509 // and is immediately followed by the tearing down of the young list.
6511 void G1CollectedHeap::abandon_collection_set(HeapRegion* cs_head) {
6512 HeapRegion* cur = cs_head;
6514 while (cur != NULL) {
6515 HeapRegion* next = cur->next_in_collection_set();
6516 assert(cur->in_collection_set(), "bad CS");
6517 cur->set_next_in_collection_set(NULL);
6518 cur->set_in_collection_set(false);
6519 cur->set_young_index_in_cset(-1);
6520 cur = next;
6521 }
6522 }
6524 void G1CollectedHeap::set_free_regions_coming() {
6525 if (G1ConcRegionFreeingVerbose) {
6526 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
6527 "setting free regions coming");
6528 }
6530 assert(!free_regions_coming(), "pre-condition");
6531 _free_regions_coming = true;
6532 }
6534 void G1CollectedHeap::reset_free_regions_coming() {
6535 assert(free_regions_coming(), "pre-condition");
6537 {
6538 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6539 _free_regions_coming = false;
6540 SecondaryFreeList_lock->notify_all();
6541 }
6543 if (G1ConcRegionFreeingVerbose) {
6544 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
6545 "reset free regions coming");
6546 }
6547 }
6549 void G1CollectedHeap::wait_while_free_regions_coming() {
6550 // Most of the time we won't have to wait, so let's do a quick test
6551 // first before we take the lock.
6552 if (!free_regions_coming()) {
6553 return;
6554 }
6556 if (G1ConcRegionFreeingVerbose) {
6557 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
6558 "waiting for free regions");
6559 }
6561 {
6562 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6563 while (free_regions_coming()) {
6564 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
6565 }
6566 }
6568 if (G1ConcRegionFreeingVerbose) {
6569 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
6570 "done waiting for free regions");
6571 }
6572 }
6574 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
6575 assert(heap_lock_held_for_gc(),
6576 "the heap lock should already be held by or for this thread");
6577 _young_list->push_region(hr);
6578 }
6580 class NoYoungRegionsClosure: public HeapRegionClosure {
6581 private:
6582 bool _success;
6583 public:
6584 NoYoungRegionsClosure() : _success(true) { }
6585 bool doHeapRegion(HeapRegion* r) {
6586 if (r->is_young()) {
6587 gclog_or_tty->print_cr("Region [" PTR_FORMAT ", " PTR_FORMAT ") tagged as young",
6588 r->bottom(), r->end());
6589 _success = false;
6590 }
6591 return false;
6592 }
6593 bool success() { return _success; }
6594 };
6596 bool G1CollectedHeap::check_young_list_empty(bool check_heap, bool check_sample) {
6597 bool ret = _young_list->check_list_empty(check_sample);
6599 if (check_heap) {
6600 NoYoungRegionsClosure closure;
6601 heap_region_iterate(&closure);
6602 ret = ret && closure.success();
6603 }
6605 return ret;
6606 }
6608 class TearDownRegionSetsClosure : public HeapRegionClosure {
6609 private:
6610 HeapRegionSet *_old_set;
6612 public:
6613 TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { }
6615 bool doHeapRegion(HeapRegion* r) {
6616 if (r->is_old()) {
6617 _old_set->remove(r);
6618 } else {
6619 // We ignore free regions, we'll empty the free list afterwards.
6620 // We ignore young regions, we'll empty the young list afterwards.
6621 // We ignore humongous regions, we're not tearing down the
6622 // humongous regions set.
6623 assert(r->is_free() || r->is_young() || r->isHumongous(),
6624 "it cannot be another type");
6625 }
6626 return false;
6627 }
6629 ~TearDownRegionSetsClosure() {
6630 assert(_old_set->is_empty(), "post-condition");
6631 }
6632 };
6634 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
6635 assert_at_safepoint(true /* should_be_vm_thread */);
6637 if (!free_list_only) {
6638 TearDownRegionSetsClosure cl(&_old_set);
6639 heap_region_iterate(&cl);
6641 // Note that emptying the _young_list is postponed and instead done as
6642 // the first step when rebuilding the regions sets again. The reason for
6643 // this is that during a full GC string deduplication needs to know if
6644 // a collected region was young or old when the full GC was initiated.
6645 }
6646 _hrm.remove_all_free_regions();
6647 }
6649 class RebuildRegionSetsClosure : public HeapRegionClosure {
6650 private:
6651 bool _free_list_only;
6652 HeapRegionSet* _old_set;
6653 HeapRegionManager* _hrm;
6654 size_t _total_used;
6656 public:
6657 RebuildRegionSetsClosure(bool free_list_only,
6658 HeapRegionSet* old_set, HeapRegionManager* hrm) :
6659 _free_list_only(free_list_only),
6660 _old_set(old_set), _hrm(hrm), _total_used(0) {
6661 assert(_hrm->num_free_regions() == 0, "pre-condition");
6662 if (!free_list_only) {
6663 assert(_old_set->is_empty(), "pre-condition");
6664 }
6665 }
6667 bool doHeapRegion(HeapRegion* r) {
6668 if (r->continuesHumongous()) {
6669 return false;
6670 }
6672 if (r->is_empty()) {
6673 // Add free regions to the free list
6674 r->set_free();
6675 r->set_allocation_context(AllocationContext::system());
6676 _hrm->insert_into_free_list(r);
6677 } else if (!_free_list_only) {
6678 assert(!r->is_young(), "we should not come across young regions");
6680 if (r->isHumongous()) {
6681 // We ignore humongous regions, we left the humongous set unchanged
6682 } else {
6683 // Objects that were compacted would have ended up on regions
6684 // that were previously old or free.
6685 assert(r->is_free() || r->is_old(), "invariant");
6686 // We now consider them old, so register as such.
6687 r->set_old();
6688 _old_set->add(r);
6689 }
6690 _total_used += r->used();
6691 }
6693 return false;
6694 }
6696 size_t total_used() {
6697 return _total_used;
6698 }
6699 };
6701 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
6702 assert_at_safepoint(true /* should_be_vm_thread */);
6704 if (!free_list_only) {
6705 _young_list->empty_list();
6706 }
6708 RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm);
6709 heap_region_iterate(&cl);
6711 if (!free_list_only) {
6712 _allocator->set_used(cl.total_used());
6713 }
6714 assert(_allocator->used_unlocked() == recalculate_used(),
6715 err_msg("inconsistent _allocator->used_unlocked(), "
6716 "value: " SIZE_FORMAT " recalculated: " SIZE_FORMAT,
6717 _allocator->used_unlocked(), recalculate_used()));
6718 }
6720 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) {
6721 _refine_cte_cl->set_concurrent(concurrent);
6722 }
6724 bool G1CollectedHeap::is_in_closed_subset(const void* p) const {
6725 HeapRegion* hr = heap_region_containing(p);
6726 return hr->is_in(p);
6727 }
6729 // Methods for the mutator alloc region
6731 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
6732 bool force) {
6733 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6734 assert(!force || g1_policy()->can_expand_young_list(),
6735 "if force is true we should be able to expand the young list");
6736 bool young_list_full = g1_policy()->is_young_list_full();
6737 if (force || !young_list_full) {
6738 HeapRegion* new_alloc_region = new_region(word_size,
6739 false /* is_old */,
6740 false /* do_expand */);
6741 if (new_alloc_region != NULL) {
6742 set_region_short_lived_locked(new_alloc_region);
6743 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Eden, young_list_full);
6744 check_bitmaps("Mutator Region Allocation", new_alloc_region);
6745 return new_alloc_region;
6746 }
6747 }
6748 return NULL;
6749 }
6751 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
6752 size_t allocated_bytes) {
6753 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6754 assert(alloc_region->is_eden(), "all mutator alloc regions should be eden");
6756 g1_policy()->add_region_to_incremental_cset_lhs(alloc_region);
6757 _allocator->increase_used(allocated_bytes);
6758 _hr_printer.retire(alloc_region);
6759 // We update the eden sizes here, when the region is retired,
6760 // instead of when it's allocated, since this is the point that its
6761 // used space has been recored in _summary_bytes_used.
6762 g1mm()->update_eden_size();
6763 }
6765 void G1CollectedHeap::set_par_threads() {
6766 // Don't change the number of workers. Use the value previously set
6767 // in the workgroup.
6768 assert(G1CollectedHeap::use_parallel_gc_threads(), "shouldn't be here otherwise");
6769 uint n_workers = workers()->active_workers();
6770 assert(UseDynamicNumberOfGCThreads ||
6771 n_workers == workers()->total_workers(),
6772 "Otherwise should be using the total number of workers");
6773 if (n_workers == 0) {
6774 assert(false, "Should have been set in prior evacuation pause.");
6775 n_workers = ParallelGCThreads;
6776 workers()->set_active_workers(n_workers);
6777 }
6778 set_par_threads(n_workers);
6779 }
6781 // Methods for the GC alloc regions
6783 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size,
6784 uint count,
6785 InCSetState dest) {
6786 assert(FreeList_lock->owned_by_self(), "pre-condition");
6788 if (count < g1_policy()->max_regions(dest)) {
6789 const bool is_survivor = (dest.is_young());
6790 HeapRegion* new_alloc_region = new_region(word_size,
6791 !is_survivor,
6792 true /* do_expand */);
6793 if (new_alloc_region != NULL) {
6794 // We really only need to do this for old regions given that we
6795 // should never scan survivors. But it doesn't hurt to do it
6796 // for survivors too.
6797 new_alloc_region->record_timestamp();
6798 if (is_survivor) {
6799 new_alloc_region->set_survivor();
6800 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Survivor);
6801 check_bitmaps("Survivor Region Allocation", new_alloc_region);
6802 } else {
6803 new_alloc_region->set_old();
6804 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Old);
6805 check_bitmaps("Old Region Allocation", new_alloc_region);
6806 }
6807 bool during_im = g1_policy()->during_initial_mark_pause();
6808 new_alloc_region->note_start_of_copying(during_im);
6809 return new_alloc_region;
6810 }
6811 }
6812 return NULL;
6813 }
6815 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
6816 size_t allocated_bytes,
6817 InCSetState dest) {
6818 bool during_im = g1_policy()->during_initial_mark_pause();
6819 alloc_region->note_end_of_copying(during_im);
6820 g1_policy()->record_bytes_copied_during_gc(allocated_bytes);
6821 if (dest.is_young()) {
6822 young_list()->add_survivor_region(alloc_region);
6823 } else {
6824 _old_set.add(alloc_region);
6825 }
6826 _hr_printer.retire(alloc_region);
6827 }
6829 // Heap region set verification
6831 class VerifyRegionListsClosure : public HeapRegionClosure {
6832 private:
6833 HeapRegionSet* _old_set;
6834 HeapRegionSet* _humongous_set;
6835 HeapRegionManager* _hrm;
6837 public:
6838 HeapRegionSetCount _old_count;
6839 HeapRegionSetCount _humongous_count;
6840 HeapRegionSetCount _free_count;
6842 VerifyRegionListsClosure(HeapRegionSet* old_set,
6843 HeapRegionSet* humongous_set,
6844 HeapRegionManager* hrm) :
6845 _old_set(old_set), _humongous_set(humongous_set), _hrm(hrm),
6846 _old_count(), _humongous_count(), _free_count(){ }
6848 bool doHeapRegion(HeapRegion* hr) {
6849 if (hr->continuesHumongous()) {
6850 return false;
6851 }
6853 if (hr->is_young()) {
6854 // TODO
6855 } else if (hr->startsHumongous()) {
6856 assert(hr->containing_set() == _humongous_set, err_msg("Heap region %u is starts humongous but not in humongous set.", hr->hrm_index()));
6857 _humongous_count.increment(1u, hr->capacity());
6858 } else if (hr->is_empty()) {
6859 assert(_hrm->is_free(hr), err_msg("Heap region %u is empty but not on the free list.", hr->hrm_index()));
6860 _free_count.increment(1u, hr->capacity());
6861 } else if (hr->is_old()) {
6862 assert(hr->containing_set() == _old_set, err_msg("Heap region %u is old but not in the old set.", hr->hrm_index()));
6863 _old_count.increment(1u, hr->capacity());
6864 } else {
6865 ShouldNotReachHere();
6866 }
6867 return false;
6868 }
6870 void verify_counts(HeapRegionSet* old_set, HeapRegionSet* humongous_set, HeapRegionManager* free_list) {
6871 guarantee(old_set->length() == _old_count.length(), err_msg("Old set count mismatch. Expected %u, actual %u.", old_set->length(), _old_count.length()));
6872 guarantee(old_set->total_capacity_bytes() == _old_count.capacity(), err_msg("Old set capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
6873 old_set->total_capacity_bytes(), _old_count.capacity()));
6875 guarantee(humongous_set->length() == _humongous_count.length(), err_msg("Hum set count mismatch. Expected %u, actual %u.", humongous_set->length(), _humongous_count.length()));
6876 guarantee(humongous_set->total_capacity_bytes() == _humongous_count.capacity(), err_msg("Hum set capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
6877 humongous_set->total_capacity_bytes(), _humongous_count.capacity()));
6879 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()));
6880 guarantee(free_list->total_capacity_bytes() == _free_count.capacity(), err_msg("Free list capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
6881 free_list->total_capacity_bytes(), _free_count.capacity()));
6882 }
6883 };
6885 void G1CollectedHeap::verify_region_sets() {
6886 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6888 // First, check the explicit lists.
6889 _hrm.verify();
6890 {
6891 // Given that a concurrent operation might be adding regions to
6892 // the secondary free list we have to take the lock before
6893 // verifying it.
6894 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6895 _secondary_free_list.verify_list();
6896 }
6898 // If a concurrent region freeing operation is in progress it will
6899 // be difficult to correctly attributed any free regions we come
6900 // across to the correct free list given that they might belong to
6901 // one of several (free_list, secondary_free_list, any local lists,
6902 // etc.). So, if that's the case we will skip the rest of the
6903 // verification operation. Alternatively, waiting for the concurrent
6904 // operation to complete will have a non-trivial effect on the GC's
6905 // operation (no concurrent operation will last longer than the
6906 // interval between two calls to verification) and it might hide
6907 // any issues that we would like to catch during testing.
6908 if (free_regions_coming()) {
6909 return;
6910 }
6912 // Make sure we append the secondary_free_list on the free_list so
6913 // that all free regions we will come across can be safely
6914 // attributed to the free_list.
6915 append_secondary_free_list_if_not_empty_with_lock();
6917 // Finally, make sure that the region accounting in the lists is
6918 // consistent with what we see in the heap.
6920 VerifyRegionListsClosure cl(&_old_set, &_humongous_set, &_hrm);
6921 heap_region_iterate(&cl);
6922 cl.verify_counts(&_old_set, &_humongous_set, &_hrm);
6923 }
6925 // Optimized nmethod scanning
6927 class RegisterNMethodOopClosure: public OopClosure {
6928 G1CollectedHeap* _g1h;
6929 nmethod* _nm;
6931 template <class T> void do_oop_work(T* p) {
6932 T heap_oop = oopDesc::load_heap_oop(p);
6933 if (!oopDesc::is_null(heap_oop)) {
6934 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
6935 HeapRegion* hr = _g1h->heap_region_containing(obj);
6936 assert(!hr->continuesHumongous(),
6937 err_msg("trying to add code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
6938 " starting at " HR_FORMAT,
6939 _nm, HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())));
6941 // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries.
6942 hr->add_strong_code_root_locked(_nm);
6943 }
6944 }
6946 public:
6947 RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
6948 _g1h(g1h), _nm(nm) {}
6950 void do_oop(oop* p) { do_oop_work(p); }
6951 void do_oop(narrowOop* p) { do_oop_work(p); }
6952 };
6954 class UnregisterNMethodOopClosure: public OopClosure {
6955 G1CollectedHeap* _g1h;
6956 nmethod* _nm;
6958 template <class T> void do_oop_work(T* p) {
6959 T heap_oop = oopDesc::load_heap_oop(p);
6960 if (!oopDesc::is_null(heap_oop)) {
6961 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
6962 HeapRegion* hr = _g1h->heap_region_containing(obj);
6963 assert(!hr->continuesHumongous(),
6964 err_msg("trying to remove code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
6965 " starting at " HR_FORMAT,
6966 _nm, HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())));
6968 hr->remove_strong_code_root(_nm);
6969 }
6970 }
6972 public:
6973 UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
6974 _g1h(g1h), _nm(nm) {}
6976 void do_oop(oop* p) { do_oop_work(p); }
6977 void do_oop(narrowOop* p) { do_oop_work(p); }
6978 };
6980 void G1CollectedHeap::register_nmethod(nmethod* nm) {
6981 CollectedHeap::register_nmethod(nm);
6983 guarantee(nm != NULL, "sanity");
6984 RegisterNMethodOopClosure reg_cl(this, nm);
6985 nm->oops_do(®_cl);
6986 }
6988 void G1CollectedHeap::unregister_nmethod(nmethod* nm) {
6989 CollectedHeap::unregister_nmethod(nm);
6991 guarantee(nm != NULL, "sanity");
6992 UnregisterNMethodOopClosure reg_cl(this, nm);
6993 nm->oops_do(®_cl, true);
6994 }
6996 void G1CollectedHeap::purge_code_root_memory() {
6997 double purge_start = os::elapsedTime();
6998 G1CodeRootSet::purge();
6999 double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0;
7000 g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms);
7001 }
7003 class RebuildStrongCodeRootClosure: public CodeBlobClosure {
7004 G1CollectedHeap* _g1h;
7006 public:
7007 RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) :
7008 _g1h(g1h) {}
7010 void do_code_blob(CodeBlob* cb) {
7011 nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL;
7012 if (nm == NULL) {
7013 return;
7014 }
7016 if (ScavengeRootsInCode) {
7017 _g1h->register_nmethod(nm);
7018 }
7019 }
7020 };
7022 void G1CollectedHeap::rebuild_strong_code_roots() {
7023 RebuildStrongCodeRootClosure blob_cl(this);
7024 CodeCache::blobs_do(&blob_cl);
7025 }