1 /*
2 * Copyright (c) 2001, 2011, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "code/icBuffer.hpp"
27 #include "gc_implementation/g1/bufferingOopClosure.hpp"
28 #include "gc_implementation/g1/concurrentG1Refine.hpp"
29 #include "gc_implementation/g1/concurrentG1RefineThread.hpp"
30 #include "gc_implementation/g1/concurrentMarkThread.inline.hpp"
31 #include "gc_implementation/g1/g1AllocRegion.inline.hpp"
32 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
33 #include "gc_implementation/g1/g1CollectorPolicy.hpp"
34 #include "gc_implementation/g1/g1ErgoVerbose.hpp"
35 #include "gc_implementation/g1/g1MarkSweep.hpp"
36 #include "gc_implementation/g1/g1OopClosures.inline.hpp"
37 #include "gc_implementation/g1/g1RemSet.inline.hpp"
38 #include "gc_implementation/g1/heapRegionRemSet.hpp"
39 #include "gc_implementation/g1/heapRegionSeq.inline.hpp"
40 #include "gc_implementation/g1/vm_operations_g1.hpp"
41 #include "gc_implementation/shared/isGCActiveMark.hpp"
42 #include "memory/gcLocker.inline.hpp"
43 #include "memory/genOopClosures.inline.hpp"
44 #include "memory/generationSpec.hpp"
45 #include "oops/oop.inline.hpp"
46 #include "oops/oop.pcgc.inline.hpp"
47 #include "runtime/aprofiler.hpp"
48 #include "runtime/vmThread.hpp"
49
50 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;
51
52 // turn it on so that the contents of the young list (scan-only /
53 // to-be-collected) are printed at "strategic" points before / during
54 // / after the collection --- this is useful for debugging
55 #define YOUNG_LIST_VERBOSE 0
56 // CURRENT STATUS
57 // This file is under construction. Search for "FIXME".
58
59 // INVARIANTS/NOTES
60 //
61 // All allocation activity covered by the G1CollectedHeap interface is
62 // serialized by acquiring the HeapLock. This happens in mem_allocate
63 // and allocate_new_tlab, which are the "entry" points to the
64 // allocation code from the rest of the JVM. (Note that this does not
65 // apply to TLAB allocation, which is not part of this interface: it
66 // is done by clients of this interface.)
67
68 // Local to this file.
69
70 class RefineCardTableEntryClosure: public CardTableEntryClosure {
71 SuspendibleThreadSet* _sts;
72 G1RemSet* _g1rs;
73 ConcurrentG1Refine* _cg1r;
74 bool _concurrent;
75 public:
76 RefineCardTableEntryClosure(SuspendibleThreadSet* sts,
77 G1RemSet* g1rs,
78 ConcurrentG1Refine* cg1r) :
79 _sts(sts), _g1rs(g1rs), _cg1r(cg1r), _concurrent(true)
80 {}
81 bool do_card_ptr(jbyte* card_ptr, int worker_i) {
82 bool oops_into_cset = _g1rs->concurrentRefineOneCard(card_ptr, worker_i, false);
83 // This path is executed by the concurrent refine or mutator threads,
84 // concurrently, and so we do not care if card_ptr contains references
85 // that point into the collection set.
86 assert(!oops_into_cset, "should be");
87
88 if (_concurrent && _sts->should_yield()) {
89 // Caller will actually yield.
90 return false;
91 }
92 // Otherwise, we finished successfully; return true.
93 return true;
94 }
95 void set_concurrent(bool b) { _concurrent = b; }
96 };
97
98
99 class ClearLoggedCardTableEntryClosure: public CardTableEntryClosure {
100 int _calls;
101 G1CollectedHeap* _g1h;
102 CardTableModRefBS* _ctbs;
103 int _histo[256];
104 public:
105 ClearLoggedCardTableEntryClosure() :
106 _calls(0)
107 {
108 _g1h = G1CollectedHeap::heap();
109 _ctbs = (CardTableModRefBS*)_g1h->barrier_set();
110 for (int i = 0; i < 256; i++) _histo[i] = 0;
111 }
112 bool do_card_ptr(jbyte* card_ptr, int worker_i) {
113 if (_g1h->is_in_reserved(_ctbs->addr_for(card_ptr))) {
114 _calls++;
115 unsigned char* ujb = (unsigned char*)card_ptr;
116 int ind = (int)(*ujb);
117 _histo[ind]++;
118 *card_ptr = -1;
119 }
120 return true;
121 }
122 int calls() { return _calls; }
123 void print_histo() {
124 gclog_or_tty->print_cr("Card table value histogram:");
125 for (int i = 0; i < 256; i++) {
126 if (_histo[i] != 0) {
127 gclog_or_tty->print_cr(" %d: %d", i, _histo[i]);
128 }
129 }
130 }
131 };
132
133 class RedirtyLoggedCardTableEntryClosure: public CardTableEntryClosure {
134 int _calls;
135 G1CollectedHeap* _g1h;
136 CardTableModRefBS* _ctbs;
137 public:
138 RedirtyLoggedCardTableEntryClosure() :
139 _calls(0)
140 {
141 _g1h = G1CollectedHeap::heap();
142 _ctbs = (CardTableModRefBS*)_g1h->barrier_set();
143 }
144 bool do_card_ptr(jbyte* card_ptr, int worker_i) {
145 if (_g1h->is_in_reserved(_ctbs->addr_for(card_ptr))) {
146 _calls++;
147 *card_ptr = 0;
148 }
149 return true;
150 }
151 int calls() { return _calls; }
152 };
153
154 class RedirtyLoggedCardTableEntryFastClosure : public CardTableEntryClosure {
155 public:
156 bool do_card_ptr(jbyte* card_ptr, int worker_i) {
157 *card_ptr = CardTableModRefBS::dirty_card_val();
158 return true;
159 }
160 };
161
162 YoungList::YoungList(G1CollectedHeap* g1h)
163 : _g1h(g1h), _head(NULL),
164 _length(0),
165 _last_sampled_rs_lengths(0),
166 _survivor_head(NULL), _survivor_tail(NULL), _survivor_length(0)
167 {
168 guarantee( check_list_empty(false), "just making sure..." );
169 }
170
171 void YoungList::push_region(HeapRegion *hr) {
172 assert(!hr->is_young(), "should not already be young");
173 assert(hr->get_next_young_region() == NULL, "cause it should!");
174
175 hr->set_next_young_region(_head);
176 _head = hr;
177
178 hr->set_young();
179 double yg_surv_rate = _g1h->g1_policy()->predict_yg_surv_rate((int)_length);
180 ++_length;
181 }
182
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!");
186
187 hr->set_next_young_region(_survivor_head);
188 if (_survivor_head == NULL) {
189 _survivor_tail = hr;
190 }
191 _survivor_head = hr;
192
193 ++_survivor_length;
194 }
195
196 void YoungList::empty_list(HeapRegion* list) {
197 while (list != NULL) {
198 HeapRegion* next = list->get_next_young_region();
199 list->set_next_young_region(NULL);
200 list->uninstall_surv_rate_group();
201 list->set_not_young();
202 list = next;
203 }
204 }
205
206 void YoungList::empty_list() {
207 assert(check_list_well_formed(), "young list should be well formed");
208
209 empty_list(_head);
210 _head = NULL;
211 _length = 0;
212
213 empty_list(_survivor_head);
214 _survivor_head = NULL;
215 _survivor_tail = NULL;
216 _survivor_length = 0;
217
218 _last_sampled_rs_lengths = 0;
219
220 assert(check_list_empty(false), "just making sure...");
221 }
222
223 bool YoungList::check_list_well_formed() {
224 bool ret = true;
225
226 size_t length = 0;
227 HeapRegion* curr = _head;
228 HeapRegion* last = NULL;
229 while (curr != NULL) {
230 if (!curr->is_young()) {
231 gclog_or_tty->print_cr("### YOUNG REGION "PTR_FORMAT"-"PTR_FORMAT" "
232 "incorrectly tagged (y: %d, surv: %d)",
233 curr->bottom(), curr->end(),
234 curr->is_young(), curr->is_survivor());
235 ret = false;
236 }
237 ++length;
238 last = curr;
239 curr = curr->get_next_young_region();
240 }
241 ret = ret && (length == _length);
242
243 if (!ret) {
244 gclog_or_tty->print_cr("### YOUNG LIST seems not well formed!");
245 gclog_or_tty->print_cr("### list has %d entries, _length is %d",
246 length, _length);
247 }
248
249 return ret;
250 }
251
252 bool YoungList::check_list_empty(bool check_sample) {
253 bool ret = true;
254
255 if (_length != 0) {
256 gclog_or_tty->print_cr("### YOUNG LIST should have 0 length, not %d",
257 _length);
258 ret = false;
259 }
260 if (check_sample && _last_sampled_rs_lengths != 0) {
261 gclog_or_tty->print_cr("### YOUNG LIST has non-zero last sampled RS lengths");
262 ret = false;
263 }
264 if (_head != NULL) {
265 gclog_or_tty->print_cr("### YOUNG LIST does not have a NULL head");
266 ret = false;
267 }
268 if (!ret) {
269 gclog_or_tty->print_cr("### YOUNG LIST does not seem empty");
270 }
271
272 return ret;
273 }
274
275 void
276 YoungList::rs_length_sampling_init() {
277 _sampled_rs_lengths = 0;
278 _curr = _head;
279 }
280
281 bool
282 YoungList::rs_length_sampling_more() {
283 return _curr != NULL;
284 }
285
286 void
287 YoungList::rs_length_sampling_next() {
288 assert( _curr != NULL, "invariant" );
289 size_t rs_length = _curr->rem_set()->occupied();
290
291 _sampled_rs_lengths += rs_length;
292
293 // The current region may not yet have been added to the
294 // incremental collection set (it gets added when it is
295 // retired as the current allocation region).
296 if (_curr->in_collection_set()) {
297 // Update the collection set policy information for this region
298 _g1h->g1_policy()->update_incremental_cset_info(_curr, rs_length);
299 }
300
301 _curr = _curr->get_next_young_region();
302 if (_curr == NULL) {
303 _last_sampled_rs_lengths = _sampled_rs_lengths;
304 // gclog_or_tty->print_cr("last sampled RS lengths = %d", _last_sampled_rs_lengths);
305 }
306 }
307
308 void
309 YoungList::reset_auxilary_lists() {
310 guarantee( is_empty(), "young list should be empty" );
311 assert(check_list_well_formed(), "young list should be well formed");
312
313 // Add survivor regions to SurvRateGroup.
314 _g1h->g1_policy()->note_start_adding_survivor_regions();
315 _g1h->g1_policy()->finished_recalculating_age_indexes(true /* is_survivors */);
316
317 for (HeapRegion* curr = _survivor_head;
318 curr != NULL;
319 curr = curr->get_next_young_region()) {
320 _g1h->g1_policy()->set_region_survivors(curr);
321
322 // The region is a non-empty survivor so let's add it to
323 // the incremental collection set for the next evacuation
324 // pause.
325 _g1h->g1_policy()->add_region_to_incremental_cset_rhs(curr);
326 }
327 _g1h->g1_policy()->note_stop_adding_survivor_regions();
328
329 _head = _survivor_head;
330 _length = _survivor_length;
331 if (_survivor_head != NULL) {
332 assert(_survivor_tail != NULL, "cause it shouldn't be");
333 assert(_survivor_length > 0, "invariant");
334 _survivor_tail->set_next_young_region(NULL);
335 }
336
337 // Don't clear the survivor list handles until the start of
338 // the next evacuation pause - we need it in order to re-tag
339 // the survivor regions from this evacuation pause as 'young'
340 // at the start of the next.
341
342 _g1h->g1_policy()->finished_recalculating_age_indexes(false /* is_survivors */);
343
344 assert(check_list_well_formed(), "young list should be well formed");
345 }
346
347 void YoungList::print() {
348 HeapRegion* lists[] = {_head, _survivor_head};
349 const char* names[] = {"YOUNG", "SURVIVOR"};
350
351 for (unsigned int list = 0; list < ARRAY_SIZE(lists); ++list) {
352 gclog_or_tty->print_cr("%s LIST CONTENTS", names[list]);
353 HeapRegion *curr = lists[list];
354 if (curr == NULL)
355 gclog_or_tty->print_cr(" empty");
356 while (curr != NULL) {
357 gclog_or_tty->print_cr(" [%08x-%08x], t: %08x, P: %08x, N: %08x, C: %08x, "
358 "age: %4d, y: %d, surv: %d",
359 curr->bottom(), curr->end(),
360 curr->top(),
361 curr->prev_top_at_mark_start(),
362 curr->next_top_at_mark_start(),
363 curr->top_at_conc_mark_count(),
364 curr->age_in_surv_rate_group_cond(),
365 curr->is_young(),
366 curr->is_survivor());
367 curr = curr->get_next_young_region();
368 }
369 }
370
371 gclog_or_tty->print_cr("");
372 }
373
374 void G1CollectedHeap::push_dirty_cards_region(HeapRegion* hr)
375 {
376 // Claim the right to put the region on the dirty cards region list
377 // by installing a self pointer.
378 HeapRegion* next = hr->get_next_dirty_cards_region();
379 if (next == NULL) {
380 HeapRegion* res = (HeapRegion*)
381 Atomic::cmpxchg_ptr(hr, hr->next_dirty_cards_region_addr(),
382 NULL);
383 if (res == NULL) {
384 HeapRegion* head;
385 do {
386 // Put the region to the dirty cards region list.
387 head = _dirty_cards_region_list;
388 next = (HeapRegion*)
389 Atomic::cmpxchg_ptr(hr, &_dirty_cards_region_list, head);
390 if (next == head) {
391 assert(hr->get_next_dirty_cards_region() == hr,
392 "hr->get_next_dirty_cards_region() != hr");
393 if (next == NULL) {
394 // The last region in the list points to itself.
395 hr->set_next_dirty_cards_region(hr);
396 } else {
397 hr->set_next_dirty_cards_region(next);
398 }
399 }
400 } while (next != head);
401 }
402 }
403 }
404
405 HeapRegion* G1CollectedHeap::pop_dirty_cards_region()
406 {
407 HeapRegion* head;
408 HeapRegion* hr;
409 do {
410 head = _dirty_cards_region_list;
411 if (head == NULL) {
412 return NULL;
413 }
414 HeapRegion* new_head = head->get_next_dirty_cards_region();
415 if (head == new_head) {
416 // The last region.
417 new_head = NULL;
418 }
419 hr = (HeapRegion*)Atomic::cmpxchg_ptr(new_head, &_dirty_cards_region_list,
420 head);
421 } while (hr != head);
422 assert(hr != NULL, "invariant");
423 hr->set_next_dirty_cards_region(NULL);
424 return hr;
425 }
426
427 void G1CollectedHeap::stop_conc_gc_threads() {
428 _cg1r->stop();
429 _cmThread->stop();
430 }
431
432 #ifdef ASSERT
433 // A region is added to the collection set as it is retired
434 // so an address p can point to a region which will be in the
435 // collection set but has not yet been retired. This method
436 // therefore is only accurate during a GC pause after all
437 // regions have been retired. It is used for debugging
438 // to check if an nmethod has references to objects that can
439 // be move during a partial collection. Though it can be
440 // inaccurate, it is sufficient for G1 because the conservative
441 // implementation of is_scavengable() for G1 will indicate that
442 // all nmethods must be scanned during a partial collection.
443 bool G1CollectedHeap::is_in_partial_collection(const void* p) {
444 HeapRegion* hr = heap_region_containing(p);
445 return hr != NULL && hr->in_collection_set();
446 }
447 #endif
448
449 // Returns true if the reference points to an object that
450 // can move in an incremental collecction.
451 bool G1CollectedHeap::is_scavengable(const void* p) {
452 G1CollectedHeap* g1h = G1CollectedHeap::heap();
453 G1CollectorPolicy* g1p = g1h->g1_policy();
454 HeapRegion* hr = heap_region_containing(p);
455 if (hr == NULL) {
456 // perm gen (or null)
457 return false;
458 } else {
459 return !hr->isHumongous();
460 }
461 }
462
463 void G1CollectedHeap::check_ct_logs_at_safepoint() {
464 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
465 CardTableModRefBS* ct_bs = (CardTableModRefBS*)barrier_set();
466
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();
471
472 // First clear the logged cards.
473 ClearLoggedCardTableEntryClosure clear;
474 dcqs.set_closure(&clear);
475 dcqs.apply_closure_to_all_completed_buffers();
476 dcqs.iterate_closure_all_threads(false);
477 clear.print_histo();
478
479 // Now ensure that there's no dirty cards.
480 CountNonCleanMemRegionClosure count2(this);
481 ct_bs->mod_card_iterate(&count2);
482 if (count2.n() != 0) {
483 gclog_or_tty->print_cr("Card table has %d entries; %d originally",
484 count2.n(), orig_count);
485 }
486 guarantee(count2.n() == 0, "Card table should be clean.");
487
488 RedirtyLoggedCardTableEntryClosure redirty;
489 JavaThread::dirty_card_queue_set().set_closure(&redirty);
490 dcqs.apply_closure_to_all_completed_buffers();
491 dcqs.iterate_closure_all_threads(false);
492 gclog_or_tty->print_cr("Log entries = %d, dirty cards = %d.",
493 clear.calls(), orig_count);
494 guarantee(redirty.calls() == clear.calls(),
495 "Or else mechanism is broken.");
496
497 CountNonCleanMemRegionClosure count3(this);
498 ct_bs->mod_card_iterate(&count3);
499 if (count3.n() != orig_count) {
500 gclog_or_tty->print_cr("Should have restored them all: orig = %d, final = %d.",
501 orig_count, count3.n());
502 guarantee(count3.n() >= orig_count, "Should have restored them all.");
503 }
504
505 JavaThread::dirty_card_queue_set().set_closure(_refine_cte_cl);
506 }
507
508 // Private class members.
509
510 G1CollectedHeap* G1CollectedHeap::_g1h;
511
512 // Private methods.
513
514 HeapRegion*
515 G1CollectedHeap::new_region_try_secondary_free_list() {
516 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
517 while (!_secondary_free_list.is_empty() || free_regions_coming()) {
518 if (!_secondary_free_list.is_empty()) {
519 if (G1ConcRegionFreeingVerbose) {
520 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
521 "secondary_free_list has "SIZE_FORMAT" entries",
522 _secondary_free_list.length());
523 }
524 // It looks as if there are free regions available on the
525 // secondary_free_list. Let's move them to the free_list and try
526 // again to allocate from it.
527 append_secondary_free_list();
528
529 assert(!_free_list.is_empty(), "if the secondary_free_list was not "
530 "empty we should have moved at least one entry to the free_list");
531 HeapRegion* res = _free_list.remove_head();
532 if (G1ConcRegionFreeingVerbose) {
533 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
534 "allocated "HR_FORMAT" from secondary_free_list",
535 HR_FORMAT_PARAMS(res));
536 }
537 return res;
538 }
539
540 // Wait here until we get notifed either when (a) there are no
541 // more free regions coming or (b) some regions have been moved on
542 // the secondary_free_list.
543 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
544 }
545
546 if (G1ConcRegionFreeingVerbose) {
547 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
548 "could not allocate from secondary_free_list");
549 }
550 return NULL;
551 }
552
553 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool do_expand) {
554 assert(!isHumongous(word_size) ||
555 word_size <= (size_t) HeapRegion::GrainWords,
556 "the only time we use this to allocate a humongous region is "
557 "when we are allocating a single humongous region");
558
559 HeapRegion* res;
560 if (G1StressConcRegionFreeing) {
561 if (!_secondary_free_list.is_empty()) {
562 if (G1ConcRegionFreeingVerbose) {
563 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
564 "forced to look at the secondary_free_list");
565 }
566 res = new_region_try_secondary_free_list();
567 if (res != NULL) {
568 return res;
569 }
570 }
571 }
572 res = _free_list.remove_head_or_null();
573 if (res == NULL) {
574 if (G1ConcRegionFreeingVerbose) {
575 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
576 "res == NULL, trying the secondary_free_list");
577 }
578 res = new_region_try_secondary_free_list();
579 }
580 if (res == NULL && do_expand) {
581 ergo_verbose1(ErgoHeapSizing,
582 "attempt heap expansion",
583 ergo_format_reason("region allocation request failed")
584 ergo_format_byte("allocation request"),
585 word_size * HeapWordSize);
586 if (expand(word_size * HeapWordSize)) {
587 // Even though the heap was expanded, it might not have reached
588 // the desired size. So, we cannot assume that the allocation
589 // will succeed.
590 res = _free_list.remove_head_or_null();
591 }
592 }
593 return res;
594 }
595
596 size_t G1CollectedHeap::humongous_obj_allocate_find_first(size_t num_regions,
597 size_t word_size) {
598 assert(isHumongous(word_size), "word_size should be humongous");
599 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
600
601 size_t first = G1_NULL_HRS_INDEX;
602 if (num_regions == 1) {
603 // Only one region to allocate, no need to go through the slower
604 // path. The caller will attempt the expasion if this fails, so
605 // let's not try to expand here too.
606 HeapRegion* hr = new_region(word_size, false /* do_expand */);
607 if (hr != NULL) {
608 first = hr->hrs_index();
609 } else {
610 first = G1_NULL_HRS_INDEX;
611 }
612 } else {
613 // We can't allocate humongous regions while cleanupComplete() is
614 // running, since some of the regions we find to be empty might not
615 // yet be added to the free list and it is not straightforward to
616 // know which list they are on so that we can remove them. Note
617 // that we only need to do this if we need to allocate more than
618 // one region to satisfy the current humongous allocation
619 // request. If we are only allocating one region we use the common
620 // region allocation code (see above).
621 wait_while_free_regions_coming();
622 append_secondary_free_list_if_not_empty_with_lock();
623
624 if (free_regions() >= num_regions) {
625 first = _hrs.find_contiguous(num_regions);
626 if (first != G1_NULL_HRS_INDEX) {
627 for (size_t i = first; i < first + num_regions; ++i) {
628 HeapRegion* hr = region_at(i);
629 assert(hr->is_empty(), "sanity");
630 assert(is_on_master_free_list(hr), "sanity");
631 hr->set_pending_removal(true);
632 }
633 _free_list.remove_all_pending(num_regions);
634 }
635 }
636 }
637 return first;
638 }
639
640 HeapWord*
641 G1CollectedHeap::humongous_obj_allocate_initialize_regions(size_t first,
642 size_t num_regions,
643 size_t word_size) {
644 assert(first != G1_NULL_HRS_INDEX, "pre-condition");
645 assert(isHumongous(word_size), "word_size should be humongous");
646 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
647
648 // Index of last region in the series + 1.
649 size_t last = first + num_regions;
650
651 // We need to initialize the region(s) we just discovered. This is
652 // a bit tricky given that it can happen concurrently with
653 // refinement threads refining cards on these regions and
654 // potentially wanting to refine the BOT as they are scanning
655 // those cards (this can happen shortly after a cleanup; see CR
656 // 6991377). So we have to set up the region(s) carefully and in
657 // a specific order.
658
659 // The word size sum of all the regions we will allocate.
660 size_t word_size_sum = num_regions * HeapRegion::GrainWords;
661 assert(word_size <= word_size_sum, "sanity");
662
663 // This will be the "starts humongous" region.
664 HeapRegion* first_hr = region_at(first);
665 // The header of the new object will be placed at the bottom of
666 // the first region.
667 HeapWord* new_obj = first_hr->bottom();
668 // This will be the new end of the first region in the series that
669 // should also match the end of the last region in the seriers.
670 HeapWord* new_end = new_obj + word_size_sum;
671 // This will be the new top of the first region that will reflect
672 // this allocation.
673 HeapWord* new_top = new_obj + word_size;
674
675 // First, we need to zero the header of the space that we will be
676 // allocating. When we update top further down, some refinement
677 // threads might try to scan the region. By zeroing the header we
678 // ensure that any thread that will try to scan the region will
679 // come across the zero klass word and bail out.
680 //
681 // NOTE: It would not have been correct to have used
682 // CollectedHeap::fill_with_object() and make the space look like
683 // an int array. The thread that is doing the allocation will
684 // later update the object header to a potentially different array
685 // type and, for a very short period of time, the klass and length
686 // fields will be inconsistent. This could cause a refinement
687 // thread to calculate the object size incorrectly.
688 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
689
690 // We will set up the first region as "starts humongous". This
691 // will also update the BOT covering all the regions to reflect
692 // that there is a single object that starts at the bottom of the
693 // first region.
694 first_hr->set_startsHumongous(new_top, new_end);
695
696 // Then, if there are any, we will set up the "continues
697 // humongous" regions.
698 HeapRegion* hr = NULL;
699 for (size_t i = first + 1; i < last; ++i) {
700 hr = region_at(i);
701 hr->set_continuesHumongous(first_hr);
702 }
703 // If we have "continues humongous" regions (hr != NULL), then the
704 // end of the last one should match new_end.
705 assert(hr == NULL || hr->end() == new_end, "sanity");
706
707 // Up to this point no concurrent thread would have been able to
708 // do any scanning on any region in this series. All the top
709 // fields still point to bottom, so the intersection between
710 // [bottom,top] and [card_start,card_end] will be empty. Before we
711 // update the top fields, we'll do a storestore to make sure that
712 // no thread sees the update to top before the zeroing of the
713 // object header and the BOT initialization.
714 OrderAccess::storestore();
715
716 // Now that the BOT and the object header have been initialized,
717 // we can update top of the "starts humongous" region.
718 assert(first_hr->bottom() < new_top && new_top <= first_hr->end(),
719 "new_top should be in this region");
720 first_hr->set_top(new_top);
721 if (_hr_printer.is_active()) {
722 HeapWord* bottom = first_hr->bottom();
723 HeapWord* end = first_hr->orig_end();
724 if ((first + 1) == last) {
725 // the series has a single humongous region
726 _hr_printer.alloc(G1HRPrinter::SingleHumongous, first_hr, new_top);
727 } else {
728 // the series has more than one humongous regions
729 _hr_printer.alloc(G1HRPrinter::StartsHumongous, first_hr, end);
730 }
731 }
732
733 // Now, we will update the top fields of the "continues humongous"
734 // regions. The reason we need to do this is that, otherwise,
735 // these regions would look empty and this will confuse parts of
736 // G1. For example, the code that looks for a consecutive number
737 // of empty regions will consider them empty and try to
738 // re-allocate them. We can extend is_empty() to also include
739 // !continuesHumongous(), but it is easier to just update the top
740 // fields here. The way we set top for all regions (i.e., top ==
741 // end for all regions but the last one, top == new_top for the
742 // last one) is actually used when we will free up the humongous
743 // region in free_humongous_region().
744 hr = NULL;
745 for (size_t i = first + 1; i < last; ++i) {
746 hr = region_at(i);
747 if ((i + 1) == last) {
748 // last continues humongous region
749 assert(hr->bottom() < new_top && new_top <= hr->end(),
750 "new_top should fall on this region");
751 hr->set_top(new_top);
752 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, new_top);
753 } else {
754 // not last one
755 assert(new_top > hr->end(), "new_top should be above this region");
756 hr->set_top(hr->end());
757 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, hr->end());
758 }
759 }
760 // If we have continues humongous regions (hr != NULL), then the
761 // end of the last one should match new_end and its top should
762 // match new_top.
763 assert(hr == NULL ||
764 (hr->end() == new_end && hr->top() == new_top), "sanity");
765
766 assert(first_hr->used() == word_size * HeapWordSize, "invariant");
767 _summary_bytes_used += first_hr->used();
768 _humongous_set.add(first_hr);
769
770 return new_obj;
771 }
772
773 // If could fit into free regions w/o expansion, try.
774 // Otherwise, if can expand, do so.
775 // Otherwise, if using ex regions might help, try with ex given back.
776 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size) {
777 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
778
779 verify_region_sets_optional();
780
781 size_t num_regions =
782 round_to(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords;
783 size_t x_size = expansion_regions();
784 size_t fs = _hrs.free_suffix();
785 size_t first = humongous_obj_allocate_find_first(num_regions, word_size);
786 if (first == G1_NULL_HRS_INDEX) {
787 // The only thing we can do now is attempt expansion.
788 if (fs + x_size >= num_regions) {
789 // If the number of regions we're trying to allocate for this
790 // object is at most the number of regions in the free suffix,
791 // then the call to humongous_obj_allocate_find_first() above
792 // should have succeeded and we wouldn't be here.
793 //
794 // We should only be trying to expand when the free suffix is
795 // not sufficient for the object _and_ we have some expansion
796 // room available.
797 assert(num_regions > fs, "earlier allocation should have succeeded");
798
799 ergo_verbose1(ErgoHeapSizing,
800 "attempt heap expansion",
801 ergo_format_reason("humongous allocation request failed")
802 ergo_format_byte("allocation request"),
803 word_size * HeapWordSize);
804 if (expand((num_regions - fs) * HeapRegion::GrainBytes)) {
805 // Even though the heap was expanded, it might not have
806 // reached the desired size. So, we cannot assume that the
807 // allocation will succeed.
808 first = humongous_obj_allocate_find_first(num_regions, word_size);
809 }
810 }
811 }
812
813 HeapWord* result = NULL;
814 if (first != G1_NULL_HRS_INDEX) {
815 result =
816 humongous_obj_allocate_initialize_regions(first, num_regions, word_size);
817 assert(result != NULL, "it should always return a valid result");
818 }
819
820 verify_region_sets_optional();
821
822 return result;
823 }
824
825 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) {
826 assert_heap_not_locked_and_not_at_safepoint();
827 assert(!isHumongous(word_size), "we do not allow humongous TLABs");
828
829 unsigned int dummy_gc_count_before;
830 return attempt_allocation(word_size, &dummy_gc_count_before);
831 }
832
833 HeapWord*
834 G1CollectedHeap::mem_allocate(size_t word_size,
835 bool* gc_overhead_limit_was_exceeded) {
836 assert_heap_not_locked_and_not_at_safepoint();
837
838 // Loop until the allocation is satisified, or unsatisfied after GC.
839 for (int try_count = 1; /* we'll return */; try_count += 1) {
840 unsigned int gc_count_before;
841
842 HeapWord* result = NULL;
843 if (!isHumongous(word_size)) {
844 result = attempt_allocation(word_size, &gc_count_before);
845 } else {
846 result = attempt_allocation_humongous(word_size, &gc_count_before);
847 }
848 if (result != NULL) {
849 return result;
850 }
851
852 // Create the garbage collection operation...
853 VM_G1CollectForAllocation op(gc_count_before, word_size);
854 // ...and get the VM thread to execute it.
855 VMThread::execute(&op);
856
857 if (op.prologue_succeeded() && op.pause_succeeded()) {
858 // If the operation was successful we'll return the result even
859 // if it is NULL. If the allocation attempt failed immediately
860 // after a Full GC, it's unlikely we'll be able to allocate now.
861 HeapWord* result = op.result();
862 if (result != NULL && !isHumongous(word_size)) {
863 // Allocations that take place on VM operations do not do any
864 // card dirtying and we have to do it here. We only have to do
865 // this for non-humongous allocations, though.
866 dirty_young_block(result, word_size);
867 }
868 return result;
869 } else {
870 assert(op.result() == NULL,
871 "the result should be NULL if the VM op did not succeed");
872 }
873
874 // Give a warning if we seem to be looping forever.
875 if ((QueuedAllocationWarningCount > 0) &&
876 (try_count % QueuedAllocationWarningCount == 0)) {
877 warning("G1CollectedHeap::mem_allocate retries %d times", try_count);
878 }
879 }
880
881 ShouldNotReachHere();
882 return NULL;
883 }
884
885 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size,
886 unsigned int *gc_count_before_ret) {
887 // Make sure you read the note in attempt_allocation_humongous().
888
889 assert_heap_not_locked_and_not_at_safepoint();
890 assert(!isHumongous(word_size), "attempt_allocation_slow() should not "
891 "be called for humongous allocation requests");
892
893 // We should only get here after the first-level allocation attempt
894 // (attempt_allocation()) failed to allocate.
895
896 // We will loop until a) we manage to successfully perform the
897 // allocation or b) we successfully schedule a collection which
898 // fails to perform the allocation. b) is the only case when we'll
899 // return NULL.
900 HeapWord* result = NULL;
901 for (int try_count = 1; /* we'll return */; try_count += 1) {
902 bool should_try_gc;
903 unsigned int gc_count_before;
904
905 {
906 MutexLockerEx x(Heap_lock);
907
908 result = _mutator_alloc_region.attempt_allocation_locked(word_size,
909 false /* bot_updates */);
910 if (result != NULL) {
911 return result;
912 }
913
914 // If we reach here, attempt_allocation_locked() above failed to
915 // allocate a new region. So the mutator alloc region should be NULL.
916 assert(_mutator_alloc_region.get() == NULL, "only way to get here");
917
918 if (GC_locker::is_active_and_needs_gc()) {
919 if (g1_policy()->can_expand_young_list()) {
920 // No need for an ergo verbose message here,
921 // can_expand_young_list() does this when it returns true.
922 result = _mutator_alloc_region.attempt_allocation_force(word_size,
923 false /* bot_updates */);
924 if (result != NULL) {
925 return result;
926 }
927 }
928 should_try_gc = false;
929 } else {
930 // Read the GC count while still holding the Heap_lock.
931 gc_count_before = SharedHeap::heap()->total_collections();
932 should_try_gc = true;
933 }
934 }
935
936 if (should_try_gc) {
937 bool succeeded;
938 result = do_collection_pause(word_size, gc_count_before, &succeeded);
939 if (result != NULL) {
940 assert(succeeded, "only way to get back a non-NULL result");
941 return result;
942 }
943
944 if (succeeded) {
945 // If we get here we successfully scheduled a collection which
946 // failed to allocate. No point in trying to allocate
947 // further. We'll just return NULL.
948 MutexLockerEx x(Heap_lock);
949 *gc_count_before_ret = SharedHeap::heap()->total_collections();
950 return NULL;
951 }
952 } else {
953 GC_locker::stall_until_clear();
954 }
955
956 // We can reach here if we were unsuccessul in scheduling a
957 // collection (because another thread beat us to it) or if we were
958 // stalled due to the GC locker. In either can we should retry the
959 // allocation attempt in case another thread successfully
960 // performed a collection and reclaimed enough space. We do the
961 // first attempt (without holding the Heap_lock) here and the
962 // follow-on attempt will be at the start of the next loop
963 // iteration (after taking the Heap_lock).
964 result = _mutator_alloc_region.attempt_allocation(word_size,
965 false /* bot_updates */);
966 if (result != NULL ){
967 return result;
968 }
969
970 // Give a warning if we seem to be looping forever.
971 if ((QueuedAllocationWarningCount > 0) &&
972 (try_count % QueuedAllocationWarningCount == 0)) {
973 warning("G1CollectedHeap::attempt_allocation_slow() "
974 "retries %d times", try_count);
975 }
976 }
977
978 ShouldNotReachHere();
979 return NULL;
980 }
981
982 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size,
983 unsigned int * gc_count_before_ret) {
984 // The structure of this method has a lot of similarities to
985 // attempt_allocation_slow(). The reason these two were not merged
986 // into a single one is that such a method would require several "if
987 // allocation is not humongous do this, otherwise do that"
988 // conditional paths which would obscure its flow. In fact, an early
989 // version of this code did use a unified method which was harder to
990 // follow and, as a result, it had subtle bugs that were hard to
991 // track down. So keeping these two methods separate allows each to
992 // be more readable. It will be good to keep these two in sync as
993 // much as possible.
994
995 assert_heap_not_locked_and_not_at_safepoint();
996 assert(isHumongous(word_size), "attempt_allocation_humongous() "
997 "should only be called for humongous allocations");
998
999 // We will loop until a) we manage to successfully perform the
1000 // allocation or b) we successfully schedule a collection which
1001 // fails to perform the allocation. b) is the only case when we'll
1002 // return NULL.
1003 HeapWord* result = NULL;
1004 for (int try_count = 1; /* we'll return */; try_count += 1) {
1005 bool should_try_gc;
1006 unsigned int gc_count_before;
1007
1008 {
1009 MutexLockerEx x(Heap_lock);
1010
1011 // Given that humongous objects are not allocated in young
1012 // regions, we'll first try to do the allocation without doing a
1013 // collection hoping that there's enough space in the heap.
1014 result = humongous_obj_allocate(word_size);
1015 if (result != NULL) {
1016 return result;
1017 }
1018
1019 if (GC_locker::is_active_and_needs_gc()) {
1020 should_try_gc = false;
1021 } else {
1022 // Read the GC count while still holding the Heap_lock.
1023 gc_count_before = SharedHeap::heap()->total_collections();
1024 should_try_gc = true;
1025 }
1026 }
1027
1028 if (should_try_gc) {
1029 // If we failed to allocate the humongous object, we should try to
1030 // do a collection pause (if we're allowed) in case it reclaims
1031 // enough space for the allocation to succeed after the pause.
1032
1033 bool succeeded;
1034 result = do_collection_pause(word_size, gc_count_before, &succeeded);
1035 if (result != NULL) {
1036 assert(succeeded, "only way to get back a non-NULL result");
1037 return result;
1038 }
1039
1040 if (succeeded) {
1041 // If we get here we successfully scheduled a collection which
1042 // failed to allocate. No point in trying to allocate
1043 // further. We'll just return NULL.
1044 MutexLockerEx x(Heap_lock);
1045 *gc_count_before_ret = SharedHeap::heap()->total_collections();
1046 return NULL;
1047 }
1048 } else {
1049 GC_locker::stall_until_clear();
1050 }
1051
1052 // We can reach here if we were unsuccessul in scheduling a
1053 // collection (because another thread beat us to it) or if we were
1054 // stalled due to the GC locker. In either can we should retry the
1055 // allocation attempt in case another thread successfully
1056 // performed a collection and reclaimed enough space. Give a
1057 // warning if we seem to be looping forever.
1058
1059 if ((QueuedAllocationWarningCount > 0) &&
1060 (try_count % QueuedAllocationWarningCount == 0)) {
1061 warning("G1CollectedHeap::attempt_allocation_humongous() "
1062 "retries %d times", try_count);
1063 }
1064 }
1065
1066 ShouldNotReachHere();
1067 return NULL;
1068 }
1069
1070 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
1071 bool expect_null_mutator_alloc_region) {
1072 assert_at_safepoint(true /* should_be_vm_thread */);
1073 assert(_mutator_alloc_region.get() == NULL ||
1074 !expect_null_mutator_alloc_region,
1075 "the current alloc region was unexpectedly found to be non-NULL");
1076
1077 if (!isHumongous(word_size)) {
1078 return _mutator_alloc_region.attempt_allocation_locked(word_size,
1079 false /* bot_updates */);
1080 } else {
1081 return humongous_obj_allocate(word_size);
1082 }
1083
1084 ShouldNotReachHere();
1085 }
1086
1087 class PostMCRemSetClearClosure: public HeapRegionClosure {
1088 ModRefBarrierSet* _mr_bs;
1089 public:
1090 PostMCRemSetClearClosure(ModRefBarrierSet* mr_bs) : _mr_bs(mr_bs) {}
1091 bool doHeapRegion(HeapRegion* r) {
1092 r->reset_gc_time_stamp();
1093 if (r->continuesHumongous())
1094 return false;
1095 HeapRegionRemSet* hrrs = r->rem_set();
1096 if (hrrs != NULL) hrrs->clear();
1097 // You might think here that we could clear just the cards
1098 // corresponding to the used region. But no: if we leave a dirty card
1099 // in a region we might allocate into, then it would prevent that card
1100 // from being enqueued, and cause it to be missed.
1101 // Re: the performance cost: we shouldn't be doing full GC anyway!
1102 _mr_bs->clear(MemRegion(r->bottom(), r->end()));
1103 return false;
1104 }
1105 };
1106
1107
1108 class PostMCRemSetInvalidateClosure: public HeapRegionClosure {
1109 ModRefBarrierSet* _mr_bs;
1110 public:
1111 PostMCRemSetInvalidateClosure(ModRefBarrierSet* mr_bs) : _mr_bs(mr_bs) {}
1112 bool doHeapRegion(HeapRegion* r) {
1113 if (r->continuesHumongous()) return false;
1114 if (r->used_region().word_size() != 0) {
1115 _mr_bs->invalidate(r->used_region(), true /*whole heap*/);
1116 }
1117 return false;
1118 }
1119 };
1120
1121 class RebuildRSOutOfRegionClosure: public HeapRegionClosure {
1122 G1CollectedHeap* _g1h;
1123 UpdateRSOopClosure _cl;
1124 int _worker_i;
1125 public:
1126 RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, int worker_i = 0) :
1127 _cl(g1->g1_rem_set(), worker_i),
1128 _worker_i(worker_i),
1129 _g1h(g1)
1130 { }
1131
1132 bool doHeapRegion(HeapRegion* r) {
1133 if (!r->continuesHumongous()) {
1134 _cl.set_from(r);
1135 r->oop_iterate(&_cl);
1136 }
1137 return false;
1138 }
1139 };
1140
1141 class ParRebuildRSTask: public AbstractGangTask {
1142 G1CollectedHeap* _g1;
1143 public:
1144 ParRebuildRSTask(G1CollectedHeap* g1)
1145 : AbstractGangTask("ParRebuildRSTask"),
1146 _g1(g1)
1147 { }
1148
1149 void work(int i) {
1150 RebuildRSOutOfRegionClosure rebuild_rs(_g1, i);
1151 _g1->heap_region_par_iterate_chunked(&rebuild_rs, i,
1152 HeapRegion::RebuildRSClaimValue);
1153 }
1154 };
1155
1156 class PostCompactionPrinterClosure: public HeapRegionClosure {
1157 private:
1158 G1HRPrinter* _hr_printer;
1159 public:
1160 bool doHeapRegion(HeapRegion* hr) {
1161 assert(!hr->is_young(), "not expecting to find young regions");
1162 // We only generate output for non-empty regions.
1163 if (!hr->is_empty()) {
1164 if (!hr->isHumongous()) {
1165 _hr_printer->post_compaction(hr, G1HRPrinter::Old);
1166 } else if (hr->startsHumongous()) {
1167 if (hr->capacity() == (size_t) HeapRegion::GrainBytes) {
1168 // single humongous region
1169 _hr_printer->post_compaction(hr, G1HRPrinter::SingleHumongous);
1170 } else {
1171 _hr_printer->post_compaction(hr, G1HRPrinter::StartsHumongous);
1172 }
1173 } else {
1174 assert(hr->continuesHumongous(), "only way to get here");
1175 _hr_printer->post_compaction(hr, G1HRPrinter::ContinuesHumongous);
1176 }
1177 }
1178 return false;
1179 }
1180
1181 PostCompactionPrinterClosure(G1HRPrinter* hr_printer)
1182 : _hr_printer(hr_printer) { }
1183 };
1184
1185 bool G1CollectedHeap::do_collection(bool explicit_gc,
1186 bool clear_all_soft_refs,
1187 size_t word_size) {
1188 assert_at_safepoint(true /* should_be_vm_thread */);
1189
1190 if (GC_locker::check_active_before_gc()) {
1191 return false;
1192 }
1193
1194 SvcGCMarker sgcm(SvcGCMarker::FULL);
1195 ResourceMark rm;
1196
1197 if (PrintHeapAtGC) {
1198 Universe::print_heap_before_gc();
1199 }
1200
1201 verify_region_sets_optional();
1202
1203 const bool do_clear_all_soft_refs = clear_all_soft_refs ||
1204 collector_policy()->should_clear_all_soft_refs();
1205
1206 ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy());
1207
1208 {
1209 IsGCActiveMark x;
1210
1211 // Timing
1212 bool system_gc = (gc_cause() == GCCause::_java_lang_system_gc);
1213 assert(!system_gc || explicit_gc, "invariant");
1214 gclog_or_tty->date_stamp(PrintGC && PrintGCDateStamps);
1215 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty);
1216 TraceTime t(system_gc ? "Full GC (System.gc())" : "Full GC",
1217 PrintGC, true, gclog_or_tty);
1218
1219 TraceCollectorStats tcs(g1mm()->full_collection_counters());
1220 TraceMemoryManagerStats tms(true /* fullGC */, gc_cause());
1221
1222 double start = os::elapsedTime();
1223 g1_policy()->record_full_collection_start();
1224
1225 wait_while_free_regions_coming();
1226 append_secondary_free_list_if_not_empty_with_lock();
1227
1228 gc_prologue(true);
1229 increment_total_collections(true /* full gc */);
1230
1231 size_t g1h_prev_used = used();
1232 assert(used() == recalculate_used(), "Should be equal");
1233
1234 if (VerifyBeforeGC && total_collections() >= VerifyGCStartAt) {
1235 HandleMark hm; // Discard invalid handles created during verification
1236 gclog_or_tty->print(" VerifyBeforeGC:");
1237 prepare_for_verify();
1238 Universe::verify(/* allow dirty */ true,
1239 /* silent */ false,
1240 /* option */ VerifyOption_G1UsePrevMarking);
1241
1242 }
1243 pre_full_gc_dump();
1244
1245 COMPILER2_PRESENT(DerivedPointerTable::clear());
1246
1247 // We want to discover references, but not process them yet.
1248 // This mode is disabled in
1249 // instanceRefKlass::process_discovered_references if the
1250 // generation does some collection work, or
1251 // instanceRefKlass::enqueue_discovered_references if the
1252 // generation returns without doing any work.
1253 ref_processor()->disable_discovery();
1254 ref_processor()->abandon_partial_discovery();
1255 ref_processor()->verify_no_references_recorded();
1256
1257 // Abandon current iterations of concurrent marking and concurrent
1258 // refinement, if any are in progress.
1259 concurrent_mark()->abort();
1260
1261 // Make sure we'll choose a new allocation region afterwards.
1262 release_mutator_alloc_region();
1263 abandon_gc_alloc_regions();
1264 g1_rem_set()->cleanupHRRS();
1265 tear_down_region_lists();
1266
1267 // We should call this after we retire any currently active alloc
1268 // regions so that all the ALLOC / RETIRE events are generated
1269 // before the start GC event.
1270 _hr_printer.start_gc(true /* full */, (size_t) total_collections());
1271
1272 // We may have added regions to the current incremental collection
1273 // set between the last GC or pause and now. We need to clear the
1274 // incremental collection set and then start rebuilding it afresh
1275 // after this full GC.
1276 abandon_collection_set(g1_policy()->inc_cset_head());
1277 g1_policy()->clear_incremental_cset();
1278 g1_policy()->stop_incremental_cset_building();
1279
1280 empty_young_list();
1281 g1_policy()->set_full_young_gcs(true);
1282
1283 // See the comment in G1CollectedHeap::ref_processing_init() about
1284 // how reference processing currently works in G1.
1285
1286 // Temporarily make reference _discovery_ single threaded (non-MT).
1287 ReferenceProcessorMTDiscoveryMutator rp_disc_ser(ref_processor(), false);
1288
1289 // Temporarily make refs discovery atomic
1290 ReferenceProcessorAtomicMutator rp_disc_atomic(ref_processor(), true);
1291
1292 // Temporarily clear _is_alive_non_header
1293 ReferenceProcessorIsAliveMutator rp_is_alive_null(ref_processor(), NULL);
1294
1295 ref_processor()->enable_discovery();
1296 ref_processor()->setup_policy(do_clear_all_soft_refs);
1297 // Do collection work
1298 {
1299 HandleMark hm; // Discard invalid handles created during gc
1300 G1MarkSweep::invoke_at_safepoint(ref_processor(), do_clear_all_soft_refs);
1301 }
1302 assert(free_regions() == 0, "we should not have added any free regions");
1303 rebuild_region_lists();
1304
1305 _summary_bytes_used = recalculate_used();
1306
1307 ref_processor()->enqueue_discovered_references();
1308
1309 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
1310
1311 MemoryService::track_memory_usage();
1312
1313 if (VerifyAfterGC && total_collections() >= VerifyGCStartAt) {
1314 HandleMark hm; // Discard invalid handles created during verification
1315 gclog_or_tty->print(" VerifyAfterGC:");
1316 prepare_for_verify();
1317 Universe::verify(/* allow dirty */ false,
1318 /* silent */ false,
1319 /* option */ VerifyOption_G1UsePrevMarking);
1320
1321 }
1322 NOT_PRODUCT(ref_processor()->verify_no_references_recorded());
1323
1324 reset_gc_time_stamp();
1325 // Since everything potentially moved, we will clear all remembered
1326 // sets, and clear all cards. Later we will rebuild remebered
1327 // sets. We will also reset the GC time stamps of the regions.
1328 PostMCRemSetClearClosure rs_clear(mr_bs());
1329 heap_region_iterate(&rs_clear);
1330
1331 // Resize the heap if necessary.
1332 resize_if_necessary_after_full_collection(explicit_gc ? 0 : word_size);
1333
1334 if (_hr_printer.is_active()) {
1335 // We should do this after we potentially resize the heap so
1336 // that all the COMMIT / UNCOMMIT events are generated before
1337 // the end GC event.
1338
1339 PostCompactionPrinterClosure cl(hr_printer());
1340 heap_region_iterate(&cl);
1341
1342 _hr_printer.end_gc(true /* full */, (size_t) total_collections());
1343 }
1344
1345 if (_cg1r->use_cache()) {
1346 _cg1r->clear_and_record_card_counts();
1347 _cg1r->clear_hot_cache();
1348 }
1349
1350 // Rebuild remembered sets of all regions.
1351
1352 if (G1CollectedHeap::use_parallel_gc_threads()) {
1353 ParRebuildRSTask rebuild_rs_task(this);
1354 assert(check_heap_region_claim_values(
1355 HeapRegion::InitialClaimValue), "sanity check");
1356 set_par_threads(workers()->total_workers());
1357 workers()->run_task(&rebuild_rs_task);
1358 set_par_threads(0);
1359 assert(check_heap_region_claim_values(
1360 HeapRegion::RebuildRSClaimValue), "sanity check");
1361 reset_heap_region_claim_values();
1362 } else {
1363 RebuildRSOutOfRegionClosure rebuild_rs(this);
1364 heap_region_iterate(&rebuild_rs);
1365 }
1366
1367 if (PrintGC) {
1368 print_size_transition(gclog_or_tty, g1h_prev_used, used(), capacity());
1369 }
1370
1371 if (true) { // FIXME
1372 // Ask the permanent generation to adjust size for full collections
1373 perm()->compute_new_size();
1374 }
1375
1376 // Start a new incremental collection set for the next pause
1377 assert(g1_policy()->collection_set() == NULL, "must be");
1378 g1_policy()->start_incremental_cset_building();
1379
1380 // Clear the _cset_fast_test bitmap in anticipation of adding
1381 // regions to the incremental collection set for the next
1382 // evacuation pause.
1383 clear_cset_fast_test();
1384
1385 init_mutator_alloc_region();
1386
1387 double end = os::elapsedTime();
1388 g1_policy()->record_full_collection_end();
1389
1390 #ifdef TRACESPINNING
1391 ParallelTaskTerminator::print_termination_counts();
1392 #endif
1393
1394 gc_epilogue(true);
1395
1396 // Discard all rset updates
1397 JavaThread::dirty_card_queue_set().abandon_logs();
1398 assert(!G1DeferredRSUpdate
1399 || (G1DeferredRSUpdate && (dirty_card_queue_set().completed_buffers_num() == 0)), "Should not be any");
1400 }
1401
1402 _young_list->reset_sampled_info();
1403 // At this point there should be no regions in the
1404 // entire heap tagged as young.
1405 assert( check_young_list_empty(true /* check_heap */),
1406 "young list should be empty at this point");
1407
1408 // Update the number of full collections that have been completed.
1409 increment_full_collections_completed(false /* concurrent */);
1410
1411 _hrs.verify_optional();
1412 verify_region_sets_optional();
1413
1414 if (PrintHeapAtGC) {
1415 Universe::print_heap_after_gc();
1416 }
1417 g1mm()->update_counters();
1418 post_full_gc_dump();
1419
1420 return true;
1421 }
1422
1423 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
1424 // do_collection() will return whether it succeeded in performing
1425 // the GC. Currently, there is no facility on the
1426 // do_full_collection() API to notify the caller than the collection
1427 // did not succeed (e.g., because it was locked out by the GC
1428 // locker). So, right now, we'll ignore the return value.
1429 bool dummy = do_collection(true, /* explicit_gc */
1430 clear_all_soft_refs,
1431 0 /* word_size */);
1432 }
1433
1434 // This code is mostly copied from TenuredGeneration.
1435 void
1436 G1CollectedHeap::
1437 resize_if_necessary_after_full_collection(size_t word_size) {
1438 assert(MinHeapFreeRatio <= MaxHeapFreeRatio, "sanity check");
1439
1440 // Include the current allocation, if any, and bytes that will be
1441 // pre-allocated to support collections, as "used".
1442 const size_t used_after_gc = used();
1443 const size_t capacity_after_gc = capacity();
1444 const size_t free_after_gc = capacity_after_gc - used_after_gc;
1445
1446 // This is enforced in arguments.cpp.
1447 assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
1448 "otherwise the code below doesn't make sense");
1449
1450 // We don't have floating point command-line arguments
1451 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
1452 const double maximum_used_percentage = 1.0 - minimum_free_percentage;
1453 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
1454 const double minimum_used_percentage = 1.0 - maximum_free_percentage;
1455
1456 const size_t min_heap_size = collector_policy()->min_heap_byte_size();
1457 const size_t max_heap_size = collector_policy()->max_heap_byte_size();
1458
1459 // We have to be careful here as these two calculations can overflow
1460 // 32-bit size_t's.
1461 double used_after_gc_d = (double) used_after_gc;
1462 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
1463 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
1464
1465 // Let's make sure that they are both under the max heap size, which
1466 // by default will make them fit into a size_t.
1467 double desired_capacity_upper_bound = (double) max_heap_size;
1468 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
1469 desired_capacity_upper_bound);
1470 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
1471 desired_capacity_upper_bound);
1472
1473 // We can now safely turn them into size_t's.
1474 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
1475 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
1476
1477 // This assert only makes sense here, before we adjust them
1478 // with respect to the min and max heap size.
1479 assert(minimum_desired_capacity <= maximum_desired_capacity,
1480 err_msg("minimum_desired_capacity = "SIZE_FORMAT", "
1481 "maximum_desired_capacity = "SIZE_FORMAT,
1482 minimum_desired_capacity, maximum_desired_capacity));
1483
1484 // Should not be greater than the heap max size. No need to adjust
1485 // it with respect to the heap min size as it's a lower bound (i.e.,
1486 // we'll try to make the capacity larger than it, not smaller).
1487 minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size);
1488 // Should not be less than the heap min size. No need to adjust it
1489 // with respect to the heap max size as it's an upper bound (i.e.,
1490 // we'll try to make the capacity smaller than it, not greater).
1491 maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size);
1492
1493 if (capacity_after_gc < minimum_desired_capacity) {
1494 // Don't expand unless it's significant
1495 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
1496 ergo_verbose4(ErgoHeapSizing,
1497 "attempt heap expansion",
1498 ergo_format_reason("capacity lower than "
1499 "min desired capacity after Full GC")
1500 ergo_format_byte("capacity")
1501 ergo_format_byte("occupancy")
1502 ergo_format_byte_perc("min desired capacity"),
1503 capacity_after_gc, used_after_gc,
1504 minimum_desired_capacity, (double) MinHeapFreeRatio);
1505 expand(expand_bytes);
1506
1507 // No expansion, now see if we want to shrink
1508 } else if (capacity_after_gc > maximum_desired_capacity) {
1509 // Capacity too large, compute shrinking size
1510 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
1511 ergo_verbose4(ErgoHeapSizing,
1512 "attempt heap shrinking",
1513 ergo_format_reason("capacity higher than "
1514 "max desired capacity after Full GC")
1515 ergo_format_byte("capacity")
1516 ergo_format_byte("occupancy")
1517 ergo_format_byte_perc("max desired capacity"),
1518 capacity_after_gc, used_after_gc,
1519 maximum_desired_capacity, (double) MaxHeapFreeRatio);
1520 shrink(shrink_bytes);
1521 }
1522 }
1523
1524
1525 HeapWord*
1526 G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
1527 bool* succeeded) {
1528 assert_at_safepoint(true /* should_be_vm_thread */);
1529
1530 *succeeded = true;
1531 // Let's attempt the allocation first.
1532 HeapWord* result =
1533 attempt_allocation_at_safepoint(word_size,
1534 false /* expect_null_mutator_alloc_region */);
1535 if (result != NULL) {
1536 assert(*succeeded, "sanity");
1537 return result;
1538 }
1539
1540 // In a G1 heap, we're supposed to keep allocation from failing by
1541 // incremental pauses. Therefore, at least for now, we'll favor
1542 // expansion over collection. (This might change in the future if we can
1543 // do something smarter than full collection to satisfy a failed alloc.)
1544 result = expand_and_allocate(word_size);
1545 if (result != NULL) {
1546 assert(*succeeded, "sanity");
1547 return result;
1548 }
1549
1550 // Expansion didn't work, we'll try to do a Full GC.
1551 bool gc_succeeded = do_collection(false, /* explicit_gc */
1552 false, /* clear_all_soft_refs */
1553 word_size);
1554 if (!gc_succeeded) {
1555 *succeeded = false;
1556 return NULL;
1557 }
1558
1559 // Retry the allocation
1560 result = attempt_allocation_at_safepoint(word_size,
1561 true /* expect_null_mutator_alloc_region */);
1562 if (result != NULL) {
1563 assert(*succeeded, "sanity");
1564 return result;
1565 }
1566
1567 // Then, try a Full GC that will collect all soft references.
1568 gc_succeeded = do_collection(false, /* explicit_gc */
1569 true, /* clear_all_soft_refs */
1570 word_size);
1571 if (!gc_succeeded) {
1572 *succeeded = false;
1573 return NULL;
1574 }
1575
1576 // Retry the allocation once more
1577 result = attempt_allocation_at_safepoint(word_size,
1578 true /* expect_null_mutator_alloc_region */);
1579 if (result != NULL) {
1580 assert(*succeeded, "sanity");
1581 return result;
1582 }
1583
1584 assert(!collector_policy()->should_clear_all_soft_refs(),
1585 "Flag should have been handled and cleared prior to this point");
1586
1587 // What else? We might try synchronous finalization later. If the total
1588 // space available is large enough for the allocation, then a more
1589 // complete compaction phase than we've tried so far might be
1590 // appropriate.
1591 assert(*succeeded, "sanity");
1592 return NULL;
1593 }
1594
1595 // Attempting to expand the heap sufficiently
1596 // to support an allocation of the given "word_size". If
1597 // successful, perform the allocation and return the address of the
1598 // allocated block, or else "NULL".
1599
1600 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size) {
1601 assert_at_safepoint(true /* should_be_vm_thread */);
1602
1603 verify_region_sets_optional();
1604
1605 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
1606 ergo_verbose1(ErgoHeapSizing,
1607 "attempt heap expansion",
1608 ergo_format_reason("allocation request failed")
1609 ergo_format_byte("allocation request"),
1610 word_size * HeapWordSize);
1611 if (expand(expand_bytes)) {
1612 _hrs.verify_optional();
1613 verify_region_sets_optional();
1614 return attempt_allocation_at_safepoint(word_size,
1615 false /* expect_null_mutator_alloc_region */);
1616 }
1617 return NULL;
1618 }
1619
1620 void G1CollectedHeap::update_committed_space(HeapWord* old_end,
1621 HeapWord* new_end) {
1622 assert(old_end != new_end, "don't call this otherwise");
1623 assert((HeapWord*) _g1_storage.high() == new_end, "invariant");
1624
1625 // Update the committed mem region.
1626 _g1_committed.set_end(new_end);
1627 // Tell the card table about the update.
1628 Universe::heap()->barrier_set()->resize_covered_region(_g1_committed);
1629 // Tell the BOT about the update.
1630 _bot_shared->resize(_g1_committed.word_size());
1631 }
1632
1633 bool G1CollectedHeap::expand(size_t expand_bytes) {
1634 size_t old_mem_size = _g1_storage.committed_size();
1635 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
1636 aligned_expand_bytes = align_size_up(aligned_expand_bytes,
1637 HeapRegion::GrainBytes);
1638 ergo_verbose2(ErgoHeapSizing,
1639 "expand the heap",
1640 ergo_format_byte("requested expansion amount")
1641 ergo_format_byte("attempted expansion amount"),
1642 expand_bytes, aligned_expand_bytes);
1643
1644 // First commit the memory.
1645 HeapWord* old_end = (HeapWord*) _g1_storage.high();
1646 bool successful = _g1_storage.expand_by(aligned_expand_bytes);
1647 if (successful) {
1648 // Then propagate this update to the necessary data structures.
1649 HeapWord* new_end = (HeapWord*) _g1_storage.high();
1650 update_committed_space(old_end, new_end);
1651
1652 FreeRegionList expansion_list("Local Expansion List");
1653 MemRegion mr = _hrs.expand_by(old_end, new_end, &expansion_list);
1654 assert(mr.start() == old_end, "post-condition");
1655 // mr might be a smaller region than what was requested if
1656 // expand_by() was unable to allocate the HeapRegion instances
1657 assert(mr.end() <= new_end, "post-condition");
1658
1659 size_t actual_expand_bytes = mr.byte_size();
1660 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
1661 assert(actual_expand_bytes == expansion_list.total_capacity_bytes(),
1662 "post-condition");
1663 if (actual_expand_bytes < aligned_expand_bytes) {
1664 // We could not expand _hrs to the desired size. In this case we
1665 // need to shrink the committed space accordingly.
1666 assert(mr.end() < new_end, "invariant");
1667
1668 size_t diff_bytes = aligned_expand_bytes - actual_expand_bytes;
1669 // First uncommit the memory.
1670 _g1_storage.shrink_by(diff_bytes);
1671 // Then propagate this update to the necessary data structures.
1672 update_committed_space(new_end, mr.end());
1673 }
1674 _free_list.add_as_tail(&expansion_list);
1675
1676 if (_hr_printer.is_active()) {
1677 HeapWord* curr = mr.start();
1678 while (curr < mr.end()) {
1679 HeapWord* curr_end = curr + HeapRegion::GrainWords;
1680 _hr_printer.commit(curr, curr_end);
1681 curr = curr_end;
1682 }
1683 assert(curr == mr.end(), "post-condition");
1684 }
1685 g1_policy()->record_new_heap_size(n_regions());
1686 } else {
1687 ergo_verbose0(ErgoHeapSizing,
1688 "did not expand the heap",
1689 ergo_format_reason("heap expansion operation failed"));
1690 // The expansion of the virtual storage space was unsuccessful.
1691 // Let's see if it was because we ran out of swap.
1692 if (G1ExitOnExpansionFailure &&
1693 _g1_storage.uncommitted_size() >= aligned_expand_bytes) {
1694 // We had head room...
1695 vm_exit_out_of_memory(aligned_expand_bytes, "G1 heap expansion");
1696 }
1697 }
1698 return successful;
1699 }
1700
1701 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
1702 size_t old_mem_size = _g1_storage.committed_size();
1703 size_t aligned_shrink_bytes =
1704 ReservedSpace::page_align_size_down(shrink_bytes);
1705 aligned_shrink_bytes = align_size_down(aligned_shrink_bytes,
1706 HeapRegion::GrainBytes);
1707 size_t num_regions_deleted = 0;
1708 MemRegion mr = _hrs.shrink_by(aligned_shrink_bytes, &num_regions_deleted);
1709 HeapWord* old_end = (HeapWord*) _g1_storage.high();
1710 assert(mr.end() == old_end, "post-condition");
1711
1712 ergo_verbose3(ErgoHeapSizing,
1713 "shrink the heap",
1714 ergo_format_byte("requested shrinking amount")
1715 ergo_format_byte("aligned shrinking amount")
1716 ergo_format_byte("attempted shrinking amount"),
1717 shrink_bytes, aligned_shrink_bytes, mr.byte_size());
1718 if (mr.byte_size() > 0) {
1719 if (_hr_printer.is_active()) {
1720 HeapWord* curr = mr.end();
1721 while (curr > mr.start()) {
1722 HeapWord* curr_end = curr;
1723 curr -= HeapRegion::GrainWords;
1724 _hr_printer.uncommit(curr, curr_end);
1725 }
1726 assert(curr == mr.start(), "post-condition");
1727 }
1728
1729 _g1_storage.shrink_by(mr.byte_size());
1730 HeapWord* new_end = (HeapWord*) _g1_storage.high();
1731 assert(mr.start() == new_end, "post-condition");
1732
1733 _expansion_regions += num_regions_deleted;
1734 update_committed_space(old_end, new_end);
1735 HeapRegionRemSet::shrink_heap(n_regions());
1736 g1_policy()->record_new_heap_size(n_regions());
1737 } else {
1738 ergo_verbose0(ErgoHeapSizing,
1739 "did not shrink the heap",
1740 ergo_format_reason("heap shrinking operation failed"));
1741 }
1742 }
1743
1744 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1745 verify_region_sets_optional();
1746
1747 // We should only reach here at the end of a Full GC which means we
1748 // should not not be holding to any GC alloc regions. The method
1749 // below will make sure of that and do any remaining clean up.
1750 abandon_gc_alloc_regions();
1751
1752 // Instead of tearing down / rebuilding the free lists here, we
1753 // could instead use the remove_all_pending() method on free_list to
1754 // remove only the ones that we need to remove.
1755 tear_down_region_lists(); // We will rebuild them in a moment.
1756 shrink_helper(shrink_bytes);
1757 rebuild_region_lists();
1758
1759 _hrs.verify_optional();
1760 verify_region_sets_optional();
1761 }
1762
1763 // Public methods.
1764
1765 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away
1766 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
1767 #endif // _MSC_VER
1768
1769
1770 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* policy_) :
1771 SharedHeap(policy_),
1772 _g1_policy(policy_),
1773 _dirty_card_queue_set(false),
1774 _into_cset_dirty_card_queue_set(false),
1775 _is_alive_closure(this),
1776 _ref_processor(NULL),
1777 _process_strong_tasks(new SubTasksDone(G1H_PS_NumElements)),
1778 _bot_shared(NULL),
1779 _objs_with_preserved_marks(NULL), _preserved_marks_of_objs(NULL),
1780 _evac_failure_scan_stack(NULL) ,
1781 _mark_in_progress(false),
1782 _cg1r(NULL), _summary_bytes_used(0),
1783 _refine_cte_cl(NULL),
1784 _full_collection(false),
1785 _free_list("Master Free List"),
1786 _secondary_free_list("Secondary Free List"),
1787 _humongous_set("Master Humongous Set"),
1788 _free_regions_coming(false),
1789 _young_list(new YoungList(this)),
1790 _gc_time_stamp(0),
1791 _retained_old_gc_alloc_region(NULL),
1792 _surviving_young_words(NULL),
1793 _full_collections_completed(0),
1794 _in_cset_fast_test(NULL),
1795 _in_cset_fast_test_base(NULL),
1796 _dirty_cards_region_list(NULL) {
1797 _g1h = this; // To catch bugs.
1798 if (_process_strong_tasks == NULL || !_process_strong_tasks->valid()) {
1799 vm_exit_during_initialization("Failed necessary allocation.");
1800 }
1801
1802 _humongous_object_threshold_in_words = HeapRegion::GrainWords / 2;
1803
1804 int n_queues = MAX2((int)ParallelGCThreads, 1);
1805 _task_queues = new RefToScanQueueSet(n_queues);
1806
1807 int n_rem_sets = HeapRegionRemSet::num_par_rem_sets();
1808 assert(n_rem_sets > 0, "Invariant.");
1809
1810 HeapRegionRemSetIterator** iter_arr =
1811 NEW_C_HEAP_ARRAY(HeapRegionRemSetIterator*, n_queues);
1812 for (int i = 0; i < n_queues; i++) {
1813 iter_arr[i] = new HeapRegionRemSetIterator();
1814 }
1815 _rem_set_iterator = iter_arr;
1816
1817 for (int i = 0; i < n_queues; i++) {
1818 RefToScanQueue* q = new RefToScanQueue();
1819 q->initialize();
1820 _task_queues->register_queue(i, q);
1821 }
1822
1823 guarantee(_task_queues != NULL, "task_queues allocation failure.");
1824 }
1825
1826 jint G1CollectedHeap::initialize() {
1827 CollectedHeap::pre_initialize();
1828 os::enable_vtime();
1829
1830 // Necessary to satisfy locking discipline assertions.
1831
1832 MutexLocker x(Heap_lock);
1833
1834 // We have to initialize the printer before committing the heap, as
1835 // it will be used then.
1836 _hr_printer.set_active(G1PrintHeapRegions);
1837
1838 // While there are no constraints in the GC code that HeapWordSize
1839 // be any particular value, there are multiple other areas in the
1840 // system which believe this to be true (e.g. oop->object_size in some
1841 // cases incorrectly returns the size in wordSize units rather than
1842 // HeapWordSize).
1843 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
1844
1845 size_t init_byte_size = collector_policy()->initial_heap_byte_size();
1846 size_t max_byte_size = collector_policy()->max_heap_byte_size();
1847
1848 // Ensure that the sizes are properly aligned.
1849 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
1850 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
1851
1852 _cg1r = new ConcurrentG1Refine();
1853
1854 // Reserve the maximum.
1855 PermanentGenerationSpec* pgs = collector_policy()->permanent_generation();
1856 // Includes the perm-gen.
1857
1858 // When compressed oops are enabled, the preferred heap base
1859 // is calculated by subtracting the requested size from the
1860 // 32Gb boundary and using the result as the base address for
1861 // heap reservation. If the requested size is not aligned to
1862 // HeapRegion::GrainBytes (i.e. the alignment that is passed
1863 // into the ReservedHeapSpace constructor) then the actual
1864 // base of the reserved heap may end up differing from the
1865 // address that was requested (i.e. the preferred heap base).
1866 // If this happens then we could end up using a non-optimal
1867 // compressed oops mode.
1868
1869 // Since max_byte_size is aligned to the size of a heap region (checked
1870 // above), we also need to align the perm gen size as it might not be.
1871 const size_t total_reserved = max_byte_size +
1872 align_size_up(pgs->max_size(), HeapRegion::GrainBytes);
1873 Universe::check_alignment(total_reserved, HeapRegion::GrainBytes, "g1 heap and perm");
1874
1875 char* addr = Universe::preferred_heap_base(total_reserved, Universe::UnscaledNarrowOop);
1876
1877 ReservedHeapSpace heap_rs(total_reserved, HeapRegion::GrainBytes,
1878 UseLargePages, addr);
1879
1880 if (UseCompressedOops) {
1881 if (addr != NULL && !heap_rs.is_reserved()) {
1882 // Failed to reserve at specified address - the requested memory
1883 // region is taken already, for example, by 'java' launcher.
1884 // Try again to reserver heap higher.
1885 addr = Universe::preferred_heap_base(total_reserved, Universe::ZeroBasedNarrowOop);
1886
1887 ReservedHeapSpace heap_rs0(total_reserved, HeapRegion::GrainBytes,
1888 UseLargePages, addr);
1889
1890 if (addr != NULL && !heap_rs0.is_reserved()) {
1891 // Failed to reserve at specified address again - give up.
1892 addr = Universe::preferred_heap_base(total_reserved, Universe::HeapBasedNarrowOop);
1893 assert(addr == NULL, "");
1894
1895 ReservedHeapSpace heap_rs1(total_reserved, HeapRegion::GrainBytes,
1896 UseLargePages, addr);
1897 heap_rs = heap_rs1;
1898 } else {
1899 heap_rs = heap_rs0;
1900 }
1901 }
1902 }
1903
1904 if (!heap_rs.is_reserved()) {
1905 vm_exit_during_initialization("Could not reserve enough space for object heap");
1906 return JNI_ENOMEM;
1907 }
1908
1909 // It is important to do this in a way such that concurrent readers can't
1910 // temporarily think somethings in the heap. (I've actually seen this
1911 // happen in asserts: DLD.)
1912 _reserved.set_word_size(0);
1913 _reserved.set_start((HeapWord*)heap_rs.base());
1914 _reserved.set_end((HeapWord*)(heap_rs.base() + heap_rs.size()));
1915
1916 _expansion_regions = max_byte_size/HeapRegion::GrainBytes;
1917
1918 // Create the gen rem set (and barrier set) for the entire reserved region.
1919 _rem_set = collector_policy()->create_rem_set(_reserved, 2);
1920 set_barrier_set(rem_set()->bs());
1921 if (barrier_set()->is_a(BarrierSet::ModRef)) {
1922 _mr_bs = (ModRefBarrierSet*)_barrier_set;
1923 } else {
1924 vm_exit_during_initialization("G1 requires a mod ref bs.");
1925 return JNI_ENOMEM;
1926 }
1927
1928 // Also create a G1 rem set.
1929 if (mr_bs()->is_a(BarrierSet::CardTableModRef)) {
1930 _g1_rem_set = new G1RemSet(this, (CardTableModRefBS*)mr_bs());
1931 } else {
1932 vm_exit_during_initialization("G1 requires a cardtable mod ref bs.");
1933 return JNI_ENOMEM;
1934 }
1935
1936 // Carve out the G1 part of the heap.
1937
1938 ReservedSpace g1_rs = heap_rs.first_part(max_byte_size);
1939 _g1_reserved = MemRegion((HeapWord*)g1_rs.base(),
1940 g1_rs.size()/HeapWordSize);
1941 ReservedSpace perm_gen_rs = heap_rs.last_part(max_byte_size);
1942
1943 _perm_gen = pgs->init(perm_gen_rs, pgs->init_size(), rem_set());
1944
1945 _g1_storage.initialize(g1_rs, 0);
1946 _g1_committed = MemRegion((HeapWord*)_g1_storage.low(), (size_t) 0);
1947 _hrs.initialize((HeapWord*) _g1_reserved.start(),
1948 (HeapWord*) _g1_reserved.end(),
1949 _expansion_regions);
1950
1951 // 6843694 - ensure that the maximum region index can fit
1952 // in the remembered set structures.
1953 const size_t max_region_idx = ((size_t)1 << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
1954 guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
1955
1956 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
1957 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
1958 guarantee((size_t) HeapRegion::CardsPerRegion < max_cards_per_region,
1959 "too many cards per region");
1960
1961 HeapRegionSet::set_unrealistically_long_length(max_regions() + 1);
1962
1963 _bot_shared = new G1BlockOffsetSharedArray(_reserved,
1964 heap_word_size(init_byte_size));
1965
1966 _g1h = this;
1967
1968 _in_cset_fast_test_length = max_regions();
1969 _in_cset_fast_test_base = NEW_C_HEAP_ARRAY(bool, _in_cset_fast_test_length);
1970
1971 // We're biasing _in_cset_fast_test to avoid subtracting the
1972 // beginning of the heap every time we want to index; basically
1973 // it's the same with what we do with the card table.
1974 _in_cset_fast_test = _in_cset_fast_test_base -
1975 ((size_t) _g1_reserved.start() >> HeapRegion::LogOfHRGrainBytes);
1976
1977 // Clear the _cset_fast_test bitmap in anticipation of adding
1978 // regions to the incremental collection set for the first
1979 // evacuation pause.
1980 clear_cset_fast_test();
1981
1982 // Create the ConcurrentMark data structure and thread.
1983 // (Must do this late, so that "max_regions" is defined.)
1984 _cm = new ConcurrentMark(heap_rs, (int) max_regions());
1985 _cmThread = _cm->cmThread();
1986
1987 // Initialize the from_card cache structure of HeapRegionRemSet.
1988 HeapRegionRemSet::init_heap(max_regions());
1989
1990 // Now expand into the initial heap size.
1991 if (!expand(init_byte_size)) {
1992 vm_exit_during_initialization("Failed to allocate initial heap.");
1993 return JNI_ENOMEM;
1994 }
1995
1996 // Perform any initialization actions delegated to the policy.
1997 g1_policy()->init();
1998
1999 g1_policy()->note_start_of_mark_thread();
2000
2001 _refine_cte_cl =
2002 new RefineCardTableEntryClosure(ConcurrentG1RefineThread::sts(),
2003 g1_rem_set(),
2004 concurrent_g1_refine());
2005 JavaThread::dirty_card_queue_set().set_closure(_refine_cte_cl);
2006
2007 JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon,
2008 SATB_Q_FL_lock,
2009 G1SATBProcessCompletedThreshold,
2010 Shared_SATB_Q_lock);
2011
2012 JavaThread::dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
2013 DirtyCardQ_FL_lock,
2014 concurrent_g1_refine()->yellow_zone(),
2015 concurrent_g1_refine()->red_zone(),
2016 Shared_DirtyCardQ_lock);
2017
2018 if (G1DeferredRSUpdate) {
2019 dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
2020 DirtyCardQ_FL_lock,
2021 -1, // never trigger processing
2022 -1, // no limit on length
2023 Shared_DirtyCardQ_lock,
2024 &JavaThread::dirty_card_queue_set());
2025 }
2026
2027 // Initialize the card queue set used to hold cards containing
2028 // references into the collection set.
2029 _into_cset_dirty_card_queue_set.initialize(DirtyCardQ_CBL_mon,
2030 DirtyCardQ_FL_lock,
2031 -1, // never trigger processing
2032 -1, // no limit on length
2033 Shared_DirtyCardQ_lock,
2034 &JavaThread::dirty_card_queue_set());
2035
2036 // In case we're keeping closure specialization stats, initialize those
2037 // counts and that mechanism.
2038 SpecializationStats::clear();
2039
2040 // Do later initialization work for concurrent refinement.
2041 _cg1r->init();
2042
2043 // Here we allocate the dummy full region that is required by the
2044 // G1AllocRegion class. If we don't pass an address in the reserved
2045 // space here, lots of asserts fire.
2046
2047 HeapRegion* dummy_region = new_heap_region(0 /* index of bottom region */,
2048 _g1_reserved.start());
2049 // We'll re-use the same region whether the alloc region will
2050 // require BOT updates or not and, if it doesn't, then a non-young
2051 // region will complain that it cannot support allocations without
2052 // BOT updates. So we'll tag the dummy region as young to avoid that.
2053 dummy_region->set_young();
2054 // Make sure it's full.
2055 dummy_region->set_top(dummy_region->end());
2056 G1AllocRegion::setup(this, dummy_region);
2057
2058 init_mutator_alloc_region();
2059
2060 // Do create of the monitoring and management support so that
2061 // values in the heap have been properly initialized.
2062 _g1mm = new G1MonitoringSupport(this, &_g1_storage);
2063
2064 return JNI_OK;
2065 }
2066
2067 void G1CollectedHeap::ref_processing_init() {
2068 // Reference processing in G1 currently works as follows:
2069 //
2070 // * There is only one reference processor instance that
2071 // 'spans' the entire heap. It is created by the code
2072 // below.
2073 // * Reference discovery is not enabled during an incremental
2074 // pause (see 6484982).
2075 // * Discoverered refs are not enqueued nor are they processed
2076 // during an incremental pause (see 6484982).
2077 // * Reference discovery is enabled at initial marking.
2078 // * Reference discovery is disabled and the discovered
2079 // references processed etc during remarking.
2080 // * Reference discovery is MT (see below).
2081 // * Reference discovery requires a barrier (see below).
2082 // * Reference processing is currently not MT (see 6608385).
2083 // * A full GC enables (non-MT) reference discovery and
2084 // processes any discovered references.
2085
2086 SharedHeap::ref_processing_init();
2087 MemRegion mr = reserved_region();
2088 _ref_processor =
2089 new ReferenceProcessor(mr, // span
2090 ParallelRefProcEnabled && (ParallelGCThreads > 1), // mt processing
2091 (int) ParallelGCThreads, // degree of mt processing
2092 ParallelGCThreads > 1 || ConcGCThreads > 1, // mt discovery
2093 (int) MAX2(ParallelGCThreads, ConcGCThreads), // degree of mt discovery
2094 false, // Reference discovery is not atomic
2095 &_is_alive_closure, // is alive closure for efficiency
2096 true); // Setting next fields of discovered
2097 // lists requires a barrier.
2098 }
2099
2100 size_t G1CollectedHeap::capacity() const {
2101 return _g1_committed.byte_size();
2102 }
2103
2104 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl,
2105 DirtyCardQueue* into_cset_dcq,
2106 bool concurrent,
2107 int worker_i) {
2108 // Clean cards in the hot card cache
2109 concurrent_g1_refine()->clean_up_cache(worker_i, g1_rem_set(), into_cset_dcq);
2110
2111 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2112 int n_completed_buffers = 0;
2113 while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) {
2114 n_completed_buffers++;
2115 }
2116 g1_policy()->record_update_rs_processed_buffers(worker_i,
2117 (double) n_completed_buffers);
2118 dcqs.clear_n_completed_buffers();
2119 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!");
2120 }
2121
2122
2123 // Computes the sum of the storage used by the various regions.
2124
2125 size_t G1CollectedHeap::used() const {
2126 assert(Heap_lock->owner() != NULL,
2127 "Should be owned on this thread's behalf.");
2128 size_t result = _summary_bytes_used;
2129 // Read only once in case it is set to NULL concurrently
2130 HeapRegion* hr = _mutator_alloc_region.get();
2131 if (hr != NULL)
2132 result += hr->used();
2133 return result;
2134 }
2135
2136 size_t G1CollectedHeap::used_unlocked() const {
2137 size_t result = _summary_bytes_used;
2138 return result;
2139 }
2140
2141 class SumUsedClosure: public HeapRegionClosure {
2142 size_t _used;
2143 public:
2144 SumUsedClosure() : _used(0) {}
2145 bool doHeapRegion(HeapRegion* r) {
2146 if (!r->continuesHumongous()) {
2147 _used += r->used();
2148 }
2149 return false;
2150 }
2151 size_t result() { return _used; }
2152 };
2153
2154 size_t G1CollectedHeap::recalculate_used() const {
2155 SumUsedClosure blk;
2156 heap_region_iterate(&blk);
2157 return blk.result();
2158 }
2159
2160 size_t G1CollectedHeap::unsafe_max_alloc() {
2161 if (free_regions() > 0) return HeapRegion::GrainBytes;
2162 // otherwise, is there space in the current allocation region?
2163
2164 // We need to store the current allocation region in a local variable
2165 // here. The problem is that this method doesn't take any locks and
2166 // there may be other threads which overwrite the current allocation
2167 // region field. attempt_allocation(), for example, sets it to NULL
2168 // and this can happen *after* the NULL check here but before the call
2169 // to free(), resulting in a SIGSEGV. Note that this doesn't appear
2170 // to be a problem in the optimized build, since the two loads of the
2171 // current allocation region field are optimized away.
2172 HeapRegion* hr = _mutator_alloc_region.get();
2173 if (hr == NULL) {
2174 return 0;
2175 }
2176 return hr->free();
2177 }
2178
2179 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
2180 return
2181 ((cause == GCCause::_gc_locker && GCLockerInvokesConcurrent) ||
2182 (cause == GCCause::_java_lang_system_gc && ExplicitGCInvokesConcurrent));
2183 }
2184
2185 #ifndef PRODUCT
2186 void G1CollectedHeap::allocate_dummy_regions() {
2187 // Let's fill up most of the region
2188 size_t word_size = HeapRegion::GrainWords - 1024;
2189 // And as a result the region we'll allocate will be humongous.
2190 guarantee(isHumongous(word_size), "sanity");
2191
2192 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
2193 // Let's use the existing mechanism for the allocation
2194 HeapWord* dummy_obj = humongous_obj_allocate(word_size);
2195 if (dummy_obj != NULL) {
2196 MemRegion mr(dummy_obj, word_size);
2197 CollectedHeap::fill_with_object(mr);
2198 } else {
2199 // If we can't allocate once, we probably cannot allocate
2200 // again. Let's get out of the loop.
2201 break;
2202 }
2203 }
2204 }
2205 #endif // !PRODUCT
2206
2207 void G1CollectedHeap::increment_full_collections_completed(bool concurrent) {
2208 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
2209
2210 // We assume that if concurrent == true, then the caller is a
2211 // concurrent thread that was joined the Suspendible Thread
2212 // Set. If there's ever a cheap way to check this, we should add an
2213 // assert here.
2214
2215 // We have already incremented _total_full_collections at the start
2216 // of the GC, so total_full_collections() represents how many full
2217 // collections have been started.
2218 unsigned int full_collections_started = total_full_collections();
2219
2220 // Given that this method is called at the end of a Full GC or of a
2221 // concurrent cycle, and those can be nested (i.e., a Full GC can
2222 // interrupt a concurrent cycle), the number of full collections
2223 // completed should be either one (in the case where there was no
2224 // nesting) or two (when a Full GC interrupted a concurrent cycle)
2225 // behind the number of full collections started.
2226
2227 // This is the case for the inner caller, i.e. a Full GC.
2228 assert(concurrent ||
2229 (full_collections_started == _full_collections_completed + 1) ||
2230 (full_collections_started == _full_collections_completed + 2),
2231 err_msg("for inner caller (Full GC): full_collections_started = %u "
2232 "is inconsistent with _full_collections_completed = %u",
2233 full_collections_started, _full_collections_completed));
2234
2235 // This is the case for the outer caller, i.e. the concurrent cycle.
2236 assert(!concurrent ||
2237 (full_collections_started == _full_collections_completed + 1),
2238 err_msg("for outer caller (concurrent cycle): "
2239 "full_collections_started = %u "
2240 "is inconsistent with _full_collections_completed = %u",
2241 full_collections_started, _full_collections_completed));
2242
2243 _full_collections_completed += 1;
2244
2245 // We need to clear the "in_progress" flag in the CM thread before
2246 // we wake up any waiters (especially when ExplicitInvokesConcurrent
2247 // is set) so that if a waiter requests another System.gc() it doesn't
2248 // incorrectly see that a marking cyle is still in progress.
2249 if (concurrent) {
2250 _cmThread->clear_in_progress();
2251 }
2252
2253 // This notify_all() will ensure that a thread that called
2254 // System.gc() with (with ExplicitGCInvokesConcurrent set or not)
2255 // and it's waiting for a full GC to finish will be woken up. It is
2256 // waiting in VM_G1IncCollectionPause::doit_epilogue().
2257 FullGCCount_lock->notify_all();
2258 }
2259
2260 void G1CollectedHeap::collect_as_vm_thread(GCCause::Cause cause) {
2261 assert_at_safepoint(true /* should_be_vm_thread */);
2262 GCCauseSetter gcs(this, cause);
2263 switch (cause) {
2264 case GCCause::_heap_inspection:
2265 case GCCause::_heap_dump: {
2266 HandleMark hm;
2267 do_full_collection(false); // don't clear all soft refs
2268 break;
2269 }
2270 default: // XXX FIX ME
2271 ShouldNotReachHere(); // Unexpected use of this function
2272 }
2273 }
2274
2275 void G1CollectedHeap::collect(GCCause::Cause cause) {
2276 // The caller doesn't have the Heap_lock
2277 assert(!Heap_lock->owned_by_self(), "this thread should not own the Heap_lock");
2278
2279 unsigned int gc_count_before;
2280 unsigned int full_gc_count_before;
2281 {
2282 MutexLocker ml(Heap_lock);
2283
2284 // Read the GC count while holding the Heap_lock
2285 gc_count_before = SharedHeap::heap()->total_collections();
2286 full_gc_count_before = SharedHeap::heap()->total_full_collections();
2287 }
2288
2289 if (should_do_concurrent_full_gc(cause)) {
2290 // Schedule an initial-mark evacuation pause that will start a
2291 // concurrent cycle. We're setting word_size to 0 which means that
2292 // we are not requesting a post-GC allocation.
2293 VM_G1IncCollectionPause op(gc_count_before,
2294 0, /* word_size */
2295 true, /* should_initiate_conc_mark */
2296 g1_policy()->max_pause_time_ms(),
2297 cause);
2298 VMThread::execute(&op);
2299 } else {
2300 if (cause == GCCause::_gc_locker
2301 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2302
2303 // Schedule a standard evacuation pause. We're setting word_size
2304 // to 0 which means that we are not requesting a post-GC allocation.
2305 VM_G1IncCollectionPause op(gc_count_before,
2306 0, /* word_size */
2307 false, /* should_initiate_conc_mark */
2308 g1_policy()->max_pause_time_ms(),
2309 cause);
2310 VMThread::execute(&op);
2311 } else {
2312 // Schedule a Full GC.
2313 VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause);
2314 VMThread::execute(&op);
2315 }
2316 }
2317 }
2318
2319 bool G1CollectedHeap::is_in(const void* p) const {
2320 HeapRegion* hr = _hrs.addr_to_region((HeapWord*) p);
2321 if (hr != NULL) {
2322 return hr->is_in(p);
2323 } else {
2324 return _perm_gen->as_gen()->is_in(p);
2325 }
2326 }
2327
2328 // Iteration functions.
2329
2330 // Iterates an OopClosure over all ref-containing fields of objects
2331 // within a HeapRegion.
2332
2333 class IterateOopClosureRegionClosure: public HeapRegionClosure {
2334 MemRegion _mr;
2335 OopClosure* _cl;
2336 public:
2337 IterateOopClosureRegionClosure(MemRegion mr, OopClosure* cl)
2338 : _mr(mr), _cl(cl) {}
2339 bool doHeapRegion(HeapRegion* r) {
2340 if (! r->continuesHumongous()) {
2341 r->oop_iterate(_cl);
2342 }
2343 return false;
2344 }
2345 };
2346
2347 void G1CollectedHeap::oop_iterate(OopClosure* cl, bool do_perm) {
2348 IterateOopClosureRegionClosure blk(_g1_committed, cl);
2349 heap_region_iterate(&blk);
2350 if (do_perm) {
2351 perm_gen()->oop_iterate(cl);
2352 }
2353 }
2354
2355 void G1CollectedHeap::oop_iterate(MemRegion mr, OopClosure* cl, bool do_perm) {
2356 IterateOopClosureRegionClosure blk(mr, cl);
2357 heap_region_iterate(&blk);
2358 if (do_perm) {
2359 perm_gen()->oop_iterate(cl);
2360 }
2361 }
2362
2363 // Iterates an ObjectClosure over all objects within a HeapRegion.
2364
2365 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2366 ObjectClosure* _cl;
2367 public:
2368 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2369 bool doHeapRegion(HeapRegion* r) {
2370 if (! r->continuesHumongous()) {
2371 r->object_iterate(_cl);
2372 }
2373 return false;
2374 }
2375 };
2376
2377 void G1CollectedHeap::object_iterate(ObjectClosure* cl, bool do_perm) {
2378 IterateObjectClosureRegionClosure blk(cl);
2379 heap_region_iterate(&blk);
2380 if (do_perm) {
2381 perm_gen()->object_iterate(cl);
2382 }
2383 }
2384
2385 void G1CollectedHeap::object_iterate_since_last_GC(ObjectClosure* cl) {
2386 // FIXME: is this right?
2387 guarantee(false, "object_iterate_since_last_GC not supported by G1 heap");
2388 }
2389
2390 // Calls a SpaceClosure on a HeapRegion.
2391
2392 class SpaceClosureRegionClosure: public HeapRegionClosure {
2393 SpaceClosure* _cl;
2394 public:
2395 SpaceClosureRegionClosure(SpaceClosure* cl) : _cl(cl) {}
2396 bool doHeapRegion(HeapRegion* r) {
2397 _cl->do_space(r);
2398 return false;
2399 }
2400 };
2401
2402 void G1CollectedHeap::space_iterate(SpaceClosure* cl) {
2403 SpaceClosureRegionClosure blk(cl);
2404 heap_region_iterate(&blk);
2405 }
2406
2407 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2408 _hrs.iterate(cl);
2409 }
2410
2411 void G1CollectedHeap::heap_region_iterate_from(HeapRegion* r,
2412 HeapRegionClosure* cl) const {
2413 _hrs.iterate_from(r, cl);
2414 }
2415
2416 void
2417 G1CollectedHeap::heap_region_par_iterate_chunked(HeapRegionClosure* cl,
2418 int worker,
2419 jint claim_value) {
2420 const size_t regions = n_regions();
2421 const size_t worker_num = (G1CollectedHeap::use_parallel_gc_threads() ? ParallelGCThreads : 1);
2422 // try to spread out the starting points of the workers
2423 const size_t start_index = regions / worker_num * (size_t) worker;
2424
2425 // each worker will actually look at all regions
2426 for (size_t count = 0; count < regions; ++count) {
2427 const size_t index = (start_index + count) % regions;
2428 assert(0 <= index && index < regions, "sanity");
2429 HeapRegion* r = region_at(index);
2430 // we'll ignore "continues humongous" regions (we'll process them
2431 // when we come across their corresponding "start humongous"
2432 // region) and regions already claimed
2433 if (r->claim_value() == claim_value || r->continuesHumongous()) {
2434 continue;
2435 }
2436 // OK, try to claim it
2437 if (r->claimHeapRegion(claim_value)) {
2438 // success!
2439 assert(!r->continuesHumongous(), "sanity");
2440 if (r->startsHumongous()) {
2441 // If the region is "starts humongous" we'll iterate over its
2442 // "continues humongous" first; in fact we'll do them
2443 // first. The order is important. In on case, calling the
2444 // closure on the "starts humongous" region might de-allocate
2445 // and clear all its "continues humongous" regions and, as a
2446 // result, we might end up processing them twice. So, we'll do
2447 // them first (notice: most closures will ignore them anyway) and
2448 // then we'll do the "starts humongous" region.
2449 for (size_t ch_index = index + 1; ch_index < regions; ++ch_index) {
2450 HeapRegion* chr = region_at(ch_index);
2451
2452 // if the region has already been claimed or it's not
2453 // "continues humongous" we're done
2454 if (chr->claim_value() == claim_value ||
2455 !chr->continuesHumongous()) {
2456 break;
2457 }
2458
2459 // Noone should have claimed it directly. We can given
2460 // that we claimed its "starts humongous" region.
2461 assert(chr->claim_value() != claim_value, "sanity");
2462 assert(chr->humongous_start_region() == r, "sanity");
2463
2464 if (chr->claimHeapRegion(claim_value)) {
2465 // we should always be able to claim it; noone else should
2466 // be trying to claim this region
2467
2468 bool res2 = cl->doHeapRegion(chr);
2469 assert(!res2, "Should not abort");
2470
2471 // Right now, this holds (i.e., no closure that actually
2472 // does something with "continues humongous" regions
2473 // clears them). We might have to weaken it in the future,
2474 // but let's leave these two asserts here for extra safety.
2475 assert(chr->continuesHumongous(), "should still be the case");
2476 assert(chr->humongous_start_region() == r, "sanity");
2477 } else {
2478 guarantee(false, "we should not reach here");
2479 }
2480 }
2481 }
2482
2483 assert(!r->continuesHumongous(), "sanity");
2484 bool res = cl->doHeapRegion(r);
2485 assert(!res, "Should not abort");
2486 }
2487 }
2488 }
2489
2490 class ResetClaimValuesClosure: public HeapRegionClosure {
2491 public:
2492 bool doHeapRegion(HeapRegion* r) {
2493 r->set_claim_value(HeapRegion::InitialClaimValue);
2494 return false;
2495 }
2496 };
2497
2498 void
2499 G1CollectedHeap::reset_heap_region_claim_values() {
2500 ResetClaimValuesClosure blk;
2501 heap_region_iterate(&blk);
2502 }
2503
2504 #ifdef ASSERT
2505 // This checks whether all regions in the heap have the correct claim
2506 // value. I also piggy-backed on this a check to ensure that the
2507 // humongous_start_region() information on "continues humongous"
2508 // regions is correct.
2509
2510 class CheckClaimValuesClosure : public HeapRegionClosure {
2511 private:
2512 jint _claim_value;
2513 size_t _failures;
2514 HeapRegion* _sh_region;
2515 public:
2516 CheckClaimValuesClosure(jint claim_value) :
2517 _claim_value(claim_value), _failures(0), _sh_region(NULL) { }
2518 bool doHeapRegion(HeapRegion* r) {
2519 if (r->claim_value() != _claim_value) {
2520 gclog_or_tty->print_cr("Region ["PTR_FORMAT","PTR_FORMAT"), "
2521 "claim value = %d, should be %d",
2522 r->bottom(), r->end(), r->claim_value(),
2523 _claim_value);
2524 ++_failures;
2525 }
2526 if (!r->isHumongous()) {
2527 _sh_region = NULL;
2528 } else if (r->startsHumongous()) {
2529 _sh_region = r;
2530 } else if (r->continuesHumongous()) {
2531 if (r->humongous_start_region() != _sh_region) {
2532 gclog_or_tty->print_cr("Region ["PTR_FORMAT","PTR_FORMAT"), "
2533 "HS = "PTR_FORMAT", should be "PTR_FORMAT,
2534 r->bottom(), r->end(),
2535 r->humongous_start_region(),
2536 _sh_region);
2537 ++_failures;
2538 }
2539 }
2540 return false;
2541 }
2542 size_t failures() {
2543 return _failures;
2544 }
2545 };
2546
2547 bool G1CollectedHeap::check_heap_region_claim_values(jint claim_value) {
2548 CheckClaimValuesClosure cl(claim_value);
2549 heap_region_iterate(&cl);
2550 return cl.failures() == 0;
2551 }
2552 #endif // ASSERT
2553
2554 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) {
2555 HeapRegion* r = g1_policy()->collection_set();
2556 while (r != NULL) {
2557 HeapRegion* next = r->next_in_collection_set();
2558 if (cl->doHeapRegion(r)) {
2559 cl->incomplete();
2560 return;
2561 }
2562 r = next;
2563 }
2564 }
2565
2566 void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r,
2567 HeapRegionClosure *cl) {
2568 if (r == NULL) {
2569 // The CSet is empty so there's nothing to do.
2570 return;
2571 }
2572
2573 assert(r->in_collection_set(),
2574 "Start region must be a member of the collection set.");
2575 HeapRegion* cur = r;
2576 while (cur != NULL) {
2577 HeapRegion* next = cur->next_in_collection_set();
2578 if (cl->doHeapRegion(cur) && false) {
2579 cl->incomplete();
2580 return;
2581 }
2582 cur = next;
2583 }
2584 cur = g1_policy()->collection_set();
2585 while (cur != r) {
2586 HeapRegion* next = cur->next_in_collection_set();
2587 if (cl->doHeapRegion(cur) && false) {
2588 cl->incomplete();
2589 return;
2590 }
2591 cur = next;
2592 }
2593 }
2594
2595 CompactibleSpace* G1CollectedHeap::first_compactible_space() {
2596 return n_regions() > 0 ? region_at(0) : NULL;
2597 }
2598
2599
2600 Space* G1CollectedHeap::space_containing(const void* addr) const {
2601 Space* res = heap_region_containing(addr);
2602 if (res == NULL)
2603 res = perm_gen()->space_containing(addr);
2604 return res;
2605 }
2606
2607 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2608 Space* sp = space_containing(addr);
2609 if (sp != NULL) {
2610 return sp->block_start(addr);
2611 }
2612 return NULL;
2613 }
2614
2615 size_t G1CollectedHeap::block_size(const HeapWord* addr) const {
2616 Space* sp = space_containing(addr);
2617 assert(sp != NULL, "block_size of address outside of heap");
2618 return sp->block_size(addr);
2619 }
2620
2621 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2622 Space* sp = space_containing(addr);
2623 return sp->block_is_obj(addr);
2624 }
2625
2626 bool G1CollectedHeap::supports_tlab_allocation() const {
2627 return true;
2628 }
2629
2630 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
2631 return HeapRegion::GrainBytes;
2632 }
2633
2634 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
2635 // Return the remaining space in the cur alloc region, but not less than
2636 // the min TLAB size.
2637
2638 // Also, this value can be at most the humongous object threshold,
2639 // since we can't allow tlabs to grow big enough to accomodate
2640 // humongous objects.
2641
2642 HeapRegion* hr = _mutator_alloc_region.get();
2643 size_t max_tlab_size = _humongous_object_threshold_in_words * wordSize;
2644 if (hr == NULL) {
2645 return max_tlab_size;
2646 } else {
2647 return MIN2(MAX2(hr->free(), (size_t) MinTLABSize), max_tlab_size);
2648 }
2649 }
2650
2651 size_t G1CollectedHeap::max_capacity() const {
2652 return _g1_reserved.byte_size();
2653 }
2654
2655 jlong G1CollectedHeap::millis_since_last_gc() {
2656 // assert(false, "NYI");
2657 return 0;
2658 }
2659
2660 void G1CollectedHeap::prepare_for_verify() {
2661 if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) {
2662 ensure_parsability(false);
2663 }
2664 g1_rem_set()->prepare_for_verify();
2665 }
2666
2667 class VerifyLivenessOopClosure: public OopClosure {
2668 G1CollectedHeap* _g1h;
2669 VerifyOption _vo;
2670 public:
2671 VerifyLivenessOopClosure(G1CollectedHeap* g1h, VerifyOption vo):
2672 _g1h(g1h), _vo(vo)
2673 { }
2674 void do_oop(narrowOop *p) { do_oop_work(p); }
2675 void do_oop( oop *p) { do_oop_work(p); }
2676
2677 template <class T> void do_oop_work(T *p) {
2678 oop obj = oopDesc::load_decode_heap_oop(p);
2679 guarantee(obj == NULL || !_g1h->is_obj_dead_cond(obj, _vo),
2680 "Dead object referenced by a not dead object");
2681 }
2682 };
2683
2684 class VerifyObjsInRegionClosure: public ObjectClosure {
2685 private:
2686 G1CollectedHeap* _g1h;
2687 size_t _live_bytes;
2688 HeapRegion *_hr;
2689 VerifyOption _vo;
2690 public:
2691 // _vo == UsePrevMarking -> use "prev" marking information,
2692 // _vo == UseNextMarking -> use "next" marking information,
2693 // _vo == UseMarkWord -> use mark word from object header.
2694 VerifyObjsInRegionClosure(HeapRegion *hr, VerifyOption vo)
2695 : _live_bytes(0), _hr(hr), _vo(vo) {
2696 _g1h = G1CollectedHeap::heap();
2697 }
2698 void do_object(oop o) {
2699 VerifyLivenessOopClosure isLive(_g1h, _vo);
2700 assert(o != NULL, "Huh?");
2701 if (!_g1h->is_obj_dead_cond(o, _vo)) {
2702 // If the object is alive according to the mark word,
2703 // then verify that the marking information agrees.
2704 // Note we can't verify the contra-positive of the
2705 // above: if the object is dead (according to the mark
2706 // word), it may not be marked, or may have been marked
2707 // but has since became dead, or may have been allocated
2708 // since the last marking.
2709 if (_vo == VerifyOption_G1UseMarkWord) {
2710 guarantee(!_g1h->is_obj_dead(o), "mark word and concurrent mark mismatch");
2711 }
2712
2713 o->oop_iterate(&isLive);
2714 if (!_hr->obj_allocated_since_prev_marking(o)) {
2715 size_t obj_size = o->size(); // Make sure we don't overflow
2716 _live_bytes += (obj_size * HeapWordSize);
2717 }
2718 }
2719 }
2720 size_t live_bytes() { return _live_bytes; }
2721 };
2722
2723 class PrintObjsInRegionClosure : public ObjectClosure {
2724 HeapRegion *_hr;
2725 G1CollectedHeap *_g1;
2726 public:
2727 PrintObjsInRegionClosure(HeapRegion *hr) : _hr(hr) {
2728 _g1 = G1CollectedHeap::heap();
2729 };
2730
2731 void do_object(oop o) {
2732 if (o != NULL) {
2733 HeapWord *start = (HeapWord *) o;
2734 size_t word_sz = o->size();
2735 gclog_or_tty->print("\nPrinting obj "PTR_FORMAT" of size " SIZE_FORMAT
2736 " isMarkedPrev %d isMarkedNext %d isAllocSince %d\n",
2737 (void*) o, word_sz,
2738 _g1->isMarkedPrev(o),
2739 _g1->isMarkedNext(o),
2740 _hr->obj_allocated_since_prev_marking(o));
2741 HeapWord *end = start + word_sz;
2742 HeapWord *cur;
2743 int *val;
2744 for (cur = start; cur < end; cur++) {
2745 val = (int *) cur;
2746 gclog_or_tty->print("\t "PTR_FORMAT":"PTR_FORMAT"\n", val, *val);
2747 }
2748 }
2749 }
2750 };
2751
2752 class VerifyRegionClosure: public HeapRegionClosure {
2753 private:
2754 bool _allow_dirty;
2755 bool _par;
2756 VerifyOption _vo;
2757 bool _failures;
2758 public:
2759 // _vo == UsePrevMarking -> use "prev" marking information,
2760 // _vo == UseNextMarking -> use "next" marking information,
2761 // _vo == UseMarkWord -> use mark word from object header.
2762 VerifyRegionClosure(bool allow_dirty, bool par, VerifyOption vo)
2763 : _allow_dirty(allow_dirty),
2764 _par(par),
2765 _vo(vo),
2766 _failures(false) {}
2767
2768 bool failures() {
2769 return _failures;
2770 }
2771
2772 bool doHeapRegion(HeapRegion* r) {
2773 guarantee(_par || r->claim_value() == HeapRegion::InitialClaimValue,
2774 "Should be unclaimed at verify points.");
2775 if (!r->continuesHumongous()) {
2776 bool failures = false;
2777 r->verify(_allow_dirty, _vo, &failures);
2778 if (failures) {
2779 _failures = true;
2780 } else {
2781 VerifyObjsInRegionClosure not_dead_yet_cl(r, _vo);
2782 r->object_iterate(¬_dead_yet_cl);
2783 if (r->max_live_bytes() < not_dead_yet_cl.live_bytes()) {
2784 gclog_or_tty->print_cr("["PTR_FORMAT","PTR_FORMAT"] "
2785 "max_live_bytes "SIZE_FORMAT" "
2786 "< calculated "SIZE_FORMAT,
2787 r->bottom(), r->end(),
2788 r->max_live_bytes(),
2789 not_dead_yet_cl.live_bytes());
2790 _failures = true;
2791 }
2792 }
2793 }
2794 return false; // stop the region iteration if we hit a failure
2795 }
2796 };
2797
2798 class VerifyRootsClosure: public OopsInGenClosure {
2799 private:
2800 G1CollectedHeap* _g1h;
2801 VerifyOption _vo;
2802 bool _failures;
2803 public:
2804 // _vo == UsePrevMarking -> use "prev" marking information,
2805 // _vo == UseNextMarking -> use "next" marking information,
2806 // _vo == UseMarkWord -> use mark word from object header.
2807 VerifyRootsClosure(VerifyOption vo) :
2808 _g1h(G1CollectedHeap::heap()),
2809 _vo(vo),
2810 _failures(false) { }
2811
2812 bool failures() { return _failures; }
2813
2814 template <class T> void do_oop_nv(T* p) {
2815 T heap_oop = oopDesc::load_heap_oop(p);
2816 if (!oopDesc::is_null(heap_oop)) {
2817 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
2818 if (_g1h->is_obj_dead_cond(obj, _vo)) {
2819 gclog_or_tty->print_cr("Root location "PTR_FORMAT" "
2820 "points to dead obj "PTR_FORMAT, p, (void*) obj);
2821 if (_vo == VerifyOption_G1UseMarkWord) {
2822 gclog_or_tty->print_cr(" Mark word: "PTR_FORMAT, (void*)(obj->mark()));
2823 }
2824 obj->print_on(gclog_or_tty);
2825 _failures = true;
2826 }
2827 }
2828 }
2829
2830 void do_oop(oop* p) { do_oop_nv(p); }
2831 void do_oop(narrowOop* p) { do_oop_nv(p); }
2832 };
2833
2834 // This is the task used for parallel heap verification.
2835
2836 class G1ParVerifyTask: public AbstractGangTask {
2837 private:
2838 G1CollectedHeap* _g1h;
2839 bool _allow_dirty;
2840 VerifyOption _vo;
2841 bool _failures;
2842
2843 public:
2844 // _vo == UsePrevMarking -> use "prev" marking information,
2845 // _vo == UseNextMarking -> use "next" marking information,
2846 // _vo == UseMarkWord -> use mark word from object header.
2847 G1ParVerifyTask(G1CollectedHeap* g1h, bool allow_dirty, VerifyOption vo) :
2848 AbstractGangTask("Parallel verify task"),
2849 _g1h(g1h),
2850 _allow_dirty(allow_dirty),
2851 _vo(vo),
2852 _failures(false) { }
2853
2854 bool failures() {
2855 return _failures;
2856 }
2857
2858 void work(int worker_i) {
2859 HandleMark hm;
2860 VerifyRegionClosure blk(_allow_dirty, true, _vo);
2861 _g1h->heap_region_par_iterate_chunked(&blk, worker_i,
2862 HeapRegion::ParVerifyClaimValue);
2863 if (blk.failures()) {
2864 _failures = true;
2865 }
2866 }
2867 };
2868
2869 void G1CollectedHeap::verify(bool allow_dirty, bool silent) {
2870 verify(allow_dirty, silent, VerifyOption_G1UsePrevMarking);
2871 }
2872
2873 void G1CollectedHeap::verify(bool allow_dirty,
2874 bool silent,
2875 VerifyOption vo) {
2876 if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) {
2877 if (!silent) { gclog_or_tty->print("Roots (excluding permgen) "); }
2878 VerifyRootsClosure rootsCl(vo);
2879 CodeBlobToOopClosure blobsCl(&rootsCl, /*do_marking=*/ false);
2880
2881 // We apply the relevant closures to all the oops in the
2882 // system dictionary, the string table and the code cache.
2883 const int so = SharedHeap::SO_AllClasses | SharedHeap::SO_Strings | SharedHeap::SO_CodeCache;
2884
2885 process_strong_roots(true, // activate StrongRootsScope
2886 true, // we set "collecting perm gen" to true,
2887 // so we don't reset the dirty cards in the perm gen.
2888 SharedHeap::ScanningOption(so), // roots scanning options
2889 &rootsCl,
2890 &blobsCl,
2891 &rootsCl);
2892
2893 // If we're verifying after the marking phase of a Full GC then we can't
2894 // treat the perm gen as roots into the G1 heap. Some of the objects in
2895 // the perm gen may be dead and hence not marked. If one of these dead
2896 // objects is considered to be a root then we may end up with a false
2897 // "Root location <x> points to dead ob <y>" failure.
2898 if (vo != VerifyOption_G1UseMarkWord) {
2899 // Since we used "collecting_perm_gen" == true above, we will not have
2900 // checked the refs from perm into the G1-collected heap. We check those
2901 // references explicitly below. Whether the relevant cards are dirty
2902 // is checked further below in the rem set verification.
2903 if (!silent) { gclog_or_tty->print("Permgen roots "); }
2904 perm_gen()->oop_iterate(&rootsCl);
2905 }
2906 bool failures = rootsCl.failures();
2907
2908 if (vo != VerifyOption_G1UseMarkWord) {
2909 // If we're verifying during a full GC then the region sets
2910 // will have been torn down at the start of the GC. Therefore
2911 // verifying the region sets will fail. So we only verify
2912 // the region sets when not in a full GC.
2913 if (!silent) { gclog_or_tty->print("HeapRegionSets "); }
2914 verify_region_sets();
2915 }
2916
2917 if (!silent) { gclog_or_tty->print("HeapRegions "); }
2918 if (GCParallelVerificationEnabled && ParallelGCThreads > 1) {
2919 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
2920 "sanity check");
2921
2922 G1ParVerifyTask task(this, allow_dirty, vo);
2923 int n_workers = workers()->total_workers();
2924 set_par_threads(n_workers);
2925 workers()->run_task(&task);
2926 set_par_threads(0);
2927 if (task.failures()) {
2928 failures = true;
2929 }
2930
2931 assert(check_heap_region_claim_values(HeapRegion::ParVerifyClaimValue),
2932 "sanity check");
2933
2934 reset_heap_region_claim_values();
2935
2936 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
2937 "sanity check");
2938 } else {
2939 VerifyRegionClosure blk(allow_dirty, false, vo);
2940 heap_region_iterate(&blk);
2941 if (blk.failures()) {
2942 failures = true;
2943 }
2944 }
2945 if (!silent) gclog_or_tty->print("RemSet ");
2946 rem_set()->verify();
2947
2948 if (failures) {
2949 gclog_or_tty->print_cr("Heap:");
2950 print_on(gclog_or_tty, true /* extended */);
2951 gclog_or_tty->print_cr("");
2952 #ifndef PRODUCT
2953 if (VerifyDuringGC && G1VerifyDuringGCPrintReachable) {
2954 concurrent_mark()->print_reachable("at-verification-failure",
2955 vo, false /* all */);
2956 }
2957 #endif
2958 gclog_or_tty->flush();
2959 }
2960 guarantee(!failures, "there should not have been any failures");
2961 } else {
2962 if (!silent) gclog_or_tty->print("(SKIPPING roots, heapRegions, remset) ");
2963 }
2964 }
2965
2966 class PrintRegionClosure: public HeapRegionClosure {
2967 outputStream* _st;
2968 public:
2969 PrintRegionClosure(outputStream* st) : _st(st) {}
2970 bool doHeapRegion(HeapRegion* r) {
2971 r->print_on(_st);
2972 return false;
2973 }
2974 };
2975
2976 void G1CollectedHeap::print() const { print_on(tty); }
2977
2978 void G1CollectedHeap::print_on(outputStream* st) const {
2979 print_on(st, PrintHeapAtGCExtended);
2980 }
2981
2982 void G1CollectedHeap::print_on(outputStream* st, bool extended) const {
2983 st->print(" %-20s", "garbage-first heap");
2984 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
2985 capacity()/K, used_unlocked()/K);
2986 st->print(" [" INTPTR_FORMAT ", " INTPTR_FORMAT ", " INTPTR_FORMAT ")",
2987 _g1_storage.low_boundary(),
2988 _g1_storage.high(),
2989 _g1_storage.high_boundary());
2990 st->cr();
2991 st->print(" region size " SIZE_FORMAT "K, ",
2992 HeapRegion::GrainBytes/K);
2993 size_t young_regions = _young_list->length();
2994 st->print(SIZE_FORMAT " young (" SIZE_FORMAT "K), ",
2995 young_regions, young_regions * HeapRegion::GrainBytes / K);
2996 size_t survivor_regions = g1_policy()->recorded_survivor_regions();
2997 st->print(SIZE_FORMAT " survivors (" SIZE_FORMAT "K)",
2998 survivor_regions, survivor_regions * HeapRegion::GrainBytes / K);
2999 st->cr();
3000 perm()->as_gen()->print_on(st);
3001 if (extended) {
3002 st->cr();
3003 print_on_extended(st);
3004 }
3005 }
3006
3007 void G1CollectedHeap::print_on_extended(outputStream* st) const {
3008 PrintRegionClosure blk(st);
3009 heap_region_iterate(&blk);
3010 }
3011
3012 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
3013 if (G1CollectedHeap::use_parallel_gc_threads()) {
3014 workers()->print_worker_threads_on(st);
3015 }
3016 _cmThread->print_on(st);
3017 st->cr();
3018 _cm->print_worker_threads_on(st);
3019 _cg1r->print_worker_threads_on(st);
3020 st->cr();
3021 }
3022
3023 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
3024 if (G1CollectedHeap::use_parallel_gc_threads()) {
3025 workers()->threads_do(tc);
3026 }
3027 tc->do_thread(_cmThread);
3028 _cg1r->threads_do(tc);
3029 }
3030
3031 void G1CollectedHeap::print_tracing_info() const {
3032 // We'll overload this to mean "trace GC pause statistics."
3033 if (TraceGen0Time || TraceGen1Time) {
3034 // The "G1CollectorPolicy" is keeping track of these stats, so delegate
3035 // to that.
3036 g1_policy()->print_tracing_info();
3037 }
3038 if (G1SummarizeRSetStats) {
3039 g1_rem_set()->print_summary_info();
3040 }
3041 if (G1SummarizeConcMark) {
3042 concurrent_mark()->print_summary_info();
3043 }
3044 g1_policy()->print_yg_surv_rate_info();
3045 SpecializationStats::print();
3046 }
3047
3048 #ifndef PRODUCT
3049 // Helpful for debugging RSet issues.
3050
3051 class PrintRSetsClosure : public HeapRegionClosure {
3052 private:
3053 const char* _msg;
3054 size_t _occupied_sum;
3055
3056 public:
3057 bool doHeapRegion(HeapRegion* r) {
3058 HeapRegionRemSet* hrrs = r->rem_set();
3059 size_t occupied = hrrs->occupied();
3060 _occupied_sum += occupied;
3061
3062 gclog_or_tty->print_cr("Printing RSet for region "HR_FORMAT,
3063 HR_FORMAT_PARAMS(r));
3064 if (occupied == 0) {
3065 gclog_or_tty->print_cr(" RSet is empty");
3066 } else {
3067 hrrs->print();
3068 }
3069 gclog_or_tty->print_cr("----------");
3070 return false;
3071 }
3072
3073 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
3074 gclog_or_tty->cr();
3075 gclog_or_tty->print_cr("========================================");
3076 gclog_or_tty->print_cr(msg);
3077 gclog_or_tty->cr();
3078 }
3079
3080 ~PrintRSetsClosure() {
3081 gclog_or_tty->print_cr("Occupied Sum: "SIZE_FORMAT, _occupied_sum);
3082 gclog_or_tty->print_cr("========================================");
3083 gclog_or_tty->cr();
3084 }
3085 };
3086
3087 void G1CollectedHeap::print_cset_rsets() {
3088 PrintRSetsClosure cl("Printing CSet RSets");
3089 collection_set_iterate(&cl);
3090 }
3091
3092 void G1CollectedHeap::print_all_rsets() {
3093 PrintRSetsClosure cl("Printing All RSets");;
3094 heap_region_iterate(&cl);
3095 }
3096 #endif // PRODUCT
3097
3098 G1CollectedHeap* G1CollectedHeap::heap() {
3099 assert(_sh->kind() == CollectedHeap::G1CollectedHeap,
3100 "not a garbage-first heap");
3101 return _g1h;
3102 }
3103
3104 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) {
3105 // always_do_update_barrier = false;
3106 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
3107 // Call allocation profiler
3108 AllocationProfiler::iterate_since_last_gc();
3109 // Fill TLAB's and such
3110 ensure_parsability(true);
3111 }
3112
3113 void G1CollectedHeap::gc_epilogue(bool full /* Ignored */) {
3114 // FIXME: what is this about?
3115 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
3116 // is set.
3117 COMPILER2_PRESENT(assert(DerivedPointerTable::is_empty(),
3118 "derived pointer present"));
3119 // always_do_update_barrier = true;
3120 }
3121
3122 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
3123 unsigned int gc_count_before,
3124 bool* succeeded) {
3125 assert_heap_not_locked_and_not_at_safepoint();
3126 g1_policy()->record_stop_world_start();
3127 VM_G1IncCollectionPause op(gc_count_before,
3128 word_size,
3129 false, /* should_initiate_conc_mark */
3130 g1_policy()->max_pause_time_ms(),
3131 GCCause::_g1_inc_collection_pause);
3132 VMThread::execute(&op);
3133
3134 HeapWord* result = op.result();
3135 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
3136 assert(result == NULL || ret_succeeded,
3137 "the result should be NULL if the VM did not succeed");
3138 *succeeded = ret_succeeded;
3139
3140 assert_heap_not_locked();
3141 return result;
3142 }
3143
3144 void
3145 G1CollectedHeap::doConcurrentMark() {
3146 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
3147 if (!_cmThread->in_progress()) {
3148 _cmThread->set_started();
3149 CGC_lock->notify();
3150 }
3151 }
3152
3153 // <NEW PREDICTION>
3154
3155 double G1CollectedHeap::predict_region_elapsed_time_ms(HeapRegion *hr,
3156 bool young) {
3157 return _g1_policy->predict_region_elapsed_time_ms(hr, young);
3158 }
3159
3160 void G1CollectedHeap::check_if_region_is_too_expensive(double
3161 predicted_time_ms) {
3162 _g1_policy->check_if_region_is_too_expensive(predicted_time_ms);
3163 }
3164
3165 size_t G1CollectedHeap::pending_card_num() {
3166 size_t extra_cards = 0;
3167 JavaThread *curr = Threads::first();
3168 while (curr != NULL) {
3169 DirtyCardQueue& dcq = curr->dirty_card_queue();
3170 extra_cards += dcq.size();
3171 curr = curr->next();
3172 }
3173 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
3174 size_t buffer_size = dcqs.buffer_size();
3175 size_t buffer_num = dcqs.completed_buffers_num();
3176 return buffer_size * buffer_num + extra_cards;
3177 }
3178
3179 size_t G1CollectedHeap::max_pending_card_num() {
3180 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
3181 size_t buffer_size = dcqs.buffer_size();
3182 size_t buffer_num = dcqs.completed_buffers_num();
3183 int thread_num = Threads::number_of_threads();
3184 return (buffer_num + thread_num) * buffer_size;
3185 }
3186
3187 size_t G1CollectedHeap::cards_scanned() {
3188 return g1_rem_set()->cardsScanned();
3189 }
3190
3191 void
3192 G1CollectedHeap::setup_surviving_young_words() {
3193 guarantee( _surviving_young_words == NULL, "pre-condition" );
3194 size_t array_length = g1_policy()->young_cset_length();
3195 _surviving_young_words = NEW_C_HEAP_ARRAY(size_t, array_length);
3196 if (_surviving_young_words == NULL) {
3197 vm_exit_out_of_memory(sizeof(size_t) * array_length,
3198 "Not enough space for young surv words summary.");
3199 }
3200 memset(_surviving_young_words, 0, array_length * sizeof(size_t));
3201 #ifdef ASSERT
3202 for (size_t i = 0; i < array_length; ++i) {
3203 assert( _surviving_young_words[i] == 0, "memset above" );
3204 }
3205 #endif // !ASSERT
3206 }
3207
3208 void
3209 G1CollectedHeap::update_surviving_young_words(size_t* surv_young_words) {
3210 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
3211 size_t array_length = g1_policy()->young_cset_length();
3212 for (size_t i = 0; i < array_length; ++i)
3213 _surviving_young_words[i] += surv_young_words[i];
3214 }
3215
3216 void
3217 G1CollectedHeap::cleanup_surviving_young_words() {
3218 guarantee( _surviving_young_words != NULL, "pre-condition" );
3219 FREE_C_HEAP_ARRAY(size_t, _surviving_young_words);
3220 _surviving_young_words = NULL;
3221 }
3222
3223 // </NEW PREDICTION>
3224
3225 #ifdef ASSERT
3226 class VerifyCSetClosure: public HeapRegionClosure {
3227 public:
3228 bool doHeapRegion(HeapRegion* hr) {
3229 // Here we check that the CSet region's RSet is ready for parallel
3230 // iteration. The fields that we'll verify are only manipulated
3231 // when the region is part of a CSet and is collected. Afterwards,
3232 // we reset these fields when we clear the region's RSet (when the
3233 // region is freed) so they are ready when the region is
3234 // re-allocated. The only exception to this is if there's an
3235 // evacuation failure and instead of freeing the region we leave
3236 // it in the heap. In that case, we reset these fields during
3237 // evacuation failure handling.
3238 guarantee(hr->rem_set()->verify_ready_for_par_iteration(), "verification");
3239
3240 // Here's a good place to add any other checks we'd like to
3241 // perform on CSet regions.
3242 return false;
3243 }
3244 };
3245 #endif // ASSERT
3246
3247 #if TASKQUEUE_STATS
3248 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
3249 st->print_raw_cr("GC Task Stats");
3250 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
3251 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
3252 }
3253
3254 void G1CollectedHeap::print_taskqueue_stats(outputStream* const st) const {
3255 print_taskqueue_stats_hdr(st);
3256
3257 TaskQueueStats totals;
3258 const int n = workers() != NULL ? workers()->total_workers() : 1;
3259 for (int i = 0; i < n; ++i) {
3260 st->print("%3d ", i); task_queue(i)->stats.print(st); st->cr();
3261 totals += task_queue(i)->stats;
3262 }
3263 st->print_raw("tot "); totals.print(st); st->cr();
3264
3265 DEBUG_ONLY(totals.verify());
3266 }
3267
3268 void G1CollectedHeap::reset_taskqueue_stats() {
3269 const int n = workers() != NULL ? workers()->total_workers() : 1;
3270 for (int i = 0; i < n; ++i) {
3271 task_queue(i)->stats.reset();
3272 }
3273 }
3274 #endif // TASKQUEUE_STATS
3275
3276 bool
3277 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
3278 assert_at_safepoint(true /* should_be_vm_thread */);
3279 guarantee(!is_gc_active(), "collection is not reentrant");
3280
3281 if (GC_locker::check_active_before_gc()) {
3282 return false;
3283 }
3284
3285 SvcGCMarker sgcm(SvcGCMarker::MINOR);
3286 ResourceMark rm;
3287
3288 if (PrintHeapAtGC) {
3289 Universe::print_heap_before_gc();
3290 }
3291
3292 verify_region_sets_optional();
3293 verify_dirty_young_regions();
3294
3295 {
3296 // This call will decide whether this pause is an initial-mark
3297 // pause. If it is, during_initial_mark_pause() will return true
3298 // for the duration of this pause.
3299 g1_policy()->decide_on_conc_mark_initiation();
3300
3301 char verbose_str[128];
3302 sprintf(verbose_str, "GC pause ");
3303 if (g1_policy()->full_young_gcs()) {
3304 strcat(verbose_str, "(young)");
3305 } else {
3306 strcat(verbose_str, "(partial)");
3307 }
3308 if (g1_policy()->during_initial_mark_pause()) {
3309 strcat(verbose_str, " (initial-mark)");
3310 // We are about to start a marking cycle, so we increment the
3311 // full collection counter.
3312 increment_total_full_collections();
3313 }
3314
3315 // if PrintGCDetails is on, we'll print long statistics information
3316 // in the collector policy code, so let's not print this as the output
3317 // is messy if we do.
3318 gclog_or_tty->date_stamp(PrintGC && PrintGCDateStamps);
3319 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty);
3320 TraceTime t(verbose_str, PrintGC && !PrintGCDetails, true, gclog_or_tty);
3321
3322 TraceCollectorStats tcs(g1mm()->incremental_collection_counters());
3323 TraceMemoryManagerStats tms(false /* fullGC */, gc_cause());
3324
3325 // If the secondary_free_list is not empty, append it to the
3326 // free_list. No need to wait for the cleanup operation to finish;
3327 // the region allocation code will check the secondary_free_list
3328 // and wait if necessary. If the G1StressConcRegionFreeing flag is
3329 // set, skip this step so that the region allocation code has to
3330 // get entries from the secondary_free_list.
3331 if (!G1StressConcRegionFreeing) {
3332 append_secondary_free_list_if_not_empty_with_lock();
3333 }
3334
3335 assert(check_young_list_well_formed(),
3336 "young list should be well formed");
3337
3338 { // Call to jvmpi::post_class_unload_events must occur outside of active GC
3339 IsGCActiveMark x;
3340
3341 gc_prologue(false);
3342 increment_total_collections(false /* full gc */);
3343 increment_gc_time_stamp();
3344
3345 if (VerifyBeforeGC && total_collections() >= VerifyGCStartAt) {
3346 HandleMark hm; // Discard invalid handles created during verification
3347 gclog_or_tty->print(" VerifyBeforeGC:");
3348 prepare_for_verify();
3349 Universe::verify(/* allow dirty */ false,
3350 /* silent */ false,
3351 /* option */ VerifyOption_G1UsePrevMarking);
3352
3353 }
3354
3355 COMPILER2_PRESENT(DerivedPointerTable::clear());
3356
3357 // Please see comment in G1CollectedHeap::ref_processing_init()
3358 // to see how reference processing currently works in G1.
3359 //
3360 // We want to turn off ref discovery, if necessary, and turn it back on
3361 // on again later if we do. XXX Dubious: why is discovery disabled?
3362 bool was_enabled = ref_processor()->discovery_enabled();
3363 if (was_enabled) ref_processor()->disable_discovery();
3364
3365 // Forget the current alloc region (we might even choose it to be part
3366 // of the collection set!).
3367 release_mutator_alloc_region();
3368
3369 // We should call this after we retire the mutator alloc
3370 // region(s) so that all the ALLOC / RETIRE events are generated
3371 // before the start GC event.
3372 _hr_printer.start_gc(false /* full */, (size_t) total_collections());
3373
3374 // The elapsed time induced by the start time below deliberately elides
3375 // the possible verification above.
3376 double start_time_sec = os::elapsedTime();
3377 size_t start_used_bytes = used();
3378
3379 #if YOUNG_LIST_VERBOSE
3380 gclog_or_tty->print_cr("\nBefore recording pause start.\nYoung_list:");
3381 _young_list->print();
3382 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3383 #endif // YOUNG_LIST_VERBOSE
3384
3385 g1_policy()->record_collection_pause_start(start_time_sec,
3386 start_used_bytes);
3387
3388 #if YOUNG_LIST_VERBOSE
3389 gclog_or_tty->print_cr("\nAfter recording pause start.\nYoung_list:");
3390 _young_list->print();
3391 #endif // YOUNG_LIST_VERBOSE
3392
3393 if (g1_policy()->during_initial_mark_pause()) {
3394 concurrent_mark()->checkpointRootsInitialPre();
3395 }
3396 perm_gen()->save_marks();
3397
3398 // We must do this before any possible evacuation that should propagate
3399 // marks.
3400 if (mark_in_progress()) {
3401 double start_time_sec = os::elapsedTime();
3402
3403 _cm->drainAllSATBBuffers();
3404 double finish_mark_ms = (os::elapsedTime() - start_time_sec) * 1000.0;
3405 g1_policy()->record_satb_drain_time(finish_mark_ms);
3406 }
3407 // Record the number of elements currently on the mark stack, so we
3408 // only iterate over these. (Since evacuation may add to the mark
3409 // stack, doing more exposes race conditions.) If no mark is in
3410 // progress, this will be zero.
3411 _cm->set_oops_do_bound();
3412
3413 if (mark_in_progress()) {
3414 concurrent_mark()->newCSet();
3415 }
3416
3417 #if YOUNG_LIST_VERBOSE
3418 gclog_or_tty->print_cr("\nBefore choosing collection set.\nYoung_list:");
3419 _young_list->print();
3420 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3421 #endif // YOUNG_LIST_VERBOSE
3422
3423 g1_policy()->choose_collection_set(target_pause_time_ms);
3424
3425 if (_hr_printer.is_active()) {
3426 HeapRegion* hr = g1_policy()->collection_set();
3427 while (hr != NULL) {
3428 G1HRPrinter::RegionType type;
3429 if (!hr->is_young()) {
3430 type = G1HRPrinter::Old;
3431 } else if (hr->is_survivor()) {
3432 type = G1HRPrinter::Survivor;
3433 } else {
3434 type = G1HRPrinter::Eden;
3435 }
3436 _hr_printer.cset(hr);
3437 hr = hr->next_in_collection_set();
3438 }
3439 }
3440
3441 // We have chosen the complete collection set. If marking is
3442 // active then, we clear the region fields of any of the
3443 // concurrent marking tasks whose region fields point into
3444 // the collection set as these values will become stale. This
3445 // will cause the owning marking threads to claim a new region
3446 // when marking restarts.
3447 if (mark_in_progress()) {
3448 concurrent_mark()->reset_active_task_region_fields_in_cset();
3449 }
3450
3451 #ifdef ASSERT
3452 VerifyCSetClosure cl;
3453 collection_set_iterate(&cl);
3454 #endif // ASSERT
3455
3456 setup_surviving_young_words();
3457
3458 // Initialize the GC alloc regions.
3459 init_gc_alloc_regions();
3460
3461 // Actually do the work...
3462 evacuate_collection_set();
3463
3464 free_collection_set(g1_policy()->collection_set());
3465 g1_policy()->clear_collection_set();
3466
3467 cleanup_surviving_young_words();
3468
3469 // Start a new incremental collection set for the next pause.
3470 g1_policy()->start_incremental_cset_building();
3471
3472 // Clear the _cset_fast_test bitmap in anticipation of adding
3473 // regions to the incremental collection set for the next
3474 // evacuation pause.
3475 clear_cset_fast_test();
3476
3477 _young_list->reset_sampled_info();
3478
3479 // Don't check the whole heap at this point as the
3480 // GC alloc regions from this pause have been tagged
3481 // as survivors and moved on to the survivor list.
3482 // Survivor regions will fail the !is_young() check.
3483 assert(check_young_list_empty(false /* check_heap */),
3484 "young list should be empty");
3485
3486 #if YOUNG_LIST_VERBOSE
3487 gclog_or_tty->print_cr("Before recording survivors.\nYoung List:");
3488 _young_list->print();
3489 #endif // YOUNG_LIST_VERBOSE
3490
3491 g1_policy()->record_survivor_regions(_young_list->survivor_length(),
3492 _young_list->first_survivor_region(),
3493 _young_list->last_survivor_region());
3494
3495 _young_list->reset_auxilary_lists();
3496
3497 if (evacuation_failed()) {
3498 _summary_bytes_used = recalculate_used();
3499 } else {
3500 // The "used" of the the collection set have already been subtracted
3501 // when they were freed. Add in the bytes evacuated.
3502 _summary_bytes_used += g1_policy()->bytes_copied_during_gc();
3503 }
3504
3505 if (g1_policy()->during_initial_mark_pause()) {
3506 concurrent_mark()->checkpointRootsInitialPost();
3507 set_marking_started();
3508 // CAUTION: after the doConcurrentMark() call below,
3509 // the concurrent marking thread(s) could be running
3510 // concurrently with us. Make sure that anything after
3511 // this point does not assume that we are the only GC thread
3512 // running. Note: of course, the actual marking work will
3513 // not start until the safepoint itself is released in
3514 // ConcurrentGCThread::safepoint_desynchronize().
3515 doConcurrentMark();
3516 }
3517
3518 allocate_dummy_regions();
3519
3520 #if YOUNG_LIST_VERBOSE
3521 gclog_or_tty->print_cr("\nEnd of the pause.\nYoung_list:");
3522 _young_list->print();
3523 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3524 #endif // YOUNG_LIST_VERBOSE
3525
3526 init_mutator_alloc_region();
3527
3528 {
3529 size_t expand_bytes = g1_policy()->expansion_amount();
3530 if (expand_bytes > 0) {
3531 size_t bytes_before = capacity();
3532 if (!expand(expand_bytes)) {
3533 // We failed to expand the heap so let's verify that
3534 // committed/uncommitted amount match the backing store
3535 assert(capacity() == _g1_storage.committed_size(), "committed size mismatch");
3536 assert(max_capacity() == _g1_storage.reserved_size(), "reserved size mismatch");
3537 }
3538 }
3539 }
3540
3541 double end_time_sec = os::elapsedTime();
3542 double pause_time_ms = (end_time_sec - start_time_sec) * MILLIUNITS;
3543 g1_policy()->record_pause_time_ms(pause_time_ms);
3544 g1_policy()->record_collection_pause_end();
3545
3546 MemoryService::track_memory_usage();
3547
3548 // In prepare_for_verify() below we'll need to scan the deferred
3549 // update buffers to bring the RSets up-to-date if
3550 // G1HRRSFlushLogBuffersOnVerify has been set. While scanning
3551 // the update buffers we'll probably need to scan cards on the
3552 // regions we just allocated to (i.e., the GC alloc
3553 // regions). However, during the last GC we called
3554 // set_saved_mark() on all the GC alloc regions, so card
3555 // scanning might skip the [saved_mark_word()...top()] area of
3556 // those regions (i.e., the area we allocated objects into
3557 // during the last GC). But it shouldn't. Given that
3558 // saved_mark_word() is conditional on whether the GC time stamp
3559 // on the region is current or not, by incrementing the GC time
3560 // stamp here we invalidate all the GC time stamps on all the
3561 // regions and saved_mark_word() will simply return top() for
3562 // all the regions. This is a nicer way of ensuring this rather
3563 // than iterating over the regions and fixing them. In fact, the
3564 // GC time stamp increment here also ensures that
3565 // saved_mark_word() will return top() between pauses, i.e.,
3566 // during concurrent refinement. So we don't need the
3567 // is_gc_active() check to decided which top to use when
3568 // scanning cards (see CR 7039627).
3569 increment_gc_time_stamp();
3570
3571 if (VerifyAfterGC && total_collections() >= VerifyGCStartAt) {
3572 HandleMark hm; // Discard invalid handles created during verification
3573 gclog_or_tty->print(" VerifyAfterGC:");
3574 prepare_for_verify();
3575 Universe::verify(/* allow dirty */ true,
3576 /* silent */ false,
3577 /* option */ VerifyOption_G1UsePrevMarking);
3578 }
3579
3580 if (was_enabled) ref_processor()->enable_discovery();
3581
3582 {
3583 size_t expand_bytes = g1_policy()->expansion_amount();
3584 if (expand_bytes > 0) {
3585 size_t bytes_before = capacity();
3586 // No need for an ergo verbose message here,
3587 // expansion_amount() does this when it returns a value > 0.
3588 if (!expand(expand_bytes)) {
3589 // We failed to expand the heap so let's verify that
3590 // committed/uncommitted amount match the backing store
3591 assert(capacity() == _g1_storage.committed_size(), "committed size mismatch");
3592 assert(max_capacity() == _g1_storage.reserved_size(), "reserved size mismatch");
3593 }
3594 }
3595 }
3596
3597 // We should do this after we potentially expand the heap so
3598 // that all the COMMIT events are generated before the end GC
3599 // event, and after we retire the GC alloc regions so that all
3600 // RETIRE events are generated before the end GC event.
3601 _hr_printer.end_gc(false /* full */, (size_t) total_collections());
3602
3603 // We have to do this after we decide whether to expand the heap or not.
3604 g1_policy()->print_heap_transition();
3605
3606 if (mark_in_progress()) {
3607 concurrent_mark()->update_g1_committed();
3608 }
3609
3610 #ifdef TRACESPINNING
3611 ParallelTaskTerminator::print_termination_counts();
3612 #endif
3613
3614 gc_epilogue(false);
3615 }
3616
3617 if (ExitAfterGCNum > 0 && total_collections() == ExitAfterGCNum) {
3618 gclog_or_tty->print_cr("Stopping after GC #%d", ExitAfterGCNum);
3619 print_tracing_info();
3620 vm_exit(-1);
3621 }
3622 }
3623
3624 _hrs.verify_optional();
3625 verify_region_sets_optional();
3626
3627 TASKQUEUE_STATS_ONLY(if (ParallelGCVerbose) print_taskqueue_stats());
3628 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
3629
3630 if (PrintHeapAtGC) {
3631 Universe::print_heap_after_gc();
3632 }
3633 g1mm()->update_counters();
3634
3635 if (G1SummarizeRSetStats &&
3636 (G1SummarizeRSetStatsPeriod > 0) &&
3637 (total_collections() % G1SummarizeRSetStatsPeriod == 0)) {
3638 g1_rem_set()->print_summary_info();
3639 }
3640
3641 return true;
3642 }
3643
3644 size_t G1CollectedHeap::desired_plab_sz(GCAllocPurpose purpose)
3645 {
3646 size_t gclab_word_size;
3647 switch (purpose) {
3648 case GCAllocForSurvived:
3649 gclab_word_size = YoungPLABSize;
3650 break;
3651 case GCAllocForTenured:
3652 gclab_word_size = OldPLABSize;
3653 break;
3654 default:
3655 assert(false, "unknown GCAllocPurpose");
3656 gclab_word_size = OldPLABSize;
3657 break;
3658 }
3659 return gclab_word_size;
3660 }
3661
3662 void G1CollectedHeap::init_mutator_alloc_region() {
3663 assert(_mutator_alloc_region.get() == NULL, "pre-condition");
3664 _mutator_alloc_region.init();
3665 }
3666
3667 void G1CollectedHeap::release_mutator_alloc_region() {
3668 _mutator_alloc_region.release();
3669 assert(_mutator_alloc_region.get() == NULL, "post-condition");
3670 }
3671
3672 void G1CollectedHeap::init_gc_alloc_regions() {
3673 assert_at_safepoint(true /* should_be_vm_thread */);
3674
3675 _survivor_gc_alloc_region.init();
3676 _old_gc_alloc_region.init();
3677 HeapRegion* retained_region = _retained_old_gc_alloc_region;
3678 _retained_old_gc_alloc_region = NULL;
3679
3680 // We will discard the current GC alloc region if:
3681 // a) it's in the collection set (it can happen!),
3682 // b) it's already full (no point in using it),
3683 // c) it's empty (this means that it was emptied during
3684 // a cleanup and it should be on the free list now), or
3685 // d) it's humongous (this means that it was emptied
3686 // during a cleanup and was added to the free list, but
3687 // has been subseqently used to allocate a humongous
3688 // object that may be less than the region size).
3689 if (retained_region != NULL &&
3690 !retained_region->in_collection_set() &&
3691 !(retained_region->top() == retained_region->end()) &&
3692 !retained_region->is_empty() &&
3693 !retained_region->isHumongous()) {
3694 retained_region->set_saved_mark();
3695 _old_gc_alloc_region.set(retained_region);
3696 _hr_printer.reuse(retained_region);
3697 }
3698 }
3699
3700 void G1CollectedHeap::release_gc_alloc_regions() {
3701 _survivor_gc_alloc_region.release();
3702 // If we have an old GC alloc region to release, we'll save it in
3703 // _retained_old_gc_alloc_region. If we don't
3704 // _retained_old_gc_alloc_region will become NULL. This is what we
3705 // want either way so no reason to check explicitly for either
3706 // condition.
3707 _retained_old_gc_alloc_region = _old_gc_alloc_region.release();
3708 }
3709
3710 void G1CollectedHeap::abandon_gc_alloc_regions() {
3711 assert(_survivor_gc_alloc_region.get() == NULL, "pre-condition");
3712 assert(_old_gc_alloc_region.get() == NULL, "pre-condition");
3713 _retained_old_gc_alloc_region = NULL;
3714 }
3715
3716 void G1CollectedHeap::init_for_evac_failure(OopsInHeapRegionClosure* cl) {
3717 _drain_in_progress = false;
3718 set_evac_failure_closure(cl);
3719 _evac_failure_scan_stack = new (ResourceObj::C_HEAP) GrowableArray<oop>(40, true);
3720 }
3721
3722 void G1CollectedHeap::finalize_for_evac_failure() {
3723 assert(_evac_failure_scan_stack != NULL &&
3724 _evac_failure_scan_stack->length() == 0,
3725 "Postcondition");
3726 assert(!_drain_in_progress, "Postcondition");
3727 delete _evac_failure_scan_stack;
3728 _evac_failure_scan_stack = NULL;
3729 }
3730
3731 // *** Sequential G1 Evacuation
3732
3733 class G1IsAliveClosure: public BoolObjectClosure {
3734 G1CollectedHeap* _g1;
3735 public:
3736 G1IsAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
3737 void do_object(oop p) { assert(false, "Do not call."); }
3738 bool do_object_b(oop p) {
3739 // It is reachable if it is outside the collection set, or is inside
3740 // and forwarded.
3741 return !_g1->obj_in_cs(p) || p->is_forwarded();
3742 }
3743 };
3744
3745 class G1KeepAliveClosure: public OopClosure {
3746 G1CollectedHeap* _g1;
3747 public:
3748 G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
3749 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
3750 void do_oop( oop* p) {
3751 oop obj = *p;
3752 if (_g1->obj_in_cs(obj)) {
3753 assert( obj->is_forwarded(), "invariant" );
3754 *p = obj->forwardee();
3755 }
3756 }
3757 };
3758
3759 class UpdateRSetDeferred : public OopsInHeapRegionClosure {
3760 private:
3761 G1CollectedHeap* _g1;
3762 DirtyCardQueue *_dcq;
3763 CardTableModRefBS* _ct_bs;
3764
3765 public:
3766 UpdateRSetDeferred(G1CollectedHeap* g1, DirtyCardQueue* dcq) :
3767 _g1(g1), _ct_bs((CardTableModRefBS*)_g1->barrier_set()), _dcq(dcq) {}
3768
3769 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
3770 virtual void do_oop( oop* p) { do_oop_work(p); }
3771 template <class T> void do_oop_work(T* p) {
3772 assert(_from->is_in_reserved(p), "paranoia");
3773 if (!_from->is_in_reserved(oopDesc::load_decode_heap_oop(p)) &&
3774 !_from->is_survivor()) {
3775 size_t card_index = _ct_bs->index_for(p);
3776 if (_ct_bs->mark_card_deferred(card_index)) {
3777 _dcq->enqueue((jbyte*)_ct_bs->byte_for_index(card_index));
3778 }
3779 }
3780 }
3781 };
3782
3783 class RemoveSelfPointerClosure: public ObjectClosure {
3784 private:
3785 G1CollectedHeap* _g1;
3786 ConcurrentMark* _cm;
3787 HeapRegion* _hr;
3788 size_t _prev_marked_bytes;
3789 size_t _next_marked_bytes;
3790 OopsInHeapRegionClosure *_cl;
3791 public:
3792 RemoveSelfPointerClosure(G1CollectedHeap* g1, HeapRegion* hr,
3793 OopsInHeapRegionClosure* cl) :
3794 _g1(g1), _hr(hr), _cm(_g1->concurrent_mark()), _prev_marked_bytes(0),
3795 _next_marked_bytes(0), _cl(cl) {}
3796
3797 size_t prev_marked_bytes() { return _prev_marked_bytes; }
3798 size_t next_marked_bytes() { return _next_marked_bytes; }
3799
3800 // <original comment>
3801 // The original idea here was to coalesce evacuated and dead objects.
3802 // However that caused complications with the block offset table (BOT).
3803 // In particular if there were two TLABs, one of them partially refined.
3804 // |----- TLAB_1--------|----TLAB_2-~~~(partially refined part)~~~|
3805 // The BOT entries of the unrefined part of TLAB_2 point to the start
3806 // of TLAB_2. If the last object of the TLAB_1 and the first object
3807 // of TLAB_2 are coalesced, then the cards of the unrefined part
3808 // would point into middle of the filler object.
3809 // The current approach is to not coalesce and leave the BOT contents intact.
3810 // </original comment>
3811 //
3812 // We now reset the BOT when we start the object iteration over the
3813 // region and refine its entries for every object we come across. So
3814 // the above comment is not really relevant and we should be able
3815 // to coalesce dead objects if we want to.
3816 void do_object(oop obj) {
3817 HeapWord* obj_addr = (HeapWord*) obj;
3818 assert(_hr->is_in(obj_addr), "sanity");
3819 size_t obj_size = obj->size();
3820 _hr->update_bot_for_object(obj_addr, obj_size);
3821 if (obj->is_forwarded() && obj->forwardee() == obj) {
3822 // The object failed to move.
3823 assert(!_g1->is_obj_dead(obj), "We should not be preserving dead objs.");
3824 _cm->markPrev(obj);
3825 assert(_cm->isPrevMarked(obj), "Should be marked!");
3826 _prev_marked_bytes += (obj_size * HeapWordSize);
3827 if (_g1->mark_in_progress() && !_g1->is_obj_ill(obj)) {
3828 _cm->markAndGrayObjectIfNecessary(obj);
3829 }
3830 obj->set_mark(markOopDesc::prototype());
3831 // While we were processing RSet buffers during the
3832 // collection, we actually didn't scan any cards on the
3833 // collection set, since we didn't want to update remebered
3834 // sets with entries that point into the collection set, given
3835 // that live objects fromthe collection set are about to move
3836 // and such entries will be stale very soon. This change also
3837 // dealt with a reliability issue which involved scanning a
3838 // card in the collection set and coming across an array that
3839 // was being chunked and looking malformed. The problem is
3840 // that, if evacuation fails, we might have remembered set
3841 // entries missing given that we skipped cards on the
3842 // collection set. So, we'll recreate such entries now.
3843 obj->oop_iterate(_cl);
3844 assert(_cm->isPrevMarked(obj), "Should be marked!");
3845 } else {
3846 // The object has been either evacuated or is dead. Fill it with a
3847 // dummy object.
3848 MemRegion mr((HeapWord*)obj, obj_size);
3849 CollectedHeap::fill_with_object(mr);
3850 _cm->clearRangeBothMaps(mr);
3851 }
3852 }
3853 };
3854
3855 void G1CollectedHeap::remove_self_forwarding_pointers() {
3856 UpdateRSetImmediate immediate_update(_g1h->g1_rem_set());
3857 DirtyCardQueue dcq(&_g1h->dirty_card_queue_set());
3858 UpdateRSetDeferred deferred_update(_g1h, &dcq);
3859 OopsInHeapRegionClosure *cl;
3860 if (G1DeferredRSUpdate) {
3861 cl = &deferred_update;
3862 } else {
3863 cl = &immediate_update;
3864 }
3865 HeapRegion* cur = g1_policy()->collection_set();
3866 while (cur != NULL) {
3867 assert(g1_policy()->assertMarkedBytesDataOK(), "Should be!");
3868 assert(!cur->isHumongous(), "sanity");
3869
3870 if (cur->evacuation_failed()) {
3871 assert(cur->in_collection_set(), "bad CS");
3872 RemoveSelfPointerClosure rspc(_g1h, cur, cl);
3873
3874 // In the common case we make sure that this is done when the
3875 // region is freed so that it is "ready-to-go" when it's
3876 // re-allocated. However, when evacuation failure happens, a
3877 // region will remain in the heap and might ultimately be added
3878 // to a CSet in the future. So we have to be careful here and
3879 // make sure the region's RSet is ready for parallel iteration
3880 // whenever this might be required in the future.
3881 cur->rem_set()->reset_for_par_iteration();
3882 cur->reset_bot();
3883 cl->set_region(cur);
3884 cur->object_iterate(&rspc);
3885
3886 // A number of manipulations to make the TAMS be the current top,
3887 // and the marked bytes be the ones observed in the iteration.
3888 if (_g1h->concurrent_mark()->at_least_one_mark_complete()) {
3889 // The comments below are the postconditions achieved by the
3890 // calls. Note especially the last such condition, which says that
3891 // the count of marked bytes has been properly restored.
3892 cur->note_start_of_marking(false);
3893 // _next_top_at_mark_start == top, _next_marked_bytes == 0
3894 cur->add_to_marked_bytes(rspc.prev_marked_bytes());
3895 // _next_marked_bytes == prev_marked_bytes.
3896 cur->note_end_of_marking();
3897 // _prev_top_at_mark_start == top(),
3898 // _prev_marked_bytes == prev_marked_bytes
3899 }
3900 // If there is no mark in progress, we modified the _next variables
3901 // above needlessly, but harmlessly.
3902 if (_g1h->mark_in_progress()) {
3903 cur->note_start_of_marking(false);
3904 // _next_top_at_mark_start == top, _next_marked_bytes == 0
3905 // _next_marked_bytes == next_marked_bytes.
3906 }
3907
3908 // Now make sure the region has the right index in the sorted array.
3909 g1_policy()->note_change_in_marked_bytes(cur);
3910 }
3911 cur = cur->next_in_collection_set();
3912 }
3913 assert(g1_policy()->assertMarkedBytesDataOK(), "Should be!");
3914
3915 // Now restore saved marks, if any.
3916 if (_objs_with_preserved_marks != NULL) {
3917 assert(_preserved_marks_of_objs != NULL, "Both or none.");
3918 guarantee(_objs_with_preserved_marks->length() ==
3919 _preserved_marks_of_objs->length(), "Both or none.");
3920 for (int i = 0; i < _objs_with_preserved_marks->length(); i++) {
3921 oop obj = _objs_with_preserved_marks->at(i);
3922 markOop m = _preserved_marks_of_objs->at(i);
3923 obj->set_mark(m);
3924 }
3925 // Delete the preserved marks growable arrays (allocated on the C heap).
3926 delete _objs_with_preserved_marks;
3927 delete _preserved_marks_of_objs;
3928 _objs_with_preserved_marks = NULL;
3929 _preserved_marks_of_objs = NULL;
3930 }
3931 }
3932
3933 void G1CollectedHeap::push_on_evac_failure_scan_stack(oop obj) {
3934 _evac_failure_scan_stack->push(obj);
3935 }
3936
3937 void G1CollectedHeap::drain_evac_failure_scan_stack() {
3938 assert(_evac_failure_scan_stack != NULL, "precondition");
3939
3940 while (_evac_failure_scan_stack->length() > 0) {
3941 oop obj = _evac_failure_scan_stack->pop();
3942 _evac_failure_closure->set_region(heap_region_containing(obj));
3943 obj->oop_iterate_backwards(_evac_failure_closure);
3944 }
3945 }
3946
3947 oop
3948 G1CollectedHeap::handle_evacuation_failure_par(OopsInHeapRegionClosure* cl,
3949 oop old) {
3950 assert(obj_in_cs(old),
3951 err_msg("obj: "PTR_FORMAT" should still be in the CSet",
3952 (HeapWord*) old));
3953 markOop m = old->mark();
3954 oop forward_ptr = old->forward_to_atomic(old);
3955 if (forward_ptr == NULL) {
3956 // Forward-to-self succeeded.
3957 if (_evac_failure_closure != cl) {
3958 MutexLockerEx x(EvacFailureStack_lock, Mutex::_no_safepoint_check_flag);
3959 assert(!_drain_in_progress,
3960 "Should only be true while someone holds the lock.");
3961 // Set the global evac-failure closure to the current thread's.
3962 assert(_evac_failure_closure == NULL, "Or locking has failed.");
3963 set_evac_failure_closure(cl);
3964 // Now do the common part.
3965 handle_evacuation_failure_common(old, m);
3966 // Reset to NULL.
3967 set_evac_failure_closure(NULL);
3968 } else {
3969 // The lock is already held, and this is recursive.
3970 assert(_drain_in_progress, "This should only be the recursive case.");
3971 handle_evacuation_failure_common(old, m);
3972 }
3973 return old;
3974 } else {
3975 // Forward-to-self failed. Either someone else managed to allocate
3976 // space for this object (old != forward_ptr) or they beat us in
3977 // self-forwarding it (old == forward_ptr).
3978 assert(old == forward_ptr || !obj_in_cs(forward_ptr),
3979 err_msg("obj: "PTR_FORMAT" forwarded to: "PTR_FORMAT" "
3980 "should not be in the CSet",
3981 (HeapWord*) old, (HeapWord*) forward_ptr));
3982 return forward_ptr;
3983 }
3984 }
3985
3986 void G1CollectedHeap::handle_evacuation_failure_common(oop old, markOop m) {
3987 set_evacuation_failed(true);
3988
3989 preserve_mark_if_necessary(old, m);
3990
3991 HeapRegion* r = heap_region_containing(old);
3992 if (!r->evacuation_failed()) {
3993 r->set_evacuation_failed(true);
3994 _hr_printer.evac_failure(r);
3995 }
3996
3997 push_on_evac_failure_scan_stack(old);
3998
3999 if (!_drain_in_progress) {
4000 // prevent recursion in copy_to_survivor_space()
4001 _drain_in_progress = true;
4002 drain_evac_failure_scan_stack();
4003 _drain_in_progress = false;
4004 }
4005 }
4006
4007 void G1CollectedHeap::preserve_mark_if_necessary(oop obj, markOop m) {
4008 assert(evacuation_failed(), "Oversaving!");
4009 // We want to call the "for_promotion_failure" version only in the
4010 // case of a promotion failure.
4011 if (m->must_be_preserved_for_promotion_failure(obj)) {
4012 if (_objs_with_preserved_marks == NULL) {
4013 assert(_preserved_marks_of_objs == NULL, "Both or none.");
4014 _objs_with_preserved_marks =
4015 new (ResourceObj::C_HEAP) GrowableArray<oop>(40, true);
4016 _preserved_marks_of_objs =
4017 new (ResourceObj::C_HEAP) GrowableArray<markOop>(40, true);
4018 }
4019 _objs_with_preserved_marks->push(obj);
4020 _preserved_marks_of_objs->push(m);
4021 }
4022 }
4023
4024 HeapWord* G1CollectedHeap::par_allocate_during_gc(GCAllocPurpose purpose,
4025 size_t word_size) {
4026 if (purpose == GCAllocForSurvived) {
4027 HeapWord* result = survivor_attempt_allocation(word_size);
4028 if (result != NULL) {
4029 return result;
4030 } else {
4031 // Let's try to allocate in the old gen in case we can fit the
4032 // object there.
4033 return old_attempt_allocation(word_size);
4034 }
4035 } else {
4036 assert(purpose == GCAllocForTenured, "sanity");
4037 HeapWord* result = old_attempt_allocation(word_size);
4038 if (result != NULL) {
4039 return result;
4040 } else {
4041 // Let's try to allocate in the survivors in case we can fit the
4042 // object there.
4043 return survivor_attempt_allocation(word_size);
4044 }
4045 }
4046
4047 ShouldNotReachHere();
4048 // Trying to keep some compilers happy.
4049 return NULL;
4050 }
4051
4052 #ifndef PRODUCT
4053 bool GCLabBitMapClosure::do_bit(size_t offset) {
4054 HeapWord* addr = _bitmap->offsetToHeapWord(offset);
4055 guarantee(_cm->isMarked(oop(addr)), "it should be!");
4056 return true;
4057 }
4058 #endif // PRODUCT
4059
4060 G1ParGCAllocBuffer::G1ParGCAllocBuffer(size_t gclab_word_size) :
4061 ParGCAllocBuffer(gclab_word_size),
4062 _should_mark_objects(false),
4063 _bitmap(G1CollectedHeap::heap()->reserved_region().start(), gclab_word_size),
4064 _retired(false)
4065 {
4066 //_should_mark_objects is set to true when G1ParCopyHelper needs to
4067 // mark the forwarded location of an evacuated object.
4068 // We set _should_mark_objects to true if marking is active, i.e. when we
4069 // need to propagate a mark, or during an initial mark pause, i.e. when we
4070 // need to mark objects immediately reachable by the roots.
4071 if (G1CollectedHeap::heap()->mark_in_progress() ||
4072 G1CollectedHeap::heap()->g1_policy()->during_initial_mark_pause()) {
4073 _should_mark_objects = true;
4074 }
4075 }
4076
4077 G1ParScanThreadState::G1ParScanThreadState(G1CollectedHeap* g1h, int queue_num)
4078 : _g1h(g1h),
4079 _refs(g1h->task_queue(queue_num)),
4080 _dcq(&g1h->dirty_card_queue_set()),
4081 _ct_bs((CardTableModRefBS*)_g1h->barrier_set()),
4082 _g1_rem(g1h->g1_rem_set()),
4083 _hash_seed(17), _queue_num(queue_num),
4084 _term_attempts(0),
4085 _surviving_alloc_buffer(g1h->desired_plab_sz(GCAllocForSurvived)),
4086 _tenured_alloc_buffer(g1h->desired_plab_sz(GCAllocForTenured)),
4087 _age_table(false),
4088 _strong_roots_time(0), _term_time(0),
4089 _alloc_buffer_waste(0), _undo_waste(0)
4090 {
4091 // we allocate G1YoungSurvRateNumRegions plus one entries, since
4092 // we "sacrifice" entry 0 to keep track of surviving bytes for
4093 // non-young regions (where the age is -1)
4094 // We also add a few elements at the beginning and at the end in
4095 // an attempt to eliminate cache contention
4096 size_t real_length = 1 + _g1h->g1_policy()->young_cset_length();
4097 size_t array_length = PADDING_ELEM_NUM +
4098 real_length +
4099 PADDING_ELEM_NUM;
4100 _surviving_young_words_base = NEW_C_HEAP_ARRAY(size_t, array_length);
4101 if (_surviving_young_words_base == NULL)
4102 vm_exit_out_of_memory(array_length * sizeof(size_t),
4103 "Not enough space for young surv histo.");
4104 _surviving_young_words = _surviving_young_words_base + PADDING_ELEM_NUM;
4105 memset(_surviving_young_words, 0, real_length * sizeof(size_t));
4106
4107 _alloc_buffers[GCAllocForSurvived] = &_surviving_alloc_buffer;
4108 _alloc_buffers[GCAllocForTenured] = &_tenured_alloc_buffer;
4109
4110 _start = os::elapsedTime();
4111 }
4112
4113 void
4114 G1ParScanThreadState::print_termination_stats_hdr(outputStream* const st)
4115 {
4116 st->print_raw_cr("GC Termination Stats");
4117 st->print_raw_cr(" elapsed --strong roots-- -------termination-------"
4118 " ------waste (KiB)------");
4119 st->print_raw_cr("thr ms ms % ms % attempts"
4120 " total alloc undo");
4121 st->print_raw_cr("--- --------- --------- ------ --------- ------ --------"
4122 " ------- ------- -------");
4123 }
4124
4125 void
4126 G1ParScanThreadState::print_termination_stats(int i,
4127 outputStream* const st) const
4128 {
4129 const double elapsed_ms = elapsed_time() * 1000.0;
4130 const double s_roots_ms = strong_roots_time() * 1000.0;
4131 const double term_ms = term_time() * 1000.0;
4132 st->print_cr("%3d %9.2f %9.2f %6.2f "
4133 "%9.2f %6.2f " SIZE_FORMAT_W(8) " "
4134 SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7),
4135 i, elapsed_ms, s_roots_ms, s_roots_ms * 100 / elapsed_ms,
4136 term_ms, term_ms * 100 / elapsed_ms, term_attempts(),
4137 (alloc_buffer_waste() + undo_waste()) * HeapWordSize / K,
4138 alloc_buffer_waste() * HeapWordSize / K,
4139 undo_waste() * HeapWordSize / K);
4140 }
4141
4142 #ifdef ASSERT
4143 bool G1ParScanThreadState::verify_ref(narrowOop* ref) const {
4144 assert(ref != NULL, "invariant");
4145 assert(UseCompressedOops, "sanity");
4146 assert(!has_partial_array_mask(ref), err_msg("ref=" PTR_FORMAT, ref));
4147 oop p = oopDesc::load_decode_heap_oop(ref);
4148 assert(_g1h->is_in_g1_reserved(p),
4149 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p)));
4150 return true;
4151 }
4152
4153 bool G1ParScanThreadState::verify_ref(oop* ref) const {
4154 assert(ref != NULL, "invariant");
4155 if (has_partial_array_mask(ref)) {
4156 // Must be in the collection set--it's already been copied.
4157 oop p = clear_partial_array_mask(ref);
4158 assert(_g1h->obj_in_cs(p),
4159 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p)));
4160 } else {
4161 oop p = oopDesc::load_decode_heap_oop(ref);
4162 assert(_g1h->is_in_g1_reserved(p),
4163 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p)));
4164 }
4165 return true;
4166 }
4167
4168 bool G1ParScanThreadState::verify_task(StarTask ref) const {
4169 if (ref.is_narrow()) {
4170 return verify_ref((narrowOop*) ref);
4171 } else {
4172 return verify_ref((oop*) ref);
4173 }
4174 }
4175 #endif // ASSERT
4176
4177 void G1ParScanThreadState::trim_queue() {
4178 StarTask ref;
4179 do {
4180 // Drain the overflow stack first, so other threads can steal.
4181 while (refs()->pop_overflow(ref)) {
4182 deal_with_reference(ref);
4183 }
4184 while (refs()->pop_local(ref)) {
4185 deal_with_reference(ref);
4186 }
4187 } while (!refs()->is_empty());
4188 }
4189
4190 G1ParClosureSuper::G1ParClosureSuper(G1CollectedHeap* g1, G1ParScanThreadState* par_scan_state) :
4191 _g1(g1), _g1_rem(_g1->g1_rem_set()), _cm(_g1->concurrent_mark()),
4192 _par_scan_state(par_scan_state),
4193 _during_initial_mark(_g1->g1_policy()->during_initial_mark_pause()),
4194 _mark_in_progress(_g1->mark_in_progress()) { }
4195
4196 template <class T> void G1ParCopyHelper::mark_object(T* p) {
4197 // This is called from do_oop_work for objects that are not
4198 // in the collection set. Objects in the collection set
4199 // are marked after they have been evacuated.
4200
4201 T heap_oop = oopDesc::load_heap_oop(p);
4202 if (!oopDesc::is_null(heap_oop)) {
4203 oop obj = oopDesc::decode_heap_oop(heap_oop);
4204 HeapWord* addr = (HeapWord*)obj;
4205 if (_g1->is_in_g1_reserved(addr)) {
4206 _cm->grayRoot(oop(addr));
4207 }
4208 }
4209 }
4210
4211 oop G1ParCopyHelper::copy_to_survivor_space(oop old, bool should_mark_copy) {
4212 size_t word_sz = old->size();
4213 HeapRegion* from_region = _g1->heap_region_containing_raw(old);
4214 // +1 to make the -1 indexes valid...
4215 int young_index = from_region->young_index_in_cset()+1;
4216 assert( (from_region->is_young() && young_index > 0) ||
4217 (!from_region->is_young() && young_index == 0), "invariant" );
4218 G1CollectorPolicy* g1p = _g1->g1_policy();
4219 markOop m = old->mark();
4220 int age = m->has_displaced_mark_helper() ? m->displaced_mark_helper()->age()
4221 : m->age();
4222 GCAllocPurpose alloc_purpose = g1p->evacuation_destination(from_region, age,
4223 word_sz);
4224 HeapWord* obj_ptr = _par_scan_state->allocate(alloc_purpose, word_sz);
4225 oop obj = oop(obj_ptr);
4226
4227 if (obj_ptr == NULL) {
4228 // This will either forward-to-self, or detect that someone else has
4229 // installed a forwarding pointer.
4230 OopsInHeapRegionClosure* cl = _par_scan_state->evac_failure_closure();
4231 return _g1->handle_evacuation_failure_par(cl, old);
4232 }
4233
4234 // We're going to allocate linearly, so might as well prefetch ahead.
4235 Prefetch::write(obj_ptr, PrefetchCopyIntervalInBytes);
4236
4237 oop forward_ptr = old->forward_to_atomic(obj);
4238 if (forward_ptr == NULL) {
4239 Copy::aligned_disjoint_words((HeapWord*) old, obj_ptr, word_sz);
4240 if (g1p->track_object_age(alloc_purpose)) {
4241 // We could simply do obj->incr_age(). However, this causes a
4242 // performance issue. obj->incr_age() will first check whether
4243 // the object has a displaced mark by checking its mark word;
4244 // getting the mark word from the new location of the object
4245 // stalls. So, given that we already have the mark word and we
4246 // are about to install it anyway, it's better to increase the
4247 // age on the mark word, when the object does not have a
4248 // displaced mark word. We're not expecting many objects to have
4249 // a displaced marked word, so that case is not optimized
4250 // further (it could be...) and we simply call obj->incr_age().
4251
4252 if (m->has_displaced_mark_helper()) {
4253 // in this case, we have to install the mark word first,
4254 // otherwise obj looks to be forwarded (the old mark word,
4255 // which contains the forward pointer, was copied)
4256 obj->set_mark(m);
4257 obj->incr_age();
4258 } else {
4259 m = m->incr_age();
4260 obj->set_mark(m);
4261 }
4262 _par_scan_state->age_table()->add(obj, word_sz);
4263 } else {
4264 obj->set_mark(m);
4265 }
4266
4267 // Mark the evacuated object or propagate "next" mark bit
4268 if (should_mark_copy) {
4269 if (!use_local_bitmaps ||
4270 !_par_scan_state->alloc_buffer(alloc_purpose)->mark(obj_ptr)) {
4271 // if we couldn't mark it on the local bitmap (this happens when
4272 // the object was not allocated in the GCLab), we have to bite
4273 // the bullet and do the standard parallel mark
4274 _cm->markAndGrayObjectIfNecessary(obj);
4275 }
4276
4277 if (_g1->isMarkedNext(old)) {
4278 // Unmark the object's old location so that marking
4279 // doesn't think the old object is alive.
4280 _cm->nextMarkBitMap()->parClear((HeapWord*)old);
4281 }
4282 }
4283
4284 size_t* surv_young_words = _par_scan_state->surviving_young_words();
4285 surv_young_words[young_index] += word_sz;
4286
4287 if (obj->is_objArray() && arrayOop(obj)->length() >= ParGCArrayScanChunk) {
4288 arrayOop(old)->set_length(0);
4289 oop* old_p = set_partial_array_mask(old);
4290 _par_scan_state->push_on_queue(old_p);
4291 } else {
4292 // No point in using the slower heap_region_containing() method,
4293 // given that we know obj is in the heap.
4294 _scanner->set_region(_g1->heap_region_containing_raw(obj));
4295 obj->oop_iterate_backwards(_scanner);
4296 }
4297 } else {
4298 _par_scan_state->undo_allocation(alloc_purpose, obj_ptr, word_sz);
4299 obj = forward_ptr;
4300 }
4301 return obj;
4302 }
4303
4304 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object>
4305 template <class T>
4306 void G1ParCopyClosure<do_gen_barrier, barrier, do_mark_object>
4307 ::do_oop_work(T* p) {
4308 oop obj = oopDesc::load_decode_heap_oop(p);
4309 assert(barrier != G1BarrierRS || obj != NULL,
4310 "Precondition: G1BarrierRS implies obj is nonNull");
4311
4312 // Marking:
4313 // If the object is in the collection set, then the thread
4314 // that copies the object should mark, or propagate the
4315 // mark to, the evacuated object.
4316 // If the object is not in the collection set then we
4317 // should call the mark_object() method depending on the
4318 // value of the template parameter do_mark_object (which will
4319 // be true for root scanning closures during an initial mark
4320 // pause).
4321 // The mark_object() method first checks whether the object
4322 // is marked and, if not, attempts to mark the object.
4323
4324 // here the null check is implicit in the cset_fast_test() test
4325 if (_g1->in_cset_fast_test(obj)) {
4326 if (obj->is_forwarded()) {
4327 oopDesc::encode_store_heap_oop(p, obj->forwardee());
4328 // If we are a root scanning closure during an initial
4329 // mark pause (i.e. do_mark_object will be true) then
4330 // we also need to handle marking of roots in the
4331 // event of an evacuation failure. In the event of an
4332 // evacuation failure, the object is forwarded to itself
4333 // and not copied so let's mark it here.
4334 if (do_mark_object && obj->forwardee() == obj) {
4335 mark_object(p);
4336 }
4337 } else {
4338 // We need to mark the copied object if we're a root scanning
4339 // closure during an initial mark pause (i.e. do_mark_object
4340 // will be true), or the object is already marked and we need
4341 // to propagate the mark to the evacuated copy.
4342 bool should_mark_copy = do_mark_object ||
4343 _during_initial_mark ||
4344 (_mark_in_progress && !_g1->is_obj_ill(obj));
4345
4346 oop copy_oop = copy_to_survivor_space(obj, should_mark_copy);
4347 oopDesc::encode_store_heap_oop(p, copy_oop);
4348 }
4349 // When scanning the RS, we only care about objs in CS.
4350 if (barrier == G1BarrierRS) {
4351 _par_scan_state->update_rs(_from, p, _par_scan_state->queue_num());
4352 }
4353 } else {
4354 // The object is not in collection set. If we're a root scanning
4355 // closure during an initial mark pause (i.e. do_mark_object will
4356 // be true) then attempt to mark the object.
4357 if (do_mark_object) {
4358 mark_object(p);
4359 }
4360 }
4361
4362 if (barrier == G1BarrierEvac && obj != NULL) {
4363 _par_scan_state->update_rs(_from, p, _par_scan_state->queue_num());
4364 }
4365
4366 if (do_gen_barrier && obj != NULL) {
4367 par_do_barrier(p);
4368 }
4369 }
4370
4371 template void G1ParCopyClosure<false, G1BarrierEvac, false>::do_oop_work(oop* p);
4372 template void G1ParCopyClosure<false, G1BarrierEvac, false>::do_oop_work(narrowOop* p);
4373
4374 template <class T> void G1ParScanPartialArrayClosure::do_oop_nv(T* p) {
4375 assert(has_partial_array_mask(p), "invariant");
4376 oop old = clear_partial_array_mask(p);
4377 assert(old->is_objArray(), "must be obj array");
4378 assert(old->is_forwarded(), "must be forwarded");
4379 assert(Universe::heap()->is_in_reserved(old), "must be in heap.");
4380
4381 objArrayOop obj = objArrayOop(old->forwardee());
4382 assert((void*)old != (void*)old->forwardee(), "self forwarding here?");
4383 // Process ParGCArrayScanChunk elements now
4384 // and push the remainder back onto queue
4385 int start = arrayOop(old)->length();
4386 int end = obj->length();
4387 int remainder = end - start;
4388 assert(start <= end, "just checking");
4389 if (remainder > 2 * ParGCArrayScanChunk) {
4390 // Test above combines last partial chunk with a full chunk
4391 end = start + ParGCArrayScanChunk;
4392 arrayOop(old)->set_length(end);
4393 // Push remainder.
4394 oop* old_p = set_partial_array_mask(old);
4395 assert(arrayOop(old)->length() < obj->length(), "Empty push?");
4396 _par_scan_state->push_on_queue(old_p);
4397 } else {
4398 // Restore length so that the heap remains parsable in
4399 // case of evacuation failure.
4400 arrayOop(old)->set_length(end);
4401 }
4402 _scanner.set_region(_g1->heap_region_containing_raw(obj));
4403 // process our set of indices (include header in first chunk)
4404 obj->oop_iterate_range(&_scanner, start, end);
4405 }
4406
4407 class G1ParEvacuateFollowersClosure : public VoidClosure {
4408 protected:
4409 G1CollectedHeap* _g1h;
4410 G1ParScanThreadState* _par_scan_state;
4411 RefToScanQueueSet* _queues;
4412 ParallelTaskTerminator* _terminator;
4413
4414 G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
4415 RefToScanQueueSet* queues() { return _queues; }
4416 ParallelTaskTerminator* terminator() { return _terminator; }
4417
4418 public:
4419 G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h,
4420 G1ParScanThreadState* par_scan_state,
4421 RefToScanQueueSet* queues,
4422 ParallelTaskTerminator* terminator)
4423 : _g1h(g1h), _par_scan_state(par_scan_state),
4424 _queues(queues), _terminator(terminator) {}
4425
4426 void do_void();
4427
4428 private:
4429 inline bool offer_termination();
4430 };
4431
4432 bool G1ParEvacuateFollowersClosure::offer_termination() {
4433 G1ParScanThreadState* const pss = par_scan_state();
4434 pss->start_term_time();
4435 const bool res = terminator()->offer_termination();
4436 pss->end_term_time();
4437 return res;
4438 }
4439
4440 void G1ParEvacuateFollowersClosure::do_void() {
4441 StarTask stolen_task;
4442 G1ParScanThreadState* const pss = par_scan_state();
4443 pss->trim_queue();
4444
4445 do {
4446 while (queues()->steal(pss->queue_num(), pss->hash_seed(), stolen_task)) {
4447 assert(pss->verify_task(stolen_task), "sanity");
4448 if (stolen_task.is_narrow()) {
4449 pss->deal_with_reference((narrowOop*) stolen_task);
4450 } else {
4451 pss->deal_with_reference((oop*) stolen_task);
4452 }
4453
4454 // We've just processed a reference and we might have made
4455 // available new entries on the queues. So we have to make sure
4456 // we drain the queues as necessary.
4457 pss->trim_queue();
4458 }
4459 } while (!offer_termination());
4460
4461 pss->retire_alloc_buffers();
4462 }
4463
4464 class G1ParTask : public AbstractGangTask {
4465 protected:
4466 G1CollectedHeap* _g1h;
4467 RefToScanQueueSet *_queues;
4468 ParallelTaskTerminator _terminator;
4469 int _n_workers;
4470
4471 Mutex _stats_lock;
4472 Mutex* stats_lock() { return &_stats_lock; }
4473
4474 size_t getNCards() {
4475 return (_g1h->capacity() + G1BlockOffsetSharedArray::N_bytes - 1)
4476 / G1BlockOffsetSharedArray::N_bytes;
4477 }
4478
4479 public:
4480 G1ParTask(G1CollectedHeap* g1h, int workers, RefToScanQueueSet *task_queues)
4481 : AbstractGangTask("G1 collection"),
4482 _g1h(g1h),
4483 _queues(task_queues),
4484 _terminator(workers, _queues),
4485 _stats_lock(Mutex::leaf, "parallel G1 stats lock", true),
4486 _n_workers(workers)
4487 {}
4488
4489 RefToScanQueueSet* queues() { return _queues; }
4490
4491 RefToScanQueue *work_queue(int i) {
4492 return queues()->queue(i);
4493 }
4494
4495 void work(int i) {
4496 if (i >= _n_workers) return; // no work needed this round
4497
4498 double start_time_ms = os::elapsedTime() * 1000.0;
4499 _g1h->g1_policy()->record_gc_worker_start_time(i, start_time_ms);
4500
4501 ResourceMark rm;
4502 HandleMark hm;
4503
4504 G1ParScanThreadState pss(_g1h, i);
4505 G1ParScanHeapEvacClosure scan_evac_cl(_g1h, &pss);
4506 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss);
4507 G1ParScanPartialArrayClosure partial_scan_cl(_g1h, &pss);
4508
4509 pss.set_evac_closure(&scan_evac_cl);
4510 pss.set_evac_failure_closure(&evac_failure_cl);
4511 pss.set_partial_scan_closure(&partial_scan_cl);
4512
4513 G1ParScanExtRootClosure only_scan_root_cl(_g1h, &pss);
4514 G1ParScanPermClosure only_scan_perm_cl(_g1h, &pss);
4515 G1ParScanHeapRSClosure only_scan_heap_rs_cl(_g1h, &pss);
4516 G1ParPushHeapRSClosure push_heap_rs_cl(_g1h, &pss);
4517
4518 G1ParScanAndMarkExtRootClosure scan_mark_root_cl(_g1h, &pss);
4519 G1ParScanAndMarkPermClosure scan_mark_perm_cl(_g1h, &pss);
4520 G1ParScanAndMarkHeapRSClosure scan_mark_heap_rs_cl(_g1h, &pss);
4521
4522 OopsInHeapRegionClosure *scan_root_cl;
4523 OopsInHeapRegionClosure *scan_perm_cl;
4524
4525 if (_g1h->g1_policy()->during_initial_mark_pause()) {
4526 scan_root_cl = &scan_mark_root_cl;
4527 scan_perm_cl = &scan_mark_perm_cl;
4528 } else {
4529 scan_root_cl = &only_scan_root_cl;
4530 scan_perm_cl = &only_scan_perm_cl;
4531 }
4532
4533 pss.start_strong_roots();
4534 _g1h->g1_process_strong_roots(/* not collecting perm */ false,
4535 SharedHeap::SO_AllClasses,
4536 scan_root_cl,
4537 &push_heap_rs_cl,
4538 scan_perm_cl,
4539 i);
4540 pss.end_strong_roots();
4541
4542 {
4543 double start = os::elapsedTime();
4544 G1ParEvacuateFollowersClosure evac(_g1h, &pss, _queues, &_terminator);
4545 evac.do_void();
4546 double elapsed_ms = (os::elapsedTime()-start)*1000.0;
4547 double term_ms = pss.term_time()*1000.0;
4548 _g1h->g1_policy()->record_obj_copy_time(i, elapsed_ms-term_ms);
4549 _g1h->g1_policy()->record_termination(i, term_ms, pss.term_attempts());
4550 }
4551 _g1h->g1_policy()->record_thread_age_table(pss.age_table());
4552 _g1h->update_surviving_young_words(pss.surviving_young_words()+1);
4553
4554 // Clean up any par-expanded rem sets.
4555 HeapRegionRemSet::par_cleanup();
4556
4557 if (ParallelGCVerbose) {
4558 MutexLocker x(stats_lock());
4559 pss.print_termination_stats(i);
4560 }
4561
4562 assert(pss.refs()->is_empty(), "should be empty");
4563 double end_time_ms = os::elapsedTime() * 1000.0;
4564 _g1h->g1_policy()->record_gc_worker_end_time(i, end_time_ms);
4565 }
4566 };
4567
4568 // *** Common G1 Evacuation Stuff
4569
4570 // This method is run in a GC worker.
4571
4572 void
4573 G1CollectedHeap::
4574 g1_process_strong_roots(bool collecting_perm_gen,
4575 SharedHeap::ScanningOption so,
4576 OopClosure* scan_non_heap_roots,
4577 OopsInHeapRegionClosure* scan_rs,
4578 OopsInGenClosure* scan_perm,
4579 int worker_i) {
4580 // First scan the strong roots, including the perm gen.
4581 double ext_roots_start = os::elapsedTime();
4582 double closure_app_time_sec = 0.0;
4583
4584 BufferingOopClosure buf_scan_non_heap_roots(scan_non_heap_roots);
4585 BufferingOopsInGenClosure buf_scan_perm(scan_perm);
4586 buf_scan_perm.set_generation(perm_gen());
4587
4588 // Walk the code cache w/o buffering, because StarTask cannot handle
4589 // unaligned oop locations.
4590 CodeBlobToOopClosure eager_scan_code_roots(scan_non_heap_roots, /*do_marking=*/ true);
4591
4592 process_strong_roots(false, // no scoping; this is parallel code
4593 collecting_perm_gen, so,
4594 &buf_scan_non_heap_roots,
4595 &eager_scan_code_roots,
4596 &buf_scan_perm);
4597
4598 // Now the ref_processor roots.
4599 if (!_process_strong_tasks->is_task_claimed(G1H_PS_refProcessor_oops_do)) {
4600 // We need to treat the discovered reference lists as roots and
4601 // keep entries (which are added by the marking threads) on them
4602 // live until they can be processed at the end of marking.
4603 ref_processor()->weak_oops_do(&buf_scan_non_heap_roots);
4604 }
4605
4606 // Finish up any enqueued closure apps (attributed as object copy time).
4607 buf_scan_non_heap_roots.done();
4608 buf_scan_perm.done();
4609
4610 double ext_roots_end = os::elapsedTime();
4611
4612 g1_policy()->reset_obj_copy_time(worker_i);
4613 double obj_copy_time_sec = buf_scan_perm.closure_app_seconds() +
4614 buf_scan_non_heap_roots.closure_app_seconds();
4615 g1_policy()->record_obj_copy_time(worker_i, obj_copy_time_sec * 1000.0);
4616
4617 double ext_root_time_ms =
4618 ((ext_roots_end - ext_roots_start) - obj_copy_time_sec) * 1000.0;
4619
4620 g1_policy()->record_ext_root_scan_time(worker_i, ext_root_time_ms);
4621
4622 // Scan strong roots in mark stack.
4623 if (!_process_strong_tasks->is_task_claimed(G1H_PS_mark_stack_oops_do)) {
4624 concurrent_mark()->oops_do(scan_non_heap_roots);
4625 }
4626 double mark_stack_scan_ms = (os::elapsedTime() - ext_roots_end) * 1000.0;
4627 g1_policy()->record_mark_stack_scan_time(worker_i, mark_stack_scan_ms);
4628
4629 // Now scan the complement of the collection set.
4630 if (scan_rs != NULL) {
4631 g1_rem_set()->oops_into_collection_set_do(scan_rs, worker_i);
4632 }
4633
4634 _process_strong_tasks->all_tasks_completed();
4635 }
4636
4637 void
4638 G1CollectedHeap::g1_process_weak_roots(OopClosure* root_closure,
4639 OopClosure* non_root_closure) {
4640 CodeBlobToOopClosure roots_in_blobs(root_closure, /*do_marking=*/ false);
4641 SharedHeap::process_weak_roots(root_closure, &roots_in_blobs, non_root_closure);
4642 }
4643
4644 void G1CollectedHeap::evacuate_collection_set() {
4645 set_evacuation_failed(false);
4646
4647 g1_rem_set()->prepare_for_oops_into_collection_set_do();
4648 concurrent_g1_refine()->set_use_cache(false);
4649 concurrent_g1_refine()->clear_hot_cache_claimed_index();
4650
4651 int n_workers = (ParallelGCThreads > 0 ? workers()->total_workers() : 1);
4652 set_par_threads(n_workers);
4653 G1ParTask g1_par_task(this, n_workers, _task_queues);
4654
4655 init_for_evac_failure(NULL);
4656
4657 rem_set()->prepare_for_younger_refs_iterate(true);
4658
4659 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
4660 double start_par = os::elapsedTime();
4661 if (G1CollectedHeap::use_parallel_gc_threads()) {
4662 // The individual threads will set their evac-failure closures.
4663 StrongRootsScope srs(this);
4664 if (ParallelGCVerbose) G1ParScanThreadState::print_termination_stats_hdr();
4665 workers()->run_task(&g1_par_task);
4666 } else {
4667 StrongRootsScope srs(this);
4668 g1_par_task.work(0);
4669 }
4670
4671 double par_time = (os::elapsedTime() - start_par) * 1000.0;
4672 g1_policy()->record_par_time(par_time);
4673 set_par_threads(0);
4674
4675 // Weak root processing.
4676 // Note: when JSR 292 is enabled and code blobs can contain
4677 // non-perm oops then we will need to process the code blobs
4678 // here too.
4679 {
4680 G1IsAliveClosure is_alive(this);
4681 G1KeepAliveClosure keep_alive(this);
4682 JNIHandles::weak_oops_do(&is_alive, &keep_alive);
4683 }
4684 release_gc_alloc_regions();
4685 g1_rem_set()->cleanup_after_oops_into_collection_set_do();
4686
4687 concurrent_g1_refine()->clear_hot_cache();
4688 concurrent_g1_refine()->set_use_cache(true);
4689
4690 finalize_for_evac_failure();
4691
4692 // Must do this before removing self-forwarding pointers, which clears
4693 // the per-region evac-failure flags.
4694 concurrent_mark()->complete_marking_in_collection_set();
4695
4696 if (evacuation_failed()) {
4697 remove_self_forwarding_pointers();
4698 if (PrintGCDetails) {
4699 gclog_or_tty->print(" (to-space overflow)");
4700 } else if (PrintGC) {
4701 gclog_or_tty->print("--");
4702 }
4703 }
4704
4705 if (G1DeferredRSUpdate) {
4706 RedirtyLoggedCardTableEntryFastClosure redirty;
4707 dirty_card_queue_set().set_closure(&redirty);
4708 dirty_card_queue_set().apply_closure_to_all_completed_buffers();
4709
4710 DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set();
4711 dcq.merge_bufferlists(&dirty_card_queue_set());
4712 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
4713 }
4714 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
4715 }
4716
4717 void G1CollectedHeap::free_region_if_empty(HeapRegion* hr,
4718 size_t* pre_used,
4719 FreeRegionList* free_list,
4720 HumongousRegionSet* humongous_proxy_set,
4721 HRRSCleanupTask* hrrs_cleanup_task,
4722 bool par) {
4723 if (hr->used() > 0 && hr->max_live_bytes() == 0 && !hr->is_young()) {
4724 if (hr->isHumongous()) {
4725 assert(hr->startsHumongous(), "we should only see starts humongous");
4726 free_humongous_region(hr, pre_used, free_list, humongous_proxy_set, par);
4727 } else {
4728 free_region(hr, pre_used, free_list, par);
4729 }
4730 } else {
4731 hr->rem_set()->do_cleanup_work(hrrs_cleanup_task);
4732 }
4733 }
4734
4735 void G1CollectedHeap::free_region(HeapRegion* hr,
4736 size_t* pre_used,
4737 FreeRegionList* free_list,
4738 bool par) {
4739 assert(!hr->isHumongous(), "this is only for non-humongous regions");
4740 assert(!hr->is_empty(), "the region should not be empty");
4741 assert(free_list != NULL, "pre-condition");
4742
4743 *pre_used += hr->used();
4744 hr->hr_clear(par, true /* clear_space */);
4745 free_list->add_as_head(hr);
4746 }
4747
4748 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
4749 size_t* pre_used,
4750 FreeRegionList* free_list,
4751 HumongousRegionSet* humongous_proxy_set,
4752 bool par) {
4753 assert(hr->startsHumongous(), "this is only for starts humongous regions");
4754 assert(free_list != NULL, "pre-condition");
4755 assert(humongous_proxy_set != NULL, "pre-condition");
4756
4757 size_t hr_used = hr->used();
4758 size_t hr_capacity = hr->capacity();
4759 size_t hr_pre_used = 0;
4760 _humongous_set.remove_with_proxy(hr, humongous_proxy_set);
4761 hr->set_notHumongous();
4762 free_region(hr, &hr_pre_used, free_list, par);
4763
4764 size_t i = hr->hrs_index() + 1;
4765 size_t num = 1;
4766 while (i < n_regions()) {
4767 HeapRegion* curr_hr = region_at(i);
4768 if (!curr_hr->continuesHumongous()) {
4769 break;
4770 }
4771 curr_hr->set_notHumongous();
4772 free_region(curr_hr, &hr_pre_used, free_list, par);
4773 num += 1;
4774 i += 1;
4775 }
4776 assert(hr_pre_used == hr_used,
4777 err_msg("hr_pre_used: "SIZE_FORMAT" and hr_used: "SIZE_FORMAT" "
4778 "should be the same", hr_pre_used, hr_used));
4779 *pre_used += hr_pre_used;
4780 }
4781
4782 void G1CollectedHeap::update_sets_after_freeing_regions(size_t pre_used,
4783 FreeRegionList* free_list,
4784 HumongousRegionSet* humongous_proxy_set,
4785 bool par) {
4786 if (pre_used > 0) {
4787 Mutex* lock = (par) ? ParGCRareEvent_lock : NULL;
4788 MutexLockerEx x(lock, Mutex::_no_safepoint_check_flag);
4789 assert(_summary_bytes_used >= pre_used,
4790 err_msg("invariant: _summary_bytes_used: "SIZE_FORMAT" "
4791 "should be >= pre_used: "SIZE_FORMAT,
4792 _summary_bytes_used, pre_used));
4793 _summary_bytes_used -= pre_used;
4794 }
4795 if (free_list != NULL && !free_list->is_empty()) {
4796 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
4797 _free_list.add_as_head(free_list);
4798 }
4799 if (humongous_proxy_set != NULL && !humongous_proxy_set->is_empty()) {
4800 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
4801 _humongous_set.update_from_proxy(humongous_proxy_set);
4802 }
4803 }
4804
4805 class G1ParCleanupCTTask : public AbstractGangTask {
4806 CardTableModRefBS* _ct_bs;
4807 G1CollectedHeap* _g1h;
4808 HeapRegion* volatile _su_head;
4809 public:
4810 G1ParCleanupCTTask(CardTableModRefBS* ct_bs,
4811 G1CollectedHeap* g1h) :
4812 AbstractGangTask("G1 Par Cleanup CT Task"),
4813 _ct_bs(ct_bs), _g1h(g1h) { }
4814
4815 void work(int i) {
4816 HeapRegion* r;
4817 while (r = _g1h->pop_dirty_cards_region()) {
4818 clear_cards(r);
4819 }
4820 }
4821
4822 void clear_cards(HeapRegion* r) {
4823 // Cards of the survivors should have already been dirtied.
4824 if (!r->is_survivor()) {
4825 _ct_bs->clear(MemRegion(r->bottom(), r->end()));
4826 }
4827 }
4828 };
4829
4830 #ifndef PRODUCT
4831 class G1VerifyCardTableCleanup: public HeapRegionClosure {
4832 G1CollectedHeap* _g1h;
4833 CardTableModRefBS* _ct_bs;
4834 public:
4835 G1VerifyCardTableCleanup(G1CollectedHeap* g1h, CardTableModRefBS* ct_bs)
4836 : _g1h(g1h), _ct_bs(ct_bs) { }
4837 virtual bool doHeapRegion(HeapRegion* r) {
4838 if (r->is_survivor()) {
4839 _g1h->verify_dirty_region(r);
4840 } else {
4841 _g1h->verify_not_dirty_region(r);
4842 }
4843 return false;
4844 }
4845 };
4846
4847 void G1CollectedHeap::verify_not_dirty_region(HeapRegion* hr) {
4848 // All of the region should be clean.
4849 CardTableModRefBS* ct_bs = (CardTableModRefBS*)barrier_set();
4850 MemRegion mr(hr->bottom(), hr->end());
4851 ct_bs->verify_not_dirty_region(mr);
4852 }
4853
4854 void G1CollectedHeap::verify_dirty_region(HeapRegion* hr) {
4855 // We cannot guarantee that [bottom(),end()] is dirty. Threads
4856 // dirty allocated blocks as they allocate them. The thread that
4857 // retires each region and replaces it with a new one will do a
4858 // maximal allocation to fill in [pre_dummy_top(),end()] but will
4859 // not dirty that area (one less thing to have to do while holding
4860 // a lock). So we can only verify that [bottom(),pre_dummy_top()]
4861 // is dirty.
4862 CardTableModRefBS* ct_bs = (CardTableModRefBS*) barrier_set();
4863 MemRegion mr(hr->bottom(), hr->pre_dummy_top());
4864 ct_bs->verify_dirty_region(mr);
4865 }
4866
4867 void G1CollectedHeap::verify_dirty_young_list(HeapRegion* head) {
4868 CardTableModRefBS* ct_bs = (CardTableModRefBS*) barrier_set();
4869 for (HeapRegion* hr = head; hr != NULL; hr = hr->get_next_young_region()) {
4870 verify_dirty_region(hr);
4871 }
4872 }
4873
4874 void G1CollectedHeap::verify_dirty_young_regions() {
4875 verify_dirty_young_list(_young_list->first_region());
4876 verify_dirty_young_list(_young_list->first_survivor_region());
4877 }
4878 #endif
4879
4880 void G1CollectedHeap::cleanUpCardTable() {
4881 CardTableModRefBS* ct_bs = (CardTableModRefBS*) (barrier_set());
4882 double start = os::elapsedTime();
4883
4884 // Iterate over the dirty cards region list.
4885 G1ParCleanupCTTask cleanup_task(ct_bs, this);
4886
4887 if (ParallelGCThreads > 0) {
4888 set_par_threads(workers()->total_workers());
4889 workers()->run_task(&cleanup_task);
4890 set_par_threads(0);
4891 } else {
4892 while (_dirty_cards_region_list) {
4893 HeapRegion* r = _dirty_cards_region_list;
4894 cleanup_task.clear_cards(r);
4895 _dirty_cards_region_list = r->get_next_dirty_cards_region();
4896 if (_dirty_cards_region_list == r) {
4897 // The last region.
4898 _dirty_cards_region_list = NULL;
4899 }
4900 r->set_next_dirty_cards_region(NULL);
4901 }
4902 }
4903
4904 double elapsed = os::elapsedTime() - start;
4905 g1_policy()->record_clear_ct_time( elapsed * 1000.0);
4906 #ifndef PRODUCT
4907 if (G1VerifyCTCleanup || VerifyAfterGC) {
4908 G1VerifyCardTableCleanup cleanup_verifier(this, ct_bs);
4909 heap_region_iterate(&cleanup_verifier);
4910 }
4911 #endif
4912 }
4913
4914 void G1CollectedHeap::free_collection_set(HeapRegion* cs_head) {
4915 size_t pre_used = 0;
4916 FreeRegionList local_free_list("Local List for CSet Freeing");
4917
4918 double young_time_ms = 0.0;
4919 double non_young_time_ms = 0.0;
4920
4921 // Since the collection set is a superset of the the young list,
4922 // all we need to do to clear the young list is clear its
4923 // head and length, and unlink any young regions in the code below
4924 _young_list->clear();
4925
4926 G1CollectorPolicy* policy = g1_policy();
4927
4928 double start_sec = os::elapsedTime();
4929 bool non_young = true;
4930
4931 HeapRegion* cur = cs_head;
4932 int age_bound = -1;
4933 size_t rs_lengths = 0;
4934
4935 while (cur != NULL) {
4936 assert(!is_on_master_free_list(cur), "sanity");
4937
4938 if (non_young) {
4939 if (cur->is_young()) {
4940 double end_sec = os::elapsedTime();
4941 double elapsed_ms = (end_sec - start_sec) * 1000.0;
4942 non_young_time_ms += elapsed_ms;
4943
4944 start_sec = os::elapsedTime();
4945 non_young = false;
4946 }
4947 } else {
4948 double end_sec = os::elapsedTime();
4949 double elapsed_ms = (end_sec - start_sec) * 1000.0;
4950 young_time_ms += elapsed_ms;
4951
4952 start_sec = os::elapsedTime();
4953 non_young = true;
4954 }
4955
4956 rs_lengths += cur->rem_set()->occupied();
4957
4958 HeapRegion* next = cur->next_in_collection_set();
4959 assert(cur->in_collection_set(), "bad CS");
4960 cur->set_next_in_collection_set(NULL);
4961 cur->set_in_collection_set(false);
4962
4963 if (cur->is_young()) {
4964 int index = cur->young_index_in_cset();
4965 guarantee( index != -1, "invariant" );
4966 guarantee( (size_t)index < policy->young_cset_length(), "invariant" );
4967 size_t words_survived = _surviving_young_words[index];
4968 cur->record_surv_words_in_group(words_survived);
4969
4970 // At this point the we have 'popped' cur from the collection set
4971 // (linked via next_in_collection_set()) but it is still in the
4972 // young list (linked via next_young_region()). Clear the
4973 // _next_young_region field.
4974 cur->set_next_young_region(NULL);
4975 } else {
4976 int index = cur->young_index_in_cset();
4977 guarantee( index == -1, "invariant" );
4978 }
4979
4980 assert( (cur->is_young() && cur->young_index_in_cset() > -1) ||
4981 (!cur->is_young() && cur->young_index_in_cset() == -1),
4982 "invariant" );
4983
4984 if (!cur->evacuation_failed()) {
4985 // And the region is empty.
4986 assert(!cur->is_empty(), "Should not have empty regions in a CS.");
4987 free_region(cur, &pre_used, &local_free_list, false /* par */);
4988 } else {
4989 cur->uninstall_surv_rate_group();
4990 if (cur->is_young())
4991 cur->set_young_index_in_cset(-1);
4992 cur->set_not_young();
4993 cur->set_evacuation_failed(false);
4994 }
4995 cur = next;
4996 }
4997
4998 policy->record_max_rs_lengths(rs_lengths);
4999 policy->cset_regions_freed();
5000
5001 double end_sec = os::elapsedTime();
5002 double elapsed_ms = (end_sec - start_sec) * 1000.0;
5003 if (non_young)
5004 non_young_time_ms += elapsed_ms;
5005 else
5006 young_time_ms += elapsed_ms;
5007
5008 update_sets_after_freeing_regions(pre_used, &local_free_list,
5009 NULL /* humongous_proxy_set */,
5010 false /* par */);
5011 policy->record_young_free_cset_time_ms(young_time_ms);
5012 policy->record_non_young_free_cset_time_ms(non_young_time_ms);
5013 }
5014
5015 // This routine is similar to the above but does not record
5016 // any policy statistics or update free lists; we are abandoning
5017 // the current incremental collection set in preparation of a
5018 // full collection. After the full GC we will start to build up
5019 // the incremental collection set again.
5020 // This is only called when we're doing a full collection
5021 // and is immediately followed by the tearing down of the young list.
5022
5023 void G1CollectedHeap::abandon_collection_set(HeapRegion* cs_head) {
5024 HeapRegion* cur = cs_head;
5025
5026 while (cur != NULL) {
5027 HeapRegion* next = cur->next_in_collection_set();
5028 assert(cur->in_collection_set(), "bad CS");
5029 cur->set_next_in_collection_set(NULL);
5030 cur->set_in_collection_set(false);
5031 cur->set_young_index_in_cset(-1);
5032 cur = next;
5033 }
5034 }
5035
5036 void G1CollectedHeap::set_free_regions_coming() {
5037 if (G1ConcRegionFreeingVerbose) {
5038 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
5039 "setting free regions coming");
5040 }
5041
5042 assert(!free_regions_coming(), "pre-condition");
5043 _free_regions_coming = true;
5044 }
5045
5046 void G1CollectedHeap::reset_free_regions_coming() {
5047 {
5048 assert(free_regions_coming(), "pre-condition");
5049 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
5050 _free_regions_coming = false;
5051 SecondaryFreeList_lock->notify_all();
5052 }
5053
5054 if (G1ConcRegionFreeingVerbose) {
5055 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
5056 "reset free regions coming");
5057 }
5058 }
5059
5060 void G1CollectedHeap::wait_while_free_regions_coming() {
5061 // Most of the time we won't have to wait, so let's do a quick test
5062 // first before we take the lock.
5063 if (!free_regions_coming()) {
5064 return;
5065 }
5066
5067 if (G1ConcRegionFreeingVerbose) {
5068 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
5069 "waiting for free regions");
5070 }
5071
5072 {
5073 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
5074 while (free_regions_coming()) {
5075 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
5076 }
5077 }
5078
5079 if (G1ConcRegionFreeingVerbose) {
5080 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
5081 "done waiting for free regions");
5082 }
5083 }
5084
5085 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
5086 assert(heap_lock_held_for_gc(),
5087 "the heap lock should already be held by or for this thread");
5088 _young_list->push_region(hr);
5089 g1_policy()->set_region_short_lived(hr);
5090 }
5091
5092 class NoYoungRegionsClosure: public HeapRegionClosure {
5093 private:
5094 bool _success;
5095 public:
5096 NoYoungRegionsClosure() : _success(true) { }
5097 bool doHeapRegion(HeapRegion* r) {
5098 if (r->is_young()) {
5099 gclog_or_tty->print_cr("Region ["PTR_FORMAT", "PTR_FORMAT") tagged as young",
5100 r->bottom(), r->end());
5101 _success = false;
5102 }
5103 return false;
5104 }
5105 bool success() { return _success; }
5106 };
5107
5108 bool G1CollectedHeap::check_young_list_empty(bool check_heap, bool check_sample) {
5109 bool ret = _young_list->check_list_empty(check_sample);
5110
5111 if (check_heap) {
5112 NoYoungRegionsClosure closure;
5113 heap_region_iterate(&closure);
5114 ret = ret && closure.success();
5115 }
5116
5117 return ret;
5118 }
5119
5120 void G1CollectedHeap::empty_young_list() {
5121 assert(heap_lock_held_for_gc(),
5122 "the heap lock should already be held by or for this thread");
5123
5124 _young_list->empty_list();
5125 }
5126
5127 // Done at the start of full GC.
5128 void G1CollectedHeap::tear_down_region_lists() {
5129 _free_list.remove_all();
5130 }
5131
5132 class RegionResetter: public HeapRegionClosure {
5133 G1CollectedHeap* _g1h;
5134 FreeRegionList _local_free_list;
5135
5136 public:
5137 RegionResetter() : _g1h(G1CollectedHeap::heap()),
5138 _local_free_list("Local Free List for RegionResetter") { }
5139
5140 bool doHeapRegion(HeapRegion* r) {
5141 if (r->continuesHumongous()) return false;
5142 if (r->top() > r->bottom()) {
5143 if (r->top() < r->end()) {
5144 Copy::fill_to_words(r->top(),
5145 pointer_delta(r->end(), r->top()));
5146 }
5147 } else {
5148 assert(r->is_empty(), "tautology");
5149 _local_free_list.add_as_tail(r);
5150 }
5151 return false;
5152 }
5153
5154 void update_free_lists() {
5155 _g1h->update_sets_after_freeing_regions(0, &_local_free_list, NULL,
5156 false /* par */);
5157 }
5158 };
5159
5160 // Done at the end of full GC.
5161 void G1CollectedHeap::rebuild_region_lists() {
5162 // This needs to go at the end of the full GC.
5163 RegionResetter rs;
5164 heap_region_iterate(&rs);
5165 rs.update_free_lists();
5166 }
5167
5168 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) {
5169 _refine_cte_cl->set_concurrent(concurrent);
5170 }
5171
5172 bool G1CollectedHeap::is_in_closed_subset(const void* p) const {
5173 HeapRegion* hr = heap_region_containing(p);
5174 if (hr == NULL) {
5175 return is_in_permanent(p);
5176 } else {
5177 return hr->is_in(p);
5178 }
5179 }
5180
5181 // Methods for the mutator alloc region
5182
5183 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
5184 bool force) {
5185 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
5186 assert(!force || g1_policy()->can_expand_young_list(),
5187 "if force is true we should be able to expand the young list");
5188 bool young_list_full = g1_policy()->is_young_list_full();
5189 if (force || !young_list_full) {
5190 HeapRegion* new_alloc_region = new_region(word_size,
5191 false /* do_expand */);
5192 if (new_alloc_region != NULL) {
5193 g1_policy()->update_region_num(true /* next_is_young */);
5194 set_region_short_lived_locked(new_alloc_region);
5195 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Eden, young_list_full);
5196 g1mm()->update_eden_counters();
5197 return new_alloc_region;
5198 }
5199 }
5200 return NULL;
5201 }
5202
5203 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
5204 size_t allocated_bytes) {
5205 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
5206 assert(alloc_region->is_young(), "all mutator alloc regions should be young");
5207
5208 g1_policy()->add_region_to_incremental_cset_lhs(alloc_region);
5209 _summary_bytes_used += allocated_bytes;
5210 _hr_printer.retire(alloc_region);
5211 }
5212
5213 HeapRegion* MutatorAllocRegion::allocate_new_region(size_t word_size,
5214 bool force) {
5215 return _g1h->new_mutator_alloc_region(word_size, force);
5216 }
5217
5218 void MutatorAllocRegion::retire_region(HeapRegion* alloc_region,
5219 size_t allocated_bytes) {
5220 _g1h->retire_mutator_alloc_region(alloc_region, allocated_bytes);
5221 }
5222
5223 // Methods for the GC alloc regions
5224
5225 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size,
5226 size_t count,
5227 GCAllocPurpose ap) {
5228 assert(FreeList_lock->owned_by_self(), "pre-condition");
5229
5230 if (count < g1_policy()->max_regions(ap)) {
5231 HeapRegion* new_alloc_region = new_region(word_size,
5232 true /* do_expand */);
5233 if (new_alloc_region != NULL) {
5234 // We really only need to do this for old regions given that we
5235 // should never scan survivors. But it doesn't hurt to do it
5236 // for survivors too.
5237 new_alloc_region->set_saved_mark();
5238 if (ap == GCAllocForSurvived) {
5239 new_alloc_region->set_survivor();
5240 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Survivor);
5241 } else {
5242 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Old);
5243 }
5244 return new_alloc_region;
5245 } else {
5246 g1_policy()->note_alloc_region_limit_reached(ap);
5247 }
5248 }
5249 return NULL;
5250 }
5251
5252 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
5253 size_t allocated_bytes,
5254 GCAllocPurpose ap) {
5255 alloc_region->note_end_of_copying();
5256 g1_policy()->record_bytes_copied_during_gc(allocated_bytes);
5257 if (ap == GCAllocForSurvived) {
5258 young_list()->add_survivor_region(alloc_region);
5259 }
5260 _hr_printer.retire(alloc_region);
5261 }
5262
5263 HeapRegion* SurvivorGCAllocRegion::allocate_new_region(size_t word_size,
5264 bool force) {
5265 assert(!force, "not supported for GC alloc regions");
5266 return _g1h->new_gc_alloc_region(word_size, count(), GCAllocForSurvived);
5267 }
5268
5269 void SurvivorGCAllocRegion::retire_region(HeapRegion* alloc_region,
5270 size_t allocated_bytes) {
5271 _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes,
5272 GCAllocForSurvived);
5273 }
5274
5275 HeapRegion* OldGCAllocRegion::allocate_new_region(size_t word_size,
5276 bool force) {
5277 assert(!force, "not supported for GC alloc regions");
5278 return _g1h->new_gc_alloc_region(word_size, count(), GCAllocForTenured);
5279 }
5280
5281 void OldGCAllocRegion::retire_region(HeapRegion* alloc_region,
5282 size_t allocated_bytes) {
5283 _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes,
5284 GCAllocForTenured);
5285 }
5286 // Heap region set verification
5287
5288 class VerifyRegionListsClosure : public HeapRegionClosure {
5289 private:
5290 HumongousRegionSet* _humongous_set;
5291 FreeRegionList* _free_list;
5292 size_t _region_count;
5293
5294 public:
5295 VerifyRegionListsClosure(HumongousRegionSet* humongous_set,
5296 FreeRegionList* free_list) :
5297 _humongous_set(humongous_set), _free_list(free_list),
5298 _region_count(0) { }
5299
5300 size_t region_count() { return _region_count; }
5301
5302 bool doHeapRegion(HeapRegion* hr) {
5303 _region_count += 1;
5304
5305 if (hr->continuesHumongous()) {
5306 return false;
5307 }
5308
5309 if (hr->is_young()) {
5310 // TODO
5311 } else if (hr->startsHumongous()) {
5312 _humongous_set->verify_next_region(hr);
5313 } else if (hr->is_empty()) {
5314 _free_list->verify_next_region(hr);
5315 }
5316 return false;
5317 }
5318 };
5319
5320 HeapRegion* G1CollectedHeap::new_heap_region(size_t hrs_index,
5321 HeapWord* bottom) {
5322 HeapWord* end = bottom + HeapRegion::GrainWords;
5323 MemRegion mr(bottom, end);
5324 assert(_g1_reserved.contains(mr), "invariant");
5325 // This might return NULL if the allocation fails
5326 return new HeapRegion(hrs_index, _bot_shared, mr, true /* is_zeroed */);
5327 }
5328
5329 void G1CollectedHeap::verify_region_sets() {
5330 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
5331
5332 // First, check the explicit lists.
5333 _free_list.verify();
5334 {
5335 // Given that a concurrent operation might be adding regions to
5336 // the secondary free list we have to take the lock before
5337 // verifying it.
5338 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
5339 _secondary_free_list.verify();
5340 }
5341 _humongous_set.verify();
5342
5343 // If a concurrent region freeing operation is in progress it will
5344 // be difficult to correctly attributed any free regions we come
5345 // across to the correct free list given that they might belong to
5346 // one of several (free_list, secondary_free_list, any local lists,
5347 // etc.). So, if that's the case we will skip the rest of the
5348 // verification operation. Alternatively, waiting for the concurrent
5349 // operation to complete will have a non-trivial effect on the GC's
5350 // operation (no concurrent operation will last longer than the
5351 // interval between two calls to verification) and it might hide
5352 // any issues that we would like to catch during testing.
5353 if (free_regions_coming()) {
5354 return;
5355 }
5356
5357 // Make sure we append the secondary_free_list on the free_list so
5358 // that all free regions we will come across can be safely
5359 // attributed to the free_list.
5360 append_secondary_free_list_if_not_empty_with_lock();
5361
5362 // Finally, make sure that the region accounting in the lists is
5363 // consistent with what we see in the heap.
5364 _humongous_set.verify_start();
5365 _free_list.verify_start();
5366
5367 VerifyRegionListsClosure cl(&_humongous_set, &_free_list);
5368 heap_region_iterate(&cl);
5369
5370 _humongous_set.verify_end();
5371 _free_list.verify_end();
5372 }