1 /*
2 * Copyright (c) 2001, 2012, 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/g1EvacFailure.hpp"
36 #include "gc_implementation/g1/g1GCPhaseTimes.hpp"
37 #include "gc_implementation/g1/g1Log.hpp"
38 #include "gc_implementation/g1/g1MarkSweep.hpp"
39 #include "gc_implementation/g1/g1OopClosures.inline.hpp"
40 #include "gc_implementation/g1/g1RemSet.inline.hpp"
41 #include "gc_implementation/g1/g1YCTypes.hpp"
42 #include "gc_implementation/g1/heapRegion.inline.hpp"
43 #include "gc_implementation/g1/heapRegionRemSet.hpp"
44 #include "gc_implementation/g1/heapRegionSeq.inline.hpp"
45 #include "gc_implementation/g1/vm_operations_g1.hpp"
46 #include "gc_implementation/shared/gcHeapSummary.hpp"
47 #include "gc_implementation/shared/gcTimer.hpp"
48 #include "gc_implementation/shared/gcTrace.hpp"
49 #include "gc_implementation/shared/gcTraceTime.hpp"
50 #include "gc_implementation/shared/isGCActiveMark.hpp"
51 #include "memory/gcLocker.inline.hpp"
52 #include "memory/genOopClosures.inline.hpp"
53 #include "memory/generationSpec.hpp"
54 #include "memory/referenceProcessor.hpp"
55 #include "oops/oop.inline.hpp"
56 #include "oops/oop.pcgc.inline.hpp"
57 #include "runtime/aprofiler.hpp"
58 #include "runtime/vmThread.hpp"
59
60 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;
61
62 // turn it on so that the contents of the young list (scan-only /
63 // to-be-collected) are printed at "strategic" points before / during
64 // / after the collection --- this is useful for debugging
65 #define YOUNG_LIST_VERBOSE 0
66 // CURRENT STATUS
67 // This file is under construction. Search for "FIXME".
68
69 // INVARIANTS/NOTES
70 //
71 // All allocation activity covered by the G1CollectedHeap interface is
72 // serialized by acquiring the HeapLock. This happens in mem_allocate
73 // and allocate_new_tlab, which are the "entry" points to the
74 // allocation code from the rest of the JVM. (Note that this does not
75 // apply to TLAB allocation, which is not part of this interface: it
76 // is done by clients of this interface.)
77
78 // Notes on implementation of parallelism in different tasks.
79 //
80 // G1ParVerifyTask uses heap_region_par_iterate_chunked() for parallelism.
81 // The number of GC workers is passed to heap_region_par_iterate_chunked().
82 // It does use run_task() which sets _n_workers in the task.
83 // G1ParTask executes g1_process_strong_roots() ->
84 // SharedHeap::process_strong_roots() which calls eventually to
85 // CardTableModRefBS::par_non_clean_card_iterate_work() which uses
86 // SequentialSubTasksDone. SharedHeap::process_strong_roots() also
87 // directly uses SubTasksDone (_process_strong_tasks field in SharedHeap).
88 //
89
90 // Local to this file.
91
92 class RefineCardTableEntryClosure: public CardTableEntryClosure {
93 SuspendibleThreadSet* _sts;
94 G1RemSet* _g1rs;
95 ConcurrentG1Refine* _cg1r;
96 bool _concurrent;
97 public:
98 RefineCardTableEntryClosure(SuspendibleThreadSet* sts,
99 G1RemSet* g1rs,
100 ConcurrentG1Refine* cg1r) :
101 _sts(sts), _g1rs(g1rs), _cg1r(cg1r), _concurrent(true)
102 {}
103 bool do_card_ptr(jbyte* card_ptr, int worker_i) {
104 bool oops_into_cset = _g1rs->concurrentRefineOneCard(card_ptr, worker_i, false);
105 // This path is executed by the concurrent refine or mutator threads,
106 // concurrently, and so we do not care if card_ptr contains references
107 // that point into the collection set.
108 assert(!oops_into_cset, "should be");
109
110 if (_concurrent && _sts->should_yield()) {
111 // Caller will actually yield.
112 return false;
113 }
114 // Otherwise, we finished successfully; return true.
115 return true;
116 }
117 void set_concurrent(bool b) { _concurrent = b; }
118 };
119
120
121 class ClearLoggedCardTableEntryClosure: public CardTableEntryClosure {
122 int _calls;
123 G1CollectedHeap* _g1h;
124 CardTableModRefBS* _ctbs;
125 int _histo[256];
126 public:
127 ClearLoggedCardTableEntryClosure() :
128 _calls(0)
129 {
130 _g1h = G1CollectedHeap::heap();
131 _ctbs = (CardTableModRefBS*)_g1h->barrier_set();
132 for (int i = 0; i < 256; i++) _histo[i] = 0;
133 }
134 bool do_card_ptr(jbyte* card_ptr, int worker_i) {
135 if (_g1h->is_in_reserved(_ctbs->addr_for(card_ptr))) {
136 _calls++;
137 unsigned char* ujb = (unsigned char*)card_ptr;
138 int ind = (int)(*ujb);
139 _histo[ind]++;
140 *card_ptr = -1;
141 }
142 return true;
143 }
144 int calls() { return _calls; }
145 void print_histo() {
146 gclog_or_tty->print_cr("Card table value histogram:");
147 for (int i = 0; i < 256; i++) {
148 if (_histo[i] != 0) {
149 gclog_or_tty->print_cr(" %d: %d", i, _histo[i]);
150 }
151 }
152 }
153 };
154
155 class RedirtyLoggedCardTableEntryClosure: public CardTableEntryClosure {
156 int _calls;
157 G1CollectedHeap* _g1h;
158 CardTableModRefBS* _ctbs;
159 public:
160 RedirtyLoggedCardTableEntryClosure() :
161 _calls(0)
162 {
163 _g1h = G1CollectedHeap::heap();
164 _ctbs = (CardTableModRefBS*)_g1h->barrier_set();
165 }
166 bool do_card_ptr(jbyte* card_ptr, int worker_i) {
167 if (_g1h->is_in_reserved(_ctbs->addr_for(card_ptr))) {
168 _calls++;
169 *card_ptr = 0;
170 }
171 return true;
172 }
173 int calls() { return _calls; }
174 };
175
176 class RedirtyLoggedCardTableEntryFastClosure : public CardTableEntryClosure {
177 public:
178 bool do_card_ptr(jbyte* card_ptr, int worker_i) {
179 *card_ptr = CardTableModRefBS::dirty_card_val();
180 return true;
181 }
182 };
183
184 YoungList::YoungList(G1CollectedHeap* g1h) :
185 _g1h(g1h), _head(NULL), _length(0), _last_sampled_rs_lengths(0),
186 _survivor_head(NULL), _survivor_tail(NULL), _survivor_length(0) {
187 guarantee(check_list_empty(false), "just making sure...");
188 }
189
190 void YoungList::push_region(HeapRegion *hr) {
191 assert(!hr->is_young(), "should not already be young");
192 assert(hr->get_next_young_region() == NULL, "cause it should!");
193
194 hr->set_next_young_region(_head);
195 _head = hr;
196
197 _g1h->g1_policy()->set_region_eden(hr, (int) _length);
198 ++_length;
199 }
200
201 void YoungList::add_survivor_region(HeapRegion* hr) {
202 assert(hr->is_survivor(), "should be flagged as survivor region");
203 assert(hr->get_next_young_region() == NULL, "cause it should!");
204
205 hr->set_next_young_region(_survivor_head);
206 if (_survivor_head == NULL) {
207 _survivor_tail = hr;
208 }
209 _survivor_head = hr;
210 ++_survivor_length;
211 }
212
213 void YoungList::empty_list(HeapRegion* list) {
214 while (list != NULL) {
215 HeapRegion* next = list->get_next_young_region();
216 list->set_next_young_region(NULL);
217 list->uninstall_surv_rate_group();
218 list->set_not_young();
219 list = next;
220 }
221 }
222
223 void YoungList::empty_list() {
224 assert(check_list_well_formed(), "young list should be well formed");
225
226 empty_list(_head);
227 _head = NULL;
228 _length = 0;
229
230 empty_list(_survivor_head);
231 _survivor_head = NULL;
232 _survivor_tail = NULL;
233 _survivor_length = 0;
234
235 _last_sampled_rs_lengths = 0;
236
237 assert(check_list_empty(false), "just making sure...");
238 }
239
240 bool YoungList::check_list_well_formed() {
241 bool ret = true;
242
243 uint length = 0;
244 HeapRegion* curr = _head;
245 HeapRegion* last = NULL;
246 while (curr != NULL) {
247 if (!curr->is_young()) {
248 gclog_or_tty->print_cr("### YOUNG REGION "PTR_FORMAT"-"PTR_FORMAT" "
249 "incorrectly tagged (y: %d, surv: %d)",
250 curr->bottom(), curr->end(),
251 curr->is_young(), curr->is_survivor());
252 ret = false;
253 }
254 ++length;
255 last = curr;
256 curr = curr->get_next_young_region();
257 }
258 ret = ret && (length == _length);
259
260 if (!ret) {
261 gclog_or_tty->print_cr("### YOUNG LIST seems not well formed!");
262 gclog_or_tty->print_cr("### list has %u entries, _length is %u",
263 length, _length);
264 }
265
266 return ret;
267 }
268
269 bool YoungList::check_list_empty(bool check_sample) {
270 bool ret = true;
271
272 if (_length != 0) {
273 gclog_or_tty->print_cr("### YOUNG LIST should have 0 length, not %u",
274 _length);
275 ret = false;
276 }
277 if (check_sample && _last_sampled_rs_lengths != 0) {
278 gclog_or_tty->print_cr("### YOUNG LIST has non-zero last sampled RS lengths");
279 ret = false;
280 }
281 if (_head != NULL) {
282 gclog_or_tty->print_cr("### YOUNG LIST does not have a NULL head");
283 ret = false;
284 }
285 if (!ret) {
286 gclog_or_tty->print_cr("### YOUNG LIST does not seem empty");
287 }
288
289 return ret;
290 }
291
292 void
293 YoungList::rs_length_sampling_init() {
294 _sampled_rs_lengths = 0;
295 _curr = _head;
296 }
297
298 bool
299 YoungList::rs_length_sampling_more() {
300 return _curr != NULL;
301 }
302
303 void
304 YoungList::rs_length_sampling_next() {
305 assert( _curr != NULL, "invariant" );
306 size_t rs_length = _curr->rem_set()->occupied();
307
308 _sampled_rs_lengths += rs_length;
309
310 // The current region may not yet have been added to the
311 // incremental collection set (it gets added when it is
312 // retired as the current allocation region).
313 if (_curr->in_collection_set()) {
314 // Update the collection set policy information for this region
315 _g1h->g1_policy()->update_incremental_cset_info(_curr, rs_length);
316 }
317
318 _curr = _curr->get_next_young_region();
319 if (_curr == NULL) {
320 _last_sampled_rs_lengths = _sampled_rs_lengths;
321 // gclog_or_tty->print_cr("last sampled RS lengths = %d", _last_sampled_rs_lengths);
322 }
323 }
324
325 void
326 YoungList::reset_auxilary_lists() {
327 guarantee( is_empty(), "young list should be empty" );
328 assert(check_list_well_formed(), "young list should be well formed");
329
330 // Add survivor regions to SurvRateGroup.
331 _g1h->g1_policy()->note_start_adding_survivor_regions();
332 _g1h->g1_policy()->finished_recalculating_age_indexes(true /* is_survivors */);
333
334 int young_index_in_cset = 0;
335 for (HeapRegion* curr = _survivor_head;
336 curr != NULL;
337 curr = curr->get_next_young_region()) {
338 _g1h->g1_policy()->set_region_survivor(curr, young_index_in_cset);
339
340 // The region is a non-empty survivor so let's add it to
341 // the incremental collection set for the next evacuation
342 // pause.
343 _g1h->g1_policy()->add_region_to_incremental_cset_rhs(curr);
344 young_index_in_cset += 1;
345 }
346 assert((uint) young_index_in_cset == _survivor_length, "post-condition");
347 _g1h->g1_policy()->note_stop_adding_survivor_regions();
348
349 _head = _survivor_head;
350 _length = _survivor_length;
351 if (_survivor_head != NULL) {
352 assert(_survivor_tail != NULL, "cause it shouldn't be");
353 assert(_survivor_length > 0, "invariant");
354 _survivor_tail->set_next_young_region(NULL);
355 }
356
357 // Don't clear the survivor list handles until the start of
358 // the next evacuation pause - we need it in order to re-tag
359 // the survivor regions from this evacuation pause as 'young'
360 // at the start of the next.
361
362 _g1h->g1_policy()->finished_recalculating_age_indexes(false /* is_survivors */);
363
364 assert(check_list_well_formed(), "young list should be well formed");
365 }
366
367 void YoungList::print() {
368 HeapRegion* lists[] = {_head, _survivor_head};
369 const char* names[] = {"YOUNG", "SURVIVOR"};
370
371 for (unsigned int list = 0; list < ARRAY_SIZE(lists); ++list) {
372 gclog_or_tty->print_cr("%s LIST CONTENTS", names[list]);
373 HeapRegion *curr = lists[list];
374 if (curr == NULL)
375 gclog_or_tty->print_cr(" empty");
376 while (curr != NULL) {
377 gclog_or_tty->print_cr(" "HR_FORMAT", P: "PTR_FORMAT "N: "PTR_FORMAT", age: %4d",
378 HR_FORMAT_PARAMS(curr),
379 curr->prev_top_at_mark_start(),
380 curr->next_top_at_mark_start(),
381 curr->age_in_surv_rate_group_cond());
382 curr = curr->get_next_young_region();
383 }
384 }
385
386 gclog_or_tty->print_cr("");
387 }
388
389 void G1CollectedHeap::push_dirty_cards_region(HeapRegion* hr)
390 {
391 // Claim the right to put the region on the dirty cards region list
392 // by installing a self pointer.
393 HeapRegion* next = hr->get_next_dirty_cards_region();
394 if (next == NULL) {
395 HeapRegion* res = (HeapRegion*)
396 Atomic::cmpxchg_ptr(hr, hr->next_dirty_cards_region_addr(),
397 NULL);
398 if (res == NULL) {
399 HeapRegion* head;
400 do {
401 // Put the region to the dirty cards region list.
402 head = _dirty_cards_region_list;
403 next = (HeapRegion*)
404 Atomic::cmpxchg_ptr(hr, &_dirty_cards_region_list, head);
405 if (next == head) {
406 assert(hr->get_next_dirty_cards_region() == hr,
407 "hr->get_next_dirty_cards_region() != hr");
408 if (next == NULL) {
409 // The last region in the list points to itself.
410 hr->set_next_dirty_cards_region(hr);
411 } else {
412 hr->set_next_dirty_cards_region(next);
413 }
414 }
415 } while (next != head);
416 }
417 }
418 }
419
420 HeapRegion* G1CollectedHeap::pop_dirty_cards_region()
421 {
422 HeapRegion* head;
423 HeapRegion* hr;
424 do {
425 head = _dirty_cards_region_list;
426 if (head == NULL) {
427 return NULL;
428 }
429 HeapRegion* new_head = head->get_next_dirty_cards_region();
430 if (head == new_head) {
431 // The last region.
432 new_head = NULL;
433 }
434 hr = (HeapRegion*)Atomic::cmpxchg_ptr(new_head, &_dirty_cards_region_list,
435 head);
436 } while (hr != head);
437 assert(hr != NULL, "invariant");
438 hr->set_next_dirty_cards_region(NULL);
439 return hr;
440 }
441
442 void G1CollectedHeap::stop_conc_gc_threads() {
443 _cg1r->stop();
444 _cmThread->stop();
445 }
446
447 #ifdef ASSERT
448 // A region is added to the collection set as it is retired
449 // so an address p can point to a region which will be in the
450 // collection set but has not yet been retired. This method
451 // therefore is only accurate during a GC pause after all
452 // regions have been retired. It is used for debugging
453 // to check if an nmethod has references to objects that can
454 // be move during a partial collection. Though it can be
455 // inaccurate, it is sufficient for G1 because the conservative
456 // implementation of is_scavengable() for G1 will indicate that
457 // all nmethods must be scanned during a partial collection.
458 bool G1CollectedHeap::is_in_partial_collection(const void* p) {
459 HeapRegion* hr = heap_region_containing(p);
460 return hr != NULL && hr->in_collection_set();
461 }
462 #endif
463
464 // Returns true if the reference points to an object that
465 // can move in an incremental collection.
466 bool G1CollectedHeap::is_scavengable(const void* p) {
467 G1CollectedHeap* g1h = G1CollectedHeap::heap();
468 G1CollectorPolicy* g1p = g1h->g1_policy();
469 HeapRegion* hr = heap_region_containing(p);
470 if (hr == NULL) {
471 // perm gen (or null)
472 return false;
473 } else {
474 return !hr->isHumongous();
475 }
476 }
477
478 void G1CollectedHeap::check_ct_logs_at_safepoint() {
479 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
480 CardTableModRefBS* ct_bs = (CardTableModRefBS*)barrier_set();
481
482 // Count the dirty cards at the start.
483 CountNonCleanMemRegionClosure count1(this);
484 ct_bs->mod_card_iterate(&count1);
485 int orig_count = count1.n();
486
487 // First clear the logged cards.
488 ClearLoggedCardTableEntryClosure clear;
489 dcqs.set_closure(&clear);
490 dcqs.apply_closure_to_all_completed_buffers();
491 dcqs.iterate_closure_all_threads(false);
492 clear.print_histo();
493
494 // Now ensure that there's no dirty cards.
495 CountNonCleanMemRegionClosure count2(this);
496 ct_bs->mod_card_iterate(&count2);
497 if (count2.n() != 0) {
498 gclog_or_tty->print_cr("Card table has %d entries; %d originally",
499 count2.n(), orig_count);
500 }
501 guarantee(count2.n() == 0, "Card table should be clean.");
502
503 RedirtyLoggedCardTableEntryClosure redirty;
504 JavaThread::dirty_card_queue_set().set_closure(&redirty);
505 dcqs.apply_closure_to_all_completed_buffers();
506 dcqs.iterate_closure_all_threads(false);
507 gclog_or_tty->print_cr("Log entries = %d, dirty cards = %d.",
508 clear.calls(), orig_count);
509 guarantee(redirty.calls() == clear.calls(),
510 "Or else mechanism is broken.");
511
512 CountNonCleanMemRegionClosure count3(this);
513 ct_bs->mod_card_iterate(&count3);
514 if (count3.n() != orig_count) {
515 gclog_or_tty->print_cr("Should have restored them all: orig = %d, final = %d.",
516 orig_count, count3.n());
517 guarantee(count3.n() >= orig_count, "Should have restored them all.");
518 }
519
520 JavaThread::dirty_card_queue_set().set_closure(_refine_cte_cl);
521 }
522
523 // Private class members.
524
525 G1CollectedHeap* G1CollectedHeap::_g1h;
526
527 // Private methods.
528
529 HeapRegion*
530 G1CollectedHeap::new_region_try_secondary_free_list() {
531 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
532 while (!_secondary_free_list.is_empty() || free_regions_coming()) {
533 if (!_secondary_free_list.is_empty()) {
534 if (G1ConcRegionFreeingVerbose) {
535 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
536 "secondary_free_list has %u entries",
537 _secondary_free_list.length());
538 }
539 // It looks as if there are free regions available on the
540 // secondary_free_list. Let's move them to the free_list and try
541 // again to allocate from it.
542 append_secondary_free_list();
543
544 assert(!_free_list.is_empty(), "if the secondary_free_list was not "
545 "empty we should have moved at least one entry to the free_list");
546 HeapRegion* res = _free_list.remove_head();
547 if (G1ConcRegionFreeingVerbose) {
548 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
549 "allocated "HR_FORMAT" from secondary_free_list",
550 HR_FORMAT_PARAMS(res));
551 }
552 return res;
553 }
554
555 // Wait here until we get notified either when (a) there are no
556 // more free regions coming or (b) some regions have been moved on
557 // the secondary_free_list.
558 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
559 }
560
561 if (G1ConcRegionFreeingVerbose) {
562 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
563 "could not allocate from secondary_free_list");
564 }
565 return NULL;
566 }
567
568 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool do_expand) {
569 assert(!isHumongous(word_size) || word_size <= HeapRegion::GrainWords,
570 "the only time we use this to allocate a humongous region is "
571 "when we are allocating a single humongous region");
572
573 HeapRegion* res;
574 if (G1StressConcRegionFreeing) {
575 if (!_secondary_free_list.is_empty()) {
576 if (G1ConcRegionFreeingVerbose) {
577 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
578 "forced to look at the secondary_free_list");
579 }
580 res = new_region_try_secondary_free_list();
581 if (res != NULL) {
582 return res;
583 }
584 }
585 }
586 res = _free_list.remove_head_or_null();
587 if (res == NULL) {
588 if (G1ConcRegionFreeingVerbose) {
589 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
590 "res == NULL, trying the secondary_free_list");
591 }
592 res = new_region_try_secondary_free_list();
593 }
594 if (res == NULL && do_expand && _expand_heap_after_alloc_failure) {
595 // Currently, only attempts to allocate GC alloc regions set
596 // do_expand to true. So, we should only reach here during a
597 // safepoint. If this assumption changes we might have to
598 // reconsider the use of _expand_heap_after_alloc_failure.
599 assert(SafepointSynchronize::is_at_safepoint(), "invariant");
600
601 ergo_verbose1(ErgoHeapSizing,
602 "attempt heap expansion",
603 ergo_format_reason("region allocation request failed")
604 ergo_format_byte("allocation request"),
605 word_size * HeapWordSize);
606 if (expand(word_size * HeapWordSize)) {
607 // Given that expand() succeeded in expanding the heap, and we
608 // always expand the heap by an amount aligned to the heap
609 // region size, the free list should in theory not be empty. So
610 // it would probably be OK to use remove_head(). But the extra
611 // check for NULL is unlikely to be a performance issue here (we
612 // just expanded the heap!) so let's just be conservative and
613 // use remove_head_or_null().
614 res = _free_list.remove_head_or_null();
615 } else {
616 _expand_heap_after_alloc_failure = false;
617 }
618 }
619 return res;
620 }
621
622 uint G1CollectedHeap::humongous_obj_allocate_find_first(uint num_regions,
623 size_t word_size) {
624 assert(isHumongous(word_size), "word_size should be humongous");
625 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
626
627 uint first = G1_NULL_HRS_INDEX;
628 if (num_regions == 1) {
629 // Only one region to allocate, no need to go through the slower
630 // path. The caller will attempt the expansion if this fails, so
631 // let's not try to expand here too.
632 HeapRegion* hr = new_region(word_size, false /* do_expand */);
633 if (hr != NULL) {
634 first = hr->hrs_index();
635 } else {
636 first = G1_NULL_HRS_INDEX;
637 }
638 } else {
639 // We can't allocate humongous regions while cleanupComplete() is
640 // running, since some of the regions we find to be empty might not
641 // yet be added to the free list and it is not straightforward to
642 // know which list they are on so that we can remove them. Note
643 // that we only need to do this if we need to allocate more than
644 // one region to satisfy the current humongous allocation
645 // request. If we are only allocating one region we use the common
646 // region allocation code (see above).
647 wait_while_free_regions_coming();
648 append_secondary_free_list_if_not_empty_with_lock();
649
650 if (free_regions() >= num_regions) {
651 first = _hrs.find_contiguous(num_regions);
652 if (first != G1_NULL_HRS_INDEX) {
653 for (uint i = first; i < first + num_regions; ++i) {
654 HeapRegion* hr = region_at(i);
655 assert(hr->is_empty(), "sanity");
656 assert(is_on_master_free_list(hr), "sanity");
657 hr->set_pending_removal(true);
658 }
659 _free_list.remove_all_pending(num_regions);
660 }
661 }
662 }
663 return first;
664 }
665
666 HeapWord*
667 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first,
668 uint num_regions,
669 size_t word_size) {
670 assert(first != G1_NULL_HRS_INDEX, "pre-condition");
671 assert(isHumongous(word_size), "word_size should be humongous");
672 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
673
674 // Index of last region in the series + 1.
675 uint last = first + num_regions;
676
677 // We need to initialize the region(s) we just discovered. This is
678 // a bit tricky given that it can happen concurrently with
679 // refinement threads refining cards on these regions and
680 // potentially wanting to refine the BOT as they are scanning
681 // those cards (this can happen shortly after a cleanup; see CR
682 // 6991377). So we have to set up the region(s) carefully and in
683 // a specific order.
684
685 // The word size sum of all the regions we will allocate.
686 size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords;
687 assert(word_size <= word_size_sum, "sanity");
688
689 // This will be the "starts humongous" region.
690 HeapRegion* first_hr = region_at(first);
691 // The header of the new object will be placed at the bottom of
692 // the first region.
693 HeapWord* new_obj = first_hr->bottom();
694 // This will be the new end of the first region in the series that
695 // should also match the end of the last region in the series.
696 HeapWord* new_end = new_obj + word_size_sum;
697 // This will be the new top of the first region that will reflect
698 // this allocation.
699 HeapWord* new_top = new_obj + word_size;
700
701 // First, we need to zero the header of the space that we will be
702 // allocating. When we update top further down, some refinement
703 // threads might try to scan the region. By zeroing the header we
704 // ensure that any thread that will try to scan the region will
705 // come across the zero klass word and bail out.
706 //
707 // NOTE: It would not have been correct to have used
708 // CollectedHeap::fill_with_object() and make the space look like
709 // an int array. The thread that is doing the allocation will
710 // later update the object header to a potentially different array
711 // type and, for a very short period of time, the klass and length
712 // fields will be inconsistent. This could cause a refinement
713 // thread to calculate the object size incorrectly.
714 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
715
716 // We will set up the first region as "starts humongous". This
717 // will also update the BOT covering all the regions to reflect
718 // that there is a single object that starts at the bottom of the
719 // first region.
720 first_hr->set_startsHumongous(new_top, new_end);
721
722 // Then, if there are any, we will set up the "continues
723 // humongous" regions.
724 HeapRegion* hr = NULL;
725 for (uint i = first + 1; i < last; ++i) {
726 hr = region_at(i);
727 hr->set_continuesHumongous(first_hr);
728 }
729 // If we have "continues humongous" regions (hr != NULL), then the
730 // end of the last one should match new_end.
731 assert(hr == NULL || hr->end() == new_end, "sanity");
732
733 // Up to this point no concurrent thread would have been able to
734 // do any scanning on any region in this series. All the top
735 // fields still point to bottom, so the intersection between
736 // [bottom,top] and [card_start,card_end] will be empty. Before we
737 // update the top fields, we'll do a storestore to make sure that
738 // no thread sees the update to top before the zeroing of the
739 // object header and the BOT initialization.
740 OrderAccess::storestore();
741
742 // Now that the BOT and the object header have been initialized,
743 // we can update top of the "starts humongous" region.
744 assert(first_hr->bottom() < new_top && new_top <= first_hr->end(),
745 "new_top should be in this region");
746 first_hr->set_top(new_top);
747 if (_hr_printer.is_active()) {
748 HeapWord* bottom = first_hr->bottom();
749 HeapWord* end = first_hr->orig_end();
750 if ((first + 1) == last) {
751 // the series has a single humongous region
752 _hr_printer.alloc(G1HRPrinter::SingleHumongous, first_hr, new_top);
753 } else {
754 // the series has more than one humongous regions
755 _hr_printer.alloc(G1HRPrinter::StartsHumongous, first_hr, end);
756 }
757 }
758
759 // Now, we will update the top fields of the "continues humongous"
760 // regions. The reason we need to do this is that, otherwise,
761 // these regions would look empty and this will confuse parts of
762 // G1. For example, the code that looks for a consecutive number
763 // of empty regions will consider them empty and try to
764 // re-allocate them. We can extend is_empty() to also include
765 // !continuesHumongous(), but it is easier to just update the top
766 // fields here. The way we set top for all regions (i.e., top ==
767 // end for all regions but the last one, top == new_top for the
768 // last one) is actually used when we will free up the humongous
769 // region in free_humongous_region().
770 hr = NULL;
771 for (uint i = first + 1; i < last; ++i) {
772 hr = region_at(i);
773 if ((i + 1) == last) {
774 // last continues humongous region
775 assert(hr->bottom() < new_top && new_top <= hr->end(),
776 "new_top should fall on this region");
777 hr->set_top(new_top);
778 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, new_top);
779 } else {
780 // not last one
781 assert(new_top > hr->end(), "new_top should be above this region");
782 hr->set_top(hr->end());
783 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, hr->end());
784 }
785 }
786 // If we have continues humongous regions (hr != NULL), then the
787 // end of the last one should match new_end and its top should
788 // match new_top.
789 assert(hr == NULL ||
790 (hr->end() == new_end && hr->top() == new_top), "sanity");
791
792 assert(first_hr->used() == word_size * HeapWordSize, "invariant");
793 _summary_bytes_used += first_hr->used();
794 _humongous_set.add(first_hr);
795
796 return new_obj;
797 }
798
799 // If could fit into free regions w/o expansion, try.
800 // Otherwise, if can expand, do so.
801 // Otherwise, if using ex regions might help, try with ex given back.
802 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size) {
803 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
804
805 verify_region_sets_optional();
806
807 size_t word_size_rounded = round_to(word_size, HeapRegion::GrainWords);
808 uint num_regions = (uint) (word_size_rounded / HeapRegion::GrainWords);
809 uint x_num = expansion_regions();
810 uint fs = _hrs.free_suffix();
811 uint first = humongous_obj_allocate_find_first(num_regions, word_size);
812 if (first == G1_NULL_HRS_INDEX) {
813 // The only thing we can do now is attempt expansion.
814 if (fs + x_num >= num_regions) {
815 // If the number of regions we're trying to allocate for this
816 // object is at most the number of regions in the free suffix,
817 // then the call to humongous_obj_allocate_find_first() above
818 // should have succeeded and we wouldn't be here.
819 //
820 // We should only be trying to expand when the free suffix is
821 // not sufficient for the object _and_ we have some expansion
822 // room available.
823 assert(num_regions > fs, "earlier allocation should have succeeded");
824
825 ergo_verbose1(ErgoHeapSizing,
826 "attempt heap expansion",
827 ergo_format_reason("humongous allocation request failed")
828 ergo_format_byte("allocation request"),
829 word_size * HeapWordSize);
830 if (expand((num_regions - fs) * HeapRegion::GrainBytes)) {
831 // Even though the heap was expanded, it might not have
832 // reached the desired size. So, we cannot assume that the
833 // allocation will succeed.
834 first = humongous_obj_allocate_find_first(num_regions, word_size);
835 }
836 }
837 }
838
839 HeapWord* result = NULL;
840 if (first != G1_NULL_HRS_INDEX) {
841 result =
842 humongous_obj_allocate_initialize_regions(first, num_regions, word_size);
843 assert(result != NULL, "it should always return a valid result");
844
845 // A successful humongous object allocation changes the used space
846 // information of the old generation so we need to recalculate the
847 // sizes and update the jstat counters here.
848 g1mm()->update_sizes();
849 }
850
851 verify_region_sets_optional();
852
853 return result;
854 }
855
856 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) {
857 assert_heap_not_locked_and_not_at_safepoint();
858 assert(!isHumongous(word_size), "we do not allow humongous TLABs");
859
860 unsigned int dummy_gc_count_before;
861 return attempt_allocation(word_size, &dummy_gc_count_before);
862 }
863
864 HeapWord*
865 G1CollectedHeap::mem_allocate(size_t word_size,
866 bool* gc_overhead_limit_was_exceeded) {
867 assert_heap_not_locked_and_not_at_safepoint();
868
869 // Loop until the allocation is satisfied, or unsatisfied after GC.
870 for (int try_count = 1; /* we'll return */; try_count += 1) {
871 unsigned int gc_count_before;
872
873 HeapWord* result = NULL;
874 if (!isHumongous(word_size)) {
875 result = attempt_allocation(word_size, &gc_count_before);
876 } else {
877 result = attempt_allocation_humongous(word_size, &gc_count_before);
878 }
879 if (result != NULL) {
880 return result;
881 }
882
883 // Create the garbage collection operation...
884 VM_G1CollectForAllocation op(gc_count_before, word_size);
885 // ...and get the VM thread to execute it.
886 VMThread::execute(&op);
887
888 if (op.prologue_succeeded() && op.pause_succeeded()) {
889 // If the operation was successful we'll return the result even
890 // if it is NULL. If the allocation attempt failed immediately
891 // after a Full GC, it's unlikely we'll be able to allocate now.
892 HeapWord* result = op.result();
893 if (result != NULL && !isHumongous(word_size)) {
894 // Allocations that take place on VM operations do not do any
895 // card dirtying and we have to do it here. We only have to do
896 // this for non-humongous allocations, though.
897 dirty_young_block(result, word_size);
898 }
899 return result;
900 } else {
901 assert(op.result() == NULL,
902 "the result should be NULL if the VM op did not succeed");
903 }
904
905 // Give a warning if we seem to be looping forever.
906 if ((QueuedAllocationWarningCount > 0) &&
907 (try_count % QueuedAllocationWarningCount == 0)) {
908 warning("G1CollectedHeap::mem_allocate retries %d times", try_count);
909 }
910 }
911
912 ShouldNotReachHere();
913 return NULL;
914 }
915
916 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size,
917 unsigned int *gc_count_before_ret) {
918 // Make sure you read the note in attempt_allocation_humongous().
919
920 assert_heap_not_locked_and_not_at_safepoint();
921 assert(!isHumongous(word_size), "attempt_allocation_slow() should not "
922 "be called for humongous allocation requests");
923
924 // We should only get here after the first-level allocation attempt
925 // (attempt_allocation()) failed to allocate.
926
927 // We will loop until a) we manage to successfully perform the
928 // allocation or b) we successfully schedule a collection which
929 // fails to perform the allocation. b) is the only case when we'll
930 // return NULL.
931 HeapWord* result = NULL;
932 for (int try_count = 1; /* we'll return */; try_count += 1) {
933 bool should_try_gc;
934 unsigned int gc_count_before;
935
936 {
937 MutexLockerEx x(Heap_lock);
938
939 result = _mutator_alloc_region.attempt_allocation_locked(word_size,
940 false /* bot_updates */);
941 if (result != NULL) {
942 return result;
943 }
944
945 // If we reach here, attempt_allocation_locked() above failed to
946 // allocate a new region. So the mutator alloc region should be NULL.
947 assert(_mutator_alloc_region.get() == NULL, "only way to get here");
948
949 if (GC_locker::is_active_and_needs_gc()) {
950 if (g1_policy()->can_expand_young_list()) {
951 // No need for an ergo verbose message here,
952 // can_expand_young_list() does this when it returns true.
953 result = _mutator_alloc_region.attempt_allocation_force(word_size,
954 false /* bot_updates */);
955 if (result != NULL) {
956 return result;
957 }
958 }
959 should_try_gc = false;
960 } else {
961 // The GCLocker may not be active but the GCLocker initiated
962 // GC may not yet have been performed (GCLocker::needs_gc()
963 // returns true). In this case we do not try this GC and
964 // wait until the GCLocker initiated GC is performed, and
965 // then retry the allocation.
966 if (GC_locker::needs_gc()) {
967 should_try_gc = false;
968 } else {
969 // Read the GC count while still holding the Heap_lock.
970 gc_count_before = total_collections();
971 should_try_gc = true;
972 }
973 }
974 }
975
976 if (should_try_gc) {
977 bool succeeded;
978 result = do_collection_pause(word_size, gc_count_before, &succeeded);
979 if (result != NULL) {
980 assert(succeeded, "only way to get back a non-NULL result");
981 return result;
982 }
983
984 if (succeeded) {
985 // If we get here we successfully scheduled a collection which
986 // failed to allocate. No point in trying to allocate
987 // further. We'll just return NULL.
988 MutexLockerEx x(Heap_lock);
989 *gc_count_before_ret = total_collections();
990 return NULL;
991 }
992 } else {
993 // The GCLocker is either active or the GCLocker initiated
994 // GC has not yet been performed. Stall until it is and
995 // then retry the allocation.
996 GC_locker::stall_until_clear();
997 }
998
999 // We can reach here if we were unsuccessful in scheduling a
1000 // collection (because another thread beat us to it) or if we were
1001 // stalled due to the GC locker. In either can we should retry the
1002 // allocation attempt in case another thread successfully
1003 // performed a collection and reclaimed enough space. We do the
1004 // first attempt (without holding the Heap_lock) here and the
1005 // follow-on attempt will be at the start of the next loop
1006 // iteration (after taking the Heap_lock).
1007 result = _mutator_alloc_region.attempt_allocation(word_size,
1008 false /* bot_updates */);
1009 if (result != NULL) {
1010 return result;
1011 }
1012
1013 // Give a warning if we seem to be looping forever.
1014 if ((QueuedAllocationWarningCount > 0) &&
1015 (try_count % QueuedAllocationWarningCount == 0)) {
1016 warning("G1CollectedHeap::attempt_allocation_slow() "
1017 "retries %d times", try_count);
1018 }
1019 }
1020
1021 ShouldNotReachHere();
1022 return NULL;
1023 }
1024
1025 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size,
1026 unsigned int * gc_count_before_ret) {
1027 // The structure of this method has a lot of similarities to
1028 // attempt_allocation_slow(). The reason these two were not merged
1029 // into a single one is that such a method would require several "if
1030 // allocation is not humongous do this, otherwise do that"
1031 // conditional paths which would obscure its flow. In fact, an early
1032 // version of this code did use a unified method which was harder to
1033 // follow and, as a result, it had subtle bugs that were hard to
1034 // track down. So keeping these two methods separate allows each to
1035 // be more readable. It will be good to keep these two in sync as
1036 // much as possible.
1037
1038 assert_heap_not_locked_and_not_at_safepoint();
1039 assert(isHumongous(word_size), "attempt_allocation_humongous() "
1040 "should only be called for humongous allocations");
1041
1042 // Humongous objects can exhaust the heap quickly, so we should check if we
1043 // need to start a marking cycle at each humongous object allocation. We do
1044 // the check before we do the actual allocation. The reason for doing it
1045 // before the allocation is that we avoid having to keep track of the newly
1046 // allocated memory while we do a GC.
1047 if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation",
1048 word_size)) {
1049 collect(GCCause::_g1_humongous_allocation);
1050 }
1051
1052 // We will loop until a) we manage to successfully perform the
1053 // allocation or b) we successfully schedule a collection which
1054 // fails to perform the allocation. b) is the only case when we'll
1055 // return NULL.
1056 HeapWord* result = NULL;
1057 for (int try_count = 1; /* we'll return */; try_count += 1) {
1058 bool should_try_gc;
1059 unsigned int gc_count_before;
1060
1061 {
1062 MutexLockerEx x(Heap_lock);
1063
1064 // Given that humongous objects are not allocated in young
1065 // regions, we'll first try to do the allocation without doing a
1066 // collection hoping that there's enough space in the heap.
1067 result = humongous_obj_allocate(word_size);
1068 if (result != NULL) {
1069 return result;
1070 }
1071
1072 if (GC_locker::is_active_and_needs_gc()) {
1073 should_try_gc = false;
1074 } else {
1075 // The GCLocker may not be active but the GCLocker initiated
1076 // GC may not yet have been performed (GCLocker::needs_gc()
1077 // returns true). In this case we do not try this GC and
1078 // wait until the GCLocker initiated GC is performed, and
1079 // then retry the allocation.
1080 if (GC_locker::needs_gc()) {
1081 should_try_gc = false;
1082 } else {
1083 // Read the GC count while still holding the Heap_lock.
1084 gc_count_before = total_collections();
1085 should_try_gc = true;
1086 }
1087 }
1088 }
1089
1090 if (should_try_gc) {
1091 // If we failed to allocate the humongous object, we should try to
1092 // do a collection pause (if we're allowed) in case it reclaims
1093 // enough space for the allocation to succeed after the pause.
1094
1095 bool succeeded;
1096 result = do_collection_pause(word_size, gc_count_before, &succeeded);
1097 if (result != NULL) {
1098 assert(succeeded, "only way to get back a non-NULL result");
1099 return result;
1100 }
1101
1102 if (succeeded) {
1103 // If we get here we successfully scheduled a collection which
1104 // failed to allocate. No point in trying to allocate
1105 // further. We'll just return NULL.
1106 MutexLockerEx x(Heap_lock);
1107 *gc_count_before_ret = total_collections();
1108 return NULL;
1109 }
1110 } else {
1111 // The GCLocker is either active or the GCLocker initiated
1112 // GC has not yet been performed. Stall until it is and
1113 // then retry the allocation.
1114 GC_locker::stall_until_clear();
1115 }
1116
1117 // We can reach here if we were unsuccessful in scheduling a
1118 // collection (because another thread beat us to it) or if we were
1119 // stalled due to the GC locker. In either can we should retry the
1120 // allocation attempt in case another thread successfully
1121 // performed a collection and reclaimed enough space. Give a
1122 // warning if we seem to be looping forever.
1123
1124 if ((QueuedAllocationWarningCount > 0) &&
1125 (try_count % QueuedAllocationWarningCount == 0)) {
1126 warning("G1CollectedHeap::attempt_allocation_humongous() "
1127 "retries %d times", try_count);
1128 }
1129 }
1130
1131 ShouldNotReachHere();
1132 return NULL;
1133 }
1134
1135 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
1136 bool expect_null_mutator_alloc_region) {
1137 assert_at_safepoint(true /* should_be_vm_thread */);
1138 assert(_mutator_alloc_region.get() == NULL ||
1139 !expect_null_mutator_alloc_region,
1140 "the current alloc region was unexpectedly found to be non-NULL");
1141
1142 if (!isHumongous(word_size)) {
1143 return _mutator_alloc_region.attempt_allocation_locked(word_size,
1144 false /* bot_updates */);
1145 } else {
1146 HeapWord* result = humongous_obj_allocate(word_size);
1147 if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) {
1148 g1_policy()->set_initiate_conc_mark_if_possible();
1149 }
1150 return result;
1151 }
1152
1153 ShouldNotReachHere();
1154 }
1155
1156 class PostMCRemSetClearClosure: public HeapRegionClosure {
1157 G1CollectedHeap* _g1h;
1158 ModRefBarrierSet* _mr_bs;
1159 public:
1160 PostMCRemSetClearClosure(G1CollectedHeap* g1h, ModRefBarrierSet* mr_bs) :
1161 _g1h(g1h), _mr_bs(mr_bs) { }
1162 bool doHeapRegion(HeapRegion* r) {
1163 if (r->continuesHumongous()) {
1164 return false;
1165 }
1166 _g1h->reset_gc_time_stamps(r);
1167 HeapRegionRemSet* hrrs = r->rem_set();
1168 if (hrrs != NULL) hrrs->clear();
1169 // You might think here that we could clear just the cards
1170 // corresponding to the used region. But no: if we leave a dirty card
1171 // in a region we might allocate into, then it would prevent that card
1172 // from being enqueued, and cause it to be missed.
1173 // Re: the performance cost: we shouldn't be doing full GC anyway!
1174 _mr_bs->clear(MemRegion(r->bottom(), r->end()));
1175 return false;
1176 }
1177 };
1178
1179 void G1CollectedHeap::clear_rsets_post_compaction() {
1180 PostMCRemSetClearClosure rs_clear(this, mr_bs());
1181 heap_region_iterate(&rs_clear);
1182 }
1183
1184 class RebuildRSOutOfRegionClosure: public HeapRegionClosure {
1185 G1CollectedHeap* _g1h;
1186 UpdateRSOopClosure _cl;
1187 int _worker_i;
1188 public:
1189 RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, int worker_i = 0) :
1190 _cl(g1->g1_rem_set(), worker_i),
1191 _worker_i(worker_i),
1192 _g1h(g1)
1193 { }
1194
1195 bool doHeapRegion(HeapRegion* r) {
1196 if (!r->continuesHumongous()) {
1197 _cl.set_from(r);
1198 r->oop_iterate(&_cl);
1199 }
1200 return false;
1201 }
1202 };
1203
1204 class ParRebuildRSTask: public AbstractGangTask {
1205 G1CollectedHeap* _g1;
1206 public:
1207 ParRebuildRSTask(G1CollectedHeap* g1)
1208 : AbstractGangTask("ParRebuildRSTask"),
1209 _g1(g1)
1210 { }
1211
1212 void work(uint worker_id) {
1213 RebuildRSOutOfRegionClosure rebuild_rs(_g1, worker_id);
1214 _g1->heap_region_par_iterate_chunked(&rebuild_rs, worker_id,
1215 _g1->workers()->active_workers(),
1216 HeapRegion::RebuildRSClaimValue);
1217 }
1218 };
1219
1220 class PostCompactionPrinterClosure: public HeapRegionClosure {
1221 private:
1222 G1HRPrinter* _hr_printer;
1223 public:
1224 bool doHeapRegion(HeapRegion* hr) {
1225 assert(!hr->is_young(), "not expecting to find young regions");
1226 // We only generate output for non-empty regions.
1227 if (!hr->is_empty()) {
1228 if (!hr->isHumongous()) {
1229 _hr_printer->post_compaction(hr, G1HRPrinter::Old);
1230 } else if (hr->startsHumongous()) {
1231 if (hr->region_num() == 1) {
1232 // single humongous region
1233 _hr_printer->post_compaction(hr, G1HRPrinter::SingleHumongous);
1234 } else {
1235 _hr_printer->post_compaction(hr, G1HRPrinter::StartsHumongous);
1236 }
1237 } else {
1238 assert(hr->continuesHumongous(), "only way to get here");
1239 _hr_printer->post_compaction(hr, G1HRPrinter::ContinuesHumongous);
1240 }
1241 }
1242 return false;
1243 }
1244
1245 PostCompactionPrinterClosure(G1HRPrinter* hr_printer)
1246 : _hr_printer(hr_printer) { }
1247 };
1248
1249 void G1CollectedHeap::print_hrs_post_compaction() {
1250 PostCompactionPrinterClosure cl(hr_printer());
1251 heap_region_iterate(&cl);
1252 }
1253
1254 double G1CollectedHeap::verify(bool guard, const char* msg) {
1255 double verify_time_ms = 0.0;
1256
1257 if (guard && total_collections() >= VerifyGCStartAt) {
1258 double verify_start = os::elapsedTime();
1259 HandleMark hm; // Discard invalid handles created during verification
1260 gclog_or_tty->print(msg);
1261 prepare_for_verify();
1262 Universe::verify(false /* silent */, VerifyOption_G1UsePrevMarking);
1263 verify_time_ms = (os::elapsedTime() - verify_start) * 1000;
1264 }
1265
1266 return verify_time_ms;
1267 }
1268
1269 void G1CollectedHeap::verify_before_gc() {
1270 double verify_time_ms = verify(VerifyBeforeGC, " VerifyBeforeGC:");
1271 g1_policy()->phase_times()->record_verify_before_time_ms(verify_time_ms);
1272 }
1273
1274 void G1CollectedHeap::verify_after_gc() {
1275 double verify_time_ms = verify(VerifyAfterGC, " VerifyAfterGC:");
1276 g1_policy()->phase_times()->record_verify_after_time_ms(verify_time_ms);
1277 }
1278
1279 bool G1CollectedHeap::do_collection(bool explicit_gc,
1280 bool clear_all_soft_refs,
1281 size_t word_size) {
1282 assert_at_safepoint(true /* should_be_vm_thread */);
1283
1284 if (GC_locker::check_active_before_gc()) {
1285 return false;
1286 }
1287
1288 STWGCTimer* gc_timer = G1MarkSweep::gc_timer();
1289 gc_timer->register_gc_start(os::elapsed_counter());
1290
1291 SerialOldTracer* gc_tracer = G1MarkSweep::gc_tracer();
1292 gc_tracer->report_gc_start(gc_cause(), gc_timer->gc_start());
1293
1294 SvcGCMarker sgcm(SvcGCMarker::FULL);
1295 ResourceMark rm;
1296
1297 print_heap_before_gc();
1298 trace_heap_before_gc(gc_tracer);
1299
1300 HRSPhaseSetter x(HRSPhaseFullGC);
1301 verify_region_sets_optional();
1302
1303 const bool do_clear_all_soft_refs = clear_all_soft_refs ||
1304 collector_policy()->should_clear_all_soft_refs();
1305
1306 ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy());
1307
1308 {
1309 IsGCActiveMark x;
1310
1311 // Timing
1312 assert(gc_cause() != GCCause::_java_lang_system_gc || explicit_gc, "invariant");
1313 gclog_or_tty->date_stamp(G1Log::fine() && PrintGCDateStamps);
1314 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
1315
1316 GCTraceTime t(GCCauseString("Full GC", gc_cause()), G1Log::fine(), true, NULL);
1317 TraceCollectorStats tcs(g1mm()->full_collection_counters());
1318 TraceMemoryManagerStats tms(true /* fullGC */, gc_cause());
1319
1320 double start = os::elapsedTime();
1321 g1_policy()->record_full_collection_start();
1322
1323 // Note: When we have a more flexible GC logging framework that
1324 // allows us to add optional attributes to a GC log record we
1325 // could consider timing and reporting how long we wait in the
1326 // following two methods.
1327 wait_while_free_regions_coming();
1328 // If we start the compaction before the CM threads finish
1329 // scanning the root regions we might trip them over as we'll
1330 // be moving objects / updating references. So let's wait until
1331 // they are done. By telling them to abort, they should complete
1332 // early.
1333 _cm->root_regions()->abort();
1334 _cm->root_regions()->wait_until_scan_finished();
1335 append_secondary_free_list_if_not_empty_with_lock();
1336
1337 gc_prologue(true);
1338 increment_total_collections(true /* full gc */);
1339 increment_old_marking_cycles_started();
1340
1341 size_t g1h_prev_used = used();
1342 assert(used() == recalculate_used(), "Should be equal");
1343
1344 verify_before_gc();
1345
1346 pre_full_gc_dump(gc_timer);
1347
1348 COMPILER2_PRESENT(DerivedPointerTable::clear());
1349
1350 // Disable discovery and empty the discovered lists
1351 // for the CM ref processor.
1352 ref_processor_cm()->disable_discovery();
1353 ref_processor_cm()->abandon_partial_discovery();
1354 ref_processor_cm()->verify_no_references_recorded();
1355
1356 // Abandon current iterations of concurrent marking and concurrent
1357 // refinement, if any are in progress. We have to do this before
1358 // wait_until_scan_finished() below.
1359 concurrent_mark()->abort();
1360
1361 // Make sure we'll choose a new allocation region afterwards.
1362 release_mutator_alloc_region();
1363 abandon_gc_alloc_regions();
1364 g1_rem_set()->cleanupHRRS();
1365
1366 // We should call this after we retire any currently active alloc
1367 // regions so that all the ALLOC / RETIRE events are generated
1368 // before the start GC event.
1369 _hr_printer.start_gc(true /* full */, (size_t) total_collections());
1370
1371 // We may have added regions to the current incremental collection
1372 // set between the last GC or pause and now. We need to clear the
1373 // incremental collection set and then start rebuilding it afresh
1374 // after this full GC.
1375 abandon_collection_set(g1_policy()->inc_cset_head());
1376 g1_policy()->clear_incremental_cset();
1377 g1_policy()->stop_incremental_cset_building();
1378
1379 tear_down_region_sets(false /* free_list_only */);
1380 g1_policy()->set_gcs_are_young(true);
1381
1382 // See the comments in g1CollectedHeap.hpp and
1383 // G1CollectedHeap::ref_processing_init() about
1384 // how reference processing currently works in G1.
1385
1386 // Temporarily make discovery by the STW ref processor single threaded (non-MT).
1387 ReferenceProcessorMTDiscoveryMutator stw_rp_disc_ser(ref_processor_stw(), false);
1388
1389 // Temporarily clear the STW ref processor's _is_alive_non_header field.
1390 ReferenceProcessorIsAliveMutator stw_rp_is_alive_null(ref_processor_stw(), NULL);
1391
1392 ref_processor_stw()->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/);
1393 ref_processor_stw()->setup_policy(do_clear_all_soft_refs);
1394
1395 // Do collection work
1396 {
1397 HandleMark hm; // Discard invalid handles created during gc
1398 G1MarkSweep::invoke_at_safepoint(ref_processor_stw(), do_clear_all_soft_refs);
1399 }
1400
1401 assert(free_regions() == 0, "we should not have added any free regions");
1402 rebuild_region_sets(false /* free_list_only */);
1403
1404 // Enqueue any discovered reference objects that have
1405 // not been removed from the discovered lists.
1406 ref_processor_stw()->enqueue_discovered_references();
1407
1408 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
1409
1410 MemoryService::track_memory_usage();
1411
1412 verify_after_gc();
1413
1414 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
1415 ref_processor_stw()->verify_no_references_recorded();
1416
1417 // Note: since we've just done a full GC, concurrent
1418 // marking is no longer active. Therefore we need not
1419 // re-enable reference discovery for the CM ref processor.
1420 // That will be done at the start of the next marking cycle.
1421 assert(!ref_processor_cm()->discovery_enabled(), "Postcondition");
1422 ref_processor_cm()->verify_no_references_recorded();
1423
1424 reset_gc_time_stamp();
1425 // Since everything potentially moved, we will clear all remembered
1426 // sets, and clear all cards. Later we will rebuild remembered
1427 // sets. We will also reset the GC time stamps of the regions.
1428 clear_rsets_post_compaction();
1429 check_gc_time_stamps();
1430
1431 // Resize the heap if necessary.
1432 resize_if_necessary_after_full_collection(explicit_gc ? 0 : word_size);
1433
1434 if (_hr_printer.is_active()) {
1435 // We should do this after we potentially resize the heap so
1436 // that all the COMMIT / UNCOMMIT events are generated before
1437 // the end GC event.
1438
1439 print_hrs_post_compaction();
1440 _hr_printer.end_gc(true /* full */, (size_t) total_collections());
1441 }
1442
1443 if (_cg1r->use_cache()) {
1444 _cg1r->clear_and_record_card_counts();
1445 _cg1r->clear_hot_cache();
1446 }
1447
1448 // Rebuild remembered sets of all regions.
1449 if (G1CollectedHeap::use_parallel_gc_threads()) {
1450 uint n_workers =
1451 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
1452 workers()->active_workers(),
1453 Threads::number_of_non_daemon_threads());
1454 assert(UseDynamicNumberOfGCThreads ||
1455 n_workers == workers()->total_workers(),
1456 "If not dynamic should be using all the workers");
1457 workers()->set_active_workers(n_workers);
1458 // Set parallel threads in the heap (_n_par_threads) only
1459 // before a parallel phase and always reset it to 0 after
1460 // the phase so that the number of parallel threads does
1461 // no get carried forward to a serial phase where there
1462 // may be code that is "possibly_parallel".
1463 set_par_threads(n_workers);
1464
1465 ParRebuildRSTask rebuild_rs_task(this);
1466 assert(check_heap_region_claim_values(
1467 HeapRegion::InitialClaimValue), "sanity check");
1468 assert(UseDynamicNumberOfGCThreads ||
1469 workers()->active_workers() == workers()->total_workers(),
1470 "Unless dynamic should use total workers");
1471 // Use the most recent number of active workers
1472 assert(workers()->active_workers() > 0,
1473 "Active workers not properly set");
1474 set_par_threads(workers()->active_workers());
1475 workers()->run_task(&rebuild_rs_task);
1476 set_par_threads(0);
1477 assert(check_heap_region_claim_values(
1478 HeapRegion::RebuildRSClaimValue), "sanity check");
1479 reset_heap_region_claim_values();
1480 } else {
1481 RebuildRSOutOfRegionClosure rebuild_rs(this);
1482 heap_region_iterate(&rebuild_rs);
1483 }
1484
1485 if (G1Log::fine()) {
1486 print_size_transition(gclog_or_tty, g1h_prev_used, used(), capacity());
1487 }
1488
1489 if (true) { // FIXME
1490 // Ask the permanent generation to adjust size for full collections
1491 perm()->compute_new_size();
1492 }
1493
1494 // Start a new incremental collection set for the next pause
1495 assert(g1_policy()->collection_set() == NULL, "must be");
1496 g1_policy()->start_incremental_cset_building();
1497
1498 // Clear the _cset_fast_test bitmap in anticipation of adding
1499 // regions to the incremental collection set for the next
1500 // evacuation pause.
1501 clear_cset_fast_test();
1502
1503 init_mutator_alloc_region();
1504
1505 double end = os::elapsedTime();
1506 g1_policy()->record_full_collection_end();
1507
1508 #ifdef TRACESPINNING
1509 ParallelTaskTerminator::print_termination_counts();
1510 #endif
1511
1512 gc_epilogue(true);
1513
1514 // Discard all rset updates
1515 JavaThread::dirty_card_queue_set().abandon_logs();
1516 assert(!G1DeferredRSUpdate
1517 || (G1DeferredRSUpdate && (dirty_card_queue_set().completed_buffers_num() == 0)), "Should not be any");
1518
1519 _young_list->reset_sampled_info();
1520 // At this point there should be no regions in the
1521 // entire heap tagged as young.
1522 assert( check_young_list_empty(true /* check_heap */),
1523 "young list should be empty at this point");
1524
1525 // Update the number of full collections that have been completed.
1526 increment_old_marking_cycles_completed(false /* concurrent */);
1527
1528 _hrs.verify_optional();
1529 verify_region_sets_optional();
1530
1531 print_heap_after_gc();
1532 trace_heap_after_gc(gc_tracer);
1533
1534 // We must call G1MonitoringSupport::update_sizes() in the same scoping level
1535 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
1536 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
1537 // before any GC notifications are raised.
1538 g1mm()->update_sizes();
1539 }
1540
1541 post_full_gc_dump(gc_timer);
1542
1543 gc_timer->register_gc_end(os::elapsed_counter());
1544
1545 gc_tracer->report_gc_end(gc_timer->gc_end(), gc_timer->time_partitions());
1546
1547 return true;
1548 }
1549
1550 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
1551 // do_collection() will return whether it succeeded in performing
1552 // the GC. Currently, there is no facility on the
1553 // do_full_collection() API to notify the caller than the collection
1554 // did not succeed (e.g., because it was locked out by the GC
1555 // locker). So, right now, we'll ignore the return value.
1556 bool dummy = do_collection(true, /* explicit_gc */
1557 clear_all_soft_refs,
1558 0 /* word_size */);
1559 }
1560
1561 // This code is mostly copied from TenuredGeneration.
1562 void
1563 G1CollectedHeap::
1564 resize_if_necessary_after_full_collection(size_t word_size) {
1565 assert(MinHeapFreeRatio <= MaxHeapFreeRatio, "sanity check");
1566
1567 // Include the current allocation, if any, and bytes that will be
1568 // pre-allocated to support collections, as "used".
1569 const size_t used_after_gc = used();
1570 const size_t capacity_after_gc = capacity();
1571 const size_t free_after_gc = capacity_after_gc - used_after_gc;
1572
1573 // This is enforced in arguments.cpp.
1574 assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
1575 "otherwise the code below doesn't make sense");
1576
1577 // We don't have floating point command-line arguments
1578 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
1579 const double maximum_used_percentage = 1.0 - minimum_free_percentage;
1580 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
1581 const double minimum_used_percentage = 1.0 - maximum_free_percentage;
1582
1583 const size_t min_heap_size = collector_policy()->min_heap_byte_size();
1584 const size_t max_heap_size = collector_policy()->max_heap_byte_size();
1585
1586 // We have to be careful here as these two calculations can overflow
1587 // 32-bit size_t's.
1588 double used_after_gc_d = (double) used_after_gc;
1589 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
1590 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
1591
1592 // Let's make sure that they are both under the max heap size, which
1593 // by default will make them fit into a size_t.
1594 double desired_capacity_upper_bound = (double) max_heap_size;
1595 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
1596 desired_capacity_upper_bound);
1597 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
1598 desired_capacity_upper_bound);
1599
1600 // We can now safely turn them into size_t's.
1601 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
1602 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
1603
1604 // This assert only makes sense here, before we adjust them
1605 // with respect to the min and max heap size.
1606 assert(minimum_desired_capacity <= maximum_desired_capacity,
1607 err_msg("minimum_desired_capacity = "SIZE_FORMAT", "
1608 "maximum_desired_capacity = "SIZE_FORMAT,
1609 minimum_desired_capacity, maximum_desired_capacity));
1610
1611 // Should not be greater than the heap max size. No need to adjust
1612 // it with respect to the heap min size as it's a lower bound (i.e.,
1613 // we'll try to make the capacity larger than it, not smaller).
1614 minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size);
1615 // Should not be less than the heap min size. No need to adjust it
1616 // with respect to the heap max size as it's an upper bound (i.e.,
1617 // we'll try to make the capacity smaller than it, not greater).
1618 maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size);
1619
1620 if (capacity_after_gc < minimum_desired_capacity) {
1621 // Don't expand unless it's significant
1622 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
1623 ergo_verbose4(ErgoHeapSizing,
1624 "attempt heap expansion",
1625 ergo_format_reason("capacity lower than "
1626 "min desired capacity after Full GC")
1627 ergo_format_byte("capacity")
1628 ergo_format_byte("occupancy")
1629 ergo_format_byte_perc("min desired capacity"),
1630 capacity_after_gc, used_after_gc,
1631 minimum_desired_capacity, (double) MinHeapFreeRatio);
1632 expand(expand_bytes);
1633
1634 // No expansion, now see if we want to shrink
1635 } else if (capacity_after_gc > maximum_desired_capacity) {
1636 // Capacity too large, compute shrinking size
1637 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
1638 ergo_verbose4(ErgoHeapSizing,
1639 "attempt heap shrinking",
1640 ergo_format_reason("capacity higher than "
1641 "max desired capacity after Full GC")
1642 ergo_format_byte("capacity")
1643 ergo_format_byte("occupancy")
1644 ergo_format_byte_perc("max desired capacity"),
1645 capacity_after_gc, used_after_gc,
1646 maximum_desired_capacity, (double) MaxHeapFreeRatio);
1647 shrink(shrink_bytes);
1648 }
1649 }
1650
1651
1652 HeapWord*
1653 G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
1654 bool* succeeded) {
1655 assert_at_safepoint(true /* should_be_vm_thread */);
1656
1657 *succeeded = true;
1658 // Let's attempt the allocation first.
1659 HeapWord* result =
1660 attempt_allocation_at_safepoint(word_size,
1661 false /* expect_null_mutator_alloc_region */);
1662 if (result != NULL) {
1663 assert(*succeeded, "sanity");
1664 return result;
1665 }
1666
1667 // In a G1 heap, we're supposed to keep allocation from failing by
1668 // incremental pauses. Therefore, at least for now, we'll favor
1669 // expansion over collection. (This might change in the future if we can
1670 // do something smarter than full collection to satisfy a failed alloc.)
1671 result = expand_and_allocate(word_size);
1672 if (result != NULL) {
1673 assert(*succeeded, "sanity");
1674 return result;
1675 }
1676
1677 // Expansion didn't work, we'll try to do a Full GC.
1678 bool gc_succeeded = do_collection(false, /* explicit_gc */
1679 false, /* clear_all_soft_refs */
1680 word_size);
1681 if (!gc_succeeded) {
1682 *succeeded = false;
1683 return NULL;
1684 }
1685
1686 // Retry the allocation
1687 result = attempt_allocation_at_safepoint(word_size,
1688 true /* expect_null_mutator_alloc_region */);
1689 if (result != NULL) {
1690 assert(*succeeded, "sanity");
1691 return result;
1692 }
1693
1694 // Then, try a Full GC that will collect all soft references.
1695 gc_succeeded = do_collection(false, /* explicit_gc */
1696 true, /* clear_all_soft_refs */
1697 word_size);
1698 if (!gc_succeeded) {
1699 *succeeded = false;
1700 return NULL;
1701 }
1702
1703 // Retry the allocation once more
1704 result = attempt_allocation_at_safepoint(word_size,
1705 true /* expect_null_mutator_alloc_region */);
1706 if (result != NULL) {
1707 assert(*succeeded, "sanity");
1708 return result;
1709 }
1710
1711 assert(!collector_policy()->should_clear_all_soft_refs(),
1712 "Flag should have been handled and cleared prior to this point");
1713
1714 // What else? We might try synchronous finalization later. If the total
1715 // space available is large enough for the allocation, then a more
1716 // complete compaction phase than we've tried so far might be
1717 // appropriate.
1718 assert(*succeeded, "sanity");
1719 return NULL;
1720 }
1721
1722 // Attempting to expand the heap sufficiently
1723 // to support an allocation of the given "word_size". If
1724 // successful, perform the allocation and return the address of the
1725 // allocated block, or else "NULL".
1726
1727 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size) {
1728 assert_at_safepoint(true /* should_be_vm_thread */);
1729
1730 verify_region_sets_optional();
1731
1732 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
1733 ergo_verbose1(ErgoHeapSizing,
1734 "attempt heap expansion",
1735 ergo_format_reason("allocation request failed")
1736 ergo_format_byte("allocation request"),
1737 word_size * HeapWordSize);
1738 if (expand(expand_bytes)) {
1739 _hrs.verify_optional();
1740 verify_region_sets_optional();
1741 return attempt_allocation_at_safepoint(word_size,
1742 false /* expect_null_mutator_alloc_region */);
1743 }
1744 return NULL;
1745 }
1746
1747 void G1CollectedHeap::update_committed_space(HeapWord* old_end,
1748 HeapWord* new_end) {
1749 assert(old_end != new_end, "don't call this otherwise");
1750 assert((HeapWord*) _g1_storage.high() == new_end, "invariant");
1751
1752 // Update the committed mem region.
1753 _g1_committed.set_end(new_end);
1754 // Tell the card table about the update.
1755 Universe::heap()->barrier_set()->resize_covered_region(_g1_committed);
1756 // Tell the BOT about the update.
1757 _bot_shared->resize(_g1_committed.word_size());
1758 }
1759
1760 bool G1CollectedHeap::expand(size_t expand_bytes) {
1761 size_t old_mem_size = _g1_storage.committed_size();
1762 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
1763 aligned_expand_bytes = align_size_up(aligned_expand_bytes,
1764 HeapRegion::GrainBytes);
1765 ergo_verbose2(ErgoHeapSizing,
1766 "expand the heap",
1767 ergo_format_byte("requested expansion amount")
1768 ergo_format_byte("attempted expansion amount"),
1769 expand_bytes, aligned_expand_bytes);
1770
1771 // First commit the memory.
1772 HeapWord* old_end = (HeapWord*) _g1_storage.high();
1773 bool successful = _g1_storage.expand_by(aligned_expand_bytes);
1774 if (successful) {
1775 // Then propagate this update to the necessary data structures.
1776 HeapWord* new_end = (HeapWord*) _g1_storage.high();
1777 update_committed_space(old_end, new_end);
1778
1779 FreeRegionList expansion_list("Local Expansion List");
1780 MemRegion mr = _hrs.expand_by(old_end, new_end, &expansion_list);
1781 assert(mr.start() == old_end, "post-condition");
1782 // mr might be a smaller region than what was requested if
1783 // expand_by() was unable to allocate the HeapRegion instances
1784 assert(mr.end() <= new_end, "post-condition");
1785
1786 size_t actual_expand_bytes = mr.byte_size();
1787 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
1788 assert(actual_expand_bytes == expansion_list.total_capacity_bytes(),
1789 "post-condition");
1790 if (actual_expand_bytes < aligned_expand_bytes) {
1791 // We could not expand _hrs to the desired size. In this case we
1792 // need to shrink the committed space accordingly.
1793 assert(mr.end() < new_end, "invariant");
1794
1795 size_t diff_bytes = aligned_expand_bytes - actual_expand_bytes;
1796 // First uncommit the memory.
1797 _g1_storage.shrink_by(diff_bytes);
1798 // Then propagate this update to the necessary data structures.
1799 update_committed_space(new_end, mr.end());
1800 }
1801 _free_list.add_as_tail(&expansion_list);
1802
1803 if (_hr_printer.is_active()) {
1804 HeapWord* curr = mr.start();
1805 while (curr < mr.end()) {
1806 HeapWord* curr_end = curr + HeapRegion::GrainWords;
1807 _hr_printer.commit(curr, curr_end);
1808 curr = curr_end;
1809 }
1810 assert(curr == mr.end(), "post-condition");
1811 }
1812 g1_policy()->record_new_heap_size(n_regions());
1813 } else {
1814 ergo_verbose0(ErgoHeapSizing,
1815 "did not expand the heap",
1816 ergo_format_reason("heap expansion operation failed"));
1817 // The expansion of the virtual storage space was unsuccessful.
1818 // Let's see if it was because we ran out of swap.
1819 if (G1ExitOnExpansionFailure &&
1820 _g1_storage.uncommitted_size() >= aligned_expand_bytes) {
1821 // We had head room...
1822 vm_exit_out_of_memory(aligned_expand_bytes, "G1 heap expansion");
1823 }
1824 }
1825 return successful;
1826 }
1827
1828 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
1829 size_t old_mem_size = _g1_storage.committed_size();
1830 size_t aligned_shrink_bytes =
1831 ReservedSpace::page_align_size_down(shrink_bytes);
1832 aligned_shrink_bytes = align_size_down(aligned_shrink_bytes,
1833 HeapRegion::GrainBytes);
1834 uint num_regions_deleted = 0;
1835 MemRegion mr = _hrs.shrink_by(aligned_shrink_bytes, &num_regions_deleted);
1836 HeapWord* old_end = (HeapWord*) _g1_storage.high();
1837 assert(mr.end() == old_end, "post-condition");
1838
1839 ergo_verbose3(ErgoHeapSizing,
1840 "shrink the heap",
1841 ergo_format_byte("requested shrinking amount")
1842 ergo_format_byte("aligned shrinking amount")
1843 ergo_format_byte("attempted shrinking amount"),
1844 shrink_bytes, aligned_shrink_bytes, mr.byte_size());
1845 if (mr.byte_size() > 0) {
1846 if (_hr_printer.is_active()) {
1847 HeapWord* curr = mr.end();
1848 while (curr > mr.start()) {
1849 HeapWord* curr_end = curr;
1850 curr -= HeapRegion::GrainWords;
1851 _hr_printer.uncommit(curr, curr_end);
1852 }
1853 assert(curr == mr.start(), "post-condition");
1854 }
1855
1856 _g1_storage.shrink_by(mr.byte_size());
1857 HeapWord* new_end = (HeapWord*) _g1_storage.high();
1858 assert(mr.start() == new_end, "post-condition");
1859
1860 _expansion_regions += num_regions_deleted;
1861 update_committed_space(old_end, new_end);
1862 HeapRegionRemSet::shrink_heap(n_regions());
1863 g1_policy()->record_new_heap_size(n_regions());
1864 } else {
1865 ergo_verbose0(ErgoHeapSizing,
1866 "did not shrink the heap",
1867 ergo_format_reason("heap shrinking operation failed"));
1868 }
1869 }
1870
1871 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1872 verify_region_sets_optional();
1873
1874 // We should only reach here at the end of a Full GC which means we
1875 // should not not be holding to any GC alloc regions. The method
1876 // below will make sure of that and do any remaining clean up.
1877 abandon_gc_alloc_regions();
1878
1879 // Instead of tearing down / rebuilding the free lists here, we
1880 // could instead use the remove_all_pending() method on free_list to
1881 // remove only the ones that we need to remove.
1882 tear_down_region_sets(true /* free_list_only */);
1883 shrink_helper(shrink_bytes);
1884 rebuild_region_sets(true /* free_list_only */);
1885
1886 _hrs.verify_optional();
1887 verify_region_sets_optional();
1888 }
1889
1890 // Public methods.
1891
1892 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away
1893 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
1894 #endif // _MSC_VER
1895
1896
1897 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* policy_) :
1898 SharedHeap(policy_),
1899 _g1_policy(policy_),
1900 _dirty_card_queue_set(false),
1901 _into_cset_dirty_card_queue_set(false),
1902 _is_alive_closure_cm(this),
1903 _is_alive_closure_stw(this),
1904 _ref_processor_cm(NULL),
1905 _ref_processor_stw(NULL),
1906 _process_strong_tasks(new SubTasksDone(G1H_PS_NumElements)),
1907 _bot_shared(NULL),
1908 _evac_failure_scan_stack(NULL) ,
1909 _mark_in_progress(false),
1910 _cg1r(NULL), _summary_bytes_used(0),
1911 _g1mm(NULL),
1912 _refine_cte_cl(NULL),
1913 _full_collection(false),
1914 _free_list("Master Free List"),
1915 _secondary_free_list("Secondary Free List"),
1916 _old_set("Old Set"),
1917 _humongous_set("Master Humongous Set"),
1918 _free_regions_coming(false),
1919 _young_list(new YoungList(this)),
1920 _gc_time_stamp(0),
1921 _retained_old_gc_alloc_region(NULL),
1922 _survivor_plab_stats(YoungPLABSize, PLABWeight),
1923 _old_plab_stats(OldPLABSize, PLABWeight),
1924 _expand_heap_after_alloc_failure(true),
1925 _surviving_young_words(NULL),
1926 _old_marking_cycles_started(0),
1927 _old_marking_cycles_completed(0),
1928 _concurrent_cycle_started(false),
1929 _in_cset_fast_test(NULL),
1930 _in_cset_fast_test_base(NULL),
1931 _dirty_cards_region_list(NULL),
1932 _worker_cset_start_region(NULL),
1933 _worker_cset_start_region_time_stamp(NULL),
1934 _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()),
1935 _gc_timer_cm(new (ResourceObj::C_HEAP, mtGC) ConcurrentGCTimer()),
1936 _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()),
1937 _gc_tracer_cm(new (ResourceObj::C_HEAP, mtGC) G1OldTracer()) {
1938
1939 _g1h = this;
1940 if (_process_strong_tasks == NULL || !_process_strong_tasks->valid()) {
1941 vm_exit_during_initialization("Failed necessary allocation.");
1942 }
1943
1944 _humongous_object_threshold_in_words = HeapRegion::GrainWords / 2;
1945
1946 int n_queues = MAX2((int)ParallelGCThreads, 1);
1947 _task_queues = new RefToScanQueueSet(n_queues);
1948
1949 int n_rem_sets = HeapRegionRemSet::num_par_rem_sets();
1950 assert(n_rem_sets > 0, "Invariant.");
1951
1952 HeapRegionRemSetIterator** iter_arr =
1953 NEW_C_HEAP_ARRAY(HeapRegionRemSetIterator*, n_queues, mtGC);
1954 for (int i = 0; i < n_queues; i++) {
1955 iter_arr[i] = new HeapRegionRemSetIterator();
1956 }
1957 _rem_set_iterator = iter_arr;
1958
1959 _worker_cset_start_region = NEW_C_HEAP_ARRAY(HeapRegion*, n_queues, mtGC);
1960 _worker_cset_start_region_time_stamp = NEW_C_HEAP_ARRAY(unsigned int, n_queues, mtGC);
1961
1962 for (int i = 0; i < n_queues; i++) {
1963 RefToScanQueue* q = new RefToScanQueue();
1964 q->initialize();
1965 _task_queues->register_queue(i, q);
1966 }
1967
1968 clear_cset_start_regions();
1969
1970 // Initialize the G1EvacuationFailureALot counters and flags.
1971 NOT_PRODUCT(reset_evacuation_should_fail();)
1972
1973 guarantee(_task_queues != NULL, "task_queues allocation failure.");
1974 }
1975
1976 jint G1CollectedHeap::initialize() {
1977 CollectedHeap::pre_initialize();
1978 os::enable_vtime();
1979
1980 G1Log::init();
1981
1982 // Necessary to satisfy locking discipline assertions.
1983
1984 MutexLocker x(Heap_lock);
1985
1986 // We have to initialize the printer before committing the heap, as
1987 // it will be used then.
1988 _hr_printer.set_active(G1PrintHeapRegions);
1989
1990 // While there are no constraints in the GC code that HeapWordSize
1991 // be any particular value, there are multiple other areas in the
1992 // system which believe this to be true (e.g. oop->object_size in some
1993 // cases incorrectly returns the size in wordSize units rather than
1994 // HeapWordSize).
1995 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
1996
1997 size_t init_byte_size = collector_policy()->initial_heap_byte_size();
1998 size_t max_byte_size = collector_policy()->max_heap_byte_size();
1999
2000 // Ensure that the sizes are properly aligned.
2001 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
2002 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
2003
2004 _cg1r = new ConcurrentG1Refine();
2005
2006 // Reserve the maximum.
2007 PermanentGenerationSpec* pgs = collector_policy()->permanent_generation();
2008 // Includes the perm-gen.
2009
2010 // When compressed oops are enabled, the preferred heap base
2011 // is calculated by subtracting the requested size from the
2012 // 32Gb boundary and using the result as the base address for
2013 // heap reservation. If the requested size is not aligned to
2014 // HeapRegion::GrainBytes (i.e. the alignment that is passed
2015 // into the ReservedHeapSpace constructor) then the actual
2016 // base of the reserved heap may end up differing from the
2017 // address that was requested (i.e. the preferred heap base).
2018 // If this happens then we could end up using a non-optimal
2019 // compressed oops mode.
2020
2021 // Since max_byte_size is aligned to the size of a heap region (checked
2022 // above), we also need to align the perm gen size as it might not be.
2023 const size_t total_reserved = max_byte_size +
2024 align_size_up(pgs->max_size(), HeapRegion::GrainBytes);
2025 Universe::check_alignment(total_reserved, HeapRegion::GrainBytes, "g1 heap and perm");
2026
2027 char* addr = Universe::preferred_heap_base(total_reserved, Universe::UnscaledNarrowOop);
2028
2029 ReservedHeapSpace heap_rs(total_reserved, HeapRegion::GrainBytes,
2030 UseLargePages, addr);
2031
2032 if (UseCompressedOops) {
2033 if (addr != NULL && !heap_rs.is_reserved()) {
2034 // Failed to reserve at specified address - the requested memory
2035 // region is taken already, for example, by 'java' launcher.
2036 // Try again to reserver heap higher.
2037 addr = Universe::preferred_heap_base(total_reserved, Universe::ZeroBasedNarrowOop);
2038
2039 ReservedHeapSpace heap_rs0(total_reserved, HeapRegion::GrainBytes,
2040 UseLargePages, addr);
2041
2042 if (addr != NULL && !heap_rs0.is_reserved()) {
2043 // Failed to reserve at specified address again - give up.
2044 addr = Universe::preferred_heap_base(total_reserved, Universe::HeapBasedNarrowOop);
2045 assert(addr == NULL, "");
2046
2047 ReservedHeapSpace heap_rs1(total_reserved, HeapRegion::GrainBytes,
2048 UseLargePages, addr);
2049 heap_rs = heap_rs1;
2050 } else {
2051 heap_rs = heap_rs0;
2052 }
2053 }
2054 }
2055
2056 if (!heap_rs.is_reserved()) {
2057 vm_exit_during_initialization("Could not reserve enough space for object heap");
2058 return JNI_ENOMEM;
2059 }
2060
2061 // It is important to do this in a way such that concurrent readers can't
2062 // temporarily think something is in the heap. (I've actually seen this
2063 // happen in asserts: DLD.)
2064 _reserved.set_word_size(0);
2065 _reserved.set_start((HeapWord*)heap_rs.base());
2066 _reserved.set_end((HeapWord*)(heap_rs.base() + heap_rs.size()));
2067
2068 _expansion_regions = (uint) (max_byte_size / HeapRegion::GrainBytes);
2069
2070 // Create the gen rem set (and barrier set) for the entire reserved region.
2071 _rem_set = collector_policy()->create_rem_set(_reserved, 2);
2072 set_barrier_set(rem_set()->bs());
2073 if (barrier_set()->is_a(BarrierSet::ModRef)) {
2074 _mr_bs = (ModRefBarrierSet*)_barrier_set;
2075 } else {
2076 vm_exit_during_initialization("G1 requires a mod ref bs.");
2077 return JNI_ENOMEM;
2078 }
2079
2080 // Also create a G1 rem set.
2081 if (mr_bs()->is_a(BarrierSet::CardTableModRef)) {
2082 _g1_rem_set = new G1RemSet(this, (CardTableModRefBS*)mr_bs());
2083 } else {
2084 vm_exit_during_initialization("G1 requires a cardtable mod ref bs.");
2085 return JNI_ENOMEM;
2086 }
2087
2088 // Carve out the G1 part of the heap.
2089
2090 ReservedSpace g1_rs = heap_rs.first_part(max_byte_size);
2091 _g1_reserved = MemRegion((HeapWord*)g1_rs.base(),
2092 g1_rs.size()/HeapWordSize);
2093 ReservedSpace perm_gen_rs = heap_rs.last_part(max_byte_size);
2094
2095 _perm_gen = pgs->init(perm_gen_rs, pgs->init_size(), rem_set());
2096
2097 _g1_storage.initialize(g1_rs, 0);
2098 _g1_committed = MemRegion((HeapWord*)_g1_storage.low(), (size_t) 0);
2099 _hrs.initialize((HeapWord*) _g1_reserved.start(),
2100 (HeapWord*) _g1_reserved.end(),
2101 _expansion_regions);
2102
2103 // 6843694 - ensure that the maximum region index can fit
2104 // in the remembered set structures.
2105 const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
2106 guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
2107
2108 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
2109 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
2110 guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
2111 "too many cards per region");
2112
2113 HeapRegionSet::set_unrealistically_long_length(max_regions() + 1);
2114
2115 _bot_shared = new G1BlockOffsetSharedArray(_reserved,
2116 heap_word_size(init_byte_size));
2117
2118 _g1h = this;
2119
2120 _in_cset_fast_test_length = max_regions();
2121 _in_cset_fast_test_base =
2122 NEW_C_HEAP_ARRAY(bool, (size_t) _in_cset_fast_test_length, mtGC);
2123
2124 // We're biasing _in_cset_fast_test to avoid subtracting the
2125 // beginning of the heap every time we want to index; basically
2126 // it's the same with what we do with the card table.
2127 _in_cset_fast_test = _in_cset_fast_test_base -
2128 ((uintx) _g1_reserved.start() >> HeapRegion::LogOfHRGrainBytes);
2129
2130 // Clear the _cset_fast_test bitmap in anticipation of adding
2131 // regions to the incremental collection set for the first
2132 // evacuation pause.
2133 clear_cset_fast_test();
2134
2135 // Create the ConcurrentMark data structure and thread.
2136 // (Must do this late, so that "max_regions" is defined.)
2137 _cm = new ConcurrentMark(heap_rs, max_regions());
2138 _cmThread = _cm->cmThread();
2139
2140 // Initialize the from_card cache structure of HeapRegionRemSet.
2141 HeapRegionRemSet::init_heap(max_regions());
2142
2143 // Now expand into the initial heap size.
2144 if (!expand(init_byte_size)) {
2145 vm_exit_during_initialization("Failed to allocate initial heap.");
2146 return JNI_ENOMEM;
2147 }
2148
2149 // Perform any initialization actions delegated to the policy.
2150 g1_policy()->init();
2151
2152 _refine_cte_cl =
2153 new RefineCardTableEntryClosure(ConcurrentG1RefineThread::sts(),
2154 g1_rem_set(),
2155 concurrent_g1_refine());
2156 JavaThread::dirty_card_queue_set().set_closure(_refine_cte_cl);
2157
2158 JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon,
2159 SATB_Q_FL_lock,
2160 G1SATBProcessCompletedThreshold,
2161 Shared_SATB_Q_lock);
2162
2163 JavaThread::dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
2164 DirtyCardQ_FL_lock,
2165 concurrent_g1_refine()->yellow_zone(),
2166 concurrent_g1_refine()->red_zone(),
2167 Shared_DirtyCardQ_lock);
2168
2169 if (G1DeferredRSUpdate) {
2170 dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
2171 DirtyCardQ_FL_lock,
2172 -1, // never trigger processing
2173 -1, // no limit on length
2174 Shared_DirtyCardQ_lock,
2175 &JavaThread::dirty_card_queue_set());
2176 }
2177
2178 // Initialize the card queue set used to hold cards containing
2179 // references into the collection set.
2180 _into_cset_dirty_card_queue_set.initialize(DirtyCardQ_CBL_mon,
2181 DirtyCardQ_FL_lock,
2182 -1, // never trigger processing
2183 -1, // no limit on length
2184 Shared_DirtyCardQ_lock,
2185 &JavaThread::dirty_card_queue_set());
2186
2187 // In case we're keeping closure specialization stats, initialize those
2188 // counts and that mechanism.
2189 SpecializationStats::clear();
2190
2191 // Do later initialization work for concurrent refinement.
2192 _cg1r->init();
2193
2194 // Here we allocate the dummy full region that is required by the
2195 // G1AllocRegion class. If we don't pass an address in the reserved
2196 // space here, lots of asserts fire.
2197
2198 HeapRegion* dummy_region = new_heap_region(0 /* index of bottom region */,
2199 _g1_reserved.start());
2200 // We'll re-use the same region whether the alloc region will
2201 // require BOT updates or not and, if it doesn't, then a non-young
2202 // region will complain that it cannot support allocations without
2203 // BOT updates. So we'll tag the dummy region as young to avoid that.
2204 dummy_region->set_young();
2205 // Make sure it's full.
2206 dummy_region->set_top(dummy_region->end());
2207 G1AllocRegion::setup(this, dummy_region);
2208
2209 init_mutator_alloc_region();
2210
2211 // Do create of the monitoring and management support so that
2212 // values in the heap have been properly initialized.
2213 _g1mm = new G1MonitoringSupport(this);
2214
2215 return JNI_OK;
2216 }
2217
2218 void G1CollectedHeap::ref_processing_init() {
2219 // Reference processing in G1 currently works as follows:
2220 //
2221 // * There are two reference processor instances. One is
2222 // used to record and process discovered references
2223 // during concurrent marking; the other is used to
2224 // record and process references during STW pauses
2225 // (both full and incremental).
2226 // * Both ref processors need to 'span' the entire heap as
2227 // the regions in the collection set may be dotted around.
2228 //
2229 // * For the concurrent marking ref processor:
2230 // * Reference discovery is enabled at initial marking.
2231 // * Reference discovery is disabled and the discovered
2232 // references processed etc during remarking.
2233 // * Reference discovery is MT (see below).
2234 // * Reference discovery requires a barrier (see below).
2235 // * Reference processing may or may not be MT
2236 // (depending on the value of ParallelRefProcEnabled
2237 // and ParallelGCThreads).
2238 // * A full GC disables reference discovery by the CM
2239 // ref processor and abandons any entries on it's
2240 // discovered lists.
2241 //
2242 // * For the STW processor:
2243 // * Non MT discovery is enabled at the start of a full GC.
2244 // * Processing and enqueueing during a full GC is non-MT.
2245 // * During a full GC, references are processed after marking.
2246 //
2247 // * Discovery (may or may not be MT) is enabled at the start
2248 // of an incremental evacuation pause.
2249 // * References are processed near the end of a STW evacuation pause.
2250 // * For both types of GC:
2251 // * Discovery is atomic - i.e. not concurrent.
2252 // * Reference discovery will not need a barrier.
2253
2254 SharedHeap::ref_processing_init();
2255 MemRegion mr = reserved_region();
2256
2257 // Concurrent Mark ref processor
2258 _ref_processor_cm =
2259 new ReferenceProcessor(mr, // span
2260 ParallelRefProcEnabled && (ParallelGCThreads > 1),
2261 // mt processing
2262 (int) ParallelGCThreads,
2263 // degree of mt processing
2264 (ParallelGCThreads > 1) || (ConcGCThreads > 1),
2265 // mt discovery
2266 (int) MAX2(ParallelGCThreads, ConcGCThreads),
2267 // degree of mt discovery
2268 false,
2269 // Reference discovery is not atomic
2270 &_is_alive_closure_cm,
2271 // is alive closure
2272 // (for efficiency/performance)
2273 true);
2274 // Setting next fields of discovered
2275 // lists requires a barrier.
2276
2277 // STW ref processor
2278 _ref_processor_stw =
2279 new ReferenceProcessor(mr, // span
2280 ParallelRefProcEnabled && (ParallelGCThreads > 1),
2281 // mt processing
2282 MAX2((int)ParallelGCThreads, 1),
2283 // degree of mt processing
2284 (ParallelGCThreads > 1),
2285 // mt discovery
2286 MAX2((int)ParallelGCThreads, 1),
2287 // degree of mt discovery
2288 true,
2289 // Reference discovery is atomic
2290 &_is_alive_closure_stw,
2291 // is alive closure
2292 // (for efficiency/performance)
2293 false);
2294 // Setting next fields of discovered
2295 // lists requires a barrier.
2296 }
2297
2298 size_t G1CollectedHeap::capacity() const {
2299 return _g1_committed.byte_size();
2300 }
2301
2302 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) {
2303 assert(!hr->continuesHumongous(), "pre-condition");
2304 hr->reset_gc_time_stamp();
2305 if (hr->startsHumongous()) {
2306 uint first_index = hr->hrs_index() + 1;
2307 uint last_index = hr->last_hc_index();
2308 for (uint i = first_index; i < last_index; i += 1) {
2309 HeapRegion* chr = region_at(i);
2310 assert(chr->continuesHumongous(), "sanity");
2311 chr->reset_gc_time_stamp();
2312 }
2313 }
2314 }
2315
2316 #ifndef PRODUCT
2317 class CheckGCTimeStampsHRClosure : public HeapRegionClosure {
2318 private:
2319 unsigned _gc_time_stamp;
2320 bool _failures;
2321
2322 public:
2323 CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) :
2324 _gc_time_stamp(gc_time_stamp), _failures(false) { }
2325
2326 virtual bool doHeapRegion(HeapRegion* hr) {
2327 unsigned region_gc_time_stamp = hr->get_gc_time_stamp();
2328 if (_gc_time_stamp != region_gc_time_stamp) {
2329 gclog_or_tty->print_cr("Region "HR_FORMAT" has GC time stamp = %d, "
2330 "expected %d", HR_FORMAT_PARAMS(hr),
2331 region_gc_time_stamp, _gc_time_stamp);
2332 _failures = true;
2333 }
2334 return false;
2335 }
2336
2337 bool failures() { return _failures; }
2338 };
2339
2340 void G1CollectedHeap::check_gc_time_stamps() {
2341 CheckGCTimeStampsHRClosure cl(_gc_time_stamp);
2342 heap_region_iterate(&cl);
2343 guarantee(!cl.failures(), "all GC time stamps should have been reset");
2344 }
2345 #endif // PRODUCT
2346
2347 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl,
2348 DirtyCardQueue* into_cset_dcq,
2349 bool concurrent,
2350 int worker_i) {
2351 // Clean cards in the hot card cache
2352 concurrent_g1_refine()->clean_up_cache(worker_i, g1_rem_set(), into_cset_dcq);
2353
2354 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2355 int n_completed_buffers = 0;
2356 while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) {
2357 n_completed_buffers++;
2358 }
2359 g1_policy()->phase_times()->record_update_rs_processed_buffers(worker_i, n_completed_buffers);
2360 dcqs.clear_n_completed_buffers();
2361 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!");
2362 }
2363
2364
2365 // Computes the sum of the storage used by the various regions.
2366
2367 size_t G1CollectedHeap::used() const {
2368 assert(Heap_lock->owner() != NULL,
2369 "Should be owned on this thread's behalf.");
2370 size_t result = _summary_bytes_used;
2371 // Read only once in case it is set to NULL concurrently
2372 HeapRegion* hr = _mutator_alloc_region.get();
2373 if (hr != NULL)
2374 result += hr->used();
2375 return result;
2376 }
2377
2378 size_t G1CollectedHeap::used_unlocked() const {
2379 size_t result = _summary_bytes_used;
2380 return result;
2381 }
2382
2383 class SumUsedClosure: public HeapRegionClosure {
2384 size_t _used;
2385 public:
2386 SumUsedClosure() : _used(0) {}
2387 bool doHeapRegion(HeapRegion* r) {
2388 if (!r->continuesHumongous()) {
2389 _used += r->used();
2390 }
2391 return false;
2392 }
2393 size_t result() { return _used; }
2394 };
2395
2396 size_t G1CollectedHeap::recalculate_used() const {
2397 SumUsedClosure blk;
2398 heap_region_iterate(&blk);
2399 return blk.result();
2400 }
2401
2402 size_t G1CollectedHeap::unsafe_max_alloc() {
2403 if (free_regions() > 0) return HeapRegion::GrainBytes;
2404 // otherwise, is there space in the current allocation region?
2405
2406 // We need to store the current allocation region in a local variable
2407 // here. The problem is that this method doesn't take any locks and
2408 // there may be other threads which overwrite the current allocation
2409 // region field. attempt_allocation(), for example, sets it to NULL
2410 // and this can happen *after* the NULL check here but before the call
2411 // to free(), resulting in a SIGSEGV. Note that this doesn't appear
2412 // to be a problem in the optimized build, since the two loads of the
2413 // current allocation region field are optimized away.
2414 HeapRegion* hr = _mutator_alloc_region.get();
2415 if (hr == NULL) {
2416 return 0;
2417 }
2418 return hr->free();
2419 }
2420
2421 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
2422 switch (cause) {
2423 case GCCause::_gc_locker: return GCLockerInvokesConcurrent;
2424 case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent;
2425 case GCCause::_g1_humongous_allocation: return true;
2426 default: return false;
2427 }
2428 }
2429
2430 #ifndef PRODUCT
2431 void G1CollectedHeap::allocate_dummy_regions() {
2432 // Let's fill up most of the region
2433 size_t word_size = HeapRegion::GrainWords - 1024;
2434 // And as a result the region we'll allocate will be humongous.
2435 guarantee(isHumongous(word_size), "sanity");
2436
2437 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
2438 // Let's use the existing mechanism for the allocation
2439 HeapWord* dummy_obj = humongous_obj_allocate(word_size);
2440 if (dummy_obj != NULL) {
2441 MemRegion mr(dummy_obj, word_size);
2442 CollectedHeap::fill_with_object(mr);
2443 } else {
2444 // If we can't allocate once, we probably cannot allocate
2445 // again. Let's get out of the loop.
2446 break;
2447 }
2448 }
2449 }
2450 #endif // !PRODUCT
2451
2452 void G1CollectedHeap::increment_old_marking_cycles_started() {
2453 assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
2454 _old_marking_cycles_started == _old_marking_cycles_completed + 1,
2455 err_msg("Wrong marking cycle count (started: %d, completed: %d)",
2456 _old_marking_cycles_started, _old_marking_cycles_completed));
2457
2458 _old_marking_cycles_started++;
2459 }
2460
2461 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) {
2462 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
2463
2464 // We assume that if concurrent == true, then the caller is a
2465 // concurrent thread that was joined the Suspendible Thread
2466 // Set. If there's ever a cheap way to check this, we should add an
2467 // assert here.
2468
2469 // Given that this method is called at the end of a Full GC or of a
2470 // concurrent cycle, and those can be nested (i.e., a Full GC can
2471 // interrupt a concurrent cycle), the number of full collections
2472 // completed should be either one (in the case where there was no
2473 // nesting) or two (when a Full GC interrupted a concurrent cycle)
2474 // behind the number of full collections started.
2475
2476 // This is the case for the inner caller, i.e. a Full GC.
2477 assert(concurrent ||
2478 (_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
2479 (_old_marking_cycles_started == _old_marking_cycles_completed + 2),
2480 err_msg("for inner caller (Full GC): _old_marking_cycles_started = %u "
2481 "is inconsistent with _old_marking_cycles_completed = %u",
2482 _old_marking_cycles_started, _old_marking_cycles_completed));
2483
2484 // This is the case for the outer caller, i.e. the concurrent cycle.
2485 assert(!concurrent ||
2486 (_old_marking_cycles_started == _old_marking_cycles_completed + 1),
2487 err_msg("for outer caller (concurrent cycle): "
2488 "_old_marking_cycles_started = %u "
2489 "is inconsistent with _old_marking_cycles_completed = %u",
2490 _old_marking_cycles_started, _old_marking_cycles_completed));
2491
2492 _old_marking_cycles_completed += 1;
2493
2494 // We need to clear the "in_progress" flag in the CM thread before
2495 // we wake up any waiters (especially when ExplicitInvokesConcurrent
2496 // is set) so that if a waiter requests another System.gc() it doesn't
2497 // incorrectly see that a marking cycle is still in progress.
2498 if (concurrent) {
2499 _cmThread->clear_in_progress();
2500 }
2501
2502 // This notify_all() will ensure that a thread that called
2503 // System.gc() with (with ExplicitGCInvokesConcurrent set or not)
2504 // and it's waiting for a full GC to finish will be woken up. It is
2505 // waiting in VM_G1IncCollectionPause::doit_epilogue().
2506 FullGCCount_lock->notify_all();
2507 }
2508
2509 void G1CollectedHeap::register_concurrent_cycle_start(jlong start_time) {
2510 _concurrent_cycle_started = true;
2511 _gc_timer_cm->register_gc_start(start_time);
2512
2513 _gc_tracer_cm->report_gc_start(gc_cause(), _gc_timer_cm->gc_start());
2514 trace_heap_before_gc(_gc_tracer_cm);
2515 }
2516
2517 void G1CollectedHeap::register_concurrent_cycle_end() {
2518 if (_concurrent_cycle_started) {
2519 _gc_timer_cm->register_gc_end(os::elapsed_counter());
2520
2521 _gc_tracer_cm->report_gc_end(_gc_timer_cm->gc_end(), _gc_timer_cm->time_partitions());
2522
2523 _concurrent_cycle_started = false;
2524 }
2525 }
2526
2527 void G1CollectedHeap::trace_heap_after_concurrent_cycle() {
2528 if (_concurrent_cycle_started) {
2529 trace_heap_after_gc(_gc_tracer_cm);
2530 }
2531 }
2532
2533 G1YCType G1CollectedHeap::yc_type() {
2534 bool is_young = g1_policy()->gcs_are_young();
2535 bool is_initial_mark = g1_policy()->during_initial_mark_pause();
2536 bool is_during_mark = mark_in_progress();
2537
2538 if (is_initial_mark) {
2539 return InitialMark;
2540 } else if (is_during_mark) {
2541 return DuringMark;
2542 } else if (is_young) {
2543 return Normal;
2544 } else {
2545 return Mixed;
2546 }
2547 }
2548
2549 void G1CollectedHeap::collect_as_vm_thread(GCCause::Cause cause) {
2550 assert_at_safepoint(true /* should_be_vm_thread */);
2551 GCCauseSetter gcs(this, cause);
2552 switch (cause) {
2553 case GCCause::_heap_inspection:
2554 case GCCause::_heap_dump: {
2555 HandleMark hm;
2556 do_full_collection(false); // don't clear all soft refs
2557 break;
2558 }
2559 default: // XXX FIX ME
2560 ShouldNotReachHere(); // Unexpected use of this function
2561 }
2562 }
2563
2564 void G1CollectedHeap::collect(GCCause::Cause cause) {
2565 assert_heap_not_locked();
2566
2567 unsigned int gc_count_before;
2568 unsigned int old_marking_count_before;
2569 bool retry_gc;
2570
2571 do {
2572 retry_gc = false;
2573
2574 {
2575 MutexLocker ml(Heap_lock);
2576
2577 // Read the GC count while holding the Heap_lock
2578 gc_count_before = total_collections();
2579 old_marking_count_before = _old_marking_cycles_started;
2580 }
2581
2582 if (should_do_concurrent_full_gc(cause)) {
2583 // Schedule an initial-mark evacuation pause that will start a
2584 // concurrent cycle. We're setting word_size to 0 which means that
2585 // we are not requesting a post-GC allocation.
2586 VM_G1IncCollectionPause op(gc_count_before,
2587 0, /* word_size */
2588 true, /* should_initiate_conc_mark */
2589 g1_policy()->max_pause_time_ms(),
2590 cause);
2591
2592 VMThread::execute(&op);
2593 if (!op.pause_succeeded()) {
2594 if (old_marking_count_before == _old_marking_cycles_started) {
2595 retry_gc = op.should_retry_gc();
2596 } else {
2597 // A Full GC happened while we were trying to schedule the
2598 // initial-mark GC. No point in starting a new cycle given
2599 // that the whole heap was collected anyway.
2600 }
2601
2602 if (retry_gc) {
2603 if (GC_locker::is_active_and_needs_gc()) {
2604 GC_locker::stall_until_clear();
2605 }
2606 }
2607 }
2608 } else {
2609 if (cause == GCCause::_gc_locker
2610 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2611
2612 // Schedule a standard evacuation pause. We're setting word_size
2613 // to 0 which means that we are not requesting a post-GC allocation.
2614 VM_G1IncCollectionPause op(gc_count_before,
2615 0, /* word_size */
2616 false, /* should_initiate_conc_mark */
2617 g1_policy()->max_pause_time_ms(),
2618 cause);
2619 VMThread::execute(&op);
2620 } else {
2621 // Schedule a Full GC.
2622 VM_G1CollectFull op(gc_count_before, old_marking_count_before, cause);
2623 VMThread::execute(&op);
2624 }
2625 }
2626 } while (retry_gc);
2627 }
2628
2629 bool G1CollectedHeap::is_in(const void* p) const {
2630 if (_g1_committed.contains(p)) {
2631 // Given that we know that p is in the committed space,
2632 // heap_region_containing_raw() should successfully
2633 // return the containing region.
2634 HeapRegion* hr = heap_region_containing_raw(p);
2635 return hr->is_in(p);
2636 } else {
2637 return _perm_gen->as_gen()->is_in(p);
2638 }
2639 }
2640
2641 // Iteration functions.
2642
2643 // Iterates an OopClosure over all ref-containing fields of objects
2644 // within a HeapRegion.
2645
2646 class IterateOopClosureRegionClosure: public HeapRegionClosure {
2647 MemRegion _mr;
2648 OopClosure* _cl;
2649 public:
2650 IterateOopClosureRegionClosure(MemRegion mr, OopClosure* cl)
2651 : _mr(mr), _cl(cl) {}
2652 bool doHeapRegion(HeapRegion* r) {
2653 if (!r->continuesHumongous()) {
2654 r->oop_iterate(_cl);
2655 }
2656 return false;
2657 }
2658 };
2659
2660 void G1CollectedHeap::oop_iterate(OopClosure* cl, bool do_perm) {
2661 IterateOopClosureRegionClosure blk(_g1_committed, cl);
2662 heap_region_iterate(&blk);
2663 if (do_perm) {
2664 perm_gen()->oop_iterate(cl);
2665 }
2666 }
2667
2668 void G1CollectedHeap::oop_iterate(MemRegion mr, OopClosure* cl, bool do_perm) {
2669 IterateOopClosureRegionClosure blk(mr, cl);
2670 heap_region_iterate(&blk);
2671 if (do_perm) {
2672 perm_gen()->oop_iterate(cl);
2673 }
2674 }
2675
2676 // Iterates an ObjectClosure over all objects within a HeapRegion.
2677
2678 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2679 ObjectClosure* _cl;
2680 public:
2681 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2682 bool doHeapRegion(HeapRegion* r) {
2683 if (! r->continuesHumongous()) {
2684 r->object_iterate(_cl);
2685 }
2686 return false;
2687 }
2688 };
2689
2690 void G1CollectedHeap::object_iterate(ObjectClosure* cl, bool do_perm) {
2691 IterateObjectClosureRegionClosure blk(cl);
2692 heap_region_iterate(&blk);
2693 if (do_perm) {
2694 perm_gen()->object_iterate(cl);
2695 }
2696 }
2697
2698 void G1CollectedHeap::object_iterate_since_last_GC(ObjectClosure* cl) {
2699 // FIXME: is this right?
2700 guarantee(false, "object_iterate_since_last_GC not supported by G1 heap");
2701 }
2702
2703 // Calls a SpaceClosure on a HeapRegion.
2704
2705 class SpaceClosureRegionClosure: public HeapRegionClosure {
2706 SpaceClosure* _cl;
2707 public:
2708 SpaceClosureRegionClosure(SpaceClosure* cl) : _cl(cl) {}
2709 bool doHeapRegion(HeapRegion* r) {
2710 _cl->do_space(r);
2711 return false;
2712 }
2713 };
2714
2715 void G1CollectedHeap::space_iterate(SpaceClosure* cl) {
2716 SpaceClosureRegionClosure blk(cl);
2717 heap_region_iterate(&blk);
2718 }
2719
2720 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2721 _hrs.iterate(cl);
2722 }
2723
2724 void
2725 G1CollectedHeap::heap_region_par_iterate_chunked(HeapRegionClosure* cl,
2726 uint worker_id,
2727 uint no_of_par_workers,
2728 jint claim_value) {
2729 const uint regions = n_regions();
2730 const uint max_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
2731 no_of_par_workers :
2732 1);
2733 assert(UseDynamicNumberOfGCThreads ||
2734 no_of_par_workers == workers()->total_workers(),
2735 "Non dynamic should use fixed number of workers");
2736 // try to spread out the starting points of the workers
2737 const HeapRegion* start_hr =
2738 start_region_for_worker(worker_id, no_of_par_workers);
2739 const uint start_index = start_hr->hrs_index();
2740
2741 // each worker will actually look at all regions
2742 for (uint count = 0; count < regions; ++count) {
2743 const uint index = (start_index + count) % regions;
2744 assert(0 <= index && index < regions, "sanity");
2745 HeapRegion* r = region_at(index);
2746 // we'll ignore "continues humongous" regions (we'll process them
2747 // when we come across their corresponding "start humongous"
2748 // region) and regions already claimed
2749 if (r->claim_value() == claim_value || r->continuesHumongous()) {
2750 continue;
2751 }
2752 // OK, try to claim it
2753 if (r->claimHeapRegion(claim_value)) {
2754 // success!
2755 assert(!r->continuesHumongous(), "sanity");
2756 if (r->startsHumongous()) {
2757 // If the region is "starts humongous" we'll iterate over its
2758 // "continues humongous" first; in fact we'll do them
2759 // first. The order is important. In on case, calling the
2760 // closure on the "starts humongous" region might de-allocate
2761 // and clear all its "continues humongous" regions and, as a
2762 // result, we might end up processing them twice. So, we'll do
2763 // them first (notice: most closures will ignore them anyway) and
2764 // then we'll do the "starts humongous" region.
2765 for (uint ch_index = index + 1; ch_index < regions; ++ch_index) {
2766 HeapRegion* chr = region_at(ch_index);
2767
2768 // if the region has already been claimed or it's not
2769 // "continues humongous" we're done
2770 if (chr->claim_value() == claim_value ||
2771 !chr->continuesHumongous()) {
2772 break;
2773 }
2774
2775 // Noone should have claimed it directly. We can given
2776 // that we claimed its "starts humongous" region.
2777 assert(chr->claim_value() != claim_value, "sanity");
2778 assert(chr->humongous_start_region() == r, "sanity");
2779
2780 if (chr->claimHeapRegion(claim_value)) {
2781 // we should always be able to claim it; noone else should
2782 // be trying to claim this region
2783
2784 bool res2 = cl->doHeapRegion(chr);
2785 assert(!res2, "Should not abort");
2786
2787 // Right now, this holds (i.e., no closure that actually
2788 // does something with "continues humongous" regions
2789 // clears them). We might have to weaken it in the future,
2790 // but let's leave these two asserts here for extra safety.
2791 assert(chr->continuesHumongous(), "should still be the case");
2792 assert(chr->humongous_start_region() == r, "sanity");
2793 } else {
2794 guarantee(false, "we should not reach here");
2795 }
2796 }
2797 }
2798
2799 assert(!r->continuesHumongous(), "sanity");
2800 bool res = cl->doHeapRegion(r);
2801 assert(!res, "Should not abort");
2802 }
2803 }
2804 }
2805
2806 class ResetClaimValuesClosure: public HeapRegionClosure {
2807 public:
2808 bool doHeapRegion(HeapRegion* r) {
2809 r->set_claim_value(HeapRegion::InitialClaimValue);
2810 return false;
2811 }
2812 };
2813
2814 void G1CollectedHeap::reset_heap_region_claim_values() {
2815 ResetClaimValuesClosure blk;
2816 heap_region_iterate(&blk);
2817 }
2818
2819 void G1CollectedHeap::reset_cset_heap_region_claim_values() {
2820 ResetClaimValuesClosure blk;
2821 collection_set_iterate(&blk);
2822 }
2823
2824 #ifdef ASSERT
2825 // This checks whether all regions in the heap have the correct claim
2826 // value. I also piggy-backed on this a check to ensure that the
2827 // humongous_start_region() information on "continues humongous"
2828 // regions is correct.
2829
2830 class CheckClaimValuesClosure : public HeapRegionClosure {
2831 private:
2832 jint _claim_value;
2833 uint _failures;
2834 HeapRegion* _sh_region;
2835
2836 public:
2837 CheckClaimValuesClosure(jint claim_value) :
2838 _claim_value(claim_value), _failures(0), _sh_region(NULL) { }
2839 bool doHeapRegion(HeapRegion* r) {
2840 if (r->claim_value() != _claim_value) {
2841 gclog_or_tty->print_cr("Region " HR_FORMAT ", "
2842 "claim value = %d, should be %d",
2843 HR_FORMAT_PARAMS(r),
2844 r->claim_value(), _claim_value);
2845 ++_failures;
2846 }
2847 if (!r->isHumongous()) {
2848 _sh_region = NULL;
2849 } else if (r->startsHumongous()) {
2850 _sh_region = r;
2851 } else if (r->continuesHumongous()) {
2852 if (r->humongous_start_region() != _sh_region) {
2853 gclog_or_tty->print_cr("Region " HR_FORMAT ", "
2854 "HS = "PTR_FORMAT", should be "PTR_FORMAT,
2855 HR_FORMAT_PARAMS(r),
2856 r->humongous_start_region(),
2857 _sh_region);
2858 ++_failures;
2859 }
2860 }
2861 return false;
2862 }
2863 uint failures() { return _failures; }
2864 };
2865
2866 bool G1CollectedHeap::check_heap_region_claim_values(jint claim_value) {
2867 CheckClaimValuesClosure cl(claim_value);
2868 heap_region_iterate(&cl);
2869 return cl.failures() == 0;
2870 }
2871
2872 class CheckClaimValuesInCSetHRClosure: public HeapRegionClosure {
2873 private:
2874 jint _claim_value;
2875 uint _failures;
2876
2877 public:
2878 CheckClaimValuesInCSetHRClosure(jint claim_value) :
2879 _claim_value(claim_value), _failures(0) { }
2880
2881 uint failures() { return _failures; }
2882
2883 bool doHeapRegion(HeapRegion* hr) {
2884 assert(hr->in_collection_set(), "how?");
2885 assert(!hr->isHumongous(), "H-region in CSet");
2886 if (hr->claim_value() != _claim_value) {
2887 gclog_or_tty->print_cr("CSet Region " HR_FORMAT ", "
2888 "claim value = %d, should be %d",
2889 HR_FORMAT_PARAMS(hr),
2890 hr->claim_value(), _claim_value);
2891 _failures += 1;
2892 }
2893 return false;
2894 }
2895 };
2896
2897 bool G1CollectedHeap::check_cset_heap_region_claim_values(jint claim_value) {
2898 CheckClaimValuesInCSetHRClosure cl(claim_value);
2899 collection_set_iterate(&cl);
2900 return cl.failures() == 0;
2901 }
2902 #endif // ASSERT
2903
2904 // Clear the cached CSet starting regions and (more importantly)
2905 // the time stamps. Called when we reset the GC time stamp.
2906 void G1CollectedHeap::clear_cset_start_regions() {
2907 assert(_worker_cset_start_region != NULL, "sanity");
2908 assert(_worker_cset_start_region_time_stamp != NULL, "sanity");
2909
2910 int n_queues = MAX2((int)ParallelGCThreads, 1);
2911 for (int i = 0; i < n_queues; i++) {
2912 _worker_cset_start_region[i] = NULL;
2913 _worker_cset_start_region_time_stamp[i] = 0;
2914 }
2915 }
2916
2917 // Given the id of a worker, obtain or calculate a suitable
2918 // starting region for iterating over the current collection set.
2919 HeapRegion* G1CollectedHeap::start_cset_region_for_worker(int worker_i) {
2920 assert(get_gc_time_stamp() > 0, "should have been updated by now");
2921
2922 HeapRegion* result = NULL;
2923 unsigned gc_time_stamp = get_gc_time_stamp();
2924
2925 if (_worker_cset_start_region_time_stamp[worker_i] == gc_time_stamp) {
2926 // Cached starting region for current worker was set
2927 // during the current pause - so it's valid.
2928 // Note: the cached starting heap region may be NULL
2929 // (when the collection set is empty).
2930 result = _worker_cset_start_region[worker_i];
2931 assert(result == NULL || result->in_collection_set(), "sanity");
2932 return result;
2933 }
2934
2935 // The cached entry was not valid so let's calculate
2936 // a suitable starting heap region for this worker.
2937
2938 // We want the parallel threads to start their collection
2939 // set iteration at different collection set regions to
2940 // avoid contention.
2941 // If we have:
2942 // n collection set regions
2943 // p threads
2944 // Then thread t will start at region floor ((t * n) / p)
2945
2946 result = g1_policy()->collection_set();
2947 if (G1CollectedHeap::use_parallel_gc_threads()) {
2948 uint cs_size = g1_policy()->cset_region_length();
2949 uint active_workers = workers()->active_workers();
2950 assert(UseDynamicNumberOfGCThreads ||
2951 active_workers == workers()->total_workers(),
2952 "Unless dynamic should use total workers");
2953
2954 uint end_ind = (cs_size * worker_i) / active_workers;
2955 uint start_ind = 0;
2956
2957 if (worker_i > 0 &&
2958 _worker_cset_start_region_time_stamp[worker_i - 1] == gc_time_stamp) {
2959 // Previous workers starting region is valid
2960 // so let's iterate from there
2961 start_ind = (cs_size * (worker_i - 1)) / active_workers;
2962 result = _worker_cset_start_region[worker_i - 1];
2963 }
2964
2965 for (uint i = start_ind; i < end_ind; i++) {
2966 result = result->next_in_collection_set();
2967 }
2968 }
2969
2970 // Note: the calculated starting heap region may be NULL
2971 // (when the collection set is empty).
2972 assert(result == NULL || result->in_collection_set(), "sanity");
2973 assert(_worker_cset_start_region_time_stamp[worker_i] != gc_time_stamp,
2974 "should be updated only once per pause");
2975 _worker_cset_start_region[worker_i] = result;
2976 OrderAccess::storestore();
2977 _worker_cset_start_region_time_stamp[worker_i] = gc_time_stamp;
2978 return result;
2979 }
2980
2981 HeapRegion* G1CollectedHeap::start_region_for_worker(uint worker_i,
2982 uint no_of_par_workers) {
2983 uint worker_num =
2984 G1CollectedHeap::use_parallel_gc_threads() ? no_of_par_workers : 1U;
2985 assert(UseDynamicNumberOfGCThreads ||
2986 no_of_par_workers == workers()->total_workers(),
2987 "Non dynamic should use fixed number of workers");
2988 const uint start_index = n_regions() * worker_i / worker_num;
2989 return region_at(start_index);
2990 }
2991
2992 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) {
2993 HeapRegion* r = g1_policy()->collection_set();
2994 while (r != NULL) {
2995 HeapRegion* next = r->next_in_collection_set();
2996 if (cl->doHeapRegion(r)) {
2997 cl->incomplete();
2998 return;
2999 }
3000 r = next;
3001 }
3002 }
3003
3004 void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r,
3005 HeapRegionClosure *cl) {
3006 if (r == NULL) {
3007 // The CSet is empty so there's nothing to do.
3008 return;
3009 }
3010
3011 assert(r->in_collection_set(),
3012 "Start region must be a member of the collection set.");
3013 HeapRegion* cur = r;
3014 while (cur != NULL) {
3015 HeapRegion* next = cur->next_in_collection_set();
3016 if (cl->doHeapRegion(cur) && false) {
3017 cl->incomplete();
3018 return;
3019 }
3020 cur = next;
3021 }
3022 cur = g1_policy()->collection_set();
3023 while (cur != r) {
3024 HeapRegion* next = cur->next_in_collection_set();
3025 if (cl->doHeapRegion(cur) && false) {
3026 cl->incomplete();
3027 return;
3028 }
3029 cur = next;
3030 }
3031 }
3032
3033 CompactibleSpace* G1CollectedHeap::first_compactible_space() {
3034 return n_regions() > 0 ? region_at(0) : NULL;
3035 }
3036
3037
3038 Space* G1CollectedHeap::space_containing(const void* addr) const {
3039 Space* res = heap_region_containing(addr);
3040 if (res == NULL)
3041 res = perm_gen()->space_containing(addr);
3042 return res;
3043 }
3044
3045 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
3046 Space* sp = space_containing(addr);
3047 if (sp != NULL) {
3048 return sp->block_start(addr);
3049 }
3050 return NULL;
3051 }
3052
3053 size_t G1CollectedHeap::block_size(const HeapWord* addr) const {
3054 Space* sp = space_containing(addr);
3055 assert(sp != NULL, "block_size of address outside of heap");
3056 return sp->block_size(addr);
3057 }
3058
3059 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
3060 Space* sp = space_containing(addr);
3061 return sp->block_is_obj(addr);
3062 }
3063
3064 bool G1CollectedHeap::supports_tlab_allocation() const {
3065 return true;
3066 }
3067
3068 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
3069 return HeapRegion::GrainBytes;
3070 }
3071
3072 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
3073 // Return the remaining space in the cur alloc region, but not less than
3074 // the min TLAB size.
3075
3076 // Also, this value can be at most the humongous object threshold,
3077 // since we can't allow tlabs to grow big enough to accommodate
3078 // humongous objects.
3079
3080 HeapRegion* hr = _mutator_alloc_region.get();
3081 size_t max_tlab_size = _humongous_object_threshold_in_words * wordSize;
3082 if (hr == NULL) {
3083 return max_tlab_size;
3084 } else {
3085 return MIN2(MAX2(hr->free(), (size_t) MinTLABSize), max_tlab_size);
3086 }
3087 }
3088
3089 size_t G1CollectedHeap::max_capacity() const {
3090 return _g1_reserved.byte_size();
3091 }
3092
3093 jlong G1CollectedHeap::millis_since_last_gc() {
3094 // assert(false, "NYI");
3095 return 0;
3096 }
3097
3098 void G1CollectedHeap::prepare_for_verify() {
3099 if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) {
3100 ensure_parsability(false);
3101 }
3102 g1_rem_set()->prepare_for_verify();
3103 }
3104
3105 bool G1CollectedHeap::allocated_since_marking(oop obj, HeapRegion* hr,
3106 VerifyOption vo) {
3107 switch (vo) {
3108 case VerifyOption_G1UsePrevMarking:
3109 return hr->obj_allocated_since_prev_marking(obj);
3110 case VerifyOption_G1UseNextMarking:
3111 return hr->obj_allocated_since_next_marking(obj);
3112 case VerifyOption_G1UseMarkWord:
3113 return false;
3114 default:
3115 ShouldNotReachHere();
3116 }
3117 return false; // keep some compilers happy
3118 }
3119
3120 HeapWord* G1CollectedHeap::top_at_mark_start(HeapRegion* hr, VerifyOption vo) {
3121 switch (vo) {
3122 case VerifyOption_G1UsePrevMarking: return hr->prev_top_at_mark_start();
3123 case VerifyOption_G1UseNextMarking: return hr->next_top_at_mark_start();
3124 case VerifyOption_G1UseMarkWord: return NULL;
3125 default: ShouldNotReachHere();
3126 }
3127 return NULL; // keep some compilers happy
3128 }
3129
3130 bool G1CollectedHeap::is_marked(oop obj, VerifyOption vo) {
3131 switch (vo) {
3132 case VerifyOption_G1UsePrevMarking: return isMarkedPrev(obj);
3133 case VerifyOption_G1UseNextMarking: return isMarkedNext(obj);
3134 case VerifyOption_G1UseMarkWord: return obj->is_gc_marked();
3135 default: ShouldNotReachHere();
3136 }
3137 return false; // keep some compilers happy
3138 }
3139
3140 const char* G1CollectedHeap::top_at_mark_start_str(VerifyOption vo) {
3141 switch (vo) {
3142 case VerifyOption_G1UsePrevMarking: return "PTAMS";
3143 case VerifyOption_G1UseNextMarking: return "NTAMS";
3144 case VerifyOption_G1UseMarkWord: return "NONE";
3145 default: ShouldNotReachHere();
3146 }
3147 return NULL; // keep some compilers happy
3148 }
3149
3150 class VerifyLivenessOopClosure: public OopClosure {
3151 G1CollectedHeap* _g1h;
3152 VerifyOption _vo;
3153 public:
3154 VerifyLivenessOopClosure(G1CollectedHeap* g1h, VerifyOption vo):
3155 _g1h(g1h), _vo(vo)
3156 { }
3157 void do_oop(narrowOop *p) { do_oop_work(p); }
3158 void do_oop( oop *p) { do_oop_work(p); }
3159
3160 template <class T> void do_oop_work(T *p) {
3161 oop obj = oopDesc::load_decode_heap_oop(p);
3162 guarantee(obj == NULL || !_g1h->is_obj_dead_cond(obj, _vo),
3163 "Dead object referenced by a not dead object");
3164 }
3165 };
3166
3167 class VerifyObjsInRegionClosure: public ObjectClosure {
3168 private:
3169 G1CollectedHeap* _g1h;
3170 size_t _live_bytes;
3171 HeapRegion *_hr;
3172 VerifyOption _vo;
3173 public:
3174 // _vo == UsePrevMarking -> use "prev" marking information,
3175 // _vo == UseNextMarking -> use "next" marking information,
3176 // _vo == UseMarkWord -> use mark word from object header.
3177 VerifyObjsInRegionClosure(HeapRegion *hr, VerifyOption vo)
3178 : _live_bytes(0), _hr(hr), _vo(vo) {
3179 _g1h = G1CollectedHeap::heap();
3180 }
3181 void do_object(oop o) {
3182 VerifyLivenessOopClosure isLive(_g1h, _vo);
3183 assert(o != NULL, "Huh?");
3184 if (!_g1h->is_obj_dead_cond(o, _vo)) {
3185 // If the object is alive according to the mark word,
3186 // then verify that the marking information agrees.
3187 // Note we can't verify the contra-positive of the
3188 // above: if the object is dead (according to the mark
3189 // word), it may not be marked, or may have been marked
3190 // but has since became dead, or may have been allocated
3191 // since the last marking.
3192 if (_vo == VerifyOption_G1UseMarkWord) {
3193 guarantee(!_g1h->is_obj_dead(o), "mark word and concurrent mark mismatch");
3194 }
3195
3196 o->oop_iterate(&isLive);
3197 if (!_hr->obj_allocated_since_prev_marking(o)) {
3198 size_t obj_size = o->size(); // Make sure we don't overflow
3199 _live_bytes += (obj_size * HeapWordSize);
3200 }
3201 }
3202 }
3203 size_t live_bytes() { return _live_bytes; }
3204 };
3205
3206 class PrintObjsInRegionClosure : public ObjectClosure {
3207 HeapRegion *_hr;
3208 G1CollectedHeap *_g1;
3209 public:
3210 PrintObjsInRegionClosure(HeapRegion *hr) : _hr(hr) {
3211 _g1 = G1CollectedHeap::heap();
3212 };
3213
3214 void do_object(oop o) {
3215 if (o != NULL) {
3216 HeapWord *start = (HeapWord *) o;
3217 size_t word_sz = o->size();
3218 gclog_or_tty->print("\nPrinting obj "PTR_FORMAT" of size " SIZE_FORMAT
3219 " isMarkedPrev %d isMarkedNext %d isAllocSince %d\n",
3220 (void*) o, word_sz,
3221 _g1->isMarkedPrev(o),
3222 _g1->isMarkedNext(o),
3223 _hr->obj_allocated_since_prev_marking(o));
3224 HeapWord *end = start + word_sz;
3225 HeapWord *cur;
3226 int *val;
3227 for (cur = start; cur < end; cur++) {
3228 val = (int *) cur;
3229 gclog_or_tty->print("\t "PTR_FORMAT":"PTR_FORMAT"\n", val, *val);
3230 }
3231 }
3232 }
3233 };
3234
3235 class VerifyRegionClosure: public HeapRegionClosure {
3236 private:
3237 bool _par;
3238 VerifyOption _vo;
3239 bool _failures;
3240 public:
3241 // _vo == UsePrevMarking -> use "prev" marking information,
3242 // _vo == UseNextMarking -> use "next" marking information,
3243 // _vo == UseMarkWord -> use mark word from object header.
3244 VerifyRegionClosure(bool par, VerifyOption vo)
3245 : _par(par),
3246 _vo(vo),
3247 _failures(false) {}
3248
3249 bool failures() {
3250 return _failures;
3251 }
3252
3253 bool doHeapRegion(HeapRegion* r) {
3254 if (!r->continuesHumongous()) {
3255 bool failures = false;
3256 r->verify(_vo, &failures);
3257 if (failures) {
3258 _failures = true;
3259 } else {
3260 VerifyObjsInRegionClosure not_dead_yet_cl(r, _vo);
3261 r->object_iterate(¬_dead_yet_cl);
3262 if (_vo != VerifyOption_G1UseNextMarking) {
3263 if (r->max_live_bytes() < not_dead_yet_cl.live_bytes()) {
3264 gclog_or_tty->print_cr("["PTR_FORMAT","PTR_FORMAT"] "
3265 "max_live_bytes "SIZE_FORMAT" "
3266 "< calculated "SIZE_FORMAT,
3267 r->bottom(), r->end(),
3268 r->max_live_bytes(),
3269 not_dead_yet_cl.live_bytes());
3270 _failures = true;
3271 }
3272 } else {
3273 // When vo == UseNextMarking we cannot currently do a sanity
3274 // check on the live bytes as the calculation has not been
3275 // finalized yet.
3276 }
3277 }
3278 }
3279 return false; // stop the region iteration if we hit a failure
3280 }
3281 };
3282
3283 class VerifyRootsClosure: public OopsInGenClosure {
3284 private:
3285 G1CollectedHeap* _g1h;
3286 VerifyOption _vo;
3287 bool _failures;
3288 public:
3289 // _vo == UsePrevMarking -> use "prev" marking information,
3290 // _vo == UseNextMarking -> use "next" marking information,
3291 // _vo == UseMarkWord -> use mark word from object header.
3292 VerifyRootsClosure(VerifyOption vo) :
3293 _g1h(G1CollectedHeap::heap()),
3294 _vo(vo),
3295 _failures(false) { }
3296
3297 bool failures() { return _failures; }
3298
3299 template <class T> void do_oop_nv(T* p) {
3300 T heap_oop = oopDesc::load_heap_oop(p);
3301 if (!oopDesc::is_null(heap_oop)) {
3302 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
3303 if (_g1h->is_obj_dead_cond(obj, _vo)) {
3304 gclog_or_tty->print_cr("Root location "PTR_FORMAT" "
3305 "points to dead obj "PTR_FORMAT, p, (void*) obj);
3306 if (_vo == VerifyOption_G1UseMarkWord) {
3307 gclog_or_tty->print_cr(" Mark word: "PTR_FORMAT, (void*)(obj->mark()));
3308 }
3309 obj->print_on(gclog_or_tty);
3310 _failures = true;
3311 }
3312 }
3313 }
3314
3315 void do_oop(oop* p) { do_oop_nv(p); }
3316 void do_oop(narrowOop* p) { do_oop_nv(p); }
3317 };
3318
3319 // This is the task used for parallel heap verification.
3320
3321 class G1ParVerifyTask: public AbstractGangTask {
3322 private:
3323 G1CollectedHeap* _g1h;
3324 VerifyOption _vo;
3325 bool _failures;
3326
3327 public:
3328 // _vo == UsePrevMarking -> use "prev" marking information,
3329 // _vo == UseNextMarking -> use "next" marking information,
3330 // _vo == UseMarkWord -> use mark word from object header.
3331 G1ParVerifyTask(G1CollectedHeap* g1h, VerifyOption vo) :
3332 AbstractGangTask("Parallel verify task"),
3333 _g1h(g1h),
3334 _vo(vo),
3335 _failures(false) { }
3336
3337 bool failures() {
3338 return _failures;
3339 }
3340
3341 void work(uint worker_id) {
3342 HandleMark hm;
3343 VerifyRegionClosure blk(true, _vo);
3344 _g1h->heap_region_par_iterate_chunked(&blk, worker_id,
3345 _g1h->workers()->active_workers(),
3346 HeapRegion::ParVerifyClaimValue);
3347 if (blk.failures()) {
3348 _failures = true;
3349 }
3350 }
3351 };
3352
3353 void G1CollectedHeap::verify(bool silent) {
3354 verify(silent, VerifyOption_G1UsePrevMarking);
3355 }
3356
3357 void G1CollectedHeap::verify(bool silent,
3358 VerifyOption vo) {
3359 if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) {
3360 if (!silent) { gclog_or_tty->print("Roots (excluding permgen) "); }
3361 VerifyRootsClosure rootsCl(vo);
3362
3363 assert(Thread::current()->is_VM_thread(),
3364 "Expected to be executed serially by the VM thread at this point");
3365
3366 CodeBlobToOopClosure blobsCl(&rootsCl, /*do_marking=*/ false);
3367
3368 // We apply the relevant closures to all the oops in the
3369 // system dictionary, the string table and the code cache.
3370 const int so = SO_AllClasses | SO_Strings | SO_CodeCache;
3371
3372 process_strong_roots(true, // activate StrongRootsScope
3373 true, // we set "collecting perm gen" to true,
3374 // so we don't reset the dirty cards in the perm gen.
3375 ScanningOption(so), // roots scanning options
3376 &rootsCl,
3377 &blobsCl,
3378 &rootsCl);
3379
3380 // If we're verifying after the marking phase of a Full GC then we can't
3381 // treat the perm gen as roots into the G1 heap. Some of the objects in
3382 // the perm gen may be dead and hence not marked. If one of these dead
3383 // objects is considered to be a root then we may end up with a false
3384 // "Root location <x> points to dead ob <y>" failure.
3385 if (vo != VerifyOption_G1UseMarkWord) {
3386 // Since we used "collecting_perm_gen" == true above, we will not have
3387 // checked the refs from perm into the G1-collected heap. We check those
3388 // references explicitly below. Whether the relevant cards are dirty
3389 // is checked further below in the rem set verification.
3390 if (!silent) { gclog_or_tty->print("Permgen roots "); }
3391 perm_gen()->oop_iterate(&rootsCl);
3392 }
3393 bool failures = rootsCl.failures();
3394
3395 if (vo != VerifyOption_G1UseMarkWord) {
3396 // If we're verifying during a full GC then the region sets
3397 // will have been torn down at the start of the GC. Therefore
3398 // verifying the region sets will fail. So we only verify
3399 // the region sets when not in a full GC.
3400 if (!silent) { gclog_or_tty->print("HeapRegionSets "); }
3401 verify_region_sets();
3402 }
3403
3404 if (!silent) { gclog_or_tty->print("HeapRegions "); }
3405 if (GCParallelVerificationEnabled && ParallelGCThreads > 1) {
3406 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3407 "sanity check");
3408
3409 G1ParVerifyTask task(this, vo);
3410 assert(UseDynamicNumberOfGCThreads ||
3411 workers()->active_workers() == workers()->total_workers(),
3412 "If not dynamic should be using all the workers");
3413 int n_workers = workers()->active_workers();
3414 set_par_threads(n_workers);
3415 workers()->run_task(&task);
3416 set_par_threads(0);
3417 if (task.failures()) {
3418 failures = true;
3419 }
3420
3421 // Checks that the expected amount of parallel work was done.
3422 // The implication is that n_workers is > 0.
3423 assert(check_heap_region_claim_values(HeapRegion::ParVerifyClaimValue),
3424 "sanity check");
3425
3426 reset_heap_region_claim_values();
3427
3428 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3429 "sanity check");
3430 } else {
3431 VerifyRegionClosure blk(false, vo);
3432 heap_region_iterate(&blk);
3433 if (blk.failures()) {
3434 failures = true;
3435 }
3436 }
3437 if (!silent) gclog_or_tty->print("RemSet ");
3438 rem_set()->verify();
3439
3440 if (failures) {
3441 gclog_or_tty->print_cr("Heap:");
3442 // It helps to have the per-region information in the output to
3443 // help us track down what went wrong. This is why we call
3444 // print_extended_on() instead of print_on().
3445 print_extended_on(gclog_or_tty);
3446 gclog_or_tty->print_cr("");
3447 #ifndef PRODUCT
3448 if (VerifyDuringGC && G1VerifyDuringGCPrintReachable) {
3449 concurrent_mark()->print_reachable("at-verification-failure",
3450 vo, false /* all */);
3451 }
3452 #endif
3453 gclog_or_tty->flush();
3454 }
3455 guarantee(!failures, "there should not have been any failures");
3456 } else {
3457 if (!silent) gclog_or_tty->print("(SKIPPING roots, heapRegions, remset) ");
3458 }
3459 }
3460
3461 class PrintRegionClosure: public HeapRegionClosure {
3462 outputStream* _st;
3463 public:
3464 PrintRegionClosure(outputStream* st) : _st(st) {}
3465 bool doHeapRegion(HeapRegion* r) {
3466 r->print_on(_st);
3467 return false;
3468 }
3469 };
3470
3471 void G1CollectedHeap::print_on(outputStream* st) const {
3472 st->print(" %-20s", "garbage-first heap");
3473 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
3474 capacity()/K, used_unlocked()/K);
3475 st->print(" [" INTPTR_FORMAT ", " INTPTR_FORMAT ", " INTPTR_FORMAT ")",
3476 _g1_storage.low_boundary(),
3477 _g1_storage.high(),
3478 _g1_storage.high_boundary());
3479 st->cr();
3480 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
3481 uint young_regions = _young_list->length();
3482 st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
3483 (size_t) young_regions * HeapRegion::GrainBytes / K);
3484 uint survivor_regions = g1_policy()->recorded_survivor_regions();
3485 st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
3486 (size_t) survivor_regions * HeapRegion::GrainBytes / K);
3487 st->cr();
3488 perm()->as_gen()->print_on(st);
3489 }
3490
3491 void G1CollectedHeap::print_extended_on(outputStream* st) const {
3492 print_on(st);
3493
3494 // Print the per-region information.
3495 st->cr();
3496 st->print_cr("Heap Regions: (Y=young(eden), SU=young(survivor), "
3497 "HS=humongous(starts), HC=humongous(continues), "
3498 "CS=collection set, F=free, TS=gc time stamp, "
3499 "PTAMS=previous top-at-mark-start, "
3500 "NTAMS=next top-at-mark-start)");
3501 PrintRegionClosure blk(st);
3502 heap_region_iterate(&blk);
3503 }
3504
3505 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
3506 if (G1CollectedHeap::use_parallel_gc_threads()) {
3507 workers()->print_worker_threads_on(st);
3508 }
3509 _cmThread->print_on(st);
3510 st->cr();
3511 _cm->print_worker_threads_on(st);
3512 _cg1r->print_worker_threads_on(st);
3513 st->cr();
3514 }
3515
3516 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
3517 if (G1CollectedHeap::use_parallel_gc_threads()) {
3518 workers()->threads_do(tc);
3519 }
3520 tc->do_thread(_cmThread);
3521 _cg1r->threads_do(tc);
3522 }
3523
3524 void G1CollectedHeap::print_tracing_info() const {
3525 // We'll overload this to mean "trace GC pause statistics."
3526 if (TraceGen0Time || TraceGen1Time) {
3527 // The "G1CollectorPolicy" is keeping track of these stats, so delegate
3528 // to that.
3529 g1_policy()->print_tracing_info();
3530 }
3531 if (G1SummarizeRSetStats) {
3532 g1_rem_set()->print_summary_info();
3533 }
3534 if (G1SummarizeConcMark) {
3535 concurrent_mark()->print_summary_info();
3536 }
3537 g1_policy()->print_yg_surv_rate_info();
3538 SpecializationStats::print();
3539 }
3540
3541 #ifndef PRODUCT
3542 // Helpful for debugging RSet issues.
3543
3544 class PrintRSetsClosure : public HeapRegionClosure {
3545 private:
3546 const char* _msg;
3547 size_t _occupied_sum;
3548
3549 public:
3550 bool doHeapRegion(HeapRegion* r) {
3551 HeapRegionRemSet* hrrs = r->rem_set();
3552 size_t occupied = hrrs->occupied();
3553 _occupied_sum += occupied;
3554
3555 gclog_or_tty->print_cr("Printing RSet for region "HR_FORMAT,
3556 HR_FORMAT_PARAMS(r));
3557 if (occupied == 0) {
3558 gclog_or_tty->print_cr(" RSet is empty");
3559 } else {
3560 hrrs->print();
3561 }
3562 gclog_or_tty->print_cr("----------");
3563 return false;
3564 }
3565
3566 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
3567 gclog_or_tty->cr();
3568 gclog_or_tty->print_cr("========================================");
3569 gclog_or_tty->print_cr(msg);
3570 gclog_or_tty->cr();
3571 }
3572
3573 ~PrintRSetsClosure() {
3574 gclog_or_tty->print_cr("Occupied Sum: "SIZE_FORMAT, _occupied_sum);
3575 gclog_or_tty->print_cr("========================================");
3576 gclog_or_tty->cr();
3577 }
3578 };
3579
3580 void G1CollectedHeap::print_cset_rsets() {
3581 PrintRSetsClosure cl("Printing CSet RSets");
3582 collection_set_iterate(&cl);
3583 }
3584
3585 void G1CollectedHeap::print_all_rsets() {
3586 PrintRSetsClosure cl("Printing All RSets");;
3587 heap_region_iterate(&cl);
3588 }
3589 #endif // PRODUCT
3590
3591 G1CollectedHeap* G1CollectedHeap::heap() {
3592 assert(_sh->kind() == CollectedHeap::G1CollectedHeap,
3593 "not a garbage-first heap");
3594 return _g1h;
3595 }
3596
3597 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) {
3598 // always_do_update_barrier = false;
3599 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
3600 // Call allocation profiler
3601 AllocationProfiler::iterate_since_last_gc();
3602 // Fill TLAB's and such
3603 ensure_parsability(true);
3604 }
3605
3606 void G1CollectedHeap::gc_epilogue(bool full /* Ignored */) {
3607 // FIXME: what is this about?
3608 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
3609 // is set.
3610 COMPILER2_PRESENT(assert(DerivedPointerTable::is_empty(),
3611 "derived pointer present"));
3612 // always_do_update_barrier = true;
3613
3614 // We have just completed a GC. Update the soft reference
3615 // policy with the new heap occupancy
3616 Universe::update_heap_info_at_gc();
3617 }
3618
3619 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
3620 unsigned int gc_count_before,
3621 bool* succeeded) {
3622 assert_heap_not_locked_and_not_at_safepoint();
3623 g1_policy()->record_stop_world_start();
3624 VM_G1IncCollectionPause op(gc_count_before,
3625 word_size,
3626 false, /* should_initiate_conc_mark */
3627 g1_policy()->max_pause_time_ms(),
3628 GCCause::_g1_inc_collection_pause);
3629 VMThread::execute(&op);
3630
3631 HeapWord* result = op.result();
3632 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
3633 assert(result == NULL || ret_succeeded,
3634 "the result should be NULL if the VM did not succeed");
3635 *succeeded = ret_succeeded;
3636
3637 assert_heap_not_locked();
3638 return result;
3639 }
3640
3641 void
3642 G1CollectedHeap::doConcurrentMark() {
3643 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
3644 if (!_cmThread->in_progress()) {
3645 _cmThread->set_started();
3646 CGC_lock->notify();
3647 }
3648 }
3649
3650 size_t G1CollectedHeap::pending_card_num() {
3651 size_t extra_cards = 0;
3652 JavaThread *curr = Threads::first();
3653 while (curr != NULL) {
3654 DirtyCardQueue& dcq = curr->dirty_card_queue();
3655 extra_cards += dcq.size();
3656 curr = curr->next();
3657 }
3658 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
3659 size_t buffer_size = dcqs.buffer_size();
3660 size_t buffer_num = dcqs.completed_buffers_num();
3661
3662 // PtrQueueSet::buffer_size() and PtrQueue:size() return sizes
3663 // in bytes - not the number of 'entries'. We need to convert
3664 // into a number of cards.
3665 return (buffer_size * buffer_num + extra_cards) / oopSize;
3666 }
3667
3668 size_t G1CollectedHeap::cards_scanned() {
3669 return g1_rem_set()->cardsScanned();
3670 }
3671
3672 void
3673 G1CollectedHeap::setup_surviving_young_words() {
3674 assert(_surviving_young_words == NULL, "pre-condition");
3675 uint array_length = g1_policy()->young_cset_region_length();
3676 _surviving_young_words = NEW_C_HEAP_ARRAY(size_t, (size_t) array_length, mtGC);
3677 if (_surviving_young_words == NULL) {
3678 vm_exit_out_of_memory(sizeof(size_t) * array_length,
3679 "Not enough space for young surv words summary.");
3680 }
3681 memset(_surviving_young_words, 0, (size_t) array_length * sizeof(size_t));
3682 #ifdef ASSERT
3683 for (uint i = 0; i < array_length; ++i) {
3684 assert( _surviving_young_words[i] == 0, "memset above" );
3685 }
3686 #endif // !ASSERT
3687 }
3688
3689 void
3690 G1CollectedHeap::update_surviving_young_words(size_t* surv_young_words) {
3691 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
3692 uint array_length = g1_policy()->young_cset_region_length();
3693 for (uint i = 0; i < array_length; ++i) {
3694 _surviving_young_words[i] += surv_young_words[i];
3695 }
3696 }
3697
3698 void
3699 G1CollectedHeap::cleanup_surviving_young_words() {
3700 guarantee( _surviving_young_words != NULL, "pre-condition" );
3701 FREE_C_HEAP_ARRAY(size_t, _surviving_young_words, mtGC);
3702 _surviving_young_words = NULL;
3703 }
3704
3705 #ifdef ASSERT
3706 class VerifyCSetClosure: public HeapRegionClosure {
3707 public:
3708 bool doHeapRegion(HeapRegion* hr) {
3709 // Here we check that the CSet region's RSet is ready for parallel
3710 // iteration. The fields that we'll verify are only manipulated
3711 // when the region is part of a CSet and is collected. Afterwards,
3712 // we reset these fields when we clear the region's RSet (when the
3713 // region is freed) so they are ready when the region is
3714 // re-allocated. The only exception to this is if there's an
3715 // evacuation failure and instead of freeing the region we leave
3716 // it in the heap. In that case, we reset these fields during
3717 // evacuation failure handling.
3718 guarantee(hr->rem_set()->verify_ready_for_par_iteration(), "verification");
3719
3720 // Here's a good place to add any other checks we'd like to
3721 // perform on CSet regions.
3722 return false;
3723 }
3724 };
3725 #endif // ASSERT
3726
3727 #if TASKQUEUE_STATS
3728 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
3729 st->print_raw_cr("GC Task Stats");
3730 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
3731 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
3732 }
3733
3734 void G1CollectedHeap::print_taskqueue_stats(outputStream* const st) const {
3735 print_taskqueue_stats_hdr(st);
3736
3737 TaskQueueStats totals;
3738 const int n = workers() != NULL ? workers()->total_workers() : 1;
3739 for (int i = 0; i < n; ++i) {
3740 st->print("%3d ", i); task_queue(i)->stats.print(st); st->cr();
3741 totals += task_queue(i)->stats;
3742 }
3743 st->print_raw("tot "); totals.print(st); st->cr();
3744
3745 DEBUG_ONLY(totals.verify());
3746 }
3747
3748 void G1CollectedHeap::reset_taskqueue_stats() {
3749 const int n = workers() != NULL ? workers()->total_workers() : 1;
3750 for (int i = 0; i < n; ++i) {
3751 task_queue(i)->stats.reset();
3752 }
3753 }
3754 #endif // TASKQUEUE_STATS
3755
3756 void G1CollectedHeap::log_gc_header() {
3757 if (!G1Log::fine()) {
3758 return;
3759 }
3760
3761 gclog_or_tty->date_stamp(PrintGCDateStamps);
3762 gclog_or_tty->stamp(PrintGCTimeStamps);
3763
3764 GCCauseString gc_cause_str = GCCauseString("GC pause", gc_cause())
3765 .append(g1_policy()->gcs_are_young() ? " (young)" : " (mixed)")
3766 .append(g1_policy()->during_initial_mark_pause() ? " (initial-mark)" : "");
3767
3768 gclog_or_tty->print("[%s", (const char*)gc_cause_str);
3769 }
3770
3771 void G1CollectedHeap::log_gc_footer(double pause_time_sec) {
3772 if (!G1Log::fine()) {
3773 return;
3774 }
3775
3776 if (G1Log::finer()) {
3777 if (evacuation_failed()) {
3778 gclog_or_tty->print(" (to-space exhausted)");
3779 }
3780 gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec);
3781 g1_policy()->phase_times()->note_gc_end();
3782 g1_policy()->phase_times()->print(pause_time_sec);
3783 g1_policy()->print_detailed_heap_transition();
3784 } else {
3785 if (evacuation_failed()) {
3786 gclog_or_tty->print("--");
3787 }
3788 g1_policy()->print_heap_transition();
3789 gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec);
3790 }
3791 gclog_or_tty->flush();
3792 }
3793
3794 bool
3795 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
3796 assert_at_safepoint(true /* should_be_vm_thread */);
3797 guarantee(!is_gc_active(), "collection is not reentrant");
3798
3799 if (GC_locker::check_active_before_gc()) {
3800 return false;
3801 }
3802
3803 _gc_timer_stw->register_gc_start(os::elapsed_counter());
3804
3805 _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start());
3806
3807 SvcGCMarker sgcm(SvcGCMarker::MINOR);
3808 ResourceMark rm;
3809
3810 print_heap_before_gc();
3811 trace_heap_before_gc(_gc_tracer_stw);
3812
3813 HRSPhaseSetter x(HRSPhaseEvacuation);
3814 verify_region_sets_optional();
3815 verify_dirty_young_regions();
3816
3817 // This call will decide whether this pause is an initial-mark
3818 // pause. If it is, during_initial_mark_pause() will return true
3819 // for the duration of this pause.
3820 g1_policy()->decide_on_conc_mark_initiation();
3821
3822 // We do not allow initial-mark to be piggy-backed on a mixed GC.
3823 assert(!g1_policy()->during_initial_mark_pause() ||
3824 g1_policy()->gcs_are_young(), "sanity");
3825
3826 // We also do not allow mixed GCs during marking.
3827 assert(!mark_in_progress() || g1_policy()->gcs_are_young(), "sanity");
3828
3829 // Record whether this pause is an initial mark. When the current
3830 // thread has completed its logging output and it's safe to signal
3831 // the CM thread, the flag's value in the policy has been reset.
3832 bool should_start_conc_mark = g1_policy()->during_initial_mark_pause();
3833
3834 // Inner scope for scope based logging, timers, and stats collection
3835 {
3836 EvacuationInfo evacuation_info;
3837
3838 if (g1_policy()->during_initial_mark_pause()) {
3839 // We are about to start a marking cycle, so we increment the
3840 // full collection counter.
3841 increment_old_marking_cycles_started();
3842 register_concurrent_cycle_start(_gc_timer_stw->gc_start());
3843 }
3844
3845 _gc_tracer_stw->report_yc_type(yc_type());
3846
3847 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
3848
3849 int active_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
3850 workers()->active_workers() : 1);
3851 double pause_start_sec = os::elapsedTime();
3852 g1_policy()->phase_times()->note_gc_start(active_workers);
3853 log_gc_header();
3854
3855 TraceCollectorStats tcs(g1mm()->incremental_collection_counters());
3856 TraceMemoryManagerStats tms(false /* fullGC */, gc_cause());
3857
3858 // If the secondary_free_list is not empty, append it to the
3859 // free_list. No need to wait for the cleanup operation to finish;
3860 // the region allocation code will check the secondary_free_list
3861 // and wait if necessary. If the G1StressConcRegionFreeing flag is
3862 // set, skip this step so that the region allocation code has to
3863 // get entries from the secondary_free_list.
3864 if (!G1StressConcRegionFreeing) {
3865 append_secondary_free_list_if_not_empty_with_lock();
3866 }
3867
3868 assert(check_young_list_well_formed(),
3869 "young list should be well formed");
3870
3871 // Don't dynamically change the number of GC threads this early. A value of
3872 // 0 is used to indicate serial work. When parallel work is done,
3873 // it will be set.
3874
3875 { // Call to jvmpi::post_class_unload_events must occur outside of active GC
3876 IsGCActiveMark x;
3877
3878 gc_prologue(false);
3879 increment_total_collections(false /* full gc */);
3880 increment_gc_time_stamp();
3881
3882 verify_before_gc();
3883
3884 COMPILER2_PRESENT(DerivedPointerTable::clear());
3885
3886 // Please see comment in g1CollectedHeap.hpp and
3887 // G1CollectedHeap::ref_processing_init() to see how
3888 // reference processing currently works in G1.
3889
3890 // Enable discovery in the STW reference processor
3891 ref_processor_stw()->enable_discovery(true /*verify_disabled*/,
3892 true /*verify_no_refs*/);
3893
3894 {
3895 // We want to temporarily turn off discovery by the
3896 // CM ref processor, if necessary, and turn it back on
3897 // on again later if we do. Using a scoped
3898 // NoRefDiscovery object will do this.
3899 NoRefDiscovery no_cm_discovery(ref_processor_cm());
3900
3901 // Forget the current alloc region (we might even choose it to be part
3902 // of the collection set!).
3903 release_mutator_alloc_region();
3904
3905 // We should call this after we retire the mutator alloc
3906 // region(s) so that all the ALLOC / RETIRE events are generated
3907 // before the start GC event.
3908 _hr_printer.start_gc(false /* full */, (size_t) total_collections());
3909
3910 // This timing is only used by the ergonomics to handle our pause target.
3911 // It is unclear why this should not include the full pause. We will
3912 // investigate this in CR 7178365.
3913 //
3914 // Preserving the old comment here if that helps the investigation:
3915 //
3916 // The elapsed time induced by the start time below deliberately elides
3917 // the possible verification above.
3918 double sample_start_time_sec = os::elapsedTime();
3919 size_t start_used_bytes = used();
3920
3921 #if YOUNG_LIST_VERBOSE
3922 gclog_or_tty->print_cr("\nBefore recording pause start.\nYoung_list:");
3923 _young_list->print();
3924 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3925 #endif // YOUNG_LIST_VERBOSE
3926
3927 g1_policy()->record_collection_pause_start(sample_start_time_sec,
3928 start_used_bytes);
3929
3930 double scan_wait_start = os::elapsedTime();
3931 // We have to wait until the CM threads finish scanning the
3932 // root regions as it's the only way to ensure that all the
3933 // objects on them have been correctly scanned before we start
3934 // moving them during the GC.
3935 bool waited = _cm->root_regions()->wait_until_scan_finished();
3936 double wait_time_ms = 0.0;
3937 if (waited) {
3938 double scan_wait_end = os::elapsedTime();
3939 wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
3940 }
3941 g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms);
3942
3943 #if YOUNG_LIST_VERBOSE
3944 gclog_or_tty->print_cr("\nAfter recording pause start.\nYoung_list:");
3945 _young_list->print();
3946 #endif // YOUNG_LIST_VERBOSE
3947
3948 if (g1_policy()->during_initial_mark_pause()) {
3949 concurrent_mark()->checkpointRootsInitialPre();
3950 }
3951 perm_gen()->save_marks();
3952
3953 #if YOUNG_LIST_VERBOSE
3954 gclog_or_tty->print_cr("\nBefore choosing collection set.\nYoung_list:");
3955 _young_list->print();
3956 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3957 #endif // YOUNG_LIST_VERBOSE
3958
3959 g1_policy()->finalize_cset(target_pause_time_ms, evacuation_info);
3960
3961 _cm->note_start_of_gc();
3962 // We should not verify the per-thread SATB buffers given that
3963 // we have not filtered them yet (we'll do so during the
3964 // GC). We also call this after finalize_cset() to
3965 // ensure that the CSet has been finalized.
3966 _cm->verify_no_cset_oops(true /* verify_stacks */,
3967 true /* verify_enqueued_buffers */,
3968 false /* verify_thread_buffers */,
3969 true /* verify_fingers */);
3970
3971 if (_hr_printer.is_active()) {
3972 HeapRegion* hr = g1_policy()->collection_set();
3973 while (hr != NULL) {
3974 G1HRPrinter::RegionType type;
3975 if (!hr->is_young()) {
3976 type = G1HRPrinter::Old;
3977 } else if (hr->is_survivor()) {
3978 type = G1HRPrinter::Survivor;
3979 } else {
3980 type = G1HRPrinter::Eden;
3981 }
3982 _hr_printer.cset(hr);
3983 hr = hr->next_in_collection_set();
3984 }
3985 }
3986
3987 #ifdef ASSERT
3988 VerifyCSetClosure cl;
3989 collection_set_iterate(&cl);
3990 #endif // ASSERT
3991
3992 setup_surviving_young_words();
3993
3994 // Initialize the GC alloc regions.
3995 init_gc_alloc_regions(evacuation_info);
3996
3997 // Actually do the work...
3998 evacuate_collection_set(evacuation_info);
3999
4000 // We do this to mainly verify the per-thread SATB buffers
4001 // (which have been filtered by now) since we didn't verify
4002 // them earlier. No point in re-checking the stacks / enqueued
4003 // buffers given that the CSet has not changed since last time
4004 // we checked.
4005 _cm->verify_no_cset_oops(false /* verify_stacks */,
4006 false /* verify_enqueued_buffers */,
4007 true /* verify_thread_buffers */,
4008 true /* verify_fingers */);
4009
4010 free_collection_set(g1_policy()->collection_set(), evacuation_info);
4011 g1_policy()->clear_collection_set();
4012
4013 cleanup_surviving_young_words();
4014
4015 // Start a new incremental collection set for the next pause.
4016 g1_policy()->start_incremental_cset_building();
4017
4018 // Clear the _cset_fast_test bitmap in anticipation of adding
4019 // regions to the incremental collection set for the next
4020 // evacuation pause.
4021 clear_cset_fast_test();
4022
4023 _young_list->reset_sampled_info();
4024
4025 // Don't check the whole heap at this point as the
4026 // GC alloc regions from this pause have been tagged
4027 // as survivors and moved on to the survivor list.
4028 // Survivor regions will fail the !is_young() check.
4029 assert(check_young_list_empty(false /* check_heap */),
4030 "young list should be empty");
4031
4032 #if YOUNG_LIST_VERBOSE
4033 gclog_or_tty->print_cr("Before recording survivors.\nYoung List:");
4034 _young_list->print();
4035 #endif // YOUNG_LIST_VERBOSE
4036
4037 g1_policy()->record_survivor_regions(_young_list->survivor_length(),
4038 _young_list->first_survivor_region(),
4039 _young_list->last_survivor_region());
4040
4041 _young_list->reset_auxilary_lists();
4042
4043 if (evacuation_failed()) {
4044 _summary_bytes_used = recalculate_used();
4045 } else {
4046 // The "used" of the the collection set have already been subtracted
4047 // when they were freed. Add in the bytes evacuated.
4048 _summary_bytes_used += g1_policy()->bytes_copied_during_gc();
4049 }
4050
4051 if (g1_policy()->during_initial_mark_pause()) {
4052 // We have to do this before we notify the CM threads that
4053 // they can start working to make sure that all the
4054 // appropriate initialization is done on the CM object.
4055 concurrent_mark()->checkpointRootsInitialPost();
4056 set_marking_started();
4057 // Note that we don't actually trigger the CM thread at
4058 // this point. We do that later when we're sure that
4059 // the current thread has completed its logging output.
4060 }
4061
4062 allocate_dummy_regions();
4063
4064 #if YOUNG_LIST_VERBOSE
4065 gclog_or_tty->print_cr("\nEnd of the pause.\nYoung_list:");
4066 _young_list->print();
4067 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
4068 #endif // YOUNG_LIST_VERBOSE
4069
4070 init_mutator_alloc_region();
4071
4072 {
4073 size_t expand_bytes = g1_policy()->expansion_amount();
4074 if (expand_bytes > 0) {
4075 size_t bytes_before = capacity();
4076 // No need for an ergo verbose message here,
4077 // expansion_amount() does this when it returns a value > 0.
4078 if (!expand(expand_bytes)) {
4079 // We failed to expand the heap so let's verify that
4080 // committed/uncommitted amount match the backing store
4081 assert(capacity() == _g1_storage.committed_size(), "committed size mismatch");
4082 assert(max_capacity() == _g1_storage.reserved_size(), "reserved size mismatch");
4083 }
4084 }
4085 }
4086
4087 // We redo the verification but now wrt to the new CSet which
4088 // has just got initialized after the previous CSet was freed.
4089 _cm->verify_no_cset_oops(true /* verify_stacks */,
4090 true /* verify_enqueued_buffers */,
4091 true /* verify_thread_buffers */,
4092 true /* verify_fingers */);
4093 _cm->note_end_of_gc();
4094
4095 // This timing is only used by the ergonomics to handle our pause target.
4096 // It is unclear why this should not include the full pause. We will
4097 // investigate this in CR 7178365.
4098 double sample_end_time_sec = os::elapsedTime();
4099 double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
4100 g1_policy()->record_collection_pause_end(pause_time_ms, evacuation_info);
4101
4102 MemoryService::track_memory_usage();
4103
4104 // In prepare_for_verify() below we'll need to scan the deferred
4105 // update buffers to bring the RSets up-to-date if
4106 // G1HRRSFlushLogBuffersOnVerify has been set. While scanning
4107 // the update buffers we'll probably need to scan cards on the
4108 // regions we just allocated to (i.e., the GC alloc
4109 // regions). However, during the last GC we called
4110 // set_saved_mark() on all the GC alloc regions, so card
4111 // scanning might skip the [saved_mark_word()...top()] area of
4112 // those regions (i.e., the area we allocated objects into
4113 // during the last GC). But it shouldn't. Given that
4114 // saved_mark_word() is conditional on whether the GC time stamp
4115 // on the region is current or not, by incrementing the GC time
4116 // stamp here we invalidate all the GC time stamps on all the
4117 // regions and saved_mark_word() will simply return top() for
4118 // all the regions. This is a nicer way of ensuring this rather
4119 // than iterating over the regions and fixing them. In fact, the
4120 // GC time stamp increment here also ensures that
4121 // saved_mark_word() will return top() between pauses, i.e.,
4122 // during concurrent refinement. So we don't need the
4123 // is_gc_active() check to decided which top to use when
4124 // scanning cards (see CR 7039627).
4125 increment_gc_time_stamp();
4126
4127 verify_after_gc();
4128
4129 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
4130 ref_processor_stw()->verify_no_references_recorded();
4131
4132 // CM reference discovery will be re-enabled if necessary.
4133 }
4134
4135 // We should do this after we potentially expand the heap so
4136 // that all the COMMIT events are generated before the end GC
4137 // event, and after we retire the GC alloc regions so that all
4138 // RETIRE events are generated before the end GC event.
4139 _hr_printer.end_gc(false /* full */, (size_t) total_collections());
4140
4141 if (mark_in_progress()) {
4142 concurrent_mark()->update_g1_committed();
4143 }
4144
4145 #ifdef TRACESPINNING
4146 ParallelTaskTerminator::print_termination_counts();
4147 #endif
4148
4149 gc_epilogue(false);
4150 }
4151
4152 // Print the remainder of the GC log output.
4153 log_gc_footer(os::elapsedTime() - pause_start_sec);
4154
4155 // It is not yet to safe to tell the concurrent mark to
4156 // start as we have some optional output below. We don't want the
4157 // output from the concurrent mark thread interfering with this
4158 // logging output either.
4159
4160 _hrs.verify_optional();
4161 verify_region_sets_optional();
4162
4163 TASKQUEUE_STATS_ONLY(if (ParallelGCVerbose) print_taskqueue_stats());
4164 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
4165
4166 print_heap_after_gc();
4167 trace_heap_after_gc(_gc_tracer_stw);
4168
4169 // We must call G1MonitoringSupport::update_sizes() in the same scoping level
4170 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
4171 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
4172 // before any GC notifications are raised.
4173 g1mm()->update_sizes();
4174
4175 _gc_tracer_stw->report_evacuation_info(&evacuation_info);
4176 _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold());
4177 _gc_timer_stw->register_gc_end(os::elapsed_counter());
4178 _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions());
4179 }
4180
4181 if (G1SummarizeRSetStats &&
4182 (G1SummarizeRSetStatsPeriod > 0) &&
4183 (total_collections() % G1SummarizeRSetStatsPeriod == 0)) {
4184 g1_rem_set()->print_summary_info();
4185 }
4186 // It should now be safe to tell the concurrent mark thread to start
4187 // without its logging output interfering with the logging output
4188 // that came from the pause.
4189
4190 if (should_start_conc_mark) {
4191 // CAUTION: after the doConcurrentMark() call below,
4192 // the concurrent marking thread(s) could be running
4193 // concurrently with us. Make sure that anything after
4194 // this point does not assume that we are the only GC thread
4195 // running. Note: of course, the actual marking work will
4196 // not start until the safepoint itself is released in
4197 // ConcurrentGCThread::safepoint_desynchronize().
4198 doConcurrentMark();
4199 }
4200
4201 return true;
4202 }
4203
4204 size_t G1CollectedHeap::desired_plab_sz(GCAllocPurpose purpose)
4205 {
4206 size_t gclab_word_size;
4207 switch (purpose) {
4208 case GCAllocForSurvived:
4209 gclab_word_size = _survivor_plab_stats.desired_plab_sz();
4210 break;
4211 case GCAllocForTenured:
4212 gclab_word_size = _old_plab_stats.desired_plab_sz();
4213 break;
4214 default:
4215 assert(false, "unknown GCAllocPurpose");
4216 gclab_word_size = _old_plab_stats.desired_plab_sz();
4217 break;
4218 }
4219
4220 // Prevent humongous PLAB sizes for two reasons:
4221 // * PLABs are allocated using a similar paths as oops, but should
4222 // never be in a humongous region
4223 // * Allowing humongous PLABs needlessly churns the region free lists
4224 return MIN2(_humongous_object_threshold_in_words, gclab_word_size);
4225 }
4226
4227 void G1CollectedHeap::init_mutator_alloc_region() {
4228 assert(_mutator_alloc_region.get() == NULL, "pre-condition");
4229 _mutator_alloc_region.init();
4230 }
4231
4232 void G1CollectedHeap::release_mutator_alloc_region() {
4233 _mutator_alloc_region.release();
4234 assert(_mutator_alloc_region.get() == NULL, "post-condition");
4235 }
4236
4237 void G1CollectedHeap::init_gc_alloc_regions(EvacuationInfo& evacuation_info) {
4238 assert_at_safepoint(true /* should_be_vm_thread */);
4239
4240 _survivor_gc_alloc_region.init();
4241 _old_gc_alloc_region.init();
4242 HeapRegion* retained_region = _retained_old_gc_alloc_region;
4243 _retained_old_gc_alloc_region = NULL;
4244
4245 // We will discard the current GC alloc region if:
4246 // a) it's in the collection set (it can happen!),
4247 // b) it's already full (no point in using it),
4248 // c) it's empty (this means that it was emptied during
4249 // a cleanup and it should be on the free list now), or
4250 // d) it's humongous (this means that it was emptied
4251 // during a cleanup and was added to the free list, but
4252 // has been subsequently used to allocate a humongous
4253 // object that may be less than the region size).
4254 if (retained_region != NULL &&
4255 !retained_region->in_collection_set() &&
4256 !(retained_region->top() == retained_region->end()) &&
4257 !retained_region->is_empty() &&
4258 !retained_region->isHumongous()) {
4259 retained_region->set_saved_mark();
4260 // The retained region was added to the old region set when it was
4261 // retired. We have to remove it now, since we don't allow regions
4262 // we allocate to in the region sets. We'll re-add it later, when
4263 // it's retired again.
4264 _old_set.remove(retained_region);
4265 bool during_im = g1_policy()->during_initial_mark_pause();
4266 retained_region->note_start_of_copying(during_im);
4267 _old_gc_alloc_region.set(retained_region);
4268 _hr_printer.reuse(retained_region);
4269 evacuation_info.set_alloc_regions_used_before(retained_region->used());
4270 }
4271 }
4272
4273 void G1CollectedHeap::release_gc_alloc_regions(uint no_of_gc_workers, EvacuationInfo& evacuation_info) {
4274 evacuation_info.set_allocation_regions(_survivor_gc_alloc_region.count() +
4275 _old_gc_alloc_region.count());
4276 _survivor_gc_alloc_region.release();
4277 // If we have an old GC alloc region to release, we'll save it in
4278 // _retained_old_gc_alloc_region. If we don't
4279 // _retained_old_gc_alloc_region will become NULL. This is what we
4280 // want either way so no reason to check explicitly for either
4281 // condition.
4282 _retained_old_gc_alloc_region = _old_gc_alloc_region.release();
4283
4284 if (ResizePLAB) {
4285 _survivor_plab_stats.adjust_desired_plab_sz(no_of_gc_workers);
4286 _old_plab_stats.adjust_desired_plab_sz(no_of_gc_workers);
4287 }
4288 }
4289
4290 void G1CollectedHeap::abandon_gc_alloc_regions() {
4291 assert(_survivor_gc_alloc_region.get() == NULL, "pre-condition");
4292 assert(_old_gc_alloc_region.get() == NULL, "pre-condition");
4293 _retained_old_gc_alloc_region = NULL;
4294 }
4295
4296 void G1CollectedHeap::init_for_evac_failure(OopsInHeapRegionClosure* cl) {
4297 _drain_in_progress = false;
4298 set_evac_failure_closure(cl);
4299 _evac_failure_scan_stack = new (ResourceObj::C_HEAP, mtGC) GrowableArray<oop>(40, true);
4300 }
4301
4302 void G1CollectedHeap::finalize_for_evac_failure() {
4303 assert(_evac_failure_scan_stack != NULL &&
4304 _evac_failure_scan_stack->length() == 0,
4305 "Postcondition");
4306 assert(!_drain_in_progress, "Postcondition");
4307 delete _evac_failure_scan_stack;
4308 _evac_failure_scan_stack = NULL;
4309 }
4310
4311 void G1CollectedHeap::remove_self_forwarding_pointers() {
4312 assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity");
4313
4314 G1ParRemoveSelfForwardPtrsTask rsfp_task(this);
4315
4316 if (G1CollectedHeap::use_parallel_gc_threads()) {
4317 set_par_threads();
4318 workers()->run_task(&rsfp_task);
4319 set_par_threads(0);
4320 } else {
4321 rsfp_task.work(0);
4322 }
4323
4324 assert(check_cset_heap_region_claim_values(HeapRegion::ParEvacFailureClaimValue), "sanity");
4325
4326 // Reset the claim values in the regions in the collection set.
4327 reset_cset_heap_region_claim_values();
4328
4329 assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity");
4330
4331 // Now restore saved marks, if any.
4332 assert(_objs_with_preserved_marks.size() ==
4333 _preserved_marks_of_objs.size(), "Both or none.");
4334 while (!_objs_with_preserved_marks.is_empty()) {
4335 oop obj = _objs_with_preserved_marks.pop();
4336 markOop m = _preserved_marks_of_objs.pop();
4337 obj->set_mark(m);
4338 }
4339 _objs_with_preserved_marks.clear(true);
4340 _preserved_marks_of_objs.clear(true);
4341 }
4342
4343 void G1CollectedHeap::push_on_evac_failure_scan_stack(oop obj) {
4344 _evac_failure_scan_stack->push(obj);
4345 }
4346
4347 void G1CollectedHeap::drain_evac_failure_scan_stack() {
4348 assert(_evac_failure_scan_stack != NULL, "precondition");
4349
4350 while (_evac_failure_scan_stack->length() > 0) {
4351 oop obj = _evac_failure_scan_stack->pop();
4352 _evac_failure_closure->set_region(heap_region_containing(obj));
4353 obj->oop_iterate_backwards(_evac_failure_closure);
4354 }
4355 }
4356
4357 oop
4358 G1CollectedHeap::handle_evacuation_failure_par(OopsInHeapRegionClosure* cl,
4359 oop old) {
4360 assert(obj_in_cs(old),
4361 err_msg("obj: "PTR_FORMAT" should still be in the CSet",
4362 (HeapWord*) old));
4363 markOop m = old->mark();
4364 oop forward_ptr = old->forward_to_atomic(old);
4365 if (forward_ptr == NULL) {
4366 // Forward-to-self succeeded.
4367
4368 if (_evac_failure_closure != cl) {
4369 MutexLockerEx x(EvacFailureStack_lock, Mutex::_no_safepoint_check_flag);
4370 assert(!_drain_in_progress,
4371 "Should only be true while someone holds the lock.");
4372 // Set the global evac-failure closure to the current thread's.
4373 assert(_evac_failure_closure == NULL, "Or locking has failed.");
4374 set_evac_failure_closure(cl);
4375 // Now do the common part.
4376 handle_evacuation_failure_common(old, m);
4377 // Reset to NULL.
4378 set_evac_failure_closure(NULL);
4379 } else {
4380 // The lock is already held, and this is recursive.
4381 assert(_drain_in_progress, "This should only be the recursive case.");
4382 handle_evacuation_failure_common(old, m);
4383 }
4384 return old;
4385 } else {
4386 // Forward-to-self failed. Either someone else managed to allocate
4387 // space for this object (old != forward_ptr) or they beat us in
4388 // self-forwarding it (old == forward_ptr).
4389 assert(old == forward_ptr || !obj_in_cs(forward_ptr),
4390 err_msg("obj: "PTR_FORMAT" forwarded to: "PTR_FORMAT" "
4391 "should not be in the CSet",
4392 (HeapWord*) old, (HeapWord*) forward_ptr));
4393 return forward_ptr;
4394 }
4395 }
4396
4397 void G1CollectedHeap::handle_evacuation_failure_common(oop old, markOop m) {
4398 set_evacuation_failed(true);
4399
4400 preserve_mark_if_necessary(old, m);
4401
4402 HeapRegion* r = heap_region_containing(old);
4403 if (!r->evacuation_failed()) {
4404 r->set_evacuation_failed(true);
4405 _hr_printer.evac_failure(r);
4406 }
4407
4408 push_on_evac_failure_scan_stack(old);
4409
4410 if (!_drain_in_progress) {
4411 // prevent recursion in copy_to_survivor_space()
4412 _drain_in_progress = true;
4413 drain_evac_failure_scan_stack();
4414 _drain_in_progress = false;
4415 }
4416 }
4417
4418 void G1CollectedHeap::preserve_mark_if_necessary(oop obj, markOop m) {
4419 assert(evacuation_failed(), "Oversaving!");
4420 // We want to call the "for_promotion_failure" version only in the
4421 // case of a promotion failure.
4422 if (m->must_be_preserved_for_promotion_failure(obj)) {
4423 _objs_with_preserved_marks.push(obj);
4424 _preserved_marks_of_objs.push(m);
4425 }
4426 }
4427
4428 HeapWord* G1CollectedHeap::par_allocate_during_gc(GCAllocPurpose purpose,
4429 size_t word_size) {
4430 if (purpose == GCAllocForSurvived) {
4431 HeapWord* result = survivor_attempt_allocation(word_size);
4432 if (result != NULL) {
4433 return result;
4434 } else {
4435 // Let's try to allocate in the old gen in case we can fit the
4436 // object there.
4437 return old_attempt_allocation(word_size);
4438 }
4439 } else {
4440 assert(purpose == GCAllocForTenured, "sanity");
4441 HeapWord* result = old_attempt_allocation(word_size);
4442 if (result != NULL) {
4443 return result;
4444 } else {
4445 // Let's try to allocate in the survivors in case we can fit the
4446 // object there.
4447 return survivor_attempt_allocation(word_size);
4448 }
4449 }
4450
4451 ShouldNotReachHere();
4452 // Trying to keep some compilers happy.
4453 return NULL;
4454 }
4455
4456 G1ParGCAllocBuffer::G1ParGCAllocBuffer(size_t gclab_word_size) :
4457 ParGCAllocBuffer(gclab_word_size), _retired(false) { }
4458
4459 G1ParScanThreadState::G1ParScanThreadState(G1CollectedHeap* g1h, uint queue_num)
4460 : _g1h(g1h),
4461 _refs(g1h->task_queue(queue_num)),
4462 _dcq(&g1h->dirty_card_queue_set()),
4463 _ct_bs((CardTableModRefBS*)_g1h->barrier_set()),
4464 _g1_rem(g1h->g1_rem_set()),
4465 _hash_seed(17), _queue_num(queue_num),
4466 _term_attempts(0),
4467 _surviving_alloc_buffer(g1h->desired_plab_sz(GCAllocForSurvived)),
4468 _tenured_alloc_buffer(g1h->desired_plab_sz(GCAllocForTenured)),
4469 _age_table(false),
4470 _strong_roots_time(0), _term_time(0),
4471 _alloc_buffer_waste(0), _undo_waste(0) {
4472 // we allocate G1YoungSurvRateNumRegions plus one entries, since
4473 // we "sacrifice" entry 0 to keep track of surviving bytes for
4474 // non-young regions (where the age is -1)
4475 // We also add a few elements at the beginning and at the end in
4476 // an attempt to eliminate cache contention
4477 uint real_length = 1 + _g1h->g1_policy()->young_cset_region_length();
4478 uint array_length = PADDING_ELEM_NUM +
4479 real_length +
4480 PADDING_ELEM_NUM;
4481 _surviving_young_words_base = NEW_C_HEAP_ARRAY(size_t, array_length, mtGC);
4482 if (_surviving_young_words_base == NULL)
4483 vm_exit_out_of_memory(array_length * sizeof(size_t),
4484 "Not enough space for young surv histo.");
4485 _surviving_young_words = _surviving_young_words_base + PADDING_ELEM_NUM;
4486 memset(_surviving_young_words, 0, (size_t) real_length * sizeof(size_t));
4487
4488 _alloc_buffers[GCAllocForSurvived] = &_surviving_alloc_buffer;
4489 _alloc_buffers[GCAllocForTenured] = &_tenured_alloc_buffer;
4490
4491 _start = os::elapsedTime();
4492 }
4493
4494 void
4495 G1ParScanThreadState::print_termination_stats_hdr(outputStream* const st)
4496 {
4497 st->print_raw_cr("GC Termination Stats");
4498 st->print_raw_cr(" elapsed --strong roots-- -------termination-------"
4499 " ------waste (KiB)------");
4500 st->print_raw_cr("thr ms ms % ms % attempts"
4501 " total alloc undo");
4502 st->print_raw_cr("--- --------- --------- ------ --------- ------ --------"
4503 " ------- ------- -------");
4504 }
4505
4506 void
4507 G1ParScanThreadState::print_termination_stats(int i,
4508 outputStream* const st) const
4509 {
4510 const double elapsed_ms = elapsed_time() * 1000.0;
4511 const double s_roots_ms = strong_roots_time() * 1000.0;
4512 const double term_ms = term_time() * 1000.0;
4513 st->print_cr("%3d %9.2f %9.2f %6.2f "
4514 "%9.2f %6.2f " SIZE_FORMAT_W(8) " "
4515 SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7),
4516 i, elapsed_ms, s_roots_ms, s_roots_ms * 100 / elapsed_ms,
4517 term_ms, term_ms * 100 / elapsed_ms, term_attempts(),
4518 (alloc_buffer_waste() + undo_waste()) * HeapWordSize / K,
4519 alloc_buffer_waste() * HeapWordSize / K,
4520 undo_waste() * HeapWordSize / K);
4521 }
4522
4523 #ifdef ASSERT
4524 bool G1ParScanThreadState::verify_ref(narrowOop* ref) const {
4525 assert(ref != NULL, "invariant");
4526 assert(UseCompressedOops, "sanity");
4527 assert(!has_partial_array_mask(ref), err_msg("ref=" PTR_FORMAT, ref));
4528 oop p = oopDesc::load_decode_heap_oop(ref);
4529 assert(_g1h->is_in_g1_reserved(p),
4530 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p)));
4531 return true;
4532 }
4533
4534 bool G1ParScanThreadState::verify_ref(oop* ref) const {
4535 assert(ref != NULL, "invariant");
4536 if (has_partial_array_mask(ref)) {
4537 // Must be in the collection set--it's already been copied.
4538 oop p = clear_partial_array_mask(ref);
4539 assert(_g1h->obj_in_cs(p),
4540 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p)));
4541 } else {
4542 oop p = oopDesc::load_decode_heap_oop(ref);
4543 assert(_g1h->is_in_g1_reserved(p),
4544 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p)));
4545 }
4546 return true;
4547 }
4548
4549 bool G1ParScanThreadState::verify_task(StarTask ref) const {
4550 if (ref.is_narrow()) {
4551 return verify_ref((narrowOop*) ref);
4552 } else {
4553 return verify_ref((oop*) ref);
4554 }
4555 }
4556 #endif // ASSERT
4557
4558 void G1ParScanThreadState::trim_queue() {
4559 assert(_evac_cl != NULL, "not set");
4560 assert(_evac_failure_cl != NULL, "not set");
4561 assert(_partial_scan_cl != NULL, "not set");
4562
4563 StarTask ref;
4564 do {
4565 // Drain the overflow stack first, so other threads can steal.
4566 while (refs()->pop_overflow(ref)) {
4567 deal_with_reference(ref);
4568 }
4569
4570 while (refs()->pop_local(ref)) {
4571 deal_with_reference(ref);
4572 }
4573 } while (!refs()->is_empty());
4574 }
4575
4576 G1ParClosureSuper::G1ParClosureSuper(G1CollectedHeap* g1,
4577 G1ParScanThreadState* par_scan_state) :
4578 _g1(g1), _g1_rem(_g1->g1_rem_set()), _cm(_g1->concurrent_mark()),
4579 _par_scan_state(par_scan_state),
4580 _worker_id(par_scan_state->queue_num()),
4581 _during_initial_mark(_g1->g1_policy()->during_initial_mark_pause()),
4582 _mark_in_progress(_g1->mark_in_progress()) { }
4583
4584 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object>
4585 void G1ParCopyClosure<do_gen_barrier, barrier, do_mark_object>::mark_object(oop obj) {
4586 #ifdef ASSERT
4587 HeapRegion* hr = _g1->heap_region_containing(obj);
4588 assert(hr != NULL, "sanity");
4589 assert(!hr->in_collection_set(), "should not mark objects in the CSet");
4590 #endif // ASSERT
4591
4592 // We know that the object is not moving so it's safe to read its size.
4593 _cm->grayRoot(obj, (size_t) obj->size(), _worker_id);
4594 }
4595
4596 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object>
4597 void G1ParCopyClosure<do_gen_barrier, barrier, do_mark_object>
4598 ::mark_forwarded_object(oop from_obj, oop to_obj) {
4599 #ifdef ASSERT
4600 assert(from_obj->is_forwarded(), "from obj should be forwarded");
4601 assert(from_obj->forwardee() == to_obj, "to obj should be the forwardee");
4602 assert(from_obj != to_obj, "should not be self-forwarded");
4603
4604 HeapRegion* from_hr = _g1->heap_region_containing(from_obj);
4605 assert(from_hr != NULL, "sanity");
4606 assert(from_hr->in_collection_set(), "from obj should be in the CSet");
4607
4608 HeapRegion* to_hr = _g1->heap_region_containing(to_obj);
4609 assert(to_hr != NULL, "sanity");
4610 assert(!to_hr->in_collection_set(), "should not mark objects in the CSet");
4611 #endif // ASSERT
4612
4613 // The object might be in the process of being copied by another
4614 // worker so we cannot trust that its to-space image is
4615 // well-formed. So we have to read its size from its from-space
4616 // image which we know should not be changing.
4617 _cm->grayRoot(to_obj, (size_t) from_obj->size(), _worker_id);
4618 }
4619
4620 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object>
4621 oop G1ParCopyClosure<do_gen_barrier, barrier, do_mark_object>
4622 ::copy_to_survivor_space(oop old) {
4623 size_t word_sz = old->size();
4624 HeapRegion* from_region = _g1->heap_region_containing_raw(old);
4625 // +1 to make the -1 indexes valid...
4626 int young_index = from_region->young_index_in_cset()+1;
4627 assert( (from_region->is_young() && young_index > 0) ||
4628 (!from_region->is_young() && young_index == 0), "invariant" );
4629 G1CollectorPolicy* g1p = _g1->g1_policy();
4630 markOop m = old->mark();
4631 int age = m->has_displaced_mark_helper() ? m->displaced_mark_helper()->age()
4632 : m->age();
4633 GCAllocPurpose alloc_purpose = g1p->evacuation_destination(from_region, age,
4634 word_sz);
4635 HeapWord* obj_ptr = _par_scan_state->allocate(alloc_purpose, word_sz);
4636 #ifndef PRODUCT
4637 // Should this evacuation fail?
4638 if (_g1->evacuation_should_fail()) {
4639 if (obj_ptr != NULL) {
4640 _par_scan_state->undo_allocation(alloc_purpose, obj_ptr, word_sz);
4641 obj_ptr = NULL;
4642 }
4643 }
4644 #endif // !PRODUCT
4645
4646 if (obj_ptr == NULL) {
4647 // This will either forward-to-self, or detect that someone else has
4648 // installed a forwarding pointer.
4649 OopsInHeapRegionClosure* cl = _par_scan_state->evac_failure_closure();
4650 return _g1->handle_evacuation_failure_par(cl, old);
4651 }
4652
4653 oop obj = oop(obj_ptr);
4654
4655 // We're going to allocate linearly, so might as well prefetch ahead.
4656 Prefetch::write(obj_ptr, PrefetchCopyIntervalInBytes);
4657
4658 oop forward_ptr = old->forward_to_atomic(obj);
4659 if (forward_ptr == NULL) {
4660 Copy::aligned_disjoint_words((HeapWord*) old, obj_ptr, word_sz);
4661 if (g1p->track_object_age(alloc_purpose)) {
4662 // We could simply do obj->incr_age(). However, this causes a
4663 // performance issue. obj->incr_age() will first check whether
4664 // the object has a displaced mark by checking its mark word;
4665 // getting the mark word from the new location of the object
4666 // stalls. So, given that we already have the mark word and we
4667 // are about to install it anyway, it's better to increase the
4668 // age on the mark word, when the object does not have a
4669 // displaced mark word. We're not expecting many objects to have
4670 // a displaced marked word, so that case is not optimized
4671 // further (it could be...) and we simply call obj->incr_age().
4672
4673 if (m->has_displaced_mark_helper()) {
4674 // in this case, we have to install the mark word first,
4675 // otherwise obj looks to be forwarded (the old mark word,
4676 // which contains the forward pointer, was copied)
4677 obj->set_mark(m);
4678 obj->incr_age();
4679 } else {
4680 m = m->incr_age();
4681 obj->set_mark(m);
4682 }
4683 _par_scan_state->age_table()->add(obj, word_sz);
4684 } else {
4685 obj->set_mark(m);
4686 }
4687
4688 size_t* surv_young_words = _par_scan_state->surviving_young_words();
4689 surv_young_words[young_index] += word_sz;
4690
4691 if (obj->is_objArray() && arrayOop(obj)->length() >= ParGCArrayScanChunk) {
4692 // We keep track of the next start index in the length field of
4693 // the to-space object. The actual length can be found in the
4694 // length field of the from-space object.
4695 arrayOop(obj)->set_length(0);
4696 oop* old_p = set_partial_array_mask(old);
4697 _par_scan_state->push_on_queue(old_p);
4698 } else {
4699 // No point in using the slower heap_region_containing() method,
4700 // given that we know obj is in the heap.
4701 _scanner.set_region(_g1->heap_region_containing_raw(obj));
4702 obj->oop_iterate_backwards(&_scanner);
4703 }
4704 } else {
4705 _par_scan_state->undo_allocation(alloc_purpose, obj_ptr, word_sz);
4706 obj = forward_ptr;
4707 }
4708 return obj;
4709 }
4710
4711 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object>
4712 template <class T>
4713 void G1ParCopyClosure<do_gen_barrier, barrier, do_mark_object>
4714 ::do_oop_work(T* p) {
4715 oop obj = oopDesc::load_decode_heap_oop(p);
4716 assert(barrier != G1BarrierRS || obj != NULL,
4717 "Precondition: G1BarrierRS implies obj is non-NULL");
4718
4719 assert(_worker_id == _par_scan_state->queue_num(), "sanity");
4720
4721 // here the null check is implicit in the cset_fast_test() test
4722 if (_g1->in_cset_fast_test(obj)) {
4723 oop forwardee;
4724 if (obj->is_forwarded()) {
4725 forwardee = obj->forwardee();
4726 } else {
4727 forwardee = copy_to_survivor_space(obj);
4728 }
4729 assert(forwardee != NULL, "forwardee should not be NULL");
4730 oopDesc::encode_store_heap_oop(p, forwardee);
4731 if (do_mark_object && forwardee != obj) {
4732 // If the object is self-forwarded we don't need to explicitly
4733 // mark it, the evacuation failure protocol will do so.
4734 mark_forwarded_object(obj, forwardee);
4735 }
4736
4737 // When scanning the RS, we only care about objs in CS.
4738 if (barrier == G1BarrierRS) {
4739 _par_scan_state->update_rs(_from, p, _worker_id);
4740 }
4741 } else {
4742 // The object is not in collection set. If we're a root scanning
4743 // closure during an initial mark pause (i.e. do_mark_object will
4744 // be true) then attempt to mark the object.
4745 if (do_mark_object && _g1->is_in_g1_reserved(obj)) {
4746 mark_object(obj);
4747 }
4748 }
4749
4750 if (barrier == G1BarrierEvac && obj != NULL) {
4751 _par_scan_state->update_rs(_from, p, _worker_id);
4752 }
4753
4754 if (do_gen_barrier && obj != NULL) {
4755 par_do_barrier(p);
4756 }
4757 }
4758
4759 template void G1ParCopyClosure<false, G1BarrierEvac, false>::do_oop_work(oop* p);
4760 template void G1ParCopyClosure<false, G1BarrierEvac, false>::do_oop_work(narrowOop* p);
4761
4762 template <class T> void G1ParScanPartialArrayClosure::do_oop_nv(T* p) {
4763 assert(has_partial_array_mask(p), "invariant");
4764 oop from_obj = clear_partial_array_mask(p);
4765
4766 assert(Universe::heap()->is_in_reserved(from_obj), "must be in heap.");
4767 assert(from_obj->is_objArray(), "must be obj array");
4768 objArrayOop from_obj_array = objArrayOop(from_obj);
4769 // The from-space object contains the real length.
4770 int length = from_obj_array->length();
4771
4772 assert(from_obj->is_forwarded(), "must be forwarded");
4773 oop to_obj = from_obj->forwardee();
4774 assert(from_obj != to_obj, "should not be chunking self-forwarded objects");
4775 objArrayOop to_obj_array = objArrayOop(to_obj);
4776 // We keep track of the next start index in the length field of the
4777 // to-space object.
4778 int next_index = to_obj_array->length();
4779 assert(0 <= next_index && next_index < length,
4780 err_msg("invariant, next index: %d, length: %d", next_index, length));
4781
4782 int start = next_index;
4783 int end = length;
4784 int remainder = end - start;
4785 // We'll try not to push a range that's smaller than ParGCArrayScanChunk.
4786 if (remainder > 2 * ParGCArrayScanChunk) {
4787 end = start + ParGCArrayScanChunk;
4788 to_obj_array->set_length(end);
4789 // Push the remainder before we process the range in case another
4790 // worker has run out of things to do and can steal it.
4791 oop* from_obj_p = set_partial_array_mask(from_obj);
4792 _par_scan_state->push_on_queue(from_obj_p);
4793 } else {
4794 assert(length == end, "sanity");
4795 // We'll process the final range for this object. Restore the length
4796 // so that the heap remains parsable in case of evacuation failure.
4797 to_obj_array->set_length(end);
4798 }
4799 _scanner.set_region(_g1->heap_region_containing_raw(to_obj));
4800 // Process indexes [start,end). It will also process the header
4801 // along with the first chunk (i.e., the chunk with start == 0).
4802 // Note that at this point the length field of to_obj_array is not
4803 // correct given that we are using it to keep track of the next
4804 // start index. oop_iterate_range() (thankfully!) ignores the length
4805 // field and only relies on the start / end parameters. It does
4806 // however return the size of the object which will be incorrect. So
4807 // we have to ignore it even if we wanted to use it.
4808 to_obj_array->oop_iterate_range(&_scanner, start, end);
4809 }
4810
4811 class G1ParEvacuateFollowersClosure : public VoidClosure {
4812 protected:
4813 G1CollectedHeap* _g1h;
4814 G1ParScanThreadState* _par_scan_state;
4815 RefToScanQueueSet* _queues;
4816 ParallelTaskTerminator* _terminator;
4817
4818 G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
4819 RefToScanQueueSet* queues() { return _queues; }
4820 ParallelTaskTerminator* terminator() { return _terminator; }
4821
4822 public:
4823 G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h,
4824 G1ParScanThreadState* par_scan_state,
4825 RefToScanQueueSet* queues,
4826 ParallelTaskTerminator* terminator)
4827 : _g1h(g1h), _par_scan_state(par_scan_state),
4828 _queues(queues), _terminator(terminator) {}
4829
4830 void do_void();
4831
4832 private:
4833 inline bool offer_termination();
4834 };
4835
4836 bool G1ParEvacuateFollowersClosure::offer_termination() {
4837 G1ParScanThreadState* const pss = par_scan_state();
4838 pss->start_term_time();
4839 const bool res = terminator()->offer_termination();
4840 pss->end_term_time();
4841 return res;
4842 }
4843
4844 void G1ParEvacuateFollowersClosure::do_void() {
4845 StarTask stolen_task;
4846 G1ParScanThreadState* const pss = par_scan_state();
4847 pss->trim_queue();
4848
4849 do {
4850 while (queues()->steal(pss->queue_num(), pss->hash_seed(), stolen_task)) {
4851 assert(pss->verify_task(stolen_task), "sanity");
4852 if (stolen_task.is_narrow()) {
4853 pss->deal_with_reference((narrowOop*) stolen_task);
4854 } else {
4855 pss->deal_with_reference((oop*) stolen_task);
4856 }
4857
4858 // We've just processed a reference and we might have made
4859 // available new entries on the queues. So we have to make sure
4860 // we drain the queues as necessary.
4861 pss->trim_queue();
4862 }
4863 } while (!offer_termination());
4864
4865 pss->retire_alloc_buffers();
4866 }
4867
4868 class G1ParTask : public AbstractGangTask {
4869 protected:
4870 G1CollectedHeap* _g1h;
4871 RefToScanQueueSet *_queues;
4872 ParallelTaskTerminator _terminator;
4873 uint _n_workers;
4874
4875 Mutex _stats_lock;
4876 Mutex* stats_lock() { return &_stats_lock; }
4877
4878 size_t getNCards() {
4879 return (_g1h->capacity() + G1BlockOffsetSharedArray::N_bytes - 1)
4880 / G1BlockOffsetSharedArray::N_bytes;
4881 }
4882
4883 public:
4884 G1ParTask(G1CollectedHeap* g1h,
4885 RefToScanQueueSet *task_queues)
4886 : AbstractGangTask("G1 collection"),
4887 _g1h(g1h),
4888 _queues(task_queues),
4889 _terminator(0, _queues),
4890 _stats_lock(Mutex::leaf, "parallel G1 stats lock", true)
4891 {}
4892
4893 RefToScanQueueSet* queues() { return _queues; }
4894
4895 RefToScanQueue *work_queue(int i) {
4896 return queues()->queue(i);
4897 }
4898
4899 ParallelTaskTerminator* terminator() { return &_terminator; }
4900
4901 virtual void set_for_termination(int active_workers) {
4902 // This task calls set_n_termination() in par_non_clean_card_iterate_work()
4903 // in the young space (_par_seq_tasks) in the G1 heap
4904 // for SequentialSubTasksDone.
4905 // This task also uses SubTasksDone in SharedHeap and G1CollectedHeap
4906 // both of which need setting by set_n_termination().
4907 _g1h->SharedHeap::set_n_termination(active_workers);
4908 _g1h->set_n_termination(active_workers);
4909 terminator()->reset_for_reuse(active_workers);
4910 _n_workers = active_workers;
4911 }
4912
4913 void work(uint worker_id) {
4914 if (worker_id >= _n_workers) return; // no work needed this round
4915
4916 double start_time_ms = os::elapsedTime() * 1000.0;
4917 _g1h->g1_policy()->phase_times()->record_gc_worker_start_time(worker_id, start_time_ms);
4918
4919 {
4920 ResourceMark rm;
4921 HandleMark hm;
4922
4923 ReferenceProcessor* rp = _g1h->ref_processor_stw();
4924
4925 G1ParScanThreadState pss(_g1h, worker_id);
4926 G1ParScanHeapEvacClosure scan_evac_cl(_g1h, &pss, rp);
4927 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, rp);
4928 G1ParScanPartialArrayClosure partial_scan_cl(_g1h, &pss, rp);
4929
4930 pss.set_evac_closure(&scan_evac_cl);
4931 pss.set_evac_failure_closure(&evac_failure_cl);
4932 pss.set_partial_scan_closure(&partial_scan_cl);
4933
4934 G1ParScanExtRootClosure only_scan_root_cl(_g1h, &pss, rp);
4935 G1ParScanPermClosure only_scan_perm_cl(_g1h, &pss, rp);
4936
4937 G1ParScanAndMarkExtRootClosure scan_mark_root_cl(_g1h, &pss, rp);
4938 G1ParScanAndMarkPermClosure scan_mark_perm_cl(_g1h, &pss, rp);
4939
4940 OopClosure* scan_root_cl = &only_scan_root_cl;
4941 OopsInHeapRegionClosure* scan_perm_cl = &only_scan_perm_cl;
4942
4943 if (_g1h->g1_policy()->during_initial_mark_pause()) {
4944 // We also need to mark copied objects.
4945 scan_root_cl = &scan_mark_root_cl;
4946 scan_perm_cl = &scan_mark_perm_cl;
4947 }
4948
4949 G1ParPushHeapRSClosure push_heap_rs_cl(_g1h, &pss);
4950
4951 pss.start_strong_roots();
4952 _g1h->g1_process_strong_roots(/* not collecting perm */ false,
4953 SharedHeap::SO_AllClasses,
4954 scan_root_cl,
4955 &push_heap_rs_cl,
4956 scan_perm_cl,
4957 worker_id);
4958 pss.end_strong_roots();
4959
4960 {
4961 double start = os::elapsedTime();
4962 G1ParEvacuateFollowersClosure evac(_g1h, &pss, _queues, &_terminator);
4963 evac.do_void();
4964 double elapsed_ms = (os::elapsedTime()-start)*1000.0;
4965 double term_ms = pss.term_time()*1000.0;
4966 _g1h->g1_policy()->phase_times()->add_obj_copy_time(worker_id, elapsed_ms-term_ms);
4967 _g1h->g1_policy()->phase_times()->record_termination(worker_id, term_ms, pss.term_attempts());
4968 }
4969 _g1h->g1_policy()->record_thread_age_table(pss.age_table());
4970 _g1h->update_surviving_young_words(pss.surviving_young_words()+1);
4971
4972 if (ParallelGCVerbose) {
4973 MutexLocker x(stats_lock());
4974 pss.print_termination_stats(worker_id);
4975 }
4976
4977 assert(pss.refs()->is_empty(), "should be empty");
4978
4979 // Close the inner scope so that the ResourceMark and HandleMark
4980 // destructors are executed here and are included as part of the
4981 // "GC Worker Time".
4982 }
4983
4984 double end_time_ms = os::elapsedTime() * 1000.0;
4985 _g1h->g1_policy()->phase_times()->record_gc_worker_end_time(worker_id, end_time_ms);
4986 }
4987 };
4988
4989 // *** Common G1 Evacuation Stuff
4990
4991 // Closures that support the filtering of CodeBlobs scanned during
4992 // external root scanning.
4993
4994 // Closure applied to reference fields in code blobs (specifically nmethods)
4995 // to determine whether an nmethod contains references that point into
4996 // the collection set. Used as a predicate when walking code roots so
4997 // that only nmethods that point into the collection set are added to the
4998 // 'marked' list.
4999
5000 class G1FilteredCodeBlobToOopClosure : public CodeBlobToOopClosure {
5001
5002 class G1PointsIntoCSOopClosure : public OopClosure {
5003 G1CollectedHeap* _g1;
5004 bool _points_into_cs;
5005 public:
5006 G1PointsIntoCSOopClosure(G1CollectedHeap* g1) :
5007 _g1(g1), _points_into_cs(false) { }
5008
5009 bool points_into_cs() const { return _points_into_cs; }
5010
5011 template <class T>
5012 void do_oop_nv(T* p) {
5013 if (!_points_into_cs) {
5014 T heap_oop = oopDesc::load_heap_oop(p);
5015 if (!oopDesc::is_null(heap_oop) &&
5016 _g1->in_cset_fast_test(oopDesc::decode_heap_oop_not_null(heap_oop))) {
5017 _points_into_cs = true;
5018 }
5019 }
5020 }
5021
5022 virtual void do_oop(oop* p) { do_oop_nv(p); }
5023 virtual void do_oop(narrowOop* p) { do_oop_nv(p); }
5024 };
5025
5026 G1CollectedHeap* _g1;
5027
5028 public:
5029 G1FilteredCodeBlobToOopClosure(G1CollectedHeap* g1, OopClosure* cl) :
5030 CodeBlobToOopClosure(cl, true), _g1(g1) { }
5031
5032 virtual void do_code_blob(CodeBlob* cb) {
5033 nmethod* nm = cb->as_nmethod_or_null();
5034 if (nm != NULL && !(nm->test_oops_do_mark())) {
5035 G1PointsIntoCSOopClosure predicate_cl(_g1);
5036 nm->oops_do(&predicate_cl);
5037
5038 if (predicate_cl.points_into_cs()) {
5039 // At least one of the reference fields or the oop relocations
5040 // in the nmethod points into the collection set. We have to
5041 // 'mark' this nmethod.
5042 // Note: Revisit the following if CodeBlobToOopClosure::do_code_blob()
5043 // or MarkingCodeBlobClosure::do_code_blob() change.
5044 if (!nm->test_set_oops_do_mark()) {
5045 do_newly_marked_nmethod(nm);
5046 }
5047 }
5048 }
5049 }
5050 };
5051
5052 // This method is run in a GC worker.
5053
5054 void
5055 G1CollectedHeap::
5056 g1_process_strong_roots(bool collecting_perm_gen,
5057 ScanningOption so,
5058 OopClosure* scan_non_heap_roots,
5059 OopsInHeapRegionClosure* scan_rs,
5060 OopsInGenClosure* scan_perm,
5061 int worker_i) {
5062
5063 // First scan the strong roots, including the perm gen.
5064 double ext_roots_start = os::elapsedTime();
5065 double closure_app_time_sec = 0.0;
5066
5067 BufferingOopClosure buf_scan_non_heap_roots(scan_non_heap_roots);
5068 BufferingOopsInGenClosure buf_scan_perm(scan_perm);
5069 buf_scan_perm.set_generation(perm_gen());
5070
5071 // Walk the code cache w/o buffering, because StarTask cannot handle
5072 // unaligned oop locations.
5073 G1FilteredCodeBlobToOopClosure eager_scan_code_roots(this, scan_non_heap_roots);
5074
5075 process_strong_roots(false, // no scoping; this is parallel code
5076 collecting_perm_gen, so,
5077 &buf_scan_non_heap_roots,
5078 &eager_scan_code_roots,
5079 &buf_scan_perm);
5080
5081 // Now the CM ref_processor roots.
5082 if (!_process_strong_tasks->is_task_claimed(G1H_PS_refProcessor_oops_do)) {
5083 // We need to treat the discovered reference lists of the
5084 // concurrent mark ref processor as roots and keep entries
5085 // (which are added by the marking threads) on them live
5086 // until they can be processed at the end of marking.
5087 ref_processor_cm()->weak_oops_do(&buf_scan_non_heap_roots);
5088 }
5089
5090 // Finish up any enqueued closure apps (attributed as object copy time).
5091 buf_scan_non_heap_roots.done();
5092 buf_scan_perm.done();
5093
5094 double obj_copy_time_sec = buf_scan_perm.closure_app_seconds() +
5095 buf_scan_non_heap_roots.closure_app_seconds();
5096 g1_policy()->phase_times()->record_obj_copy_time(worker_i, obj_copy_time_sec * 1000.0);
5097
5098 double ext_root_time_ms =
5099 ((os::elapsedTime() - ext_roots_start) - obj_copy_time_sec) * 1000.0;
5100
5101 g1_policy()->phase_times()->record_ext_root_scan_time(worker_i, ext_root_time_ms);
5102
5103 // During conc marking we have to filter the per-thread SATB buffers
5104 // to make sure we remove any oops into the CSet (which will show up
5105 // as implicitly live).
5106 double satb_filtering_ms = 0.0;
5107 if (!_process_strong_tasks->is_task_claimed(G1H_PS_filter_satb_buffers)) {
5108 if (mark_in_progress()) {
5109 double satb_filter_start = os::elapsedTime();
5110
5111 JavaThread::satb_mark_queue_set().filter_thread_buffers();
5112
5113 satb_filtering_ms = (os::elapsedTime() - satb_filter_start) * 1000.0;
5114 }
5115 }
5116 g1_policy()->phase_times()->record_satb_filtering_time(worker_i, satb_filtering_ms);
5117
5118 // Now scan the complement of the collection set.
5119 if (scan_rs != NULL) {
5120 g1_rem_set()->oops_into_collection_set_do(scan_rs, worker_i);
5121 }
5122
5123 _process_strong_tasks->all_tasks_completed();
5124 }
5125
5126 void
5127 G1CollectedHeap::g1_process_weak_roots(OopClosure* root_closure,
5128 OopClosure* non_root_closure) {
5129 CodeBlobToOopClosure roots_in_blobs(root_closure, /*do_marking=*/ false);
5130 SharedHeap::process_weak_roots(root_closure, &roots_in_blobs, non_root_closure);
5131 }
5132
5133 // Weak Reference Processing support
5134
5135 // An always "is_alive" closure that is used to preserve referents.
5136 // If the object is non-null then it's alive. Used in the preservation
5137 // of referent objects that are pointed to by reference objects
5138 // discovered by the CM ref processor.
5139 class G1AlwaysAliveClosure: public BoolObjectClosure {
5140 G1CollectedHeap* _g1;
5141 public:
5142 G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
5143 void do_object(oop p) { assert(false, "Do not call."); }
5144 bool do_object_b(oop p) {
5145 if (p != NULL) {
5146 return true;
5147 }
5148 return false;
5149 }
5150 };
5151
5152 bool G1STWIsAliveClosure::do_object_b(oop p) {
5153 // An object is reachable if it is outside the collection set,
5154 // or is inside and copied.
5155 return !_g1->obj_in_cs(p) || p->is_forwarded();
5156 }
5157
5158 // Non Copying Keep Alive closure
5159 class G1KeepAliveClosure: public OopClosure {
5160 G1CollectedHeap* _g1;
5161 public:
5162 G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
5163 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
5164 void do_oop( oop* p) {
5165 oop obj = *p;
5166
5167 if (_g1->obj_in_cs(obj)) {
5168 assert( obj->is_forwarded(), "invariant" );
5169 *p = obj->forwardee();
5170 }
5171 }
5172 };
5173
5174 // Copying Keep Alive closure - can be called from both
5175 // serial and parallel code as long as different worker
5176 // threads utilize different G1ParScanThreadState instances
5177 // and different queues.
5178
5179 class G1CopyingKeepAliveClosure: public OopClosure {
5180 G1CollectedHeap* _g1h;
5181 OopClosure* _copy_non_heap_obj_cl;
5182 OopsInHeapRegionClosure* _copy_perm_obj_cl;
5183 G1ParScanThreadState* _par_scan_state;
5184
5185 public:
5186 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
5187 OopClosure* non_heap_obj_cl,
5188 OopsInHeapRegionClosure* perm_obj_cl,
5189 G1ParScanThreadState* pss):
5190 _g1h(g1h),
5191 _copy_non_heap_obj_cl(non_heap_obj_cl),
5192 _copy_perm_obj_cl(perm_obj_cl),
5193 _par_scan_state(pss)
5194 {}
5195
5196 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
5197 virtual void do_oop( oop* p) { do_oop_work(p); }
5198
5199 template <class T> void do_oop_work(T* p) {
5200 oop obj = oopDesc::load_decode_heap_oop(p);
5201
5202 if (_g1h->obj_in_cs(obj)) {
5203 // If the referent object has been forwarded (either copied
5204 // to a new location or to itself in the event of an
5205 // evacuation failure) then we need to update the reference
5206 // field and, if both reference and referent are in the G1
5207 // heap, update the RSet for the referent.
5208 //
5209 // If the referent has not been forwarded then we have to keep
5210 // it alive by policy. Therefore we have copy the referent.
5211 //
5212 // If the reference field is in the G1 heap then we can push
5213 // on the PSS queue. When the queue is drained (after each
5214 // phase of reference processing) the object and it's followers
5215 // will be copied, the reference field set to point to the
5216 // new location, and the RSet updated. Otherwise we need to
5217 // use the the non-heap or perm closures directly to copy
5218 // the referent object and update the pointer, while avoiding
5219 // updating the RSet.
5220
5221 if (_g1h->is_in_g1_reserved(p)) {
5222 _par_scan_state->push_on_queue(p);
5223 } else {
5224 // The reference field is not in the G1 heap.
5225 if (_g1h->perm_gen()->is_in(p)) {
5226 _copy_perm_obj_cl->do_oop(p);
5227 } else {
5228 _copy_non_heap_obj_cl->do_oop(p);
5229 }
5230 }
5231 }
5232 }
5233 };
5234
5235 // Serial drain queue closure. Called as the 'complete_gc'
5236 // closure for each discovered list in some of the
5237 // reference processing phases.
5238
5239 class G1STWDrainQueueClosure: public VoidClosure {
5240 protected:
5241 G1CollectedHeap* _g1h;
5242 G1ParScanThreadState* _par_scan_state;
5243
5244 G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
5245
5246 public:
5247 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
5248 _g1h(g1h),
5249 _par_scan_state(pss)
5250 { }
5251
5252 void do_void() {
5253 G1ParScanThreadState* const pss = par_scan_state();
5254 pss->trim_queue();
5255 }
5256 };
5257
5258 // Parallel Reference Processing closures
5259
5260 // Implementation of AbstractRefProcTaskExecutor for parallel reference
5261 // processing during G1 evacuation pauses.
5262
5263 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
5264 private:
5265 G1CollectedHeap* _g1h;
5266 RefToScanQueueSet* _queues;
5267 FlexibleWorkGang* _workers;
5268 int _active_workers;
5269
5270 public:
5271 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
5272 FlexibleWorkGang* workers,
5273 RefToScanQueueSet *task_queues,
5274 int n_workers) :
5275 _g1h(g1h),
5276 _queues(task_queues),
5277 _workers(workers),
5278 _active_workers(n_workers)
5279 {
5280 assert(n_workers > 0, "shouldn't call this otherwise");
5281 }
5282
5283 // Executes the given task using concurrent marking worker threads.
5284 virtual void execute(ProcessTask& task);
5285 virtual void execute(EnqueueTask& task);
5286 };
5287
5288 // Gang task for possibly parallel reference processing
5289
5290 class G1STWRefProcTaskProxy: public AbstractGangTask {
5291 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
5292 ProcessTask& _proc_task;
5293 G1CollectedHeap* _g1h;
5294 RefToScanQueueSet *_task_queues;
5295 ParallelTaskTerminator* _terminator;
5296
5297 public:
5298 G1STWRefProcTaskProxy(ProcessTask& proc_task,
5299 G1CollectedHeap* g1h,
5300 RefToScanQueueSet *task_queues,
5301 ParallelTaskTerminator* terminator) :
5302 AbstractGangTask("Process reference objects in parallel"),
5303 _proc_task(proc_task),
5304 _g1h(g1h),
5305 _task_queues(task_queues),
5306 _terminator(terminator)
5307 {}
5308
5309 virtual void work(uint worker_id) {
5310 // The reference processing task executed by a single worker.
5311 ResourceMark rm;
5312 HandleMark hm;
5313
5314 G1STWIsAliveClosure is_alive(_g1h);
5315
5316 G1ParScanThreadState pss(_g1h, worker_id);
5317
5318 G1ParScanHeapEvacClosure scan_evac_cl(_g1h, &pss, NULL);
5319 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5320 G1ParScanPartialArrayClosure partial_scan_cl(_g1h, &pss, NULL);
5321
5322 pss.set_evac_closure(&scan_evac_cl);
5323 pss.set_evac_failure_closure(&evac_failure_cl);
5324 pss.set_partial_scan_closure(&partial_scan_cl);
5325
5326 G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL);
5327 G1ParScanPermClosure only_copy_perm_cl(_g1h, &pss, NULL);
5328
5329 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5330 G1ParScanAndMarkPermClosure copy_mark_perm_cl(_g1h, &pss, NULL);
5331
5332 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5333 OopsInHeapRegionClosure* copy_perm_cl = &only_copy_perm_cl;
5334
5335 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5336 // We also need to mark copied objects.
5337 copy_non_heap_cl = ©_mark_non_heap_cl;
5338 copy_perm_cl = ©_mark_perm_cl;
5339 }
5340
5341 // Keep alive closure.
5342 G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, copy_perm_cl, &pss);
5343
5344 // Complete GC closure
5345 G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _task_queues, _terminator);
5346
5347 // Call the reference processing task's work routine.
5348 _proc_task.work(worker_id, is_alive, keep_alive, drain_queue);
5349
5350 // Note we cannot assert that the refs array is empty here as not all
5351 // of the processing tasks (specifically phase2 - pp2_work) execute
5352 // the complete_gc closure (which ordinarily would drain the queue) so
5353 // the queue may not be empty.
5354 }
5355 };
5356
5357 // Driver routine for parallel reference processing.
5358 // Creates an instance of the ref processing gang
5359 // task and has the worker threads execute it.
5360 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) {
5361 assert(_workers != NULL, "Need parallel worker threads.");
5362
5363 ParallelTaskTerminator terminator(_active_workers, _queues);
5364 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _queues, &terminator);
5365
5366 _g1h->set_par_threads(_active_workers);
5367 _workers->run_task(&proc_task_proxy);
5368 _g1h->set_par_threads(0);
5369 }
5370
5371 // Gang task for parallel reference enqueueing.
5372
5373 class G1STWRefEnqueueTaskProxy: public AbstractGangTask {
5374 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
5375 EnqueueTask& _enq_task;
5376
5377 public:
5378 G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) :
5379 AbstractGangTask("Enqueue reference objects in parallel"),
5380 _enq_task(enq_task)
5381 { }
5382
5383 virtual void work(uint worker_id) {
5384 _enq_task.work(worker_id);
5385 }
5386 };
5387
5388 // Driver routine for parallel reference enqueueing.
5389 // Creates an instance of the ref enqueueing gang
5390 // task and has the worker threads execute it.
5391
5392 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
5393 assert(_workers != NULL, "Need parallel worker threads.");
5394
5395 G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task);
5396
5397 _g1h->set_par_threads(_active_workers);
5398 _workers->run_task(&enq_task_proxy);
5399 _g1h->set_par_threads(0);
5400 }
5401
5402 // End of weak reference support closures
5403
5404 // Abstract task used to preserve (i.e. copy) any referent objects
5405 // that are in the collection set and are pointed to by reference
5406 // objects discovered by the CM ref processor.
5407
5408 class G1ParPreserveCMReferentsTask: public AbstractGangTask {
5409 protected:
5410 G1CollectedHeap* _g1h;
5411 RefToScanQueueSet *_queues;
5412 ParallelTaskTerminator _terminator;
5413 uint _n_workers;
5414
5415 public:
5416 G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h,int workers, RefToScanQueueSet *task_queues) :
5417 AbstractGangTask("ParPreserveCMReferents"),
5418 _g1h(g1h),
5419 _queues(task_queues),
5420 _terminator(workers, _queues),
5421 _n_workers(workers)
5422 { }
5423
5424 void work(uint worker_id) {
5425 ResourceMark rm;
5426 HandleMark hm;
5427
5428 G1ParScanThreadState pss(_g1h, worker_id);
5429 G1ParScanHeapEvacClosure scan_evac_cl(_g1h, &pss, NULL);
5430 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5431 G1ParScanPartialArrayClosure partial_scan_cl(_g1h, &pss, NULL);
5432
5433 pss.set_evac_closure(&scan_evac_cl);
5434 pss.set_evac_failure_closure(&evac_failure_cl);
5435 pss.set_partial_scan_closure(&partial_scan_cl);
5436
5437 assert(pss.refs()->is_empty(), "both queue and overflow should be empty");
5438
5439
5440 G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL);
5441 G1ParScanPermClosure only_copy_perm_cl(_g1h, &pss, NULL);
5442
5443 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5444 G1ParScanAndMarkPermClosure copy_mark_perm_cl(_g1h, &pss, NULL);
5445
5446 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5447 OopsInHeapRegionClosure* copy_perm_cl = &only_copy_perm_cl;
5448
5449 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5450 // We also need to mark copied objects.
5451 copy_non_heap_cl = ©_mark_non_heap_cl;
5452 copy_perm_cl = ©_mark_perm_cl;
5453 }
5454
5455 // Is alive closure
5456 G1AlwaysAliveClosure always_alive(_g1h);
5457
5458 // Copying keep alive closure. Applied to referent objects that need
5459 // to be copied.
5460 G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, copy_perm_cl, &pss);
5461
5462 ReferenceProcessor* rp = _g1h->ref_processor_cm();
5463
5464 uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q();
5465 uint stride = MIN2(MAX2(_n_workers, 1U), limit);
5466
5467 // limit is set using max_num_q() - which was set using ParallelGCThreads.
5468 // So this must be true - but assert just in case someone decides to
5469 // change the worker ids.
5470 assert(0 <= worker_id && worker_id < limit, "sanity");
5471 assert(!rp->discovery_is_atomic(), "check this code");
5472
5473 // Select discovered lists [i, i+stride, i+2*stride,...,limit)
5474 for (uint idx = worker_id; idx < limit; idx += stride) {
5475 DiscoveredList& ref_list = rp->discovered_refs()[idx];
5476
5477 DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive);
5478 while (iter.has_next()) {
5479 // Since discovery is not atomic for the CM ref processor, we
5480 // can see some null referent objects.
5481 iter.load_ptrs(DEBUG_ONLY(true));
5482 oop ref = iter.obj();
5483
5484 // This will filter nulls.
5485 if (iter.is_referent_alive()) {
5486 iter.make_referent_alive();
5487 }
5488 iter.move_to_next();
5489 }
5490 }
5491
5492 // Drain the queue - which may cause stealing
5493 G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _queues, &_terminator);
5494 drain_queue.do_void();
5495 // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure
5496 assert(pss.refs()->is_empty(), "should be");
5497 }
5498 };
5499
5500 // Weak Reference processing during an evacuation pause (part 1).
5501 void G1CollectedHeap::process_discovered_references(uint no_of_gc_workers) {
5502 double ref_proc_start = os::elapsedTime();
5503
5504 ReferenceProcessor* rp = _ref_processor_stw;
5505 assert(rp->discovery_enabled(), "should have been enabled");
5506
5507 // Any reference objects, in the collection set, that were 'discovered'
5508 // by the CM ref processor should have already been copied (either by
5509 // applying the external root copy closure to the discovered lists, or
5510 // by following an RSet entry).
5511 //
5512 // But some of the referents, that are in the collection set, that these
5513 // reference objects point to may not have been copied: the STW ref
5514 // processor would have seen that the reference object had already
5515 // been 'discovered' and would have skipped discovering the reference,
5516 // but would not have treated the reference object as a regular oop.
5517 // As a result the copy closure would not have been applied to the
5518 // referent object.
5519 //
5520 // We need to explicitly copy these referent objects - the references
5521 // will be processed at the end of remarking.
5522 //
5523 // We also need to do this copying before we process the reference
5524 // objects discovered by the STW ref processor in case one of these
5525 // referents points to another object which is also referenced by an
5526 // object discovered by the STW ref processor.
5527
5528 assert(!G1CollectedHeap::use_parallel_gc_threads() ||
5529 no_of_gc_workers == workers()->active_workers(),
5530 "Need to reset active GC workers");
5531
5532 set_par_threads(no_of_gc_workers);
5533 G1ParPreserveCMReferentsTask keep_cm_referents(this,
5534 no_of_gc_workers,
5535 _task_queues);
5536
5537 if (G1CollectedHeap::use_parallel_gc_threads()) {
5538 workers()->run_task(&keep_cm_referents);
5539 } else {
5540 keep_cm_referents.work(0);
5541 }
5542
5543 set_par_threads(0);
5544
5545 // Closure to test whether a referent is alive.
5546 G1STWIsAliveClosure is_alive(this);
5547
5548 // Even when parallel reference processing is enabled, the processing
5549 // of JNI refs is serial and performed serially by the current thread
5550 // rather than by a worker. The following PSS will be used for processing
5551 // JNI refs.
5552
5553 // Use only a single queue for this PSS.
5554 G1ParScanThreadState pss(this, 0);
5555
5556 // We do not embed a reference processor in the copying/scanning
5557 // closures while we're actually processing the discovered
5558 // reference objects.
5559 G1ParScanHeapEvacClosure scan_evac_cl(this, &pss, NULL);
5560 G1ParScanHeapEvacFailureClosure evac_failure_cl(this, &pss, NULL);
5561 G1ParScanPartialArrayClosure partial_scan_cl(this, &pss, NULL);
5562
5563 pss.set_evac_closure(&scan_evac_cl);
5564 pss.set_evac_failure_closure(&evac_failure_cl);
5565 pss.set_partial_scan_closure(&partial_scan_cl);
5566
5567 assert(pss.refs()->is_empty(), "pre-condition");
5568
5569 G1ParScanExtRootClosure only_copy_non_heap_cl(this, &pss, NULL);
5570 G1ParScanPermClosure only_copy_perm_cl(this, &pss, NULL);
5571
5572 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(this, &pss, NULL);
5573 G1ParScanAndMarkPermClosure copy_mark_perm_cl(this, &pss, NULL);
5574
5575 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5576 OopsInHeapRegionClosure* copy_perm_cl = &only_copy_perm_cl;
5577
5578 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5579 // We also need to mark copied objects.
5580 copy_non_heap_cl = ©_mark_non_heap_cl;
5581 copy_perm_cl = ©_mark_perm_cl;
5582 }
5583
5584 // Keep alive closure.
5585 G1CopyingKeepAliveClosure keep_alive(this, copy_non_heap_cl, copy_perm_cl, &pss);
5586
5587 // Serial Complete GC closure
5588 G1STWDrainQueueClosure drain_queue(this, &pss);
5589
5590 // Setup the soft refs policy...
5591 rp->setup_policy(false);
5592
5593 ReferenceProcessorStats stats;
5594 if (!rp->processing_is_mt()) {
5595 // Serial reference processing...
5596 stats = rp->process_discovered_references(&is_alive,
5597 &keep_alive,
5598 &drain_queue,
5599 NULL,
5600 _gc_timer_stw);
5601 } else {
5602 // Parallel reference processing
5603 assert(rp->num_q() == no_of_gc_workers, "sanity");
5604 assert(no_of_gc_workers <= rp->max_num_q(), "sanity");
5605
5606 G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers);
5607 stats = rp->process_discovered_references(&is_alive,
5608 &keep_alive,
5609 &drain_queue,
5610 &par_task_executor,
5611 _gc_timer_stw);
5612 }
5613
5614 _gc_tracer_stw->report_gc_reference_stats(stats);
5615 // We have completed copying any necessary live referent objects
5616 // (that were not copied during the actual pause) so we can
5617 // retire any active alloc buffers
5618 pss.retire_alloc_buffers();
5619 assert(pss.refs()->is_empty(), "both queue and overflow should be empty");
5620
5621 double ref_proc_time = os::elapsedTime() - ref_proc_start;
5622 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
5623 }
5624
5625 // Weak Reference processing during an evacuation pause (part 2).
5626 void G1CollectedHeap::enqueue_discovered_references(uint no_of_gc_workers) {
5627 double ref_enq_start = os::elapsedTime();
5628
5629 ReferenceProcessor* rp = _ref_processor_stw;
5630 assert(!rp->discovery_enabled(), "should have been disabled as part of processing");
5631
5632 // Now enqueue any remaining on the discovered lists on to
5633 // the pending list.
5634 if (!rp->processing_is_mt()) {
5635 // Serial reference processing...
5636 rp->enqueue_discovered_references();
5637 } else {
5638 // Parallel reference enqueueing
5639
5640 assert(no_of_gc_workers == workers()->active_workers(),
5641 "Need to reset active workers");
5642 assert(rp->num_q() == no_of_gc_workers, "sanity");
5643 assert(no_of_gc_workers <= rp->max_num_q(), "sanity");
5644
5645 G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers);
5646 rp->enqueue_discovered_references(&par_task_executor);
5647 }
5648
5649 rp->verify_no_references_recorded();
5650 assert(!rp->discovery_enabled(), "should have been disabled");
5651
5652 // FIXME
5653 // CM's reference processing also cleans up the string and symbol tables.
5654 // Should we do that here also? We could, but it is a serial operation
5655 // and could significantly increase the pause time.
5656
5657 double ref_enq_time = os::elapsedTime() - ref_enq_start;
5658 g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0);
5659 }
5660
5661 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info) {
5662 _expand_heap_after_alloc_failure = true;
5663 set_evacuation_failed(false);
5664
5665 // Should G1EvacuationFailureALot be in effect for this GC?
5666 NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();)
5667
5668 g1_rem_set()->prepare_for_oops_into_collection_set_do();
5669 concurrent_g1_refine()->set_use_cache(false);
5670 concurrent_g1_refine()->clear_hot_cache_claimed_index();
5671
5672 uint n_workers;
5673 if (G1CollectedHeap::use_parallel_gc_threads()) {
5674 n_workers =
5675 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
5676 workers()->active_workers(),
5677 Threads::number_of_non_daemon_threads());
5678 assert(UseDynamicNumberOfGCThreads ||
5679 n_workers == workers()->total_workers(),
5680 "If not dynamic should be using all the workers");
5681 workers()->set_active_workers(n_workers);
5682 set_par_threads(n_workers);
5683 } else {
5684 assert(n_par_threads() == 0,
5685 "Should be the original non-parallel value");
5686 n_workers = 1;
5687 }
5688
5689 G1ParTask g1_par_task(this, _task_queues);
5690
5691 init_for_evac_failure(NULL);
5692
5693 rem_set()->prepare_for_younger_refs_iterate(true);
5694
5695 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
5696 double start_par_time_sec = os::elapsedTime();
5697 double end_par_time_sec;
5698
5699 {
5700 StrongRootsScope srs(this);
5701
5702 if (G1CollectedHeap::use_parallel_gc_threads()) {
5703 // The individual threads will set their evac-failure closures.
5704 if (ParallelGCVerbose) G1ParScanThreadState::print_termination_stats_hdr();
5705 // These tasks use ShareHeap::_process_strong_tasks
5706 assert(UseDynamicNumberOfGCThreads ||
5707 workers()->active_workers() == workers()->total_workers(),
5708 "If not dynamic should be using all the workers");
5709 workers()->run_task(&g1_par_task);
5710 } else {
5711 g1_par_task.set_for_termination(n_workers);
5712 g1_par_task.work(0);
5713 }
5714 end_par_time_sec = os::elapsedTime();
5715
5716 // Closing the inner scope will execute the destructor
5717 // for the StrongRootsScope object. We record the current
5718 // elapsed time before closing the scope so that time
5719 // taken for the SRS destructor is NOT included in the
5720 // reported parallel time.
5721 }
5722
5723 double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0;
5724 g1_policy()->phase_times()->record_par_time(par_time_ms);
5725
5726 double code_root_fixup_time_ms =
5727 (os::elapsedTime() - end_par_time_sec) * 1000.0;
5728 g1_policy()->phase_times()->record_code_root_fixup_time(code_root_fixup_time_ms);
5729
5730 set_par_threads(0);
5731
5732 // Process any discovered reference objects - we have
5733 // to do this _before_ we retire the GC alloc regions
5734 // as we may have to copy some 'reachable' referent
5735 // objects (and their reachable sub-graphs) that were
5736 // not copied during the pause.
5737 process_discovered_references(n_workers);
5738
5739 // Weak root processing.
5740 // Note: when JSR 292 is enabled and code blobs can contain
5741 // non-perm oops then we will need to process the code blobs
5742 // here too.
5743 {
5744 G1STWIsAliveClosure is_alive(this);
5745 G1KeepAliveClosure keep_alive(this);
5746 JNIHandles::weak_oops_do(&is_alive, &keep_alive);
5747 }
5748
5749 release_gc_alloc_regions(n_workers, evacuation_info);
5750 g1_rem_set()->cleanup_after_oops_into_collection_set_do();
5751
5752 concurrent_g1_refine()->clear_hot_cache();
5753 concurrent_g1_refine()->set_use_cache(true);
5754
5755 finalize_for_evac_failure();
5756
5757 if (evacuation_failed()) {
5758 remove_self_forwarding_pointers();
5759
5760 // Reset the G1EvacuationFailureALot counters and flags
5761 // Note: the values are reset only when an actual
5762 // evacuation failure occurs.
5763 NOT_PRODUCT(reset_evacuation_should_fail();)
5764 }
5765
5766 // Enqueue any remaining references remaining on the STW
5767 // reference processor's discovered lists. We need to do
5768 // this after the card table is cleaned (and verified) as
5769 // the act of enqueueing entries on to the pending list
5770 // will log these updates (and dirty their associated
5771 // cards). We need these updates logged to update any
5772 // RSets.
5773 enqueue_discovered_references(n_workers);
5774
5775 if (G1DeferredRSUpdate) {
5776 RedirtyLoggedCardTableEntryFastClosure redirty;
5777 dirty_card_queue_set().set_closure(&redirty);
5778 dirty_card_queue_set().apply_closure_to_all_completed_buffers();
5779
5780 DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set();
5781 dcq.merge_bufferlists(&dirty_card_queue_set());
5782 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
5783 }
5784 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
5785 }
5786
5787 void G1CollectedHeap::free_region_if_empty(HeapRegion* hr,
5788 size_t* pre_used,
5789 FreeRegionList* free_list,
5790 OldRegionSet* old_proxy_set,
5791 HumongousRegionSet* humongous_proxy_set,
5792 HRRSCleanupTask* hrrs_cleanup_task,
5793 bool par) {
5794 if (hr->used() > 0 && hr->max_live_bytes() == 0 && !hr->is_young()) {
5795 if (hr->isHumongous()) {
5796 assert(hr->startsHumongous(), "we should only see starts humongous");
5797 free_humongous_region(hr, pre_used, free_list, humongous_proxy_set, par);
5798 } else {
5799 _old_set.remove_with_proxy(hr, old_proxy_set);
5800 free_region(hr, pre_used, free_list, par);
5801 }
5802 } else {
5803 hr->rem_set()->do_cleanup_work(hrrs_cleanup_task);
5804 }
5805 }
5806
5807 void G1CollectedHeap::free_region(HeapRegion* hr,
5808 size_t* pre_used,
5809 FreeRegionList* free_list,
5810 bool par) {
5811 assert(!hr->isHumongous(), "this is only for non-humongous regions");
5812 assert(!hr->is_empty(), "the region should not be empty");
5813 assert(free_list != NULL, "pre-condition");
5814
5815 *pre_used += hr->used();
5816 hr->hr_clear(par, true /* clear_space */);
5817 free_list->add_as_head(hr);
5818 }
5819
5820 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
5821 size_t* pre_used,
5822 FreeRegionList* free_list,
5823 HumongousRegionSet* humongous_proxy_set,
5824 bool par) {
5825 assert(hr->startsHumongous(), "this is only for starts humongous regions");
5826 assert(free_list != NULL, "pre-condition");
5827 assert(humongous_proxy_set != NULL, "pre-condition");
5828
5829 size_t hr_used = hr->used();
5830 size_t hr_capacity = hr->capacity();
5831 size_t hr_pre_used = 0;
5832 _humongous_set.remove_with_proxy(hr, humongous_proxy_set);
5833 // We need to read this before we make the region non-humongous,
5834 // otherwise the information will be gone.
5835 uint last_index = hr->last_hc_index();
5836 hr->set_notHumongous();
5837 free_region(hr, &hr_pre_used, free_list, par);
5838
5839 uint i = hr->hrs_index() + 1;
5840 while (i < last_index) {
5841 HeapRegion* curr_hr = region_at(i);
5842 assert(curr_hr->continuesHumongous(), "invariant");
5843 curr_hr->set_notHumongous();
5844 free_region(curr_hr, &hr_pre_used, free_list, par);
5845 i += 1;
5846 }
5847 assert(hr_pre_used == hr_used,
5848 err_msg("hr_pre_used: "SIZE_FORMAT" and hr_used: "SIZE_FORMAT" "
5849 "should be the same", hr_pre_used, hr_used));
5850 *pre_used += hr_pre_used;
5851 }
5852
5853 void G1CollectedHeap::update_sets_after_freeing_regions(size_t pre_used,
5854 FreeRegionList* free_list,
5855 OldRegionSet* old_proxy_set,
5856 HumongousRegionSet* humongous_proxy_set,
5857 bool par) {
5858 if (pre_used > 0) {
5859 Mutex* lock = (par) ? ParGCRareEvent_lock : NULL;
5860 MutexLockerEx x(lock, Mutex::_no_safepoint_check_flag);
5861 assert(_summary_bytes_used >= pre_used,
5862 err_msg("invariant: _summary_bytes_used: "SIZE_FORMAT" "
5863 "should be >= pre_used: "SIZE_FORMAT,
5864 _summary_bytes_used, pre_used));
5865 _summary_bytes_used -= pre_used;
5866 }
5867 if (free_list != NULL && !free_list->is_empty()) {
5868 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
5869 _free_list.add_as_head(free_list);
5870 }
5871 if (old_proxy_set != NULL && !old_proxy_set->is_empty()) {
5872 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
5873 _old_set.update_from_proxy(old_proxy_set);
5874 }
5875 if (humongous_proxy_set != NULL && !humongous_proxy_set->is_empty()) {
5876 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
5877 _humongous_set.update_from_proxy(humongous_proxy_set);
5878 }
5879 }
5880
5881 class G1ParCleanupCTTask : public AbstractGangTask {
5882 CardTableModRefBS* _ct_bs;
5883 G1CollectedHeap* _g1h;
5884 HeapRegion* volatile _su_head;
5885 public:
5886 G1ParCleanupCTTask(CardTableModRefBS* ct_bs,
5887 G1CollectedHeap* g1h) :
5888 AbstractGangTask("G1 Par Cleanup CT Task"),
5889 _ct_bs(ct_bs), _g1h(g1h) { }
5890
5891 void work(uint worker_id) {
5892 HeapRegion* r;
5893 while (r = _g1h->pop_dirty_cards_region()) {
5894 clear_cards(r);
5895 }
5896 }
5897
5898 void clear_cards(HeapRegion* r) {
5899 // Cards of the survivors should have already been dirtied.
5900 if (!r->is_survivor()) {
5901 _ct_bs->clear(MemRegion(r->bottom(), r->end()));
5902 }
5903 }
5904 };
5905
5906 #ifndef PRODUCT
5907 class G1VerifyCardTableCleanup: public HeapRegionClosure {
5908 G1CollectedHeap* _g1h;
5909 CardTableModRefBS* _ct_bs;
5910 public:
5911 G1VerifyCardTableCleanup(G1CollectedHeap* g1h, CardTableModRefBS* ct_bs)
5912 : _g1h(g1h), _ct_bs(ct_bs) { }
5913 virtual bool doHeapRegion(HeapRegion* r) {
5914 if (r->is_survivor()) {
5915 _g1h->verify_dirty_region(r);
5916 } else {
5917 _g1h->verify_not_dirty_region(r);
5918 }
5919 return false;
5920 }
5921 };
5922
5923 void G1CollectedHeap::verify_not_dirty_region(HeapRegion* hr) {
5924 // All of the region should be clean.
5925 CardTableModRefBS* ct_bs = (CardTableModRefBS*)barrier_set();
5926 MemRegion mr(hr->bottom(), hr->end());
5927 ct_bs->verify_not_dirty_region(mr);
5928 }
5929
5930 void G1CollectedHeap::verify_dirty_region(HeapRegion* hr) {
5931 // We cannot guarantee that [bottom(),end()] is dirty. Threads
5932 // dirty allocated blocks as they allocate them. The thread that
5933 // retires each region and replaces it with a new one will do a
5934 // maximal allocation to fill in [pre_dummy_top(),end()] but will
5935 // not dirty that area (one less thing to have to do while holding
5936 // a lock). So we can only verify that [bottom(),pre_dummy_top()]
5937 // is dirty.
5938 CardTableModRefBS* ct_bs = (CardTableModRefBS*) barrier_set();
5939 MemRegion mr(hr->bottom(), hr->pre_dummy_top());
5940 ct_bs->verify_dirty_region(mr);
5941 }
5942
5943 void G1CollectedHeap::verify_dirty_young_list(HeapRegion* head) {
5944 CardTableModRefBS* ct_bs = (CardTableModRefBS*) barrier_set();
5945 for (HeapRegion* hr = head; hr != NULL; hr = hr->get_next_young_region()) {
5946 verify_dirty_region(hr);
5947 }
5948 }
5949
5950 void G1CollectedHeap::verify_dirty_young_regions() {
5951 verify_dirty_young_list(_young_list->first_region());
5952 }
5953 #endif
5954
5955 void G1CollectedHeap::cleanUpCardTable() {
5956 CardTableModRefBS* ct_bs = (CardTableModRefBS*) (barrier_set());
5957 double start = os::elapsedTime();
5958
5959 {
5960 // Iterate over the dirty cards region list.
5961 G1ParCleanupCTTask cleanup_task(ct_bs, this);
5962
5963 if (G1CollectedHeap::use_parallel_gc_threads()) {
5964 set_par_threads();
5965 workers()->run_task(&cleanup_task);
5966 set_par_threads(0);
5967 } else {
5968 while (_dirty_cards_region_list) {
5969 HeapRegion* r = _dirty_cards_region_list;
5970 cleanup_task.clear_cards(r);
5971 _dirty_cards_region_list = r->get_next_dirty_cards_region();
5972 if (_dirty_cards_region_list == r) {
5973 // The last region.
5974 _dirty_cards_region_list = NULL;
5975 }
5976 r->set_next_dirty_cards_region(NULL);
5977 }
5978 }
5979 #ifndef PRODUCT
5980 if (G1VerifyCTCleanup || VerifyAfterGC) {
5981 G1VerifyCardTableCleanup cleanup_verifier(this, ct_bs);
5982 heap_region_iterate(&cleanup_verifier);
5983 }
5984 #endif
5985 }
5986
5987 double elapsed = os::elapsedTime() - start;
5988 g1_policy()->phase_times()->record_clear_ct_time(elapsed * 1000.0);
5989 }
5990
5991 void G1CollectedHeap::free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info) {
5992 size_t pre_used = 0;
5993 FreeRegionList local_free_list("Local List for CSet Freeing");
5994
5995 double young_time_ms = 0.0;
5996 double non_young_time_ms = 0.0;
5997
5998 // Since the collection set is a superset of the the young list,
5999 // all we need to do to clear the young list is clear its
6000 // head and length, and unlink any young regions in the code below
6001 _young_list->clear();
6002
6003 G1CollectorPolicy* policy = g1_policy();
6004
6005 double start_sec = os::elapsedTime();
6006 bool non_young = true;
6007
6008 HeapRegion* cur = cs_head;
6009 int age_bound = -1;
6010 size_t rs_lengths = 0;
6011
6012 while (cur != NULL) {
6013 assert(!is_on_master_free_list(cur), "sanity");
6014 if (non_young) {
6015 if (cur->is_young()) {
6016 double end_sec = os::elapsedTime();
6017 double elapsed_ms = (end_sec - start_sec) * 1000.0;
6018 non_young_time_ms += elapsed_ms;
6019
6020 start_sec = os::elapsedTime();
6021 non_young = false;
6022 }
6023 } else {
6024 if (!cur->is_young()) {
6025 double end_sec = os::elapsedTime();
6026 double elapsed_ms = (end_sec - start_sec) * 1000.0;
6027 young_time_ms += elapsed_ms;
6028
6029 start_sec = os::elapsedTime();
6030 non_young = true;
6031 }
6032 }
6033
6034 rs_lengths += cur->rem_set()->occupied();
6035
6036 HeapRegion* next = cur->next_in_collection_set();
6037 assert(cur->in_collection_set(), "bad CS");
6038 cur->set_next_in_collection_set(NULL);
6039 cur->set_in_collection_set(false);
6040
6041 if (cur->is_young()) {
6042 int index = cur->young_index_in_cset();
6043 assert(index != -1, "invariant");
6044 assert((uint) index < policy->young_cset_region_length(), "invariant");
6045 size_t words_survived = _surviving_young_words[index];
6046 cur->record_surv_words_in_group(words_survived);
6047
6048 // At this point the we have 'popped' cur from the collection set
6049 // (linked via next_in_collection_set()) but it is still in the
6050 // young list (linked via next_young_region()). Clear the
6051 // _next_young_region field.
6052 cur->set_next_young_region(NULL);
6053 } else {
6054 int index = cur->young_index_in_cset();
6055 assert(index == -1, "invariant");
6056 }
6057
6058 assert( (cur->is_young() && cur->young_index_in_cset() > -1) ||
6059 (!cur->is_young() && cur->young_index_in_cset() == -1),
6060 "invariant" );
6061
6062 if (!cur->evacuation_failed()) {
6063 MemRegion used_mr = cur->used_region();
6064
6065 // And the region is empty.
6066 assert(!used_mr.is_empty(), "Should not have empty regions in a CS.");
6067 free_region(cur, &pre_used, &local_free_list, false /* par */);
6068 } else {
6069 cur->uninstall_surv_rate_group();
6070 if (cur->is_young()) {
6071 cur->set_young_index_in_cset(-1);
6072 }
6073 cur->set_not_young();
6074 cur->set_evacuation_failed(false);
6075 // The region is now considered to be old.
6076 _old_set.add(cur);
6077 evacuation_info.increment_collectionset_used_after(cur->used());
6078 }
6079 cur = next;
6080 }
6081
6082 evacuation_info.set_regions_freed(local_free_list.length());
6083 policy->record_max_rs_lengths(rs_lengths);
6084 policy->cset_regions_freed();
6085
6086 double end_sec = os::elapsedTime();
6087 double elapsed_ms = (end_sec - start_sec) * 1000.0;
6088
6089 if (non_young) {
6090 non_young_time_ms += elapsed_ms;
6091 } else {
6092 young_time_ms += elapsed_ms;
6093 }
6094
6095 update_sets_after_freeing_regions(pre_used, &local_free_list,
6096 NULL /* old_proxy_set */,
6097 NULL /* humongous_proxy_set */,
6098 false /* par */);
6099 policy->phase_times()->record_young_free_cset_time_ms(young_time_ms);
6100 policy->phase_times()->record_non_young_free_cset_time_ms(non_young_time_ms);
6101 }
6102
6103 // This routine is similar to the above but does not record
6104 // any policy statistics or update free lists; we are abandoning
6105 // the current incremental collection set in preparation of a
6106 // full collection. After the full GC we will start to build up
6107 // the incremental collection set again.
6108 // This is only called when we're doing a full collection
6109 // and is immediately followed by the tearing down of the young list.
6110
6111 void G1CollectedHeap::abandon_collection_set(HeapRegion* cs_head) {
6112 HeapRegion* cur = cs_head;
6113
6114 while (cur != NULL) {
6115 HeapRegion* next = cur->next_in_collection_set();
6116 assert(cur->in_collection_set(), "bad CS");
6117 cur->set_next_in_collection_set(NULL);
6118 cur->set_in_collection_set(false);
6119 cur->set_young_index_in_cset(-1);
6120 cur = next;
6121 }
6122 }
6123
6124 void G1CollectedHeap::set_free_regions_coming() {
6125 if (G1ConcRegionFreeingVerbose) {
6126 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
6127 "setting free regions coming");
6128 }
6129
6130 assert(!free_regions_coming(), "pre-condition");
6131 _free_regions_coming = true;
6132 }
6133
6134 void G1CollectedHeap::reset_free_regions_coming() {
6135 assert(free_regions_coming(), "pre-condition");
6136
6137 {
6138 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6139 _free_regions_coming = false;
6140 SecondaryFreeList_lock->notify_all();
6141 }
6142
6143 if (G1ConcRegionFreeingVerbose) {
6144 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
6145 "reset free regions coming");
6146 }
6147 }
6148
6149 void G1CollectedHeap::wait_while_free_regions_coming() {
6150 // Most of the time we won't have to wait, so let's do a quick test
6151 // first before we take the lock.
6152 if (!free_regions_coming()) {
6153 return;
6154 }
6155
6156 if (G1ConcRegionFreeingVerbose) {
6157 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
6158 "waiting for free regions");
6159 }
6160
6161 {
6162 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6163 while (free_regions_coming()) {
6164 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
6165 }
6166 }
6167
6168 if (G1ConcRegionFreeingVerbose) {
6169 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
6170 "done waiting for free regions");
6171 }
6172 }
6173
6174 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
6175 assert(heap_lock_held_for_gc(),
6176 "the heap lock should already be held by or for this thread");
6177 _young_list->push_region(hr);
6178 }
6179
6180 class NoYoungRegionsClosure: public HeapRegionClosure {
6181 private:
6182 bool _success;
6183 public:
6184 NoYoungRegionsClosure() : _success(true) { }
6185 bool doHeapRegion(HeapRegion* r) {
6186 if (r->is_young()) {
6187 gclog_or_tty->print_cr("Region ["PTR_FORMAT", "PTR_FORMAT") tagged as young",
6188 r->bottom(), r->end());
6189 _success = false;
6190 }
6191 return false;
6192 }
6193 bool success() { return _success; }
6194 };
6195
6196 bool G1CollectedHeap::check_young_list_empty(bool check_heap, bool check_sample) {
6197 bool ret = _young_list->check_list_empty(check_sample);
6198
6199 if (check_heap) {
6200 NoYoungRegionsClosure closure;
6201 heap_region_iterate(&closure);
6202 ret = ret && closure.success();
6203 }
6204
6205 return ret;
6206 }
6207
6208 class TearDownRegionSetsClosure : public HeapRegionClosure {
6209 private:
6210 OldRegionSet *_old_set;
6211
6212 public:
6213 TearDownRegionSetsClosure(OldRegionSet* old_set) : _old_set(old_set) { }
6214
6215 bool doHeapRegion(HeapRegion* r) {
6216 if (r->is_empty()) {
6217 // We ignore empty regions, we'll empty the free list afterwards
6218 } else if (r->is_young()) {
6219 // We ignore young regions, we'll empty the young list afterwards
6220 } else if (r->isHumongous()) {
6221 // We ignore humongous regions, we're not tearing down the
6222 // humongous region set
6223 } else {
6224 // The rest should be old
6225 _old_set->remove(r);
6226 }
6227 return false;
6228 }
6229
6230 ~TearDownRegionSetsClosure() {
6231 assert(_old_set->is_empty(), "post-condition");
6232 }
6233 };
6234
6235 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
6236 assert_at_safepoint(true /* should_be_vm_thread */);
6237
6238 if (!free_list_only) {
6239 TearDownRegionSetsClosure cl(&_old_set);
6240 heap_region_iterate(&cl);
6241
6242 // Need to do this after the heap iteration to be able to
6243 // recognize the young regions and ignore them during the iteration.
6244 _young_list->empty_list();
6245 }
6246 _free_list.remove_all();
6247 }
6248
6249 class RebuildRegionSetsClosure : public HeapRegionClosure {
6250 private:
6251 bool _free_list_only;
6252 OldRegionSet* _old_set;
6253 FreeRegionList* _free_list;
6254 size_t _total_used;
6255
6256 public:
6257 RebuildRegionSetsClosure(bool free_list_only,
6258 OldRegionSet* old_set, FreeRegionList* free_list) :
6259 _free_list_only(free_list_only),
6260 _old_set(old_set), _free_list(free_list), _total_used(0) {
6261 assert(_free_list->is_empty(), "pre-condition");
6262 if (!free_list_only) {
6263 assert(_old_set->is_empty(), "pre-condition");
6264 }
6265 }
6266
6267 bool doHeapRegion(HeapRegion* r) {
6268 if (r->continuesHumongous()) {
6269 return false;
6270 }
6271
6272 if (r->is_empty()) {
6273 // Add free regions to the free list
6274 _free_list->add_as_tail(r);
6275 } else if (!_free_list_only) {
6276 assert(!r->is_young(), "we should not come across young regions");
6277
6278 if (r->isHumongous()) {
6279 // We ignore humongous regions, we left the humongous set unchanged
6280 } else {
6281 // The rest should be old, add them to the old set
6282 _old_set->add(r);
6283 }
6284 _total_used += r->used();
6285 }
6286
6287 return false;
6288 }
6289
6290 size_t total_used() {
6291 return _total_used;
6292 }
6293 };
6294
6295 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
6296 assert_at_safepoint(true /* should_be_vm_thread */);
6297
6298 RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_free_list);
6299 heap_region_iterate(&cl);
6300
6301 if (!free_list_only) {
6302 _summary_bytes_used = cl.total_used();
6303 }
6304 assert(_summary_bytes_used == recalculate_used(),
6305 err_msg("inconsistent _summary_bytes_used, "
6306 "value: "SIZE_FORMAT" recalculated: "SIZE_FORMAT,
6307 _summary_bytes_used, recalculate_used()));
6308 }
6309
6310 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) {
6311 _refine_cte_cl->set_concurrent(concurrent);
6312 }
6313
6314 bool G1CollectedHeap::is_in_closed_subset(const void* p) const {
6315 HeapRegion* hr = heap_region_containing(p);
6316 if (hr == NULL) {
6317 return is_in_permanent(p);
6318 } else {
6319 return hr->is_in(p);
6320 }
6321 }
6322
6323 // Methods for the mutator alloc region
6324
6325 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
6326 bool force) {
6327 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6328 assert(!force || g1_policy()->can_expand_young_list(),
6329 "if force is true we should be able to expand the young list");
6330 bool young_list_full = g1_policy()->is_young_list_full();
6331 if (force || !young_list_full) {
6332 HeapRegion* new_alloc_region = new_region(word_size,
6333 false /* do_expand */);
6334 if (new_alloc_region != NULL) {
6335 set_region_short_lived_locked(new_alloc_region);
6336 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Eden, young_list_full);
6337 return new_alloc_region;
6338 }
6339 }
6340 return NULL;
6341 }
6342
6343 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
6344 size_t allocated_bytes) {
6345 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6346 assert(alloc_region->is_young(), "all mutator alloc regions should be young");
6347
6348 g1_policy()->add_region_to_incremental_cset_lhs(alloc_region);
6349 _summary_bytes_used += allocated_bytes;
6350 _hr_printer.retire(alloc_region);
6351 // We update the eden sizes here, when the region is retired,
6352 // instead of when it's allocated, since this is the point that its
6353 // used space has been recored in _summary_bytes_used.
6354 g1mm()->update_eden_size();
6355 }
6356
6357 HeapRegion* MutatorAllocRegion::allocate_new_region(size_t word_size,
6358 bool force) {
6359 return _g1h->new_mutator_alloc_region(word_size, force);
6360 }
6361
6362 void G1CollectedHeap::set_par_threads() {
6363 // Don't change the number of workers. Use the value previously set
6364 // in the workgroup.
6365 assert(G1CollectedHeap::use_parallel_gc_threads(), "shouldn't be here otherwise");
6366 uint n_workers = workers()->active_workers();
6367 assert(UseDynamicNumberOfGCThreads ||
6368 n_workers == workers()->total_workers(),
6369 "Otherwise should be using the total number of workers");
6370 if (n_workers == 0) {
6371 assert(false, "Should have been set in prior evacuation pause.");
6372 n_workers = ParallelGCThreads;
6373 workers()->set_active_workers(n_workers);
6374 }
6375 set_par_threads(n_workers);
6376 }
6377
6378 void MutatorAllocRegion::retire_region(HeapRegion* alloc_region,
6379 size_t allocated_bytes) {
6380 _g1h->retire_mutator_alloc_region(alloc_region, allocated_bytes);
6381 }
6382
6383 // Methods for the GC alloc regions
6384
6385 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size,
6386 uint count,
6387 GCAllocPurpose ap) {
6388 assert(FreeList_lock->owned_by_self(), "pre-condition");
6389
6390 if (count < g1_policy()->max_regions(ap)) {
6391 HeapRegion* new_alloc_region = new_region(word_size,
6392 true /* do_expand */);
6393 if (new_alloc_region != NULL) {
6394 // We really only need to do this for old regions given that we
6395 // should never scan survivors. But it doesn't hurt to do it
6396 // for survivors too.
6397 new_alloc_region->set_saved_mark();
6398 if (ap == GCAllocForSurvived) {
6399 new_alloc_region->set_survivor();
6400 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Survivor);
6401 } else {
6402 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Old);
6403 }
6404 bool during_im = g1_policy()->during_initial_mark_pause();
6405 new_alloc_region->note_start_of_copying(during_im);
6406 return new_alloc_region;
6407 } else {
6408 g1_policy()->note_alloc_region_limit_reached(ap);
6409 }
6410 }
6411 return NULL;
6412 }
6413
6414 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
6415 size_t allocated_bytes,
6416 GCAllocPurpose ap) {
6417 bool during_im = g1_policy()->during_initial_mark_pause();
6418 alloc_region->note_end_of_copying(during_im);
6419 g1_policy()->record_bytes_copied_during_gc(allocated_bytes);
6420 if (ap == GCAllocForSurvived) {
6421 young_list()->add_survivor_region(alloc_region);
6422 } else {
6423 _old_set.add(alloc_region);
6424 }
6425 _hr_printer.retire(alloc_region);
6426 }
6427
6428 HeapRegion* SurvivorGCAllocRegion::allocate_new_region(size_t word_size,
6429 bool force) {
6430 assert(!force, "not supported for GC alloc regions");
6431 return _g1h->new_gc_alloc_region(word_size, count(), GCAllocForSurvived);
6432 }
6433
6434 void SurvivorGCAllocRegion::retire_region(HeapRegion* alloc_region,
6435 size_t allocated_bytes) {
6436 _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes,
6437 GCAllocForSurvived);
6438 }
6439
6440 HeapRegion* OldGCAllocRegion::allocate_new_region(size_t word_size,
6441 bool force) {
6442 assert(!force, "not supported for GC alloc regions");
6443 return _g1h->new_gc_alloc_region(word_size, count(), GCAllocForTenured);
6444 }
6445
6446 void OldGCAllocRegion::retire_region(HeapRegion* alloc_region,
6447 size_t allocated_bytes) {
6448 _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes,
6449 GCAllocForTenured);
6450 }
6451 // Heap region set verification
6452
6453 class VerifyRegionListsClosure : public HeapRegionClosure {
6454 private:
6455 FreeRegionList* _free_list;
6456 OldRegionSet* _old_set;
6457 HumongousRegionSet* _humongous_set;
6458 uint _region_count;
6459
6460 public:
6461 VerifyRegionListsClosure(OldRegionSet* old_set,
6462 HumongousRegionSet* humongous_set,
6463 FreeRegionList* free_list) :
6464 _old_set(old_set), _humongous_set(humongous_set),
6465 _free_list(free_list), _region_count(0) { }
6466
6467 uint region_count() { return _region_count; }
6468
6469 bool doHeapRegion(HeapRegion* hr) {
6470 _region_count += 1;
6471
6472 if (hr->continuesHumongous()) {
6473 return false;
6474 }
6475
6476 if (hr->is_young()) {
6477 // TODO
6478 } else if (hr->startsHumongous()) {
6479 _humongous_set->verify_next_region(hr);
6480 } else if (hr->is_empty()) {
6481 _free_list->verify_next_region(hr);
6482 } else {
6483 _old_set->verify_next_region(hr);
6484 }
6485 return false;
6486 }
6487 };
6488
6489 HeapRegion* G1CollectedHeap::new_heap_region(uint hrs_index,
6490 HeapWord* bottom) {
6491 HeapWord* end = bottom + HeapRegion::GrainWords;
6492 MemRegion mr(bottom, end);
6493 assert(_g1_reserved.contains(mr), "invariant");
6494 // This might return NULL if the allocation fails
6495 return new HeapRegion(hrs_index, _bot_shared, mr, true /* is_zeroed */);
6496 }
6497
6498 void G1CollectedHeap::verify_region_sets() {
6499 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6500
6501 // First, check the explicit lists.
6502 _free_list.verify();
6503 {
6504 // Given that a concurrent operation might be adding regions to
6505 // the secondary free list we have to take the lock before
6506 // verifying it.
6507 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6508 _secondary_free_list.verify();
6509 }
6510 _old_set.verify();
6511 _humongous_set.verify();
6512
6513 // If a concurrent region freeing operation is in progress it will
6514 // be difficult to correctly attributed any free regions we come
6515 // across to the correct free list given that they might belong to
6516 // one of several (free_list, secondary_free_list, any local lists,
6517 // etc.). So, if that's the case we will skip the rest of the
6518 // verification operation. Alternatively, waiting for the concurrent
6519 // operation to complete will have a non-trivial effect on the GC's
6520 // operation (no concurrent operation will last longer than the
6521 // interval between two calls to verification) and it might hide
6522 // any issues that we would like to catch during testing.
6523 if (free_regions_coming()) {
6524 return;
6525 }
6526
6527 // Make sure we append the secondary_free_list on the free_list so
6528 // that all free regions we will come across can be safely
6529 // attributed to the free_list.
6530 append_secondary_free_list_if_not_empty_with_lock();
6531
6532 // Finally, make sure that the region accounting in the lists is
6533 // consistent with what we see in the heap.
6534 _old_set.verify_start();
6535 _humongous_set.verify_start();
6536 _free_list.verify_start();
6537
6538 VerifyRegionListsClosure cl(&_old_set, &_humongous_set, &_free_list);
6539 heap_region_iterate(&cl);
6540
6541 _old_set.verify_end();
6542 _humongous_set.verify_end();
6543 _free_list.verify_end();
6544 }