1 /*
2 * Copyright (c) 2001, 2013, 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/heapRegion.inline.hpp"
42 #include "gc_implementation/g1/heapRegionRemSet.hpp"
43 #include "gc_implementation/g1/heapRegionSeq.inline.hpp"
44 #include "gc_implementation/g1/vm_operations_g1.hpp"
45 #include "gc_implementation/shared/isGCActiveMark.hpp"
46 #include "memory/gcLocker.inline.hpp"
47 #include "memory/genOopClosures.inline.hpp"
48 #include "memory/generationSpec.hpp"
49 #include "memory/referenceProcessor.hpp"
50 #include "oops/oop.inline.hpp"
51 #include "oops/oop.pcgc.inline.hpp"
52 #include "runtime/aprofiler.hpp"
53 #include "runtime/vmThread.hpp"
54
55 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;
56
57 // turn it on so that the contents of the young list (scan-only /
58 // to-be-collected) are printed at "strategic" points before / during
59 // / after the collection --- this is useful for debugging
60 #define YOUNG_LIST_VERBOSE 0
61 // CURRENT STATUS
62 // This file is under construction. Search for "FIXME".
63
64 // INVARIANTS/NOTES
65 //
66 // All allocation activity covered by the G1CollectedHeap interface is
67 // serialized by acquiring the HeapLock. This happens in mem_allocate
68 // and allocate_new_tlab, which are the "entry" points to the
69 // allocation code from the rest of the JVM. (Note that this does not
70 // apply to TLAB allocation, which is not part of this interface: it
71 // is done by clients of this interface.)
72
73 // Notes on implementation of parallelism in different tasks.
74 //
75 // G1ParVerifyTask uses heap_region_par_iterate_chunked() for parallelism.
76 // The number of GC workers is passed to heap_region_par_iterate_chunked().
77 // It does use run_task() which sets _n_workers in the task.
78 // G1ParTask executes g1_process_strong_roots() ->
79 // SharedHeap::process_strong_roots() which calls eventuall to
80 // CardTableModRefBS::par_non_clean_card_iterate_work() which uses
81 // SequentialSubTasksDone. SharedHeap::process_strong_roots() also
82 // directly uses SubTasksDone (_process_strong_tasks field in SharedHeap).
83 //
84
85 // Local to this file.
86
87 class RefineCardTableEntryClosure: public CardTableEntryClosure {
88 SuspendibleThreadSet* _sts;
89 G1RemSet* _g1rs;
90 ConcurrentG1Refine* _cg1r;
91 bool _concurrent;
92 public:
93 RefineCardTableEntryClosure(SuspendibleThreadSet* sts,
94 G1RemSet* g1rs,
95 ConcurrentG1Refine* cg1r) :
96 _sts(sts), _g1rs(g1rs), _cg1r(cg1r), _concurrent(true)
97 {}
98 bool do_card_ptr(jbyte* card_ptr, int worker_i) {
99 bool oops_into_cset = _g1rs->concurrentRefineOneCard(card_ptr, worker_i, false);
100 // This path is executed by the concurrent refine or mutator threads,
101 // concurrently, and so we do not care if card_ptr contains references
102 // that point into the collection set.
103 assert(!oops_into_cset, "should be");
104
105 if (_concurrent && _sts->should_yield()) {
106 // Caller will actually yield.
107 return false;
108 }
109 // Otherwise, we finished successfully; return true.
110 return true;
111 }
112 void set_concurrent(bool b) { _concurrent = b; }
113 };
114
115
116 class ClearLoggedCardTableEntryClosure: public CardTableEntryClosure {
117 int _calls;
118 G1CollectedHeap* _g1h;
119 CardTableModRefBS* _ctbs;
120 int _histo[256];
121 public:
122 ClearLoggedCardTableEntryClosure() :
123 _calls(0)
124 {
125 _g1h = G1CollectedHeap::heap();
126 _ctbs = (CardTableModRefBS*)_g1h->barrier_set();
127 for (int i = 0; i < 256; i++) _histo[i] = 0;
128 }
129 bool do_card_ptr(jbyte* card_ptr, int worker_i) {
130 if (_g1h->is_in_reserved(_ctbs->addr_for(card_ptr))) {
131 _calls++;
132 unsigned char* ujb = (unsigned char*)card_ptr;
133 int ind = (int)(*ujb);
134 _histo[ind]++;
135 *card_ptr = -1;
136 }
137 return true;
138 }
139 int calls() { return _calls; }
140 void print_histo() {
141 gclog_or_tty->print_cr("Card table value histogram:");
142 for (int i = 0; i < 256; i++) {
143 if (_histo[i] != 0) {
144 gclog_or_tty->print_cr(" %d: %d", i, _histo[i]);
145 }
146 }
147 }
148 };
149
150 class RedirtyLoggedCardTableEntryClosure: public CardTableEntryClosure {
151 int _calls;
152 G1CollectedHeap* _g1h;
153 CardTableModRefBS* _ctbs;
154 public:
155 RedirtyLoggedCardTableEntryClosure() :
156 _calls(0)
157 {
158 _g1h = G1CollectedHeap::heap();
159 _ctbs = (CardTableModRefBS*)_g1h->barrier_set();
160 }
161 bool do_card_ptr(jbyte* card_ptr, int worker_i) {
162 if (_g1h->is_in_reserved(_ctbs->addr_for(card_ptr))) {
163 _calls++;
164 *card_ptr = 0;
165 }
166 return true;
167 }
168 int calls() { return _calls; }
169 };
170
171 class RedirtyLoggedCardTableEntryFastClosure : public CardTableEntryClosure {
172 public:
173 bool do_card_ptr(jbyte* card_ptr, int worker_i) {
174 *card_ptr = CardTableModRefBS::dirty_card_val();
175 return true;
176 }
177 };
178
179 YoungList::YoungList(G1CollectedHeap* g1h) :
180 _g1h(g1h), _head(NULL), _length(0), _last_sampled_rs_lengths(0),
181 _survivor_head(NULL), _survivor_tail(NULL), _survivor_length(0) {
182 guarantee(check_list_empty(false), "just making sure...");
183 }
184
185 void YoungList::push_region(HeapRegion *hr) {
186 assert(!hr->is_young(), "should not already be young");
187 assert(hr->get_next_young_region() == NULL, "cause it should!");
188
189 hr->set_next_young_region(_head);
190 _head = hr;
191
192 _g1h->g1_policy()->set_region_eden(hr, (int) _length);
193 ++_length;
194 }
195
196 void YoungList::add_survivor_region(HeapRegion* hr) {
197 assert(hr->is_survivor(), "should be flagged as survivor region");
198 assert(hr->get_next_young_region() == NULL, "cause it should!");
199
200 hr->set_next_young_region(_survivor_head);
201 if (_survivor_head == NULL) {
202 _survivor_tail = hr;
203 }
204 _survivor_head = hr;
205 ++_survivor_length;
206 }
207
208 void YoungList::empty_list(HeapRegion* list) {
209 while (list != NULL) {
210 HeapRegion* next = list->get_next_young_region();
211 list->set_next_young_region(NULL);
212 list->uninstall_surv_rate_group();
213 list->set_not_young();
214 list = next;
215 }
216 }
217
218 void YoungList::empty_list() {
219 assert(check_list_well_formed(), "young list should be well formed");
220
221 empty_list(_head);
222 _head = NULL;
223 _length = 0;
224
225 empty_list(_survivor_head);
226 _survivor_head = NULL;
227 _survivor_tail = NULL;
228 _survivor_length = 0;
229
230 _last_sampled_rs_lengths = 0;
231
232 assert(check_list_empty(false), "just making sure...");
233 }
234
235 bool YoungList::check_list_well_formed() {
236 bool ret = true;
237
238 uint length = 0;
239 HeapRegion* curr = _head;
240 HeapRegion* last = NULL;
241 while (curr != NULL) {
242 if (!curr->is_young()) {
243 gclog_or_tty->print_cr("### YOUNG REGION "PTR_FORMAT"-"PTR_FORMAT" "
244 "incorrectly tagged (y: %d, surv: %d)",
245 curr->bottom(), curr->end(),
246 curr->is_young(), curr->is_survivor());
247 ret = false;
248 }
249 ++length;
250 last = curr;
251 curr = curr->get_next_young_region();
252 }
253 ret = ret && (length == _length);
254
255 if (!ret) {
256 gclog_or_tty->print_cr("### YOUNG LIST seems not well formed!");
257 gclog_or_tty->print_cr("### list has %u entries, _length is %u",
258 length, _length);
259 }
260
261 return ret;
262 }
263
264 bool YoungList::check_list_empty(bool check_sample) {
265 bool ret = true;
266
267 if (_length != 0) {
268 gclog_or_tty->print_cr("### YOUNG LIST should have 0 length, not %u",
269 _length);
270 ret = false;
271 }
272 if (check_sample && _last_sampled_rs_lengths != 0) {
273 gclog_or_tty->print_cr("### YOUNG LIST has non-zero last sampled RS lengths");
274 ret = false;
275 }
276 if (_head != NULL) {
277 gclog_or_tty->print_cr("### YOUNG LIST does not have a NULL head");
278 ret = false;
279 }
280 if (!ret) {
281 gclog_or_tty->print_cr("### YOUNG LIST does not seem empty");
282 }
283
284 return ret;
285 }
286
287 void
288 YoungList::rs_length_sampling_init() {
289 _sampled_rs_lengths = 0;
290 _curr = _head;
291 }
292
293 bool
294 YoungList::rs_length_sampling_more() {
295 return _curr != NULL;
296 }
297
298 void
299 YoungList::rs_length_sampling_next() {
300 assert( _curr != NULL, "invariant" );
301 size_t rs_length = _curr->rem_set()->occupied();
302
303 _sampled_rs_lengths += rs_length;
304
305 // The current region may not yet have been added to the
306 // incremental collection set (it gets added when it is
307 // retired as the current allocation region).
308 if (_curr->in_collection_set()) {
309 // Update the collection set policy information for this region
310 _g1h->g1_policy()->update_incremental_cset_info(_curr, rs_length);
311 }
312
313 _curr = _curr->get_next_young_region();
314 if (_curr == NULL) {
315 _last_sampled_rs_lengths = _sampled_rs_lengths;
316 // gclog_or_tty->print_cr("last sampled RS lengths = %d", _last_sampled_rs_lengths);
317 }
318 }
319
320 void
321 YoungList::reset_auxilary_lists() {
322 guarantee( is_empty(), "young list should be empty" );
323 assert(check_list_well_formed(), "young list should be well formed");
324
325 // Add survivor regions to SurvRateGroup.
326 _g1h->g1_policy()->note_start_adding_survivor_regions();
327 _g1h->g1_policy()->finished_recalculating_age_indexes(true /* is_survivors */);
328
329 int young_index_in_cset = 0;
330 for (HeapRegion* curr = _survivor_head;
331 curr != NULL;
332 curr = curr->get_next_young_region()) {
333 _g1h->g1_policy()->set_region_survivor(curr, young_index_in_cset);
334
335 // The region is a non-empty survivor so let's add it to
336 // the incremental collection set for the next evacuation
337 // pause.
338 _g1h->g1_policy()->add_region_to_incremental_cset_rhs(curr);
339 young_index_in_cset += 1;
340 }
341 assert((uint) young_index_in_cset == _survivor_length, "post-condition");
342 _g1h->g1_policy()->note_stop_adding_survivor_regions();
343
344 _head = _survivor_head;
345 _length = _survivor_length;
346 if (_survivor_head != NULL) {
347 assert(_survivor_tail != NULL, "cause it shouldn't be");
348 assert(_survivor_length > 0, "invariant");
349 _survivor_tail->set_next_young_region(NULL);
350 }
351
352 // Don't clear the survivor list handles until the start of
353 // the next evacuation pause - we need it in order to re-tag
354 // the survivor regions from this evacuation pause as 'young'
355 // at the start of the next.
356
357 _g1h->g1_policy()->finished_recalculating_age_indexes(false /* is_survivors */);
358
359 assert(check_list_well_formed(), "young list should be well formed");
360 }
361
362 void YoungList::print() {
363 HeapRegion* lists[] = {_head, _survivor_head};
364 const char* names[] = {"YOUNG", "SURVIVOR"};
365
366 for (unsigned int list = 0; list < ARRAY_SIZE(lists); ++list) {
367 gclog_or_tty->print_cr("%s LIST CONTENTS", names[list]);
368 HeapRegion *curr = lists[list];
369 if (curr == NULL)
370 gclog_or_tty->print_cr(" empty");
371 while (curr != NULL) {
372 gclog_or_tty->print_cr(" "HR_FORMAT", P: "PTR_FORMAT "N: "PTR_FORMAT", age: %4d",
373 HR_FORMAT_PARAMS(curr),
374 curr->prev_top_at_mark_start(),
375 curr->next_top_at_mark_start(),
376 curr->age_in_surv_rate_group_cond());
377 curr = curr->get_next_young_region();
378 }
379 }
380
381 gclog_or_tty->print_cr("");
382 }
383
384 void G1CollectedHeap::push_dirty_cards_region(HeapRegion* hr)
385 {
386 // Claim the right to put the region on the dirty cards region list
387 // by installing a self pointer.
388 HeapRegion* next = hr->get_next_dirty_cards_region();
389 if (next == NULL) {
390 HeapRegion* res = (HeapRegion*)
391 Atomic::cmpxchg_ptr(hr, hr->next_dirty_cards_region_addr(),
392 NULL);
393 if (res == NULL) {
394 HeapRegion* head;
395 do {
396 // Put the region to the dirty cards region list.
397 head = _dirty_cards_region_list;
398 next = (HeapRegion*)
399 Atomic::cmpxchg_ptr(hr, &_dirty_cards_region_list, head);
400 if (next == head) {
401 assert(hr->get_next_dirty_cards_region() == hr,
402 "hr->get_next_dirty_cards_region() != hr");
403 if (next == NULL) {
404 // The last region in the list points to itself.
405 hr->set_next_dirty_cards_region(hr);
406 } else {
407 hr->set_next_dirty_cards_region(next);
408 }
409 }
410 } while (next != head);
411 }
412 }
413 }
414
415 HeapRegion* G1CollectedHeap::pop_dirty_cards_region()
416 {
417 HeapRegion* head;
418 HeapRegion* hr;
419 do {
420 head = _dirty_cards_region_list;
421 if (head == NULL) {
422 return NULL;
423 }
424 HeapRegion* new_head = head->get_next_dirty_cards_region();
425 if (head == new_head) {
426 // The last region.
427 new_head = NULL;
428 }
429 hr = (HeapRegion*)Atomic::cmpxchg_ptr(new_head, &_dirty_cards_region_list,
430 head);
431 } while (hr != head);
432 assert(hr != NULL, "invariant");
433 hr->set_next_dirty_cards_region(NULL);
434 return hr;
435 }
436
437 void G1CollectedHeap::stop_conc_gc_threads() {
438 _cg1r->stop();
439 _cmThread->stop();
440 }
441
442 #ifdef ASSERT
443 // A region is added to the collection set as it is retired
444 // so an address p can point to a region which will be in the
445 // collection set but has not yet been retired. This method
446 // therefore is only accurate during a GC pause after all
447 // regions have been retired. It is used for debugging
448 // to check if an nmethod has references to objects that can
449 // be move during a partial collection. Though it can be
450 // inaccurate, it is sufficient for G1 because the conservative
451 // implementation of is_scavengable() for G1 will indicate that
452 // all nmethods must be scanned during a partial collection.
453 bool G1CollectedHeap::is_in_partial_collection(const void* p) {
454 HeapRegion* hr = heap_region_containing(p);
455 return hr != NULL && hr->in_collection_set();
456 }
457 #endif
458
459 // Returns true if the reference points to an object that
460 // can move in an incremental collecction.
461 bool G1CollectedHeap::is_scavengable(const void* p) {
462 G1CollectedHeap* g1h = G1CollectedHeap::heap();
463 G1CollectorPolicy* g1p = g1h->g1_policy();
464 HeapRegion* hr = heap_region_containing(p);
465 if (hr == NULL) {
466 // null
467 assert(p == NULL, err_msg("Not NULL " PTR_FORMAT ,p));
468 return false;
469 } else {
470 return !hr->isHumongous();
471 }
472 }
473
474 void G1CollectedHeap::check_ct_logs_at_safepoint() {
475 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
476 CardTableModRefBS* ct_bs = (CardTableModRefBS*)barrier_set();
477
478 // Count the dirty cards at the start.
479 CountNonCleanMemRegionClosure count1(this);
480 ct_bs->mod_card_iterate(&count1);
481 int orig_count = count1.n();
482
483 // First clear the logged cards.
484 ClearLoggedCardTableEntryClosure clear;
485 dcqs.set_closure(&clear);
486 dcqs.apply_closure_to_all_completed_buffers();
487 dcqs.iterate_closure_all_threads(false);
488 clear.print_histo();
489
490 // Now ensure that there's no dirty cards.
491 CountNonCleanMemRegionClosure count2(this);
492 ct_bs->mod_card_iterate(&count2);
493 if (count2.n() != 0) {
494 gclog_or_tty->print_cr("Card table has %d entries; %d originally",
495 count2.n(), orig_count);
496 }
497 guarantee(count2.n() == 0, "Card table should be clean.");
498
499 RedirtyLoggedCardTableEntryClosure redirty;
500 JavaThread::dirty_card_queue_set().set_closure(&redirty);
501 dcqs.apply_closure_to_all_completed_buffers();
502 dcqs.iterate_closure_all_threads(false);
503 gclog_or_tty->print_cr("Log entries = %d, dirty cards = %d.",
504 clear.calls(), orig_count);
505 guarantee(redirty.calls() == clear.calls(),
506 "Or else mechanism is broken.");
507
508 CountNonCleanMemRegionClosure count3(this);
509 ct_bs->mod_card_iterate(&count3);
510 if (count3.n() != orig_count) {
511 gclog_or_tty->print_cr("Should have restored them all: orig = %d, final = %d.",
512 orig_count, count3.n());
513 guarantee(count3.n() >= orig_count, "Should have restored them all.");
514 }
515
516 JavaThread::dirty_card_queue_set().set_closure(_refine_cte_cl);
517 }
518
519 // Private class members.
520
521 G1CollectedHeap* G1CollectedHeap::_g1h;
522
523 // Private methods.
524
525 HeapRegion*
526 G1CollectedHeap::new_region_try_secondary_free_list() {
527 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
528 while (!_secondary_free_list.is_empty() || free_regions_coming()) {
529 if (!_secondary_free_list.is_empty()) {
530 if (G1ConcRegionFreeingVerbose) {
531 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
532 "secondary_free_list has %u entries",
533 _secondary_free_list.length());
534 }
535 // It looks as if there are free regions available on the
536 // secondary_free_list. Let's move them to the free_list and try
537 // again to allocate from it.
538 append_secondary_free_list();
539
540 assert(!_free_list.is_empty(), "if the secondary_free_list was not "
541 "empty we should have moved at least one entry to the free_list");
542 HeapRegion* res = _free_list.remove_head();
543 if (G1ConcRegionFreeingVerbose) {
544 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
545 "allocated "HR_FORMAT" from secondary_free_list",
546 HR_FORMAT_PARAMS(res));
547 }
548 return res;
549 }
550
551 // Wait here until we get notifed either when (a) there are no
552 // more free regions coming or (b) some regions have been moved on
553 // the secondary_free_list.
554 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
555 }
556
557 if (G1ConcRegionFreeingVerbose) {
558 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
559 "could not allocate from secondary_free_list");
560 }
561 return NULL;
562 }
563
564 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool do_expand) {
565 assert(!isHumongous(word_size) || word_size <= HeapRegion::GrainWords,
566 "the only time we use this to allocate a humongous region is "
567 "when we are allocating a single humongous region");
568
569 HeapRegion* res;
570 if (G1StressConcRegionFreeing) {
571 if (!_secondary_free_list.is_empty()) {
572 if (G1ConcRegionFreeingVerbose) {
573 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
574 "forced to look at the secondary_free_list");
575 }
576 res = new_region_try_secondary_free_list();
577 if (res != NULL) {
578 return res;
579 }
580 }
581 }
582 res = _free_list.remove_head_or_null();
583 if (res == NULL) {
584 if (G1ConcRegionFreeingVerbose) {
585 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
586 "res == NULL, trying the secondary_free_list");
587 }
588 res = new_region_try_secondary_free_list();
589 }
590 if (res == NULL && do_expand && _expand_heap_after_alloc_failure) {
591 // Currently, only attempts to allocate GC alloc regions set
592 // do_expand to true. So, we should only reach here during a
593 // safepoint. If this assumption changes we might have to
594 // reconsider the use of _expand_heap_after_alloc_failure.
595 assert(SafepointSynchronize::is_at_safepoint(), "invariant");
596
597 ergo_verbose1(ErgoHeapSizing,
598 "attempt heap expansion",
599 ergo_format_reason("region allocation request failed")
600 ergo_format_byte("allocation request"),
601 word_size * HeapWordSize);
602 if (expand(word_size * HeapWordSize)) {
603 // Given that expand() succeeded in expanding the heap, and we
604 // always expand the heap by an amount aligned to the heap
605 // region size, the free list should in theory not be empty. So
606 // it would probably be OK to use remove_head(). But the extra
607 // check for NULL is unlikely to be a performance issue here (we
608 // just expanded the heap!) so let's just be conservative and
609 // use remove_head_or_null().
610 res = _free_list.remove_head_or_null();
611 } else {
612 _expand_heap_after_alloc_failure = false;
613 }
614 }
615 return res;
616 }
617
618 uint G1CollectedHeap::humongous_obj_allocate_find_first(uint num_regions,
619 size_t word_size) {
620 assert(isHumongous(word_size), "word_size should be humongous");
621 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
622
623 uint first = G1_NULL_HRS_INDEX;
624 if (num_regions == 1) {
625 // Only one region to allocate, no need to go through the slower
626 // path. The caller will attempt the expasion if this fails, so
627 // let's not try to expand here too.
628 HeapRegion* hr = new_region(word_size, false /* do_expand */);
629 if (hr != NULL) {
630 first = hr->hrs_index();
631 } else {
632 first = G1_NULL_HRS_INDEX;
633 }
634 } else {
635 // We can't allocate humongous regions while cleanupComplete() is
636 // running, since some of the regions we find to be empty might not
637 // yet be added to the free list and it is not straightforward to
638 // know which list they are on so that we can remove them. Note
639 // that we only need to do this if we need to allocate more than
640 // one region to satisfy the current humongous allocation
641 // request. If we are only allocating one region we use the common
642 // region allocation code (see above).
643 wait_while_free_regions_coming();
644 append_secondary_free_list_if_not_empty_with_lock();
645
646 if (free_regions() >= num_regions) {
647 first = _hrs.find_contiguous(num_regions);
648 if (first != G1_NULL_HRS_INDEX) {
649 for (uint i = first; i < first + num_regions; ++i) {
650 HeapRegion* hr = region_at(i);
651 assert(hr->is_empty(), "sanity");
652 assert(is_on_master_free_list(hr), "sanity");
653 hr->set_pending_removal(true);
654 }
655 _free_list.remove_all_pending(num_regions);
656 }
657 }
658 }
659 return first;
660 }
661
662 HeapWord*
663 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first,
664 uint num_regions,
665 size_t word_size) {
666 assert(first != G1_NULL_HRS_INDEX, "pre-condition");
667 assert(isHumongous(word_size), "word_size should be humongous");
668 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
669
670 // Index of last region in the series + 1.
671 uint last = first + num_regions;
672
673 // We need to initialize the region(s) we just discovered. This is
674 // a bit tricky given that it can happen concurrently with
675 // refinement threads refining cards on these regions and
676 // potentially wanting to refine the BOT as they are scanning
677 // those cards (this can happen shortly after a cleanup; see CR
678 // 6991377). So we have to set up the region(s) carefully and in
679 // a specific order.
680
681 // The word size sum of all the regions we will allocate.
682 size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords;
683 assert(word_size <= word_size_sum, "sanity");
684
685 // This will be the "starts humongous" region.
686 HeapRegion* first_hr = region_at(first);
687 // The header of the new object will be placed at the bottom of
688 // the first region.
689 HeapWord* new_obj = first_hr->bottom();
690 // This will be the new end of the first region in the series that
691 // should also match the end of the last region in the seriers.
692 HeapWord* new_end = new_obj + word_size_sum;
693 // This will be the new top of the first region that will reflect
694 // this allocation.
695 HeapWord* new_top = new_obj + word_size;
696
697 // First, we need to zero the header of the space that we will be
698 // allocating. When we update top further down, some refinement
699 // threads might try to scan the region. By zeroing the header we
700 // ensure that any thread that will try to scan the region will
701 // come across the zero klass word and bail out.
702 //
703 // NOTE: It would not have been correct to have used
704 // CollectedHeap::fill_with_object() and make the space look like
705 // an int array. The thread that is doing the allocation will
706 // later update the object header to a potentially different array
707 // type and, for a very short period of time, the klass and length
708 // fields will be inconsistent. This could cause a refinement
709 // thread to calculate the object size incorrectly.
710 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
711
712 // We will set up the first region as "starts humongous". This
713 // will also update the BOT covering all the regions to reflect
714 // that there is a single object that starts at the bottom of the
715 // first region.
716 first_hr->set_startsHumongous(new_top, new_end);
717
718 // Then, if there are any, we will set up the "continues
719 // humongous" regions.
720 HeapRegion* hr = NULL;
721 for (uint i = first + 1; i < last; ++i) {
722 hr = region_at(i);
723 hr->set_continuesHumongous(first_hr);
724 }
725 // If we have "continues humongous" regions (hr != NULL), then the
726 // end of the last one should match new_end.
727 assert(hr == NULL || hr->end() == new_end, "sanity");
728
729 // Up to this point no concurrent thread would have been able to
730 // do any scanning on any region in this series. All the top
731 // fields still point to bottom, so the intersection between
732 // [bottom,top] and [card_start,card_end] will be empty. Before we
733 // update the top fields, we'll do a storestore to make sure that
734 // no thread sees the update to top before the zeroing of the
735 // object header and the BOT initialization.
736 OrderAccess::storestore();
737
738 // Now that the BOT and the object header have been initialized,
739 // we can update top of the "starts humongous" region.
740 assert(first_hr->bottom() < new_top && new_top <= first_hr->end(),
741 "new_top should be in this region");
742 first_hr->set_top(new_top);
743 if (_hr_printer.is_active()) {
744 HeapWord* bottom = first_hr->bottom();
745 HeapWord* end = first_hr->orig_end();
746 if ((first + 1) == last) {
747 // the series has a single humongous region
748 _hr_printer.alloc(G1HRPrinter::SingleHumongous, first_hr, new_top);
749 } else {
750 // the series has more than one humongous regions
751 _hr_printer.alloc(G1HRPrinter::StartsHumongous, first_hr, end);
752 }
753 }
754
755 // Now, we will update the top fields of the "continues humongous"
756 // regions. The reason we need to do this is that, otherwise,
757 // these regions would look empty and this will confuse parts of
758 // G1. For example, the code that looks for a consecutive number
759 // of empty regions will consider them empty and try to
760 // re-allocate them. We can extend is_empty() to also include
761 // !continuesHumongous(), but it is easier to just update the top
762 // fields here. The way we set top for all regions (i.e., top ==
763 // end for all regions but the last one, top == new_top for the
764 // last one) is actually used when we will free up the humongous
765 // region in free_humongous_region().
766 hr = NULL;
767 for (uint i = first + 1; i < last; ++i) {
768 hr = region_at(i);
769 if ((i + 1) == last) {
770 // last continues humongous region
771 assert(hr->bottom() < new_top && new_top <= hr->end(),
772 "new_top should fall on this region");
773 hr->set_top(new_top);
774 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, new_top);
775 } else {
776 // not last one
777 assert(new_top > hr->end(), "new_top should be above this region");
778 hr->set_top(hr->end());
779 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, hr->end());
780 }
781 }
782 // If we have continues humongous regions (hr != NULL), then the
783 // end of the last one should match new_end and its top should
784 // match new_top.
785 assert(hr == NULL ||
786 (hr->end() == new_end && hr->top() == new_top), "sanity");
787 check_bitmaps("Humongous Region Allocation", first_hr);
788
789 assert(first_hr->used() == word_size * HeapWordSize, "invariant");
790 _summary_bytes_used += first_hr->used();
791 _humongous_set.add(first_hr);
792
793 return new_obj;
794 }
795
796 // If could fit into free regions w/o expansion, try.
797 // Otherwise, if can expand, do so.
798 // Otherwise, if using ex regions might help, try with ex given back.
799 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size) {
800 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
801
802 verify_region_sets_optional();
803
804 size_t word_size_rounded = round_to(word_size, HeapRegion::GrainWords);
805 uint num_regions = (uint) (word_size_rounded / HeapRegion::GrainWords);
806 uint x_num = expansion_regions();
807 uint fs = _hrs.free_suffix();
808 uint first = humongous_obj_allocate_find_first(num_regions, word_size);
809 if (first == G1_NULL_HRS_INDEX) {
810 // The only thing we can do now is attempt expansion.
811 if (fs + x_num >= num_regions) {
812 // If the number of regions we're trying to allocate for this
813 // object is at most the number of regions in the free suffix,
814 // then the call to humongous_obj_allocate_find_first() above
815 // should have succeeded and we wouldn't be here.
816 //
817 // We should only be trying to expand when the free suffix is
818 // not sufficient for the object _and_ we have some expansion
819 // room available.
820 assert(num_regions > fs, "earlier allocation should have succeeded");
821
822 ergo_verbose1(ErgoHeapSizing,
823 "attempt heap expansion",
824 ergo_format_reason("humongous allocation request failed")
825 ergo_format_byte("allocation request"),
826 word_size * HeapWordSize);
827 if (expand((num_regions - fs) * HeapRegion::GrainBytes)) {
828 // Even though the heap was expanded, it might not have
829 // reached the desired size. So, we cannot assume that the
830 // allocation will succeed.
831 first = humongous_obj_allocate_find_first(num_regions, word_size);
832 }
833 }
834 }
835
836 HeapWord* result = NULL;
837 if (first != G1_NULL_HRS_INDEX) {
838 result =
839 humongous_obj_allocate_initialize_regions(first, num_regions, word_size);
840 assert(result != NULL, "it should always return a valid result");
841
842 // A successful humongous object allocation changes the used space
843 // information of the old generation so we need to recalculate the
844 // sizes and update the jstat counters here.
845 g1mm()->update_sizes();
846 }
847
848 verify_region_sets_optional();
849
850 return result;
851 }
852
853 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) {
854 assert_heap_not_locked_and_not_at_safepoint();
855 assert(!isHumongous(word_size), "we do not allow humongous TLABs");
856
857 unsigned int dummy_gc_count_before;
858 return attempt_allocation(word_size, &dummy_gc_count_before);
859 }
860
861 HeapWord*
862 G1CollectedHeap::mem_allocate(size_t word_size,
863 bool* gc_overhead_limit_was_exceeded) {
864 assert_heap_not_locked_and_not_at_safepoint();
865
866 // Loop until the allocation is satisified, or unsatisfied after GC.
867 for (int try_count = 1; /* we'll return */; try_count += 1) {
868 unsigned int gc_count_before;
869
870 HeapWord* result = NULL;
871 if (!isHumongous(word_size)) {
872 result = attempt_allocation(word_size, &gc_count_before);
873 } else {
874 result = attempt_allocation_humongous(word_size, &gc_count_before);
875 }
876 if (result != NULL) {
877 return result;
878 }
879
880 // Create the garbage collection operation...
881 VM_G1CollectForAllocation op(gc_count_before, word_size);
882 // ...and get the VM thread to execute it.
883 VMThread::execute(&op);
884
885 if (op.prologue_succeeded() && op.pause_succeeded()) {
886 // If the operation was successful we'll return the result even
887 // if it is NULL. If the allocation attempt failed immediately
888 // after a Full GC, it's unlikely we'll be able to allocate now.
889 HeapWord* result = op.result();
890 if (result != NULL && !isHumongous(word_size)) {
891 // Allocations that take place on VM operations do not do any
892 // card dirtying and we have to do it here. We only have to do
893 // this for non-humongous allocations, though.
894 dirty_young_block(result, word_size);
895 }
896 return result;
897 } else {
898 assert(op.result() == NULL,
899 "the result should be NULL if the VM op did not succeed");
900 }
901
902 // Give a warning if we seem to be looping forever.
903 if ((QueuedAllocationWarningCount > 0) &&
904 (try_count % QueuedAllocationWarningCount == 0)) {
905 warning("G1CollectedHeap::mem_allocate retries %d times", try_count);
906 }
907 }
908
909 ShouldNotReachHere();
910 return NULL;
911 }
912
913 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size,
914 unsigned int *gc_count_before_ret) {
915 // Make sure you read the note in attempt_allocation_humongous().
916
917 assert_heap_not_locked_and_not_at_safepoint();
918 assert(!isHumongous(word_size), "attempt_allocation_slow() should not "
919 "be called for humongous allocation requests");
920
921 // We should only get here after the first-level allocation attempt
922 // (attempt_allocation()) failed to allocate.
923
924 // We will loop until a) we manage to successfully perform the
925 // allocation or b) we successfully schedule a collection which
926 // fails to perform the allocation. b) is the only case when we'll
927 // return NULL.
928 HeapWord* result = NULL;
929 for (int try_count = 1; /* we'll return */; try_count += 1) {
930 bool should_try_gc;
931 unsigned int gc_count_before;
932
933 {
934 MutexLockerEx x(Heap_lock);
935
936 result = _mutator_alloc_region.attempt_allocation_locked(word_size,
937 false /* bot_updates */);
938 if (result != NULL) {
939 return result;
940 }
941
942 // If we reach here, attempt_allocation_locked() above failed to
943 // allocate a new region. So the mutator alloc region should be NULL.
944 assert(_mutator_alloc_region.get() == NULL, "only way to get here");
945
946 if (GC_locker::is_active_and_needs_gc()) {
947 if (g1_policy()->can_expand_young_list()) {
948 // No need for an ergo verbose message here,
949 // can_expand_young_list() does this when it returns true.
950 result = _mutator_alloc_region.attempt_allocation_force(word_size,
951 false /* bot_updates */);
952 if (result != NULL) {
953 return result;
954 }
955 }
956 should_try_gc = false;
957 } else {
958 // The GCLocker may not be active but the GCLocker initiated
959 // GC may not yet have been performed (GCLocker::needs_gc()
960 // returns true). In this case we do not try this GC and
961 // wait until the GCLocker initiated GC is performed, and
962 // then retry the allocation.
963 if (GC_locker::needs_gc()) {
964 should_try_gc = false;
965 } else {
966 // Read the GC count while still holding the Heap_lock.
967 gc_count_before = total_collections();
968 should_try_gc = true;
969 }
970 }
971 }
972
973 if (should_try_gc) {
974 bool succeeded;
975 result = do_collection_pause(word_size, gc_count_before, &succeeded);
976 if (result != NULL) {
977 assert(succeeded, "only way to get back a non-NULL result");
978 return result;
979 }
980
981 if (succeeded) {
982 // If we get here we successfully scheduled a collection which
983 // failed to allocate. No point in trying to allocate
984 // further. We'll just return NULL.
985 MutexLockerEx x(Heap_lock);
986 *gc_count_before_ret = total_collections();
987 return NULL;
988 }
989 } else {
990 // The GCLocker is either active or the GCLocker initiated
991 // GC has not yet been performed. Stall until it is and
992 // then retry the allocation.
993 GC_locker::stall_until_clear();
994 }
995
996 // We can reach here if we were unsuccessul in scheduling a
997 // collection (because another thread beat us to it) or if we were
998 // stalled due to the GC locker. In either can we should retry the
999 // allocation attempt in case another thread successfully
1000 // performed a collection and reclaimed enough space. We do the
1001 // first attempt (without holding the Heap_lock) here and the
1002 // follow-on attempt will be at the start of the next loop
1003 // iteration (after taking the Heap_lock).
1004 result = _mutator_alloc_region.attempt_allocation(word_size,
1005 false /* bot_updates */);
1006 if (result != NULL) {
1007 return result;
1008 }
1009
1010 // Give a warning if we seem to be looping forever.
1011 if ((QueuedAllocationWarningCount > 0) &&
1012 (try_count % QueuedAllocationWarningCount == 0)) {
1013 warning("G1CollectedHeap::attempt_allocation_slow() "
1014 "retries %d times", try_count);
1015 }
1016 }
1017
1018 ShouldNotReachHere();
1019 return NULL;
1020 }
1021
1022 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size,
1023 unsigned int * gc_count_before_ret) {
1024 // The structure of this method has a lot of similarities to
1025 // attempt_allocation_slow(). The reason these two were not merged
1026 // into a single one is that such a method would require several "if
1027 // allocation is not humongous do this, otherwise do that"
1028 // conditional paths which would obscure its flow. In fact, an early
1029 // version of this code did use a unified method which was harder to
1030 // follow and, as a result, it had subtle bugs that were hard to
1031 // track down. So keeping these two methods separate allows each to
1032 // be more readable. It will be good to keep these two in sync as
1033 // much as possible.
1034
1035 assert_heap_not_locked_and_not_at_safepoint();
1036 assert(isHumongous(word_size), "attempt_allocation_humongous() "
1037 "should only be called for humongous allocations");
1038
1039 // Humongous objects can exhaust the heap quickly, so we should check if we
1040 // need to start a marking cycle at each humongous object allocation. We do
1041 // the check before we do the actual allocation. The reason for doing it
1042 // before the allocation is that we avoid having to keep track of the newly
1043 // allocated memory while we do a GC.
1044 if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation",
1045 word_size)) {
1046 collect(GCCause::_g1_humongous_allocation);
1047 }
1048
1049 // We will loop until a) we manage to successfully perform the
1050 // allocation or b) we successfully schedule a collection which
1051 // fails to perform the allocation. b) is the only case when we'll
1052 // return NULL.
1053 HeapWord* result = NULL;
1054 for (int try_count = 1; /* we'll return */; try_count += 1) {
1055 bool should_try_gc;
1056 unsigned int gc_count_before;
1057
1058 {
1059 MutexLockerEx x(Heap_lock);
1060
1061 // Given that humongous objects are not allocated in young
1062 // regions, we'll first try to do the allocation without doing a
1063 // collection hoping that there's enough space in the heap.
1064 result = humongous_obj_allocate(word_size);
1065 if (result != NULL) {
1066 return result;
1067 }
1068
1069 if (GC_locker::is_active_and_needs_gc()) {
1070 should_try_gc = false;
1071 } else {
1072 // The GCLocker may not be active but the GCLocker initiated
1073 // GC may not yet have been performed (GCLocker::needs_gc()
1074 // returns true). In this case we do not try this GC and
1075 // wait until the GCLocker initiated GC is performed, and
1076 // then retry the allocation.
1077 if (GC_locker::needs_gc()) {
1078 should_try_gc = false;
1079 } else {
1080 // Read the GC count while still holding the Heap_lock.
1081 gc_count_before = total_collections();
1082 should_try_gc = true;
1083 }
1084 }
1085 }
1086
1087 if (should_try_gc) {
1088 // If we failed to allocate the humongous object, we should try to
1089 // do a collection pause (if we're allowed) in case it reclaims
1090 // enough space for the allocation to succeed after the pause.
1091
1092 bool succeeded;
1093 result = do_collection_pause(word_size, gc_count_before, &succeeded);
1094 if (result != NULL) {
1095 assert(succeeded, "only way to get back a non-NULL result");
1096 return result;
1097 }
1098
1099 if (succeeded) {
1100 // If we get here we successfully scheduled a collection which
1101 // failed to allocate. No point in trying to allocate
1102 // further. We'll just return NULL.
1103 MutexLockerEx x(Heap_lock);
1104 *gc_count_before_ret = total_collections();
1105 return NULL;
1106 }
1107 } else {
1108 // The GCLocker is either active or the GCLocker initiated
1109 // GC has not yet been performed. Stall until it is and
1110 // then retry the allocation.
1111 GC_locker::stall_until_clear();
1112 }
1113
1114 // We can reach here if we were unsuccessul in scheduling a
1115 // collection (because another thread beat us to it) or if we were
1116 // stalled due to the GC locker. In either can we should retry the
1117 // allocation attempt in case another thread successfully
1118 // performed a collection and reclaimed enough space. Give a
1119 // warning if we seem to be looping forever.
1120
1121 if ((QueuedAllocationWarningCount > 0) &&
1122 (try_count % QueuedAllocationWarningCount == 0)) {
1123 warning("G1CollectedHeap::attempt_allocation_humongous() "
1124 "retries %d times", try_count);
1125 }
1126 }
1127
1128 ShouldNotReachHere();
1129 return NULL;
1130 }
1131
1132 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
1133 bool expect_null_mutator_alloc_region) {
1134 assert_at_safepoint(true /* should_be_vm_thread */);
1135 assert(_mutator_alloc_region.get() == NULL ||
1136 !expect_null_mutator_alloc_region,
1137 "the current alloc region was unexpectedly found to be non-NULL");
1138
1139 if (!isHumongous(word_size)) {
1140 return _mutator_alloc_region.attempt_allocation_locked(word_size,
1141 false /* bot_updates */);
1142 } else {
1143 HeapWord* result = humongous_obj_allocate(word_size);
1144 if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) {
1145 g1_policy()->set_initiate_conc_mark_if_possible();
1146 }
1147 return result;
1148 }
1149
1150 ShouldNotReachHere();
1151 }
1152
1153 class PostMCRemSetClearClosure: public HeapRegionClosure {
1154 G1CollectedHeap* _g1h;
1155 ModRefBarrierSet* _mr_bs;
1156 public:
1157 PostMCRemSetClearClosure(G1CollectedHeap* g1h, ModRefBarrierSet* mr_bs) :
1158 _g1h(g1h), _mr_bs(mr_bs) { }
1159 bool doHeapRegion(HeapRegion* r) {
1160 if (r->continuesHumongous()) {
1161 return false;
1162 }
1163 _g1h->reset_gc_time_stamps(r);
1164 HeapRegionRemSet* hrrs = r->rem_set();
1165 if (hrrs != NULL) hrrs->clear();
1166 // You might think here that we could clear just the cards
1167 // corresponding to the used region. But no: if we leave a dirty card
1168 // in a region we might allocate into, then it would prevent that card
1169 // from being enqueued, and cause it to be missed.
1170 // Re: the performance cost: we shouldn't be doing full GC anyway!
1171 _mr_bs->clear(MemRegion(r->bottom(), r->end()));
1172 return false;
1173 }
1174 };
1175
1176 void G1CollectedHeap::clear_rsets_post_compaction() {
1177 PostMCRemSetClearClosure rs_clear(this, mr_bs());
1178 heap_region_iterate(&rs_clear);
1179 }
1180
1181 class RebuildRSOutOfRegionClosure: public HeapRegionClosure {
1182 G1CollectedHeap* _g1h;
1183 UpdateRSOopClosure _cl;
1184 int _worker_i;
1185 public:
1186 RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, int worker_i = 0) :
1187 _cl(g1->g1_rem_set(), worker_i),
1188 _worker_i(worker_i),
1189 _g1h(g1)
1190 { }
1191
1192 bool doHeapRegion(HeapRegion* r) {
1193 if (!r->continuesHumongous()) {
1194 _cl.set_from(r);
1195 r->oop_iterate(&_cl);
1196 }
1197 return false;
1198 }
1199 };
1200
1201 class ParRebuildRSTask: public AbstractGangTask {
1202 G1CollectedHeap* _g1;
1203 public:
1204 ParRebuildRSTask(G1CollectedHeap* g1)
1205 : AbstractGangTask("ParRebuildRSTask"),
1206 _g1(g1)
1207 { }
1208
1209 void work(uint worker_id) {
1210 RebuildRSOutOfRegionClosure rebuild_rs(_g1, worker_id);
1211 _g1->heap_region_par_iterate_chunked(&rebuild_rs, worker_id,
1212 _g1->workers()->active_workers(),
1213 HeapRegion::RebuildRSClaimValue);
1214 }
1215 };
1216
1217 class PostCompactionPrinterClosure: public HeapRegionClosure {
1218 private:
1219 G1HRPrinter* _hr_printer;
1220 public:
1221 bool doHeapRegion(HeapRegion* hr) {
1222 assert(!hr->is_young(), "not expecting to find young regions");
1223 // We only generate output for non-empty regions.
1224 if (!hr->is_empty()) {
1225 if (!hr->isHumongous()) {
1226 _hr_printer->post_compaction(hr, G1HRPrinter::Old);
1227 } else if (hr->startsHumongous()) {
1228 if (hr->region_num() == 1) {
1229 // single humongous region
1230 _hr_printer->post_compaction(hr, G1HRPrinter::SingleHumongous);
1231 } else {
1232 _hr_printer->post_compaction(hr, G1HRPrinter::StartsHumongous);
1233 }
1234 } else {
1235 assert(hr->continuesHumongous(), "only way to get here");
1236 _hr_printer->post_compaction(hr, G1HRPrinter::ContinuesHumongous);
1237 }
1238 }
1239 return false;
1240 }
1241
1242 PostCompactionPrinterClosure(G1HRPrinter* hr_printer)
1243 : _hr_printer(hr_printer) { }
1244 };
1245
1246 void G1CollectedHeap::print_hrs_post_compaction() {
1247 PostCompactionPrinterClosure cl(hr_printer());
1248 heap_region_iterate(&cl);
1249 }
1250
1251 double G1CollectedHeap::verify(bool guard, const char* msg) {
1252 double verify_time_ms = 0.0;
1253
1254 if (guard && total_collections() >= VerifyGCStartAt) {
1255 double verify_start = os::elapsedTime();
1256 HandleMark hm; // Discard invalid handles created during verification
1257 gclog_or_tty->print(msg);
1258 prepare_for_verify();
1259 Universe::verify(false /* silent */, VerifyOption_G1UsePrevMarking);
1260 verify_time_ms = (os::elapsedTime() - verify_start) * 1000;
1261 }
1262
1263 return verify_time_ms;
1264 }
1265
1266 void G1CollectedHeap::verify_before_gc() {
1267 double verify_time_ms = verify(VerifyBeforeGC, " VerifyBeforeGC:");
1268 g1_policy()->phase_times()->record_verify_before_time_ms(verify_time_ms);
1269 }
1270
1271 void G1CollectedHeap::verify_after_gc() {
1272 double verify_time_ms = verify(VerifyAfterGC, " VerifyAfterGC:");
1273 g1_policy()->phase_times()->record_verify_after_time_ms(verify_time_ms);
1274 }
1275
1276 bool G1CollectedHeap::do_collection(bool explicit_gc,
1277 bool clear_all_soft_refs,
1278 size_t word_size) {
1279 assert_at_safepoint(true /* should_be_vm_thread */);
1280
1281 if (GC_locker::check_active_before_gc()) {
1282 return false;
1283 }
1284
1285 SvcGCMarker sgcm(SvcGCMarker::FULL);
1286 ResourceMark rm;
1287
1288 print_heap_before_gc();
1289
1290 size_t metadata_prev_used = MetaspaceAux::used_in_bytes();
1291
1292 HRSPhaseSetter x(HRSPhaseFullGC);
1293 verify_region_sets_optional();
1294
1295 const bool do_clear_all_soft_refs = clear_all_soft_refs ||
1296 collector_policy()->should_clear_all_soft_refs();
1297
1298 ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy());
1299
1300 {
1301 IsGCActiveMark x;
1302
1303 // Timing
1304 assert(gc_cause() != GCCause::_java_lang_system_gc || explicit_gc, "invariant");
1305 gclog_or_tty->date_stamp(G1Log::fine() && PrintGCDateStamps);
1306 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
1307
1308 TraceTime t(GCCauseString("Full GC", gc_cause()), G1Log::fine(), true, gclog_or_tty);
1309 TraceCollectorStats tcs(g1mm()->full_collection_counters());
1310 TraceMemoryManagerStats tms(true /* fullGC */, gc_cause());
1311
1312 double start = os::elapsedTime();
1313 g1_policy()->record_full_collection_start();
1314
1315 // Note: When we have a more flexible GC logging framework that
1316 // allows us to add optional attributes to a GC log record we
1317 // could consider timing and reporting how long we wait in the
1318 // following two methods.
1319 wait_while_free_regions_coming();
1320 // If we start the compaction before the CM threads finish
1321 // scanning the root regions we might trip them over as we'll
1322 // be moving objects / updating references. So let's wait until
1323 // they are done. By telling them to abort, they should complete
1324 // early.
1325 _cm->root_regions()->abort();
1326 _cm->root_regions()->wait_until_scan_finished();
1327 append_secondary_free_list_if_not_empty_with_lock();
1328
1329 gc_prologue(true);
1330 increment_total_collections(true /* full gc */);
1331 increment_old_marking_cycles_started();
1332
1333 size_t g1h_prev_used = used();
1334 assert(used() == recalculate_used(), "Should be equal");
1335
1336 verify_before_gc();
1337
1338 check_bitmaps("Full GC Start");
1339 pre_full_gc_dump();
1340
1341 COMPILER2_PRESENT(DerivedPointerTable::clear());
1342
1343 // Disable discovery and empty the discovered lists
1344 // for the CM ref processor.
1345 ref_processor_cm()->disable_discovery();
1346 ref_processor_cm()->abandon_partial_discovery();
1347 ref_processor_cm()->verify_no_references_recorded();
1348
1349 // Abandon current iterations of concurrent marking and concurrent
1350 // refinement, if any are in progress.
1351 concurrent_mark()->abort();
1352
1353 // Make sure we'll choose a new allocation region afterwards.
1354 release_mutator_alloc_region();
1355 abandon_gc_alloc_regions();
1356 g1_rem_set()->cleanupHRRS();
1357
1358 // We should call this after we retire any currently active alloc
1359 // regions so that all the ALLOC / RETIRE events are generated
1360 // before the start GC event.
1361 _hr_printer.start_gc(true /* full */, (size_t) total_collections());
1362
1363 // We may have added regions to the current incremental collection
1364 // set between the last GC or pause and now. We need to clear the
1365 // incremental collection set and then start rebuilding it afresh
1366 // after this full GC.
1367 abandon_collection_set(g1_policy()->inc_cset_head());
1368 g1_policy()->clear_incremental_cset();
1369 g1_policy()->stop_incremental_cset_building();
1370
1371 tear_down_region_sets(false /* free_list_only */);
1372 g1_policy()->set_gcs_are_young(true);
1373
1374 // See the comments in g1CollectedHeap.hpp and
1375 // G1CollectedHeap::ref_processing_init() about
1376 // how reference processing currently works in G1.
1377
1378 // Temporarily make discovery by the STW ref processor single threaded (non-MT).
1379 ReferenceProcessorMTDiscoveryMutator stw_rp_disc_ser(ref_processor_stw(), false);
1380
1381 // Temporarily clear the STW ref processor's _is_alive_non_header field.
1382 ReferenceProcessorIsAliveMutator stw_rp_is_alive_null(ref_processor_stw(), NULL);
1383
1384 ref_processor_stw()->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/);
1385 ref_processor_stw()->setup_policy(do_clear_all_soft_refs);
1386
1387 // Do collection work
1388 {
1389 HandleMark hm; // Discard invalid handles created during gc
1390 G1MarkSweep::invoke_at_safepoint(ref_processor_stw(), do_clear_all_soft_refs);
1391 }
1392
1393 // Clear the previous marking bitmap, if needed for bitmap verification.
1394 // Note we cannot do this when we clear the next marking bitmap in
1395 // ConcurrentMark::abort() above since VerifyDuringGC verifies the
1396 // objects marked during a full GC against the previous bitmap.
1397 if (G1VerifyPrevBitmap) {
1398 ((CMBitMap*) concurrent_mark()->prevMarkBitMap())->clearAll();
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 check_bitmaps("Full GC End");
1415
1416 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
1417 ref_processor_stw()->verify_no_references_recorded();
1418
1419 // Delete metaspaces for unloaded class loaders and clean up loader_data graph
1420 ClassLoaderDataGraph::purge();
1421
1422 // Note: since we've just done a full GC, concurrent
1423 // marking is no longer active. Therefore we need not
1424 // re-enable reference discovery for the CM ref processor.
1425 // That will be done at the start of the next marking cycle.
1426 assert(!ref_processor_cm()->discovery_enabled(), "Postcondition");
1427 ref_processor_cm()->verify_no_references_recorded();
1428
1429 reset_gc_time_stamp();
1430 // Since everything potentially moved, we will clear all remembered
1431 // sets, and clear all cards. Later we will rebuild remebered
1432 // sets. We will also reset the GC time stamps of the regions.
1433 clear_rsets_post_compaction();
1434 check_gc_time_stamps();
1435
1436 // Resize the heap if necessary.
1437 resize_if_necessary_after_full_collection(explicit_gc ? 0 : word_size);
1438
1439 if (_hr_printer.is_active()) {
1440 // We should do this after we potentially resize the heap so
1441 // that all the COMMIT / UNCOMMIT events are generated before
1442 // the end GC event.
1443
1444 print_hrs_post_compaction();
1445 _hr_printer.end_gc(true /* full */, (size_t) total_collections());
1446 }
1447
1448 if (_cg1r->use_cache()) {
1449 _cg1r->clear_and_record_card_counts();
1450 _cg1r->clear_hot_cache();
1451 }
1452
1453 // Rebuild remembered sets of all regions.
1454 if (G1CollectedHeap::use_parallel_gc_threads()) {
1455 uint n_workers =
1456 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
1457 workers()->active_workers(),
1458 Threads::number_of_non_daemon_threads());
1459 assert(UseDynamicNumberOfGCThreads ||
1460 n_workers == workers()->total_workers(),
1461 "If not dynamic should be using all the workers");
1462 workers()->set_active_workers(n_workers);
1463 // Set parallel threads in the heap (_n_par_threads) only
1464 // before a parallel phase and always reset it to 0 after
1465 // the phase so that the number of parallel threads does
1466 // no get carried forward to a serial phase where there
1467 // may be code that is "possibly_parallel".
1468 set_par_threads(n_workers);
1469
1470 ParRebuildRSTask rebuild_rs_task(this);
1471 assert(check_heap_region_claim_values(
1472 HeapRegion::InitialClaimValue), "sanity check");
1473 assert(UseDynamicNumberOfGCThreads ||
1474 workers()->active_workers() == workers()->total_workers(),
1475 "Unless dynamic should use total workers");
1476 // Use the most recent number of active workers
1477 assert(workers()->active_workers() > 0,
1478 "Active workers not properly set");
1479 set_par_threads(workers()->active_workers());
1480 workers()->run_task(&rebuild_rs_task);
1481 set_par_threads(0);
1482 assert(check_heap_region_claim_values(
1483 HeapRegion::RebuildRSClaimValue), "sanity check");
1484 reset_heap_region_claim_values();
1485 } else {
1486 RebuildRSOutOfRegionClosure rebuild_rs(this);
1487 heap_region_iterate(&rebuild_rs);
1488 }
1489
1490 if (G1Log::fine()) {
1491 print_size_transition(gclog_or_tty, g1h_prev_used, used(), capacity());
1492 }
1493
1494 if (true) { // FIXME
1495 MetaspaceGC::compute_new_size();
1496 }
1497
1498 // Start a new incremental collection set for the next pause
1499 assert(g1_policy()->collection_set() == NULL, "must be");
1500 g1_policy()->start_incremental_cset_building();
1501
1502 // Clear the _cset_fast_test bitmap in anticipation of adding
1503 // regions to the incremental collection set for the next
1504 // evacuation pause.
1505 clear_cset_fast_test();
1506
1507 init_mutator_alloc_region();
1508
1509 double end = os::elapsedTime();
1510 g1_policy()->record_full_collection_end();
1511
1512 #ifdef TRACESPINNING
1513 ParallelTaskTerminator::print_termination_counts();
1514 #endif
1515
1516 gc_epilogue(true);
1517
1518 // Discard all rset updates
1519 JavaThread::dirty_card_queue_set().abandon_logs();
1520 assert(!G1DeferredRSUpdate
1521 || (G1DeferredRSUpdate && (dirty_card_queue_set().completed_buffers_num() == 0)), "Should not be any");
1522
1523 _young_list->reset_sampled_info();
1524 // At this point there should be no regions in the
1525 // entire heap tagged as young.
1526 assert( check_young_list_empty(true /* check_heap */),
1527 "young list should be empty at this point");
1528
1529 // Update the number of full collections that have been completed.
1530 increment_old_marking_cycles_completed(false /* concurrent */);
1531
1532 _hrs.verify_optional();
1533 verify_region_sets_optional();
1534
1535 print_heap_after_gc();
1536
1537 // We must call G1MonitoringSupport::update_sizes() in the same scoping level
1538 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
1539 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
1540 // before any GC notifications are raised.
1541 g1mm()->update_sizes();
1542 }
1543
1544 post_full_gc_dump();
1545
1546 return true;
1547 }
1548
1549 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
1550 // do_collection() will return whether it succeeded in performing
1551 // the GC. Currently, there is no facility on the
1552 // do_full_collection() API to notify the caller than the collection
1553 // did not succeed (e.g., because it was locked out by the GC
1554 // locker). So, right now, we'll ignore the return value.
1555 bool dummy = do_collection(true, /* explicit_gc */
1556 clear_all_soft_refs,
1557 0 /* word_size */);
1558 }
1559
1560 // This code is mostly copied from TenuredGeneration.
1561 void
1562 G1CollectedHeap::
1563 resize_if_necessary_after_full_collection(size_t word_size) {
1564 assert(MinHeapFreeRatio <= MaxHeapFreeRatio, "sanity check");
1565
1566 // Include the current allocation, if any, and bytes that will be
1567 // pre-allocated to support collections, as "used".
1568 const size_t used_after_gc = used();
1569 const size_t capacity_after_gc = capacity();
1570 const size_t free_after_gc = capacity_after_gc - used_after_gc;
1571
1572 // This is enforced in arguments.cpp.
1573 assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
1574 "otherwise the code below doesn't make sense");
1575
1576 // We don't have floating point command-line arguments
1577 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
1578 const double maximum_used_percentage = 1.0 - minimum_free_percentage;
1579 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
1580 const double minimum_used_percentage = 1.0 - maximum_free_percentage;
1581
1582 const size_t min_heap_size = collector_policy()->min_heap_byte_size();
1583 const size_t max_heap_size = collector_policy()->max_heap_byte_size();
1584
1585 // We have to be careful here as these two calculations can overflow
1586 // 32-bit size_t's.
1587 double used_after_gc_d = (double) used_after_gc;
1588 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
1589 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
1590
1591 // Let's make sure that they are both under the max heap size, which
1592 // by default will make them fit into a size_t.
1593 double desired_capacity_upper_bound = (double) max_heap_size;
1594 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
1595 desired_capacity_upper_bound);
1596 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
1597 desired_capacity_upper_bound);
1598
1599 // We can now safely turn them into size_t's.
1600 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
1601 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
1602
1603 // This assert only makes sense here, before we adjust them
1604 // with respect to the min and max heap size.
1605 assert(minimum_desired_capacity <= maximum_desired_capacity,
1606 err_msg("minimum_desired_capacity = "SIZE_FORMAT", "
1607 "maximum_desired_capacity = "SIZE_FORMAT,
1608 minimum_desired_capacity, maximum_desired_capacity));
1609
1610 // Should not be greater than the heap max size. No need to adjust
1611 // it with respect to the heap min size as it's a lower bound (i.e.,
1612 // we'll try to make the capacity larger than it, not smaller).
1613 minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size);
1614 // Should not be less than the heap min size. No need to adjust it
1615 // with respect to the heap max size as it's an upper bound (i.e.,
1616 // we'll try to make the capacity smaller than it, not greater).
1617 maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size);
1618
1619 if (capacity_after_gc < minimum_desired_capacity) {
1620 // Don't expand unless it's significant
1621 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
1622 ergo_verbose4(ErgoHeapSizing,
1623 "attempt heap expansion",
1624 ergo_format_reason("capacity lower than "
1625 "min desired capacity after Full GC")
1626 ergo_format_byte("capacity")
1627 ergo_format_byte("occupancy")
1628 ergo_format_byte_perc("min desired capacity"),
1629 capacity_after_gc, used_after_gc,
1630 minimum_desired_capacity, (double) MinHeapFreeRatio);
1631 expand(expand_bytes);
1632
1633 // No expansion, now see if we want to shrink
1634 } else if (capacity_after_gc > maximum_desired_capacity) {
1635 // Capacity too large, compute shrinking size
1636 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
1637 ergo_verbose4(ErgoHeapSizing,
1638 "attempt heap shrinking",
1639 ergo_format_reason("capacity higher than "
1640 "max desired capacity after Full GC")
1641 ergo_format_byte("capacity")
1642 ergo_format_byte("occupancy")
1643 ergo_format_byte_perc("max desired capacity"),
1644 capacity_after_gc, used_after_gc,
1645 maximum_desired_capacity, (double) MaxHeapFreeRatio);
1646 shrink(shrink_bytes);
1647 }
1648 }
1649
1650
1651 HeapWord*
1652 G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
1653 bool* succeeded) {
1654 assert_at_safepoint(true /* should_be_vm_thread */);
1655
1656 *succeeded = true;
1657 // Let's attempt the allocation first.
1658 HeapWord* result =
1659 attempt_allocation_at_safepoint(word_size,
1660 false /* expect_null_mutator_alloc_region */);
1661 if (result != NULL) {
1662 assert(*succeeded, "sanity");
1663 return result;
1664 }
1665
1666 // In a G1 heap, we're supposed to keep allocation from failing by
1667 // incremental pauses. Therefore, at least for now, we'll favor
1668 // expansion over collection. (This might change in the future if we can
1669 // do something smarter than full collection to satisfy a failed alloc.)
1670 result = expand_and_allocate(word_size);
1671 if (result != NULL) {
1672 assert(*succeeded, "sanity");
1673 return result;
1674 }
1675
1676 // Expansion didn't work, we'll try to do a Full GC.
1677 bool gc_succeeded = do_collection(false, /* explicit_gc */
1678 false, /* clear_all_soft_refs */
1679 word_size);
1680 if (!gc_succeeded) {
1681 *succeeded = false;
1682 return NULL;
1683 }
1684
1685 // Retry the allocation
1686 result = attempt_allocation_at_safepoint(word_size,
1687 true /* expect_null_mutator_alloc_region */);
1688 if (result != NULL) {
1689 assert(*succeeded, "sanity");
1690 return result;
1691 }
1692
1693 // Then, try a Full GC that will collect all soft references.
1694 gc_succeeded = do_collection(false, /* explicit_gc */
1695 true, /* clear_all_soft_refs */
1696 word_size);
1697 if (!gc_succeeded) {
1698 *succeeded = false;
1699 return NULL;
1700 }
1701
1702 // Retry the allocation once more
1703 result = attempt_allocation_at_safepoint(word_size,
1704 true /* expect_null_mutator_alloc_region */);
1705 if (result != NULL) {
1706 assert(*succeeded, "sanity");
1707 return result;
1708 }
1709
1710 assert(!collector_policy()->should_clear_all_soft_refs(),
1711 "Flag should have been handled and cleared prior to this point");
1712
1713 // What else? We might try synchronous finalization later. If the total
1714 // space available is large enough for the allocation, then a more
1715 // complete compaction phase than we've tried so far might be
1716 // appropriate.
1717 assert(*succeeded, "sanity");
1718 return NULL;
1719 }
1720
1721 // Attempting to expand the heap sufficiently
1722 // to support an allocation of the given "word_size". If
1723 // successful, perform the allocation and return the address of the
1724 // allocated block, or else "NULL".
1725
1726 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size) {
1727 assert_at_safepoint(true /* should_be_vm_thread */);
1728
1729 verify_region_sets_optional();
1730
1731 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
1732 ergo_verbose1(ErgoHeapSizing,
1733 "attempt heap expansion",
1734 ergo_format_reason("allocation request failed")
1735 ergo_format_byte("allocation request"),
1736 word_size * HeapWordSize);
1737 if (expand(expand_bytes)) {
1738 _hrs.verify_optional();
1739 verify_region_sets_optional();
1740 return attempt_allocation_at_safepoint(word_size,
1741 false /* expect_null_mutator_alloc_region */);
1742 }
1743 return NULL;
1744 }
1745
1746 void G1CollectedHeap::update_committed_space(HeapWord* old_end,
1747 HeapWord* new_end) {
1748 assert(old_end != new_end, "don't call this otherwise");
1749 assert((HeapWord*) _g1_storage.high() == new_end, "invariant");
1750
1751 // Update the committed mem region.
1752 _g1_committed.set_end(new_end);
1753 // Tell the card table about the update.
1754 Universe::heap()->barrier_set()->resize_covered_region(_g1_committed);
1755 // Tell the BOT about the update.
1756 _bot_shared->resize(_g1_committed.word_size());
1757 }
1758
1759 bool G1CollectedHeap::expand(size_t expand_bytes) {
1760 size_t old_mem_size = _g1_storage.committed_size();
1761 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
1762 aligned_expand_bytes = align_size_up(aligned_expand_bytes,
1763 HeapRegion::GrainBytes);
1764 ergo_verbose2(ErgoHeapSizing,
1765 "expand the heap",
1766 ergo_format_byte("requested expansion amount")
1767 ergo_format_byte("attempted expansion amount"),
1768 expand_bytes, aligned_expand_bytes);
1769
1770 // First commit the memory.
1771 HeapWord* old_end = (HeapWord*) _g1_storage.high();
1772 bool successful = _g1_storage.expand_by(aligned_expand_bytes);
1773 if (successful) {
1774 // Then propagate this update to the necessary data structures.
1775 HeapWord* new_end = (HeapWord*) _g1_storage.high();
1776 update_committed_space(old_end, new_end);
1777
1778 FreeRegionList expansion_list("Local Expansion List");
1779 MemRegion mr = _hrs.expand_by(old_end, new_end, &expansion_list);
1780 assert(mr.start() == old_end, "post-condition");
1781 // mr might be a smaller region than what was requested if
1782 // expand_by() was unable to allocate the HeapRegion instances
1783 assert(mr.end() <= new_end, "post-condition");
1784
1785 size_t actual_expand_bytes = mr.byte_size();
1786 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
1787 assert(actual_expand_bytes == expansion_list.total_capacity_bytes(),
1788 "post-condition");
1789 if (actual_expand_bytes < aligned_expand_bytes) {
1790 // We could not expand _hrs to the desired size. In this case we
1791 // need to shrink the committed space accordingly.
1792 assert(mr.end() < new_end, "invariant");
1793
1794 size_t diff_bytes = aligned_expand_bytes - actual_expand_bytes;
1795 // First uncommit the memory.
1796 _g1_storage.shrink_by(diff_bytes);
1797 // Then propagate this update to the necessary data structures.
1798 update_committed_space(new_end, mr.end());
1799 }
1800 _free_list.add_as_tail(&expansion_list);
1801
1802 if (_hr_printer.is_active()) {
1803 HeapWord* curr = mr.start();
1804 while (curr < mr.end()) {
1805 HeapWord* curr_end = curr + HeapRegion::GrainWords;
1806 _hr_printer.commit(curr, curr_end);
1807 curr = curr_end;
1808 }
1809 assert(curr == mr.end(), "post-condition");
1810 }
1811 g1_policy()->record_new_heap_size(n_regions());
1812 } else {
1813 ergo_verbose0(ErgoHeapSizing,
1814 "did not expand the heap",
1815 ergo_format_reason("heap expansion operation failed"));
1816 // The expansion of the virtual storage space was unsuccessful.
1817 // Let's see if it was because we ran out of swap.
1818 if (G1ExitOnExpansionFailure &&
1819 _g1_storage.uncommitted_size() >= aligned_expand_bytes) {
1820 // We had head room...
1821 vm_exit_out_of_memory(aligned_expand_bytes, "G1 heap expansion");
1822 }
1823 }
1824 return successful;
1825 }
1826
1827 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
1828 size_t old_mem_size = _g1_storage.committed_size();
1829 size_t aligned_shrink_bytes =
1830 ReservedSpace::page_align_size_down(shrink_bytes);
1831 aligned_shrink_bytes = align_size_down(aligned_shrink_bytes,
1832 HeapRegion::GrainBytes);
1833 uint num_regions_deleted = 0;
1834 MemRegion mr = _hrs.shrink_by(aligned_shrink_bytes, &num_regions_deleted);
1835 HeapWord* old_end = (HeapWord*) _g1_storage.high();
1836 assert(mr.end() == old_end, "post-condition");
1837
1838 ergo_verbose3(ErgoHeapSizing,
1839 "shrink the heap",
1840 ergo_format_byte("requested shrinking amount")
1841 ergo_format_byte("aligned shrinking amount")
1842 ergo_format_byte("attempted shrinking amount"),
1843 shrink_bytes, aligned_shrink_bytes, mr.byte_size());
1844 if (mr.byte_size() > 0) {
1845 if (_hr_printer.is_active()) {
1846 HeapWord* curr = mr.end();
1847 while (curr > mr.start()) {
1848 HeapWord* curr_end = curr;
1849 curr -= HeapRegion::GrainWords;
1850 _hr_printer.uncommit(curr, curr_end);
1851 }
1852 assert(curr == mr.start(), "post-condition");
1853 }
1854
1855 _g1_storage.shrink_by(mr.byte_size());
1856 HeapWord* new_end = (HeapWord*) _g1_storage.high();
1857 assert(mr.start() == new_end, "post-condition");
1858
1859 _expansion_regions += num_regions_deleted;
1860 update_committed_space(old_end, new_end);
1861 HeapRegionRemSet::shrink_heap(n_regions());
1862 g1_policy()->record_new_heap_size(n_regions());
1863 } else {
1864 ergo_verbose0(ErgoHeapSizing,
1865 "did not shrink the heap",
1866 ergo_format_reason("heap shrinking operation failed"));
1867 }
1868 }
1869
1870 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1871 verify_region_sets_optional();
1872
1873 // We should only reach here at the end of a Full GC which means we
1874 // should not not be holding to any GC alloc regions. The method
1875 // below will make sure of that and do any remaining clean up.
1876 abandon_gc_alloc_regions();
1877
1878 // Instead of tearing down / rebuilding the free lists here, we
1879 // could instead use the remove_all_pending() method on free_list to
1880 // remove only the ones that we need to remove.
1881 tear_down_region_sets(true /* free_list_only */);
1882 shrink_helper(shrink_bytes);
1883 rebuild_region_sets(true /* free_list_only */);
1884
1885 _hrs.verify_optional();
1886 verify_region_sets_optional();
1887 }
1888
1889 // Public methods.
1890
1891 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away
1892 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
1893 #endif // _MSC_VER
1894
1895
1896 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* policy_) :
1897 SharedHeap(policy_),
1898 _g1_policy(policy_),
1899 _dirty_card_queue_set(false),
1900 _into_cset_dirty_card_queue_set(false),
1901 _is_alive_closure_cm(this),
1902 _is_alive_closure_stw(this),
1903 _ref_processor_cm(NULL),
1904 _ref_processor_stw(NULL),
1905 _process_strong_tasks(new SubTasksDone(G1H_PS_NumElements)),
1906 _bot_shared(NULL),
1907 _objs_with_preserved_marks(NULL), _preserved_marks_of_objs(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 _in_cset_fast_test(NULL),
1929 _in_cset_fast_test_base(NULL),
1930 _dirty_cards_region_list(NULL),
1931 _worker_cset_start_region(NULL),
1932 _worker_cset_start_region_time_stamp(NULL) {
1933 _g1h = this; // To catch bugs.
1934 if (_process_strong_tasks == NULL || !_process_strong_tasks->valid()) {
1935 vm_exit_during_initialization("Failed necessary allocation.");
1936 }
1937
1938 _humongous_object_threshold_in_words = HeapRegion::GrainWords / 2;
1939
1940 int n_queues = MAX2((int)ParallelGCThreads, 1);
1941 _task_queues = new RefToScanQueueSet(n_queues);
1942
1943 int n_rem_sets = HeapRegionRemSet::num_par_rem_sets();
1944 assert(n_rem_sets > 0, "Invariant.");
1945
1946 HeapRegionRemSetIterator** iter_arr =
1947 NEW_C_HEAP_ARRAY(HeapRegionRemSetIterator*, n_queues, mtGC);
1948 for (int i = 0; i < n_queues; i++) {
1949 iter_arr[i] = new HeapRegionRemSetIterator();
1950 }
1951 _rem_set_iterator = iter_arr;
1952
1953 _worker_cset_start_region = NEW_C_HEAP_ARRAY(HeapRegion*, n_queues, mtGC);
1954 _worker_cset_start_region_time_stamp = NEW_C_HEAP_ARRAY(unsigned int, n_queues, mtGC);
1955
1956 for (int i = 0; i < n_queues; i++) {
1957 RefToScanQueue* q = new RefToScanQueue();
1958 q->initialize();
1959 _task_queues->register_queue(i, q);
1960 }
1961
1962 clear_cset_start_regions();
1963
1964 // Initialize the G1EvacuationFailureALot counters and flags.
1965 NOT_PRODUCT(reset_evacuation_should_fail();)
1966
1967 guarantee(_task_queues != NULL, "task_queues allocation failure.");
1968 }
1969
1970 jint G1CollectedHeap::initialize() {
1971 CollectedHeap::pre_initialize();
1972 os::enable_vtime();
1973
1974 G1Log::init();
1975
1976 // Necessary to satisfy locking discipline assertions.
1977
1978 MutexLocker x(Heap_lock);
1979
1980 // We have to initialize the printer before committing the heap, as
1981 // it will be used then.
1982 _hr_printer.set_active(G1PrintHeapRegions);
1983
1984 // While there are no constraints in the GC code that HeapWordSize
1985 // be any particular value, there are multiple other areas in the
1986 // system which believe this to be true (e.g. oop->object_size in some
1987 // cases incorrectly returns the size in wordSize units rather than
1988 // HeapWordSize).
1989 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
1990
1991 size_t init_byte_size = collector_policy()->initial_heap_byte_size();
1992 size_t max_byte_size = collector_policy()->max_heap_byte_size();
1993
1994 // Ensure that the sizes are properly aligned.
1995 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
1996 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
1997
1998 _cg1r = new ConcurrentG1Refine();
1999
2000 // Reserve the maximum.
2001
2002 // When compressed oops are enabled, the preferred heap base
2003 // is calculated by subtracting the requested size from the
2004 // 32Gb boundary and using the result as the base address for
2005 // heap reservation. If the requested size is not aligned to
2006 // HeapRegion::GrainBytes (i.e. the alignment that is passed
2007 // into the ReservedHeapSpace constructor) then the actual
2008 // base of the reserved heap may end up differing from the
2009 // address that was requested (i.e. the preferred heap base).
2010 // If this happens then we could end up using a non-optimal
2011 // compressed oops mode.
2012
2013 // Since max_byte_size is aligned to the size of a heap region (checked
2014 // above).
2015 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
2016
2017 ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size,
2018 HeapRegion::GrainBytes);
2019
2020 // It is important to do this in a way such that concurrent readers can't
2021 // temporarily think somethings in the heap. (I've actually seen this
2022 // happen in asserts: DLD.)
2023 _reserved.set_word_size(0);
2024 _reserved.set_start((HeapWord*)heap_rs.base());
2025 _reserved.set_end((HeapWord*)(heap_rs.base() + heap_rs.size()));
2026
2027 _expansion_regions = (uint) (max_byte_size / HeapRegion::GrainBytes);
2028
2029 // Create the gen rem set (and barrier set) for the entire reserved region.
2030 _rem_set = collector_policy()->create_rem_set(_reserved, 2);
2031 set_barrier_set(rem_set()->bs());
2032 if (barrier_set()->is_a(BarrierSet::ModRef)) {
2033 _mr_bs = (ModRefBarrierSet*)_barrier_set;
2034 } else {
2035 vm_exit_during_initialization("G1 requires a mod ref bs.");
2036 return JNI_ENOMEM;
2037 }
2038
2039 // Also create a G1 rem set.
2040 if (mr_bs()->is_a(BarrierSet::CardTableModRef)) {
2041 _g1_rem_set = new G1RemSet(this, (CardTableModRefBS*)mr_bs());
2042 } else {
2043 vm_exit_during_initialization("G1 requires a cardtable mod ref bs.");
2044 return JNI_ENOMEM;
2045 }
2046
2047 // Carve out the G1 part of the heap.
2048
2049 ReservedSpace g1_rs = heap_rs.first_part(max_byte_size);
2050 _g1_reserved = MemRegion((HeapWord*)g1_rs.base(),
2051 g1_rs.size()/HeapWordSize);
2052
2053 _g1_storage.initialize(g1_rs, 0);
2054 _g1_committed = MemRegion((HeapWord*)_g1_storage.low(), (size_t) 0);
2055 _hrs.initialize((HeapWord*) _g1_reserved.start(),
2056 (HeapWord*) _g1_reserved.end(),
2057 _expansion_regions);
2058
2059 // 6843694 - ensure that the maximum region index can fit
2060 // in the remembered set structures.
2061 const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
2062 guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
2063
2064 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
2065 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
2066 guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
2067 "too many cards per region");
2068
2069 HeapRegionSet::set_unrealistically_long_length(max_regions() + 1);
2070
2071 _bot_shared = new G1BlockOffsetSharedArray(_reserved,
2072 heap_word_size(init_byte_size));
2073
2074 _g1h = this;
2075
2076 _in_cset_fast_test_length = max_regions();
2077 _in_cset_fast_test_base =
2078 NEW_C_HEAP_ARRAY(bool, (size_t) _in_cset_fast_test_length, mtGC);
2079
2080 // We're biasing _in_cset_fast_test to avoid subtracting the
2081 // beginning of the heap every time we want to index; basically
2082 // it's the same with what we do with the card table.
2083 _in_cset_fast_test = _in_cset_fast_test_base -
2084 ((uintx) _g1_reserved.start() >> HeapRegion::LogOfHRGrainBytes);
2085
2086 // Clear the _cset_fast_test bitmap in anticipation of adding
2087 // regions to the incremental collection set for the first
2088 // evacuation pause.
2089 clear_cset_fast_test();
2090
2091 // Create the ConcurrentMark data structure and thread.
2092 // (Must do this late, so that "max_regions" is defined.)
2093 _cm = new ConcurrentMark(this, heap_rs);
2094 if (_cm == NULL || !_cm->completed_initialization()) {
2095 vm_shutdown_during_initialization("Could not create/initialize ConcurrentMark");
2096 return JNI_ENOMEM;
2097 }
2098 _cmThread = _cm->cmThread();
2099
2100 // Initialize the from_card cache structure of HeapRegionRemSet.
2101 HeapRegionRemSet::init_heap(max_regions());
2102
2103 // Now expand into the initial heap size.
2104 if (!expand(init_byte_size)) {
2105 vm_shutdown_during_initialization("Failed to allocate initial heap.");
2106 return JNI_ENOMEM;
2107 }
2108
2109 // Perform any initialization actions delegated to the policy.
2110 g1_policy()->init();
2111
2112 _refine_cte_cl =
2113 new RefineCardTableEntryClosure(ConcurrentG1RefineThread::sts(),
2114 g1_rem_set(),
2115 concurrent_g1_refine());
2116 JavaThread::dirty_card_queue_set().set_closure(_refine_cte_cl);
2117
2118 JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon,
2119 SATB_Q_FL_lock,
2120 G1SATBProcessCompletedThreshold,
2121 Shared_SATB_Q_lock);
2122
2123 JavaThread::dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
2124 DirtyCardQ_FL_lock,
2125 concurrent_g1_refine()->yellow_zone(),
2126 concurrent_g1_refine()->red_zone(),
2127 Shared_DirtyCardQ_lock);
2128
2129 if (G1DeferredRSUpdate) {
2130 dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
2131 DirtyCardQ_FL_lock,
2132 -1, // never trigger processing
2133 -1, // no limit on length
2134 Shared_DirtyCardQ_lock,
2135 &JavaThread::dirty_card_queue_set());
2136 }
2137
2138 // Initialize the card queue set used to hold cards containing
2139 // references into the collection set.
2140 _into_cset_dirty_card_queue_set.initialize(DirtyCardQ_CBL_mon,
2141 DirtyCardQ_FL_lock,
2142 -1, // never trigger processing
2143 -1, // no limit on length
2144 Shared_DirtyCardQ_lock,
2145 &JavaThread::dirty_card_queue_set());
2146
2147 // In case we're keeping closure specialization stats, initialize those
2148 // counts and that mechanism.
2149 SpecializationStats::clear();
2150
2151 // Do later initialization work for concurrent refinement.
2152 _cg1r->init();
2153
2154 // Here we allocate the dummy full region that is required by the
2155 // G1AllocRegion class. If we don't pass an address in the reserved
2156 // space here, lots of asserts fire.
2157
2158 HeapRegion* dummy_region = new_heap_region(0 /* index of bottom region */,
2159 _g1_reserved.start());
2160 // We'll re-use the same region whether the alloc region will
2161 // require BOT updates or not and, if it doesn't, then a non-young
2162 // region will complain that it cannot support allocations without
2163 // BOT updates. So we'll tag the dummy region as young to avoid that.
2164 dummy_region->set_young();
2165 // Make sure it's full.
2166 dummy_region->set_top(dummy_region->end());
2167 G1AllocRegion::setup(this, dummy_region);
2168
2169 init_mutator_alloc_region();
2170
2171 // Do create of the monitoring and management support so that
2172 // values in the heap have been properly initialized.
2173 _g1mm = new G1MonitoringSupport(this);
2174
2175 return JNI_OK;
2176 }
2177
2178 void G1CollectedHeap::ref_processing_init() {
2179 // Reference processing in G1 currently works as follows:
2180 //
2181 // * There are two reference processor instances. One is
2182 // used to record and process discovered references
2183 // during concurrent marking; the other is used to
2184 // record and process references during STW pauses
2185 // (both full and incremental).
2186 // * Both ref processors need to 'span' the entire heap as
2187 // the regions in the collection set may be dotted around.
2188 //
2189 // * For the concurrent marking ref processor:
2190 // * Reference discovery is enabled at initial marking.
2191 // * Reference discovery is disabled and the discovered
2192 // references processed etc during remarking.
2193 // * Reference discovery is MT (see below).
2194 // * Reference discovery requires a barrier (see below).
2195 // * Reference processing may or may not be MT
2196 // (depending on the value of ParallelRefProcEnabled
2197 // and ParallelGCThreads).
2198 // * A full GC disables reference discovery by the CM
2199 // ref processor and abandons any entries on it's
2200 // discovered lists.
2201 //
2202 // * For the STW processor:
2203 // * Non MT discovery is enabled at the start of a full GC.
2204 // * Processing and enqueueing during a full GC is non-MT.
2205 // * During a full GC, references are processed after marking.
2206 //
2207 // * Discovery (may or may not be MT) is enabled at the start
2208 // of an incremental evacuation pause.
2209 // * References are processed near the end of a STW evacuation pause.
2210 // * For both types of GC:
2211 // * Discovery is atomic - i.e. not concurrent.
2212 // * Reference discovery will not need a barrier.
2213
2214 SharedHeap::ref_processing_init();
2215 MemRegion mr = reserved_region();
2216
2217 // Concurrent Mark ref processor
2218 _ref_processor_cm =
2219 new ReferenceProcessor(mr, // span
2220 ParallelRefProcEnabled && (ParallelGCThreads > 1),
2221 // mt processing
2222 (int) ParallelGCThreads,
2223 // degree of mt processing
2224 (ParallelGCThreads > 1) || (ConcGCThreads > 1),
2225 // mt discovery
2226 (int) MAX2(ParallelGCThreads, ConcGCThreads),
2227 // degree of mt discovery
2228 false,
2229 // Reference discovery is not atomic
2230 &_is_alive_closure_cm,
2231 // is alive closure
2232 // (for efficiency/performance)
2233 true);
2234 // Setting next fields of discovered
2235 // lists requires a barrier.
2236
2237 // STW ref processor
2238 _ref_processor_stw =
2239 new ReferenceProcessor(mr, // span
2240 ParallelRefProcEnabled && (ParallelGCThreads > 1),
2241 // mt processing
2242 MAX2((int)ParallelGCThreads, 1),
2243 // degree of mt processing
2244 (ParallelGCThreads > 1),
2245 // mt discovery
2246 MAX2((int)ParallelGCThreads, 1),
2247 // degree of mt discovery
2248 true,
2249 // Reference discovery is atomic
2250 &_is_alive_closure_stw,
2251 // is alive closure
2252 // (for efficiency/performance)
2253 false);
2254 // Setting next fields of discovered
2255 // lists requires a barrier.
2256 }
2257
2258 size_t G1CollectedHeap::capacity() const {
2259 return _g1_committed.byte_size();
2260 }
2261
2262 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) {
2263 assert(!hr->continuesHumongous(), "pre-condition");
2264 hr->reset_gc_time_stamp();
2265 if (hr->startsHumongous()) {
2266 uint first_index = hr->hrs_index() + 1;
2267 uint last_index = hr->last_hc_index();
2268 for (uint i = first_index; i < last_index; i += 1) {
2269 HeapRegion* chr = region_at(i);
2270 assert(chr->continuesHumongous(), "sanity");
2271 chr->reset_gc_time_stamp();
2272 }
2273 }
2274 }
2275
2276 #ifndef PRODUCT
2277 class CheckGCTimeStampsHRClosure : public HeapRegionClosure {
2278 private:
2279 unsigned _gc_time_stamp;
2280 bool _failures;
2281
2282 public:
2283 CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) :
2284 _gc_time_stamp(gc_time_stamp), _failures(false) { }
2285
2286 virtual bool doHeapRegion(HeapRegion* hr) {
2287 unsigned region_gc_time_stamp = hr->get_gc_time_stamp();
2288 if (_gc_time_stamp != region_gc_time_stamp) {
2289 gclog_or_tty->print_cr("Region "HR_FORMAT" has GC time stamp = %d, "
2290 "expected %d", HR_FORMAT_PARAMS(hr),
2291 region_gc_time_stamp, _gc_time_stamp);
2292 _failures = true;
2293 }
2294 return false;
2295 }
2296
2297 bool failures() { return _failures; }
2298 };
2299
2300 void G1CollectedHeap::check_gc_time_stamps() {
2301 CheckGCTimeStampsHRClosure cl(_gc_time_stamp);
2302 heap_region_iterate(&cl);
2303 guarantee(!cl.failures(), "all GC time stamps should have been reset");
2304 }
2305 #endif // PRODUCT
2306
2307 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl,
2308 DirtyCardQueue* into_cset_dcq,
2309 bool concurrent,
2310 int worker_i) {
2311 // Clean cards in the hot card cache
2312 concurrent_g1_refine()->clean_up_cache(worker_i, g1_rem_set(), into_cset_dcq);
2313
2314 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2315 int n_completed_buffers = 0;
2316 while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) {
2317 n_completed_buffers++;
2318 }
2319 g1_policy()->phase_times()->record_update_rs_processed_buffers(worker_i, n_completed_buffers);
2320 dcqs.clear_n_completed_buffers();
2321 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!");
2322 }
2323
2324
2325 // Computes the sum of the storage used by the various regions.
2326
2327 size_t G1CollectedHeap::used() const {
2328 assert(Heap_lock->owner() != NULL,
2329 "Should be owned on this thread's behalf.");
2330 size_t result = _summary_bytes_used;
2331 // Read only once in case it is set to NULL concurrently
2332 HeapRegion* hr = _mutator_alloc_region.get();
2333 if (hr != NULL)
2334 result += hr->used();
2335 return result;
2336 }
2337
2338 size_t G1CollectedHeap::used_unlocked() const {
2339 size_t result = _summary_bytes_used;
2340 return result;
2341 }
2342
2343 class SumUsedClosure: public HeapRegionClosure {
2344 size_t _used;
2345 public:
2346 SumUsedClosure() : _used(0) {}
2347 bool doHeapRegion(HeapRegion* r) {
2348 if (!r->continuesHumongous()) {
2349 _used += r->used();
2350 }
2351 return false;
2352 }
2353 size_t result() { return _used; }
2354 };
2355
2356 size_t G1CollectedHeap::recalculate_used() const {
2357 SumUsedClosure blk;
2358 heap_region_iterate(&blk);
2359 return blk.result();
2360 }
2361
2362 size_t G1CollectedHeap::unsafe_max_alloc() {
2363 if (free_regions() > 0) return HeapRegion::GrainBytes;
2364 // otherwise, is there space in the current allocation region?
2365
2366 // We need to store the current allocation region in a local variable
2367 // here. The problem is that this method doesn't take any locks and
2368 // there may be other threads which overwrite the current allocation
2369 // region field. attempt_allocation(), for example, sets it to NULL
2370 // and this can happen *after* the NULL check here but before the call
2371 // to free(), resulting in a SIGSEGV. Note that this doesn't appear
2372 // to be a problem in the optimized build, since the two loads of the
2373 // current allocation region field are optimized away.
2374 HeapRegion* hr = _mutator_alloc_region.get();
2375 if (hr == NULL) {
2376 return 0;
2377 }
2378 return hr->free();
2379 }
2380
2381 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
2382 switch (cause) {
2383 case GCCause::_gc_locker: return GCLockerInvokesConcurrent;
2384 case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent;
2385 case GCCause::_g1_humongous_allocation: return true;
2386 default: return false;
2387 }
2388 }
2389
2390 #ifndef PRODUCT
2391 void G1CollectedHeap::allocate_dummy_regions() {
2392 // Let's fill up most of the region
2393 size_t word_size = HeapRegion::GrainWords - 1024;
2394 // And as a result the region we'll allocate will be humongous.
2395 guarantee(isHumongous(word_size), "sanity");
2396
2397 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
2398 // Let's use the existing mechanism for the allocation
2399 HeapWord* dummy_obj = humongous_obj_allocate(word_size);
2400 if (dummy_obj != NULL) {
2401 MemRegion mr(dummy_obj, word_size);
2402 CollectedHeap::fill_with_object(mr);
2403 } else {
2404 // If we can't allocate once, we probably cannot allocate
2405 // again. Let's get out of the loop.
2406 break;
2407 }
2408 }
2409 }
2410 #endif // !PRODUCT
2411
2412 void G1CollectedHeap::increment_old_marking_cycles_started() {
2413 assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
2414 _old_marking_cycles_started == _old_marking_cycles_completed + 1,
2415 err_msg("Wrong marking cycle count (started: %d, completed: %d)",
2416 _old_marking_cycles_started, _old_marking_cycles_completed));
2417
2418 _old_marking_cycles_started++;
2419 }
2420
2421 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) {
2422 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
2423
2424 // We assume that if concurrent == true, then the caller is a
2425 // concurrent thread that was joined the Suspendible Thread
2426 // Set. If there's ever a cheap way to check this, we should add an
2427 // assert here.
2428
2429 // Given that this method is called at the end of a Full GC or of a
2430 // concurrent cycle, and those can be nested (i.e., a Full GC can
2431 // interrupt a concurrent cycle), the number of full collections
2432 // completed should be either one (in the case where there was no
2433 // nesting) or two (when a Full GC interrupted a concurrent cycle)
2434 // behind the number of full collections started.
2435
2436 // This is the case for the inner caller, i.e. a Full GC.
2437 assert(concurrent ||
2438 (_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
2439 (_old_marking_cycles_started == _old_marking_cycles_completed + 2),
2440 err_msg("for inner caller (Full GC): _old_marking_cycles_started = %u "
2441 "is inconsistent with _old_marking_cycles_completed = %u",
2442 _old_marking_cycles_started, _old_marking_cycles_completed));
2443
2444 // This is the case for the outer caller, i.e. the concurrent cycle.
2445 assert(!concurrent ||
2446 (_old_marking_cycles_started == _old_marking_cycles_completed + 1),
2447 err_msg("for outer caller (concurrent cycle): "
2448 "_old_marking_cycles_started = %u "
2449 "is inconsistent with _old_marking_cycles_completed = %u",
2450 _old_marking_cycles_started, _old_marking_cycles_completed));
2451
2452 _old_marking_cycles_completed += 1;
2453
2454 // We need to clear the "in_progress" flag in the CM thread before
2455 // we wake up any waiters (especially when ExplicitInvokesConcurrent
2456 // is set) so that if a waiter requests another System.gc() it doesn't
2457 // incorrectly see that a marking cyle is still in progress.
2458 if (concurrent) {
2459 _cmThread->clear_in_progress();
2460 }
2461
2462 // This notify_all() will ensure that a thread that called
2463 // System.gc() with (with ExplicitGCInvokesConcurrent set or not)
2464 // and it's waiting for a full GC to finish will be woken up. It is
2465 // waiting in VM_G1IncCollectionPause::doit_epilogue().
2466 FullGCCount_lock->notify_all();
2467 }
2468
2469 void G1CollectedHeap::collect(GCCause::Cause cause) {
2470 assert_heap_not_locked();
2471
2472 unsigned int gc_count_before;
2473 unsigned int old_marking_count_before;
2474 bool retry_gc;
2475
2476 do {
2477 retry_gc = false;
2478
2479 {
2480 MutexLocker ml(Heap_lock);
2481
2482 // Read the GC count while holding the Heap_lock
2483 gc_count_before = total_collections();
2484 old_marking_count_before = _old_marking_cycles_started;
2485 }
2486
2487 if (should_do_concurrent_full_gc(cause)) {
2488 // Schedule an initial-mark evacuation pause that will start a
2489 // concurrent cycle. We're setting word_size to 0 which means that
2490 // we are not requesting a post-GC allocation.
2491 VM_G1IncCollectionPause op(gc_count_before,
2492 0, /* word_size */
2493 true, /* should_initiate_conc_mark */
2494 g1_policy()->max_pause_time_ms(),
2495 cause);
2496
2497 VMThread::execute(&op);
2498 if (!op.pause_succeeded()) {
2499 if (old_marking_count_before == _old_marking_cycles_started) {
2500 retry_gc = op.should_retry_gc();
2501 } else {
2502 // A Full GC happened while we were trying to schedule the
2503 // initial-mark GC. No point in starting a new cycle given
2504 // that the whole heap was collected anyway.
2505 }
2506
2507 if (retry_gc) {
2508 if (GC_locker::is_active_and_needs_gc()) {
2509 GC_locker::stall_until_clear();
2510 }
2511 }
2512 }
2513 } else {
2514 if (cause == GCCause::_gc_locker
2515 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2516
2517 // Schedule a standard evacuation pause. We're setting word_size
2518 // to 0 which means that we are not requesting a post-GC allocation.
2519 VM_G1IncCollectionPause op(gc_count_before,
2520 0, /* word_size */
2521 false, /* should_initiate_conc_mark */
2522 g1_policy()->max_pause_time_ms(),
2523 cause);
2524 VMThread::execute(&op);
2525 } else {
2526 // Schedule a Full GC.
2527 VM_G1CollectFull op(gc_count_before, old_marking_count_before, cause);
2528 VMThread::execute(&op);
2529 }
2530 }
2531 } while (retry_gc);
2532 }
2533
2534 bool G1CollectedHeap::is_in(const void* p) const {
2535 if (_g1_committed.contains(p)) {
2536 // Given that we know that p is in the committed space,
2537 // heap_region_containing_raw() should successfully
2538 // return the containing region.
2539 HeapRegion* hr = heap_region_containing_raw(p);
2540 return hr->is_in(p);
2541 } else {
2542 return false;
2543 }
2544 }
2545
2546 // Iteration functions.
2547
2548 // Iterates an OopClosure over all ref-containing fields of objects
2549 // within a HeapRegion.
2550
2551 class IterateOopClosureRegionClosure: public HeapRegionClosure {
2552 MemRegion _mr;
2553 ExtendedOopClosure* _cl;
2554 public:
2555 IterateOopClosureRegionClosure(MemRegion mr, ExtendedOopClosure* cl)
2556 : _mr(mr), _cl(cl) {}
2557 bool doHeapRegion(HeapRegion* r) {
2558 if (!r->continuesHumongous()) {
2559 r->oop_iterate(_cl);
2560 }
2561 return false;
2562 }
2563 };
2564
2565 void G1CollectedHeap::oop_iterate(ExtendedOopClosure* cl) {
2566 IterateOopClosureRegionClosure blk(_g1_committed, cl);
2567 heap_region_iterate(&blk);
2568 }
2569
2570 void G1CollectedHeap::oop_iterate(MemRegion mr, ExtendedOopClosure* cl) {
2571 IterateOopClosureRegionClosure blk(mr, cl);
2572 heap_region_iterate(&blk);
2573 }
2574
2575 // Iterates an ObjectClosure over all objects within a HeapRegion.
2576
2577 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2578 ObjectClosure* _cl;
2579 public:
2580 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2581 bool doHeapRegion(HeapRegion* r) {
2582 if (! r->continuesHumongous()) {
2583 r->object_iterate(_cl);
2584 }
2585 return false;
2586 }
2587 };
2588
2589 void G1CollectedHeap::object_iterate(ObjectClosure* cl) {
2590 IterateObjectClosureRegionClosure blk(cl);
2591 heap_region_iterate(&blk);
2592 }
2593
2594 void G1CollectedHeap::object_iterate_since_last_GC(ObjectClosure* cl) {
2595 // FIXME: is this right?
2596 guarantee(false, "object_iterate_since_last_GC not supported by G1 heap");
2597 }
2598
2599 // Calls a SpaceClosure on a HeapRegion.
2600
2601 class SpaceClosureRegionClosure: public HeapRegionClosure {
2602 SpaceClosure* _cl;
2603 public:
2604 SpaceClosureRegionClosure(SpaceClosure* cl) : _cl(cl) {}
2605 bool doHeapRegion(HeapRegion* r) {
2606 _cl->do_space(r);
2607 return false;
2608 }
2609 };
2610
2611 void G1CollectedHeap::space_iterate(SpaceClosure* cl) {
2612 SpaceClosureRegionClosure blk(cl);
2613 heap_region_iterate(&blk);
2614 }
2615
2616 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2617 _hrs.iterate(cl);
2618 }
2619
2620 void
2621 G1CollectedHeap::heap_region_par_iterate_chunked(HeapRegionClosure* cl,
2622 uint worker_id,
2623 uint no_of_par_workers,
2624 jint claim_value) {
2625 const uint regions = n_regions();
2626 const uint max_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
2627 no_of_par_workers :
2628 1);
2629 assert(UseDynamicNumberOfGCThreads ||
2630 no_of_par_workers == workers()->total_workers(),
2631 "Non dynamic should use fixed number of workers");
2632 // try to spread out the starting points of the workers
2633 const HeapRegion* start_hr =
2634 start_region_for_worker(worker_id, no_of_par_workers);
2635 const uint start_index = start_hr->hrs_index();
2636
2637 // each worker will actually look at all regions
2638 for (uint count = 0; count < regions; ++count) {
2639 const uint index = (start_index + count) % regions;
2640 assert(0 <= index && index < regions, "sanity");
2641 HeapRegion* r = region_at(index);
2642 // we'll ignore "continues humongous" regions (we'll process them
2643 // when we come across their corresponding "start humongous"
2644 // region) and regions already claimed
2645 if (r->claim_value() == claim_value || r->continuesHumongous()) {
2646 continue;
2647 }
2648 // OK, try to claim it
2649 if (r->claimHeapRegion(claim_value)) {
2650 // success!
2651 assert(!r->continuesHumongous(), "sanity");
2652 if (r->startsHumongous()) {
2653 // If the region is "starts humongous" we'll iterate over its
2654 // "continues humongous" first; in fact we'll do them
2655 // first. The order is important. In on case, calling the
2656 // closure on the "starts humongous" region might de-allocate
2657 // and clear all its "continues humongous" regions and, as a
2658 // result, we might end up processing them twice. So, we'll do
2659 // them first (notice: most closures will ignore them anyway) and
2660 // then we'll do the "starts humongous" region.
2661 for (uint ch_index = index + 1; ch_index < regions; ++ch_index) {
2662 HeapRegion* chr = region_at(ch_index);
2663
2664 // if the region has already been claimed or it's not
2665 // "continues humongous" we're done
2666 if (chr->claim_value() == claim_value ||
2667 !chr->continuesHumongous()) {
2668 break;
2669 }
2670
2671 // Noone should have claimed it directly. We can given
2672 // that we claimed its "starts humongous" region.
2673 assert(chr->claim_value() != claim_value, "sanity");
2674 assert(chr->humongous_start_region() == r, "sanity");
2675
2676 if (chr->claimHeapRegion(claim_value)) {
2677 // we should always be able to claim it; noone else should
2678 // be trying to claim this region
2679
2680 bool res2 = cl->doHeapRegion(chr);
2681 assert(!res2, "Should not abort");
2682
2683 // Right now, this holds (i.e., no closure that actually
2684 // does something with "continues humongous" regions
2685 // clears them). We might have to weaken it in the future,
2686 // but let's leave these two asserts here for extra safety.
2687 assert(chr->continuesHumongous(), "should still be the case");
2688 assert(chr->humongous_start_region() == r, "sanity");
2689 } else {
2690 guarantee(false, "we should not reach here");
2691 }
2692 }
2693 }
2694
2695 assert(!r->continuesHumongous(), "sanity");
2696 bool res = cl->doHeapRegion(r);
2697 assert(!res, "Should not abort");
2698 }
2699 }
2700 }
2701
2702 class ResetClaimValuesClosure: public HeapRegionClosure {
2703 public:
2704 bool doHeapRegion(HeapRegion* r) {
2705 r->set_claim_value(HeapRegion::InitialClaimValue);
2706 return false;
2707 }
2708 };
2709
2710 void G1CollectedHeap::reset_heap_region_claim_values() {
2711 ResetClaimValuesClosure blk;
2712 heap_region_iterate(&blk);
2713 }
2714
2715 void G1CollectedHeap::reset_cset_heap_region_claim_values() {
2716 ResetClaimValuesClosure blk;
2717 collection_set_iterate(&blk);
2718 }
2719
2720 #ifdef ASSERT
2721 // This checks whether all regions in the heap have the correct claim
2722 // value. I also piggy-backed on this a check to ensure that the
2723 // humongous_start_region() information on "continues humongous"
2724 // regions is correct.
2725
2726 class CheckClaimValuesClosure : public HeapRegionClosure {
2727 private:
2728 jint _claim_value;
2729 uint _failures;
2730 HeapRegion* _sh_region;
2731
2732 public:
2733 CheckClaimValuesClosure(jint claim_value) :
2734 _claim_value(claim_value), _failures(0), _sh_region(NULL) { }
2735 bool doHeapRegion(HeapRegion* r) {
2736 if (r->claim_value() != _claim_value) {
2737 gclog_or_tty->print_cr("Region " HR_FORMAT ", "
2738 "claim value = %d, should be %d",
2739 HR_FORMAT_PARAMS(r),
2740 r->claim_value(), _claim_value);
2741 ++_failures;
2742 }
2743 if (!r->isHumongous()) {
2744 _sh_region = NULL;
2745 } else if (r->startsHumongous()) {
2746 _sh_region = r;
2747 } else if (r->continuesHumongous()) {
2748 if (r->humongous_start_region() != _sh_region) {
2749 gclog_or_tty->print_cr("Region " HR_FORMAT ", "
2750 "HS = "PTR_FORMAT", should be "PTR_FORMAT,
2751 HR_FORMAT_PARAMS(r),
2752 r->humongous_start_region(),
2753 _sh_region);
2754 ++_failures;
2755 }
2756 }
2757 return false;
2758 }
2759 uint failures() { return _failures; }
2760 };
2761
2762 bool G1CollectedHeap::check_heap_region_claim_values(jint claim_value) {
2763 CheckClaimValuesClosure cl(claim_value);
2764 heap_region_iterate(&cl);
2765 return cl.failures() == 0;
2766 }
2767
2768 class CheckClaimValuesInCSetHRClosure: public HeapRegionClosure {
2769 private:
2770 jint _claim_value;
2771 uint _failures;
2772
2773 public:
2774 CheckClaimValuesInCSetHRClosure(jint claim_value) :
2775 _claim_value(claim_value), _failures(0) { }
2776
2777 uint failures() { return _failures; }
2778
2779 bool doHeapRegion(HeapRegion* hr) {
2780 assert(hr->in_collection_set(), "how?");
2781 assert(!hr->isHumongous(), "H-region in CSet");
2782 if (hr->claim_value() != _claim_value) {
2783 gclog_or_tty->print_cr("CSet Region " HR_FORMAT ", "
2784 "claim value = %d, should be %d",
2785 HR_FORMAT_PARAMS(hr),
2786 hr->claim_value(), _claim_value);
2787 _failures += 1;
2788 }
2789 return false;
2790 }
2791 };
2792
2793 bool G1CollectedHeap::check_cset_heap_region_claim_values(jint claim_value) {
2794 CheckClaimValuesInCSetHRClosure cl(claim_value);
2795 collection_set_iterate(&cl);
2796 return cl.failures() == 0;
2797 }
2798 #endif // ASSERT
2799
2800 // Clear the cached CSet starting regions and (more importantly)
2801 // the time stamps. Called when we reset the GC time stamp.
2802 void G1CollectedHeap::clear_cset_start_regions() {
2803 assert(_worker_cset_start_region != NULL, "sanity");
2804 assert(_worker_cset_start_region_time_stamp != NULL, "sanity");
2805
2806 int n_queues = MAX2((int)ParallelGCThreads, 1);
2807 for (int i = 0; i < n_queues; i++) {
2808 _worker_cset_start_region[i] = NULL;
2809 _worker_cset_start_region_time_stamp[i] = 0;
2810 }
2811 }
2812
2813 // Given the id of a worker, obtain or calculate a suitable
2814 // starting region for iterating over the current collection set.
2815 HeapRegion* G1CollectedHeap::start_cset_region_for_worker(int worker_i) {
2816 assert(get_gc_time_stamp() > 0, "should have been updated by now");
2817
2818 HeapRegion* result = NULL;
2819 unsigned gc_time_stamp = get_gc_time_stamp();
2820
2821 if (_worker_cset_start_region_time_stamp[worker_i] == gc_time_stamp) {
2822 // Cached starting region for current worker was set
2823 // during the current pause - so it's valid.
2824 // Note: the cached starting heap region may be NULL
2825 // (when the collection set is empty).
2826 result = _worker_cset_start_region[worker_i];
2827 assert(result == NULL || result->in_collection_set(), "sanity");
2828 return result;
2829 }
2830
2831 // The cached entry was not valid so let's calculate
2832 // a suitable starting heap region for this worker.
2833
2834 // We want the parallel threads to start their collection
2835 // set iteration at different collection set regions to
2836 // avoid contention.
2837 // If we have:
2838 // n collection set regions
2839 // p threads
2840 // Then thread t will start at region floor ((t * n) / p)
2841
2842 result = g1_policy()->collection_set();
2843 if (G1CollectedHeap::use_parallel_gc_threads()) {
2844 uint cs_size = g1_policy()->cset_region_length();
2845 uint active_workers = workers()->active_workers();
2846 assert(UseDynamicNumberOfGCThreads ||
2847 active_workers == workers()->total_workers(),
2848 "Unless dynamic should use total workers");
2849
2850 uint end_ind = (cs_size * worker_i) / active_workers;
2851 uint start_ind = 0;
2852
2853 if (worker_i > 0 &&
2854 _worker_cset_start_region_time_stamp[worker_i - 1] == gc_time_stamp) {
2855 // Previous workers starting region is valid
2856 // so let's iterate from there
2857 start_ind = (cs_size * (worker_i - 1)) / active_workers;
2858 result = _worker_cset_start_region[worker_i - 1];
2859 }
2860
2861 for (uint i = start_ind; i < end_ind; i++) {
2862 result = result->next_in_collection_set();
2863 }
2864 }
2865
2866 // Note: the calculated starting heap region may be NULL
2867 // (when the collection set is empty).
2868 assert(result == NULL || result->in_collection_set(), "sanity");
2869 assert(_worker_cset_start_region_time_stamp[worker_i] != gc_time_stamp,
2870 "should be updated only once per pause");
2871 _worker_cset_start_region[worker_i] = result;
2872 OrderAccess::storestore();
2873 _worker_cset_start_region_time_stamp[worker_i] = gc_time_stamp;
2874 return result;
2875 }
2876
2877 HeapRegion* G1CollectedHeap::start_region_for_worker(uint worker_i,
2878 uint no_of_par_workers) {
2879 uint worker_num =
2880 G1CollectedHeap::use_parallel_gc_threads() ? no_of_par_workers : 1U;
2881 assert(UseDynamicNumberOfGCThreads ||
2882 no_of_par_workers == workers()->total_workers(),
2883 "Non dynamic should use fixed number of workers");
2884 const uint start_index = n_regions() * worker_i / worker_num;
2885 return region_at(start_index);
2886 }
2887
2888 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) {
2889 HeapRegion* r = g1_policy()->collection_set();
2890 while (r != NULL) {
2891 HeapRegion* next = r->next_in_collection_set();
2892 if (cl->doHeapRegion(r)) {
2893 cl->incomplete();
2894 return;
2895 }
2896 r = next;
2897 }
2898 }
2899
2900 void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r,
2901 HeapRegionClosure *cl) {
2902 if (r == NULL) {
2903 // The CSet is empty so there's nothing to do.
2904 return;
2905 }
2906
2907 assert(r->in_collection_set(),
2908 "Start region must be a member of the collection set.");
2909 HeapRegion* cur = r;
2910 while (cur != NULL) {
2911 HeapRegion* next = cur->next_in_collection_set();
2912 if (cl->doHeapRegion(cur) && false) {
2913 cl->incomplete();
2914 return;
2915 }
2916 cur = next;
2917 }
2918 cur = g1_policy()->collection_set();
2919 while (cur != r) {
2920 HeapRegion* next = cur->next_in_collection_set();
2921 if (cl->doHeapRegion(cur) && false) {
2922 cl->incomplete();
2923 return;
2924 }
2925 cur = next;
2926 }
2927 }
2928
2929 CompactibleSpace* G1CollectedHeap::first_compactible_space() {
2930 return n_regions() > 0 ? region_at(0) : NULL;
2931 }
2932
2933
2934 Space* G1CollectedHeap::space_containing(const void* addr) const {
2935 Space* res = heap_region_containing(addr);
2936 return res;
2937 }
2938
2939 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2940 Space* sp = space_containing(addr);
2941 if (sp != NULL) {
2942 return sp->block_start(addr);
2943 }
2944 return NULL;
2945 }
2946
2947 size_t G1CollectedHeap::block_size(const HeapWord* addr) const {
2948 Space* sp = space_containing(addr);
2949 assert(sp != NULL, "block_size of address outside of heap");
2950 return sp->block_size(addr);
2951 }
2952
2953 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2954 Space* sp = space_containing(addr);
2955 return sp->block_is_obj(addr);
2956 }
2957
2958 bool G1CollectedHeap::supports_tlab_allocation() const {
2959 return true;
2960 }
2961
2962 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
2963 return HeapRegion::GrainBytes;
2964 }
2965
2966 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
2967 // Return the remaining space in the cur alloc region, but not less than
2968 // the min TLAB size.
2969
2970 // Also, this value can be at most the humongous object threshold,
2971 // since we can't allow tlabs to grow big enough to accomodate
2972 // humongous objects.
2973
2974 HeapRegion* hr = _mutator_alloc_region.get();
2975 size_t max_tlab_size = _humongous_object_threshold_in_words * wordSize;
2976 if (hr == NULL) {
2977 return max_tlab_size;
2978 } else {
2979 return MIN2(MAX2(hr->free(), (size_t) MinTLABSize), max_tlab_size);
2980 }
2981 }
2982
2983 size_t G1CollectedHeap::max_capacity() const {
2984 return _g1_reserved.byte_size();
2985 }
2986
2987 jlong G1CollectedHeap::millis_since_last_gc() {
2988 // assert(false, "NYI");
2989 return 0;
2990 }
2991
2992 void G1CollectedHeap::prepare_for_verify() {
2993 if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) {
2994 ensure_parsability(false);
2995 }
2996 g1_rem_set()->prepare_for_verify();
2997 }
2998
2999 bool G1CollectedHeap::allocated_since_marking(oop obj, HeapRegion* hr,
3000 VerifyOption vo) {
3001 switch (vo) {
3002 case VerifyOption_G1UsePrevMarking:
3003 return hr->obj_allocated_since_prev_marking(obj);
3004 case VerifyOption_G1UseNextMarking:
3005 return hr->obj_allocated_since_next_marking(obj);
3006 case VerifyOption_G1UseMarkWord:
3007 return false;
3008 default:
3009 ShouldNotReachHere();
3010 }
3011 return false; // keep some compilers happy
3012 }
3013
3014 HeapWord* G1CollectedHeap::top_at_mark_start(HeapRegion* hr, VerifyOption vo) {
3015 switch (vo) {
3016 case VerifyOption_G1UsePrevMarking: return hr->prev_top_at_mark_start();
3017 case VerifyOption_G1UseNextMarking: return hr->next_top_at_mark_start();
3018 case VerifyOption_G1UseMarkWord: return NULL;
3019 default: ShouldNotReachHere();
3020 }
3021 return NULL; // keep some compilers happy
3022 }
3023
3024 bool G1CollectedHeap::is_marked(oop obj, VerifyOption vo) {
3025 switch (vo) {
3026 case VerifyOption_G1UsePrevMarking: return isMarkedPrev(obj);
3027 case VerifyOption_G1UseNextMarking: return isMarkedNext(obj);
3028 case VerifyOption_G1UseMarkWord: return obj->is_gc_marked();
3029 default: ShouldNotReachHere();
3030 }
3031 return false; // keep some compilers happy
3032 }
3033
3034 const char* G1CollectedHeap::top_at_mark_start_str(VerifyOption vo) {
3035 switch (vo) {
3036 case VerifyOption_G1UsePrevMarking: return "PTAMS";
3037 case VerifyOption_G1UseNextMarking: return "NTAMS";
3038 case VerifyOption_G1UseMarkWord: return "NONE";
3039 default: ShouldNotReachHere();
3040 }
3041 return NULL; // keep some compilers happy
3042 }
3043
3044 class VerifyLivenessOopClosure: public OopClosure {
3045 G1CollectedHeap* _g1h;
3046 VerifyOption _vo;
3047 public:
3048 VerifyLivenessOopClosure(G1CollectedHeap* g1h, VerifyOption vo):
3049 _g1h(g1h), _vo(vo)
3050 { }
3051 void do_oop(narrowOop *p) { do_oop_work(p); }
3052 void do_oop( oop *p) { do_oop_work(p); }
3053
3054 template <class T> void do_oop_work(T *p) {
3055 oop obj = oopDesc::load_decode_heap_oop(p);
3056 guarantee(obj == NULL || !_g1h->is_obj_dead_cond(obj, _vo),
3057 "Dead object referenced by a not dead object");
3058 }
3059 };
3060
3061 class VerifyObjsInRegionClosure: public ObjectClosure {
3062 private:
3063 G1CollectedHeap* _g1h;
3064 size_t _live_bytes;
3065 HeapRegion *_hr;
3066 VerifyOption _vo;
3067 public:
3068 // _vo == UsePrevMarking -> use "prev" marking information,
3069 // _vo == UseNextMarking -> use "next" marking information,
3070 // _vo == UseMarkWord -> use mark word from object header.
3071 VerifyObjsInRegionClosure(HeapRegion *hr, VerifyOption vo)
3072 : _live_bytes(0), _hr(hr), _vo(vo) {
3073 _g1h = G1CollectedHeap::heap();
3074 }
3075 void do_object(oop o) {
3076 VerifyLivenessOopClosure isLive(_g1h, _vo);
3077 assert(o != NULL, "Huh?");
3078 if (!_g1h->is_obj_dead_cond(o, _vo)) {
3079 // If the object is alive according to the mark word,
3080 // then verify that the marking information agrees.
3081 // Note we can't verify the contra-positive of the
3082 // above: if the object is dead (according to the mark
3083 // word), it may not be marked, or may have been marked
3084 // but has since became dead, or may have been allocated
3085 // since the last marking.
3086 if (_vo == VerifyOption_G1UseMarkWord) {
3087 guarantee(!_g1h->is_obj_dead(o), "mark word and concurrent mark mismatch");
3088 }
3089
3090 o->oop_iterate_no_header(&isLive);
3091 if (!_hr->obj_allocated_since_prev_marking(o)) {
3092 size_t obj_size = o->size(); // Make sure we don't overflow
3093 _live_bytes += (obj_size * HeapWordSize);
3094 }
3095 }
3096 }
3097 size_t live_bytes() { return _live_bytes; }
3098 };
3099
3100 class PrintObjsInRegionClosure : public ObjectClosure {
3101 HeapRegion *_hr;
3102 G1CollectedHeap *_g1;
3103 public:
3104 PrintObjsInRegionClosure(HeapRegion *hr) : _hr(hr) {
3105 _g1 = G1CollectedHeap::heap();
3106 };
3107
3108 void do_object(oop o) {
3109 if (o != NULL) {
3110 HeapWord *start = (HeapWord *) o;
3111 size_t word_sz = o->size();
3112 gclog_or_tty->print("\nPrinting obj "PTR_FORMAT" of size " SIZE_FORMAT
3113 " isMarkedPrev %d isMarkedNext %d isAllocSince %d\n",
3114 (void*) o, word_sz,
3115 _g1->isMarkedPrev(o),
3116 _g1->isMarkedNext(o),
3117 _hr->obj_allocated_since_prev_marking(o));
3118 HeapWord *end = start + word_sz;
3119 HeapWord *cur;
3120 int *val;
3121 for (cur = start; cur < end; cur++) {
3122 val = (int *) cur;
3123 gclog_or_tty->print("\t "PTR_FORMAT":"PTR_FORMAT"\n", val, *val);
3124 }
3125 }
3126 }
3127 };
3128
3129 class VerifyRegionClosure: public HeapRegionClosure {
3130 private:
3131 bool _par;
3132 VerifyOption _vo;
3133 bool _failures;
3134 public:
3135 // _vo == UsePrevMarking -> use "prev" marking information,
3136 // _vo == UseNextMarking -> use "next" marking information,
3137 // _vo == UseMarkWord -> use mark word from object header.
3138 VerifyRegionClosure(bool par, VerifyOption vo)
3139 : _par(par),
3140 _vo(vo),
3141 _failures(false) {}
3142
3143 bool failures() {
3144 return _failures;
3145 }
3146
3147 bool doHeapRegion(HeapRegion* r) {
3148 if (!r->continuesHumongous()) {
3149 bool failures = false;
3150 r->verify(_vo, &failures);
3151 if (failures) {
3152 _failures = true;
3153 } else {
3154 VerifyObjsInRegionClosure not_dead_yet_cl(r, _vo);
3155 r->object_iterate(¬_dead_yet_cl);
3156 if (_vo != VerifyOption_G1UseNextMarking) {
3157 if (r->max_live_bytes() < not_dead_yet_cl.live_bytes()) {
3158 gclog_or_tty->print_cr("["PTR_FORMAT","PTR_FORMAT"] "
3159 "max_live_bytes "SIZE_FORMAT" "
3160 "< calculated "SIZE_FORMAT,
3161 r->bottom(), r->end(),
3162 r->max_live_bytes(),
3163 not_dead_yet_cl.live_bytes());
3164 _failures = true;
3165 }
3166 } else {
3167 // When vo == UseNextMarking we cannot currently do a sanity
3168 // check on the live bytes as the calculation has not been
3169 // finalized yet.
3170 }
3171 }
3172 }
3173 return false; // stop the region iteration if we hit a failure
3174 }
3175 };
3176
3177 class YoungRefCounterClosure : public OopClosure {
3178 G1CollectedHeap* _g1h;
3179 int _count;
3180 public:
3181 YoungRefCounterClosure(G1CollectedHeap* g1h) : _g1h(g1h), _count(0) {}
3182 void do_oop(oop* p) { if (_g1h->is_in_young(*p)) { _count++; } }
3183 void do_oop(narrowOop* p) { ShouldNotReachHere(); }
3184
3185 int count() { return _count; }
3186 void reset_count() { _count = 0; };
3187 };
3188
3189 class VerifyKlassClosure: public KlassClosure {
3190 YoungRefCounterClosure _young_ref_counter_closure;
3191 OopClosure *_oop_closure;
3192 public:
3193 VerifyKlassClosure(G1CollectedHeap* g1h, OopClosure* cl) : _young_ref_counter_closure(g1h), _oop_closure(cl) {}
3194 void do_klass(Klass* k) {
3195 k->oops_do(_oop_closure);
3196
3197 _young_ref_counter_closure.reset_count();
3198 k->oops_do(&_young_ref_counter_closure);
3199 if (_young_ref_counter_closure.count() > 0) {
3200 guarantee(k->has_modified_oops(), err_msg("Klass %p, has young refs but is not dirty.", k));
3201 }
3202 }
3203 };
3204
3205 // TODO: VerifyRootsClosure extends OopsInGenClosure so that we can
3206 // pass it as the perm_blk to SharedHeap::process_strong_roots.
3207 // When process_strong_roots stop calling perm_blk->younger_refs_iterate
3208 // we can change this closure to extend the simpler OopClosure.
3209 class VerifyRootsClosure: public OopsInGenClosure {
3210 private:
3211 G1CollectedHeap* _g1h;
3212 VerifyOption _vo;
3213 bool _failures;
3214 public:
3215 // _vo == UsePrevMarking -> use "prev" marking information,
3216 // _vo == UseNextMarking -> use "next" marking information,
3217 // _vo == UseMarkWord -> use mark word from object header.
3218 VerifyRootsClosure(VerifyOption vo) :
3219 _g1h(G1CollectedHeap::heap()),
3220 _vo(vo),
3221 _failures(false) { }
3222
3223 bool failures() { return _failures; }
3224
3225 template <class T> void do_oop_nv(T* p) {
3226 T heap_oop = oopDesc::load_heap_oop(p);
3227 if (!oopDesc::is_null(heap_oop)) {
3228 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
3229 if (_g1h->is_obj_dead_cond(obj, _vo)) {
3230 gclog_or_tty->print_cr("Root location "PTR_FORMAT" "
3231 "points to dead obj "PTR_FORMAT, p, (void*) obj);
3232 if (_vo == VerifyOption_G1UseMarkWord) {
3233 gclog_or_tty->print_cr(" Mark word: "PTR_FORMAT, (void*)(obj->mark()));
3234 }
3235 obj->print_on(gclog_or_tty);
3236 _failures = true;
3237 }
3238 }
3239 }
3240
3241 void do_oop(oop* p) { do_oop_nv(p); }
3242 void do_oop(narrowOop* p) { do_oop_nv(p); }
3243 };
3244
3245 // This is the task used for parallel heap verification.
3246
3247 class G1ParVerifyTask: public AbstractGangTask {
3248 private:
3249 G1CollectedHeap* _g1h;
3250 VerifyOption _vo;
3251 bool _failures;
3252
3253 public:
3254 // _vo == UsePrevMarking -> use "prev" marking information,
3255 // _vo == UseNextMarking -> use "next" marking information,
3256 // _vo == UseMarkWord -> use mark word from object header.
3257 G1ParVerifyTask(G1CollectedHeap* g1h, VerifyOption vo) :
3258 AbstractGangTask("Parallel verify task"),
3259 _g1h(g1h),
3260 _vo(vo),
3261 _failures(false) { }
3262
3263 bool failures() {
3264 return _failures;
3265 }
3266
3267 void work(uint worker_id) {
3268 HandleMark hm;
3269 VerifyRegionClosure blk(true, _vo);
3270 _g1h->heap_region_par_iterate_chunked(&blk, worker_id,
3271 _g1h->workers()->active_workers(),
3272 HeapRegion::ParVerifyClaimValue);
3273 if (blk.failures()) {
3274 _failures = true;
3275 }
3276 }
3277 };
3278
3279 void G1CollectedHeap::verify(bool silent) {
3280 verify(silent, VerifyOption_G1UsePrevMarking);
3281 }
3282
3283 void G1CollectedHeap::verify(bool silent,
3284 VerifyOption vo) {
3285 if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) {
3286 if (!silent) { gclog_or_tty->print("Roots "); }
3287 VerifyRootsClosure rootsCl(vo);
3288
3289 assert(Thread::current()->is_VM_thread(),
3290 "Expected to be executed serially by the VM thread at this point");
3291
3292 CodeBlobToOopClosure blobsCl(&rootsCl, /*do_marking=*/ false);
3293 VerifyKlassClosure klassCl(this, &rootsCl);
3294
3295 // We apply the relevant closures to all the oops in the
3296 // system dictionary, the string table and the code cache.
3297 const int so = SO_AllClasses | SO_Strings | SO_CodeCache;
3298
3299 // Need cleared claim bits for the strong roots processing
3300 ClassLoaderDataGraph::clear_claimed_marks();
3301
3302 process_strong_roots(true, // activate StrongRootsScope
3303 false, // we set "is scavenging" to false,
3304 // so we don't reset the dirty cards.
3305 ScanningOption(so), // roots scanning options
3306 &rootsCl,
3307 &blobsCl,
3308 &klassCl
3309 );
3310
3311 bool failures = rootsCl.failures();
3312
3313 if (vo != VerifyOption_G1UseMarkWord) {
3314 // If we're verifying during a full GC then the region sets
3315 // will have been torn down at the start of the GC. Therefore
3316 // verifying the region sets will fail. So we only verify
3317 // the region sets when not in a full GC.
3318 if (!silent) { gclog_or_tty->print("HeapRegionSets "); }
3319 verify_region_sets();
3320 }
3321
3322 if (!silent) { gclog_or_tty->print("HeapRegions "); }
3323 if (GCParallelVerificationEnabled && ParallelGCThreads > 1) {
3324 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3325 "sanity check");
3326
3327 G1ParVerifyTask task(this, vo);
3328 assert(UseDynamicNumberOfGCThreads ||
3329 workers()->active_workers() == workers()->total_workers(),
3330 "If not dynamic should be using all the workers");
3331 int n_workers = workers()->active_workers();
3332 set_par_threads(n_workers);
3333 workers()->run_task(&task);
3334 set_par_threads(0);
3335 if (task.failures()) {
3336 failures = true;
3337 }
3338
3339 // Checks that the expected amount of parallel work was done.
3340 // The implication is that n_workers is > 0.
3341 assert(check_heap_region_claim_values(HeapRegion::ParVerifyClaimValue),
3342 "sanity check");
3343
3344 reset_heap_region_claim_values();
3345
3346 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3347 "sanity check");
3348 } else {
3349 VerifyRegionClosure blk(false, vo);
3350 heap_region_iterate(&blk);
3351 if (blk.failures()) {
3352 failures = true;
3353 }
3354 }
3355 if (!silent) gclog_or_tty->print("RemSet ");
3356 rem_set()->verify();
3357
3358 if (failures) {
3359 gclog_or_tty->print_cr("Heap:");
3360 // It helps to have the per-region information in the output to
3361 // help us track down what went wrong. This is why we call
3362 // print_extended_on() instead of print_on().
3363 print_extended_on(gclog_or_tty);
3364 gclog_or_tty->print_cr("");
3365 #ifndef PRODUCT
3366 if (VerifyDuringGC && G1VerifyDuringGCPrintReachable) {
3367 concurrent_mark()->print_reachable("at-verification-failure",
3368 vo, false /* all */);
3369 }
3370 #endif
3371 gclog_or_tty->flush();
3372 }
3373 guarantee(!failures, "there should not have been any failures");
3374 } else {
3375 if (!silent) gclog_or_tty->print("(SKIPPING roots, heapRegions, remset) ");
3376 }
3377 }
3378
3379 class PrintRegionClosure: public HeapRegionClosure {
3380 outputStream* _st;
3381 public:
3382 PrintRegionClosure(outputStream* st) : _st(st) {}
3383 bool doHeapRegion(HeapRegion* r) {
3384 r->print_on(_st);
3385 return false;
3386 }
3387 };
3388
3389 void G1CollectedHeap::print_on(outputStream* st) const {
3390 st->print(" %-20s", "garbage-first heap");
3391 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
3392 capacity()/K, used_unlocked()/K);
3393 st->print(" [" INTPTR_FORMAT ", " INTPTR_FORMAT ", " INTPTR_FORMAT ")",
3394 _g1_storage.low_boundary(),
3395 _g1_storage.high(),
3396 _g1_storage.high_boundary());
3397 st->cr();
3398 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
3399 uint young_regions = _young_list->length();
3400 st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
3401 (size_t) young_regions * HeapRegion::GrainBytes / K);
3402 uint survivor_regions = g1_policy()->recorded_survivor_regions();
3403 st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
3404 (size_t) survivor_regions * HeapRegion::GrainBytes / K);
3405 st->cr();
3406 MetaspaceAux::print_on(st);
3407 }
3408
3409 void G1CollectedHeap::print_extended_on(outputStream* st) const {
3410 print_on(st);
3411
3412 // Print the per-region information.
3413 st->cr();
3414 st->print_cr("Heap Regions: (Y=young(eden), SU=young(survivor), "
3415 "HS=humongous(starts), HC=humongous(continues), "
3416 "CS=collection set, F=free, TS=gc time stamp, "
3417 "PTAMS=previous top-at-mark-start, "
3418 "NTAMS=next top-at-mark-start)");
3419 PrintRegionClosure blk(st);
3420 heap_region_iterate(&blk);
3421 }
3422
3423 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
3424 if (G1CollectedHeap::use_parallel_gc_threads()) {
3425 workers()->print_worker_threads_on(st);
3426 }
3427 _cmThread->print_on(st);
3428 st->cr();
3429 _cm->print_worker_threads_on(st);
3430 _cg1r->print_worker_threads_on(st);
3431 }
3432
3433 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
3434 if (G1CollectedHeap::use_parallel_gc_threads()) {
3435 workers()->threads_do(tc);
3436 }
3437 tc->do_thread(_cmThread);
3438 _cg1r->threads_do(tc);
3439 }
3440
3441 void G1CollectedHeap::print_tracing_info() const {
3442 // We'll overload this to mean "trace GC pause statistics."
3443 if (TraceGen0Time || TraceGen1Time) {
3444 // The "G1CollectorPolicy" is keeping track of these stats, so delegate
3445 // to that.
3446 g1_policy()->print_tracing_info();
3447 }
3448 if (G1SummarizeRSetStats) {
3449 g1_rem_set()->print_summary_info();
3450 }
3451 if (G1SummarizeConcMark) {
3452 concurrent_mark()->print_summary_info();
3453 }
3454 g1_policy()->print_yg_surv_rate_info();
3455 SpecializationStats::print();
3456 }
3457
3458 #ifndef PRODUCT
3459 // Helpful for debugging RSet issues.
3460
3461 class PrintRSetsClosure : public HeapRegionClosure {
3462 private:
3463 const char* _msg;
3464 size_t _occupied_sum;
3465
3466 public:
3467 bool doHeapRegion(HeapRegion* r) {
3468 HeapRegionRemSet* hrrs = r->rem_set();
3469 size_t occupied = hrrs->occupied();
3470 _occupied_sum += occupied;
3471
3472 gclog_or_tty->print_cr("Printing RSet for region "HR_FORMAT,
3473 HR_FORMAT_PARAMS(r));
3474 if (occupied == 0) {
3475 gclog_or_tty->print_cr(" RSet is empty");
3476 } else {
3477 hrrs->print();
3478 }
3479 gclog_or_tty->print_cr("----------");
3480 return false;
3481 }
3482
3483 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
3484 gclog_or_tty->cr();
3485 gclog_or_tty->print_cr("========================================");
3486 gclog_or_tty->print_cr(msg);
3487 gclog_or_tty->cr();
3488 }
3489
3490 ~PrintRSetsClosure() {
3491 gclog_or_tty->print_cr("Occupied Sum: "SIZE_FORMAT, _occupied_sum);
3492 gclog_or_tty->print_cr("========================================");
3493 gclog_or_tty->cr();
3494 }
3495 };
3496
3497 void G1CollectedHeap::print_cset_rsets() {
3498 PrintRSetsClosure cl("Printing CSet RSets");
3499 collection_set_iterate(&cl);
3500 }
3501
3502 void G1CollectedHeap::print_all_rsets() {
3503 PrintRSetsClosure cl("Printing All RSets");;
3504 heap_region_iterate(&cl);
3505 }
3506 #endif // PRODUCT
3507
3508 G1CollectedHeap* G1CollectedHeap::heap() {
3509 assert(_sh->kind() == CollectedHeap::G1CollectedHeap,
3510 "not a garbage-first heap");
3511 return _g1h;
3512 }
3513
3514 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) {
3515 // always_do_update_barrier = false;
3516 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
3517 // Call allocation profiler
3518 AllocationProfiler::iterate_since_last_gc();
3519 // Fill TLAB's and such
3520 ensure_parsability(true);
3521 }
3522
3523 void G1CollectedHeap::gc_epilogue(bool full /* Ignored */) {
3524 // FIXME: what is this about?
3525 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
3526 // is set.
3527 COMPILER2_PRESENT(assert(DerivedPointerTable::is_empty(),
3528 "derived pointer present"));
3529 // always_do_update_barrier = true;
3530
3531 // We have just completed a GC. Update the soft reference
3532 // policy with the new heap occupancy
3533 Universe::update_heap_info_at_gc();
3534 }
3535
3536 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
3537 unsigned int gc_count_before,
3538 bool* succeeded) {
3539 assert_heap_not_locked_and_not_at_safepoint();
3540 g1_policy()->record_stop_world_start();
3541 VM_G1IncCollectionPause op(gc_count_before,
3542 word_size,
3543 false, /* should_initiate_conc_mark */
3544 g1_policy()->max_pause_time_ms(),
3545 GCCause::_g1_inc_collection_pause);
3546 VMThread::execute(&op);
3547
3548 HeapWord* result = op.result();
3549 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
3550 assert(result == NULL || ret_succeeded,
3551 "the result should be NULL if the VM did not succeed");
3552 *succeeded = ret_succeeded;
3553
3554 assert_heap_not_locked();
3555 return result;
3556 }
3557
3558 void
3559 G1CollectedHeap::doConcurrentMark() {
3560 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
3561 if (!_cmThread->in_progress()) {
3562 _cmThread->set_started();
3563 CGC_lock->notify();
3564 }
3565 }
3566
3567 size_t G1CollectedHeap::pending_card_num() {
3568 size_t extra_cards = 0;
3569 JavaThread *curr = Threads::first();
3570 while (curr != NULL) {
3571 DirtyCardQueue& dcq = curr->dirty_card_queue();
3572 extra_cards += dcq.size();
3573 curr = curr->next();
3574 }
3575 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
3576 size_t buffer_size = dcqs.buffer_size();
3577 size_t buffer_num = dcqs.completed_buffers_num();
3578
3579 // PtrQueueSet::buffer_size() and PtrQueue:size() return sizes
3580 // in bytes - not the number of 'entries'. We need to convert
3581 // into a number of cards.
3582 return (buffer_size * buffer_num + extra_cards) / oopSize;
3583 }
3584
3585 size_t G1CollectedHeap::cards_scanned() {
3586 return g1_rem_set()->cardsScanned();
3587 }
3588
3589 void
3590 G1CollectedHeap::setup_surviving_young_words() {
3591 assert(_surviving_young_words == NULL, "pre-condition");
3592 uint array_length = g1_policy()->young_cset_region_length();
3593 _surviving_young_words = NEW_C_HEAP_ARRAY(size_t, (size_t) array_length, mtGC);
3594 if (_surviving_young_words == NULL) {
3595 vm_exit_out_of_memory(sizeof(size_t) * array_length,
3596 "Not enough space for young surv words summary.");
3597 }
3598 memset(_surviving_young_words, 0, (size_t) array_length * sizeof(size_t));
3599 #ifdef ASSERT
3600 for (uint i = 0; i < array_length; ++i) {
3601 assert( _surviving_young_words[i] == 0, "memset above" );
3602 }
3603 #endif // !ASSERT
3604 }
3605
3606 void
3607 G1CollectedHeap::update_surviving_young_words(size_t* surv_young_words) {
3608 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
3609 uint array_length = g1_policy()->young_cset_region_length();
3610 for (uint i = 0; i < array_length; ++i) {
3611 _surviving_young_words[i] += surv_young_words[i];
3612 }
3613 }
3614
3615 void
3616 G1CollectedHeap::cleanup_surviving_young_words() {
3617 guarantee( _surviving_young_words != NULL, "pre-condition" );
3618 FREE_C_HEAP_ARRAY(size_t, _surviving_young_words, mtGC);
3619 _surviving_young_words = NULL;
3620 }
3621
3622 #ifdef ASSERT
3623 class VerifyCSetClosure: public HeapRegionClosure {
3624 public:
3625 bool doHeapRegion(HeapRegion* hr) {
3626 // Here we check that the CSet region's RSet is ready for parallel
3627 // iteration. The fields that we'll verify are only manipulated
3628 // when the region is part of a CSet and is collected. Afterwards,
3629 // we reset these fields when we clear the region's RSet (when the
3630 // region is freed) so they are ready when the region is
3631 // re-allocated. The only exception to this is if there's an
3632 // evacuation failure and instead of freeing the region we leave
3633 // it in the heap. In that case, we reset these fields during
3634 // evacuation failure handling.
3635 guarantee(hr->rem_set()->verify_ready_for_par_iteration(), "verification");
3636
3637 // Here's a good place to add any other checks we'd like to
3638 // perform on CSet regions.
3639 return false;
3640 }
3641 };
3642 #endif // ASSERT
3643
3644 #if TASKQUEUE_STATS
3645 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
3646 st->print_raw_cr("GC Task Stats");
3647 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
3648 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
3649 }
3650
3651 void G1CollectedHeap::print_taskqueue_stats(outputStream* const st) const {
3652 print_taskqueue_stats_hdr(st);
3653
3654 TaskQueueStats totals;
3655 const int n = workers() != NULL ? workers()->total_workers() : 1;
3656 for (int i = 0; i < n; ++i) {
3657 st->print("%3d ", i); task_queue(i)->stats.print(st); st->cr();
3658 totals += task_queue(i)->stats;
3659 }
3660 st->print_raw("tot "); totals.print(st); st->cr();
3661
3662 DEBUG_ONLY(totals.verify());
3663 }
3664
3665 void G1CollectedHeap::reset_taskqueue_stats() {
3666 const int n = workers() != NULL ? workers()->total_workers() : 1;
3667 for (int i = 0; i < n; ++i) {
3668 task_queue(i)->stats.reset();
3669 }
3670 }
3671 #endif // TASKQUEUE_STATS
3672
3673 void G1CollectedHeap::log_gc_header() {
3674 if (!G1Log::fine()) {
3675 return;
3676 }
3677
3678 gclog_or_tty->date_stamp(PrintGCDateStamps);
3679 gclog_or_tty->stamp(PrintGCTimeStamps);
3680
3681 GCCauseString gc_cause_str = GCCauseString("GC pause", gc_cause())
3682 .append(g1_policy()->gcs_are_young() ? "(young)" : "(mixed)")
3683 .append(g1_policy()->during_initial_mark_pause() ? " (initial-mark)" : "");
3684
3685 gclog_or_tty->print("[%s", (const char*)gc_cause_str);
3686 }
3687
3688 void G1CollectedHeap::log_gc_footer(double pause_time_sec) {
3689 if (!G1Log::fine()) {
3690 return;
3691 }
3692
3693 if (G1Log::finer()) {
3694 if (evacuation_failed()) {
3695 gclog_or_tty->print(" (to-space exhausted)");
3696 }
3697 gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec);
3698 g1_policy()->phase_times()->note_gc_end();
3699 g1_policy()->phase_times()->print(pause_time_sec);
3700 g1_policy()->print_detailed_heap_transition();
3701 } else {
3702 if (evacuation_failed()) {
3703 gclog_or_tty->print("--");
3704 }
3705 g1_policy()->print_heap_transition();
3706 gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec);
3707 }
3708 gclog_or_tty->flush();
3709 }
3710
3711 bool
3712 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
3713 assert_at_safepoint(true /* should_be_vm_thread */);
3714 guarantee(!is_gc_active(), "collection is not reentrant");
3715
3716 if (GC_locker::check_active_before_gc()) {
3717 return false;
3718 }
3719
3720 SvcGCMarker sgcm(SvcGCMarker::MINOR);
3721 ResourceMark rm;
3722
3723 print_heap_before_gc();
3724
3725 HRSPhaseSetter x(HRSPhaseEvacuation);
3726 verify_region_sets_optional();
3727 verify_dirty_young_regions();
3728
3729 // This call will decide whether this pause is an initial-mark
3730 // pause. If it is, during_initial_mark_pause() will return true
3731 // for the duration of this pause.
3732 g1_policy()->decide_on_conc_mark_initiation();
3733
3734 // We do not allow initial-mark to be piggy-backed on a mixed GC.
3735 assert(!g1_policy()->during_initial_mark_pause() ||
3736 g1_policy()->gcs_are_young(), "sanity");
3737
3738 // We also do not allow mixed GCs during marking.
3739 assert(!mark_in_progress() || g1_policy()->gcs_are_young(), "sanity");
3740
3741 // Record whether this pause is an initial mark. When the current
3742 // thread has completed its logging output and it's safe to signal
3743 // the CM thread, the flag's value in the policy has been reset.
3744 bool should_start_conc_mark = g1_policy()->during_initial_mark_pause();
3745
3746 // Inner scope for scope based logging, timers, and stats collection
3747 {
3748 if (g1_policy()->during_initial_mark_pause()) {
3749 // We are about to start a marking cycle, so we increment the
3750 // full collection counter.
3751 increment_old_marking_cycles_started();
3752 }
3753 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
3754
3755 int active_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
3756 workers()->active_workers() : 1);
3757 double pause_start_sec = os::elapsedTime();
3758 g1_policy()->phase_times()->note_gc_start(active_workers);
3759 log_gc_header();
3760
3761 TraceCollectorStats tcs(g1mm()->incremental_collection_counters());
3762 TraceMemoryManagerStats tms(false /* fullGC */, gc_cause());
3763
3764 // If the secondary_free_list is not empty, append it to the
3765 // free_list. No need to wait for the cleanup operation to finish;
3766 // the region allocation code will check the secondary_free_list
3767 // and wait if necessary. If the G1StressConcRegionFreeing flag is
3768 // set, skip this step so that the region allocation code has to
3769 // get entries from the secondary_free_list.
3770 if (!G1StressConcRegionFreeing) {
3771 append_secondary_free_list_if_not_empty_with_lock();
3772 }
3773
3774 assert(check_young_list_well_formed(),
3775 "young list should be well formed");
3776
3777 // Don't dynamically change the number of GC threads this early. A value of
3778 // 0 is used to indicate serial work. When parallel work is done,
3779 // it will be set.
3780
3781 { // Call to jvmpi::post_class_unload_events must occur outside of active GC
3782 IsGCActiveMark x;
3783
3784 gc_prologue(false);
3785 increment_total_collections(false /* full gc */);
3786 increment_gc_time_stamp();
3787
3788 verify_before_gc();
3789 check_bitmaps("GC Start");
3790
3791 COMPILER2_PRESENT(DerivedPointerTable::clear());
3792
3793 // Please see comment in g1CollectedHeap.hpp and
3794 // G1CollectedHeap::ref_processing_init() to see how
3795 // reference processing currently works in G1.
3796
3797 // Enable discovery in the STW reference processor
3798 ref_processor_stw()->enable_discovery(true /*verify_disabled*/,
3799 true /*verify_no_refs*/);
3800
3801 {
3802 // We want to temporarily turn off discovery by the
3803 // CM ref processor, if necessary, and turn it back on
3804 // on again later if we do. Using a scoped
3805 // NoRefDiscovery object will do this.
3806 NoRefDiscovery no_cm_discovery(ref_processor_cm());
3807
3808 // Forget the current alloc region (we might even choose it to be part
3809 // of the collection set!).
3810 release_mutator_alloc_region();
3811
3812 // We should call this after we retire the mutator alloc
3813 // region(s) so that all the ALLOC / RETIRE events are generated
3814 // before the start GC event.
3815 _hr_printer.start_gc(false /* full */, (size_t) total_collections());
3816
3817 // This timing is only used by the ergonomics to handle our pause target.
3818 // It is unclear why this should not include the full pause. We will
3819 // investigate this in CR 7178365.
3820 //
3821 // Preserving the old comment here if that helps the investigation:
3822 //
3823 // The elapsed time induced by the start time below deliberately elides
3824 // the possible verification above.
3825 double sample_start_time_sec = os::elapsedTime();
3826 size_t start_used_bytes = used();
3827
3828 #if YOUNG_LIST_VERBOSE
3829 gclog_or_tty->print_cr("\nBefore recording pause start.\nYoung_list:");
3830 _young_list->print();
3831 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3832 #endif // YOUNG_LIST_VERBOSE
3833
3834 g1_policy()->record_collection_pause_start(sample_start_time_sec,
3835 start_used_bytes);
3836
3837 double scan_wait_start = os::elapsedTime();
3838 // We have to wait until the CM threads finish scanning the
3839 // root regions as it's the only way to ensure that all the
3840 // objects on them have been correctly scanned before we start
3841 // moving them during the GC.
3842 bool waited = _cm->root_regions()->wait_until_scan_finished();
3843 double wait_time_ms = 0.0;
3844 if (waited) {
3845 double scan_wait_end = os::elapsedTime();
3846 wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
3847 }
3848 g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms);
3849
3850 #if YOUNG_LIST_VERBOSE
3851 gclog_or_tty->print_cr("\nAfter recording pause start.\nYoung_list:");
3852 _young_list->print();
3853 #endif // YOUNG_LIST_VERBOSE
3854
3855 if (g1_policy()->during_initial_mark_pause()) {
3856 concurrent_mark()->checkpointRootsInitialPre();
3857 }
3858
3859 #if YOUNG_LIST_VERBOSE
3860 gclog_or_tty->print_cr("\nBefore choosing collection set.\nYoung_list:");
3861 _young_list->print();
3862 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3863 #endif // YOUNG_LIST_VERBOSE
3864
3865 g1_policy()->finalize_cset(target_pause_time_ms);
3866
3867 _cm->note_start_of_gc();
3868 // We should not verify the per-thread SATB buffers given that
3869 // we have not filtered them yet (we'll do so during the
3870 // GC). We also call this after finalize_cset() to
3871 // ensure that the CSet has been finalized.
3872 _cm->verify_no_cset_oops(true /* verify_stacks */,
3873 true /* verify_enqueued_buffers */,
3874 false /* verify_thread_buffers */,
3875 true /* verify_fingers */);
3876
3877 if (_hr_printer.is_active()) {
3878 HeapRegion* hr = g1_policy()->collection_set();
3879 while (hr != NULL) {
3880 G1HRPrinter::RegionType type;
3881 if (!hr->is_young()) {
3882 type = G1HRPrinter::Old;
3883 } else if (hr->is_survivor()) {
3884 type = G1HRPrinter::Survivor;
3885 } else {
3886 type = G1HRPrinter::Eden;
3887 }
3888 _hr_printer.cset(hr);
3889 hr = hr->next_in_collection_set();
3890 }
3891 }
3892
3893 #ifdef ASSERT
3894 VerifyCSetClosure cl;
3895 collection_set_iterate(&cl);
3896 #endif // ASSERT
3897
3898 setup_surviving_young_words();
3899
3900 // Initialize the GC alloc regions.
3901 init_gc_alloc_regions();
3902
3903 // Actually do the work...
3904 evacuate_collection_set();
3905
3906 // We do this to mainly verify the per-thread SATB buffers
3907 // (which have been filtered by now) since we didn't verify
3908 // them earlier. No point in re-checking the stacks / enqueued
3909 // buffers given that the CSet has not changed since last time
3910 // we checked.
3911 _cm->verify_no_cset_oops(false /* verify_stacks */,
3912 false /* verify_enqueued_buffers */,
3913 true /* verify_thread_buffers */,
3914 true /* verify_fingers */);
3915
3916 free_collection_set(g1_policy()->collection_set());
3917 g1_policy()->clear_collection_set();
3918
3919 cleanup_surviving_young_words();
3920
3921 // Start a new incremental collection set for the next pause.
3922 g1_policy()->start_incremental_cset_building();
3923
3924 // Clear the _cset_fast_test bitmap in anticipation of adding
3925 // regions to the incremental collection set for the next
3926 // evacuation pause.
3927 clear_cset_fast_test();
3928
3929 _young_list->reset_sampled_info();
3930
3931 // Don't check the whole heap at this point as the
3932 // GC alloc regions from this pause have been tagged
3933 // as survivors and moved on to the survivor list.
3934 // Survivor regions will fail the !is_young() check.
3935 assert(check_young_list_empty(false /* check_heap */),
3936 "young list should be empty");
3937
3938 #if YOUNG_LIST_VERBOSE
3939 gclog_or_tty->print_cr("Before recording survivors.\nYoung List:");
3940 _young_list->print();
3941 #endif // YOUNG_LIST_VERBOSE
3942
3943 g1_policy()->record_survivor_regions(_young_list->survivor_length(),
3944 _young_list->first_survivor_region(),
3945 _young_list->last_survivor_region());
3946
3947 _young_list->reset_auxilary_lists();
3948
3949 if (evacuation_failed()) {
3950 _summary_bytes_used = recalculate_used();
3951 } else {
3952 // The "used" of the the collection set have already been subtracted
3953 // when they were freed. Add in the bytes evacuated.
3954 _summary_bytes_used += g1_policy()->bytes_copied_during_gc();
3955 }
3956
3957 if (g1_policy()->during_initial_mark_pause()) {
3958 // We have to do this before we notify the CM threads that
3959 // they can start working to make sure that all the
3960 // appropriate initialization is done on the CM object.
3961 concurrent_mark()->checkpointRootsInitialPost();
3962 set_marking_started();
3963 // Note that we don't actually trigger the CM thread at
3964 // this point. We do that later when we're sure that
3965 // the current thread has completed its logging output.
3966 }
3967
3968 allocate_dummy_regions();
3969
3970 #if YOUNG_LIST_VERBOSE
3971 gclog_or_tty->print_cr("\nEnd of the pause.\nYoung_list:");
3972 _young_list->print();
3973 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3974 #endif // YOUNG_LIST_VERBOSE
3975
3976 init_mutator_alloc_region();
3977
3978 {
3979 size_t expand_bytes = g1_policy()->expansion_amount();
3980 if (expand_bytes > 0) {
3981 size_t bytes_before = capacity();
3982 // No need for an ergo verbose message here,
3983 // expansion_amount() does this when it returns a value > 0.
3984 if (!expand(expand_bytes)) {
3985 // We failed to expand the heap so let's verify that
3986 // committed/uncommitted amount match the backing store
3987 assert(capacity() == _g1_storage.committed_size(), "committed size mismatch");
3988 assert(max_capacity() == _g1_storage.reserved_size(), "reserved size mismatch");
3989 }
3990 }
3991 }
3992
3993 // We redo the verificaiton but now wrt to the new CSet which
3994 // has just got initialized after the previous CSet was freed.
3995 _cm->verify_no_cset_oops(true /* verify_stacks */,
3996 true /* verify_enqueued_buffers */,
3997 true /* verify_thread_buffers */,
3998 true /* verify_fingers */);
3999 _cm->note_end_of_gc();
4000
4001 // This timing is only used by the ergonomics to handle our pause target.
4002 // It is unclear why this should not include the full pause. We will
4003 // investigate this in CR 7178365.
4004 double sample_end_time_sec = os::elapsedTime();
4005 double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
4006 g1_policy()->record_collection_pause_end(pause_time_ms);
4007
4008 MemoryService::track_memory_usage();
4009
4010 // In prepare_for_verify() below we'll need to scan the deferred
4011 // update buffers to bring the RSets up-to-date if
4012 // G1HRRSFlushLogBuffersOnVerify has been set. While scanning
4013 // the update buffers we'll probably need to scan cards on the
4014 // regions we just allocated to (i.e., the GC alloc
4015 // regions). However, during the last GC we called
4016 // set_saved_mark() on all the GC alloc regions, so card
4017 // scanning might skip the [saved_mark_word()...top()] area of
4018 // those regions (i.e., the area we allocated objects into
4019 // during the last GC). But it shouldn't. Given that
4020 // saved_mark_word() is conditional on whether the GC time stamp
4021 // on the region is current or not, by incrementing the GC time
4022 // stamp here we invalidate all the GC time stamps on all the
4023 // regions and saved_mark_word() will simply return top() for
4024 // all the regions. This is a nicer way of ensuring this rather
4025 // than iterating over the regions and fixing them. In fact, the
4026 // GC time stamp increment here also ensures that
4027 // saved_mark_word() will return top() between pauses, i.e.,
4028 // during concurrent refinement. So we don't need the
4029 // is_gc_active() check to decided which top to use when
4030 // scanning cards (see CR 7039627).
4031 increment_gc_time_stamp();
4032
4033 verify_after_gc();
4034 check_bitmaps("GC End");
4035
4036 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
4037 ref_processor_stw()->verify_no_references_recorded();
4038
4039 // CM reference discovery will be re-enabled if necessary.
4040 }
4041
4042 // We should do this after we potentially expand the heap so
4043 // that all the COMMIT events are generated before the end GC
4044 // event, and after we retire the GC alloc regions so that all
4045 // RETIRE events are generated before the end GC event.
4046 _hr_printer.end_gc(false /* full */, (size_t) total_collections());
4047
4048 if (mark_in_progress()) {
4049 concurrent_mark()->update_g1_committed();
4050 }
4051
4052 #ifdef TRACESPINNING
4053 ParallelTaskTerminator::print_termination_counts();
4054 #endif
4055
4056 gc_epilogue(false);
4057 }
4058
4059 // Print the remainder of the GC log output.
4060 log_gc_footer(os::elapsedTime() - pause_start_sec);
4061
4062 // It is not yet to safe to tell the concurrent mark to
4063 // start as we have some optional output below. We don't want the
4064 // output from the concurrent mark thread interfering with this
4065 // logging output either.
4066
4067 _hrs.verify_optional();
4068 verify_region_sets_optional();
4069
4070 TASKQUEUE_STATS_ONLY(if (ParallelGCVerbose) print_taskqueue_stats());
4071 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
4072
4073 print_heap_after_gc();
4074
4075 // We must call G1MonitoringSupport::update_sizes() in the same scoping level
4076 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
4077 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
4078 // before any GC notifications are raised.
4079 g1mm()->update_sizes();
4080 }
4081
4082 if (G1SummarizeRSetStats &&
4083 (G1SummarizeRSetStatsPeriod > 0) &&
4084 (total_collections() % G1SummarizeRSetStatsPeriod == 0)) {
4085 g1_rem_set()->print_summary_info();
4086 }
4087
4088 // It should now be safe to tell the concurrent mark thread to start
4089 // without its logging output interfering with the logging output
4090 // that came from the pause.
4091
4092 if (should_start_conc_mark) {
4093 // CAUTION: after the doConcurrentMark() call below,
4094 // the concurrent marking thread(s) could be running
4095 // concurrently with us. Make sure that anything after
4096 // this point does not assume that we are the only GC thread
4097 // running. Note: of course, the actual marking work will
4098 // not start until the safepoint itself is released in
4099 // ConcurrentGCThread::safepoint_desynchronize().
4100 doConcurrentMark();
4101 }
4102
4103 return true;
4104 }
4105
4106 size_t G1CollectedHeap::desired_plab_sz(GCAllocPurpose purpose)
4107 {
4108 size_t gclab_word_size;
4109 switch (purpose) {
4110 case GCAllocForSurvived:
4111 gclab_word_size = _survivor_plab_stats.desired_plab_sz();
4112 break;
4113 case GCAllocForTenured:
4114 gclab_word_size = _old_plab_stats.desired_plab_sz();
4115 break;
4116 default:
4117 assert(false, "unknown GCAllocPurpose");
4118 gclab_word_size = _old_plab_stats.desired_plab_sz();
4119 break;
4120 }
4121
4122 // Prevent humongous PLAB sizes for two reasons:
4123 // * PLABs are allocated using a similar paths as oops, but should
4124 // never be in a humongous region
4125 // * Allowing humongous PLABs needlessly churns the region free lists
4126 return MIN2(_humongous_object_threshold_in_words, gclab_word_size);
4127 }
4128
4129 void G1CollectedHeap::init_mutator_alloc_region() {
4130 assert(_mutator_alloc_region.get() == NULL, "pre-condition");
4131 _mutator_alloc_region.init();
4132 }
4133
4134 void G1CollectedHeap::release_mutator_alloc_region() {
4135 _mutator_alloc_region.release();
4136 assert(_mutator_alloc_region.get() == NULL, "post-condition");
4137 }
4138
4139 void G1CollectedHeap::init_gc_alloc_regions() {
4140 assert_at_safepoint(true /* should_be_vm_thread */);
4141
4142 _survivor_gc_alloc_region.init();
4143 _old_gc_alloc_region.init();
4144 HeapRegion* retained_region = _retained_old_gc_alloc_region;
4145 _retained_old_gc_alloc_region = NULL;
4146
4147 // We will discard the current GC alloc region if:
4148 // a) it's in the collection set (it can happen!),
4149 // b) it's already full (no point in using it),
4150 // c) it's empty (this means that it was emptied during
4151 // a cleanup and it should be on the free list now), or
4152 // d) it's humongous (this means that it was emptied
4153 // during a cleanup and was added to the free list, but
4154 // has been subseqently used to allocate a humongous
4155 // object that may be less than the region size).
4156 if (retained_region != NULL &&
4157 !retained_region->in_collection_set() &&
4158 !(retained_region->top() == retained_region->end()) &&
4159 !retained_region->is_empty() &&
4160 !retained_region->isHumongous()) {
4161 retained_region->set_saved_mark();
4162 // The retained region was added to the old region set when it was
4163 // retired. We have to remove it now, since we don't allow regions
4164 // we allocate to in the region sets. We'll re-add it later, when
4165 // it's retired again.
4166 _old_set.remove(retained_region);
4167 bool during_im = g1_policy()->during_initial_mark_pause();
4168 retained_region->note_start_of_copying(during_im);
4169 _old_gc_alloc_region.set(retained_region);
4170 _hr_printer.reuse(retained_region);
4171 }
4172 }
4173
4174 void G1CollectedHeap::release_gc_alloc_regions(uint no_of_gc_workers) {
4175 _survivor_gc_alloc_region.release();
4176 // If we have an old GC alloc region to release, we'll save it in
4177 // _retained_old_gc_alloc_region. If we don't
4178 // _retained_old_gc_alloc_region will become NULL. This is what we
4179 // want either way so no reason to check explicitly for either
4180 // condition.
4181 _retained_old_gc_alloc_region = _old_gc_alloc_region.release();
4182
4183 if (ResizePLAB) {
4184 _survivor_plab_stats.adjust_desired_plab_sz(no_of_gc_workers);
4185 _old_plab_stats.adjust_desired_plab_sz(no_of_gc_workers);
4186 }
4187 }
4188
4189 void G1CollectedHeap::abandon_gc_alloc_regions() {
4190 assert(_survivor_gc_alloc_region.get() == NULL, "pre-condition");
4191 assert(_old_gc_alloc_region.get() == NULL, "pre-condition");
4192 _retained_old_gc_alloc_region = NULL;
4193 }
4194
4195 void G1CollectedHeap::init_for_evac_failure(OopsInHeapRegionClosure* cl) {
4196 _drain_in_progress = false;
4197 set_evac_failure_closure(cl);
4198 _evac_failure_scan_stack = new (ResourceObj::C_HEAP, mtGC) GrowableArray<oop>(40, true);
4199 }
4200
4201 void G1CollectedHeap::finalize_for_evac_failure() {
4202 assert(_evac_failure_scan_stack != NULL &&
4203 _evac_failure_scan_stack->length() == 0,
4204 "Postcondition");
4205 assert(!_drain_in_progress, "Postcondition");
4206 delete _evac_failure_scan_stack;
4207 _evac_failure_scan_stack = NULL;
4208 }
4209
4210 void G1CollectedHeap::remove_self_forwarding_pointers() {
4211 assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity");
4212
4213 G1ParRemoveSelfForwardPtrsTask rsfp_task(this);
4214
4215 if (G1CollectedHeap::use_parallel_gc_threads()) {
4216 set_par_threads();
4217 workers()->run_task(&rsfp_task);
4218 set_par_threads(0);
4219 } else {
4220 rsfp_task.work(0);
4221 }
4222
4223 assert(check_cset_heap_region_claim_values(HeapRegion::ParEvacFailureClaimValue), "sanity");
4224
4225 // Reset the claim values in the regions in the collection set.
4226 reset_cset_heap_region_claim_values();
4227
4228 assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity");
4229
4230 // Now restore saved marks, if any.
4231 if (_objs_with_preserved_marks != NULL) {
4232 assert(_preserved_marks_of_objs != NULL, "Both or none.");
4233 guarantee(_objs_with_preserved_marks->length() ==
4234 _preserved_marks_of_objs->length(), "Both or none.");
4235 for (int i = 0; i < _objs_with_preserved_marks->length(); i++) {
4236 oop obj = _objs_with_preserved_marks->at(i);
4237 markOop m = _preserved_marks_of_objs->at(i);
4238 obj->set_mark(m);
4239 }
4240
4241 // Delete the preserved marks growable arrays (allocated on the C heap).
4242 delete _objs_with_preserved_marks;
4243 delete _preserved_marks_of_objs;
4244 _objs_with_preserved_marks = NULL;
4245 _preserved_marks_of_objs = NULL;
4246 }
4247 }
4248
4249 void G1CollectedHeap::push_on_evac_failure_scan_stack(oop obj) {
4250 _evac_failure_scan_stack->push(obj);
4251 }
4252
4253 void G1CollectedHeap::drain_evac_failure_scan_stack() {
4254 assert(_evac_failure_scan_stack != NULL, "precondition");
4255
4256 while (_evac_failure_scan_stack->length() > 0) {
4257 oop obj = _evac_failure_scan_stack->pop();
4258 _evac_failure_closure->set_region(heap_region_containing(obj));
4259 obj->oop_iterate_backwards(_evac_failure_closure);
4260 }
4261 }
4262
4263 oop
4264 G1CollectedHeap::handle_evacuation_failure_par(OopsInHeapRegionClosure* cl,
4265 oop old) {
4266 assert(obj_in_cs(old),
4267 err_msg("obj: "PTR_FORMAT" should still be in the CSet",
4268 (HeapWord*) old));
4269 markOop m = old->mark();
4270 oop forward_ptr = old->forward_to_atomic(old);
4271 if (forward_ptr == NULL) {
4272 // Forward-to-self succeeded.
4273
4274 if (_evac_failure_closure != cl) {
4275 MutexLockerEx x(EvacFailureStack_lock, Mutex::_no_safepoint_check_flag);
4276 assert(!_drain_in_progress,
4277 "Should only be true while someone holds the lock.");
4278 // Set the global evac-failure closure to the current thread's.
4279 assert(_evac_failure_closure == NULL, "Or locking has failed.");
4280 set_evac_failure_closure(cl);
4281 // Now do the common part.
4282 handle_evacuation_failure_common(old, m);
4283 // Reset to NULL.
4284 set_evac_failure_closure(NULL);
4285 } else {
4286 // The lock is already held, and this is recursive.
4287 assert(_drain_in_progress, "This should only be the recursive case.");
4288 handle_evacuation_failure_common(old, m);
4289 }
4290 return old;
4291 } else {
4292 // Forward-to-self failed. Either someone else managed to allocate
4293 // space for this object (old != forward_ptr) or they beat us in
4294 // self-forwarding it (old == forward_ptr).
4295 assert(old == forward_ptr || !obj_in_cs(forward_ptr),
4296 err_msg("obj: "PTR_FORMAT" forwarded to: "PTR_FORMAT" "
4297 "should not be in the CSet",
4298 (HeapWord*) old, (HeapWord*) forward_ptr));
4299 return forward_ptr;
4300 }
4301 }
4302
4303 void G1CollectedHeap::handle_evacuation_failure_common(oop old, markOop m) {
4304 set_evacuation_failed(true);
4305
4306 preserve_mark_if_necessary(old, m);
4307
4308 HeapRegion* r = heap_region_containing(old);
4309 if (!r->evacuation_failed()) {
4310 r->set_evacuation_failed(true);
4311 _hr_printer.evac_failure(r);
4312 }
4313
4314 push_on_evac_failure_scan_stack(old);
4315
4316 if (!_drain_in_progress) {
4317 // prevent recursion in copy_to_survivor_space()
4318 _drain_in_progress = true;
4319 drain_evac_failure_scan_stack();
4320 _drain_in_progress = false;
4321 }
4322 }
4323
4324 void G1CollectedHeap::preserve_mark_if_necessary(oop obj, markOop m) {
4325 assert(evacuation_failed(), "Oversaving!");
4326 // We want to call the "for_promotion_failure" version only in the
4327 // case of a promotion failure.
4328 if (m->must_be_preserved_for_promotion_failure(obj)) {
4329 if (_objs_with_preserved_marks == NULL) {
4330 assert(_preserved_marks_of_objs == NULL, "Both or none.");
4331 _objs_with_preserved_marks =
4332 new (ResourceObj::C_HEAP, mtGC) GrowableArray<oop>(40, true);
4333 _preserved_marks_of_objs =
4334 new (ResourceObj::C_HEAP, mtGC) GrowableArray<markOop>(40, true);
4335 }
4336 _objs_with_preserved_marks->push(obj);
4337 _preserved_marks_of_objs->push(m);
4338 }
4339 }
4340
4341 HeapWord* G1CollectedHeap::par_allocate_during_gc(GCAllocPurpose purpose,
4342 size_t word_size) {
4343 if (purpose == GCAllocForSurvived) {
4344 HeapWord* result = survivor_attempt_allocation(word_size);
4345 if (result != NULL) {
4346 return result;
4347 } else {
4348 // Let's try to allocate in the old gen in case we can fit the
4349 // object there.
4350 return old_attempt_allocation(word_size);
4351 }
4352 } else {
4353 assert(purpose == GCAllocForTenured, "sanity");
4354 HeapWord* result = old_attempt_allocation(word_size);
4355 if (result != NULL) {
4356 return result;
4357 } else {
4358 // Let's try to allocate in the survivors in case we can fit the
4359 // object there.
4360 return survivor_attempt_allocation(word_size);
4361 }
4362 }
4363
4364 ShouldNotReachHere();
4365 // Trying to keep some compilers happy.
4366 return NULL;
4367 }
4368
4369 G1ParGCAllocBuffer::G1ParGCAllocBuffer(size_t gclab_word_size) :
4370 ParGCAllocBuffer(gclab_word_size), _retired(false) { }
4371
4372 G1ParScanThreadState::G1ParScanThreadState(G1CollectedHeap* g1h, uint queue_num)
4373 : _g1h(g1h),
4374 _refs(g1h->task_queue(queue_num)),
4375 _dcq(&g1h->dirty_card_queue_set()),
4376 _ct_bs((CardTableModRefBS*)_g1h->barrier_set()),
4377 _g1_rem(g1h->g1_rem_set()),
4378 _hash_seed(17), _queue_num(queue_num),
4379 _term_attempts(0),
4380 _surviving_alloc_buffer(g1h->desired_plab_sz(GCAllocForSurvived)),
4381 _tenured_alloc_buffer(g1h->desired_plab_sz(GCAllocForTenured)),
4382 _age_table(false),
4383 _strong_roots_time(0), _term_time(0),
4384 _alloc_buffer_waste(0), _undo_waste(0) {
4385 // we allocate G1YoungSurvRateNumRegions plus one entries, since
4386 // we "sacrifice" entry 0 to keep track of surviving bytes for
4387 // non-young regions (where the age is -1)
4388 // We also add a few elements at the beginning and at the end in
4389 // an attempt to eliminate cache contention
4390 uint real_length = 1 + _g1h->g1_policy()->young_cset_region_length();
4391 uint array_length = PADDING_ELEM_NUM +
4392 real_length +
4393 PADDING_ELEM_NUM;
4394 _surviving_young_words_base = NEW_C_HEAP_ARRAY(size_t, array_length, mtGC);
4395 if (_surviving_young_words_base == NULL)
4396 vm_exit_out_of_memory(array_length * sizeof(size_t),
4397 "Not enough space for young surv histo.");
4398 _surviving_young_words = _surviving_young_words_base + PADDING_ELEM_NUM;
4399 memset(_surviving_young_words, 0, (size_t) real_length * sizeof(size_t));
4400
4401 _alloc_buffers[GCAllocForSurvived] = &_surviving_alloc_buffer;
4402 _alloc_buffers[GCAllocForTenured] = &_tenured_alloc_buffer;
4403
4404 _start = os::elapsedTime();
4405 }
4406
4407 void
4408 G1ParScanThreadState::print_termination_stats_hdr(outputStream* const st)
4409 {
4410 st->print_raw_cr("GC Termination Stats");
4411 st->print_raw_cr(" elapsed --strong roots-- -------termination-------"
4412 " ------waste (KiB)------");
4413 st->print_raw_cr("thr ms ms % ms % attempts"
4414 " total alloc undo");
4415 st->print_raw_cr("--- --------- --------- ------ --------- ------ --------"
4416 " ------- ------- -------");
4417 }
4418
4419 void
4420 G1ParScanThreadState::print_termination_stats(int i,
4421 outputStream* const st) const
4422 {
4423 const double elapsed_ms = elapsed_time() * 1000.0;
4424 const double s_roots_ms = strong_roots_time() * 1000.0;
4425 const double term_ms = term_time() * 1000.0;
4426 st->print_cr("%3d %9.2f %9.2f %6.2f "
4427 "%9.2f %6.2f " SIZE_FORMAT_W(8) " "
4428 SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7),
4429 i, elapsed_ms, s_roots_ms, s_roots_ms * 100 / elapsed_ms,
4430 term_ms, term_ms * 100 / elapsed_ms, term_attempts(),
4431 (alloc_buffer_waste() + undo_waste()) * HeapWordSize / K,
4432 alloc_buffer_waste() * HeapWordSize / K,
4433 undo_waste() * HeapWordSize / K);
4434 }
4435
4436 #ifdef ASSERT
4437 bool G1ParScanThreadState::verify_ref(narrowOop* ref) const {
4438 assert(ref != NULL, "invariant");
4439 assert(UseCompressedOops, "sanity");
4440 assert(!has_partial_array_mask(ref), err_msg("ref=" PTR_FORMAT, ref));
4441 oop p = oopDesc::load_decode_heap_oop(ref);
4442 assert(_g1h->is_in_g1_reserved(p),
4443 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p)));
4444 return true;
4445 }
4446
4447 bool G1ParScanThreadState::verify_ref(oop* ref) const {
4448 assert(ref != NULL, "invariant");
4449 if (has_partial_array_mask(ref)) {
4450 // Must be in the collection set--it's already been copied.
4451 oop p = clear_partial_array_mask(ref);
4452 assert(_g1h->obj_in_cs(p),
4453 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p)));
4454 } else {
4455 oop p = oopDesc::load_decode_heap_oop(ref);
4456 assert(_g1h->is_in_g1_reserved(p),
4457 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p)));
4458 }
4459 return true;
4460 }
4461
4462 bool G1ParScanThreadState::verify_task(StarTask ref) const {
4463 if (ref.is_narrow()) {
4464 return verify_ref((narrowOop*) ref);
4465 } else {
4466 return verify_ref((oop*) ref);
4467 }
4468 }
4469 #endif // ASSERT
4470
4471 void G1ParScanThreadState::trim_queue() {
4472 assert(_evac_cl != NULL, "not set");
4473 assert(_evac_failure_cl != NULL, "not set");
4474 assert(_partial_scan_cl != NULL, "not set");
4475
4476 StarTask ref;
4477 do {
4478 // Drain the overflow stack first, so other threads can steal.
4479 while (refs()->pop_overflow(ref)) {
4480 deal_with_reference(ref);
4481 }
4482
4483 while (refs()->pop_local(ref)) {
4484 deal_with_reference(ref);
4485 }
4486 } while (!refs()->is_empty());
4487 }
4488
4489 G1ParClosureSuper::G1ParClosureSuper(G1CollectedHeap* g1,
4490 G1ParScanThreadState* par_scan_state) :
4491 _g1(g1), _g1_rem(_g1->g1_rem_set()), _cm(_g1->concurrent_mark()),
4492 _par_scan_state(par_scan_state),
4493 _worker_id(par_scan_state->queue_num()),
4494 _during_initial_mark(_g1->g1_policy()->during_initial_mark_pause()),
4495 _mark_in_progress(_g1->mark_in_progress()) { }
4496
4497 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object>
4498 void G1ParCopyClosure<do_gen_barrier, barrier, do_mark_object>::mark_object(oop obj) {
4499 #ifdef ASSERT
4500 HeapRegion* hr = _g1->heap_region_containing(obj);
4501 assert(hr != NULL, "sanity");
4502 assert(!hr->in_collection_set(), "should not mark objects in the CSet");
4503 #endif // ASSERT
4504
4505 // We know that the object is not moving so it's safe to read its size.
4506 _cm->grayRoot(obj, (size_t) obj->size(), _worker_id);
4507 }
4508
4509 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object>
4510 void G1ParCopyClosure<do_gen_barrier, barrier, do_mark_object>
4511 ::mark_forwarded_object(oop from_obj, oop to_obj) {
4512 #ifdef ASSERT
4513 assert(from_obj->is_forwarded(), "from obj should be forwarded");
4514 assert(from_obj->forwardee() == to_obj, "to obj should be the forwardee");
4515 assert(from_obj != to_obj, "should not be self-forwarded");
4516
4517 HeapRegion* from_hr = _g1->heap_region_containing(from_obj);
4518 assert(from_hr != NULL, "sanity");
4519 assert(from_hr->in_collection_set(), "from obj should be in the CSet");
4520
4521 HeapRegion* to_hr = _g1->heap_region_containing(to_obj);
4522 assert(to_hr != NULL, "sanity");
4523 assert(!to_hr->in_collection_set(), "should not mark objects in the CSet");
4524 #endif // ASSERT
4525
4526 // The object might be in the process of being copied by another
4527 // worker so we cannot trust that its to-space image is
4528 // well-formed. So we have to read its size from its from-space
4529 // image which we know should not be changing.
4530 _cm->grayRoot(to_obj, (size_t) from_obj->size(), _worker_id);
4531 }
4532
4533 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object>
4534 oop G1ParCopyClosure<do_gen_barrier, barrier, do_mark_object>
4535 ::copy_to_survivor_space(oop old) {
4536 size_t word_sz = old->size();
4537 HeapRegion* from_region = _g1->heap_region_containing_raw(old);
4538 // +1 to make the -1 indexes valid...
4539 int young_index = from_region->young_index_in_cset()+1;
4540 assert( (from_region->is_young() && young_index > 0) ||
4541 (!from_region->is_young() && young_index == 0), "invariant" );
4542 G1CollectorPolicy* g1p = _g1->g1_policy();
4543 markOop m = old->mark();
4544 int age = m->has_displaced_mark_helper() ? m->displaced_mark_helper()->age()
4545 : m->age();
4546 GCAllocPurpose alloc_purpose = g1p->evacuation_destination(from_region, age,
4547 word_sz);
4548 HeapWord* obj_ptr = _par_scan_state->allocate(alloc_purpose, word_sz);
4549 #ifndef PRODUCT
4550 // Should this evacuation fail?
4551 if (_g1->evacuation_should_fail()) {
4552 if (obj_ptr != NULL) {
4553 _par_scan_state->undo_allocation(alloc_purpose, obj_ptr, word_sz);
4554 obj_ptr = NULL;
4555 }
4556 }
4557 #endif // !PRODUCT
4558
4559 if (obj_ptr == NULL) {
4560 // This will either forward-to-self, or detect that someone else has
4561 // installed a forwarding pointer.
4562 OopsInHeapRegionClosure* cl = _par_scan_state->evac_failure_closure();
4563 return _g1->handle_evacuation_failure_par(cl, old);
4564 }
4565
4566 oop obj = oop(obj_ptr);
4567
4568 // We're going to allocate linearly, so might as well prefetch ahead.
4569 Prefetch::write(obj_ptr, PrefetchCopyIntervalInBytes);
4570
4571 oop forward_ptr = old->forward_to_atomic(obj);
4572 if (forward_ptr == NULL) {
4573 Copy::aligned_disjoint_words((HeapWord*) old, obj_ptr, word_sz);
4574 if (g1p->track_object_age(alloc_purpose)) {
4575 // We could simply do obj->incr_age(). However, this causes a
4576 // performance issue. obj->incr_age() will first check whether
4577 // the object has a displaced mark by checking its mark word;
4578 // getting the mark word from the new location of the object
4579 // stalls. So, given that we already have the mark word and we
4580 // are about to install it anyway, it's better to increase the
4581 // age on the mark word, when the object does not have a
4582 // displaced mark word. We're not expecting many objects to have
4583 // a displaced marked word, so that case is not optimized
4584 // further (it could be...) and we simply call obj->incr_age().
4585
4586 if (m->has_displaced_mark_helper()) {
4587 // in this case, we have to install the mark word first,
4588 // otherwise obj looks to be forwarded (the old mark word,
4589 // which contains the forward pointer, was copied)
4590 obj->set_mark(m);
4591 obj->incr_age();
4592 } else {
4593 m = m->incr_age();
4594 obj->set_mark(m);
4595 }
4596 _par_scan_state->age_table()->add(obj, word_sz);
4597 } else {
4598 obj->set_mark(m);
4599 }
4600
4601 size_t* surv_young_words = _par_scan_state->surviving_young_words();
4602 surv_young_words[young_index] += word_sz;
4603
4604 if (obj->is_objArray() && arrayOop(obj)->length() >= ParGCArrayScanChunk) {
4605 // We keep track of the next start index in the length field of
4606 // the to-space object. The actual length can be found in the
4607 // length field of the from-space object.
4608 arrayOop(obj)->set_length(0);
4609 oop* old_p = set_partial_array_mask(old);
4610 _par_scan_state->push_on_queue(old_p);
4611 } else {
4612 // No point in using the slower heap_region_containing() method,
4613 // given that we know obj is in the heap.
4614 _scanner.set_region(_g1->heap_region_containing_raw(obj));
4615 obj->oop_iterate_backwards(&_scanner);
4616 }
4617 } else {
4618 _par_scan_state->undo_allocation(alloc_purpose, obj_ptr, word_sz);
4619 obj = forward_ptr;
4620 }
4621 return obj;
4622 }
4623
4624 template <class T>
4625 void G1ParCopyHelper::do_klass_barrier(T* p, oop new_obj) {
4626 if (_g1->heap_region_containing_raw(new_obj)->is_young()) {
4627 _scanned_klass->record_modified_oops();
4628 }
4629 }
4630
4631 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object>
4632 template <class T>
4633 void G1ParCopyClosure<do_gen_barrier, barrier, do_mark_object>
4634 ::do_oop_work(T* p) {
4635 oop obj = oopDesc::load_decode_heap_oop(p);
4636 assert(barrier != G1BarrierRS || obj != NULL,
4637 "Precondition: G1BarrierRS implies obj is non-NULL");
4638
4639 assert(_worker_id == _par_scan_state->queue_num(), "sanity");
4640
4641 // here the null check is implicit in the cset_fast_test() test
4642 if (_g1->in_cset_fast_test(obj)) {
4643 oop forwardee;
4644 if (obj->is_forwarded()) {
4645 forwardee = obj->forwardee();
4646 } else {
4647 forwardee = copy_to_survivor_space(obj);
4648 }
4649 assert(forwardee != NULL, "forwardee should not be NULL");
4650 oopDesc::encode_store_heap_oop(p, forwardee);
4651 if (do_mark_object && forwardee != obj) {
4652 // If the object is self-forwarded we don't need to explicitly
4653 // mark it, the evacuation failure protocol will do so.
4654 mark_forwarded_object(obj, forwardee);
4655 }
4656
4657 // When scanning the RS, we only care about objs in CS.
4658 if (barrier == G1BarrierRS) {
4659 _par_scan_state->update_rs(_from, p, _worker_id);
4660 } else if (barrier == G1BarrierKlass) {
4661 do_klass_barrier(p, forwardee);
4662 }
4663 } else {
4664 // The object is not in collection set. If we're a root scanning
4665 // closure during an initial mark pause (i.e. do_mark_object will
4666 // be true) then attempt to mark the object.
4667 if (do_mark_object && _g1->is_in_g1_reserved(obj)) {
4668 mark_object(obj);
4669 }
4670 }
4671
4672 if (barrier == G1BarrierEvac && obj != NULL) {
4673 _par_scan_state->update_rs(_from, p, _worker_id);
4674 }
4675
4676 if (do_gen_barrier && obj != NULL) {
4677 par_do_barrier(p);
4678 }
4679 }
4680
4681 template void G1ParCopyClosure<false, G1BarrierEvac, false>::do_oop_work(oop* p);
4682 template void G1ParCopyClosure<false, G1BarrierEvac, false>::do_oop_work(narrowOop* p);
4683
4684 template <class T> void G1ParScanPartialArrayClosure::do_oop_nv(T* p) {
4685 assert(has_partial_array_mask(p), "invariant");
4686 oop from_obj = clear_partial_array_mask(p);
4687
4688 assert(Universe::heap()->is_in_reserved(from_obj), "must be in heap.");
4689 assert(from_obj->is_objArray(), "must be obj array");
4690 objArrayOop from_obj_array = objArrayOop(from_obj);
4691 // The from-space object contains the real length.
4692 int length = from_obj_array->length();
4693
4694 assert(from_obj->is_forwarded(), "must be forwarded");
4695 oop to_obj = from_obj->forwardee();
4696 assert(from_obj != to_obj, "should not be chunking self-forwarded objects");
4697 objArrayOop to_obj_array = objArrayOop(to_obj);
4698 // We keep track of the next start index in the length field of the
4699 // to-space object.
4700 int next_index = to_obj_array->length();
4701 assert(0 <= next_index && next_index < length,
4702 err_msg("invariant, next index: %d, length: %d", next_index, length));
4703
4704 int start = next_index;
4705 int end = length;
4706 int remainder = end - start;
4707 // We'll try not to push a range that's smaller than ParGCArrayScanChunk.
4708 if (remainder > 2 * ParGCArrayScanChunk) {
4709 end = start + ParGCArrayScanChunk;
4710 to_obj_array->set_length(end);
4711 // Push the remainder before we process the range in case another
4712 // worker has run out of things to do and can steal it.
4713 oop* from_obj_p = set_partial_array_mask(from_obj);
4714 _par_scan_state->push_on_queue(from_obj_p);
4715 } else {
4716 assert(length == end, "sanity");
4717 // We'll process the final range for this object. Restore the length
4718 // so that the heap remains parsable in case of evacuation failure.
4719 to_obj_array->set_length(end);
4720 }
4721 _scanner.set_region(_g1->heap_region_containing_raw(to_obj));
4722 // Process indexes [start,end). It will also process the header
4723 // along with the first chunk (i.e., the chunk with start == 0).
4724 // Note that at this point the length field of to_obj_array is not
4725 // correct given that we are using it to keep track of the next
4726 // start index. oop_iterate_range() (thankfully!) ignores the length
4727 // field and only relies on the start / end parameters. It does
4728 // however return the size of the object which will be incorrect. So
4729 // we have to ignore it even if we wanted to use it.
4730 to_obj_array->oop_iterate_range(&_scanner, start, end);
4731 }
4732
4733 class G1ParEvacuateFollowersClosure : public VoidClosure {
4734 protected:
4735 G1CollectedHeap* _g1h;
4736 G1ParScanThreadState* _par_scan_state;
4737 RefToScanQueueSet* _queues;
4738 ParallelTaskTerminator* _terminator;
4739
4740 G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
4741 RefToScanQueueSet* queues() { return _queues; }
4742 ParallelTaskTerminator* terminator() { return _terminator; }
4743
4744 public:
4745 G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h,
4746 G1ParScanThreadState* par_scan_state,
4747 RefToScanQueueSet* queues,
4748 ParallelTaskTerminator* terminator)
4749 : _g1h(g1h), _par_scan_state(par_scan_state),
4750 _queues(queues), _terminator(terminator) {}
4751
4752 void do_void();
4753
4754 private:
4755 inline bool offer_termination();
4756 };
4757
4758 bool G1ParEvacuateFollowersClosure::offer_termination() {
4759 G1ParScanThreadState* const pss = par_scan_state();
4760 pss->start_term_time();
4761 const bool res = terminator()->offer_termination();
4762 pss->end_term_time();
4763 return res;
4764 }
4765
4766 void G1ParEvacuateFollowersClosure::do_void() {
4767 StarTask stolen_task;
4768 G1ParScanThreadState* const pss = par_scan_state();
4769 pss->trim_queue();
4770
4771 do {
4772 while (queues()->steal(pss->queue_num(), pss->hash_seed(), stolen_task)) {
4773 assert(pss->verify_task(stolen_task), "sanity");
4774 if (stolen_task.is_narrow()) {
4775 pss->deal_with_reference((narrowOop*) stolen_task);
4776 } else {
4777 pss->deal_with_reference((oop*) stolen_task);
4778 }
4779
4780 // We've just processed a reference and we might have made
4781 // available new entries on the queues. So we have to make sure
4782 // we drain the queues as necessary.
4783 pss->trim_queue();
4784 }
4785 } while (!offer_termination());
4786
4787 pss->retire_alloc_buffers();
4788 }
4789
4790 class G1KlassScanClosure : public KlassClosure {
4791 G1ParCopyHelper* _closure;
4792 bool _process_only_dirty;
4793 int _count;
4794 public:
4795 G1KlassScanClosure(G1ParCopyHelper* closure, bool process_only_dirty)
4796 : _process_only_dirty(process_only_dirty), _closure(closure), _count(0) {}
4797 void do_klass(Klass* klass) {
4798 // If the klass has not been dirtied we know that there's
4799 // no references into the young gen and we can skip it.
4800 if (!_process_only_dirty || klass->has_modified_oops()) {
4801 // Clean the klass since we're going to scavenge all the metadata.
4802 klass->clear_modified_oops();
4803
4804 // Tell the closure that this klass is the Klass to scavenge
4805 // and is the one to dirty if oops are left pointing into the young gen.
4806 _closure->set_scanned_klass(klass);
4807
4808 klass->oops_do(_closure);
4809
4810 _closure->set_scanned_klass(NULL);
4811 }
4812 _count++;
4813 }
4814 };
4815
4816 class G1ParTask : public AbstractGangTask {
4817 protected:
4818 G1CollectedHeap* _g1h;
4819 RefToScanQueueSet *_queues;
4820 ParallelTaskTerminator _terminator;
4821 uint _n_workers;
4822
4823 Mutex _stats_lock;
4824 Mutex* stats_lock() { return &_stats_lock; }
4825
4826 size_t getNCards() {
4827 return (_g1h->capacity() + G1BlockOffsetSharedArray::N_bytes - 1)
4828 / G1BlockOffsetSharedArray::N_bytes;
4829 }
4830
4831 public:
4832 G1ParTask(G1CollectedHeap* g1h,
4833 RefToScanQueueSet *task_queues)
4834 : AbstractGangTask("G1 collection"),
4835 _g1h(g1h),
4836 _queues(task_queues),
4837 _terminator(0, _queues),
4838 _stats_lock(Mutex::leaf, "parallel G1 stats lock", true)
4839 {}
4840
4841 RefToScanQueueSet* queues() { return _queues; }
4842
4843 RefToScanQueue *work_queue(int i) {
4844 return queues()->queue(i);
4845 }
4846
4847 ParallelTaskTerminator* terminator() { return &_terminator; }
4848
4849 virtual void set_for_termination(int active_workers) {
4850 // This task calls set_n_termination() in par_non_clean_card_iterate_work()
4851 // in the young space (_par_seq_tasks) in the G1 heap
4852 // for SequentialSubTasksDone.
4853 // This task also uses SubTasksDone in SharedHeap and G1CollectedHeap
4854 // both of which need setting by set_n_termination().
4855 _g1h->SharedHeap::set_n_termination(active_workers);
4856 _g1h->set_n_termination(active_workers);
4857 terminator()->reset_for_reuse(active_workers);
4858 _n_workers = active_workers;
4859 }
4860
4861 void work(uint worker_id) {
4862 if (worker_id >= _n_workers) return; // no work needed this round
4863
4864 double start_time_ms = os::elapsedTime() * 1000.0;
4865 _g1h->g1_policy()->phase_times()->record_gc_worker_start_time(worker_id, start_time_ms);
4866
4867 {
4868 ResourceMark rm;
4869 HandleMark hm;
4870
4871 ReferenceProcessor* rp = _g1h->ref_processor_stw();
4872
4873 G1ParScanThreadState pss(_g1h, worker_id);
4874 G1ParScanHeapEvacClosure scan_evac_cl(_g1h, &pss, rp);
4875 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, rp);
4876 G1ParScanPartialArrayClosure partial_scan_cl(_g1h, &pss, rp);
4877
4878 pss.set_evac_closure(&scan_evac_cl);
4879 pss.set_evac_failure_closure(&evac_failure_cl);
4880 pss.set_partial_scan_closure(&partial_scan_cl);
4881
4882 G1ParScanExtRootClosure only_scan_root_cl(_g1h, &pss, rp);
4883 G1ParScanMetadataClosure only_scan_metadata_cl(_g1h, &pss, rp);
4884
4885 G1ParScanAndMarkExtRootClosure scan_mark_root_cl(_g1h, &pss, rp);
4886 G1ParScanAndMarkMetadataClosure scan_mark_metadata_cl(_g1h, &pss, rp);
4887
4888 bool only_young = _g1h->g1_policy()->gcs_are_young();
4889 G1KlassScanClosure scan_mark_klasses_cl_s(&scan_mark_metadata_cl, false);
4890 G1KlassScanClosure only_scan_klasses_cl_s(&only_scan_metadata_cl, only_young);
4891
4892 OopClosure* scan_root_cl = &only_scan_root_cl;
4893 G1KlassScanClosure* scan_klasses_cl = &only_scan_klasses_cl_s;
4894
4895 if (_g1h->g1_policy()->during_initial_mark_pause()) {
4896 // We also need to mark copied objects.
4897 scan_root_cl = &scan_mark_root_cl;
4898 scan_klasses_cl = &scan_mark_klasses_cl_s;
4899 }
4900
4901 G1ParPushHeapRSClosure push_heap_rs_cl(_g1h, &pss);
4902
4903 int so = SharedHeap::SO_AllClasses | SharedHeap::SO_Strings | SharedHeap::SO_CodeCache;
4904
4905 pss.start_strong_roots();
4906 _g1h->g1_process_strong_roots(/* is scavenging */ true,
4907 SharedHeap::ScanningOption(so),
4908 scan_root_cl,
4909 &push_heap_rs_cl,
4910 scan_klasses_cl,
4911 worker_id);
4912 pss.end_strong_roots();
4913
4914 {
4915 double start = os::elapsedTime();
4916 G1ParEvacuateFollowersClosure evac(_g1h, &pss, _queues, &_terminator);
4917 evac.do_void();
4918 double elapsed_ms = (os::elapsedTime()-start)*1000.0;
4919 double term_ms = pss.term_time()*1000.0;
4920 _g1h->g1_policy()->phase_times()->add_obj_copy_time(worker_id, elapsed_ms-term_ms);
4921 _g1h->g1_policy()->phase_times()->record_termination(worker_id, term_ms, pss.term_attempts());
4922 }
4923 _g1h->g1_policy()->record_thread_age_table(pss.age_table());
4924 _g1h->update_surviving_young_words(pss.surviving_young_words()+1);
4925
4926 if (ParallelGCVerbose) {
4927 MutexLocker x(stats_lock());
4928 pss.print_termination_stats(worker_id);
4929 }
4930
4931 assert(pss.refs()->is_empty(), "should be empty");
4932
4933 // Close the inner scope so that the ResourceMark and HandleMark
4934 // destructors are executed here and are included as part of the
4935 // "GC Worker Time".
4936 }
4937
4938 double end_time_ms = os::elapsedTime() * 1000.0;
4939 _g1h->g1_policy()->phase_times()->record_gc_worker_end_time(worker_id, end_time_ms);
4940 }
4941 };
4942
4943 // *** Common G1 Evacuation Stuff
4944
4945 // Closures that support the filtering of CodeBlobs scanned during
4946 // external root scanning.
4947
4948 // Closure applied to reference fields in code blobs (specifically nmethods)
4949 // to determine whether an nmethod contains references that point into
4950 // the collection set. Used as a predicate when walking code roots so
4951 // that only nmethods that point into the collection set are added to the
4952 // 'marked' list.
4953
4954 class G1FilteredCodeBlobToOopClosure : public CodeBlobToOopClosure {
4955
4956 class G1PointsIntoCSOopClosure : public OopClosure {
4957 G1CollectedHeap* _g1;
4958 bool _points_into_cs;
4959 public:
4960 G1PointsIntoCSOopClosure(G1CollectedHeap* g1) :
4961 _g1(g1), _points_into_cs(false) { }
4962
4963 bool points_into_cs() const { return _points_into_cs; }
4964
4965 template <class T>
4966 void do_oop_nv(T* p) {
4967 if (!_points_into_cs) {
4968 T heap_oop = oopDesc::load_heap_oop(p);
4969 if (!oopDesc::is_null(heap_oop) &&
4970 _g1->in_cset_fast_test(oopDesc::decode_heap_oop_not_null(heap_oop))) {
4971 _points_into_cs = true;
4972 }
4973 }
4974 }
4975
4976 virtual void do_oop(oop* p) { do_oop_nv(p); }
4977 virtual void do_oop(narrowOop* p) { do_oop_nv(p); }
4978 };
4979
4980 G1CollectedHeap* _g1;
4981
4982 public:
4983 G1FilteredCodeBlobToOopClosure(G1CollectedHeap* g1, OopClosure* cl) :
4984 CodeBlobToOopClosure(cl, true), _g1(g1) { }
4985
4986 virtual void do_code_blob(CodeBlob* cb) {
4987 nmethod* nm = cb->as_nmethod_or_null();
4988 if (nm != NULL && !(nm->test_oops_do_mark())) {
4989 G1PointsIntoCSOopClosure predicate_cl(_g1);
4990 nm->oops_do(&predicate_cl);
4991
4992 if (predicate_cl.points_into_cs()) {
4993 // At least one of the reference fields or the oop relocations
4994 // in the nmethod points into the collection set. We have to
4995 // 'mark' this nmethod.
4996 // Note: Revisit the following if CodeBlobToOopClosure::do_code_blob()
4997 // or MarkingCodeBlobClosure::do_code_blob() change.
4998 if (!nm->test_set_oops_do_mark()) {
4999 do_newly_marked_nmethod(nm);
5000 }
5001 }
5002 }
5003 }
5004 };
5005
5006 // This method is run in a GC worker.
5007
5008 void
5009 G1CollectedHeap::
5010 g1_process_strong_roots(bool is_scavenging,
5011 ScanningOption so,
5012 OopClosure* scan_non_heap_roots,
5013 OopsInHeapRegionClosure* scan_rs,
5014 G1KlassScanClosure* scan_klasses,
5015 int worker_i) {
5016
5017 // First scan the strong roots
5018 double ext_roots_start = os::elapsedTime();
5019 double closure_app_time_sec = 0.0;
5020
5021 BufferingOopClosure buf_scan_non_heap_roots(scan_non_heap_roots);
5022
5023 // Walk the code cache w/o buffering, because StarTask cannot handle
5024 // unaligned oop locations.
5025 G1FilteredCodeBlobToOopClosure eager_scan_code_roots(this, scan_non_heap_roots);
5026
5027 process_strong_roots(false, // no scoping; this is parallel code
5028 is_scavenging, so,
5029 &buf_scan_non_heap_roots,
5030 &eager_scan_code_roots,
5031 scan_klasses
5032 );
5033
5034 // Now the CM ref_processor roots.
5035 if (!_process_strong_tasks->is_task_claimed(G1H_PS_refProcessor_oops_do)) {
5036 // We need to treat the discovered reference lists of the
5037 // concurrent mark ref processor as roots and keep entries
5038 // (which are added by the marking threads) on them live
5039 // until they can be processed at the end of marking.
5040 ref_processor_cm()->weak_oops_do(&buf_scan_non_heap_roots);
5041 }
5042
5043 // Finish up any enqueued closure apps (attributed as object copy time).
5044 buf_scan_non_heap_roots.done();
5045
5046 double obj_copy_time_sec = buf_scan_non_heap_roots.closure_app_seconds();
5047
5048 g1_policy()->phase_times()->record_obj_copy_time(worker_i, obj_copy_time_sec * 1000.0);
5049
5050 double ext_root_time_ms =
5051 ((os::elapsedTime() - ext_roots_start) - obj_copy_time_sec) * 1000.0;
5052
5053 g1_policy()->phase_times()->record_ext_root_scan_time(worker_i, ext_root_time_ms);
5054
5055 // During conc marking we have to filter the per-thread SATB buffers
5056 // to make sure we remove any oops into the CSet (which will show up
5057 // as implicitly live).
5058 double satb_filtering_ms = 0.0;
5059 if (!_process_strong_tasks->is_task_claimed(G1H_PS_filter_satb_buffers)) {
5060 if (mark_in_progress()) {
5061 double satb_filter_start = os::elapsedTime();
5062
5063 JavaThread::satb_mark_queue_set().filter_thread_buffers();
5064
5065 satb_filtering_ms = (os::elapsedTime() - satb_filter_start) * 1000.0;
5066 }
5067 }
5068 g1_policy()->phase_times()->record_satb_filtering_time(worker_i, satb_filtering_ms);
5069
5070 // Now scan the complement of the collection set.
5071 if (scan_rs != NULL) {
5072 g1_rem_set()->oops_into_collection_set_do(scan_rs, worker_i);
5073 }
5074 _process_strong_tasks->all_tasks_completed();
5075 }
5076
5077 void
5078 G1CollectedHeap::g1_process_weak_roots(OopClosure* root_closure,
5079 OopClosure* non_root_closure) {
5080 CodeBlobToOopClosure roots_in_blobs(root_closure, /*do_marking=*/ false);
5081 SharedHeap::process_weak_roots(root_closure, &roots_in_blobs, non_root_closure);
5082 }
5083
5084 // Weak Reference Processing support
5085
5086 // An always "is_alive" closure that is used to preserve referents.
5087 // If the object is non-null then it's alive. Used in the preservation
5088 // of referent objects that are pointed to by reference objects
5089 // discovered by the CM ref processor.
5090 class G1AlwaysAliveClosure: public BoolObjectClosure {
5091 G1CollectedHeap* _g1;
5092 public:
5093 G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
5094 void do_object(oop p) { assert(false, "Do not call."); }
5095 bool do_object_b(oop p) {
5096 if (p != NULL) {
5097 return true;
5098 }
5099 return false;
5100 }
5101 };
5102
5103 bool G1STWIsAliveClosure::do_object_b(oop p) {
5104 // An object is reachable if it is outside the collection set,
5105 // or is inside and copied.
5106 return !_g1->obj_in_cs(p) || p->is_forwarded();
5107 }
5108
5109 // Non Copying Keep Alive closure
5110 class G1KeepAliveClosure: public OopClosure {
5111 G1CollectedHeap* _g1;
5112 public:
5113 G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
5114 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
5115 void do_oop( oop* p) {
5116 oop obj = *p;
5117
5118 if (_g1->obj_in_cs(obj)) {
5119 assert( obj->is_forwarded(), "invariant" );
5120 *p = obj->forwardee();
5121 }
5122 }
5123 };
5124
5125 // Copying Keep Alive closure - can be called from both
5126 // serial and parallel code as long as different worker
5127 // threads utilize different G1ParScanThreadState instances
5128 // and different queues.
5129
5130 class G1CopyingKeepAliveClosure: public OopClosure {
5131 G1CollectedHeap* _g1h;
5132 OopClosure* _copy_non_heap_obj_cl;
5133 OopsInHeapRegionClosure* _copy_metadata_obj_cl;
5134 G1ParScanThreadState* _par_scan_state;
5135
5136 public:
5137 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
5138 OopClosure* non_heap_obj_cl,
5139 OopsInHeapRegionClosure* metadata_obj_cl,
5140 G1ParScanThreadState* pss):
5141 _g1h(g1h),
5142 _copy_non_heap_obj_cl(non_heap_obj_cl),
5143 _copy_metadata_obj_cl(metadata_obj_cl),
5144 _par_scan_state(pss)
5145 {}
5146
5147 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
5148 virtual void do_oop( oop* p) { do_oop_work(p); }
5149
5150 template <class T> void do_oop_work(T* p) {
5151 oop obj = oopDesc::load_decode_heap_oop(p);
5152
5153 if (_g1h->obj_in_cs(obj)) {
5154 // If the referent object has been forwarded (either copied
5155 // to a new location or to itself in the event of an
5156 // evacuation failure) then we need to update the reference
5157 // field and, if both reference and referent are in the G1
5158 // heap, update the RSet for the referent.
5159 //
5160 // If the referent has not been forwarded then we have to keep
5161 // it alive by policy. Therefore we have copy the referent.
5162 //
5163 // If the reference field is in the G1 heap then we can push
5164 // on the PSS queue. When the queue is drained (after each
5165 // phase of reference processing) the object and it's followers
5166 // will be copied, the reference field set to point to the
5167 // new location, and the RSet updated. Otherwise we need to
5168 // use the the non-heap or metadata closures directly to copy
5169 // the refernt object and update the pointer, while avoiding
5170 // updating the RSet.
5171
5172 if (_g1h->is_in_g1_reserved(p)) {
5173 _par_scan_state->push_on_queue(p);
5174 } else {
5175 assert(!ClassLoaderDataGraph::contains((address)p),
5176 err_msg("Otherwise need to call _copy_metadata_obj_cl->do_oop(p) "
5177 PTR_FORMAT, p));
5178 _copy_non_heap_obj_cl->do_oop(p);
5179 }
5180 }
5181 }
5182 };
5183
5184 // Serial drain queue closure. Called as the 'complete_gc'
5185 // closure for each discovered list in some of the
5186 // reference processing phases.
5187
5188 class G1STWDrainQueueClosure: public VoidClosure {
5189 protected:
5190 G1CollectedHeap* _g1h;
5191 G1ParScanThreadState* _par_scan_state;
5192
5193 G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
5194
5195 public:
5196 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
5197 _g1h(g1h),
5198 _par_scan_state(pss)
5199 { }
5200
5201 void do_void() {
5202 G1ParScanThreadState* const pss = par_scan_state();
5203 pss->trim_queue();
5204 }
5205 };
5206
5207 // Parallel Reference Processing closures
5208
5209 // Implementation of AbstractRefProcTaskExecutor for parallel reference
5210 // processing during G1 evacuation pauses.
5211
5212 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
5213 private:
5214 G1CollectedHeap* _g1h;
5215 RefToScanQueueSet* _queues;
5216 FlexibleWorkGang* _workers;
5217 int _active_workers;
5218
5219 public:
5220 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
5221 FlexibleWorkGang* workers,
5222 RefToScanQueueSet *task_queues,
5223 int n_workers) :
5224 _g1h(g1h),
5225 _queues(task_queues),
5226 _workers(workers),
5227 _active_workers(n_workers)
5228 {
5229 assert(n_workers > 0, "shouldn't call this otherwise");
5230 }
5231
5232 // Executes the given task using concurrent marking worker threads.
5233 virtual void execute(ProcessTask& task);
5234 virtual void execute(EnqueueTask& task);
5235 };
5236
5237 // Gang task for possibly parallel reference processing
5238
5239 class G1STWRefProcTaskProxy: public AbstractGangTask {
5240 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
5241 ProcessTask& _proc_task;
5242 G1CollectedHeap* _g1h;
5243 RefToScanQueueSet *_task_queues;
5244 ParallelTaskTerminator* _terminator;
5245
5246 public:
5247 G1STWRefProcTaskProxy(ProcessTask& proc_task,
5248 G1CollectedHeap* g1h,
5249 RefToScanQueueSet *task_queues,
5250 ParallelTaskTerminator* terminator) :
5251 AbstractGangTask("Process reference objects in parallel"),
5252 _proc_task(proc_task),
5253 _g1h(g1h),
5254 _task_queues(task_queues),
5255 _terminator(terminator)
5256 {}
5257
5258 virtual void work(uint worker_id) {
5259 // The reference processing task executed by a single worker.
5260 ResourceMark rm;
5261 HandleMark hm;
5262
5263 G1STWIsAliveClosure is_alive(_g1h);
5264
5265 G1ParScanThreadState pss(_g1h, worker_id);
5266
5267 G1ParScanHeapEvacClosure scan_evac_cl(_g1h, &pss, NULL);
5268 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5269 G1ParScanPartialArrayClosure partial_scan_cl(_g1h, &pss, NULL);
5270
5271 pss.set_evac_closure(&scan_evac_cl);
5272 pss.set_evac_failure_closure(&evac_failure_cl);
5273 pss.set_partial_scan_closure(&partial_scan_cl);
5274
5275 G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL);
5276 G1ParScanMetadataClosure only_copy_metadata_cl(_g1h, &pss, NULL);
5277
5278 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5279 G1ParScanAndMarkMetadataClosure copy_mark_metadata_cl(_g1h, &pss, NULL);
5280
5281 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5282 OopsInHeapRegionClosure* copy_metadata_cl = &only_copy_metadata_cl;
5283
5284 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5285 // We also need to mark copied objects.
5286 copy_non_heap_cl = ©_mark_non_heap_cl;
5287 copy_metadata_cl = ©_mark_metadata_cl;
5288 }
5289
5290 // Keep alive closure.
5291 G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, copy_metadata_cl, &pss);
5292
5293 // Complete GC closure
5294 G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _task_queues, _terminator);
5295
5296 // Call the reference processing task's work routine.
5297 _proc_task.work(worker_id, is_alive, keep_alive, drain_queue);
5298
5299 // Note we cannot assert that the refs array is empty here as not all
5300 // of the processing tasks (specifically phase2 - pp2_work) execute
5301 // the complete_gc closure (which ordinarily would drain the queue) so
5302 // the queue may not be empty.
5303 }
5304 };
5305
5306 // Driver routine for parallel reference processing.
5307 // Creates an instance of the ref processing gang
5308 // task and has the worker threads execute it.
5309 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) {
5310 assert(_workers != NULL, "Need parallel worker threads.");
5311
5312 ParallelTaskTerminator terminator(_active_workers, _queues);
5313 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _queues, &terminator);
5314
5315 _g1h->set_par_threads(_active_workers);
5316 _workers->run_task(&proc_task_proxy);
5317 _g1h->set_par_threads(0);
5318 }
5319
5320 // Gang task for parallel reference enqueueing.
5321
5322 class G1STWRefEnqueueTaskProxy: public AbstractGangTask {
5323 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
5324 EnqueueTask& _enq_task;
5325
5326 public:
5327 G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) :
5328 AbstractGangTask("Enqueue reference objects in parallel"),
5329 _enq_task(enq_task)
5330 { }
5331
5332 virtual void work(uint worker_id) {
5333 _enq_task.work(worker_id);
5334 }
5335 };
5336
5337 // Driver routine for parallel reference enqueing.
5338 // Creates an instance of the ref enqueueing gang
5339 // task and has the worker threads execute it.
5340
5341 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
5342 assert(_workers != NULL, "Need parallel worker threads.");
5343
5344 G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task);
5345
5346 _g1h->set_par_threads(_active_workers);
5347 _workers->run_task(&enq_task_proxy);
5348 _g1h->set_par_threads(0);
5349 }
5350
5351 // End of weak reference support closures
5352
5353 // Abstract task used to preserve (i.e. copy) any referent objects
5354 // that are in the collection set and are pointed to by reference
5355 // objects discovered by the CM ref processor.
5356
5357 class G1ParPreserveCMReferentsTask: public AbstractGangTask {
5358 protected:
5359 G1CollectedHeap* _g1h;
5360 RefToScanQueueSet *_queues;
5361 ParallelTaskTerminator _terminator;
5362 uint _n_workers;
5363
5364 public:
5365 G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h,int workers, RefToScanQueueSet *task_queues) :
5366 AbstractGangTask("ParPreserveCMReferents"),
5367 _g1h(g1h),
5368 _queues(task_queues),
5369 _terminator(workers, _queues),
5370 _n_workers(workers)
5371 { }
5372
5373 void work(uint worker_id) {
5374 ResourceMark rm;
5375 HandleMark hm;
5376
5377 G1ParScanThreadState pss(_g1h, worker_id);
5378 G1ParScanHeapEvacClosure scan_evac_cl(_g1h, &pss, NULL);
5379 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5380 G1ParScanPartialArrayClosure partial_scan_cl(_g1h, &pss, NULL);
5381
5382 pss.set_evac_closure(&scan_evac_cl);
5383 pss.set_evac_failure_closure(&evac_failure_cl);
5384 pss.set_partial_scan_closure(&partial_scan_cl);
5385
5386 assert(pss.refs()->is_empty(), "both queue and overflow should be empty");
5387
5388
5389 G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL);
5390 G1ParScanMetadataClosure only_copy_metadata_cl(_g1h, &pss, NULL);
5391
5392 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5393 G1ParScanAndMarkMetadataClosure copy_mark_metadata_cl(_g1h, &pss, NULL);
5394
5395 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5396 OopsInHeapRegionClosure* copy_metadata_cl = &only_copy_metadata_cl;
5397
5398 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5399 // We also need to mark copied objects.
5400 copy_non_heap_cl = ©_mark_non_heap_cl;
5401 copy_metadata_cl = ©_mark_metadata_cl;
5402 }
5403
5404 // Is alive closure
5405 G1AlwaysAliveClosure always_alive(_g1h);
5406
5407 // Copying keep alive closure. Applied to referent objects that need
5408 // to be copied.
5409 G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, copy_metadata_cl, &pss);
5410
5411 ReferenceProcessor* rp = _g1h->ref_processor_cm();
5412
5413 uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q();
5414 uint stride = MIN2(MAX2(_n_workers, 1U), limit);
5415
5416 // limit is set using max_num_q() - which was set using ParallelGCThreads.
5417 // So this must be true - but assert just in case someone decides to
5418 // change the worker ids.
5419 assert(0 <= worker_id && worker_id < limit, "sanity");
5420 assert(!rp->discovery_is_atomic(), "check this code");
5421
5422 // Select discovered lists [i, i+stride, i+2*stride,...,limit)
5423 for (uint idx = worker_id; idx < limit; idx += stride) {
5424 DiscoveredList& ref_list = rp->discovered_refs()[idx];
5425
5426 DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive);
5427 while (iter.has_next()) {
5428 // Since discovery is not atomic for the CM ref processor, we
5429 // can see some null referent objects.
5430 iter.load_ptrs(DEBUG_ONLY(true));
5431 oop ref = iter.obj();
5432
5433 // This will filter nulls.
5434 if (iter.is_referent_alive()) {
5435 iter.make_referent_alive();
5436 }
5437 iter.move_to_next();
5438 }
5439 }
5440
5441 // Drain the queue - which may cause stealing
5442 G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _queues, &_terminator);
5443 drain_queue.do_void();
5444 // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure
5445 assert(pss.refs()->is_empty(), "should be");
5446 }
5447 };
5448
5449 // Weak Reference processing during an evacuation pause (part 1).
5450 void G1CollectedHeap::process_discovered_references(uint no_of_gc_workers) {
5451 double ref_proc_start = os::elapsedTime();
5452
5453 ReferenceProcessor* rp = _ref_processor_stw;
5454 assert(rp->discovery_enabled(), "should have been enabled");
5455
5456 // Any reference objects, in the collection set, that were 'discovered'
5457 // by the CM ref processor should have already been copied (either by
5458 // applying the external root copy closure to the discovered lists, or
5459 // by following an RSet entry).
5460 //
5461 // But some of the referents, that are in the collection set, that these
5462 // reference objects point to may not have been copied: the STW ref
5463 // processor would have seen that the reference object had already
5464 // been 'discovered' and would have skipped discovering the reference,
5465 // but would not have treated the reference object as a regular oop.
5466 // As a reult the copy closure would not have been applied to the
5467 // referent object.
5468 //
5469 // We need to explicitly copy these referent objects - the references
5470 // will be processed at the end of remarking.
5471 //
5472 // We also need to do this copying before we process the reference
5473 // objects discovered by the STW ref processor in case one of these
5474 // referents points to another object which is also referenced by an
5475 // object discovered by the STW ref processor.
5476
5477 assert(!G1CollectedHeap::use_parallel_gc_threads() ||
5478 no_of_gc_workers == workers()->active_workers(),
5479 "Need to reset active GC workers");
5480
5481 set_par_threads(no_of_gc_workers);
5482 G1ParPreserveCMReferentsTask keep_cm_referents(this,
5483 no_of_gc_workers,
5484 _task_queues);
5485
5486 if (G1CollectedHeap::use_parallel_gc_threads()) {
5487 workers()->run_task(&keep_cm_referents);
5488 } else {
5489 keep_cm_referents.work(0);
5490 }
5491
5492 set_par_threads(0);
5493
5494 // Closure to test whether a referent is alive.
5495 G1STWIsAliveClosure is_alive(this);
5496
5497 // Even when parallel reference processing is enabled, the processing
5498 // of JNI refs is serial and performed serially by the current thread
5499 // rather than by a worker. The following PSS will be used for processing
5500 // JNI refs.
5501
5502 // Use only a single queue for this PSS.
5503 G1ParScanThreadState pss(this, 0);
5504
5505 // We do not embed a reference processor in the copying/scanning
5506 // closures while we're actually processing the discovered
5507 // reference objects.
5508 G1ParScanHeapEvacClosure scan_evac_cl(this, &pss, NULL);
5509 G1ParScanHeapEvacFailureClosure evac_failure_cl(this, &pss, NULL);
5510 G1ParScanPartialArrayClosure partial_scan_cl(this, &pss, NULL);
5511
5512 pss.set_evac_closure(&scan_evac_cl);
5513 pss.set_evac_failure_closure(&evac_failure_cl);
5514 pss.set_partial_scan_closure(&partial_scan_cl);
5515
5516 assert(pss.refs()->is_empty(), "pre-condition");
5517
5518 G1ParScanExtRootClosure only_copy_non_heap_cl(this, &pss, NULL);
5519 G1ParScanMetadataClosure only_copy_metadata_cl(this, &pss, NULL);
5520
5521 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(this, &pss, NULL);
5522 G1ParScanAndMarkMetadataClosure copy_mark_metadata_cl(this, &pss, NULL);
5523
5524 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5525 OopsInHeapRegionClosure* copy_metadata_cl = &only_copy_metadata_cl;
5526
5527 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5528 // We also need to mark copied objects.
5529 copy_non_heap_cl = ©_mark_non_heap_cl;
5530 copy_metadata_cl = ©_mark_metadata_cl;
5531 }
5532
5533 // Keep alive closure.
5534 G1CopyingKeepAliveClosure keep_alive(this, copy_non_heap_cl, copy_metadata_cl, &pss);
5535
5536 // Serial Complete GC closure
5537 G1STWDrainQueueClosure drain_queue(this, &pss);
5538
5539 // Setup the soft refs policy...
5540 rp->setup_policy(false);
5541
5542 if (!rp->processing_is_mt()) {
5543 // Serial reference processing...
5544 rp->process_discovered_references(&is_alive,
5545 &keep_alive,
5546 &drain_queue,
5547 NULL);
5548 } else {
5549 // Parallel reference processing
5550 assert(rp->num_q() == no_of_gc_workers, "sanity");
5551 assert(no_of_gc_workers <= rp->max_num_q(), "sanity");
5552
5553 G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers);
5554 rp->process_discovered_references(&is_alive, &keep_alive, &drain_queue, &par_task_executor);
5555 }
5556
5557 // We have completed copying any necessary live referent objects
5558 // (that were not copied during the actual pause) so we can
5559 // retire any active alloc buffers
5560 pss.retire_alloc_buffers();
5561 assert(pss.refs()->is_empty(), "both queue and overflow should be empty");
5562
5563 double ref_proc_time = os::elapsedTime() - ref_proc_start;
5564 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
5565 }
5566
5567 // Weak Reference processing during an evacuation pause (part 2).
5568 void G1CollectedHeap::enqueue_discovered_references(uint no_of_gc_workers) {
5569 double ref_enq_start = os::elapsedTime();
5570
5571 ReferenceProcessor* rp = _ref_processor_stw;
5572 assert(!rp->discovery_enabled(), "should have been disabled as part of processing");
5573
5574 // Now enqueue any remaining on the discovered lists on to
5575 // the pending list.
5576 if (!rp->processing_is_mt()) {
5577 // Serial reference processing...
5578 rp->enqueue_discovered_references();
5579 } else {
5580 // Parallel reference enqueuing
5581
5582 assert(no_of_gc_workers == workers()->active_workers(),
5583 "Need to reset active workers");
5584 assert(rp->num_q() == no_of_gc_workers, "sanity");
5585 assert(no_of_gc_workers <= rp->max_num_q(), "sanity");
5586
5587 G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers);
5588 rp->enqueue_discovered_references(&par_task_executor);
5589 }
5590
5591 rp->verify_no_references_recorded();
5592 assert(!rp->discovery_enabled(), "should have been disabled");
5593
5594 // FIXME
5595 // CM's reference processing also cleans up the string and symbol tables.
5596 // Should we do that here also? We could, but it is a serial operation
5597 // and could signicantly increase the pause time.
5598
5599 double ref_enq_time = os::elapsedTime() - ref_enq_start;
5600 g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0);
5601 }
5602
5603 void G1CollectedHeap::evacuate_collection_set() {
5604 _expand_heap_after_alloc_failure = true;
5605 set_evacuation_failed(false);
5606
5607 // Should G1EvacuationFailureALot be in effect for this GC?
5608 NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();)
5609
5610 g1_rem_set()->prepare_for_oops_into_collection_set_do();
5611 concurrent_g1_refine()->set_use_cache(false);
5612 concurrent_g1_refine()->clear_hot_cache_claimed_index();
5613
5614 uint n_workers;
5615 if (G1CollectedHeap::use_parallel_gc_threads()) {
5616 n_workers =
5617 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
5618 workers()->active_workers(),
5619 Threads::number_of_non_daemon_threads());
5620 assert(UseDynamicNumberOfGCThreads ||
5621 n_workers == workers()->total_workers(),
5622 "If not dynamic should be using all the workers");
5623 workers()->set_active_workers(n_workers);
5624 set_par_threads(n_workers);
5625 } else {
5626 assert(n_par_threads() == 0,
5627 "Should be the original non-parallel value");
5628 n_workers = 1;
5629 }
5630
5631 G1ParTask g1_par_task(this, _task_queues);
5632
5633 init_for_evac_failure(NULL);
5634
5635 rem_set()->prepare_for_younger_refs_iterate(true);
5636
5637 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
5638 double start_par_time_sec = os::elapsedTime();
5639 double end_par_time_sec;
5640
5641 {
5642 StrongRootsScope srs(this);
5643
5644 if (G1CollectedHeap::use_parallel_gc_threads()) {
5645 // The individual threads will set their evac-failure closures.
5646 if (ParallelGCVerbose) G1ParScanThreadState::print_termination_stats_hdr();
5647 // These tasks use ShareHeap::_process_strong_tasks
5648 assert(UseDynamicNumberOfGCThreads ||
5649 workers()->active_workers() == workers()->total_workers(),
5650 "If not dynamic should be using all the workers");
5651 workers()->run_task(&g1_par_task);
5652 } else {
5653 g1_par_task.set_for_termination(n_workers);
5654 g1_par_task.work(0);
5655 }
5656 end_par_time_sec = os::elapsedTime();
5657
5658 // Closing the inner scope will execute the destructor
5659 // for the StrongRootsScope object. We record the current
5660 // elapsed time before closing the scope so that time
5661 // taken for the SRS destructor is NOT included in the
5662 // reported parallel time.
5663 }
5664
5665 double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0;
5666 g1_policy()->phase_times()->record_par_time(par_time_ms);
5667
5668 double code_root_fixup_time_ms =
5669 (os::elapsedTime() - end_par_time_sec) * 1000.0;
5670 g1_policy()->phase_times()->record_code_root_fixup_time(code_root_fixup_time_ms);
5671
5672 set_par_threads(0);
5673
5674 // Process any discovered reference objects - we have
5675 // to do this _before_ we retire the GC alloc regions
5676 // as we may have to copy some 'reachable' referent
5677 // objects (and their reachable sub-graphs) that were
5678 // not copied during the pause.
5679 process_discovered_references(n_workers);
5680
5681 // Weak root processing.
5682 // Note: when JSR 292 is enabled and code blobs can contain
5683 // non-perm oops then we will need to process the code blobs
5684 // here too.
5685 {
5686 G1STWIsAliveClosure is_alive(this);
5687 G1KeepAliveClosure keep_alive(this);
5688 JNIHandles::weak_oops_do(&is_alive, &keep_alive);
5689 }
5690
5691 release_gc_alloc_regions(n_workers);
5692 g1_rem_set()->cleanup_after_oops_into_collection_set_do();
5693
5694 concurrent_g1_refine()->clear_hot_cache();
5695 concurrent_g1_refine()->set_use_cache(true);
5696
5697 finalize_for_evac_failure();
5698
5699 if (evacuation_failed()) {
5700 remove_self_forwarding_pointers();
5701
5702 // Reset the G1EvacuationFailureALot counters and flags
5703 // Note: the values are reset only when an actual
5704 // evacuation failure occurs.
5705 NOT_PRODUCT(reset_evacuation_should_fail();)
5706 }
5707
5708 // Enqueue any remaining references remaining on the STW
5709 // reference processor's discovered lists. We need to do
5710 // this after the card table is cleaned (and verified) as
5711 // the act of enqueuing entries on to the pending list
5712 // will log these updates (and dirty their associated
5713 // cards). We need these updates logged to update any
5714 // RSets.
5715 enqueue_discovered_references(n_workers);
5716
5717 if (G1DeferredRSUpdate) {
5718 RedirtyLoggedCardTableEntryFastClosure redirty;
5719 dirty_card_queue_set().set_closure(&redirty);
5720 dirty_card_queue_set().apply_closure_to_all_completed_buffers();
5721
5722 DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set();
5723 dcq.merge_bufferlists(&dirty_card_queue_set());
5724 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
5725 }
5726 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
5727 }
5728
5729 void G1CollectedHeap::free_region_if_empty(HeapRegion* hr,
5730 size_t* pre_used,
5731 FreeRegionList* free_list,
5732 OldRegionSet* old_proxy_set,
5733 HumongousRegionSet* humongous_proxy_set,
5734 HRRSCleanupTask* hrrs_cleanup_task,
5735 bool par) {
5736 if (hr->used() > 0 && hr->max_live_bytes() == 0 && !hr->is_young()) {
5737 if (hr->isHumongous()) {
5738 assert(hr->startsHumongous(), "we should only see starts humongous");
5739 free_humongous_region(hr, pre_used, free_list, humongous_proxy_set, par);
5740 } else {
5741 _old_set.remove_with_proxy(hr, old_proxy_set);
5742 free_region(hr, pre_used, free_list, par);
5743 }
5744 } else {
5745 hr->rem_set()->do_cleanup_work(hrrs_cleanup_task);
5746 }
5747 }
5748
5749 void G1CollectedHeap::free_region(HeapRegion* hr,
5750 size_t* pre_used,
5751 FreeRegionList* free_list,
5752 bool par) {
5753 assert(!hr->isHumongous(), "this is only for non-humongous regions");
5754 assert(!hr->is_empty(), "the region should not be empty");
5755 assert(free_list != NULL, "pre-condition");
5756
5757 if (G1VerifyPrevBitmap) {
5758 MemRegion mr(hr->bottom(), hr->end());
5759 concurrent_mark()->clearRangePrevBitmap(mr);
5760 }
5761 *pre_used += hr->used();
5762 hr->hr_clear(par, true /* clear_space */);
5763 free_list->add_as_head(hr);
5764 }
5765
5766 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
5767 size_t* pre_used,
5768 FreeRegionList* free_list,
5769 HumongousRegionSet* humongous_proxy_set,
5770 bool par) {
5771 assert(hr->startsHumongous(), "this is only for starts humongous regions");
5772 assert(free_list != NULL, "pre-condition");
5773 assert(humongous_proxy_set != NULL, "pre-condition");
5774
5775 size_t hr_used = hr->used();
5776 size_t hr_capacity = hr->capacity();
5777 size_t hr_pre_used = 0;
5778 _humongous_set.remove_with_proxy(hr, humongous_proxy_set);
5779 // We need to read this before we make the region non-humongous,
5780 // otherwise the information will be gone.
5781 uint last_index = hr->last_hc_index();
5782 hr->set_notHumongous();
5783 free_region(hr, &hr_pre_used, free_list, par);
5784
5785 uint i = hr->hrs_index() + 1;
5786 while (i < last_index) {
5787 HeapRegion* curr_hr = region_at(i);
5788 assert(curr_hr->continuesHumongous(), "invariant");
5789 curr_hr->set_notHumongous();
5790 free_region(curr_hr, &hr_pre_used, free_list, par);
5791 i += 1;
5792 }
5793 assert(hr_pre_used == hr_used,
5794 err_msg("hr_pre_used: "SIZE_FORMAT" and hr_used: "SIZE_FORMAT" "
5795 "should be the same", hr_pre_used, hr_used));
5796 *pre_used += hr_pre_used;
5797 }
5798
5799 void G1CollectedHeap::update_sets_after_freeing_regions(size_t pre_used,
5800 FreeRegionList* free_list,
5801 OldRegionSet* old_proxy_set,
5802 HumongousRegionSet* humongous_proxy_set,
5803 bool par) {
5804 if (pre_used > 0) {
5805 Mutex* lock = (par) ? ParGCRareEvent_lock : NULL;
5806 MutexLockerEx x(lock, Mutex::_no_safepoint_check_flag);
5807 assert(_summary_bytes_used >= pre_used,
5808 err_msg("invariant: _summary_bytes_used: "SIZE_FORMAT" "
5809 "should be >= pre_used: "SIZE_FORMAT,
5810 _summary_bytes_used, pre_used));
5811 _summary_bytes_used -= pre_used;
5812 }
5813 if (free_list != NULL && !free_list->is_empty()) {
5814 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
5815 _free_list.add_as_head(free_list);
5816 }
5817 if (old_proxy_set != NULL && !old_proxy_set->is_empty()) {
5818 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
5819 _old_set.update_from_proxy(old_proxy_set);
5820 }
5821 if (humongous_proxy_set != NULL && !humongous_proxy_set->is_empty()) {
5822 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
5823 _humongous_set.update_from_proxy(humongous_proxy_set);
5824 }
5825 }
5826
5827 class G1ParCleanupCTTask : public AbstractGangTask {
5828 CardTableModRefBS* _ct_bs;
5829 G1CollectedHeap* _g1h;
5830 HeapRegion* volatile _su_head;
5831 public:
5832 G1ParCleanupCTTask(CardTableModRefBS* ct_bs,
5833 G1CollectedHeap* g1h) :
5834 AbstractGangTask("G1 Par Cleanup CT Task"),
5835 _ct_bs(ct_bs), _g1h(g1h) { }
5836
5837 void work(uint worker_id) {
5838 HeapRegion* r;
5839 while (r = _g1h->pop_dirty_cards_region()) {
5840 clear_cards(r);
5841 }
5842 }
5843
5844 void clear_cards(HeapRegion* r) {
5845 // Cards of the survivors should have already been dirtied.
5846 if (!r->is_survivor()) {
5847 _ct_bs->clear(MemRegion(r->bottom(), r->end()));
5848 }
5849 }
5850 };
5851
5852 #ifndef PRODUCT
5853 class G1VerifyCardTableCleanup: public HeapRegionClosure {
5854 G1CollectedHeap* _g1h;
5855 CardTableModRefBS* _ct_bs;
5856 public:
5857 G1VerifyCardTableCleanup(G1CollectedHeap* g1h, CardTableModRefBS* ct_bs)
5858 : _g1h(g1h), _ct_bs(ct_bs) { }
5859 virtual bool doHeapRegion(HeapRegion* r) {
5860 if (r->is_survivor()) {
5861 _g1h->verify_dirty_region(r);
5862 } else {
5863 _g1h->verify_not_dirty_region(r);
5864 }
5865 return false;
5866 }
5867 };
5868
5869 void G1CollectedHeap::verify_not_dirty_region(HeapRegion* hr) {
5870 // All of the region should be clean.
5871 CardTableModRefBS* ct_bs = (CardTableModRefBS*)barrier_set();
5872 MemRegion mr(hr->bottom(), hr->end());
5873 ct_bs->verify_not_dirty_region(mr);
5874 }
5875
5876 void G1CollectedHeap::verify_dirty_region(HeapRegion* hr) {
5877 // We cannot guarantee that [bottom(),end()] is dirty. Threads
5878 // dirty allocated blocks as they allocate them. The thread that
5879 // retires each region and replaces it with a new one will do a
5880 // maximal allocation to fill in [pre_dummy_top(),end()] but will
5881 // not dirty that area (one less thing to have to do while holding
5882 // a lock). So we can only verify that [bottom(),pre_dummy_top()]
5883 // is dirty.
5884 CardTableModRefBS* ct_bs = (CardTableModRefBS*) barrier_set();
5885 MemRegion mr(hr->bottom(), hr->pre_dummy_top());
5886 ct_bs->verify_dirty_region(mr);
5887 }
5888
5889 void G1CollectedHeap::verify_dirty_young_list(HeapRegion* head) {
5890 CardTableModRefBS* ct_bs = (CardTableModRefBS*) barrier_set();
5891 for (HeapRegion* hr = head; hr != NULL; hr = hr->get_next_young_region()) {
5892 verify_dirty_region(hr);
5893 }
5894 }
5895
5896 void G1CollectedHeap::verify_dirty_young_regions() {
5897 verify_dirty_young_list(_young_list->first_region());
5898 }
5899
5900 bool G1CollectedHeap::verify_bitmap(const char* bitmap_name, CMBitMapRO* bitmap,
5901 HeapWord* tams, HeapWord* end) {
5902 guarantee(tams <= end,
5903 err_msg("tams: "PTR_FORMAT" end: "PTR_FORMAT, tams, end));
5904 HeapWord* result = bitmap->getNextMarkedWordAddress(tams, end);
5905 guarantee(result <= end,
5906 err_msg("result: "PTR_FORMAT" end: "PTR_FORMAT, result, end));
5907 if (result < end) {
5908 gclog_or_tty->cr();
5909 gclog_or_tty->print_cr("## wrong marked address on %s bitmap: "PTR_FORMAT,
5910 bitmap_name, result);
5911 gclog_or_tty->print_cr("## %s tams: "PTR_FORMAT" end: "PTR_FORMAT,
5912 bitmap_name, tams, end);
5913 return false;
5914 }
5915 return true;
5916 }
5917
5918 bool G1CollectedHeap::verify_bitmaps(const char* caller, HeapRegion* hr) {
5919 CMBitMapRO* prev_bitmap = concurrent_mark()->prevMarkBitMap();
5920 CMBitMapRO* next_bitmap = (CMBitMapRO*) concurrent_mark()->nextMarkBitMap();
5921
5922 HeapWord* bottom = hr->bottom();
5923 HeapWord* ptams = hr->prev_top_at_mark_start();
5924 HeapWord* ntams = hr->next_top_at_mark_start();
5925 HeapWord* end = hr->end();
5926
5927 bool res_p = true;
5928 if (G1VerifyPrevBitmap) {
5929 res_p = verify_bitmap("prev", prev_bitmap, ptams, end);
5930 }
5931
5932 bool res_n = true;
5933 if (mark_in_progress() || !_cmThread->in_progress()) {
5934 res_n = verify_bitmap("next", next_bitmap, ntams, end);
5935 }
5936 if (!res_p || !res_n) {
5937 gclog_or_tty->print_cr("#### Bitmap verification failed for "HR_FORMAT,
5938 HR_FORMAT_PARAMS(hr));
5939 gclog_or_tty->print_cr("#### Caller: %s", caller);
5940 return false;
5941 }
5942 return true;
5943 }
5944
5945 void G1CollectedHeap::check_bitmaps(const char* caller, HeapRegion* hr) {
5946 if (!G1VerifyBitmaps) return;
5947
5948 guarantee(verify_bitmaps(caller, hr), "bitmap verification");
5949 }
5950
5951 class G1VerifyBitmapClosure : public HeapRegionClosure {
5952 private:
5953 const char* _caller;
5954 G1CollectedHeap* _g1h;
5955 bool _failures;
5956
5957 public:
5958 G1VerifyBitmapClosure(const char* caller, G1CollectedHeap* g1h) :
5959 _caller(caller), _g1h(g1h), _failures(false) { }
5960
5961 bool failures() { return _failures; }
5962
5963 virtual bool doHeapRegion(HeapRegion* hr) {
5964 if (hr->continuesHumongous()) return false;
5965
5966 bool result = _g1h->verify_bitmaps(_caller, hr);
5967 if (!result) {
5968 _failures = true;
5969 }
5970 return false;
5971 }
5972 };
5973
5974 void G1CollectedHeap::check_bitmaps(const char* caller) {
5975 if (!G1VerifyBitmaps) return;
5976
5977 G1VerifyBitmapClosure cl(caller, this);
5978 heap_region_iterate(&cl);
5979 guarantee(!cl.failures(), "bitmap verification");
5980 }
5981 #endif // PRODUCT
5982
5983 void G1CollectedHeap::cleanUpCardTable() {
5984 CardTableModRefBS* ct_bs = (CardTableModRefBS*) (barrier_set());
5985 double start = os::elapsedTime();
5986
5987 {
5988 // Iterate over the dirty cards region list.
5989 G1ParCleanupCTTask cleanup_task(ct_bs, this);
5990
5991 if (G1CollectedHeap::use_parallel_gc_threads()) {
5992 set_par_threads();
5993 workers()->run_task(&cleanup_task);
5994 set_par_threads(0);
5995 } else {
5996 while (_dirty_cards_region_list) {
5997 HeapRegion* r = _dirty_cards_region_list;
5998 cleanup_task.clear_cards(r);
5999 _dirty_cards_region_list = r->get_next_dirty_cards_region();
6000 if (_dirty_cards_region_list == r) {
6001 // The last region.
6002 _dirty_cards_region_list = NULL;
6003 }
6004 r->set_next_dirty_cards_region(NULL);
6005 }
6006 }
6007 #ifndef PRODUCT
6008 if (G1VerifyCTCleanup || VerifyAfterGC) {
6009 G1VerifyCardTableCleanup cleanup_verifier(this, ct_bs);
6010 heap_region_iterate(&cleanup_verifier);
6011 }
6012 #endif
6013 }
6014
6015 double elapsed = os::elapsedTime() - start;
6016 g1_policy()->phase_times()->record_clear_ct_time(elapsed * 1000.0);
6017 }
6018
6019 void G1CollectedHeap::free_collection_set(HeapRegion* cs_head) {
6020 size_t pre_used = 0;
6021 FreeRegionList local_free_list("Local List for CSet Freeing");
6022
6023 double young_time_ms = 0.0;
6024 double non_young_time_ms = 0.0;
6025
6026 // Since the collection set is a superset of the the young list,
6027 // all we need to do to clear the young list is clear its
6028 // head and length, and unlink any young regions in the code below
6029 _young_list->clear();
6030
6031 G1CollectorPolicy* policy = g1_policy();
6032
6033 double start_sec = os::elapsedTime();
6034 bool non_young = true;
6035
6036 HeapRegion* cur = cs_head;
6037 int age_bound = -1;
6038 size_t rs_lengths = 0;
6039
6040 while (cur != NULL) {
6041 assert(!is_on_master_free_list(cur), "sanity");
6042 if (non_young) {
6043 if (cur->is_young()) {
6044 double end_sec = os::elapsedTime();
6045 double elapsed_ms = (end_sec - start_sec) * 1000.0;
6046 non_young_time_ms += elapsed_ms;
6047
6048 start_sec = os::elapsedTime();
6049 non_young = false;
6050 }
6051 } else {
6052 if (!cur->is_young()) {
6053 double end_sec = os::elapsedTime();
6054 double elapsed_ms = (end_sec - start_sec) * 1000.0;
6055 young_time_ms += elapsed_ms;
6056
6057 start_sec = os::elapsedTime();
6058 non_young = true;
6059 }
6060 }
6061
6062 rs_lengths += cur->rem_set()->occupied();
6063
6064 HeapRegion* next = cur->next_in_collection_set();
6065 assert(cur->in_collection_set(), "bad CS");
6066 cur->set_next_in_collection_set(NULL);
6067 cur->set_in_collection_set(false);
6068
6069 if (cur->is_young()) {
6070 int index = cur->young_index_in_cset();
6071 assert(index != -1, "invariant");
6072 assert((uint) index < policy->young_cset_region_length(), "invariant");
6073 size_t words_survived = _surviving_young_words[index];
6074 cur->record_surv_words_in_group(words_survived);
6075
6076 // At this point the we have 'popped' cur from the collection set
6077 // (linked via next_in_collection_set()) but it is still in the
6078 // young list (linked via next_young_region()). Clear the
6079 // _next_young_region field.
6080 cur->set_next_young_region(NULL);
6081 } else {
6082 int index = cur->young_index_in_cset();
6083 assert(index == -1, "invariant");
6084 }
6085
6086 assert( (cur->is_young() && cur->young_index_in_cset() > -1) ||
6087 (!cur->is_young() && cur->young_index_in_cset() == -1),
6088 "invariant" );
6089
6090 if (!cur->evacuation_failed()) {
6091 MemRegion used_mr = cur->used_region();
6092
6093 // And the region is empty.
6094 assert(!used_mr.is_empty(), "Should not have empty regions in a CS.");
6095 free_region(cur, &pre_used, &local_free_list, false /* par */);
6096 } else {
6097 cur->uninstall_surv_rate_group();
6098 if (cur->is_young()) {
6099 cur->set_young_index_in_cset(-1);
6100 }
6101 cur->set_not_young();
6102 cur->set_evacuation_failed(false);
6103 // The region is now considered to be old.
6104 _old_set.add(cur);
6105 }
6106 cur = next;
6107 }
6108
6109 policy->record_max_rs_lengths(rs_lengths);
6110 policy->cset_regions_freed();
6111
6112 double end_sec = os::elapsedTime();
6113 double elapsed_ms = (end_sec - start_sec) * 1000.0;
6114
6115 if (non_young) {
6116 non_young_time_ms += elapsed_ms;
6117 } else {
6118 young_time_ms += elapsed_ms;
6119 }
6120
6121 update_sets_after_freeing_regions(pre_used, &local_free_list,
6122 NULL /* old_proxy_set */,
6123 NULL /* humongous_proxy_set */,
6124 false /* par */);
6125 policy->phase_times()->record_young_free_cset_time_ms(young_time_ms);
6126 policy->phase_times()->record_non_young_free_cset_time_ms(non_young_time_ms);
6127 }
6128
6129 // This routine is similar to the above but does not record
6130 // any policy statistics or update free lists; we are abandoning
6131 // the current incremental collection set in preparation of a
6132 // full collection. After the full GC we will start to build up
6133 // the incremental collection set again.
6134 // This is only called when we're doing a full collection
6135 // and is immediately followed by the tearing down of the young list.
6136
6137 void G1CollectedHeap::abandon_collection_set(HeapRegion* cs_head) {
6138 HeapRegion* cur = cs_head;
6139
6140 while (cur != NULL) {
6141 HeapRegion* next = cur->next_in_collection_set();
6142 assert(cur->in_collection_set(), "bad CS");
6143 cur->set_next_in_collection_set(NULL);
6144 cur->set_in_collection_set(false);
6145 cur->set_young_index_in_cset(-1);
6146 cur = next;
6147 }
6148 }
6149
6150 void G1CollectedHeap::set_free_regions_coming() {
6151 if (G1ConcRegionFreeingVerbose) {
6152 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
6153 "setting free regions coming");
6154 }
6155
6156 assert(!free_regions_coming(), "pre-condition");
6157 _free_regions_coming = true;
6158 }
6159
6160 void G1CollectedHeap::reset_free_regions_coming() {
6161 assert(free_regions_coming(), "pre-condition");
6162
6163 {
6164 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6165 _free_regions_coming = false;
6166 SecondaryFreeList_lock->notify_all();
6167 }
6168
6169 if (G1ConcRegionFreeingVerbose) {
6170 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
6171 "reset free regions coming");
6172 }
6173 }
6174
6175 void G1CollectedHeap::wait_while_free_regions_coming() {
6176 // Most of the time we won't have to wait, so let's do a quick test
6177 // first before we take the lock.
6178 if (!free_regions_coming()) {
6179 return;
6180 }
6181
6182 if (G1ConcRegionFreeingVerbose) {
6183 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
6184 "waiting for free regions");
6185 }
6186
6187 {
6188 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6189 while (free_regions_coming()) {
6190 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
6191 }
6192 }
6193
6194 if (G1ConcRegionFreeingVerbose) {
6195 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
6196 "done waiting for free regions");
6197 }
6198 }
6199
6200 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
6201 assert(heap_lock_held_for_gc(),
6202 "the heap lock should already be held by or for this thread");
6203 _young_list->push_region(hr);
6204 }
6205
6206 class NoYoungRegionsClosure: public HeapRegionClosure {
6207 private:
6208 bool _success;
6209 public:
6210 NoYoungRegionsClosure() : _success(true) { }
6211 bool doHeapRegion(HeapRegion* r) {
6212 if (r->is_young()) {
6213 gclog_or_tty->print_cr("Region ["PTR_FORMAT", "PTR_FORMAT") tagged as young",
6214 r->bottom(), r->end());
6215 _success = false;
6216 }
6217 return false;
6218 }
6219 bool success() { return _success; }
6220 };
6221
6222 bool G1CollectedHeap::check_young_list_empty(bool check_heap, bool check_sample) {
6223 bool ret = _young_list->check_list_empty(check_sample);
6224
6225 if (check_heap) {
6226 NoYoungRegionsClosure closure;
6227 heap_region_iterate(&closure);
6228 ret = ret && closure.success();
6229 }
6230
6231 return ret;
6232 }
6233
6234 class TearDownRegionSetsClosure : public HeapRegionClosure {
6235 private:
6236 OldRegionSet *_old_set;
6237
6238 public:
6239 TearDownRegionSetsClosure(OldRegionSet* old_set) : _old_set(old_set) { }
6240
6241 bool doHeapRegion(HeapRegion* r) {
6242 if (r->is_empty()) {
6243 // We ignore empty regions, we'll empty the free list afterwards
6244 } else if (r->is_young()) {
6245 // We ignore young regions, we'll empty the young list afterwards
6246 } else if (r->isHumongous()) {
6247 // We ignore humongous regions, we're not tearing down the
6248 // humongous region set
6249 } else {
6250 // The rest should be old
6251 _old_set->remove(r);
6252 }
6253 return false;
6254 }
6255
6256 ~TearDownRegionSetsClosure() {
6257 assert(_old_set->is_empty(), "post-condition");
6258 }
6259 };
6260
6261 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
6262 assert_at_safepoint(true /* should_be_vm_thread */);
6263
6264 if (!free_list_only) {
6265 TearDownRegionSetsClosure cl(&_old_set);
6266 heap_region_iterate(&cl);
6267
6268 // Need to do this after the heap iteration to be able to
6269 // recognize the young regions and ignore them during the iteration.
6270 _young_list->empty_list();
6271 }
6272 _free_list.remove_all();
6273 }
6274
6275 class RebuildRegionSetsClosure : public HeapRegionClosure {
6276 private:
6277 bool _free_list_only;
6278 OldRegionSet* _old_set;
6279 FreeRegionList* _free_list;
6280 size_t _total_used;
6281
6282 public:
6283 RebuildRegionSetsClosure(bool free_list_only,
6284 OldRegionSet* old_set, FreeRegionList* free_list) :
6285 _free_list_only(free_list_only),
6286 _old_set(old_set), _free_list(free_list), _total_used(0) {
6287 assert(_free_list->is_empty(), "pre-condition");
6288 if (!free_list_only) {
6289 assert(_old_set->is_empty(), "pre-condition");
6290 }
6291 }
6292
6293 bool doHeapRegion(HeapRegion* r) {
6294 if (r->continuesHumongous()) {
6295 return false;
6296 }
6297
6298 if (r->is_empty()) {
6299 // Add free regions to the free list
6300 _free_list->add_as_tail(r);
6301 } else if (!_free_list_only) {
6302 assert(!r->is_young(), "we should not come across young regions");
6303
6304 if (r->isHumongous()) {
6305 // We ignore humongous regions, we left the humongous set unchanged
6306 } else {
6307 // The rest should be old, add them to the old set
6308 _old_set->add(r);
6309 }
6310 _total_used += r->used();
6311 }
6312
6313 return false;
6314 }
6315
6316 size_t total_used() {
6317 return _total_used;
6318 }
6319 };
6320
6321 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
6322 assert_at_safepoint(true /* should_be_vm_thread */);
6323
6324 RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_free_list);
6325 heap_region_iterate(&cl);
6326
6327 if (!free_list_only) {
6328 _summary_bytes_used = cl.total_used();
6329 }
6330 assert(_summary_bytes_used == recalculate_used(),
6331 err_msg("inconsistent _summary_bytes_used, "
6332 "value: "SIZE_FORMAT" recalculated: "SIZE_FORMAT,
6333 _summary_bytes_used, recalculate_used()));
6334 }
6335
6336 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) {
6337 _refine_cte_cl->set_concurrent(concurrent);
6338 }
6339
6340 bool G1CollectedHeap::is_in_closed_subset(const void* p) const {
6341 HeapRegion* hr = heap_region_containing(p);
6342 if (hr == NULL) {
6343 return false;
6344 } else {
6345 return hr->is_in(p);
6346 }
6347 }
6348
6349 // Methods for the mutator alloc region
6350
6351 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
6352 bool force) {
6353 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6354 assert(!force || g1_policy()->can_expand_young_list(),
6355 "if force is true we should be able to expand the young list");
6356 bool young_list_full = g1_policy()->is_young_list_full();
6357 if (force || !young_list_full) {
6358 HeapRegion* new_alloc_region = new_region(word_size,
6359 false /* do_expand */);
6360 if (new_alloc_region != NULL) {
6361 set_region_short_lived_locked(new_alloc_region);
6362 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Eden, young_list_full);
6363 check_bitmaps("Mutator Region Allocation", new_alloc_region);
6364 return new_alloc_region;
6365 }
6366 }
6367 return NULL;
6368 }
6369
6370 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
6371 size_t allocated_bytes) {
6372 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6373 assert(alloc_region->is_young(), "all mutator alloc regions should be young");
6374
6375 g1_policy()->add_region_to_incremental_cset_lhs(alloc_region);
6376 _summary_bytes_used += allocated_bytes;
6377 _hr_printer.retire(alloc_region);
6378 // We update the eden sizes here, when the region is retired,
6379 // instead of when it's allocated, since this is the point that its
6380 // used space has been recored in _summary_bytes_used.
6381 g1mm()->update_eden_size();
6382 }
6383
6384 HeapRegion* MutatorAllocRegion::allocate_new_region(size_t word_size,
6385 bool force) {
6386 return _g1h->new_mutator_alloc_region(word_size, force);
6387 }
6388
6389 void G1CollectedHeap::set_par_threads() {
6390 // Don't change the number of workers. Use the value previously set
6391 // in the workgroup.
6392 assert(G1CollectedHeap::use_parallel_gc_threads(), "shouldn't be here otherwise");
6393 uint n_workers = workers()->active_workers();
6394 assert(UseDynamicNumberOfGCThreads ||
6395 n_workers == workers()->total_workers(),
6396 "Otherwise should be using the total number of workers");
6397 if (n_workers == 0) {
6398 assert(false, "Should have been set in prior evacuation pause.");
6399 n_workers = ParallelGCThreads;
6400 workers()->set_active_workers(n_workers);
6401 }
6402 set_par_threads(n_workers);
6403 }
6404
6405 void MutatorAllocRegion::retire_region(HeapRegion* alloc_region,
6406 size_t allocated_bytes) {
6407 _g1h->retire_mutator_alloc_region(alloc_region, allocated_bytes);
6408 }
6409
6410 // Methods for the GC alloc regions
6411
6412 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size,
6413 uint count,
6414 GCAllocPurpose ap) {
6415 assert(FreeList_lock->owned_by_self(), "pre-condition");
6416
6417 if (count < g1_policy()->max_regions(ap)) {
6418 HeapRegion* new_alloc_region = new_region(word_size,
6419 true /* do_expand */);
6420 if (new_alloc_region != NULL) {
6421 // We really only need to do this for old regions given that we
6422 // should never scan survivors. But it doesn't hurt to do it
6423 // for survivors too.
6424 new_alloc_region->set_saved_mark();
6425 if (ap == GCAllocForSurvived) {
6426 new_alloc_region->set_survivor();
6427 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Survivor);
6428 check_bitmaps("Survivor Region Allocation", new_alloc_region);
6429 } else {
6430 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Old);
6431 check_bitmaps("Old Region Allocation", new_alloc_region);
6432 }
6433 bool during_im = g1_policy()->during_initial_mark_pause();
6434 new_alloc_region->note_start_of_copying(during_im);
6435 return new_alloc_region;
6436 } else {
6437 g1_policy()->note_alloc_region_limit_reached(ap);
6438 }
6439 }
6440 return NULL;
6441 }
6442
6443 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
6444 size_t allocated_bytes,
6445 GCAllocPurpose ap) {
6446 bool during_im = g1_policy()->during_initial_mark_pause();
6447 alloc_region->note_end_of_copying(during_im);
6448 g1_policy()->record_bytes_copied_during_gc(allocated_bytes);
6449 if (ap == GCAllocForSurvived) {
6450 young_list()->add_survivor_region(alloc_region);
6451 } else {
6452 _old_set.add(alloc_region);
6453 }
6454 _hr_printer.retire(alloc_region);
6455 }
6456
6457 HeapRegion* SurvivorGCAllocRegion::allocate_new_region(size_t word_size,
6458 bool force) {
6459 assert(!force, "not supported for GC alloc regions");
6460 return _g1h->new_gc_alloc_region(word_size, count(), GCAllocForSurvived);
6461 }
6462
6463 void SurvivorGCAllocRegion::retire_region(HeapRegion* alloc_region,
6464 size_t allocated_bytes) {
6465 _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes,
6466 GCAllocForSurvived);
6467 }
6468
6469 HeapRegion* OldGCAllocRegion::allocate_new_region(size_t word_size,
6470 bool force) {
6471 assert(!force, "not supported for GC alloc regions");
6472 return _g1h->new_gc_alloc_region(word_size, count(), GCAllocForTenured);
6473 }
6474
6475 void OldGCAllocRegion::retire_region(HeapRegion* alloc_region,
6476 size_t allocated_bytes) {
6477 _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes,
6478 GCAllocForTenured);
6479 }
6480 // Heap region set verification
6481
6482 class VerifyRegionListsClosure : public HeapRegionClosure {
6483 private:
6484 FreeRegionList* _free_list;
6485 OldRegionSet* _old_set;
6486 HumongousRegionSet* _humongous_set;
6487 uint _region_count;
6488
6489 public:
6490 VerifyRegionListsClosure(OldRegionSet* old_set,
6491 HumongousRegionSet* humongous_set,
6492 FreeRegionList* free_list) :
6493 _old_set(old_set), _humongous_set(humongous_set),
6494 _free_list(free_list), _region_count(0) { }
6495
6496 uint region_count() { return _region_count; }
6497
6498 bool doHeapRegion(HeapRegion* hr) {
6499 _region_count += 1;
6500
6501 if (hr->continuesHumongous()) {
6502 return false;
6503 }
6504
6505 if (hr->is_young()) {
6506 // TODO
6507 } else if (hr->startsHumongous()) {
6508 _humongous_set->verify_next_region(hr);
6509 } else if (hr->is_empty()) {
6510 _free_list->verify_next_region(hr);
6511 } else {
6512 _old_set->verify_next_region(hr);
6513 }
6514 return false;
6515 }
6516 };
6517
6518 HeapRegion* G1CollectedHeap::new_heap_region(uint hrs_index,
6519 HeapWord* bottom) {
6520 HeapWord* end = bottom + HeapRegion::GrainWords;
6521 MemRegion mr(bottom, end);
6522 assert(_g1_reserved.contains(mr), "invariant");
6523 // This might return NULL if the allocation fails
6524 return new HeapRegion(hrs_index, _bot_shared, mr);
6525 }
6526
6527 void G1CollectedHeap::verify_region_sets() {
6528 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6529
6530 // First, check the explicit lists.
6531 _free_list.verify();
6532 {
6533 // Given that a concurrent operation might be adding regions to
6534 // the secondary free list we have to take the lock before
6535 // verifying it.
6536 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6537 _secondary_free_list.verify();
6538 }
6539 _old_set.verify();
6540 _humongous_set.verify();
6541
6542 // If a concurrent region freeing operation is in progress it will
6543 // be difficult to correctly attributed any free regions we come
6544 // across to the correct free list given that they might belong to
6545 // one of several (free_list, secondary_free_list, any local lists,
6546 // etc.). So, if that's the case we will skip the rest of the
6547 // verification operation. Alternatively, waiting for the concurrent
6548 // operation to complete will have a non-trivial effect on the GC's
6549 // operation (no concurrent operation will last longer than the
6550 // interval between two calls to verification) and it might hide
6551 // any issues that we would like to catch during testing.
6552 if (free_regions_coming()) {
6553 return;
6554 }
6555
6556 // Make sure we append the secondary_free_list on the free_list so
6557 // that all free regions we will come across can be safely
6558 // attributed to the free_list.
6559 append_secondary_free_list_if_not_empty_with_lock();
6560
6561 // Finally, make sure that the region accounting in the lists is
6562 // consistent with what we see in the heap.
6563 _old_set.verify_start();
6564 _humongous_set.verify_start();
6565 _free_list.verify_start();
6566
6567 VerifyRegionListsClosure cl(&_old_set, &_humongous_set, &_free_list);
6568 heap_region_iterate(&cl);
6569
6570 _old_set.verify_end();
6571 _humongous_set.verify_end();
6572 _free_list.verify_end();
6573 }