1 /*
2 * Copyright (c) 2001, 2014, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #if !defined(__clang_major__) && defined(__GNUC__)
26 // FIXME, formats have issues. Disable this macro definition, compile, and study warnings for more information.
27 #define ATTRIBUTE_PRINTF(x,y)
28 #endif
29
30 #include "precompiled.hpp"
31 #include "classfile/stringTable.hpp"
32 #include "code/codeCache.hpp"
33 #include "code/icBuffer.hpp"
34 #include "gc_implementation/g1/bufferingOopClosure.hpp"
35 #include "gc_implementation/g1/concurrentG1Refine.hpp"
36 #include "gc_implementation/g1/concurrentG1RefineThread.hpp"
37 #include "gc_implementation/g1/concurrentMarkThread.inline.hpp"
38 #include "gc_implementation/g1/g1AllocRegion.inline.hpp"
39 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
40 #include "gc_implementation/g1/g1CollectorPolicy.hpp"
41 #include "gc_implementation/g1/g1ErgoVerbose.hpp"
42 #include "gc_implementation/g1/g1EvacFailure.hpp"
43 #include "gc_implementation/g1/g1GCPhaseTimes.hpp"
44 #include "gc_implementation/g1/g1Log.hpp"
45 #include "gc_implementation/g1/g1MarkSweep.hpp"
46 #include "gc_implementation/g1/g1OopClosures.inline.hpp"
47 #include "gc_implementation/g1/g1ParScanThreadState.inline.hpp"
48 #include "gc_implementation/g1/g1RegionToSpaceMapper.hpp"
49 #include "gc_implementation/g1/g1RemSet.inline.hpp"
50 #include "gc_implementation/g1/g1StringDedup.hpp"
51 #include "gc_implementation/g1/g1YCTypes.hpp"
52 #include "gc_implementation/g1/heapRegion.inline.hpp"
53 #include "gc_implementation/g1/heapRegionRemSet.hpp"
54 #include "gc_implementation/g1/heapRegionSet.inline.hpp"
55 #include "gc_implementation/g1/vm_operations_g1.hpp"
56 #include "gc_implementation/shared/gcHeapSummary.hpp"
57 #include "gc_implementation/shared/gcTimer.hpp"
58 #include "gc_implementation/shared/gcTrace.hpp"
59 #include "gc_implementation/shared/gcTraceTime.hpp"
60 #include "gc_implementation/shared/isGCActiveMark.hpp"
61 #include "memory/allocation.hpp"
62 #include "memory/gcLocker.inline.hpp"
63 #include "memory/generationSpec.hpp"
64 #include "memory/iterator.hpp"
65 #include "memory/referenceProcessor.hpp"
66 #include "oops/oop.inline.hpp"
67 #include "oops/oop.pcgc.inline.hpp"
68 #include "runtime/atomic.inline.hpp"
69 #include "runtime/orderAccess.inline.hpp"
70 #include "runtime/vmThread.hpp"
71 #include "utilities/globalDefinitions.hpp"
72
73 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;
74
75 // turn it on so that the contents of the young list (scan-only /
76 // to-be-collected) are printed at "strategic" points before / during
77 // / after the collection --- this is useful for debugging
78 #define YOUNG_LIST_VERBOSE 0
79 // CURRENT STATUS
80 // This file is under construction. Search for "FIXME".
81
82 // INVARIANTS/NOTES
83 //
84 // All allocation activity covered by the G1CollectedHeap interface is
85 // serialized by acquiring the HeapLock. This happens in mem_allocate
86 // and allocate_new_tlab, which are the "entry" points to the
87 // allocation code from the rest of the JVM. (Note that this does not
88 // apply to TLAB allocation, which is not part of this interface: it
89 // is done by clients of this interface.)
90
91 // Notes on implementation of parallelism in different tasks.
92 //
93 // G1ParVerifyTask uses heap_region_par_iterate_chunked() for parallelism.
94 // The number of GC workers is passed to heap_region_par_iterate_chunked().
95 // It does use run_task() which sets _n_workers in the task.
96 // G1ParTask executes g1_process_roots() ->
97 // SharedHeap::process_roots() which calls eventually to
98 // CardTableModRefBS::par_non_clean_card_iterate_work() which uses
99 // SequentialSubTasksDone. SharedHeap::process_roots() also
100 // directly uses SubTasksDone (_process_strong_tasks field in SharedHeap).
101 //
102
103 // Local to this file.
104
105 class RefineCardTableEntryClosure: public CardTableEntryClosure {
106 bool _concurrent;
107 public:
108 RefineCardTableEntryClosure() : _concurrent(true) { }
109
110 bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
111 bool oops_into_cset = G1CollectedHeap::heap()->g1_rem_set()->refine_card(card_ptr, worker_i, false);
112 // This path is executed by the concurrent refine or mutator threads,
113 // concurrently, and so we do not care if card_ptr contains references
114 // that point into the collection set.
115 assert(!oops_into_cset, "should be");
116
117 if (_concurrent && SuspendibleThreadSet::should_yield()) {
118 // Caller will actually yield.
119 return false;
120 }
121 // Otherwise, we finished successfully; return true.
122 return true;
123 }
124
125 void set_concurrent(bool b) { _concurrent = b; }
126 };
127
128
129 class ClearLoggedCardTableEntryClosure: public CardTableEntryClosure {
130 size_t _num_processed;
131 CardTableModRefBS* _ctbs;
132 int _histo[256];
133
134 public:
135 ClearLoggedCardTableEntryClosure() :
136 _num_processed(0), _ctbs(G1CollectedHeap::heap()->g1_barrier_set())
137 {
138 for (int i = 0; i < 256; i++) _histo[i] = 0;
139 }
140
141 bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
142 unsigned char* ujb = (unsigned char*)card_ptr;
143 int ind = (int)(*ujb);
144 _histo[ind]++;
145
146 *card_ptr = (jbyte)CardTableModRefBS::clean_card_val();
147 _num_processed++;
148
149 return true;
150 }
151
152 size_t num_processed() { return _num_processed; }
153
154 void print_histo() {
155 gclog_or_tty->print_cr("Card table value histogram:");
156 for (int i = 0; i < 256; i++) {
157 if (_histo[i] != 0) {
158 gclog_or_tty->print_cr(" %d: %d", i, _histo[i]);
159 }
160 }
161 }
162 };
163
164 class RedirtyLoggedCardTableEntryClosure : public CardTableEntryClosure {
165 private:
166 size_t _num_processed;
167
168 public:
169 RedirtyLoggedCardTableEntryClosure() : CardTableEntryClosure(), _num_processed(0) { }
170
171 bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
172 *card_ptr = CardTableModRefBS::dirty_card_val();
173 _num_processed++;
174 return true;
175 }
176
177 size_t num_processed() const { return _num_processed; }
178 };
179
180 YoungList::YoungList(G1CollectedHeap* g1h) :
181 _g1h(g1h), _head(NULL), _length(0), _last_sampled_rs_lengths(0),
182 _survivor_head(NULL), _survivor_tail(NULL), _survivor_length(0) {
183 guarantee(check_list_empty(false), "just making sure...");
184 }
185
186 void YoungList::push_region(HeapRegion *hr) {
187 assert(!hr->is_young(), "should not already be young");
188 assert(hr->get_next_young_region() == NULL, "cause it should!");
189
190 hr->set_next_young_region(_head);
191 _head = hr;
192
193 _g1h->g1_policy()->set_region_eden(hr, (int) _length);
194 ++_length;
195 }
196
197 void YoungList::add_survivor_region(HeapRegion* hr) {
198 assert(hr->is_survivor(), "should be flagged as survivor region");
199 assert(hr->get_next_young_region() == NULL, "cause it should!");
200
201 hr->set_next_young_region(_survivor_head);
202 if (_survivor_head == NULL) {
203 _survivor_tail = hr;
204 }
205 _survivor_head = hr;
206 ++_survivor_length;
207 }
208
209 void YoungList::empty_list(HeapRegion* list) {
210 while (list != NULL) {
211 HeapRegion* next = list->get_next_young_region();
212 list->set_next_young_region(NULL);
213 list->uninstall_surv_rate_group();
214 // This is called before a Full GC and all the non-empty /
215 // non-humongous regions at the end of the Full GC will end up as
216 // old anyway.
217 list->set_old();
218 list = next;
219 }
220 }
221
222 void YoungList::empty_list() {
223 assert(check_list_well_formed(), "young list should be well formed");
224
225 empty_list(_head);
226 _head = NULL;
227 _length = 0;
228
229 empty_list(_survivor_head);
230 _survivor_head = NULL;
231 _survivor_tail = NULL;
232 _survivor_length = 0;
233
234 _last_sampled_rs_lengths = 0;
235
236 assert(check_list_empty(false), "just making sure...");
237 }
238
239 bool YoungList::check_list_well_formed() {
240 bool ret = true;
241
242 uint length = 0;
243 HeapRegion* curr = _head;
244 HeapRegion* last = NULL;
245 while (curr != NULL) {
246 if (!curr->is_young()) {
247 gclog_or_tty->print_cr("### YOUNG REGION "PTR_FORMAT"-"PTR_FORMAT" "
248 "incorrectly tagged (y: %d, surv: %d)",
249 curr->bottom(), curr->end(),
250 curr->is_young(), curr->is_survivor());
251 ret = false;
252 }
253 ++length;
254 last = curr;
255 curr = curr->get_next_young_region();
256 }
257 ret = ret && (length == _length);
258
259 if (!ret) {
260 gclog_or_tty->print_cr("### YOUNG LIST seems not well formed!");
261 gclog_or_tty->print_cr("### list has %u entries, _length is %u",
262 length, _length);
263 }
264
265 return ret;
266 }
267
268 bool YoungList::check_list_empty(bool check_sample) {
269 bool ret = true;
270
271 if (_length != 0) {
272 gclog_or_tty->print_cr("### YOUNG LIST should have 0 length, not %u",
273 _length);
274 ret = false;
275 }
276 if (check_sample && _last_sampled_rs_lengths != 0) {
277 gclog_or_tty->print_cr("### YOUNG LIST has non-zero last sampled RS lengths");
278 ret = false;
279 }
280 if (_head != NULL) {
281 gclog_or_tty->print_cr("### YOUNG LIST does not have a NULL head");
282 ret = false;
283 }
284 if (!ret) {
285 gclog_or_tty->print_cr("### YOUNG LIST does not seem empty");
286 }
287
288 return ret;
289 }
290
291 void
292 YoungList::rs_length_sampling_init() {
293 _sampled_rs_lengths = 0;
294 _curr = _head;
295 }
296
297 bool
298 YoungList::rs_length_sampling_more() {
299 return _curr != NULL;
300 }
301
302 void
303 YoungList::rs_length_sampling_next() {
304 assert( _curr != NULL, "invariant" );
305 size_t rs_length = _curr->rem_set()->occupied();
306
307 _sampled_rs_lengths += rs_length;
308
309 // The current region may not yet have been added to the
310 // incremental collection set (it gets added when it is
311 // retired as the current allocation region).
312 if (_curr->in_collection_set()) {
313 // Update the collection set policy information for this region
314 _g1h->g1_policy()->update_incremental_cset_info(_curr, rs_length);
315 }
316
317 _curr = _curr->get_next_young_region();
318 if (_curr == NULL) {
319 _last_sampled_rs_lengths = _sampled_rs_lengths;
320 // gclog_or_tty->print_cr("last sampled RS lengths = %d", _last_sampled_rs_lengths);
321 }
322 }
323
324 void
325 YoungList::reset_auxilary_lists() {
326 guarantee( is_empty(), "young list should be empty" );
327 assert(check_list_well_formed(), "young list should be well formed");
328
329 // Add survivor regions to SurvRateGroup.
330 _g1h->g1_policy()->note_start_adding_survivor_regions();
331 _g1h->g1_policy()->finished_recalculating_age_indexes(true /* is_survivors */);
332
333 int young_index_in_cset = 0;
334 for (HeapRegion* curr = _survivor_head;
335 curr != NULL;
336 curr = curr->get_next_young_region()) {
337 _g1h->g1_policy()->set_region_survivor(curr, young_index_in_cset);
338
339 // The region is a non-empty survivor so let's add it to
340 // the incremental collection set for the next evacuation
341 // pause.
342 _g1h->g1_policy()->add_region_to_incremental_cset_rhs(curr);
343 young_index_in_cset += 1;
344 }
345 assert((uint) young_index_in_cset == _survivor_length, "post-condition");
346 _g1h->g1_policy()->note_stop_adding_survivor_regions();
347
348 _head = _survivor_head;
349 _length = _survivor_length;
350 if (_survivor_head != NULL) {
351 assert(_survivor_tail != NULL, "cause it shouldn't be");
352 assert(_survivor_length > 0, "invariant");
353 _survivor_tail->set_next_young_region(NULL);
354 }
355
356 // Don't clear the survivor list handles until the start of
357 // the next evacuation pause - we need it in order to re-tag
358 // the survivor regions from this evacuation pause as 'young'
359 // at the start of the next.
360
361 _g1h->g1_policy()->finished_recalculating_age_indexes(false /* is_survivors */);
362
363 assert(check_list_well_formed(), "young list should be well formed");
364 }
365
366 void YoungList::print() {
367 HeapRegion* lists[] = {_head, _survivor_head};
368 const char* names[] = {"YOUNG", "SURVIVOR"};
369
370 for (unsigned int list = 0; list < ARRAY_SIZE(lists); ++list) {
371 gclog_or_tty->print_cr("%s LIST CONTENTS", names[list]);
372 HeapRegion *curr = lists[list];
373 if (curr == NULL)
374 gclog_or_tty->print_cr(" empty");
375 while (curr != NULL) {
376 gclog_or_tty->print_cr(" "HR_FORMAT", P: "PTR_FORMAT ", N: "PTR_FORMAT", age: %4d",
377 HR_FORMAT_PARAMS(curr),
378 curr->prev_top_at_mark_start(),
379 curr->next_top_at_mark_start(),
380 curr->age_in_surv_rate_group_cond());
381 curr = curr->get_next_young_region();
382 }
383 }
384
385 gclog_or_tty->cr();
386 }
387
388 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) {
389 OtherRegionsTable::invalidate(start_idx, num_regions);
390 }
391
392 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions) {
393 reset_from_card_cache(start_idx, num_regions);
394 }
395
396 void G1CollectedHeap::push_dirty_cards_region(HeapRegion* hr)
397 {
398 // Claim the right to put the region on the dirty cards region list
399 // by installing a self pointer.
400 HeapRegion* next = hr->get_next_dirty_cards_region();
401 if (next == NULL) {
402 HeapRegion* res = (HeapRegion*)
403 Atomic::cmpxchg_ptr(hr, hr->next_dirty_cards_region_addr(),
404 NULL);
405 if (res == NULL) {
406 HeapRegion* head;
407 do {
408 // Put the region to the dirty cards region list.
409 head = _dirty_cards_region_list;
410 next = (HeapRegion*)
411 Atomic::cmpxchg_ptr(hr, &_dirty_cards_region_list, head);
412 if (next == head) {
413 assert(hr->get_next_dirty_cards_region() == hr,
414 "hr->get_next_dirty_cards_region() != hr");
415 if (next == NULL) {
416 // The last region in the list points to itself.
417 hr->set_next_dirty_cards_region(hr);
418 } else {
419 hr->set_next_dirty_cards_region(next);
420 }
421 }
422 } while (next != head);
423 }
424 }
425 }
426
427 HeapRegion* G1CollectedHeap::pop_dirty_cards_region()
428 {
429 HeapRegion* head;
430 HeapRegion* hr;
431 do {
432 head = _dirty_cards_region_list;
433 if (head == NULL) {
434 return NULL;
435 }
436 HeapRegion* new_head = head->get_next_dirty_cards_region();
437 if (head == new_head) {
438 // The last region.
439 new_head = NULL;
440 }
441 hr = (HeapRegion*)Atomic::cmpxchg_ptr(new_head, &_dirty_cards_region_list,
442 head);
443 } while (hr != head);
444 assert(hr != NULL, "invariant");
445 hr->set_next_dirty_cards_region(NULL);
446 return hr;
447 }
448
449 #ifdef ASSERT
450 // A region is added to the collection set as it is retired
451 // so an address p can point to a region which will be in the
452 // collection set but has not yet been retired. This method
453 // therefore is only accurate during a GC pause after all
454 // regions have been retired. It is used for debugging
455 // to check if an nmethod has references to objects that can
456 // be move during a partial collection. Though it can be
457 // inaccurate, it is sufficient for G1 because the conservative
458 // implementation of is_scavengable() for G1 will indicate that
459 // all nmethods must be scanned during a partial collection.
460 bool G1CollectedHeap::is_in_partial_collection(const void* p) {
461 if (p == NULL) {
462 return false;
463 }
464 return heap_region_containing(p)->in_collection_set();
465 }
466 #endif
467
468 // Returns true if the reference points to an object that
469 // can move in an incremental collection.
470 bool G1CollectedHeap::is_scavengable(const void* p) {
471 HeapRegion* hr = heap_region_containing(p);
472 return !hr->is_humongous();
473 }
474
475 void G1CollectedHeap::check_ct_logs_at_safepoint() {
476 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
477 CardTableModRefBS* ct_bs = g1_barrier_set();
478
479 // Count the dirty cards at the start.
480 CountNonCleanMemRegionClosure count1(this);
481 ct_bs->mod_card_iterate(&count1);
482 int orig_count = count1.n();
483
484 // First clear the logged cards.
485 ClearLoggedCardTableEntryClosure clear;
486 dcqs.apply_closure_to_all_completed_buffers(&clear);
487 dcqs.iterate_closure_all_threads(&clear, 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 dcqs.apply_closure_to_all_completed_buffers(&redirty);
501 dcqs.iterate_closure_all_threads(&redirty, false);
502 gclog_or_tty->print_cr("Log entries = %d, dirty cards = %d.",
503 clear.num_processed(), orig_count);
504 guarantee(redirty.num_processed() == clear.num_processed(),
505 err_msg("Redirtied "SIZE_FORMAT" cards, bug cleared "SIZE_FORMAT,
506 redirty.num_processed(), clear.num_processed()));
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
517 // Private class members.
518
519 G1CollectedHeap* G1CollectedHeap::_g1h;
520
521 // Private methods.
522
523 HeapRegion*
524 G1CollectedHeap::new_region_try_secondary_free_list(bool is_old) {
525 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
526 while (!_secondary_free_list.is_empty() || free_regions_coming()) {
527 if (!_secondary_free_list.is_empty()) {
528 if (G1ConcRegionFreeingVerbose) {
529 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
530 "secondary_free_list has %u entries",
531 _secondary_free_list.length());
532 }
533 // It looks as if there are free regions available on the
534 // secondary_free_list. Let's move them to the free_list and try
535 // again to allocate from it.
536 append_secondary_free_list();
537
538 assert(_hrm.num_free_regions() > 0, "if the secondary_free_list was not "
539 "empty we should have moved at least one entry to the free_list");
540 HeapRegion* res = _hrm.allocate_free_region(is_old);
541 if (G1ConcRegionFreeingVerbose) {
542 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
543 "allocated "HR_FORMAT" from secondary_free_list",
544 HR_FORMAT_PARAMS(res));
545 }
546 return res;
547 }
548
549 // Wait here until we get notified either when (a) there are no
550 // more free regions coming or (b) some regions have been moved on
551 // the secondary_free_list.
552 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
553 }
554
555 if (G1ConcRegionFreeingVerbose) {
556 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
557 "could not allocate from secondary_free_list");
558 }
559 return NULL;
560 }
561
562 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) {
563 assert(!is_humongous(word_size) || word_size <= HeapRegion::GrainWords,
564 "the only time we use this to allocate a humongous region is "
565 "when we are allocating a single humongous region");
566
567 HeapRegion* res;
568 if (G1StressConcRegionFreeing) {
569 if (!_secondary_free_list.is_empty()) {
570 if (G1ConcRegionFreeingVerbose) {
571 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
572 "forced to look at the secondary_free_list");
573 }
574 res = new_region_try_secondary_free_list(is_old);
575 if (res != NULL) {
576 return res;
577 }
578 }
579 }
580
581 res = _hrm.allocate_free_region(is_old);
582
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(is_old);
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.
606 // In either case allocate_free_region() will check for NULL.
607 res = _hrm.allocate_free_region(is_old);
608 } else {
609 _expand_heap_after_alloc_failure = false;
610 }
611 }
612 return res;
613 }
614
615 HeapWord*
616 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first,
617 uint num_regions,
618 size_t word_size,
619 AllocationContext_t context) {
620 assert(first != G1_NO_HRM_INDEX, "pre-condition");
621 assert(is_humongous(word_size), "word_size should be humongous");
622 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
623
624 // Index of last region in the series + 1.
625 uint last = first + num_regions;
626
627 // We need to initialize the region(s) we just discovered. This is
628 // a bit tricky given that it can happen concurrently with
629 // refinement threads refining cards on these regions and
630 // potentially wanting to refine the BOT as they are scanning
631 // those cards (this can happen shortly after a cleanup; see CR
632 // 6991377). So we have to set up the region(s) carefully and in
633 // a specific order.
634
635 // The word size sum of all the regions we will allocate.
636 size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords;
637 assert(word_size <= word_size_sum, "sanity");
638
639 // This will be the "starts humongous" region.
640 HeapRegion* first_hr = region_at(first);
641 // The header of the new object will be placed at the bottom of
642 // the first region.
643 HeapWord* new_obj = first_hr->bottom();
644 // This will be the new end of the first region in the series that
645 // should also match the end of the last region in the series.
646 HeapWord* new_end = new_obj + word_size_sum;
647 // This will be the new top of the first region that will reflect
648 // this allocation.
649 HeapWord* new_top = new_obj + word_size;
650
651 // First, we need to zero the header of the space that we will be
652 // allocating. When we update top further down, some refinement
653 // threads might try to scan the region. By zeroing the header we
654 // ensure that any thread that will try to scan the region will
655 // come across the zero klass word and bail out.
656 //
657 // NOTE: It would not have been correct to have used
658 // CollectedHeap::fill_with_object() and make the space look like
659 // an int array. The thread that is doing the allocation will
660 // later update the object header to a potentially different array
661 // type and, for a very short period of time, the klass and length
662 // fields will be inconsistent. This could cause a refinement
663 // thread to calculate the object size incorrectly.
664 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
665
666 // We will set up the first region as "starts humongous". This
667 // will also update the BOT covering all the regions to reflect
668 // that there is a single object that starts at the bottom of the
669 // first region.
670 first_hr->set_starts_humongous(new_top, new_end);
671 first_hr->set_allocation_context(context);
672 // Then, if there are any, we will set up the "continues
673 // humongous" regions.
674 HeapRegion* hr = NULL;
675 for (uint i = first + 1; i < last; ++i) {
676 hr = region_at(i);
677 hr->set_continues_humongous(first_hr);
678 hr->set_allocation_context(context);
679 }
680 // If we have "continues humongous" regions (hr != NULL), then the
681 // end of the last one should match new_end.
682 assert(hr == NULL || hr->end() == new_end, "sanity");
683
684 // Up to this point no concurrent thread would have been able to
685 // do any scanning on any region in this series. All the top
686 // fields still point to bottom, so the intersection between
687 // [bottom,top] and [card_start,card_end] will be empty. Before we
688 // update the top fields, we'll do a storestore to make sure that
689 // no thread sees the update to top before the zeroing of the
690 // object header and the BOT initialization.
691 OrderAccess::storestore();
692
693 // Now that the BOT and the object header have been initialized,
694 // we can update top of the "starts humongous" region.
695 assert(first_hr->bottom() < new_top && new_top <= first_hr->end(),
696 "new_top should be in this region");
697 first_hr->set_top(new_top);
698 if (_hr_printer.is_active()) {
699 HeapWord* bottom = first_hr->bottom();
700 HeapWord* end = first_hr->orig_end();
701 if ((first + 1) == last) {
702 // the series has a single humongous region
703 _hr_printer.alloc(G1HRPrinter::SingleHumongous, first_hr, new_top);
704 } else {
705 // the series has more than one humongous regions
706 _hr_printer.alloc(G1HRPrinter::StartsHumongous, first_hr, end);
707 }
708 }
709
710 // Now, we will update the top fields of the "continues humongous"
711 // regions. The reason we need to do this is that, otherwise,
712 // these regions would look empty and this will confuse parts of
713 // G1. For example, the code that looks for a consecutive number
714 // of empty regions will consider them empty and try to
715 // re-allocate them. We can extend is_empty() to also include
716 // !is_continues_humongous(), but it is easier to just update the top
717 // fields here. The way we set top for all regions (i.e., top ==
718 // end for all regions but the last one, top == new_top for the
719 // last one) is actually used when we will free up the humongous
720 // region in free_humongous_region().
721 hr = NULL;
722 for (uint i = first + 1; i < last; ++i) {
723 hr = region_at(i);
724 if ((i + 1) == last) {
725 // last continues humongous region
726 assert(hr->bottom() < new_top && new_top <= hr->end(),
727 "new_top should fall on this region");
728 hr->set_top(new_top);
729 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, new_top);
730 } else {
731 // not last one
732 assert(new_top > hr->end(), "new_top should be above this region");
733 hr->set_top(hr->end());
734 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, hr->end());
735 }
736 }
737 // If we have continues humongous regions (hr != NULL), then the
738 // end of the last one should match new_end and its top should
739 // match new_top.
740 assert(hr == NULL ||
741 (hr->end() == new_end && hr->top() == new_top), "sanity");
742 check_bitmaps("Humongous Region Allocation", first_hr);
743
744 assert(first_hr->used() == word_size * HeapWordSize, "invariant");
745 _allocator->increase_used(first_hr->used());
746 _humongous_set.add(first_hr);
747
748 return new_obj;
749 }
750
751 // If could fit into free regions w/o expansion, try.
752 // Otherwise, if can expand, do so.
753 // Otherwise, if using ex regions might help, try with ex given back.
754 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size, AllocationContext_t context) {
755 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
756
757 verify_region_sets_optional();
758
759 uint first = G1_NO_HRM_INDEX;
760 uint obj_regions = (uint)(align_size_up_(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords);
761
762 if (obj_regions == 1) {
763 // Only one region to allocate, try to use a fast path by directly allocating
764 // from the free lists. Do not try to expand here, we will potentially do that
765 // later.
766 HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */);
767 if (hr != NULL) {
768 first = hr->hrm_index();
769 }
770 } else {
771 // We can't allocate humongous regions spanning more than one region while
772 // cleanupComplete() is running, since some of the regions we find to be
773 // empty might not yet be added to the free list. It is not straightforward
774 // to know in which list they are on so that we can remove them. We only
775 // need to do this if we need to allocate more than one region to satisfy the
776 // current humongous allocation request. If we are only allocating one region
777 // we use the one-region region allocation code (see above), that already
778 // potentially waits for regions from the secondary free list.
779 wait_while_free_regions_coming();
780 append_secondary_free_list_if_not_empty_with_lock();
781
782 // Policy: Try only empty regions (i.e. already committed first). Maybe we
783 // are lucky enough to find some.
784 first = _hrm.find_contiguous_only_empty(obj_regions);
785 if (first != G1_NO_HRM_INDEX) {
786 _hrm.allocate_free_regions_starting_at(first, obj_regions);
787 }
788 }
789
790 if (first == G1_NO_HRM_INDEX) {
791 // Policy: We could not find enough regions for the humongous object in the
792 // free list. Look through the heap to find a mix of free and uncommitted regions.
793 // If so, try expansion.
794 first = _hrm.find_contiguous_empty_or_unavailable(obj_regions);
795 if (first != G1_NO_HRM_INDEX) {
796 // We found something. Make sure these regions are committed, i.e. expand
797 // the heap. Alternatively we could do a defragmentation GC.
798 ergo_verbose1(ErgoHeapSizing,
799 "attempt heap expansion",
800 ergo_format_reason("humongous allocation request failed")
801 ergo_format_byte("allocation request"),
802 word_size * HeapWordSize);
803
804 _hrm.expand_at(first, obj_regions);
805 g1_policy()->record_new_heap_size(num_regions());
806
807 #ifdef ASSERT
808 for (uint i = first; i < first + obj_regions; ++i) {
809 HeapRegion* hr = region_at(i);
810 assert(hr->is_free(), "sanity");
811 assert(hr->is_empty(), "sanity");
812 assert(is_on_master_free_list(hr), "sanity");
813 }
814 #endif
815 _hrm.allocate_free_regions_starting_at(first, obj_regions);
816 } else {
817 // Policy: Potentially trigger a defragmentation GC.
818 }
819 }
820
821 HeapWord* result = NULL;
822 if (first != G1_NO_HRM_INDEX) {
823 result = humongous_obj_allocate_initialize_regions(first, obj_regions,
824 word_size, context);
825 assert(result != NULL, "it should always return a valid result");
826
827 // A successful humongous object allocation changes the used space
828 // information of the old generation so we need to recalculate the
829 // sizes and update the jstat counters here.
830 g1mm()->update_sizes();
831 }
832
833 verify_region_sets_optional();
834
835 return result;
836 }
837
838 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) {
839 assert_heap_not_locked_and_not_at_safepoint();
840 assert(!is_humongous(word_size), "we do not allow humongous TLABs");
841
842 unsigned int dummy_gc_count_before;
843 int dummy_gclocker_retry_count = 0;
844 return attempt_allocation(word_size, &dummy_gc_count_before, &dummy_gclocker_retry_count);
845 }
846
847 HeapWord*
848 G1CollectedHeap::mem_allocate(size_t word_size,
849 bool* gc_overhead_limit_was_exceeded) {
850 assert_heap_not_locked_and_not_at_safepoint();
851
852 // Loop until the allocation is satisfied, or unsatisfied after GC.
853 for (int try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
854 unsigned int gc_count_before;
855
856 HeapWord* result = NULL;
857 if (!is_humongous(word_size)) {
858 result = attempt_allocation(word_size, &gc_count_before, &gclocker_retry_count);
859 } else {
860 result = attempt_allocation_humongous(word_size, &gc_count_before, &gclocker_retry_count);
861 }
862 if (result != NULL) {
863 return result;
864 }
865
866 // Create the garbage collection operation...
867 VM_G1CollectForAllocation op(gc_count_before, word_size);
868 op.set_allocation_context(AllocationContext::current());
869
870 // ...and get the VM thread to execute it.
871 VMThread::execute(&op);
872
873 if (op.prologue_succeeded() && op.pause_succeeded()) {
874 // If the operation was successful we'll return the result even
875 // if it is NULL. If the allocation attempt failed immediately
876 // after a Full GC, it's unlikely we'll be able to allocate now.
877 HeapWord* result = op.result();
878 if (result != NULL && !is_humongous(word_size)) {
879 // Allocations that take place on VM operations do not do any
880 // card dirtying and we have to do it here. We only have to do
881 // this for non-humongous allocations, though.
882 dirty_young_block(result, word_size);
883 }
884 return result;
885 } else {
886 if (gclocker_retry_count > GCLockerRetryAllocationCount) {
887 return NULL;
888 }
889 assert(op.result() == NULL,
890 "the result should be NULL if the VM op did not succeed");
891 }
892
893 // Give a warning if we seem to be looping forever.
894 if ((QueuedAllocationWarningCount > 0) &&
895 (try_count % QueuedAllocationWarningCount == 0)) {
896 warning("G1CollectedHeap::mem_allocate retries %d times", try_count);
897 }
898 }
899
900 ShouldNotReachHere();
901 return NULL;
902 }
903
904 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size,
905 AllocationContext_t context,
906 unsigned int *gc_count_before_ret,
907 int* gclocker_retry_count_ret) {
908 // Make sure you read the note in attempt_allocation_humongous().
909
910 assert_heap_not_locked_and_not_at_safepoint();
911 assert(!is_humongous(word_size), "attempt_allocation_slow() should not "
912 "be called for humongous allocation requests");
913
914 // We should only get here after the first-level allocation attempt
915 // (attempt_allocation()) failed to allocate.
916
917 // We will loop until a) we manage to successfully perform the
918 // allocation or b) we successfully schedule a collection which
919 // fails to perform the allocation. b) is the only case when we'll
920 // return NULL.
921 HeapWord* result = NULL;
922 for (int try_count = 1; /* we'll return */; try_count += 1) {
923 bool should_try_gc;
924 unsigned int gc_count_before;
925
926 {
927 MutexLockerEx x(Heap_lock);
928 result = _allocator->mutator_alloc_region(context)->attempt_allocation_locked(word_size,
929 false /* bot_updates */);
930 if (result != NULL) {
931 return result;
932 }
933
934 // If we reach here, attempt_allocation_locked() above failed to
935 // allocate a new region. So the mutator alloc region should be NULL.
936 assert(_allocator->mutator_alloc_region(context)->get() == NULL, "only way to get here");
937
938 if (GC_locker::is_active_and_needs_gc()) {
939 if (g1_policy()->can_expand_young_list()) {
940 // No need for an ergo verbose message here,
941 // can_expand_young_list() does this when it returns true.
942 result = _allocator->mutator_alloc_region(context)->attempt_allocation_force(word_size,
943 false /* bot_updates */);
944 if (result != NULL) {
945 return result;
946 }
947 }
948 should_try_gc = false;
949 } else {
950 // The GCLocker may not be active but the GCLocker initiated
951 // GC may not yet have been performed (GCLocker::needs_gc()
952 // returns true). In this case we do not try this GC and
953 // wait until the GCLocker initiated GC is performed, and
954 // then retry the allocation.
955 if (GC_locker::needs_gc()) {
956 should_try_gc = false;
957 } else {
958 // Read the GC count while still holding the Heap_lock.
959 gc_count_before = total_collections();
960 should_try_gc = true;
961 }
962 }
963 }
964
965 if (should_try_gc) {
966 bool succeeded;
967 result = do_collection_pause(word_size, gc_count_before, &succeeded,
968 GCCause::_g1_inc_collection_pause);
969 if (result != NULL) {
970 assert(succeeded, "only way to get back a non-NULL result");
971 return result;
972 }
973
974 if (succeeded) {
975 // If we get here we successfully scheduled a collection which
976 // failed to allocate. No point in trying to allocate
977 // further. We'll just return NULL.
978 MutexLockerEx x(Heap_lock);
979 *gc_count_before_ret = total_collections();
980 return NULL;
981 }
982 } else {
983 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
984 MutexLockerEx x(Heap_lock);
985 *gc_count_before_ret = total_collections();
986 return NULL;
987 }
988 // The GCLocker is either active or the GCLocker initiated
989 // GC has not yet been performed. Stall until it is and
990 // then retry the allocation.
991 GC_locker::stall_until_clear();
992 (*gclocker_retry_count_ret) += 1;
993 }
994
995 // We can reach here if we were unsuccessful in scheduling a
996 // collection (because another thread beat us to it) or if we were
997 // stalled due to the GC locker. In either can we should retry the
998 // allocation attempt in case another thread successfully
999 // performed a collection and reclaimed enough space. We do the
1000 // first attempt (without holding the Heap_lock) here and the
1001 // follow-on attempt will be at the start of the next loop
1002 // iteration (after taking the Heap_lock).
1003 result = _allocator->mutator_alloc_region(context)->attempt_allocation(word_size,
1004 false /* bot_updates */);
1005 if (result != NULL) {
1006 return result;
1007 }
1008
1009 // Give a warning if we seem to be looping forever.
1010 if ((QueuedAllocationWarningCount > 0) &&
1011 (try_count % QueuedAllocationWarningCount == 0)) {
1012 warning("G1CollectedHeap::attempt_allocation_slow() "
1013 "retries %d times", try_count);
1014 }
1015 }
1016
1017 ShouldNotReachHere();
1018 return NULL;
1019 }
1020
1021 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size,
1022 unsigned int * gc_count_before_ret,
1023 int* gclocker_retry_count_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(is_humongous(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, AllocationContext::current());
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 GCCause::_g1_humongous_allocation);
1095 if (result != NULL) {
1096 assert(succeeded, "only way to get back a non-NULL result");
1097 return result;
1098 }
1099
1100 if (succeeded) {
1101 // If we get here we successfully scheduled a collection which
1102 // failed to allocate. No point in trying to allocate
1103 // further. We'll just return NULL.
1104 MutexLockerEx x(Heap_lock);
1105 *gc_count_before_ret = total_collections();
1106 return NULL;
1107 }
1108 } else {
1109 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
1110 MutexLockerEx x(Heap_lock);
1111 *gc_count_before_ret = total_collections();
1112 return NULL;
1113 }
1114 // The GCLocker is either active or the GCLocker initiated
1115 // GC has not yet been performed. Stall until it is and
1116 // then retry the allocation.
1117 GC_locker::stall_until_clear();
1118 (*gclocker_retry_count_ret) += 1;
1119 }
1120
1121 // We can reach here if we were unsuccessful in scheduling a
1122 // collection (because another thread beat us to it) or if we were
1123 // stalled due to the GC locker. In either can we should retry the
1124 // allocation attempt in case another thread successfully
1125 // performed a collection and reclaimed enough space. Give a
1126 // warning if we seem to be looping forever.
1127
1128 if ((QueuedAllocationWarningCount > 0) &&
1129 (try_count % QueuedAllocationWarningCount == 0)) {
1130 warning("G1CollectedHeap::attempt_allocation_humongous() "
1131 "retries %d times", try_count);
1132 }
1133 }
1134
1135 ShouldNotReachHere();
1136 return NULL;
1137 }
1138
1139 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
1140 AllocationContext_t context,
1141 bool expect_null_mutator_alloc_region) {
1142 assert_at_safepoint(true /* should_be_vm_thread */);
1143 assert(_allocator->mutator_alloc_region(context)->get() == NULL ||
1144 !expect_null_mutator_alloc_region,
1145 "the current alloc region was unexpectedly found to be non-NULL");
1146
1147 if (!is_humongous(word_size)) {
1148 return _allocator->mutator_alloc_region(context)->attempt_allocation_locked(word_size,
1149 false /* bot_updates */);
1150 } else {
1151 HeapWord* result = humongous_obj_allocate(word_size, context);
1152 if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) {
1153 g1_policy()->set_initiate_conc_mark_if_possible();
1154 }
1155 return result;
1156 }
1157
1158 ShouldNotReachHere();
1159 }
1160
1161 class PostMCRemSetClearClosure: public HeapRegionClosure {
1162 G1CollectedHeap* _g1h;
1163 ModRefBarrierSet* _mr_bs;
1164 public:
1165 PostMCRemSetClearClosure(G1CollectedHeap* g1h, ModRefBarrierSet* mr_bs) :
1166 _g1h(g1h), _mr_bs(mr_bs) {}
1167
1168 bool doHeapRegion(HeapRegion* r) {
1169 HeapRegionRemSet* hrrs = r->rem_set();
1170
1171 if (r->is_continues_humongous()) {
1172 // We'll assert that the strong code root list and RSet is empty
1173 assert(hrrs->strong_code_roots_list_length() == 0, "sanity");
1174 assert(hrrs->occupied() == 0, "RSet should be empty");
1175 return false;
1176 }
1177
1178 _g1h->reset_gc_time_stamps(r);
1179 hrrs->clear();
1180 // You might think here that we could clear just the cards
1181 // corresponding to the used region. But no: if we leave a dirty card
1182 // in a region we might allocate into, then it would prevent that card
1183 // from being enqueued, and cause it to be missed.
1184 // Re: the performance cost: we shouldn't be doing full GC anyway!
1185 _mr_bs->clear(MemRegion(r->bottom(), r->end()));
1186
1187 return false;
1188 }
1189 };
1190
1191 void G1CollectedHeap::clear_rsets_post_compaction() {
1192 PostMCRemSetClearClosure rs_clear(this, g1_barrier_set());
1193 heap_region_iterate(&rs_clear);
1194 }
1195
1196 class RebuildRSOutOfRegionClosure: public HeapRegionClosure {
1197 G1CollectedHeap* _g1h;
1198 UpdateRSOopClosure _cl;
1199 int _worker_i;
1200 public:
1201 RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, int worker_i = 0) :
1202 _cl(g1->g1_rem_set(), worker_i),
1203 _worker_i(worker_i),
1204 _g1h(g1)
1205 { }
1206
1207 bool doHeapRegion(HeapRegion* r) {
1208 if (!r->is_continues_humongous()) {
1209 _cl.set_from(r);
1210 r->oop_iterate(&_cl);
1211 }
1212 return false;
1213 }
1214 };
1215
1216 class ParRebuildRSTask: public AbstractGangTask {
1217 G1CollectedHeap* _g1;
1218 public:
1219 ParRebuildRSTask(G1CollectedHeap* g1)
1220 : AbstractGangTask("ParRebuildRSTask"),
1221 _g1(g1)
1222 { }
1223
1224 void work(uint worker_id) {
1225 RebuildRSOutOfRegionClosure rebuild_rs(_g1, worker_id);
1226 _g1->heap_region_par_iterate_chunked(&rebuild_rs, worker_id,
1227 _g1->workers()->active_workers(),
1228 HeapRegion::RebuildRSClaimValue);
1229 }
1230 };
1231
1232 class PostCompactionPrinterClosure: public HeapRegionClosure {
1233 private:
1234 G1HRPrinter* _hr_printer;
1235 public:
1236 bool doHeapRegion(HeapRegion* hr) {
1237 assert(!hr->is_young(), "not expecting to find young regions");
1238 if (hr->is_free()) {
1239 // We only generate output for non-empty regions.
1240 } else if (hr->is_starts_humongous()) {
1241 if (hr->region_num() == 1) {
1242 // single humongous region
1243 _hr_printer->post_compaction(hr, G1HRPrinter::SingleHumongous);
1244 } else {
1245 _hr_printer->post_compaction(hr, G1HRPrinter::StartsHumongous);
1246 }
1247 } else if (hr->is_continues_humongous()) {
1248 _hr_printer->post_compaction(hr, G1HRPrinter::ContinuesHumongous);
1249 } else if (hr->is_old()) {
1250 _hr_printer->post_compaction(hr, G1HRPrinter::Old);
1251 } else {
1252 ShouldNotReachHere();
1253 }
1254 return false;
1255 }
1256
1257 PostCompactionPrinterClosure(G1HRPrinter* hr_printer)
1258 : _hr_printer(hr_printer) { }
1259 };
1260
1261 void G1CollectedHeap::print_hrm_post_compaction() {
1262 PostCompactionPrinterClosure cl(hr_printer());
1263 heap_region_iterate(&cl);
1264 }
1265
1266 bool G1CollectedHeap::do_collection(bool explicit_gc,
1267 bool clear_all_soft_refs,
1268 size_t word_size) {
1269 assert_at_safepoint(true /* should_be_vm_thread */);
1270
1271 if (GC_locker::check_active_before_gc()) {
1272 return false;
1273 }
1274
1275 STWGCTimer* gc_timer = G1MarkSweep::gc_timer();
1276 gc_timer->register_gc_start();
1277
1278 SerialOldTracer* gc_tracer = G1MarkSweep::gc_tracer();
1279 gc_tracer->report_gc_start(gc_cause(), gc_timer->gc_start());
1280
1281 SvcGCMarker sgcm(SvcGCMarker::FULL);
1282 ResourceMark rm;
1283
1284 print_heap_before_gc();
1285 trace_heap_before_gc(gc_tracer);
1286
1287 size_t metadata_prev_used = MetaspaceAux::used_bytes();
1288
1289 verify_region_sets_optional();
1290
1291 const bool do_clear_all_soft_refs = clear_all_soft_refs ||
1292 collector_policy()->should_clear_all_soft_refs();
1293
1294 ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy());
1295
1296 {
1297 IsGCActiveMark x;
1298
1299 // Timing
1300 assert(gc_cause() != GCCause::_java_lang_system_gc || explicit_gc, "invariant");
1301 gclog_or_tty->date_stamp(G1Log::fine() && PrintGCDateStamps);
1302 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
1303
1304 {
1305 GCTraceTime t(GCCauseString("Full GC", gc_cause()), G1Log::fine(), true, NULL, gc_tracer->gc_id());
1306 TraceCollectorStats tcs(g1mm()->full_collection_counters());
1307 TraceMemoryManagerStats tms(true /* fullGC */, gc_cause());
1308
1309 double start = os::elapsedTime();
1310 g1_policy()->record_full_collection_start();
1311
1312 // Note: When we have a more flexible GC logging framework that
1313 // allows us to add optional attributes to a GC log record we
1314 // could consider timing and reporting how long we wait in the
1315 // following two methods.
1316 wait_while_free_regions_coming();
1317 // If we start the compaction before the CM threads finish
1318 // scanning the root regions we might trip them over as we'll
1319 // be moving objects / updating references. So let's wait until
1320 // they are done. By telling them to abort, they should complete
1321 // early.
1322 _cm->root_regions()->abort();
1323 _cm->root_regions()->wait_until_scan_finished();
1324 append_secondary_free_list_if_not_empty_with_lock();
1325
1326 gc_prologue(true);
1327 increment_total_collections(true /* full gc */);
1328 increment_old_marking_cycles_started();
1329
1330 assert(used() == recalculate_used(), "Should be equal");
1331
1332 verify_before_gc();
1333
1334 check_bitmaps("Full GC Start");
1335 pre_full_gc_dump(gc_timer);
1336
1337 COMPILER2_PRESENT(DerivedPointerTable::clear());
1338
1339 // Disable discovery and empty the discovered lists
1340 // for the CM ref processor.
1341 ref_processor_cm()->disable_discovery();
1342 ref_processor_cm()->abandon_partial_discovery();
1343 ref_processor_cm()->verify_no_references_recorded();
1344
1345 // Abandon current iterations of concurrent marking and concurrent
1346 // refinement, if any are in progress. We have to do this before
1347 // wait_until_scan_finished() below.
1348 concurrent_mark()->abort();
1349
1350 // Make sure we'll choose a new allocation region afterwards.
1351 _allocator->release_mutator_alloc_region();
1352 _allocator->abandon_gc_alloc_regions();
1353 g1_rem_set()->cleanupHRRS();
1354
1355 // We should call this after we retire any currently active alloc
1356 // regions so that all the ALLOC / RETIRE events are generated
1357 // before the start GC event.
1358 _hr_printer.start_gc(true /* full */, (size_t) total_collections());
1359
1360 // We may have added regions to the current incremental collection
1361 // set between the last GC or pause and now. We need to clear the
1362 // incremental collection set and then start rebuilding it afresh
1363 // after this full GC.
1364 abandon_collection_set(g1_policy()->inc_cset_head());
1365 g1_policy()->clear_incremental_cset();
1366 g1_policy()->stop_incremental_cset_building();
1367
1368 tear_down_region_sets(false /* free_list_only */);
1369 g1_policy()->set_gcs_are_young(true);
1370
1371 // See the comments in g1CollectedHeap.hpp and
1372 // G1CollectedHeap::ref_processing_init() about
1373 // how reference processing currently works in G1.
1374
1375 // Temporarily make discovery by the STW ref processor single threaded (non-MT).
1376 ReferenceProcessorMTDiscoveryMutator stw_rp_disc_ser(ref_processor_stw(), false);
1377
1378 // Temporarily clear the STW ref processor's _is_alive_non_header field.
1379 ReferenceProcessorIsAliveMutator stw_rp_is_alive_null(ref_processor_stw(), NULL);
1380
1381 ref_processor_stw()->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/);
1382 ref_processor_stw()->setup_policy(do_clear_all_soft_refs);
1383
1384 // Do collection work
1385 {
1386 HandleMark hm; // Discard invalid handles created during gc
1387 G1MarkSweep::invoke_at_safepoint(ref_processor_stw(), do_clear_all_soft_refs);
1388 }
1389
1390 assert(num_free_regions() == 0, "we should not have added any free regions");
1391 rebuild_region_sets(false /* free_list_only */);
1392
1393 // Enqueue any discovered reference objects that have
1394 // not been removed from the discovered lists.
1395 ref_processor_stw()->enqueue_discovered_references();
1396
1397 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
1398
1399 MemoryService::track_memory_usage();
1400
1401 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
1402 ref_processor_stw()->verify_no_references_recorded();
1403
1404 // Delete metaspaces for unloaded class loaders and clean up loader_data graph
1405 ClassLoaderDataGraph::purge();
1406 MetaspaceAux::verify_metrics();
1407
1408 // Note: since we've just done a full GC, concurrent
1409 // marking is no longer active. Therefore we need not
1410 // re-enable reference discovery for the CM ref processor.
1411 // That will be done at the start of the next marking cycle.
1412 assert(!ref_processor_cm()->discovery_enabled(), "Postcondition");
1413 ref_processor_cm()->verify_no_references_recorded();
1414
1415 reset_gc_time_stamp();
1416 // Since everything potentially moved, we will clear all remembered
1417 // sets, and clear all cards. Later we will rebuild remembered
1418 // sets. We will also reset the GC time stamps of the regions.
1419 clear_rsets_post_compaction();
1420 check_gc_time_stamps();
1421
1422 // Resize the heap if necessary.
1423 resize_if_necessary_after_full_collection(explicit_gc ? 0 : word_size);
1424
1425 if (_hr_printer.is_active()) {
1426 // We should do this after we potentially resize the heap so
1427 // that all the COMMIT / UNCOMMIT events are generated before
1428 // the end GC event.
1429
1430 print_hrm_post_compaction();
1431 _hr_printer.end_gc(true /* full */, (size_t) total_collections());
1432 }
1433
1434 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
1435 if (hot_card_cache->use_cache()) {
1436 hot_card_cache->reset_card_counts();
1437 hot_card_cache->reset_hot_cache();
1438 }
1439
1440 // Rebuild remembered sets of all regions.
1441 if (G1CollectedHeap::use_parallel_gc_threads()) {
1442 uint n_workers =
1443 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
1444 workers()->active_workers(),
1445 Threads::number_of_non_daemon_threads());
1446 assert(UseDynamicNumberOfGCThreads ||
1447 n_workers == workers()->total_workers(),
1448 "If not dynamic should be using all the workers");
1449 workers()->set_active_workers(n_workers);
1450 // Set parallel threads in the heap (_n_par_threads) only
1451 // before a parallel phase and always reset it to 0 after
1452 // the phase so that the number of parallel threads does
1453 // no get carried forward to a serial phase where there
1454 // may be code that is "possibly_parallel".
1455 set_par_threads(n_workers);
1456
1457 ParRebuildRSTask rebuild_rs_task(this);
1458 assert(check_heap_region_claim_values(
1459 HeapRegion::InitialClaimValue), "sanity check");
1460 assert(UseDynamicNumberOfGCThreads ||
1461 workers()->active_workers() == workers()->total_workers(),
1462 "Unless dynamic should use total workers");
1463 // Use the most recent number of active workers
1464 assert(workers()->active_workers() > 0,
1465 "Active workers not properly set");
1466 set_par_threads(workers()->active_workers());
1467 workers()->run_task(&rebuild_rs_task);
1468 set_par_threads(0);
1469 assert(check_heap_region_claim_values(
1470 HeapRegion::RebuildRSClaimValue), "sanity check");
1471 reset_heap_region_claim_values();
1472 } else {
1473 RebuildRSOutOfRegionClosure rebuild_rs(this);
1474 heap_region_iterate(&rebuild_rs);
1475 }
1476
1477 // Rebuild the strong code root lists for each region
1478 rebuild_strong_code_roots();
1479
1480 if (true) { // FIXME
1481 MetaspaceGC::compute_new_size();
1482 }
1483
1484 #ifdef TRACESPINNING
1485 ParallelTaskTerminator::print_termination_counts();
1486 #endif
1487
1488 // Discard all rset updates
1489 JavaThread::dirty_card_queue_set().abandon_logs();
1490 assert(dirty_card_queue_set().completed_buffers_num() == 0, "DCQS should be empty");
1491
1492 _young_list->reset_sampled_info();
1493 // At this point there should be no regions in the
1494 // entire heap tagged as young.
1495 assert(check_young_list_empty(true /* check_heap */),
1496 "young list should be empty at this point");
1497
1498 // Update the number of full collections that have been completed.
1499 increment_old_marking_cycles_completed(false /* concurrent */);
1500
1501 _hrm.verify_optional();
1502 verify_region_sets_optional();
1503
1504 verify_after_gc();
1505
1506 // Clear the previous marking bitmap, if needed for bitmap verification.
1507 // Note we cannot do this when we clear the next marking bitmap in
1508 // ConcurrentMark::abort() above since VerifyDuringGC verifies the
1509 // objects marked during a full GC against the previous bitmap.
1510 // But we need to clear it before calling check_bitmaps below since
1511 // the full GC has compacted objects and updated TAMS but not updated
1512 // the prev bitmap.
1513 if (G1VerifyBitmaps) {
1514 ((CMBitMap*) concurrent_mark()->prevMarkBitMap())->clearAll();
1515 }
1516 check_bitmaps("Full GC End");
1517
1518 // Start a new incremental collection set for the next pause
1519 assert(g1_policy()->collection_set() == NULL, "must be");
1520 g1_policy()->start_incremental_cset_building();
1521
1522 clear_cset_fast_test();
1523
1524 _allocator->init_mutator_alloc_region();
1525
1526 double end = os::elapsedTime();
1527 g1_policy()->record_full_collection_end();
1528
1529 if (G1Log::fine()) {
1530 g1_policy()->print_heap_transition();
1531 }
1532
1533 // We must call G1MonitoringSupport::update_sizes() in the same scoping level
1534 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
1535 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
1536 // before any GC notifications are raised.
1537 g1mm()->update_sizes();
1538
1539 gc_epilogue(true);
1540 }
1541
1542 if (G1Log::finer()) {
1543 g1_policy()->print_detailed_heap_transition(true /* full */);
1544 }
1545
1546 print_heap_after_gc();
1547 trace_heap_after_gc(gc_tracer);
1548
1549 post_full_gc_dump(gc_timer);
1550
1551 gc_timer->register_gc_end();
1552 gc_tracer->report_gc_end(gc_timer->gc_end(), gc_timer->time_partitions());
1553 }
1554
1555 return true;
1556 }
1557
1558 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
1559 // do_collection() will return whether it succeeded in performing
1560 // the GC. Currently, there is no facility on the
1561 // do_full_collection() API to notify the caller than the collection
1562 // did not succeed (e.g., because it was locked out by the GC
1563 // locker). So, right now, we'll ignore the return value.
1564 bool dummy = do_collection(true, /* explicit_gc */
1565 clear_all_soft_refs,
1566 0 /* word_size */);
1567 }
1568
1569 // This code is mostly copied from TenuredGeneration.
1570 void
1571 G1CollectedHeap::
1572 resize_if_necessary_after_full_collection(size_t word_size) {
1573 // Include the current allocation, if any, and bytes that will be
1574 // pre-allocated to support collections, as "used".
1575 const size_t used_after_gc = used();
1576 const size_t capacity_after_gc = capacity();
1577 const size_t free_after_gc = capacity_after_gc - used_after_gc;
1578
1579 // This is enforced in arguments.cpp.
1580 assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
1581 "otherwise the code below doesn't make sense");
1582
1583 // We don't have floating point command-line arguments
1584 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
1585 const double maximum_used_percentage = 1.0 - minimum_free_percentage;
1586 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
1587 const double minimum_used_percentage = 1.0 - maximum_free_percentage;
1588
1589 const size_t min_heap_size = collector_policy()->min_heap_byte_size();
1590 const size_t max_heap_size = collector_policy()->max_heap_byte_size();
1591
1592 // We have to be careful here as these two calculations can overflow
1593 // 32-bit size_t's.
1594 double used_after_gc_d = (double) used_after_gc;
1595 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
1596 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
1597
1598 // Let's make sure that they are both under the max heap size, which
1599 // by default will make them fit into a size_t.
1600 double desired_capacity_upper_bound = (double) max_heap_size;
1601 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
1602 desired_capacity_upper_bound);
1603 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
1604 desired_capacity_upper_bound);
1605
1606 // We can now safely turn them into size_t's.
1607 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
1608 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
1609
1610 // This assert only makes sense here, before we adjust them
1611 // with respect to the min and max heap size.
1612 assert(minimum_desired_capacity <= maximum_desired_capacity,
1613 err_msg("minimum_desired_capacity = "SIZE_FORMAT", "
1614 "maximum_desired_capacity = "SIZE_FORMAT,
1615 minimum_desired_capacity, maximum_desired_capacity));
1616
1617 // Should not be greater than the heap max size. No need to adjust
1618 // it with respect to the heap min size as it's a lower bound (i.e.,
1619 // we'll try to make the capacity larger than it, not smaller).
1620 minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size);
1621 // Should not be less than the heap min size. No need to adjust it
1622 // with respect to the heap max size as it's an upper bound (i.e.,
1623 // we'll try to make the capacity smaller than it, not greater).
1624 maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size);
1625
1626 if (capacity_after_gc < minimum_desired_capacity) {
1627 // Don't expand unless it's significant
1628 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
1629 ergo_verbose4(ErgoHeapSizing,
1630 "attempt heap expansion",
1631 ergo_format_reason("capacity lower than "
1632 "min desired capacity after Full GC")
1633 ergo_format_byte("capacity")
1634 ergo_format_byte("occupancy")
1635 ergo_format_byte_perc("min desired capacity"),
1636 capacity_after_gc, used_after_gc,
1637 minimum_desired_capacity, (double) MinHeapFreeRatio);
1638 expand(expand_bytes);
1639
1640 // No expansion, now see if we want to shrink
1641 } else if (capacity_after_gc > maximum_desired_capacity) {
1642 // Capacity too large, compute shrinking size
1643 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
1644 ergo_verbose4(ErgoHeapSizing,
1645 "attempt heap shrinking",
1646 ergo_format_reason("capacity higher than "
1647 "max desired capacity after Full GC")
1648 ergo_format_byte("capacity")
1649 ergo_format_byte("occupancy")
1650 ergo_format_byte_perc("max desired capacity"),
1651 capacity_after_gc, used_after_gc,
1652 maximum_desired_capacity, (double) MaxHeapFreeRatio);
1653 shrink(shrink_bytes);
1654 }
1655 }
1656
1657
1658 HeapWord*
1659 G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
1660 AllocationContext_t context,
1661 bool* succeeded) {
1662 assert_at_safepoint(true /* should_be_vm_thread */);
1663
1664 *succeeded = true;
1665 // Let's attempt the allocation first.
1666 HeapWord* result =
1667 attempt_allocation_at_safepoint(word_size,
1668 context,
1669 false /* expect_null_mutator_alloc_region */);
1670 if (result != NULL) {
1671 assert(*succeeded, "sanity");
1672 return result;
1673 }
1674
1675 // In a G1 heap, we're supposed to keep allocation from failing by
1676 // incremental pauses. Therefore, at least for now, we'll favor
1677 // expansion over collection. (This might change in the future if we can
1678 // do something smarter than full collection to satisfy a failed alloc.)
1679 result = expand_and_allocate(word_size, context);
1680 if (result != NULL) {
1681 assert(*succeeded, "sanity");
1682 return result;
1683 }
1684
1685 // Expansion didn't work, we'll try to do a Full GC.
1686 bool gc_succeeded = do_collection(false, /* explicit_gc */
1687 false, /* clear_all_soft_refs */
1688 word_size);
1689 if (!gc_succeeded) {
1690 *succeeded = false;
1691 return NULL;
1692 }
1693
1694 // Retry the allocation
1695 result = attempt_allocation_at_safepoint(word_size,
1696 context,
1697 true /* expect_null_mutator_alloc_region */);
1698 if (result != NULL) {
1699 assert(*succeeded, "sanity");
1700 return result;
1701 }
1702
1703 // Then, try a Full GC that will collect all soft references.
1704 gc_succeeded = do_collection(false, /* explicit_gc */
1705 true, /* clear_all_soft_refs */
1706 word_size);
1707 if (!gc_succeeded) {
1708 *succeeded = false;
1709 return NULL;
1710 }
1711
1712 // Retry the allocation once more
1713 result = attempt_allocation_at_safepoint(word_size,
1714 context,
1715 true /* expect_null_mutator_alloc_region */);
1716 if (result != NULL) {
1717 assert(*succeeded, "sanity");
1718 return result;
1719 }
1720
1721 assert(!collector_policy()->should_clear_all_soft_refs(),
1722 "Flag should have been handled and cleared prior to this point");
1723
1724 // What else? We might try synchronous finalization later. If the total
1725 // space available is large enough for the allocation, then a more
1726 // complete compaction phase than we've tried so far might be
1727 // appropriate.
1728 assert(*succeeded, "sanity");
1729 return NULL;
1730 }
1731
1732 // Attempting to expand the heap sufficiently
1733 // to support an allocation of the given "word_size". If
1734 // successful, perform the allocation and return the address of the
1735 // allocated block, or else "NULL".
1736
1737 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size, AllocationContext_t context) {
1738 assert_at_safepoint(true /* should_be_vm_thread */);
1739
1740 verify_region_sets_optional();
1741
1742 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
1743 ergo_verbose1(ErgoHeapSizing,
1744 "attempt heap expansion",
1745 ergo_format_reason("allocation request failed")
1746 ergo_format_byte("allocation request"),
1747 word_size * HeapWordSize);
1748 if (expand(expand_bytes)) {
1749 _hrm.verify_optional();
1750 verify_region_sets_optional();
1751 return attempt_allocation_at_safepoint(word_size,
1752 context,
1753 false /* expect_null_mutator_alloc_region */);
1754 }
1755 return NULL;
1756 }
1757
1758 bool G1CollectedHeap::expand(size_t expand_bytes) {
1759 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
1760 aligned_expand_bytes = align_size_up(aligned_expand_bytes,
1761 HeapRegion::GrainBytes);
1762 ergo_verbose2(ErgoHeapSizing,
1763 "expand the heap",
1764 ergo_format_byte("requested expansion amount")
1765 ergo_format_byte("attempted expansion amount"),
1766 expand_bytes, aligned_expand_bytes);
1767
1768 if (is_maximal_no_gc()) {
1769 ergo_verbose0(ErgoHeapSizing,
1770 "did not expand the heap",
1771 ergo_format_reason("heap already fully expanded"));
1772 return false;
1773 }
1774
1775 uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes);
1776 assert(regions_to_expand > 0, "Must expand by at least one region");
1777
1778 uint expanded_by = _hrm.expand_by(regions_to_expand);
1779
1780 if (expanded_by > 0) {
1781 size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes;
1782 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
1783 g1_policy()->record_new_heap_size(num_regions());
1784 } else {
1785 ergo_verbose0(ErgoHeapSizing,
1786 "did not expand the heap",
1787 ergo_format_reason("heap expansion operation failed"));
1788 // The expansion of the virtual storage space was unsuccessful.
1789 // Let's see if it was because we ran out of swap.
1790 if (G1ExitOnExpansionFailure &&
1791 _hrm.available() >= regions_to_expand) {
1792 // We had head room...
1793 vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion");
1794 }
1795 }
1796 return regions_to_expand > 0;
1797 }
1798
1799 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
1800 size_t aligned_shrink_bytes =
1801 ReservedSpace::page_align_size_down(shrink_bytes);
1802 aligned_shrink_bytes = align_size_down(aligned_shrink_bytes,
1803 HeapRegion::GrainBytes);
1804 uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes);
1805
1806 uint num_regions_removed = _hrm.shrink_by(num_regions_to_remove);
1807 size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes;
1808
1809 ergo_verbose3(ErgoHeapSizing,
1810 "shrink the heap",
1811 ergo_format_byte("requested shrinking amount")
1812 ergo_format_byte("aligned shrinking amount")
1813 ergo_format_byte("attempted shrinking amount"),
1814 shrink_bytes, aligned_shrink_bytes, shrunk_bytes);
1815 if (num_regions_removed > 0) {
1816 g1_policy()->record_new_heap_size(num_regions());
1817 } else {
1818 ergo_verbose0(ErgoHeapSizing,
1819 "did not shrink the heap",
1820 ergo_format_reason("heap shrinking operation failed"));
1821 }
1822 }
1823
1824 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1825 verify_region_sets_optional();
1826
1827 // We should only reach here at the end of a Full GC which means we
1828 // should not not be holding to any GC alloc regions. The method
1829 // below will make sure of that and do any remaining clean up.
1830 _allocator->abandon_gc_alloc_regions();
1831
1832 // Instead of tearing down / rebuilding the free lists here, we
1833 // could instead use the remove_all_pending() method on free_list to
1834 // remove only the ones that we need to remove.
1835 tear_down_region_sets(true /* free_list_only */);
1836 shrink_helper(shrink_bytes);
1837 rebuild_region_sets(true /* free_list_only */);
1838
1839 _hrm.verify_optional();
1840 verify_region_sets_optional();
1841 }
1842
1843 // Public methods.
1844
1845 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away
1846 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
1847 #endif // _MSC_VER
1848
1849
1850 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* policy_) :
1851 SharedHeap(policy_),
1852 _g1_policy(policy_),
1853 _dirty_card_queue_set(false),
1854 _into_cset_dirty_card_queue_set(false),
1855 _is_alive_closure_cm(this),
1856 _is_alive_closure_stw(this),
1857 _ref_processor_cm(NULL),
1858 _ref_processor_stw(NULL),
1859 _process_strong_tasks(new SubTasksDone(G1H_PS_NumElements)),
1860 _bot_shared(NULL),
1861 _evac_failure_scan_stack(NULL),
1862 _mark_in_progress(false),
1863 _cg1r(NULL),
1864 _g1mm(NULL),
1865 _refine_cte_cl(NULL),
1866 _full_collection(false),
1867 _secondary_free_list("Secondary Free List", new SecondaryFreeRegionListMtSafeChecker()),
1868 _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()),
1869 _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()),
1870 _humongous_is_live(),
1871 _has_humongous_reclaim_candidates(false),
1872 _free_regions_coming(false),
1873 _young_list(new YoungList(this)),
1874 _gc_time_stamp(0),
1875 _survivor_plab_stats(YoungPLABSize, PLABWeight),
1876 _old_plab_stats(OldPLABSize, PLABWeight),
1877 _expand_heap_after_alloc_failure(true),
1878 _surviving_young_words(NULL),
1879 _old_marking_cycles_started(0),
1880 _old_marking_cycles_completed(0),
1881 _concurrent_cycle_started(false),
1882 _heap_summary_sent(false),
1883 _in_cset_fast_test(),
1884 _dirty_cards_region_list(NULL),
1885 _worker_cset_start_region(NULL),
1886 _worker_cset_start_region_time_stamp(NULL),
1887 _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()),
1888 _gc_timer_cm(new (ResourceObj::C_HEAP, mtGC) ConcurrentGCTimer()),
1889 _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()),
1890 _gc_tracer_cm(new (ResourceObj::C_HEAP, mtGC) G1OldTracer()) {
1891
1892 _g1h = this;
1893 if (_process_strong_tasks == NULL || !_process_strong_tasks->valid()) {
1894 vm_exit_during_initialization("Failed necessary allocation.");
1895 }
1896
1897 _allocator = G1Allocator::create_allocator(_g1h);
1898 _humongous_object_threshold_in_words = HeapRegion::GrainWords / 2;
1899
1900 int n_queues = MAX2((int)ParallelGCThreads, 1);
1901 _task_queues = new RefToScanQueueSet(n_queues);
1902
1903 uint n_rem_sets = HeapRegionRemSet::num_par_rem_sets();
1904 assert(n_rem_sets > 0, "Invariant.");
1905
1906 _worker_cset_start_region = NEW_C_HEAP_ARRAY(HeapRegion*, n_queues, mtGC);
1907 _worker_cset_start_region_time_stamp = NEW_C_HEAP_ARRAY(unsigned int, n_queues, mtGC);
1908 _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC);
1909
1910 for (int i = 0; i < n_queues; i++) {
1911 RefToScanQueue* q = new RefToScanQueue();
1912 q->initialize();
1913 _task_queues->register_queue(i, q);
1914 ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo();
1915 }
1916 clear_cset_start_regions();
1917
1918 // Initialize the G1EvacuationFailureALot counters and flags.
1919 NOT_PRODUCT(reset_evacuation_should_fail();)
1920
1921 guarantee(_task_queues != NULL, "task_queues allocation failure.");
1922 }
1923
1924 jint G1CollectedHeap::initialize() {
1925 CollectedHeap::pre_initialize();
1926 os::enable_vtime();
1927
1928 G1Log::init();
1929
1930 // Necessary to satisfy locking discipline assertions.
1931
1932 MutexLocker x(Heap_lock);
1933
1934 // We have to initialize the printer before committing the heap, as
1935 // it will be used then.
1936 _hr_printer.set_active(G1PrintHeapRegions);
1937
1938 // While there are no constraints in the GC code that HeapWordSize
1939 // be any particular value, there are multiple other areas in the
1940 // system which believe this to be true (e.g. oop->object_size in some
1941 // cases incorrectly returns the size in wordSize units rather than
1942 // HeapWordSize).
1943 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
1944
1945 size_t init_byte_size = collector_policy()->initial_heap_byte_size();
1946 size_t max_byte_size = collector_policy()->max_heap_byte_size();
1947 size_t heap_alignment = collector_policy()->heap_alignment();
1948
1949 // Ensure that the sizes are properly aligned.
1950 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
1951 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
1952 Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap");
1953
1954 _refine_cte_cl = new RefineCardTableEntryClosure();
1955
1956 _cg1r = new ConcurrentG1Refine(this, _refine_cte_cl);
1957
1958 // Reserve the maximum.
1959
1960 // When compressed oops are enabled, the preferred heap base
1961 // is calculated by subtracting the requested size from the
1962 // 32Gb boundary and using the result as the base address for
1963 // heap reservation. If the requested size is not aligned to
1964 // HeapRegion::GrainBytes (i.e. the alignment that is passed
1965 // into the ReservedHeapSpace constructor) then the actual
1966 // base of the reserved heap may end up differing from the
1967 // address that was requested (i.e. the preferred heap base).
1968 // If this happens then we could end up using a non-optimal
1969 // compressed oops mode.
1970
1971 ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size,
1972 heap_alignment);
1973
1974 initialize_reserved_region((HeapWord*)heap_rs.base(), (HeapWord*)(heap_rs.base() + heap_rs.size()));
1975
1976 // Create the gen rem set (and barrier set) for the entire reserved region.
1977 _rem_set = collector_policy()->create_rem_set(reserved_region(), 2);
1978 set_barrier_set(rem_set()->bs());
1979 if (!barrier_set()->is_a(BarrierSet::G1SATBCTLogging)) {
1980 vm_exit_during_initialization("G1 requires a G1SATBLoggingCardTableModRefBS");
1981 return JNI_ENOMEM;
1982 }
1983
1984 // Also create a G1 rem set.
1985 _g1_rem_set = new G1RemSet(this, g1_barrier_set());
1986
1987 // Carve out the G1 part of the heap.
1988
1989 ReservedSpace g1_rs = heap_rs.first_part(max_byte_size);
1990 G1RegionToSpaceMapper* heap_storage =
1991 G1RegionToSpaceMapper::create_mapper(g1_rs,
1992 UseLargePages ? os::large_page_size() : os::vm_page_size(),
1993 HeapRegion::GrainBytes,
1994 1,
1995 mtJavaHeap);
1996 heap_storage->set_mapping_changed_listener(&_listener);
1997
1998 // Reserve space for the block offset table. We do not support automatic uncommit
1999 // for the card table at this time. BOT only.
2000 ReservedSpace bot_rs(G1BlockOffsetSharedArray::compute_size(g1_rs.size() / HeapWordSize));
2001 G1RegionToSpaceMapper* bot_storage =
2002 G1RegionToSpaceMapper::create_mapper(bot_rs,
2003 os::vm_page_size(),
2004 HeapRegion::GrainBytes,
2005 G1BlockOffsetSharedArray::N_bytes,
2006 mtGC);
2007
2008 ReservedSpace cardtable_rs(G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize));
2009 G1RegionToSpaceMapper* cardtable_storage =
2010 G1RegionToSpaceMapper::create_mapper(cardtable_rs,
2011 os::vm_page_size(),
2012 HeapRegion::GrainBytes,
2013 G1BlockOffsetSharedArray::N_bytes,
2014 mtGC);
2015
2016 // Reserve space for the card counts table.
2017 ReservedSpace card_counts_rs(G1BlockOffsetSharedArray::compute_size(g1_rs.size() / HeapWordSize));
2018 G1RegionToSpaceMapper* card_counts_storage =
2019 G1RegionToSpaceMapper::create_mapper(card_counts_rs,
2020 os::vm_page_size(),
2021 HeapRegion::GrainBytes,
2022 G1BlockOffsetSharedArray::N_bytes,
2023 mtGC);
2024
2025 // Reserve space for prev and next bitmap.
2026 size_t bitmap_size = CMBitMap::compute_size(g1_rs.size());
2027
2028 ReservedSpace prev_bitmap_rs(ReservedSpace::allocation_align_size_up(bitmap_size));
2029 G1RegionToSpaceMapper* prev_bitmap_storage =
2030 G1RegionToSpaceMapper::create_mapper(prev_bitmap_rs,
2031 os::vm_page_size(),
2032 HeapRegion::GrainBytes,
2033 CMBitMap::mark_distance(),
2034 mtGC);
2035
2036 ReservedSpace next_bitmap_rs(ReservedSpace::allocation_align_size_up(bitmap_size));
2037 G1RegionToSpaceMapper* next_bitmap_storage =
2038 G1RegionToSpaceMapper::create_mapper(next_bitmap_rs,
2039 os::vm_page_size(),
2040 HeapRegion::GrainBytes,
2041 CMBitMap::mark_distance(),
2042 mtGC);
2043
2044 _hrm.initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage);
2045 g1_barrier_set()->initialize(cardtable_storage);
2046 // Do later initialization work for concurrent refinement.
2047 _cg1r->init(card_counts_storage);
2048
2049 // 6843694 - ensure that the maximum region index can fit
2050 // in the remembered set structures.
2051 const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
2052 guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
2053
2054 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
2055 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
2056 guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
2057 "too many cards per region");
2058
2059 FreeRegionList::set_unrealistically_long_length(max_regions() + 1);
2060
2061 _bot_shared = new G1BlockOffsetSharedArray(reserved_region(), bot_storage);
2062
2063 _g1h = this;
2064
2065 _in_cset_fast_test.initialize(_hrm.reserved().start(), _hrm.reserved().end(), HeapRegion::GrainBytes);
2066 _humongous_is_live.initialize(_hrm.reserved().start(), _hrm.reserved().end(), HeapRegion::GrainBytes);
2067
2068 // Create the ConcurrentMark data structure and thread.
2069 // (Must do this late, so that "max_regions" is defined.)
2070 _cm = new ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage);
2071 if (_cm == NULL || !_cm->completed_initialization()) {
2072 vm_shutdown_during_initialization("Could not create/initialize ConcurrentMark");
2073 return JNI_ENOMEM;
2074 }
2075 _cmThread = _cm->cmThread();
2076
2077 // Initialize the from_card cache structure of HeapRegionRemSet.
2078 HeapRegionRemSet::init_heap(max_regions());
2079
2080 // Now expand into the initial heap size.
2081 if (!expand(init_byte_size)) {
2082 vm_shutdown_during_initialization("Failed to allocate initial heap.");
2083 return JNI_ENOMEM;
2084 }
2085
2086 // Perform any initialization actions delegated to the policy.
2087 g1_policy()->init();
2088
2089 JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon,
2090 SATB_Q_FL_lock,
2091 G1SATBProcessCompletedThreshold,
2092 Shared_SATB_Q_lock);
2093
2094 JavaThread::dirty_card_queue_set().initialize(_refine_cte_cl,
2095 DirtyCardQ_CBL_mon,
2096 DirtyCardQ_FL_lock,
2097 concurrent_g1_refine()->yellow_zone(),
2098 concurrent_g1_refine()->red_zone(),
2099 Shared_DirtyCardQ_lock);
2100
2101 dirty_card_queue_set().initialize(NULL, // Should never be called by the Java code
2102 DirtyCardQ_CBL_mon,
2103 DirtyCardQ_FL_lock,
2104 -1, // never trigger processing
2105 -1, // no limit on length
2106 Shared_DirtyCardQ_lock,
2107 &JavaThread::dirty_card_queue_set());
2108
2109 // Initialize the card queue set used to hold cards containing
2110 // references into the collection set.
2111 _into_cset_dirty_card_queue_set.initialize(NULL, // Should never be called by the Java code
2112 DirtyCardQ_CBL_mon,
2113 DirtyCardQ_FL_lock,
2114 -1, // never trigger processing
2115 -1, // no limit on length
2116 Shared_DirtyCardQ_lock,
2117 &JavaThread::dirty_card_queue_set());
2118
2119 // In case we're keeping closure specialization stats, initialize those
2120 // counts and that mechanism.
2121 SpecializationStats::clear();
2122
2123 // Here we allocate the dummy HeapRegion that is required by the
2124 // G1AllocRegion class.
2125 HeapRegion* dummy_region = _hrm.get_dummy_region();
2126
2127 // We'll re-use the same region whether the alloc region will
2128 // require BOT updates or not and, if it doesn't, then a non-young
2129 // region will complain that it cannot support allocations without
2130 // BOT updates. So we'll tag the dummy region as eden to avoid that.
2131 dummy_region->set_eden();
2132 // Make sure it's full.
2133 dummy_region->set_top(dummy_region->end());
2134 G1AllocRegion::setup(this, dummy_region);
2135
2136 _allocator->init_mutator_alloc_region();
2137
2138 // Do create of the monitoring and management support so that
2139 // values in the heap have been properly initialized.
2140 _g1mm = new G1MonitoringSupport(this);
2141
2142 G1StringDedup::initialize();
2143
2144 return JNI_OK;
2145 }
2146
2147 void G1CollectedHeap::stop() {
2148 // Stop all concurrent threads. We do this to make sure these threads
2149 // do not continue to execute and access resources (e.g. gclog_or_tty)
2150 // that are destroyed during shutdown.
2151 _cg1r->stop();
2152 _cmThread->stop();
2153 if (G1StringDedup::is_enabled()) {
2154 G1StringDedup::stop();
2155 }
2156 }
2157
2158 void G1CollectedHeap::clear_humongous_is_live_table() {
2159 guarantee(G1ReclaimDeadHumongousObjectsAtYoungGC, "Should only be called if true");
2160 _humongous_is_live.clear();
2161 }
2162
2163 size_t G1CollectedHeap::conservative_max_heap_alignment() {
2164 return HeapRegion::max_region_size();
2165 }
2166
2167 void G1CollectedHeap::ref_processing_init() {
2168 // Reference processing in G1 currently works as follows:
2169 //
2170 // * There are two reference processor instances. One is
2171 // used to record and process discovered references
2172 // during concurrent marking; the other is used to
2173 // record and process references during STW pauses
2174 // (both full and incremental).
2175 // * Both ref processors need to 'span' the entire heap as
2176 // the regions in the collection set may be dotted around.
2177 //
2178 // * For the concurrent marking ref processor:
2179 // * Reference discovery is enabled at initial marking.
2180 // * Reference discovery is disabled and the discovered
2181 // references processed etc during remarking.
2182 // * Reference discovery is MT (see below).
2183 // * Reference discovery requires a barrier (see below).
2184 // * Reference processing may or may not be MT
2185 // (depending on the value of ParallelRefProcEnabled
2186 // and ParallelGCThreads).
2187 // * A full GC disables reference discovery by the CM
2188 // ref processor and abandons any entries on it's
2189 // discovered lists.
2190 //
2191 // * For the STW processor:
2192 // * Non MT discovery is enabled at the start of a full GC.
2193 // * Processing and enqueueing during a full GC is non-MT.
2194 // * During a full GC, references are processed after marking.
2195 //
2196 // * Discovery (may or may not be MT) is enabled at the start
2197 // of an incremental evacuation pause.
2198 // * References are processed near the end of a STW evacuation pause.
2199 // * For both types of GC:
2200 // * Discovery is atomic - i.e. not concurrent.
2201 // * Reference discovery will not need a barrier.
2202
2203 SharedHeap::ref_processing_init();
2204 MemRegion mr = reserved_region();
2205
2206 // Concurrent Mark ref processor
2207 _ref_processor_cm =
2208 new ReferenceProcessor(mr, // span
2209 ParallelRefProcEnabled && (ParallelGCThreads > 1),
2210 // mt processing
2211 (int) ParallelGCThreads,
2212 // degree of mt processing
2213 (ParallelGCThreads > 1) || (ConcGCThreads > 1),
2214 // mt discovery
2215 (int) MAX2(ParallelGCThreads, ConcGCThreads),
2216 // degree of mt discovery
2217 false,
2218 // Reference discovery is not atomic
2219 &_is_alive_closure_cm);
2220 // is alive closure
2221 // (for efficiency/performance)
2222
2223 // STW ref processor
2224 _ref_processor_stw =
2225 new ReferenceProcessor(mr, // span
2226 ParallelRefProcEnabled && (ParallelGCThreads > 1),
2227 // mt processing
2228 MAX2((int)ParallelGCThreads, 1),
2229 // degree of mt processing
2230 (ParallelGCThreads > 1),
2231 // mt discovery
2232 MAX2((int)ParallelGCThreads, 1),
2233 // degree of mt discovery
2234 true,
2235 // Reference discovery is atomic
2236 &_is_alive_closure_stw);
2237 // is alive closure
2238 // (for efficiency/performance)
2239 }
2240
2241 size_t G1CollectedHeap::capacity() const {
2242 return _hrm.length() * HeapRegion::GrainBytes;
2243 }
2244
2245 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) {
2246 assert(!hr->is_continues_humongous(), "pre-condition");
2247 hr->reset_gc_time_stamp();
2248 if (hr->is_starts_humongous()) {
2249 uint first_index = hr->hrm_index() + 1;
2250 uint last_index = hr->last_hc_index();
2251 for (uint i = first_index; i < last_index; i += 1) {
2252 HeapRegion* chr = region_at(i);
2253 assert(chr->is_continues_humongous(), "sanity");
2254 chr->reset_gc_time_stamp();
2255 }
2256 }
2257 }
2258
2259 #ifndef PRODUCT
2260 class CheckGCTimeStampsHRClosure : public HeapRegionClosure {
2261 private:
2262 unsigned _gc_time_stamp;
2263 bool _failures;
2264
2265 public:
2266 CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) :
2267 _gc_time_stamp(gc_time_stamp), _failures(false) { }
2268
2269 virtual bool doHeapRegion(HeapRegion* hr) {
2270 unsigned region_gc_time_stamp = hr->get_gc_time_stamp();
2271 if (_gc_time_stamp != region_gc_time_stamp) {
2272 gclog_or_tty->print_cr("Region "HR_FORMAT" has GC time stamp = %d, "
2273 "expected %d", HR_FORMAT_PARAMS(hr),
2274 region_gc_time_stamp, _gc_time_stamp);
2275 _failures = true;
2276 }
2277 return false;
2278 }
2279
2280 bool failures() { return _failures; }
2281 };
2282
2283 void G1CollectedHeap::check_gc_time_stamps() {
2284 CheckGCTimeStampsHRClosure cl(_gc_time_stamp);
2285 heap_region_iterate(&cl);
2286 guarantee(!cl.failures(), "all GC time stamps should have been reset");
2287 }
2288 #endif // PRODUCT
2289
2290 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl,
2291 DirtyCardQueue* into_cset_dcq,
2292 bool concurrent,
2293 uint worker_i) {
2294 // Clean cards in the hot card cache
2295 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
2296 hot_card_cache->drain(worker_i, g1_rem_set(), into_cset_dcq);
2297
2298 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2299 int n_completed_buffers = 0;
2300 while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) {
2301 n_completed_buffers++;
2302 }
2303 g1_policy()->phase_times()->record_update_rs_processed_buffers(worker_i, n_completed_buffers);
2304 dcqs.clear_n_completed_buffers();
2305 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!");
2306 }
2307
2308
2309 // Computes the sum of the storage used by the various regions.
2310 size_t G1CollectedHeap::used() const {
2311 return _allocator->used();
2312 }
2313
2314 size_t G1CollectedHeap::used_unlocked() const {
2315 return _allocator->used_unlocked();
2316 }
2317
2318 class SumUsedClosure: public HeapRegionClosure {
2319 size_t _used;
2320 public:
2321 SumUsedClosure() : _used(0) {}
2322 bool doHeapRegion(HeapRegion* r) {
2323 if (!r->is_continues_humongous()) {
2324 _used += r->used();
2325 }
2326 return false;
2327 }
2328 size_t result() { return _used; }
2329 };
2330
2331 size_t G1CollectedHeap::recalculate_used() const {
2332 double recalculate_used_start = os::elapsedTime();
2333
2334 SumUsedClosure blk;
2335 heap_region_iterate(&blk);
2336
2337 g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0);
2338 return blk.result();
2339 }
2340
2341 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
2342 switch (cause) {
2343 case GCCause::_gc_locker: return GCLockerInvokesConcurrent;
2344 case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent;
2345 case GCCause::_g1_humongous_allocation: return true;
2346 default: return false;
2347 }
2348 }
2349
2350 #ifndef PRODUCT
2351 void G1CollectedHeap::allocate_dummy_regions() {
2352 // Let's fill up most of the region
2353 size_t word_size = HeapRegion::GrainWords - 1024;
2354 // And as a result the region we'll allocate will be humongous.
2355 guarantee(is_humongous(word_size), "sanity");
2356
2357 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
2358 // Let's use the existing mechanism for the allocation
2359 HeapWord* dummy_obj = humongous_obj_allocate(word_size,
2360 AllocationContext::system());
2361 if (dummy_obj != NULL) {
2362 MemRegion mr(dummy_obj, word_size);
2363 CollectedHeap::fill_with_object(mr);
2364 } else {
2365 // If we can't allocate once, we probably cannot allocate
2366 // again. Let's get out of the loop.
2367 break;
2368 }
2369 }
2370 }
2371 #endif // !PRODUCT
2372
2373 void G1CollectedHeap::increment_old_marking_cycles_started() {
2374 assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
2375 _old_marking_cycles_started == _old_marking_cycles_completed + 1,
2376 err_msg("Wrong marking cycle count (started: %d, completed: %d)",
2377 _old_marking_cycles_started, _old_marking_cycles_completed));
2378
2379 _old_marking_cycles_started++;
2380 }
2381
2382 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) {
2383 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
2384
2385 // We assume that if concurrent == true, then the caller is a
2386 // concurrent thread that was joined the Suspendible Thread
2387 // Set. If there's ever a cheap way to check this, we should add an
2388 // assert here.
2389
2390 // Given that this method is called at the end of a Full GC or of a
2391 // concurrent cycle, and those can be nested (i.e., a Full GC can
2392 // interrupt a concurrent cycle), the number of full collections
2393 // completed should be either one (in the case where there was no
2394 // nesting) or two (when a Full GC interrupted a concurrent cycle)
2395 // behind the number of full collections started.
2396
2397 // This is the case for the inner caller, i.e. a Full GC.
2398 assert(concurrent ||
2399 (_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
2400 (_old_marking_cycles_started == _old_marking_cycles_completed + 2),
2401 err_msg("for inner caller (Full GC): _old_marking_cycles_started = %u "
2402 "is inconsistent with _old_marking_cycles_completed = %u",
2403 _old_marking_cycles_started, _old_marking_cycles_completed));
2404
2405 // This is the case for the outer caller, i.e. the concurrent cycle.
2406 assert(!concurrent ||
2407 (_old_marking_cycles_started == _old_marking_cycles_completed + 1),
2408 err_msg("for outer caller (concurrent cycle): "
2409 "_old_marking_cycles_started = %u "
2410 "is inconsistent with _old_marking_cycles_completed = %u",
2411 _old_marking_cycles_started, _old_marking_cycles_completed));
2412
2413 _old_marking_cycles_completed += 1;
2414
2415 // We need to clear the "in_progress" flag in the CM thread before
2416 // we wake up any waiters (especially when ExplicitInvokesConcurrent
2417 // is set) so that if a waiter requests another System.gc() it doesn't
2418 // incorrectly see that a marking cycle is still in progress.
2419 if (concurrent) {
2420 _cmThread->clear_in_progress();
2421 }
2422
2423 // This notify_all() will ensure that a thread that called
2424 // System.gc() with (with ExplicitGCInvokesConcurrent set or not)
2425 // and it's waiting for a full GC to finish will be woken up. It is
2426 // waiting in VM_G1IncCollectionPause::doit_epilogue().
2427 FullGCCount_lock->notify_all();
2428 }
2429
2430 void G1CollectedHeap::register_concurrent_cycle_start(const Ticks& start_time) {
2431 _concurrent_cycle_started = true;
2432 _gc_timer_cm->register_gc_start(start_time);
2433
2434 _gc_tracer_cm->report_gc_start(gc_cause(), _gc_timer_cm->gc_start());
2435 trace_heap_before_gc(_gc_tracer_cm);
2436 }
2437
2438 void G1CollectedHeap::register_concurrent_cycle_end() {
2439 if (_concurrent_cycle_started) {
2440 if (_cm->has_aborted()) {
2441 _gc_tracer_cm->report_concurrent_mode_failure();
2442 }
2443
2444 _gc_timer_cm->register_gc_end();
2445 _gc_tracer_cm->report_gc_end(_gc_timer_cm->gc_end(), _gc_timer_cm->time_partitions());
2446
2447 // Clear state variables to prepare for the next concurrent cycle.
2448 _concurrent_cycle_started = false;
2449 _heap_summary_sent = false;
2450 }
2451 }
2452
2453 void G1CollectedHeap::trace_heap_after_concurrent_cycle() {
2454 if (_concurrent_cycle_started) {
2455 // This function can be called when:
2456 // the cleanup pause is run
2457 // the concurrent cycle is aborted before the cleanup pause.
2458 // the concurrent cycle is aborted after the cleanup pause,
2459 // but before the concurrent cycle end has been registered.
2460 // Make sure that we only send the heap information once.
2461 if (!_heap_summary_sent) {
2462 trace_heap_after_gc(_gc_tracer_cm);
2463 _heap_summary_sent = true;
2464 }
2465 }
2466 }
2467
2468 G1YCType G1CollectedHeap::yc_type() {
2469 bool is_young = g1_policy()->gcs_are_young();
2470 bool is_initial_mark = g1_policy()->during_initial_mark_pause();
2471 bool is_during_mark = mark_in_progress();
2472
2473 if (is_initial_mark) {
2474 return InitialMark;
2475 } else if (is_during_mark) {
2476 return DuringMark;
2477 } else if (is_young) {
2478 return Normal;
2479 } else {
2480 return Mixed;
2481 }
2482 }
2483
2484 void G1CollectedHeap::collect(GCCause::Cause cause) {
2485 assert_heap_not_locked();
2486
2487 unsigned int gc_count_before;
2488 unsigned int old_marking_count_before;
2489 bool retry_gc;
2490
2491 do {
2492 retry_gc = false;
2493
2494 {
2495 MutexLocker ml(Heap_lock);
2496
2497 // Read the GC count while holding the Heap_lock
2498 gc_count_before = total_collections();
2499 old_marking_count_before = _old_marking_cycles_started;
2500 }
2501
2502 if (should_do_concurrent_full_gc(cause)) {
2503 // Schedule an initial-mark evacuation pause that will start a
2504 // concurrent cycle. We're setting word_size to 0 which means that
2505 // we are not requesting a post-GC allocation.
2506 VM_G1IncCollectionPause op(gc_count_before,
2507 0, /* word_size */
2508 true, /* should_initiate_conc_mark */
2509 g1_policy()->max_pause_time_ms(),
2510 cause);
2511 op.set_allocation_context(AllocationContext::current());
2512
2513 VMThread::execute(&op);
2514 if (!op.pause_succeeded()) {
2515 if (old_marking_count_before == _old_marking_cycles_started) {
2516 retry_gc = op.should_retry_gc();
2517 } else {
2518 // A Full GC happened while we were trying to schedule the
2519 // initial-mark GC. No point in starting a new cycle given
2520 // that the whole heap was collected anyway.
2521 }
2522
2523 if (retry_gc) {
2524 if (GC_locker::is_active_and_needs_gc()) {
2525 GC_locker::stall_until_clear();
2526 }
2527 }
2528 }
2529 } else {
2530 if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc
2531 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2532
2533 // Schedule a standard evacuation pause. We're setting word_size
2534 // to 0 which means that we are not requesting a post-GC allocation.
2535 VM_G1IncCollectionPause op(gc_count_before,
2536 0, /* word_size */
2537 false, /* should_initiate_conc_mark */
2538 g1_policy()->max_pause_time_ms(),
2539 cause);
2540 VMThread::execute(&op);
2541 } else {
2542 // Schedule a Full GC.
2543 VM_G1CollectFull op(gc_count_before, old_marking_count_before, cause);
2544 VMThread::execute(&op);
2545 }
2546 }
2547 } while (retry_gc);
2548 }
2549
2550 bool G1CollectedHeap::is_in(const void* p) const {
2551 if (_hrm.reserved().contains(p)) {
2552 // Given that we know that p is in the reserved space,
2553 // heap_region_containing_raw() should successfully
2554 // return the containing region.
2555 HeapRegion* hr = heap_region_containing_raw(p);
2556 return hr->is_in(p);
2557 } else {
2558 return false;
2559 }
2560 }
2561
2562 #ifdef ASSERT
2563 bool G1CollectedHeap::is_in_exact(const void* p) const {
2564 bool contains = reserved_region().contains(p);
2565 bool available = _hrm.is_available(addr_to_region((HeapWord*)p));
2566 if (contains && available) {
2567 return true;
2568 } else {
2569 return false;
2570 }
2571 }
2572 #endif
2573
2574 // Iteration functions.
2575
2576 // Applies an ExtendedOopClosure onto all references of objects within a HeapRegion.
2577
2578 class IterateOopClosureRegionClosure: public HeapRegionClosure {
2579 ExtendedOopClosure* _cl;
2580 public:
2581 IterateOopClosureRegionClosure(ExtendedOopClosure* cl) : _cl(cl) {}
2582 bool doHeapRegion(HeapRegion* r) {
2583 if (!r->is_continues_humongous()) {
2584 r->oop_iterate(_cl);
2585 }
2586 return false;
2587 }
2588 };
2589
2590 void G1CollectedHeap::oop_iterate(ExtendedOopClosure* cl) {
2591 IterateOopClosureRegionClosure blk(cl);
2592 heap_region_iterate(&blk);
2593 }
2594
2595 // Iterates an ObjectClosure over all objects within a HeapRegion.
2596
2597 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2598 ObjectClosure* _cl;
2599 public:
2600 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2601 bool doHeapRegion(HeapRegion* r) {
2602 if (!r->is_continues_humongous()) {
2603 r->object_iterate(_cl);
2604 }
2605 return false;
2606 }
2607 };
2608
2609 void G1CollectedHeap::object_iterate(ObjectClosure* cl) {
2610 IterateObjectClosureRegionClosure blk(cl);
2611 heap_region_iterate(&blk);
2612 }
2613
2614 // Calls a SpaceClosure on a HeapRegion.
2615
2616 class SpaceClosureRegionClosure: public HeapRegionClosure {
2617 SpaceClosure* _cl;
2618 public:
2619 SpaceClosureRegionClosure(SpaceClosure* cl) : _cl(cl) {}
2620 bool doHeapRegion(HeapRegion* r) {
2621 _cl->do_space(r);
2622 return false;
2623 }
2624 };
2625
2626 void G1CollectedHeap::space_iterate(SpaceClosure* cl) {
2627 SpaceClosureRegionClosure blk(cl);
2628 heap_region_iterate(&blk);
2629 }
2630
2631 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2632 _hrm.iterate(cl);
2633 }
2634
2635 void
2636 G1CollectedHeap::heap_region_par_iterate_chunked(HeapRegionClosure* cl,
2637 uint worker_id,
2638 uint num_workers,
2639 jint claim_value) const {
2640 _hrm.par_iterate(cl, worker_id, num_workers, claim_value);
2641 }
2642
2643 class ResetClaimValuesClosure: public HeapRegionClosure {
2644 public:
2645 bool doHeapRegion(HeapRegion* r) {
2646 r->set_claim_value(HeapRegion::InitialClaimValue);
2647 return false;
2648 }
2649 };
2650
2651 void G1CollectedHeap::reset_heap_region_claim_values() {
2652 ResetClaimValuesClosure blk;
2653 heap_region_iterate(&blk);
2654 }
2655
2656 void G1CollectedHeap::reset_cset_heap_region_claim_values() {
2657 ResetClaimValuesClosure blk;
2658 collection_set_iterate(&blk);
2659 }
2660
2661 #ifdef ASSERT
2662 // This checks whether all regions in the heap have the correct claim
2663 // value. I also piggy-backed on this a check to ensure that the
2664 // humongous_start_region() information on "continues humongous"
2665 // regions is correct.
2666
2667 class CheckClaimValuesClosure : public HeapRegionClosure {
2668 private:
2669 jint _claim_value;
2670 uint _failures;
2671 HeapRegion* _sh_region;
2672
2673 public:
2674 CheckClaimValuesClosure(jint claim_value) :
2675 _claim_value(claim_value), _failures(0), _sh_region(NULL) { }
2676 bool doHeapRegion(HeapRegion* r) {
2677 if (r->claim_value() != _claim_value) {
2678 gclog_or_tty->print_cr("Region " HR_FORMAT ", "
2679 "claim value = %d, should be %d",
2680 HR_FORMAT_PARAMS(r),
2681 r->claim_value(), _claim_value);
2682 ++_failures;
2683 }
2684 if (!r->is_humongous()) {
2685 _sh_region = NULL;
2686 } else if (r->is_starts_humongous()) {
2687 _sh_region = r;
2688 } else if (r->is_continues_humongous()) {
2689 if (r->humongous_start_region() != _sh_region) {
2690 gclog_or_tty->print_cr("Region " HR_FORMAT ", "
2691 "HS = "PTR_FORMAT", should be "PTR_FORMAT,
2692 HR_FORMAT_PARAMS(r),
2693 r->humongous_start_region(),
2694 _sh_region);
2695 ++_failures;
2696 }
2697 }
2698 return false;
2699 }
2700 uint failures() { return _failures; }
2701 };
2702
2703 bool G1CollectedHeap::check_heap_region_claim_values(jint claim_value) {
2704 CheckClaimValuesClosure cl(claim_value);
2705 heap_region_iterate(&cl);
2706 return cl.failures() == 0;
2707 }
2708
2709 class CheckClaimValuesInCSetHRClosure: public HeapRegionClosure {
2710 private:
2711 jint _claim_value;
2712 uint _failures;
2713
2714 public:
2715 CheckClaimValuesInCSetHRClosure(jint claim_value) :
2716 _claim_value(claim_value), _failures(0) { }
2717
2718 uint failures() { return _failures; }
2719
2720 bool doHeapRegion(HeapRegion* hr) {
2721 assert(hr->in_collection_set(), "how?");
2722 assert(!hr->is_humongous(), "H-region in CSet");
2723 if (hr->claim_value() != _claim_value) {
2724 gclog_or_tty->print_cr("CSet Region " HR_FORMAT ", "
2725 "claim value = %d, should be %d",
2726 HR_FORMAT_PARAMS(hr),
2727 hr->claim_value(), _claim_value);
2728 _failures += 1;
2729 }
2730 return false;
2731 }
2732 };
2733
2734 bool G1CollectedHeap::check_cset_heap_region_claim_values(jint claim_value) {
2735 CheckClaimValuesInCSetHRClosure cl(claim_value);
2736 collection_set_iterate(&cl);
2737 return cl.failures() == 0;
2738 }
2739 #endif // ASSERT
2740
2741 // Clear the cached CSet starting regions and (more importantly)
2742 // the time stamps. Called when we reset the GC time stamp.
2743 void G1CollectedHeap::clear_cset_start_regions() {
2744 assert(_worker_cset_start_region != NULL, "sanity");
2745 assert(_worker_cset_start_region_time_stamp != NULL, "sanity");
2746
2747 int n_queues = MAX2((int)ParallelGCThreads, 1);
2748 for (int i = 0; i < n_queues; i++) {
2749 _worker_cset_start_region[i] = NULL;
2750 _worker_cset_start_region_time_stamp[i] = 0;
2751 }
2752 }
2753
2754 // Given the id of a worker, obtain or calculate a suitable
2755 // starting region for iterating over the current collection set.
2756 HeapRegion* G1CollectedHeap::start_cset_region_for_worker(uint worker_i) {
2757 assert(get_gc_time_stamp() > 0, "should have been updated by now");
2758
2759 HeapRegion* result = NULL;
2760 unsigned gc_time_stamp = get_gc_time_stamp();
2761
2762 if (_worker_cset_start_region_time_stamp[worker_i] == gc_time_stamp) {
2763 // Cached starting region for current worker was set
2764 // during the current pause - so it's valid.
2765 // Note: the cached starting heap region may be NULL
2766 // (when the collection set is empty).
2767 result = _worker_cset_start_region[worker_i];
2768 assert(result == NULL || result->in_collection_set(), "sanity");
2769 return result;
2770 }
2771
2772 // The cached entry was not valid so let's calculate
2773 // a suitable starting heap region for this worker.
2774
2775 // We want the parallel threads to start their collection
2776 // set iteration at different collection set regions to
2777 // avoid contention.
2778 // If we have:
2779 // n collection set regions
2780 // p threads
2781 // Then thread t will start at region floor ((t * n) / p)
2782
2783 result = g1_policy()->collection_set();
2784 if (G1CollectedHeap::use_parallel_gc_threads()) {
2785 uint cs_size = g1_policy()->cset_region_length();
2786 uint active_workers = workers()->active_workers();
2787 assert(UseDynamicNumberOfGCThreads ||
2788 active_workers == workers()->total_workers(),
2789 "Unless dynamic should use total workers");
2790
2791 uint end_ind = (cs_size * worker_i) / active_workers;
2792 uint start_ind = 0;
2793
2794 if (worker_i > 0 &&
2795 _worker_cset_start_region_time_stamp[worker_i - 1] == gc_time_stamp) {
2796 // Previous workers starting region is valid
2797 // so let's iterate from there
2798 start_ind = (cs_size * (worker_i - 1)) / active_workers;
2799 result = _worker_cset_start_region[worker_i - 1];
2800 }
2801
2802 for (uint i = start_ind; i < end_ind; i++) {
2803 result = result->next_in_collection_set();
2804 }
2805 }
2806
2807 // Note: the calculated starting heap region may be NULL
2808 // (when the collection set is empty).
2809 assert(result == NULL || result->in_collection_set(), "sanity");
2810 assert(_worker_cset_start_region_time_stamp[worker_i] != gc_time_stamp,
2811 "should be updated only once per pause");
2812 _worker_cset_start_region[worker_i] = result;
2813 OrderAccess::storestore();
2814 _worker_cset_start_region_time_stamp[worker_i] = gc_time_stamp;
2815 return result;
2816 }
2817
2818 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) {
2819 HeapRegion* r = g1_policy()->collection_set();
2820 while (r != NULL) {
2821 HeapRegion* next = r->next_in_collection_set();
2822 if (cl->doHeapRegion(r)) {
2823 cl->incomplete();
2824 return;
2825 }
2826 r = next;
2827 }
2828 }
2829
2830 void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r,
2831 HeapRegionClosure *cl) {
2832 if (r == NULL) {
2833 // The CSet is empty so there's nothing to do.
2834 return;
2835 }
2836
2837 assert(r->in_collection_set(),
2838 "Start region must be a member of the collection set.");
2839 HeapRegion* cur = r;
2840 while (cur != NULL) {
2841 HeapRegion* next = cur->next_in_collection_set();
2842 if (cl->doHeapRegion(cur) && false) {
2843 cl->incomplete();
2844 return;
2845 }
2846 cur = next;
2847 }
2848 cur = g1_policy()->collection_set();
2849 while (cur != r) {
2850 HeapRegion* next = cur->next_in_collection_set();
2851 if (cl->doHeapRegion(cur) && false) {
2852 cl->incomplete();
2853 return;
2854 }
2855 cur = next;
2856 }
2857 }
2858
2859 HeapRegion* G1CollectedHeap::next_compaction_region(const HeapRegion* from) const {
2860 HeapRegion* result = _hrm.next_region_in_heap(from);
2861 while (result != NULL && result->is_humongous()) {
2862 result = _hrm.next_region_in_heap(result);
2863 }
2864 return result;
2865 }
2866
2867 Space* G1CollectedHeap::space_containing(const void* addr) const {
2868 return heap_region_containing(addr);
2869 }
2870
2871 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2872 Space* sp = space_containing(addr);
2873 return sp->block_start(addr);
2874 }
2875
2876 size_t G1CollectedHeap::block_size(const HeapWord* addr) const {
2877 Space* sp = space_containing(addr);
2878 return sp->block_size(addr);
2879 }
2880
2881 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2882 Space* sp = space_containing(addr);
2883 return sp->block_is_obj(addr);
2884 }
2885
2886 bool G1CollectedHeap::supports_tlab_allocation() const {
2887 return true;
2888 }
2889
2890 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
2891 return (_g1_policy->young_list_target_length() - young_list()->survivor_length()) * HeapRegion::GrainBytes;
2892 }
2893
2894 size_t G1CollectedHeap::tlab_used(Thread* ignored) const {
2895 return young_list()->eden_used_bytes();
2896 }
2897
2898 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size
2899 // must be smaller than the humongous object limit.
2900 size_t G1CollectedHeap::max_tlab_size() const {
2901 return align_size_down(_humongous_object_threshold_in_words - 1, MinObjAlignment);
2902 }
2903
2904 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
2905 // Return the remaining space in the cur alloc region, but not less than
2906 // the min TLAB size.
2907
2908 // Also, this value can be at most the humongous object threshold,
2909 // since we can't allow tlabs to grow big enough to accommodate
2910 // humongous objects.
2911
2912 HeapRegion* hr = _allocator->mutator_alloc_region(AllocationContext::current())->get();
2913 size_t max_tlab = max_tlab_size() * wordSize;
2914 if (hr == NULL) {
2915 return max_tlab;
2916 } else {
2917 return MIN2(MAX2(hr->free(), (size_t) MinTLABSize), max_tlab);
2918 }
2919 }
2920
2921 size_t G1CollectedHeap::max_capacity() const {
2922 return _hrm.reserved().byte_size();
2923 }
2924
2925 jlong G1CollectedHeap::millis_since_last_gc() {
2926 // assert(false, "NYI");
2927 return 0;
2928 }
2929
2930 void G1CollectedHeap::prepare_for_verify() {
2931 if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) {
2932 ensure_parsability(false);
2933 }
2934 g1_rem_set()->prepare_for_verify();
2935 }
2936
2937 bool G1CollectedHeap::allocated_since_marking(oop obj, HeapRegion* hr,
2938 VerifyOption vo) {
2939 switch (vo) {
2940 case VerifyOption_G1UsePrevMarking:
2941 return hr->obj_allocated_since_prev_marking(obj);
2942 case VerifyOption_G1UseNextMarking:
2943 return hr->obj_allocated_since_next_marking(obj);
2944 case VerifyOption_G1UseMarkWord:
2945 return false;
2946 default:
2947 ShouldNotReachHere();
2948 }
2949 return false; // keep some compilers happy
2950 }
2951
2952 HeapWord* G1CollectedHeap::top_at_mark_start(HeapRegion* hr, VerifyOption vo) {
2953 switch (vo) {
2954 case VerifyOption_G1UsePrevMarking: return hr->prev_top_at_mark_start();
2955 case VerifyOption_G1UseNextMarking: return hr->next_top_at_mark_start();
2956 case VerifyOption_G1UseMarkWord: return NULL;
2957 default: ShouldNotReachHere();
2958 }
2959 return NULL; // keep some compilers happy
2960 }
2961
2962 bool G1CollectedHeap::is_marked(oop obj, VerifyOption vo) {
2963 switch (vo) {
2964 case VerifyOption_G1UsePrevMarking: return isMarkedPrev(obj);
2965 case VerifyOption_G1UseNextMarking: return isMarkedNext(obj);
2966 case VerifyOption_G1UseMarkWord: return obj->is_gc_marked();
2967 default: ShouldNotReachHere();
2968 }
2969 return false; // keep some compilers happy
2970 }
2971
2972 const char* G1CollectedHeap::top_at_mark_start_str(VerifyOption vo) {
2973 switch (vo) {
2974 case VerifyOption_G1UsePrevMarking: return "PTAMS";
2975 case VerifyOption_G1UseNextMarking: return "NTAMS";
2976 case VerifyOption_G1UseMarkWord: return "NONE";
2977 default: ShouldNotReachHere();
2978 }
2979 return NULL; // keep some compilers happy
2980 }
2981
2982 class VerifyRootsClosure: public OopClosure {
2983 private:
2984 G1CollectedHeap* _g1h;
2985 VerifyOption _vo;
2986 bool _failures;
2987 public:
2988 // _vo == UsePrevMarking -> use "prev" marking information,
2989 // _vo == UseNextMarking -> use "next" marking information,
2990 // _vo == UseMarkWord -> use mark word from object header.
2991 VerifyRootsClosure(VerifyOption vo) :
2992 _g1h(G1CollectedHeap::heap()),
2993 _vo(vo),
2994 _failures(false) { }
2995
2996 bool failures() { return _failures; }
2997
2998 template <class T> void do_oop_nv(T* p) {
2999 T heap_oop = oopDesc::load_heap_oop(p);
3000 if (!oopDesc::is_null(heap_oop)) {
3001 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
3002 if (_g1h->is_obj_dead_cond(obj, _vo)) {
3003 gclog_or_tty->print_cr("Root location "PTR_FORMAT" "
3004 "points to dead obj "PTR_FORMAT, p, (void*) obj);
3005 if (_vo == VerifyOption_G1UseMarkWord) {
3006 gclog_or_tty->print_cr(" Mark word: "PTR_FORMAT, (void*)(obj->mark()));
3007 }
3008 obj->print_on(gclog_or_tty);
3009 _failures = true;
3010 }
3011 }
3012 }
3013
3014 void do_oop(oop* p) { do_oop_nv(p); }
3015 void do_oop(narrowOop* p) { do_oop_nv(p); }
3016 };
3017
3018 class G1VerifyCodeRootOopClosure: public OopClosure {
3019 G1CollectedHeap* _g1h;
3020 OopClosure* _root_cl;
3021 nmethod* _nm;
3022 VerifyOption _vo;
3023 bool _failures;
3024
3025 template <class T> void do_oop_work(T* p) {
3026 // First verify that this root is live
3027 _root_cl->do_oop(p);
3028
3029 if (!G1VerifyHeapRegionCodeRoots) {
3030 // We're not verifying the code roots attached to heap region.
3031 return;
3032 }
3033
3034 // Don't check the code roots during marking verification in a full GC
3035 if (_vo == VerifyOption_G1UseMarkWord) {
3036 return;
3037 }
3038
3039 // Now verify that the current nmethod (which contains p) is
3040 // in the code root list of the heap region containing the
3041 // object referenced by p.
3042
3043 T heap_oop = oopDesc::load_heap_oop(p);
3044 if (!oopDesc::is_null(heap_oop)) {
3045 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
3046
3047 // Now fetch the region containing the object
3048 HeapRegion* hr = _g1h->heap_region_containing(obj);
3049 HeapRegionRemSet* hrrs = hr->rem_set();
3050 // Verify that the strong code root list for this region
3051 // contains the nmethod
3052 if (!hrrs->strong_code_roots_list_contains(_nm)) {
3053 gclog_or_tty->print_cr("Code root location "PTR_FORMAT" "
3054 "from nmethod "PTR_FORMAT" not in strong "
3055 "code roots for region ["PTR_FORMAT","PTR_FORMAT")",
3056 p, _nm, hr->bottom(), hr->end());
3057 _failures = true;
3058 }
3059 }
3060 }
3061
3062 public:
3063 G1VerifyCodeRootOopClosure(G1CollectedHeap* g1h, OopClosure* root_cl, VerifyOption vo):
3064 _g1h(g1h), _root_cl(root_cl), _vo(vo), _nm(NULL), _failures(false) {}
3065
3066 void do_oop(oop* p) { do_oop_work(p); }
3067 void do_oop(narrowOop* p) { do_oop_work(p); }
3068
3069 void set_nmethod(nmethod* nm) { _nm = nm; }
3070 bool failures() { return _failures; }
3071 };
3072
3073 class G1VerifyCodeRootBlobClosure: public CodeBlobClosure {
3074 G1VerifyCodeRootOopClosure* _oop_cl;
3075
3076 public:
3077 G1VerifyCodeRootBlobClosure(G1VerifyCodeRootOopClosure* oop_cl):
3078 _oop_cl(oop_cl) {}
3079
3080 void do_code_blob(CodeBlob* cb) {
3081 nmethod* nm = cb->as_nmethod_or_null();
3082 if (nm != NULL) {
3083 _oop_cl->set_nmethod(nm);
3084 nm->oops_do(_oop_cl);
3085 }
3086 }
3087 };
3088
3089 class YoungRefCounterClosure : public OopClosure {
3090 G1CollectedHeap* _g1h;
3091 int _count;
3092 public:
3093 YoungRefCounterClosure(G1CollectedHeap* g1h) : _g1h(g1h), _count(0) {}
3094 void do_oop(oop* p) { if (_g1h->is_in_young(*p)) { _count++; } }
3095 void do_oop(narrowOop* p) { ShouldNotReachHere(); }
3096
3097 int count() { return _count; }
3098 void reset_count() { _count = 0; };
3099 };
3100
3101 class VerifyKlassClosure: public KlassClosure {
3102 YoungRefCounterClosure _young_ref_counter_closure;
3103 OopClosure *_oop_closure;
3104 public:
3105 VerifyKlassClosure(G1CollectedHeap* g1h, OopClosure* cl) : _young_ref_counter_closure(g1h), _oop_closure(cl) {}
3106 void do_klass(Klass* k) {
3107 k->oops_do(_oop_closure);
3108
3109 _young_ref_counter_closure.reset_count();
3110 k->oops_do(&_young_ref_counter_closure);
3111 if (_young_ref_counter_closure.count() > 0) {
3112 guarantee(k->has_modified_oops(), err_msg("Klass " PTR_FORMAT ", has young refs but is not dirty.", k));
3113 }
3114 }
3115 };
3116
3117 class VerifyLivenessOopClosure: public OopClosure {
3118 G1CollectedHeap* _g1h;
3119 VerifyOption _vo;
3120 public:
3121 VerifyLivenessOopClosure(G1CollectedHeap* g1h, VerifyOption vo):
3122 _g1h(g1h), _vo(vo)
3123 { }
3124 void do_oop(narrowOop *p) { do_oop_work(p); }
3125 void do_oop( oop *p) { do_oop_work(p); }
3126
3127 template <class T> void do_oop_work(T *p) {
3128 oop obj = oopDesc::load_decode_heap_oop(p);
3129 guarantee(obj == NULL || !_g1h->is_obj_dead_cond(obj, _vo),
3130 "Dead object referenced by a not dead object");
3131 }
3132 };
3133
3134 class VerifyObjsInRegionClosure: public ObjectClosure {
3135 private:
3136 G1CollectedHeap* _g1h;
3137 size_t _live_bytes;
3138 HeapRegion *_hr;
3139 VerifyOption _vo;
3140 public:
3141 // _vo == UsePrevMarking -> use "prev" marking information,
3142 // _vo == UseNextMarking -> use "next" marking information,
3143 // _vo == UseMarkWord -> use mark word from object header.
3144 VerifyObjsInRegionClosure(HeapRegion *hr, VerifyOption vo)
3145 : _live_bytes(0), _hr(hr), _vo(vo) {
3146 _g1h = G1CollectedHeap::heap();
3147 }
3148 void do_object(oop o) {
3149 VerifyLivenessOopClosure isLive(_g1h, _vo);
3150 assert(o != NULL, "Huh?");
3151 if (!_g1h->is_obj_dead_cond(o, _vo)) {
3152 // If the object is alive according to the mark word,
3153 // then verify that the marking information agrees.
3154 // Note we can't verify the contra-positive of the
3155 // above: if the object is dead (according to the mark
3156 // word), it may not be marked, or may have been marked
3157 // but has since became dead, or may have been allocated
3158 // since the last marking.
3159 if (_vo == VerifyOption_G1UseMarkWord) {
3160 guarantee(!_g1h->is_obj_dead(o), "mark word and concurrent mark mismatch");
3161 }
3162
3163 o->oop_iterate_no_header(&isLive);
3164 if (!_hr->obj_allocated_since_prev_marking(o)) {
3165 size_t obj_size = o->size(); // Make sure we don't overflow
3166 _live_bytes += (obj_size * HeapWordSize);
3167 }
3168 }
3169 }
3170 size_t live_bytes() { return _live_bytes; }
3171 };
3172
3173 class PrintObjsInRegionClosure : public ObjectClosure {
3174 HeapRegion *_hr;
3175 G1CollectedHeap *_g1;
3176 public:
3177 PrintObjsInRegionClosure(HeapRegion *hr) : _hr(hr) {
3178 _g1 = G1CollectedHeap::heap();
3179 };
3180
3181 void do_object(oop o) {
3182 if (o != NULL) {
3183 HeapWord *start = (HeapWord *) o;
3184 size_t word_sz = o->size();
3185 gclog_or_tty->print("\nPrinting obj "PTR_FORMAT" of size " SIZE_FORMAT
3186 " isMarkedPrev %d isMarkedNext %d isAllocSince %d\n",
3187 (void*) o, word_sz,
3188 _g1->isMarkedPrev(o),
3189 _g1->isMarkedNext(o),
3190 _hr->obj_allocated_since_prev_marking(o));
3191 HeapWord *end = start + word_sz;
3192 HeapWord *cur;
3193 int *val;
3194 for (cur = start; cur < end; cur++) {
3195 val = (int *) cur;
3196 gclog_or_tty->print("\t "PTR_FORMAT":%d\n", val, *val);
3197 }
3198 }
3199 }
3200 };
3201
3202 class VerifyRegionClosure: public HeapRegionClosure {
3203 private:
3204 bool _par;
3205 VerifyOption _vo;
3206 bool _failures;
3207 public:
3208 // _vo == UsePrevMarking -> use "prev" marking information,
3209 // _vo == UseNextMarking -> use "next" marking information,
3210 // _vo == UseMarkWord -> use mark word from object header.
3211 VerifyRegionClosure(bool par, VerifyOption vo)
3212 : _par(par),
3213 _vo(vo),
3214 _failures(false) {}
3215
3216 bool failures() {
3217 return _failures;
3218 }
3219
3220 bool doHeapRegion(HeapRegion* r) {
3221 if (!r->is_continues_humongous()) {
3222 bool failures = false;
3223 r->verify(_vo, &failures);
3224 if (failures) {
3225 _failures = true;
3226 } else {
3227 VerifyObjsInRegionClosure not_dead_yet_cl(r, _vo);
3228 r->object_iterate(¬_dead_yet_cl);
3229 if (_vo != VerifyOption_G1UseNextMarking) {
3230 if (r->max_live_bytes() < not_dead_yet_cl.live_bytes()) {
3231 gclog_or_tty->print_cr("["PTR_FORMAT","PTR_FORMAT"] "
3232 "max_live_bytes "SIZE_FORMAT" "
3233 "< calculated "SIZE_FORMAT,
3234 r->bottom(), r->end(),
3235 r->max_live_bytes(),
3236 not_dead_yet_cl.live_bytes());
3237 _failures = true;
3238 }
3239 } else {
3240 // When vo == UseNextMarking we cannot currently do a sanity
3241 // check on the live bytes as the calculation has not been
3242 // finalized yet.
3243 }
3244 }
3245 }
3246 return false; // stop the region iteration if we hit a failure
3247 }
3248 };
3249
3250 // This is the task used for parallel verification of the heap regions
3251
3252 class G1ParVerifyTask: public AbstractGangTask {
3253 private:
3254 G1CollectedHeap* _g1h;
3255 VerifyOption _vo;
3256 bool _failures;
3257
3258 public:
3259 // _vo == UsePrevMarking -> use "prev" marking information,
3260 // _vo == UseNextMarking -> use "next" marking information,
3261 // _vo == UseMarkWord -> use mark word from object header.
3262 G1ParVerifyTask(G1CollectedHeap* g1h, VerifyOption vo) :
3263 AbstractGangTask("Parallel verify task"),
3264 _g1h(g1h),
3265 _vo(vo),
3266 _failures(false) { }
3267
3268 bool failures() {
3269 return _failures;
3270 }
3271
3272 void work(uint worker_id) {
3273 HandleMark hm;
3274 VerifyRegionClosure blk(true, _vo);
3275 _g1h->heap_region_par_iterate_chunked(&blk, worker_id,
3276 _g1h->workers()->active_workers(),
3277 HeapRegion::ParVerifyClaimValue);
3278 if (blk.failures()) {
3279 _failures = true;
3280 }
3281 }
3282 };
3283
3284 void G1CollectedHeap::verify(bool silent, VerifyOption vo) {
3285 if (SafepointSynchronize::is_at_safepoint()) {
3286 assert(Thread::current()->is_VM_thread(),
3287 "Expected to be executed serially by the VM thread at this point");
3288
3289 if (!silent) { gclog_or_tty->print("Roots "); }
3290 VerifyRootsClosure rootsCl(vo);
3291 VerifyKlassClosure klassCl(this, &rootsCl);
3292 CLDToKlassAndOopClosure cldCl(&klassCl, &rootsCl, false);
3293
3294 // We apply the relevant closures to all the oops in the
3295 // system dictionary, class loader data graph, the string table
3296 // and the nmethods in the code cache.
3297 G1VerifyCodeRootOopClosure codeRootsCl(this, &rootsCl, vo);
3298 G1VerifyCodeRootBlobClosure blobsCl(&codeRootsCl);
3299
3300 process_all_roots(true, // activate StrongRootsScope
3301 SO_AllCodeCache, // roots scanning options
3302 &rootsCl,
3303 &cldCl,
3304 &blobsCl);
3305
3306 bool failures = rootsCl.failures() || codeRootsCl.failures();
3307
3308 if (vo != VerifyOption_G1UseMarkWord) {
3309 // If we're verifying during a full GC then the region sets
3310 // will have been torn down at the start of the GC. Therefore
3311 // verifying the region sets will fail. So we only verify
3312 // the region sets when not in a full GC.
3313 if (!silent) { gclog_or_tty->print("HeapRegionSets "); }
3314 verify_region_sets();
3315 }
3316
3317 if (!silent) { gclog_or_tty->print("HeapRegions "); }
3318 if (GCParallelVerificationEnabled && ParallelGCThreads > 1) {
3319 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3320 "sanity check");
3321
3322 G1ParVerifyTask task(this, vo);
3323 assert(UseDynamicNumberOfGCThreads ||
3324 workers()->active_workers() == workers()->total_workers(),
3325 "If not dynamic should be using all the workers");
3326 int n_workers = workers()->active_workers();
3327 set_par_threads(n_workers);
3328 workers()->run_task(&task);
3329 set_par_threads(0);
3330 if (task.failures()) {
3331 failures = true;
3332 }
3333
3334 // Checks that the expected amount of parallel work was done.
3335 // The implication is that n_workers is > 0.
3336 assert(check_heap_region_claim_values(HeapRegion::ParVerifyClaimValue),
3337 "sanity check");
3338
3339 reset_heap_region_claim_values();
3340
3341 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3342 "sanity check");
3343 } else {
3344 VerifyRegionClosure blk(false, vo);
3345 heap_region_iterate(&blk);
3346 if (blk.failures()) {
3347 failures = true;
3348 }
3349 }
3350 if (!silent) gclog_or_tty->print("RemSet ");
3351 rem_set()->verify();
3352
3353 if (G1StringDedup::is_enabled()) {
3354 if (!silent) gclog_or_tty->print("StrDedup ");
3355 G1StringDedup::verify();
3356 }
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->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) {
3376 gclog_or_tty->print("(SKIPPING Roots, HeapRegionSets, HeapRegions, RemSet");
3377 if (G1StringDedup::is_enabled()) {
3378 gclog_or_tty->print(", StrDedup");
3379 }
3380 gclog_or_tty->print(") ");
3381 }
3382 }
3383 }
3384
3385 void G1CollectedHeap::verify(bool silent) {
3386 verify(silent, VerifyOption_G1UsePrevMarking);
3387 }
3388
3389 double G1CollectedHeap::verify(bool guard, const char* msg) {
3390 double verify_time_ms = 0.0;
3391
3392 if (guard && total_collections() >= VerifyGCStartAt) {
3393 double verify_start = os::elapsedTime();
3394 HandleMark hm; // Discard invalid handles created during verification
3395 prepare_for_verify();
3396 Universe::verify(VerifyOption_G1UsePrevMarking, msg);
3397 verify_time_ms = (os::elapsedTime() - verify_start) * 1000;
3398 }
3399
3400 return verify_time_ms;
3401 }
3402
3403 void G1CollectedHeap::verify_before_gc() {
3404 double verify_time_ms = verify(VerifyBeforeGC, " VerifyBeforeGC:");
3405 g1_policy()->phase_times()->record_verify_before_time_ms(verify_time_ms);
3406 }
3407
3408 void G1CollectedHeap::verify_after_gc() {
3409 double verify_time_ms = verify(VerifyAfterGC, " VerifyAfterGC:");
3410 g1_policy()->phase_times()->record_verify_after_time_ms(verify_time_ms);
3411 }
3412
3413 class PrintRegionClosure: public HeapRegionClosure {
3414 outputStream* _st;
3415 public:
3416 PrintRegionClosure(outputStream* st) : _st(st) {}
3417 bool doHeapRegion(HeapRegion* r) {
3418 r->print_on(_st);
3419 return false;
3420 }
3421 };
3422
3423 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
3424 const HeapRegion* hr,
3425 const VerifyOption vo) const {
3426 switch (vo) {
3427 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr);
3428 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr);
3429 case VerifyOption_G1UseMarkWord: return !obj->is_gc_marked();
3430 default: ShouldNotReachHere();
3431 }
3432 return false; // keep some compilers happy
3433 }
3434
3435 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
3436 const VerifyOption vo) const {
3437 switch (vo) {
3438 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj);
3439 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj);
3440 case VerifyOption_G1UseMarkWord: return !obj->is_gc_marked();
3441 default: ShouldNotReachHere();
3442 }
3443 return false; // keep some compilers happy
3444 }
3445
3446 void G1CollectedHeap::print_on(outputStream* st) const {
3447 st->print(" %-20s", "garbage-first heap");
3448 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
3449 capacity()/K, used_unlocked()/K);
3450 st->print(" [" INTPTR_FORMAT ", " INTPTR_FORMAT ", " INTPTR_FORMAT ")",
3451 _hrm.reserved().start(),
3452 _hrm.reserved().start() + _hrm.length() + HeapRegion::GrainWords,
3453 _hrm.reserved().end());
3454 st->cr();
3455 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
3456 uint young_regions = _young_list->length();
3457 st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
3458 (size_t) young_regions * HeapRegion::GrainBytes / K);
3459 uint survivor_regions = g1_policy()->recorded_survivor_regions();
3460 st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
3461 (size_t) survivor_regions * HeapRegion::GrainBytes / K);
3462 st->cr();
3463 MetaspaceAux::print_on(st);
3464 }
3465
3466 void G1CollectedHeap::print_extended_on(outputStream* st) const {
3467 print_on(st);
3468
3469 // Print the per-region information.
3470 st->cr();
3471 st->print_cr("Heap Regions: (Y=young(eden), SU=young(survivor), "
3472 "HS=humongous(starts), HC=humongous(continues), "
3473 "CS=collection set, F=free, TS=gc time stamp, "
3474 "PTAMS=previous top-at-mark-start, "
3475 "NTAMS=next top-at-mark-start)");
3476 PrintRegionClosure blk(st);
3477 heap_region_iterate(&blk);
3478 }
3479
3480 void G1CollectedHeap::print_on_error(outputStream* st) const {
3481 this->CollectedHeap::print_on_error(st);
3482
3483 if (_cm != NULL) {
3484 st->cr();
3485 _cm->print_on_error(st);
3486 }
3487 }
3488
3489 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
3490 if (G1CollectedHeap::use_parallel_gc_threads()) {
3491 workers()->print_worker_threads_on(st);
3492 }
3493 _cmThread->print_on(st);
3494 st->cr();
3495 _cm->print_worker_threads_on(st);
3496 _cg1r->print_worker_threads_on(st);
3497 if (G1StringDedup::is_enabled()) {
3498 G1StringDedup::print_worker_threads_on(st);
3499 }
3500 }
3501
3502 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
3503 if (G1CollectedHeap::use_parallel_gc_threads()) {
3504 workers()->threads_do(tc);
3505 }
3506 tc->do_thread(_cmThread);
3507 _cg1r->threads_do(tc);
3508 if (G1StringDedup::is_enabled()) {
3509 G1StringDedup::threads_do(tc);
3510 }
3511 }
3512
3513 void G1CollectedHeap::print_tracing_info() const {
3514 // We'll overload this to mean "trace GC pause statistics."
3515 if (TraceYoungGenTime || TraceOldGenTime) {
3516 // The "G1CollectorPolicy" is keeping track of these stats, so delegate
3517 // to that.
3518 g1_policy()->print_tracing_info();
3519 }
3520 if (G1SummarizeRSetStats) {
3521 g1_rem_set()->print_summary_info();
3522 }
3523 if (G1SummarizeConcMark) {
3524 concurrent_mark()->print_summary_info();
3525 }
3526 g1_policy()->print_yg_surv_rate_info();
3527 SpecializationStats::print();
3528 }
3529
3530 #ifndef PRODUCT
3531 // Helpful for debugging RSet issues.
3532
3533 class PrintRSetsClosure : public HeapRegionClosure {
3534 private:
3535 const char* _msg;
3536 size_t _occupied_sum;
3537
3538 public:
3539 bool doHeapRegion(HeapRegion* r) {
3540 HeapRegionRemSet* hrrs = r->rem_set();
3541 size_t occupied = hrrs->occupied();
3542 _occupied_sum += occupied;
3543
3544 gclog_or_tty->print_cr("Printing RSet for region "HR_FORMAT,
3545 HR_FORMAT_PARAMS(r));
3546 if (occupied == 0) {
3547 gclog_or_tty->print_cr(" RSet is empty");
3548 } else {
3549 hrrs->print();
3550 }
3551 gclog_or_tty->print_cr("----------");
3552 return false;
3553 }
3554
3555 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
3556 gclog_or_tty->cr();
3557 gclog_or_tty->print_cr("========================================");
3558 gclog_or_tty->print_cr("%s", msg);
3559 gclog_or_tty->cr();
3560 }
3561
3562 ~PrintRSetsClosure() {
3563 gclog_or_tty->print_cr("Occupied Sum: "SIZE_FORMAT, _occupied_sum);
3564 gclog_or_tty->print_cr("========================================");
3565 gclog_or_tty->cr();
3566 }
3567 };
3568
3569 void G1CollectedHeap::print_cset_rsets() {
3570 PrintRSetsClosure cl("Printing CSet RSets");
3571 collection_set_iterate(&cl);
3572 }
3573
3574 void G1CollectedHeap::print_all_rsets() {
3575 PrintRSetsClosure cl("Printing All RSets");;
3576 heap_region_iterate(&cl);
3577 }
3578 #endif // PRODUCT
3579
3580 G1CollectedHeap* G1CollectedHeap::heap() {
3581 assert(_sh->kind() == CollectedHeap::G1CollectedHeap,
3582 "not a garbage-first heap");
3583 return _g1h;
3584 }
3585
3586 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) {
3587 // always_do_update_barrier = false;
3588 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
3589 // Fill TLAB's and such
3590 accumulate_statistics_all_tlabs();
3591 ensure_parsability(true);
3592
3593 if (G1SummarizeRSetStats && (G1SummarizeRSetStatsPeriod > 0) &&
3594 (total_collections() % G1SummarizeRSetStatsPeriod == 0)) {
3595 g1_rem_set()->print_periodic_summary_info("Before GC RS summary");
3596 }
3597 }
3598
3599 void G1CollectedHeap::gc_epilogue(bool full) {
3600
3601 if (G1SummarizeRSetStats &&
3602 (G1SummarizeRSetStatsPeriod > 0) &&
3603 // we are at the end of the GC. Total collections has already been increased.
3604 ((total_collections() - 1) % G1SummarizeRSetStatsPeriod == 0)) {
3605 g1_rem_set()->print_periodic_summary_info("After GC RS summary");
3606 }
3607
3608 // FIXME: what is this about?
3609 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
3610 // is set.
3611 COMPILER2_PRESENT(assert(DerivedPointerTable::is_empty(),
3612 "derived pointer present"));
3613 // always_do_update_barrier = true;
3614
3615 resize_all_tlabs();
3616 allocation_context_stats().update(full);
3617
3618 // We have just completed a GC. Update the soft reference
3619 // policy with the new heap occupancy
3620 Universe::update_heap_info_at_gc();
3621 }
3622
3623 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
3624 unsigned int gc_count_before,
3625 bool* succeeded,
3626 GCCause::Cause gc_cause) {
3627 assert_heap_not_locked_and_not_at_safepoint();
3628 g1_policy()->record_stop_world_start();
3629 VM_G1IncCollectionPause op(gc_count_before,
3630 word_size,
3631 false, /* should_initiate_conc_mark */
3632 g1_policy()->max_pause_time_ms(),
3633 gc_cause);
3634
3635 op.set_allocation_context(AllocationContext::current());
3636 VMThread::execute(&op);
3637
3638 HeapWord* result = op.result();
3639 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
3640 assert(result == NULL || ret_succeeded,
3641 "the result should be NULL if the VM did not succeed");
3642 *succeeded = ret_succeeded;
3643
3644 assert_heap_not_locked();
3645 return result;
3646 }
3647
3648 void
3649 G1CollectedHeap::doConcurrentMark() {
3650 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
3651 if (!_cmThread->in_progress()) {
3652 _cmThread->set_started();
3653 CGC_lock->notify();
3654 }
3655 }
3656
3657 size_t G1CollectedHeap::pending_card_num() {
3658 size_t extra_cards = 0;
3659 JavaThread *curr = Threads::first();
3660 while (curr != NULL) {
3661 DirtyCardQueue& dcq = curr->dirty_card_queue();
3662 extra_cards += dcq.size();
3663 curr = curr->next();
3664 }
3665 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
3666 size_t buffer_size = dcqs.buffer_size();
3667 size_t buffer_num = dcqs.completed_buffers_num();
3668
3669 // PtrQueueSet::buffer_size() and PtrQueue:size() return sizes
3670 // in bytes - not the number of 'entries'. We need to convert
3671 // into a number of cards.
3672 return (buffer_size * buffer_num + extra_cards) / oopSize;
3673 }
3674
3675 size_t G1CollectedHeap::cards_scanned() {
3676 return g1_rem_set()->cardsScanned();
3677 }
3678
3679 bool G1CollectedHeap::humongous_region_is_always_live(uint index) {
3680 HeapRegion* region = region_at(index);
3681 assert(region->is_starts_humongous(), "Must start a humongous object");
3682 return oop(region->bottom())->is_objArray() || !region->rem_set()->is_empty();
3683 }
3684
3685 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure {
3686 private:
3687 size_t _total_humongous;
3688 size_t _candidate_humongous;
3689 public:
3690 RegisterHumongousWithInCSetFastTestClosure() : _total_humongous(0), _candidate_humongous(0) {
3691 }
3692
3693 virtual bool doHeapRegion(HeapRegion* r) {
3694 if (!r->is_starts_humongous()) {
3695 return false;
3696 }
3697 G1CollectedHeap* g1h = G1CollectedHeap::heap();
3698
3699 uint region_idx = r->hrm_index();
3700 bool is_candidate = !g1h->humongous_region_is_always_live(region_idx);
3701 // Is_candidate already filters out humongous regions with some remembered set.
3702 // This will not lead to humongous object that we mistakenly keep alive because
3703 // during young collection the remembered sets will only be added to.
3704 if (is_candidate) {
3705 g1h->register_humongous_region_with_in_cset_fast_test(region_idx);
3706 _candidate_humongous++;
3707 }
3708 _total_humongous++;
3709
3710 return false;
3711 }
3712
3713 size_t total_humongous() const { return _total_humongous; }
3714 size_t candidate_humongous() const { return _candidate_humongous; }
3715 };
3716
3717 void G1CollectedHeap::register_humongous_regions_with_in_cset_fast_test() {
3718 if (!G1ReclaimDeadHumongousObjectsAtYoungGC) {
3719 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0, 0);
3720 return;
3721 }
3722
3723 RegisterHumongousWithInCSetFastTestClosure cl;
3724 heap_region_iterate(&cl);
3725 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(cl.total_humongous(),
3726 cl.candidate_humongous());
3727 _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0;
3728
3729 if (_has_humongous_reclaim_candidates) {
3730 clear_humongous_is_live_table();
3731 }
3732 }
3733
3734 void
3735 G1CollectedHeap::setup_surviving_young_words() {
3736 assert(_surviving_young_words == NULL, "pre-condition");
3737 uint array_length = g1_policy()->young_cset_region_length();
3738 _surviving_young_words = NEW_C_HEAP_ARRAY(size_t, (size_t) array_length, mtGC);
3739 if (_surviving_young_words == NULL) {
3740 vm_exit_out_of_memory(sizeof(size_t) * array_length, OOM_MALLOC_ERROR,
3741 "Not enough space for young surv words summary.");
3742 }
3743 memset(_surviving_young_words, 0, (size_t) array_length * sizeof(size_t));
3744 #ifdef ASSERT
3745 for (uint i = 0; i < array_length; ++i) {
3746 assert( _surviving_young_words[i] == 0, "memset above" );
3747 }
3748 #endif // !ASSERT
3749 }
3750
3751 void
3752 G1CollectedHeap::update_surviving_young_words(size_t* surv_young_words) {
3753 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
3754 uint array_length = g1_policy()->young_cset_region_length();
3755 for (uint i = 0; i < array_length; ++i) {
3756 _surviving_young_words[i] += surv_young_words[i];
3757 }
3758 }
3759
3760 void
3761 G1CollectedHeap::cleanup_surviving_young_words() {
3762 guarantee( _surviving_young_words != NULL, "pre-condition" );
3763 FREE_C_HEAP_ARRAY(size_t, _surviving_young_words, mtGC);
3764 _surviving_young_words = NULL;
3765 }
3766
3767 #ifdef ASSERT
3768 class VerifyCSetClosure: public HeapRegionClosure {
3769 public:
3770 bool doHeapRegion(HeapRegion* hr) {
3771 // Here we check that the CSet region's RSet is ready for parallel
3772 // iteration. The fields that we'll verify are only manipulated
3773 // when the region is part of a CSet and is collected. Afterwards,
3774 // we reset these fields when we clear the region's RSet (when the
3775 // region is freed) so they are ready when the region is
3776 // re-allocated. The only exception to this is if there's an
3777 // evacuation failure and instead of freeing the region we leave
3778 // it in the heap. In that case, we reset these fields during
3779 // evacuation failure handling.
3780 guarantee(hr->rem_set()->verify_ready_for_par_iteration(), "verification");
3781
3782 // Here's a good place to add any other checks we'd like to
3783 // perform on CSet regions.
3784 return false;
3785 }
3786 };
3787 #endif // ASSERT
3788
3789 #if TASKQUEUE_STATS
3790 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
3791 st->print_raw_cr("GC Task Stats");
3792 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
3793 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
3794 }
3795
3796 void G1CollectedHeap::print_taskqueue_stats(outputStream* const st) const {
3797 print_taskqueue_stats_hdr(st);
3798
3799 TaskQueueStats totals;
3800 const int n = workers() != NULL ? workers()->total_workers() : 1;
3801 for (int i = 0; i < n; ++i) {
3802 st->print("%3d ", i); task_queue(i)->stats.print(st); st->cr();
3803 totals += task_queue(i)->stats;
3804 }
3805 st->print_raw("tot "); totals.print(st); st->cr();
3806
3807 DEBUG_ONLY(totals.verify());
3808 }
3809
3810 void G1CollectedHeap::reset_taskqueue_stats() {
3811 const int n = workers() != NULL ? workers()->total_workers() : 1;
3812 for (int i = 0; i < n; ++i) {
3813 task_queue(i)->stats.reset();
3814 }
3815 }
3816 #endif // TASKQUEUE_STATS
3817
3818 void G1CollectedHeap::log_gc_header() {
3819 if (!G1Log::fine()) {
3820 return;
3821 }
3822
3823 gclog_or_tty->gclog_stamp(_gc_tracer_stw->gc_id());
3824
3825 GCCauseString gc_cause_str = GCCauseString("GC pause", gc_cause())
3826 .append(g1_policy()->gcs_are_young() ? "(young)" : "(mixed)")
3827 .append(g1_policy()->during_initial_mark_pause() ? " (initial-mark)" : "");
3828
3829 gclog_or_tty->print("[%s", (const char*)gc_cause_str);
3830 }
3831
3832 void G1CollectedHeap::log_gc_footer(double pause_time_sec) {
3833 if (!G1Log::fine()) {
3834 return;
3835 }
3836
3837 if (G1Log::finer()) {
3838 if (evacuation_failed()) {
3839 gclog_or_tty->print(" (to-space exhausted)");
3840 }
3841 gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec);
3842 g1_policy()->phase_times()->note_gc_end();
3843 g1_policy()->phase_times()->print(pause_time_sec);
3844 g1_policy()->print_detailed_heap_transition();
3845 } else {
3846 if (evacuation_failed()) {
3847 gclog_or_tty->print("--");
3848 }
3849 g1_policy()->print_heap_transition();
3850 gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec);
3851 }
3852 gclog_or_tty->flush();
3853 }
3854
3855 bool
3856 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
3857 assert_at_safepoint(true /* should_be_vm_thread */);
3858 guarantee(!is_gc_active(), "collection is not reentrant");
3859
3860 if (GC_locker::check_active_before_gc()) {
3861 return false;
3862 }
3863
3864 _gc_timer_stw->register_gc_start();
3865
3866 _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start());
3867
3868 SvcGCMarker sgcm(SvcGCMarker::MINOR);
3869 ResourceMark rm;
3870
3871 print_heap_before_gc();
3872 trace_heap_before_gc(_gc_tracer_stw);
3873
3874 verify_region_sets_optional();
3875 verify_dirty_young_regions();
3876
3877 // This call will decide whether this pause is an initial-mark
3878 // pause. If it is, during_initial_mark_pause() will return true
3879 // for the duration of this pause.
3880 g1_policy()->decide_on_conc_mark_initiation();
3881
3882 // We do not allow initial-mark to be piggy-backed on a mixed GC.
3883 assert(!g1_policy()->during_initial_mark_pause() ||
3884 g1_policy()->gcs_are_young(), "sanity");
3885
3886 // We also do not allow mixed GCs during marking.
3887 assert(!mark_in_progress() || g1_policy()->gcs_are_young(), "sanity");
3888
3889 // Record whether this pause is an initial mark. When the current
3890 // thread has completed its logging output and it's safe to signal
3891 // the CM thread, the flag's value in the policy has been reset.
3892 bool should_start_conc_mark = g1_policy()->during_initial_mark_pause();
3893
3894 // Inner scope for scope based logging, timers, and stats collection
3895 {
3896 EvacuationInfo evacuation_info;
3897
3898 if (g1_policy()->during_initial_mark_pause()) {
3899 // We are about to start a marking cycle, so we increment the
3900 // full collection counter.
3901 increment_old_marking_cycles_started();
3902 register_concurrent_cycle_start(_gc_timer_stw->gc_start());
3903 }
3904
3905 _gc_tracer_stw->report_yc_type(yc_type());
3906
3907 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
3908
3909 int active_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
3910 workers()->active_workers() : 1);
3911 double pause_start_sec = os::elapsedTime();
3912 g1_policy()->phase_times()->note_gc_start(active_workers);
3913 log_gc_header();
3914
3915 TraceCollectorStats tcs(g1mm()->incremental_collection_counters());
3916 TraceMemoryManagerStats tms(false /* fullGC */, gc_cause());
3917
3918 // If the secondary_free_list is not empty, append it to the
3919 // free_list. No need to wait for the cleanup operation to finish;
3920 // the region allocation code will check the secondary_free_list
3921 // and wait if necessary. If the G1StressConcRegionFreeing flag is
3922 // set, skip this step so that the region allocation code has to
3923 // get entries from the secondary_free_list.
3924 if (!G1StressConcRegionFreeing) {
3925 append_secondary_free_list_if_not_empty_with_lock();
3926 }
3927
3928 assert(check_young_list_well_formed(), "young list should be well formed");
3929 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3930 "sanity check");
3931
3932 // Don't dynamically change the number of GC threads this early. A value of
3933 // 0 is used to indicate serial work. When parallel work is done,
3934 // it will be set.
3935
3936 { // Call to jvmpi::post_class_unload_events must occur outside of active GC
3937 IsGCActiveMark x;
3938
3939 gc_prologue(false);
3940 increment_total_collections(false /* full gc */);
3941 increment_gc_time_stamp();
3942
3943 verify_before_gc();
3944
3945 check_bitmaps("GC Start");
3946
3947 COMPILER2_PRESENT(DerivedPointerTable::clear());
3948
3949 // Please see comment in g1CollectedHeap.hpp and
3950 // G1CollectedHeap::ref_processing_init() to see how
3951 // reference processing currently works in G1.
3952
3953 // Enable discovery in the STW reference processor
3954 ref_processor_stw()->enable_discovery(true /*verify_disabled*/,
3955 true /*verify_no_refs*/);
3956
3957 {
3958 // We want to temporarily turn off discovery by the
3959 // CM ref processor, if necessary, and turn it back on
3960 // on again later if we do. Using a scoped
3961 // NoRefDiscovery object will do this.
3962 NoRefDiscovery no_cm_discovery(ref_processor_cm());
3963
3964 // Forget the current alloc region (we might even choose it to be part
3965 // of the collection set!).
3966 _allocator->release_mutator_alloc_region();
3967
3968 // We should call this after we retire the mutator alloc
3969 // region(s) so that all the ALLOC / RETIRE events are generated
3970 // before the start GC event.
3971 _hr_printer.start_gc(false /* full */, (size_t) total_collections());
3972
3973 // This timing is only used by the ergonomics to handle our pause target.
3974 // It is unclear why this should not include the full pause. We will
3975 // investigate this in CR 7178365.
3976 //
3977 // Preserving the old comment here if that helps the investigation:
3978 //
3979 // The elapsed time induced by the start time below deliberately elides
3980 // the possible verification above.
3981 double sample_start_time_sec = os::elapsedTime();
3982
3983 #if YOUNG_LIST_VERBOSE
3984 gclog_or_tty->print_cr("\nBefore recording pause start.\nYoung_list:");
3985 _young_list->print();
3986 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3987 #endif // YOUNG_LIST_VERBOSE
3988
3989 g1_policy()->record_collection_pause_start(sample_start_time_sec);
3990
3991 double scan_wait_start = os::elapsedTime();
3992 // We have to wait until the CM threads finish scanning the
3993 // root regions as it's the only way to ensure that all the
3994 // objects on them have been correctly scanned before we start
3995 // moving them during the GC.
3996 bool waited = _cm->root_regions()->wait_until_scan_finished();
3997 double wait_time_ms = 0.0;
3998 if (waited) {
3999 double scan_wait_end = os::elapsedTime();
4000 wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
4001 }
4002 g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms);
4003
4004 #if YOUNG_LIST_VERBOSE
4005 gclog_or_tty->print_cr("\nAfter recording pause start.\nYoung_list:");
4006 _young_list->print();
4007 #endif // YOUNG_LIST_VERBOSE
4008
4009 if (g1_policy()->during_initial_mark_pause()) {
4010 concurrent_mark()->checkpointRootsInitialPre();
4011 }
4012
4013 #if YOUNG_LIST_VERBOSE
4014 gclog_or_tty->print_cr("\nBefore choosing collection set.\nYoung_list:");
4015 _young_list->print();
4016 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
4017 #endif // YOUNG_LIST_VERBOSE
4018
4019 g1_policy()->finalize_cset(target_pause_time_ms, evacuation_info);
4020
4021 register_humongous_regions_with_in_cset_fast_test();
4022
4023 _cm->note_start_of_gc();
4024 // We should not verify the per-thread SATB buffers given that
4025 // we have not filtered them yet (we'll do so during the
4026 // GC). We also call this after finalize_cset() to
4027 // ensure that the CSet has been finalized.
4028 _cm->verify_no_cset_oops(true /* verify_stacks */,
4029 true /* verify_enqueued_buffers */,
4030 false /* verify_thread_buffers */,
4031 true /* verify_fingers */);
4032
4033 if (_hr_printer.is_active()) {
4034 HeapRegion* hr = g1_policy()->collection_set();
4035 while (hr != NULL) {
4036 _hr_printer.cset(hr);
4037 hr = hr->next_in_collection_set();
4038 }
4039 }
4040
4041 #ifdef ASSERT
4042 VerifyCSetClosure cl;
4043 collection_set_iterate(&cl);
4044 #endif // ASSERT
4045
4046 setup_surviving_young_words();
4047
4048 // Initialize the GC alloc regions.
4049 _allocator->init_gc_alloc_regions(evacuation_info);
4050
4051 // Actually do the work...
4052 evacuate_collection_set(evacuation_info);
4053
4054 // We do this to mainly verify the per-thread SATB buffers
4055 // (which have been filtered by now) since we didn't verify
4056 // them earlier. No point in re-checking the stacks / enqueued
4057 // buffers given that the CSet has not changed since last time
4058 // we checked.
4059 _cm->verify_no_cset_oops(false /* verify_stacks */,
4060 false /* verify_enqueued_buffers */,
4061 true /* verify_thread_buffers */,
4062 true /* verify_fingers */);
4063
4064 free_collection_set(g1_policy()->collection_set(), evacuation_info);
4065
4066 eagerly_reclaim_humongous_regions();
4067
4068 g1_policy()->clear_collection_set();
4069
4070 cleanup_surviving_young_words();
4071
4072 // Start a new incremental collection set for the next pause.
4073 g1_policy()->start_incremental_cset_building();
4074
4075 clear_cset_fast_test();
4076
4077 _young_list->reset_sampled_info();
4078
4079 // Don't check the whole heap at this point as the
4080 // GC alloc regions from this pause have been tagged
4081 // as survivors and moved on to the survivor list.
4082 // Survivor regions will fail the !is_young() check.
4083 assert(check_young_list_empty(false /* check_heap */),
4084 "young list should be empty");
4085
4086 #if YOUNG_LIST_VERBOSE
4087 gclog_or_tty->print_cr("Before recording survivors.\nYoung List:");
4088 _young_list->print();
4089 #endif // YOUNG_LIST_VERBOSE
4090
4091 g1_policy()->record_survivor_regions(_young_list->survivor_length(),
4092 _young_list->first_survivor_region(),
4093 _young_list->last_survivor_region());
4094
4095 _young_list->reset_auxilary_lists();
4096
4097 if (evacuation_failed()) {
4098 _allocator->set_used(recalculate_used());
4099 uint n_queues = MAX2((int)ParallelGCThreads, 1);
4100 for (uint i = 0; i < n_queues; i++) {
4101 if (_evacuation_failed_info_array[i].has_failed()) {
4102 _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]);
4103 }
4104 }
4105 } else {
4106 // The "used" of the the collection set have already been subtracted
4107 // when they were freed. Add in the bytes evacuated.
4108 _allocator->increase_used(g1_policy()->bytes_copied_during_gc());
4109 }
4110
4111 if (g1_policy()->during_initial_mark_pause()) {
4112 // We have to do this before we notify the CM threads that
4113 // they can start working to make sure that all the
4114 // appropriate initialization is done on the CM object.
4115 concurrent_mark()->checkpointRootsInitialPost();
4116 set_marking_started();
4117 // Note that we don't actually trigger the CM thread at
4118 // this point. We do that later when we're sure that
4119 // the current thread has completed its logging output.
4120 }
4121
4122 allocate_dummy_regions();
4123
4124 #if YOUNG_LIST_VERBOSE
4125 gclog_or_tty->print_cr("\nEnd of the pause.\nYoung_list:");
4126 _young_list->print();
4127 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
4128 #endif // YOUNG_LIST_VERBOSE
4129
4130 _allocator->init_mutator_alloc_region();
4131
4132 {
4133 size_t expand_bytes = g1_policy()->expansion_amount();
4134 if (expand_bytes > 0) {
4135 size_t bytes_before = capacity();
4136 // No need for an ergo verbose message here,
4137 // expansion_amount() does this when it returns a value > 0.
4138 if (!expand(expand_bytes)) {
4139 // We failed to expand the heap. Cannot do anything about it.
4140 }
4141 }
4142 }
4143
4144 // We redo the verification but now wrt to the new CSet which
4145 // has just got initialized after the previous CSet was freed.
4146 _cm->verify_no_cset_oops(true /* verify_stacks */,
4147 true /* verify_enqueued_buffers */,
4148 true /* verify_thread_buffers */,
4149 true /* verify_fingers */);
4150 _cm->note_end_of_gc();
4151
4152 // This timing is only used by the ergonomics to handle our pause target.
4153 // It is unclear why this should not include the full pause. We will
4154 // investigate this in CR 7178365.
4155 double sample_end_time_sec = os::elapsedTime();
4156 double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
4157 g1_policy()->record_collection_pause_end(pause_time_ms, evacuation_info);
4158
4159 MemoryService::track_memory_usage();
4160
4161 // In prepare_for_verify() below we'll need to scan the deferred
4162 // update buffers to bring the RSets up-to-date if
4163 // G1HRRSFlushLogBuffersOnVerify has been set. While scanning
4164 // the update buffers we'll probably need to scan cards on the
4165 // regions we just allocated to (i.e., the GC alloc
4166 // regions). However, during the last GC we called
4167 // set_saved_mark() on all the GC alloc regions, so card
4168 // scanning might skip the [saved_mark_word()...top()] area of
4169 // those regions (i.e., the area we allocated objects into
4170 // during the last GC). But it shouldn't. Given that
4171 // saved_mark_word() is conditional on whether the GC time stamp
4172 // on the region is current or not, by incrementing the GC time
4173 // stamp here we invalidate all the GC time stamps on all the
4174 // regions and saved_mark_word() will simply return top() for
4175 // all the regions. This is a nicer way of ensuring this rather
4176 // than iterating over the regions and fixing them. In fact, the
4177 // GC time stamp increment here also ensures that
4178 // saved_mark_word() will return top() between pauses, i.e.,
4179 // during concurrent refinement. So we don't need the
4180 // is_gc_active() check to decided which top to use when
4181 // scanning cards (see CR 7039627).
4182 increment_gc_time_stamp();
4183
4184 verify_after_gc();
4185 check_bitmaps("GC End");
4186
4187 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
4188 ref_processor_stw()->verify_no_references_recorded();
4189
4190 // CM reference discovery will be re-enabled if necessary.
4191 }
4192
4193 // We should do this after we potentially expand the heap so
4194 // that all the COMMIT events are generated before the end GC
4195 // event, and after we retire the GC alloc regions so that all
4196 // RETIRE events are generated before the end GC event.
4197 _hr_printer.end_gc(false /* full */, (size_t) total_collections());
4198
4199 #ifdef TRACESPINNING
4200 ParallelTaskTerminator::print_termination_counts();
4201 #endif
4202
4203 gc_epilogue(false);
4204 }
4205
4206 // Print the remainder of the GC log output.
4207 log_gc_footer(os::elapsedTime() - pause_start_sec);
4208
4209 // It is not yet to safe to tell the concurrent mark to
4210 // start as we have some optional output below. We don't want the
4211 // output from the concurrent mark thread interfering with this
4212 // logging output either.
4213
4214 _hrm.verify_optional();
4215 verify_region_sets_optional();
4216
4217 TASKQUEUE_STATS_ONLY(if (ParallelGCVerbose) print_taskqueue_stats());
4218 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
4219
4220 print_heap_after_gc();
4221 trace_heap_after_gc(_gc_tracer_stw);
4222
4223 // We must call G1MonitoringSupport::update_sizes() in the same scoping level
4224 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
4225 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
4226 // before any GC notifications are raised.
4227 g1mm()->update_sizes();
4228
4229 _gc_tracer_stw->report_evacuation_info(&evacuation_info);
4230 _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold());
4231 _gc_timer_stw->register_gc_end();
4232 _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions());
4233 }
4234 // It should now be safe to tell the concurrent mark thread to start
4235 // without its logging output interfering with the logging output
4236 // that came from the pause.
4237
4238 if (should_start_conc_mark) {
4239 // CAUTION: after the doConcurrentMark() call below,
4240 // the concurrent marking thread(s) could be running
4241 // concurrently with us. Make sure that anything after
4242 // this point does not assume that we are the only GC thread
4243 // running. Note: of course, the actual marking work will
4244 // not start until the safepoint itself is released in
4245 // SuspendibleThreadSet::desynchronize().
4246 doConcurrentMark();
4247 }
4248
4249 return true;
4250 }
4251
4252 size_t G1CollectedHeap::desired_plab_sz(GCAllocPurpose purpose)
4253 {
4254 size_t gclab_word_size;
4255 switch (purpose) {
4256 case GCAllocForSurvived:
4257 gclab_word_size = _survivor_plab_stats.desired_plab_sz();
4258 break;
4259 case GCAllocForTenured:
4260 gclab_word_size = _old_plab_stats.desired_plab_sz();
4261 break;
4262 default:
4263 assert(false, "unknown GCAllocPurpose");
4264 gclab_word_size = _old_plab_stats.desired_plab_sz();
4265 break;
4266 }
4267
4268 // Prevent humongous PLAB sizes for two reasons:
4269 // * PLABs are allocated using a similar paths as oops, but should
4270 // never be in a humongous region
4271 // * Allowing humongous PLABs needlessly churns the region free lists
4272 return MIN2(_humongous_object_threshold_in_words, gclab_word_size);
4273 }
4274
4275 void G1CollectedHeap::init_for_evac_failure(OopsInHeapRegionClosure* cl) {
4276 _drain_in_progress = false;
4277 set_evac_failure_closure(cl);
4278 _evac_failure_scan_stack = new (ResourceObj::C_HEAP, mtGC) GrowableArray<oop>(40, true);
4279 }
4280
4281 void G1CollectedHeap::finalize_for_evac_failure() {
4282 assert(_evac_failure_scan_stack != NULL &&
4283 _evac_failure_scan_stack->length() == 0,
4284 "Postcondition");
4285 assert(!_drain_in_progress, "Postcondition");
4286 delete _evac_failure_scan_stack;
4287 _evac_failure_scan_stack = NULL;
4288 }
4289
4290 void G1CollectedHeap::remove_self_forwarding_pointers() {
4291 assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity");
4292
4293 double remove_self_forwards_start = os::elapsedTime();
4294
4295 G1ParRemoveSelfForwardPtrsTask rsfp_task(this);
4296
4297 if (G1CollectedHeap::use_parallel_gc_threads()) {
4298 set_par_threads();
4299 workers()->run_task(&rsfp_task);
4300 set_par_threads(0);
4301 } else {
4302 rsfp_task.work(0);
4303 }
4304
4305 assert(check_cset_heap_region_claim_values(HeapRegion::ParEvacFailureClaimValue), "sanity");
4306
4307 // Reset the claim values in the regions in the collection set.
4308 reset_cset_heap_region_claim_values();
4309
4310 assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity");
4311
4312 // Now restore saved marks, if any.
4313 assert(_objs_with_preserved_marks.size() ==
4314 _preserved_marks_of_objs.size(), "Both or none.");
4315 while (!_objs_with_preserved_marks.is_empty()) {
4316 oop obj = _objs_with_preserved_marks.pop();
4317 markOop m = _preserved_marks_of_objs.pop();
4318 obj->set_mark(m);
4319 }
4320 _objs_with_preserved_marks.clear(true);
4321 _preserved_marks_of_objs.clear(true);
4322
4323 g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0);
4324 }
4325
4326 void G1CollectedHeap::push_on_evac_failure_scan_stack(oop obj) {
4327 _evac_failure_scan_stack->push(obj);
4328 }
4329
4330 void G1CollectedHeap::drain_evac_failure_scan_stack() {
4331 assert(_evac_failure_scan_stack != NULL, "precondition");
4332
4333 while (_evac_failure_scan_stack->length() > 0) {
4334 oop obj = _evac_failure_scan_stack->pop();
4335 _evac_failure_closure->set_region(heap_region_containing(obj));
4336 obj->oop_iterate_backwards(_evac_failure_closure);
4337 }
4338 }
4339
4340 oop
4341 G1CollectedHeap::handle_evacuation_failure_par(G1ParScanThreadState* _par_scan_state,
4342 oop old) {
4343 assert(obj_in_cs(old),
4344 err_msg("obj: "PTR_FORMAT" should still be in the CSet",
4345 (HeapWord*) old));
4346 markOop m = old->mark();
4347 oop forward_ptr = old->forward_to_atomic(old);
4348 if (forward_ptr == NULL) {
4349 // Forward-to-self succeeded.
4350 assert(_par_scan_state != NULL, "par scan state");
4351 OopsInHeapRegionClosure* cl = _par_scan_state->evac_failure_closure();
4352 uint queue_num = _par_scan_state->queue_num();
4353
4354 _evacuation_failed = true;
4355 _evacuation_failed_info_array[queue_num].register_copy_failure(old->size());
4356 if (_evac_failure_closure != cl) {
4357 MutexLockerEx x(EvacFailureStack_lock, Mutex::_no_safepoint_check_flag);
4358 assert(!_drain_in_progress,
4359 "Should only be true while someone holds the lock.");
4360 // Set the global evac-failure closure to the current thread's.
4361 assert(_evac_failure_closure == NULL, "Or locking has failed.");
4362 set_evac_failure_closure(cl);
4363 // Now do the common part.
4364 handle_evacuation_failure_common(old, m);
4365 // Reset to NULL.
4366 set_evac_failure_closure(NULL);
4367 } else {
4368 // The lock is already held, and this is recursive.
4369 assert(_drain_in_progress, "This should only be the recursive case.");
4370 handle_evacuation_failure_common(old, m);
4371 }
4372 return old;
4373 } else {
4374 // Forward-to-self failed. Either someone else managed to allocate
4375 // space for this object (old != forward_ptr) or they beat us in
4376 // self-forwarding it (old == forward_ptr).
4377 assert(old == forward_ptr || !obj_in_cs(forward_ptr),
4378 err_msg("obj: "PTR_FORMAT" forwarded to: "PTR_FORMAT" "
4379 "should not be in the CSet",
4380 (HeapWord*) old, (HeapWord*) forward_ptr));
4381 return forward_ptr;
4382 }
4383 }
4384
4385 void G1CollectedHeap::handle_evacuation_failure_common(oop old, markOop m) {
4386 preserve_mark_if_necessary(old, m);
4387
4388 HeapRegion* r = heap_region_containing(old);
4389 if (!r->evacuation_failed()) {
4390 r->set_evacuation_failed(true);
4391 _hr_printer.evac_failure(r);
4392 }
4393
4394 push_on_evac_failure_scan_stack(old);
4395
4396 if (!_drain_in_progress) {
4397 // prevent recursion in copy_to_survivor_space()
4398 _drain_in_progress = true;
4399 drain_evac_failure_scan_stack();
4400 _drain_in_progress = false;
4401 }
4402 }
4403
4404 void G1CollectedHeap::preserve_mark_if_necessary(oop obj, markOop m) {
4405 assert(evacuation_failed(), "Oversaving!");
4406 // We want to call the "for_promotion_failure" version only in the
4407 // case of a promotion failure.
4408 if (m->must_be_preserved_for_promotion_failure(obj)) {
4409 _objs_with_preserved_marks.push(obj);
4410 _preserved_marks_of_objs.push(m);
4411 }
4412 }
4413
4414 HeapWord* G1CollectedHeap::par_allocate_during_gc(GCAllocPurpose purpose,
4415 size_t word_size,
4416 AllocationContext_t context) {
4417 if (purpose == GCAllocForSurvived) {
4418 HeapWord* result = survivor_attempt_allocation(word_size, context);
4419 if (result != NULL) {
4420 return result;
4421 } else {
4422 // Let's try to allocate in the old gen in case we can fit the
4423 // object there.
4424 return old_attempt_allocation(word_size, context);
4425 }
4426 } else {
4427 assert(purpose == GCAllocForTenured, "sanity");
4428 HeapWord* result = old_attempt_allocation(word_size, context);
4429 if (result != NULL) {
4430 return result;
4431 } else {
4432 // Let's try to allocate in the survivors in case we can fit the
4433 // object there.
4434 return survivor_attempt_allocation(word_size, context);
4435 }
4436 }
4437
4438 ShouldNotReachHere();
4439 // Trying to keep some compilers happy.
4440 return NULL;
4441 }
4442
4443 void G1ParCopyHelper::mark_object(oop obj) {
4444 assert(!_g1->heap_region_containing(obj)->in_collection_set(), "should not mark objects in the CSet");
4445
4446 // We know that the object is not moving so it's safe to read its size.
4447 _cm->grayRoot(obj, (size_t) obj->size(), _worker_id);
4448 }
4449
4450 void G1ParCopyHelper::mark_forwarded_object(oop from_obj, oop to_obj) {
4451 assert(from_obj->is_forwarded(), "from obj should be forwarded");
4452 assert(from_obj->forwardee() == to_obj, "to obj should be the forwardee");
4453 assert(from_obj != to_obj, "should not be self-forwarded");
4454
4455 assert(_g1->heap_region_containing(from_obj)->in_collection_set(), "from obj should be in the CSet");
4456 assert(!_g1->heap_region_containing(to_obj)->in_collection_set(), "should not mark objects in the CSet");
4457
4458 // The object might be in the process of being copied by another
4459 // worker so we cannot trust that its to-space image is
4460 // well-formed. So we have to read its size from its from-space
4461 // image which we know should not be changing.
4462 _cm->grayRoot(to_obj, (size_t) from_obj->size(), _worker_id);
4463 }
4464
4465 template <class T>
4466 void G1ParCopyHelper::do_klass_barrier(T* p, oop new_obj) {
4467 if (_g1->heap_region_containing_raw(new_obj)->is_young()) {
4468 _scanned_klass->record_modified_oops();
4469 }
4470 }
4471
4472 template <G1Barrier barrier, G1Mark do_mark_object>
4473 template <class T>
4474 void G1ParCopyClosure<barrier, do_mark_object>::do_oop_work(T* p) {
4475 T heap_oop = oopDesc::load_heap_oop(p);
4476
4477 if (oopDesc::is_null(heap_oop)) {
4478 return;
4479 }
4480
4481 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
4482
4483 assert(_worker_id == _par_scan_state->queue_num(), "sanity");
4484
4485 G1CollectedHeap::in_cset_state_t state = _g1->in_cset_state(obj);
4486
4487 if (state == G1CollectedHeap::InCSet) {
4488 oop forwardee;
4489 if (obj->is_forwarded()) {
4490 forwardee = obj->forwardee();
4491 } else {
4492 forwardee = _par_scan_state->copy_to_survivor_space(obj);
4493 }
4494 assert(forwardee != NULL, "forwardee should not be NULL");
4495 oopDesc::encode_store_heap_oop(p, forwardee);
4496 if (do_mark_object != G1MarkNone && forwardee != obj) {
4497 // If the object is self-forwarded we don't need to explicitly
4498 // mark it, the evacuation failure protocol will do so.
4499 mark_forwarded_object(obj, forwardee);
4500 }
4501
4502 if (barrier == G1BarrierKlass) {
4503 do_klass_barrier(p, forwardee);
4504 }
4505 } else {
4506 if (state == G1CollectedHeap::IsHumongous) {
4507 _g1->set_humongous_is_live(obj);
4508 }
4509 // The object is not in collection set. If we're a root scanning
4510 // closure during an initial mark pause then attempt to mark the object.
4511 if (do_mark_object == G1MarkFromRoot) {
4512 mark_object(obj);
4513 }
4514 }
4515
4516 if (barrier == G1BarrierEvac) {
4517 _par_scan_state->update_rs(_from, p, _worker_id);
4518 }
4519 }
4520
4521 template void G1ParCopyClosure<G1BarrierEvac, G1MarkNone>::do_oop_work(oop* p);
4522 template void G1ParCopyClosure<G1BarrierEvac, G1MarkNone>::do_oop_work(narrowOop* p);
4523
4524 class G1ParEvacuateFollowersClosure : public VoidClosure {
4525 protected:
4526 G1CollectedHeap* _g1h;
4527 G1ParScanThreadState* _par_scan_state;
4528 RefToScanQueueSet* _queues;
4529 ParallelTaskTerminator* _terminator;
4530
4531 G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
4532 RefToScanQueueSet* queues() { return _queues; }
4533 ParallelTaskTerminator* terminator() { return _terminator; }
4534
4535 public:
4536 G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h,
4537 G1ParScanThreadState* par_scan_state,
4538 RefToScanQueueSet* queues,
4539 ParallelTaskTerminator* terminator)
4540 : _g1h(g1h), _par_scan_state(par_scan_state),
4541 _queues(queues), _terminator(terminator) {}
4542
4543 void do_void();
4544
4545 private:
4546 inline bool offer_termination();
4547 };
4548
4549 bool G1ParEvacuateFollowersClosure::offer_termination() {
4550 G1ParScanThreadState* const pss = par_scan_state();
4551 pss->start_term_time();
4552 const bool res = terminator()->offer_termination();
4553 pss->end_term_time();
4554 return res;
4555 }
4556
4557 void G1ParEvacuateFollowersClosure::do_void() {
4558 G1ParScanThreadState* const pss = par_scan_state();
4559 pss->trim_queue();
4560 do {
4561 pss->steal_and_trim_queue(queues());
4562 } while (!offer_termination());
4563 }
4564
4565 class G1KlassScanClosure : public KlassClosure {
4566 G1ParCopyHelper* _closure;
4567 bool _process_only_dirty;
4568 int _count;
4569 public:
4570 G1KlassScanClosure(G1ParCopyHelper* closure, bool process_only_dirty)
4571 : _process_only_dirty(process_only_dirty), _closure(closure), _count(0) {}
4572 void do_klass(Klass* klass) {
4573 // If the klass has not been dirtied we know that there's
4574 // no references into the young gen and we can skip it.
4575 if (!_process_only_dirty || klass->has_modified_oops()) {
4576 // Clean the klass since we're going to scavenge all the metadata.
4577 klass->clear_modified_oops();
4578
4579 // Tell the closure that this klass is the Klass to scavenge
4580 // and is the one to dirty if oops are left pointing into the young gen.
4581 _closure->set_scanned_klass(klass);
4582
4583 klass->oops_do(_closure);
4584
4585 _closure->set_scanned_klass(NULL);
4586 }
4587 _count++;
4588 }
4589 };
4590
4591 class G1CodeBlobClosure : public CodeBlobClosure {
4592 class HeapRegionGatheringOopClosure : public OopClosure {
4593 G1CollectedHeap* _g1h;
4594 OopClosure* _work;
4595 nmethod* _nm;
4596
4597 template <typename T>
4598 void do_oop_work(T* p) {
4599 _work->do_oop(p);
4600 T oop_or_narrowoop = oopDesc::load_heap_oop(p);
4601 if (!oopDesc::is_null(oop_or_narrowoop)) {
4602 oop o = oopDesc::decode_heap_oop_not_null(oop_or_narrowoop);
4603 HeapRegion* hr = _g1h->heap_region_containing_raw(o);
4604 assert(!_g1h->obj_in_cs(o) || hr->rem_set()->strong_code_roots_list_contains(_nm), "if o still in CS then evacuation failed and nm must already be in the remset");
4605 hr->add_strong_code_root(_nm);
4606 }
4607 }
4608
4609 public:
4610 HeapRegionGatheringOopClosure(OopClosure* oc) : _g1h(G1CollectedHeap::heap()), _work(oc), _nm(NULL) {}
4611
4612 void do_oop(oop* o) {
4613 do_oop_work(o);
4614 }
4615
4616 void do_oop(narrowOop* o) {
4617 do_oop_work(o);
4618 }
4619
4620 void set_nm(nmethod* nm) {
4621 _nm = nm;
4622 }
4623 };
4624
4625 HeapRegionGatheringOopClosure _oc;
4626 public:
4627 G1CodeBlobClosure(OopClosure* oc) : _oc(oc) {}
4628
4629 void do_code_blob(CodeBlob* cb) {
4630 nmethod* nm = cb->as_nmethod_or_null();
4631 if (nm != NULL) {
4632 if (!nm->test_set_oops_do_mark()) {
4633 _oc.set_nm(nm);
4634 nm->oops_do(&_oc);
4635 nm->fix_oop_relocations();
4636 }
4637 }
4638 }
4639 };
4640
4641 class G1ParTask : public AbstractGangTask {
4642 protected:
4643 G1CollectedHeap* _g1h;
4644 RefToScanQueueSet *_queues;
4645 ParallelTaskTerminator _terminator;
4646 uint _n_workers;
4647
4648 Mutex _stats_lock;
4649 Mutex* stats_lock() { return &_stats_lock; }
4650
4651 public:
4652 G1ParTask(G1CollectedHeap* g1h, RefToScanQueueSet *task_queues)
4653 : AbstractGangTask("G1 collection"),
4654 _g1h(g1h),
4655 _queues(task_queues),
4656 _terminator(0, _queues),
4657 _stats_lock(Mutex::leaf, "parallel G1 stats lock", true)
4658 {}
4659
4660 RefToScanQueueSet* queues() { return _queues; }
4661
4662 RefToScanQueue *work_queue(int i) {
4663 return queues()->queue(i);
4664 }
4665
4666 ParallelTaskTerminator* terminator() { return &_terminator; }
4667
4668 virtual void set_for_termination(int active_workers) {
4669 // This task calls set_n_termination() in par_non_clean_card_iterate_work()
4670 // in the young space (_par_seq_tasks) in the G1 heap
4671 // for SequentialSubTasksDone.
4672 // This task also uses SubTasksDone in SharedHeap and G1CollectedHeap
4673 // both of which need setting by set_n_termination().
4674 _g1h->SharedHeap::set_n_termination(active_workers);
4675 _g1h->set_n_termination(active_workers);
4676 terminator()->reset_for_reuse(active_workers);
4677 _n_workers = active_workers;
4678 }
4679
4680 // Helps out with CLD processing.
4681 //
4682 // During InitialMark we need to:
4683 // 1) Scavenge all CLDs for the young GC.
4684 // 2) Mark all objects directly reachable from strong CLDs.
4685 template <G1Mark do_mark_object>
4686 class G1CLDClosure : public CLDClosure {
4687 G1ParCopyClosure<G1BarrierNone, do_mark_object>* _oop_closure;
4688 G1ParCopyClosure<G1BarrierKlass, do_mark_object> _oop_in_klass_closure;
4689 G1KlassScanClosure _klass_in_cld_closure;
4690 bool _claim;
4691
4692 public:
4693 G1CLDClosure(G1ParCopyClosure<G1BarrierNone, do_mark_object>* oop_closure,
4694 bool only_young, bool claim)
4695 : _oop_closure(oop_closure),
4696 _oop_in_klass_closure(oop_closure->g1(),
4697 oop_closure->pss(),
4698 oop_closure->rp()),
4699 _klass_in_cld_closure(&_oop_in_klass_closure, only_young),
4700 _claim(claim) {
4701
4702 }
4703
4704 void do_cld(ClassLoaderData* cld) {
4705 cld->oops_do(_oop_closure, &_klass_in_cld_closure, _claim);
4706 }
4707 };
4708
4709 void work(uint worker_id) {
4710 if (worker_id >= _n_workers) return; // no work needed this round
4711
4712 double start_time_ms = os::elapsedTime() * 1000.0;
4713 _g1h->g1_policy()->phase_times()->record_gc_worker_start_time(worker_id, start_time_ms);
4714
4715 {
4716 ResourceMark rm;
4717 HandleMark hm;
4718
4719 ReferenceProcessor* rp = _g1h->ref_processor_stw();
4720
4721 G1ParScanThreadState pss(_g1h, worker_id, rp);
4722 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, rp);
4723
4724 pss.set_evac_failure_closure(&evac_failure_cl);
4725
4726 bool only_young = _g1h->g1_policy()->gcs_are_young();
4727
4728 // Non-IM young GC.
4729 G1ParCopyClosure<G1BarrierNone, G1MarkNone> scan_only_root_cl(_g1h, &pss, rp);
4730 G1CLDClosure<G1MarkNone> scan_only_cld_cl(&scan_only_root_cl,
4731 only_young, // Only process dirty klasses.
4732 false); // No need to claim CLDs.
4733 // IM young GC.
4734 // Strong roots closures.
4735 G1ParCopyClosure<G1BarrierNone, G1MarkFromRoot> scan_mark_root_cl(_g1h, &pss, rp);
4736 G1CLDClosure<G1MarkFromRoot> scan_mark_cld_cl(&scan_mark_root_cl,
4737 false, // Process all klasses.
4738 true); // Need to claim CLDs.
4739 // Weak roots closures.
4740 G1ParCopyClosure<G1BarrierNone, G1MarkPromotedFromRoot> scan_mark_weak_root_cl(_g1h, &pss, rp);
4741 G1CLDClosure<G1MarkPromotedFromRoot> scan_mark_weak_cld_cl(&scan_mark_weak_root_cl,
4742 false, // Process all klasses.
4743 true); // Need to claim CLDs.
4744
4745 G1CodeBlobClosure scan_only_code_cl(&scan_only_root_cl);
4746 G1CodeBlobClosure scan_mark_code_cl(&scan_mark_root_cl);
4747 // IM Weak code roots are handled later.
4748
4749 OopClosure* strong_root_cl;
4750 OopClosure* weak_root_cl;
4751 CLDClosure* strong_cld_cl;
4752 CLDClosure* weak_cld_cl;
4753 CodeBlobClosure* strong_code_cl;
4754
4755 if (_g1h->g1_policy()->during_initial_mark_pause()) {
4756 // We also need to mark copied objects.
4757 strong_root_cl = &scan_mark_root_cl;
4758 strong_cld_cl = &scan_mark_cld_cl;
4759 strong_code_cl = &scan_mark_code_cl;
4760 if (ClassUnloadingWithConcurrentMark) {
4761 weak_root_cl = &scan_mark_weak_root_cl;
4762 weak_cld_cl = &scan_mark_weak_cld_cl;
4763 } else {
4764 weak_root_cl = &scan_mark_root_cl;
4765 weak_cld_cl = &scan_mark_cld_cl;
4766 }
4767 } else {
4768 strong_root_cl = &scan_only_root_cl;
4769 weak_root_cl = &scan_only_root_cl;
4770 strong_cld_cl = &scan_only_cld_cl;
4771 weak_cld_cl = &scan_only_cld_cl;
4772 strong_code_cl = &scan_only_code_cl;
4773 }
4774
4775
4776 G1ParPushHeapRSClosure push_heap_rs_cl(_g1h, &pss);
4777
4778 pss.start_strong_roots();
4779 _g1h->g1_process_roots(strong_root_cl,
4780 weak_root_cl,
4781 &push_heap_rs_cl,
4782 strong_cld_cl,
4783 weak_cld_cl,
4784 strong_code_cl,
4785 worker_id);
4786
4787 pss.end_strong_roots();
4788
4789 {
4790 double start = os::elapsedTime();
4791 G1ParEvacuateFollowersClosure evac(_g1h, &pss, _queues, &_terminator);
4792 evac.do_void();
4793 double elapsed_ms = (os::elapsedTime()-start)*1000.0;
4794 double term_ms = pss.term_time()*1000.0;
4795 _g1h->g1_policy()->phase_times()->add_obj_copy_time(worker_id, elapsed_ms-term_ms);
4796 _g1h->g1_policy()->phase_times()->record_termination(worker_id, term_ms, pss.term_attempts());
4797 }
4798 _g1h->g1_policy()->record_thread_age_table(pss.age_table());
4799 _g1h->update_surviving_young_words(pss.surviving_young_words()+1);
4800
4801 if (ParallelGCVerbose) {
4802 MutexLocker x(stats_lock());
4803 pss.print_termination_stats(worker_id);
4804 }
4805
4806 assert(pss.queue_is_empty(), "should be empty");
4807
4808 // Close the inner scope so that the ResourceMark and HandleMark
4809 // destructors are executed here and are included as part of the
4810 // "GC Worker Time".
4811 }
4812
4813 double end_time_ms = os::elapsedTime() * 1000.0;
4814 _g1h->g1_policy()->phase_times()->record_gc_worker_end_time(worker_id, end_time_ms);
4815 }
4816 };
4817
4818 // *** Common G1 Evacuation Stuff
4819
4820 // This method is run in a GC worker.
4821
4822 void
4823 G1CollectedHeap::
4824 g1_process_roots(OopClosure* scan_non_heap_roots,
4825 OopClosure* scan_non_heap_weak_roots,
4826 OopsInHeapRegionClosure* scan_rs,
4827 CLDClosure* scan_strong_clds,
4828 CLDClosure* scan_weak_clds,
4829 CodeBlobClosure* scan_strong_code,
4830 uint worker_i) {
4831
4832 // First scan the shared roots.
4833 double ext_roots_start = os::elapsedTime();
4834 double closure_app_time_sec = 0.0;
4835
4836 bool during_im = _g1h->g1_policy()->during_initial_mark_pause();
4837 bool trace_metadata = during_im && ClassUnloadingWithConcurrentMark;
4838
4839 BufferingOopClosure buf_scan_non_heap_roots(scan_non_heap_roots);
4840 BufferingOopClosure buf_scan_non_heap_weak_roots(scan_non_heap_weak_roots);
4841
4842 process_roots(false, // no scoping; this is parallel code
4843 SharedHeap::SO_None,
4844 &buf_scan_non_heap_roots,
4845 &buf_scan_non_heap_weak_roots,
4846 scan_strong_clds,
4847 // Unloading Initial Marks handle the weak CLDs separately.
4848 (trace_metadata ? NULL : scan_weak_clds),
4849 scan_strong_code);
4850
4851 // Now the CM ref_processor roots.
4852 if (!_process_strong_tasks->is_task_claimed(G1H_PS_refProcessor_oops_do)) {
4853 // We need to treat the discovered reference lists of the
4854 // concurrent mark ref processor as roots and keep entries
4855 // (which are added by the marking threads) on them live
4856 // until they can be processed at the end of marking.
4857 ref_processor_cm()->weak_oops_do(&buf_scan_non_heap_roots);
4858 }
4859
4860 if (trace_metadata) {
4861 // Barrier to make sure all workers passed
4862 // the strong CLD and strong nmethods phases.
4863 active_strong_roots_scope()->wait_until_all_workers_done_with_threads(n_par_threads());
4864
4865 // Now take the complement of the strong CLDs.
4866 ClassLoaderDataGraph::roots_cld_do(NULL, scan_weak_clds);
4867 }
4868
4869 // Finish up any enqueued closure apps (attributed as object copy time).
4870 buf_scan_non_heap_roots.done();
4871 buf_scan_non_heap_weak_roots.done();
4872
4873 double obj_copy_time_sec = buf_scan_non_heap_roots.closure_app_seconds()
4874 + buf_scan_non_heap_weak_roots.closure_app_seconds();
4875
4876 g1_policy()->phase_times()->record_obj_copy_time(worker_i, obj_copy_time_sec * 1000.0);
4877
4878 double ext_root_time_ms =
4879 ((os::elapsedTime() - ext_roots_start) - obj_copy_time_sec) * 1000.0;
4880
4881 g1_policy()->phase_times()->record_ext_root_scan_time(worker_i, ext_root_time_ms);
4882
4883 // During conc marking we have to filter the per-thread SATB buffers
4884 // to make sure we remove any oops into the CSet (which will show up
4885 // as implicitly live).
4886 double satb_filtering_ms = 0.0;
4887 if (!_process_strong_tasks->is_task_claimed(G1H_PS_filter_satb_buffers)) {
4888 if (mark_in_progress()) {
4889 double satb_filter_start = os::elapsedTime();
4890
4891 JavaThread::satb_mark_queue_set().filter_thread_buffers();
4892
4893 satb_filtering_ms = (os::elapsedTime() - satb_filter_start) * 1000.0;
4894 }
4895 }
4896 g1_policy()->phase_times()->record_satb_filtering_time(worker_i, satb_filtering_ms);
4897
4898 // Now scan the complement of the collection set.
4899 G1CodeBlobClosure scavenge_cs_nmethods(scan_non_heap_weak_roots);
4900
4901 g1_rem_set()->oops_into_collection_set_do(scan_rs, &scavenge_cs_nmethods, worker_i);
4902
4903 _process_strong_tasks->all_tasks_completed();
4904 }
4905
4906 class G1StringSymbolTableUnlinkTask : public AbstractGangTask {
4907 private:
4908 BoolObjectClosure* _is_alive;
4909 int _initial_string_table_size;
4910 int _initial_symbol_table_size;
4911
4912 bool _process_strings;
4913 int _strings_processed;
4914 int _strings_removed;
4915
4916 bool _process_symbols;
4917 int _symbols_processed;
4918 int _symbols_removed;
4919
4920 bool _do_in_parallel;
4921 public:
4922 G1StringSymbolTableUnlinkTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols) :
4923 AbstractGangTask("String/Symbol Unlinking"),
4924 _is_alive(is_alive),
4925 _do_in_parallel(G1CollectedHeap::use_parallel_gc_threads()),
4926 _process_strings(process_strings), _strings_processed(0), _strings_removed(0),
4927 _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0) {
4928
4929 _initial_string_table_size = StringTable::the_table()->table_size();
4930 _initial_symbol_table_size = SymbolTable::the_table()->table_size();
4931 if (process_strings) {
4932 StringTable::clear_parallel_claimed_index();
4933 }
4934 if (process_symbols) {
4935 SymbolTable::clear_parallel_claimed_index();
4936 }
4937 }
4938
4939 ~G1StringSymbolTableUnlinkTask() {
4940 guarantee(!_process_strings || !_do_in_parallel || StringTable::parallel_claimed_index() >= _initial_string_table_size,
4941 err_msg("claim value %d after unlink less than initial string table size %d",
4942 StringTable::parallel_claimed_index(), _initial_string_table_size));
4943 guarantee(!_process_symbols || !_do_in_parallel || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size,
4944 err_msg("claim value %d after unlink less than initial symbol table size %d",
4945 SymbolTable::parallel_claimed_index(), _initial_symbol_table_size));
4946
4947 if (G1TraceStringSymbolTableScrubbing) {
4948 gclog_or_tty->print_cr("Cleaned string and symbol table, "
4949 "strings: "SIZE_FORMAT" processed, "SIZE_FORMAT" removed, "
4950 "symbols: "SIZE_FORMAT" processed, "SIZE_FORMAT" removed",
4951 strings_processed(), strings_removed(),
4952 symbols_processed(), symbols_removed());
4953 }
4954 }
4955
4956 void work(uint worker_id) {
4957 if (_do_in_parallel) {
4958 int strings_processed = 0;
4959 int strings_removed = 0;
4960 int symbols_processed = 0;
4961 int symbols_removed = 0;
4962 if (_process_strings) {
4963 StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed);
4964 Atomic::add(strings_processed, &_strings_processed);
4965 Atomic::add(strings_removed, &_strings_removed);
4966 }
4967 if (_process_symbols) {
4968 SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed);
4969 Atomic::add(symbols_processed, &_symbols_processed);
4970 Atomic::add(symbols_removed, &_symbols_removed);
4971 }
4972 } else {
4973 if (_process_strings) {
4974 StringTable::unlink(_is_alive, &_strings_processed, &_strings_removed);
4975 }
4976 if (_process_symbols) {
4977 SymbolTable::unlink(&_symbols_processed, &_symbols_removed);
4978 }
4979 }
4980 }
4981
4982 size_t strings_processed() const { return (size_t)_strings_processed; }
4983 size_t strings_removed() const { return (size_t)_strings_removed; }
4984
4985 size_t symbols_processed() const { return (size_t)_symbols_processed; }
4986 size_t symbols_removed() const { return (size_t)_symbols_removed; }
4987 };
4988
4989 class G1CodeCacheUnloadingTask VALUE_OBJ_CLASS_SPEC {
4990 private:
4991 static Monitor* _lock;
4992
4993 BoolObjectClosure* const _is_alive;
4994 const bool _unloading_occurred;
4995 const uint _num_workers;
4996
4997 // Variables used to claim nmethods.
4998 nmethod* _first_nmethod;
4999 volatile nmethod* _claimed_nmethod;
5000
5001 // The list of nmethods that need to be processed by the second pass.
5002 volatile nmethod* _postponed_list;
5003 volatile uint _num_entered_barrier;
5004
5005 public:
5006 G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) :
5007 _is_alive(is_alive),
5008 _unloading_occurred(unloading_occurred),
5009 _num_workers(num_workers),
5010 _first_nmethod(NULL),
5011 _claimed_nmethod(NULL),
5012 _postponed_list(NULL),
5013 _num_entered_barrier(0)
5014 {
5015 nmethod::increase_unloading_clock();
5016 _first_nmethod = CodeCache::alive_nmethod(CodeCache::first());
5017 _claimed_nmethod = (volatile nmethod*)_first_nmethod;
5018 }
5019
5020 ~G1CodeCacheUnloadingTask() {
5021 CodeCache::verify_clean_inline_caches();
5022
5023 CodeCache::set_needs_cache_clean(false);
5024 guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be");
5025
5026 CodeCache::verify_icholder_relocations();
5027 }
5028
5029 private:
5030 void add_to_postponed_list(nmethod* nm) {
5031 nmethod* old;
5032 do {
5033 old = (nmethod*)_postponed_list;
5034 nm->set_unloading_next(old);
5035 } while ((nmethod*)Atomic::cmpxchg_ptr(nm, &_postponed_list, old) != old);
5036 }
5037
5038 void clean_nmethod(nmethod* nm) {
5039 bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred);
5040
5041 if (postponed) {
5042 // This nmethod referred to an nmethod that has not been cleaned/unloaded yet.
5043 add_to_postponed_list(nm);
5044 }
5045
5046 // Mark that this thread has been cleaned/unloaded.
5047 // After this call, it will be safe to ask if this nmethod was unloaded or not.
5048 nm->set_unloading_clock(nmethod::global_unloading_clock());
5049 }
5050
5051 void clean_nmethod_postponed(nmethod* nm) {
5052 nm->do_unloading_parallel_postponed(_is_alive, _unloading_occurred);
5053 }
5054
5055 static const int MaxClaimNmethods = 16;
5056
5057 void claim_nmethods(nmethod** claimed_nmethods, int *num_claimed_nmethods) {
5058 nmethod* first;
5059 nmethod* last;
5060
5061 do {
5062 *num_claimed_nmethods = 0;
5063
5064 first = last = (nmethod*)_claimed_nmethod;
5065
5066 if (first != NULL) {
5067 for (int i = 0; i < MaxClaimNmethods; i++) {
5068 last = CodeCache::alive_nmethod(CodeCache::next(last));
5069
5070 if (last == NULL) {
5071 break;
5072 }
5073
5074 claimed_nmethods[i] = last;
5075 (*num_claimed_nmethods)++;
5076 }
5077 }
5078
5079 } while ((nmethod*)Atomic::cmpxchg_ptr(last, &_claimed_nmethod, first) != first);
5080 }
5081
5082 nmethod* claim_postponed_nmethod() {
5083 nmethod* claim;
5084 nmethod* next;
5085
5086 do {
5087 claim = (nmethod*)_postponed_list;
5088 if (claim == NULL) {
5089 return NULL;
5090 }
5091
5092 next = claim->unloading_next();
5093
5094 } while ((nmethod*)Atomic::cmpxchg_ptr(next, &_postponed_list, claim) != claim);
5095
5096 return claim;
5097 }
5098
5099 public:
5100 // Mark that we're done with the first pass of nmethod cleaning.
5101 void barrier_mark(uint worker_id) {
5102 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
5103 _num_entered_barrier++;
5104 if (_num_entered_barrier == _num_workers) {
5105 ml.notify_all();
5106 }
5107 }
5108
5109 // See if we have to wait for the other workers to
5110 // finish their first-pass nmethod cleaning work.
5111 void barrier_wait(uint worker_id) {
5112 if (_num_entered_barrier < _num_workers) {
5113 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
5114 while (_num_entered_barrier < _num_workers) {
5115 ml.wait(Mutex::_no_safepoint_check_flag, 0, false);
5116 }
5117 }
5118 }
5119
5120 // Cleaning and unloading of nmethods. Some work has to be postponed
5121 // to the second pass, when we know which nmethods survive.
5122 void work_first_pass(uint worker_id) {
5123 // The first nmethods is claimed by the first worker.
5124 if (worker_id == 0 && _first_nmethod != NULL) {
5125 clean_nmethod(_first_nmethod);
5126 _first_nmethod = NULL;
5127 }
5128
5129 int num_claimed_nmethods;
5130 nmethod* claimed_nmethods[MaxClaimNmethods];
5131
5132 while (true) {
5133 claim_nmethods(claimed_nmethods, &num_claimed_nmethods);
5134
5135 if (num_claimed_nmethods == 0) {
5136 break;
5137 }
5138
5139 for (int i = 0; i < num_claimed_nmethods; i++) {
5140 clean_nmethod(claimed_nmethods[i]);
5141 }
5142 }
5143 }
5144
5145 void work_second_pass(uint worker_id) {
5146 nmethod* nm;
5147 // Take care of postponed nmethods.
5148 while ((nm = claim_postponed_nmethod()) != NULL) {
5149 clean_nmethod_postponed(nm);
5150 }
5151 }
5152 };
5153
5154 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock");
5155
5156 class G1KlassCleaningTask : public StackObj {
5157 BoolObjectClosure* _is_alive;
5158 volatile jint _clean_klass_tree_claimed;
5159 ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator;
5160
5161 public:
5162 G1KlassCleaningTask(BoolObjectClosure* is_alive) :
5163 _is_alive(is_alive),
5164 _clean_klass_tree_claimed(0),
5165 _klass_iterator() {
5166 }
5167
5168 private:
5169 bool claim_clean_klass_tree_task() {
5170 if (_clean_klass_tree_claimed) {
5171 return false;
5172 }
5173
5174 return Atomic::cmpxchg(1, (jint*)&_clean_klass_tree_claimed, 0) == 0;
5175 }
5176
5177 InstanceKlass* claim_next_klass() {
5178 Klass* klass;
5179 do {
5180 klass =_klass_iterator.next_klass();
5181 } while (klass != NULL && !klass->oop_is_instance());
5182
5183 return (InstanceKlass*)klass;
5184 }
5185
5186 public:
5187
5188 void clean_klass(InstanceKlass* ik) {
5189 ik->clean_implementors_list(_is_alive);
5190 ik->clean_method_data(_is_alive);
5191
5192 // G1 specific cleanup work that has
5193 // been moved here to be done in parallel.
5194 ik->clean_dependent_nmethods();
5195 }
5196
5197 void work() {
5198 ResourceMark rm;
5199
5200 // One worker will clean the subklass/sibling klass tree.
5201 if (claim_clean_klass_tree_task()) {
5202 Klass::clean_subklass_tree(_is_alive);
5203 }
5204
5205 // All workers will help cleaning the classes,
5206 InstanceKlass* klass;
5207 while ((klass = claim_next_klass()) != NULL) {
5208 clean_klass(klass);
5209 }
5210 }
5211 };
5212
5213 // To minimize the remark pause times, the tasks below are done in parallel.
5214 class G1ParallelCleaningTask : public AbstractGangTask {
5215 private:
5216 G1StringSymbolTableUnlinkTask _string_symbol_task;
5217 G1CodeCacheUnloadingTask _code_cache_task;
5218 G1KlassCleaningTask _klass_cleaning_task;
5219
5220 public:
5221 // The constructor is run in the VMThread.
5222 G1ParallelCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, uint num_workers, bool unloading_occurred) :
5223 AbstractGangTask("Parallel Cleaning"),
5224 _string_symbol_task(is_alive, process_strings, process_symbols),
5225 _code_cache_task(num_workers, is_alive, unloading_occurred),
5226 _klass_cleaning_task(is_alive) {
5227 }
5228
5229 // The parallel work done by all worker threads.
5230 void work(uint worker_id) {
5231 // Do first pass of code cache cleaning.
5232 _code_cache_task.work_first_pass(worker_id);
5233
5234 // Let the threads mark that the first pass is done.
5235 _code_cache_task.barrier_mark(worker_id);
5236
5237 // Clean the Strings and Symbols.
5238 _string_symbol_task.work(worker_id);
5239
5240 // Wait for all workers to finish the first code cache cleaning pass.
5241 _code_cache_task.barrier_wait(worker_id);
5242
5243 // Do the second code cache cleaning work, which realize on
5244 // the liveness information gathered during the first pass.
5245 _code_cache_task.work_second_pass(worker_id);
5246
5247 // Clean all klasses that were not unloaded.
5248 _klass_cleaning_task.work();
5249 }
5250 };
5251
5252
5253 void G1CollectedHeap::parallel_cleaning(BoolObjectClosure* is_alive,
5254 bool process_strings,
5255 bool process_symbols,
5256 bool class_unloading_occurred) {
5257 uint n_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
5258 workers()->active_workers() : 1);
5259
5260 G1ParallelCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols,
5261 n_workers, class_unloading_occurred);
5262 if (G1CollectedHeap::use_parallel_gc_threads()) {
5263 set_par_threads(n_workers);
5264 workers()->run_task(&g1_unlink_task);
5265 set_par_threads(0);
5266 } else {
5267 g1_unlink_task.work(0);
5268 }
5269 }
5270
5271 void G1CollectedHeap::unlink_string_and_symbol_table(BoolObjectClosure* is_alive,
5272 bool process_strings, bool process_symbols) {
5273 {
5274 uint n_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
5275 _g1h->workers()->active_workers() : 1);
5276 G1StringSymbolTableUnlinkTask g1_unlink_task(is_alive, process_strings, process_symbols);
5277 if (G1CollectedHeap::use_parallel_gc_threads()) {
5278 set_par_threads(n_workers);
5279 workers()->run_task(&g1_unlink_task);
5280 set_par_threads(0);
5281 } else {
5282 g1_unlink_task.work(0);
5283 }
5284 }
5285
5286 if (G1StringDedup::is_enabled()) {
5287 G1StringDedup::unlink(is_alive);
5288 }
5289 }
5290
5291 class G1RedirtyLoggedCardsTask : public AbstractGangTask {
5292 private:
5293 DirtyCardQueueSet* _queue;
5294 public:
5295 G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue) : AbstractGangTask("Redirty Cards"), _queue(queue) { }
5296
5297 virtual void work(uint worker_id) {
5298 double start_time = os::elapsedTime();
5299
5300 RedirtyLoggedCardTableEntryClosure cl;
5301 if (G1CollectedHeap::heap()->use_parallel_gc_threads()) {
5302 _queue->par_apply_closure_to_all_completed_buffers(&cl);
5303 } else {
5304 _queue->apply_closure_to_all_completed_buffers(&cl);
5305 }
5306
5307 G1GCPhaseTimes* timer = G1CollectedHeap::heap()->g1_policy()->phase_times();
5308 timer->record_redirty_logged_cards_time_ms(worker_id, (os::elapsedTime() - start_time) * 1000.0);
5309 timer->record_redirty_logged_cards_processed_cards(worker_id, cl.num_processed());
5310 }
5311 };
5312
5313 void G1CollectedHeap::redirty_logged_cards() {
5314 double redirty_logged_cards_start = os::elapsedTime();
5315
5316 uint n_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
5317 _g1h->workers()->active_workers() : 1);
5318
5319 G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set());
5320 dirty_card_queue_set().reset_for_par_iteration();
5321 if (use_parallel_gc_threads()) {
5322 set_par_threads(n_workers);
5323 workers()->run_task(&redirty_task);
5324 set_par_threads(0);
5325 } else {
5326 redirty_task.work(0);
5327 }
5328
5329 DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set();
5330 dcq.merge_bufferlists(&dirty_card_queue_set());
5331 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
5332
5333 g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0);
5334 }
5335
5336 // Weak Reference Processing support
5337
5338 // An always "is_alive" closure that is used to preserve referents.
5339 // If the object is non-null then it's alive. Used in the preservation
5340 // of referent objects that are pointed to by reference objects
5341 // discovered by the CM ref processor.
5342 class G1AlwaysAliveClosure: public BoolObjectClosure {
5343 G1CollectedHeap* _g1;
5344 public:
5345 G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
5346 bool do_object_b(oop p) {
5347 if (p != NULL) {
5348 return true;
5349 }
5350 return false;
5351 }
5352 };
5353
5354 bool G1STWIsAliveClosure::do_object_b(oop p) {
5355 // An object is reachable if it is outside the collection set,
5356 // or is inside and copied.
5357 return !_g1->obj_in_cs(p) || p->is_forwarded();
5358 }
5359
5360 // Non Copying Keep Alive closure
5361 class G1KeepAliveClosure: public OopClosure {
5362 G1CollectedHeap* _g1;
5363 public:
5364 G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
5365 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
5366 void do_oop(oop* p) {
5367 oop obj = *p;
5368 assert(obj != NULL, "the caller should have filtered out NULL values");
5369
5370 G1CollectedHeap::in_cset_state_t cset_state = _g1->in_cset_state(obj);
5371 if (cset_state == G1CollectedHeap::InNeither) {
5372 return;
5373 }
5374 if (cset_state == G1CollectedHeap::InCSet) {
5375 assert( obj->is_forwarded(), "invariant" );
5376 *p = obj->forwardee();
5377 } else {
5378 assert(!obj->is_forwarded(), "invariant" );
5379 assert(cset_state == G1CollectedHeap::IsHumongous,
5380 err_msg("Only allowed InCSet state is IsHumongous, but is %d", cset_state));
5381 _g1->set_humongous_is_live(obj);
5382 }
5383 }
5384 };
5385
5386 // Copying Keep Alive closure - can be called from both
5387 // serial and parallel code as long as different worker
5388 // threads utilize different G1ParScanThreadState instances
5389 // and different queues.
5390
5391 class G1CopyingKeepAliveClosure: public OopClosure {
5392 G1CollectedHeap* _g1h;
5393 OopClosure* _copy_non_heap_obj_cl;
5394 G1ParScanThreadState* _par_scan_state;
5395
5396 public:
5397 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
5398 OopClosure* non_heap_obj_cl,
5399 G1ParScanThreadState* pss):
5400 _g1h(g1h),
5401 _copy_non_heap_obj_cl(non_heap_obj_cl),
5402 _par_scan_state(pss)
5403 {}
5404
5405 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
5406 virtual void do_oop( oop* p) { do_oop_work(p); }
5407
5408 template <class T> void do_oop_work(T* p) {
5409 oop obj = oopDesc::load_decode_heap_oop(p);
5410
5411 if (_g1h->is_in_cset_or_humongous(obj)) {
5412 // If the referent object has been forwarded (either copied
5413 // to a new location or to itself in the event of an
5414 // evacuation failure) then we need to update the reference
5415 // field and, if both reference and referent are in the G1
5416 // heap, update the RSet for the referent.
5417 //
5418 // If the referent has not been forwarded then we have to keep
5419 // it alive by policy. Therefore we have copy the referent.
5420 //
5421 // If the reference field is in the G1 heap then we can push
5422 // on the PSS queue. When the queue is drained (after each
5423 // phase of reference processing) the object and it's followers
5424 // will be copied, the reference field set to point to the
5425 // new location, and the RSet updated. Otherwise we need to
5426 // use the the non-heap or metadata closures directly to copy
5427 // the referent object and update the pointer, while avoiding
5428 // updating the RSet.
5429
5430 if (_g1h->is_in_g1_reserved(p)) {
5431 _par_scan_state->push_on_queue(p);
5432 } else {
5433 assert(!Metaspace::contains((const void*)p),
5434 err_msg("Unexpectedly found a pointer from metadata: "
5435 PTR_FORMAT, p));
5436 _copy_non_heap_obj_cl->do_oop(p);
5437 }
5438 }
5439 }
5440 };
5441
5442 // Serial drain queue closure. Called as the 'complete_gc'
5443 // closure for each discovered list in some of the
5444 // reference processing phases.
5445
5446 class G1STWDrainQueueClosure: public VoidClosure {
5447 protected:
5448 G1CollectedHeap* _g1h;
5449 G1ParScanThreadState* _par_scan_state;
5450
5451 G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
5452
5453 public:
5454 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
5455 _g1h(g1h),
5456 _par_scan_state(pss)
5457 { }
5458
5459 void do_void() {
5460 G1ParScanThreadState* const pss = par_scan_state();
5461 pss->trim_queue();
5462 }
5463 };
5464
5465 // Parallel Reference Processing closures
5466
5467 // Implementation of AbstractRefProcTaskExecutor for parallel reference
5468 // processing during G1 evacuation pauses.
5469
5470 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
5471 private:
5472 G1CollectedHeap* _g1h;
5473 RefToScanQueueSet* _queues;
5474 FlexibleWorkGang* _workers;
5475 int _active_workers;
5476
5477 public:
5478 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
5479 FlexibleWorkGang* workers,
5480 RefToScanQueueSet *task_queues,
5481 int n_workers) :
5482 _g1h(g1h),
5483 _queues(task_queues),
5484 _workers(workers),
5485 _active_workers(n_workers)
5486 {
5487 assert(n_workers > 0, "shouldn't call this otherwise");
5488 }
5489
5490 // Executes the given task using concurrent marking worker threads.
5491 virtual void execute(ProcessTask& task);
5492 virtual void execute(EnqueueTask& task);
5493 };
5494
5495 // Gang task for possibly parallel reference processing
5496
5497 class G1STWRefProcTaskProxy: public AbstractGangTask {
5498 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
5499 ProcessTask& _proc_task;
5500 G1CollectedHeap* _g1h;
5501 RefToScanQueueSet *_task_queues;
5502 ParallelTaskTerminator* _terminator;
5503
5504 public:
5505 G1STWRefProcTaskProxy(ProcessTask& proc_task,
5506 G1CollectedHeap* g1h,
5507 RefToScanQueueSet *task_queues,
5508 ParallelTaskTerminator* terminator) :
5509 AbstractGangTask("Process reference objects in parallel"),
5510 _proc_task(proc_task),
5511 _g1h(g1h),
5512 _task_queues(task_queues),
5513 _terminator(terminator)
5514 {}
5515
5516 virtual void work(uint worker_id) {
5517 // The reference processing task executed by a single worker.
5518 ResourceMark rm;
5519 HandleMark hm;
5520
5521 G1STWIsAliveClosure is_alive(_g1h);
5522
5523 G1ParScanThreadState pss(_g1h, worker_id, NULL);
5524 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5525
5526 pss.set_evac_failure_closure(&evac_failure_cl);
5527
5528 G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL);
5529
5530 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5531
5532 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5533
5534 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5535 // We also need to mark copied objects.
5536 copy_non_heap_cl = ©_mark_non_heap_cl;
5537 }
5538
5539 // Keep alive closure.
5540 G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, &pss);
5541
5542 // Complete GC closure
5543 G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _task_queues, _terminator);
5544
5545 // Call the reference processing task's work routine.
5546 _proc_task.work(worker_id, is_alive, keep_alive, drain_queue);
5547
5548 // Note we cannot assert that the refs array is empty here as not all
5549 // of the processing tasks (specifically phase2 - pp2_work) execute
5550 // the complete_gc closure (which ordinarily would drain the queue) so
5551 // the queue may not be empty.
5552 }
5553 };
5554
5555 // Driver routine for parallel reference processing.
5556 // Creates an instance of the ref processing gang
5557 // task and has the worker threads execute it.
5558 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) {
5559 assert(_workers != NULL, "Need parallel worker threads.");
5560
5561 ParallelTaskTerminator terminator(_active_workers, _queues);
5562 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _queues, &terminator);
5563
5564 _g1h->set_par_threads(_active_workers);
5565 _workers->run_task(&proc_task_proxy);
5566 _g1h->set_par_threads(0);
5567 }
5568
5569 // Gang task for parallel reference enqueueing.
5570
5571 class G1STWRefEnqueueTaskProxy: public AbstractGangTask {
5572 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
5573 EnqueueTask& _enq_task;
5574
5575 public:
5576 G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) :
5577 AbstractGangTask("Enqueue reference objects in parallel"),
5578 _enq_task(enq_task)
5579 { }
5580
5581 virtual void work(uint worker_id) {
5582 _enq_task.work(worker_id);
5583 }
5584 };
5585
5586 // Driver routine for parallel reference enqueueing.
5587 // Creates an instance of the ref enqueueing gang
5588 // task and has the worker threads execute it.
5589
5590 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
5591 assert(_workers != NULL, "Need parallel worker threads.");
5592
5593 G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task);
5594
5595 _g1h->set_par_threads(_active_workers);
5596 _workers->run_task(&enq_task_proxy);
5597 _g1h->set_par_threads(0);
5598 }
5599
5600 // End of weak reference support closures
5601
5602 // Abstract task used to preserve (i.e. copy) any referent objects
5603 // that are in the collection set and are pointed to by reference
5604 // objects discovered by the CM ref processor.
5605
5606 class G1ParPreserveCMReferentsTask: public AbstractGangTask {
5607 protected:
5608 G1CollectedHeap* _g1h;
5609 RefToScanQueueSet *_queues;
5610 ParallelTaskTerminator _terminator;
5611 uint _n_workers;
5612
5613 public:
5614 G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h,int workers, RefToScanQueueSet *task_queues) :
5615 AbstractGangTask("ParPreserveCMReferents"),
5616 _g1h(g1h),
5617 _queues(task_queues),
5618 _terminator(workers, _queues),
5619 _n_workers(workers)
5620 { }
5621
5622 void work(uint worker_id) {
5623 ResourceMark rm;
5624 HandleMark hm;
5625
5626 G1ParScanThreadState pss(_g1h, worker_id, NULL);
5627 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5628
5629 pss.set_evac_failure_closure(&evac_failure_cl);
5630
5631 assert(pss.queue_is_empty(), "both queue and overflow should be empty");
5632
5633 G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL);
5634
5635 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5636
5637 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5638
5639 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5640 // We also need to mark copied objects.
5641 copy_non_heap_cl = ©_mark_non_heap_cl;
5642 }
5643
5644 // Is alive closure
5645 G1AlwaysAliveClosure always_alive(_g1h);
5646
5647 // Copying keep alive closure. Applied to referent objects that need
5648 // to be copied.
5649 G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, &pss);
5650
5651 ReferenceProcessor* rp = _g1h->ref_processor_cm();
5652
5653 uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q();
5654 uint stride = MIN2(MAX2(_n_workers, 1U), limit);
5655
5656 // limit is set using max_num_q() - which was set using ParallelGCThreads.
5657 // So this must be true - but assert just in case someone decides to
5658 // change the worker ids.
5659 assert(0 <= worker_id && worker_id < limit, "sanity");
5660 assert(!rp->discovery_is_atomic(), "check this code");
5661
5662 // Select discovered lists [i, i+stride, i+2*stride,...,limit)
5663 for (uint idx = worker_id; idx < limit; idx += stride) {
5664 DiscoveredList& ref_list = rp->discovered_refs()[idx];
5665
5666 DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive);
5667 while (iter.has_next()) {
5668 // Since discovery is not atomic for the CM ref processor, we
5669 // can see some null referent objects.
5670 iter.load_ptrs(DEBUG_ONLY(true));
5671 oop ref = iter.obj();
5672
5673 // This will filter nulls.
5674 if (iter.is_referent_alive()) {
5675 iter.make_referent_alive();
5676 }
5677 iter.move_to_next();
5678 }
5679 }
5680
5681 // Drain the queue - which may cause stealing
5682 G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _queues, &_terminator);
5683 drain_queue.do_void();
5684 // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure
5685 assert(pss.queue_is_empty(), "should be");
5686 }
5687 };
5688
5689 // Weak Reference processing during an evacuation pause (part 1).
5690 void G1CollectedHeap::process_discovered_references(uint no_of_gc_workers) {
5691 double ref_proc_start = os::elapsedTime();
5692
5693 ReferenceProcessor* rp = _ref_processor_stw;
5694 assert(rp->discovery_enabled(), "should have been enabled");
5695
5696 // Any reference objects, in the collection set, that were 'discovered'
5697 // by the CM ref processor should have already been copied (either by
5698 // applying the external root copy closure to the discovered lists, or
5699 // by following an RSet entry).
5700 //
5701 // But some of the referents, that are in the collection set, that these
5702 // reference objects point to may not have been copied: the STW ref
5703 // processor would have seen that the reference object had already
5704 // been 'discovered' and would have skipped discovering the reference,
5705 // but would not have treated the reference object as a regular oop.
5706 // As a result the copy closure would not have been applied to the
5707 // referent object.
5708 //
5709 // We need to explicitly copy these referent objects - the references
5710 // will be processed at the end of remarking.
5711 //
5712 // We also need to do this copying before we process the reference
5713 // objects discovered by the STW ref processor in case one of these
5714 // referents points to another object which is also referenced by an
5715 // object discovered by the STW ref processor.
5716
5717 assert(!G1CollectedHeap::use_parallel_gc_threads() ||
5718 no_of_gc_workers == workers()->active_workers(),
5719 "Need to reset active GC workers");
5720
5721 set_par_threads(no_of_gc_workers);
5722 G1ParPreserveCMReferentsTask keep_cm_referents(this,
5723 no_of_gc_workers,
5724 _task_queues);
5725
5726 if (G1CollectedHeap::use_parallel_gc_threads()) {
5727 workers()->run_task(&keep_cm_referents);
5728 } else {
5729 keep_cm_referents.work(0);
5730 }
5731
5732 set_par_threads(0);
5733
5734 // Closure to test whether a referent is alive.
5735 G1STWIsAliveClosure is_alive(this);
5736
5737 // Even when parallel reference processing is enabled, the processing
5738 // of JNI refs is serial and performed serially by the current thread
5739 // rather than by a worker. The following PSS will be used for processing
5740 // JNI refs.
5741
5742 // Use only a single queue for this PSS.
5743 G1ParScanThreadState pss(this, 0, NULL);
5744
5745 // We do not embed a reference processor in the copying/scanning
5746 // closures while we're actually processing the discovered
5747 // reference objects.
5748 G1ParScanHeapEvacFailureClosure evac_failure_cl(this, &pss, NULL);
5749
5750 pss.set_evac_failure_closure(&evac_failure_cl);
5751
5752 assert(pss.queue_is_empty(), "pre-condition");
5753
5754 G1ParScanExtRootClosure only_copy_non_heap_cl(this, &pss, NULL);
5755
5756 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(this, &pss, NULL);
5757
5758 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5759
5760 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5761 // We also need to mark copied objects.
5762 copy_non_heap_cl = ©_mark_non_heap_cl;
5763 }
5764
5765 // Keep alive closure.
5766 G1CopyingKeepAliveClosure keep_alive(this, copy_non_heap_cl, &pss);
5767
5768 // Serial Complete GC closure
5769 G1STWDrainQueueClosure drain_queue(this, &pss);
5770
5771 // Setup the soft refs policy...
5772 rp->setup_policy(false);
5773
5774 ReferenceProcessorStats stats;
5775 if (!rp->processing_is_mt()) {
5776 // Serial reference processing...
5777 stats = rp->process_discovered_references(&is_alive,
5778 &keep_alive,
5779 &drain_queue,
5780 NULL,
5781 _gc_timer_stw,
5782 _gc_tracer_stw->gc_id());
5783 } else {
5784 // Parallel reference processing
5785 assert(rp->num_q() == no_of_gc_workers, "sanity");
5786 assert(no_of_gc_workers <= rp->max_num_q(), "sanity");
5787
5788 G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers);
5789 stats = rp->process_discovered_references(&is_alive,
5790 &keep_alive,
5791 &drain_queue,
5792 &par_task_executor,
5793 _gc_timer_stw,
5794 _gc_tracer_stw->gc_id());
5795 }
5796
5797 _gc_tracer_stw->report_gc_reference_stats(stats);
5798
5799 // We have completed copying any necessary live referent objects.
5800 assert(pss.queue_is_empty(), "both queue and overflow should be empty");
5801
5802 double ref_proc_time = os::elapsedTime() - ref_proc_start;
5803 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
5804 }
5805
5806 // Weak Reference processing during an evacuation pause (part 2).
5807 void G1CollectedHeap::enqueue_discovered_references(uint no_of_gc_workers) {
5808 double ref_enq_start = os::elapsedTime();
5809
5810 ReferenceProcessor* rp = _ref_processor_stw;
5811 assert(!rp->discovery_enabled(), "should have been disabled as part of processing");
5812
5813 // Now enqueue any remaining on the discovered lists on to
5814 // the pending list.
5815 if (!rp->processing_is_mt()) {
5816 // Serial reference processing...
5817 rp->enqueue_discovered_references();
5818 } else {
5819 // Parallel reference enqueueing
5820
5821 assert(no_of_gc_workers == workers()->active_workers(),
5822 "Need to reset active workers");
5823 assert(rp->num_q() == no_of_gc_workers, "sanity");
5824 assert(no_of_gc_workers <= rp->max_num_q(), "sanity");
5825
5826 G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers);
5827 rp->enqueue_discovered_references(&par_task_executor);
5828 }
5829
5830 rp->verify_no_references_recorded();
5831 assert(!rp->discovery_enabled(), "should have been disabled");
5832
5833 // FIXME
5834 // CM's reference processing also cleans up the string and symbol tables.
5835 // Should we do that here also? We could, but it is a serial operation
5836 // and could significantly increase the pause time.
5837
5838 double ref_enq_time = os::elapsedTime() - ref_enq_start;
5839 g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0);
5840 }
5841
5842 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info) {
5843 _expand_heap_after_alloc_failure = true;
5844 _evacuation_failed = false;
5845
5846 // Should G1EvacuationFailureALot be in effect for this GC?
5847 NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();)
5848
5849 g1_rem_set()->prepare_for_oops_into_collection_set_do();
5850
5851 // Disable the hot card cache.
5852 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
5853 hot_card_cache->reset_hot_cache_claimed_index();
5854 hot_card_cache->set_use_cache(false);
5855
5856 uint n_workers;
5857 if (G1CollectedHeap::use_parallel_gc_threads()) {
5858 n_workers =
5859 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
5860 workers()->active_workers(),
5861 Threads::number_of_non_daemon_threads());
5862 assert(UseDynamicNumberOfGCThreads ||
5863 n_workers == workers()->total_workers(),
5864 "If not dynamic should be using all the workers");
5865 workers()->set_active_workers(n_workers);
5866 set_par_threads(n_workers);
5867 } else {
5868 assert(n_par_threads() == 0,
5869 "Should be the original non-parallel value");
5870 n_workers = 1;
5871 }
5872
5873 G1ParTask g1_par_task(this, _task_queues);
5874
5875 init_for_evac_failure(NULL);
5876
5877 rem_set()->prepare_for_younger_refs_iterate(true);
5878
5879 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
5880 double start_par_time_sec = os::elapsedTime();
5881 double end_par_time_sec;
5882
5883 {
5884 StrongRootsScope srs(this);
5885 // InitialMark needs claim bits to keep track of the marked-through CLDs.
5886 if (g1_policy()->during_initial_mark_pause()) {
5887 ClassLoaderDataGraph::clear_claimed_marks();
5888 }
5889
5890 if (G1CollectedHeap::use_parallel_gc_threads()) {
5891 // The individual threads will set their evac-failure closures.
5892 if (ParallelGCVerbose) G1ParScanThreadState::print_termination_stats_hdr();
5893 // These tasks use ShareHeap::_process_strong_tasks
5894 assert(UseDynamicNumberOfGCThreads ||
5895 workers()->active_workers() == workers()->total_workers(),
5896 "If not dynamic should be using all the workers");
5897 workers()->run_task(&g1_par_task);
5898 } else {
5899 g1_par_task.set_for_termination(n_workers);
5900 g1_par_task.work(0);
5901 }
5902 end_par_time_sec = os::elapsedTime();
5903
5904 // Closing the inner scope will execute the destructor
5905 // for the StrongRootsScope object. We record the current
5906 // elapsed time before closing the scope so that time
5907 // taken for the SRS destructor is NOT included in the
5908 // reported parallel time.
5909 }
5910
5911 double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0;
5912 g1_policy()->phase_times()->record_par_time(par_time_ms);
5913
5914 double code_root_fixup_time_ms =
5915 (os::elapsedTime() - end_par_time_sec) * 1000.0;
5916 g1_policy()->phase_times()->record_code_root_fixup_time(code_root_fixup_time_ms);
5917
5918 set_par_threads(0);
5919
5920 // Process any discovered reference objects - we have
5921 // to do this _before_ we retire the GC alloc regions
5922 // as we may have to copy some 'reachable' referent
5923 // objects (and their reachable sub-graphs) that were
5924 // not copied during the pause.
5925 process_discovered_references(n_workers);
5926
5927 // Weak root processing.
5928 {
5929 G1STWIsAliveClosure is_alive(this);
5930 G1KeepAliveClosure keep_alive(this);
5931 JNIHandles::weak_oops_do(&is_alive, &keep_alive);
5932 if (G1StringDedup::is_enabled()) {
5933 G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive);
5934 }
5935 }
5936
5937 _allocator->release_gc_alloc_regions(n_workers, evacuation_info);
5938 g1_rem_set()->cleanup_after_oops_into_collection_set_do();
5939
5940 // Reset and re-enable the hot card cache.
5941 // Note the counts for the cards in the regions in the
5942 // collection set are reset when the collection set is freed.
5943 hot_card_cache->reset_hot_cache();
5944 hot_card_cache->set_use_cache(true);
5945
5946 purge_code_root_memory();
5947
5948 if (g1_policy()->during_initial_mark_pause()) {
5949 // Reset the claim values set during marking the strong code roots
5950 reset_heap_region_claim_values();
5951 }
5952
5953 finalize_for_evac_failure();
5954
5955 if (evacuation_failed()) {
5956 remove_self_forwarding_pointers();
5957
5958 // Reset the G1EvacuationFailureALot counters and flags
5959 // Note: the values are reset only when an actual
5960 // evacuation failure occurs.
5961 NOT_PRODUCT(reset_evacuation_should_fail();)
5962 }
5963
5964 // Enqueue any remaining references remaining on the STW
5965 // reference processor's discovered lists. We need to do
5966 // this after the card table is cleaned (and verified) as
5967 // the act of enqueueing entries on to the pending list
5968 // will log these updates (and dirty their associated
5969 // cards). We need these updates logged to update any
5970 // RSets.
5971 enqueue_discovered_references(n_workers);
5972
5973 redirty_logged_cards();
5974 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
5975 }
5976
5977 void G1CollectedHeap::free_region(HeapRegion* hr,
5978 FreeRegionList* free_list,
5979 bool par,
5980 bool locked) {
5981 assert(!hr->is_free(), "the region should not be free");
5982 assert(!hr->is_empty(), "the region should not be empty");
5983 assert(_hrm.is_available(hr->hrm_index()), "region should be committed");
5984 assert(free_list != NULL, "pre-condition");
5985
5986 if (G1VerifyBitmaps) {
5987 MemRegion mr(hr->bottom(), hr->end());
5988 concurrent_mark()->clearRangePrevBitmap(mr);
5989 }
5990
5991 // Clear the card counts for this region.
5992 // Note: we only need to do this if the region is not young
5993 // (since we don't refine cards in young regions).
5994 if (!hr->is_young()) {
5995 _cg1r->hot_card_cache()->reset_card_counts(hr);
5996 }
5997 hr->hr_clear(par, true /* clear_space */, locked /* locked */);
5998 free_list->add_ordered(hr);
5999 }
6000
6001 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
6002 FreeRegionList* free_list,
6003 bool par) {
6004 assert(hr->is_starts_humongous(), "this is only for starts humongous regions");
6005 assert(free_list != NULL, "pre-condition");
6006
6007 size_t hr_capacity = hr->capacity();
6008 // We need to read this before we make the region non-humongous,
6009 // otherwise the information will be gone.
6010 uint last_index = hr->last_hc_index();
6011 hr->clear_humongous();
6012 free_region(hr, free_list, par);
6013
6014 uint i = hr->hrm_index() + 1;
6015 while (i < last_index) {
6016 HeapRegion* curr_hr = region_at(i);
6017 assert(curr_hr->is_continues_humongous(), "invariant");
6018 curr_hr->clear_humongous();
6019 free_region(curr_hr, free_list, par);
6020 i += 1;
6021 }
6022 }
6023
6024 void G1CollectedHeap::remove_from_old_sets(const HeapRegionSetCount& old_regions_removed,
6025 const HeapRegionSetCount& humongous_regions_removed) {
6026 if (old_regions_removed.length() > 0 || humongous_regions_removed.length() > 0) {
6027 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
6028 _old_set.bulk_remove(old_regions_removed);
6029 _humongous_set.bulk_remove(humongous_regions_removed);
6030 }
6031
6032 }
6033
6034 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) {
6035 assert(list != NULL, "list can't be null");
6036 if (!list->is_empty()) {
6037 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
6038 _hrm.insert_list_into_free_list(list);
6039 }
6040 }
6041
6042 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) {
6043 _allocator->decrease_used(bytes);
6044 }
6045
6046 class G1ParCleanupCTTask : public AbstractGangTask {
6047 G1SATBCardTableModRefBS* _ct_bs;
6048 G1CollectedHeap* _g1h;
6049 HeapRegion* volatile _su_head;
6050 public:
6051 G1ParCleanupCTTask(G1SATBCardTableModRefBS* ct_bs,
6052 G1CollectedHeap* g1h) :
6053 AbstractGangTask("G1 Par Cleanup CT Task"),
6054 _ct_bs(ct_bs), _g1h(g1h) { }
6055
6056 void work(uint worker_id) {
6057 HeapRegion* r;
6058 while (r = _g1h->pop_dirty_cards_region()) {
6059 clear_cards(r);
6060 }
6061 }
6062
6063 void clear_cards(HeapRegion* r) {
6064 // Cards of the survivors should have already been dirtied.
6065 if (!r->is_survivor()) {
6066 _ct_bs->clear(MemRegion(r->bottom(), r->end()));
6067 }
6068 }
6069 };
6070
6071 #ifndef PRODUCT
6072 class G1VerifyCardTableCleanup: public HeapRegionClosure {
6073 G1CollectedHeap* _g1h;
6074 G1SATBCardTableModRefBS* _ct_bs;
6075 public:
6076 G1VerifyCardTableCleanup(G1CollectedHeap* g1h, G1SATBCardTableModRefBS* ct_bs)
6077 : _g1h(g1h), _ct_bs(ct_bs) { }
6078 virtual bool doHeapRegion(HeapRegion* r) {
6079 if (r->is_survivor()) {
6080 _g1h->verify_dirty_region(r);
6081 } else {
6082 _g1h->verify_not_dirty_region(r);
6083 }
6084 return false;
6085 }
6086 };
6087
6088 void G1CollectedHeap::verify_not_dirty_region(HeapRegion* hr) {
6089 // All of the region should be clean.
6090 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
6091 MemRegion mr(hr->bottom(), hr->end());
6092 ct_bs->verify_not_dirty_region(mr);
6093 }
6094
6095 void G1CollectedHeap::verify_dirty_region(HeapRegion* hr) {
6096 // We cannot guarantee that [bottom(),end()] is dirty. Threads
6097 // dirty allocated blocks as they allocate them. The thread that
6098 // retires each region and replaces it with a new one will do a
6099 // maximal allocation to fill in [pre_dummy_top(),end()] but will
6100 // not dirty that area (one less thing to have to do while holding
6101 // a lock). So we can only verify that [bottom(),pre_dummy_top()]
6102 // is dirty.
6103 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
6104 MemRegion mr(hr->bottom(), hr->pre_dummy_top());
6105 if (hr->is_young()) {
6106 ct_bs->verify_g1_young_region(mr);
6107 } else {
6108 ct_bs->verify_dirty_region(mr);
6109 }
6110 }
6111
6112 void G1CollectedHeap::verify_dirty_young_list(HeapRegion* head) {
6113 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
6114 for (HeapRegion* hr = head; hr != NULL; hr = hr->get_next_young_region()) {
6115 verify_dirty_region(hr);
6116 }
6117 }
6118
6119 void G1CollectedHeap::verify_dirty_young_regions() {
6120 verify_dirty_young_list(_young_list->first_region());
6121 }
6122
6123 bool G1CollectedHeap::verify_no_bits_over_tams(const char* bitmap_name, CMBitMapRO* bitmap,
6124 HeapWord* tams, HeapWord* end) {
6125 guarantee(tams <= end,
6126 err_msg("tams: "PTR_FORMAT" end: "PTR_FORMAT, tams, end));
6127 HeapWord* result = bitmap->getNextMarkedWordAddress(tams, end);
6128 if (result < end) {
6129 gclog_or_tty->cr();
6130 gclog_or_tty->print_cr("## wrong marked address on %s bitmap: "PTR_FORMAT,
6131 bitmap_name, result);
6132 gclog_or_tty->print_cr("## %s tams: "PTR_FORMAT" end: "PTR_FORMAT,
6133 bitmap_name, tams, end);
6134 return false;
6135 }
6136 return true;
6137 }
6138
6139 bool G1CollectedHeap::verify_bitmaps(const char* caller, HeapRegion* hr) {
6140 CMBitMapRO* prev_bitmap = concurrent_mark()->prevMarkBitMap();
6141 CMBitMapRO* next_bitmap = (CMBitMapRO*) concurrent_mark()->nextMarkBitMap();
6142
6143 HeapWord* bottom = hr->bottom();
6144 HeapWord* ptams = hr->prev_top_at_mark_start();
6145 HeapWord* ntams = hr->next_top_at_mark_start();
6146 HeapWord* end = hr->end();
6147
6148 bool res_p = verify_no_bits_over_tams("prev", prev_bitmap, ptams, end);
6149
6150 bool res_n = true;
6151 // We reset mark_in_progress() before we reset _cmThread->in_progress() and in this window
6152 // we do the clearing of the next bitmap concurrently. Thus, we can not verify the bitmap
6153 // if we happen to be in that state.
6154 if (mark_in_progress() || !_cmThread->in_progress()) {
6155 res_n = verify_no_bits_over_tams("next", next_bitmap, ntams, end);
6156 }
6157 if (!res_p || !res_n) {
6158 gclog_or_tty->print_cr("#### Bitmap verification failed for "HR_FORMAT,
6159 HR_FORMAT_PARAMS(hr));
6160 gclog_or_tty->print_cr("#### Caller: %s", caller);
6161 return false;
6162 }
6163 return true;
6164 }
6165
6166 void G1CollectedHeap::check_bitmaps(const char* caller, HeapRegion* hr) {
6167 if (!G1VerifyBitmaps) return;
6168
6169 guarantee(verify_bitmaps(caller, hr), "bitmap verification");
6170 }
6171
6172 class G1VerifyBitmapClosure : public HeapRegionClosure {
6173 private:
6174 const char* _caller;
6175 G1CollectedHeap* _g1h;
6176 bool _failures;
6177
6178 public:
6179 G1VerifyBitmapClosure(const char* caller, G1CollectedHeap* g1h) :
6180 _caller(caller), _g1h(g1h), _failures(false) { }
6181
6182 bool failures() { return _failures; }
6183
6184 virtual bool doHeapRegion(HeapRegion* hr) {
6185 if (hr->is_continues_humongous()) return false;
6186
6187 bool result = _g1h->verify_bitmaps(_caller, hr);
6188 if (!result) {
6189 _failures = true;
6190 }
6191 return false;
6192 }
6193 };
6194
6195 void G1CollectedHeap::check_bitmaps(const char* caller) {
6196 if (!G1VerifyBitmaps) return;
6197
6198 G1VerifyBitmapClosure cl(caller, this);
6199 heap_region_iterate(&cl);
6200 guarantee(!cl.failures(), "bitmap verification");
6201 }
6202 #endif // PRODUCT
6203
6204 void G1CollectedHeap::cleanUpCardTable() {
6205 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
6206 double start = os::elapsedTime();
6207
6208 {
6209 // Iterate over the dirty cards region list.
6210 G1ParCleanupCTTask cleanup_task(ct_bs, this);
6211
6212 if (G1CollectedHeap::use_parallel_gc_threads()) {
6213 set_par_threads();
6214 workers()->run_task(&cleanup_task);
6215 set_par_threads(0);
6216 } else {
6217 while (_dirty_cards_region_list) {
6218 HeapRegion* r = _dirty_cards_region_list;
6219 cleanup_task.clear_cards(r);
6220 _dirty_cards_region_list = r->get_next_dirty_cards_region();
6221 if (_dirty_cards_region_list == r) {
6222 // The last region.
6223 _dirty_cards_region_list = NULL;
6224 }
6225 r->set_next_dirty_cards_region(NULL);
6226 }
6227 }
6228 #ifndef PRODUCT
6229 if (G1VerifyCTCleanup || VerifyAfterGC) {
6230 G1VerifyCardTableCleanup cleanup_verifier(this, ct_bs);
6231 heap_region_iterate(&cleanup_verifier);
6232 }
6233 #endif
6234 }
6235
6236 double elapsed = os::elapsedTime() - start;
6237 g1_policy()->phase_times()->record_clear_ct_time(elapsed * 1000.0);
6238 }
6239
6240 void G1CollectedHeap::free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info) {
6241 size_t pre_used = 0;
6242 FreeRegionList local_free_list("Local List for CSet Freeing");
6243
6244 double young_time_ms = 0.0;
6245 double non_young_time_ms = 0.0;
6246
6247 // Since the collection set is a superset of the the young list,
6248 // all we need to do to clear the young list is clear its
6249 // head and length, and unlink any young regions in the code below
6250 _young_list->clear();
6251
6252 G1CollectorPolicy* policy = g1_policy();
6253
6254 double start_sec = os::elapsedTime();
6255 bool non_young = true;
6256
6257 HeapRegion* cur = cs_head;
6258 int age_bound = -1;
6259 size_t rs_lengths = 0;
6260
6261 while (cur != NULL) {
6262 assert(!is_on_master_free_list(cur), "sanity");
6263 if (non_young) {
6264 if (cur->is_young()) {
6265 double end_sec = os::elapsedTime();
6266 double elapsed_ms = (end_sec - start_sec) * 1000.0;
6267 non_young_time_ms += elapsed_ms;
6268
6269 start_sec = os::elapsedTime();
6270 non_young = false;
6271 }
6272 } else {
6273 if (!cur->is_young()) {
6274 double end_sec = os::elapsedTime();
6275 double elapsed_ms = (end_sec - start_sec) * 1000.0;
6276 young_time_ms += elapsed_ms;
6277
6278 start_sec = os::elapsedTime();
6279 non_young = true;
6280 }
6281 }
6282
6283 rs_lengths += cur->rem_set()->occupied_locked();
6284
6285 HeapRegion* next = cur->next_in_collection_set();
6286 assert(cur->in_collection_set(), "bad CS");
6287 cur->set_next_in_collection_set(NULL);
6288 cur->set_in_collection_set(false);
6289
6290 if (cur->is_young()) {
6291 int index = cur->young_index_in_cset();
6292 assert(index != -1, "invariant");
6293 assert((uint) index < policy->young_cset_region_length(), "invariant");
6294 size_t words_survived = _surviving_young_words[index];
6295 cur->record_surv_words_in_group(words_survived);
6296
6297 // At this point the we have 'popped' cur from the collection set
6298 // (linked via next_in_collection_set()) but it is still in the
6299 // young list (linked via next_young_region()). Clear the
6300 // _next_young_region field.
6301 cur->set_next_young_region(NULL);
6302 } else {
6303 int index = cur->young_index_in_cset();
6304 assert(index == -1, "invariant");
6305 }
6306
6307 assert( (cur->is_young() && cur->young_index_in_cset() > -1) ||
6308 (!cur->is_young() && cur->young_index_in_cset() == -1),
6309 "invariant" );
6310
6311 if (!cur->evacuation_failed()) {
6312 MemRegion used_mr = cur->used_region();
6313
6314 // And the region is empty.
6315 assert(!used_mr.is_empty(), "Should not have empty regions in a CS.");
6316 pre_used += cur->used();
6317 free_region(cur, &local_free_list, false /* par */, true /* locked */);
6318 } else {
6319 cur->uninstall_surv_rate_group();
6320 if (cur->is_young()) {
6321 cur->set_young_index_in_cset(-1);
6322 }
6323 cur->set_evacuation_failed(false);
6324 // The region is now considered to be old.
6325 cur->set_old();
6326 _old_set.add(cur);
6327 evacuation_info.increment_collectionset_used_after(cur->used());
6328 }
6329 cur = next;
6330 }
6331
6332 evacuation_info.set_regions_freed(local_free_list.length());
6333 policy->record_max_rs_lengths(rs_lengths);
6334 policy->cset_regions_freed();
6335
6336 double end_sec = os::elapsedTime();
6337 double elapsed_ms = (end_sec - start_sec) * 1000.0;
6338
6339 if (non_young) {
6340 non_young_time_ms += elapsed_ms;
6341 } else {
6342 young_time_ms += elapsed_ms;
6343 }
6344
6345 prepend_to_freelist(&local_free_list);
6346 decrement_summary_bytes(pre_used);
6347 policy->phase_times()->record_young_free_cset_time_ms(young_time_ms);
6348 policy->phase_times()->record_non_young_free_cset_time_ms(non_young_time_ms);
6349 }
6350
6351 class G1FreeHumongousRegionClosure : public HeapRegionClosure {
6352 private:
6353 FreeRegionList* _free_region_list;
6354 HeapRegionSet* _proxy_set;
6355 HeapRegionSetCount _humongous_regions_removed;
6356 size_t _freed_bytes;
6357 public:
6358
6359 G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) :
6360 _free_region_list(free_region_list), _humongous_regions_removed(), _freed_bytes(0) {
6361 }
6362
6363 virtual bool doHeapRegion(HeapRegion* r) {
6364 if (!r->is_starts_humongous()) {
6365 return false;
6366 }
6367
6368 G1CollectedHeap* g1h = G1CollectedHeap::heap();
6369
6370 oop obj = (oop)r->bottom();
6371 CMBitMap* next_bitmap = g1h->concurrent_mark()->nextMarkBitMap();
6372
6373 // The following checks whether the humongous object is live are sufficient.
6374 // The main additional check (in addition to having a reference from the roots
6375 // or the young gen) is whether the humongous object has a remembered set entry.
6376 //
6377 // A humongous object cannot be live if there is no remembered set for it
6378 // because:
6379 // - there can be no references from within humongous starts regions referencing
6380 // the object because we never allocate other objects into them.
6381 // (I.e. there are no intra-region references that may be missed by the
6382 // remembered set)
6383 // - as soon there is a remembered set entry to the humongous starts region
6384 // (i.e. it has "escaped" to an old object) this remembered set entry will stay
6385 // until the end of a concurrent mark.
6386 //
6387 // It is not required to check whether the object has been found dead by marking
6388 // or not, in fact it would prevent reclamation within a concurrent cycle, as
6389 // all objects allocated during that time are considered live.
6390 // SATB marking is even more conservative than the remembered set.
6391 // So if at this point in the collection there is no remembered set entry,
6392 // nobody has a reference to it.
6393 // At the start of collection we flush all refinement logs, and remembered sets
6394 // are completely up-to-date wrt to references to the humongous object.
6395 //
6396 // Other implementation considerations:
6397 // - never consider object arrays: while they are a valid target, they have not
6398 // been observed to be used as temporary objects.
6399 // - they would also pose considerable effort for cleaning up the the remembered
6400 // sets.
6401 // While this cleanup is not strictly necessary to be done (or done instantly),
6402 // given that their occurrence is very low, this saves us this additional
6403 // complexity.
6404 uint region_idx = r->hrm_index();
6405 if (g1h->humongous_is_live(region_idx) ||
6406 g1h->humongous_region_is_always_live(region_idx)) {
6407
6408 if (G1TraceReclaimDeadHumongousObjectsAtYoungGC) {
6409 gclog_or_tty->print_cr("Live humongous %d region %d with remset "SIZE_FORMAT" code roots "SIZE_FORMAT" is marked %d live-other %d obj array %d",
6410 r->is_humongous(),
6411 region_idx,
6412 r->rem_set()->occupied(),
6413 r->rem_set()->strong_code_roots_list_length(),
6414 next_bitmap->isMarked(r->bottom()),
6415 g1h->humongous_is_live(region_idx),
6416 obj->is_objArray()
6417 );
6418 }
6419
6420 return false;
6421 }
6422
6423 guarantee(!obj->is_objArray(),
6424 err_msg("Eagerly reclaiming object arrays is not supported, but the object "PTR_FORMAT" is.",
6425 r->bottom()));
6426
6427 if (G1TraceReclaimDeadHumongousObjectsAtYoungGC) {
6428 gclog_or_tty->print_cr("Reclaim humongous region %d start "PTR_FORMAT" region %d length "UINT32_FORMAT" with remset "SIZE_FORMAT" code roots "SIZE_FORMAT" is marked %d live-other %d obj array %d",
6429 r->is_humongous(),
6430 r->bottom(),
6431 region_idx,
6432 r->region_num(),
6433 r->rem_set()->occupied(),
6434 r->rem_set()->strong_code_roots_list_length(),
6435 next_bitmap->isMarked(r->bottom()),
6436 g1h->humongous_is_live(region_idx),
6437 obj->is_objArray()
6438 );
6439 }
6440 // Need to clear mark bit of the humongous object if already set.
6441 if (next_bitmap->isMarked(r->bottom())) {
6442 next_bitmap->clear(r->bottom());
6443 }
6444 _freed_bytes += r->used();
6445 r->set_containing_set(NULL);
6446 _humongous_regions_removed.increment(1u, r->capacity());
6447 g1h->free_humongous_region(r, _free_region_list, false);
6448
6449 return false;
6450 }
6451
6452 HeapRegionSetCount& humongous_free_count() {
6453 return _humongous_regions_removed;
6454 }
6455
6456 size_t bytes_freed() const {
6457 return _freed_bytes;
6458 }
6459
6460 size_t humongous_reclaimed() const {
6461 return _humongous_regions_removed.length();
6462 }
6463 };
6464
6465 void G1CollectedHeap::eagerly_reclaim_humongous_regions() {
6466 assert_at_safepoint(true);
6467
6468 if (!G1ReclaimDeadHumongousObjectsAtYoungGC || !_has_humongous_reclaim_candidates) {
6469 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0);
6470 return;
6471 }
6472
6473 double start_time = os::elapsedTime();
6474
6475 FreeRegionList local_cleanup_list("Local Humongous Cleanup List");
6476
6477 G1FreeHumongousRegionClosure cl(&local_cleanup_list);
6478 heap_region_iterate(&cl);
6479
6480 HeapRegionSetCount empty_set;
6481 remove_from_old_sets(empty_set, cl.humongous_free_count());
6482
6483 G1HRPrinter* hr_printer = _g1h->hr_printer();
6484 if (hr_printer->is_active()) {
6485 FreeRegionListIterator iter(&local_cleanup_list);
6486 while (iter.more_available()) {
6487 HeapRegion* hr = iter.get_next();
6488 hr_printer->cleanup(hr);
6489 }
6490 }
6491
6492 prepend_to_freelist(&local_cleanup_list);
6493 decrement_summary_bytes(cl.bytes_freed());
6494
6495 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0,
6496 cl.humongous_reclaimed());
6497 }
6498
6499 // This routine is similar to the above but does not record
6500 // any policy statistics or update free lists; we are abandoning
6501 // the current incremental collection set in preparation of a
6502 // full collection. After the full GC we will start to build up
6503 // the incremental collection set again.
6504 // This is only called when we're doing a full collection
6505 // and is immediately followed by the tearing down of the young list.
6506
6507 void G1CollectedHeap::abandon_collection_set(HeapRegion* cs_head) {
6508 HeapRegion* cur = cs_head;
6509
6510 while (cur != NULL) {
6511 HeapRegion* next = cur->next_in_collection_set();
6512 assert(cur->in_collection_set(), "bad CS");
6513 cur->set_next_in_collection_set(NULL);
6514 cur->set_in_collection_set(false);
6515 cur->set_young_index_in_cset(-1);
6516 cur = next;
6517 }
6518 }
6519
6520 void G1CollectedHeap::set_free_regions_coming() {
6521 if (G1ConcRegionFreeingVerbose) {
6522 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
6523 "setting free regions coming");
6524 }
6525
6526 assert(!free_regions_coming(), "pre-condition");
6527 _free_regions_coming = true;
6528 }
6529
6530 void G1CollectedHeap::reset_free_regions_coming() {
6531 assert(free_regions_coming(), "pre-condition");
6532
6533 {
6534 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6535 _free_regions_coming = false;
6536 SecondaryFreeList_lock->notify_all();
6537 }
6538
6539 if (G1ConcRegionFreeingVerbose) {
6540 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
6541 "reset free regions coming");
6542 }
6543 }
6544
6545 void G1CollectedHeap::wait_while_free_regions_coming() {
6546 // Most of the time we won't have to wait, so let's do a quick test
6547 // first before we take the lock.
6548 if (!free_regions_coming()) {
6549 return;
6550 }
6551
6552 if (G1ConcRegionFreeingVerbose) {
6553 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
6554 "waiting for free regions");
6555 }
6556
6557 {
6558 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6559 while (free_regions_coming()) {
6560 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
6561 }
6562 }
6563
6564 if (G1ConcRegionFreeingVerbose) {
6565 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
6566 "done waiting for free regions");
6567 }
6568 }
6569
6570 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
6571 assert(heap_lock_held_for_gc(),
6572 "the heap lock should already be held by or for this thread");
6573 _young_list->push_region(hr);
6574 }
6575
6576 class NoYoungRegionsClosure: public HeapRegionClosure {
6577 private:
6578 bool _success;
6579 public:
6580 NoYoungRegionsClosure() : _success(true) { }
6581 bool doHeapRegion(HeapRegion* r) {
6582 if (r->is_young()) {
6583 gclog_or_tty->print_cr("Region ["PTR_FORMAT", "PTR_FORMAT") tagged as young",
6584 r->bottom(), r->end());
6585 _success = false;
6586 }
6587 return false;
6588 }
6589 bool success() { return _success; }
6590 };
6591
6592 bool G1CollectedHeap::check_young_list_empty(bool check_heap, bool check_sample) {
6593 bool ret = _young_list->check_list_empty(check_sample);
6594
6595 if (check_heap) {
6596 NoYoungRegionsClosure closure;
6597 heap_region_iterate(&closure);
6598 ret = ret && closure.success();
6599 }
6600
6601 return ret;
6602 }
6603
6604 class TearDownRegionSetsClosure : public HeapRegionClosure {
6605 private:
6606 HeapRegionSet *_old_set;
6607
6608 public:
6609 TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { }
6610
6611 bool doHeapRegion(HeapRegion* r) {
6612 if (r->is_old()) {
6613 _old_set->remove(r);
6614 } else {
6615 // We ignore free regions, we'll empty the free list afterwards.
6616 // We ignore young regions, we'll empty the young list afterwards.
6617 // We ignore humongous regions, we're not tearing down the
6618 // humongous regions set.
6619 assert(r->is_free() || r->is_young() || r->is_humongous(),
6620 "it cannot be another type");
6621 }
6622 return false;
6623 }
6624
6625 ~TearDownRegionSetsClosure() {
6626 assert(_old_set->is_empty(), "post-condition");
6627 }
6628 };
6629
6630 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
6631 assert_at_safepoint(true /* should_be_vm_thread */);
6632
6633 if (!free_list_only) {
6634 TearDownRegionSetsClosure cl(&_old_set);
6635 heap_region_iterate(&cl);
6636
6637 // Note that emptying the _young_list is postponed and instead done as
6638 // the first step when rebuilding the regions sets again. The reason for
6639 // this is that during a full GC string deduplication needs to know if
6640 // a collected region was young or old when the full GC was initiated.
6641 }
6642 _hrm.remove_all_free_regions();
6643 }
6644
6645 class RebuildRegionSetsClosure : public HeapRegionClosure {
6646 private:
6647 bool _free_list_only;
6648 HeapRegionSet* _old_set;
6649 HeapRegionManager* _hrm;
6650 size_t _total_used;
6651
6652 public:
6653 RebuildRegionSetsClosure(bool free_list_only,
6654 HeapRegionSet* old_set, HeapRegionManager* hrm) :
6655 _free_list_only(free_list_only),
6656 _old_set(old_set), _hrm(hrm), _total_used(0) {
6657 assert(_hrm->num_free_regions() == 0, "pre-condition");
6658 if (!free_list_only) {
6659 assert(_old_set->is_empty(), "pre-condition");
6660 }
6661 }
6662
6663 bool doHeapRegion(HeapRegion* r) {
6664 if (r->is_continues_humongous()) {
6665 return false;
6666 }
6667
6668 if (r->is_empty()) {
6669 // Add free regions to the free list
6670 r->set_free();
6671 r->set_allocation_context(AllocationContext::system());
6672 _hrm->insert_into_free_list(r);
6673 } else if (!_free_list_only) {
6674 assert(!r->is_young(), "we should not come across young regions");
6675
6676 if (r->is_humongous()) {
6677 // We ignore humongous regions, we left the humongous set unchanged
6678 } else {
6679 // Objects that were compacted would have ended up on regions
6680 // that were previously old or free.
6681 assert(r->is_free() || r->is_old(), "invariant");
6682 // We now consider them old, so register as such.
6683 r->set_old();
6684 _old_set->add(r);
6685 }
6686 _total_used += r->used();
6687 }
6688
6689 return false;
6690 }
6691
6692 size_t total_used() {
6693 return _total_used;
6694 }
6695 };
6696
6697 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
6698 assert_at_safepoint(true /* should_be_vm_thread */);
6699
6700 if (!free_list_only) {
6701 _young_list->empty_list();
6702 }
6703
6704 RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm);
6705 heap_region_iterate(&cl);
6706
6707 if (!free_list_only) {
6708 _allocator->set_used(cl.total_used());
6709 }
6710 assert(_allocator->used_unlocked() == recalculate_used(),
6711 err_msg("inconsistent _allocator->used_unlocked(), "
6712 "value: "SIZE_FORMAT" recalculated: "SIZE_FORMAT,
6713 _allocator->used_unlocked(), recalculate_used()));
6714 }
6715
6716 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) {
6717 _refine_cte_cl->set_concurrent(concurrent);
6718 }
6719
6720 bool G1CollectedHeap::is_in_closed_subset(const void* p) const {
6721 HeapRegion* hr = heap_region_containing(p);
6722 return hr->is_in(p);
6723 }
6724
6725 // Methods for the mutator alloc region
6726
6727 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
6728 bool force) {
6729 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6730 assert(!force || g1_policy()->can_expand_young_list(),
6731 "if force is true we should be able to expand the young list");
6732 bool young_list_full = g1_policy()->is_young_list_full();
6733 if (force || !young_list_full) {
6734 HeapRegion* new_alloc_region = new_region(word_size,
6735 false /* is_old */,
6736 false /* do_expand */);
6737 if (new_alloc_region != NULL) {
6738 set_region_short_lived_locked(new_alloc_region);
6739 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Eden, young_list_full);
6740 check_bitmaps("Mutator Region Allocation", new_alloc_region);
6741 return new_alloc_region;
6742 }
6743 }
6744 return NULL;
6745 }
6746
6747 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
6748 size_t allocated_bytes) {
6749 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6750 assert(alloc_region->is_eden(), "all mutator alloc regions should be eden");
6751
6752 g1_policy()->add_region_to_incremental_cset_lhs(alloc_region);
6753 _allocator->increase_used(allocated_bytes);
6754 _hr_printer.retire(alloc_region);
6755 // We update the eden sizes here, when the region is retired,
6756 // instead of when it's allocated, since this is the point that its
6757 // used space has been recored in _summary_bytes_used.
6758 g1mm()->update_eden_size();
6759 }
6760
6761 void G1CollectedHeap::set_par_threads() {
6762 // Don't change the number of workers. Use the value previously set
6763 // in the workgroup.
6764 assert(G1CollectedHeap::use_parallel_gc_threads(), "shouldn't be here otherwise");
6765 uint n_workers = workers()->active_workers();
6766 assert(UseDynamicNumberOfGCThreads ||
6767 n_workers == workers()->total_workers(),
6768 "Otherwise should be using the total number of workers");
6769 if (n_workers == 0) {
6770 assert(false, "Should have been set in prior evacuation pause.");
6771 n_workers = ParallelGCThreads;
6772 workers()->set_active_workers(n_workers);
6773 }
6774 set_par_threads(n_workers);
6775 }
6776
6777 // Methods for the GC alloc regions
6778
6779 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size,
6780 uint count,
6781 GCAllocPurpose ap) {
6782 assert(FreeList_lock->owned_by_self(), "pre-condition");
6783
6784 if (count < g1_policy()->max_regions(ap)) {
6785 bool survivor = (ap == GCAllocForSurvived);
6786 HeapRegion* new_alloc_region = new_region(word_size,
6787 !survivor,
6788 true /* do_expand */);
6789 if (new_alloc_region != NULL) {
6790 // We really only need to do this for old regions given that we
6791 // should never scan survivors. But it doesn't hurt to do it
6792 // for survivors too.
6793 new_alloc_region->record_top_and_timestamp();
6794 if (survivor) {
6795 new_alloc_region->set_survivor();
6796 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Survivor);
6797 check_bitmaps("Survivor Region Allocation", new_alloc_region);
6798 } else {
6799 new_alloc_region->set_old();
6800 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Old);
6801 check_bitmaps("Old Region Allocation", new_alloc_region);
6802 }
6803 bool during_im = g1_policy()->during_initial_mark_pause();
6804 new_alloc_region->note_start_of_copying(during_im);
6805 return new_alloc_region;
6806 } else {
6807 g1_policy()->note_alloc_region_limit_reached(ap);
6808 }
6809 }
6810 return NULL;
6811 }
6812
6813 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
6814 size_t allocated_bytes,
6815 GCAllocPurpose ap) {
6816 bool during_im = g1_policy()->during_initial_mark_pause();
6817 alloc_region->note_end_of_copying(during_im);
6818 g1_policy()->record_bytes_copied_during_gc(allocated_bytes);
6819 if (ap == GCAllocForSurvived) {
6820 young_list()->add_survivor_region(alloc_region);
6821 } else {
6822 _old_set.add(alloc_region);
6823 }
6824 _hr_printer.retire(alloc_region);
6825 }
6826
6827 // Heap region set verification
6828
6829 class VerifyRegionListsClosure : public HeapRegionClosure {
6830 private:
6831 HeapRegionSet* _old_set;
6832 HeapRegionSet* _humongous_set;
6833 HeapRegionManager* _hrm;
6834
6835 public:
6836 HeapRegionSetCount _old_count;
6837 HeapRegionSetCount _humongous_count;
6838 HeapRegionSetCount _free_count;
6839
6840 VerifyRegionListsClosure(HeapRegionSet* old_set,
6841 HeapRegionSet* humongous_set,
6842 HeapRegionManager* hrm) :
6843 _old_set(old_set), _humongous_set(humongous_set), _hrm(hrm),
6844 _old_count(), _humongous_count(), _free_count(){ }
6845
6846 bool doHeapRegion(HeapRegion* hr) {
6847 if (hr->is_continues_humongous()) {
6848 return false;
6849 }
6850
6851 if (hr->is_young()) {
6852 // TODO
6853 } else if (hr->is_starts_humongous()) {
6854 assert(hr->containing_set() == _humongous_set, err_msg("Heap region %u is starts humongous but not in humongous set.", hr->hrm_index()));
6855 _humongous_count.increment(1u, hr->capacity());
6856 } else if (hr->is_empty()) {
6857 assert(_hrm->is_free(hr), err_msg("Heap region %u is empty but not on the free list.", hr->hrm_index()));
6858 _free_count.increment(1u, hr->capacity());
6859 } else if (hr->is_old()) {
6860 assert(hr->containing_set() == _old_set, err_msg("Heap region %u is old but not in the old set.", hr->hrm_index()));
6861 _old_count.increment(1u, hr->capacity());
6862 } else {
6863 ShouldNotReachHere();
6864 }
6865 return false;
6866 }
6867
6868 void verify_counts(HeapRegionSet* old_set, HeapRegionSet* humongous_set, HeapRegionManager* free_list) {
6869 guarantee(old_set->length() == _old_count.length(), err_msg("Old set count mismatch. Expected %u, actual %u.", old_set->length(), _old_count.length()));
6870 guarantee(old_set->total_capacity_bytes() == _old_count.capacity(), err_msg("Old set capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
6871 old_set->total_capacity_bytes(), _old_count.capacity()));
6872
6873 guarantee(humongous_set->length() == _humongous_count.length(), err_msg("Hum set count mismatch. Expected %u, actual %u.", humongous_set->length(), _humongous_count.length()));
6874 guarantee(humongous_set->total_capacity_bytes() == _humongous_count.capacity(), err_msg("Hum set capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
6875 humongous_set->total_capacity_bytes(), _humongous_count.capacity()));
6876
6877 guarantee(free_list->num_free_regions() == _free_count.length(), err_msg("Free list count mismatch. Expected %u, actual %u.", free_list->num_free_regions(), _free_count.length()));
6878 guarantee(free_list->total_capacity_bytes() == _free_count.capacity(), err_msg("Free list capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
6879 free_list->total_capacity_bytes(), _free_count.capacity()));
6880 }
6881 };
6882
6883 void G1CollectedHeap::verify_region_sets() {
6884 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6885
6886 // First, check the explicit lists.
6887 _hrm.verify();
6888 {
6889 // Given that a concurrent operation might be adding regions to
6890 // the secondary free list we have to take the lock before
6891 // verifying it.
6892 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6893 _secondary_free_list.verify_list();
6894 }
6895
6896 // If a concurrent region freeing operation is in progress it will
6897 // be difficult to correctly attributed any free regions we come
6898 // across to the correct free list given that they might belong to
6899 // one of several (free_list, secondary_free_list, any local lists,
6900 // etc.). So, if that's the case we will skip the rest of the
6901 // verification operation. Alternatively, waiting for the concurrent
6902 // operation to complete will have a non-trivial effect on the GC's
6903 // operation (no concurrent operation will last longer than the
6904 // interval between two calls to verification) and it might hide
6905 // any issues that we would like to catch during testing.
6906 if (free_regions_coming()) {
6907 return;
6908 }
6909
6910 // Make sure we append the secondary_free_list on the free_list so
6911 // that all free regions we will come across can be safely
6912 // attributed to the free_list.
6913 append_secondary_free_list_if_not_empty_with_lock();
6914
6915 // Finally, make sure that the region accounting in the lists is
6916 // consistent with what we see in the heap.
6917
6918 VerifyRegionListsClosure cl(&_old_set, &_humongous_set, &_hrm);
6919 heap_region_iterate(&cl);
6920 cl.verify_counts(&_old_set, &_humongous_set, &_hrm);
6921 }
6922
6923 // Optimized nmethod scanning
6924
6925 class RegisterNMethodOopClosure: public OopClosure {
6926 G1CollectedHeap* _g1h;
6927 nmethod* _nm;
6928
6929 template <class T> void do_oop_work(T* p) {
6930 T heap_oop = oopDesc::load_heap_oop(p);
6931 if (!oopDesc::is_null(heap_oop)) {
6932 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
6933 HeapRegion* hr = _g1h->heap_region_containing(obj);
6934 assert(!hr->is_continues_humongous(),
6935 err_msg("trying to add code root "PTR_FORMAT" in continuation of humongous region "HR_FORMAT
6936 " starting at "HR_FORMAT,
6937 _nm, HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())));
6938
6939 // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries.
6940 hr->add_strong_code_root_locked(_nm);
6941 }
6942 }
6943
6944 public:
6945 RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
6946 _g1h(g1h), _nm(nm) {}
6947
6948 void do_oop(oop* p) { do_oop_work(p); }
6949 void do_oop(narrowOop* p) { do_oop_work(p); }
6950 };
6951
6952 class UnregisterNMethodOopClosure: public OopClosure {
6953 G1CollectedHeap* _g1h;
6954 nmethod* _nm;
6955
6956 template <class T> void do_oop_work(T* p) {
6957 T heap_oop = oopDesc::load_heap_oop(p);
6958 if (!oopDesc::is_null(heap_oop)) {
6959 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
6960 HeapRegion* hr = _g1h->heap_region_containing(obj);
6961 assert(!hr->is_continues_humongous(),
6962 err_msg("trying to remove code root "PTR_FORMAT" in continuation of humongous region "HR_FORMAT
6963 " starting at "HR_FORMAT,
6964 _nm, HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())));
6965
6966 hr->remove_strong_code_root(_nm);
6967 }
6968 }
6969
6970 public:
6971 UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
6972 _g1h(g1h), _nm(nm) {}
6973
6974 void do_oop(oop* p) { do_oop_work(p); }
6975 void do_oop(narrowOop* p) { do_oop_work(p); }
6976 };
6977
6978 void G1CollectedHeap::register_nmethod(nmethod* nm) {
6979 CollectedHeap::register_nmethod(nm);
6980
6981 guarantee(nm != NULL, "sanity");
6982 RegisterNMethodOopClosure reg_cl(this, nm);
6983 nm->oops_do(®_cl);
6984 }
6985
6986 void G1CollectedHeap::unregister_nmethod(nmethod* nm) {
6987 CollectedHeap::unregister_nmethod(nm);
6988
6989 guarantee(nm != NULL, "sanity");
6990 UnregisterNMethodOopClosure reg_cl(this, nm);
6991 nm->oops_do(®_cl, true);
6992 }
6993
6994 void G1CollectedHeap::purge_code_root_memory() {
6995 double purge_start = os::elapsedTime();
6996 G1CodeRootSet::purge();
6997 double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0;
6998 g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms);
6999 }
7000
7001 class RebuildStrongCodeRootClosure: public CodeBlobClosure {
7002 G1CollectedHeap* _g1h;
7003
7004 public:
7005 RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) :
7006 _g1h(g1h) {}
7007
7008 void do_code_blob(CodeBlob* cb) {
7009 nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL;
7010 if (nm == NULL) {
7011 return;
7012 }
7013
7014 if (ScavengeRootsInCode) {
7015 _g1h->register_nmethod(nm);
7016 }
7017 }
7018 };
7019
7020 void G1CollectedHeap::rebuild_strong_code_roots() {
7021 RebuildStrongCodeRootClosure blob_cl(this);
7022 CodeCache::blobs_do(&blob_cl);
7023 }