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() for parallelism.
94 // The number of GC workers is passed to heap_region_par_iterate().
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 list->set_not_young();
215 list = next;
216 }
217 }
218
219 void YoungList::empty_list() {
220 assert(check_list_well_formed(), "young list should be well formed");
221
222 empty_list(_head);
223 _head = NULL;
224 _length = 0;
225
226 empty_list(_survivor_head);
227 _survivor_head = NULL;
228 _survivor_tail = NULL;
229 _survivor_length = 0;
230
231 _last_sampled_rs_lengths = 0;
232
233 assert(check_list_empty(false), "just making sure...");
234 }
235
236 bool YoungList::check_list_well_formed() {
237 bool ret = true;
238
239 uint length = 0;
240 HeapRegion* curr = _head;
241 HeapRegion* last = NULL;
242 while (curr != NULL) {
243 if (!curr->is_young()) {
244 gclog_or_tty->print_cr("### YOUNG REGION "PTR_FORMAT"-"PTR_FORMAT" "
245 "incorrectly tagged (y: %d, surv: %d)",
246 curr->bottom(), curr->end(),
247 curr->is_young(), curr->is_survivor());
248 ret = false;
249 }
250 ++length;
251 last = curr;
252 curr = curr->get_next_young_region();
253 }
254 ret = ret && (length == _length);
255
256 if (!ret) {
257 gclog_or_tty->print_cr("### YOUNG LIST seems not well formed!");
258 gclog_or_tty->print_cr("### list has %u entries, _length is %u",
259 length, _length);
260 }
261
262 return ret;
263 }
264
265 bool YoungList::check_list_empty(bool check_sample) {
266 bool ret = true;
267
268 if (_length != 0) {
269 gclog_or_tty->print_cr("### YOUNG LIST should have 0 length, not %u",
270 _length);
271 ret = false;
272 }
273 if (check_sample && _last_sampled_rs_lengths != 0) {
274 gclog_or_tty->print_cr("### YOUNG LIST has non-zero last sampled RS lengths");
275 ret = false;
276 }
277 if (_head != NULL) {
278 gclog_or_tty->print_cr("### YOUNG LIST does not have a NULL head");
279 ret = false;
280 }
281 if (!ret) {
282 gclog_or_tty->print_cr("### YOUNG LIST does not seem empty");
283 }
284
285 return ret;
286 }
287
288 void
289 YoungList::rs_length_sampling_init() {
290 _sampled_rs_lengths = 0;
291 _curr = _head;
292 }
293
294 bool
295 YoungList::rs_length_sampling_more() {
296 return _curr != NULL;
297 }
298
299 void
300 YoungList::rs_length_sampling_next() {
301 assert( _curr != NULL, "invariant" );
302 size_t rs_length = _curr->rem_set()->occupied();
303
304 _sampled_rs_lengths += rs_length;
305
306 // The current region may not yet have been added to the
307 // incremental collection set (it gets added when it is
308 // retired as the current allocation region).
309 if (_curr->in_collection_set()) {
310 // Update the collection set policy information for this region
311 _g1h->g1_policy()->update_incremental_cset_info(_curr, rs_length);
312 }
313
314 _curr = _curr->get_next_young_region();
315 if (_curr == NULL) {
316 _last_sampled_rs_lengths = _sampled_rs_lengths;
317 // gclog_or_tty->print_cr("last sampled RS lengths = %d", _last_sampled_rs_lengths);
318 }
319 }
320
321 void
322 YoungList::reset_auxilary_lists() {
323 guarantee( is_empty(), "young list should be empty" );
324 assert(check_list_well_formed(), "young list should be well formed");
325
326 // Add survivor regions to SurvRateGroup.
327 _g1h->g1_policy()->note_start_adding_survivor_regions();
328 _g1h->g1_policy()->finished_recalculating_age_indexes(true /* is_survivors */);
329
330 int young_index_in_cset = 0;
331 for (HeapRegion* curr = _survivor_head;
332 curr != NULL;
333 curr = curr->get_next_young_region()) {
334 _g1h->g1_policy()->set_region_survivor(curr, young_index_in_cset);
335
336 // The region is a non-empty survivor so let's add it to
337 // the incremental collection set for the next evacuation
338 // pause.
339 _g1h->g1_policy()->add_region_to_incremental_cset_rhs(curr);
340 young_index_in_cset += 1;
341 }
342 assert((uint) young_index_in_cset == _survivor_length, "post-condition");
343 _g1h->g1_policy()->note_stop_adding_survivor_regions();
344
345 _head = _survivor_head;
346 _length = _survivor_length;
347 if (_survivor_head != NULL) {
348 assert(_survivor_tail != NULL, "cause it shouldn't be");
349 assert(_survivor_length > 0, "invariant");
350 _survivor_tail->set_next_young_region(NULL);
351 }
352
353 // Don't clear the survivor list handles until the start of
354 // the next evacuation pause - we need it in order to re-tag
355 // the survivor regions from this evacuation pause as 'young'
356 // at the start of the next.
357
358 _g1h->g1_policy()->finished_recalculating_age_indexes(false /* is_survivors */);
359
360 assert(check_list_well_formed(), "young list should be well formed");
361 }
362
363 void YoungList::print() {
364 HeapRegion* lists[] = {_head, _survivor_head};
365 const char* names[] = {"YOUNG", "SURVIVOR"};
366
367 for (unsigned int list = 0; list < ARRAY_SIZE(lists); ++list) {
368 gclog_or_tty->print_cr("%s LIST CONTENTS", names[list]);
369 HeapRegion *curr = lists[list];
370 if (curr == NULL)
371 gclog_or_tty->print_cr(" empty");
372 while (curr != NULL) {
373 gclog_or_tty->print_cr(" "HR_FORMAT", P: "PTR_FORMAT "N: "PTR_FORMAT", age: %4d",
374 HR_FORMAT_PARAMS(curr),
375 curr->prev_top_at_mark_start(),
376 curr->next_top_at_mark_start(),
377 curr->age_in_surv_rate_group_cond());
378 curr = curr->get_next_young_region();
379 }
380 }
381
382 gclog_or_tty->cr();
383 }
384
385 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) {
386 OtherRegionsTable::invalidate(start_idx, num_regions);
387 }
388
389 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions) {
390 reset_from_card_cache(start_idx, num_regions);
391 }
392
393 void G1CollectedHeap::push_dirty_cards_region(HeapRegion* hr)
394 {
395 // Claim the right to put the region on the dirty cards region list
396 // by installing a self pointer.
397 HeapRegion* next = hr->get_next_dirty_cards_region();
398 if (next == NULL) {
399 HeapRegion* res = (HeapRegion*)
400 Atomic::cmpxchg_ptr(hr, hr->next_dirty_cards_region_addr(),
401 NULL);
402 if (res == NULL) {
403 HeapRegion* head;
404 do {
405 // Put the region to the dirty cards region list.
406 head = _dirty_cards_region_list;
407 next = (HeapRegion*)
408 Atomic::cmpxchg_ptr(hr, &_dirty_cards_region_list, head);
409 if (next == head) {
410 assert(hr->get_next_dirty_cards_region() == hr,
411 "hr->get_next_dirty_cards_region() != hr");
412 if (next == NULL) {
413 // The last region in the list points to itself.
414 hr->set_next_dirty_cards_region(hr);
415 } else {
416 hr->set_next_dirty_cards_region(next);
417 }
418 }
419 } while (next != head);
420 }
421 }
422 }
423
424 HeapRegion* G1CollectedHeap::pop_dirty_cards_region()
425 {
426 HeapRegion* head;
427 HeapRegion* hr;
428 do {
429 head = _dirty_cards_region_list;
430 if (head == NULL) {
431 return NULL;
432 }
433 HeapRegion* new_head = head->get_next_dirty_cards_region();
434 if (head == new_head) {
435 // The last region.
436 new_head = NULL;
437 }
438 hr = (HeapRegion*)Atomic::cmpxchg_ptr(new_head, &_dirty_cards_region_list,
439 head);
440 } while (hr != head);
441 assert(hr != NULL, "invariant");
442 hr->set_next_dirty_cards_region(NULL);
443 return hr;
444 }
445
446 #ifdef ASSERT
447 // A region is added to the collection set as it is retired
448 // so an address p can point to a region which will be in the
449 // collection set but has not yet been retired. This method
450 // therefore is only accurate during a GC pause after all
451 // regions have been retired. It is used for debugging
452 // to check if an nmethod has references to objects that can
453 // be move during a partial collection. Though it can be
454 // inaccurate, it is sufficient for G1 because the conservative
455 // implementation of is_scavengable() for G1 will indicate that
456 // all nmethods must be scanned during a partial collection.
457 bool G1CollectedHeap::is_in_partial_collection(const void* p) {
458 if (p == NULL) {
459 return false;
460 }
461 return heap_region_containing(p)->in_collection_set();
462 }
463 #endif
464
465 // Returns true if the reference points to an object that
466 // can move in an incremental collection.
467 bool G1CollectedHeap::is_scavengable(const void* p) {
468 HeapRegion* hr = heap_region_containing(p);
469 return !hr->isHumongous();
470 }
471
472 void G1CollectedHeap::check_ct_logs_at_safepoint() {
473 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
474 CardTableModRefBS* ct_bs = g1_barrier_set();
475
476 // Count the dirty cards at the start.
477 CountNonCleanMemRegionClosure count1(this);
478 ct_bs->mod_card_iterate(&count1);
479 int orig_count = count1.n();
480
481 // First clear the logged cards.
482 ClearLoggedCardTableEntryClosure clear;
483 dcqs.apply_closure_to_all_completed_buffers(&clear);
484 dcqs.iterate_closure_all_threads(&clear, false);
485 clear.print_histo();
486
487 // Now ensure that there's no dirty cards.
488 CountNonCleanMemRegionClosure count2(this);
489 ct_bs->mod_card_iterate(&count2);
490 if (count2.n() != 0) {
491 gclog_or_tty->print_cr("Card table has %d entries; %d originally",
492 count2.n(), orig_count);
493 }
494 guarantee(count2.n() == 0, "Card table should be clean.");
495
496 RedirtyLoggedCardTableEntryClosure redirty;
497 dcqs.apply_closure_to_all_completed_buffers(&redirty);
498 dcqs.iterate_closure_all_threads(&redirty, false);
499 gclog_or_tty->print_cr("Log entries = %d, dirty cards = %d.",
500 clear.num_processed(), orig_count);
501 guarantee(redirty.num_processed() == clear.num_processed(),
502 err_msg("Redirtied "SIZE_FORMAT" cards, bug cleared "SIZE_FORMAT,
503 redirty.num_processed(), clear.num_processed()));
504
505 CountNonCleanMemRegionClosure count3(this);
506 ct_bs->mod_card_iterate(&count3);
507 if (count3.n() != orig_count) {
508 gclog_or_tty->print_cr("Should have restored them all: orig = %d, final = %d.",
509 orig_count, count3.n());
510 guarantee(count3.n() >= orig_count, "Should have restored them all.");
511 }
512 }
513
514 // Private class members.
515
516 G1CollectedHeap* G1CollectedHeap::_g1h;
517
518 // Private methods.
519
520 HeapRegion*
521 G1CollectedHeap::new_region_try_secondary_free_list(bool is_old) {
522 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
523 while (!_secondary_free_list.is_empty() || free_regions_coming()) {
524 if (!_secondary_free_list.is_empty()) {
525 if (G1ConcRegionFreeingVerbose) {
526 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
527 "secondary_free_list has %u entries",
528 _secondary_free_list.length());
529 }
530 // It looks as if there are free regions available on the
531 // secondary_free_list. Let's move them to the free_list and try
532 // again to allocate from it.
533 append_secondary_free_list();
534
535 assert(_hrm.num_free_regions() > 0, "if the secondary_free_list was not "
536 "empty we should have moved at least one entry to the free_list");
537 HeapRegion* res = _hrm.allocate_free_region(is_old);
538 if (G1ConcRegionFreeingVerbose) {
539 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
540 "allocated "HR_FORMAT" from secondary_free_list",
541 HR_FORMAT_PARAMS(res));
542 }
543 return res;
544 }
545
546 // Wait here until we get notified either when (a) there are no
547 // more free regions coming or (b) some regions have been moved on
548 // the secondary_free_list.
549 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
550 }
551
552 if (G1ConcRegionFreeingVerbose) {
553 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
554 "could not allocate from secondary_free_list");
555 }
556 return NULL;
557 }
558
559 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) {
560 assert(!isHumongous(word_size) || word_size <= HeapRegion::GrainWords,
561 "the only time we use this to allocate a humongous region is "
562 "when we are allocating a single humongous region");
563
564 HeapRegion* res;
565 if (G1StressConcRegionFreeing) {
566 if (!_secondary_free_list.is_empty()) {
567 if (G1ConcRegionFreeingVerbose) {
568 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
569 "forced to look at the secondary_free_list");
570 }
571 res = new_region_try_secondary_free_list(is_old);
572 if (res != NULL) {
573 return res;
574 }
575 }
576 }
577
578 res = _hrm.allocate_free_region(is_old);
579
580 if (res == NULL) {
581 if (G1ConcRegionFreeingVerbose) {
582 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
583 "res == NULL, trying the secondary_free_list");
584 }
585 res = new_region_try_secondary_free_list(is_old);
586 }
587 if (res == NULL && do_expand && _expand_heap_after_alloc_failure) {
588 // Currently, only attempts to allocate GC alloc regions set
589 // do_expand to true. So, we should only reach here during a
590 // safepoint. If this assumption changes we might have to
591 // reconsider the use of _expand_heap_after_alloc_failure.
592 assert(SafepointSynchronize::is_at_safepoint(), "invariant");
593
594 ergo_verbose1(ErgoHeapSizing,
595 "attempt heap expansion",
596 ergo_format_reason("region allocation request failed")
597 ergo_format_byte("allocation request"),
598 word_size * HeapWordSize);
599 if (expand(word_size * HeapWordSize)) {
600 // Given that expand() succeeded in expanding the heap, and we
601 // always expand the heap by an amount aligned to the heap
602 // region size, the free list should in theory not be empty.
603 // In either case allocate_free_region() will check for NULL.
604 res = _hrm.allocate_free_region(is_old);
605 } else {
606 _expand_heap_after_alloc_failure = false;
607 }
608 }
609 return res;
610 }
611
612 HeapWord*
613 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first,
614 uint num_regions,
615 size_t word_size) {
616 assert(first != G1_NO_HRM_INDEX, "pre-condition");
617 assert(isHumongous(word_size), "word_size should be humongous");
618 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
619
620 // Index of last region in the series + 1.
621 uint last = first + num_regions;
622
623 // We need to initialize the region(s) we just discovered. This is
624 // a bit tricky given that it can happen concurrently with
625 // refinement threads refining cards on these regions and
626 // potentially wanting to refine the BOT as they are scanning
627 // those cards (this can happen shortly after a cleanup; see CR
628 // 6991377). So we have to set up the region(s) carefully and in
629 // a specific order.
630
631 // The word size sum of all the regions we will allocate.
632 size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords;
633 assert(word_size <= word_size_sum, "sanity");
634
635 // This will be the "starts humongous" region.
636 HeapRegion* first_hr = region_at(first);
637 // The header of the new object will be placed at the bottom of
638 // the first region.
639 HeapWord* new_obj = first_hr->bottom();
640 // This will be the new end of the first region in the series that
641 // should also match the end of the last region in the series.
642 HeapWord* new_end = new_obj + word_size_sum;
643 // This will be the new top of the first region that will reflect
644 // this allocation.
645 HeapWord* new_top = new_obj + word_size;
646
647 // First, we need to zero the header of the space that we will be
648 // allocating. When we update top further down, some refinement
649 // threads might try to scan the region. By zeroing the header we
650 // ensure that any thread that will try to scan the region will
651 // come across the zero klass word and bail out.
652 //
653 // NOTE: It would not have been correct to have used
654 // CollectedHeap::fill_with_object() and make the space look like
655 // an int array. The thread that is doing the allocation will
656 // later update the object header to a potentially different array
657 // type and, for a very short period of time, the klass and length
658 // fields will be inconsistent. This could cause a refinement
659 // thread to calculate the object size incorrectly.
660 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
661
662 // We will set up the first region as "starts humongous". This
663 // will also update the BOT covering all the regions to reflect
664 // that there is a single object that starts at the bottom of the
665 // first region.
666 first_hr->set_startsHumongous(new_top, new_end);
667
668 // Then, if there are any, we will set up the "continues
669 // humongous" regions.
670 HeapRegion* hr = NULL;
671 for (uint i = first + 1; i < last; ++i) {
672 hr = region_at(i);
673 hr->set_continuesHumongous(first_hr);
674 }
675 // If we have "continues humongous" regions (hr != NULL), then the
676 // end of the last one should match new_end.
677 assert(hr == NULL || hr->end() == new_end, "sanity");
678
679 // Up to this point no concurrent thread would have been able to
680 // do any scanning on any region in this series. All the top
681 // fields still point to bottom, so the intersection between
682 // [bottom,top] and [card_start,card_end] will be empty. Before we
683 // update the top fields, we'll do a storestore to make sure that
684 // no thread sees the update to top before the zeroing of the
685 // object header and the BOT initialization.
686 OrderAccess::storestore();
687
688 // Now that the BOT and the object header have been initialized,
689 // we can update top of the "starts humongous" region.
690 assert(first_hr->bottom() < new_top && new_top <= first_hr->end(),
691 "new_top should be in this region");
692 first_hr->set_top(new_top);
693 if (_hr_printer.is_active()) {
694 HeapWord* bottom = first_hr->bottom();
695 HeapWord* end = first_hr->orig_end();
696 if ((first + 1) == last) {
697 // the series has a single humongous region
698 _hr_printer.alloc(G1HRPrinter::SingleHumongous, first_hr, new_top);
699 } else {
700 // the series has more than one humongous regions
701 _hr_printer.alloc(G1HRPrinter::StartsHumongous, first_hr, end);
702 }
703 }
704
705 // Now, we will update the top fields of the "continues humongous"
706 // regions. The reason we need to do this is that, otherwise,
707 // these regions would look empty and this will confuse parts of
708 // G1. For example, the code that looks for a consecutive number
709 // of empty regions will consider them empty and try to
710 // re-allocate them. We can extend is_empty() to also include
711 // !continuesHumongous(), but it is easier to just update the top
712 // fields here. The way we set top for all regions (i.e., top ==
713 // end for all regions but the last one, top == new_top for the
714 // last one) is actually used when we will free up the humongous
715 // region in free_humongous_region().
716 hr = NULL;
717 for (uint i = first + 1; i < last; ++i) {
718 hr = region_at(i);
719 if ((i + 1) == last) {
720 // last continues humongous region
721 assert(hr->bottom() < new_top && new_top <= hr->end(),
722 "new_top should fall on this region");
723 hr->set_top(new_top);
724 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, new_top);
725 } else {
726 // not last one
727 assert(new_top > hr->end(), "new_top should be above this region");
728 hr->set_top(hr->end());
729 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, hr->end());
730 }
731 }
732 // If we have continues humongous regions (hr != NULL), then the
733 // end of the last one should match new_end and its top should
734 // match new_top.
735 assert(hr == NULL ||
736 (hr->end() == new_end && hr->top() == new_top), "sanity");
737 check_bitmaps("Humongous Region Allocation", first_hr);
738
739 assert(first_hr->used() == word_size * HeapWordSize, "invariant");
740 _summary_bytes_used += first_hr->used();
741 _humongous_set.add(first_hr);
742
743 return new_obj;
744 }
745
746 // If could fit into free regions w/o expansion, try.
747 // Otherwise, if can expand, do so.
748 // Otherwise, if using ex regions might help, try with ex given back.
749 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size) {
750 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
751
752 verify_region_sets_optional();
753
754 uint first = G1_NO_HRM_INDEX;
755 uint obj_regions = (uint)(align_size_up_(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords);
756
757 if (obj_regions == 1) {
758 // Only one region to allocate, try to use a fast path by directly allocating
759 // from the free lists. Do not try to expand here, we will potentially do that
760 // later.
761 HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */);
762 if (hr != NULL) {
763 first = hr->hrm_index();
764 }
765 } else {
766 // We can't allocate humongous regions spanning more than one region while
767 // cleanupComplete() is running, since some of the regions we find to be
768 // empty might not yet be added to the free list. It is not straightforward
769 // to know in which list they are on so that we can remove them. We only
770 // need to do this if we need to allocate more than one region to satisfy the
771 // current humongous allocation request. If we are only allocating one region
772 // we use the one-region region allocation code (see above), that already
773 // potentially waits for regions from the secondary free list.
774 wait_while_free_regions_coming();
775 append_secondary_free_list_if_not_empty_with_lock();
776
777 // Policy: Try only empty regions (i.e. already committed first). Maybe we
778 // are lucky enough to find some.
779 first = _hrm.find_contiguous_only_empty(obj_regions);
780 if (first != G1_NO_HRM_INDEX) {
781 _hrm.allocate_free_regions_starting_at(first, obj_regions);
782 }
783 }
784
785 if (first == G1_NO_HRM_INDEX) {
786 // Policy: We could not find enough regions for the humongous object in the
787 // free list. Look through the heap to find a mix of free and uncommitted regions.
788 // If so, try expansion.
789 first = _hrm.find_contiguous_empty_or_unavailable(obj_regions);
790 if (first != G1_NO_HRM_INDEX) {
791 // We found something. Make sure these regions are committed, i.e. expand
792 // the heap. Alternatively we could do a defragmentation GC.
793 ergo_verbose1(ErgoHeapSizing,
794 "attempt heap expansion",
795 ergo_format_reason("humongous allocation request failed")
796 ergo_format_byte("allocation request"),
797 word_size * HeapWordSize);
798
799 _hrm.expand_at(first, obj_regions);
800 g1_policy()->record_new_heap_size(num_regions());
801
802 #ifdef ASSERT
803 for (uint i = first; i < first + obj_regions; ++i) {
804 HeapRegion* hr = region_at(i);
805 assert(hr->is_empty(), "sanity");
806 assert(is_on_master_free_list(hr), "sanity");
807 }
808 #endif
809 _hrm.allocate_free_regions_starting_at(first, obj_regions);
810 } else {
811 // Policy: Potentially trigger a defragmentation GC.
812 }
813 }
814
815 HeapWord* result = NULL;
816 if (first != G1_NO_HRM_INDEX) {
817 result = humongous_obj_allocate_initialize_regions(first, obj_regions, word_size);
818 assert(result != NULL, "it should always return a valid result");
819
820 // A successful humongous object allocation changes the used space
821 // information of the old generation so we need to recalculate the
822 // sizes and update the jstat counters here.
823 g1mm()->update_sizes();
824 }
825
826 verify_region_sets_optional();
827
828 return result;
829 }
830
831 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) {
832 assert_heap_not_locked_and_not_at_safepoint();
833 assert(!isHumongous(word_size), "we do not allow humongous TLABs");
834
835 unsigned int dummy_gc_count_before;
836 int dummy_gclocker_retry_count = 0;
837 return attempt_allocation(word_size, &dummy_gc_count_before, &dummy_gclocker_retry_count);
838 }
839
840 HeapWord*
841 G1CollectedHeap::mem_allocate(size_t word_size,
842 bool* gc_overhead_limit_was_exceeded) {
843 assert_heap_not_locked_and_not_at_safepoint();
844
845 // Loop until the allocation is satisfied, or unsatisfied after GC.
846 for (int try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
847 unsigned int gc_count_before;
848
849 HeapWord* result = NULL;
850 if (!isHumongous(word_size)) {
851 result = attempt_allocation(word_size, &gc_count_before, &gclocker_retry_count);
852 } else {
853 result = attempt_allocation_humongous(word_size, &gc_count_before, &gclocker_retry_count);
854 }
855 if (result != NULL) {
856 return result;
857 }
858
859 // Create the garbage collection operation...
860 VM_G1CollectForAllocation op(gc_count_before, word_size);
861 // ...and get the VM thread to execute it.
862 VMThread::execute(&op);
863
864 if (op.prologue_succeeded() && op.pause_succeeded()) {
865 // If the operation was successful we'll return the result even
866 // if it is NULL. If the allocation attempt failed immediately
867 // after a Full GC, it's unlikely we'll be able to allocate now.
868 HeapWord* result = op.result();
869 if (result != NULL && !isHumongous(word_size)) {
870 // Allocations that take place on VM operations do not do any
871 // card dirtying and we have to do it here. We only have to do
872 // this for non-humongous allocations, though.
873 dirty_young_block(result, word_size);
874 }
875 return result;
876 } else {
877 if (gclocker_retry_count > GCLockerRetryAllocationCount) {
878 return NULL;
879 }
880 assert(op.result() == NULL,
881 "the result should be NULL if the VM op did not succeed");
882 }
883
884 // Give a warning if we seem to be looping forever.
885 if ((QueuedAllocationWarningCount > 0) &&
886 (try_count % QueuedAllocationWarningCount == 0)) {
887 warning("G1CollectedHeap::mem_allocate retries %d times", try_count);
888 }
889 }
890
891 ShouldNotReachHere();
892 return NULL;
893 }
894
895 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size,
896 unsigned int *gc_count_before_ret,
897 int* gclocker_retry_count_ret) {
898 // Make sure you read the note in attempt_allocation_humongous().
899
900 assert_heap_not_locked_and_not_at_safepoint();
901 assert(!isHumongous(word_size), "attempt_allocation_slow() should not "
902 "be called for humongous allocation requests");
903
904 // We should only get here after the first-level allocation attempt
905 // (attempt_allocation()) failed to allocate.
906
907 // We will loop until a) we manage to successfully perform the
908 // allocation or b) we successfully schedule a collection which
909 // fails to perform the allocation. b) is the only case when we'll
910 // return NULL.
911 HeapWord* result = NULL;
912 for (int try_count = 1; /* we'll return */; try_count += 1) {
913 bool should_try_gc;
914 unsigned int gc_count_before;
915
916 {
917 MutexLockerEx x(Heap_lock);
918
919 result = _mutator_alloc_region.attempt_allocation_locked(word_size,
920 false /* bot_updates */);
921 if (result != NULL) {
922 return result;
923 }
924
925 // If we reach here, attempt_allocation_locked() above failed to
926 // allocate a new region. So the mutator alloc region should be NULL.
927 assert(_mutator_alloc_region.get() == NULL, "only way to get here");
928
929 if (GC_locker::is_active_and_needs_gc()) {
930 if (g1_policy()->can_expand_young_list()) {
931 // No need for an ergo verbose message here,
932 // can_expand_young_list() does this when it returns true.
933 result = _mutator_alloc_region.attempt_allocation_force(word_size,
934 false /* bot_updates */);
935 if (result != NULL) {
936 return result;
937 }
938 }
939 should_try_gc = false;
940 } else {
941 // The GCLocker may not be active but the GCLocker initiated
942 // GC may not yet have been performed (GCLocker::needs_gc()
943 // returns true). In this case we do not try this GC and
944 // wait until the GCLocker initiated GC is performed, and
945 // then retry the allocation.
946 if (GC_locker::needs_gc()) {
947 should_try_gc = false;
948 } else {
949 // Read the GC count while still holding the Heap_lock.
950 gc_count_before = total_collections();
951 should_try_gc = true;
952 }
953 }
954 }
955
956 if (should_try_gc) {
957 bool succeeded;
958 result = do_collection_pause(word_size, gc_count_before, &succeeded,
959 GCCause::_g1_inc_collection_pause);
960 if (result != NULL) {
961 assert(succeeded, "only way to get back a non-NULL result");
962 return result;
963 }
964
965 if (succeeded) {
966 // If we get here we successfully scheduled a collection which
967 // failed to allocate. No point in trying to allocate
968 // further. We'll just return NULL.
969 MutexLockerEx x(Heap_lock);
970 *gc_count_before_ret = total_collections();
971 return NULL;
972 }
973 } else {
974 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
975 MutexLockerEx x(Heap_lock);
976 *gc_count_before_ret = total_collections();
977 return NULL;
978 }
979 // The GCLocker is either active or the GCLocker initiated
980 // GC has not yet been performed. Stall until it is and
981 // then retry the allocation.
982 GC_locker::stall_until_clear();
983 (*gclocker_retry_count_ret) += 1;
984 }
985
986 // We can reach here if we were unsuccessful in scheduling a
987 // collection (because another thread beat us to it) or if we were
988 // stalled due to the GC locker. In either can we should retry the
989 // allocation attempt in case another thread successfully
990 // performed a collection and reclaimed enough space. We do the
991 // first attempt (without holding the Heap_lock) here and the
992 // follow-on attempt will be at the start of the next loop
993 // iteration (after taking the Heap_lock).
994 result = _mutator_alloc_region.attempt_allocation(word_size,
995 false /* bot_updates */);
996 if (result != NULL) {
997 return result;
998 }
999
1000 // Give a warning if we seem to be looping forever.
1001 if ((QueuedAllocationWarningCount > 0) &&
1002 (try_count % QueuedAllocationWarningCount == 0)) {
1003 warning("G1CollectedHeap::attempt_allocation_slow() "
1004 "retries %d times", try_count);
1005 }
1006 }
1007
1008 ShouldNotReachHere();
1009 return NULL;
1010 }
1011
1012 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size,
1013 unsigned int * gc_count_before_ret,
1014 int* gclocker_retry_count_ret) {
1015 // The structure of this method has a lot of similarities to
1016 // attempt_allocation_slow(). The reason these two were not merged
1017 // into a single one is that such a method would require several "if
1018 // allocation is not humongous do this, otherwise do that"
1019 // conditional paths which would obscure its flow. In fact, an early
1020 // version of this code did use a unified method which was harder to
1021 // follow and, as a result, it had subtle bugs that were hard to
1022 // track down. So keeping these two methods separate allows each to
1023 // be more readable. It will be good to keep these two in sync as
1024 // much as possible.
1025
1026 assert_heap_not_locked_and_not_at_safepoint();
1027 assert(isHumongous(word_size), "attempt_allocation_humongous() "
1028 "should only be called for humongous allocations");
1029
1030 // Humongous objects can exhaust the heap quickly, so we should check if we
1031 // need to start a marking cycle at each humongous object allocation. We do
1032 // the check before we do the actual allocation. The reason for doing it
1033 // before the allocation is that we avoid having to keep track of the newly
1034 // allocated memory while we do a GC.
1035 if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation",
1036 word_size)) {
1037 collect(GCCause::_g1_humongous_allocation);
1038 }
1039
1040 // We will loop until a) we manage to successfully perform the
1041 // allocation or b) we successfully schedule a collection which
1042 // fails to perform the allocation. b) is the only case when we'll
1043 // return NULL.
1044 HeapWord* result = NULL;
1045 for (int try_count = 1; /* we'll return */; try_count += 1) {
1046 bool should_try_gc;
1047 unsigned int gc_count_before;
1048
1049 {
1050 MutexLockerEx x(Heap_lock);
1051
1052 // Given that humongous objects are not allocated in young
1053 // regions, we'll first try to do the allocation without doing a
1054 // collection hoping that there's enough space in the heap.
1055 result = humongous_obj_allocate(word_size);
1056 if (result != NULL) {
1057 return result;
1058 }
1059
1060 if (GC_locker::is_active_and_needs_gc()) {
1061 should_try_gc = false;
1062 } else {
1063 // The GCLocker may not be active but the GCLocker initiated
1064 // GC may not yet have been performed (GCLocker::needs_gc()
1065 // returns true). In this case we do not try this GC and
1066 // wait until the GCLocker initiated GC is performed, and
1067 // then retry the allocation.
1068 if (GC_locker::needs_gc()) {
1069 should_try_gc = false;
1070 } else {
1071 // Read the GC count while still holding the Heap_lock.
1072 gc_count_before = total_collections();
1073 should_try_gc = true;
1074 }
1075 }
1076 }
1077
1078 if (should_try_gc) {
1079 // If we failed to allocate the humongous object, we should try to
1080 // do a collection pause (if we're allowed) in case it reclaims
1081 // enough space for the allocation to succeed after the pause.
1082
1083 bool succeeded;
1084 result = do_collection_pause(word_size, gc_count_before, &succeeded,
1085 GCCause::_g1_humongous_allocation);
1086 if (result != NULL) {
1087 assert(succeeded, "only way to get back a non-NULL result");
1088 return result;
1089 }
1090
1091 if (succeeded) {
1092 // If we get here we successfully scheduled a collection which
1093 // failed to allocate. No point in trying to allocate
1094 // further. We'll just return NULL.
1095 MutexLockerEx x(Heap_lock);
1096 *gc_count_before_ret = total_collections();
1097 return NULL;
1098 }
1099 } else {
1100 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
1101 MutexLockerEx x(Heap_lock);
1102 *gc_count_before_ret = total_collections();
1103 return NULL;
1104 }
1105 // The GCLocker is either active or the GCLocker initiated
1106 // GC has not yet been performed. Stall until it is and
1107 // then retry the allocation.
1108 GC_locker::stall_until_clear();
1109 (*gclocker_retry_count_ret) += 1;
1110 }
1111
1112 // We can reach here if we were unsuccessful in scheduling a
1113 // collection (because another thread beat us to it) or if we were
1114 // stalled due to the GC locker. In either can we should retry the
1115 // allocation attempt in case another thread successfully
1116 // performed a collection and reclaimed enough space. Give a
1117 // warning if we seem to be looping forever.
1118
1119 if ((QueuedAllocationWarningCount > 0) &&
1120 (try_count % QueuedAllocationWarningCount == 0)) {
1121 warning("G1CollectedHeap::attempt_allocation_humongous() "
1122 "retries %d times", try_count);
1123 }
1124 }
1125
1126 ShouldNotReachHere();
1127 return NULL;
1128 }
1129
1130 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
1131 bool expect_null_mutator_alloc_region) {
1132 assert_at_safepoint(true /* should_be_vm_thread */);
1133 assert(_mutator_alloc_region.get() == NULL ||
1134 !expect_null_mutator_alloc_region,
1135 "the current alloc region was unexpectedly found to be non-NULL");
1136
1137 if (!isHumongous(word_size)) {
1138 return _mutator_alloc_region.attempt_allocation_locked(word_size,
1139 false /* bot_updates */);
1140 } else {
1141 HeapWord* result = humongous_obj_allocate(word_size);
1142 if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) {
1143 g1_policy()->set_initiate_conc_mark_if_possible();
1144 }
1145 return result;
1146 }
1147
1148 ShouldNotReachHere();
1149 }
1150
1151 class PostMCRemSetClearClosure: public HeapRegionClosure {
1152 G1CollectedHeap* _g1h;
1153 ModRefBarrierSet* _mr_bs;
1154 public:
1155 PostMCRemSetClearClosure(G1CollectedHeap* g1h, ModRefBarrierSet* mr_bs) :
1156 _g1h(g1h), _mr_bs(mr_bs) {}
1157
1158 bool doHeapRegion(HeapRegion* r) {
1159 HeapRegionRemSet* hrrs = r->rem_set();
1160
1161 if (r->continuesHumongous()) {
1162 // We'll assert that the strong code root list and RSet is empty
1163 assert(hrrs->strong_code_roots_list_length() == 0, "sanity");
1164 assert(hrrs->occupied() == 0, "RSet should be empty");
1165 return false;
1166 }
1167
1168 _g1h->reset_gc_time_stamps(r);
1169 hrrs->clear();
1170 // You might think here that we could clear just the cards
1171 // corresponding to the used region. But no: if we leave a dirty card
1172 // in a region we might allocate into, then it would prevent that card
1173 // from being enqueued, and cause it to be missed.
1174 // Re: the performance cost: we shouldn't be doing full GC anyway!
1175 _mr_bs->clear(MemRegion(r->bottom(), r->end()));
1176
1177 return false;
1178 }
1179 };
1180
1181 void G1CollectedHeap::clear_rsets_post_compaction() {
1182 PostMCRemSetClearClosure rs_clear(this, g1_barrier_set());
1183 heap_region_iterate(&rs_clear);
1184 }
1185
1186 class RebuildRSOutOfRegionClosure: public HeapRegionClosure {
1187 G1CollectedHeap* _g1h;
1188 UpdateRSOopClosure _cl;
1189 int _worker_i;
1190 public:
1191 RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, int worker_i = 0) :
1192 _cl(g1->g1_rem_set(), worker_i),
1193 _worker_i(worker_i),
1194 _g1h(g1)
1195 { }
1196
1197 bool doHeapRegion(HeapRegion* r) {
1198 if (!r->continuesHumongous()) {
1199 _cl.set_from(r);
1200 r->oop_iterate(&_cl);
1201 }
1202 return false;
1203 }
1204 };
1205
1206 class ParRebuildRSTask: public AbstractGangTask {
1207 G1CollectedHeap* _g1;
1208 HeapRegionClaimer _hrclaimer;
1209
1210 public:
1211 ParRebuildRSTask(G1CollectedHeap* g1) :
1212 AbstractGangTask("ParRebuildRSTask"), _g1(g1), _hrclaimer(g1->workers()->active_workers()) {}
1213
1214 void work(uint worker_id) {
1215 RebuildRSOutOfRegionClosure rebuild_rs(_g1, worker_id);
1216 _g1->heap_region_par_iterate(&rebuild_rs, worker_id, &_hrclaimer);
1217 }
1218 };
1219
1220 class PostCompactionPrinterClosure: public HeapRegionClosure {
1221 private:
1222 G1HRPrinter* _hr_printer;
1223 public:
1224 bool doHeapRegion(HeapRegion* hr) {
1225 assert(!hr->is_young(), "not expecting to find young regions");
1226 // We only generate output for non-empty regions.
1227 if (!hr->is_empty()) {
1228 if (!hr->isHumongous()) {
1229 _hr_printer->post_compaction(hr, G1HRPrinter::Old);
1230 } else if (hr->startsHumongous()) {
1231 if (hr->region_num() == 1) {
1232 // single humongous region
1233 _hr_printer->post_compaction(hr, G1HRPrinter::SingleHumongous);
1234 } else {
1235 _hr_printer->post_compaction(hr, G1HRPrinter::StartsHumongous);
1236 }
1237 } else {
1238 assert(hr->continuesHumongous(), "only way to get here");
1239 _hr_printer->post_compaction(hr, G1HRPrinter::ContinuesHumongous);
1240 }
1241 }
1242 return false;
1243 }
1244
1245 PostCompactionPrinterClosure(G1HRPrinter* hr_printer)
1246 : _hr_printer(hr_printer) { }
1247 };
1248
1249 void G1CollectedHeap::print_hrm_post_compaction() {
1250 PostCompactionPrinterClosure cl(hr_printer());
1251 heap_region_iterate(&cl);
1252 }
1253
1254 bool G1CollectedHeap::do_collection(bool explicit_gc,
1255 bool clear_all_soft_refs,
1256 size_t word_size) {
1257 assert_at_safepoint(true /* should_be_vm_thread */);
1258
1259 if (GC_locker::check_active_before_gc()) {
1260 return false;
1261 }
1262
1263 STWGCTimer* gc_timer = G1MarkSweep::gc_timer();
1264 gc_timer->register_gc_start();
1265
1266 SerialOldTracer* gc_tracer = G1MarkSweep::gc_tracer();
1267 gc_tracer->report_gc_start(gc_cause(), gc_timer->gc_start());
1268
1269 SvcGCMarker sgcm(SvcGCMarker::FULL);
1270 ResourceMark rm;
1271
1272 print_heap_before_gc();
1273 trace_heap_before_gc(gc_tracer);
1274
1275 size_t metadata_prev_used = MetaspaceAux::used_bytes();
1276
1277 verify_region_sets_optional();
1278
1279 const bool do_clear_all_soft_refs = clear_all_soft_refs ||
1280 collector_policy()->should_clear_all_soft_refs();
1281
1282 ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy());
1283
1284 {
1285 IsGCActiveMark x;
1286
1287 // Timing
1288 assert(gc_cause() != GCCause::_java_lang_system_gc || explicit_gc, "invariant");
1289 gclog_or_tty->date_stamp(G1Log::fine() && PrintGCDateStamps);
1290 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
1291
1292 {
1293 GCTraceTime t(GCCauseString("Full GC", gc_cause()), G1Log::fine(), true, NULL, gc_tracer->gc_id());
1294 TraceCollectorStats tcs(g1mm()->full_collection_counters());
1295 TraceMemoryManagerStats tms(true /* fullGC */, gc_cause());
1296
1297 double start = os::elapsedTime();
1298 g1_policy()->record_full_collection_start();
1299
1300 // Note: When we have a more flexible GC logging framework that
1301 // allows us to add optional attributes to a GC log record we
1302 // could consider timing and reporting how long we wait in the
1303 // following two methods.
1304 wait_while_free_regions_coming();
1305 // If we start the compaction before the CM threads finish
1306 // scanning the root regions we might trip them over as we'll
1307 // be moving objects / updating references. So let's wait until
1308 // they are done. By telling them to abort, they should complete
1309 // early.
1310 _cm->root_regions()->abort();
1311 _cm->root_regions()->wait_until_scan_finished();
1312 append_secondary_free_list_if_not_empty_with_lock();
1313
1314 gc_prologue(true);
1315 increment_total_collections(true /* full gc */);
1316 increment_old_marking_cycles_started();
1317
1318 assert(used() == recalculate_used(), "Should be equal");
1319
1320 verify_before_gc();
1321
1322 check_bitmaps("Full GC Start");
1323 pre_full_gc_dump(gc_timer);
1324
1325 COMPILER2_PRESENT(DerivedPointerTable::clear());
1326
1327 // Disable discovery and empty the discovered lists
1328 // for the CM ref processor.
1329 ref_processor_cm()->disable_discovery();
1330 ref_processor_cm()->abandon_partial_discovery();
1331 ref_processor_cm()->verify_no_references_recorded();
1332
1333 // Abandon current iterations of concurrent marking and concurrent
1334 // refinement, if any are in progress. We have to do this before
1335 // wait_until_scan_finished() below.
1336 concurrent_mark()->abort();
1337
1338 // Make sure we'll choose a new allocation region afterwards.
1339 release_mutator_alloc_region();
1340 abandon_gc_alloc_regions();
1341 g1_rem_set()->cleanupHRRS();
1342
1343 // We should call this after we retire any currently active alloc
1344 // regions so that all the ALLOC / RETIRE events are generated
1345 // before the start GC event.
1346 _hr_printer.start_gc(true /* full */, (size_t) total_collections());
1347
1348 // We may have added regions to the current incremental collection
1349 // set between the last GC or pause and now. We need to clear the
1350 // incremental collection set and then start rebuilding it afresh
1351 // after this full GC.
1352 abandon_collection_set(g1_policy()->inc_cset_head());
1353 g1_policy()->clear_incremental_cset();
1354 g1_policy()->stop_incremental_cset_building();
1355
1356 tear_down_region_sets(false /* free_list_only */);
1357 g1_policy()->set_gcs_are_young(true);
1358
1359 // See the comments in g1CollectedHeap.hpp and
1360 // G1CollectedHeap::ref_processing_init() about
1361 // how reference processing currently works in G1.
1362
1363 // Temporarily make discovery by the STW ref processor single threaded (non-MT).
1364 ReferenceProcessorMTDiscoveryMutator stw_rp_disc_ser(ref_processor_stw(), false);
1365
1366 // Temporarily clear the STW ref processor's _is_alive_non_header field.
1367 ReferenceProcessorIsAliveMutator stw_rp_is_alive_null(ref_processor_stw(), NULL);
1368
1369 ref_processor_stw()->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/);
1370 ref_processor_stw()->setup_policy(do_clear_all_soft_refs);
1371
1372 // Do collection work
1373 {
1374 HandleMark hm; // Discard invalid handles created during gc
1375 G1MarkSweep::invoke_at_safepoint(ref_processor_stw(), do_clear_all_soft_refs);
1376 }
1377
1378 assert(num_free_regions() == 0, "we should not have added any free regions");
1379 rebuild_region_sets(false /* free_list_only */);
1380
1381 // Enqueue any discovered reference objects that have
1382 // not been removed from the discovered lists.
1383 ref_processor_stw()->enqueue_discovered_references();
1384
1385 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
1386
1387 MemoryService::track_memory_usage();
1388
1389 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
1390 ref_processor_stw()->verify_no_references_recorded();
1391
1392 // Delete metaspaces for unloaded class loaders and clean up loader_data graph
1393 ClassLoaderDataGraph::purge();
1394 MetaspaceAux::verify_metrics();
1395
1396 // Note: since we've just done a full GC, concurrent
1397 // marking is no longer active. Therefore we need not
1398 // re-enable reference discovery for the CM ref processor.
1399 // That will be done at the start of the next marking cycle.
1400 assert(!ref_processor_cm()->discovery_enabled(), "Postcondition");
1401 ref_processor_cm()->verify_no_references_recorded();
1402
1403 reset_gc_time_stamp();
1404 // Since everything potentially moved, we will clear all remembered
1405 // sets, and clear all cards. Later we will rebuild remembered
1406 // sets. We will also reset the GC time stamps of the regions.
1407 clear_rsets_post_compaction();
1408 check_gc_time_stamps();
1409
1410 // Resize the heap if necessary.
1411 resize_if_necessary_after_full_collection(explicit_gc ? 0 : word_size);
1412
1413 if (_hr_printer.is_active()) {
1414 // We should do this after we potentially resize the heap so
1415 // that all the COMMIT / UNCOMMIT events are generated before
1416 // the end GC event.
1417
1418 print_hrm_post_compaction();
1419 _hr_printer.end_gc(true /* full */, (size_t) total_collections());
1420 }
1421
1422 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
1423 if (hot_card_cache->use_cache()) {
1424 hot_card_cache->reset_card_counts();
1425 hot_card_cache->reset_hot_cache();
1426 }
1427
1428 // Rebuild remembered sets of all regions.
1429 if (G1CollectedHeap::use_parallel_gc_threads()) {
1430 uint n_workers =
1431 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
1432 workers()->active_workers(),
1433 Threads::number_of_non_daemon_threads());
1434 assert(UseDynamicNumberOfGCThreads ||
1435 n_workers == workers()->total_workers(),
1436 "If not dynamic should be using all the workers");
1437 workers()->set_active_workers(n_workers);
1438 // Set parallel threads in the heap (_n_par_threads) only
1439 // before a parallel phase and always reset it to 0 after
1440 // the phase so that the number of parallel threads does
1441 // no get carried forward to a serial phase where there
1442 // may be code that is "possibly_parallel".
1443 set_par_threads(n_workers);
1444
1445 ParRebuildRSTask rebuild_rs_task(this);
1446 assert(UseDynamicNumberOfGCThreads ||
1447 workers()->active_workers() == workers()->total_workers(),
1448 "Unless dynamic should use total workers");
1449 // Use the most recent number of active workers
1450 assert(workers()->active_workers() > 0,
1451 "Active workers not properly set");
1452 set_par_threads(workers()->active_workers());
1453 workers()->run_task(&rebuild_rs_task);
1454 set_par_threads(0);
1455 } else {
1456 RebuildRSOutOfRegionClosure rebuild_rs(this);
1457 heap_region_iterate(&rebuild_rs);
1458 }
1459
1460 // Rebuild the strong code root lists for each region
1461 rebuild_strong_code_roots();
1462
1463 if (true) { // FIXME
1464 MetaspaceGC::compute_new_size();
1465 }
1466
1467 #ifdef TRACESPINNING
1468 ParallelTaskTerminator::print_termination_counts();
1469 #endif
1470
1471 // Discard all rset updates
1472 JavaThread::dirty_card_queue_set().abandon_logs();
1473 assert(!G1DeferredRSUpdate
1474 || (G1DeferredRSUpdate &&
1475 (dirty_card_queue_set().completed_buffers_num() == 0)), "Should not be any");
1476
1477 _young_list->reset_sampled_info();
1478 // At this point there should be no regions in the
1479 // entire heap tagged as young.
1480 assert(check_young_list_empty(true /* check_heap */),
1481 "young list should be empty at this point");
1482
1483 // Update the number of full collections that have been completed.
1484 increment_old_marking_cycles_completed(false /* concurrent */);
1485
1486 _hrm.verify_optional();
1487 verify_region_sets_optional();
1488
1489 verify_after_gc();
1490
1491 // Clear the previous marking bitmap, if needed for bitmap verification.
1492 // Note we cannot do this when we clear the next marking bitmap in
1493 // ConcurrentMark::abort() above since VerifyDuringGC verifies the
1494 // objects marked during a full GC against the previous bitmap.
1495 // But we need to clear it before calling check_bitmaps below since
1496 // the full GC has compacted objects and updated TAMS but not updated
1497 // the prev bitmap.
1498 if (G1VerifyBitmaps) {
1499 ((CMBitMap*) concurrent_mark()->prevMarkBitMap())->clearAll();
1500 }
1501 check_bitmaps("Full GC End");
1502
1503 // Start a new incremental collection set for the next pause
1504 assert(g1_policy()->collection_set() == NULL, "must be");
1505 g1_policy()->start_incremental_cset_building();
1506
1507 clear_cset_fast_test();
1508
1509 init_mutator_alloc_region();
1510
1511 double end = os::elapsedTime();
1512 g1_policy()->record_full_collection_end();
1513
1514 if (G1Log::fine()) {
1515 g1_policy()->print_heap_transition();
1516 }
1517
1518 // We must call G1MonitoringSupport::update_sizes() in the same scoping level
1519 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
1520 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
1521 // before any GC notifications are raised.
1522 g1mm()->update_sizes();
1523
1524 gc_epilogue(true);
1525 }
1526
1527 if (G1Log::finer()) {
1528 g1_policy()->print_detailed_heap_transition(true /* full */);
1529 }
1530
1531 print_heap_after_gc();
1532 trace_heap_after_gc(gc_tracer);
1533
1534 post_full_gc_dump(gc_timer);
1535
1536 gc_timer->register_gc_end();
1537 gc_tracer->report_gc_end(gc_timer->gc_end(), gc_timer->time_partitions());
1538 }
1539
1540 return true;
1541 }
1542
1543 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
1544 // do_collection() will return whether it succeeded in performing
1545 // the GC. Currently, there is no facility on the
1546 // do_full_collection() API to notify the caller than the collection
1547 // did not succeed (e.g., because it was locked out by the GC
1548 // locker). So, right now, we'll ignore the return value.
1549 bool dummy = do_collection(true, /* explicit_gc */
1550 clear_all_soft_refs,
1551 0 /* word_size */);
1552 }
1553
1554 // This code is mostly copied from TenuredGeneration.
1555 void
1556 G1CollectedHeap::
1557 resize_if_necessary_after_full_collection(size_t word_size) {
1558 // Include the current allocation, if any, and bytes that will be
1559 // pre-allocated to support collections, as "used".
1560 const size_t used_after_gc = used();
1561 const size_t capacity_after_gc = capacity();
1562 const size_t free_after_gc = capacity_after_gc - used_after_gc;
1563
1564 // This is enforced in arguments.cpp.
1565 assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
1566 "otherwise the code below doesn't make sense");
1567
1568 // We don't have floating point command-line arguments
1569 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
1570 const double maximum_used_percentage = 1.0 - minimum_free_percentage;
1571 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
1572 const double minimum_used_percentage = 1.0 - maximum_free_percentage;
1573
1574 const size_t min_heap_size = collector_policy()->min_heap_byte_size();
1575 const size_t max_heap_size = collector_policy()->max_heap_byte_size();
1576
1577 // We have to be careful here as these two calculations can overflow
1578 // 32-bit size_t's.
1579 double used_after_gc_d = (double) used_after_gc;
1580 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
1581 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
1582
1583 // Let's make sure that they are both under the max heap size, which
1584 // by default will make them fit into a size_t.
1585 double desired_capacity_upper_bound = (double) max_heap_size;
1586 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
1587 desired_capacity_upper_bound);
1588 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
1589 desired_capacity_upper_bound);
1590
1591 // We can now safely turn them into size_t's.
1592 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
1593 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
1594
1595 // This assert only makes sense here, before we adjust them
1596 // with respect to the min and max heap size.
1597 assert(minimum_desired_capacity <= maximum_desired_capacity,
1598 err_msg("minimum_desired_capacity = "SIZE_FORMAT", "
1599 "maximum_desired_capacity = "SIZE_FORMAT,
1600 minimum_desired_capacity, maximum_desired_capacity));
1601
1602 // Should not be greater than the heap max size. No need to adjust
1603 // it with respect to the heap min size as it's a lower bound (i.e.,
1604 // we'll try to make the capacity larger than it, not smaller).
1605 minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size);
1606 // Should not be less than the heap min size. No need to adjust it
1607 // with respect to the heap max size as it's an upper bound (i.e.,
1608 // we'll try to make the capacity smaller than it, not greater).
1609 maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size);
1610
1611 if (capacity_after_gc < minimum_desired_capacity) {
1612 // Don't expand unless it's significant
1613 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
1614 ergo_verbose4(ErgoHeapSizing,
1615 "attempt heap expansion",
1616 ergo_format_reason("capacity lower than "
1617 "min desired capacity after Full GC")
1618 ergo_format_byte("capacity")
1619 ergo_format_byte("occupancy")
1620 ergo_format_byte_perc("min desired capacity"),
1621 capacity_after_gc, used_after_gc,
1622 minimum_desired_capacity, (double) MinHeapFreeRatio);
1623 expand(expand_bytes);
1624
1625 // No expansion, now see if we want to shrink
1626 } else if (capacity_after_gc > maximum_desired_capacity) {
1627 // Capacity too large, compute shrinking size
1628 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
1629 ergo_verbose4(ErgoHeapSizing,
1630 "attempt heap shrinking",
1631 ergo_format_reason("capacity higher than "
1632 "max desired capacity after Full GC")
1633 ergo_format_byte("capacity")
1634 ergo_format_byte("occupancy")
1635 ergo_format_byte_perc("max desired capacity"),
1636 capacity_after_gc, used_after_gc,
1637 maximum_desired_capacity, (double) MaxHeapFreeRatio);
1638 shrink(shrink_bytes);
1639 }
1640 }
1641
1642
1643 HeapWord*
1644 G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
1645 bool* succeeded) {
1646 assert_at_safepoint(true /* should_be_vm_thread */);
1647
1648 *succeeded = true;
1649 // Let's attempt the allocation first.
1650 HeapWord* result =
1651 attempt_allocation_at_safepoint(word_size,
1652 false /* expect_null_mutator_alloc_region */);
1653 if (result != NULL) {
1654 assert(*succeeded, "sanity");
1655 return result;
1656 }
1657
1658 // In a G1 heap, we're supposed to keep allocation from failing by
1659 // incremental pauses. Therefore, at least for now, we'll favor
1660 // expansion over collection. (This might change in the future if we can
1661 // do something smarter than full collection to satisfy a failed alloc.)
1662 result = expand_and_allocate(word_size);
1663 if (result != NULL) {
1664 assert(*succeeded, "sanity");
1665 return result;
1666 }
1667
1668 // Expansion didn't work, we'll try to do a Full GC.
1669 bool gc_succeeded = do_collection(false, /* explicit_gc */
1670 false, /* clear_all_soft_refs */
1671 word_size);
1672 if (!gc_succeeded) {
1673 *succeeded = false;
1674 return NULL;
1675 }
1676
1677 // Retry the allocation
1678 result = attempt_allocation_at_safepoint(word_size,
1679 true /* expect_null_mutator_alloc_region */);
1680 if (result != NULL) {
1681 assert(*succeeded, "sanity");
1682 return result;
1683 }
1684
1685 // Then, try a Full GC that will collect all soft references.
1686 gc_succeeded = do_collection(false, /* explicit_gc */
1687 true, /* clear_all_soft_refs */
1688 word_size);
1689 if (!gc_succeeded) {
1690 *succeeded = false;
1691 return NULL;
1692 }
1693
1694 // Retry the allocation once more
1695 result = attempt_allocation_at_safepoint(word_size,
1696 true /* expect_null_mutator_alloc_region */);
1697 if (result != NULL) {
1698 assert(*succeeded, "sanity");
1699 return result;
1700 }
1701
1702 assert(!collector_policy()->should_clear_all_soft_refs(),
1703 "Flag should have been handled and cleared prior to this point");
1704
1705 // What else? We might try synchronous finalization later. If the total
1706 // space available is large enough for the allocation, then a more
1707 // complete compaction phase than we've tried so far might be
1708 // appropriate.
1709 assert(*succeeded, "sanity");
1710 return NULL;
1711 }
1712
1713 // Attempting to expand the heap sufficiently
1714 // to support an allocation of the given "word_size". If
1715 // successful, perform the allocation and return the address of the
1716 // allocated block, or else "NULL".
1717
1718 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size) {
1719 assert_at_safepoint(true /* should_be_vm_thread */);
1720
1721 verify_region_sets_optional();
1722
1723 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
1724 ergo_verbose1(ErgoHeapSizing,
1725 "attempt heap expansion",
1726 ergo_format_reason("allocation request failed")
1727 ergo_format_byte("allocation request"),
1728 word_size * HeapWordSize);
1729 if (expand(expand_bytes)) {
1730 _hrm.verify_optional();
1731 verify_region_sets_optional();
1732 return attempt_allocation_at_safepoint(word_size,
1733 false /* expect_null_mutator_alloc_region */);
1734 }
1735 return NULL;
1736 }
1737
1738 bool G1CollectedHeap::expand(size_t expand_bytes) {
1739 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
1740 aligned_expand_bytes = align_size_up(aligned_expand_bytes,
1741 HeapRegion::GrainBytes);
1742 ergo_verbose2(ErgoHeapSizing,
1743 "expand the heap",
1744 ergo_format_byte("requested expansion amount")
1745 ergo_format_byte("attempted expansion amount"),
1746 expand_bytes, aligned_expand_bytes);
1747
1748 if (is_maximal_no_gc()) {
1749 ergo_verbose0(ErgoHeapSizing,
1750 "did not expand the heap",
1751 ergo_format_reason("heap already fully expanded"));
1752 return false;
1753 }
1754
1755 uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes);
1756 assert(regions_to_expand > 0, "Must expand by at least one region");
1757
1758 uint expanded_by = _hrm.expand_by(regions_to_expand);
1759
1760 if (expanded_by > 0) {
1761 size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes;
1762 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
1763 g1_policy()->record_new_heap_size(num_regions());
1764 } else {
1765 ergo_verbose0(ErgoHeapSizing,
1766 "did not expand the heap",
1767 ergo_format_reason("heap expansion operation failed"));
1768 // The expansion of the virtual storage space was unsuccessful.
1769 // Let's see if it was because we ran out of swap.
1770 if (G1ExitOnExpansionFailure &&
1771 _hrm.available() >= regions_to_expand) {
1772 // We had head room...
1773 vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion");
1774 }
1775 }
1776 return regions_to_expand > 0;
1777 }
1778
1779 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
1780 size_t aligned_shrink_bytes =
1781 ReservedSpace::page_align_size_down(shrink_bytes);
1782 aligned_shrink_bytes = align_size_down(aligned_shrink_bytes,
1783 HeapRegion::GrainBytes);
1784 uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes);
1785
1786 uint num_regions_removed = _hrm.shrink_by(num_regions_to_remove);
1787 size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes;
1788
1789 ergo_verbose3(ErgoHeapSizing,
1790 "shrink the heap",
1791 ergo_format_byte("requested shrinking amount")
1792 ergo_format_byte("aligned shrinking amount")
1793 ergo_format_byte("attempted shrinking amount"),
1794 shrink_bytes, aligned_shrink_bytes, shrunk_bytes);
1795 if (num_regions_removed > 0) {
1796 g1_policy()->record_new_heap_size(num_regions());
1797 } else {
1798 ergo_verbose0(ErgoHeapSizing,
1799 "did not shrink the heap",
1800 ergo_format_reason("heap shrinking operation failed"));
1801 }
1802 }
1803
1804 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1805 verify_region_sets_optional();
1806
1807 // We should only reach here at the end of a Full GC which means we
1808 // should not not be holding to any GC alloc regions. The method
1809 // below will make sure of that and do any remaining clean up.
1810 abandon_gc_alloc_regions();
1811
1812 // Instead of tearing down / rebuilding the free lists here, we
1813 // could instead use the remove_all_pending() method on free_list to
1814 // remove only the ones that we need to remove.
1815 tear_down_region_sets(true /* free_list_only */);
1816 shrink_helper(shrink_bytes);
1817 rebuild_region_sets(true /* free_list_only */);
1818
1819 _hrm.verify_optional();
1820 verify_region_sets_optional();
1821 }
1822
1823 // Public methods.
1824
1825 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away
1826 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
1827 #endif // _MSC_VER
1828
1829
1830 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* policy_) :
1831 SharedHeap(policy_),
1832 _g1_policy(policy_),
1833 _dirty_card_queue_set(false),
1834 _into_cset_dirty_card_queue_set(false),
1835 _is_alive_closure_cm(this),
1836 _is_alive_closure_stw(this),
1837 _ref_processor_cm(NULL),
1838 _ref_processor_stw(NULL),
1839 _process_strong_tasks(new SubTasksDone(G1H_PS_NumElements)),
1840 _bot_shared(NULL),
1841 _evac_failure_scan_stack(NULL),
1842 _mark_in_progress(false),
1843 _cg1r(NULL), _summary_bytes_used(0),
1844 _g1mm(NULL),
1845 _refine_cte_cl(NULL),
1846 _full_collection(false),
1847 _secondary_free_list("Secondary Free List", new SecondaryFreeRegionListMtSafeChecker()),
1848 _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()),
1849 _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()),
1850 _humongous_is_live(),
1851 _has_humongous_reclaim_candidates(false),
1852 _free_regions_coming(false),
1853 _young_list(new YoungList(this)),
1854 _gc_time_stamp(0),
1855 _retained_old_gc_alloc_region(NULL),
1856 _survivor_plab_stats(YoungPLABSize, PLABWeight),
1857 _old_plab_stats(OldPLABSize, PLABWeight),
1858 _expand_heap_after_alloc_failure(true),
1859 _surviving_young_words(NULL),
1860 _old_marking_cycles_started(0),
1861 _old_marking_cycles_completed(0),
1862 _concurrent_cycle_started(false),
1863 _heap_summary_sent(false),
1864 _in_cset_fast_test(),
1865 _dirty_cards_region_list(NULL),
1866 _worker_cset_start_region(NULL),
1867 _worker_cset_start_region_time_stamp(NULL),
1868 _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()),
1869 _gc_timer_cm(new (ResourceObj::C_HEAP, mtGC) ConcurrentGCTimer()),
1870 _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()),
1871 _gc_tracer_cm(new (ResourceObj::C_HEAP, mtGC) G1OldTracer()) {
1872
1873 _g1h = this;
1874 if (_process_strong_tasks == NULL || !_process_strong_tasks->valid()) {
1875 vm_exit_during_initialization("Failed necessary allocation.");
1876 }
1877
1878 _humongous_object_threshold_in_words = HeapRegion::GrainWords / 2;
1879
1880 int n_queues = MAX2((int)ParallelGCThreads, 1);
1881 _task_queues = new RefToScanQueueSet(n_queues);
1882
1883 uint n_rem_sets = HeapRegionRemSet::num_par_rem_sets();
1884 assert(n_rem_sets > 0, "Invariant.");
1885
1886 _worker_cset_start_region = NEW_C_HEAP_ARRAY(HeapRegion*, n_queues, mtGC);
1887 _worker_cset_start_region_time_stamp = NEW_C_HEAP_ARRAY(unsigned int, n_queues, mtGC);
1888 _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC);
1889
1890 for (int i = 0; i < n_queues; i++) {
1891 RefToScanQueue* q = new RefToScanQueue();
1892 q->initialize();
1893 _task_queues->register_queue(i, q);
1894 ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo();
1895 }
1896 clear_cset_start_regions();
1897
1898 // Initialize the G1EvacuationFailureALot counters and flags.
1899 NOT_PRODUCT(reset_evacuation_should_fail();)
1900
1901 guarantee(_task_queues != NULL, "task_queues allocation failure.");
1902 }
1903
1904 jint G1CollectedHeap::initialize() {
1905 CollectedHeap::pre_initialize();
1906 os::enable_vtime();
1907
1908 G1Log::init();
1909
1910 // Necessary to satisfy locking discipline assertions.
1911
1912 MutexLocker x(Heap_lock);
1913
1914 // We have to initialize the printer before committing the heap, as
1915 // it will be used then.
1916 _hr_printer.set_active(G1PrintHeapRegions);
1917
1918 // While there are no constraints in the GC code that HeapWordSize
1919 // be any particular value, there are multiple other areas in the
1920 // system which believe this to be true (e.g. oop->object_size in some
1921 // cases incorrectly returns the size in wordSize units rather than
1922 // HeapWordSize).
1923 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
1924
1925 size_t init_byte_size = collector_policy()->initial_heap_byte_size();
1926 size_t max_byte_size = collector_policy()->max_heap_byte_size();
1927 size_t heap_alignment = collector_policy()->heap_alignment();
1928
1929 // Ensure that the sizes are properly aligned.
1930 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
1931 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
1932 Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap");
1933
1934 _refine_cte_cl = new RefineCardTableEntryClosure();
1935
1936 _cg1r = new ConcurrentG1Refine(this, _refine_cte_cl);
1937
1938 // Reserve the maximum.
1939
1940 // When compressed oops are enabled, the preferred heap base
1941 // is calculated by subtracting the requested size from the
1942 // 32Gb boundary and using the result as the base address for
1943 // heap reservation. If the requested size is not aligned to
1944 // HeapRegion::GrainBytes (i.e. the alignment that is passed
1945 // into the ReservedHeapSpace constructor) then the actual
1946 // base of the reserved heap may end up differing from the
1947 // address that was requested (i.e. the preferred heap base).
1948 // If this happens then we could end up using a non-optimal
1949 // compressed oops mode.
1950
1951 ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size,
1952 heap_alignment);
1953
1954 // It is important to do this in a way such that concurrent readers can't
1955 // temporarily think something is in the heap. (I've actually seen this
1956 // happen in asserts: DLD.)
1957 _reserved.set_word_size(0);
1958 _reserved.set_start((HeapWord*)heap_rs.base());
1959 _reserved.set_end((HeapWord*)(heap_rs.base() + heap_rs.size()));
1960
1961 // Create the gen rem set (and barrier set) for the entire reserved region.
1962 _rem_set = collector_policy()->create_rem_set(_reserved, 2);
1963 set_barrier_set(rem_set()->bs());
1964 if (!barrier_set()->is_a(BarrierSet::G1SATBCTLogging)) {
1965 vm_exit_during_initialization("G1 requires a G1SATBLoggingCardTableModRefBS");
1966 return JNI_ENOMEM;
1967 }
1968
1969 // Also create a G1 rem set.
1970 _g1_rem_set = new G1RemSet(this, g1_barrier_set());
1971
1972 // Carve out the G1 part of the heap.
1973
1974 ReservedSpace g1_rs = heap_rs.first_part(max_byte_size);
1975 G1RegionToSpaceMapper* heap_storage =
1976 G1RegionToSpaceMapper::create_mapper(g1_rs,
1977 UseLargePages ? os::large_page_size() : os::vm_page_size(),
1978 HeapRegion::GrainBytes,
1979 1,
1980 mtJavaHeap);
1981 heap_storage->set_mapping_changed_listener(&_listener);
1982
1983 // Reserve space for the block offset table. We do not support automatic uncommit
1984 // for the card table at this time. BOT only.
1985 ReservedSpace bot_rs(G1BlockOffsetSharedArray::compute_size(g1_rs.size() / HeapWordSize));
1986 G1RegionToSpaceMapper* bot_storage =
1987 G1RegionToSpaceMapper::create_mapper(bot_rs,
1988 os::vm_page_size(),
1989 HeapRegion::GrainBytes,
1990 G1BlockOffsetSharedArray::N_bytes,
1991 mtGC);
1992
1993 ReservedSpace cardtable_rs(G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize));
1994 G1RegionToSpaceMapper* cardtable_storage =
1995 G1RegionToSpaceMapper::create_mapper(cardtable_rs,
1996 os::vm_page_size(),
1997 HeapRegion::GrainBytes,
1998 G1BlockOffsetSharedArray::N_bytes,
1999 mtGC);
2000
2001 // Reserve space for the card counts table.
2002 ReservedSpace card_counts_rs(G1BlockOffsetSharedArray::compute_size(g1_rs.size() / HeapWordSize));
2003 G1RegionToSpaceMapper* card_counts_storage =
2004 G1RegionToSpaceMapper::create_mapper(card_counts_rs,
2005 os::vm_page_size(),
2006 HeapRegion::GrainBytes,
2007 G1BlockOffsetSharedArray::N_bytes,
2008 mtGC);
2009
2010 // Reserve space for prev and next bitmap.
2011 size_t bitmap_size = CMBitMap::compute_size(g1_rs.size());
2012
2013 ReservedSpace prev_bitmap_rs(ReservedSpace::allocation_align_size_up(bitmap_size));
2014 G1RegionToSpaceMapper* prev_bitmap_storage =
2015 G1RegionToSpaceMapper::create_mapper(prev_bitmap_rs,
2016 os::vm_page_size(),
2017 HeapRegion::GrainBytes,
2018 CMBitMap::mark_distance(),
2019 mtGC);
2020
2021 ReservedSpace next_bitmap_rs(ReservedSpace::allocation_align_size_up(bitmap_size));
2022 G1RegionToSpaceMapper* next_bitmap_storage =
2023 G1RegionToSpaceMapper::create_mapper(next_bitmap_rs,
2024 os::vm_page_size(),
2025 HeapRegion::GrainBytes,
2026 CMBitMap::mark_distance(),
2027 mtGC);
2028
2029 _hrm.initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage);
2030 g1_barrier_set()->initialize(cardtable_storage);
2031 // Do later initialization work for concurrent refinement.
2032 _cg1r->init(card_counts_storage);
2033
2034 // 6843694 - ensure that the maximum region index can fit
2035 // in the remembered set structures.
2036 const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
2037 guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
2038
2039 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
2040 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
2041 guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
2042 "too many cards per region");
2043
2044 FreeRegionList::set_unrealistically_long_length(max_regions() + 1);
2045
2046 _bot_shared = new G1BlockOffsetSharedArray(_reserved, bot_storage);
2047
2048 _g1h = this;
2049
2050 _in_cset_fast_test.initialize(_hrm.reserved().start(), _hrm.reserved().end(), HeapRegion::GrainBytes);
2051 _humongous_is_live.initialize(_hrm.reserved().start(), _hrm.reserved().end(), HeapRegion::GrainBytes);
2052
2053 // Create the ConcurrentMark data structure and thread.
2054 // (Must do this late, so that "max_regions" is defined.)
2055 _cm = new ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage);
2056 if (_cm == NULL || !_cm->completed_initialization()) {
2057 vm_shutdown_during_initialization("Could not create/initialize ConcurrentMark");
2058 return JNI_ENOMEM;
2059 }
2060 _cmThread = _cm->cmThread();
2061
2062 // Initialize the from_card cache structure of HeapRegionRemSet.
2063 HeapRegionRemSet::init_heap(max_regions());
2064
2065 // Now expand into the initial heap size.
2066 if (!expand(init_byte_size)) {
2067 vm_shutdown_during_initialization("Failed to allocate initial heap.");
2068 return JNI_ENOMEM;
2069 }
2070
2071 // Perform any initialization actions delegated to the policy.
2072 g1_policy()->init();
2073
2074 JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon,
2075 SATB_Q_FL_lock,
2076 G1SATBProcessCompletedThreshold,
2077 Shared_SATB_Q_lock);
2078
2079 JavaThread::dirty_card_queue_set().initialize(_refine_cte_cl,
2080 DirtyCardQ_CBL_mon,
2081 DirtyCardQ_FL_lock,
2082 concurrent_g1_refine()->yellow_zone(),
2083 concurrent_g1_refine()->red_zone(),
2084 Shared_DirtyCardQ_lock);
2085
2086 if (G1DeferredRSUpdate) {
2087 dirty_card_queue_set().initialize(NULL, // Should never be called by the Java code
2088 DirtyCardQ_CBL_mon,
2089 DirtyCardQ_FL_lock,
2090 -1, // never trigger processing
2091 -1, // no limit on length
2092 Shared_DirtyCardQ_lock,
2093 &JavaThread::dirty_card_queue_set());
2094 }
2095
2096 // Initialize the card queue set used to hold cards containing
2097 // references into the collection set.
2098 _into_cset_dirty_card_queue_set.initialize(NULL, // Should never be called by the Java code
2099 DirtyCardQ_CBL_mon,
2100 DirtyCardQ_FL_lock,
2101 -1, // never trigger processing
2102 -1, // no limit on length
2103 Shared_DirtyCardQ_lock,
2104 &JavaThread::dirty_card_queue_set());
2105
2106 // In case we're keeping closure specialization stats, initialize those
2107 // counts and that mechanism.
2108 SpecializationStats::clear();
2109
2110 // Here we allocate the dummy HeapRegion that is required by the
2111 // G1AllocRegion class.
2112 HeapRegion* dummy_region = _hrm.get_dummy_region();
2113
2114 // We'll re-use the same region whether the alloc region will
2115 // require BOT updates or not and, if it doesn't, then a non-young
2116 // region will complain that it cannot support allocations without
2117 // BOT updates. So we'll tag the dummy region as young to avoid that.
2118 dummy_region->set_young();
2119 // Make sure it's full.
2120 dummy_region->set_top(dummy_region->end());
2121 G1AllocRegion::setup(this, dummy_region);
2122
2123 init_mutator_alloc_region();
2124
2125 // Do create of the monitoring and management support so that
2126 // values in the heap have been properly initialized.
2127 _g1mm = new G1MonitoringSupport(this);
2128
2129 G1StringDedup::initialize();
2130
2131 return JNI_OK;
2132 }
2133
2134 void G1CollectedHeap::stop() {
2135 // Stop all concurrent threads. We do this to make sure these threads
2136 // do not continue to execute and access resources (e.g. gclog_or_tty)
2137 // that are destroyed during shutdown.
2138 _cg1r->stop();
2139 _cmThread->stop();
2140 if (G1StringDedup::is_enabled()) {
2141 G1StringDedup::stop();
2142 }
2143 }
2144
2145 void G1CollectedHeap::clear_humongous_is_live_table() {
2146 guarantee(G1ReclaimDeadHumongousObjectsAtYoungGC, "Should only be called if true");
2147 _humongous_is_live.clear();
2148 }
2149
2150 size_t G1CollectedHeap::conservative_max_heap_alignment() {
2151 return HeapRegion::max_region_size();
2152 }
2153
2154 void G1CollectedHeap::ref_processing_init() {
2155 // Reference processing in G1 currently works as follows:
2156 //
2157 // * There are two reference processor instances. One is
2158 // used to record and process discovered references
2159 // during concurrent marking; the other is used to
2160 // record and process references during STW pauses
2161 // (both full and incremental).
2162 // * Both ref processors need to 'span' the entire heap as
2163 // the regions in the collection set may be dotted around.
2164 //
2165 // * For the concurrent marking ref processor:
2166 // * Reference discovery is enabled at initial marking.
2167 // * Reference discovery is disabled and the discovered
2168 // references processed etc during remarking.
2169 // * Reference discovery is MT (see below).
2170 // * Reference discovery requires a barrier (see below).
2171 // * Reference processing may or may not be MT
2172 // (depending on the value of ParallelRefProcEnabled
2173 // and ParallelGCThreads).
2174 // * A full GC disables reference discovery by the CM
2175 // ref processor and abandons any entries on it's
2176 // discovered lists.
2177 //
2178 // * For the STW processor:
2179 // * Non MT discovery is enabled at the start of a full GC.
2180 // * Processing and enqueueing during a full GC is non-MT.
2181 // * During a full GC, references are processed after marking.
2182 //
2183 // * Discovery (may or may not be MT) is enabled at the start
2184 // of an incremental evacuation pause.
2185 // * References are processed near the end of a STW evacuation pause.
2186 // * For both types of GC:
2187 // * Discovery is atomic - i.e. not concurrent.
2188 // * Reference discovery will not need a barrier.
2189
2190 SharedHeap::ref_processing_init();
2191 MemRegion mr = reserved_region();
2192
2193 // Concurrent Mark ref processor
2194 _ref_processor_cm =
2195 new ReferenceProcessor(mr, // span
2196 ParallelRefProcEnabled && (ParallelGCThreads > 1),
2197 // mt processing
2198 (int) ParallelGCThreads,
2199 // degree of mt processing
2200 (ParallelGCThreads > 1) || (ConcGCThreads > 1),
2201 // mt discovery
2202 (int) MAX2(ParallelGCThreads, ConcGCThreads),
2203 // degree of mt discovery
2204 false,
2205 // Reference discovery is not atomic
2206 &_is_alive_closure_cm);
2207 // is alive closure
2208 // (for efficiency/performance)
2209
2210 // STW ref processor
2211 _ref_processor_stw =
2212 new ReferenceProcessor(mr, // span
2213 ParallelRefProcEnabled && (ParallelGCThreads > 1),
2214 // mt processing
2215 MAX2((int)ParallelGCThreads, 1),
2216 // degree of mt processing
2217 (ParallelGCThreads > 1),
2218 // mt discovery
2219 MAX2((int)ParallelGCThreads, 1),
2220 // degree of mt discovery
2221 true,
2222 // Reference discovery is atomic
2223 &_is_alive_closure_stw);
2224 // is alive closure
2225 // (for efficiency/performance)
2226 }
2227
2228 size_t G1CollectedHeap::capacity() const {
2229 return _hrm.length() * HeapRegion::GrainBytes;
2230 }
2231
2232 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) {
2233 assert(!hr->continuesHumongous(), "pre-condition");
2234 hr->reset_gc_time_stamp();
2235 if (hr->startsHumongous()) {
2236 uint first_index = hr->hrm_index() + 1;
2237 uint last_index = hr->last_hc_index();
2238 for (uint i = first_index; i < last_index; i += 1) {
2239 HeapRegion* chr = region_at(i);
2240 assert(chr->continuesHumongous(), "sanity");
2241 chr->reset_gc_time_stamp();
2242 }
2243 }
2244 }
2245
2246 #ifndef PRODUCT
2247 class CheckGCTimeStampsHRClosure : public HeapRegionClosure {
2248 private:
2249 unsigned _gc_time_stamp;
2250 bool _failures;
2251
2252 public:
2253 CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) :
2254 _gc_time_stamp(gc_time_stamp), _failures(false) { }
2255
2256 virtual bool doHeapRegion(HeapRegion* hr) {
2257 unsigned region_gc_time_stamp = hr->get_gc_time_stamp();
2258 if (_gc_time_stamp != region_gc_time_stamp) {
2259 gclog_or_tty->print_cr("Region "HR_FORMAT" has GC time stamp = %d, "
2260 "expected %d", HR_FORMAT_PARAMS(hr),
2261 region_gc_time_stamp, _gc_time_stamp);
2262 _failures = true;
2263 }
2264 return false;
2265 }
2266
2267 bool failures() { return _failures; }
2268 };
2269
2270 void G1CollectedHeap::check_gc_time_stamps() {
2271 CheckGCTimeStampsHRClosure cl(_gc_time_stamp);
2272 heap_region_iterate(&cl);
2273 guarantee(!cl.failures(), "all GC time stamps should have been reset");
2274 }
2275 #endif // PRODUCT
2276
2277 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl,
2278 DirtyCardQueue* into_cset_dcq,
2279 bool concurrent,
2280 uint worker_i) {
2281 // Clean cards in the hot card cache
2282 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
2283 hot_card_cache->drain(worker_i, g1_rem_set(), into_cset_dcq);
2284
2285 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2286 int n_completed_buffers = 0;
2287 while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) {
2288 n_completed_buffers++;
2289 }
2290 g1_policy()->phase_times()->record_update_rs_processed_buffers(worker_i, n_completed_buffers);
2291 dcqs.clear_n_completed_buffers();
2292 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!");
2293 }
2294
2295
2296 // Computes the sum of the storage used by the various regions.
2297
2298 size_t G1CollectedHeap::used() const {
2299 assert(Heap_lock->owner() != NULL,
2300 "Should be owned on this thread's behalf.");
2301 size_t result = _summary_bytes_used;
2302 // Read only once in case it is set to NULL concurrently
2303 HeapRegion* hr = _mutator_alloc_region.get();
2304 if (hr != NULL)
2305 result += hr->used();
2306 return result;
2307 }
2308
2309 size_t G1CollectedHeap::used_unlocked() const {
2310 size_t result = _summary_bytes_used;
2311 return result;
2312 }
2313
2314 class SumUsedClosure: public HeapRegionClosure {
2315 size_t _used;
2316 public:
2317 SumUsedClosure() : _used(0) {}
2318 bool doHeapRegion(HeapRegion* r) {
2319 if (!r->continuesHumongous()) {
2320 _used += r->used();
2321 }
2322 return false;
2323 }
2324 size_t result() { return _used; }
2325 };
2326
2327 size_t G1CollectedHeap::recalculate_used() const {
2328 double recalculate_used_start = os::elapsedTime();
2329
2330 SumUsedClosure blk;
2331 heap_region_iterate(&blk);
2332
2333 g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0);
2334 return blk.result();
2335 }
2336
2337 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
2338 switch (cause) {
2339 case GCCause::_gc_locker: return GCLockerInvokesConcurrent;
2340 case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent;
2341 case GCCause::_g1_humongous_allocation: return true;
2342 default: return false;
2343 }
2344 }
2345
2346 #ifndef PRODUCT
2347 void G1CollectedHeap::allocate_dummy_regions() {
2348 // Let's fill up most of the region
2349 size_t word_size = HeapRegion::GrainWords - 1024;
2350 // And as a result the region we'll allocate will be humongous.
2351 guarantee(isHumongous(word_size), "sanity");
2352
2353 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
2354 // Let's use the existing mechanism for the allocation
2355 HeapWord* dummy_obj = humongous_obj_allocate(word_size);
2356 if (dummy_obj != NULL) {
2357 MemRegion mr(dummy_obj, word_size);
2358 CollectedHeap::fill_with_object(mr);
2359 } else {
2360 // If we can't allocate once, we probably cannot allocate
2361 // again. Let's get out of the loop.
2362 break;
2363 }
2364 }
2365 }
2366 #endif // !PRODUCT
2367
2368 void G1CollectedHeap::increment_old_marking_cycles_started() {
2369 assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
2370 _old_marking_cycles_started == _old_marking_cycles_completed + 1,
2371 err_msg("Wrong marking cycle count (started: %d, completed: %d)",
2372 _old_marking_cycles_started, _old_marking_cycles_completed));
2373
2374 _old_marking_cycles_started++;
2375 }
2376
2377 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) {
2378 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
2379
2380 // We assume that if concurrent == true, then the caller is a
2381 // concurrent thread that was joined the Suspendible Thread
2382 // Set. If there's ever a cheap way to check this, we should add an
2383 // assert here.
2384
2385 // Given that this method is called at the end of a Full GC or of a
2386 // concurrent cycle, and those can be nested (i.e., a Full GC can
2387 // interrupt a concurrent cycle), the number of full collections
2388 // completed should be either one (in the case where there was no
2389 // nesting) or two (when a Full GC interrupted a concurrent cycle)
2390 // behind the number of full collections started.
2391
2392 // This is the case for the inner caller, i.e. a Full GC.
2393 assert(concurrent ||
2394 (_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
2395 (_old_marking_cycles_started == _old_marking_cycles_completed + 2),
2396 err_msg("for inner caller (Full GC): _old_marking_cycles_started = %u "
2397 "is inconsistent with _old_marking_cycles_completed = %u",
2398 _old_marking_cycles_started, _old_marking_cycles_completed));
2399
2400 // This is the case for the outer caller, i.e. the concurrent cycle.
2401 assert(!concurrent ||
2402 (_old_marking_cycles_started == _old_marking_cycles_completed + 1),
2403 err_msg("for outer caller (concurrent cycle): "
2404 "_old_marking_cycles_started = %u "
2405 "is inconsistent with _old_marking_cycles_completed = %u",
2406 _old_marking_cycles_started, _old_marking_cycles_completed));
2407
2408 _old_marking_cycles_completed += 1;
2409
2410 // We need to clear the "in_progress" flag in the CM thread before
2411 // we wake up any waiters (especially when ExplicitInvokesConcurrent
2412 // is set) so that if a waiter requests another System.gc() it doesn't
2413 // incorrectly see that a marking cycle is still in progress.
2414 if (concurrent) {
2415 _cmThread->clear_in_progress();
2416 }
2417
2418 // This notify_all() will ensure that a thread that called
2419 // System.gc() with (with ExplicitGCInvokesConcurrent set or not)
2420 // and it's waiting for a full GC to finish will be woken up. It is
2421 // waiting in VM_G1IncCollectionPause::doit_epilogue().
2422 FullGCCount_lock->notify_all();
2423 }
2424
2425 void G1CollectedHeap::register_concurrent_cycle_start(const Ticks& start_time) {
2426 _concurrent_cycle_started = true;
2427 _gc_timer_cm->register_gc_start(start_time);
2428
2429 _gc_tracer_cm->report_gc_start(gc_cause(), _gc_timer_cm->gc_start());
2430 trace_heap_before_gc(_gc_tracer_cm);
2431 }
2432
2433 void G1CollectedHeap::register_concurrent_cycle_end() {
2434 if (_concurrent_cycle_started) {
2435 if (_cm->has_aborted()) {
2436 _gc_tracer_cm->report_concurrent_mode_failure();
2437 }
2438
2439 _gc_timer_cm->register_gc_end();
2440 _gc_tracer_cm->report_gc_end(_gc_timer_cm->gc_end(), _gc_timer_cm->time_partitions());
2441
2442 // Clear state variables to prepare for the next concurrent cycle.
2443 _concurrent_cycle_started = false;
2444 _heap_summary_sent = false;
2445 }
2446 }
2447
2448 void G1CollectedHeap::trace_heap_after_concurrent_cycle() {
2449 if (_concurrent_cycle_started) {
2450 // This function can be called when:
2451 // the cleanup pause is run
2452 // the concurrent cycle is aborted before the cleanup pause.
2453 // the concurrent cycle is aborted after the cleanup pause,
2454 // but before the concurrent cycle end has been registered.
2455 // Make sure that we only send the heap information once.
2456 if (!_heap_summary_sent) {
2457 trace_heap_after_gc(_gc_tracer_cm);
2458 _heap_summary_sent = true;
2459 }
2460 }
2461 }
2462
2463 G1YCType G1CollectedHeap::yc_type() {
2464 bool is_young = g1_policy()->gcs_are_young();
2465 bool is_initial_mark = g1_policy()->during_initial_mark_pause();
2466 bool is_during_mark = mark_in_progress();
2467
2468 if (is_initial_mark) {
2469 return InitialMark;
2470 } else if (is_during_mark) {
2471 return DuringMark;
2472 } else if (is_young) {
2473 return Normal;
2474 } else {
2475 return Mixed;
2476 }
2477 }
2478
2479 void G1CollectedHeap::collect(GCCause::Cause cause) {
2480 assert_heap_not_locked();
2481
2482 unsigned int gc_count_before;
2483 unsigned int old_marking_count_before;
2484 bool retry_gc;
2485
2486 do {
2487 retry_gc = false;
2488
2489 {
2490 MutexLocker ml(Heap_lock);
2491
2492 // Read the GC count while holding the Heap_lock
2493 gc_count_before = total_collections();
2494 old_marking_count_before = _old_marking_cycles_started;
2495 }
2496
2497 if (should_do_concurrent_full_gc(cause)) {
2498 // Schedule an initial-mark evacuation pause that will start a
2499 // concurrent cycle. We're setting word_size to 0 which means that
2500 // we are not requesting a post-GC allocation.
2501 VM_G1IncCollectionPause op(gc_count_before,
2502 0, /* word_size */
2503 true, /* should_initiate_conc_mark */
2504 g1_policy()->max_pause_time_ms(),
2505 cause);
2506
2507 VMThread::execute(&op);
2508 if (!op.pause_succeeded()) {
2509 if (old_marking_count_before == _old_marking_cycles_started) {
2510 retry_gc = op.should_retry_gc();
2511 } else {
2512 // A Full GC happened while we were trying to schedule the
2513 // initial-mark GC. No point in starting a new cycle given
2514 // that the whole heap was collected anyway.
2515 }
2516
2517 if (retry_gc) {
2518 if (GC_locker::is_active_and_needs_gc()) {
2519 GC_locker::stall_until_clear();
2520 }
2521 }
2522 }
2523 } else {
2524 if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc
2525 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2526
2527 // Schedule a standard evacuation pause. We're setting word_size
2528 // to 0 which means that we are not requesting a post-GC allocation.
2529 VM_G1IncCollectionPause op(gc_count_before,
2530 0, /* word_size */
2531 false, /* should_initiate_conc_mark */
2532 g1_policy()->max_pause_time_ms(),
2533 cause);
2534 VMThread::execute(&op);
2535 } else {
2536 // Schedule a Full GC.
2537 VM_G1CollectFull op(gc_count_before, old_marking_count_before, cause);
2538 VMThread::execute(&op);
2539 }
2540 }
2541 } while (retry_gc);
2542 }
2543
2544 bool G1CollectedHeap::is_in(const void* p) const {
2545 if (_hrm.reserved().contains(p)) {
2546 // Given that we know that p is in the reserved space,
2547 // heap_region_containing_raw() should successfully
2548 // return the containing region.
2549 HeapRegion* hr = heap_region_containing_raw(p);
2550 return hr->is_in(p);
2551 } else {
2552 return false;
2553 }
2554 }
2555
2556 #ifdef ASSERT
2557 bool G1CollectedHeap::is_in_exact(const void* p) const {
2558 bool contains = reserved_region().contains(p);
2559 bool available = _hrm.is_available(addr_to_region((HeapWord*)p));
2560 if (contains && available) {
2561 return true;
2562 } else {
2563 return false;
2564 }
2565 }
2566 #endif
2567
2568 // Iteration functions.
2569
2570 // Applies an ExtendedOopClosure onto all references of objects within a HeapRegion.
2571
2572 class IterateOopClosureRegionClosure: public HeapRegionClosure {
2573 ExtendedOopClosure* _cl;
2574 public:
2575 IterateOopClosureRegionClosure(ExtendedOopClosure* cl) : _cl(cl) {}
2576 bool doHeapRegion(HeapRegion* r) {
2577 if (!r->continuesHumongous()) {
2578 r->oop_iterate(_cl);
2579 }
2580 return false;
2581 }
2582 };
2583
2584 void G1CollectedHeap::oop_iterate(ExtendedOopClosure* cl) {
2585 IterateOopClosureRegionClosure blk(cl);
2586 heap_region_iterate(&blk);
2587 }
2588
2589 // Iterates an ObjectClosure over all objects within a HeapRegion.
2590
2591 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2592 ObjectClosure* _cl;
2593 public:
2594 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2595 bool doHeapRegion(HeapRegion* r) {
2596 if (! r->continuesHumongous()) {
2597 r->object_iterate(_cl);
2598 }
2599 return false;
2600 }
2601 };
2602
2603 void G1CollectedHeap::object_iterate(ObjectClosure* cl) {
2604 IterateObjectClosureRegionClosure blk(cl);
2605 heap_region_iterate(&blk);
2606 }
2607
2608 // Calls a SpaceClosure on a HeapRegion.
2609
2610 class SpaceClosureRegionClosure: public HeapRegionClosure {
2611 SpaceClosure* _cl;
2612 public:
2613 SpaceClosureRegionClosure(SpaceClosure* cl) : _cl(cl) {}
2614 bool doHeapRegion(HeapRegion* r) {
2615 _cl->do_space(r);
2616 return false;
2617 }
2618 };
2619
2620 void G1CollectedHeap::space_iterate(SpaceClosure* cl) {
2621 SpaceClosureRegionClosure blk(cl);
2622 heap_region_iterate(&blk);
2623 }
2624
2625 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2626 _hrm.iterate(cl);
2627 }
2628
2629 void G1CollectedHeap::heap_region_par_iterate(HeapRegionClosure* cl,
2630 uint worker_id,
2631 HeapRegionClaimer* hrclaimer) const {
2632 _hrm.par_iterate(cl, worker_id, hrclaimer);
2633 }
2634
2635 // Clear the cached CSet starting regions and (more importantly)
2636 // the time stamps. Called when we reset the GC time stamp.
2637 void G1CollectedHeap::clear_cset_start_regions() {
2638 assert(_worker_cset_start_region != NULL, "sanity");
2639 assert(_worker_cset_start_region_time_stamp != NULL, "sanity");
2640
2641 int n_queues = MAX2((int)ParallelGCThreads, 1);
2642 for (int i = 0; i < n_queues; i++) {
2643 _worker_cset_start_region[i] = NULL;
2644 _worker_cset_start_region_time_stamp[i] = 0;
2645 }
2646 }
2647
2648 // Given the id of a worker, obtain or calculate a suitable
2649 // starting region for iterating over the current collection set.
2650 HeapRegion* G1CollectedHeap::start_cset_region_for_worker(uint worker_i) {
2651 assert(get_gc_time_stamp() > 0, "should have been updated by now");
2652
2653 HeapRegion* result = NULL;
2654 unsigned gc_time_stamp = get_gc_time_stamp();
2655
2656 if (_worker_cset_start_region_time_stamp[worker_i] == gc_time_stamp) {
2657 // Cached starting region for current worker was set
2658 // during the current pause - so it's valid.
2659 // Note: the cached starting heap region may be NULL
2660 // (when the collection set is empty).
2661 result = _worker_cset_start_region[worker_i];
2662 assert(result == NULL || result->in_collection_set(), "sanity");
2663 return result;
2664 }
2665
2666 // The cached entry was not valid so let's calculate
2667 // a suitable starting heap region for this worker.
2668
2669 // We want the parallel threads to start their collection
2670 // set iteration at different collection set regions to
2671 // avoid contention.
2672 // If we have:
2673 // n collection set regions
2674 // p threads
2675 // Then thread t will start at region floor ((t * n) / p)
2676
2677 result = g1_policy()->collection_set();
2678 if (G1CollectedHeap::use_parallel_gc_threads()) {
2679 uint cs_size = g1_policy()->cset_region_length();
2680 uint active_workers = workers()->active_workers();
2681 assert(UseDynamicNumberOfGCThreads ||
2682 active_workers == workers()->total_workers(),
2683 "Unless dynamic should use total workers");
2684
2685 uint end_ind = (cs_size * worker_i) / active_workers;
2686 uint start_ind = 0;
2687
2688 if (worker_i > 0 &&
2689 _worker_cset_start_region_time_stamp[worker_i - 1] == gc_time_stamp) {
2690 // Previous workers starting region is valid
2691 // so let's iterate from there
2692 start_ind = (cs_size * (worker_i - 1)) / active_workers;
2693 result = _worker_cset_start_region[worker_i - 1];
2694 }
2695
2696 for (uint i = start_ind; i < end_ind; i++) {
2697 result = result->next_in_collection_set();
2698 }
2699 }
2700
2701 // Note: the calculated starting heap region may be NULL
2702 // (when the collection set is empty).
2703 assert(result == NULL || result->in_collection_set(), "sanity");
2704 assert(_worker_cset_start_region_time_stamp[worker_i] != gc_time_stamp,
2705 "should be updated only once per pause");
2706 _worker_cset_start_region[worker_i] = result;
2707 OrderAccess::storestore();
2708 _worker_cset_start_region_time_stamp[worker_i] = gc_time_stamp;
2709 return result;
2710 }
2711
2712 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) {
2713 HeapRegion* r = g1_policy()->collection_set();
2714 while (r != NULL) {
2715 HeapRegion* next = r->next_in_collection_set();
2716 if (cl->doHeapRegion(r)) {
2717 cl->incomplete();
2718 return;
2719 }
2720 r = next;
2721 }
2722 }
2723
2724 void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r,
2725 HeapRegionClosure *cl) {
2726 if (r == NULL) {
2727 // The CSet is empty so there's nothing to do.
2728 return;
2729 }
2730
2731 assert(r->in_collection_set(),
2732 "Start region must be a member of the collection set.");
2733 HeapRegion* cur = r;
2734 while (cur != NULL) {
2735 HeapRegion* next = cur->next_in_collection_set();
2736 if (cl->doHeapRegion(cur) && false) {
2737 cl->incomplete();
2738 return;
2739 }
2740 cur = next;
2741 }
2742 cur = g1_policy()->collection_set();
2743 while (cur != r) {
2744 HeapRegion* next = cur->next_in_collection_set();
2745 if (cl->doHeapRegion(cur) && false) {
2746 cl->incomplete();
2747 return;
2748 }
2749 cur = next;
2750 }
2751 }
2752
2753 HeapRegion* G1CollectedHeap::next_compaction_region(const HeapRegion* from) const {
2754 HeapRegion* result = _hrm.next_region_in_heap(from);
2755 while (result != NULL && result->isHumongous()) {
2756 result = _hrm.next_region_in_heap(result);
2757 }
2758 return result;
2759 }
2760
2761 Space* G1CollectedHeap::space_containing(const void* addr) const {
2762 return heap_region_containing(addr);
2763 }
2764
2765 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2766 Space* sp = space_containing(addr);
2767 return sp->block_start(addr);
2768 }
2769
2770 size_t G1CollectedHeap::block_size(const HeapWord* addr) const {
2771 Space* sp = space_containing(addr);
2772 return sp->block_size(addr);
2773 }
2774
2775 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2776 Space* sp = space_containing(addr);
2777 return sp->block_is_obj(addr);
2778 }
2779
2780 bool G1CollectedHeap::supports_tlab_allocation() const {
2781 return true;
2782 }
2783
2784 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
2785 return (_g1_policy->young_list_target_length() - young_list()->survivor_length()) * HeapRegion::GrainBytes;
2786 }
2787
2788 size_t G1CollectedHeap::tlab_used(Thread* ignored) const {
2789 return young_list()->eden_used_bytes();
2790 }
2791
2792 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size
2793 // must be smaller than the humongous object limit.
2794 size_t G1CollectedHeap::max_tlab_size() const {
2795 return align_size_down(_humongous_object_threshold_in_words - 1, MinObjAlignment);
2796 }
2797
2798 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
2799 // Return the remaining space in the cur alloc region, but not less than
2800 // the min TLAB size.
2801
2802 // Also, this value can be at most the humongous object threshold,
2803 // since we can't allow tlabs to grow big enough to accommodate
2804 // humongous objects.
2805
2806 HeapRegion* hr = _mutator_alloc_region.get();
2807 size_t max_tlab = max_tlab_size() * wordSize;
2808 if (hr == NULL) {
2809 return max_tlab;
2810 } else {
2811 return MIN2(MAX2(hr->free(), (size_t) MinTLABSize), max_tlab);
2812 }
2813 }
2814
2815 size_t G1CollectedHeap::max_capacity() const {
2816 return _hrm.reserved().byte_size();
2817 }
2818
2819 jlong G1CollectedHeap::millis_since_last_gc() {
2820 // assert(false, "NYI");
2821 return 0;
2822 }
2823
2824 void G1CollectedHeap::prepare_for_verify() {
2825 if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) {
2826 ensure_parsability(false);
2827 }
2828 g1_rem_set()->prepare_for_verify();
2829 }
2830
2831 bool G1CollectedHeap::allocated_since_marking(oop obj, HeapRegion* hr,
2832 VerifyOption vo) {
2833 switch (vo) {
2834 case VerifyOption_G1UsePrevMarking:
2835 return hr->obj_allocated_since_prev_marking(obj);
2836 case VerifyOption_G1UseNextMarking:
2837 return hr->obj_allocated_since_next_marking(obj);
2838 case VerifyOption_G1UseMarkWord:
2839 return false;
2840 default:
2841 ShouldNotReachHere();
2842 }
2843 return false; // keep some compilers happy
2844 }
2845
2846 HeapWord* G1CollectedHeap::top_at_mark_start(HeapRegion* hr, VerifyOption vo) {
2847 switch (vo) {
2848 case VerifyOption_G1UsePrevMarking: return hr->prev_top_at_mark_start();
2849 case VerifyOption_G1UseNextMarking: return hr->next_top_at_mark_start();
2850 case VerifyOption_G1UseMarkWord: return NULL;
2851 default: ShouldNotReachHere();
2852 }
2853 return NULL; // keep some compilers happy
2854 }
2855
2856 bool G1CollectedHeap::is_marked(oop obj, VerifyOption vo) {
2857 switch (vo) {
2858 case VerifyOption_G1UsePrevMarking: return isMarkedPrev(obj);
2859 case VerifyOption_G1UseNextMarking: return isMarkedNext(obj);
2860 case VerifyOption_G1UseMarkWord: return obj->is_gc_marked();
2861 default: ShouldNotReachHere();
2862 }
2863 return false; // keep some compilers happy
2864 }
2865
2866 const char* G1CollectedHeap::top_at_mark_start_str(VerifyOption vo) {
2867 switch (vo) {
2868 case VerifyOption_G1UsePrevMarking: return "PTAMS";
2869 case VerifyOption_G1UseNextMarking: return "NTAMS";
2870 case VerifyOption_G1UseMarkWord: return "NONE";
2871 default: ShouldNotReachHere();
2872 }
2873 return NULL; // keep some compilers happy
2874 }
2875
2876 class VerifyRootsClosure: public OopClosure {
2877 private:
2878 G1CollectedHeap* _g1h;
2879 VerifyOption _vo;
2880 bool _failures;
2881 public:
2882 // _vo == UsePrevMarking -> use "prev" marking information,
2883 // _vo == UseNextMarking -> use "next" marking information,
2884 // _vo == UseMarkWord -> use mark word from object header.
2885 VerifyRootsClosure(VerifyOption vo) :
2886 _g1h(G1CollectedHeap::heap()),
2887 _vo(vo),
2888 _failures(false) { }
2889
2890 bool failures() { return _failures; }
2891
2892 template <class T> void do_oop_nv(T* p) {
2893 T heap_oop = oopDesc::load_heap_oop(p);
2894 if (!oopDesc::is_null(heap_oop)) {
2895 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
2896 if (_g1h->is_obj_dead_cond(obj, _vo)) {
2897 gclog_or_tty->print_cr("Root location "PTR_FORMAT" "
2898 "points to dead obj "PTR_FORMAT, p, (void*) obj);
2899 if (_vo == VerifyOption_G1UseMarkWord) {
2900 gclog_or_tty->print_cr(" Mark word: "PTR_FORMAT, (void*)(obj->mark()));
2901 }
2902 obj->print_on(gclog_or_tty);
2903 _failures = true;
2904 }
2905 }
2906 }
2907
2908 void do_oop(oop* p) { do_oop_nv(p); }
2909 void do_oop(narrowOop* p) { do_oop_nv(p); }
2910 };
2911
2912 class G1VerifyCodeRootOopClosure: public OopClosure {
2913 G1CollectedHeap* _g1h;
2914 OopClosure* _root_cl;
2915 nmethod* _nm;
2916 VerifyOption _vo;
2917 bool _failures;
2918
2919 template <class T> void do_oop_work(T* p) {
2920 // First verify that this root is live
2921 _root_cl->do_oop(p);
2922
2923 if (!G1VerifyHeapRegionCodeRoots) {
2924 // We're not verifying the code roots attached to heap region.
2925 return;
2926 }
2927
2928 // Don't check the code roots during marking verification in a full GC
2929 if (_vo == VerifyOption_G1UseMarkWord) {
2930 return;
2931 }
2932
2933 // Now verify that the current nmethod (which contains p) is
2934 // in the code root list of the heap region containing the
2935 // object referenced by p.
2936
2937 T heap_oop = oopDesc::load_heap_oop(p);
2938 if (!oopDesc::is_null(heap_oop)) {
2939 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
2940
2941 // Now fetch the region containing the object
2942 HeapRegion* hr = _g1h->heap_region_containing(obj);
2943 HeapRegionRemSet* hrrs = hr->rem_set();
2944 // Verify that the strong code root list for this region
2945 // contains the nmethod
2946 if (!hrrs->strong_code_roots_list_contains(_nm)) {
2947 gclog_or_tty->print_cr("Code root location "PTR_FORMAT" "
2948 "from nmethod "PTR_FORMAT" not in strong "
2949 "code roots for region ["PTR_FORMAT","PTR_FORMAT")",
2950 p, _nm, hr->bottom(), hr->end());
2951 _failures = true;
2952 }
2953 }
2954 }
2955
2956 public:
2957 G1VerifyCodeRootOopClosure(G1CollectedHeap* g1h, OopClosure* root_cl, VerifyOption vo):
2958 _g1h(g1h), _root_cl(root_cl), _vo(vo), _nm(NULL), _failures(false) {}
2959
2960 void do_oop(oop* p) { do_oop_work(p); }
2961 void do_oop(narrowOop* p) { do_oop_work(p); }
2962
2963 void set_nmethod(nmethod* nm) { _nm = nm; }
2964 bool failures() { return _failures; }
2965 };
2966
2967 class G1VerifyCodeRootBlobClosure: public CodeBlobClosure {
2968 G1VerifyCodeRootOopClosure* _oop_cl;
2969
2970 public:
2971 G1VerifyCodeRootBlobClosure(G1VerifyCodeRootOopClosure* oop_cl):
2972 _oop_cl(oop_cl) {}
2973
2974 void do_code_blob(CodeBlob* cb) {
2975 nmethod* nm = cb->as_nmethod_or_null();
2976 if (nm != NULL) {
2977 _oop_cl->set_nmethod(nm);
2978 nm->oops_do(_oop_cl);
2979 }
2980 }
2981 };
2982
2983 class YoungRefCounterClosure : public OopClosure {
2984 G1CollectedHeap* _g1h;
2985 int _count;
2986 public:
2987 YoungRefCounterClosure(G1CollectedHeap* g1h) : _g1h(g1h), _count(0) {}
2988 void do_oop(oop* p) { if (_g1h->is_in_young(*p)) { _count++; } }
2989 void do_oop(narrowOop* p) { ShouldNotReachHere(); }
2990
2991 int count() { return _count; }
2992 void reset_count() { _count = 0; };
2993 };
2994
2995 class VerifyKlassClosure: public KlassClosure {
2996 YoungRefCounterClosure _young_ref_counter_closure;
2997 OopClosure *_oop_closure;
2998 public:
2999 VerifyKlassClosure(G1CollectedHeap* g1h, OopClosure* cl) : _young_ref_counter_closure(g1h), _oop_closure(cl) {}
3000 void do_klass(Klass* k) {
3001 k->oops_do(_oop_closure);
3002
3003 _young_ref_counter_closure.reset_count();
3004 k->oops_do(&_young_ref_counter_closure);
3005 if (_young_ref_counter_closure.count() > 0) {
3006 guarantee(k->has_modified_oops(), err_msg("Klass " PTR_FORMAT ", has young refs but is not dirty.", k));
3007 }
3008 }
3009 };
3010
3011 class VerifyLivenessOopClosure: public OopClosure {
3012 G1CollectedHeap* _g1h;
3013 VerifyOption _vo;
3014 public:
3015 VerifyLivenessOopClosure(G1CollectedHeap* g1h, VerifyOption vo):
3016 _g1h(g1h), _vo(vo)
3017 { }
3018 void do_oop(narrowOop *p) { do_oop_work(p); }
3019 void do_oop( oop *p) { do_oop_work(p); }
3020
3021 template <class T> void do_oop_work(T *p) {
3022 oop obj = oopDesc::load_decode_heap_oop(p);
3023 guarantee(obj == NULL || !_g1h->is_obj_dead_cond(obj, _vo),
3024 "Dead object referenced by a not dead object");
3025 }
3026 };
3027
3028 class VerifyObjsInRegionClosure: public ObjectClosure {
3029 private:
3030 G1CollectedHeap* _g1h;
3031 size_t _live_bytes;
3032 HeapRegion *_hr;
3033 VerifyOption _vo;
3034 public:
3035 // _vo == UsePrevMarking -> use "prev" marking information,
3036 // _vo == UseNextMarking -> use "next" marking information,
3037 // _vo == UseMarkWord -> use mark word from object header.
3038 VerifyObjsInRegionClosure(HeapRegion *hr, VerifyOption vo)
3039 : _live_bytes(0), _hr(hr), _vo(vo) {
3040 _g1h = G1CollectedHeap::heap();
3041 }
3042 void do_object(oop o) {
3043 VerifyLivenessOopClosure isLive(_g1h, _vo);
3044 assert(o != NULL, "Huh?");
3045 if (!_g1h->is_obj_dead_cond(o, _vo)) {
3046 // If the object is alive according to the mark word,
3047 // then verify that the marking information agrees.
3048 // Note we can't verify the contra-positive of the
3049 // above: if the object is dead (according to the mark
3050 // word), it may not be marked, or may have been marked
3051 // but has since became dead, or may have been allocated
3052 // since the last marking.
3053 if (_vo == VerifyOption_G1UseMarkWord) {
3054 guarantee(!_g1h->is_obj_dead(o), "mark word and concurrent mark mismatch");
3055 }
3056
3057 o->oop_iterate_no_header(&isLive);
3058 if (!_hr->obj_allocated_since_prev_marking(o)) {
3059 size_t obj_size = o->size(); // Make sure we don't overflow
3060 _live_bytes += (obj_size * HeapWordSize);
3061 }
3062 }
3063 }
3064 size_t live_bytes() { return _live_bytes; }
3065 };
3066
3067 class PrintObjsInRegionClosure : public ObjectClosure {
3068 HeapRegion *_hr;
3069 G1CollectedHeap *_g1;
3070 public:
3071 PrintObjsInRegionClosure(HeapRegion *hr) : _hr(hr) {
3072 _g1 = G1CollectedHeap::heap();
3073 };
3074
3075 void do_object(oop o) {
3076 if (o != NULL) {
3077 HeapWord *start = (HeapWord *) o;
3078 size_t word_sz = o->size();
3079 gclog_or_tty->print("\nPrinting obj "PTR_FORMAT" of size " SIZE_FORMAT
3080 " isMarkedPrev %d isMarkedNext %d isAllocSince %d\n",
3081 (void*) o, word_sz,
3082 _g1->isMarkedPrev(o),
3083 _g1->isMarkedNext(o),
3084 _hr->obj_allocated_since_prev_marking(o));
3085 HeapWord *end = start + word_sz;
3086 HeapWord *cur;
3087 int *val;
3088 for (cur = start; cur < end; cur++) {
3089 val = (int *) cur;
3090 gclog_or_tty->print("\t "PTR_FORMAT":%d\n", val, *val);
3091 }
3092 }
3093 }
3094 };
3095
3096 class VerifyRegionClosure: public HeapRegionClosure {
3097 private:
3098 bool _par;
3099 VerifyOption _vo;
3100 bool _failures;
3101 public:
3102 // _vo == UsePrevMarking -> use "prev" marking information,
3103 // _vo == UseNextMarking -> use "next" marking information,
3104 // _vo == UseMarkWord -> use mark word from object header.
3105 VerifyRegionClosure(bool par, VerifyOption vo)
3106 : _par(par),
3107 _vo(vo),
3108 _failures(false) {}
3109
3110 bool failures() {
3111 return _failures;
3112 }
3113
3114 bool doHeapRegion(HeapRegion* r) {
3115 if (!r->continuesHumongous()) {
3116 bool failures = false;
3117 r->verify(_vo, &failures);
3118 if (failures) {
3119 _failures = true;
3120 } else {
3121 VerifyObjsInRegionClosure not_dead_yet_cl(r, _vo);
3122 r->object_iterate(¬_dead_yet_cl);
3123 if (_vo != VerifyOption_G1UseNextMarking) {
3124 if (r->max_live_bytes() < not_dead_yet_cl.live_bytes()) {
3125 gclog_or_tty->print_cr("["PTR_FORMAT","PTR_FORMAT"] "
3126 "max_live_bytes "SIZE_FORMAT" "
3127 "< calculated "SIZE_FORMAT,
3128 r->bottom(), r->end(),
3129 r->max_live_bytes(),
3130 not_dead_yet_cl.live_bytes());
3131 _failures = true;
3132 }
3133 } else {
3134 // When vo == UseNextMarking we cannot currently do a sanity
3135 // check on the live bytes as the calculation has not been
3136 // finalized yet.
3137 }
3138 }
3139 }
3140 return false; // stop the region iteration if we hit a failure
3141 }
3142 };
3143
3144 // This is the task used for parallel verification of the heap regions
3145
3146 class G1ParVerifyTask: public AbstractGangTask {
3147 private:
3148 G1CollectedHeap* _g1h;
3149 VerifyOption _vo;
3150 bool _failures;
3151 HeapRegionClaimer _hrclaimer;
3152
3153 public:
3154 // _vo == UsePrevMarking -> use "prev" marking information,
3155 // _vo == UseNextMarking -> use "next" marking information,
3156 // _vo == UseMarkWord -> use mark word from object header.
3157 G1ParVerifyTask(G1CollectedHeap* g1h, VerifyOption vo) :
3158 AbstractGangTask("Parallel verify task"),
3159 _g1h(g1h),
3160 _vo(vo),
3161 _failures(false),
3162 _hrclaimer(g1h->workers()->active_workers()) {}
3163
3164 bool failures() {
3165 return _failures;
3166 }
3167
3168 void work(uint worker_id) {
3169 HandleMark hm;
3170 VerifyRegionClosure blk(true, _vo);
3171 _g1h->heap_region_par_iterate(&blk, worker_id, &_hrclaimer);
3172 if (blk.failures()) {
3173 _failures = true;
3174 }
3175 }
3176 };
3177
3178 void G1CollectedHeap::verify(bool silent, VerifyOption vo) {
3179 if (SafepointSynchronize::is_at_safepoint()) {
3180 assert(Thread::current()->is_VM_thread(),
3181 "Expected to be executed serially by the VM thread at this point");
3182
3183 if (!silent) { gclog_or_tty->print("Roots "); }
3184 VerifyRootsClosure rootsCl(vo);
3185 VerifyKlassClosure klassCl(this, &rootsCl);
3186 CLDToKlassAndOopClosure cldCl(&klassCl, &rootsCl, false);
3187
3188 // We apply the relevant closures to all the oops in the
3189 // system dictionary, class loader data graph, the string table
3190 // and the nmethods in the code cache.
3191 G1VerifyCodeRootOopClosure codeRootsCl(this, &rootsCl, vo);
3192 G1VerifyCodeRootBlobClosure blobsCl(&codeRootsCl);
3193
3194 process_all_roots(true, // activate StrongRootsScope
3195 SO_AllCodeCache, // roots scanning options
3196 &rootsCl,
3197 &cldCl,
3198 &blobsCl);
3199
3200 bool failures = rootsCl.failures() || codeRootsCl.failures();
3201
3202 if (vo != VerifyOption_G1UseMarkWord) {
3203 // If we're verifying during a full GC then the region sets
3204 // will have been torn down at the start of the GC. Therefore
3205 // verifying the region sets will fail. So we only verify
3206 // the region sets when not in a full GC.
3207 if (!silent) { gclog_or_tty->print("HeapRegionSets "); }
3208 verify_region_sets();
3209 }
3210
3211 if (!silent) { gclog_or_tty->print("HeapRegions "); }
3212 if (GCParallelVerificationEnabled && ParallelGCThreads > 1) {
3213
3214 G1ParVerifyTask task(this, vo);
3215 assert(UseDynamicNumberOfGCThreads ||
3216 workers()->active_workers() == workers()->total_workers(),
3217 "If not dynamic should be using all the workers");
3218 int n_workers = workers()->active_workers();
3219 set_par_threads(n_workers);
3220 workers()->run_task(&task);
3221 set_par_threads(0);
3222 if (task.failures()) {
3223 failures = true;
3224 }
3225
3226 } else {
3227 VerifyRegionClosure blk(false, vo);
3228 heap_region_iterate(&blk);
3229 if (blk.failures()) {
3230 failures = true;
3231 }
3232 }
3233 if (!silent) gclog_or_tty->print("RemSet ");
3234 rem_set()->verify();
3235
3236 if (G1StringDedup::is_enabled()) {
3237 if (!silent) gclog_or_tty->print("StrDedup ");
3238 G1StringDedup::verify();
3239 }
3240
3241 if (failures) {
3242 gclog_or_tty->print_cr("Heap:");
3243 // It helps to have the per-region information in the output to
3244 // help us track down what went wrong. This is why we call
3245 // print_extended_on() instead of print_on().
3246 print_extended_on(gclog_or_tty);
3247 gclog_or_tty->cr();
3248 #ifndef PRODUCT
3249 if (VerifyDuringGC && G1VerifyDuringGCPrintReachable) {
3250 concurrent_mark()->print_reachable("at-verification-failure",
3251 vo, false /* all */);
3252 }
3253 #endif
3254 gclog_or_tty->flush();
3255 }
3256 guarantee(!failures, "there should not have been any failures");
3257 } else {
3258 if (!silent) {
3259 gclog_or_tty->print("(SKIPPING Roots, HeapRegionSets, HeapRegions, RemSet");
3260 if (G1StringDedup::is_enabled()) {
3261 gclog_or_tty->print(", StrDedup");
3262 }
3263 gclog_or_tty->print(") ");
3264 }
3265 }
3266 }
3267
3268 void G1CollectedHeap::verify(bool silent) {
3269 verify(silent, VerifyOption_G1UsePrevMarking);
3270 }
3271
3272 double G1CollectedHeap::verify(bool guard, const char* msg) {
3273 double verify_time_ms = 0.0;
3274
3275 if (guard && total_collections() >= VerifyGCStartAt) {
3276 double verify_start = os::elapsedTime();
3277 HandleMark hm; // Discard invalid handles created during verification
3278 prepare_for_verify();
3279 Universe::verify(VerifyOption_G1UsePrevMarking, msg);
3280 verify_time_ms = (os::elapsedTime() - verify_start) * 1000;
3281 }
3282
3283 return verify_time_ms;
3284 }
3285
3286 void G1CollectedHeap::verify_before_gc() {
3287 double verify_time_ms = verify(VerifyBeforeGC, " VerifyBeforeGC:");
3288 g1_policy()->phase_times()->record_verify_before_time_ms(verify_time_ms);
3289 }
3290
3291 void G1CollectedHeap::verify_after_gc() {
3292 double verify_time_ms = verify(VerifyAfterGC, " VerifyAfterGC:");
3293 g1_policy()->phase_times()->record_verify_after_time_ms(verify_time_ms);
3294 }
3295
3296 class PrintRegionClosure: public HeapRegionClosure {
3297 outputStream* _st;
3298 public:
3299 PrintRegionClosure(outputStream* st) : _st(st) {}
3300 bool doHeapRegion(HeapRegion* r) {
3301 r->print_on(_st);
3302 return false;
3303 }
3304 };
3305
3306 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
3307 const HeapRegion* hr,
3308 const VerifyOption vo) const {
3309 switch (vo) {
3310 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr);
3311 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr);
3312 case VerifyOption_G1UseMarkWord: return !obj->is_gc_marked();
3313 default: ShouldNotReachHere();
3314 }
3315 return false; // keep some compilers happy
3316 }
3317
3318 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
3319 const VerifyOption vo) const {
3320 switch (vo) {
3321 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj);
3322 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj);
3323 case VerifyOption_G1UseMarkWord: return !obj->is_gc_marked();
3324 default: ShouldNotReachHere();
3325 }
3326 return false; // keep some compilers happy
3327 }
3328
3329 void G1CollectedHeap::print_on(outputStream* st) const {
3330 st->print(" %-20s", "garbage-first heap");
3331 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
3332 capacity()/K, used_unlocked()/K);
3333 st->print(" [" INTPTR_FORMAT ", " INTPTR_FORMAT ", " INTPTR_FORMAT ")",
3334 _hrm.reserved().start(),
3335 _hrm.reserved().start() + _hrm.length() + HeapRegion::GrainWords,
3336 _hrm.reserved().end());
3337 st->cr();
3338 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
3339 uint young_regions = _young_list->length();
3340 st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
3341 (size_t) young_regions * HeapRegion::GrainBytes / K);
3342 uint survivor_regions = g1_policy()->recorded_survivor_regions();
3343 st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
3344 (size_t) survivor_regions * HeapRegion::GrainBytes / K);
3345 st->cr();
3346 MetaspaceAux::print_on(st);
3347 }
3348
3349 void G1CollectedHeap::print_extended_on(outputStream* st) const {
3350 print_on(st);
3351
3352 // Print the per-region information.
3353 st->cr();
3354 st->print_cr("Heap Regions: (Y=young(eden), SU=young(survivor), "
3355 "HS=humongous(starts), HC=humongous(continues), "
3356 "CS=collection set, F=free, TS=gc time stamp, "
3357 "PTAMS=previous top-at-mark-start, "
3358 "NTAMS=next top-at-mark-start)");
3359 PrintRegionClosure blk(st);
3360 heap_region_iterate(&blk);
3361 }
3362
3363 void G1CollectedHeap::print_on_error(outputStream* st) const {
3364 this->CollectedHeap::print_on_error(st);
3365
3366 if (_cm != NULL) {
3367 st->cr();
3368 _cm->print_on_error(st);
3369 }
3370 }
3371
3372 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
3373 if (G1CollectedHeap::use_parallel_gc_threads()) {
3374 workers()->print_worker_threads_on(st);
3375 }
3376 _cmThread->print_on(st);
3377 st->cr();
3378 _cm->print_worker_threads_on(st);
3379 _cg1r->print_worker_threads_on(st);
3380 if (G1StringDedup::is_enabled()) {
3381 G1StringDedup::print_worker_threads_on(st);
3382 }
3383 }
3384
3385 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
3386 if (G1CollectedHeap::use_parallel_gc_threads()) {
3387 workers()->threads_do(tc);
3388 }
3389 tc->do_thread(_cmThread);
3390 _cg1r->threads_do(tc);
3391 if (G1StringDedup::is_enabled()) {
3392 G1StringDedup::threads_do(tc);
3393 }
3394 }
3395
3396 void G1CollectedHeap::print_tracing_info() const {
3397 // We'll overload this to mean "trace GC pause statistics."
3398 if (TraceYoungGenTime || TraceOldGenTime) {
3399 // The "G1CollectorPolicy" is keeping track of these stats, so delegate
3400 // to that.
3401 g1_policy()->print_tracing_info();
3402 }
3403 if (G1SummarizeRSetStats) {
3404 g1_rem_set()->print_summary_info();
3405 }
3406 if (G1SummarizeConcMark) {
3407 concurrent_mark()->print_summary_info();
3408 }
3409 g1_policy()->print_yg_surv_rate_info();
3410 SpecializationStats::print();
3411 }
3412
3413 #ifndef PRODUCT
3414 // Helpful for debugging RSet issues.
3415
3416 class PrintRSetsClosure : public HeapRegionClosure {
3417 private:
3418 const char* _msg;
3419 size_t _occupied_sum;
3420
3421 public:
3422 bool doHeapRegion(HeapRegion* r) {
3423 HeapRegionRemSet* hrrs = r->rem_set();
3424 size_t occupied = hrrs->occupied();
3425 _occupied_sum += occupied;
3426
3427 gclog_or_tty->print_cr("Printing RSet for region "HR_FORMAT,
3428 HR_FORMAT_PARAMS(r));
3429 if (occupied == 0) {
3430 gclog_or_tty->print_cr(" RSet is empty");
3431 } else {
3432 hrrs->print();
3433 }
3434 gclog_or_tty->print_cr("----------");
3435 return false;
3436 }
3437
3438 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
3439 gclog_or_tty->cr();
3440 gclog_or_tty->print_cr("========================================");
3441 gclog_or_tty->print_cr("%s", msg);
3442 gclog_or_tty->cr();
3443 }
3444
3445 ~PrintRSetsClosure() {
3446 gclog_or_tty->print_cr("Occupied Sum: "SIZE_FORMAT, _occupied_sum);
3447 gclog_or_tty->print_cr("========================================");
3448 gclog_or_tty->cr();
3449 }
3450 };
3451
3452 void G1CollectedHeap::print_cset_rsets() {
3453 PrintRSetsClosure cl("Printing CSet RSets");
3454 collection_set_iterate(&cl);
3455 }
3456
3457 void G1CollectedHeap::print_all_rsets() {
3458 PrintRSetsClosure cl("Printing All RSets");;
3459 heap_region_iterate(&cl);
3460 }
3461 #endif // PRODUCT
3462
3463 G1CollectedHeap* G1CollectedHeap::heap() {
3464 assert(_sh->kind() == CollectedHeap::G1CollectedHeap,
3465 "not a garbage-first heap");
3466 return _g1h;
3467 }
3468
3469 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) {
3470 // always_do_update_barrier = false;
3471 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
3472 // Fill TLAB's and such
3473 accumulate_statistics_all_tlabs();
3474 ensure_parsability(true);
3475
3476 if (G1SummarizeRSetStats && (G1SummarizeRSetStatsPeriod > 0) &&
3477 (total_collections() % G1SummarizeRSetStatsPeriod == 0)) {
3478 g1_rem_set()->print_periodic_summary_info("Before GC RS summary");
3479 }
3480 }
3481
3482 void G1CollectedHeap::gc_epilogue(bool full /* Ignored */) {
3483
3484 if (G1SummarizeRSetStats &&
3485 (G1SummarizeRSetStatsPeriod > 0) &&
3486 // we are at the end of the GC. Total collections has already been increased.
3487 ((total_collections() - 1) % G1SummarizeRSetStatsPeriod == 0)) {
3488 g1_rem_set()->print_periodic_summary_info("After GC RS summary");
3489 }
3490
3491 // FIXME: what is this about?
3492 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
3493 // is set.
3494 COMPILER2_PRESENT(assert(DerivedPointerTable::is_empty(),
3495 "derived pointer present"));
3496 // always_do_update_barrier = true;
3497
3498 resize_all_tlabs();
3499
3500 // We have just completed a GC. Update the soft reference
3501 // policy with the new heap occupancy
3502 Universe::update_heap_info_at_gc();
3503 }
3504
3505 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
3506 unsigned int gc_count_before,
3507 bool* succeeded,
3508 GCCause::Cause gc_cause) {
3509 assert_heap_not_locked_and_not_at_safepoint();
3510 g1_policy()->record_stop_world_start();
3511 VM_G1IncCollectionPause op(gc_count_before,
3512 word_size,
3513 false, /* should_initiate_conc_mark */
3514 g1_policy()->max_pause_time_ms(),
3515 gc_cause);
3516 VMThread::execute(&op);
3517
3518 HeapWord* result = op.result();
3519 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
3520 assert(result == NULL || ret_succeeded,
3521 "the result should be NULL if the VM did not succeed");
3522 *succeeded = ret_succeeded;
3523
3524 assert_heap_not_locked();
3525 return result;
3526 }
3527
3528 void
3529 G1CollectedHeap::doConcurrentMark() {
3530 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
3531 if (!_cmThread->in_progress()) {
3532 _cmThread->set_started();
3533 CGC_lock->notify();
3534 }
3535 }
3536
3537 size_t G1CollectedHeap::pending_card_num() {
3538 size_t extra_cards = 0;
3539 JavaThread *curr = Threads::first();
3540 while (curr != NULL) {
3541 DirtyCardQueue& dcq = curr->dirty_card_queue();
3542 extra_cards += dcq.size();
3543 curr = curr->next();
3544 }
3545 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
3546 size_t buffer_size = dcqs.buffer_size();
3547 size_t buffer_num = dcqs.completed_buffers_num();
3548
3549 // PtrQueueSet::buffer_size() and PtrQueue:size() return sizes
3550 // in bytes - not the number of 'entries'. We need to convert
3551 // into a number of cards.
3552 return (buffer_size * buffer_num + extra_cards) / oopSize;
3553 }
3554
3555 size_t G1CollectedHeap::cards_scanned() {
3556 return g1_rem_set()->cardsScanned();
3557 }
3558
3559 bool G1CollectedHeap::humongous_region_is_always_live(uint index) {
3560 HeapRegion* region = region_at(index);
3561 assert(region->startsHumongous(), "Must start a humongous object");
3562 return oop(region->bottom())->is_objArray() || !region->rem_set()->is_empty();
3563 }
3564
3565 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure {
3566 private:
3567 size_t _total_humongous;
3568 size_t _candidate_humongous;
3569 public:
3570 RegisterHumongousWithInCSetFastTestClosure() : _total_humongous(0), _candidate_humongous(0) {
3571 }
3572
3573 virtual bool doHeapRegion(HeapRegion* r) {
3574 if (!r->startsHumongous()) {
3575 return false;
3576 }
3577 G1CollectedHeap* g1h = G1CollectedHeap::heap();
3578
3579 uint region_idx = r->hrm_index();
3580 bool is_candidate = !g1h->humongous_region_is_always_live(region_idx);
3581 // Is_candidate already filters out humongous regions with some remembered set.
3582 // This will not lead to humongous object that we mistakenly keep alive because
3583 // during young collection the remembered sets will only be added to.
3584 if (is_candidate) {
3585 g1h->register_humongous_region_with_in_cset_fast_test(region_idx);
3586 _candidate_humongous++;
3587 }
3588 _total_humongous++;
3589
3590 return false;
3591 }
3592
3593 size_t total_humongous() const { return _total_humongous; }
3594 size_t candidate_humongous() const { return _candidate_humongous; }
3595 };
3596
3597 void G1CollectedHeap::register_humongous_regions_with_in_cset_fast_test() {
3598 if (!G1ReclaimDeadHumongousObjectsAtYoungGC) {
3599 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0, 0);
3600 return;
3601 }
3602
3603 RegisterHumongousWithInCSetFastTestClosure cl;
3604 heap_region_iterate(&cl);
3605 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(cl.total_humongous(),
3606 cl.candidate_humongous());
3607 _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0;
3608
3609 if (_has_humongous_reclaim_candidates) {
3610 clear_humongous_is_live_table();
3611 }
3612 }
3613
3614 void
3615 G1CollectedHeap::setup_surviving_young_words() {
3616 assert(_surviving_young_words == NULL, "pre-condition");
3617 uint array_length = g1_policy()->young_cset_region_length();
3618 _surviving_young_words = NEW_C_HEAP_ARRAY(size_t, (size_t) array_length, mtGC);
3619 if (_surviving_young_words == NULL) {
3620 vm_exit_out_of_memory(sizeof(size_t) * array_length, OOM_MALLOC_ERROR,
3621 "Not enough space for young surv words summary.");
3622 }
3623 memset(_surviving_young_words, 0, (size_t) array_length * sizeof(size_t));
3624 #ifdef ASSERT
3625 for (uint i = 0; i < array_length; ++i) {
3626 assert( _surviving_young_words[i] == 0, "memset above" );
3627 }
3628 #endif // !ASSERT
3629 }
3630
3631 void
3632 G1CollectedHeap::update_surviving_young_words(size_t* surv_young_words) {
3633 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
3634 uint array_length = g1_policy()->young_cset_region_length();
3635 for (uint i = 0; i < array_length; ++i) {
3636 _surviving_young_words[i] += surv_young_words[i];
3637 }
3638 }
3639
3640 void
3641 G1CollectedHeap::cleanup_surviving_young_words() {
3642 guarantee( _surviving_young_words != NULL, "pre-condition" );
3643 FREE_C_HEAP_ARRAY(size_t, _surviving_young_words, mtGC);
3644 _surviving_young_words = NULL;
3645 }
3646
3647 #ifdef ASSERT
3648 class VerifyCSetClosure: public HeapRegionClosure {
3649 public:
3650 bool doHeapRegion(HeapRegion* hr) {
3651 // Here we check that the CSet region's RSet is ready for parallel
3652 // iteration. The fields that we'll verify are only manipulated
3653 // when the region is part of a CSet and is collected. Afterwards,
3654 // we reset these fields when we clear the region's RSet (when the
3655 // region is freed) so they are ready when the region is
3656 // re-allocated. The only exception to this is if there's an
3657 // evacuation failure and instead of freeing the region we leave
3658 // it in the heap. In that case, we reset these fields during
3659 // evacuation failure handling.
3660 guarantee(hr->rem_set()->verify_ready_for_par_iteration(), "verification");
3661
3662 // Here's a good place to add any other checks we'd like to
3663 // perform on CSet regions.
3664 return false;
3665 }
3666 };
3667 #endif // ASSERT
3668
3669 #if TASKQUEUE_STATS
3670 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
3671 st->print_raw_cr("GC Task Stats");
3672 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
3673 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
3674 }
3675
3676 void G1CollectedHeap::print_taskqueue_stats(outputStream* const st) const {
3677 print_taskqueue_stats_hdr(st);
3678
3679 TaskQueueStats totals;
3680 const int n = workers() != NULL ? workers()->total_workers() : 1;
3681 for (int i = 0; i < n; ++i) {
3682 st->print("%3d ", i); task_queue(i)->stats.print(st); st->cr();
3683 totals += task_queue(i)->stats;
3684 }
3685 st->print_raw("tot "); totals.print(st); st->cr();
3686
3687 DEBUG_ONLY(totals.verify());
3688 }
3689
3690 void G1CollectedHeap::reset_taskqueue_stats() {
3691 const int n = workers() != NULL ? workers()->total_workers() : 1;
3692 for (int i = 0; i < n; ++i) {
3693 task_queue(i)->stats.reset();
3694 }
3695 }
3696 #endif // TASKQUEUE_STATS
3697
3698 void G1CollectedHeap::log_gc_header() {
3699 if (!G1Log::fine()) {
3700 return;
3701 }
3702
3703 gclog_or_tty->gclog_stamp(_gc_tracer_stw->gc_id());
3704
3705 GCCauseString gc_cause_str = GCCauseString("GC pause", gc_cause())
3706 .append(g1_policy()->gcs_are_young() ? "(young)" : "(mixed)")
3707 .append(g1_policy()->during_initial_mark_pause() ? " (initial-mark)" : "");
3708
3709 gclog_or_tty->print("[%s", (const char*)gc_cause_str);
3710 }
3711
3712 void G1CollectedHeap::log_gc_footer(double pause_time_sec) {
3713 if (!G1Log::fine()) {
3714 return;
3715 }
3716
3717 if (G1Log::finer()) {
3718 if (evacuation_failed()) {
3719 gclog_or_tty->print(" (to-space exhausted)");
3720 }
3721 gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec);
3722 g1_policy()->phase_times()->note_gc_end();
3723 g1_policy()->phase_times()->print(pause_time_sec);
3724 g1_policy()->print_detailed_heap_transition();
3725 } else {
3726 if (evacuation_failed()) {
3727 gclog_or_tty->print("--");
3728 }
3729 g1_policy()->print_heap_transition();
3730 gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec);
3731 }
3732 gclog_or_tty->flush();
3733 }
3734
3735 bool
3736 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
3737 assert_at_safepoint(true /* should_be_vm_thread */);
3738 guarantee(!is_gc_active(), "collection is not reentrant");
3739
3740 if (GC_locker::check_active_before_gc()) {
3741 return false;
3742 }
3743
3744 _gc_timer_stw->register_gc_start();
3745
3746 _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start());
3747
3748 SvcGCMarker sgcm(SvcGCMarker::MINOR);
3749 ResourceMark rm;
3750
3751 print_heap_before_gc();
3752 trace_heap_before_gc(_gc_tracer_stw);
3753
3754 verify_region_sets_optional();
3755 verify_dirty_young_regions();
3756
3757 // This call will decide whether this pause is an initial-mark
3758 // pause. If it is, during_initial_mark_pause() will return true
3759 // for the duration of this pause.
3760 g1_policy()->decide_on_conc_mark_initiation();
3761
3762 // We do not allow initial-mark to be piggy-backed on a mixed GC.
3763 assert(!g1_policy()->during_initial_mark_pause() ||
3764 g1_policy()->gcs_are_young(), "sanity");
3765
3766 // We also do not allow mixed GCs during marking.
3767 assert(!mark_in_progress() || g1_policy()->gcs_are_young(), "sanity");
3768
3769 // Record whether this pause is an initial mark. When the current
3770 // thread has completed its logging output and it's safe to signal
3771 // the CM thread, the flag's value in the policy has been reset.
3772 bool should_start_conc_mark = g1_policy()->during_initial_mark_pause();
3773
3774 // Inner scope for scope based logging, timers, and stats collection
3775 {
3776 EvacuationInfo evacuation_info;
3777
3778 if (g1_policy()->during_initial_mark_pause()) {
3779 // We are about to start a marking cycle, so we increment the
3780 // full collection counter.
3781 increment_old_marking_cycles_started();
3782 register_concurrent_cycle_start(_gc_timer_stw->gc_start());
3783 }
3784
3785 _gc_tracer_stw->report_yc_type(yc_type());
3786
3787 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
3788
3789 int active_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
3790 workers()->active_workers() : 1);
3791 double pause_start_sec = os::elapsedTime();
3792 g1_policy()->phase_times()->note_gc_start(active_workers);
3793 log_gc_header();
3794
3795 TraceCollectorStats tcs(g1mm()->incremental_collection_counters());
3796 TraceMemoryManagerStats tms(false /* fullGC */, gc_cause());
3797
3798 // If the secondary_free_list is not empty, append it to the
3799 // free_list. No need to wait for the cleanup operation to finish;
3800 // the region allocation code will check the secondary_free_list
3801 // and wait if necessary. If the G1StressConcRegionFreeing flag is
3802 // set, skip this step so that the region allocation code has to
3803 // get entries from the secondary_free_list.
3804 if (!G1StressConcRegionFreeing) {
3805 append_secondary_free_list_if_not_empty_with_lock();
3806 }
3807
3808 assert(check_young_list_well_formed(), "young list should be well formed");
3809
3810 // Don't dynamically change the number of GC threads this early. A value of
3811 // 0 is used to indicate serial work. When parallel work is done,
3812 // it will be set.
3813
3814 { // Call to jvmpi::post_class_unload_events must occur outside of active GC
3815 IsGCActiveMark x;
3816
3817 gc_prologue(false);
3818 increment_total_collections(false /* full gc */);
3819 increment_gc_time_stamp();
3820
3821 verify_before_gc();
3822
3823 check_bitmaps("GC Start");
3824
3825 COMPILER2_PRESENT(DerivedPointerTable::clear());
3826
3827 // Please see comment in g1CollectedHeap.hpp and
3828 // G1CollectedHeap::ref_processing_init() to see how
3829 // reference processing currently works in G1.
3830
3831 // Enable discovery in the STW reference processor
3832 ref_processor_stw()->enable_discovery(true /*verify_disabled*/,
3833 true /*verify_no_refs*/);
3834
3835 {
3836 // We want to temporarily turn off discovery by the
3837 // CM ref processor, if necessary, and turn it back on
3838 // on again later if we do. Using a scoped
3839 // NoRefDiscovery object will do this.
3840 NoRefDiscovery no_cm_discovery(ref_processor_cm());
3841
3842 // Forget the current alloc region (we might even choose it to be part
3843 // of the collection set!).
3844 release_mutator_alloc_region();
3845
3846 // We should call this after we retire the mutator alloc
3847 // region(s) so that all the ALLOC / RETIRE events are generated
3848 // before the start GC event.
3849 _hr_printer.start_gc(false /* full */, (size_t) total_collections());
3850
3851 // This timing is only used by the ergonomics to handle our pause target.
3852 // It is unclear why this should not include the full pause. We will
3853 // investigate this in CR 7178365.
3854 //
3855 // Preserving the old comment here if that helps the investigation:
3856 //
3857 // The elapsed time induced by the start time below deliberately elides
3858 // the possible verification above.
3859 double sample_start_time_sec = os::elapsedTime();
3860
3861 #if YOUNG_LIST_VERBOSE
3862 gclog_or_tty->print_cr("\nBefore recording pause start.\nYoung_list:");
3863 _young_list->print();
3864 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3865 #endif // YOUNG_LIST_VERBOSE
3866
3867 g1_policy()->record_collection_pause_start(sample_start_time_sec);
3868
3869 double scan_wait_start = os::elapsedTime();
3870 // We have to wait until the CM threads finish scanning the
3871 // root regions as it's the only way to ensure that all the
3872 // objects on them have been correctly scanned before we start
3873 // moving them during the GC.
3874 bool waited = _cm->root_regions()->wait_until_scan_finished();
3875 double wait_time_ms = 0.0;
3876 if (waited) {
3877 double scan_wait_end = os::elapsedTime();
3878 wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
3879 }
3880 g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms);
3881
3882 #if YOUNG_LIST_VERBOSE
3883 gclog_or_tty->print_cr("\nAfter recording pause start.\nYoung_list:");
3884 _young_list->print();
3885 #endif // YOUNG_LIST_VERBOSE
3886
3887 if (g1_policy()->during_initial_mark_pause()) {
3888 concurrent_mark()->checkpointRootsInitialPre();
3889 }
3890
3891 #if YOUNG_LIST_VERBOSE
3892 gclog_or_tty->print_cr("\nBefore choosing collection set.\nYoung_list:");
3893 _young_list->print();
3894 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3895 #endif // YOUNG_LIST_VERBOSE
3896
3897 g1_policy()->finalize_cset(target_pause_time_ms, evacuation_info);
3898
3899 register_humongous_regions_with_in_cset_fast_test();
3900
3901 _cm->note_start_of_gc();
3902 // We should not verify the per-thread SATB buffers given that
3903 // we have not filtered them yet (we'll do so during the
3904 // GC). We also call this after finalize_cset() to
3905 // ensure that the CSet has been finalized.
3906 _cm->verify_no_cset_oops(true /* verify_stacks */,
3907 true /* verify_enqueued_buffers */,
3908 false /* verify_thread_buffers */,
3909 true /* verify_fingers */);
3910
3911 if (_hr_printer.is_active()) {
3912 HeapRegion* hr = g1_policy()->collection_set();
3913 while (hr != NULL) {
3914 G1HRPrinter::RegionType type;
3915 if (!hr->is_young()) {
3916 type = G1HRPrinter::Old;
3917 } else if (hr->is_survivor()) {
3918 type = G1HRPrinter::Survivor;
3919 } else {
3920 type = G1HRPrinter::Eden;
3921 }
3922 _hr_printer.cset(hr);
3923 hr = hr->next_in_collection_set();
3924 }
3925 }
3926
3927 #ifdef ASSERT
3928 VerifyCSetClosure cl;
3929 collection_set_iterate(&cl);
3930 #endif // ASSERT
3931
3932 setup_surviving_young_words();
3933
3934 // Initialize the GC alloc regions.
3935 init_gc_alloc_regions(evacuation_info);
3936
3937 // Actually do the work...
3938 evacuate_collection_set(evacuation_info);
3939
3940 // We do this to mainly verify the per-thread SATB buffers
3941 // (which have been filtered by now) since we didn't verify
3942 // them earlier. No point in re-checking the stacks / enqueued
3943 // buffers given that the CSet has not changed since last time
3944 // we checked.
3945 _cm->verify_no_cset_oops(false /* verify_stacks */,
3946 false /* verify_enqueued_buffers */,
3947 true /* verify_thread_buffers */,
3948 true /* verify_fingers */);
3949
3950 free_collection_set(g1_policy()->collection_set(), evacuation_info);
3951
3952 eagerly_reclaim_humongous_regions();
3953
3954 g1_policy()->clear_collection_set();
3955
3956 cleanup_surviving_young_words();
3957
3958 // Start a new incremental collection set for the next pause.
3959 g1_policy()->start_incremental_cset_building();
3960
3961 clear_cset_fast_test();
3962
3963 _young_list->reset_sampled_info();
3964
3965 // Don't check the whole heap at this point as the
3966 // GC alloc regions from this pause have been tagged
3967 // as survivors and moved on to the survivor list.
3968 // Survivor regions will fail the !is_young() check.
3969 assert(check_young_list_empty(false /* check_heap */),
3970 "young list should be empty");
3971
3972 #if YOUNG_LIST_VERBOSE
3973 gclog_or_tty->print_cr("Before recording survivors.\nYoung List:");
3974 _young_list->print();
3975 #endif // YOUNG_LIST_VERBOSE
3976
3977 g1_policy()->record_survivor_regions(_young_list->survivor_length(),
3978 _young_list->first_survivor_region(),
3979 _young_list->last_survivor_region());
3980
3981 _young_list->reset_auxilary_lists();
3982
3983 if (evacuation_failed()) {
3984 _summary_bytes_used = recalculate_used();
3985 uint n_queues = MAX2((int)ParallelGCThreads, 1);
3986 for (uint i = 0; i < n_queues; i++) {
3987 if (_evacuation_failed_info_array[i].has_failed()) {
3988 _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]);
3989 }
3990 }
3991 } else {
3992 // The "used" of the the collection set have already been subtracted
3993 // when they were freed. Add in the bytes evacuated.
3994 _summary_bytes_used += g1_policy()->bytes_copied_during_gc();
3995 }
3996
3997 if (g1_policy()->during_initial_mark_pause()) {
3998 // We have to do this before we notify the CM threads that
3999 // they can start working to make sure that all the
4000 // appropriate initialization is done on the CM object.
4001 concurrent_mark()->checkpointRootsInitialPost();
4002 set_marking_started();
4003 // Note that we don't actually trigger the CM thread at
4004 // this point. We do that later when we're sure that
4005 // the current thread has completed its logging output.
4006 }
4007
4008 allocate_dummy_regions();
4009
4010 #if YOUNG_LIST_VERBOSE
4011 gclog_or_tty->print_cr("\nEnd of the pause.\nYoung_list:");
4012 _young_list->print();
4013 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
4014 #endif // YOUNG_LIST_VERBOSE
4015
4016 init_mutator_alloc_region();
4017
4018 {
4019 size_t expand_bytes = g1_policy()->expansion_amount();
4020 if (expand_bytes > 0) {
4021 size_t bytes_before = capacity();
4022 // No need for an ergo verbose message here,
4023 // expansion_amount() does this when it returns a value > 0.
4024 if (!expand(expand_bytes)) {
4025 // We failed to expand the heap. Cannot do anything about it.
4026 }
4027 }
4028 }
4029
4030 // We redo the verification but now wrt to the new CSet which
4031 // has just got initialized after the previous CSet was freed.
4032 _cm->verify_no_cset_oops(true /* verify_stacks */,
4033 true /* verify_enqueued_buffers */,
4034 true /* verify_thread_buffers */,
4035 true /* verify_fingers */);
4036 _cm->note_end_of_gc();
4037
4038 // This timing is only used by the ergonomics to handle our pause target.
4039 // It is unclear why this should not include the full pause. We will
4040 // investigate this in CR 7178365.
4041 double sample_end_time_sec = os::elapsedTime();
4042 double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
4043 g1_policy()->record_collection_pause_end(pause_time_ms, evacuation_info);
4044
4045 MemoryService::track_memory_usage();
4046
4047 // In prepare_for_verify() below we'll need to scan the deferred
4048 // update buffers to bring the RSets up-to-date if
4049 // G1HRRSFlushLogBuffersOnVerify has been set. While scanning
4050 // the update buffers we'll probably need to scan cards on the
4051 // regions we just allocated to (i.e., the GC alloc
4052 // regions). However, during the last GC we called
4053 // set_saved_mark() on all the GC alloc regions, so card
4054 // scanning might skip the [saved_mark_word()...top()] area of
4055 // those regions (i.e., the area we allocated objects into
4056 // during the last GC). But it shouldn't. Given that
4057 // saved_mark_word() is conditional on whether the GC time stamp
4058 // on the region is current or not, by incrementing the GC time
4059 // stamp here we invalidate all the GC time stamps on all the
4060 // regions and saved_mark_word() will simply return top() for
4061 // all the regions. This is a nicer way of ensuring this rather
4062 // than iterating over the regions and fixing them. In fact, the
4063 // GC time stamp increment here also ensures that
4064 // saved_mark_word() will return top() between pauses, i.e.,
4065 // during concurrent refinement. So we don't need the
4066 // is_gc_active() check to decided which top to use when
4067 // scanning cards (see CR 7039627).
4068 increment_gc_time_stamp();
4069
4070 verify_after_gc();
4071 check_bitmaps("GC End");
4072
4073 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
4074 ref_processor_stw()->verify_no_references_recorded();
4075
4076 // CM reference discovery will be re-enabled if necessary.
4077 }
4078
4079 // We should do this after we potentially expand the heap so
4080 // that all the COMMIT events are generated before the end GC
4081 // event, and after we retire the GC alloc regions so that all
4082 // RETIRE events are generated before the end GC event.
4083 _hr_printer.end_gc(false /* full */, (size_t) total_collections());
4084
4085 #ifdef TRACESPINNING
4086 ParallelTaskTerminator::print_termination_counts();
4087 #endif
4088
4089 gc_epilogue(false);
4090 }
4091
4092 // Print the remainder of the GC log output.
4093 log_gc_footer(os::elapsedTime() - pause_start_sec);
4094
4095 // It is not yet to safe to tell the concurrent mark to
4096 // start as we have some optional output below. We don't want the
4097 // output from the concurrent mark thread interfering with this
4098 // logging output either.
4099
4100 _hrm.verify_optional();
4101 verify_region_sets_optional();
4102
4103 TASKQUEUE_STATS_ONLY(if (ParallelGCVerbose) print_taskqueue_stats());
4104 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
4105
4106 print_heap_after_gc();
4107 trace_heap_after_gc(_gc_tracer_stw);
4108
4109 // We must call G1MonitoringSupport::update_sizes() in the same scoping level
4110 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
4111 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
4112 // before any GC notifications are raised.
4113 g1mm()->update_sizes();
4114
4115 _gc_tracer_stw->report_evacuation_info(&evacuation_info);
4116 _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold());
4117 _gc_timer_stw->register_gc_end();
4118 _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions());
4119 }
4120 // It should now be safe to tell the concurrent mark thread to start
4121 // without its logging output interfering with the logging output
4122 // that came from the pause.
4123
4124 if (should_start_conc_mark) {
4125 // CAUTION: after the doConcurrentMark() call below,
4126 // the concurrent marking thread(s) could be running
4127 // concurrently with us. Make sure that anything after
4128 // this point does not assume that we are the only GC thread
4129 // running. Note: of course, the actual marking work will
4130 // not start until the safepoint itself is released in
4131 // SuspendibleThreadSet::desynchronize().
4132 doConcurrentMark();
4133 }
4134
4135 return true;
4136 }
4137
4138 size_t G1CollectedHeap::desired_plab_sz(GCAllocPurpose purpose)
4139 {
4140 size_t gclab_word_size;
4141 switch (purpose) {
4142 case GCAllocForSurvived:
4143 gclab_word_size = _survivor_plab_stats.desired_plab_sz();
4144 break;
4145 case GCAllocForTenured:
4146 gclab_word_size = _old_plab_stats.desired_plab_sz();
4147 break;
4148 default:
4149 assert(false, "unknown GCAllocPurpose");
4150 gclab_word_size = _old_plab_stats.desired_plab_sz();
4151 break;
4152 }
4153
4154 // Prevent humongous PLAB sizes for two reasons:
4155 // * PLABs are allocated using a similar paths as oops, but should
4156 // never be in a humongous region
4157 // * Allowing humongous PLABs needlessly churns the region free lists
4158 return MIN2(_humongous_object_threshold_in_words, gclab_word_size);
4159 }
4160
4161 void G1CollectedHeap::init_mutator_alloc_region() {
4162 assert(_mutator_alloc_region.get() == NULL, "pre-condition");
4163 _mutator_alloc_region.init();
4164 }
4165
4166 void G1CollectedHeap::release_mutator_alloc_region() {
4167 _mutator_alloc_region.release();
4168 assert(_mutator_alloc_region.get() == NULL, "post-condition");
4169 }
4170
4171 void G1CollectedHeap::use_retained_old_gc_alloc_region(EvacuationInfo& evacuation_info) {
4172 HeapRegion* retained_region = _retained_old_gc_alloc_region;
4173 _retained_old_gc_alloc_region = NULL;
4174
4175 // We will discard the current GC alloc region if:
4176 // a) it's in the collection set (it can happen!),
4177 // b) it's already full (no point in using it),
4178 // c) it's empty (this means that it was emptied during
4179 // a cleanup and it should be on the free list now), or
4180 // d) it's humongous (this means that it was emptied
4181 // during a cleanup and was added to the free list, but
4182 // has been subsequently used to allocate a humongous
4183 // object that may be less than the region size).
4184 if (retained_region != NULL &&
4185 !retained_region->in_collection_set() &&
4186 !(retained_region->top() == retained_region->end()) &&
4187 !retained_region->is_empty() &&
4188 !retained_region->isHumongous()) {
4189 retained_region->record_top_and_timestamp();
4190 // The retained region was added to the old region set when it was
4191 // retired. We have to remove it now, since we don't allow regions
4192 // we allocate to in the region sets. We'll re-add it later, when
4193 // it's retired again.
4194 _old_set.remove(retained_region);
4195 bool during_im = g1_policy()->during_initial_mark_pause();
4196 retained_region->note_start_of_copying(during_im);
4197 _old_gc_alloc_region.set(retained_region);
4198 _hr_printer.reuse(retained_region);
4199 evacuation_info.set_alloc_regions_used_before(retained_region->used());
4200 }
4201 }
4202
4203 void G1CollectedHeap::init_gc_alloc_regions(EvacuationInfo& evacuation_info) {
4204 assert_at_safepoint(true /* should_be_vm_thread */);
4205
4206 _survivor_gc_alloc_region.init();
4207 _old_gc_alloc_region.init();
4208
4209 use_retained_old_gc_alloc_region(evacuation_info);
4210 }
4211
4212 void G1CollectedHeap::release_gc_alloc_regions(uint no_of_gc_workers, EvacuationInfo& evacuation_info) {
4213 evacuation_info.set_allocation_regions(_survivor_gc_alloc_region.count() +
4214 _old_gc_alloc_region.count());
4215 _survivor_gc_alloc_region.release();
4216 // If we have an old GC alloc region to release, we'll save it in
4217 // _retained_old_gc_alloc_region. If we don't
4218 // _retained_old_gc_alloc_region will become NULL. This is what we
4219 // want either way so no reason to check explicitly for either
4220 // condition.
4221 _retained_old_gc_alloc_region = _old_gc_alloc_region.release();
4222
4223 if (ResizePLAB) {
4224 _survivor_plab_stats.adjust_desired_plab_sz(no_of_gc_workers);
4225 _old_plab_stats.adjust_desired_plab_sz(no_of_gc_workers);
4226 }
4227 }
4228
4229 void G1CollectedHeap::abandon_gc_alloc_regions() {
4230 assert(_survivor_gc_alloc_region.get() == NULL, "pre-condition");
4231 assert(_old_gc_alloc_region.get() == NULL, "pre-condition");
4232 _retained_old_gc_alloc_region = NULL;
4233 }
4234
4235 void G1CollectedHeap::init_for_evac_failure(OopsInHeapRegionClosure* cl) {
4236 _drain_in_progress = false;
4237 set_evac_failure_closure(cl);
4238 _evac_failure_scan_stack = new (ResourceObj::C_HEAP, mtGC) GrowableArray<oop>(40, true);
4239 }
4240
4241 void G1CollectedHeap::finalize_for_evac_failure() {
4242 assert(_evac_failure_scan_stack != NULL &&
4243 _evac_failure_scan_stack->length() == 0,
4244 "Postcondition");
4245 assert(!_drain_in_progress, "Postcondition");
4246 delete _evac_failure_scan_stack;
4247 _evac_failure_scan_stack = NULL;
4248 }
4249
4250 void G1CollectedHeap::remove_self_forwarding_pointers() {
4251 double remove_self_forwards_start = os::elapsedTime();
4252
4253 HeapRegionClaimer hrclaimer;
4254 G1ParRemoveSelfForwardPtrsTask rsfp_task(this, &hrclaimer);
4255
4256 if (G1CollectedHeap::use_parallel_gc_threads()) {
4257 set_par_threads();
4258 hrclaimer.initialize(workers()->active_workers());
4259 workers()->run_task(&rsfp_task);
4260 set_par_threads(0);
4261 } else {
4262 rsfp_task.work(0);
4263 }
4264
4265 // Now restore saved marks, if any.
4266 assert(_objs_with_preserved_marks.size() ==
4267 _preserved_marks_of_objs.size(), "Both or none.");
4268 while (!_objs_with_preserved_marks.is_empty()) {
4269 oop obj = _objs_with_preserved_marks.pop();
4270 markOop m = _preserved_marks_of_objs.pop();
4271 obj->set_mark(m);
4272 }
4273 _objs_with_preserved_marks.clear(true);
4274 _preserved_marks_of_objs.clear(true);
4275
4276 g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0);
4277 }
4278
4279 void G1CollectedHeap::push_on_evac_failure_scan_stack(oop obj) {
4280 _evac_failure_scan_stack->push(obj);
4281 }
4282
4283 void G1CollectedHeap::drain_evac_failure_scan_stack() {
4284 assert(_evac_failure_scan_stack != NULL, "precondition");
4285
4286 while (_evac_failure_scan_stack->length() > 0) {
4287 oop obj = _evac_failure_scan_stack->pop();
4288 _evac_failure_closure->set_region(heap_region_containing(obj));
4289 obj->oop_iterate_backwards(_evac_failure_closure);
4290 }
4291 }
4292
4293 oop
4294 G1CollectedHeap::handle_evacuation_failure_par(G1ParScanThreadState* _par_scan_state,
4295 oop old) {
4296 assert(obj_in_cs(old),
4297 err_msg("obj: "PTR_FORMAT" should still be in the CSet",
4298 (HeapWord*) old));
4299 markOop m = old->mark();
4300 oop forward_ptr = old->forward_to_atomic(old);
4301 if (forward_ptr == NULL) {
4302 // Forward-to-self succeeded.
4303 assert(_par_scan_state != NULL, "par scan state");
4304 OopsInHeapRegionClosure* cl = _par_scan_state->evac_failure_closure();
4305 uint queue_num = _par_scan_state->queue_num();
4306
4307 _evacuation_failed = true;
4308 _evacuation_failed_info_array[queue_num].register_copy_failure(old->size());
4309 if (_evac_failure_closure != cl) {
4310 MutexLockerEx x(EvacFailureStack_lock, Mutex::_no_safepoint_check_flag);
4311 assert(!_drain_in_progress,
4312 "Should only be true while someone holds the lock.");
4313 // Set the global evac-failure closure to the current thread's.
4314 assert(_evac_failure_closure == NULL, "Or locking has failed.");
4315 set_evac_failure_closure(cl);
4316 // Now do the common part.
4317 handle_evacuation_failure_common(old, m);
4318 // Reset to NULL.
4319 set_evac_failure_closure(NULL);
4320 } else {
4321 // The lock is already held, and this is recursive.
4322 assert(_drain_in_progress, "This should only be the recursive case.");
4323 handle_evacuation_failure_common(old, m);
4324 }
4325 return old;
4326 } else {
4327 // Forward-to-self failed. Either someone else managed to allocate
4328 // space for this object (old != forward_ptr) or they beat us in
4329 // self-forwarding it (old == forward_ptr).
4330 assert(old == forward_ptr || !obj_in_cs(forward_ptr),
4331 err_msg("obj: "PTR_FORMAT" forwarded to: "PTR_FORMAT" "
4332 "should not be in the CSet",
4333 (HeapWord*) old, (HeapWord*) forward_ptr));
4334 return forward_ptr;
4335 }
4336 }
4337
4338 void G1CollectedHeap::handle_evacuation_failure_common(oop old, markOop m) {
4339 preserve_mark_if_necessary(old, m);
4340
4341 HeapRegion* r = heap_region_containing(old);
4342 if (!r->evacuation_failed()) {
4343 r->set_evacuation_failed(true);
4344 _hr_printer.evac_failure(r);
4345 }
4346
4347 push_on_evac_failure_scan_stack(old);
4348
4349 if (!_drain_in_progress) {
4350 // prevent recursion in copy_to_survivor_space()
4351 _drain_in_progress = true;
4352 drain_evac_failure_scan_stack();
4353 _drain_in_progress = false;
4354 }
4355 }
4356
4357 void G1CollectedHeap::preserve_mark_if_necessary(oop obj, markOop m) {
4358 assert(evacuation_failed(), "Oversaving!");
4359 // We want to call the "for_promotion_failure" version only in the
4360 // case of a promotion failure.
4361 if (m->must_be_preserved_for_promotion_failure(obj)) {
4362 _objs_with_preserved_marks.push(obj);
4363 _preserved_marks_of_objs.push(m);
4364 }
4365 }
4366
4367 HeapWord* G1CollectedHeap::par_allocate_during_gc(GCAllocPurpose purpose,
4368 size_t word_size) {
4369 if (purpose == GCAllocForSurvived) {
4370 HeapWord* result = survivor_attempt_allocation(word_size);
4371 if (result != NULL) {
4372 return result;
4373 } else {
4374 // Let's try to allocate in the old gen in case we can fit the
4375 // object there.
4376 return old_attempt_allocation(word_size);
4377 }
4378 } else {
4379 assert(purpose == GCAllocForTenured, "sanity");
4380 HeapWord* result = old_attempt_allocation(word_size);
4381 if (result != NULL) {
4382 return result;
4383 } else {
4384 // Let's try to allocate in the survivors in case we can fit the
4385 // object there.
4386 return survivor_attempt_allocation(word_size);
4387 }
4388 }
4389
4390 ShouldNotReachHere();
4391 // Trying to keep some compilers happy.
4392 return NULL;
4393 }
4394
4395 G1ParGCAllocBuffer::G1ParGCAllocBuffer(size_t gclab_word_size) :
4396 ParGCAllocBuffer(gclab_word_size), _retired(true) { }
4397
4398 void G1ParCopyHelper::mark_object(oop obj) {
4399 assert(!_g1->heap_region_containing(obj)->in_collection_set(), "should not mark objects in the CSet");
4400
4401 // We know that the object is not moving so it's safe to read its size.
4402 _cm->grayRoot(obj, (size_t) obj->size(), _worker_id);
4403 }
4404
4405 void G1ParCopyHelper::mark_forwarded_object(oop from_obj, oop to_obj) {
4406 assert(from_obj->is_forwarded(), "from obj should be forwarded");
4407 assert(from_obj->forwardee() == to_obj, "to obj should be the forwardee");
4408 assert(from_obj != to_obj, "should not be self-forwarded");
4409
4410 assert(_g1->heap_region_containing(from_obj)->in_collection_set(), "from obj should be in the CSet");
4411 assert(!_g1->heap_region_containing(to_obj)->in_collection_set(), "should not mark objects in the CSet");
4412
4413 // The object might be in the process of being copied by another
4414 // worker so we cannot trust that its to-space image is
4415 // well-formed. So we have to read its size from its from-space
4416 // image which we know should not be changing.
4417 _cm->grayRoot(to_obj, (size_t) from_obj->size(), _worker_id);
4418 }
4419
4420 template <class T>
4421 void G1ParCopyHelper::do_klass_barrier(T* p, oop new_obj) {
4422 if (_g1->heap_region_containing_raw(new_obj)->is_young()) {
4423 _scanned_klass->record_modified_oops();
4424 }
4425 }
4426
4427 template <G1Barrier barrier, G1Mark do_mark_object>
4428 template <class T>
4429 void G1ParCopyClosure<barrier, do_mark_object>::do_oop_work(T* p) {
4430 T heap_oop = oopDesc::load_heap_oop(p);
4431
4432 if (oopDesc::is_null(heap_oop)) {
4433 return;
4434 }
4435
4436 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
4437
4438 assert(_worker_id == _par_scan_state->queue_num(), "sanity");
4439
4440 G1CollectedHeap::in_cset_state_t state = _g1->in_cset_state(obj);
4441
4442 if (state == G1CollectedHeap::InCSet) {
4443 oop forwardee;
4444 if (obj->is_forwarded()) {
4445 forwardee = obj->forwardee();
4446 } else {
4447 forwardee = _par_scan_state->copy_to_survivor_space(obj);
4448 }
4449 assert(forwardee != NULL, "forwardee should not be NULL");
4450 oopDesc::encode_store_heap_oop(p, forwardee);
4451 if (do_mark_object != G1MarkNone && forwardee != obj) {
4452 // If the object is self-forwarded we don't need to explicitly
4453 // mark it, the evacuation failure protocol will do so.
4454 mark_forwarded_object(obj, forwardee);
4455 }
4456
4457 if (barrier == G1BarrierKlass) {
4458 do_klass_barrier(p, forwardee);
4459 }
4460 } else {
4461 if (state == G1CollectedHeap::IsHumongous) {
4462 _g1->set_humongous_is_live(obj);
4463 }
4464 // The object is not in collection set. If we're a root scanning
4465 // closure during an initial mark pause then attempt to mark the object.
4466 if (do_mark_object == G1MarkFromRoot) {
4467 mark_object(obj);
4468 }
4469 }
4470
4471 if (barrier == G1BarrierEvac) {
4472 _par_scan_state->update_rs(_from, p, _worker_id);
4473 }
4474 }
4475
4476 template void G1ParCopyClosure<G1BarrierEvac, G1MarkNone>::do_oop_work(oop* p);
4477 template void G1ParCopyClosure<G1BarrierEvac, G1MarkNone>::do_oop_work(narrowOop* p);
4478
4479 class G1ParEvacuateFollowersClosure : public VoidClosure {
4480 protected:
4481 G1CollectedHeap* _g1h;
4482 G1ParScanThreadState* _par_scan_state;
4483 RefToScanQueueSet* _queues;
4484 ParallelTaskTerminator* _terminator;
4485
4486 G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
4487 RefToScanQueueSet* queues() { return _queues; }
4488 ParallelTaskTerminator* terminator() { return _terminator; }
4489
4490 public:
4491 G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h,
4492 G1ParScanThreadState* par_scan_state,
4493 RefToScanQueueSet* queues,
4494 ParallelTaskTerminator* terminator)
4495 : _g1h(g1h), _par_scan_state(par_scan_state),
4496 _queues(queues), _terminator(terminator) {}
4497
4498 void do_void();
4499
4500 private:
4501 inline bool offer_termination();
4502 };
4503
4504 bool G1ParEvacuateFollowersClosure::offer_termination() {
4505 G1ParScanThreadState* const pss = par_scan_state();
4506 pss->start_term_time();
4507 const bool res = terminator()->offer_termination();
4508 pss->end_term_time();
4509 return res;
4510 }
4511
4512 void G1ParEvacuateFollowersClosure::do_void() {
4513 G1ParScanThreadState* const pss = par_scan_state();
4514 pss->trim_queue();
4515 do {
4516 pss->steal_and_trim_queue(queues());
4517 } while (!offer_termination());
4518 }
4519
4520 class G1KlassScanClosure : public KlassClosure {
4521 G1ParCopyHelper* _closure;
4522 bool _process_only_dirty;
4523 int _count;
4524 public:
4525 G1KlassScanClosure(G1ParCopyHelper* closure, bool process_only_dirty)
4526 : _process_only_dirty(process_only_dirty), _closure(closure), _count(0) {}
4527 void do_klass(Klass* klass) {
4528 // If the klass has not been dirtied we know that there's
4529 // no references into the young gen and we can skip it.
4530 if (!_process_only_dirty || klass->has_modified_oops()) {
4531 // Clean the klass since we're going to scavenge all the metadata.
4532 klass->clear_modified_oops();
4533
4534 // Tell the closure that this klass is the Klass to scavenge
4535 // and is the one to dirty if oops are left pointing into the young gen.
4536 _closure->set_scanned_klass(klass);
4537
4538 klass->oops_do(_closure);
4539
4540 _closure->set_scanned_klass(NULL);
4541 }
4542 _count++;
4543 }
4544 };
4545
4546 class G1CodeBlobClosure : public CodeBlobClosure {
4547 class HeapRegionGatheringOopClosure : public OopClosure {
4548 G1CollectedHeap* _g1h;
4549 OopClosure* _work;
4550 nmethod* _nm;
4551
4552 template <typename T>
4553 void do_oop_work(T* p) {
4554 _work->do_oop(p);
4555 T oop_or_narrowoop = oopDesc::load_heap_oop(p);
4556 if (!oopDesc::is_null(oop_or_narrowoop)) {
4557 oop o = oopDesc::decode_heap_oop_not_null(oop_or_narrowoop);
4558 HeapRegion* hr = _g1h->heap_region_containing_raw(o);
4559 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");
4560 hr->add_strong_code_root(_nm);
4561 }
4562 }
4563
4564 public:
4565 HeapRegionGatheringOopClosure(OopClosure* oc) : _g1h(G1CollectedHeap::heap()), _work(oc), _nm(NULL) {}
4566
4567 void do_oop(oop* o) {
4568 do_oop_work(o);
4569 }
4570
4571 void do_oop(narrowOop* o) {
4572 do_oop_work(o);
4573 }
4574
4575 void set_nm(nmethod* nm) {
4576 _nm = nm;
4577 }
4578 };
4579
4580 HeapRegionGatheringOopClosure _oc;
4581 public:
4582 G1CodeBlobClosure(OopClosure* oc) : _oc(oc) {}
4583
4584 void do_code_blob(CodeBlob* cb) {
4585 nmethod* nm = cb->as_nmethod_or_null();
4586 if (nm != NULL) {
4587 if (!nm->test_set_oops_do_mark()) {
4588 _oc.set_nm(nm);
4589 nm->oops_do(&_oc);
4590 nm->fix_oop_relocations();
4591 }
4592 }
4593 }
4594 };
4595
4596 class G1ParTask : public AbstractGangTask {
4597 protected:
4598 G1CollectedHeap* _g1h;
4599 RefToScanQueueSet *_queues;
4600 ParallelTaskTerminator _terminator;
4601 uint _n_workers;
4602
4603 Mutex _stats_lock;
4604 Mutex* stats_lock() { return &_stats_lock; }
4605
4606 public:
4607 G1ParTask(G1CollectedHeap* g1h, RefToScanQueueSet *task_queues)
4608 : AbstractGangTask("G1 collection"),
4609 _g1h(g1h),
4610 _queues(task_queues),
4611 _terminator(0, _queues),
4612 _stats_lock(Mutex::leaf, "parallel G1 stats lock", true)
4613 {}
4614
4615 RefToScanQueueSet* queues() { return _queues; }
4616
4617 RefToScanQueue *work_queue(int i) {
4618 return queues()->queue(i);
4619 }
4620
4621 ParallelTaskTerminator* terminator() { return &_terminator; }
4622
4623 virtual void set_for_termination(int active_workers) {
4624 // This task calls set_n_termination() in par_non_clean_card_iterate_work()
4625 // in the young space (_par_seq_tasks) in the G1 heap
4626 // for SequentialSubTasksDone.
4627 // This task also uses SubTasksDone in SharedHeap and G1CollectedHeap
4628 // both of which need setting by set_n_termination().
4629 _g1h->SharedHeap::set_n_termination(active_workers);
4630 _g1h->set_n_termination(active_workers);
4631 terminator()->reset_for_reuse(active_workers);
4632 _n_workers = active_workers;
4633 }
4634
4635 // Helps out with CLD processing.
4636 //
4637 // During InitialMark we need to:
4638 // 1) Scavenge all CLDs for the young GC.
4639 // 2) Mark all objects directly reachable from strong CLDs.
4640 template <G1Mark do_mark_object>
4641 class G1CLDClosure : public CLDClosure {
4642 G1ParCopyClosure<G1BarrierNone, do_mark_object>* _oop_closure;
4643 G1ParCopyClosure<G1BarrierKlass, do_mark_object> _oop_in_klass_closure;
4644 G1KlassScanClosure _klass_in_cld_closure;
4645 bool _claim;
4646
4647 public:
4648 G1CLDClosure(G1ParCopyClosure<G1BarrierNone, do_mark_object>* oop_closure,
4649 bool only_young, bool claim)
4650 : _oop_closure(oop_closure),
4651 _oop_in_klass_closure(oop_closure->g1(),
4652 oop_closure->pss(),
4653 oop_closure->rp()),
4654 _klass_in_cld_closure(&_oop_in_klass_closure, only_young),
4655 _claim(claim) {
4656
4657 }
4658
4659 void do_cld(ClassLoaderData* cld) {
4660 cld->oops_do(_oop_closure, &_klass_in_cld_closure, _claim);
4661 }
4662 };
4663
4664 void work(uint worker_id) {
4665 if (worker_id >= _n_workers) return; // no work needed this round
4666
4667 double start_time_ms = os::elapsedTime() * 1000.0;
4668 _g1h->g1_policy()->phase_times()->record_gc_worker_start_time(worker_id, start_time_ms);
4669
4670 {
4671 ResourceMark rm;
4672 HandleMark hm;
4673
4674 ReferenceProcessor* rp = _g1h->ref_processor_stw();
4675
4676 G1ParScanThreadState pss(_g1h, worker_id, rp);
4677 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, rp);
4678
4679 pss.set_evac_failure_closure(&evac_failure_cl);
4680
4681 bool only_young = _g1h->g1_policy()->gcs_are_young();
4682
4683 // Non-IM young GC.
4684 G1ParCopyClosure<G1BarrierNone, G1MarkNone> scan_only_root_cl(_g1h, &pss, rp);
4685 G1CLDClosure<G1MarkNone> scan_only_cld_cl(&scan_only_root_cl,
4686 only_young, // Only process dirty klasses.
4687 false); // No need to claim CLDs.
4688 // IM young GC.
4689 // Strong roots closures.
4690 G1ParCopyClosure<G1BarrierNone, G1MarkFromRoot> scan_mark_root_cl(_g1h, &pss, rp);
4691 G1CLDClosure<G1MarkFromRoot> scan_mark_cld_cl(&scan_mark_root_cl,
4692 false, // Process all klasses.
4693 true); // Need to claim CLDs.
4694 // Weak roots closures.
4695 G1ParCopyClosure<G1BarrierNone, G1MarkPromotedFromRoot> scan_mark_weak_root_cl(_g1h, &pss, rp);
4696 G1CLDClosure<G1MarkPromotedFromRoot> scan_mark_weak_cld_cl(&scan_mark_weak_root_cl,
4697 false, // Process all klasses.
4698 true); // Need to claim CLDs.
4699
4700 G1CodeBlobClosure scan_only_code_cl(&scan_only_root_cl);
4701 G1CodeBlobClosure scan_mark_code_cl(&scan_mark_root_cl);
4702 // IM Weak code roots are handled later.
4703
4704 OopClosure* strong_root_cl;
4705 OopClosure* weak_root_cl;
4706 CLDClosure* strong_cld_cl;
4707 CLDClosure* weak_cld_cl;
4708 CodeBlobClosure* strong_code_cl;
4709
4710 if (_g1h->g1_policy()->during_initial_mark_pause()) {
4711 // We also need to mark copied objects.
4712 strong_root_cl = &scan_mark_root_cl;
4713 strong_cld_cl = &scan_mark_cld_cl;
4714 strong_code_cl = &scan_mark_code_cl;
4715 if (ClassUnloadingWithConcurrentMark) {
4716 weak_root_cl = &scan_mark_weak_root_cl;
4717 weak_cld_cl = &scan_mark_weak_cld_cl;
4718 } else {
4719 weak_root_cl = &scan_mark_root_cl;
4720 weak_cld_cl = &scan_mark_cld_cl;
4721 }
4722 } else {
4723 strong_root_cl = &scan_only_root_cl;
4724 weak_root_cl = &scan_only_root_cl;
4725 strong_cld_cl = &scan_only_cld_cl;
4726 weak_cld_cl = &scan_only_cld_cl;
4727 strong_code_cl = &scan_only_code_cl;
4728 }
4729
4730
4731 G1ParPushHeapRSClosure push_heap_rs_cl(_g1h, &pss);
4732
4733 pss.start_strong_roots();
4734 _g1h->g1_process_roots(strong_root_cl,
4735 weak_root_cl,
4736 &push_heap_rs_cl,
4737 strong_cld_cl,
4738 weak_cld_cl,
4739 strong_code_cl,
4740 worker_id);
4741
4742 pss.end_strong_roots();
4743
4744 {
4745 double start = os::elapsedTime();
4746 G1ParEvacuateFollowersClosure evac(_g1h, &pss, _queues, &_terminator);
4747 evac.do_void();
4748 double elapsed_ms = (os::elapsedTime()-start)*1000.0;
4749 double term_ms = pss.term_time()*1000.0;
4750 _g1h->g1_policy()->phase_times()->add_obj_copy_time(worker_id, elapsed_ms-term_ms);
4751 _g1h->g1_policy()->phase_times()->record_termination(worker_id, term_ms, pss.term_attempts());
4752 }
4753 _g1h->g1_policy()->record_thread_age_table(pss.age_table());
4754 _g1h->update_surviving_young_words(pss.surviving_young_words()+1);
4755
4756 if (ParallelGCVerbose) {
4757 MutexLocker x(stats_lock());
4758 pss.print_termination_stats(worker_id);
4759 }
4760
4761 assert(pss.queue_is_empty(), "should be empty");
4762
4763 // Close the inner scope so that the ResourceMark and HandleMark
4764 // destructors are executed here and are included as part of the
4765 // "GC Worker Time".
4766 }
4767
4768 double end_time_ms = os::elapsedTime() * 1000.0;
4769 _g1h->g1_policy()->phase_times()->record_gc_worker_end_time(worker_id, end_time_ms);
4770 }
4771 };
4772
4773 // *** Common G1 Evacuation Stuff
4774
4775 // This method is run in a GC worker.
4776
4777 void
4778 G1CollectedHeap::
4779 g1_process_roots(OopClosure* scan_non_heap_roots,
4780 OopClosure* scan_non_heap_weak_roots,
4781 OopsInHeapRegionClosure* scan_rs,
4782 CLDClosure* scan_strong_clds,
4783 CLDClosure* scan_weak_clds,
4784 CodeBlobClosure* scan_strong_code,
4785 uint worker_i) {
4786
4787 // First scan the shared roots.
4788 double ext_roots_start = os::elapsedTime();
4789 double closure_app_time_sec = 0.0;
4790
4791 bool during_im = _g1h->g1_policy()->during_initial_mark_pause();
4792 bool trace_metadata = during_im && ClassUnloadingWithConcurrentMark;
4793
4794 BufferingOopClosure buf_scan_non_heap_roots(scan_non_heap_roots);
4795 BufferingOopClosure buf_scan_non_heap_weak_roots(scan_non_heap_weak_roots);
4796
4797 process_roots(false, // no scoping; this is parallel code
4798 SharedHeap::SO_None,
4799 &buf_scan_non_heap_roots,
4800 &buf_scan_non_heap_weak_roots,
4801 scan_strong_clds,
4802 // Unloading Initial Marks handle the weak CLDs separately.
4803 (trace_metadata ? NULL : scan_weak_clds),
4804 scan_strong_code);
4805
4806 // Now the CM ref_processor roots.
4807 if (!_process_strong_tasks->is_task_claimed(G1H_PS_refProcessor_oops_do)) {
4808 // We need to treat the discovered reference lists of the
4809 // concurrent mark ref processor as roots and keep entries
4810 // (which are added by the marking threads) on them live
4811 // until they can be processed at the end of marking.
4812 ref_processor_cm()->weak_oops_do(&buf_scan_non_heap_roots);
4813 }
4814
4815 if (trace_metadata) {
4816 // Barrier to make sure all workers passed
4817 // the strong CLD and strong nmethods phases.
4818 active_strong_roots_scope()->wait_until_all_workers_done_with_threads(n_par_threads());
4819
4820 // Now take the complement of the strong CLDs.
4821 ClassLoaderDataGraph::roots_cld_do(NULL, scan_weak_clds);
4822 }
4823
4824 // Finish up any enqueued closure apps (attributed as object copy time).
4825 buf_scan_non_heap_roots.done();
4826 buf_scan_non_heap_weak_roots.done();
4827
4828 double obj_copy_time_sec = buf_scan_non_heap_roots.closure_app_seconds()
4829 + buf_scan_non_heap_weak_roots.closure_app_seconds();
4830
4831 g1_policy()->phase_times()->record_obj_copy_time(worker_i, obj_copy_time_sec * 1000.0);
4832
4833 double ext_root_time_ms =
4834 ((os::elapsedTime() - ext_roots_start) - obj_copy_time_sec) * 1000.0;
4835
4836 g1_policy()->phase_times()->record_ext_root_scan_time(worker_i, ext_root_time_ms);
4837
4838 // During conc marking we have to filter the per-thread SATB buffers
4839 // to make sure we remove any oops into the CSet (which will show up
4840 // as implicitly live).
4841 double satb_filtering_ms = 0.0;
4842 if (!_process_strong_tasks->is_task_claimed(G1H_PS_filter_satb_buffers)) {
4843 if (mark_in_progress()) {
4844 double satb_filter_start = os::elapsedTime();
4845
4846 JavaThread::satb_mark_queue_set().filter_thread_buffers();
4847
4848 satb_filtering_ms = (os::elapsedTime() - satb_filter_start) * 1000.0;
4849 }
4850 }
4851 g1_policy()->phase_times()->record_satb_filtering_time(worker_i, satb_filtering_ms);
4852
4853 // Now scan the complement of the collection set.
4854 G1CodeBlobClosure scavenge_cs_nmethods(scan_non_heap_weak_roots);
4855
4856 g1_rem_set()->oops_into_collection_set_do(scan_rs, &scavenge_cs_nmethods, worker_i);
4857
4858 _process_strong_tasks->all_tasks_completed();
4859 }
4860
4861 class G1StringSymbolTableUnlinkTask : public AbstractGangTask {
4862 private:
4863 BoolObjectClosure* _is_alive;
4864 int _initial_string_table_size;
4865 int _initial_symbol_table_size;
4866
4867 bool _process_strings;
4868 int _strings_processed;
4869 int _strings_removed;
4870
4871 bool _process_symbols;
4872 int _symbols_processed;
4873 int _symbols_removed;
4874
4875 bool _do_in_parallel;
4876 public:
4877 G1StringSymbolTableUnlinkTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols) :
4878 AbstractGangTask("String/Symbol Unlinking"),
4879 _is_alive(is_alive),
4880 _do_in_parallel(G1CollectedHeap::use_parallel_gc_threads()),
4881 _process_strings(process_strings), _strings_processed(0), _strings_removed(0),
4882 _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0) {
4883
4884 _initial_string_table_size = StringTable::the_table()->table_size();
4885 _initial_symbol_table_size = SymbolTable::the_table()->table_size();
4886 if (process_strings) {
4887 StringTable::clear_parallel_claimed_index();
4888 }
4889 if (process_symbols) {
4890 SymbolTable::clear_parallel_claimed_index();
4891 }
4892 }
4893
4894 ~G1StringSymbolTableUnlinkTask() {
4895 guarantee(!_process_strings || !_do_in_parallel || StringTable::parallel_claimed_index() >= _initial_string_table_size,
4896 err_msg("claim value %d after unlink less than initial string table size %d",
4897 StringTable::parallel_claimed_index(), _initial_string_table_size));
4898 guarantee(!_process_symbols || !_do_in_parallel || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size,
4899 err_msg("claim value %d after unlink less than initial symbol table size %d",
4900 SymbolTable::parallel_claimed_index(), _initial_symbol_table_size));
4901
4902 if (G1TraceStringSymbolTableScrubbing) {
4903 gclog_or_tty->print_cr("Cleaned string and symbol table, "
4904 "strings: "SIZE_FORMAT" processed, "SIZE_FORMAT" removed, "
4905 "symbols: "SIZE_FORMAT" processed, "SIZE_FORMAT" removed",
4906 strings_processed(), strings_removed(),
4907 symbols_processed(), symbols_removed());
4908 }
4909 }
4910
4911 void work(uint worker_id) {
4912 if (_do_in_parallel) {
4913 int strings_processed = 0;
4914 int strings_removed = 0;
4915 int symbols_processed = 0;
4916 int symbols_removed = 0;
4917 if (_process_strings) {
4918 StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed);
4919 Atomic::add(strings_processed, &_strings_processed);
4920 Atomic::add(strings_removed, &_strings_removed);
4921 }
4922 if (_process_symbols) {
4923 SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed);
4924 Atomic::add(symbols_processed, &_symbols_processed);
4925 Atomic::add(symbols_removed, &_symbols_removed);
4926 }
4927 } else {
4928 if (_process_strings) {
4929 StringTable::unlink(_is_alive, &_strings_processed, &_strings_removed);
4930 }
4931 if (_process_symbols) {
4932 SymbolTable::unlink(&_symbols_processed, &_symbols_removed);
4933 }
4934 }
4935 }
4936
4937 size_t strings_processed() const { return (size_t)_strings_processed; }
4938 size_t strings_removed() const { return (size_t)_strings_removed; }
4939
4940 size_t symbols_processed() const { return (size_t)_symbols_processed; }
4941 size_t symbols_removed() const { return (size_t)_symbols_removed; }
4942 };
4943
4944 class G1CodeCacheUnloadingTask VALUE_OBJ_CLASS_SPEC {
4945 private:
4946 static Monitor* _lock;
4947
4948 BoolObjectClosure* const _is_alive;
4949 const bool _unloading_occurred;
4950 const uint _num_workers;
4951
4952 // Variables used to claim nmethods.
4953 nmethod* _first_nmethod;
4954 volatile nmethod* _claimed_nmethod;
4955
4956 // The list of nmethods that need to be processed by the second pass.
4957 volatile nmethod* _postponed_list;
4958 volatile uint _num_entered_barrier;
4959
4960 public:
4961 G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) :
4962 _is_alive(is_alive),
4963 _unloading_occurred(unloading_occurred),
4964 _num_workers(num_workers),
4965 _first_nmethod(NULL),
4966 _claimed_nmethod(NULL),
4967 _postponed_list(NULL),
4968 _num_entered_barrier(0)
4969 {
4970 nmethod::increase_unloading_clock();
4971 _first_nmethod = CodeCache::alive_nmethod(CodeCache::first());
4972 _claimed_nmethod = (volatile nmethod*)_first_nmethod;
4973 }
4974
4975 ~G1CodeCacheUnloadingTask() {
4976 CodeCache::verify_clean_inline_caches();
4977
4978 CodeCache::set_needs_cache_clean(false);
4979 guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be");
4980
4981 CodeCache::verify_icholder_relocations();
4982 }
4983
4984 private:
4985 void add_to_postponed_list(nmethod* nm) {
4986 nmethod* old;
4987 do {
4988 old = (nmethod*)_postponed_list;
4989 nm->set_unloading_next(old);
4990 } while ((nmethod*)Atomic::cmpxchg_ptr(nm, &_postponed_list, old) != old);
4991 }
4992
4993 void clean_nmethod(nmethod* nm) {
4994 bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred);
4995
4996 if (postponed) {
4997 // This nmethod referred to an nmethod that has not been cleaned/unloaded yet.
4998 add_to_postponed_list(nm);
4999 }
5000
5001 // Mark that this thread has been cleaned/unloaded.
5002 // After this call, it will be safe to ask if this nmethod was unloaded or not.
5003 nm->set_unloading_clock(nmethod::global_unloading_clock());
5004 }
5005
5006 void clean_nmethod_postponed(nmethod* nm) {
5007 nm->do_unloading_parallel_postponed(_is_alive, _unloading_occurred);
5008 }
5009
5010 static const int MaxClaimNmethods = 16;
5011
5012 void claim_nmethods(nmethod** claimed_nmethods, int *num_claimed_nmethods) {
5013 nmethod* first;
5014 nmethod* last;
5015
5016 do {
5017 *num_claimed_nmethods = 0;
5018
5019 first = last = (nmethod*)_claimed_nmethod;
5020
5021 if (first != NULL) {
5022 for (int i = 0; i < MaxClaimNmethods; i++) {
5023 last = CodeCache::alive_nmethod(CodeCache::next(last));
5024
5025 if (last == NULL) {
5026 break;
5027 }
5028
5029 claimed_nmethods[i] = last;
5030 (*num_claimed_nmethods)++;
5031 }
5032 }
5033
5034 } while ((nmethod*)Atomic::cmpxchg_ptr(last, &_claimed_nmethod, first) != first);
5035 }
5036
5037 nmethod* claim_postponed_nmethod() {
5038 nmethod* claim;
5039 nmethod* next;
5040
5041 do {
5042 claim = (nmethod*)_postponed_list;
5043 if (claim == NULL) {
5044 return NULL;
5045 }
5046
5047 next = claim->unloading_next();
5048
5049 } while ((nmethod*)Atomic::cmpxchg_ptr(next, &_postponed_list, claim) != claim);
5050
5051 return claim;
5052 }
5053
5054 public:
5055 // Mark that we're done with the first pass of nmethod cleaning.
5056 void barrier_mark(uint worker_id) {
5057 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
5058 _num_entered_barrier++;
5059 if (_num_entered_barrier == _num_workers) {
5060 ml.notify_all();
5061 }
5062 }
5063
5064 // See if we have to wait for the other workers to
5065 // finish their first-pass nmethod cleaning work.
5066 void barrier_wait(uint worker_id) {
5067 if (_num_entered_barrier < _num_workers) {
5068 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
5069 while (_num_entered_barrier < _num_workers) {
5070 ml.wait(Mutex::_no_safepoint_check_flag, 0, false);
5071 }
5072 }
5073 }
5074
5075 // Cleaning and unloading of nmethods. Some work has to be postponed
5076 // to the second pass, when we know which nmethods survive.
5077 void work_first_pass(uint worker_id) {
5078 // The first nmethods is claimed by the first worker.
5079 if (worker_id == 0 && _first_nmethod != NULL) {
5080 clean_nmethod(_first_nmethod);
5081 _first_nmethod = NULL;
5082 }
5083
5084 int num_claimed_nmethods;
5085 nmethod* claimed_nmethods[MaxClaimNmethods];
5086
5087 while (true) {
5088 claim_nmethods(claimed_nmethods, &num_claimed_nmethods);
5089
5090 if (num_claimed_nmethods == 0) {
5091 break;
5092 }
5093
5094 for (int i = 0; i < num_claimed_nmethods; i++) {
5095 clean_nmethod(claimed_nmethods[i]);
5096 }
5097 }
5098 }
5099
5100 void work_second_pass(uint worker_id) {
5101 nmethod* nm;
5102 // Take care of postponed nmethods.
5103 while ((nm = claim_postponed_nmethod()) != NULL) {
5104 clean_nmethod_postponed(nm);
5105 }
5106 }
5107 };
5108
5109 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock");
5110
5111 class G1KlassCleaningTask : public StackObj {
5112 BoolObjectClosure* _is_alive;
5113 volatile jint _clean_klass_tree_claimed;
5114 ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator;
5115
5116 public:
5117 G1KlassCleaningTask(BoolObjectClosure* is_alive) :
5118 _is_alive(is_alive),
5119 _clean_klass_tree_claimed(0),
5120 _klass_iterator() {
5121 }
5122
5123 private:
5124 bool claim_clean_klass_tree_task() {
5125 if (_clean_klass_tree_claimed) {
5126 return false;
5127 }
5128
5129 return Atomic::cmpxchg(1, (jint*)&_clean_klass_tree_claimed, 0) == 0;
5130 }
5131
5132 InstanceKlass* claim_next_klass() {
5133 Klass* klass;
5134 do {
5135 klass =_klass_iterator.next_klass();
5136 } while (klass != NULL && !klass->oop_is_instance());
5137
5138 return (InstanceKlass*)klass;
5139 }
5140
5141 public:
5142
5143 void clean_klass(InstanceKlass* ik) {
5144 ik->clean_implementors_list(_is_alive);
5145 ik->clean_method_data(_is_alive);
5146
5147 // G1 specific cleanup work that has
5148 // been moved here to be done in parallel.
5149 ik->clean_dependent_nmethods();
5150 }
5151
5152 void work() {
5153 ResourceMark rm;
5154
5155 // One worker will clean the subklass/sibling klass tree.
5156 if (claim_clean_klass_tree_task()) {
5157 Klass::clean_subklass_tree(_is_alive);
5158 }
5159
5160 // All workers will help cleaning the classes,
5161 InstanceKlass* klass;
5162 while ((klass = claim_next_klass()) != NULL) {
5163 clean_klass(klass);
5164 }
5165 }
5166 };
5167
5168 // To minimize the remark pause times, the tasks below are done in parallel.
5169 class G1ParallelCleaningTask : public AbstractGangTask {
5170 private:
5171 G1StringSymbolTableUnlinkTask _string_symbol_task;
5172 G1CodeCacheUnloadingTask _code_cache_task;
5173 G1KlassCleaningTask _klass_cleaning_task;
5174
5175 public:
5176 // The constructor is run in the VMThread.
5177 G1ParallelCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, uint num_workers, bool unloading_occurred) :
5178 AbstractGangTask("Parallel Cleaning"),
5179 _string_symbol_task(is_alive, process_strings, process_symbols),
5180 _code_cache_task(num_workers, is_alive, unloading_occurred),
5181 _klass_cleaning_task(is_alive) {
5182 }
5183
5184 // The parallel work done by all worker threads.
5185 void work(uint worker_id) {
5186 // Do first pass of code cache cleaning.
5187 _code_cache_task.work_first_pass(worker_id);
5188
5189 // Let the threads mark that the first pass is done.
5190 _code_cache_task.barrier_mark(worker_id);
5191
5192 // Clean the Strings and Symbols.
5193 _string_symbol_task.work(worker_id);
5194
5195 // Wait for all workers to finish the first code cache cleaning pass.
5196 _code_cache_task.barrier_wait(worker_id);
5197
5198 // Do the second code cache cleaning work, which realize on
5199 // the liveness information gathered during the first pass.
5200 _code_cache_task.work_second_pass(worker_id);
5201
5202 // Clean all klasses that were not unloaded.
5203 _klass_cleaning_task.work();
5204 }
5205 };
5206
5207
5208 void G1CollectedHeap::parallel_cleaning(BoolObjectClosure* is_alive,
5209 bool process_strings,
5210 bool process_symbols,
5211 bool class_unloading_occurred) {
5212 uint n_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
5213 workers()->active_workers() : 1);
5214
5215 G1ParallelCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols,
5216 n_workers, class_unloading_occurred);
5217 if (G1CollectedHeap::use_parallel_gc_threads()) {
5218 set_par_threads(n_workers);
5219 workers()->run_task(&g1_unlink_task);
5220 set_par_threads(0);
5221 } else {
5222 g1_unlink_task.work(0);
5223 }
5224 }
5225
5226 void G1CollectedHeap::unlink_string_and_symbol_table(BoolObjectClosure* is_alive,
5227 bool process_strings, bool process_symbols) {
5228 {
5229 uint n_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
5230 _g1h->workers()->active_workers() : 1);
5231 G1StringSymbolTableUnlinkTask g1_unlink_task(is_alive, process_strings, process_symbols);
5232 if (G1CollectedHeap::use_parallel_gc_threads()) {
5233 set_par_threads(n_workers);
5234 workers()->run_task(&g1_unlink_task);
5235 set_par_threads(0);
5236 } else {
5237 g1_unlink_task.work(0);
5238 }
5239 }
5240
5241 if (G1StringDedup::is_enabled()) {
5242 G1StringDedup::unlink(is_alive);
5243 }
5244 }
5245
5246 class G1RedirtyLoggedCardsTask : public AbstractGangTask {
5247 private:
5248 DirtyCardQueueSet* _queue;
5249 public:
5250 G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue) : AbstractGangTask("Redirty Cards"), _queue(queue) { }
5251
5252 virtual void work(uint worker_id) {
5253 double start_time = os::elapsedTime();
5254
5255 RedirtyLoggedCardTableEntryClosure cl;
5256 if (G1CollectedHeap::heap()->use_parallel_gc_threads()) {
5257 _queue->par_apply_closure_to_all_completed_buffers(&cl);
5258 } else {
5259 _queue->apply_closure_to_all_completed_buffers(&cl);
5260 }
5261
5262 G1GCPhaseTimes* timer = G1CollectedHeap::heap()->g1_policy()->phase_times();
5263 timer->record_redirty_logged_cards_time_ms(worker_id, (os::elapsedTime() - start_time) * 1000.0);
5264 timer->record_redirty_logged_cards_processed_cards(worker_id, cl.num_processed());
5265 }
5266 };
5267
5268 void G1CollectedHeap::redirty_logged_cards() {
5269 guarantee(G1DeferredRSUpdate, "Must only be called when using deferred RS updates.");
5270 double redirty_logged_cards_start = os::elapsedTime();
5271
5272 uint n_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
5273 _g1h->workers()->active_workers() : 1);
5274
5275 G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set());
5276 dirty_card_queue_set().reset_for_par_iteration();
5277 if (use_parallel_gc_threads()) {
5278 set_par_threads(n_workers);
5279 workers()->run_task(&redirty_task);
5280 set_par_threads(0);
5281 } else {
5282 redirty_task.work(0);
5283 }
5284
5285 DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set();
5286 dcq.merge_bufferlists(&dirty_card_queue_set());
5287 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
5288
5289 g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0);
5290 }
5291
5292 // Weak Reference Processing support
5293
5294 // An always "is_alive" closure that is used to preserve referents.
5295 // If the object is non-null then it's alive. Used in the preservation
5296 // of referent objects that are pointed to by reference objects
5297 // discovered by the CM ref processor.
5298 class G1AlwaysAliveClosure: public BoolObjectClosure {
5299 G1CollectedHeap* _g1;
5300 public:
5301 G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
5302 bool do_object_b(oop p) {
5303 if (p != NULL) {
5304 return true;
5305 }
5306 return false;
5307 }
5308 };
5309
5310 bool G1STWIsAliveClosure::do_object_b(oop p) {
5311 // An object is reachable if it is outside the collection set,
5312 // or is inside and copied.
5313 return !_g1->obj_in_cs(p) || p->is_forwarded();
5314 }
5315
5316 // Non Copying Keep Alive closure
5317 class G1KeepAliveClosure: public OopClosure {
5318 G1CollectedHeap* _g1;
5319 public:
5320 G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
5321 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
5322 void do_oop(oop* p) {
5323 oop obj = *p;
5324 assert(obj != NULL, "the caller should have filtered out NULL values");
5325
5326 G1CollectedHeap::in_cset_state_t cset_state = _g1->in_cset_state(obj);
5327 if (cset_state == G1CollectedHeap::InNeither) {
5328 return;
5329 }
5330 if (cset_state == G1CollectedHeap::InCSet) {
5331 assert( obj->is_forwarded(), "invariant" );
5332 *p = obj->forwardee();
5333 } else {
5334 assert(!obj->is_forwarded(), "invariant" );
5335 assert(cset_state == G1CollectedHeap::IsHumongous,
5336 err_msg("Only allowed InCSet state is IsHumongous, but is %d", cset_state));
5337 _g1->set_humongous_is_live(obj);
5338 }
5339 }
5340 };
5341
5342 // Copying Keep Alive closure - can be called from both
5343 // serial and parallel code as long as different worker
5344 // threads utilize different G1ParScanThreadState instances
5345 // and different queues.
5346
5347 class G1CopyingKeepAliveClosure: public OopClosure {
5348 G1CollectedHeap* _g1h;
5349 OopClosure* _copy_non_heap_obj_cl;
5350 G1ParScanThreadState* _par_scan_state;
5351
5352 public:
5353 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
5354 OopClosure* non_heap_obj_cl,
5355 G1ParScanThreadState* pss):
5356 _g1h(g1h),
5357 _copy_non_heap_obj_cl(non_heap_obj_cl),
5358 _par_scan_state(pss)
5359 {}
5360
5361 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
5362 virtual void do_oop( oop* p) { do_oop_work(p); }
5363
5364 template <class T> void do_oop_work(T* p) {
5365 oop obj = oopDesc::load_decode_heap_oop(p);
5366
5367 if (_g1h->is_in_cset_or_humongous(obj)) {
5368 // If the referent object has been forwarded (either copied
5369 // to a new location or to itself in the event of an
5370 // evacuation failure) then we need to update the reference
5371 // field and, if both reference and referent are in the G1
5372 // heap, update the RSet for the referent.
5373 //
5374 // If the referent has not been forwarded then we have to keep
5375 // it alive by policy. Therefore we have copy the referent.
5376 //
5377 // If the reference field is in the G1 heap then we can push
5378 // on the PSS queue. When the queue is drained (after each
5379 // phase of reference processing) the object and it's followers
5380 // will be copied, the reference field set to point to the
5381 // new location, and the RSet updated. Otherwise we need to
5382 // use the the non-heap or metadata closures directly to copy
5383 // the referent object and update the pointer, while avoiding
5384 // updating the RSet.
5385
5386 if (_g1h->is_in_g1_reserved(p)) {
5387 _par_scan_state->push_on_queue(p);
5388 } else {
5389 assert(!Metaspace::contains((const void*)p),
5390 err_msg("Unexpectedly found a pointer from metadata: "
5391 PTR_FORMAT, p));
5392 _copy_non_heap_obj_cl->do_oop(p);
5393 }
5394 }
5395 }
5396 };
5397
5398 // Serial drain queue closure. Called as the 'complete_gc'
5399 // closure for each discovered list in some of the
5400 // reference processing phases.
5401
5402 class G1STWDrainQueueClosure: public VoidClosure {
5403 protected:
5404 G1CollectedHeap* _g1h;
5405 G1ParScanThreadState* _par_scan_state;
5406
5407 G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
5408
5409 public:
5410 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
5411 _g1h(g1h),
5412 _par_scan_state(pss)
5413 { }
5414
5415 void do_void() {
5416 G1ParScanThreadState* const pss = par_scan_state();
5417 pss->trim_queue();
5418 }
5419 };
5420
5421 // Parallel Reference Processing closures
5422
5423 // Implementation of AbstractRefProcTaskExecutor for parallel reference
5424 // processing during G1 evacuation pauses.
5425
5426 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
5427 private:
5428 G1CollectedHeap* _g1h;
5429 RefToScanQueueSet* _queues;
5430 FlexibleWorkGang* _workers;
5431 int _active_workers;
5432
5433 public:
5434 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
5435 FlexibleWorkGang* workers,
5436 RefToScanQueueSet *task_queues,
5437 int n_workers) :
5438 _g1h(g1h),
5439 _queues(task_queues),
5440 _workers(workers),
5441 _active_workers(n_workers)
5442 {
5443 assert(n_workers > 0, "shouldn't call this otherwise");
5444 }
5445
5446 // Executes the given task using concurrent marking worker threads.
5447 virtual void execute(ProcessTask& task);
5448 virtual void execute(EnqueueTask& task);
5449 };
5450
5451 // Gang task for possibly parallel reference processing
5452
5453 class G1STWRefProcTaskProxy: public AbstractGangTask {
5454 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
5455 ProcessTask& _proc_task;
5456 G1CollectedHeap* _g1h;
5457 RefToScanQueueSet *_task_queues;
5458 ParallelTaskTerminator* _terminator;
5459
5460 public:
5461 G1STWRefProcTaskProxy(ProcessTask& proc_task,
5462 G1CollectedHeap* g1h,
5463 RefToScanQueueSet *task_queues,
5464 ParallelTaskTerminator* terminator) :
5465 AbstractGangTask("Process reference objects in parallel"),
5466 _proc_task(proc_task),
5467 _g1h(g1h),
5468 _task_queues(task_queues),
5469 _terminator(terminator)
5470 {}
5471
5472 virtual void work(uint worker_id) {
5473 // The reference processing task executed by a single worker.
5474 ResourceMark rm;
5475 HandleMark hm;
5476
5477 G1STWIsAliveClosure is_alive(_g1h);
5478
5479 G1ParScanThreadState pss(_g1h, worker_id, NULL);
5480 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5481
5482 pss.set_evac_failure_closure(&evac_failure_cl);
5483
5484 G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL);
5485
5486 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5487
5488 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5489
5490 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5491 // We also need to mark copied objects.
5492 copy_non_heap_cl = ©_mark_non_heap_cl;
5493 }
5494
5495 // Keep alive closure.
5496 G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, &pss);
5497
5498 // Complete GC closure
5499 G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _task_queues, _terminator);
5500
5501 // Call the reference processing task's work routine.
5502 _proc_task.work(worker_id, is_alive, keep_alive, drain_queue);
5503
5504 // Note we cannot assert that the refs array is empty here as not all
5505 // of the processing tasks (specifically phase2 - pp2_work) execute
5506 // the complete_gc closure (which ordinarily would drain the queue) so
5507 // the queue may not be empty.
5508 }
5509 };
5510
5511 // Driver routine for parallel reference processing.
5512 // Creates an instance of the ref processing gang
5513 // task and has the worker threads execute it.
5514 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) {
5515 assert(_workers != NULL, "Need parallel worker threads.");
5516
5517 ParallelTaskTerminator terminator(_active_workers, _queues);
5518 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _queues, &terminator);
5519
5520 _g1h->set_par_threads(_active_workers);
5521 _workers->run_task(&proc_task_proxy);
5522 _g1h->set_par_threads(0);
5523 }
5524
5525 // Gang task for parallel reference enqueueing.
5526
5527 class G1STWRefEnqueueTaskProxy: public AbstractGangTask {
5528 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
5529 EnqueueTask& _enq_task;
5530
5531 public:
5532 G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) :
5533 AbstractGangTask("Enqueue reference objects in parallel"),
5534 _enq_task(enq_task)
5535 { }
5536
5537 virtual void work(uint worker_id) {
5538 _enq_task.work(worker_id);
5539 }
5540 };
5541
5542 // Driver routine for parallel reference enqueueing.
5543 // Creates an instance of the ref enqueueing gang
5544 // task and has the worker threads execute it.
5545
5546 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
5547 assert(_workers != NULL, "Need parallel worker threads.");
5548
5549 G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task);
5550
5551 _g1h->set_par_threads(_active_workers);
5552 _workers->run_task(&enq_task_proxy);
5553 _g1h->set_par_threads(0);
5554 }
5555
5556 // End of weak reference support closures
5557
5558 // Abstract task used to preserve (i.e. copy) any referent objects
5559 // that are in the collection set and are pointed to by reference
5560 // objects discovered by the CM ref processor.
5561
5562 class G1ParPreserveCMReferentsTask: public AbstractGangTask {
5563 protected:
5564 G1CollectedHeap* _g1h;
5565 RefToScanQueueSet *_queues;
5566 ParallelTaskTerminator _terminator;
5567 uint _n_workers;
5568
5569 public:
5570 G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h,int workers, RefToScanQueueSet *task_queues) :
5571 AbstractGangTask("ParPreserveCMReferents"),
5572 _g1h(g1h),
5573 _queues(task_queues),
5574 _terminator(workers, _queues),
5575 _n_workers(workers)
5576 { }
5577
5578 void work(uint worker_id) {
5579 ResourceMark rm;
5580 HandleMark hm;
5581
5582 G1ParScanThreadState pss(_g1h, worker_id, NULL);
5583 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5584
5585 pss.set_evac_failure_closure(&evac_failure_cl);
5586
5587 assert(pss.queue_is_empty(), "both queue and overflow should be empty");
5588
5589 G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL);
5590
5591 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5592
5593 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5594
5595 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5596 // We also need to mark copied objects.
5597 copy_non_heap_cl = ©_mark_non_heap_cl;
5598 }
5599
5600 // Is alive closure
5601 G1AlwaysAliveClosure always_alive(_g1h);
5602
5603 // Copying keep alive closure. Applied to referent objects that need
5604 // to be copied.
5605 G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, &pss);
5606
5607 ReferenceProcessor* rp = _g1h->ref_processor_cm();
5608
5609 uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q();
5610 uint stride = MIN2(MAX2(_n_workers, 1U), limit);
5611
5612 // limit is set using max_num_q() - which was set using ParallelGCThreads.
5613 // So this must be true - but assert just in case someone decides to
5614 // change the worker ids.
5615 assert(0 <= worker_id && worker_id < limit, "sanity");
5616 assert(!rp->discovery_is_atomic(), "check this code");
5617
5618 // Select discovered lists [i, i+stride, i+2*stride,...,limit)
5619 for (uint idx = worker_id; idx < limit; idx += stride) {
5620 DiscoveredList& ref_list = rp->discovered_refs()[idx];
5621
5622 DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive);
5623 while (iter.has_next()) {
5624 // Since discovery is not atomic for the CM ref processor, we
5625 // can see some null referent objects.
5626 iter.load_ptrs(DEBUG_ONLY(true));
5627 oop ref = iter.obj();
5628
5629 // This will filter nulls.
5630 if (iter.is_referent_alive()) {
5631 iter.make_referent_alive();
5632 }
5633 iter.move_to_next();
5634 }
5635 }
5636
5637 // Drain the queue - which may cause stealing
5638 G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _queues, &_terminator);
5639 drain_queue.do_void();
5640 // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure
5641 assert(pss.queue_is_empty(), "should be");
5642 }
5643 };
5644
5645 // Weak Reference processing during an evacuation pause (part 1).
5646 void G1CollectedHeap::process_discovered_references(uint no_of_gc_workers) {
5647 double ref_proc_start = os::elapsedTime();
5648
5649 ReferenceProcessor* rp = _ref_processor_stw;
5650 assert(rp->discovery_enabled(), "should have been enabled");
5651
5652 // Any reference objects, in the collection set, that were 'discovered'
5653 // by the CM ref processor should have already been copied (either by
5654 // applying the external root copy closure to the discovered lists, or
5655 // by following an RSet entry).
5656 //
5657 // But some of the referents, that are in the collection set, that these
5658 // reference objects point to may not have been copied: the STW ref
5659 // processor would have seen that the reference object had already
5660 // been 'discovered' and would have skipped discovering the reference,
5661 // but would not have treated the reference object as a regular oop.
5662 // As a result the copy closure would not have been applied to the
5663 // referent object.
5664 //
5665 // We need to explicitly copy these referent objects - the references
5666 // will be processed at the end of remarking.
5667 //
5668 // We also need to do this copying before we process the reference
5669 // objects discovered by the STW ref processor in case one of these
5670 // referents points to another object which is also referenced by an
5671 // object discovered by the STW ref processor.
5672
5673 assert(!G1CollectedHeap::use_parallel_gc_threads() ||
5674 no_of_gc_workers == workers()->active_workers(),
5675 "Need to reset active GC workers");
5676
5677 set_par_threads(no_of_gc_workers);
5678 G1ParPreserveCMReferentsTask keep_cm_referents(this,
5679 no_of_gc_workers,
5680 _task_queues);
5681
5682 if (G1CollectedHeap::use_parallel_gc_threads()) {
5683 workers()->run_task(&keep_cm_referents);
5684 } else {
5685 keep_cm_referents.work(0);
5686 }
5687
5688 set_par_threads(0);
5689
5690 // Closure to test whether a referent is alive.
5691 G1STWIsAliveClosure is_alive(this);
5692
5693 // Even when parallel reference processing is enabled, the processing
5694 // of JNI refs is serial and performed serially by the current thread
5695 // rather than by a worker. The following PSS will be used for processing
5696 // JNI refs.
5697
5698 // Use only a single queue for this PSS.
5699 G1ParScanThreadState pss(this, 0, NULL);
5700
5701 // We do not embed a reference processor in the copying/scanning
5702 // closures while we're actually processing the discovered
5703 // reference objects.
5704 G1ParScanHeapEvacFailureClosure evac_failure_cl(this, &pss, NULL);
5705
5706 pss.set_evac_failure_closure(&evac_failure_cl);
5707
5708 assert(pss.queue_is_empty(), "pre-condition");
5709
5710 G1ParScanExtRootClosure only_copy_non_heap_cl(this, &pss, NULL);
5711
5712 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(this, &pss, NULL);
5713
5714 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5715
5716 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5717 // We also need to mark copied objects.
5718 copy_non_heap_cl = ©_mark_non_heap_cl;
5719 }
5720
5721 // Keep alive closure.
5722 G1CopyingKeepAliveClosure keep_alive(this, copy_non_heap_cl, &pss);
5723
5724 // Serial Complete GC closure
5725 G1STWDrainQueueClosure drain_queue(this, &pss);
5726
5727 // Setup the soft refs policy...
5728 rp->setup_policy(false);
5729
5730 ReferenceProcessorStats stats;
5731 if (!rp->processing_is_mt()) {
5732 // Serial reference processing...
5733 stats = rp->process_discovered_references(&is_alive,
5734 &keep_alive,
5735 &drain_queue,
5736 NULL,
5737 _gc_timer_stw,
5738 _gc_tracer_stw->gc_id());
5739 } else {
5740 // Parallel reference processing
5741 assert(rp->num_q() == no_of_gc_workers, "sanity");
5742 assert(no_of_gc_workers <= rp->max_num_q(), "sanity");
5743
5744 G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers);
5745 stats = rp->process_discovered_references(&is_alive,
5746 &keep_alive,
5747 &drain_queue,
5748 &par_task_executor,
5749 _gc_timer_stw,
5750 _gc_tracer_stw->gc_id());
5751 }
5752
5753 _gc_tracer_stw->report_gc_reference_stats(stats);
5754
5755 // We have completed copying any necessary live referent objects.
5756 assert(pss.queue_is_empty(), "both queue and overflow should be empty");
5757
5758 double ref_proc_time = os::elapsedTime() - ref_proc_start;
5759 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
5760 }
5761
5762 // Weak Reference processing during an evacuation pause (part 2).
5763 void G1CollectedHeap::enqueue_discovered_references(uint no_of_gc_workers) {
5764 double ref_enq_start = os::elapsedTime();
5765
5766 ReferenceProcessor* rp = _ref_processor_stw;
5767 assert(!rp->discovery_enabled(), "should have been disabled as part of processing");
5768
5769 // Now enqueue any remaining on the discovered lists on to
5770 // the pending list.
5771 if (!rp->processing_is_mt()) {
5772 // Serial reference processing...
5773 rp->enqueue_discovered_references();
5774 } else {
5775 // Parallel reference enqueueing
5776
5777 assert(no_of_gc_workers == workers()->active_workers(),
5778 "Need to reset active workers");
5779 assert(rp->num_q() == no_of_gc_workers, "sanity");
5780 assert(no_of_gc_workers <= rp->max_num_q(), "sanity");
5781
5782 G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers);
5783 rp->enqueue_discovered_references(&par_task_executor);
5784 }
5785
5786 rp->verify_no_references_recorded();
5787 assert(!rp->discovery_enabled(), "should have been disabled");
5788
5789 // FIXME
5790 // CM's reference processing also cleans up the string and symbol tables.
5791 // Should we do that here also? We could, but it is a serial operation
5792 // and could significantly increase the pause time.
5793
5794 double ref_enq_time = os::elapsedTime() - ref_enq_start;
5795 g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0);
5796 }
5797
5798 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info) {
5799 _expand_heap_after_alloc_failure = true;
5800 _evacuation_failed = false;
5801
5802 // Should G1EvacuationFailureALot be in effect for this GC?
5803 NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();)
5804
5805 g1_rem_set()->prepare_for_oops_into_collection_set_do();
5806
5807 // Disable the hot card cache.
5808 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
5809 hot_card_cache->reset_hot_cache_claimed_index();
5810 hot_card_cache->set_use_cache(false);
5811
5812 uint n_workers;
5813 if (G1CollectedHeap::use_parallel_gc_threads()) {
5814 n_workers =
5815 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
5816 workers()->active_workers(),
5817 Threads::number_of_non_daemon_threads());
5818 assert(UseDynamicNumberOfGCThreads ||
5819 n_workers == workers()->total_workers(),
5820 "If not dynamic should be using all the workers");
5821 workers()->set_active_workers(n_workers);
5822 set_par_threads(n_workers);
5823 } else {
5824 assert(n_par_threads() == 0,
5825 "Should be the original non-parallel value");
5826 n_workers = 1;
5827 }
5828
5829 G1ParTask g1_par_task(this, _task_queues);
5830
5831 init_for_evac_failure(NULL);
5832
5833 rem_set()->prepare_for_younger_refs_iterate(true);
5834
5835 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
5836 double start_par_time_sec = os::elapsedTime();
5837 double end_par_time_sec;
5838
5839 {
5840 StrongRootsScope srs(this);
5841 // InitialMark needs claim bits to keep track of the marked-through CLDs.
5842 if (g1_policy()->during_initial_mark_pause()) {
5843 ClassLoaderDataGraph::clear_claimed_marks();
5844 }
5845
5846 if (G1CollectedHeap::use_parallel_gc_threads()) {
5847 // The individual threads will set their evac-failure closures.
5848 if (ParallelGCVerbose) G1ParScanThreadState::print_termination_stats_hdr();
5849 // These tasks use ShareHeap::_process_strong_tasks
5850 assert(UseDynamicNumberOfGCThreads ||
5851 workers()->active_workers() == workers()->total_workers(),
5852 "If not dynamic should be using all the workers");
5853 workers()->run_task(&g1_par_task);
5854 } else {
5855 g1_par_task.set_for_termination(n_workers);
5856 g1_par_task.work(0);
5857 }
5858 end_par_time_sec = os::elapsedTime();
5859
5860 // Closing the inner scope will execute the destructor
5861 // for the StrongRootsScope object. We record the current
5862 // elapsed time before closing the scope so that time
5863 // taken for the SRS destructor is NOT included in the
5864 // reported parallel time.
5865 }
5866
5867 double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0;
5868 g1_policy()->phase_times()->record_par_time(par_time_ms);
5869
5870 double code_root_fixup_time_ms =
5871 (os::elapsedTime() - end_par_time_sec) * 1000.0;
5872 g1_policy()->phase_times()->record_code_root_fixup_time(code_root_fixup_time_ms);
5873
5874 set_par_threads(0);
5875
5876 // Process any discovered reference objects - we have
5877 // to do this _before_ we retire the GC alloc regions
5878 // as we may have to copy some 'reachable' referent
5879 // objects (and their reachable sub-graphs) that were
5880 // not copied during the pause.
5881 process_discovered_references(n_workers);
5882
5883 // Weak root processing.
5884 {
5885 G1STWIsAliveClosure is_alive(this);
5886 G1KeepAliveClosure keep_alive(this);
5887 JNIHandles::weak_oops_do(&is_alive, &keep_alive);
5888 if (G1StringDedup::is_enabled()) {
5889 G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive);
5890 }
5891 }
5892
5893 release_gc_alloc_regions(n_workers, evacuation_info);
5894 g1_rem_set()->cleanup_after_oops_into_collection_set_do();
5895
5896 // Reset and re-enable the hot card cache.
5897 // Note the counts for the cards in the regions in the
5898 // collection set are reset when the collection set is freed.
5899 hot_card_cache->reset_hot_cache();
5900 hot_card_cache->set_use_cache(true);
5901
5902 purge_code_root_memory();
5903
5904 finalize_for_evac_failure();
5905
5906 if (evacuation_failed()) {
5907 remove_self_forwarding_pointers();
5908
5909 // Reset the G1EvacuationFailureALot counters and flags
5910 // Note: the values are reset only when an actual
5911 // evacuation failure occurs.
5912 NOT_PRODUCT(reset_evacuation_should_fail();)
5913 }
5914
5915 // Enqueue any remaining references remaining on the STW
5916 // reference processor's discovered lists. We need to do
5917 // this after the card table is cleaned (and verified) as
5918 // the act of enqueueing entries on to the pending list
5919 // will log these updates (and dirty their associated
5920 // cards). We need these updates logged to update any
5921 // RSets.
5922 enqueue_discovered_references(n_workers);
5923
5924 if (G1DeferredRSUpdate) {
5925 redirty_logged_cards();
5926 }
5927 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
5928 }
5929
5930 void G1CollectedHeap::free_region(HeapRegion* hr,
5931 FreeRegionList* free_list,
5932 bool par,
5933 bool locked) {
5934 assert(!hr->isHumongous(), "this is only for non-humongous regions");
5935 assert(!hr->is_empty(), "the region should not be empty");
5936 assert(_hrm.is_available(hr->hrm_index()), "region should be committed");
5937 assert(free_list != NULL, "pre-condition");
5938
5939 if (G1VerifyBitmaps) {
5940 MemRegion mr(hr->bottom(), hr->end());
5941 concurrent_mark()->clearRangePrevBitmap(mr);
5942 }
5943
5944 // Clear the card counts for this region.
5945 // Note: we only need to do this if the region is not young
5946 // (since we don't refine cards in young regions).
5947 if (!hr->is_young()) {
5948 _cg1r->hot_card_cache()->reset_card_counts(hr);
5949 }
5950 hr->hr_clear(par, true /* clear_space */, locked /* locked */);
5951 free_list->add_ordered(hr);
5952 }
5953
5954 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
5955 FreeRegionList* free_list,
5956 bool par) {
5957 assert(hr->startsHumongous(), "this is only for starts humongous regions");
5958 assert(free_list != NULL, "pre-condition");
5959
5960 size_t hr_capacity = hr->capacity();
5961 // We need to read this before we make the region non-humongous,
5962 // otherwise the information will be gone.
5963 uint last_index = hr->last_hc_index();
5964 hr->set_notHumongous();
5965 free_region(hr, free_list, par);
5966
5967 uint i = hr->hrm_index() + 1;
5968 while (i < last_index) {
5969 HeapRegion* curr_hr = region_at(i);
5970 assert(curr_hr->continuesHumongous(), "invariant");
5971 curr_hr->set_notHumongous();
5972 free_region(curr_hr, free_list, par);
5973 i += 1;
5974 }
5975 }
5976
5977 void G1CollectedHeap::remove_from_old_sets(const HeapRegionSetCount& old_regions_removed,
5978 const HeapRegionSetCount& humongous_regions_removed) {
5979 if (old_regions_removed.length() > 0 || humongous_regions_removed.length() > 0) {
5980 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
5981 _old_set.bulk_remove(old_regions_removed);
5982 _humongous_set.bulk_remove(humongous_regions_removed);
5983 }
5984
5985 }
5986
5987 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) {
5988 assert(list != NULL, "list can't be null");
5989 if (!list->is_empty()) {
5990 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
5991 _hrm.insert_list_into_free_list(list);
5992 }
5993 }
5994
5995 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) {
5996 assert(_summary_bytes_used >= bytes,
5997 err_msg("invariant: _summary_bytes_used: "SIZE_FORMAT" should be >= bytes: "SIZE_FORMAT,
5998 _summary_bytes_used, bytes));
5999 _summary_bytes_used -= bytes;
6000 }
6001
6002 class G1ParCleanupCTTask : public AbstractGangTask {
6003 G1SATBCardTableModRefBS* _ct_bs;
6004 G1CollectedHeap* _g1h;
6005 HeapRegion* volatile _su_head;
6006 public:
6007 G1ParCleanupCTTask(G1SATBCardTableModRefBS* ct_bs,
6008 G1CollectedHeap* g1h) :
6009 AbstractGangTask("G1 Par Cleanup CT Task"),
6010 _ct_bs(ct_bs), _g1h(g1h) { }
6011
6012 void work(uint worker_id) {
6013 HeapRegion* r;
6014 while (r = _g1h->pop_dirty_cards_region()) {
6015 clear_cards(r);
6016 }
6017 }
6018
6019 void clear_cards(HeapRegion* r) {
6020 // Cards of the survivors should have already been dirtied.
6021 if (!r->is_survivor()) {
6022 _ct_bs->clear(MemRegion(r->bottom(), r->end()));
6023 }
6024 }
6025 };
6026
6027 #ifndef PRODUCT
6028 class G1VerifyCardTableCleanup: public HeapRegionClosure {
6029 G1CollectedHeap* _g1h;
6030 G1SATBCardTableModRefBS* _ct_bs;
6031 public:
6032 G1VerifyCardTableCleanup(G1CollectedHeap* g1h, G1SATBCardTableModRefBS* ct_bs)
6033 : _g1h(g1h), _ct_bs(ct_bs) { }
6034 virtual bool doHeapRegion(HeapRegion* r) {
6035 if (r->is_survivor()) {
6036 _g1h->verify_dirty_region(r);
6037 } else {
6038 _g1h->verify_not_dirty_region(r);
6039 }
6040 return false;
6041 }
6042 };
6043
6044 void G1CollectedHeap::verify_not_dirty_region(HeapRegion* hr) {
6045 // All of the region should be clean.
6046 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
6047 MemRegion mr(hr->bottom(), hr->end());
6048 ct_bs->verify_not_dirty_region(mr);
6049 }
6050
6051 void G1CollectedHeap::verify_dirty_region(HeapRegion* hr) {
6052 // We cannot guarantee that [bottom(),end()] is dirty. Threads
6053 // dirty allocated blocks as they allocate them. The thread that
6054 // retires each region and replaces it with a new one will do a
6055 // maximal allocation to fill in [pre_dummy_top(),end()] but will
6056 // not dirty that area (one less thing to have to do while holding
6057 // a lock). So we can only verify that [bottom(),pre_dummy_top()]
6058 // is dirty.
6059 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
6060 MemRegion mr(hr->bottom(), hr->pre_dummy_top());
6061 if (hr->is_young()) {
6062 ct_bs->verify_g1_young_region(mr);
6063 } else {
6064 ct_bs->verify_dirty_region(mr);
6065 }
6066 }
6067
6068 void G1CollectedHeap::verify_dirty_young_list(HeapRegion* head) {
6069 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
6070 for (HeapRegion* hr = head; hr != NULL; hr = hr->get_next_young_region()) {
6071 verify_dirty_region(hr);
6072 }
6073 }
6074
6075 void G1CollectedHeap::verify_dirty_young_regions() {
6076 verify_dirty_young_list(_young_list->first_region());
6077 }
6078
6079 bool G1CollectedHeap::verify_no_bits_over_tams(const char* bitmap_name, CMBitMapRO* bitmap,
6080 HeapWord* tams, HeapWord* end) {
6081 guarantee(tams <= end,
6082 err_msg("tams: "PTR_FORMAT" end: "PTR_FORMAT, tams, end));
6083 HeapWord* result = bitmap->getNextMarkedWordAddress(tams, end);
6084 if (result < end) {
6085 gclog_or_tty->cr();
6086 gclog_or_tty->print_cr("## wrong marked address on %s bitmap: "PTR_FORMAT,
6087 bitmap_name, result);
6088 gclog_or_tty->print_cr("## %s tams: "PTR_FORMAT" end: "PTR_FORMAT,
6089 bitmap_name, tams, end);
6090 return false;
6091 }
6092 return true;
6093 }
6094
6095 bool G1CollectedHeap::verify_bitmaps(const char* caller, HeapRegion* hr) {
6096 CMBitMapRO* prev_bitmap = concurrent_mark()->prevMarkBitMap();
6097 CMBitMapRO* next_bitmap = (CMBitMapRO*) concurrent_mark()->nextMarkBitMap();
6098
6099 HeapWord* bottom = hr->bottom();
6100 HeapWord* ptams = hr->prev_top_at_mark_start();
6101 HeapWord* ntams = hr->next_top_at_mark_start();
6102 HeapWord* end = hr->end();
6103
6104 bool res_p = verify_no_bits_over_tams("prev", prev_bitmap, ptams, end);
6105
6106 bool res_n = true;
6107 // We reset mark_in_progress() before we reset _cmThread->in_progress() and in this window
6108 // we do the clearing of the next bitmap concurrently. Thus, we can not verify the bitmap
6109 // if we happen to be in that state.
6110 if (mark_in_progress() || !_cmThread->in_progress()) {
6111 res_n = verify_no_bits_over_tams("next", next_bitmap, ntams, end);
6112 }
6113 if (!res_p || !res_n) {
6114 gclog_or_tty->print_cr("#### Bitmap verification failed for "HR_FORMAT,
6115 HR_FORMAT_PARAMS(hr));
6116 gclog_or_tty->print_cr("#### Caller: %s", caller);
6117 return false;
6118 }
6119 return true;
6120 }
6121
6122 void G1CollectedHeap::check_bitmaps(const char* caller, HeapRegion* hr) {
6123 if (!G1VerifyBitmaps) return;
6124
6125 guarantee(verify_bitmaps(caller, hr), "bitmap verification");
6126 }
6127
6128 class G1VerifyBitmapClosure : public HeapRegionClosure {
6129 private:
6130 const char* _caller;
6131 G1CollectedHeap* _g1h;
6132 bool _failures;
6133
6134 public:
6135 G1VerifyBitmapClosure(const char* caller, G1CollectedHeap* g1h) :
6136 _caller(caller), _g1h(g1h), _failures(false) { }
6137
6138 bool failures() { return _failures; }
6139
6140 virtual bool doHeapRegion(HeapRegion* hr) {
6141 if (hr->continuesHumongous()) return false;
6142
6143 bool result = _g1h->verify_bitmaps(_caller, hr);
6144 if (!result) {
6145 _failures = true;
6146 }
6147 return false;
6148 }
6149 };
6150
6151 void G1CollectedHeap::check_bitmaps(const char* caller) {
6152 if (!G1VerifyBitmaps) return;
6153
6154 G1VerifyBitmapClosure cl(caller, this);
6155 heap_region_iterate(&cl);
6156 guarantee(!cl.failures(), "bitmap verification");
6157 }
6158 #endif // PRODUCT
6159
6160 void G1CollectedHeap::cleanUpCardTable() {
6161 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
6162 double start = os::elapsedTime();
6163
6164 {
6165 // Iterate over the dirty cards region list.
6166 G1ParCleanupCTTask cleanup_task(ct_bs, this);
6167
6168 if (G1CollectedHeap::use_parallel_gc_threads()) {
6169 set_par_threads();
6170 workers()->run_task(&cleanup_task);
6171 set_par_threads(0);
6172 } else {
6173 while (_dirty_cards_region_list) {
6174 HeapRegion* r = _dirty_cards_region_list;
6175 cleanup_task.clear_cards(r);
6176 _dirty_cards_region_list = r->get_next_dirty_cards_region();
6177 if (_dirty_cards_region_list == r) {
6178 // The last region.
6179 _dirty_cards_region_list = NULL;
6180 }
6181 r->set_next_dirty_cards_region(NULL);
6182 }
6183 }
6184 #ifndef PRODUCT
6185 if (G1VerifyCTCleanup || VerifyAfterGC) {
6186 G1VerifyCardTableCleanup cleanup_verifier(this, ct_bs);
6187 heap_region_iterate(&cleanup_verifier);
6188 }
6189 #endif
6190 }
6191
6192 double elapsed = os::elapsedTime() - start;
6193 g1_policy()->phase_times()->record_clear_ct_time(elapsed * 1000.0);
6194 }
6195
6196 void G1CollectedHeap::free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info) {
6197 size_t pre_used = 0;
6198 FreeRegionList local_free_list("Local List for CSet Freeing");
6199
6200 double young_time_ms = 0.0;
6201 double non_young_time_ms = 0.0;
6202
6203 // Since the collection set is a superset of the the young list,
6204 // all we need to do to clear the young list is clear its
6205 // head and length, and unlink any young regions in the code below
6206 _young_list->clear();
6207
6208 G1CollectorPolicy* policy = g1_policy();
6209
6210 double start_sec = os::elapsedTime();
6211 bool non_young = true;
6212
6213 HeapRegion* cur = cs_head;
6214 int age_bound = -1;
6215 size_t rs_lengths = 0;
6216
6217 while (cur != NULL) {
6218 assert(!is_on_master_free_list(cur), "sanity");
6219 if (non_young) {
6220 if (cur->is_young()) {
6221 double end_sec = os::elapsedTime();
6222 double elapsed_ms = (end_sec - start_sec) * 1000.0;
6223 non_young_time_ms += elapsed_ms;
6224
6225 start_sec = os::elapsedTime();
6226 non_young = false;
6227 }
6228 } else {
6229 if (!cur->is_young()) {
6230 double end_sec = os::elapsedTime();
6231 double elapsed_ms = (end_sec - start_sec) * 1000.0;
6232 young_time_ms += elapsed_ms;
6233
6234 start_sec = os::elapsedTime();
6235 non_young = true;
6236 }
6237 }
6238
6239 rs_lengths += cur->rem_set()->occupied_locked();
6240
6241 HeapRegion* next = cur->next_in_collection_set();
6242 assert(cur->in_collection_set(), "bad CS");
6243 cur->set_next_in_collection_set(NULL);
6244 cur->set_in_collection_set(false);
6245
6246 if (cur->is_young()) {
6247 int index = cur->young_index_in_cset();
6248 assert(index != -1, "invariant");
6249 assert((uint) index < policy->young_cset_region_length(), "invariant");
6250 size_t words_survived = _surviving_young_words[index];
6251 cur->record_surv_words_in_group(words_survived);
6252
6253 // At this point the we have 'popped' cur from the collection set
6254 // (linked via next_in_collection_set()) but it is still in the
6255 // young list (linked via next_young_region()). Clear the
6256 // _next_young_region field.
6257 cur->set_next_young_region(NULL);
6258 } else {
6259 int index = cur->young_index_in_cset();
6260 assert(index == -1, "invariant");
6261 }
6262
6263 assert( (cur->is_young() && cur->young_index_in_cset() > -1) ||
6264 (!cur->is_young() && cur->young_index_in_cset() == -1),
6265 "invariant" );
6266
6267 if (!cur->evacuation_failed()) {
6268 MemRegion used_mr = cur->used_region();
6269
6270 // And the region is empty.
6271 assert(!used_mr.is_empty(), "Should not have empty regions in a CS.");
6272 pre_used += cur->used();
6273 free_region(cur, &local_free_list, false /* par */, true /* locked */);
6274 } else {
6275 cur->uninstall_surv_rate_group();
6276 if (cur->is_young()) {
6277 cur->set_young_index_in_cset(-1);
6278 }
6279 cur->set_not_young();
6280 cur->set_evacuation_failed(false);
6281 // The region is now considered to be old.
6282 _old_set.add(cur);
6283 evacuation_info.increment_collectionset_used_after(cur->used());
6284 }
6285 cur = next;
6286 }
6287
6288 evacuation_info.set_regions_freed(local_free_list.length());
6289 policy->record_max_rs_lengths(rs_lengths);
6290 policy->cset_regions_freed();
6291
6292 double end_sec = os::elapsedTime();
6293 double elapsed_ms = (end_sec - start_sec) * 1000.0;
6294
6295 if (non_young) {
6296 non_young_time_ms += elapsed_ms;
6297 } else {
6298 young_time_ms += elapsed_ms;
6299 }
6300
6301 prepend_to_freelist(&local_free_list);
6302 decrement_summary_bytes(pre_used);
6303 policy->phase_times()->record_young_free_cset_time_ms(young_time_ms);
6304 policy->phase_times()->record_non_young_free_cset_time_ms(non_young_time_ms);
6305 }
6306
6307 class G1FreeHumongousRegionClosure : public HeapRegionClosure {
6308 private:
6309 FreeRegionList* _free_region_list;
6310 HeapRegionSet* _proxy_set;
6311 HeapRegionSetCount _humongous_regions_removed;
6312 size_t _freed_bytes;
6313 public:
6314
6315 G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) :
6316 _free_region_list(free_region_list), _humongous_regions_removed(), _freed_bytes(0) {
6317 }
6318
6319 virtual bool doHeapRegion(HeapRegion* r) {
6320 if (!r->startsHumongous()) {
6321 return false;
6322 }
6323
6324 G1CollectedHeap* g1h = G1CollectedHeap::heap();
6325
6326 oop obj = (oop)r->bottom();
6327 CMBitMap* next_bitmap = g1h->concurrent_mark()->nextMarkBitMap();
6328
6329 // The following checks whether the humongous object is live are sufficient.
6330 // The main additional check (in addition to having a reference from the roots
6331 // or the young gen) is whether the humongous object has a remembered set entry.
6332 //
6333 // A humongous object cannot be live if there is no remembered set for it
6334 // because:
6335 // - there can be no references from within humongous starts regions referencing
6336 // the object because we never allocate other objects into them.
6337 // (I.e. there are no intra-region references that may be missed by the
6338 // remembered set)
6339 // - as soon there is a remembered set entry to the humongous starts region
6340 // (i.e. it has "escaped" to an old object) this remembered set entry will stay
6341 // until the end of a concurrent mark.
6342 //
6343 // It is not required to check whether the object has been found dead by marking
6344 // or not, in fact it would prevent reclamation within a concurrent cycle, as
6345 // all objects allocated during that time are considered live.
6346 // SATB marking is even more conservative than the remembered set.
6347 // So if at this point in the collection there is no remembered set entry,
6348 // nobody has a reference to it.
6349 // At the start of collection we flush all refinement logs, and remembered sets
6350 // are completely up-to-date wrt to references to the humongous object.
6351 //
6352 // Other implementation considerations:
6353 // - never consider object arrays: while they are a valid target, they have not
6354 // been observed to be used as temporary objects.
6355 // - they would also pose considerable effort for cleaning up the the remembered
6356 // sets.
6357 // While this cleanup is not strictly necessary to be done (or done instantly),
6358 // given that their occurrence is very low, this saves us this additional
6359 // complexity.
6360 uint region_idx = r->hrm_index();
6361 if (g1h->humongous_is_live(region_idx) ||
6362 g1h->humongous_region_is_always_live(region_idx)) {
6363
6364 if (G1TraceReclaimDeadHumongousObjectsAtYoungGC) {
6365 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",
6366 r->isHumongous(),
6367 region_idx,
6368 r->rem_set()->occupied(),
6369 r->rem_set()->strong_code_roots_list_length(),
6370 next_bitmap->isMarked(r->bottom()),
6371 g1h->humongous_is_live(region_idx),
6372 obj->is_objArray()
6373 );
6374 }
6375
6376 return false;
6377 }
6378
6379 guarantee(!obj->is_objArray(),
6380 err_msg("Eagerly reclaiming object arrays is not supported, but the object "PTR_FORMAT" is.",
6381 r->bottom()));
6382
6383 if (G1TraceReclaimDeadHumongousObjectsAtYoungGC) {
6384 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",
6385 r->isHumongous(),
6386 r->bottom(),
6387 region_idx,
6388 r->region_num(),
6389 r->rem_set()->occupied(),
6390 r->rem_set()->strong_code_roots_list_length(),
6391 next_bitmap->isMarked(r->bottom()),
6392 g1h->humongous_is_live(region_idx),
6393 obj->is_objArray()
6394 );
6395 }
6396 // Need to clear mark bit of the humongous object if already set.
6397 if (next_bitmap->isMarked(r->bottom())) {
6398 next_bitmap->clear(r->bottom());
6399 }
6400 _freed_bytes += r->used();
6401 r->set_containing_set(NULL);
6402 _humongous_regions_removed.increment(1u, r->capacity());
6403 g1h->free_humongous_region(r, _free_region_list, false);
6404
6405 return false;
6406 }
6407
6408 HeapRegionSetCount& humongous_free_count() {
6409 return _humongous_regions_removed;
6410 }
6411
6412 size_t bytes_freed() const {
6413 return _freed_bytes;
6414 }
6415
6416 size_t humongous_reclaimed() const {
6417 return _humongous_regions_removed.length();
6418 }
6419 };
6420
6421 void G1CollectedHeap::eagerly_reclaim_humongous_regions() {
6422 assert_at_safepoint(true);
6423
6424 if (!G1ReclaimDeadHumongousObjectsAtYoungGC || !_has_humongous_reclaim_candidates) {
6425 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0);
6426 return;
6427 }
6428
6429 double start_time = os::elapsedTime();
6430
6431 FreeRegionList local_cleanup_list("Local Humongous Cleanup List");
6432
6433 G1FreeHumongousRegionClosure cl(&local_cleanup_list);
6434 heap_region_iterate(&cl);
6435
6436 HeapRegionSetCount empty_set;
6437 remove_from_old_sets(empty_set, cl.humongous_free_count());
6438
6439 G1HRPrinter* hr_printer = _g1h->hr_printer();
6440 if (hr_printer->is_active()) {
6441 FreeRegionListIterator iter(&local_cleanup_list);
6442 while (iter.more_available()) {
6443 HeapRegion* hr = iter.get_next();
6444 hr_printer->cleanup(hr);
6445 }
6446 }
6447
6448 prepend_to_freelist(&local_cleanup_list);
6449 decrement_summary_bytes(cl.bytes_freed());
6450
6451 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0,
6452 cl.humongous_reclaimed());
6453 }
6454
6455 // This routine is similar to the above but does not record
6456 // any policy statistics or update free lists; we are abandoning
6457 // the current incremental collection set in preparation of a
6458 // full collection. After the full GC we will start to build up
6459 // the incremental collection set again.
6460 // This is only called when we're doing a full collection
6461 // and is immediately followed by the tearing down of the young list.
6462
6463 void G1CollectedHeap::abandon_collection_set(HeapRegion* cs_head) {
6464 HeapRegion* cur = cs_head;
6465
6466 while (cur != NULL) {
6467 HeapRegion* next = cur->next_in_collection_set();
6468 assert(cur->in_collection_set(), "bad CS");
6469 cur->set_next_in_collection_set(NULL);
6470 cur->set_in_collection_set(false);
6471 cur->set_young_index_in_cset(-1);
6472 cur = next;
6473 }
6474 }
6475
6476 void G1CollectedHeap::set_free_regions_coming() {
6477 if (G1ConcRegionFreeingVerbose) {
6478 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
6479 "setting free regions coming");
6480 }
6481
6482 assert(!free_regions_coming(), "pre-condition");
6483 _free_regions_coming = true;
6484 }
6485
6486 void G1CollectedHeap::reset_free_regions_coming() {
6487 assert(free_regions_coming(), "pre-condition");
6488
6489 {
6490 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6491 _free_regions_coming = false;
6492 SecondaryFreeList_lock->notify_all();
6493 }
6494
6495 if (G1ConcRegionFreeingVerbose) {
6496 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
6497 "reset free regions coming");
6498 }
6499 }
6500
6501 void G1CollectedHeap::wait_while_free_regions_coming() {
6502 // Most of the time we won't have to wait, so let's do a quick test
6503 // first before we take the lock.
6504 if (!free_regions_coming()) {
6505 return;
6506 }
6507
6508 if (G1ConcRegionFreeingVerbose) {
6509 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
6510 "waiting for free regions");
6511 }
6512
6513 {
6514 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6515 while (free_regions_coming()) {
6516 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
6517 }
6518 }
6519
6520 if (G1ConcRegionFreeingVerbose) {
6521 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
6522 "done waiting for free regions");
6523 }
6524 }
6525
6526 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
6527 assert(heap_lock_held_for_gc(),
6528 "the heap lock should already be held by or for this thread");
6529 _young_list->push_region(hr);
6530 }
6531
6532 class NoYoungRegionsClosure: public HeapRegionClosure {
6533 private:
6534 bool _success;
6535 public:
6536 NoYoungRegionsClosure() : _success(true) { }
6537 bool doHeapRegion(HeapRegion* r) {
6538 if (r->is_young()) {
6539 gclog_or_tty->print_cr("Region ["PTR_FORMAT", "PTR_FORMAT") tagged as young",
6540 r->bottom(), r->end());
6541 _success = false;
6542 }
6543 return false;
6544 }
6545 bool success() { return _success; }
6546 };
6547
6548 bool G1CollectedHeap::check_young_list_empty(bool check_heap, bool check_sample) {
6549 bool ret = _young_list->check_list_empty(check_sample);
6550
6551 if (check_heap) {
6552 NoYoungRegionsClosure closure;
6553 heap_region_iterate(&closure);
6554 ret = ret && closure.success();
6555 }
6556
6557 return ret;
6558 }
6559
6560 class TearDownRegionSetsClosure : public HeapRegionClosure {
6561 private:
6562 HeapRegionSet *_old_set;
6563
6564 public:
6565 TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { }
6566
6567 bool doHeapRegion(HeapRegion* r) {
6568 if (r->is_empty()) {
6569 // We ignore empty regions, we'll empty the free list afterwards
6570 } else if (r->is_young()) {
6571 // We ignore young regions, we'll empty the young list afterwards
6572 } else if (r->isHumongous()) {
6573 // We ignore humongous regions, we're not tearing down the
6574 // humongous region set
6575 } else {
6576 // The rest should be old
6577 _old_set->remove(r);
6578 }
6579 return false;
6580 }
6581
6582 ~TearDownRegionSetsClosure() {
6583 assert(_old_set->is_empty(), "post-condition");
6584 }
6585 };
6586
6587 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
6588 assert_at_safepoint(true /* should_be_vm_thread */);
6589
6590 if (!free_list_only) {
6591 TearDownRegionSetsClosure cl(&_old_set);
6592 heap_region_iterate(&cl);
6593
6594 // Note that emptying the _young_list is postponed and instead done as
6595 // the first step when rebuilding the regions sets again. The reason for
6596 // this is that during a full GC string deduplication needs to know if
6597 // a collected region was young or old when the full GC was initiated.
6598 }
6599 _hrm.remove_all_free_regions();
6600 }
6601
6602 class RebuildRegionSetsClosure : public HeapRegionClosure {
6603 private:
6604 bool _free_list_only;
6605 HeapRegionSet* _old_set;
6606 HeapRegionManager* _hrm;
6607 size_t _total_used;
6608
6609 public:
6610 RebuildRegionSetsClosure(bool free_list_only,
6611 HeapRegionSet* old_set, HeapRegionManager* hrm) :
6612 _free_list_only(free_list_only),
6613 _old_set(old_set), _hrm(hrm), _total_used(0) {
6614 assert(_hrm->num_free_regions() == 0, "pre-condition");
6615 if (!free_list_only) {
6616 assert(_old_set->is_empty(), "pre-condition");
6617 }
6618 }
6619
6620 bool doHeapRegion(HeapRegion* r) {
6621 if (r->continuesHumongous()) {
6622 return false;
6623 }
6624
6625 if (r->is_empty()) {
6626 // Add free regions to the free list
6627 _hrm->insert_into_free_list(r);
6628 } else if (!_free_list_only) {
6629 assert(!r->is_young(), "we should not come across young regions");
6630
6631 if (r->isHumongous()) {
6632 // We ignore humongous regions, we left the humongous set unchanged
6633 } else {
6634 // The rest should be old, add them to the old set
6635 _old_set->add(r);
6636 }
6637 _total_used += r->used();
6638 }
6639
6640 return false;
6641 }
6642
6643 size_t total_used() {
6644 return _total_used;
6645 }
6646 };
6647
6648 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
6649 assert_at_safepoint(true /* should_be_vm_thread */);
6650
6651 if (!free_list_only) {
6652 _young_list->empty_list();
6653 }
6654
6655 RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm);
6656 heap_region_iterate(&cl);
6657
6658 if (!free_list_only) {
6659 _summary_bytes_used = cl.total_used();
6660 }
6661 assert(_summary_bytes_used == recalculate_used(),
6662 err_msg("inconsistent _summary_bytes_used, "
6663 "value: "SIZE_FORMAT" recalculated: "SIZE_FORMAT,
6664 _summary_bytes_used, recalculate_used()));
6665 }
6666
6667 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) {
6668 _refine_cte_cl->set_concurrent(concurrent);
6669 }
6670
6671 bool G1CollectedHeap::is_in_closed_subset(const void* p) const {
6672 HeapRegion* hr = heap_region_containing(p);
6673 return hr->is_in(p);
6674 }
6675
6676 // Methods for the mutator alloc region
6677
6678 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
6679 bool force) {
6680 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6681 assert(!force || g1_policy()->can_expand_young_list(),
6682 "if force is true we should be able to expand the young list");
6683 bool young_list_full = g1_policy()->is_young_list_full();
6684 if (force || !young_list_full) {
6685 HeapRegion* new_alloc_region = new_region(word_size,
6686 false /* is_old */,
6687 false /* do_expand */);
6688 if (new_alloc_region != NULL) {
6689 set_region_short_lived_locked(new_alloc_region);
6690 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Eden, young_list_full);
6691 check_bitmaps("Mutator Region Allocation", new_alloc_region);
6692 return new_alloc_region;
6693 }
6694 }
6695 return NULL;
6696 }
6697
6698 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
6699 size_t allocated_bytes) {
6700 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6701 assert(alloc_region->is_young(), "all mutator alloc regions should be young");
6702
6703 g1_policy()->add_region_to_incremental_cset_lhs(alloc_region);
6704 _summary_bytes_used += allocated_bytes;
6705 _hr_printer.retire(alloc_region);
6706 // We update the eden sizes here, when the region is retired,
6707 // instead of when it's allocated, since this is the point that its
6708 // used space has been recored in _summary_bytes_used.
6709 g1mm()->update_eden_size();
6710 }
6711
6712 HeapRegion* MutatorAllocRegion::allocate_new_region(size_t word_size,
6713 bool force) {
6714 return _g1h->new_mutator_alloc_region(word_size, force);
6715 }
6716
6717 void G1CollectedHeap::set_par_threads() {
6718 // Don't change the number of workers. Use the value previously set
6719 // in the workgroup.
6720 assert(G1CollectedHeap::use_parallel_gc_threads(), "shouldn't be here otherwise");
6721 uint n_workers = workers()->active_workers();
6722 assert(UseDynamicNumberOfGCThreads ||
6723 n_workers == workers()->total_workers(),
6724 "Otherwise should be using the total number of workers");
6725 if (n_workers == 0) {
6726 assert(false, "Should have been set in prior evacuation pause.");
6727 n_workers = ParallelGCThreads;
6728 workers()->set_active_workers(n_workers);
6729 }
6730 set_par_threads(n_workers);
6731 }
6732
6733 void MutatorAllocRegion::retire_region(HeapRegion* alloc_region,
6734 size_t allocated_bytes) {
6735 _g1h->retire_mutator_alloc_region(alloc_region, allocated_bytes);
6736 }
6737
6738 // Methods for the GC alloc regions
6739
6740 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size,
6741 uint count,
6742 GCAllocPurpose ap) {
6743 assert(FreeList_lock->owned_by_self(), "pre-condition");
6744
6745 if (count < g1_policy()->max_regions(ap)) {
6746 bool survivor = (ap == GCAllocForSurvived);
6747 HeapRegion* new_alloc_region = new_region(word_size,
6748 !survivor,
6749 true /* do_expand */);
6750 if (new_alloc_region != NULL) {
6751 // We really only need to do this for old regions given that we
6752 // should never scan survivors. But it doesn't hurt to do it
6753 // for survivors too.
6754 new_alloc_region->record_top_and_timestamp();
6755 if (survivor) {
6756 new_alloc_region->set_survivor();
6757 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Survivor);
6758 check_bitmaps("Survivor Region Allocation", new_alloc_region);
6759 } else {
6760 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Old);
6761 check_bitmaps("Old Region Allocation", new_alloc_region);
6762 }
6763 bool during_im = g1_policy()->during_initial_mark_pause();
6764 new_alloc_region->note_start_of_copying(during_im);
6765 return new_alloc_region;
6766 } else {
6767 g1_policy()->note_alloc_region_limit_reached(ap);
6768 }
6769 }
6770 return NULL;
6771 }
6772
6773 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
6774 size_t allocated_bytes,
6775 GCAllocPurpose ap) {
6776 bool during_im = g1_policy()->during_initial_mark_pause();
6777 alloc_region->note_end_of_copying(during_im);
6778 g1_policy()->record_bytes_copied_during_gc(allocated_bytes);
6779 if (ap == GCAllocForSurvived) {
6780 young_list()->add_survivor_region(alloc_region);
6781 } else {
6782 _old_set.add(alloc_region);
6783 }
6784 _hr_printer.retire(alloc_region);
6785 }
6786
6787 HeapRegion* SurvivorGCAllocRegion::allocate_new_region(size_t word_size,
6788 bool force) {
6789 assert(!force, "not supported for GC alloc regions");
6790 return _g1h->new_gc_alloc_region(word_size, count(), GCAllocForSurvived);
6791 }
6792
6793 void SurvivorGCAllocRegion::retire_region(HeapRegion* alloc_region,
6794 size_t allocated_bytes) {
6795 _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes,
6796 GCAllocForSurvived);
6797 }
6798
6799 HeapRegion* OldGCAllocRegion::allocate_new_region(size_t word_size,
6800 bool force) {
6801 assert(!force, "not supported for GC alloc regions");
6802 return _g1h->new_gc_alloc_region(word_size, count(), GCAllocForTenured);
6803 }
6804
6805 void OldGCAllocRegion::retire_region(HeapRegion* alloc_region,
6806 size_t allocated_bytes) {
6807 _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes,
6808 GCAllocForTenured);
6809 }
6810
6811 HeapRegion* OldGCAllocRegion::release() {
6812 HeapRegion* cur = get();
6813 if (cur != NULL) {
6814 // Determine how far we are from the next card boundary. If it is smaller than
6815 // the minimum object size we can allocate into, expand into the next card.
6816 HeapWord* top = cur->top();
6817 HeapWord* aligned_top = (HeapWord*)align_ptr_up(top, G1BlockOffsetSharedArray::N_bytes);
6818
6819 size_t to_allocate_words = pointer_delta(aligned_top, top, HeapWordSize);
6820
6821 if (to_allocate_words != 0) {
6822 // We are not at a card boundary. Fill up, possibly into the next, taking the
6823 // end of the region and the minimum object size into account.
6824 to_allocate_words = MIN2(pointer_delta(cur->end(), cur->top(), HeapWordSize),
6825 MAX2(to_allocate_words, G1CollectedHeap::min_fill_size()));
6826
6827 // Skip allocation if there is not enough space to allocate even the smallest
6828 // possible object. In this case this region will not be retained, so the
6829 // original problem cannot occur.
6830 if (to_allocate_words >= G1CollectedHeap::min_fill_size()) {
6831 HeapWord* dummy = attempt_allocation(to_allocate_words, true /* bot_updates */);
6832 CollectedHeap::fill_with_object(dummy, to_allocate_words);
6833 }
6834 }
6835 }
6836 return G1AllocRegion::release();
6837 }
6838
6839 // Heap region set verification
6840
6841 class VerifyRegionListsClosure : public HeapRegionClosure {
6842 private:
6843 HeapRegionSet* _old_set;
6844 HeapRegionSet* _humongous_set;
6845 HeapRegionManager* _hrm;
6846
6847 public:
6848 HeapRegionSetCount _old_count;
6849 HeapRegionSetCount _humongous_count;
6850 HeapRegionSetCount _free_count;
6851
6852 VerifyRegionListsClosure(HeapRegionSet* old_set,
6853 HeapRegionSet* humongous_set,
6854 HeapRegionManager* hrm) :
6855 _old_set(old_set), _humongous_set(humongous_set), _hrm(hrm),
6856 _old_count(), _humongous_count(), _free_count(){ }
6857
6858 bool doHeapRegion(HeapRegion* hr) {
6859 if (hr->continuesHumongous()) {
6860 return false;
6861 }
6862
6863 if (hr->is_young()) {
6864 // TODO
6865 } else if (hr->startsHumongous()) {
6866 assert(hr->containing_set() == _humongous_set, err_msg("Heap region %u is starts humongous but not in humongous set.", hr->hrm_index()));
6867 _humongous_count.increment(1u, hr->capacity());
6868 } else if (hr->is_empty()) {
6869 assert(_hrm->is_free(hr), err_msg("Heap region %u is empty but not on the free list.", hr->hrm_index()));
6870 _free_count.increment(1u, hr->capacity());
6871 } else {
6872 assert(hr->containing_set() == _old_set, err_msg("Heap region %u is old but not in the old set.", hr->hrm_index()));
6873 _old_count.increment(1u, hr->capacity());
6874 }
6875 return false;
6876 }
6877
6878 void verify_counts(HeapRegionSet* old_set, HeapRegionSet* humongous_set, HeapRegionManager* free_list) {
6879 guarantee(old_set->length() == _old_count.length(), err_msg("Old set count mismatch. Expected %u, actual %u.", old_set->length(), _old_count.length()));
6880 guarantee(old_set->total_capacity_bytes() == _old_count.capacity(), err_msg("Old set capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
6881 old_set->total_capacity_bytes(), _old_count.capacity()));
6882
6883 guarantee(humongous_set->length() == _humongous_count.length(), err_msg("Hum set count mismatch. Expected %u, actual %u.", humongous_set->length(), _humongous_count.length()));
6884 guarantee(humongous_set->total_capacity_bytes() == _humongous_count.capacity(), err_msg("Hum set capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
6885 humongous_set->total_capacity_bytes(), _humongous_count.capacity()));
6886
6887 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()));
6888 guarantee(free_list->total_capacity_bytes() == _free_count.capacity(), err_msg("Free list capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
6889 free_list->total_capacity_bytes(), _free_count.capacity()));
6890 }
6891 };
6892
6893 void G1CollectedHeap::verify_region_sets() {
6894 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6895
6896 // First, check the explicit lists.
6897 _hrm.verify();
6898 {
6899 // Given that a concurrent operation might be adding regions to
6900 // the secondary free list we have to take the lock before
6901 // verifying it.
6902 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6903 _secondary_free_list.verify_list();
6904 }
6905
6906 // If a concurrent region freeing operation is in progress it will
6907 // be difficult to correctly attributed any free regions we come
6908 // across to the correct free list given that they might belong to
6909 // one of several (free_list, secondary_free_list, any local lists,
6910 // etc.). So, if that's the case we will skip the rest of the
6911 // verification operation. Alternatively, waiting for the concurrent
6912 // operation to complete will have a non-trivial effect on the GC's
6913 // operation (no concurrent operation will last longer than the
6914 // interval between two calls to verification) and it might hide
6915 // any issues that we would like to catch during testing.
6916 if (free_regions_coming()) {
6917 return;
6918 }
6919
6920 // Make sure we append the secondary_free_list on the free_list so
6921 // that all free regions we will come across can be safely
6922 // attributed to the free_list.
6923 append_secondary_free_list_if_not_empty_with_lock();
6924
6925 // Finally, make sure that the region accounting in the lists is
6926 // consistent with what we see in the heap.
6927
6928 VerifyRegionListsClosure cl(&_old_set, &_humongous_set, &_hrm);
6929 heap_region_iterate(&cl);
6930 cl.verify_counts(&_old_set, &_humongous_set, &_hrm);
6931 }
6932
6933 // Optimized nmethod scanning
6934
6935 class RegisterNMethodOopClosure: public OopClosure {
6936 G1CollectedHeap* _g1h;
6937 nmethod* _nm;
6938
6939 template <class T> void do_oop_work(T* p) {
6940 T heap_oop = oopDesc::load_heap_oop(p);
6941 if (!oopDesc::is_null(heap_oop)) {
6942 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
6943 HeapRegion* hr = _g1h->heap_region_containing(obj);
6944 assert(!hr->continuesHumongous(),
6945 err_msg("trying to add code root "PTR_FORMAT" in continuation of humongous region "HR_FORMAT
6946 " starting at "HR_FORMAT,
6947 _nm, HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())));
6948
6949 // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries.
6950 hr->add_strong_code_root_locked(_nm);
6951 }
6952 }
6953
6954 public:
6955 RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
6956 _g1h(g1h), _nm(nm) {}
6957
6958 void do_oop(oop* p) { do_oop_work(p); }
6959 void do_oop(narrowOop* p) { do_oop_work(p); }
6960 };
6961
6962 class UnregisterNMethodOopClosure: public OopClosure {
6963 G1CollectedHeap* _g1h;
6964 nmethod* _nm;
6965
6966 template <class T> void do_oop_work(T* p) {
6967 T heap_oop = oopDesc::load_heap_oop(p);
6968 if (!oopDesc::is_null(heap_oop)) {
6969 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
6970 HeapRegion* hr = _g1h->heap_region_containing(obj);
6971 assert(!hr->continuesHumongous(),
6972 err_msg("trying to remove code root "PTR_FORMAT" in continuation of humongous region "HR_FORMAT
6973 " starting at "HR_FORMAT,
6974 _nm, HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())));
6975
6976 hr->remove_strong_code_root(_nm);
6977 }
6978 }
6979
6980 public:
6981 UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
6982 _g1h(g1h), _nm(nm) {}
6983
6984 void do_oop(oop* p) { do_oop_work(p); }
6985 void do_oop(narrowOop* p) { do_oop_work(p); }
6986 };
6987
6988 void G1CollectedHeap::register_nmethod(nmethod* nm) {
6989 CollectedHeap::register_nmethod(nm);
6990
6991 guarantee(nm != NULL, "sanity");
6992 RegisterNMethodOopClosure reg_cl(this, nm);
6993 nm->oops_do(®_cl);
6994 }
6995
6996 void G1CollectedHeap::unregister_nmethod(nmethod* nm) {
6997 CollectedHeap::unregister_nmethod(nm);
6998
6999 guarantee(nm != NULL, "sanity");
7000 UnregisterNMethodOopClosure reg_cl(this, nm);
7001 nm->oops_do(®_cl, true);
7002 }
7003
7004 void G1CollectedHeap::purge_code_root_memory() {
7005 double purge_start = os::elapsedTime();
7006 G1CodeRootSet::purge();
7007 double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0;
7008 g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms);
7009 }
7010
7011 class RebuildStrongCodeRootClosure: public CodeBlobClosure {
7012 G1CollectedHeap* _g1h;
7013
7014 public:
7015 RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) :
7016 _g1h(g1h) {}
7017
7018 void do_code_blob(CodeBlob* cb) {
7019 nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL;
7020 if (nm == NULL) {
7021 return;
7022 }
7023
7024 if (ScavengeRootsInCode) {
7025 _g1h->register_nmethod(nm);
7026 }
7027 }
7028 };
7029
7030 void G1CollectedHeap::rebuild_strong_code_roots() {
7031 RebuildStrongCodeRootClosure blob_cl(this);
7032 CodeCache::blobs_do(&blob_cl);
7033 }