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/g1RemSet.inline.hpp"
48 #include "gc_implementation/g1/g1StringDedup.hpp"
49 #include "gc_implementation/g1/g1YCTypes.hpp"
50 #include "gc_implementation/g1/heapRegion.inline.hpp"
51 #include "gc_implementation/g1/heapRegionRemSet.hpp"
52 #include "gc_implementation/g1/heapRegionSeq.inline.hpp"
53 #include "gc_implementation/g1/vm_operations_g1.hpp"
54 #include "gc_implementation/shared/gcHeapSummary.hpp"
55 #include "gc_implementation/shared/gcTimer.hpp"
56 #include "gc_implementation/shared/gcTrace.hpp"
57 #include "gc_implementation/shared/gcTraceTime.hpp"
58 #include "gc_implementation/shared/isGCActiveMark.hpp"
59 #include "memory/gcLocker.inline.hpp"
60 #include "memory/generationSpec.hpp"
61 #include "memory/iterator.hpp"
62 #include "memory/referenceProcessor.hpp"
63 #include "oops/oop.inline.hpp"
64 #include "oops/oop.pcgc.inline.hpp"
65 #include "runtime/prefetch.inline.hpp"
66 #include "runtime/orderAccess.inline.hpp"
67 #include "runtime/vmThread.hpp"
68 #include "utilities/globalDefinitions.hpp"
69 #include "utilities/ticks.hpp"
70
71 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;
72
73 // turn it on so that the contents of the young list (scan-only /
74 // to-be-collected) are printed at "strategic" points before / during
75 // / after the collection --- this is useful for debugging
76 #define YOUNG_LIST_VERBOSE 0
77 // CURRENT STATUS
78 // This file is under construction. Search for "FIXME".
79
80 // INVARIANTS/NOTES
81 //
82 // All allocation activity covered by the G1CollectedHeap interface is
83 // serialized by acquiring the HeapLock. This happens in mem_allocate
84 // and allocate_new_tlab, which are the "entry" points to the
85 // allocation code from the rest of the JVM. (Note that this does not
86 // apply to TLAB allocation, which is not part of this interface: it
87 // is done by clients of this interface.)
88
89 // Notes on implementation of parallelism in different tasks.
90 //
91 // G1ParVerifyTask uses heap_region_par_iterate_chunked() for parallelism.
92 // The number of GC workers is passed to heap_region_par_iterate_chunked().
93 // It does use run_task() which sets _n_workers in the task.
94 // G1ParTask executes g1_process_strong_roots() ->
95 // SharedHeap::process_strong_roots() which calls eventually to
96 // CardTableModRefBS::par_non_clean_card_iterate_work() which uses
97 // SequentialSubTasksDone. SharedHeap::process_strong_roots() also
98 // directly uses SubTasksDone (_process_strong_tasks field in SharedHeap).
99 //
100
101 // Local to this file.
102
103 class RefineCardTableEntryClosure: public CardTableEntryClosure {
104 bool _concurrent;
105 public:
106 RefineCardTableEntryClosure() : _concurrent(true) { }
107
108 bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
109 bool oops_into_cset = G1CollectedHeap::heap()->g1_rem_set()->refine_card(card_ptr, worker_i, false);
110 // This path is executed by the concurrent refine or mutator threads,
111 // concurrently, and so we do not care if card_ptr contains references
112 // that point into the collection set.
113 assert(!oops_into_cset, "should be");
114
115 if (_concurrent && SuspendibleThreadSet::should_yield()) {
116 // Caller will actually yield.
117 return false;
118 }
119 // Otherwise, we finished successfully; return true.
120 return true;
121 }
122
123 void set_concurrent(bool b) { _concurrent = b; }
124 };
125
126
127 class ClearLoggedCardTableEntryClosure: public CardTableEntryClosure {
128 size_t _num_processed;
129 CardTableModRefBS* _ctbs;
130 int _histo[256];
131
132 public:
133 ClearLoggedCardTableEntryClosure() :
134 _num_processed(0), _ctbs(G1CollectedHeap::heap()->g1_barrier_set())
135 {
136 for (int i = 0; i < 256; i++) _histo[i] = 0;
137 }
138
139 bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
140 unsigned char* ujb = (unsigned char*)card_ptr;
141 int ind = (int)(*ujb);
142 _histo[ind]++;
143
144 *card_ptr = (jbyte)CardTableModRefBS::clean_card_val();
145 _num_processed++;
146
147 return true;
148 }
149
150 size_t num_processed() { return _num_processed; }
151
152 void print_histo() {
153 gclog_or_tty->print_cr("Card table value histogram:");
154 for (int i = 0; i < 256; i++) {
155 if (_histo[i] != 0) {
156 gclog_or_tty->print_cr(" %d: %d", i, _histo[i]);
157 }
158 }
159 }
160 };
161
162 class RedirtyLoggedCardTableEntryClosure : public CardTableEntryClosure {
163 private:
164 size_t _num_processed;
165
166 public:
167 RedirtyLoggedCardTableEntryClosure() : CardTableEntryClosure(), _num_processed(0) { }
168
169 bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
170 *card_ptr = CardTableModRefBS::dirty_card_val();
171 _num_processed++;
172 return true;
173 }
174
175 size_t num_processed() const { return _num_processed; }
176 };
177
178 YoungList::YoungList(G1CollectedHeap* g1h) :
179 _g1h(g1h), _head(NULL), _length(0), _last_sampled_rs_lengths(0),
180 _survivor_head(NULL), _survivor_tail(NULL), _survivor_length(0) {
181 guarantee(check_list_empty(false), "just making sure...");
182 }
183
184 void YoungList::push_region(HeapRegion *hr) {
185 assert(!hr->is_young(), "should not already be young");
186 assert(hr->get_next_young_region() == NULL, "cause it should!");
187
188 hr->set_next_young_region(_head);
189 _head = hr;
190
191 _g1h->g1_policy()->set_region_eden(hr, (int) _length);
192 ++_length;
193 }
194
195 void YoungList::add_survivor_region(HeapRegion* hr) {
196 assert(hr->is_survivor(), "should be flagged as survivor region");
197 assert(hr->get_next_young_region() == NULL, "cause it should!");
198
199 hr->set_next_young_region(_survivor_head);
200 if (_survivor_head == NULL) {
201 _survivor_tail = hr;
202 }
203 _survivor_head = hr;
204 ++_survivor_length;
205 }
206
207 void YoungList::empty_list(HeapRegion* list) {
208 while (list != NULL) {
209 HeapRegion* next = list->get_next_young_region();
210 list->set_next_young_region(NULL);
211 list->uninstall_surv_rate_group();
212 list->set_not_young();
213 list = next;
214 }
215 }
216
217 void YoungList::empty_list() {
218 assert(check_list_well_formed(), "young list should be well formed");
219
220 empty_list(_head);
221 _head = NULL;
222 _length = 0;
223
224 empty_list(_survivor_head);
225 _survivor_head = NULL;
226 _survivor_tail = NULL;
227 _survivor_length = 0;
228
229 _last_sampled_rs_lengths = 0;
230
231 assert(check_list_empty(false), "just making sure...");
232 }
233
234 bool YoungList::check_list_well_formed() {
235 bool ret = true;
236
237 uint length = 0;
238 HeapRegion* curr = _head;
239 HeapRegion* last = NULL;
240 while (curr != NULL) {
241 if (!curr->is_young()) {
242 gclog_or_tty->print_cr("### YOUNG REGION "PTR_FORMAT"-"PTR_FORMAT" "
243 "incorrectly tagged (y: %d, surv: %d)",
244 curr->bottom(), curr->end(),
245 curr->is_young(), curr->is_survivor());
246 ret = false;
247 }
248 ++length;
249 last = curr;
250 curr = curr->get_next_young_region();
251 }
252 ret = ret && (length == _length);
253
254 if (!ret) {
255 gclog_or_tty->print_cr("### YOUNG LIST seems not well formed!");
256 gclog_or_tty->print_cr("### list has %u entries, _length is %u",
257 length, _length);
258 }
259
260 return ret;
261 }
262
263 bool YoungList::check_list_empty(bool check_sample) {
264 bool ret = true;
265
266 if (_length != 0) {
267 gclog_or_tty->print_cr("### YOUNG LIST should have 0 length, not %u",
268 _length);
269 ret = false;
270 }
271 if (check_sample && _last_sampled_rs_lengths != 0) {
272 gclog_or_tty->print_cr("### YOUNG LIST has non-zero last sampled RS lengths");
273 ret = false;
274 }
275 if (_head != NULL) {
276 gclog_or_tty->print_cr("### YOUNG LIST does not have a NULL head");
277 ret = false;
278 }
279 if (!ret) {
280 gclog_or_tty->print_cr("### YOUNG LIST does not seem empty");
281 }
282
283 return ret;
284 }
285
286 void
287 YoungList::rs_length_sampling_init() {
288 _sampled_rs_lengths = 0;
289 _curr = _head;
290 }
291
292 bool
293 YoungList::rs_length_sampling_more() {
294 return _curr != NULL;
295 }
296
297 void
298 YoungList::rs_length_sampling_next() {
299 assert( _curr != NULL, "invariant" );
300 size_t rs_length = _curr->rem_set()->occupied();
301
302 _sampled_rs_lengths += rs_length;
303
304 // The current region may not yet have been added to the
305 // incremental collection set (it gets added when it is
306 // retired as the current allocation region).
307 if (_curr->in_collection_set()) {
308 // Update the collection set policy information for this region
309 _g1h->g1_policy()->update_incremental_cset_info(_curr, rs_length);
310 }
311
312 _curr = _curr->get_next_young_region();
313 if (_curr == NULL) {
314 _last_sampled_rs_lengths = _sampled_rs_lengths;
315 // gclog_or_tty->print_cr("last sampled RS lengths = %d", _last_sampled_rs_lengths);
316 }
317 }
318
319 void
320 YoungList::reset_auxilary_lists() {
321 guarantee( is_empty(), "young list should be empty" );
322 assert(check_list_well_formed(), "young list should be well formed");
323
324 // Add survivor regions to SurvRateGroup.
325 _g1h->g1_policy()->note_start_adding_survivor_regions();
326 _g1h->g1_policy()->finished_recalculating_age_indexes(true /* is_survivors */);
327
328 int young_index_in_cset = 0;
329 for (HeapRegion* curr = _survivor_head;
330 curr != NULL;
331 curr = curr->get_next_young_region()) {
332 _g1h->g1_policy()->set_region_survivor(curr, young_index_in_cset);
333
334 // The region is a non-empty survivor so let's add it to
335 // the incremental collection set for the next evacuation
336 // pause.
337 _g1h->g1_policy()->add_region_to_incremental_cset_rhs(curr);
338 young_index_in_cset += 1;
339 }
340 assert((uint) young_index_in_cset == _survivor_length, "post-condition");
341 _g1h->g1_policy()->note_stop_adding_survivor_regions();
342
343 _head = _survivor_head;
344 _length = _survivor_length;
345 if (_survivor_head != NULL) {
346 assert(_survivor_tail != NULL, "cause it shouldn't be");
347 assert(_survivor_length > 0, "invariant");
348 _survivor_tail->set_next_young_region(NULL);
349 }
350
351 // Don't clear the survivor list handles until the start of
352 // the next evacuation pause - we need it in order to re-tag
353 // the survivor regions from this evacuation pause as 'young'
354 // at the start of the next.
355
356 _g1h->g1_policy()->finished_recalculating_age_indexes(false /* is_survivors */);
357
358 assert(check_list_well_formed(), "young list should be well formed");
359 }
360
361 void YoungList::print() {
362 HeapRegion* lists[] = {_head, _survivor_head};
363 const char* names[] = {"YOUNG", "SURVIVOR"};
364
365 for (unsigned int list = 0; list < ARRAY_SIZE(lists); ++list) {
366 gclog_or_tty->print_cr("%s LIST CONTENTS", names[list]);
367 HeapRegion *curr = lists[list];
368 if (curr == NULL)
369 gclog_or_tty->print_cr(" empty");
370 while (curr != NULL) {
371 gclog_or_tty->print_cr(" "HR_FORMAT", P: "PTR_FORMAT "N: "PTR_FORMAT", age: %4d",
372 HR_FORMAT_PARAMS(curr),
373 curr->prev_top_at_mark_start(),
374 curr->next_top_at_mark_start(),
375 curr->age_in_surv_rate_group_cond());
376 curr = curr->get_next_young_region();
377 }
378 }
379
380 gclog_or_tty->cr();
381 }
382
383 void G1CollectedHeap::push_dirty_cards_region(HeapRegion* hr)
384 {
385 // Claim the right to put the region on the dirty cards region list
386 // by installing a self pointer.
387 HeapRegion* next = hr->get_next_dirty_cards_region();
388 if (next == NULL) {
389 HeapRegion* res = (HeapRegion*)
390 Atomic::cmpxchg_ptr(hr, hr->next_dirty_cards_region_addr(),
391 NULL);
392 if (res == NULL) {
393 HeapRegion* head;
394 do {
395 // Put the region to the dirty cards region list.
396 head = _dirty_cards_region_list;
397 next = (HeapRegion*)
398 Atomic::cmpxchg_ptr(hr, &_dirty_cards_region_list, head);
399 if (next == head) {
400 assert(hr->get_next_dirty_cards_region() == hr,
401 "hr->get_next_dirty_cards_region() != hr");
402 if (next == NULL) {
403 // The last region in the list points to itself.
404 hr->set_next_dirty_cards_region(hr);
405 } else {
406 hr->set_next_dirty_cards_region(next);
407 }
408 }
409 } while (next != head);
410 }
411 }
412 }
413
414 HeapRegion* G1CollectedHeap::pop_dirty_cards_region()
415 {
416 HeapRegion* head;
417 HeapRegion* hr;
418 do {
419 head = _dirty_cards_region_list;
420 if (head == NULL) {
421 return NULL;
422 }
423 HeapRegion* new_head = head->get_next_dirty_cards_region();
424 if (head == new_head) {
425 // The last region.
426 new_head = NULL;
427 }
428 hr = (HeapRegion*)Atomic::cmpxchg_ptr(new_head, &_dirty_cards_region_list,
429 head);
430 } while (hr != head);
431 assert(hr != NULL, "invariant");
432 hr->set_next_dirty_cards_region(NULL);
433 return hr;
434 }
435
436 #ifdef ASSERT
437 // A region is added to the collection set as it is retired
438 // so an address p can point to a region which will be in the
439 // collection set but has not yet been retired. This method
440 // therefore is only accurate during a GC pause after all
441 // regions have been retired. It is used for debugging
442 // to check if an nmethod has references to objects that can
443 // be move during a partial collection. Though it can be
444 // inaccurate, it is sufficient for G1 because the conservative
445 // implementation of is_scavengable() for G1 will indicate that
446 // all nmethods must be scanned during a partial collection.
447 bool G1CollectedHeap::is_in_partial_collection(const void* p) {
448 if (p == NULL) {
449 return false;
450 }
451 return heap_region_containing(p)->in_collection_set();
452 }
453 #endif
454
455 // Returns true if the reference points to an object that
456 // can move in an incremental collection.
457 bool G1CollectedHeap::is_scavengable(const void* p) {
458 HeapRegion* hr = heap_region_containing(p);
459 return !hr->isHumongous();
460 }
461
462 void G1CollectedHeap::check_ct_logs_at_safepoint() {
463 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
464 CardTableModRefBS* ct_bs = g1_barrier_set();
465
466 // Count the dirty cards at the start.
467 CountNonCleanMemRegionClosure count1(this);
468 ct_bs->mod_card_iterate(&count1);
469 int orig_count = count1.n();
470
471 // First clear the logged cards.
472 ClearLoggedCardTableEntryClosure clear;
473 dcqs.apply_closure_to_all_completed_buffers(&clear);
474 dcqs.iterate_closure_all_threads(&clear, false);
475 clear.print_histo();
476
477 // Now ensure that there's no dirty cards.
478 CountNonCleanMemRegionClosure count2(this);
479 ct_bs->mod_card_iterate(&count2);
480 if (count2.n() != 0) {
481 gclog_or_tty->print_cr("Card table has %d entries; %d originally",
482 count2.n(), orig_count);
483 }
484 guarantee(count2.n() == 0, "Card table should be clean.");
485
486 RedirtyLoggedCardTableEntryClosure redirty;
487 dcqs.apply_closure_to_all_completed_buffers(&redirty);
488 dcqs.iterate_closure_all_threads(&redirty, false);
489 gclog_or_tty->print_cr("Log entries = %d, dirty cards = %d.",
490 clear.num_processed(), orig_count);
491 guarantee(redirty.num_processed() == clear.num_processed(),
492 err_msg("Redirtied "SIZE_FORMAT" cards, bug cleared "SIZE_FORMAT,
493 redirty.num_processed(), clear.num_processed()));
494
495 CountNonCleanMemRegionClosure count3(this);
496 ct_bs->mod_card_iterate(&count3);
497 if (count3.n() != orig_count) {
498 gclog_or_tty->print_cr("Should have restored them all: orig = %d, final = %d.",
499 orig_count, count3.n());
500 guarantee(count3.n() >= orig_count, "Should have restored them all.");
501 }
502 }
503
504 // Private class members.
505
506 G1CollectedHeap* G1CollectedHeap::_g1h;
507
508 // Private methods.
509
510 HeapRegion*
511 G1CollectedHeap::new_region_try_secondary_free_list(bool is_old) {
512 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
513 while (!_secondary_free_list.is_empty() || free_regions_coming()) {
514 if (!_secondary_free_list.is_empty()) {
515 if (G1ConcRegionFreeingVerbose) {
516 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
517 "secondary_free_list has %u entries",
518 _secondary_free_list.length());
519 }
520 // It looks as if there are free regions available on the
521 // secondary_free_list. Let's move them to the free_list and try
522 // again to allocate from it.
523 append_secondary_free_list();
524
525 assert(!_free_list.is_empty(), "if the secondary_free_list was not "
526 "empty we should have moved at least one entry to the free_list");
527 HeapRegion* res = _free_list.remove_region(is_old);
528 if (G1ConcRegionFreeingVerbose) {
529 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
530 "allocated "HR_FORMAT" from secondary_free_list",
531 HR_FORMAT_PARAMS(res));
532 }
533 return res;
534 }
535
536 // Wait here until we get notified either when (a) there are no
537 // more free regions coming or (b) some regions have been moved on
538 // the secondary_free_list.
539 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
540 }
541
542 if (G1ConcRegionFreeingVerbose) {
543 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
544 "could not allocate from secondary_free_list");
545 }
546 return NULL;
547 }
548
549 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) {
550 assert(!isHumongous(word_size) || word_size <= HeapRegion::GrainWords,
551 "the only time we use this to allocate a humongous region is "
552 "when we are allocating a single humongous region");
553
554 HeapRegion* res;
555 if (G1StressConcRegionFreeing) {
556 if (!_secondary_free_list.is_empty()) {
557 if (G1ConcRegionFreeingVerbose) {
558 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
559 "forced to look at the secondary_free_list");
560 }
561 res = new_region_try_secondary_free_list(is_old);
562 if (res != NULL) {
563 return res;
564 }
565 }
566 }
567
568 res = _free_list.remove_region(is_old);
569
570 if (res == NULL) {
571 if (G1ConcRegionFreeingVerbose) {
572 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
573 "res == NULL, trying the secondary_free_list");
574 }
575 res = new_region_try_secondary_free_list(is_old);
576 }
577 if (res == NULL && do_expand && _expand_heap_after_alloc_failure) {
578 // Currently, only attempts to allocate GC alloc regions set
579 // do_expand to true. So, we should only reach here during a
580 // safepoint. If this assumption changes we might have to
581 // reconsider the use of _expand_heap_after_alloc_failure.
582 assert(SafepointSynchronize::is_at_safepoint(), "invariant");
583
584 ergo_verbose1(ErgoHeapSizing,
585 "attempt heap expansion",
586 ergo_format_reason("region allocation request failed")
587 ergo_format_byte("allocation request"),
588 word_size * HeapWordSize);
589 if (expand(word_size * HeapWordSize)) {
590 // Given that expand() succeeded in expanding the heap, and we
591 // always expand the heap by an amount aligned to the heap
592 // region size, the free list should in theory not be empty.
593 // In either case remove_region() will check for NULL.
594 res = _free_list.remove_region(is_old);
595 } else {
596 _expand_heap_after_alloc_failure = false;
597 }
598 }
599 return res;
600 }
601
602 uint G1CollectedHeap::humongous_obj_allocate_find_first(uint num_regions,
603 size_t word_size) {
604 assert(isHumongous(word_size), "word_size should be humongous");
605 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
606
607 uint first = G1_NULL_HRS_INDEX;
608 if (num_regions == 1) {
609 // Only one region to allocate, no need to go through the slower
610 // path. The caller will attempt the expansion if this fails, so
611 // let's not try to expand here too.
612 HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */);
613 if (hr != NULL) {
614 first = hr->hrs_index();
615 } else {
616 first = G1_NULL_HRS_INDEX;
617 }
618 } else {
619 // We can't allocate humongous regions while cleanupComplete() is
620 // running, since some of the regions we find to be empty might not
621 // yet be added to the free list and it is not straightforward to
622 // know which list they are on so that we can remove them. Note
623 // that we only need to do this if we need to allocate more than
624 // one region to satisfy the current humongous allocation
625 // request. If we are only allocating one region we use the common
626 // region allocation code (see above).
627 wait_while_free_regions_coming();
628 append_secondary_free_list_if_not_empty_with_lock();
629
630 if (free_regions() >= num_regions) {
631 first = _hrs.find_contiguous(num_regions);
632 if (first != G1_NULL_HRS_INDEX) {
633 for (uint i = first; i < first + num_regions; ++i) {
634 HeapRegion* hr = region_at(i);
635 assert(hr->is_empty(), "sanity");
636 assert(is_on_master_free_list(hr), "sanity");
637 hr->set_pending_removal(true);
638 }
639 _free_list.remove_all_pending(num_regions);
640 }
641 }
642 }
643 return first;
644 }
645
646 HeapWord*
647 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first,
648 uint num_regions,
649 size_t word_size) {
650 assert(first != G1_NULL_HRS_INDEX, "pre-condition");
651 assert(isHumongous(word_size), "word_size should be humongous");
652 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
653
654 // Index of last region in the series + 1.
655 uint last = first + num_regions;
656
657 // We need to initialize the region(s) we just discovered. This is
658 // a bit tricky given that it can happen concurrently with
659 // refinement threads refining cards on these regions and
660 // potentially wanting to refine the BOT as they are scanning
661 // those cards (this can happen shortly after a cleanup; see CR
662 // 6991377). So we have to set up the region(s) carefully and in
663 // a specific order.
664
665 // The word size sum of all the regions we will allocate.
666 size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords;
667 assert(word_size <= word_size_sum, "sanity");
668
669 // This will be the "starts humongous" region.
670 HeapRegion* first_hr = region_at(first);
671 // The header of the new object will be placed at the bottom of
672 // the first region.
673 HeapWord* new_obj = first_hr->bottom();
674 // This will be the new end of the first region in the series that
675 // should also match the end of the last region in the series.
676 HeapWord* new_end = new_obj + word_size_sum;
677 // This will be the new top of the first region that will reflect
678 // this allocation.
679 HeapWord* new_top = new_obj + word_size;
680
681 // First, we need to zero the header of the space that we will be
682 // allocating. When we update top further down, some refinement
683 // threads might try to scan the region. By zeroing the header we
684 // ensure that any thread that will try to scan the region will
685 // come across the zero klass word and bail out.
686 //
687 // NOTE: It would not have been correct to have used
688 // CollectedHeap::fill_with_object() and make the space look like
689 // an int array. The thread that is doing the allocation will
690 // later update the object header to a potentially different array
691 // type and, for a very short period of time, the klass and length
692 // fields will be inconsistent. This could cause a refinement
693 // thread to calculate the object size incorrectly.
694 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
695
696 // We will set up the first region as "starts humongous". This
697 // will also update the BOT covering all the regions to reflect
698 // that there is a single object that starts at the bottom of the
699 // first region.
700 first_hr->set_startsHumongous(new_top, new_end);
701
702 // Then, if there are any, we will set up the "continues
703 // humongous" regions.
704 HeapRegion* hr = NULL;
705 for (uint i = first + 1; i < last; ++i) {
706 hr = region_at(i);
707 hr->set_continuesHumongous(first_hr);
708 }
709 // If we have "continues humongous" regions (hr != NULL), then the
710 // end of the last one should match new_end.
711 assert(hr == NULL || hr->end() == new_end, "sanity");
712
713 // Up to this point no concurrent thread would have been able to
714 // do any scanning on any region in this series. All the top
715 // fields still point to bottom, so the intersection between
716 // [bottom,top] and [card_start,card_end] will be empty. Before we
717 // update the top fields, we'll do a storestore to make sure that
718 // no thread sees the update to top before the zeroing of the
719 // object header and the BOT initialization.
720 OrderAccess::storestore();
721
722 // Now that the BOT and the object header have been initialized,
723 // we can update top of the "starts humongous" region.
724 assert(first_hr->bottom() < new_top && new_top <= first_hr->end(),
725 "new_top should be in this region");
726 first_hr->set_top(new_top);
727 if (_hr_printer.is_active()) {
728 HeapWord* bottom = first_hr->bottom();
729 HeapWord* end = first_hr->orig_end();
730 if ((first + 1) == last) {
731 // the series has a single humongous region
732 _hr_printer.alloc(G1HRPrinter::SingleHumongous, first_hr, new_top);
733 } else {
734 // the series has more than one humongous regions
735 _hr_printer.alloc(G1HRPrinter::StartsHumongous, first_hr, end);
736 }
737 }
738
739 // Now, we will update the top fields of the "continues humongous"
740 // regions. The reason we need to do this is that, otherwise,
741 // these regions would look empty and this will confuse parts of
742 // G1. For example, the code that looks for a consecutive number
743 // of empty regions will consider them empty and try to
744 // re-allocate them. We can extend is_empty() to also include
745 // !continuesHumongous(), but it is easier to just update the top
746 // fields here. The way we set top for all regions (i.e., top ==
747 // end for all regions but the last one, top == new_top for the
748 // last one) is actually used when we will free up the humongous
749 // region in free_humongous_region().
750 hr = NULL;
751 for (uint i = first + 1; i < last; ++i) {
752 hr = region_at(i);
753 if ((i + 1) == last) {
754 // last continues humongous region
755 assert(hr->bottom() < new_top && new_top <= hr->end(),
756 "new_top should fall on this region");
757 hr->set_top(new_top);
758 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, new_top);
759 } else {
760 // not last one
761 assert(new_top > hr->end(), "new_top should be above this region");
762 hr->set_top(hr->end());
763 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, hr->end());
764 }
765 }
766 // If we have continues humongous regions (hr != NULL), then the
767 // end of the last one should match new_end and its top should
768 // match new_top.
769 assert(hr == NULL ||
770 (hr->end() == new_end && hr->top() == new_top), "sanity");
771 check_bitmaps("Humongous Region Allocation", first_hr);
772
773 assert(first_hr->used() == word_size * HeapWordSize, "invariant");
774 _summary_bytes_used += first_hr->used();
775 _humongous_set.add(first_hr);
776
777 return new_obj;
778 }
779
780 // If could fit into free regions w/o expansion, try.
781 // Otherwise, if can expand, do so.
782 // Otherwise, if using ex regions might help, try with ex given back.
783 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size) {
784 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
785
786 verify_region_sets_optional();
787
788 size_t word_size_rounded = round_to(word_size, HeapRegion::GrainWords);
789 uint num_regions = (uint) (word_size_rounded / HeapRegion::GrainWords);
790 uint x_num = expansion_regions();
791 uint fs = _hrs.free_suffix();
792 uint first = humongous_obj_allocate_find_first(num_regions, word_size);
793 if (first == G1_NULL_HRS_INDEX) {
794 // The only thing we can do now is attempt expansion.
795 if (fs + x_num >= num_regions) {
796 // If the number of regions we're trying to allocate for this
797 // object is at most the number of regions in the free suffix,
798 // then the call to humongous_obj_allocate_find_first() above
799 // should have succeeded and we wouldn't be here.
800 //
801 // We should only be trying to expand when the free suffix is
802 // not sufficient for the object _and_ we have some expansion
803 // room available.
804 assert(num_regions > fs, "earlier allocation should have succeeded");
805
806 ergo_verbose1(ErgoHeapSizing,
807 "attempt heap expansion",
808 ergo_format_reason("humongous allocation request failed")
809 ergo_format_byte("allocation request"),
810 word_size * HeapWordSize);
811 if (expand((num_regions - fs) * HeapRegion::GrainBytes)) {
812 // Even though the heap was expanded, it might not have
813 // reached the desired size. So, we cannot assume that the
814 // allocation will succeed.
815 first = humongous_obj_allocate_find_first(num_regions, word_size);
816 }
817 }
818 }
819
820 HeapWord* result = NULL;
821 if (first != G1_NULL_HRS_INDEX) {
822 result =
823 humongous_obj_allocate_initialize_regions(first, num_regions, word_size);
824 assert(result != NULL, "it should always return a valid result");
825
826 // A successful humongous object allocation changes the used space
827 // information of the old generation so we need to recalculate the
828 // sizes and update the jstat counters here.
829 g1mm()->update_sizes();
830 }
831
832 verify_region_sets_optional();
833
834 return result;
835 }
836
837 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) {
838 assert_heap_not_locked_and_not_at_safepoint();
839 assert(!isHumongous(word_size), "we do not allow humongous TLABs");
840
841 unsigned int dummy_gc_count_before;
842 int dummy_gclocker_retry_count = 0;
843 return attempt_allocation(word_size, &dummy_gc_count_before, &dummy_gclocker_retry_count);
844 }
845
846 HeapWord*
847 G1CollectedHeap::mem_allocate(size_t word_size,
848 bool* gc_overhead_limit_was_exceeded) {
849 assert_heap_not_locked_and_not_at_safepoint();
850
851 // Loop until the allocation is satisfied, or unsatisfied after GC.
852 for (int try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
853 unsigned int gc_count_before;
854
855 HeapWord* result = NULL;
856 if (!isHumongous(word_size)) {
857 result = attempt_allocation(word_size, &gc_count_before, &gclocker_retry_count);
858 } else {
859 result = attempt_allocation_humongous(word_size, &gc_count_before, &gclocker_retry_count);
860 }
861 if (result != NULL) {
862 return result;
863 }
864
865 // Create the garbage collection operation...
866 VM_G1CollectForAllocation op(gc_count_before, word_size);
867 // ...and get the VM thread to execute it.
868 VMThread::execute(&op);
869
870 if (op.prologue_succeeded() && op.pause_succeeded()) {
871 // If the operation was successful we'll return the result even
872 // if it is NULL. If the allocation attempt failed immediately
873 // after a Full GC, it's unlikely we'll be able to allocate now.
874 HeapWord* result = op.result();
875 if (result != NULL && !isHumongous(word_size)) {
876 // Allocations that take place on VM operations do not do any
877 // card dirtying and we have to do it here. We only have to do
878 // this for non-humongous allocations, though.
879 dirty_young_block(result, word_size);
880 }
881 return result;
882 } else {
883 if (gclocker_retry_count > GCLockerRetryAllocationCount) {
884 return NULL;
885 }
886 assert(op.result() == NULL,
887 "the result should be NULL if the VM op did not succeed");
888 }
889
890 // Give a warning if we seem to be looping forever.
891 if ((QueuedAllocationWarningCount > 0) &&
892 (try_count % QueuedAllocationWarningCount == 0)) {
893 warning("G1CollectedHeap::mem_allocate retries %d times", try_count);
894 }
895 }
896
897 ShouldNotReachHere();
898 return NULL;
899 }
900
901 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size,
902 unsigned int *gc_count_before_ret,
903 int* gclocker_retry_count_ret) {
904 // Make sure you read the note in attempt_allocation_humongous().
905
906 assert_heap_not_locked_and_not_at_safepoint();
907 assert(!isHumongous(word_size), "attempt_allocation_slow() should not "
908 "be called for humongous allocation requests");
909
910 // We should only get here after the first-level allocation attempt
911 // (attempt_allocation()) failed to allocate.
912
913 // We will loop until a) we manage to successfully perform the
914 // allocation or b) we successfully schedule a collection which
915 // fails to perform the allocation. b) is the only case when we'll
916 // return NULL.
917 HeapWord* result = NULL;
918 for (int try_count = 1; /* we'll return */; try_count += 1) {
919 bool should_try_gc;
920 unsigned int gc_count_before;
921
922 {
923 MutexLockerEx x(Heap_lock);
924
925 result = _mutator_alloc_region.attempt_allocation_locked(word_size,
926 false /* bot_updates */);
927 if (result != NULL) {
928 return result;
929 }
930
931 // If we reach here, attempt_allocation_locked() above failed to
932 // allocate a new region. So the mutator alloc region should be NULL.
933 assert(_mutator_alloc_region.get() == NULL, "only way to get here");
934
935 if (GC_locker::is_active_and_needs_gc()) {
936 if (g1_policy()->can_expand_young_list()) {
937 // No need for an ergo verbose message here,
938 // can_expand_young_list() does this when it returns true.
939 result = _mutator_alloc_region.attempt_allocation_force(word_size,
940 false /* bot_updates */);
941 if (result != NULL) {
942 return result;
943 }
944 }
945 should_try_gc = false;
946 } else {
947 // The GCLocker may not be active but the GCLocker initiated
948 // GC may not yet have been performed (GCLocker::needs_gc()
949 // returns true). In this case we do not try this GC and
950 // wait until the GCLocker initiated GC is performed, and
951 // then retry the allocation.
952 if (GC_locker::needs_gc()) {
953 should_try_gc = false;
954 } else {
955 // Read the GC count while still holding the Heap_lock.
956 gc_count_before = total_collections();
957 should_try_gc = true;
958 }
959 }
960 }
961
962 if (should_try_gc) {
963 bool succeeded;
964 result = do_collection_pause(word_size, gc_count_before, &succeeded,
965 GCCause::_g1_inc_collection_pause);
966 if (result != NULL) {
967 assert(succeeded, "only way to get back a non-NULL result");
968 return result;
969 }
970
971 if (succeeded) {
972 // If we get here we successfully scheduled a collection which
973 // failed to allocate. No point in trying to allocate
974 // further. We'll just return NULL.
975 MutexLockerEx x(Heap_lock);
976 *gc_count_before_ret = total_collections();
977 return NULL;
978 }
979 } else {
980 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
981 MutexLockerEx x(Heap_lock);
982 *gc_count_before_ret = total_collections();
983 return NULL;
984 }
985 // The GCLocker is either active or the GCLocker initiated
986 // GC has not yet been performed. Stall until it is and
987 // then retry the allocation.
988 GC_locker::stall_until_clear();
989 (*gclocker_retry_count_ret) += 1;
990 }
991
992 // We can reach here if we were unsuccessful in scheduling a
993 // collection (because another thread beat us to it) or if we were
994 // stalled due to the GC locker. In either can we should retry the
995 // allocation attempt in case another thread successfully
996 // performed a collection and reclaimed enough space. We do the
997 // first attempt (without holding the Heap_lock) here and the
998 // follow-on attempt will be at the start of the next loop
999 // iteration (after taking the Heap_lock).
1000 result = _mutator_alloc_region.attempt_allocation(word_size,
1001 false /* bot_updates */);
1002 if (result != NULL) {
1003 return result;
1004 }
1005
1006 // Give a warning if we seem to be looping forever.
1007 if ((QueuedAllocationWarningCount > 0) &&
1008 (try_count % QueuedAllocationWarningCount == 0)) {
1009 warning("G1CollectedHeap::attempt_allocation_slow() "
1010 "retries %d times", try_count);
1011 }
1012 }
1013
1014 ShouldNotReachHere();
1015 return NULL;
1016 }
1017
1018 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size,
1019 unsigned int * gc_count_before_ret,
1020 int* gclocker_retry_count_ret) {
1021 // The structure of this method has a lot of similarities to
1022 // attempt_allocation_slow(). The reason these two were not merged
1023 // into a single one is that such a method would require several "if
1024 // allocation is not humongous do this, otherwise do that"
1025 // conditional paths which would obscure its flow. In fact, an early
1026 // version of this code did use a unified method which was harder to
1027 // follow and, as a result, it had subtle bugs that were hard to
1028 // track down. So keeping these two methods separate allows each to
1029 // be more readable. It will be good to keep these two in sync as
1030 // much as possible.
1031
1032 assert_heap_not_locked_and_not_at_safepoint();
1033 assert(isHumongous(word_size), "attempt_allocation_humongous() "
1034 "should only be called for humongous allocations");
1035
1036 // Humongous objects can exhaust the heap quickly, so we should check if we
1037 // need to start a marking cycle at each humongous object allocation. We do
1038 // the check before we do the actual allocation. The reason for doing it
1039 // before the allocation is that we avoid having to keep track of the newly
1040 // allocated memory while we do a GC.
1041 if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation",
1042 word_size)) {
1043 collect(GCCause::_g1_humongous_allocation);
1044 }
1045
1046 // We will loop until a) we manage to successfully perform the
1047 // allocation or b) we successfully schedule a collection which
1048 // fails to perform the allocation. b) is the only case when we'll
1049 // return NULL.
1050 HeapWord* result = NULL;
1051 for (int try_count = 1; /* we'll return */; try_count += 1) {
1052 bool should_try_gc;
1053 unsigned int gc_count_before;
1054
1055 {
1056 MutexLockerEx x(Heap_lock);
1057
1058 // Given that humongous objects are not allocated in young
1059 // regions, we'll first try to do the allocation without doing a
1060 // collection hoping that there's enough space in the heap.
1061 result = humongous_obj_allocate(word_size);
1062 if (result != NULL) {
1063 return result;
1064 }
1065
1066 if (GC_locker::is_active_and_needs_gc()) {
1067 should_try_gc = false;
1068 } else {
1069 // The GCLocker may not be active but the GCLocker initiated
1070 // GC may not yet have been performed (GCLocker::needs_gc()
1071 // returns true). In this case we do not try this GC and
1072 // wait until the GCLocker initiated GC is performed, and
1073 // then retry the allocation.
1074 if (GC_locker::needs_gc()) {
1075 should_try_gc = false;
1076 } else {
1077 // Read the GC count while still holding the Heap_lock.
1078 gc_count_before = total_collections();
1079 should_try_gc = true;
1080 }
1081 }
1082 }
1083
1084 if (should_try_gc) {
1085 // If we failed to allocate the humongous object, we should try to
1086 // do a collection pause (if we're allowed) in case it reclaims
1087 // enough space for the allocation to succeed after the pause.
1088
1089 bool succeeded;
1090 result = do_collection_pause(word_size, gc_count_before, &succeeded,
1091 GCCause::_g1_humongous_allocation);
1092 if (result != NULL) {
1093 assert(succeeded, "only way to get back a non-NULL result");
1094 return result;
1095 }
1096
1097 if (succeeded) {
1098 // If we get here we successfully scheduled a collection which
1099 // failed to allocate. No point in trying to allocate
1100 // further. We'll just return NULL.
1101 MutexLockerEx x(Heap_lock);
1102 *gc_count_before_ret = total_collections();
1103 return NULL;
1104 }
1105 } else {
1106 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
1107 MutexLockerEx x(Heap_lock);
1108 *gc_count_before_ret = total_collections();
1109 return NULL;
1110 }
1111 // The GCLocker is either active or the GCLocker initiated
1112 // GC has not yet been performed. Stall until it is and
1113 // then retry the allocation.
1114 GC_locker::stall_until_clear();
1115 (*gclocker_retry_count_ret) += 1;
1116 }
1117
1118 // We can reach here if we were unsuccessful in scheduling a
1119 // collection (because another thread beat us to it) or if we were
1120 // stalled due to the GC locker. In either can we should retry the
1121 // allocation attempt in case another thread successfully
1122 // performed a collection and reclaimed enough space. Give a
1123 // warning if we seem to be looping forever.
1124
1125 if ((QueuedAllocationWarningCount > 0) &&
1126 (try_count % QueuedAllocationWarningCount == 0)) {
1127 warning("G1CollectedHeap::attempt_allocation_humongous() "
1128 "retries %d times", try_count);
1129 }
1130 }
1131
1132 ShouldNotReachHere();
1133 return NULL;
1134 }
1135
1136 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
1137 bool expect_null_mutator_alloc_region) {
1138 assert_at_safepoint(true /* should_be_vm_thread */);
1139 assert(_mutator_alloc_region.get() == NULL ||
1140 !expect_null_mutator_alloc_region,
1141 "the current alloc region was unexpectedly found to be non-NULL");
1142
1143 if (!isHumongous(word_size)) {
1144 return _mutator_alloc_region.attempt_allocation_locked(word_size,
1145 false /* bot_updates */);
1146 } else {
1147 HeapWord* result = humongous_obj_allocate(word_size);
1148 if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) {
1149 g1_policy()->set_initiate_conc_mark_if_possible();
1150 }
1151 return result;
1152 }
1153
1154 ShouldNotReachHere();
1155 }
1156
1157 class PostMCRemSetClearClosure: public HeapRegionClosure {
1158 G1CollectedHeap* _g1h;
1159 ModRefBarrierSet* _mr_bs;
1160 public:
1161 PostMCRemSetClearClosure(G1CollectedHeap* g1h, ModRefBarrierSet* mr_bs) :
1162 _g1h(g1h), _mr_bs(mr_bs) {}
1163
1164 bool doHeapRegion(HeapRegion* r) {
1165 HeapRegionRemSet* hrrs = r->rem_set();
1166
1167 if (r->continuesHumongous()) {
1168 // We'll assert that the strong code root list and RSet is empty
1169 assert(hrrs->strong_code_roots_list_length() == 0, "sanity");
1170 assert(hrrs->occupied() == 0, "RSet should be empty");
1171 return false;
1172 }
1173
1174 _g1h->reset_gc_time_stamps(r);
1175 hrrs->clear();
1176 // You might think here that we could clear just the cards
1177 // corresponding to the used region. But no: if we leave a dirty card
1178 // in a region we might allocate into, then it would prevent that card
1179 // from being enqueued, and cause it to be missed.
1180 // Re: the performance cost: we shouldn't be doing full GC anyway!
1181 _mr_bs->clear(MemRegion(r->bottom(), r->end()));
1182
1183 return false;
1184 }
1185 };
1186
1187 void G1CollectedHeap::clear_rsets_post_compaction() {
1188 PostMCRemSetClearClosure rs_clear(this, g1_barrier_set());
1189 heap_region_iterate(&rs_clear);
1190 }
1191
1192 class RebuildRSOutOfRegionClosure: public HeapRegionClosure {
1193 G1CollectedHeap* _g1h;
1194 UpdateRSOopClosure _cl;
1195 int _worker_i;
1196 public:
1197 RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, int worker_i = 0) :
1198 _cl(g1->g1_rem_set(), worker_i),
1199 _worker_i(worker_i),
1200 _g1h(g1)
1201 { }
1202
1203 bool doHeapRegion(HeapRegion* r) {
1204 if (!r->continuesHumongous()) {
1205 _cl.set_from(r);
1206 r->oop_iterate(&_cl);
1207 }
1208 return false;
1209 }
1210 };
1211
1212 class ParRebuildRSTask: public AbstractGangTask {
1213 G1CollectedHeap* _g1;
1214 public:
1215 ParRebuildRSTask(G1CollectedHeap* g1)
1216 : AbstractGangTask("ParRebuildRSTask"),
1217 _g1(g1)
1218 { }
1219
1220 void work(uint worker_id) {
1221 RebuildRSOutOfRegionClosure rebuild_rs(_g1, worker_id);
1222 _g1->heap_region_par_iterate_chunked(&rebuild_rs, worker_id,
1223 _g1->workers()->active_workers(),
1224 HeapRegion::RebuildRSClaimValue);
1225 }
1226 };
1227
1228 class PostCompactionPrinterClosure: public HeapRegionClosure {
1229 private:
1230 G1HRPrinter* _hr_printer;
1231 public:
1232 bool doHeapRegion(HeapRegion* hr) {
1233 assert(!hr->is_young(), "not expecting to find young regions");
1234 // We only generate output for non-empty regions.
1235 if (!hr->is_empty()) {
1236 if (!hr->isHumongous()) {
1237 _hr_printer->post_compaction(hr, G1HRPrinter::Old);
1238 } else if (hr->startsHumongous()) {
1239 if (hr->region_num() == 1) {
1240 // single humongous region
1241 _hr_printer->post_compaction(hr, G1HRPrinter::SingleHumongous);
1242 } else {
1243 _hr_printer->post_compaction(hr, G1HRPrinter::StartsHumongous);
1244 }
1245 } else {
1246 assert(hr->continuesHumongous(), "only way to get here");
1247 _hr_printer->post_compaction(hr, G1HRPrinter::ContinuesHumongous);
1248 }
1249 }
1250 return false;
1251 }
1252
1253 PostCompactionPrinterClosure(G1HRPrinter* hr_printer)
1254 : _hr_printer(hr_printer) { }
1255 };
1256
1257 void G1CollectedHeap::print_hrs_post_compaction() {
1258 PostCompactionPrinterClosure cl(hr_printer());
1259 heap_region_iterate(&cl);
1260 }
1261
1262 bool G1CollectedHeap::do_collection(bool explicit_gc,
1263 bool clear_all_soft_refs,
1264 size_t word_size) {
1265 assert_at_safepoint(true /* should_be_vm_thread */);
1266
1267 if (GC_locker::check_active_before_gc()) {
1268 return false;
1269 }
1270
1271 STWGCTimer* gc_timer = G1MarkSweep::gc_timer();
1272 gc_timer->register_gc_start();
1273
1274 SerialOldTracer* gc_tracer = G1MarkSweep::gc_tracer();
1275 gc_tracer->report_gc_start(gc_cause(), gc_timer->gc_start());
1276
1277 SvcGCMarker sgcm(SvcGCMarker::FULL);
1278 ResourceMark rm;
1279
1280 print_heap_before_gc();
1281 trace_heap_before_gc(gc_tracer);
1282
1283 size_t metadata_prev_used = MetaspaceAux::used_bytes();
1284
1285 verify_region_sets_optional();
1286
1287 const bool do_clear_all_soft_refs = clear_all_soft_refs ||
1288 collector_policy()->should_clear_all_soft_refs();
1289
1290 ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy());
1291
1292 {
1293 IsGCActiveMark x;
1294
1295 // Timing
1296 assert(gc_cause() != GCCause::_java_lang_system_gc || explicit_gc, "invariant");
1297 gclog_or_tty->date_stamp(G1Log::fine() && PrintGCDateStamps);
1298 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
1299
1300 {
1301 GCTraceTime t(GCCauseString("Full GC", gc_cause()), G1Log::fine(), true, NULL);
1302 TraceCollectorStats tcs(g1mm()->full_collection_counters());
1303 TraceMemoryManagerStats tms(true /* fullGC */, gc_cause());
1304
1305 double start = os::elapsedTime();
1306 g1_policy()->record_full_collection_start();
1307
1308 // Note: When we have a more flexible GC logging framework that
1309 // allows us to add optional attributes to a GC log record we
1310 // could consider timing and reporting how long we wait in the
1311 // following two methods.
1312 wait_while_free_regions_coming();
1313 // If we start the compaction before the CM threads finish
1314 // scanning the root regions we might trip them over as we'll
1315 // be moving objects / updating references. So let's wait until
1316 // they are done. By telling them to abort, they should complete
1317 // early.
1318 _cm->root_regions()->abort();
1319 _cm->root_regions()->wait_until_scan_finished();
1320 append_secondary_free_list_if_not_empty_with_lock();
1321
1322 gc_prologue(true);
1323 increment_total_collections(true /* full gc */);
1324 increment_old_marking_cycles_started();
1325
1326 assert(used() == recalculate_used(), "Should be equal");
1327
1328 verify_before_gc();
1329
1330 check_bitmaps("Full GC Start");
1331 pre_full_gc_dump(gc_timer);
1332
1333 COMPILER2_PRESENT(DerivedPointerTable::clear());
1334
1335 // Disable discovery and empty the discovered lists
1336 // for the CM ref processor.
1337 ref_processor_cm()->disable_discovery();
1338 ref_processor_cm()->abandon_partial_discovery();
1339 ref_processor_cm()->verify_no_references_recorded();
1340
1341 // Abandon current iterations of concurrent marking and concurrent
1342 // refinement, if any are in progress. We have to do this before
1343 // wait_until_scan_finished() below.
1344 concurrent_mark()->abort();
1345
1346 // Make sure we'll choose a new allocation region afterwards.
1347 release_mutator_alloc_region();
1348 abandon_gc_alloc_regions();
1349 g1_rem_set()->cleanupHRRS();
1350
1351 // We should call this after we retire any currently active alloc
1352 // regions so that all the ALLOC / RETIRE events are generated
1353 // before the start GC event.
1354 _hr_printer.start_gc(true /* full */, (size_t) total_collections());
1355
1356 // We may have added regions to the current incremental collection
1357 // set between the last GC or pause and now. We need to clear the
1358 // incremental collection set and then start rebuilding it afresh
1359 // after this full GC.
1360 abandon_collection_set(g1_policy()->inc_cset_head());
1361 g1_policy()->clear_incremental_cset();
1362 g1_policy()->stop_incremental_cset_building();
1363
1364 tear_down_region_sets(false /* free_list_only */);
1365 g1_policy()->set_gcs_are_young(true);
1366
1367 // See the comments in g1CollectedHeap.hpp and
1368 // G1CollectedHeap::ref_processing_init() about
1369 // how reference processing currently works in G1.
1370
1371 // Temporarily make discovery by the STW ref processor single threaded (non-MT).
1372 ReferenceProcessorMTDiscoveryMutator stw_rp_disc_ser(ref_processor_stw(), false);
1373
1374 // Temporarily clear the STW ref processor's _is_alive_non_header field.
1375 ReferenceProcessorIsAliveMutator stw_rp_is_alive_null(ref_processor_stw(), NULL);
1376
1377 ref_processor_stw()->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/);
1378 ref_processor_stw()->setup_policy(do_clear_all_soft_refs);
1379
1380 // Do collection work
1381 {
1382 HandleMark hm; // Discard invalid handles created during gc
1383 G1MarkSweep::invoke_at_safepoint(ref_processor_stw(), do_clear_all_soft_refs);
1384 }
1385
1386 assert(free_regions() == 0, "we should not have added any free regions");
1387 rebuild_region_sets(false /* free_list_only */);
1388
1389 // Enqueue any discovered reference objects that have
1390 // not been removed from the discovered lists.
1391 ref_processor_stw()->enqueue_discovered_references();
1392
1393 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
1394
1395 MemoryService::track_memory_usage();
1396
1397 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
1398 ref_processor_stw()->verify_no_references_recorded();
1399
1400 // Delete metaspaces for unloaded class loaders and clean up loader_data graph
1401 ClassLoaderDataGraph::purge();
1402 MetaspaceAux::verify_metrics();
1403
1404 // Note: since we've just done a full GC, concurrent
1405 // marking is no longer active. Therefore we need not
1406 // re-enable reference discovery for the CM ref processor.
1407 // That will be done at the start of the next marking cycle.
1408 assert(!ref_processor_cm()->discovery_enabled(), "Postcondition");
1409 ref_processor_cm()->verify_no_references_recorded();
1410
1411 reset_gc_time_stamp();
1412 // Since everything potentially moved, we will clear all remembered
1413 // sets, and clear all cards. Later we will rebuild remembered
1414 // sets. We will also reset the GC time stamps of the regions.
1415 clear_rsets_post_compaction();
1416 check_gc_time_stamps();
1417
1418 // Resize the heap if necessary.
1419 resize_if_necessary_after_full_collection(explicit_gc ? 0 : word_size);
1420
1421 if (_hr_printer.is_active()) {
1422 // We should do this after we potentially resize the heap so
1423 // that all the COMMIT / UNCOMMIT events are generated before
1424 // the end GC event.
1425
1426 print_hrs_post_compaction();
1427 _hr_printer.end_gc(true /* full */, (size_t) total_collections());
1428 }
1429
1430 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
1431 if (hot_card_cache->use_cache()) {
1432 hot_card_cache->reset_card_counts();
1433 hot_card_cache->reset_hot_cache();
1434 }
1435
1436 // Rebuild remembered sets of all regions.
1437 if (G1CollectedHeap::use_parallel_gc_threads()) {
1438 uint n_workers =
1439 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
1440 workers()->active_workers(),
1441 Threads::number_of_non_daemon_threads());
1442 assert(UseDynamicNumberOfGCThreads ||
1443 n_workers == workers()->total_workers(),
1444 "If not dynamic should be using all the workers");
1445 workers()->set_active_workers(n_workers);
1446 // Set parallel threads in the heap (_n_par_threads) only
1447 // before a parallel phase and always reset it to 0 after
1448 // the phase so that the number of parallel threads does
1449 // no get carried forward to a serial phase where there
1450 // may be code that is "possibly_parallel".
1451 set_par_threads(n_workers);
1452
1453 ParRebuildRSTask rebuild_rs_task(this);
1454 assert(check_heap_region_claim_values(
1455 HeapRegion::InitialClaimValue), "sanity check");
1456 assert(UseDynamicNumberOfGCThreads ||
1457 workers()->active_workers() == workers()->total_workers(),
1458 "Unless dynamic should use total workers");
1459 // Use the most recent number of active workers
1460 assert(workers()->active_workers() > 0,
1461 "Active workers not properly set");
1462 set_par_threads(workers()->active_workers());
1463 workers()->run_task(&rebuild_rs_task);
1464 set_par_threads(0);
1465 assert(check_heap_region_claim_values(
1466 HeapRegion::RebuildRSClaimValue), "sanity check");
1467 reset_heap_region_claim_values();
1468 } else {
1469 RebuildRSOutOfRegionClosure rebuild_rs(this);
1470 heap_region_iterate(&rebuild_rs);
1471 }
1472
1473 // Rebuild the strong code root lists for each region
1474 rebuild_strong_code_roots();
1475
1476 if (true) { // FIXME
1477 MetaspaceGC::compute_new_size();
1478 }
1479
1480 #ifdef TRACESPINNING
1481 ParallelTaskTerminator::print_termination_counts();
1482 #endif
1483
1484 // Discard all rset updates
1485 JavaThread::dirty_card_queue_set().abandon_logs();
1486 assert(!G1DeferredRSUpdate
1487 || (G1DeferredRSUpdate &&
1488 (dirty_card_queue_set().completed_buffers_num() == 0)), "Should not be any");
1489
1490 _young_list->reset_sampled_info();
1491 // At this point there should be no regions in the
1492 // entire heap tagged as young.
1493 assert(check_young_list_empty(true /* check_heap */),
1494 "young list should be empty at this point");
1495
1496 // Update the number of full collections that have been completed.
1497 increment_old_marking_cycles_completed(false /* concurrent */);
1498
1499 _hrs.verify_optional();
1500 verify_region_sets_optional();
1501
1502 verify_after_gc();
1503
1504 // Clear the previous marking bitmap, if needed for bitmap verification.
1505 // Note we cannot do this when we clear the next marking bitmap in
1506 // ConcurrentMark::abort() above since VerifyDuringGC verifies the
1507 // objects marked during a full GC against the previous bitmap.
1508 // But we need to clear it before calling check_bitmaps below since
1509 // the full GC has compacted objects and updated TAMS but not updated
1510 // the prev bitmap.
1511 if (G1VerifyBitmaps) {
1512 ((CMBitMap*) concurrent_mark()->prevMarkBitMap())->clearAll();
1513 }
1514 check_bitmaps("Full GC End");
1515
1516 // Start a new incremental collection set for the next pause
1517 assert(g1_policy()->collection_set() == NULL, "must be");
1518 g1_policy()->start_incremental_cset_building();
1519
1520 clear_cset_fast_test();
1521
1522 init_mutator_alloc_region();
1523
1524 double end = os::elapsedTime();
1525 g1_policy()->record_full_collection_end();
1526
1527 if (G1Log::fine()) {
1528 g1_policy()->print_heap_transition();
1529 }
1530
1531 // We must call G1MonitoringSupport::update_sizes() in the same scoping level
1532 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
1533 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
1534 // before any GC notifications are raised.
1535 g1mm()->update_sizes();
1536
1537 gc_epilogue(true);
1538 }
1539
1540 if (G1Log::finer()) {
1541 g1_policy()->print_detailed_heap_transition(true /* full */);
1542 }
1543
1544 print_heap_after_gc();
1545 trace_heap_after_gc(gc_tracer);
1546
1547 post_full_gc_dump(gc_timer);
1548
1549 gc_timer->register_gc_end();
1550 gc_tracer->report_gc_end(gc_timer->gc_end(), gc_timer->time_partitions());
1551 }
1552
1553 return true;
1554 }
1555
1556 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
1557 // do_collection() will return whether it succeeded in performing
1558 // the GC. Currently, there is no facility on the
1559 // do_full_collection() API to notify the caller than the collection
1560 // did not succeed (e.g., because it was locked out by the GC
1561 // locker). So, right now, we'll ignore the return value.
1562 bool dummy = do_collection(true, /* explicit_gc */
1563 clear_all_soft_refs,
1564 0 /* word_size */);
1565 }
1566
1567 // This code is mostly copied from TenuredGeneration.
1568 void
1569 G1CollectedHeap::
1570 resize_if_necessary_after_full_collection(size_t word_size) {
1571 // Include the current allocation, if any, and bytes that will be
1572 // pre-allocated to support collections, as "used".
1573 const size_t used_after_gc = used();
1574 const size_t capacity_after_gc = capacity();
1575 const size_t free_after_gc = capacity_after_gc - used_after_gc;
1576
1577 // This is enforced in arguments.cpp.
1578 assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
1579 "otherwise the code below doesn't make sense");
1580
1581 // We don't have floating point command-line arguments
1582 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
1583 const double maximum_used_percentage = 1.0 - minimum_free_percentage;
1584 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
1585 const double minimum_used_percentage = 1.0 - maximum_free_percentage;
1586
1587 const size_t min_heap_size = collector_policy()->min_heap_byte_size();
1588 const size_t max_heap_size = collector_policy()->max_heap_byte_size();
1589
1590 // We have to be careful here as these two calculations can overflow
1591 // 32-bit size_t's.
1592 double used_after_gc_d = (double) used_after_gc;
1593 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
1594 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
1595
1596 // Let's make sure that they are both under the max heap size, which
1597 // by default will make them fit into a size_t.
1598 double desired_capacity_upper_bound = (double) max_heap_size;
1599 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
1600 desired_capacity_upper_bound);
1601 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
1602 desired_capacity_upper_bound);
1603
1604 // We can now safely turn them into size_t's.
1605 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
1606 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
1607
1608 // This assert only makes sense here, before we adjust them
1609 // with respect to the min and max heap size.
1610 assert(minimum_desired_capacity <= maximum_desired_capacity,
1611 err_msg("minimum_desired_capacity = "SIZE_FORMAT", "
1612 "maximum_desired_capacity = "SIZE_FORMAT,
1613 minimum_desired_capacity, maximum_desired_capacity));
1614
1615 // Should not be greater than the heap max size. No need to adjust
1616 // it with respect to the heap min size as it's a lower bound (i.e.,
1617 // we'll try to make the capacity larger than it, not smaller).
1618 minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size);
1619 // Should not be less than the heap min size. No need to adjust it
1620 // with respect to the heap max size as it's an upper bound (i.e.,
1621 // we'll try to make the capacity smaller than it, not greater).
1622 maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size);
1623
1624 if (capacity_after_gc < minimum_desired_capacity) {
1625 // Don't expand unless it's significant
1626 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
1627 ergo_verbose4(ErgoHeapSizing,
1628 "attempt heap expansion",
1629 ergo_format_reason("capacity lower than "
1630 "min desired capacity after Full GC")
1631 ergo_format_byte("capacity")
1632 ergo_format_byte("occupancy")
1633 ergo_format_byte_perc("min desired capacity"),
1634 capacity_after_gc, used_after_gc,
1635 minimum_desired_capacity, (double) MinHeapFreeRatio);
1636 expand(expand_bytes);
1637
1638 // No expansion, now see if we want to shrink
1639 } else if (capacity_after_gc > maximum_desired_capacity) {
1640 // Capacity too large, compute shrinking size
1641 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
1642 ergo_verbose4(ErgoHeapSizing,
1643 "attempt heap shrinking",
1644 ergo_format_reason("capacity higher than "
1645 "max desired capacity after Full GC")
1646 ergo_format_byte("capacity")
1647 ergo_format_byte("occupancy")
1648 ergo_format_byte_perc("max desired capacity"),
1649 capacity_after_gc, used_after_gc,
1650 maximum_desired_capacity, (double) MaxHeapFreeRatio);
1651 shrink(shrink_bytes);
1652 }
1653 }
1654
1655
1656 HeapWord*
1657 G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
1658 bool* succeeded) {
1659 assert_at_safepoint(true /* should_be_vm_thread */);
1660
1661 *succeeded = true;
1662 // Let's attempt the allocation first.
1663 HeapWord* result =
1664 attempt_allocation_at_safepoint(word_size,
1665 false /* expect_null_mutator_alloc_region */);
1666 if (result != NULL) {
1667 assert(*succeeded, "sanity");
1668 return result;
1669 }
1670
1671 // In a G1 heap, we're supposed to keep allocation from failing by
1672 // incremental pauses. Therefore, at least for now, we'll favor
1673 // expansion over collection. (This might change in the future if we can
1674 // do something smarter than full collection to satisfy a failed alloc.)
1675 result = expand_and_allocate(word_size);
1676 if (result != NULL) {
1677 assert(*succeeded, "sanity");
1678 return result;
1679 }
1680
1681 // Expansion didn't work, we'll try to do a Full GC.
1682 bool gc_succeeded = do_collection(false, /* explicit_gc */
1683 false, /* clear_all_soft_refs */
1684 word_size);
1685 if (!gc_succeeded) {
1686 *succeeded = false;
1687 return NULL;
1688 }
1689
1690 // Retry the allocation
1691 result = attempt_allocation_at_safepoint(word_size,
1692 true /* expect_null_mutator_alloc_region */);
1693 if (result != NULL) {
1694 assert(*succeeded, "sanity");
1695 return result;
1696 }
1697
1698 // Then, try a Full GC that will collect all soft references.
1699 gc_succeeded = do_collection(false, /* explicit_gc */
1700 true, /* clear_all_soft_refs */
1701 word_size);
1702 if (!gc_succeeded) {
1703 *succeeded = false;
1704 return NULL;
1705 }
1706
1707 // Retry the allocation once more
1708 result = attempt_allocation_at_safepoint(word_size,
1709 true /* expect_null_mutator_alloc_region */);
1710 if (result != NULL) {
1711 assert(*succeeded, "sanity");
1712 return result;
1713 }
1714
1715 assert(!collector_policy()->should_clear_all_soft_refs(),
1716 "Flag should have been handled and cleared prior to this point");
1717
1718 // What else? We might try synchronous finalization later. If the total
1719 // space available is large enough for the allocation, then a more
1720 // complete compaction phase than we've tried so far might be
1721 // appropriate.
1722 assert(*succeeded, "sanity");
1723 return NULL;
1724 }
1725
1726 // Attempting to expand the heap sufficiently
1727 // to support an allocation of the given "word_size". If
1728 // successful, perform the allocation and return the address of the
1729 // allocated block, or else "NULL".
1730
1731 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size) {
1732 assert_at_safepoint(true /* should_be_vm_thread */);
1733
1734 verify_region_sets_optional();
1735
1736 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
1737 ergo_verbose1(ErgoHeapSizing,
1738 "attempt heap expansion",
1739 ergo_format_reason("allocation request failed")
1740 ergo_format_byte("allocation request"),
1741 word_size * HeapWordSize);
1742 if (expand(expand_bytes)) {
1743 _hrs.verify_optional();
1744 verify_region_sets_optional();
1745 return attempt_allocation_at_safepoint(word_size,
1746 false /* expect_null_mutator_alloc_region */);
1747 }
1748 return NULL;
1749 }
1750
1751 void G1CollectedHeap::update_committed_space(HeapWord* old_end,
1752 HeapWord* new_end) {
1753 assert(old_end != new_end, "don't call this otherwise");
1754 assert((HeapWord*) _g1_storage.high() == new_end, "invariant");
1755
1756 // Update the committed mem region.
1757 _g1_committed.set_end(new_end);
1758 // Tell the card table about the update.
1759 Universe::heap()->barrier_set()->resize_covered_region(_g1_committed);
1760 // Tell the BOT about the update.
1761 _bot_shared->resize(_g1_committed.word_size());
1762 // Tell the hot card cache about the update
1763 _cg1r->hot_card_cache()->resize_card_counts(capacity());
1764 }
1765
1766 bool G1CollectedHeap::expand(size_t expand_bytes) {
1767 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
1768 aligned_expand_bytes = align_size_up(aligned_expand_bytes,
1769 HeapRegion::GrainBytes);
1770 ergo_verbose2(ErgoHeapSizing,
1771 "expand the heap",
1772 ergo_format_byte("requested expansion amount")
1773 ergo_format_byte("attempted expansion amount"),
1774 expand_bytes, aligned_expand_bytes);
1775
1776 if (_g1_storage.uncommitted_size() == 0) {
1777 ergo_verbose0(ErgoHeapSizing,
1778 "did not expand the heap",
1779 ergo_format_reason("heap already fully expanded"));
1780 return false;
1781 }
1782
1783 // First commit the memory.
1784 HeapWord* old_end = (HeapWord*) _g1_storage.high();
1785 bool successful = _g1_storage.expand_by(aligned_expand_bytes);
1786 if (successful) {
1787 // Then propagate this update to the necessary data structures.
1788 HeapWord* new_end = (HeapWord*) _g1_storage.high();
1789 update_committed_space(old_end, new_end);
1790
1791 FreeRegionList expansion_list("Local Expansion List");
1792 MemRegion mr = _hrs.expand_by(old_end, new_end, &expansion_list);
1793 assert(mr.start() == old_end, "post-condition");
1794 // mr might be a smaller region than what was requested if
1795 // expand_by() was unable to allocate the HeapRegion instances
1796 assert(mr.end() <= new_end, "post-condition");
1797
1798 size_t actual_expand_bytes = mr.byte_size();
1799 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
1800 assert(actual_expand_bytes == expansion_list.total_capacity_bytes(),
1801 "post-condition");
1802 if (actual_expand_bytes < aligned_expand_bytes) {
1803 // We could not expand _hrs to the desired size. In this case we
1804 // need to shrink the committed space accordingly.
1805 assert(mr.end() < new_end, "invariant");
1806
1807 size_t diff_bytes = aligned_expand_bytes - actual_expand_bytes;
1808 // First uncommit the memory.
1809 _g1_storage.shrink_by(diff_bytes);
1810 // Then propagate this update to the necessary data structures.
1811 update_committed_space(new_end, mr.end());
1812 }
1813 _free_list.add_as_tail(&expansion_list);
1814
1815 if (_hr_printer.is_active()) {
1816 HeapWord* curr = mr.start();
1817 while (curr < mr.end()) {
1818 HeapWord* curr_end = curr + HeapRegion::GrainWords;
1819 _hr_printer.commit(curr, curr_end);
1820 curr = curr_end;
1821 }
1822 assert(curr == mr.end(), "post-condition");
1823 }
1824 g1_policy()->record_new_heap_size(n_regions());
1825 } else {
1826 ergo_verbose0(ErgoHeapSizing,
1827 "did not expand the heap",
1828 ergo_format_reason("heap expansion operation failed"));
1829 // The expansion of the virtual storage space was unsuccessful.
1830 // Let's see if it was because we ran out of swap.
1831 if (G1ExitOnExpansionFailure &&
1832 _g1_storage.uncommitted_size() >= aligned_expand_bytes) {
1833 // We had head room...
1834 vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion");
1835 }
1836 }
1837 return successful;
1838 }
1839
1840 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
1841 size_t aligned_shrink_bytes =
1842 ReservedSpace::page_align_size_down(shrink_bytes);
1843 aligned_shrink_bytes = align_size_down(aligned_shrink_bytes,
1844 HeapRegion::GrainBytes);
1845 uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes);
1846
1847 uint num_regions_removed = _hrs.shrink_by(num_regions_to_remove);
1848 HeapWord* old_end = (HeapWord*) _g1_storage.high();
1849 size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes;
1850
1851 ergo_verbose3(ErgoHeapSizing,
1852 "shrink the heap",
1853 ergo_format_byte("requested shrinking amount")
1854 ergo_format_byte("aligned shrinking amount")
1855 ergo_format_byte("attempted shrinking amount"),
1856 shrink_bytes, aligned_shrink_bytes, shrunk_bytes);
1857 if (num_regions_removed > 0) {
1858 _g1_storage.shrink_by(shrunk_bytes);
1859 HeapWord* new_end = (HeapWord*) _g1_storage.high();
1860
1861 if (_hr_printer.is_active()) {
1862 HeapWord* curr = old_end;
1863 while (curr > new_end) {
1864 HeapWord* curr_end = curr;
1865 curr -= HeapRegion::GrainWords;
1866 _hr_printer.uncommit(curr, curr_end);
1867 }
1868 }
1869
1870 _expansion_regions += num_regions_removed;
1871 update_committed_space(old_end, new_end);
1872 HeapRegionRemSet::shrink_heap(n_regions());
1873 g1_policy()->record_new_heap_size(n_regions());
1874 } else {
1875 ergo_verbose0(ErgoHeapSizing,
1876 "did not shrink the heap",
1877 ergo_format_reason("heap shrinking operation failed"));
1878 }
1879 }
1880
1881 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1882 verify_region_sets_optional();
1883
1884 // We should only reach here at the end of a Full GC which means we
1885 // should not not be holding to any GC alloc regions. The method
1886 // below will make sure of that and do any remaining clean up.
1887 abandon_gc_alloc_regions();
1888
1889 // Instead of tearing down / rebuilding the free lists here, we
1890 // could instead use the remove_all_pending() method on free_list to
1891 // remove only the ones that we need to remove.
1892 tear_down_region_sets(true /* free_list_only */);
1893 shrink_helper(shrink_bytes);
1894 rebuild_region_sets(true /* free_list_only */);
1895
1896 _hrs.verify_optional();
1897 verify_region_sets_optional();
1898 }
1899
1900 // Public methods.
1901
1902 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away
1903 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
1904 #endif // _MSC_VER
1905
1906
1907 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* policy_) :
1908 SharedHeap(policy_),
1909 _g1_policy(policy_),
1910 _dirty_card_queue_set(false),
1911 _into_cset_dirty_card_queue_set(false),
1912 _is_alive_closure_cm(this),
1913 _is_alive_closure_stw(this),
1914 _ref_processor_cm(NULL),
1915 _ref_processor_stw(NULL),
1916 _process_strong_tasks(new SubTasksDone(G1H_PS_NumElements)),
1917 _bot_shared(NULL),
1918 _evac_failure_scan_stack(NULL),
1919 _mark_in_progress(false),
1920 _cg1r(NULL), _summary_bytes_used(0),
1921 _g1mm(NULL),
1922 _refine_cte_cl(NULL),
1923 _full_collection(false),
1924 _free_list("Master Free List", new MasterFreeRegionListMtSafeChecker()),
1925 _secondary_free_list("Secondary Free List", new SecondaryFreeRegionListMtSafeChecker()),
1926 _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()),
1927 _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()),
1928 _free_regions_coming(false),
1929 _young_list(new YoungList(this)),
1930 _gc_time_stamp(0),
1931 _retained_old_gc_alloc_region(NULL),
1932 _survivor_plab_stats(YoungPLABSize, PLABWeight),
1933 _old_plab_stats(OldPLABSize, PLABWeight),
1934 _expand_heap_after_alloc_failure(true),
1935 _surviving_young_words(NULL),
1936 _old_marking_cycles_started(0),
1937 _old_marking_cycles_completed(0),
1938 _concurrent_cycle_started(false),
1939 _in_cset_fast_test(),
1940 _dirty_cards_region_list(NULL),
1941 _worker_cset_start_region(NULL),
1942 _worker_cset_start_region_time_stamp(NULL),
1943 _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()),
1944 _gc_timer_cm(new (ResourceObj::C_HEAP, mtGC) ConcurrentGCTimer()),
1945 _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()),
1946 _gc_tracer_cm(new (ResourceObj::C_HEAP, mtGC) G1OldTracer()) {
1947
1948 _g1h = this;
1949 if (_process_strong_tasks == NULL || !_process_strong_tasks->valid()) {
1950 vm_exit_during_initialization("Failed necessary allocation.");
1951 }
1952
1953 _humongous_object_threshold_in_words = HeapRegion::GrainWords / 2;
1954
1955 int n_queues = MAX2((int)ParallelGCThreads, 1);
1956 _task_queues = new RefToScanQueueSet(n_queues);
1957
1958 uint n_rem_sets = HeapRegionRemSet::num_par_rem_sets();
1959 assert(n_rem_sets > 0, "Invariant.");
1960
1961 _worker_cset_start_region = NEW_C_HEAP_ARRAY(HeapRegion*, n_queues, mtGC);
1962 _worker_cset_start_region_time_stamp = NEW_C_HEAP_ARRAY(unsigned int, n_queues, mtGC);
1963 _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC);
1964
1965 for (int i = 0; i < n_queues; i++) {
1966 RefToScanQueue* q = new RefToScanQueue();
1967 q->initialize();
1968 _task_queues->register_queue(i, q);
1969 ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo();
1970 }
1971 clear_cset_start_regions();
1972
1973 // Initialize the G1EvacuationFailureALot counters and flags.
1974 NOT_PRODUCT(reset_evacuation_should_fail();)
1975
1976 guarantee(_task_queues != NULL, "task_queues allocation failure.");
1977 }
1978
1979 jint G1CollectedHeap::initialize() {
1980 CollectedHeap::pre_initialize();
1981 os::enable_vtime();
1982
1983 G1Log::init();
1984
1985 // Necessary to satisfy locking discipline assertions.
1986
1987 MutexLocker x(Heap_lock);
1988
1989 // We have to initialize the printer before committing the heap, as
1990 // it will be used then.
1991 _hr_printer.set_active(G1PrintHeapRegions);
1992
1993 // While there are no constraints in the GC code that HeapWordSize
1994 // be any particular value, there are multiple other areas in the
1995 // system which believe this to be true (e.g. oop->object_size in some
1996 // cases incorrectly returns the size in wordSize units rather than
1997 // HeapWordSize).
1998 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
1999
2000 size_t init_byte_size = collector_policy()->initial_heap_byte_size();
2001 size_t max_byte_size = collector_policy()->max_heap_byte_size();
2002 size_t heap_alignment = collector_policy()->heap_alignment();
2003
2004 // Ensure that the sizes are properly aligned.
2005 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
2006 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
2007 Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap");
2008
2009 _refine_cte_cl = new RefineCardTableEntryClosure();
2010
2011 _cg1r = new ConcurrentG1Refine(this, _refine_cte_cl);
2012
2013 // Reserve the maximum.
2014
2015 // When compressed oops are enabled, the preferred heap base
2016 // is calculated by subtracting the requested size from the
2017 // 32Gb boundary and using the result as the base address for
2018 // heap reservation. If the requested size is not aligned to
2019 // HeapRegion::GrainBytes (i.e. the alignment that is passed
2020 // into the ReservedHeapSpace constructor) then the actual
2021 // base of the reserved heap may end up differing from the
2022 // address that was requested (i.e. the preferred heap base).
2023 // If this happens then we could end up using a non-optimal
2024 // compressed oops mode.
2025
2026 ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size,
2027 heap_alignment);
2028
2029 // It is important to do this in a way such that concurrent readers can't
2030 // temporarily think something is in the heap. (I've actually seen this
2031 // happen in asserts: DLD.)
2032 _reserved.set_word_size(0);
2033 _reserved.set_start((HeapWord*)heap_rs.base());
2034 _reserved.set_end((HeapWord*)(heap_rs.base() + heap_rs.size()));
2035
2036 _expansion_regions = (uint) (max_byte_size / HeapRegion::GrainBytes);
2037
2038 // Create the gen rem set (and barrier set) for the entire reserved region.
2039 _rem_set = collector_policy()->create_rem_set(_reserved, 2);
2040 set_barrier_set(rem_set()->bs());
2041 if (!barrier_set()->is_a(BarrierSet::G1SATBCTLogging)) {
2042 vm_exit_during_initialization("G1 requires a G1SATBLoggingCardTableModRefBS");
2043 return JNI_ENOMEM;
2044 }
2045
2046 // Also create a G1 rem set.
2047 _g1_rem_set = new G1RemSet(this, g1_barrier_set());
2048
2049 // Carve out the G1 part of the heap.
2050
2051 ReservedSpace g1_rs = heap_rs.first_part(max_byte_size);
2052 _g1_reserved = MemRegion((HeapWord*)g1_rs.base(),
2053 g1_rs.size()/HeapWordSize);
2054
2055 _g1_storage.initialize(g1_rs, 0);
2056 _g1_committed = MemRegion((HeapWord*)_g1_storage.low(), (size_t) 0);
2057 _hrs.initialize((HeapWord*) _g1_reserved.start(),
2058 (HeapWord*) _g1_reserved.end());
2059 assert(_hrs.max_length() == _expansion_regions,
2060 err_msg("max length: %u expansion regions: %u",
2061 _hrs.max_length(), _expansion_regions));
2062
2063 // Do later initialization work for concurrent refinement.
2064 _cg1r->init();
2065
2066 // 6843694 - ensure that the maximum region index can fit
2067 // in the remembered set structures.
2068 const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
2069 guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
2070
2071 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
2072 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
2073 guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
2074 "too many cards per region");
2075
2076 FreeRegionList::set_unrealistically_long_length(max_regions() + 1);
2077
2078 _bot_shared = new G1BlockOffsetSharedArray(_reserved,
2079 heap_word_size(init_byte_size));
2080
2081 _g1h = this;
2082
2083 _in_cset_fast_test.initialize(_g1_reserved.start(), _g1_reserved.end(), HeapRegion::GrainBytes);
2084
2085 // Create the ConcurrentMark data structure and thread.
2086 // (Must do this late, so that "max_regions" is defined.)
2087 _cm = new ConcurrentMark(this, heap_rs);
2088 if (_cm == NULL || !_cm->completed_initialization()) {
2089 vm_shutdown_during_initialization("Could not create/initialize ConcurrentMark");
2090 return JNI_ENOMEM;
2091 }
2092 _cmThread = _cm->cmThread();
2093
2094 // Initialize the from_card cache structure of HeapRegionRemSet.
2095 HeapRegionRemSet::init_heap(max_regions());
2096
2097 // Now expand into the initial heap size.
2098 if (!expand(init_byte_size)) {
2099 vm_shutdown_during_initialization("Failed to allocate initial heap.");
2100 return JNI_ENOMEM;
2101 }
2102
2103 // Perform any initialization actions delegated to the policy.
2104 g1_policy()->init();
2105
2106 JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon,
2107 SATB_Q_FL_lock,
2108 G1SATBProcessCompletedThreshold,
2109 Shared_SATB_Q_lock);
2110
2111 JavaThread::dirty_card_queue_set().initialize(_refine_cte_cl,
2112 DirtyCardQ_CBL_mon,
2113 DirtyCardQ_FL_lock,
2114 concurrent_g1_refine()->yellow_zone(),
2115 concurrent_g1_refine()->red_zone(),
2116 Shared_DirtyCardQ_lock);
2117
2118 if (G1DeferredRSUpdate) {
2119 dirty_card_queue_set().initialize(NULL, // Should never be called by the Java code
2120 DirtyCardQ_CBL_mon,
2121 DirtyCardQ_FL_lock,
2122 -1, // never trigger processing
2123 -1, // no limit on length
2124 Shared_DirtyCardQ_lock,
2125 &JavaThread::dirty_card_queue_set());
2126 }
2127
2128 // Initialize the card queue set used to hold cards containing
2129 // references into the collection set.
2130 _into_cset_dirty_card_queue_set.initialize(NULL, // Should never be called by the Java code
2131 DirtyCardQ_CBL_mon,
2132 DirtyCardQ_FL_lock,
2133 -1, // never trigger processing
2134 -1, // no limit on length
2135 Shared_DirtyCardQ_lock,
2136 &JavaThread::dirty_card_queue_set());
2137
2138 // In case we're keeping closure specialization stats, initialize those
2139 // counts and that mechanism.
2140 SpecializationStats::clear();
2141
2142 // Here we allocate the dummy full region that is required by the
2143 // G1AllocRegion class. If we don't pass an address in the reserved
2144 // space here, lots of asserts fire.
2145
2146 HeapRegion* dummy_region = new_heap_region(0 /* index of bottom region */,
2147 _g1_reserved.start());
2148 // We'll re-use the same region whether the alloc region will
2149 // require BOT updates or not and, if it doesn't, then a non-young
2150 // region will complain that it cannot support allocations without
2151 // BOT updates. So we'll tag the dummy region as young to avoid that.
2152 dummy_region->set_young();
2153 // Make sure it's full.
2154 dummy_region->set_top(dummy_region->end());
2155 G1AllocRegion::setup(this, dummy_region);
2156
2157 init_mutator_alloc_region();
2158
2159 // Do create of the monitoring and management support so that
2160 // values in the heap have been properly initialized.
2161 _g1mm = new G1MonitoringSupport(this);
2162
2163 G1StringDedup::initialize();
2164
2165 return JNI_OK;
2166 }
2167
2168 void G1CollectedHeap::stop() {
2169 // Stop all concurrent threads. We do this to make sure these threads
2170 // do not continue to execute and access resources (e.g. gclog_or_tty)
2171 // that are destroyed during shutdown.
2172 _cg1r->stop();
2173 _cmThread->stop();
2174 if (G1StringDedup::is_enabled()) {
2175 G1StringDedup::stop();
2176 }
2177 }
2178
2179 size_t G1CollectedHeap::conservative_max_heap_alignment() {
2180 return HeapRegion::max_region_size();
2181 }
2182
2183 void G1CollectedHeap::ref_processing_init() {
2184 // Reference processing in G1 currently works as follows:
2185 //
2186 // * There are two reference processor instances. One is
2187 // used to record and process discovered references
2188 // during concurrent marking; the other is used to
2189 // record and process references during STW pauses
2190 // (both full and incremental).
2191 // * Both ref processors need to 'span' the entire heap as
2192 // the regions in the collection set may be dotted around.
2193 //
2194 // * For the concurrent marking ref processor:
2195 // * Reference discovery is enabled at initial marking.
2196 // * Reference discovery is disabled and the discovered
2197 // references processed etc during remarking.
2198 // * Reference discovery is MT (see below).
2199 // * Reference discovery requires a barrier (see below).
2200 // * Reference processing may or may not be MT
2201 // (depending on the value of ParallelRefProcEnabled
2202 // and ParallelGCThreads).
2203 // * A full GC disables reference discovery by the CM
2204 // ref processor and abandons any entries on it's
2205 // discovered lists.
2206 //
2207 // * For the STW processor:
2208 // * Non MT discovery is enabled at the start of a full GC.
2209 // * Processing and enqueueing during a full GC is non-MT.
2210 // * During a full GC, references are processed after marking.
2211 //
2212 // * Discovery (may or may not be MT) is enabled at the start
2213 // of an incremental evacuation pause.
2214 // * References are processed near the end of a STW evacuation pause.
2215 // * For both types of GC:
2216 // * Discovery is atomic - i.e. not concurrent.
2217 // * Reference discovery will not need a barrier.
2218
2219 SharedHeap::ref_processing_init();
2220 MemRegion mr = reserved_region();
2221
2222 // Concurrent Mark ref processor
2223 _ref_processor_cm =
2224 new ReferenceProcessor(mr, // span
2225 ParallelRefProcEnabled && (ParallelGCThreads > 1),
2226 // mt processing
2227 (int) ParallelGCThreads,
2228 // degree of mt processing
2229 (ParallelGCThreads > 1) || (ConcGCThreads > 1),
2230 // mt discovery
2231 (int) MAX2(ParallelGCThreads, ConcGCThreads),
2232 // degree of mt discovery
2233 false,
2234 // Reference discovery is not atomic
2235 &_is_alive_closure_cm);
2236 // is alive closure
2237 // (for efficiency/performance)
2238
2239 // STW ref processor
2240 _ref_processor_stw =
2241 new ReferenceProcessor(mr, // span
2242 ParallelRefProcEnabled && (ParallelGCThreads > 1),
2243 // mt processing
2244 MAX2((int)ParallelGCThreads, 1),
2245 // degree of mt processing
2246 (ParallelGCThreads > 1),
2247 // mt discovery
2248 MAX2((int)ParallelGCThreads, 1),
2249 // degree of mt discovery
2250 true,
2251 // Reference discovery is atomic
2252 &_is_alive_closure_stw);
2253 // is alive closure
2254 // (for efficiency/performance)
2255 }
2256
2257 size_t G1CollectedHeap::capacity() const {
2258 return _g1_committed.byte_size();
2259 }
2260
2261 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) {
2262 assert(!hr->continuesHumongous(), "pre-condition");
2263 hr->reset_gc_time_stamp();
2264 if (hr->startsHumongous()) {
2265 uint first_index = hr->hrs_index() + 1;
2266 uint last_index = hr->last_hc_index();
2267 for (uint i = first_index; i < last_index; i += 1) {
2268 HeapRegion* chr = region_at(i);
2269 assert(chr->continuesHumongous(), "sanity");
2270 chr->reset_gc_time_stamp();
2271 }
2272 }
2273 }
2274
2275 #ifndef PRODUCT
2276 class CheckGCTimeStampsHRClosure : public HeapRegionClosure {
2277 private:
2278 unsigned _gc_time_stamp;
2279 bool _failures;
2280
2281 public:
2282 CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) :
2283 _gc_time_stamp(gc_time_stamp), _failures(false) { }
2284
2285 virtual bool doHeapRegion(HeapRegion* hr) {
2286 unsigned region_gc_time_stamp = hr->get_gc_time_stamp();
2287 if (_gc_time_stamp != region_gc_time_stamp) {
2288 gclog_or_tty->print_cr("Region "HR_FORMAT" has GC time stamp = %d, "
2289 "expected %d", HR_FORMAT_PARAMS(hr),
2290 region_gc_time_stamp, _gc_time_stamp);
2291 _failures = true;
2292 }
2293 return false;
2294 }
2295
2296 bool failures() { return _failures; }
2297 };
2298
2299 void G1CollectedHeap::check_gc_time_stamps() {
2300 CheckGCTimeStampsHRClosure cl(_gc_time_stamp);
2301 heap_region_iterate(&cl);
2302 guarantee(!cl.failures(), "all GC time stamps should have been reset");
2303 }
2304 #endif // PRODUCT
2305
2306 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl,
2307 DirtyCardQueue* into_cset_dcq,
2308 bool concurrent,
2309 uint worker_i) {
2310 // Clean cards in the hot card cache
2311 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
2312 hot_card_cache->drain(worker_i, g1_rem_set(), into_cset_dcq);
2313
2314 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2315 int n_completed_buffers = 0;
2316 while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) {
2317 n_completed_buffers++;
2318 }
2319 g1_policy()->phase_times()->record_update_rs_processed_buffers(worker_i, n_completed_buffers);
2320 dcqs.clear_n_completed_buffers();
2321 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!");
2322 }
2323
2324
2325 // Computes the sum of the storage used by the various regions.
2326
2327 size_t G1CollectedHeap::used() const {
2328 assert(Heap_lock->owner() != NULL,
2329 "Should be owned on this thread's behalf.");
2330 size_t result = _summary_bytes_used;
2331 // Read only once in case it is set to NULL concurrently
2332 HeapRegion* hr = _mutator_alloc_region.get();
2333 if (hr != NULL)
2334 result += hr->used();
2335 return result;
2336 }
2337
2338 size_t G1CollectedHeap::used_unlocked() const {
2339 size_t result = _summary_bytes_used;
2340 return result;
2341 }
2342
2343 class SumUsedClosure: public HeapRegionClosure {
2344 size_t _used;
2345 public:
2346 SumUsedClosure() : _used(0) {}
2347 bool doHeapRegion(HeapRegion* r) {
2348 if (!r->continuesHumongous()) {
2349 _used += r->used();
2350 }
2351 return false;
2352 }
2353 size_t result() { return _used; }
2354 };
2355
2356 size_t G1CollectedHeap::recalculate_used() const {
2357 double recalculate_used_start = os::elapsedTime();
2358
2359 SumUsedClosure blk;
2360 heap_region_iterate(&blk);
2361
2362 g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0);
2363 return blk.result();
2364 }
2365
2366 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
2367 switch (cause) {
2368 case GCCause::_gc_locker: return GCLockerInvokesConcurrent;
2369 case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent;
2370 case GCCause::_g1_humongous_allocation: return true;
2371 default: return false;
2372 }
2373 }
2374
2375 #ifndef PRODUCT
2376 void G1CollectedHeap::allocate_dummy_regions() {
2377 // Let's fill up most of the region
2378 size_t word_size = HeapRegion::GrainWords - 1024;
2379 // And as a result the region we'll allocate will be humongous.
2380 guarantee(isHumongous(word_size), "sanity");
2381
2382 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
2383 // Let's use the existing mechanism for the allocation
2384 HeapWord* dummy_obj = humongous_obj_allocate(word_size);
2385 if (dummy_obj != NULL) {
2386 MemRegion mr(dummy_obj, word_size);
2387 CollectedHeap::fill_with_object(mr);
2388 } else {
2389 // If we can't allocate once, we probably cannot allocate
2390 // again. Let's get out of the loop.
2391 break;
2392 }
2393 }
2394 }
2395 #endif // !PRODUCT
2396
2397 void G1CollectedHeap::increment_old_marking_cycles_started() {
2398 assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
2399 _old_marking_cycles_started == _old_marking_cycles_completed + 1,
2400 err_msg("Wrong marking cycle count (started: %d, completed: %d)",
2401 _old_marking_cycles_started, _old_marking_cycles_completed));
2402
2403 _old_marking_cycles_started++;
2404 }
2405
2406 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) {
2407 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
2408
2409 // We assume that if concurrent == true, then the caller is a
2410 // concurrent thread that was joined the Suspendible Thread
2411 // Set. If there's ever a cheap way to check this, we should add an
2412 // assert here.
2413
2414 // Given that this method is called at the end of a Full GC or of a
2415 // concurrent cycle, and those can be nested (i.e., a Full GC can
2416 // interrupt a concurrent cycle), the number of full collections
2417 // completed should be either one (in the case where there was no
2418 // nesting) or two (when a Full GC interrupted a concurrent cycle)
2419 // behind the number of full collections started.
2420
2421 // This is the case for the inner caller, i.e. a Full GC.
2422 assert(concurrent ||
2423 (_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
2424 (_old_marking_cycles_started == _old_marking_cycles_completed + 2),
2425 err_msg("for inner caller (Full GC): _old_marking_cycles_started = %u "
2426 "is inconsistent with _old_marking_cycles_completed = %u",
2427 _old_marking_cycles_started, _old_marking_cycles_completed));
2428
2429 // This is the case for the outer caller, i.e. the concurrent cycle.
2430 assert(!concurrent ||
2431 (_old_marking_cycles_started == _old_marking_cycles_completed + 1),
2432 err_msg("for outer caller (concurrent cycle): "
2433 "_old_marking_cycles_started = %u "
2434 "is inconsistent with _old_marking_cycles_completed = %u",
2435 _old_marking_cycles_started, _old_marking_cycles_completed));
2436
2437 _old_marking_cycles_completed += 1;
2438
2439 // We need to clear the "in_progress" flag in the CM thread before
2440 // we wake up any waiters (especially when ExplicitInvokesConcurrent
2441 // is set) so that if a waiter requests another System.gc() it doesn't
2442 // incorrectly see that a marking cycle is still in progress.
2443 if (concurrent) {
2444 _cmThread->clear_in_progress();
2445 }
2446
2447 // This notify_all() will ensure that a thread that called
2448 // System.gc() with (with ExplicitGCInvokesConcurrent set or not)
2449 // and it's waiting for a full GC to finish will be woken up. It is
2450 // waiting in VM_G1IncCollectionPause::doit_epilogue().
2451 FullGCCount_lock->notify_all();
2452 }
2453
2454 void G1CollectedHeap::register_concurrent_cycle_start(const Ticks& start_time) {
2455 _concurrent_cycle_started = true;
2456 _gc_timer_cm->register_gc_start(start_time);
2457
2458 _gc_tracer_cm->report_gc_start(gc_cause(), _gc_timer_cm->gc_start());
2459 trace_heap_before_gc(_gc_tracer_cm);
2460 }
2461
2462 void G1CollectedHeap::register_concurrent_cycle_end() {
2463 if (_concurrent_cycle_started) {
2464 if (_cm->has_aborted()) {
2465 _gc_tracer_cm->report_concurrent_mode_failure();
2466 }
2467
2468 _gc_timer_cm->register_gc_end();
2469 _gc_tracer_cm->report_gc_end(_gc_timer_cm->gc_end(), _gc_timer_cm->time_partitions());
2470
2471 _concurrent_cycle_started = false;
2472 }
2473 }
2474
2475 void G1CollectedHeap::trace_heap_after_concurrent_cycle() {
2476 if (_concurrent_cycle_started) {
2477 trace_heap_after_gc(_gc_tracer_cm);
2478 }
2479 }
2480
2481 G1YCType G1CollectedHeap::yc_type() {
2482 bool is_young = g1_policy()->gcs_are_young();
2483 bool is_initial_mark = g1_policy()->during_initial_mark_pause();
2484 bool is_during_mark = mark_in_progress();
2485
2486 if (is_initial_mark) {
2487 return InitialMark;
2488 } else if (is_during_mark) {
2489 return DuringMark;
2490 } else if (is_young) {
2491 return Normal;
2492 } else {
2493 return Mixed;
2494 }
2495 }
2496
2497 void G1CollectedHeap::collect(GCCause::Cause cause) {
2498 assert_heap_not_locked();
2499
2500 unsigned int gc_count_before;
2501 unsigned int old_marking_count_before;
2502 bool retry_gc;
2503
2504 do {
2505 retry_gc = false;
2506
2507 {
2508 MutexLocker ml(Heap_lock);
2509
2510 // Read the GC count while holding the Heap_lock
2511 gc_count_before = total_collections();
2512 old_marking_count_before = _old_marking_cycles_started;
2513 }
2514
2515 if (should_do_concurrent_full_gc(cause)) {
2516 // Schedule an initial-mark evacuation pause that will start a
2517 // concurrent cycle. We're setting word_size to 0 which means that
2518 // we are not requesting a post-GC allocation.
2519 VM_G1IncCollectionPause op(gc_count_before,
2520 0, /* word_size */
2521 true, /* should_initiate_conc_mark */
2522 g1_policy()->max_pause_time_ms(),
2523 cause);
2524
2525 VMThread::execute(&op);
2526 if (!op.pause_succeeded()) {
2527 if (old_marking_count_before == _old_marking_cycles_started) {
2528 retry_gc = op.should_retry_gc();
2529 } else {
2530 // A Full GC happened while we were trying to schedule the
2531 // initial-mark GC. No point in starting a new cycle given
2532 // that the whole heap was collected anyway.
2533 }
2534
2535 if (retry_gc) {
2536 if (GC_locker::is_active_and_needs_gc()) {
2537 GC_locker::stall_until_clear();
2538 }
2539 }
2540 }
2541 } else {
2542 if (cause == GCCause::_gc_locker
2543 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2544
2545 // Schedule a standard evacuation pause. We're setting word_size
2546 // to 0 which means that we are not requesting a post-GC allocation.
2547 VM_G1IncCollectionPause op(gc_count_before,
2548 0, /* word_size */
2549 false, /* should_initiate_conc_mark */
2550 g1_policy()->max_pause_time_ms(),
2551 cause);
2552 VMThread::execute(&op);
2553 } else {
2554 // Schedule a Full GC.
2555 VM_G1CollectFull op(gc_count_before, old_marking_count_before, cause);
2556 VMThread::execute(&op);
2557 }
2558 }
2559 } while (retry_gc);
2560 }
2561
2562 bool G1CollectedHeap::is_in(const void* p) const {
2563 if (_g1_committed.contains(p)) {
2564 // Given that we know that p is in the committed space,
2565 // heap_region_containing_raw() should successfully
2566 // return the containing region.
2567 HeapRegion* hr = heap_region_containing_raw(p);
2568 return hr->is_in(p);
2569 } else {
2570 return false;
2571 }
2572 }
2573
2574 // Iteration functions.
2575
2576 // Iterates an OopClosure over all ref-containing fields of objects
2577 // within a HeapRegion.
2578
2579 class IterateOopClosureRegionClosure: public HeapRegionClosure {
2580 MemRegion _mr;
2581 ExtendedOopClosure* _cl;
2582 public:
2583 IterateOopClosureRegionClosure(MemRegion mr, ExtendedOopClosure* cl)
2584 : _mr(mr), _cl(cl) {}
2585 bool doHeapRegion(HeapRegion* r) {
2586 if (!r->continuesHumongous()) {
2587 r->oop_iterate(_cl);
2588 }
2589 return false;
2590 }
2591 };
2592
2593 void G1CollectedHeap::oop_iterate(ExtendedOopClosure* cl) {
2594 IterateOopClosureRegionClosure blk(_g1_committed, cl);
2595 heap_region_iterate(&blk);
2596 }
2597
2598 void G1CollectedHeap::oop_iterate(MemRegion mr, ExtendedOopClosure* cl) {
2599 IterateOopClosureRegionClosure blk(mr, cl);
2600 heap_region_iterate(&blk);
2601 }
2602
2603 // Iterates an ObjectClosure over all objects within a HeapRegion.
2604
2605 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2606 ObjectClosure* _cl;
2607 public:
2608 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2609 bool doHeapRegion(HeapRegion* r) {
2610 if (! r->continuesHumongous()) {
2611 r->object_iterate(_cl);
2612 }
2613 return false;
2614 }
2615 };
2616
2617 void G1CollectedHeap::object_iterate(ObjectClosure* cl) {
2618 IterateObjectClosureRegionClosure blk(cl);
2619 heap_region_iterate(&blk);
2620 }
2621
2622 // Calls a SpaceClosure on a HeapRegion.
2623
2624 class SpaceClosureRegionClosure: public HeapRegionClosure {
2625 SpaceClosure* _cl;
2626 public:
2627 SpaceClosureRegionClosure(SpaceClosure* cl) : _cl(cl) {}
2628 bool doHeapRegion(HeapRegion* r) {
2629 _cl->do_space(r);
2630 return false;
2631 }
2632 };
2633
2634 void G1CollectedHeap::space_iterate(SpaceClosure* cl) {
2635 SpaceClosureRegionClosure blk(cl);
2636 heap_region_iterate(&blk);
2637 }
2638
2639 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2640 _hrs.iterate(cl);
2641 }
2642
2643 void
2644 G1CollectedHeap::heap_region_par_iterate_chunked(HeapRegionClosure* cl,
2645 uint worker_id,
2646 uint no_of_par_workers,
2647 jint claim_value) {
2648 const uint regions = n_regions();
2649 const uint max_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
2650 no_of_par_workers :
2651 1);
2652 assert(UseDynamicNumberOfGCThreads ||
2653 no_of_par_workers == workers()->total_workers(),
2654 "Non dynamic should use fixed number of workers");
2655 // try to spread out the starting points of the workers
2656 const HeapRegion* start_hr =
2657 start_region_for_worker(worker_id, no_of_par_workers);
2658 const uint start_index = start_hr->hrs_index();
2659
2660 // each worker will actually look at all regions
2661 for (uint count = 0; count < regions; ++count) {
2662 const uint index = (start_index + count) % regions;
2663 assert(0 <= index && index < regions, "sanity");
2664 HeapRegion* r = region_at(index);
2665 // we'll ignore "continues humongous" regions (we'll process them
2666 // when we come across their corresponding "start humongous"
2667 // region) and regions already claimed
2668 if (r->claim_value() == claim_value || r->continuesHumongous()) {
2669 continue;
2670 }
2671 // OK, try to claim it
2672 if (r->claimHeapRegion(claim_value)) {
2673 // success!
2674 assert(!r->continuesHumongous(), "sanity");
2675 if (r->startsHumongous()) {
2676 // If the region is "starts humongous" we'll iterate over its
2677 // "continues humongous" first; in fact we'll do them
2678 // first. The order is important. In on case, calling the
2679 // closure on the "starts humongous" region might de-allocate
2680 // and clear all its "continues humongous" regions and, as a
2681 // result, we might end up processing them twice. So, we'll do
2682 // them first (notice: most closures will ignore them anyway) and
2683 // then we'll do the "starts humongous" region.
2684 for (uint ch_index = index + 1; ch_index < regions; ++ch_index) {
2685 HeapRegion* chr = region_at(ch_index);
2686
2687 // if the region has already been claimed or it's not
2688 // "continues humongous" we're done
2689 if (chr->claim_value() == claim_value ||
2690 !chr->continuesHumongous()) {
2691 break;
2692 }
2693
2694 // No one should have claimed it directly. We can given
2695 // that we claimed its "starts humongous" region.
2696 assert(chr->claim_value() != claim_value, "sanity");
2697 assert(chr->humongous_start_region() == r, "sanity");
2698
2699 if (chr->claimHeapRegion(claim_value)) {
2700 // we should always be able to claim it; no one else should
2701 // be trying to claim this region
2702
2703 bool res2 = cl->doHeapRegion(chr);
2704 assert(!res2, "Should not abort");
2705
2706 // Right now, this holds (i.e., no closure that actually
2707 // does something with "continues humongous" regions
2708 // clears them). We might have to weaken it in the future,
2709 // but let's leave these two asserts here for extra safety.
2710 assert(chr->continuesHumongous(), "should still be the case");
2711 assert(chr->humongous_start_region() == r, "sanity");
2712 } else {
2713 guarantee(false, "we should not reach here");
2714 }
2715 }
2716 }
2717
2718 assert(!r->continuesHumongous(), "sanity");
2719 bool res = cl->doHeapRegion(r);
2720 assert(!res, "Should not abort");
2721 }
2722 }
2723 }
2724
2725 class ResetClaimValuesClosure: public HeapRegionClosure {
2726 public:
2727 bool doHeapRegion(HeapRegion* r) {
2728 r->set_claim_value(HeapRegion::InitialClaimValue);
2729 return false;
2730 }
2731 };
2732
2733 void G1CollectedHeap::reset_heap_region_claim_values() {
2734 ResetClaimValuesClosure blk;
2735 heap_region_iterate(&blk);
2736 }
2737
2738 void G1CollectedHeap::reset_cset_heap_region_claim_values() {
2739 ResetClaimValuesClosure blk;
2740 collection_set_iterate(&blk);
2741 }
2742
2743 #ifdef ASSERT
2744 // This checks whether all regions in the heap have the correct claim
2745 // value. I also piggy-backed on this a check to ensure that the
2746 // humongous_start_region() information on "continues humongous"
2747 // regions is correct.
2748
2749 class CheckClaimValuesClosure : public HeapRegionClosure {
2750 private:
2751 jint _claim_value;
2752 uint _failures;
2753 HeapRegion* _sh_region;
2754
2755 public:
2756 CheckClaimValuesClosure(jint claim_value) :
2757 _claim_value(claim_value), _failures(0), _sh_region(NULL) { }
2758 bool doHeapRegion(HeapRegion* r) {
2759 if (r->claim_value() != _claim_value) {
2760 gclog_or_tty->print_cr("Region " HR_FORMAT ", "
2761 "claim value = %d, should be %d",
2762 HR_FORMAT_PARAMS(r),
2763 r->claim_value(), _claim_value);
2764 ++_failures;
2765 }
2766 if (!r->isHumongous()) {
2767 _sh_region = NULL;
2768 } else if (r->startsHumongous()) {
2769 _sh_region = r;
2770 } else if (r->continuesHumongous()) {
2771 if (r->humongous_start_region() != _sh_region) {
2772 gclog_or_tty->print_cr("Region " HR_FORMAT ", "
2773 "HS = "PTR_FORMAT", should be "PTR_FORMAT,
2774 HR_FORMAT_PARAMS(r),
2775 r->humongous_start_region(),
2776 _sh_region);
2777 ++_failures;
2778 }
2779 }
2780 return false;
2781 }
2782 uint failures() { return _failures; }
2783 };
2784
2785 bool G1CollectedHeap::check_heap_region_claim_values(jint claim_value) {
2786 CheckClaimValuesClosure cl(claim_value);
2787 heap_region_iterate(&cl);
2788 return cl.failures() == 0;
2789 }
2790
2791 class CheckClaimValuesInCSetHRClosure: public HeapRegionClosure {
2792 private:
2793 jint _claim_value;
2794 uint _failures;
2795
2796 public:
2797 CheckClaimValuesInCSetHRClosure(jint claim_value) :
2798 _claim_value(claim_value), _failures(0) { }
2799
2800 uint failures() { return _failures; }
2801
2802 bool doHeapRegion(HeapRegion* hr) {
2803 assert(hr->in_collection_set(), "how?");
2804 assert(!hr->isHumongous(), "H-region in CSet");
2805 if (hr->claim_value() != _claim_value) {
2806 gclog_or_tty->print_cr("CSet Region " HR_FORMAT ", "
2807 "claim value = %d, should be %d",
2808 HR_FORMAT_PARAMS(hr),
2809 hr->claim_value(), _claim_value);
2810 _failures += 1;
2811 }
2812 return false;
2813 }
2814 };
2815
2816 bool G1CollectedHeap::check_cset_heap_region_claim_values(jint claim_value) {
2817 CheckClaimValuesInCSetHRClosure cl(claim_value);
2818 collection_set_iterate(&cl);
2819 return cl.failures() == 0;
2820 }
2821 #endif // ASSERT
2822
2823 // Clear the cached CSet starting regions and (more importantly)
2824 // the time stamps. Called when we reset the GC time stamp.
2825 void G1CollectedHeap::clear_cset_start_regions() {
2826 assert(_worker_cset_start_region != NULL, "sanity");
2827 assert(_worker_cset_start_region_time_stamp != NULL, "sanity");
2828
2829 int n_queues = MAX2((int)ParallelGCThreads, 1);
2830 for (int i = 0; i < n_queues; i++) {
2831 _worker_cset_start_region[i] = NULL;
2832 _worker_cset_start_region_time_stamp[i] = 0;
2833 }
2834 }
2835
2836 // Given the id of a worker, obtain or calculate a suitable
2837 // starting region for iterating over the current collection set.
2838 HeapRegion* G1CollectedHeap::start_cset_region_for_worker(uint worker_i) {
2839 assert(get_gc_time_stamp() > 0, "should have been updated by now");
2840
2841 HeapRegion* result = NULL;
2842 unsigned gc_time_stamp = get_gc_time_stamp();
2843
2844 if (_worker_cset_start_region_time_stamp[worker_i] == gc_time_stamp) {
2845 // Cached starting region for current worker was set
2846 // during the current pause - so it's valid.
2847 // Note: the cached starting heap region may be NULL
2848 // (when the collection set is empty).
2849 result = _worker_cset_start_region[worker_i];
2850 assert(result == NULL || result->in_collection_set(), "sanity");
2851 return result;
2852 }
2853
2854 // The cached entry was not valid so let's calculate
2855 // a suitable starting heap region for this worker.
2856
2857 // We want the parallel threads to start their collection
2858 // set iteration at different collection set regions to
2859 // avoid contention.
2860 // If we have:
2861 // n collection set regions
2862 // p threads
2863 // Then thread t will start at region floor ((t * n) / p)
2864
2865 result = g1_policy()->collection_set();
2866 if (G1CollectedHeap::use_parallel_gc_threads()) {
2867 uint cs_size = g1_policy()->cset_region_length();
2868 uint active_workers = workers()->active_workers();
2869 assert(UseDynamicNumberOfGCThreads ||
2870 active_workers == workers()->total_workers(),
2871 "Unless dynamic should use total workers");
2872
2873 uint end_ind = (cs_size * worker_i) / active_workers;
2874 uint start_ind = 0;
2875
2876 if (worker_i > 0 &&
2877 _worker_cset_start_region_time_stamp[worker_i - 1] == gc_time_stamp) {
2878 // Previous workers starting region is valid
2879 // so let's iterate from there
2880 start_ind = (cs_size * (worker_i - 1)) / active_workers;
2881 result = _worker_cset_start_region[worker_i - 1];
2882 }
2883
2884 for (uint i = start_ind; i < end_ind; i++) {
2885 result = result->next_in_collection_set();
2886 }
2887 }
2888
2889 // Note: the calculated starting heap region may be NULL
2890 // (when the collection set is empty).
2891 assert(result == NULL || result->in_collection_set(), "sanity");
2892 assert(_worker_cset_start_region_time_stamp[worker_i] != gc_time_stamp,
2893 "should be updated only once per pause");
2894 _worker_cset_start_region[worker_i] = result;
2895 OrderAccess::storestore();
2896 _worker_cset_start_region_time_stamp[worker_i] = gc_time_stamp;
2897 return result;
2898 }
2899
2900 HeapRegion* G1CollectedHeap::start_region_for_worker(uint worker_i,
2901 uint no_of_par_workers) {
2902 uint worker_num =
2903 G1CollectedHeap::use_parallel_gc_threads() ? no_of_par_workers : 1U;
2904 assert(UseDynamicNumberOfGCThreads ||
2905 no_of_par_workers == workers()->total_workers(),
2906 "Non dynamic should use fixed number of workers");
2907 const uint start_index = n_regions() * worker_i / worker_num;
2908 return region_at(start_index);
2909 }
2910
2911 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) {
2912 HeapRegion* r = g1_policy()->collection_set();
2913 while (r != NULL) {
2914 HeapRegion* next = r->next_in_collection_set();
2915 if (cl->doHeapRegion(r)) {
2916 cl->incomplete();
2917 return;
2918 }
2919 r = next;
2920 }
2921 }
2922
2923 void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r,
2924 HeapRegionClosure *cl) {
2925 if (r == NULL) {
2926 // The CSet is empty so there's nothing to do.
2927 return;
2928 }
2929
2930 assert(r->in_collection_set(),
2931 "Start region must be a member of the collection set.");
2932 HeapRegion* cur = r;
2933 while (cur != NULL) {
2934 HeapRegion* next = cur->next_in_collection_set();
2935 if (cl->doHeapRegion(cur) && false) {
2936 cl->incomplete();
2937 return;
2938 }
2939 cur = next;
2940 }
2941 cur = g1_policy()->collection_set();
2942 while (cur != r) {
2943 HeapRegion* next = cur->next_in_collection_set();
2944 if (cl->doHeapRegion(cur) && false) {
2945 cl->incomplete();
2946 return;
2947 }
2948 cur = next;
2949 }
2950 }
2951
2952 CompactibleSpace* G1CollectedHeap::first_compactible_space() {
2953 return n_regions() > 0 ? region_at(0) : NULL;
2954 }
2955
2956
2957 Space* G1CollectedHeap::space_containing(const void* addr) const {
2958 return heap_region_containing(addr);
2959 }
2960
2961 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2962 Space* sp = space_containing(addr);
2963 return sp->block_start(addr);
2964 }
2965
2966 size_t G1CollectedHeap::block_size(const HeapWord* addr) const {
2967 Space* sp = space_containing(addr);
2968 return sp->block_size(addr);
2969 }
2970
2971 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2972 Space* sp = space_containing(addr);
2973 return sp->block_is_obj(addr);
2974 }
2975
2976 bool G1CollectedHeap::supports_tlab_allocation() const {
2977 return true;
2978 }
2979
2980 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
2981 return (_g1_policy->young_list_target_length() - young_list()->survivor_length()) * HeapRegion::GrainBytes;
2982 }
2983
2984 size_t G1CollectedHeap::tlab_used(Thread* ignored) const {
2985 return young_list()->eden_used_bytes();
2986 }
2987
2988 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size
2989 // must be smaller than the humongous object limit.
2990 size_t G1CollectedHeap::max_tlab_size() const {
2991 return align_size_down(_humongous_object_threshold_in_words - 1, MinObjAlignment);
2992 }
2993
2994 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
2995 // Return the remaining space in the cur alloc region, but not less than
2996 // the min TLAB size.
2997
2998 // Also, this value can be at most the humongous object threshold,
2999 // since we can't allow tlabs to grow big enough to accommodate
3000 // humongous objects.
3001
3002 HeapRegion* hr = _mutator_alloc_region.get();
3003 size_t max_tlab = max_tlab_size() * wordSize;
3004 if (hr == NULL) {
3005 return max_tlab;
3006 } else {
3007 return MIN2(MAX2(hr->free(), (size_t) MinTLABSize), max_tlab);
3008 }
3009 }
3010
3011 size_t G1CollectedHeap::max_capacity() const {
3012 return _g1_reserved.byte_size();
3013 }
3014
3015 jlong G1CollectedHeap::millis_since_last_gc() {
3016 // assert(false, "NYI");
3017 return 0;
3018 }
3019
3020 void G1CollectedHeap::prepare_for_verify() {
3021 if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) {
3022 ensure_parsability(false);
3023 }
3024 g1_rem_set()->prepare_for_verify();
3025 }
3026
3027 bool G1CollectedHeap::allocated_since_marking(oop obj, HeapRegion* hr,
3028 VerifyOption vo) {
3029 switch (vo) {
3030 case VerifyOption_G1UsePrevMarking:
3031 return hr->obj_allocated_since_prev_marking(obj);
3032 case VerifyOption_G1UseNextMarking:
3033 return hr->obj_allocated_since_next_marking(obj);
3034 case VerifyOption_G1UseMarkWord:
3035 return false;
3036 default:
3037 ShouldNotReachHere();
3038 }
3039 return false; // keep some compilers happy
3040 }
3041
3042 HeapWord* G1CollectedHeap::top_at_mark_start(HeapRegion* hr, VerifyOption vo) {
3043 switch (vo) {
3044 case VerifyOption_G1UsePrevMarking: return hr->prev_top_at_mark_start();
3045 case VerifyOption_G1UseNextMarking: return hr->next_top_at_mark_start();
3046 case VerifyOption_G1UseMarkWord: return NULL;
3047 default: ShouldNotReachHere();
3048 }
3049 return NULL; // keep some compilers happy
3050 }
3051
3052 bool G1CollectedHeap::is_marked(oop obj, VerifyOption vo) {
3053 switch (vo) {
3054 case VerifyOption_G1UsePrevMarking: return isMarkedPrev(obj);
3055 case VerifyOption_G1UseNextMarking: return isMarkedNext(obj);
3056 case VerifyOption_G1UseMarkWord: return obj->is_gc_marked();
3057 default: ShouldNotReachHere();
3058 }
3059 return false; // keep some compilers happy
3060 }
3061
3062 const char* G1CollectedHeap::top_at_mark_start_str(VerifyOption vo) {
3063 switch (vo) {
3064 case VerifyOption_G1UsePrevMarking: return "PTAMS";
3065 case VerifyOption_G1UseNextMarking: return "NTAMS";
3066 case VerifyOption_G1UseMarkWord: return "NONE";
3067 default: ShouldNotReachHere();
3068 }
3069 return NULL; // keep some compilers happy
3070 }
3071
3072 class VerifyRootsClosure: public OopClosure {
3073 private:
3074 G1CollectedHeap* _g1h;
3075 VerifyOption _vo;
3076 bool _failures;
3077 public:
3078 // _vo == UsePrevMarking -> use "prev" marking information,
3079 // _vo == UseNextMarking -> use "next" marking information,
3080 // _vo == UseMarkWord -> use mark word from object header.
3081 VerifyRootsClosure(VerifyOption vo) :
3082 _g1h(G1CollectedHeap::heap()),
3083 _vo(vo),
3084 _failures(false) { }
3085
3086 bool failures() { return _failures; }
3087
3088 template <class T> void do_oop_nv(T* p) {
3089 T heap_oop = oopDesc::load_heap_oop(p);
3090 if (!oopDesc::is_null(heap_oop)) {
3091 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
3092 if (_g1h->is_obj_dead_cond(obj, _vo)) {
3093 gclog_or_tty->print_cr("Root location "PTR_FORMAT" "
3094 "points to dead obj "PTR_FORMAT, p, (void*) obj);
3095 if (_vo == VerifyOption_G1UseMarkWord) {
3096 gclog_or_tty->print_cr(" Mark word: "PTR_FORMAT, (void*)(obj->mark()));
3097 }
3098 obj->print_on(gclog_or_tty);
3099 _failures = true;
3100 }
3101 }
3102 }
3103
3104 void do_oop(oop* p) { do_oop_nv(p); }
3105 void do_oop(narrowOop* p) { do_oop_nv(p); }
3106 };
3107
3108 class G1VerifyCodeRootOopClosure: public OopClosure {
3109 G1CollectedHeap* _g1h;
3110 OopClosure* _root_cl;
3111 nmethod* _nm;
3112 VerifyOption _vo;
3113 bool _failures;
3114
3115 template <class T> void do_oop_work(T* p) {
3116 // First verify that this root is live
3117 _root_cl->do_oop(p);
3118
3119 if (!G1VerifyHeapRegionCodeRoots) {
3120 // We're not verifying the code roots attached to heap region.
3121 return;
3122 }
3123
3124 // Don't check the code roots during marking verification in a full GC
3125 if (_vo == VerifyOption_G1UseMarkWord) {
3126 return;
3127 }
3128
3129 // Now verify that the current nmethod (which contains p) is
3130 // in the code root list of the heap region containing the
3131 // object referenced by p.
3132
3133 T heap_oop = oopDesc::load_heap_oop(p);
3134 if (!oopDesc::is_null(heap_oop)) {
3135 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
3136
3137 // Now fetch the region containing the object
3138 HeapRegion* hr = _g1h->heap_region_containing(obj);
3139 HeapRegionRemSet* hrrs = hr->rem_set();
3140 // Verify that the strong code root list for this region
3141 // contains the nmethod
3142 if (!hrrs->strong_code_roots_list_contains(_nm)) {
3143 gclog_or_tty->print_cr("Code root location "PTR_FORMAT" "
3144 "from nmethod "PTR_FORMAT" not in strong "
3145 "code roots for region ["PTR_FORMAT","PTR_FORMAT")",
3146 p, _nm, hr->bottom(), hr->end());
3147 _failures = true;
3148 }
3149 }
3150 }
3151
3152 public:
3153 G1VerifyCodeRootOopClosure(G1CollectedHeap* g1h, OopClosure* root_cl, VerifyOption vo):
3154 _g1h(g1h), _root_cl(root_cl), _vo(vo), _nm(NULL), _failures(false) {}
3155
3156 void do_oop(oop* p) { do_oop_work(p); }
3157 void do_oop(narrowOop* p) { do_oop_work(p); }
3158
3159 void set_nmethod(nmethod* nm) { _nm = nm; }
3160 bool failures() { return _failures; }
3161 };
3162
3163 class G1VerifyCodeRootBlobClosure: public CodeBlobClosure {
3164 G1VerifyCodeRootOopClosure* _oop_cl;
3165
3166 public:
3167 G1VerifyCodeRootBlobClosure(G1VerifyCodeRootOopClosure* oop_cl):
3168 _oop_cl(oop_cl) {}
3169
3170 void do_code_blob(CodeBlob* cb) {
3171 nmethod* nm = cb->as_nmethod_or_null();
3172 if (nm != NULL) {
3173 _oop_cl->set_nmethod(nm);
3174 nm->oops_do(_oop_cl);
3175 }
3176 }
3177 };
3178
3179 class YoungRefCounterClosure : public OopClosure {
3180 G1CollectedHeap* _g1h;
3181 int _count;
3182 public:
3183 YoungRefCounterClosure(G1CollectedHeap* g1h) : _g1h(g1h), _count(0) {}
3184 void do_oop(oop* p) { if (_g1h->is_in_young(*p)) { _count++; } }
3185 void do_oop(narrowOop* p) { ShouldNotReachHere(); }
3186
3187 int count() { return _count; }
3188 void reset_count() { _count = 0; };
3189 };
3190
3191 class VerifyKlassClosure: public KlassClosure {
3192 YoungRefCounterClosure _young_ref_counter_closure;
3193 OopClosure *_oop_closure;
3194 public:
3195 VerifyKlassClosure(G1CollectedHeap* g1h, OopClosure* cl) : _young_ref_counter_closure(g1h), _oop_closure(cl) {}
3196 void do_klass(Klass* k) {
3197 k->oops_do(_oop_closure);
3198
3199 _young_ref_counter_closure.reset_count();
3200 k->oops_do(&_young_ref_counter_closure);
3201 if (_young_ref_counter_closure.count() > 0) {
3202 guarantee(k->has_modified_oops(), err_msg("Klass " PTR_FORMAT ", has young refs but is not dirty.", k));
3203 }
3204 }
3205 };
3206
3207 class VerifyLivenessOopClosure: public OopClosure {
3208 G1CollectedHeap* _g1h;
3209 VerifyOption _vo;
3210 public:
3211 VerifyLivenessOopClosure(G1CollectedHeap* g1h, VerifyOption vo):
3212 _g1h(g1h), _vo(vo)
3213 { }
3214 void do_oop(narrowOop *p) { do_oop_work(p); }
3215 void do_oop( oop *p) { do_oop_work(p); }
3216
3217 template <class T> void do_oop_work(T *p) {
3218 oop obj = oopDesc::load_decode_heap_oop(p);
3219 guarantee(obj == NULL || !_g1h->is_obj_dead_cond(obj, _vo),
3220 "Dead object referenced by a not dead object");
3221 }
3222 };
3223
3224 class VerifyObjsInRegionClosure: public ObjectClosure {
3225 private:
3226 G1CollectedHeap* _g1h;
3227 size_t _live_bytes;
3228 HeapRegion *_hr;
3229 VerifyOption _vo;
3230 public:
3231 // _vo == UsePrevMarking -> use "prev" marking information,
3232 // _vo == UseNextMarking -> use "next" marking information,
3233 // _vo == UseMarkWord -> use mark word from object header.
3234 VerifyObjsInRegionClosure(HeapRegion *hr, VerifyOption vo)
3235 : _live_bytes(0), _hr(hr), _vo(vo) {
3236 _g1h = G1CollectedHeap::heap();
3237 }
3238 void do_object(oop o) {
3239 VerifyLivenessOopClosure isLive(_g1h, _vo);
3240 assert(o != NULL, "Huh?");
3241 if (!_g1h->is_obj_dead_cond(o, _vo)) {
3242 // If the object is alive according to the mark word,
3243 // then verify that the marking information agrees.
3244 // Note we can't verify the contra-positive of the
3245 // above: if the object is dead (according to the mark
3246 // word), it may not be marked, or may have been marked
3247 // but has since became dead, or may have been allocated
3248 // since the last marking.
3249 if (_vo == VerifyOption_G1UseMarkWord) {
3250 guarantee(!_g1h->is_obj_dead(o), "mark word and concurrent mark mismatch");
3251 }
3252
3253 o->oop_iterate_no_header(&isLive);
3254 if (!_hr->obj_allocated_since_prev_marking(o)) {
3255 size_t obj_size = o->size(); // Make sure we don't overflow
3256 _live_bytes += (obj_size * HeapWordSize);
3257 }
3258 }
3259 }
3260 size_t live_bytes() { return _live_bytes; }
3261 };
3262
3263 class PrintObjsInRegionClosure : public ObjectClosure {
3264 HeapRegion *_hr;
3265 G1CollectedHeap *_g1;
3266 public:
3267 PrintObjsInRegionClosure(HeapRegion *hr) : _hr(hr) {
3268 _g1 = G1CollectedHeap::heap();
3269 };
3270
3271 void do_object(oop o) {
3272 if (o != NULL) {
3273 HeapWord *start = (HeapWord *) o;
3274 size_t word_sz = o->size();
3275 gclog_or_tty->print("\nPrinting obj "PTR_FORMAT" of size " SIZE_FORMAT
3276 " isMarkedPrev %d isMarkedNext %d isAllocSince %d\n",
3277 (void*) o, word_sz,
3278 _g1->isMarkedPrev(o),
3279 _g1->isMarkedNext(o),
3280 _hr->obj_allocated_since_prev_marking(o));
3281 HeapWord *end = start + word_sz;
3282 HeapWord *cur;
3283 int *val;
3284 for (cur = start; cur < end; cur++) {
3285 val = (int *) cur;
3286 gclog_or_tty->print("\t "PTR_FORMAT":%d\n", val, *val);
3287 }
3288 }
3289 }
3290 };
3291
3292 class VerifyRegionClosure: public HeapRegionClosure {
3293 private:
3294 bool _par;
3295 VerifyOption _vo;
3296 bool _failures;
3297 public:
3298 // _vo == UsePrevMarking -> use "prev" marking information,
3299 // _vo == UseNextMarking -> use "next" marking information,
3300 // _vo == UseMarkWord -> use mark word from object header.
3301 VerifyRegionClosure(bool par, VerifyOption vo)
3302 : _par(par),
3303 _vo(vo),
3304 _failures(false) {}
3305
3306 bool failures() {
3307 return _failures;
3308 }
3309
3310 bool doHeapRegion(HeapRegion* r) {
3311 if (!r->continuesHumongous()) {
3312 bool failures = false;
3313 r->verify(_vo, &failures);
3314 if (failures) {
3315 _failures = true;
3316 } else {
3317 VerifyObjsInRegionClosure not_dead_yet_cl(r, _vo);
3318 r->object_iterate(¬_dead_yet_cl);
3319 if (_vo != VerifyOption_G1UseNextMarking) {
3320 if (r->max_live_bytes() < not_dead_yet_cl.live_bytes()) {
3321 gclog_or_tty->print_cr("["PTR_FORMAT","PTR_FORMAT"] "
3322 "max_live_bytes "SIZE_FORMAT" "
3323 "< calculated "SIZE_FORMAT,
3324 r->bottom(), r->end(),
3325 r->max_live_bytes(),
3326 not_dead_yet_cl.live_bytes());
3327 _failures = true;
3328 }
3329 } else {
3330 // When vo == UseNextMarking we cannot currently do a sanity
3331 // check on the live bytes as the calculation has not been
3332 // finalized yet.
3333 }
3334 }
3335 }
3336 return false; // stop the region iteration if we hit a failure
3337 }
3338 };
3339
3340 // This is the task used for parallel verification of the heap regions
3341
3342 class G1ParVerifyTask: public AbstractGangTask {
3343 private:
3344 G1CollectedHeap* _g1h;
3345 VerifyOption _vo;
3346 bool _failures;
3347
3348 public:
3349 // _vo == UsePrevMarking -> use "prev" marking information,
3350 // _vo == UseNextMarking -> use "next" marking information,
3351 // _vo == UseMarkWord -> use mark word from object header.
3352 G1ParVerifyTask(G1CollectedHeap* g1h, VerifyOption vo) :
3353 AbstractGangTask("Parallel verify task"),
3354 _g1h(g1h),
3355 _vo(vo),
3356 _failures(false) { }
3357
3358 bool failures() {
3359 return _failures;
3360 }
3361
3362 void work(uint worker_id) {
3363 HandleMark hm;
3364 VerifyRegionClosure blk(true, _vo);
3365 _g1h->heap_region_par_iterate_chunked(&blk, worker_id,
3366 _g1h->workers()->active_workers(),
3367 HeapRegion::ParVerifyClaimValue);
3368 if (blk.failures()) {
3369 _failures = true;
3370 }
3371 }
3372 };
3373
3374 void G1CollectedHeap::verify(bool silent, VerifyOption vo) {
3375 if (SafepointSynchronize::is_at_safepoint()) {
3376 assert(Thread::current()->is_VM_thread(),
3377 "Expected to be executed serially by the VM thread at this point");
3378
3379 if (!silent) { gclog_or_tty->print("Roots "); }
3380 VerifyRootsClosure rootsCl(vo);
3381 VerifyKlassClosure klassCl(this, &rootsCl);
3382
3383 // We apply the relevant closures to all the oops in the
3384 // system dictionary, class loader data graph and the string table.
3385 // Don't verify the code cache here, since it's verified below.
3386 const int so = SO_AllClasses | SO_Strings;
3387
3388 // Need cleared claim bits for the strong roots processing
3389 ClassLoaderDataGraph::clear_claimed_marks();
3390
3391 process_strong_roots(true, // activate StrongRootsScope
3392 ScanningOption(so), // roots scanning options
3393 &rootsCl,
3394 &klassCl
3395 );
3396
3397 // Verify the nmethods in the code cache.
3398 G1VerifyCodeRootOopClosure codeRootsCl(this, &rootsCl, vo);
3399 G1VerifyCodeRootBlobClosure blobsCl(&codeRootsCl);
3400 CodeCache::blobs_do(&blobsCl);
3401
3402 bool failures = rootsCl.failures() || codeRootsCl.failures();
3403
3404 if (vo != VerifyOption_G1UseMarkWord) {
3405 // If we're verifying during a full GC then the region sets
3406 // will have been torn down at the start of the GC. Therefore
3407 // verifying the region sets will fail. So we only verify
3408 // the region sets when not in a full GC.
3409 if (!silent) { gclog_or_tty->print("HeapRegionSets "); }
3410 verify_region_sets();
3411 }
3412
3413 if (!silent) { gclog_or_tty->print("HeapRegions "); }
3414 if (GCParallelVerificationEnabled && ParallelGCThreads > 1) {
3415 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3416 "sanity check");
3417
3418 G1ParVerifyTask task(this, vo);
3419 assert(UseDynamicNumberOfGCThreads ||
3420 workers()->active_workers() == workers()->total_workers(),
3421 "If not dynamic should be using all the workers");
3422 int n_workers = workers()->active_workers();
3423 set_par_threads(n_workers);
3424 workers()->run_task(&task);
3425 set_par_threads(0);
3426 if (task.failures()) {
3427 failures = true;
3428 }
3429
3430 // Checks that the expected amount of parallel work was done.
3431 // The implication is that n_workers is > 0.
3432 assert(check_heap_region_claim_values(HeapRegion::ParVerifyClaimValue),
3433 "sanity check");
3434
3435 reset_heap_region_claim_values();
3436
3437 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3438 "sanity check");
3439 } else {
3440 VerifyRegionClosure blk(false, vo);
3441 heap_region_iterate(&blk);
3442 if (blk.failures()) {
3443 failures = true;
3444 }
3445 }
3446 if (!silent) gclog_or_tty->print("RemSet ");
3447 rem_set()->verify();
3448
3449 if (G1StringDedup::is_enabled()) {
3450 if (!silent) gclog_or_tty->print("StrDedup ");
3451 G1StringDedup::verify();
3452 }
3453
3454 if (failures) {
3455 gclog_or_tty->print_cr("Heap:");
3456 // It helps to have the per-region information in the output to
3457 // help us track down what went wrong. This is why we call
3458 // print_extended_on() instead of print_on().
3459 print_extended_on(gclog_or_tty);
3460 gclog_or_tty->cr();
3461 #ifndef PRODUCT
3462 if (VerifyDuringGC && G1VerifyDuringGCPrintReachable) {
3463 concurrent_mark()->print_reachable("at-verification-failure",
3464 vo, false /* all */);
3465 }
3466 #endif
3467 gclog_or_tty->flush();
3468 }
3469 guarantee(!failures, "there should not have been any failures");
3470 } else {
3471 if (!silent) {
3472 gclog_or_tty->print("(SKIPPING Roots, HeapRegionSets, HeapRegions, RemSet");
3473 if (G1StringDedup::is_enabled()) {
3474 gclog_or_tty->print(", StrDedup");
3475 }
3476 gclog_or_tty->print(") ");
3477 }
3478 }
3479 }
3480
3481 void G1CollectedHeap::verify(bool silent) {
3482 verify(silent, VerifyOption_G1UsePrevMarking);
3483 }
3484
3485 double G1CollectedHeap::verify(bool guard, const char* msg) {
3486 double verify_time_ms = 0.0;
3487
3488 if (guard && total_collections() >= VerifyGCStartAt) {
3489 double verify_start = os::elapsedTime();
3490 HandleMark hm; // Discard invalid handles created during verification
3491 prepare_for_verify();
3492 Universe::verify(VerifyOption_G1UsePrevMarking, msg);
3493 verify_time_ms = (os::elapsedTime() - verify_start) * 1000;
3494 }
3495
3496 return verify_time_ms;
3497 }
3498
3499 void G1CollectedHeap::verify_before_gc() {
3500 double verify_time_ms = verify(VerifyBeforeGC, " VerifyBeforeGC:");
3501 g1_policy()->phase_times()->record_verify_before_time_ms(verify_time_ms);
3502 }
3503
3504 void G1CollectedHeap::verify_after_gc() {
3505 double verify_time_ms = verify(VerifyAfterGC, " VerifyAfterGC:");
3506 g1_policy()->phase_times()->record_verify_after_time_ms(verify_time_ms);
3507 }
3508
3509 class PrintRegionClosure: public HeapRegionClosure {
3510 outputStream* _st;
3511 public:
3512 PrintRegionClosure(outputStream* st) : _st(st) {}
3513 bool doHeapRegion(HeapRegion* r) {
3514 r->print_on(_st);
3515 return false;
3516 }
3517 };
3518
3519 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
3520 const HeapRegion* hr,
3521 const VerifyOption vo) const {
3522 switch (vo) {
3523 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr);
3524 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr);
3525 case VerifyOption_G1UseMarkWord: return !obj->is_gc_marked();
3526 default: ShouldNotReachHere();
3527 }
3528 return false; // keep some compilers happy
3529 }
3530
3531 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
3532 const VerifyOption vo) const {
3533 switch (vo) {
3534 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj);
3535 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj);
3536 case VerifyOption_G1UseMarkWord: return !obj->is_gc_marked();
3537 default: ShouldNotReachHere();
3538 }
3539 return false; // keep some compilers happy
3540 }
3541
3542 void G1CollectedHeap::print_on(outputStream* st) const {
3543 st->print(" %-20s", "garbage-first heap");
3544 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
3545 capacity()/K, used_unlocked()/K);
3546 st->print(" [" INTPTR_FORMAT ", " INTPTR_FORMAT ", " INTPTR_FORMAT ")",
3547 _g1_storage.low_boundary(),
3548 _g1_storage.high(),
3549 _g1_storage.high_boundary());
3550 st->cr();
3551 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
3552 uint young_regions = _young_list->length();
3553 st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
3554 (size_t) young_regions * HeapRegion::GrainBytes / K);
3555 uint survivor_regions = g1_policy()->recorded_survivor_regions();
3556 st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
3557 (size_t) survivor_regions * HeapRegion::GrainBytes / K);
3558 st->cr();
3559 MetaspaceAux::print_on(st);
3560 }
3561
3562 void G1CollectedHeap::print_extended_on(outputStream* st) const {
3563 print_on(st);
3564
3565 // Print the per-region information.
3566 st->cr();
3567 st->print_cr("Heap Regions: (Y=young(eden), SU=young(survivor), "
3568 "HS=humongous(starts), HC=humongous(continues), "
3569 "CS=collection set, F=free, TS=gc time stamp, "
3570 "PTAMS=previous top-at-mark-start, "
3571 "NTAMS=next top-at-mark-start)");
3572 PrintRegionClosure blk(st);
3573 heap_region_iterate(&blk);
3574 }
3575
3576 void G1CollectedHeap::print_on_error(outputStream* st) const {
3577 this->CollectedHeap::print_on_error(st);
3578
3579 if (_cm != NULL) {
3580 st->cr();
3581 _cm->print_on_error(st);
3582 }
3583 }
3584
3585 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
3586 if (G1CollectedHeap::use_parallel_gc_threads()) {
3587 workers()->print_worker_threads_on(st);
3588 }
3589 _cmThread->print_on(st);
3590 st->cr();
3591 _cm->print_worker_threads_on(st);
3592 _cg1r->print_worker_threads_on(st);
3593 if (G1StringDedup::is_enabled()) {
3594 G1StringDedup::print_worker_threads_on(st);
3595 }
3596 }
3597
3598 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
3599 if (G1CollectedHeap::use_parallel_gc_threads()) {
3600 workers()->threads_do(tc);
3601 }
3602 tc->do_thread(_cmThread);
3603 _cg1r->threads_do(tc);
3604 if (G1StringDedup::is_enabled()) {
3605 G1StringDedup::threads_do(tc);
3606 }
3607 }
3608
3609 void G1CollectedHeap::print_tracing_info() const {
3610 // We'll overload this to mean "trace GC pause statistics."
3611 if (TraceGen0Time || TraceGen1Time) {
3612 // The "G1CollectorPolicy" is keeping track of these stats, so delegate
3613 // to that.
3614 g1_policy()->print_tracing_info();
3615 }
3616 if (G1SummarizeRSetStats) {
3617 g1_rem_set()->print_summary_info();
3618 }
3619 if (G1SummarizeConcMark) {
3620 concurrent_mark()->print_summary_info();
3621 }
3622 g1_policy()->print_yg_surv_rate_info();
3623 SpecializationStats::print();
3624 }
3625
3626 #ifndef PRODUCT
3627 // Helpful for debugging RSet issues.
3628
3629 class PrintRSetsClosure : public HeapRegionClosure {
3630 private:
3631 const char* _msg;
3632 size_t _occupied_sum;
3633
3634 public:
3635 bool doHeapRegion(HeapRegion* r) {
3636 HeapRegionRemSet* hrrs = r->rem_set();
3637 size_t occupied = hrrs->occupied();
3638 _occupied_sum += occupied;
3639
3640 gclog_or_tty->print_cr("Printing RSet for region "HR_FORMAT,
3641 HR_FORMAT_PARAMS(r));
3642 if (occupied == 0) {
3643 gclog_or_tty->print_cr(" RSet is empty");
3644 } else {
3645 hrrs->print();
3646 }
3647 gclog_or_tty->print_cr("----------");
3648 return false;
3649 }
3650
3651 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
3652 gclog_or_tty->cr();
3653 gclog_or_tty->print_cr("========================================");
3654 gclog_or_tty->print_cr("%s", msg);
3655 gclog_or_tty->cr();
3656 }
3657
3658 ~PrintRSetsClosure() {
3659 gclog_or_tty->print_cr("Occupied Sum: "SIZE_FORMAT, _occupied_sum);
3660 gclog_or_tty->print_cr("========================================");
3661 gclog_or_tty->cr();
3662 }
3663 };
3664
3665 void G1CollectedHeap::print_cset_rsets() {
3666 PrintRSetsClosure cl("Printing CSet RSets");
3667 collection_set_iterate(&cl);
3668 }
3669
3670 void G1CollectedHeap::print_all_rsets() {
3671 PrintRSetsClosure cl("Printing All RSets");;
3672 heap_region_iterate(&cl);
3673 }
3674 #endif // PRODUCT
3675
3676 G1CollectedHeap* G1CollectedHeap::heap() {
3677 assert(_sh->kind() == CollectedHeap::G1CollectedHeap,
3678 "not a garbage-first heap");
3679 return _g1h;
3680 }
3681
3682 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) {
3683 // always_do_update_barrier = false;
3684 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
3685 // Fill TLAB's and such
3686 accumulate_statistics_all_tlabs();
3687 ensure_parsability(true);
3688
3689 if (G1SummarizeRSetStats && (G1SummarizeRSetStatsPeriod > 0) &&
3690 (total_collections() % G1SummarizeRSetStatsPeriod == 0)) {
3691 g1_rem_set()->print_periodic_summary_info("Before GC RS summary");
3692 }
3693 }
3694
3695 void G1CollectedHeap::gc_epilogue(bool full /* Ignored */) {
3696
3697 if (G1SummarizeRSetStats &&
3698 (G1SummarizeRSetStatsPeriod > 0) &&
3699 // we are at the end of the GC. Total collections has already been increased.
3700 ((total_collections() - 1) % G1SummarizeRSetStatsPeriod == 0)) {
3701 g1_rem_set()->print_periodic_summary_info("After GC RS summary");
3702 }
3703
3704 // FIXME: what is this about?
3705 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
3706 // is set.
3707 COMPILER2_PRESENT(assert(DerivedPointerTable::is_empty(),
3708 "derived pointer present"));
3709 // always_do_update_barrier = true;
3710
3711 resize_all_tlabs();
3712
3713 // We have just completed a GC. Update the soft reference
3714 // policy with the new heap occupancy
3715 Universe::update_heap_info_at_gc();
3716 }
3717
3718 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
3719 unsigned int gc_count_before,
3720 bool* succeeded,
3721 GCCause::Cause gc_cause) {
3722 assert_heap_not_locked_and_not_at_safepoint();
3723 g1_policy()->record_stop_world_start();
3724 VM_G1IncCollectionPause op(gc_count_before,
3725 word_size,
3726 false, /* should_initiate_conc_mark */
3727 g1_policy()->max_pause_time_ms(),
3728 gc_cause);
3729 VMThread::execute(&op);
3730
3731 HeapWord* result = op.result();
3732 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
3733 assert(result == NULL || ret_succeeded,
3734 "the result should be NULL if the VM did not succeed");
3735 *succeeded = ret_succeeded;
3736
3737 assert_heap_not_locked();
3738 return result;
3739 }
3740
3741 void
3742 G1CollectedHeap::doConcurrentMark() {
3743 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
3744 if (!_cmThread->in_progress()) {
3745 _cmThread->set_started();
3746 CGC_lock->notify();
3747 }
3748 }
3749
3750 size_t G1CollectedHeap::pending_card_num() {
3751 size_t extra_cards = 0;
3752 JavaThread *curr = Threads::first();
3753 while (curr != NULL) {
3754 DirtyCardQueue& dcq = curr->dirty_card_queue();
3755 extra_cards += dcq.size();
3756 curr = curr->next();
3757 }
3758 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
3759 size_t buffer_size = dcqs.buffer_size();
3760 size_t buffer_num = dcqs.completed_buffers_num();
3761
3762 // PtrQueueSet::buffer_size() and PtrQueue:size() return sizes
3763 // in bytes - not the number of 'entries'. We need to convert
3764 // into a number of cards.
3765 return (buffer_size * buffer_num + extra_cards) / oopSize;
3766 }
3767
3768 size_t G1CollectedHeap::cards_scanned() {
3769 return g1_rem_set()->cardsScanned();
3770 }
3771
3772 void
3773 G1CollectedHeap::setup_surviving_young_words() {
3774 assert(_surviving_young_words == NULL, "pre-condition");
3775 uint array_length = g1_policy()->young_cset_region_length();
3776 _surviving_young_words = NEW_C_HEAP_ARRAY(size_t, (size_t) array_length, mtGC);
3777 if (_surviving_young_words == NULL) {
3778 vm_exit_out_of_memory(sizeof(size_t) * array_length, OOM_MALLOC_ERROR,
3779 "Not enough space for young surv words summary.");
3780 }
3781 memset(_surviving_young_words, 0, (size_t) array_length * sizeof(size_t));
3782 #ifdef ASSERT
3783 for (uint i = 0; i < array_length; ++i) {
3784 assert( _surviving_young_words[i] == 0, "memset above" );
3785 }
3786 #endif // !ASSERT
3787 }
3788
3789 void
3790 G1CollectedHeap::update_surviving_young_words(size_t* surv_young_words) {
3791 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
3792 uint array_length = g1_policy()->young_cset_region_length();
3793 for (uint i = 0; i < array_length; ++i) {
3794 _surviving_young_words[i] += surv_young_words[i];
3795 }
3796 }
3797
3798 void
3799 G1CollectedHeap::cleanup_surviving_young_words() {
3800 guarantee( _surviving_young_words != NULL, "pre-condition" );
3801 FREE_C_HEAP_ARRAY(size_t, _surviving_young_words, mtGC);
3802 _surviving_young_words = NULL;
3803 }
3804
3805 #ifdef ASSERT
3806 class VerifyCSetClosure: public HeapRegionClosure {
3807 public:
3808 bool doHeapRegion(HeapRegion* hr) {
3809 // Here we check that the CSet region's RSet is ready for parallel
3810 // iteration. The fields that we'll verify are only manipulated
3811 // when the region is part of a CSet and is collected. Afterwards,
3812 // we reset these fields when we clear the region's RSet (when the
3813 // region is freed) so they are ready when the region is
3814 // re-allocated. The only exception to this is if there's an
3815 // evacuation failure and instead of freeing the region we leave
3816 // it in the heap. In that case, we reset these fields during
3817 // evacuation failure handling.
3818 guarantee(hr->rem_set()->verify_ready_for_par_iteration(), "verification");
3819
3820 // Here's a good place to add any other checks we'd like to
3821 // perform on CSet regions.
3822 return false;
3823 }
3824 };
3825 #endif // ASSERT
3826
3827 #if TASKQUEUE_STATS
3828 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
3829 st->print_raw_cr("GC Task Stats");
3830 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
3831 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
3832 }
3833
3834 void G1CollectedHeap::print_taskqueue_stats(outputStream* const st) const {
3835 print_taskqueue_stats_hdr(st);
3836
3837 TaskQueueStats totals;
3838 const int n = workers() != NULL ? workers()->total_workers() : 1;
3839 for (int i = 0; i < n; ++i) {
3840 st->print("%3d ", i); task_queue(i)->stats.print(st); st->cr();
3841 totals += task_queue(i)->stats;
3842 }
3843 st->print_raw("tot "); totals.print(st); st->cr();
3844
3845 DEBUG_ONLY(totals.verify());
3846 }
3847
3848 void G1CollectedHeap::reset_taskqueue_stats() {
3849 const int n = workers() != NULL ? workers()->total_workers() : 1;
3850 for (int i = 0; i < n; ++i) {
3851 task_queue(i)->stats.reset();
3852 }
3853 }
3854 #endif // TASKQUEUE_STATS
3855
3856 void G1CollectedHeap::log_gc_header() {
3857 if (!G1Log::fine()) {
3858 return;
3859 }
3860
3861 gclog_or_tty->date_stamp(PrintGCDateStamps);
3862 gclog_or_tty->stamp(PrintGCTimeStamps);
3863
3864 GCCauseString gc_cause_str = GCCauseString("GC pause", gc_cause())
3865 .append(g1_policy()->gcs_are_young() ? "(young)" : "(mixed)")
3866 .append(g1_policy()->during_initial_mark_pause() ? " (initial-mark)" : "");
3867
3868 gclog_or_tty->print("[%s", (const char*)gc_cause_str);
3869 }
3870
3871 void G1CollectedHeap::log_gc_footer(double pause_time_sec) {
3872 if (!G1Log::fine()) {
3873 return;
3874 }
3875
3876 if (G1Log::finer()) {
3877 if (evacuation_failed()) {
3878 gclog_or_tty->print(" (to-space exhausted)");
3879 }
3880 gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec);
3881 g1_policy()->phase_times()->note_gc_end();
3882 g1_policy()->phase_times()->print(pause_time_sec);
3883 g1_policy()->print_detailed_heap_transition();
3884 } else {
3885 if (evacuation_failed()) {
3886 gclog_or_tty->print("--");
3887 }
3888 g1_policy()->print_heap_transition();
3889 gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec);
3890 }
3891 gclog_or_tty->flush();
3892 }
3893
3894 bool
3895 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
3896 assert_at_safepoint(true /* should_be_vm_thread */);
3897 guarantee(!is_gc_active(), "collection is not reentrant");
3898
3899 if (GC_locker::check_active_before_gc()) {
3900 return false;
3901 }
3902
3903 _gc_timer_stw->register_gc_start();
3904
3905 _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start());
3906
3907 SvcGCMarker sgcm(SvcGCMarker::MINOR);
3908 ResourceMark rm;
3909
3910 print_heap_before_gc();
3911 trace_heap_before_gc(_gc_tracer_stw);
3912
3913 verify_region_sets_optional();
3914 verify_dirty_young_regions();
3915
3916 // This call will decide whether this pause is an initial-mark
3917 // pause. If it is, during_initial_mark_pause() will return true
3918 // for the duration of this pause.
3919 g1_policy()->decide_on_conc_mark_initiation();
3920
3921 // We do not allow initial-mark to be piggy-backed on a mixed GC.
3922 assert(!g1_policy()->during_initial_mark_pause() ||
3923 g1_policy()->gcs_are_young(), "sanity");
3924
3925 // We also do not allow mixed GCs during marking.
3926 assert(!mark_in_progress() || g1_policy()->gcs_are_young(), "sanity");
3927
3928 // Record whether this pause is an initial mark. When the current
3929 // thread has completed its logging output and it's safe to signal
3930 // the CM thread, the flag's value in the policy has been reset.
3931 bool should_start_conc_mark = g1_policy()->during_initial_mark_pause();
3932
3933 // Inner scope for scope based logging, timers, and stats collection
3934 {
3935 EvacuationInfo evacuation_info;
3936
3937 if (g1_policy()->during_initial_mark_pause()) {
3938 // We are about to start a marking cycle, so we increment the
3939 // full collection counter.
3940 increment_old_marking_cycles_started();
3941 register_concurrent_cycle_start(_gc_timer_stw->gc_start());
3942 }
3943
3944 _gc_tracer_stw->report_yc_type(yc_type());
3945
3946 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
3947
3948 int active_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
3949 workers()->active_workers() : 1);
3950 double pause_start_sec = os::elapsedTime();
3951 g1_policy()->phase_times()->note_gc_start(active_workers);
3952 log_gc_header();
3953
3954 TraceCollectorStats tcs(g1mm()->incremental_collection_counters());
3955 TraceMemoryManagerStats tms(false /* fullGC */, gc_cause());
3956
3957 // If the secondary_free_list is not empty, append it to the
3958 // free_list. No need to wait for the cleanup operation to finish;
3959 // the region allocation code will check the secondary_free_list
3960 // and wait if necessary. If the G1StressConcRegionFreeing flag is
3961 // set, skip this step so that the region allocation code has to
3962 // get entries from the secondary_free_list.
3963 if (!G1StressConcRegionFreeing) {
3964 append_secondary_free_list_if_not_empty_with_lock();
3965 }
3966
3967 assert(check_young_list_well_formed(), "young list should be well formed");
3968 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3969 "sanity check");
3970
3971 // Don't dynamically change the number of GC threads this early. A value of
3972 // 0 is used to indicate serial work. When parallel work is done,
3973 // it will be set.
3974
3975 { // Call to jvmpi::post_class_unload_events must occur outside of active GC
3976 IsGCActiveMark x;
3977
3978 gc_prologue(false);
3979 increment_total_collections(false /* full gc */);
3980 increment_gc_time_stamp();
3981
3982 verify_before_gc();
3983 check_bitmaps("GC Start");
3984
3985 COMPILER2_PRESENT(DerivedPointerTable::clear());
3986
3987 // Please see comment in g1CollectedHeap.hpp and
3988 // G1CollectedHeap::ref_processing_init() to see how
3989 // reference processing currently works in G1.
3990
3991 // Enable discovery in the STW reference processor
3992 ref_processor_stw()->enable_discovery(true /*verify_disabled*/,
3993 true /*verify_no_refs*/);
3994
3995 {
3996 // We want to temporarily turn off discovery by the
3997 // CM ref processor, if necessary, and turn it back on
3998 // on again later if we do. Using a scoped
3999 // NoRefDiscovery object will do this.
4000 NoRefDiscovery no_cm_discovery(ref_processor_cm());
4001
4002 // Forget the current alloc region (we might even choose it to be part
4003 // of the collection set!).
4004 release_mutator_alloc_region();
4005
4006 // We should call this after we retire the mutator alloc
4007 // region(s) so that all the ALLOC / RETIRE events are generated
4008 // before the start GC event.
4009 _hr_printer.start_gc(false /* full */, (size_t) total_collections());
4010
4011 // This timing is only used by the ergonomics to handle our pause target.
4012 // It is unclear why this should not include the full pause. We will
4013 // investigate this in CR 7178365.
4014 //
4015 // Preserving the old comment here if that helps the investigation:
4016 //
4017 // The elapsed time induced by the start time below deliberately elides
4018 // the possible verification above.
4019 double sample_start_time_sec = os::elapsedTime();
4020
4021 #if YOUNG_LIST_VERBOSE
4022 gclog_or_tty->print_cr("\nBefore recording pause start.\nYoung_list:");
4023 _young_list->print();
4024 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
4025 #endif // YOUNG_LIST_VERBOSE
4026
4027 g1_policy()->record_collection_pause_start(sample_start_time_sec);
4028
4029 double scan_wait_start = os::elapsedTime();
4030 // We have to wait until the CM threads finish scanning the
4031 // root regions as it's the only way to ensure that all the
4032 // objects on them have been correctly scanned before we start
4033 // moving them during the GC.
4034 bool waited = _cm->root_regions()->wait_until_scan_finished();
4035 double wait_time_ms = 0.0;
4036 if (waited) {
4037 double scan_wait_end = os::elapsedTime();
4038 wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
4039 }
4040 g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms);
4041
4042 #if YOUNG_LIST_VERBOSE
4043 gclog_or_tty->print_cr("\nAfter recording pause start.\nYoung_list:");
4044 _young_list->print();
4045 #endif // YOUNG_LIST_VERBOSE
4046
4047 if (g1_policy()->during_initial_mark_pause()) {
4048 concurrent_mark()->checkpointRootsInitialPre();
4049 }
4050
4051 #if YOUNG_LIST_VERBOSE
4052 gclog_or_tty->print_cr("\nBefore choosing collection set.\nYoung_list:");
4053 _young_list->print();
4054 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
4055 #endif // YOUNG_LIST_VERBOSE
4056
4057 g1_policy()->finalize_cset(target_pause_time_ms, evacuation_info);
4058
4059 _cm->note_start_of_gc();
4060 // We should not verify the per-thread SATB buffers given that
4061 // we have not filtered them yet (we'll do so during the
4062 // GC). We also call this after finalize_cset() to
4063 // ensure that the CSet has been finalized.
4064 _cm->verify_no_cset_oops(true /* verify_stacks */,
4065 true /* verify_enqueued_buffers */,
4066 false /* verify_thread_buffers */,
4067 true /* verify_fingers */);
4068
4069 if (_hr_printer.is_active()) {
4070 HeapRegion* hr = g1_policy()->collection_set();
4071 while (hr != NULL) {
4072 G1HRPrinter::RegionType type;
4073 if (!hr->is_young()) {
4074 type = G1HRPrinter::Old;
4075 } else if (hr->is_survivor()) {
4076 type = G1HRPrinter::Survivor;
4077 } else {
4078 type = G1HRPrinter::Eden;
4079 }
4080 _hr_printer.cset(hr);
4081 hr = hr->next_in_collection_set();
4082 }
4083 }
4084
4085 #ifdef ASSERT
4086 VerifyCSetClosure cl;
4087 collection_set_iterate(&cl);
4088 #endif // ASSERT
4089
4090 setup_surviving_young_words();
4091
4092 // Initialize the GC alloc regions.
4093 init_gc_alloc_regions(evacuation_info);
4094
4095 // Actually do the work...
4096 evacuate_collection_set(evacuation_info);
4097
4098 // We do this to mainly verify the per-thread SATB buffers
4099 // (which have been filtered by now) since we didn't verify
4100 // them earlier. No point in re-checking the stacks / enqueued
4101 // buffers given that the CSet has not changed since last time
4102 // we checked.
4103 _cm->verify_no_cset_oops(false /* verify_stacks */,
4104 false /* verify_enqueued_buffers */,
4105 true /* verify_thread_buffers */,
4106 true /* verify_fingers */);
4107
4108 free_collection_set(g1_policy()->collection_set(), evacuation_info);
4109 g1_policy()->clear_collection_set();
4110
4111 cleanup_surviving_young_words();
4112
4113 // Start a new incremental collection set for the next pause.
4114 g1_policy()->start_incremental_cset_building();
4115
4116 clear_cset_fast_test();
4117
4118 _young_list->reset_sampled_info();
4119
4120 // Don't check the whole heap at this point as the
4121 // GC alloc regions from this pause have been tagged
4122 // as survivors and moved on to the survivor list.
4123 // Survivor regions will fail the !is_young() check.
4124 assert(check_young_list_empty(false /* check_heap */),
4125 "young list should be empty");
4126
4127 #if YOUNG_LIST_VERBOSE
4128 gclog_or_tty->print_cr("Before recording survivors.\nYoung List:");
4129 _young_list->print();
4130 #endif // YOUNG_LIST_VERBOSE
4131
4132 g1_policy()->record_survivor_regions(_young_list->survivor_length(),
4133 _young_list->first_survivor_region(),
4134 _young_list->last_survivor_region());
4135
4136 _young_list->reset_auxilary_lists();
4137
4138 if (evacuation_failed()) {
4139 _summary_bytes_used = recalculate_used();
4140 uint n_queues = MAX2((int)ParallelGCThreads, 1);
4141 for (uint i = 0; i < n_queues; i++) {
4142 if (_evacuation_failed_info_array[i].has_failed()) {
4143 _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]);
4144 }
4145 }
4146 } else {
4147 // The "used" of the the collection set have already been subtracted
4148 // when they were freed. Add in the bytes evacuated.
4149 _summary_bytes_used += g1_policy()->bytes_copied_during_gc();
4150 }
4151
4152 if (g1_policy()->during_initial_mark_pause()) {
4153 // We have to do this before we notify the CM threads that
4154 // they can start working to make sure that all the
4155 // appropriate initialization is done on the CM object.
4156 concurrent_mark()->checkpointRootsInitialPost();
4157 set_marking_started();
4158 // Note that we don't actually trigger the CM thread at
4159 // this point. We do that later when we're sure that
4160 // the current thread has completed its logging output.
4161 }
4162
4163 allocate_dummy_regions();
4164
4165 #if YOUNG_LIST_VERBOSE
4166 gclog_or_tty->print_cr("\nEnd of the pause.\nYoung_list:");
4167 _young_list->print();
4168 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
4169 #endif // YOUNG_LIST_VERBOSE
4170
4171 init_mutator_alloc_region();
4172
4173 {
4174 size_t expand_bytes = g1_policy()->expansion_amount();
4175 if (expand_bytes > 0) {
4176 size_t bytes_before = capacity();
4177 // No need for an ergo verbose message here,
4178 // expansion_amount() does this when it returns a value > 0.
4179 if (!expand(expand_bytes)) {
4180 // We failed to expand the heap so let's verify that
4181 // committed/uncommitted amount match the backing store
4182 assert(capacity() == _g1_storage.committed_size(), "committed size mismatch");
4183 assert(max_capacity() == _g1_storage.reserved_size(), "reserved size mismatch");
4184 }
4185 }
4186 }
4187
4188 // We redo the verification but now wrt to the new CSet which
4189 // has just got initialized after the previous CSet was freed.
4190 _cm->verify_no_cset_oops(true /* verify_stacks */,
4191 true /* verify_enqueued_buffers */,
4192 true /* verify_thread_buffers */,
4193 true /* verify_fingers */);
4194 _cm->note_end_of_gc();
4195
4196 // This timing is only used by the ergonomics to handle our pause target.
4197 // It is unclear why this should not include the full pause. We will
4198 // investigate this in CR 7178365.
4199 double sample_end_time_sec = os::elapsedTime();
4200 double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
4201 g1_policy()->record_collection_pause_end(pause_time_ms, evacuation_info);
4202
4203 MemoryService::track_memory_usage();
4204
4205 // In prepare_for_verify() below we'll need to scan the deferred
4206 // update buffers to bring the RSets up-to-date if
4207 // G1HRRSFlushLogBuffersOnVerify has been set. While scanning
4208 // the update buffers we'll probably need to scan cards on the
4209 // regions we just allocated to (i.e., the GC alloc
4210 // regions). However, during the last GC we called
4211 // set_saved_mark() on all the GC alloc regions, so card
4212 // scanning might skip the [saved_mark_word()...top()] area of
4213 // those regions (i.e., the area we allocated objects into
4214 // during the last GC). But it shouldn't. Given that
4215 // saved_mark_word() is conditional on whether the GC time stamp
4216 // on the region is current or not, by incrementing the GC time
4217 // stamp here we invalidate all the GC time stamps on all the
4218 // regions and saved_mark_word() will simply return top() for
4219 // all the regions. This is a nicer way of ensuring this rather
4220 // than iterating over the regions and fixing them. In fact, the
4221 // GC time stamp increment here also ensures that
4222 // saved_mark_word() will return top() between pauses, i.e.,
4223 // during concurrent refinement. So we don't need the
4224 // is_gc_active() check to decided which top to use when
4225 // scanning cards (see CR 7039627).
4226 increment_gc_time_stamp();
4227
4228 verify_after_gc();
4229 check_bitmaps("GC End");
4230
4231 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
4232 ref_processor_stw()->verify_no_references_recorded();
4233
4234 // CM reference discovery will be re-enabled if necessary.
4235 }
4236
4237 // We should do this after we potentially expand the heap so
4238 // that all the COMMIT events are generated before the end GC
4239 // event, and after we retire the GC alloc regions so that all
4240 // RETIRE events are generated before the end GC event.
4241 _hr_printer.end_gc(false /* full */, (size_t) total_collections());
4242
4243 if (mark_in_progress()) {
4244 concurrent_mark()->update_g1_committed();
4245 }
4246
4247 #ifdef TRACESPINNING
4248 ParallelTaskTerminator::print_termination_counts();
4249 #endif
4250
4251 gc_epilogue(false);
4252 }
4253
4254 // Print the remainder of the GC log output.
4255 log_gc_footer(os::elapsedTime() - pause_start_sec);
4256
4257 // It is not yet to safe to tell the concurrent mark to
4258 // start as we have some optional output below. We don't want the
4259 // output from the concurrent mark thread interfering with this
4260 // logging output either.
4261
4262 _hrs.verify_optional();
4263 verify_region_sets_optional();
4264
4265 TASKQUEUE_STATS_ONLY(if (ParallelGCVerbose) print_taskqueue_stats());
4266 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
4267
4268 print_heap_after_gc();
4269 trace_heap_after_gc(_gc_tracer_stw);
4270
4271 // We must call G1MonitoringSupport::update_sizes() in the same scoping level
4272 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
4273 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
4274 // before any GC notifications are raised.
4275 g1mm()->update_sizes();
4276
4277 _gc_tracer_stw->report_evacuation_info(&evacuation_info);
4278 _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold());
4279 _gc_timer_stw->register_gc_end();
4280 _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions());
4281 }
4282 // It should now be safe to tell the concurrent mark thread to start
4283 // without its logging output interfering with the logging output
4284 // that came from the pause.
4285
4286 if (should_start_conc_mark) {
4287 // CAUTION: after the doConcurrentMark() call below,
4288 // the concurrent marking thread(s) could be running
4289 // concurrently with us. Make sure that anything after
4290 // this point does not assume that we are the only GC thread
4291 // running. Note: of course, the actual marking work will
4292 // not start until the safepoint itself is released in
4293 // SuspendibleThreadSet::desynchronize().
4294 doConcurrentMark();
4295 }
4296
4297 return true;
4298 }
4299
4300 size_t G1CollectedHeap::desired_plab_sz(GCAllocPurpose purpose)
4301 {
4302 size_t gclab_word_size;
4303 switch (purpose) {
4304 case GCAllocForSurvived:
4305 gclab_word_size = _survivor_plab_stats.desired_plab_sz();
4306 break;
4307 case GCAllocForTenured:
4308 gclab_word_size = _old_plab_stats.desired_plab_sz();
4309 break;
4310 default:
4311 assert(false, "unknown GCAllocPurpose");
4312 gclab_word_size = _old_plab_stats.desired_plab_sz();
4313 break;
4314 }
4315
4316 // Prevent humongous PLAB sizes for two reasons:
4317 // * PLABs are allocated using a similar paths as oops, but should
4318 // never be in a humongous region
4319 // * Allowing humongous PLABs needlessly churns the region free lists
4320 return MIN2(_humongous_object_threshold_in_words, gclab_word_size);
4321 }
4322
4323 void G1CollectedHeap::init_mutator_alloc_region() {
4324 assert(_mutator_alloc_region.get() == NULL, "pre-condition");
4325 _mutator_alloc_region.init();
4326 }
4327
4328 void G1CollectedHeap::release_mutator_alloc_region() {
4329 _mutator_alloc_region.release();
4330 assert(_mutator_alloc_region.get() == NULL, "post-condition");
4331 }
4332
4333 void G1CollectedHeap::init_gc_alloc_regions(EvacuationInfo& evacuation_info) {
4334 assert_at_safepoint(true /* should_be_vm_thread */);
4335
4336 _survivor_gc_alloc_region.init();
4337 _old_gc_alloc_region.init();
4338 HeapRegion* retained_region = _retained_old_gc_alloc_region;
4339 _retained_old_gc_alloc_region = NULL;
4340
4341 // We will discard the current GC alloc region if:
4342 // a) it's in the collection set (it can happen!),
4343 // b) it's already full (no point in using it),
4344 // c) it's empty (this means that it was emptied during
4345 // a cleanup and it should be on the free list now), or
4346 // d) it's humongous (this means that it was emptied
4347 // during a cleanup and was added to the free list, but
4348 // has been subsequently used to allocate a humongous
4349 // object that may be less than the region size).
4350 if (retained_region != NULL &&
4351 !retained_region->in_collection_set() &&
4352 !(retained_region->top() == retained_region->end()) &&
4353 !retained_region->is_empty() &&
4354 !retained_region->isHumongous()) {
4355 retained_region->set_saved_mark();
4356 // The retained region was added to the old region set when it was
4357 // retired. We have to remove it now, since we don't allow regions
4358 // we allocate to in the region sets. We'll re-add it later, when
4359 // it's retired again.
4360 _old_set.remove(retained_region);
4361 bool during_im = g1_policy()->during_initial_mark_pause();
4362 retained_region->note_start_of_copying(during_im);
4363 _old_gc_alloc_region.set(retained_region);
4364 _hr_printer.reuse(retained_region);
4365 evacuation_info.set_alloc_regions_used_before(retained_region->used());
4366 }
4367 }
4368
4369 void G1CollectedHeap::release_gc_alloc_regions(uint no_of_gc_workers, EvacuationInfo& evacuation_info) {
4370 evacuation_info.set_allocation_regions(_survivor_gc_alloc_region.count() +
4371 _old_gc_alloc_region.count());
4372 _survivor_gc_alloc_region.release();
4373 // If we have an old GC alloc region to release, we'll save it in
4374 // _retained_old_gc_alloc_region. If we don't
4375 // _retained_old_gc_alloc_region will become NULL. This is what we
4376 // want either way so no reason to check explicitly for either
4377 // condition.
4378 _retained_old_gc_alloc_region = _old_gc_alloc_region.release();
4379
4380 if (ResizePLAB) {
4381 _survivor_plab_stats.adjust_desired_plab_sz(no_of_gc_workers);
4382 _old_plab_stats.adjust_desired_plab_sz(no_of_gc_workers);
4383 }
4384 }
4385
4386 void G1CollectedHeap::abandon_gc_alloc_regions() {
4387 assert(_survivor_gc_alloc_region.get() == NULL, "pre-condition");
4388 assert(_old_gc_alloc_region.get() == NULL, "pre-condition");
4389 _retained_old_gc_alloc_region = NULL;
4390 }
4391
4392 void G1CollectedHeap::init_for_evac_failure(OopsInHeapRegionClosure* cl) {
4393 _drain_in_progress = false;
4394 set_evac_failure_closure(cl);
4395 _evac_failure_scan_stack = new (ResourceObj::C_HEAP, mtGC) GrowableArray<oop>(40, true);
4396 }
4397
4398 void G1CollectedHeap::finalize_for_evac_failure() {
4399 assert(_evac_failure_scan_stack != NULL &&
4400 _evac_failure_scan_stack->length() == 0,
4401 "Postcondition");
4402 assert(!_drain_in_progress, "Postcondition");
4403 delete _evac_failure_scan_stack;
4404 _evac_failure_scan_stack = NULL;
4405 }
4406
4407 void G1CollectedHeap::remove_self_forwarding_pointers() {
4408 assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity");
4409
4410 double remove_self_forwards_start = os::elapsedTime();
4411
4412 G1ParRemoveSelfForwardPtrsTask rsfp_task(this);
4413
4414 if (G1CollectedHeap::use_parallel_gc_threads()) {
4415 set_par_threads();
4416 workers()->run_task(&rsfp_task);
4417 set_par_threads(0);
4418 } else {
4419 rsfp_task.work(0);
4420 }
4421
4422 assert(check_cset_heap_region_claim_values(HeapRegion::ParEvacFailureClaimValue), "sanity");
4423
4424 // Reset the claim values in the regions in the collection set.
4425 reset_cset_heap_region_claim_values();
4426
4427 assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity");
4428
4429 // Now restore saved marks, if any.
4430 assert(_objs_with_preserved_marks.size() ==
4431 _preserved_marks_of_objs.size(), "Both or none.");
4432 while (!_objs_with_preserved_marks.is_empty()) {
4433 oop obj = _objs_with_preserved_marks.pop();
4434 markOop m = _preserved_marks_of_objs.pop();
4435 obj->set_mark(m);
4436 }
4437 _objs_with_preserved_marks.clear(true);
4438 _preserved_marks_of_objs.clear(true);
4439
4440 g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0);
4441 }
4442
4443 void G1CollectedHeap::push_on_evac_failure_scan_stack(oop obj) {
4444 _evac_failure_scan_stack->push(obj);
4445 }
4446
4447 void G1CollectedHeap::drain_evac_failure_scan_stack() {
4448 assert(_evac_failure_scan_stack != NULL, "precondition");
4449
4450 while (_evac_failure_scan_stack->length() > 0) {
4451 oop obj = _evac_failure_scan_stack->pop();
4452 _evac_failure_closure->set_region(heap_region_containing(obj));
4453 obj->oop_iterate_backwards(_evac_failure_closure);
4454 }
4455 }
4456
4457 oop
4458 G1CollectedHeap::handle_evacuation_failure_par(G1ParScanThreadState* _par_scan_state,
4459 oop old) {
4460 assert(obj_in_cs(old),
4461 err_msg("obj: "PTR_FORMAT" should still be in the CSet",
4462 (HeapWord*) old));
4463 markOop m = old->mark();
4464 oop forward_ptr = old->forward_to_atomic(old);
4465 if (forward_ptr == NULL) {
4466 // Forward-to-self succeeded.
4467 assert(_par_scan_state != NULL, "par scan state");
4468 OopsInHeapRegionClosure* cl = _par_scan_state->evac_failure_closure();
4469 uint queue_num = _par_scan_state->queue_num();
4470
4471 _evacuation_failed = true;
4472 _evacuation_failed_info_array[queue_num].register_copy_failure(old->size());
4473 if (_evac_failure_closure != cl) {
4474 MutexLockerEx x(EvacFailureStack_lock, Mutex::_no_safepoint_check_flag);
4475 assert(!_drain_in_progress,
4476 "Should only be true while someone holds the lock.");
4477 // Set the global evac-failure closure to the current thread's.
4478 assert(_evac_failure_closure == NULL, "Or locking has failed.");
4479 set_evac_failure_closure(cl);
4480 // Now do the common part.
4481 handle_evacuation_failure_common(old, m);
4482 // Reset to NULL.
4483 set_evac_failure_closure(NULL);
4484 } else {
4485 // The lock is already held, and this is recursive.
4486 assert(_drain_in_progress, "This should only be the recursive case.");
4487 handle_evacuation_failure_common(old, m);
4488 }
4489 return old;
4490 } else {
4491 // Forward-to-self failed. Either someone else managed to allocate
4492 // space for this object (old != forward_ptr) or they beat us in
4493 // self-forwarding it (old == forward_ptr).
4494 assert(old == forward_ptr || !obj_in_cs(forward_ptr),
4495 err_msg("obj: "PTR_FORMAT" forwarded to: "PTR_FORMAT" "
4496 "should not be in the CSet",
4497 (HeapWord*) old, (HeapWord*) forward_ptr));
4498 return forward_ptr;
4499 }
4500 }
4501
4502 void G1CollectedHeap::handle_evacuation_failure_common(oop old, markOop m) {
4503 preserve_mark_if_necessary(old, m);
4504
4505 HeapRegion* r = heap_region_containing(old);
4506 if (!r->evacuation_failed()) {
4507 r->set_evacuation_failed(true);
4508 _hr_printer.evac_failure(r);
4509 }
4510
4511 push_on_evac_failure_scan_stack(old);
4512
4513 if (!_drain_in_progress) {
4514 // prevent recursion in copy_to_survivor_space()
4515 _drain_in_progress = true;
4516 drain_evac_failure_scan_stack();
4517 _drain_in_progress = false;
4518 }
4519 }
4520
4521 void G1CollectedHeap::preserve_mark_if_necessary(oop obj, markOop m) {
4522 assert(evacuation_failed(), "Oversaving!");
4523 // We want to call the "for_promotion_failure" version only in the
4524 // case of a promotion failure.
4525 if (m->must_be_preserved_for_promotion_failure(obj)) {
4526 _objs_with_preserved_marks.push(obj);
4527 _preserved_marks_of_objs.push(m);
4528 }
4529 }
4530
4531 HeapWord* G1CollectedHeap::par_allocate_during_gc(GCAllocPurpose purpose,
4532 size_t word_size) {
4533 if (purpose == GCAllocForSurvived) {
4534 HeapWord* result = survivor_attempt_allocation(word_size);
4535 if (result != NULL) {
4536 return result;
4537 } else {
4538 // Let's try to allocate in the old gen in case we can fit the
4539 // object there.
4540 return old_attempt_allocation(word_size);
4541 }
4542 } else {
4543 assert(purpose == GCAllocForTenured, "sanity");
4544 HeapWord* result = old_attempt_allocation(word_size);
4545 if (result != NULL) {
4546 return result;
4547 } else {
4548 // Let's try to allocate in the survivors in case we can fit the
4549 // object there.
4550 return survivor_attempt_allocation(word_size);
4551 }
4552 }
4553
4554 ShouldNotReachHere();
4555 // Trying to keep some compilers happy.
4556 return NULL;
4557 }
4558
4559 G1ParGCAllocBuffer::G1ParGCAllocBuffer(size_t gclab_word_size) :
4560 ParGCAllocBuffer(gclab_word_size), _retired(true) { }
4561
4562 G1ParScanThreadState::G1ParScanThreadState(G1CollectedHeap* g1h, uint queue_num, ReferenceProcessor* rp)
4563 : _g1h(g1h),
4564 _refs(g1h->task_queue(queue_num)),
4565 _dcq(&g1h->dirty_card_queue_set()),
4566 _ct_bs(g1h->g1_barrier_set()),
4567 _g1_rem(g1h->g1_rem_set()),
4568 _hash_seed(17), _queue_num(queue_num),
4569 _term_attempts(0),
4570 _surviving_alloc_buffer(g1h->desired_plab_sz(GCAllocForSurvived)),
4571 _tenured_alloc_buffer(g1h->desired_plab_sz(GCAllocForTenured)),
4572 _age_table(false), _scanner(g1h, this, rp),
4573 _strong_roots_time(0), _term_time(0),
4574 _alloc_buffer_waste(0), _undo_waste(0) {
4575 // we allocate G1YoungSurvRateNumRegions plus one entries, since
4576 // we "sacrifice" entry 0 to keep track of surviving bytes for
4577 // non-young regions (where the age is -1)
4578 // We also add a few elements at the beginning and at the end in
4579 // an attempt to eliminate cache contention
4580 uint real_length = 1 + _g1h->g1_policy()->young_cset_region_length();
4581 uint array_length = PADDING_ELEM_NUM +
4582 real_length +
4583 PADDING_ELEM_NUM;
4584 _surviving_young_words_base = NEW_C_HEAP_ARRAY(size_t, array_length, mtGC);
4585 if (_surviving_young_words_base == NULL)
4586 vm_exit_out_of_memory(array_length * sizeof(size_t), OOM_MALLOC_ERROR,
4587 "Not enough space for young surv histo.");
4588 _surviving_young_words = _surviving_young_words_base + PADDING_ELEM_NUM;
4589 memset(_surviving_young_words, 0, (size_t) real_length * sizeof(size_t));
4590
4591 _alloc_buffers[GCAllocForSurvived] = &_surviving_alloc_buffer;
4592 _alloc_buffers[GCAllocForTenured] = &_tenured_alloc_buffer;
4593
4594 _start = os::elapsedTime();
4595 }
4596
4597 void
4598 G1ParScanThreadState::print_termination_stats_hdr(outputStream* const st)
4599 {
4600 st->print_raw_cr("GC Termination Stats");
4601 st->print_raw_cr(" elapsed --strong roots-- -------termination-------"
4602 " ------waste (KiB)------");
4603 st->print_raw_cr("thr ms ms % ms % attempts"
4604 " total alloc undo");
4605 st->print_raw_cr("--- --------- --------- ------ --------- ------ --------"
4606 " ------- ------- -------");
4607 }
4608
4609 void
4610 G1ParScanThreadState::print_termination_stats(int i,
4611 outputStream* const st) const
4612 {
4613 const double elapsed_ms = elapsed_time() * 1000.0;
4614 const double s_roots_ms = strong_roots_time() * 1000.0;
4615 const double term_ms = term_time() * 1000.0;
4616 st->print_cr("%3d %9.2f %9.2f %6.2f "
4617 "%9.2f %6.2f " SIZE_FORMAT_W(8) " "
4618 SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7),
4619 i, elapsed_ms, s_roots_ms, s_roots_ms * 100 / elapsed_ms,
4620 term_ms, term_ms * 100 / elapsed_ms, term_attempts(),
4621 (alloc_buffer_waste() + undo_waste()) * HeapWordSize / K,
4622 alloc_buffer_waste() * HeapWordSize / K,
4623 undo_waste() * HeapWordSize / K);
4624 }
4625
4626 #ifdef ASSERT
4627 bool G1ParScanThreadState::verify_ref(narrowOop* ref) const {
4628 assert(ref != NULL, "invariant");
4629 assert(UseCompressedOops, "sanity");
4630 assert(!has_partial_array_mask(ref), err_msg("ref=" PTR_FORMAT, ref));
4631 oop p = oopDesc::load_decode_heap_oop(ref);
4632 assert(_g1h->is_in_g1_reserved(p),
4633 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, (void *)p));
4634 return true;
4635 }
4636
4637 bool G1ParScanThreadState::verify_ref(oop* ref) const {
4638 assert(ref != NULL, "invariant");
4639 if (has_partial_array_mask(ref)) {
4640 // Must be in the collection set--it's already been copied.
4641 oop p = clear_partial_array_mask(ref);
4642 assert(_g1h->obj_in_cs(p),
4643 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, (void *)p));
4644 } else {
4645 oop p = oopDesc::load_decode_heap_oop(ref);
4646 assert(_g1h->is_in_g1_reserved(p),
4647 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, (void *)p));
4648 }
4649 return true;
4650 }
4651
4652 bool G1ParScanThreadState::verify_task(StarTask ref) const {
4653 if (ref.is_narrow()) {
4654 return verify_ref((narrowOop*) ref);
4655 } else {
4656 return verify_ref((oop*) ref);
4657 }
4658 }
4659 #endif // ASSERT
4660
4661 void G1ParScanThreadState::trim_queue() {
4662 assert(_evac_failure_cl != NULL, "not set");
4663
4664 StarTask ref;
4665 do {
4666 // Drain the overflow stack first, so other threads can steal.
4667 while (refs()->pop_overflow(ref)) {
4668 deal_with_reference(ref);
4669 }
4670
4671 while (refs()->pop_local(ref)) {
4672 deal_with_reference(ref);
4673 }
4674 } while (!refs()->is_empty());
4675 }
4676
4677 G1ParClosureSuper::G1ParClosureSuper(G1CollectedHeap* g1,
4678 G1ParScanThreadState* par_scan_state) :
4679 _g1(g1), _par_scan_state(par_scan_state),
4680 _worker_id(par_scan_state->queue_num()) { }
4681
4682 void G1ParCopyHelper::mark_object(oop obj) {
4683 assert(!_g1->heap_region_containing(obj)->in_collection_set(), "should not mark objects in the CSet");
4684
4685 // We know that the object is not moving so it's safe to read its size.
4686 _cm->grayRoot(obj, (size_t) obj->size(), _worker_id);
4687 }
4688
4689 void G1ParCopyHelper::mark_forwarded_object(oop from_obj, oop to_obj) {
4690 assert(from_obj->is_forwarded(), "from obj should be forwarded");
4691 assert(from_obj->forwardee() == to_obj, "to obj should be the forwardee");
4692 assert(from_obj != to_obj, "should not be self-forwarded");
4693
4694 assert(_g1->heap_region_containing(from_obj)->in_collection_set(), "from obj should be in the CSet");
4695 assert(!_g1->heap_region_containing(to_obj)->in_collection_set(), "should not mark objects in the CSet");
4696
4697 // The object might be in the process of being copied by another
4698 // worker so we cannot trust that its to-space image is
4699 // well-formed. So we have to read its size from its from-space
4700 // image which we know should not be changing.
4701 _cm->grayRoot(to_obj, (size_t) from_obj->size(), _worker_id);
4702 }
4703
4704 oop G1ParScanThreadState::copy_to_survivor_space(oop const old) {
4705 size_t word_sz = old->size();
4706 HeapRegion* from_region = _g1h->heap_region_containing_raw(old);
4707 // +1 to make the -1 indexes valid...
4708 int young_index = from_region->young_index_in_cset()+1;
4709 assert( (from_region->is_young() && young_index > 0) ||
4710 (!from_region->is_young() && young_index == 0), "invariant" );
4711 G1CollectorPolicy* g1p = _g1h->g1_policy();
4712 markOop m = old->mark();
4713 int age = m->has_displaced_mark_helper() ? m->displaced_mark_helper()->age()
4714 : m->age();
4715 GCAllocPurpose alloc_purpose = g1p->evacuation_destination(from_region, age,
4716 word_sz);
4717 HeapWord* obj_ptr = allocate(alloc_purpose, word_sz);
4718 #ifndef PRODUCT
4719 // Should this evacuation fail?
4720 if (_g1h->evacuation_should_fail()) {
4721 if (obj_ptr != NULL) {
4722 undo_allocation(alloc_purpose, obj_ptr, word_sz);
4723 obj_ptr = NULL;
4724 }
4725 }
4726 #endif // !PRODUCT
4727
4728 if (obj_ptr == NULL) {
4729 // This will either forward-to-self, or detect that someone else has
4730 // installed a forwarding pointer.
4731 return _g1h->handle_evacuation_failure_par(this, old);
4732 }
4733
4734 oop obj = oop(obj_ptr);
4735
4736 // We're going to allocate linearly, so might as well prefetch ahead.
4737 Prefetch::write(obj_ptr, PrefetchCopyIntervalInBytes);
4738
4739 oop forward_ptr = old->forward_to_atomic(obj);
4740 if (forward_ptr == NULL) {
4741 Copy::aligned_disjoint_words((HeapWord*) old, obj_ptr, word_sz);
4742
4743 // alloc_purpose is just a hint to allocate() above, recheck the type of region
4744 // we actually allocated from and update alloc_purpose accordingly
4745 HeapRegion* to_region = _g1h->heap_region_containing_raw(obj_ptr);
4746 alloc_purpose = to_region->is_young() ? GCAllocForSurvived : GCAllocForTenured;
4747
4748 if (g1p->track_object_age(alloc_purpose)) {
4749 // We could simply do obj->incr_age(). However, this causes a
4750 // performance issue. obj->incr_age() will first check whether
4751 // the object has a displaced mark by checking its mark word;
4752 // getting the mark word from the new location of the object
4753 // stalls. So, given that we already have the mark word and we
4754 // are about to install it anyway, it's better to increase the
4755 // age on the mark word, when the object does not have a
4756 // displaced mark word. We're not expecting many objects to have
4757 // a displaced marked word, so that case is not optimized
4758 // further (it could be...) and we simply call obj->incr_age().
4759
4760 if (m->has_displaced_mark_helper()) {
4761 // in this case, we have to install the mark word first,
4762 // otherwise obj looks to be forwarded (the old mark word,
4763 // which contains the forward pointer, was copied)
4764 obj->set_mark(m);
4765 obj->incr_age();
4766 } else {
4767 m = m->incr_age();
4768 obj->set_mark(m);
4769 }
4770 age_table()->add(obj, word_sz);
4771 } else {
4772 obj->set_mark(m);
4773 }
4774
4775 if (G1StringDedup::is_enabled()) {
4776 G1StringDedup::enqueue_from_evacuation(from_region->is_young(),
4777 to_region->is_young(),
4778 queue_num(),
4779 obj);
4780 }
4781
4782 size_t* surv_young_words = surviving_young_words();
4783 surv_young_words[young_index] += word_sz;
4784
4785 if (obj->is_objArray() && arrayOop(obj)->length() >= ParGCArrayScanChunk) {
4786 // We keep track of the next start index in the length field of
4787 // the to-space object. The actual length can be found in the
4788 // length field of the from-space object.
4789 arrayOop(obj)->set_length(0);
4790 oop* old_p = set_partial_array_mask(old);
4791 push_on_queue(old_p);
4792 } else {
4793 // No point in using the slower heap_region_containing() method,
4794 // given that we know obj is in the heap.
4795 _scanner.set_region(_g1h->heap_region_containing_raw(obj));
4796 obj->oop_iterate_backwards(&_scanner);
4797 }
4798 } else {
4799 undo_allocation(alloc_purpose, obj_ptr, word_sz);
4800 obj = forward_ptr;
4801 }
4802 return obj;
4803 }
4804
4805 template <class T>
4806 void G1ParCopyHelper::do_klass_barrier(T* p, oop new_obj) {
4807 if (_g1->heap_region_containing_raw(new_obj)->is_young()) {
4808 _scanned_klass->record_modified_oops();
4809 }
4810 }
4811
4812 template <G1Barrier barrier, bool do_mark_object>
4813 template <class T>
4814 void G1ParCopyClosure<barrier, do_mark_object>::do_oop_work(T* p) {
4815 T heap_oop = oopDesc::load_heap_oop(p);
4816
4817 if (oopDesc::is_null(heap_oop)) {
4818 return;
4819 }
4820
4821 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
4822
4823 assert(_worker_id == _par_scan_state->queue_num(), "sanity");
4824
4825 if (_g1->in_cset_fast_test(obj)) {
4826 oop forwardee;
4827 if (obj->is_forwarded()) {
4828 forwardee = obj->forwardee();
4829 } else {
4830 forwardee = _par_scan_state->copy_to_survivor_space(obj);
4831 }
4832 assert(forwardee != NULL, "forwardee should not be NULL");
4833 oopDesc::encode_store_heap_oop(p, forwardee);
4834 if (do_mark_object && forwardee != obj) {
4835 // If the object is self-forwarded we don't need to explicitly
4836 // mark it, the evacuation failure protocol will do so.
4837 mark_forwarded_object(obj, forwardee);
4838 }
4839
4840 if (barrier == G1BarrierKlass) {
4841 do_klass_barrier(p, forwardee);
4842 }
4843 } else {
4844 // The object is not in collection set. If we're a root scanning
4845 // closure during an initial mark pause (i.e. do_mark_object will
4846 // be true) then attempt to mark the object.
4847 if (do_mark_object) {
4848 mark_object(obj);
4849 }
4850 }
4851
4852 if (barrier == G1BarrierEvac) {
4853 _par_scan_state->update_rs(_from, p, _worker_id);
4854 }
4855 }
4856
4857 template void G1ParCopyClosure<G1BarrierEvac, false>::do_oop_work(oop* p);
4858 template void G1ParCopyClosure<G1BarrierEvac, false>::do_oop_work(narrowOop* p);
4859
4860 class G1ParEvacuateFollowersClosure : public VoidClosure {
4861 protected:
4862 G1CollectedHeap* _g1h;
4863 G1ParScanThreadState* _par_scan_state;
4864 RefToScanQueueSet* _queues;
4865 ParallelTaskTerminator* _terminator;
4866
4867 G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
4868 RefToScanQueueSet* queues() { return _queues; }
4869 ParallelTaskTerminator* terminator() { return _terminator; }
4870
4871 public:
4872 G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h,
4873 G1ParScanThreadState* par_scan_state,
4874 RefToScanQueueSet* queues,
4875 ParallelTaskTerminator* terminator)
4876 : _g1h(g1h), _par_scan_state(par_scan_state),
4877 _queues(queues), _terminator(terminator) {}
4878
4879 void do_void();
4880
4881 private:
4882 inline bool offer_termination();
4883 };
4884
4885 bool G1ParEvacuateFollowersClosure::offer_termination() {
4886 G1ParScanThreadState* const pss = par_scan_state();
4887 pss->start_term_time();
4888 const bool res = terminator()->offer_termination();
4889 pss->end_term_time();
4890 return res;
4891 }
4892
4893 void G1ParEvacuateFollowersClosure::do_void() {
4894 StarTask stolen_task;
4895 G1ParScanThreadState* const pss = par_scan_state();
4896 pss->trim_queue();
4897
4898 do {
4899 while (queues()->steal(pss->queue_num(), pss->hash_seed(), stolen_task)) {
4900 assert(pss->verify_task(stolen_task), "sanity");
4901 if (stolen_task.is_narrow()) {
4902 pss->deal_with_reference((narrowOop*) stolen_task);
4903 } else {
4904 pss->deal_with_reference((oop*) stolen_task);
4905 }
4906
4907 // We've just processed a reference and we might have made
4908 // available new entries on the queues. So we have to make sure
4909 // we drain the queues as necessary.
4910 pss->trim_queue();
4911 }
4912 } while (!offer_termination());
4913 }
4914
4915 class G1KlassScanClosure : public KlassClosure {
4916 G1ParCopyHelper* _closure;
4917 bool _process_only_dirty;
4918 int _count;
4919 public:
4920 G1KlassScanClosure(G1ParCopyHelper* closure, bool process_only_dirty)
4921 : _process_only_dirty(process_only_dirty), _closure(closure), _count(0) {}
4922 void do_klass(Klass* klass) {
4923 // If the klass has not been dirtied we know that there's
4924 // no references into the young gen and we can skip it.
4925 if (!_process_only_dirty || klass->has_modified_oops()) {
4926 // Clean the klass since we're going to scavenge all the metadata.
4927 klass->clear_modified_oops();
4928
4929 // Tell the closure that this klass is the Klass to scavenge
4930 // and is the one to dirty if oops are left pointing into the young gen.
4931 _closure->set_scanned_klass(klass);
4932
4933 klass->oops_do(_closure);
4934
4935 _closure->set_scanned_klass(NULL);
4936 }
4937 _count++;
4938 }
4939 };
4940
4941 class G1ParTask : public AbstractGangTask {
4942 protected:
4943 G1CollectedHeap* _g1h;
4944 RefToScanQueueSet *_queues;
4945 ParallelTaskTerminator _terminator;
4946 uint _n_workers;
4947
4948 Mutex _stats_lock;
4949 Mutex* stats_lock() { return &_stats_lock; }
4950
4951 size_t getNCards() {
4952 return (_g1h->capacity() + G1BlockOffsetSharedArray::N_bytes - 1)
4953 / G1BlockOffsetSharedArray::N_bytes;
4954 }
4955
4956 public:
4957 G1ParTask(G1CollectedHeap* g1h,
4958 RefToScanQueueSet *task_queues)
4959 : AbstractGangTask("G1 collection"),
4960 _g1h(g1h),
4961 _queues(task_queues),
4962 _terminator(0, _queues),
4963 _stats_lock(Mutex::leaf, "parallel G1 stats lock", true)
4964 {}
4965
4966 RefToScanQueueSet* queues() { return _queues; }
4967
4968 RefToScanQueue *work_queue(int i) {
4969 return queues()->queue(i);
4970 }
4971
4972 ParallelTaskTerminator* terminator() { return &_terminator; }
4973
4974 virtual void set_for_termination(int active_workers) {
4975 // This task calls set_n_termination() in par_non_clean_card_iterate_work()
4976 // in the young space (_par_seq_tasks) in the G1 heap
4977 // for SequentialSubTasksDone.
4978 // This task also uses SubTasksDone in SharedHeap and G1CollectedHeap
4979 // both of which need setting by set_n_termination().
4980 _g1h->SharedHeap::set_n_termination(active_workers);
4981 _g1h->set_n_termination(active_workers);
4982 terminator()->reset_for_reuse(active_workers);
4983 _n_workers = active_workers;
4984 }
4985
4986 void work(uint worker_id) {
4987 if (worker_id >= _n_workers) return; // no work needed this round
4988
4989 double start_time_ms = os::elapsedTime() * 1000.0;
4990 _g1h->g1_policy()->phase_times()->record_gc_worker_start_time(worker_id, start_time_ms);
4991
4992 {
4993 ResourceMark rm;
4994 HandleMark hm;
4995
4996 ReferenceProcessor* rp = _g1h->ref_processor_stw();
4997
4998 G1ParScanThreadState pss(_g1h, worker_id, rp);
4999 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, rp);
5000
5001 pss.set_evac_failure_closure(&evac_failure_cl);
5002
5003 G1ParScanExtRootClosure only_scan_root_cl(_g1h, &pss, rp);
5004 G1ParScanMetadataClosure only_scan_metadata_cl(_g1h, &pss, rp);
5005
5006 G1ParScanAndMarkExtRootClosure scan_mark_root_cl(_g1h, &pss, rp);
5007 G1ParScanAndMarkMetadataClosure scan_mark_metadata_cl(_g1h, &pss, rp);
5008
5009 bool only_young = _g1h->g1_policy()->gcs_are_young();
5010 G1KlassScanClosure scan_mark_klasses_cl_s(&scan_mark_metadata_cl, false);
5011 G1KlassScanClosure only_scan_klasses_cl_s(&only_scan_metadata_cl, only_young);
5012
5013 OopClosure* scan_root_cl = &only_scan_root_cl;
5014 G1KlassScanClosure* scan_klasses_cl = &only_scan_klasses_cl_s;
5015
5016 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5017 // We also need to mark copied objects.
5018 scan_root_cl = &scan_mark_root_cl;
5019 scan_klasses_cl = &scan_mark_klasses_cl_s;
5020 }
5021
5022 G1ParPushHeapRSClosure push_heap_rs_cl(_g1h, &pss);
5023
5024 // Don't scan the scavengable methods in the code cache as part
5025 // of strong root scanning. The code roots that point into a
5026 // region in the collection set are scanned when we scan the
5027 // region's RSet.
5028 int so = SharedHeap::SO_AllClasses | SharedHeap::SO_Strings;
5029
5030 pss.start_strong_roots();
5031 _g1h->g1_process_strong_roots(/* is scavenging */ true,
5032 SharedHeap::ScanningOption(so),
5033 scan_root_cl,
5034 &push_heap_rs_cl,
5035 scan_klasses_cl,
5036 worker_id);
5037 pss.end_strong_roots();
5038
5039 {
5040 double start = os::elapsedTime();
5041 G1ParEvacuateFollowersClosure evac(_g1h, &pss, _queues, &_terminator);
5042 evac.do_void();
5043 double elapsed_ms = (os::elapsedTime()-start)*1000.0;
5044 double term_ms = pss.term_time()*1000.0;
5045 _g1h->g1_policy()->phase_times()->add_obj_copy_time(worker_id, elapsed_ms-term_ms);
5046 _g1h->g1_policy()->phase_times()->record_termination(worker_id, term_ms, pss.term_attempts());
5047 }
5048 _g1h->g1_policy()->record_thread_age_table(pss.age_table());
5049 _g1h->update_surviving_young_words(pss.surviving_young_words()+1);
5050
5051 if (ParallelGCVerbose) {
5052 MutexLocker x(stats_lock());
5053 pss.print_termination_stats(worker_id);
5054 }
5055
5056 assert(pss.refs()->is_empty(), "should be empty");
5057
5058 // Close the inner scope so that the ResourceMark and HandleMark
5059 // destructors are executed here and are included as part of the
5060 // "GC Worker Time".
5061 }
5062
5063 double end_time_ms = os::elapsedTime() * 1000.0;
5064 _g1h->g1_policy()->phase_times()->record_gc_worker_end_time(worker_id, end_time_ms);
5065 }
5066 };
5067
5068 // *** Common G1 Evacuation Stuff
5069
5070 // This method is run in a GC worker.
5071
5072 void
5073 G1CollectedHeap::
5074 g1_process_strong_roots(bool is_scavenging,
5075 ScanningOption so,
5076 OopClosure* scan_non_heap_roots,
5077 OopsInHeapRegionClosure* scan_rs,
5078 G1KlassScanClosure* scan_klasses,
5079 uint worker_i) {
5080
5081 // First scan the strong roots
5082 double ext_roots_start = os::elapsedTime();
5083 double closure_app_time_sec = 0.0;
5084
5085 BufferingOopClosure buf_scan_non_heap_roots(scan_non_heap_roots);
5086
5087 process_strong_roots(false, // no scoping; this is parallel code
5088 so,
5089 &buf_scan_non_heap_roots,
5090 scan_klasses
5091 );
5092
5093 // Now the CM ref_processor roots.
5094 if (!_process_strong_tasks->is_task_claimed(G1H_PS_refProcessor_oops_do)) {
5095 // We need to treat the discovered reference lists of the
5096 // concurrent mark ref processor as roots and keep entries
5097 // (which are added by the marking threads) on them live
5098 // until they can be processed at the end of marking.
5099 ref_processor_cm()->weak_oops_do(&buf_scan_non_heap_roots);
5100 }
5101
5102 // Finish up any enqueued closure apps (attributed as object copy time).
5103 buf_scan_non_heap_roots.done();
5104
5105 double obj_copy_time_sec = buf_scan_non_heap_roots.closure_app_seconds();
5106
5107 g1_policy()->phase_times()->record_obj_copy_time(worker_i, obj_copy_time_sec * 1000.0);
5108
5109 double ext_root_time_ms =
5110 ((os::elapsedTime() - ext_roots_start) - obj_copy_time_sec) * 1000.0;
5111
5112 g1_policy()->phase_times()->record_ext_root_scan_time(worker_i, ext_root_time_ms);
5113
5114 // During conc marking we have to filter the per-thread SATB buffers
5115 // to make sure we remove any oops into the CSet (which will show up
5116 // as implicitly live).
5117 double satb_filtering_ms = 0.0;
5118 if (!_process_strong_tasks->is_task_claimed(G1H_PS_filter_satb_buffers)) {
5119 if (mark_in_progress()) {
5120 double satb_filter_start = os::elapsedTime();
5121
5122 JavaThread::satb_mark_queue_set().filter_thread_buffers();
5123
5124 satb_filtering_ms = (os::elapsedTime() - satb_filter_start) * 1000.0;
5125 }
5126 }
5127 g1_policy()->phase_times()->record_satb_filtering_time(worker_i, satb_filtering_ms);
5128
5129 // If this is an initial mark pause, and we're not scanning
5130 // the entire code cache, we need to mark the oops in the
5131 // strong code root lists for the regions that are not in
5132 // the collection set.
5133 // Note all threads participate in this set of root tasks.
5134 double mark_strong_code_roots_ms = 0.0;
5135 if (g1_policy()->during_initial_mark_pause() && !(so & SO_AllCodeCache)) {
5136 double mark_strong_roots_start = os::elapsedTime();
5137 mark_strong_code_roots(worker_i);
5138 mark_strong_code_roots_ms = (os::elapsedTime() - mark_strong_roots_start) * 1000.0;
5139 }
5140 g1_policy()->phase_times()->record_strong_code_root_mark_time(worker_i, mark_strong_code_roots_ms);
5141
5142 // Now scan the complement of the collection set.
5143 CodeBlobToOopClosure eager_scan_code_roots(scan_non_heap_roots, true /* do_marking */);
5144 g1_rem_set()->oops_into_collection_set_do(scan_rs, &eager_scan_code_roots, worker_i);
5145
5146 _process_strong_tasks->all_tasks_completed();
5147 }
5148
5149 class G1StringSymbolTableUnlinkTask : public AbstractGangTask {
5150 private:
5151 BoolObjectClosure* _is_alive;
5152 int _initial_string_table_size;
5153 int _initial_symbol_table_size;
5154
5155 bool _process_strings;
5156 int _strings_processed;
5157 int _strings_removed;
5158
5159 bool _process_symbols;
5160 int _symbols_processed;
5161 int _symbols_removed;
5162
5163 bool _do_in_parallel;
5164 public:
5165 G1StringSymbolTableUnlinkTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols) :
5166 AbstractGangTask("Par String/Symbol table unlink"), _is_alive(is_alive),
5167 _do_in_parallel(G1CollectedHeap::use_parallel_gc_threads()),
5168 _process_strings(process_strings), _strings_processed(0), _strings_removed(0),
5169 _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0) {
5170
5171 _initial_string_table_size = StringTable::the_table()->table_size();
5172 _initial_symbol_table_size = SymbolTable::the_table()->table_size();
5173 if (process_strings) {
5174 StringTable::clear_parallel_claimed_index();
5175 }
5176 if (process_symbols) {
5177 SymbolTable::clear_parallel_claimed_index();
5178 }
5179 }
5180
5181 ~G1StringSymbolTableUnlinkTask() {
5182 guarantee(!_process_strings || !_do_in_parallel || StringTable::parallel_claimed_index() >= _initial_string_table_size,
5183 err_msg("claim value %d after unlink less than initial string table size %d",
5184 StringTable::parallel_claimed_index(), _initial_string_table_size));
5185 guarantee(!_process_symbols || !_do_in_parallel || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size,
5186 err_msg("claim value %d after unlink less than initial symbol table size %d",
5187 SymbolTable::parallel_claimed_index(), _initial_symbol_table_size));
5188 }
5189
5190 void work(uint worker_id) {
5191 if (_do_in_parallel) {
5192 int strings_processed = 0;
5193 int strings_removed = 0;
5194 int symbols_processed = 0;
5195 int symbols_removed = 0;
5196 if (_process_strings) {
5197 StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed);
5198 Atomic::add(strings_processed, &_strings_processed);
5199 Atomic::add(strings_removed, &_strings_removed);
5200 }
5201 if (_process_symbols) {
5202 SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed);
5203 Atomic::add(symbols_processed, &_symbols_processed);
5204 Atomic::add(symbols_removed, &_symbols_removed);
5205 }
5206 } else {
5207 if (_process_strings) {
5208 StringTable::unlink(_is_alive, &_strings_processed, &_strings_removed);
5209 }
5210 if (_process_symbols) {
5211 SymbolTable::unlink(&_symbols_processed, &_symbols_removed);
5212 }
5213 }
5214 }
5215
5216 size_t strings_processed() const { return (size_t)_strings_processed; }
5217 size_t strings_removed() const { return (size_t)_strings_removed; }
5218
5219 size_t symbols_processed() const { return (size_t)_symbols_processed; }
5220 size_t symbols_removed() const { return (size_t)_symbols_removed; }
5221 };
5222
5223 void G1CollectedHeap::unlink_string_and_symbol_table(BoolObjectClosure* is_alive,
5224 bool process_strings, bool process_symbols) {
5225 uint n_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
5226 _g1h->workers()->active_workers() : 1);
5227
5228 G1StringSymbolTableUnlinkTask g1_unlink_task(is_alive, process_strings, process_symbols);
5229 if (G1CollectedHeap::use_parallel_gc_threads()) {
5230 set_par_threads(n_workers);
5231 workers()->run_task(&g1_unlink_task);
5232 set_par_threads(0);
5233 } else {
5234 g1_unlink_task.work(0);
5235 }
5236 if (G1TraceStringSymbolTableScrubbing) {
5237 gclog_or_tty->print_cr("Cleaned string and symbol table, "
5238 "strings: "SIZE_FORMAT" processed, "SIZE_FORMAT" removed, "
5239 "symbols: "SIZE_FORMAT" processed, "SIZE_FORMAT" removed",
5240 g1_unlink_task.strings_processed(), g1_unlink_task.strings_removed(),
5241 g1_unlink_task.symbols_processed(), g1_unlink_task.symbols_removed());
5242 }
5243
5244 if (G1StringDedup::is_enabled()) {
5245 G1StringDedup::unlink(is_alive);
5246 }
5247 }
5248
5249 class G1RedirtyLoggedCardsTask : public AbstractGangTask {
5250 private:
5251 DirtyCardQueueSet* _queue;
5252 public:
5253 G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue) : AbstractGangTask("Redirty Cards"), _queue(queue) { }
5254
5255 virtual void work(uint worker_id) {
5256 double start_time = os::elapsedTime();
5257
5258 RedirtyLoggedCardTableEntryClosure cl;
5259 if (G1CollectedHeap::heap()->use_parallel_gc_threads()) {
5260 _queue->par_apply_closure_to_all_completed_buffers(&cl);
5261 } else {
5262 _queue->apply_closure_to_all_completed_buffers(&cl);
5263 }
5264
5265 G1GCPhaseTimes* timer = G1CollectedHeap::heap()->g1_policy()->phase_times();
5266 timer->record_redirty_logged_cards_time_ms(worker_id, (os::elapsedTime() - start_time) * 1000.0);
5267 timer->record_redirty_logged_cards_processed_cards(worker_id, cl.num_processed());
5268 }
5269 };
5270
5271 void G1CollectedHeap::redirty_logged_cards() {
5272 guarantee(G1DeferredRSUpdate, "Must only be called when using deferred RS updates.");
5273 double redirty_logged_cards_start = os::elapsedTime();
5274
5275 uint n_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
5276 _g1h->workers()->active_workers() : 1);
5277
5278 G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set());
5279 dirty_card_queue_set().reset_for_par_iteration();
5280 if (use_parallel_gc_threads()) {
5281 set_par_threads(n_workers);
5282 workers()->run_task(&redirty_task);
5283 set_par_threads(0);
5284 } else {
5285 redirty_task.work(0);
5286 }
5287
5288 DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set();
5289 dcq.merge_bufferlists(&dirty_card_queue_set());
5290 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
5291
5292 g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0);
5293 }
5294
5295 // Weak Reference Processing support
5296
5297 // An always "is_alive" closure that is used to preserve referents.
5298 // If the object is non-null then it's alive. Used in the preservation
5299 // of referent objects that are pointed to by reference objects
5300 // discovered by the CM ref processor.
5301 class G1AlwaysAliveClosure: public BoolObjectClosure {
5302 G1CollectedHeap* _g1;
5303 public:
5304 G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
5305 bool do_object_b(oop p) {
5306 if (p != NULL) {
5307 return true;
5308 }
5309 return false;
5310 }
5311 };
5312
5313 bool G1STWIsAliveClosure::do_object_b(oop p) {
5314 // An object is reachable if it is outside the collection set,
5315 // or is inside and copied.
5316 return !_g1->obj_in_cs(p) || p->is_forwarded();
5317 }
5318
5319 // Non Copying Keep Alive closure
5320 class G1KeepAliveClosure: public OopClosure {
5321 G1CollectedHeap* _g1;
5322 public:
5323 G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
5324 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
5325 void do_oop( oop* p) {
5326 oop obj = *p;
5327
5328 if (_g1->obj_in_cs(obj)) {
5329 assert( obj->is_forwarded(), "invariant" );
5330 *p = obj->forwardee();
5331 }
5332 }
5333 };
5334
5335 // Copying Keep Alive closure - can be called from both
5336 // serial and parallel code as long as different worker
5337 // threads utilize different G1ParScanThreadState instances
5338 // and different queues.
5339
5340 class G1CopyingKeepAliveClosure: public OopClosure {
5341 G1CollectedHeap* _g1h;
5342 OopClosure* _copy_non_heap_obj_cl;
5343 OopsInHeapRegionClosure* _copy_metadata_obj_cl;
5344 G1ParScanThreadState* _par_scan_state;
5345
5346 public:
5347 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
5348 OopClosure* non_heap_obj_cl,
5349 OopsInHeapRegionClosure* metadata_obj_cl,
5350 G1ParScanThreadState* pss):
5351 _g1h(g1h),
5352 _copy_non_heap_obj_cl(non_heap_obj_cl),
5353 _copy_metadata_obj_cl(metadata_obj_cl),
5354 _par_scan_state(pss)
5355 {}
5356
5357 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
5358 virtual void do_oop( oop* p) { do_oop_work(p); }
5359
5360 template <class T> void do_oop_work(T* p) {
5361 oop obj = oopDesc::load_decode_heap_oop(p);
5362
5363 if (_g1h->obj_in_cs(obj)) {
5364 // If the referent object has been forwarded (either copied
5365 // to a new location or to itself in the event of an
5366 // evacuation failure) then we need to update the reference
5367 // field and, if both reference and referent are in the G1
5368 // heap, update the RSet for the referent.
5369 //
5370 // If the referent has not been forwarded then we have to keep
5371 // it alive by policy. Therefore we have copy the referent.
5372 //
5373 // If the reference field is in the G1 heap then we can push
5374 // on the PSS queue. When the queue is drained (after each
5375 // phase of reference processing) the object and it's followers
5376 // will be copied, the reference field set to point to the
5377 // new location, and the RSet updated. Otherwise we need to
5378 // use the the non-heap or metadata closures directly to copy
5379 // the referent object and update the pointer, while avoiding
5380 // updating the RSet.
5381
5382 if (_g1h->is_in_g1_reserved(p)) {
5383 _par_scan_state->push_on_queue(p);
5384 } else {
5385 assert(!Metaspace::contains((const void*)p),
5386 err_msg("Otherwise need to call _copy_metadata_obj_cl->do_oop(p) "
5387 PTR_FORMAT, p));
5388 _copy_non_heap_obj_cl->do_oop(p);
5389 }
5390 }
5391 }
5392 };
5393
5394 // Serial drain queue closure. Called as the 'complete_gc'
5395 // closure for each discovered list in some of the
5396 // reference processing phases.
5397
5398 class G1STWDrainQueueClosure: public VoidClosure {
5399 protected:
5400 G1CollectedHeap* _g1h;
5401 G1ParScanThreadState* _par_scan_state;
5402
5403 G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
5404
5405 public:
5406 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
5407 _g1h(g1h),
5408 _par_scan_state(pss)
5409 { }
5410
5411 void do_void() {
5412 G1ParScanThreadState* const pss = par_scan_state();
5413 pss->trim_queue();
5414 }
5415 };
5416
5417 // Parallel Reference Processing closures
5418
5419 // Implementation of AbstractRefProcTaskExecutor for parallel reference
5420 // processing during G1 evacuation pauses.
5421
5422 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
5423 private:
5424 G1CollectedHeap* _g1h;
5425 RefToScanQueueSet* _queues;
5426 FlexibleWorkGang* _workers;
5427 int _active_workers;
5428
5429 public:
5430 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
5431 FlexibleWorkGang* workers,
5432 RefToScanQueueSet *task_queues,
5433 int n_workers) :
5434 _g1h(g1h),
5435 _queues(task_queues),
5436 _workers(workers),
5437 _active_workers(n_workers)
5438 {
5439 assert(n_workers > 0, "shouldn't call this otherwise");
5440 }
5441
5442 // Executes the given task using concurrent marking worker threads.
5443 virtual void execute(ProcessTask& task);
5444 virtual void execute(EnqueueTask& task);
5445 };
5446
5447 // Gang task for possibly parallel reference processing
5448
5449 class G1STWRefProcTaskProxy: public AbstractGangTask {
5450 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
5451 ProcessTask& _proc_task;
5452 G1CollectedHeap* _g1h;
5453 RefToScanQueueSet *_task_queues;
5454 ParallelTaskTerminator* _terminator;
5455
5456 public:
5457 G1STWRefProcTaskProxy(ProcessTask& proc_task,
5458 G1CollectedHeap* g1h,
5459 RefToScanQueueSet *task_queues,
5460 ParallelTaskTerminator* terminator) :
5461 AbstractGangTask("Process reference objects in parallel"),
5462 _proc_task(proc_task),
5463 _g1h(g1h),
5464 _task_queues(task_queues),
5465 _terminator(terminator)
5466 {}
5467
5468 virtual void work(uint worker_id) {
5469 // The reference processing task executed by a single worker.
5470 ResourceMark rm;
5471 HandleMark hm;
5472
5473 G1STWIsAliveClosure is_alive(_g1h);
5474
5475 G1ParScanThreadState pss(_g1h, worker_id, NULL);
5476 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5477
5478 pss.set_evac_failure_closure(&evac_failure_cl);
5479
5480 G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL);
5481 G1ParScanMetadataClosure only_copy_metadata_cl(_g1h, &pss, NULL);
5482
5483 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5484 G1ParScanAndMarkMetadataClosure copy_mark_metadata_cl(_g1h, &pss, NULL);
5485
5486 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5487 OopsInHeapRegionClosure* copy_metadata_cl = &only_copy_metadata_cl;
5488
5489 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5490 // We also need to mark copied objects.
5491 copy_non_heap_cl = ©_mark_non_heap_cl;
5492 copy_metadata_cl = ©_mark_metadata_cl;
5493 }
5494
5495 // Keep alive closure.
5496 G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, copy_metadata_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.refs()->is_empty(), "both queue and overflow should be empty");
5588
5589
5590 G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL);
5591 G1ParScanMetadataClosure only_copy_metadata_cl(_g1h, &pss, NULL);
5592
5593 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5594 G1ParScanAndMarkMetadataClosure copy_mark_metadata_cl(_g1h, &pss, NULL);
5595
5596 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5597 OopsInHeapRegionClosure* copy_metadata_cl = &only_copy_metadata_cl;
5598
5599 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5600 // We also need to mark copied objects.
5601 copy_non_heap_cl = ©_mark_non_heap_cl;
5602 copy_metadata_cl = ©_mark_metadata_cl;
5603 }
5604
5605 // Is alive closure
5606 G1AlwaysAliveClosure always_alive(_g1h);
5607
5608 // Copying keep alive closure. Applied to referent objects that need
5609 // to be copied.
5610 G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, copy_metadata_cl, &pss);
5611
5612 ReferenceProcessor* rp = _g1h->ref_processor_cm();
5613
5614 uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q();
5615 uint stride = MIN2(MAX2(_n_workers, 1U), limit);
5616
5617 // limit is set using max_num_q() - which was set using ParallelGCThreads.
5618 // So this must be true - but assert just in case someone decides to
5619 // change the worker ids.
5620 assert(0 <= worker_id && worker_id < limit, "sanity");
5621 assert(!rp->discovery_is_atomic(), "check this code");
5622
5623 // Select discovered lists [i, i+stride, i+2*stride,...,limit)
5624 for (uint idx = worker_id; idx < limit; idx += stride) {
5625 DiscoveredList& ref_list = rp->discovered_refs()[idx];
5626
5627 DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive);
5628 while (iter.has_next()) {
5629 // Since discovery is not atomic for the CM ref processor, we
5630 // can see some null referent objects.
5631 iter.load_ptrs(DEBUG_ONLY(true));
5632 oop ref = iter.obj();
5633
5634 // This will filter nulls.
5635 if (iter.is_referent_alive()) {
5636 iter.make_referent_alive();
5637 }
5638 iter.move_to_next();
5639 }
5640 }
5641
5642 // Drain the queue - which may cause stealing
5643 G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _queues, &_terminator);
5644 drain_queue.do_void();
5645 // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure
5646 assert(pss.refs()->is_empty(), "should be");
5647 }
5648 };
5649
5650 // Weak Reference processing during an evacuation pause (part 1).
5651 void G1CollectedHeap::process_discovered_references(uint no_of_gc_workers) {
5652 double ref_proc_start = os::elapsedTime();
5653
5654 ReferenceProcessor* rp = _ref_processor_stw;
5655 assert(rp->discovery_enabled(), "should have been enabled");
5656
5657 // Any reference objects, in the collection set, that were 'discovered'
5658 // by the CM ref processor should have already been copied (either by
5659 // applying the external root copy closure to the discovered lists, or
5660 // by following an RSet entry).
5661 //
5662 // But some of the referents, that are in the collection set, that these
5663 // reference objects point to may not have been copied: the STW ref
5664 // processor would have seen that the reference object had already
5665 // been 'discovered' and would have skipped discovering the reference,
5666 // but would not have treated the reference object as a regular oop.
5667 // As a result the copy closure would not have been applied to the
5668 // referent object.
5669 //
5670 // We need to explicitly copy these referent objects - the references
5671 // will be processed at the end of remarking.
5672 //
5673 // We also need to do this copying before we process the reference
5674 // objects discovered by the STW ref processor in case one of these
5675 // referents points to another object which is also referenced by an
5676 // object discovered by the STW ref processor.
5677
5678 assert(!G1CollectedHeap::use_parallel_gc_threads() ||
5679 no_of_gc_workers == workers()->active_workers(),
5680 "Need to reset active GC workers");
5681
5682 set_par_threads(no_of_gc_workers);
5683 G1ParPreserveCMReferentsTask keep_cm_referents(this,
5684 no_of_gc_workers,
5685 _task_queues);
5686
5687 if (G1CollectedHeap::use_parallel_gc_threads()) {
5688 workers()->run_task(&keep_cm_referents);
5689 } else {
5690 keep_cm_referents.work(0);
5691 }
5692
5693 set_par_threads(0);
5694
5695 // Closure to test whether a referent is alive.
5696 G1STWIsAliveClosure is_alive(this);
5697
5698 // Even when parallel reference processing is enabled, the processing
5699 // of JNI refs is serial and performed serially by the current thread
5700 // rather than by a worker. The following PSS will be used for processing
5701 // JNI refs.
5702
5703 // Use only a single queue for this PSS.
5704 G1ParScanThreadState pss(this, 0, NULL);
5705
5706 // We do not embed a reference processor in the copying/scanning
5707 // closures while we're actually processing the discovered
5708 // reference objects.
5709 G1ParScanHeapEvacFailureClosure evac_failure_cl(this, &pss, NULL);
5710
5711 pss.set_evac_failure_closure(&evac_failure_cl);
5712
5713 assert(pss.refs()->is_empty(), "pre-condition");
5714
5715 G1ParScanExtRootClosure only_copy_non_heap_cl(this, &pss, NULL);
5716 G1ParScanMetadataClosure only_copy_metadata_cl(this, &pss, NULL);
5717
5718 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(this, &pss, NULL);
5719 G1ParScanAndMarkMetadataClosure copy_mark_metadata_cl(this, &pss, NULL);
5720
5721 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5722 OopsInHeapRegionClosure* copy_metadata_cl = &only_copy_metadata_cl;
5723
5724 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5725 // We also need to mark copied objects.
5726 copy_non_heap_cl = ©_mark_non_heap_cl;
5727 copy_metadata_cl = ©_mark_metadata_cl;
5728 }
5729
5730 // Keep alive closure.
5731 G1CopyingKeepAliveClosure keep_alive(this, copy_non_heap_cl, copy_metadata_cl, &pss);
5732
5733 // Serial Complete GC closure
5734 G1STWDrainQueueClosure drain_queue(this, &pss);
5735
5736 // Setup the soft refs policy...
5737 rp->setup_policy(false);
5738
5739 ReferenceProcessorStats stats;
5740 if (!rp->processing_is_mt()) {
5741 // Serial reference processing...
5742 stats = rp->process_discovered_references(&is_alive,
5743 &keep_alive,
5744 &drain_queue,
5745 NULL,
5746 _gc_timer_stw);
5747 } else {
5748 // Parallel reference processing
5749 assert(rp->num_q() == no_of_gc_workers, "sanity");
5750 assert(no_of_gc_workers <= rp->max_num_q(), "sanity");
5751
5752 G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers);
5753 stats = rp->process_discovered_references(&is_alive,
5754 &keep_alive,
5755 &drain_queue,
5756 &par_task_executor,
5757 _gc_timer_stw);
5758 }
5759
5760 _gc_tracer_stw->report_gc_reference_stats(stats);
5761
5762 // We have completed copying any necessary live referent objects.
5763 assert(pss.refs()->is_empty(), "both queue and overflow should be empty");
5764
5765 double ref_proc_time = os::elapsedTime() - ref_proc_start;
5766 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
5767 }
5768
5769 // Weak Reference processing during an evacuation pause (part 2).
5770 void G1CollectedHeap::enqueue_discovered_references(uint no_of_gc_workers) {
5771 double ref_enq_start = os::elapsedTime();
5772
5773 ReferenceProcessor* rp = _ref_processor_stw;
5774 assert(!rp->discovery_enabled(), "should have been disabled as part of processing");
5775
5776 // Now enqueue any remaining on the discovered lists on to
5777 // the pending list.
5778 if (!rp->processing_is_mt()) {
5779 // Serial reference processing...
5780 rp->enqueue_discovered_references();
5781 } else {
5782 // Parallel reference enqueueing
5783
5784 assert(no_of_gc_workers == workers()->active_workers(),
5785 "Need to reset active workers");
5786 assert(rp->num_q() == no_of_gc_workers, "sanity");
5787 assert(no_of_gc_workers <= rp->max_num_q(), "sanity");
5788
5789 G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers);
5790 rp->enqueue_discovered_references(&par_task_executor);
5791 }
5792
5793 rp->verify_no_references_recorded();
5794 assert(!rp->discovery_enabled(), "should have been disabled");
5795
5796 // FIXME
5797 // CM's reference processing also cleans up the string and symbol tables.
5798 // Should we do that here also? We could, but it is a serial operation
5799 // and could significantly increase the pause time.
5800
5801 double ref_enq_time = os::elapsedTime() - ref_enq_start;
5802 g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0);
5803 }
5804
5805 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info) {
5806 _expand_heap_after_alloc_failure = true;
5807 _evacuation_failed = false;
5808
5809 // Should G1EvacuationFailureALot be in effect for this GC?
5810 NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();)
5811
5812 g1_rem_set()->prepare_for_oops_into_collection_set_do();
5813
5814 // Disable the hot card cache.
5815 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
5816 hot_card_cache->reset_hot_cache_claimed_index();
5817 hot_card_cache->set_use_cache(false);
5818
5819 uint n_workers;
5820 if (G1CollectedHeap::use_parallel_gc_threads()) {
5821 n_workers =
5822 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
5823 workers()->active_workers(),
5824 Threads::number_of_non_daemon_threads());
5825 assert(UseDynamicNumberOfGCThreads ||
5826 n_workers == workers()->total_workers(),
5827 "If not dynamic should be using all the workers");
5828 workers()->set_active_workers(n_workers);
5829 set_par_threads(n_workers);
5830 } else {
5831 assert(n_par_threads() == 0,
5832 "Should be the original non-parallel value");
5833 n_workers = 1;
5834 }
5835
5836 G1ParTask g1_par_task(this, _task_queues);
5837
5838 init_for_evac_failure(NULL);
5839
5840 rem_set()->prepare_for_younger_refs_iterate(true);
5841
5842 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
5843 double start_par_time_sec = os::elapsedTime();
5844 double end_par_time_sec;
5845
5846 {
5847 StrongRootsScope srs(this);
5848
5849 if (G1CollectedHeap::use_parallel_gc_threads()) {
5850 // The individual threads will set their evac-failure closures.
5851 if (ParallelGCVerbose) G1ParScanThreadState::print_termination_stats_hdr();
5852 // These tasks use ShareHeap::_process_strong_tasks
5853 assert(UseDynamicNumberOfGCThreads ||
5854 workers()->active_workers() == workers()->total_workers(),
5855 "If not dynamic should be using all the workers");
5856 workers()->run_task(&g1_par_task);
5857 } else {
5858 g1_par_task.set_for_termination(n_workers);
5859 g1_par_task.work(0);
5860 }
5861 end_par_time_sec = os::elapsedTime();
5862
5863 // Closing the inner scope will execute the destructor
5864 // for the StrongRootsScope object. We record the current
5865 // elapsed time before closing the scope so that time
5866 // taken for the SRS destructor is NOT included in the
5867 // reported parallel time.
5868 }
5869
5870 double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0;
5871 g1_policy()->phase_times()->record_par_time(par_time_ms);
5872
5873 double code_root_fixup_time_ms =
5874 (os::elapsedTime() - end_par_time_sec) * 1000.0;
5875 g1_policy()->phase_times()->record_code_root_fixup_time(code_root_fixup_time_ms);
5876
5877 set_par_threads(0);
5878
5879 // Process any discovered reference objects - we have
5880 // to do this _before_ we retire the GC alloc regions
5881 // as we may have to copy some 'reachable' referent
5882 // objects (and their reachable sub-graphs) that were
5883 // not copied during the pause.
5884 process_discovered_references(n_workers);
5885
5886 // Weak root processing.
5887 {
5888 G1STWIsAliveClosure is_alive(this);
5889 G1KeepAliveClosure keep_alive(this);
5890 JNIHandles::weak_oops_do(&is_alive, &keep_alive);
5891 if (G1StringDedup::is_enabled()) {
5892 G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive);
5893 }
5894 }
5895
5896 release_gc_alloc_regions(n_workers, evacuation_info);
5897 g1_rem_set()->cleanup_after_oops_into_collection_set_do();
5898
5899 // Reset and re-enable the hot card cache.
5900 // Note the counts for the cards in the regions in the
5901 // collection set are reset when the collection set is freed.
5902 hot_card_cache->reset_hot_cache();
5903 hot_card_cache->set_use_cache(true);
5904
5905 // Migrate the strong code roots attached to each region in
5906 // the collection set. Ideally we would like to do this
5907 // after we have finished the scanning/evacuation of the
5908 // strong code roots for a particular heap region.
5909 migrate_strong_code_roots();
5910
5911 purge_code_root_memory();
5912
5913 if (g1_policy()->during_initial_mark_pause()) {
5914 // Reset the claim values set during marking the strong code roots
5915 reset_heap_region_claim_values();
5916 }
5917
5918 finalize_for_evac_failure();
5919
5920 if (evacuation_failed()) {
5921 remove_self_forwarding_pointers();
5922
5923 // Reset the G1EvacuationFailureALot counters and flags
5924 // Note: the values are reset only when an actual
5925 // evacuation failure occurs.
5926 NOT_PRODUCT(reset_evacuation_should_fail();)
5927 }
5928
5929 // Enqueue any remaining references remaining on the STW
5930 // reference processor's discovered lists. We need to do
5931 // this after the card table is cleaned (and verified) as
5932 // the act of enqueueing entries on to the pending list
5933 // will log these updates (and dirty their associated
5934 // cards). We need these updates logged to update any
5935 // RSets.
5936 enqueue_discovered_references(n_workers);
5937
5938 if (G1DeferredRSUpdate) {
5939 redirty_logged_cards();
5940 }
5941 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
5942 }
5943
5944 void G1CollectedHeap::free_region(HeapRegion* hr,
5945 FreeRegionList* free_list,
5946 bool par,
5947 bool locked) {
5948 assert(!hr->isHumongous(), "this is only for non-humongous regions");
5949 assert(!hr->is_empty(), "the region should not be empty");
5950 assert(free_list != NULL, "pre-condition");
5951
5952 if (G1VerifyBitmaps) {
5953 MemRegion mr(hr->bottom(), hr->end());
5954 concurrent_mark()->clearRangePrevBitmap(mr);
5955 }
5956
5957 // Clear the card counts for this region.
5958 // Note: we only need to do this if the region is not young
5959 // (since we don't refine cards in young regions).
5960 if (!hr->is_young()) {
5961 _cg1r->hot_card_cache()->reset_card_counts(hr);
5962 }
5963 hr->hr_clear(par, true /* clear_space */, locked /* locked */);
5964 free_list->add_ordered(hr);
5965 }
5966
5967 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
5968 FreeRegionList* free_list,
5969 bool par) {
5970 assert(hr->startsHumongous(), "this is only for starts humongous regions");
5971 assert(free_list != NULL, "pre-condition");
5972
5973 size_t hr_capacity = hr->capacity();
5974 // We need to read this before we make the region non-humongous,
5975 // otherwise the information will be gone.
5976 uint last_index = hr->last_hc_index();
5977 hr->set_notHumongous();
5978 free_region(hr, free_list, par);
5979
5980 uint i = hr->hrs_index() + 1;
5981 while (i < last_index) {
5982 HeapRegion* curr_hr = region_at(i);
5983 assert(curr_hr->continuesHumongous(), "invariant");
5984 curr_hr->set_notHumongous();
5985 free_region(curr_hr, free_list, par);
5986 i += 1;
5987 }
5988 }
5989
5990 void G1CollectedHeap::remove_from_old_sets(const HeapRegionSetCount& old_regions_removed,
5991 const HeapRegionSetCount& humongous_regions_removed) {
5992 if (old_regions_removed.length() > 0 || humongous_regions_removed.length() > 0) {
5993 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
5994 _old_set.bulk_remove(old_regions_removed);
5995 _humongous_set.bulk_remove(humongous_regions_removed);
5996 }
5997
5998 }
5999
6000 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) {
6001 assert(list != NULL, "list can't be null");
6002 if (!list->is_empty()) {
6003 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
6004 _free_list.add_ordered(list);
6005 }
6006 }
6007
6008 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) {
6009 assert(_summary_bytes_used >= bytes,
6010 err_msg("invariant: _summary_bytes_used: "SIZE_FORMAT" should be >= bytes: "SIZE_FORMAT,
6011 _summary_bytes_used, bytes));
6012 _summary_bytes_used -= bytes;
6013 }
6014
6015 class G1ParCleanupCTTask : public AbstractGangTask {
6016 G1SATBCardTableModRefBS* _ct_bs;
6017 G1CollectedHeap* _g1h;
6018 HeapRegion* volatile _su_head;
6019 public:
6020 G1ParCleanupCTTask(G1SATBCardTableModRefBS* ct_bs,
6021 G1CollectedHeap* g1h) :
6022 AbstractGangTask("G1 Par Cleanup CT Task"),
6023 _ct_bs(ct_bs), _g1h(g1h) { }
6024
6025 void work(uint worker_id) {
6026 HeapRegion* r;
6027 while (r = _g1h->pop_dirty_cards_region()) {
6028 clear_cards(r);
6029 }
6030 }
6031
6032 void clear_cards(HeapRegion* r) {
6033 // Cards of the survivors should have already been dirtied.
6034 if (!r->is_survivor()) {
6035 _ct_bs->clear(MemRegion(r->bottom(), r->end()));
6036 }
6037 }
6038 };
6039
6040 #ifndef PRODUCT
6041 class G1VerifyCardTableCleanup: public HeapRegionClosure {
6042 G1CollectedHeap* _g1h;
6043 G1SATBCardTableModRefBS* _ct_bs;
6044 public:
6045 G1VerifyCardTableCleanup(G1CollectedHeap* g1h, G1SATBCardTableModRefBS* ct_bs)
6046 : _g1h(g1h), _ct_bs(ct_bs) { }
6047 virtual bool doHeapRegion(HeapRegion* r) {
6048 if (r->is_survivor()) {
6049 _g1h->verify_dirty_region(r);
6050 } else {
6051 _g1h->verify_not_dirty_region(r);
6052 }
6053 return false;
6054 }
6055 };
6056
6057 void G1CollectedHeap::verify_not_dirty_region(HeapRegion* hr) {
6058 // All of the region should be clean.
6059 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
6060 MemRegion mr(hr->bottom(), hr->end());
6061 ct_bs->verify_not_dirty_region(mr);
6062 }
6063
6064 void G1CollectedHeap::verify_dirty_region(HeapRegion* hr) {
6065 // We cannot guarantee that [bottom(),end()] is dirty. Threads
6066 // dirty allocated blocks as they allocate them. The thread that
6067 // retires each region and replaces it with a new one will do a
6068 // maximal allocation to fill in [pre_dummy_top(),end()] but will
6069 // not dirty that area (one less thing to have to do while holding
6070 // a lock). So we can only verify that [bottom(),pre_dummy_top()]
6071 // is dirty.
6072 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
6073 MemRegion mr(hr->bottom(), hr->pre_dummy_top());
6074 if (hr->is_young()) {
6075 ct_bs->verify_g1_young_region(mr);
6076 } else {
6077 ct_bs->verify_dirty_region(mr);
6078 }
6079 }
6080
6081 void G1CollectedHeap::verify_dirty_young_list(HeapRegion* head) {
6082 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
6083 for (HeapRegion* hr = head; hr != NULL; hr = hr->get_next_young_region()) {
6084 verify_dirty_region(hr);
6085 }
6086 }
6087
6088 void G1CollectedHeap::verify_dirty_young_regions() {
6089 verify_dirty_young_list(_young_list->first_region());
6090 }
6091
6092 bool G1CollectedHeap::verify_no_bits_over_tams(const char* bitmap_name, CMBitMapRO* bitmap,
6093 HeapWord* tams, HeapWord* end) {
6094 guarantee(tams <= end,
6095 err_msg("tams: "PTR_FORMAT" end: "PTR_FORMAT, tams, end));
6096 HeapWord* result = bitmap->getNextMarkedWordAddress(tams, end);
6097 if (result < end) {
6098 gclog_or_tty->cr();
6099 gclog_or_tty->print_cr("## wrong marked address on %s bitmap: "PTR_FORMAT,
6100 bitmap_name, result);
6101 gclog_or_tty->print_cr("## %s tams: "PTR_FORMAT" end: "PTR_FORMAT,
6102 bitmap_name, tams, end);
6103 return false;
6104 }
6105 return true;
6106 }
6107
6108 bool G1CollectedHeap::verify_bitmaps(const char* caller, HeapRegion* hr) {
6109 CMBitMapRO* prev_bitmap = concurrent_mark()->prevMarkBitMap();
6110 CMBitMapRO* next_bitmap = (CMBitMapRO*) concurrent_mark()->nextMarkBitMap();
6111
6112 HeapWord* bottom = hr->bottom();
6113 HeapWord* ptams = hr->prev_top_at_mark_start();
6114 HeapWord* ntams = hr->next_top_at_mark_start();
6115 HeapWord* end = hr->end();
6116
6117 bool res_p = verify_no_bits_over_tams("prev", prev_bitmap, ptams, end);
6118
6119 bool res_n = true;
6120 // We reset mark_in_progress() before we reset _cmThread->in_progress() and in this window
6121 // we do the clearing of the next bitmap concurrently. Thus, we can not verify the bitmap
6122 // if we happen to be in that state.
6123 if (mark_in_progress() || !_cmThread->in_progress()) {
6124 res_n = verify_no_bits_over_tams("next", next_bitmap, ntams, end);
6125 }
6126 if (!res_p || !res_n) {
6127 gclog_or_tty->print_cr("#### Bitmap verification failed for "HR_FORMAT,
6128 HR_FORMAT_PARAMS(hr));
6129 gclog_or_tty->print_cr("#### Caller: %s", caller);
6130 return false;
6131 }
6132 return true;
6133 }
6134
6135 void G1CollectedHeap::check_bitmaps(const char* caller, HeapRegion* hr) {
6136 if (!G1VerifyBitmaps) return;
6137
6138 guarantee(verify_bitmaps(caller, hr), "bitmap verification");
6139 }
6140
6141 class G1VerifyBitmapClosure : public HeapRegionClosure {
6142 private:
6143 const char* _caller;
6144 G1CollectedHeap* _g1h;
6145 bool _failures;
6146
6147 public:
6148 G1VerifyBitmapClosure(const char* caller, G1CollectedHeap* g1h) :
6149 _caller(caller), _g1h(g1h), _failures(false) { }
6150
6151 bool failures() { return _failures; }
6152
6153 virtual bool doHeapRegion(HeapRegion* hr) {
6154 if (hr->continuesHumongous()) return false;
6155
6156 bool result = _g1h->verify_bitmaps(_caller, hr);
6157 if (!result) {
6158 _failures = true;
6159 }
6160 return false;
6161 }
6162 };
6163
6164 void G1CollectedHeap::check_bitmaps(const char* caller) {
6165 if (!G1VerifyBitmaps) return;
6166
6167 G1VerifyBitmapClosure cl(caller, this);
6168 heap_region_iterate(&cl);
6169 guarantee(!cl.failures(), "bitmap verification");
6170 }
6171 #endif // PRODUCT
6172
6173 void G1CollectedHeap::cleanUpCardTable() {
6174 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
6175 double start = os::elapsedTime();
6176
6177 {
6178 // Iterate over the dirty cards region list.
6179 G1ParCleanupCTTask cleanup_task(ct_bs, this);
6180
6181 if (G1CollectedHeap::use_parallel_gc_threads()) {
6182 set_par_threads();
6183 workers()->run_task(&cleanup_task);
6184 set_par_threads(0);
6185 } else {
6186 while (_dirty_cards_region_list) {
6187 HeapRegion* r = _dirty_cards_region_list;
6188 cleanup_task.clear_cards(r);
6189 _dirty_cards_region_list = r->get_next_dirty_cards_region();
6190 if (_dirty_cards_region_list == r) {
6191 // The last region.
6192 _dirty_cards_region_list = NULL;
6193 }
6194 r->set_next_dirty_cards_region(NULL);
6195 }
6196 }
6197 #ifndef PRODUCT
6198 if (G1VerifyCTCleanup || VerifyAfterGC) {
6199 G1VerifyCardTableCleanup cleanup_verifier(this, ct_bs);
6200 heap_region_iterate(&cleanup_verifier);
6201 }
6202 #endif
6203 }
6204
6205 double elapsed = os::elapsedTime() - start;
6206 g1_policy()->phase_times()->record_clear_ct_time(elapsed * 1000.0);
6207 }
6208
6209 void G1CollectedHeap::free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info) {
6210 size_t pre_used = 0;
6211 FreeRegionList local_free_list("Local List for CSet Freeing");
6212
6213 double young_time_ms = 0.0;
6214 double non_young_time_ms = 0.0;
6215
6216 // Since the collection set is a superset of the the young list,
6217 // all we need to do to clear the young list is clear its
6218 // head and length, and unlink any young regions in the code below
6219 _young_list->clear();
6220
6221 G1CollectorPolicy* policy = g1_policy();
6222
6223 double start_sec = os::elapsedTime();
6224 bool non_young = true;
6225
6226 HeapRegion* cur = cs_head;
6227 int age_bound = -1;
6228 size_t rs_lengths = 0;
6229
6230 while (cur != NULL) {
6231 assert(!is_on_master_free_list(cur), "sanity");
6232 if (non_young) {
6233 if (cur->is_young()) {
6234 double end_sec = os::elapsedTime();
6235 double elapsed_ms = (end_sec - start_sec) * 1000.0;
6236 non_young_time_ms += elapsed_ms;
6237
6238 start_sec = os::elapsedTime();
6239 non_young = false;
6240 }
6241 } else {
6242 if (!cur->is_young()) {
6243 double end_sec = os::elapsedTime();
6244 double elapsed_ms = (end_sec - start_sec) * 1000.0;
6245 young_time_ms += elapsed_ms;
6246
6247 start_sec = os::elapsedTime();
6248 non_young = true;
6249 }
6250 }
6251
6252 rs_lengths += cur->rem_set()->occupied_locked();
6253
6254 HeapRegion* next = cur->next_in_collection_set();
6255 assert(cur->in_collection_set(), "bad CS");
6256 cur->set_next_in_collection_set(NULL);
6257 cur->set_in_collection_set(false);
6258
6259 if (cur->is_young()) {
6260 int index = cur->young_index_in_cset();
6261 assert(index != -1, "invariant");
6262 assert((uint) index < policy->young_cset_region_length(), "invariant");
6263 size_t words_survived = _surviving_young_words[index];
6264 cur->record_surv_words_in_group(words_survived);
6265
6266 // At this point the we have 'popped' cur from the collection set
6267 // (linked via next_in_collection_set()) but it is still in the
6268 // young list (linked via next_young_region()). Clear the
6269 // _next_young_region field.
6270 cur->set_next_young_region(NULL);
6271 } else {
6272 int index = cur->young_index_in_cset();
6273 assert(index == -1, "invariant");
6274 }
6275
6276 assert( (cur->is_young() && cur->young_index_in_cset() > -1) ||
6277 (!cur->is_young() && cur->young_index_in_cset() == -1),
6278 "invariant" );
6279
6280 if (!cur->evacuation_failed()) {
6281 MemRegion used_mr = cur->used_region();
6282
6283 // And the region is empty.
6284 assert(!used_mr.is_empty(), "Should not have empty regions in a CS.");
6285 pre_used += cur->used();
6286 free_region(cur, &local_free_list, false /* par */, true /* locked */);
6287 } else {
6288 cur->uninstall_surv_rate_group();
6289 if (cur->is_young()) {
6290 cur->set_young_index_in_cset(-1);
6291 }
6292 cur->set_not_young();
6293 cur->set_evacuation_failed(false);
6294 // The region is now considered to be old.
6295 _old_set.add(cur);
6296 evacuation_info.increment_collectionset_used_after(cur->used());
6297 }
6298 cur = next;
6299 }
6300
6301 evacuation_info.set_regions_freed(local_free_list.length());
6302 policy->record_max_rs_lengths(rs_lengths);
6303 policy->cset_regions_freed();
6304
6305 double end_sec = os::elapsedTime();
6306 double elapsed_ms = (end_sec - start_sec) * 1000.0;
6307
6308 if (non_young) {
6309 non_young_time_ms += elapsed_ms;
6310 } else {
6311 young_time_ms += elapsed_ms;
6312 }
6313
6314 prepend_to_freelist(&local_free_list);
6315 decrement_summary_bytes(pre_used);
6316 policy->phase_times()->record_young_free_cset_time_ms(young_time_ms);
6317 policy->phase_times()->record_non_young_free_cset_time_ms(non_young_time_ms);
6318 }
6319
6320 // This routine is similar to the above but does not record
6321 // any policy statistics or update free lists; we are abandoning
6322 // the current incremental collection set in preparation of a
6323 // full collection. After the full GC we will start to build up
6324 // the incremental collection set again.
6325 // This is only called when we're doing a full collection
6326 // and is immediately followed by the tearing down of the young list.
6327
6328 void G1CollectedHeap::abandon_collection_set(HeapRegion* cs_head) {
6329 HeapRegion* cur = cs_head;
6330
6331 while (cur != NULL) {
6332 HeapRegion* next = cur->next_in_collection_set();
6333 assert(cur->in_collection_set(), "bad CS");
6334 cur->set_next_in_collection_set(NULL);
6335 cur->set_in_collection_set(false);
6336 cur->set_young_index_in_cset(-1);
6337 cur = next;
6338 }
6339 }
6340
6341 void G1CollectedHeap::set_free_regions_coming() {
6342 if (G1ConcRegionFreeingVerbose) {
6343 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
6344 "setting free regions coming");
6345 }
6346
6347 assert(!free_regions_coming(), "pre-condition");
6348 _free_regions_coming = true;
6349 }
6350
6351 void G1CollectedHeap::reset_free_regions_coming() {
6352 assert(free_regions_coming(), "pre-condition");
6353
6354 {
6355 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6356 _free_regions_coming = false;
6357 SecondaryFreeList_lock->notify_all();
6358 }
6359
6360 if (G1ConcRegionFreeingVerbose) {
6361 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
6362 "reset free regions coming");
6363 }
6364 }
6365
6366 void G1CollectedHeap::wait_while_free_regions_coming() {
6367 // Most of the time we won't have to wait, so let's do a quick test
6368 // first before we take the lock.
6369 if (!free_regions_coming()) {
6370 return;
6371 }
6372
6373 if (G1ConcRegionFreeingVerbose) {
6374 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
6375 "waiting for free regions");
6376 }
6377
6378 {
6379 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6380 while (free_regions_coming()) {
6381 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
6382 }
6383 }
6384
6385 if (G1ConcRegionFreeingVerbose) {
6386 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
6387 "done waiting for free regions");
6388 }
6389 }
6390
6391 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
6392 assert(heap_lock_held_for_gc(),
6393 "the heap lock should already be held by or for this thread");
6394 _young_list->push_region(hr);
6395 }
6396
6397 class NoYoungRegionsClosure: public HeapRegionClosure {
6398 private:
6399 bool _success;
6400 public:
6401 NoYoungRegionsClosure() : _success(true) { }
6402 bool doHeapRegion(HeapRegion* r) {
6403 if (r->is_young()) {
6404 gclog_or_tty->print_cr("Region ["PTR_FORMAT", "PTR_FORMAT") tagged as young",
6405 r->bottom(), r->end());
6406 _success = false;
6407 }
6408 return false;
6409 }
6410 bool success() { return _success; }
6411 };
6412
6413 bool G1CollectedHeap::check_young_list_empty(bool check_heap, bool check_sample) {
6414 bool ret = _young_list->check_list_empty(check_sample);
6415
6416 if (check_heap) {
6417 NoYoungRegionsClosure closure;
6418 heap_region_iterate(&closure);
6419 ret = ret && closure.success();
6420 }
6421
6422 return ret;
6423 }
6424
6425 class TearDownRegionSetsClosure : public HeapRegionClosure {
6426 private:
6427 HeapRegionSet *_old_set;
6428
6429 public:
6430 TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { }
6431
6432 bool doHeapRegion(HeapRegion* r) {
6433 if (r->is_empty()) {
6434 // We ignore empty regions, we'll empty the free list afterwards
6435 } else if (r->is_young()) {
6436 // We ignore young regions, we'll empty the young list afterwards
6437 } else if (r->isHumongous()) {
6438 // We ignore humongous regions, we're not tearing down the
6439 // humongous region set
6440 } else {
6441 // The rest should be old
6442 _old_set->remove(r);
6443 }
6444 return false;
6445 }
6446
6447 ~TearDownRegionSetsClosure() {
6448 assert(_old_set->is_empty(), "post-condition");
6449 }
6450 };
6451
6452 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
6453 assert_at_safepoint(true /* should_be_vm_thread */);
6454
6455 if (!free_list_only) {
6456 TearDownRegionSetsClosure cl(&_old_set);
6457 heap_region_iterate(&cl);
6458
6459 // Note that emptying the _young_list is postponed and instead done as
6460 // the first step when rebuilding the regions sets again. The reason for
6461 // this is that during a full GC string deduplication needs to know if
6462 // a collected region was young or old when the full GC was initiated.
6463 }
6464 _free_list.remove_all();
6465 }
6466
6467 class RebuildRegionSetsClosure : public HeapRegionClosure {
6468 private:
6469 bool _free_list_only;
6470 HeapRegionSet* _old_set;
6471 FreeRegionList* _free_list;
6472 size_t _total_used;
6473
6474 public:
6475 RebuildRegionSetsClosure(bool free_list_only,
6476 HeapRegionSet* old_set, FreeRegionList* free_list) :
6477 _free_list_only(free_list_only),
6478 _old_set(old_set), _free_list(free_list), _total_used(0) {
6479 assert(_free_list->is_empty(), "pre-condition");
6480 if (!free_list_only) {
6481 assert(_old_set->is_empty(), "pre-condition");
6482 }
6483 }
6484
6485 bool doHeapRegion(HeapRegion* r) {
6486 if (r->continuesHumongous()) {
6487 return false;
6488 }
6489
6490 if (r->is_empty()) {
6491 // Add free regions to the free list
6492 _free_list->add_as_tail(r);
6493 } else if (!_free_list_only) {
6494 assert(!r->is_young(), "we should not come across young regions");
6495
6496 if (r->isHumongous()) {
6497 // We ignore humongous regions, we left the humongous set unchanged
6498 } else {
6499 // The rest should be old, add them to the old set
6500 _old_set->add(r);
6501 }
6502 _total_used += r->used();
6503 }
6504
6505 return false;
6506 }
6507
6508 size_t total_used() {
6509 return _total_used;
6510 }
6511 };
6512
6513 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
6514 assert_at_safepoint(true /* should_be_vm_thread */);
6515
6516 if (!free_list_only) {
6517 _young_list->empty_list();
6518 }
6519
6520 RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_free_list);
6521 heap_region_iterate(&cl);
6522
6523 if (!free_list_only) {
6524 _summary_bytes_used = cl.total_used();
6525 }
6526 assert(_summary_bytes_used == recalculate_used(),
6527 err_msg("inconsistent _summary_bytes_used, "
6528 "value: "SIZE_FORMAT" recalculated: "SIZE_FORMAT,
6529 _summary_bytes_used, recalculate_used()));
6530 }
6531
6532 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) {
6533 _refine_cte_cl->set_concurrent(concurrent);
6534 }
6535
6536 bool G1CollectedHeap::is_in_closed_subset(const void* p) const {
6537 HeapRegion* hr = heap_region_containing(p);
6538 return hr->is_in(p);
6539 }
6540
6541 // Methods for the mutator alloc region
6542
6543 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
6544 bool force) {
6545 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6546 assert(!force || g1_policy()->can_expand_young_list(),
6547 "if force is true we should be able to expand the young list");
6548 bool young_list_full = g1_policy()->is_young_list_full();
6549 if (force || !young_list_full) {
6550 HeapRegion* new_alloc_region = new_region(word_size,
6551 false /* is_old */,
6552 false /* do_expand */);
6553 if (new_alloc_region != NULL) {
6554 set_region_short_lived_locked(new_alloc_region);
6555 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Eden, young_list_full);
6556 check_bitmaps("Mutator Region Allocation", new_alloc_region);
6557 return new_alloc_region;
6558 }
6559 }
6560 return NULL;
6561 }
6562
6563 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
6564 size_t allocated_bytes) {
6565 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6566 assert(alloc_region->is_young(), "all mutator alloc regions should be young");
6567
6568 g1_policy()->add_region_to_incremental_cset_lhs(alloc_region);
6569 _summary_bytes_used += allocated_bytes;
6570 _hr_printer.retire(alloc_region);
6571 // We update the eden sizes here, when the region is retired,
6572 // instead of when it's allocated, since this is the point that its
6573 // used space has been recored in _summary_bytes_used.
6574 g1mm()->update_eden_size();
6575 }
6576
6577 HeapRegion* MutatorAllocRegion::allocate_new_region(size_t word_size,
6578 bool force) {
6579 return _g1h->new_mutator_alloc_region(word_size, force);
6580 }
6581
6582 void G1CollectedHeap::set_par_threads() {
6583 // Don't change the number of workers. Use the value previously set
6584 // in the workgroup.
6585 assert(G1CollectedHeap::use_parallel_gc_threads(), "shouldn't be here otherwise");
6586 uint n_workers = workers()->active_workers();
6587 assert(UseDynamicNumberOfGCThreads ||
6588 n_workers == workers()->total_workers(),
6589 "Otherwise should be using the total number of workers");
6590 if (n_workers == 0) {
6591 assert(false, "Should have been set in prior evacuation pause.");
6592 n_workers = ParallelGCThreads;
6593 workers()->set_active_workers(n_workers);
6594 }
6595 set_par_threads(n_workers);
6596 }
6597
6598 void MutatorAllocRegion::retire_region(HeapRegion* alloc_region,
6599 size_t allocated_bytes) {
6600 _g1h->retire_mutator_alloc_region(alloc_region, allocated_bytes);
6601 }
6602
6603 // Methods for the GC alloc regions
6604
6605 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size,
6606 uint count,
6607 GCAllocPurpose ap) {
6608 assert(FreeList_lock->owned_by_self(), "pre-condition");
6609
6610 if (count < g1_policy()->max_regions(ap)) {
6611 bool survivor = (ap == GCAllocForSurvived);
6612 HeapRegion* new_alloc_region = new_region(word_size,
6613 !survivor,
6614 true /* do_expand */);
6615 if (new_alloc_region != NULL) {
6616 // We really only need to do this for old regions given that we
6617 // should never scan survivors. But it doesn't hurt to do it
6618 // for survivors too.
6619 new_alloc_region->set_saved_mark();
6620 if (survivor) {
6621 new_alloc_region->set_survivor();
6622 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Survivor);
6623 check_bitmaps("Survivor Region Allocation", new_alloc_region);
6624 } else {
6625 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Old);
6626 check_bitmaps("Old Region Allocation", new_alloc_region);
6627 }
6628 bool during_im = g1_policy()->during_initial_mark_pause();
6629 new_alloc_region->note_start_of_copying(during_im);
6630 return new_alloc_region;
6631 } else {
6632 g1_policy()->note_alloc_region_limit_reached(ap);
6633 }
6634 }
6635 return NULL;
6636 }
6637
6638 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
6639 size_t allocated_bytes,
6640 GCAllocPurpose ap) {
6641 bool during_im = g1_policy()->during_initial_mark_pause();
6642 alloc_region->note_end_of_copying(during_im);
6643 g1_policy()->record_bytes_copied_during_gc(allocated_bytes);
6644 if (ap == GCAllocForSurvived) {
6645 young_list()->add_survivor_region(alloc_region);
6646 } else {
6647 _old_set.add(alloc_region);
6648 }
6649 _hr_printer.retire(alloc_region);
6650 }
6651
6652 HeapRegion* SurvivorGCAllocRegion::allocate_new_region(size_t word_size,
6653 bool force) {
6654 assert(!force, "not supported for GC alloc regions");
6655 return _g1h->new_gc_alloc_region(word_size, count(), GCAllocForSurvived);
6656 }
6657
6658 void SurvivorGCAllocRegion::retire_region(HeapRegion* alloc_region,
6659 size_t allocated_bytes) {
6660 _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes,
6661 GCAllocForSurvived);
6662 }
6663
6664 HeapRegion* OldGCAllocRegion::allocate_new_region(size_t word_size,
6665 bool force) {
6666 assert(!force, "not supported for GC alloc regions");
6667 return _g1h->new_gc_alloc_region(word_size, count(), GCAllocForTenured);
6668 }
6669
6670 void OldGCAllocRegion::retire_region(HeapRegion* alloc_region,
6671 size_t allocated_bytes) {
6672 _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes,
6673 GCAllocForTenured);
6674 }
6675 // Heap region set verification
6676
6677 class VerifyRegionListsClosure : public HeapRegionClosure {
6678 private:
6679 HeapRegionSet* _old_set;
6680 HeapRegionSet* _humongous_set;
6681 FreeRegionList* _free_list;
6682
6683 public:
6684 HeapRegionSetCount _old_count;
6685 HeapRegionSetCount _humongous_count;
6686 HeapRegionSetCount _free_count;
6687
6688 VerifyRegionListsClosure(HeapRegionSet* old_set,
6689 HeapRegionSet* humongous_set,
6690 FreeRegionList* free_list) :
6691 _old_set(old_set), _humongous_set(humongous_set), _free_list(free_list),
6692 _old_count(), _humongous_count(), _free_count(){ }
6693
6694 bool doHeapRegion(HeapRegion* hr) {
6695 if (hr->continuesHumongous()) {
6696 return false;
6697 }
6698
6699 if (hr->is_young()) {
6700 // TODO
6701 } else if (hr->startsHumongous()) {
6702 assert(hr->containing_set() == _humongous_set, err_msg("Heap region %u is starts humongous but not in humongous set.", hr->hrs_index()));
6703 _humongous_count.increment(1u, hr->capacity());
6704 } else if (hr->is_empty()) {
6705 assert(hr->containing_set() == _free_list, err_msg("Heap region %u is empty but not on the free list.", hr->hrs_index()));
6706 _free_count.increment(1u, hr->capacity());
6707 } else {
6708 assert(hr->containing_set() == _old_set, err_msg("Heap region %u is old but not in the old set.", hr->hrs_index()));
6709 _old_count.increment(1u, hr->capacity());
6710 }
6711 return false;
6712 }
6713
6714 void verify_counts(HeapRegionSet* old_set, HeapRegionSet* humongous_set, FreeRegionList* free_list) {
6715 guarantee(old_set->length() == _old_count.length(), err_msg("Old set count mismatch. Expected %u, actual %u.", old_set->length(), _old_count.length()));
6716 guarantee(old_set->total_capacity_bytes() == _old_count.capacity(), err_msg("Old set capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
6717 old_set->total_capacity_bytes(), _old_count.capacity()));
6718
6719 guarantee(humongous_set->length() == _humongous_count.length(), err_msg("Hum set count mismatch. Expected %u, actual %u.", humongous_set->length(), _humongous_count.length()));
6720 guarantee(humongous_set->total_capacity_bytes() == _humongous_count.capacity(), err_msg("Hum set capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
6721 humongous_set->total_capacity_bytes(), _humongous_count.capacity()));
6722
6723 guarantee(free_list->length() == _free_count.length(), err_msg("Free list count mismatch. Expected %u, actual %u.", free_list->length(), _free_count.length()));
6724 guarantee(free_list->total_capacity_bytes() == _free_count.capacity(), err_msg("Free list capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
6725 free_list->total_capacity_bytes(), _free_count.capacity()));
6726 }
6727 };
6728
6729 HeapRegion* G1CollectedHeap::new_heap_region(uint hrs_index,
6730 HeapWord* bottom) {
6731 HeapWord* end = bottom + HeapRegion::GrainWords;
6732 MemRegion mr(bottom, end);
6733 assert(_g1_reserved.contains(mr), "invariant");
6734 // This might return NULL if the allocation fails
6735 return new HeapRegion(hrs_index, _bot_shared, mr);
6736 }
6737
6738 void G1CollectedHeap::verify_region_sets() {
6739 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6740
6741 // First, check the explicit lists.
6742 _free_list.verify_list();
6743 {
6744 // Given that a concurrent operation might be adding regions to
6745 // the secondary free list we have to take the lock before
6746 // verifying it.
6747 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6748 _secondary_free_list.verify_list();
6749 }
6750
6751 // If a concurrent region freeing operation is in progress it will
6752 // be difficult to correctly attributed any free regions we come
6753 // across to the correct free list given that they might belong to
6754 // one of several (free_list, secondary_free_list, any local lists,
6755 // etc.). So, if that's the case we will skip the rest of the
6756 // verification operation. Alternatively, waiting for the concurrent
6757 // operation to complete will have a non-trivial effect on the GC's
6758 // operation (no concurrent operation will last longer than the
6759 // interval between two calls to verification) and it might hide
6760 // any issues that we would like to catch during testing.
6761 if (free_regions_coming()) {
6762 return;
6763 }
6764
6765 // Make sure we append the secondary_free_list on the free_list so
6766 // that all free regions we will come across can be safely
6767 // attributed to the free_list.
6768 append_secondary_free_list_if_not_empty_with_lock();
6769
6770 // Finally, make sure that the region accounting in the lists is
6771 // consistent with what we see in the heap.
6772
6773 VerifyRegionListsClosure cl(&_old_set, &_humongous_set, &_free_list);
6774 heap_region_iterate(&cl);
6775 cl.verify_counts(&_old_set, &_humongous_set, &_free_list);
6776 }
6777
6778 // Optimized nmethod scanning
6779
6780 class RegisterNMethodOopClosure: public OopClosure {
6781 G1CollectedHeap* _g1h;
6782 nmethod* _nm;
6783
6784 template <class T> void do_oop_work(T* p) {
6785 T heap_oop = oopDesc::load_heap_oop(p);
6786 if (!oopDesc::is_null(heap_oop)) {
6787 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
6788 HeapRegion* hr = _g1h->heap_region_containing(obj);
6789 assert(!hr->continuesHumongous(),
6790 err_msg("trying to add code root "PTR_FORMAT" in continuation of humongous region "HR_FORMAT
6791 " starting at "HR_FORMAT,
6792 _nm, HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())));
6793
6794 // HeapRegion::add_strong_code_root() avoids adding duplicate
6795 // entries but having duplicates is OK since we "mark" nmethods
6796 // as visited when we scan the strong code root lists during the GC.
6797 hr->add_strong_code_root(_nm);
6798 assert(hr->rem_set()->strong_code_roots_list_contains(_nm),
6799 err_msg("failed to add code root "PTR_FORMAT" to remembered set of region "HR_FORMAT,
6800 _nm, HR_FORMAT_PARAMS(hr)));
6801 }
6802 }
6803
6804 public:
6805 RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
6806 _g1h(g1h), _nm(nm) {}
6807
6808 void do_oop(oop* p) { do_oop_work(p); }
6809 void do_oop(narrowOop* p) { do_oop_work(p); }
6810 };
6811
6812 class UnregisterNMethodOopClosure: public OopClosure {
6813 G1CollectedHeap* _g1h;
6814 nmethod* _nm;
6815
6816 template <class T> void do_oop_work(T* p) {
6817 T heap_oop = oopDesc::load_heap_oop(p);
6818 if (!oopDesc::is_null(heap_oop)) {
6819 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
6820 HeapRegion* hr = _g1h->heap_region_containing(obj);
6821 assert(!hr->continuesHumongous(),
6822 err_msg("trying to remove code root "PTR_FORMAT" in continuation of humongous region "HR_FORMAT
6823 " starting at "HR_FORMAT,
6824 _nm, HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())));
6825
6826 hr->remove_strong_code_root(_nm);
6827 assert(!hr->rem_set()->strong_code_roots_list_contains(_nm),
6828 err_msg("failed to remove code root "PTR_FORMAT" of region "HR_FORMAT,
6829 _nm, HR_FORMAT_PARAMS(hr)));
6830 }
6831 }
6832
6833 public:
6834 UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
6835 _g1h(g1h), _nm(nm) {}
6836
6837 void do_oop(oop* p) { do_oop_work(p); }
6838 void do_oop(narrowOop* p) { do_oop_work(p); }
6839 };
6840
6841 void G1CollectedHeap::register_nmethod(nmethod* nm) {
6842 CollectedHeap::register_nmethod(nm);
6843
6844 guarantee(nm != NULL, "sanity");
6845 RegisterNMethodOopClosure reg_cl(this, nm);
6846 nm->oops_do(®_cl);
6847 }
6848
6849 void G1CollectedHeap::unregister_nmethod(nmethod* nm) {
6850 CollectedHeap::unregister_nmethod(nm);
6851
6852 guarantee(nm != NULL, "sanity");
6853 UnregisterNMethodOopClosure reg_cl(this, nm);
6854 nm->oops_do(®_cl, true);
6855 }
6856
6857 class MigrateCodeRootsHeapRegionClosure: public HeapRegionClosure {
6858 public:
6859 bool doHeapRegion(HeapRegion *hr) {
6860 assert(!hr->isHumongous(),
6861 err_msg("humongous region "HR_FORMAT" should not have been added to collection set",
6862 HR_FORMAT_PARAMS(hr)));
6863 hr->migrate_strong_code_roots();
6864 return false;
6865 }
6866 };
6867
6868 void G1CollectedHeap::migrate_strong_code_roots() {
6869 MigrateCodeRootsHeapRegionClosure cl;
6870 double migrate_start = os::elapsedTime();
6871 collection_set_iterate(&cl);
6872 double migration_time_ms = (os::elapsedTime() - migrate_start) * 1000.0;
6873 g1_policy()->phase_times()->record_strong_code_root_migration_time(migration_time_ms);
6874 }
6875
6876 void G1CollectedHeap::purge_code_root_memory() {
6877 double purge_start = os::elapsedTime();
6878 G1CodeRootSet::purge_chunks(G1CodeRootsChunkCacheKeepPercent);
6879 double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0;
6880 g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms);
6881 }
6882
6883 // Mark all the code roots that point into regions *not* in the
6884 // collection set.
6885 //
6886 // Note we do not want to use a "marking" CodeBlobToOopClosure while
6887 // walking the the code roots lists of regions not in the collection
6888 // set. Suppose we have an nmethod (M) that points to objects in two
6889 // separate regions - one in the collection set (R1) and one not (R2).
6890 // Using a "marking" CodeBlobToOopClosure here would result in "marking"
6891 // nmethod M when walking the code roots for R1. When we come to scan
6892 // the code roots for R2, we would see that M is already marked and it
6893 // would be skipped and the objects in R2 that are referenced from M
6894 // would not be evacuated.
6895
6896 class MarkStrongCodeRootCodeBlobClosure: public CodeBlobClosure {
6897
6898 class MarkStrongCodeRootOopClosure: public OopClosure {
6899 ConcurrentMark* _cm;
6900 HeapRegion* _hr;
6901 uint _worker_id;
6902
6903 template <class T> void do_oop_work(T* p) {
6904 T heap_oop = oopDesc::load_heap_oop(p);
6905 if (!oopDesc::is_null(heap_oop)) {
6906 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
6907 // Only mark objects in the region (which is assumed
6908 // to be not in the collection set).
6909 if (_hr->is_in(obj)) {
6910 _cm->grayRoot(obj, (size_t) obj->size(), _worker_id);
6911 }
6912 }
6913 }
6914
6915 public:
6916 MarkStrongCodeRootOopClosure(ConcurrentMark* cm, HeapRegion* hr, uint worker_id) :
6917 _cm(cm), _hr(hr), _worker_id(worker_id) {
6918 assert(!_hr->in_collection_set(), "sanity");
6919 }
6920
6921 void do_oop(narrowOop* p) { do_oop_work(p); }
6922 void do_oop(oop* p) { do_oop_work(p); }
6923 };
6924
6925 MarkStrongCodeRootOopClosure _oop_cl;
6926
6927 public:
6928 MarkStrongCodeRootCodeBlobClosure(ConcurrentMark* cm, HeapRegion* hr, uint worker_id):
6929 _oop_cl(cm, hr, worker_id) {}
6930
6931 void do_code_blob(CodeBlob* cb) {
6932 nmethod* nm = (cb == NULL) ? NULL : cb->as_nmethod_or_null();
6933 if (nm != NULL) {
6934 nm->oops_do(&_oop_cl);
6935 }
6936 }
6937 };
6938
6939 class MarkStrongCodeRootsHRClosure: public HeapRegionClosure {
6940 G1CollectedHeap* _g1h;
6941 uint _worker_id;
6942
6943 public:
6944 MarkStrongCodeRootsHRClosure(G1CollectedHeap* g1h, uint worker_id) :
6945 _g1h(g1h), _worker_id(worker_id) {}
6946
6947 bool doHeapRegion(HeapRegion *hr) {
6948 HeapRegionRemSet* hrrs = hr->rem_set();
6949 if (hr->continuesHumongous()) {
6950 // Code roots should never be attached to a continuation of a humongous region
6951 assert(hrrs->strong_code_roots_list_length() == 0,
6952 err_msg("code roots should never be attached to continuations of humongous region "HR_FORMAT
6953 " starting at "HR_FORMAT", but has "SIZE_FORMAT,
6954 HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()),
6955 hrrs->strong_code_roots_list_length()));
6956 return false;
6957 }
6958
6959 if (hr->in_collection_set()) {
6960 // Don't mark code roots into regions in the collection set here.
6961 // They will be marked when we scan them.
6962 return false;
6963 }
6964
6965 MarkStrongCodeRootCodeBlobClosure cb_cl(_g1h->concurrent_mark(), hr, _worker_id);
6966 hr->strong_code_roots_do(&cb_cl);
6967 return false;
6968 }
6969 };
6970
6971 void G1CollectedHeap::mark_strong_code_roots(uint worker_id) {
6972 MarkStrongCodeRootsHRClosure cl(this, worker_id);
6973 if (G1CollectedHeap::use_parallel_gc_threads()) {
6974 heap_region_par_iterate_chunked(&cl,
6975 worker_id,
6976 workers()->active_workers(),
6977 HeapRegion::ParMarkRootClaimValue);
6978 } else {
6979 heap_region_iterate(&cl);
6980 }
6981 }
6982
6983 class RebuildStrongCodeRootClosure: public CodeBlobClosure {
6984 G1CollectedHeap* _g1h;
6985
6986 public:
6987 RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) :
6988 _g1h(g1h) {}
6989
6990 void do_code_blob(CodeBlob* cb) {
6991 nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL;
6992 if (nm == NULL) {
6993 return;
6994 }
6995
6996 if (ScavengeRootsInCode && nm->detect_scavenge_root_oops()) {
6997 _g1h->register_nmethod(nm);
6998 }
6999 }
7000 };
7001
7002 void G1CollectedHeap::rebuild_strong_code_roots() {
7003 RebuildStrongCodeRootClosure blob_cl(this);
7004 CodeCache::blobs_do(&blob_cl);
7005 }