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 #include "precompiled.hpp"
26 #include "code/codeCache.hpp"
27 #include "code/icBuffer.hpp"
28 #include "gc_implementation/g1/bufferingOopClosure.hpp"
29 #include "gc_implementation/g1/concurrentG1Refine.hpp"
30 #include "gc_implementation/g1/concurrentG1RefineThread.hpp"
31 #include "gc_implementation/g1/concurrentMarkThread.inline.hpp"
32 #include "gc_implementation/g1/g1AllocRegion.inline.hpp"
33 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
34 #include "gc_implementation/g1/g1CollectorPolicy.hpp"
35 #include "gc_implementation/g1/g1ErgoVerbose.hpp"
36 #include "gc_implementation/g1/g1EvacFailure.hpp"
37 #include "gc_implementation/g1/g1GCPhaseTimes.hpp"
38 #include "gc_implementation/g1/g1Log.hpp"
39 #include "gc_implementation/g1/g1MarkSweep.hpp"
40 #include "gc_implementation/g1/g1OopClosures.inline.hpp"
41 #include "gc_implementation/g1/g1ParScanThreadState.inline.hpp"
42 #include "gc_implementation/g1/g1RemSet.inline.hpp"
43 #include "gc_implementation/g1/g1StringDedup.hpp"
44 #include "gc_implementation/g1/g1YCTypes.hpp"
45 #include "gc_implementation/g1/heapRegion.inline.hpp"
46 #include "gc_implementation/g1/heapRegionRemSet.hpp"
47 #include "gc_implementation/g1/heapRegionSeq.inline.hpp"
48 #include "gc_implementation/g1/vm_operations_g1.hpp"
49 #include "gc_implementation/shared/gcHeapSummary.hpp"
50 #include "gc_implementation/shared/gcTimer.hpp"
51 #include "gc_implementation/shared/gcTrace.hpp"
52 #include "gc_implementation/shared/gcTraceTime.hpp"
53 #include "gc_implementation/shared/isGCActiveMark.hpp"
54 #include "memory/gcLocker.inline.hpp"
55 #include "memory/generationSpec.hpp"
56 #include "memory/iterator.hpp"
57 #include "memory/referenceProcessor.hpp"
58 #include "oops/oop.inline.hpp"
59 #include "oops/oop.pcgc.inline.hpp"
60 #include "runtime/vmThread.hpp"
61 #include "utilities/globalDefinitions.hpp"
62 #include "utilities/ticks.hpp"
63
64 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;
65
66 // turn it on so that the contents of the young list (scan-only /
67 // to-be-collected) are printed at "strategic" points before / during
68 // / after the collection --- this is useful for debugging
69 #define YOUNG_LIST_VERBOSE 0
70 // CURRENT STATUS
71 // This file is under construction. Search for "FIXME".
72
73 // INVARIANTS/NOTES
74 //
75 // All allocation activity covered by the G1CollectedHeap interface is
76 // serialized by acquiring the HeapLock. This happens in mem_allocate
77 // and allocate_new_tlab, which are the "entry" points to the
78 // allocation code from the rest of the JVM. (Note that this does not
79 // apply to TLAB allocation, which is not part of this interface: it
80 // is done by clients of this interface.)
81
82 // Notes on implementation of parallelism in different tasks.
83 //
84 // G1ParVerifyTask uses heap_region_par_iterate_chunked() for parallelism.
85 // The number of GC workers is passed to heap_region_par_iterate_chunked().
86 // It does use run_task() which sets _n_workers in the task.
87 // G1ParTask executes g1_process_strong_roots() ->
88 // SharedHeap::process_strong_roots() which calls eventually to
89 // CardTableModRefBS::par_non_clean_card_iterate_work() which uses
90 // SequentialSubTasksDone. SharedHeap::process_strong_roots() also
91 // directly uses SubTasksDone (_process_strong_tasks field in SharedHeap).
92 //
93
94 // Local to this file.
95
96 class RefineCardTableEntryClosure: public CardTableEntryClosure {
97 bool _concurrent;
98 public:
99 RefineCardTableEntryClosure() : _concurrent(true) { }
100
101 bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
102 bool oops_into_cset = G1CollectedHeap::heap()->g1_rem_set()->refine_card(card_ptr, worker_i, false);
103 // This path is executed by the concurrent refine or mutator threads,
104 // concurrently, and so we do not care if card_ptr contains references
105 // that point into the collection set.
106 assert(!oops_into_cset, "should be");
107
108 if (_concurrent && SuspendibleThreadSet::should_yield()) {
109 // Caller will actually yield.
110 return false;
111 }
112 // Otherwise, we finished successfully; return true.
113 return true;
114 }
115
116 void set_concurrent(bool b) { _concurrent = b; }
117 };
118
119
120 class ClearLoggedCardTableEntryClosure: public CardTableEntryClosure {
121 size_t _num_processed;
122 CardTableModRefBS* _ctbs;
123 int _histo[256];
124
125 public:
126 ClearLoggedCardTableEntryClosure() :
127 _num_processed(0), _ctbs(G1CollectedHeap::heap()->g1_barrier_set())
128 {
129 for (int i = 0; i < 256; i++) _histo[i] = 0;
130 }
131
132 bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
133 unsigned char* ujb = (unsigned char*)card_ptr;
134 int ind = (int)(*ujb);
135 _histo[ind]++;
136
137 *card_ptr = (jbyte)CardTableModRefBS::clean_card_val();
138 _num_processed++;
139
140 return true;
141 }
142
143 size_t num_processed() { return _num_processed; }
144
145 void print_histo() {
146 gclog_or_tty->print_cr("Card table value histogram:");
147 for (int i = 0; i < 256; i++) {
148 if (_histo[i] != 0) {
149 gclog_or_tty->print_cr(" %d: %d", i, _histo[i]);
150 }
151 }
152 }
153 };
154
155 class RedirtyLoggedCardTableEntryClosure : public CardTableEntryClosure {
156 private:
157 size_t _num_processed;
158
159 public:
160 RedirtyLoggedCardTableEntryClosure() : CardTableEntryClosure(), _num_processed(0) { }
161
162 bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
163 *card_ptr = CardTableModRefBS::dirty_card_val();
164 _num_processed++;
165 return true;
166 }
167
168 size_t num_processed() const { return _num_processed; }
169 };
170
171 YoungList::YoungList(G1CollectedHeap* g1h) :
172 _g1h(g1h), _head(NULL), _length(0), _last_sampled_rs_lengths(0),
173 _survivor_head(NULL), _survivor_tail(NULL), _survivor_length(0) {
174 guarantee(check_list_empty(false), "just making sure...");
175 }
176
177 void YoungList::push_region(HeapRegion *hr) {
178 assert(!hr->is_young(), "should not already be young");
179 assert(hr->get_next_young_region() == NULL, "cause it should!");
180
181 hr->set_next_young_region(_head);
182 _head = hr;
183
184 _g1h->g1_policy()->set_region_eden(hr, (int) _length);
185 ++_length;
186 }
187
188 void YoungList::add_survivor_region(HeapRegion* hr) {
189 assert(hr->is_survivor(), "should be flagged as survivor region");
190 assert(hr->get_next_young_region() == NULL, "cause it should!");
191
192 hr->set_next_young_region(_survivor_head);
193 if (_survivor_head == NULL) {
194 _survivor_tail = hr;
195 }
196 _survivor_head = hr;
197 ++_survivor_length;
198 }
199
200 void YoungList::empty_list(HeapRegion* list) {
201 while (list != NULL) {
202 HeapRegion* next = list->get_next_young_region();
203 list->set_next_young_region(NULL);
204 list->uninstall_surv_rate_group();
205 list->set_not_young();
206 list = next;
207 }
208 }
209
210 void YoungList::empty_list() {
211 assert(check_list_well_formed(), "young list should be well formed");
212
213 empty_list(_head);
214 _head = NULL;
215 _length = 0;
216
217 empty_list(_survivor_head);
218 _survivor_head = NULL;
219 _survivor_tail = NULL;
220 _survivor_length = 0;
221
222 _last_sampled_rs_lengths = 0;
223
224 assert(check_list_empty(false), "just making sure...");
225 }
226
227 bool YoungList::check_list_well_formed() {
228 bool ret = true;
229
230 uint length = 0;
231 HeapRegion* curr = _head;
232 HeapRegion* last = NULL;
233 while (curr != NULL) {
234 if (!curr->is_young()) {
235 gclog_or_tty->print_cr("### YOUNG REGION "PTR_FORMAT"-"PTR_FORMAT" "
236 "incorrectly tagged (y: %d, surv: %d)",
237 curr->bottom(), curr->end(),
238 curr->is_young(), curr->is_survivor());
239 ret = false;
240 }
241 ++length;
242 last = curr;
243 curr = curr->get_next_young_region();
244 }
245 ret = ret && (length == _length);
246
247 if (!ret) {
248 gclog_or_tty->print_cr("### YOUNG LIST seems not well formed!");
249 gclog_or_tty->print_cr("### list has %u entries, _length is %u",
250 length, _length);
251 }
252
253 return ret;
254 }
255
256 bool YoungList::check_list_empty(bool check_sample) {
257 bool ret = true;
258
259 if (_length != 0) {
260 gclog_or_tty->print_cr("### YOUNG LIST should have 0 length, not %u",
261 _length);
262 ret = false;
263 }
264 if (check_sample && _last_sampled_rs_lengths != 0) {
265 gclog_or_tty->print_cr("### YOUNG LIST has non-zero last sampled RS lengths");
266 ret = false;
267 }
268 if (_head != NULL) {
269 gclog_or_tty->print_cr("### YOUNG LIST does not have a NULL head");
270 ret = false;
271 }
272 if (!ret) {
273 gclog_or_tty->print_cr("### YOUNG LIST does not seem empty");
274 }
275
276 return ret;
277 }
278
279 void
280 YoungList::rs_length_sampling_init() {
281 _sampled_rs_lengths = 0;
282 _curr = _head;
283 }
284
285 bool
286 YoungList::rs_length_sampling_more() {
287 return _curr != NULL;
288 }
289
290 void
291 YoungList::rs_length_sampling_next() {
292 assert( _curr != NULL, "invariant" );
293 size_t rs_length = _curr->rem_set()->occupied();
294
295 _sampled_rs_lengths += rs_length;
296
297 // The current region may not yet have been added to the
298 // incremental collection set (it gets added when it is
299 // retired as the current allocation region).
300 if (_curr->in_collection_set()) {
301 // Update the collection set policy information for this region
302 _g1h->g1_policy()->update_incremental_cset_info(_curr, rs_length);
303 }
304
305 _curr = _curr->get_next_young_region();
306 if (_curr == NULL) {
307 _last_sampled_rs_lengths = _sampled_rs_lengths;
308 // gclog_or_tty->print_cr("last sampled RS lengths = %d", _last_sampled_rs_lengths);
309 }
310 }
311
312 void
313 YoungList::reset_auxilary_lists() {
314 guarantee( is_empty(), "young list should be empty" );
315 assert(check_list_well_formed(), "young list should be well formed");
316
317 // Add survivor regions to SurvRateGroup.
318 _g1h->g1_policy()->note_start_adding_survivor_regions();
319 _g1h->g1_policy()->finished_recalculating_age_indexes(true /* is_survivors */);
320
321 int young_index_in_cset = 0;
322 for (HeapRegion* curr = _survivor_head;
323 curr != NULL;
324 curr = curr->get_next_young_region()) {
325 _g1h->g1_policy()->set_region_survivor(curr, young_index_in_cset);
326
327 // The region is a non-empty survivor so let's add it to
328 // the incremental collection set for the next evacuation
329 // pause.
330 _g1h->g1_policy()->add_region_to_incremental_cset_rhs(curr);
331 young_index_in_cset += 1;
332 }
333 assert((uint) young_index_in_cset == _survivor_length, "post-condition");
334 _g1h->g1_policy()->note_stop_adding_survivor_regions();
335
336 _head = _survivor_head;
337 _length = _survivor_length;
338 if (_survivor_head != NULL) {
339 assert(_survivor_tail != NULL, "cause it shouldn't be");
340 assert(_survivor_length > 0, "invariant");
341 _survivor_tail->set_next_young_region(NULL);
342 }
343
344 // Don't clear the survivor list handles until the start of
345 // the next evacuation pause - we need it in order to re-tag
346 // the survivor regions from this evacuation pause as 'young'
347 // at the start of the next.
348
349 _g1h->g1_policy()->finished_recalculating_age_indexes(false /* is_survivors */);
350
351 assert(check_list_well_formed(), "young list should be well formed");
352 }
353
354 void YoungList::print() {
355 HeapRegion* lists[] = {_head, _survivor_head};
356 const char* names[] = {"YOUNG", "SURVIVOR"};
357
358 for (unsigned int list = 0; list < ARRAY_SIZE(lists); ++list) {
359 gclog_or_tty->print_cr("%s LIST CONTENTS", names[list]);
360 HeapRegion *curr = lists[list];
361 if (curr == NULL)
362 gclog_or_tty->print_cr(" empty");
363 while (curr != NULL) {
364 gclog_or_tty->print_cr(" "HR_FORMAT", P: "PTR_FORMAT "N: "PTR_FORMAT", age: %4d",
365 HR_FORMAT_PARAMS(curr),
366 curr->prev_top_at_mark_start(),
367 curr->next_top_at_mark_start(),
368 curr->age_in_surv_rate_group_cond());
369 curr = curr->get_next_young_region();
370 }
371 }
372
373 gclog_or_tty->print_cr("");
374 }
375
376 void G1CollectedHeap::push_dirty_cards_region(HeapRegion* hr)
377 {
378 // Claim the right to put the region on the dirty cards region list
379 // by installing a self pointer.
380 HeapRegion* next = hr->get_next_dirty_cards_region();
381 if (next == NULL) {
382 HeapRegion* res = (HeapRegion*)
383 Atomic::cmpxchg_ptr(hr, hr->next_dirty_cards_region_addr(),
384 NULL);
385 if (res == NULL) {
386 HeapRegion* head;
387 do {
388 // Put the region to the dirty cards region list.
389 head = _dirty_cards_region_list;
390 next = (HeapRegion*)
391 Atomic::cmpxchg_ptr(hr, &_dirty_cards_region_list, head);
392 if (next == head) {
393 assert(hr->get_next_dirty_cards_region() == hr,
394 "hr->get_next_dirty_cards_region() != hr");
395 if (next == NULL) {
396 // The last region in the list points to itself.
397 hr->set_next_dirty_cards_region(hr);
398 } else {
399 hr->set_next_dirty_cards_region(next);
400 }
401 }
402 } while (next != head);
403 }
404 }
405 }
406
407 HeapRegion* G1CollectedHeap::pop_dirty_cards_region()
408 {
409 HeapRegion* head;
410 HeapRegion* hr;
411 do {
412 head = _dirty_cards_region_list;
413 if (head == NULL) {
414 return NULL;
415 }
416 HeapRegion* new_head = head->get_next_dirty_cards_region();
417 if (head == new_head) {
418 // The last region.
419 new_head = NULL;
420 }
421 hr = (HeapRegion*)Atomic::cmpxchg_ptr(new_head, &_dirty_cards_region_list,
422 head);
423 } while (hr != head);
424 assert(hr != NULL, "invariant");
425 hr->set_next_dirty_cards_region(NULL);
426 return hr;
427 }
428
429 void G1CollectedHeap::stop_conc_gc_threads() {
430 _cg1r->stop();
431 _cmThread->stop();
432 if (G1StringDedup::is_enabled()) {
433 G1StringDedup::stop();
434 }
435 }
436
437 #ifdef ASSERT
438 // A region is added to the collection set as it is retired
439 // so an address p can point to a region which will be in the
440 // collection set but has not yet been retired. This method
441 // therefore is only accurate during a GC pause after all
442 // regions have been retired. It is used for debugging
443 // to check if an nmethod has references to objects that can
444 // be move during a partial collection. Though it can be
445 // inaccurate, it is sufficient for G1 because the conservative
446 // implementation of is_scavengable() for G1 will indicate that
447 // all nmethods must be scanned during a partial collection.
448 bool G1CollectedHeap::is_in_partial_collection(const void* p) {
449 if (p == NULL) {
450 return false;
451 }
452 return heap_region_containing(p)->in_collection_set();
453 }
454 #endif
455
456 // Returns true if the reference points to an object that
457 // can move in an incremental collection.
458 bool G1CollectedHeap::is_scavengable(const void* p) {
459 HeapRegion* hr = heap_region_containing(p);
460 return !hr->isHumongous();
461 }
462
463 void G1CollectedHeap::check_ct_logs_at_safepoint() {
464 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
465 CardTableModRefBS* ct_bs = g1_barrier_set();
466
467 // Count the dirty cards at the start.
468 CountNonCleanMemRegionClosure count1(this);
469 ct_bs->mod_card_iterate(&count1);
470 int orig_count = count1.n();
471
472 // First clear the logged cards.
473 ClearLoggedCardTableEntryClosure clear;
474 dcqs.apply_closure_to_all_completed_buffers(&clear);
475 dcqs.iterate_closure_all_threads(&clear, false);
476 clear.print_histo();
477
478 // Now ensure that there's no dirty cards.
479 CountNonCleanMemRegionClosure count2(this);
480 ct_bs->mod_card_iterate(&count2);
481 if (count2.n() != 0) {
482 gclog_or_tty->print_cr("Card table has %d entries; %d originally",
483 count2.n(), orig_count);
484 }
485 guarantee(count2.n() == 0, "Card table should be clean.");
486
487 RedirtyLoggedCardTableEntryClosure redirty;
488 dcqs.apply_closure_to_all_completed_buffers(&redirty);
489 dcqs.iterate_closure_all_threads(&redirty, false);
490 gclog_or_tty->print_cr("Log entries = %d, dirty cards = %d.",
491 clear.num_processed(), orig_count);
492 guarantee(redirty.num_processed() == clear.num_processed(),
493 err_msg("Redirtied "SIZE_FORMAT" cards, bug cleared "SIZE_FORMAT,
494 redirty.num_processed(), clear.num_processed()));
495
496 CountNonCleanMemRegionClosure count3(this);
497 ct_bs->mod_card_iterate(&count3);
498 if (count3.n() != orig_count) {
499 gclog_or_tty->print_cr("Should have restored them all: orig = %d, final = %d.",
500 orig_count, count3.n());
501 guarantee(count3.n() >= orig_count, "Should have restored them all.");
502 }
503 }
504
505 // Private class members.
506
507 G1CollectedHeap* G1CollectedHeap::_g1h;
508
509 // Private methods.
510
511 HeapRegion*
512 G1CollectedHeap::new_region_try_secondary_free_list(bool is_old) {
513 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
514 while (!_secondary_free_list.is_empty() || free_regions_coming()) {
515 if (!_secondary_free_list.is_empty()) {
516 if (G1ConcRegionFreeingVerbose) {
517 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
518 "secondary_free_list has %u entries",
519 _secondary_free_list.length());
520 }
521 // It looks as if there are free regions available on the
522 // secondary_free_list. Let's move them to the free_list and try
523 // again to allocate from it.
524 append_secondary_free_list();
525
526 assert(!_free_list.is_empty(), "if the secondary_free_list was not "
527 "empty we should have moved at least one entry to the free_list");
528 HeapRegion* res = _free_list.remove_region(is_old);
529 if (G1ConcRegionFreeingVerbose) {
530 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
531 "allocated "HR_FORMAT" from secondary_free_list",
532 HR_FORMAT_PARAMS(res));
533 }
534 return res;
535 }
536
537 // Wait here until we get notified either when (a) there are no
538 // more free regions coming or (b) some regions have been moved on
539 // the secondary_free_list.
540 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
541 }
542
543 if (G1ConcRegionFreeingVerbose) {
544 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
545 "could not allocate from secondary_free_list");
546 }
547 return NULL;
548 }
549
550 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) {
551 assert(!isHumongous(word_size) || word_size <= HeapRegion::GrainWords,
552 "the only time we use this to allocate a humongous region is "
553 "when we are allocating a single humongous region");
554
555 HeapRegion* res;
556 if (G1StressConcRegionFreeing) {
557 if (!_secondary_free_list.is_empty()) {
558 if (G1ConcRegionFreeingVerbose) {
559 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
560 "forced to look at the secondary_free_list");
561 }
562 res = new_region_try_secondary_free_list(is_old);
563 if (res != NULL) {
564 return res;
565 }
566 }
567 }
568
569 res = _free_list.remove_region(is_old);
570
571 if (res == NULL) {
572 if (G1ConcRegionFreeingVerbose) {
573 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
574 "res == NULL, trying the secondary_free_list");
575 }
576 res = new_region_try_secondary_free_list(is_old);
577 }
578 if (res == NULL && do_expand && _expand_heap_after_alloc_failure) {
579 // Currently, only attempts to allocate GC alloc regions set
580 // do_expand to true. So, we should only reach here during a
581 // safepoint. If this assumption changes we might have to
582 // reconsider the use of _expand_heap_after_alloc_failure.
583 assert(SafepointSynchronize::is_at_safepoint(), "invariant");
584
585 ergo_verbose1(ErgoHeapSizing,
586 "attempt heap expansion",
587 ergo_format_reason("region allocation request failed")
588 ergo_format_byte("allocation request"),
589 word_size * HeapWordSize);
590 if (expand(word_size * HeapWordSize)) {
591 // Given that expand() succeeded in expanding the heap, and we
592 // always expand the heap by an amount aligned to the heap
593 // region size, the free list should in theory not be empty.
594 // In either case remove_region() will check for NULL.
595 res = _free_list.remove_region(is_old);
596 } else {
597 _expand_heap_after_alloc_failure = false;
598 }
599 }
600 return res;
601 }
602
603 uint G1CollectedHeap::humongous_obj_allocate_find_first(uint num_regions,
604 size_t word_size) {
605 assert(isHumongous(word_size), "word_size should be humongous");
606 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
607
608 uint first = G1_NULL_HRS_INDEX;
609 if (num_regions == 1) {
610 // Only one region to allocate, no need to go through the slower
611 // path. The caller will attempt the expansion if this fails, so
612 // let's not try to expand here too.
613 HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */);
614 if (hr != NULL) {
615 first = hr->hrs_index();
616 } else {
617 first = G1_NULL_HRS_INDEX;
618 }
619 } else {
620 // We can't allocate humongous regions while cleanupComplete() is
621 // running, since some of the regions we find to be empty might not
622 // yet be added to the free list and it is not straightforward to
623 // know which list they are on so that we can remove them. Note
624 // that we only need to do this if we need to allocate more than
625 // one region to satisfy the current humongous allocation
626 // request. If we are only allocating one region we use the common
627 // region allocation code (see above).
628 wait_while_free_regions_coming();
629 append_secondary_free_list_if_not_empty_with_lock();
630
631 if (free_regions() >= num_regions) {
632 first = _hrs.find_contiguous(num_regions);
633 if (first != G1_NULL_HRS_INDEX) {
634 for (uint i = first; i < first + num_regions; ++i) {
635 HeapRegion* hr = region_at(i);
636 assert(hr->is_empty(), "sanity");
637 assert(is_on_master_free_list(hr), "sanity");
638 hr->set_pending_removal(true);
639 }
640 _free_list.remove_all_pending(num_regions);
641 }
642 }
643 }
644 return first;
645 }
646
647 HeapWord*
648 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first,
649 uint num_regions,
650 size_t word_size) {
651 assert(first != G1_NULL_HRS_INDEX, "pre-condition");
652 assert(isHumongous(word_size), "word_size should be humongous");
653 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
654
655 // Index of last region in the series + 1.
656 uint last = first + num_regions;
657
658 // We need to initialize the region(s) we just discovered. This is
659 // a bit tricky given that it can happen concurrently with
660 // refinement threads refining cards on these regions and
661 // potentially wanting to refine the BOT as they are scanning
662 // those cards (this can happen shortly after a cleanup; see CR
663 // 6991377). So we have to set up the region(s) carefully and in
664 // a specific order.
665
666 // The word size sum of all the regions we will allocate.
667 size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords;
668 assert(word_size <= word_size_sum, "sanity");
669
670 // This will be the "starts humongous" region.
671 HeapRegion* first_hr = region_at(first);
672 // The header of the new object will be placed at the bottom of
673 // the first region.
674 HeapWord* new_obj = first_hr->bottom();
675 // This will be the new end of the first region in the series that
676 // should also match the end of the last region in the series.
677 HeapWord* new_end = new_obj + word_size_sum;
678 // This will be the new top of the first region that will reflect
679 // this allocation.
680 HeapWord* new_top = new_obj + word_size;
681
682 // First, we need to zero the header of the space that we will be
683 // allocating. When we update top further down, some refinement
684 // threads might try to scan the region. By zeroing the header we
685 // ensure that any thread that will try to scan the region will
686 // come across the zero klass word and bail out.
687 //
688 // NOTE: It would not have been correct to have used
689 // CollectedHeap::fill_with_object() and make the space look like
690 // an int array. The thread that is doing the allocation will
691 // later update the object header to a potentially different array
692 // type and, for a very short period of time, the klass and length
693 // fields will be inconsistent. This could cause a refinement
694 // thread to calculate the object size incorrectly.
695 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
696
697 // We will set up the first region as "starts humongous". This
698 // will also update the BOT covering all the regions to reflect
699 // that there is a single object that starts at the bottom of the
700 // first region.
701 first_hr->set_startsHumongous(new_top, new_end);
702
703 // Then, if there are any, we will set up the "continues
704 // humongous" regions.
705 HeapRegion* hr = NULL;
706 for (uint i = first + 1; i < last; ++i) {
707 hr = region_at(i);
708 hr->set_continuesHumongous(first_hr);
709 }
710 // If we have "continues humongous" regions (hr != NULL), then the
711 // end of the last one should match new_end.
712 assert(hr == NULL || hr->end() == new_end, "sanity");
713
714 // Up to this point no concurrent thread would have been able to
715 // do any scanning on any region in this series. All the top
716 // fields still point to bottom, so the intersection between
717 // [bottom,top] and [card_start,card_end] will be empty. Before we
718 // update the top fields, we'll do a storestore to make sure that
719 // no thread sees the update to top before the zeroing of the
720 // object header and the BOT initialization.
721 OrderAccess::storestore();
722
723 // Now that the BOT and the object header have been initialized,
724 // we can update top of the "starts humongous" region.
725 assert(first_hr->bottom() < new_top && new_top <= first_hr->end(),
726 "new_top should be in this region");
727 first_hr->set_top(new_top);
728 if (_hr_printer.is_active()) {
729 HeapWord* bottom = first_hr->bottom();
730 HeapWord* end = first_hr->orig_end();
731 if ((first + 1) == last) {
732 // the series has a single humongous region
733 _hr_printer.alloc(G1HRPrinter::SingleHumongous, first_hr, new_top);
734 } else {
735 // the series has more than one humongous regions
736 _hr_printer.alloc(G1HRPrinter::StartsHumongous, first_hr, end);
737 }
738 }
739
740 // Now, we will update the top fields of the "continues humongous"
741 // regions. The reason we need to do this is that, otherwise,
742 // these regions would look empty and this will confuse parts of
743 // G1. For example, the code that looks for a consecutive number
744 // of empty regions will consider them empty and try to
745 // re-allocate them. We can extend is_empty() to also include
746 // !continuesHumongous(), but it is easier to just update the top
747 // fields here. The way we set top for all regions (i.e., top ==
748 // end for all regions but the last one, top == new_top for the
749 // last one) is actually used when we will free up the humongous
750 // region in free_humongous_region().
751 hr = NULL;
752 for (uint i = first + 1; i < last; ++i) {
753 hr = region_at(i);
754 if ((i + 1) == last) {
755 // last continues humongous region
756 assert(hr->bottom() < new_top && new_top <= hr->end(),
757 "new_top should fall on this region");
758 hr->set_top(new_top);
759 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, new_top);
760 } else {
761 // not last one
762 assert(new_top > hr->end(), "new_top should be above this region");
763 hr->set_top(hr->end());
764 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, hr->end());
765 }
766 }
767 // If we have continues humongous regions (hr != NULL), then the
768 // end of the last one should match new_end and its top should
769 // match new_top.
770 assert(hr == NULL ||
771 (hr->end() == new_end && hr->top() == new_top), "sanity");
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 pre_full_gc_dump(gc_timer);
1331
1332 COMPILER2_PRESENT(DerivedPointerTable::clear());
1333
1334 // Disable discovery and empty the discovered lists
1335 // for the CM ref processor.
1336 ref_processor_cm()->disable_discovery();
1337 ref_processor_cm()->abandon_partial_discovery();
1338 ref_processor_cm()->verify_no_references_recorded();
1339
1340 // Abandon current iterations of concurrent marking and concurrent
1341 // refinement, if any are in progress. We have to do this before
1342 // wait_until_scan_finished() below.
1343 concurrent_mark()->abort();
1344
1345 // Make sure we'll choose a new allocation region afterwards.
1346 release_mutator_alloc_region();
1347 abandon_gc_alloc_regions();
1348 g1_rem_set()->cleanupHRRS();
1349
1350 // We should call this after we retire any currently active alloc
1351 // regions so that all the ALLOC / RETIRE events are generated
1352 // before the start GC event.
1353 _hr_printer.start_gc(true /* full */, (size_t) total_collections());
1354
1355 // We may have added regions to the current incremental collection
1356 // set between the last GC or pause and now. We need to clear the
1357 // incremental collection set and then start rebuilding it afresh
1358 // after this full GC.
1359 abandon_collection_set(g1_policy()->inc_cset_head());
1360 g1_policy()->clear_incremental_cset();
1361 g1_policy()->stop_incremental_cset_building();
1362
1363 tear_down_region_sets(false /* free_list_only */);
1364 g1_policy()->set_gcs_are_young(true);
1365
1366 // See the comments in g1CollectedHeap.hpp and
1367 // G1CollectedHeap::ref_processing_init() about
1368 // how reference processing currently works in G1.
1369
1370 // Temporarily make discovery by the STW ref processor single threaded (non-MT).
1371 ReferenceProcessorMTDiscoveryMutator stw_rp_disc_ser(ref_processor_stw(), false);
1372
1373 // Temporarily clear the STW ref processor's _is_alive_non_header field.
1374 ReferenceProcessorIsAliveMutator stw_rp_is_alive_null(ref_processor_stw(), NULL);
1375
1376 ref_processor_stw()->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/);
1377 ref_processor_stw()->setup_policy(do_clear_all_soft_refs);
1378
1379 // Do collection work
1380 {
1381 HandleMark hm; // Discard invalid handles created during gc
1382 G1MarkSweep::invoke_at_safepoint(ref_processor_stw(), do_clear_all_soft_refs);
1383 }
1384
1385 assert(free_regions() == 0, "we should not have added any free regions");
1386 rebuild_region_sets(false /* free_list_only */);
1387
1388 // Enqueue any discovered reference objects that have
1389 // not been removed from the discovered lists.
1390 ref_processor_stw()->enqueue_discovered_references();
1391
1392 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
1393
1394 MemoryService::track_memory_usage();
1395
1396 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
1397 ref_processor_stw()->verify_no_references_recorded();
1398
1399 // Delete metaspaces for unloaded class loaders and clean up loader_data graph
1400 ClassLoaderDataGraph::purge();
1401 MetaspaceAux::verify_metrics();
1402
1403 // Note: since we've just done a full GC, concurrent
1404 // marking is no longer active. Therefore we need not
1405 // re-enable reference discovery for the CM ref processor.
1406 // That will be done at the start of the next marking cycle.
1407 assert(!ref_processor_cm()->discovery_enabled(), "Postcondition");
1408 ref_processor_cm()->verify_no_references_recorded();
1409
1410 reset_gc_time_stamp();
1411 // Since everything potentially moved, we will clear all remembered
1412 // sets, and clear all cards. Later we will rebuild remembered
1413 // sets. We will also reset the GC time stamps of the regions.
1414 clear_rsets_post_compaction();
1415 check_gc_time_stamps();
1416
1417 // Resize the heap if necessary.
1418 resize_if_necessary_after_full_collection(explicit_gc ? 0 : word_size);
1419
1420 if (_hr_printer.is_active()) {
1421 // We should do this after we potentially resize the heap so
1422 // that all the COMMIT / UNCOMMIT events are generated before
1423 // the end GC event.
1424
1425 print_hrs_post_compaction();
1426 _hr_printer.end_gc(true /* full */, (size_t) total_collections());
1427 }
1428
1429 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
1430 if (hot_card_cache->use_cache()) {
1431 hot_card_cache->reset_card_counts();
1432 hot_card_cache->reset_hot_cache();
1433 }
1434
1435 // Rebuild remembered sets of all regions.
1436 if (G1CollectedHeap::use_parallel_gc_threads()) {
1437 uint n_workers =
1438 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
1439 workers()->active_workers(),
1440 Threads::number_of_non_daemon_threads());
1441 assert(UseDynamicNumberOfGCThreads ||
1442 n_workers == workers()->total_workers(),
1443 "If not dynamic should be using all the workers");
1444 workers()->set_active_workers(n_workers);
1445 // Set parallel threads in the heap (_n_par_threads) only
1446 // before a parallel phase and always reset it to 0 after
1447 // the phase so that the number of parallel threads does
1448 // no get carried forward to a serial phase where there
1449 // may be code that is "possibly_parallel".
1450 set_par_threads(n_workers);
1451
1452 ParRebuildRSTask rebuild_rs_task(this);
1453 assert(check_heap_region_claim_values(
1454 HeapRegion::InitialClaimValue), "sanity check");
1455 assert(UseDynamicNumberOfGCThreads ||
1456 workers()->active_workers() == workers()->total_workers(),
1457 "Unless dynamic should use total workers");
1458 // Use the most recent number of active workers
1459 assert(workers()->active_workers() > 0,
1460 "Active workers not properly set");
1461 set_par_threads(workers()->active_workers());
1462 workers()->run_task(&rebuild_rs_task);
1463 set_par_threads(0);
1464 assert(check_heap_region_claim_values(
1465 HeapRegion::RebuildRSClaimValue), "sanity check");
1466 reset_heap_region_claim_values();
1467 } else {
1468 RebuildRSOutOfRegionClosure rebuild_rs(this);
1469 heap_region_iterate(&rebuild_rs);
1470 }
1471
1472 // Rebuild the strong code root lists for each region
1473 rebuild_strong_code_roots();
1474
1475 if (true) { // FIXME
1476 MetaspaceGC::compute_new_size();
1477 }
1478
1479 #ifdef TRACESPINNING
1480 ParallelTaskTerminator::print_termination_counts();
1481 #endif
1482
1483 // Discard all rset updates
1484 JavaThread::dirty_card_queue_set().abandon_logs();
1485 assert(!G1DeferredRSUpdate
1486 || (G1DeferredRSUpdate &&
1487 (dirty_card_queue_set().completed_buffers_num() == 0)), "Should not be any");
1488
1489 _young_list->reset_sampled_info();
1490 // At this point there should be no regions in the
1491 // entire heap tagged as young.
1492 assert(check_young_list_empty(true /* check_heap */),
1493 "young list should be empty at this point");
1494
1495 // Update the number of full collections that have been completed.
1496 increment_old_marking_cycles_completed(false /* concurrent */);
1497
1498 _hrs.verify_optional();
1499 verify_region_sets_optional();
1500
1501 verify_after_gc();
1502
1503 // Start a new incremental collection set for the next pause
1504 assert(g1_policy()->collection_set() == NULL, "must be");
1505 g1_policy()->start_incremental_cset_building();
1506
1507 clear_cset_fast_test();
1508
1509 init_mutator_alloc_region();
1510
1511 double end = os::elapsedTime();
1512 g1_policy()->record_full_collection_end();
1513
1514 if (G1Log::fine()) {
1515 g1_policy()->print_heap_transition();
1516 }
1517
1518 // We must call G1MonitoringSupport::update_sizes() in the same scoping level
1519 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
1520 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
1521 // before any GC notifications are raised.
1522 g1mm()->update_sizes();
1523
1524 gc_epilogue(true);
1525 }
1526
1527 if (G1Log::finer()) {
1528 g1_policy()->print_detailed_heap_transition(true /* full */);
1529 }
1530
1531 print_heap_after_gc();
1532 trace_heap_after_gc(gc_tracer);
1533
1534 post_full_gc_dump(gc_timer);
1535
1536 gc_timer->register_gc_end();
1537 gc_tracer->report_gc_end(gc_timer->gc_end(), gc_timer->time_partitions());
1538 }
1539
1540 return true;
1541 }
1542
1543 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
1544 // do_collection() will return whether it succeeded in performing
1545 // the GC. Currently, there is no facility on the
1546 // do_full_collection() API to notify the caller than the collection
1547 // did not succeed (e.g., because it was locked out by the GC
1548 // locker). So, right now, we'll ignore the return value.
1549 bool dummy = do_collection(true, /* explicit_gc */
1550 clear_all_soft_refs,
1551 0 /* word_size */);
1552 }
1553
1554 // This code is mostly copied from TenuredGeneration.
1555 void
1556 G1CollectedHeap::
1557 resize_if_necessary_after_full_collection(size_t word_size) {
1558 // Include the current allocation, if any, and bytes that will be
1559 // pre-allocated to support collections, as "used".
1560 const size_t used_after_gc = used();
1561 const size_t capacity_after_gc = capacity();
1562 const size_t free_after_gc = capacity_after_gc - used_after_gc;
1563
1564 // This is enforced in arguments.cpp.
1565 assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
1566 "otherwise the code below doesn't make sense");
1567
1568 // We don't have floating point command-line arguments
1569 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
1570 const double maximum_used_percentage = 1.0 - minimum_free_percentage;
1571 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
1572 const double minimum_used_percentage = 1.0 - maximum_free_percentage;
1573
1574 const size_t min_heap_size = collector_policy()->min_heap_byte_size();
1575 const size_t max_heap_size = collector_policy()->max_heap_byte_size();
1576
1577 // We have to be careful here as these two calculations can overflow
1578 // 32-bit size_t's.
1579 double used_after_gc_d = (double) used_after_gc;
1580 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
1581 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
1582
1583 // Let's make sure that they are both under the max heap size, which
1584 // by default will make them fit into a size_t.
1585 double desired_capacity_upper_bound = (double) max_heap_size;
1586 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
1587 desired_capacity_upper_bound);
1588 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
1589 desired_capacity_upper_bound);
1590
1591 // We can now safely turn them into size_t's.
1592 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
1593 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
1594
1595 // This assert only makes sense here, before we adjust them
1596 // with respect to the min and max heap size.
1597 assert(minimum_desired_capacity <= maximum_desired_capacity,
1598 err_msg("minimum_desired_capacity = "SIZE_FORMAT", "
1599 "maximum_desired_capacity = "SIZE_FORMAT,
1600 minimum_desired_capacity, maximum_desired_capacity));
1601
1602 // Should not be greater than the heap max size. No need to adjust
1603 // it with respect to the heap min size as it's a lower bound (i.e.,
1604 // we'll try to make the capacity larger than it, not smaller).
1605 minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size);
1606 // Should not be less than the heap min size. No need to adjust it
1607 // with respect to the heap max size as it's an upper bound (i.e.,
1608 // we'll try to make the capacity smaller than it, not greater).
1609 maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size);
1610
1611 if (capacity_after_gc < minimum_desired_capacity) {
1612 // Don't expand unless it's significant
1613 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
1614 ergo_verbose4(ErgoHeapSizing,
1615 "attempt heap expansion",
1616 ergo_format_reason("capacity lower than "
1617 "min desired capacity after Full GC")
1618 ergo_format_byte("capacity")
1619 ergo_format_byte("occupancy")
1620 ergo_format_byte_perc("min desired capacity"),
1621 capacity_after_gc, used_after_gc,
1622 minimum_desired_capacity, (double) MinHeapFreeRatio);
1623 expand(expand_bytes);
1624
1625 // No expansion, now see if we want to shrink
1626 } else if (capacity_after_gc > maximum_desired_capacity) {
1627 // Capacity too large, compute shrinking size
1628 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
1629 ergo_verbose4(ErgoHeapSizing,
1630 "attempt heap shrinking",
1631 ergo_format_reason("capacity higher than "
1632 "max desired capacity after Full GC")
1633 ergo_format_byte("capacity")
1634 ergo_format_byte("occupancy")
1635 ergo_format_byte_perc("max desired capacity"),
1636 capacity_after_gc, used_after_gc,
1637 maximum_desired_capacity, (double) MaxHeapFreeRatio);
1638 shrink(shrink_bytes);
1639 }
1640 }
1641
1642
1643 HeapWord*
1644 G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
1645 bool* succeeded) {
1646 assert_at_safepoint(true /* should_be_vm_thread */);
1647
1648 *succeeded = true;
1649 // Let's attempt the allocation first.
1650 HeapWord* result =
1651 attempt_allocation_at_safepoint(word_size,
1652 false /* expect_null_mutator_alloc_region */);
1653 if (result != NULL) {
1654 assert(*succeeded, "sanity");
1655 return result;
1656 }
1657
1658 // In a G1 heap, we're supposed to keep allocation from failing by
1659 // incremental pauses. Therefore, at least for now, we'll favor
1660 // expansion over collection. (This might change in the future if we can
1661 // do something smarter than full collection to satisfy a failed alloc.)
1662 result = expand_and_allocate(word_size);
1663 if (result != NULL) {
1664 assert(*succeeded, "sanity");
1665 return result;
1666 }
1667
1668 // Expansion didn't work, we'll try to do a Full GC.
1669 bool gc_succeeded = do_collection(false, /* explicit_gc */
1670 false, /* clear_all_soft_refs */
1671 word_size);
1672 if (!gc_succeeded) {
1673 *succeeded = false;
1674 return NULL;
1675 }
1676
1677 // Retry the allocation
1678 result = attempt_allocation_at_safepoint(word_size,
1679 true /* expect_null_mutator_alloc_region */);
1680 if (result != NULL) {
1681 assert(*succeeded, "sanity");
1682 return result;
1683 }
1684
1685 // Then, try a Full GC that will collect all soft references.
1686 gc_succeeded = do_collection(false, /* explicit_gc */
1687 true, /* clear_all_soft_refs */
1688 word_size);
1689 if (!gc_succeeded) {
1690 *succeeded = false;
1691 return NULL;
1692 }
1693
1694 // Retry the allocation once more
1695 result = attempt_allocation_at_safepoint(word_size,
1696 true /* expect_null_mutator_alloc_region */);
1697 if (result != NULL) {
1698 assert(*succeeded, "sanity");
1699 return result;
1700 }
1701
1702 assert(!collector_policy()->should_clear_all_soft_refs(),
1703 "Flag should have been handled and cleared prior to this point");
1704
1705 // What else? We might try synchronous finalization later. If the total
1706 // space available is large enough for the allocation, then a more
1707 // complete compaction phase than we've tried so far might be
1708 // appropriate.
1709 assert(*succeeded, "sanity");
1710 return NULL;
1711 }
1712
1713 // Attempting to expand the heap sufficiently
1714 // to support an allocation of the given "word_size". If
1715 // successful, perform the allocation and return the address of the
1716 // allocated block, or else "NULL".
1717
1718 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size) {
1719 assert_at_safepoint(true /* should_be_vm_thread */);
1720
1721 verify_region_sets_optional();
1722
1723 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
1724 ergo_verbose1(ErgoHeapSizing,
1725 "attempt heap expansion",
1726 ergo_format_reason("allocation request failed")
1727 ergo_format_byte("allocation request"),
1728 word_size * HeapWordSize);
1729 if (expand(expand_bytes)) {
1730 _hrs.verify_optional();
1731 verify_region_sets_optional();
1732 return attempt_allocation_at_safepoint(word_size,
1733 false /* expect_null_mutator_alloc_region */);
1734 }
1735 return NULL;
1736 }
1737
1738 void G1CollectedHeap::update_committed_space(HeapWord* old_end,
1739 HeapWord* new_end) {
1740 assert(old_end != new_end, "don't call this otherwise");
1741 assert((HeapWord*) _g1_storage.high() == new_end, "invariant");
1742
1743 // Update the committed mem region.
1744 _g1_committed.set_end(new_end);
1745 // Tell the card table about the update.
1746 Universe::heap()->barrier_set()->resize_covered_region(_g1_committed);
1747 // Tell the BOT about the update.
1748 _bot_shared->resize(_g1_committed.word_size());
1749 // Tell the hot card cache about the update
1750 _cg1r->hot_card_cache()->resize_card_counts(capacity());
1751 }
1752
1753 bool G1CollectedHeap::expand(size_t expand_bytes) {
1754 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
1755 aligned_expand_bytes = align_size_up(aligned_expand_bytes,
1756 HeapRegion::GrainBytes);
1757 ergo_verbose2(ErgoHeapSizing,
1758 "expand the heap",
1759 ergo_format_byte("requested expansion amount")
1760 ergo_format_byte("attempted expansion amount"),
1761 expand_bytes, aligned_expand_bytes);
1762
1763 if (_g1_storage.uncommitted_size() == 0) {
1764 ergo_verbose0(ErgoHeapSizing,
1765 "did not expand the heap",
1766 ergo_format_reason("heap already fully expanded"));
1767 return false;
1768 }
1769
1770 // First commit the memory.
1771 HeapWord* old_end = (HeapWord*) _g1_storage.high();
1772 bool successful = _g1_storage.expand_by(aligned_expand_bytes);
1773 if (successful) {
1774 // Then propagate this update to the necessary data structures.
1775 HeapWord* new_end = (HeapWord*) _g1_storage.high();
1776 update_committed_space(old_end, new_end);
1777
1778 FreeRegionList expansion_list("Local Expansion List");
1779 MemRegion mr = _hrs.expand_by(old_end, new_end, &expansion_list);
1780 assert(mr.start() == old_end, "post-condition");
1781 // mr might be a smaller region than what was requested if
1782 // expand_by() was unable to allocate the HeapRegion instances
1783 assert(mr.end() <= new_end, "post-condition");
1784
1785 size_t actual_expand_bytes = mr.byte_size();
1786 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
1787 assert(actual_expand_bytes == expansion_list.total_capacity_bytes(),
1788 "post-condition");
1789 if (actual_expand_bytes < aligned_expand_bytes) {
1790 // We could not expand _hrs to the desired size. In this case we
1791 // need to shrink the committed space accordingly.
1792 assert(mr.end() < new_end, "invariant");
1793
1794 size_t diff_bytes = aligned_expand_bytes - actual_expand_bytes;
1795 // First uncommit the memory.
1796 _g1_storage.shrink_by(diff_bytes);
1797 // Then propagate this update to the necessary data structures.
1798 update_committed_space(new_end, mr.end());
1799 }
1800 _free_list.add_as_tail(&expansion_list);
1801
1802 if (_hr_printer.is_active()) {
1803 HeapWord* curr = mr.start();
1804 while (curr < mr.end()) {
1805 HeapWord* curr_end = curr + HeapRegion::GrainWords;
1806 _hr_printer.commit(curr, curr_end);
1807 curr = curr_end;
1808 }
1809 assert(curr == mr.end(), "post-condition");
1810 }
1811 g1_policy()->record_new_heap_size(n_regions());
1812 } else {
1813 ergo_verbose0(ErgoHeapSizing,
1814 "did not expand the heap",
1815 ergo_format_reason("heap expansion operation failed"));
1816 // The expansion of the virtual storage space was unsuccessful.
1817 // Let's see if it was because we ran out of swap.
1818 if (G1ExitOnExpansionFailure &&
1819 _g1_storage.uncommitted_size() >= aligned_expand_bytes) {
1820 // We had head room...
1821 vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion");
1822 }
1823 }
1824 return successful;
1825 }
1826
1827 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
1828 size_t aligned_shrink_bytes =
1829 ReservedSpace::page_align_size_down(shrink_bytes);
1830 aligned_shrink_bytes = align_size_down(aligned_shrink_bytes,
1831 HeapRegion::GrainBytes);
1832 uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes);
1833
1834 uint num_regions_removed = _hrs.shrink_by(num_regions_to_remove);
1835 HeapWord* old_end = (HeapWord*) _g1_storage.high();
1836 size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes;
1837
1838 ergo_verbose3(ErgoHeapSizing,
1839 "shrink the heap",
1840 ergo_format_byte("requested shrinking amount")
1841 ergo_format_byte("aligned shrinking amount")
1842 ergo_format_byte("attempted shrinking amount"),
1843 shrink_bytes, aligned_shrink_bytes, shrunk_bytes);
1844 if (num_regions_removed > 0) {
1845 _g1_storage.shrink_by(shrunk_bytes);
1846 HeapWord* new_end = (HeapWord*) _g1_storage.high();
1847
1848 if (_hr_printer.is_active()) {
1849 HeapWord* curr = old_end;
1850 while (curr > new_end) {
1851 HeapWord* curr_end = curr;
1852 curr -= HeapRegion::GrainWords;
1853 _hr_printer.uncommit(curr, curr_end);
1854 }
1855 }
1856
1857 _expansion_regions += num_regions_removed;
1858 update_committed_space(old_end, new_end);
1859 HeapRegionRemSet::shrink_heap(n_regions());
1860 g1_policy()->record_new_heap_size(n_regions());
1861 } else {
1862 ergo_verbose0(ErgoHeapSizing,
1863 "did not shrink the heap",
1864 ergo_format_reason("heap shrinking operation failed"));
1865 }
1866 }
1867
1868 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1869 verify_region_sets_optional();
1870
1871 // We should only reach here at the end of a Full GC which means we
1872 // should not not be holding to any GC alloc regions. The method
1873 // below will make sure of that and do any remaining clean up.
1874 abandon_gc_alloc_regions();
1875
1876 // Instead of tearing down / rebuilding the free lists here, we
1877 // could instead use the remove_all_pending() method on free_list to
1878 // remove only the ones that we need to remove.
1879 tear_down_region_sets(true /* free_list_only */);
1880 shrink_helper(shrink_bytes);
1881 rebuild_region_sets(true /* free_list_only */);
1882
1883 _hrs.verify_optional();
1884 verify_region_sets_optional();
1885 }
1886
1887 // Public methods.
1888
1889 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away
1890 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
1891 #endif // _MSC_VER
1892
1893
1894 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* policy_) :
1895 SharedHeap(policy_),
1896 _g1_policy(policy_),
1897 _dirty_card_queue_set(false),
1898 _into_cset_dirty_card_queue_set(false),
1899 _is_alive_closure_cm(this),
1900 _is_alive_closure_stw(this),
1901 _ref_processor_cm(NULL),
1902 _ref_processor_stw(NULL),
1903 _process_strong_tasks(new SubTasksDone(G1H_PS_NumElements)),
1904 _bot_shared(NULL),
1905 _evac_failure_scan_stack(NULL),
1906 _mark_in_progress(false),
1907 _cg1r(NULL), _summary_bytes_used(0),
1908 _g1mm(NULL),
1909 _refine_cte_cl(NULL),
1910 _full_collection(false),
1911 _free_list("Master Free List", new MasterFreeRegionListMtSafeChecker()),
1912 _secondary_free_list("Secondary Free List", new SecondaryFreeRegionListMtSafeChecker()),
1913 _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()),
1914 _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()),
1915 _free_regions_coming(false),
1916 _young_list(new YoungList(this)),
1917 _gc_time_stamp(0),
1918 _retained_old_gc_alloc_region(NULL),
1919 _survivor_plab_stats(YoungPLABSize, PLABWeight),
1920 _old_plab_stats(OldPLABSize, PLABWeight),
1921 _expand_heap_after_alloc_failure(true),
1922 _surviving_young_words(NULL),
1923 _old_marking_cycles_started(0),
1924 _old_marking_cycles_completed(0),
1925 _concurrent_cycle_started(false),
1926 _in_cset_fast_test(),
1927 _dirty_cards_region_list(NULL),
1928 _worker_cset_start_region(NULL),
1929 _worker_cset_start_region_time_stamp(NULL),
1930 _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()),
1931 _gc_timer_cm(new (ResourceObj::C_HEAP, mtGC) ConcurrentGCTimer()),
1932 _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()),
1933 _gc_tracer_cm(new (ResourceObj::C_HEAP, mtGC) G1OldTracer()) {
1934
1935 _g1h = this;
1936 if (_process_strong_tasks == NULL || !_process_strong_tasks->valid()) {
1937 vm_exit_during_initialization("Failed necessary allocation.");
1938 }
1939
1940 _humongous_object_threshold_in_words = HeapRegion::GrainWords / 2;
1941
1942 int n_queues = MAX2((int)ParallelGCThreads, 1);
1943 _task_queues = new RefToScanQueueSet(n_queues);
1944
1945 uint n_rem_sets = HeapRegionRemSet::num_par_rem_sets();
1946 assert(n_rem_sets > 0, "Invariant.");
1947
1948 _worker_cset_start_region = NEW_C_HEAP_ARRAY(HeapRegion*, n_queues, mtGC);
1949 _worker_cset_start_region_time_stamp = NEW_C_HEAP_ARRAY(unsigned int, n_queues, mtGC);
1950 _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC);
1951
1952 for (int i = 0; i < n_queues; i++) {
1953 RefToScanQueue* q = new RefToScanQueue();
1954 q->initialize();
1955 _task_queues->register_queue(i, q);
1956 ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo();
1957 }
1958 clear_cset_start_regions();
1959
1960 // Initialize the G1EvacuationFailureALot counters and flags.
1961 NOT_PRODUCT(reset_evacuation_should_fail();)
1962
1963 guarantee(_task_queues != NULL, "task_queues allocation failure.");
1964 }
1965
1966 jint G1CollectedHeap::initialize() {
1967 CollectedHeap::pre_initialize();
1968 os::enable_vtime();
1969
1970 G1Log::init();
1971
1972 // Necessary to satisfy locking discipline assertions.
1973
1974 MutexLocker x(Heap_lock);
1975
1976 // We have to initialize the printer before committing the heap, as
1977 // it will be used then.
1978 _hr_printer.set_active(G1PrintHeapRegions);
1979
1980 // While there are no constraints in the GC code that HeapWordSize
1981 // be any particular value, there are multiple other areas in the
1982 // system which believe this to be true (e.g. oop->object_size in some
1983 // cases incorrectly returns the size in wordSize units rather than
1984 // HeapWordSize).
1985 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
1986
1987 size_t init_byte_size = collector_policy()->initial_heap_byte_size();
1988 size_t max_byte_size = collector_policy()->max_heap_byte_size();
1989 size_t heap_alignment = collector_policy()->heap_alignment();
1990
1991 // Ensure that the sizes are properly aligned.
1992 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
1993 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
1994 Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap");
1995
1996 _refine_cte_cl = new RefineCardTableEntryClosure();
1997
1998 _cg1r = new ConcurrentG1Refine(this, _refine_cte_cl);
1999
2000 // Reserve the maximum.
2001
2002 // When compressed oops are enabled, the preferred heap base
2003 // is calculated by subtracting the requested size from the
2004 // 32Gb boundary and using the result as the base address for
2005 // heap reservation. If the requested size is not aligned to
2006 // HeapRegion::GrainBytes (i.e. the alignment that is passed
2007 // into the ReservedHeapSpace constructor) then the actual
2008 // base of the reserved heap may end up differing from the
2009 // address that was requested (i.e. the preferred heap base).
2010 // If this happens then we could end up using a non-optimal
2011 // compressed oops mode.
2012
2013 ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size,
2014 heap_alignment);
2015
2016 // It is important to do this in a way such that concurrent readers can't
2017 // temporarily think something is in the heap. (I've actually seen this
2018 // happen in asserts: DLD.)
2019 _reserved.set_word_size(0);
2020 _reserved.set_start((HeapWord*)heap_rs.base());
2021 _reserved.set_end((HeapWord*)(heap_rs.base() + heap_rs.size()));
2022
2023 _expansion_regions = (uint) (max_byte_size / HeapRegion::GrainBytes);
2024
2025 // Create the gen rem set (and barrier set) for the entire reserved region.
2026 _rem_set = collector_policy()->create_rem_set(_reserved, 2);
2027 set_barrier_set(rem_set()->bs());
2028 if (!barrier_set()->is_a(BarrierSet::G1SATBCTLogging)) {
2029 vm_exit_during_initialization("G1 requires a G1SATBLoggingCardTableModRefBS");
2030 return JNI_ENOMEM;
2031 }
2032
2033 // Also create a G1 rem set.
2034 _g1_rem_set = new G1RemSet(this, g1_barrier_set());
2035
2036 // Carve out the G1 part of the heap.
2037
2038 ReservedSpace g1_rs = heap_rs.first_part(max_byte_size);
2039 _g1_reserved = MemRegion((HeapWord*)g1_rs.base(),
2040 g1_rs.size()/HeapWordSize);
2041
2042 _g1_storage.initialize(g1_rs, 0);
2043 _g1_committed = MemRegion((HeapWord*)_g1_storage.low(), (size_t) 0);
2044 _hrs.initialize((HeapWord*) _g1_reserved.start(),
2045 (HeapWord*) _g1_reserved.end());
2046 assert(_hrs.max_length() == _expansion_regions,
2047 err_msg("max length: %u expansion regions: %u",
2048 _hrs.max_length(), _expansion_regions));
2049
2050 // Do later initialization work for concurrent refinement.
2051 _cg1r->init();
2052
2053 // 6843694 - ensure that the maximum region index can fit
2054 // in the remembered set structures.
2055 const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
2056 guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
2057
2058 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
2059 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
2060 guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
2061 "too many cards per region");
2062
2063 FreeRegionList::set_unrealistically_long_length(max_regions() + 1);
2064
2065 _bot_shared = new G1BlockOffsetSharedArray(_reserved,
2066 heap_word_size(init_byte_size));
2067
2068 _g1h = this;
2069
2070 _in_cset_fast_test.initialize(_g1_reserved.start(), _g1_reserved.end(), HeapRegion::GrainBytes);
2071
2072 // Create the ConcurrentMark data structure and thread.
2073 // (Must do this late, so that "max_regions" is defined.)
2074 _cm = new ConcurrentMark(this, heap_rs);
2075 if (_cm == NULL || !_cm->completed_initialization()) {
2076 vm_shutdown_during_initialization("Could not create/initialize ConcurrentMark");
2077 return JNI_ENOMEM;
2078 }
2079 _cmThread = _cm->cmThread();
2080
2081 // Initialize the from_card cache structure of HeapRegionRemSet.
2082 HeapRegionRemSet::init_heap(max_regions());
2083
2084 // Now expand into the initial heap size.
2085 if (!expand(init_byte_size)) {
2086 vm_shutdown_during_initialization("Failed to allocate initial heap.");
2087 return JNI_ENOMEM;
2088 }
2089
2090 // Perform any initialization actions delegated to the policy.
2091 g1_policy()->init();
2092
2093 JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon,
2094 SATB_Q_FL_lock,
2095 G1SATBProcessCompletedThreshold,
2096 Shared_SATB_Q_lock);
2097
2098 JavaThread::dirty_card_queue_set().initialize(_refine_cte_cl,
2099 DirtyCardQ_CBL_mon,
2100 DirtyCardQ_FL_lock,
2101 concurrent_g1_refine()->yellow_zone(),
2102 concurrent_g1_refine()->red_zone(),
2103 Shared_DirtyCardQ_lock);
2104
2105 if (G1DeferredRSUpdate) {
2106 dirty_card_queue_set().initialize(NULL, // Should never be called by the Java code
2107 DirtyCardQ_CBL_mon,
2108 DirtyCardQ_FL_lock,
2109 -1, // never trigger processing
2110 -1, // no limit on length
2111 Shared_DirtyCardQ_lock,
2112 &JavaThread::dirty_card_queue_set());
2113 }
2114
2115 // Initialize the card queue set used to hold cards containing
2116 // references into the collection set.
2117 _into_cset_dirty_card_queue_set.initialize(NULL, // Should never be called by the Java code
2118 DirtyCardQ_CBL_mon,
2119 DirtyCardQ_FL_lock,
2120 -1, // never trigger processing
2121 -1, // no limit on length
2122 Shared_DirtyCardQ_lock,
2123 &JavaThread::dirty_card_queue_set());
2124
2125 // In case we're keeping closure specialization stats, initialize those
2126 // counts and that mechanism.
2127 SpecializationStats::clear();
2128
2129 // Here we allocate the dummy full region that is required by the
2130 // G1AllocRegion class. If we don't pass an address in the reserved
2131 // space here, lots of asserts fire.
2132
2133 HeapRegion* dummy_region = new_heap_region(0 /* index of bottom region */,
2134 _g1_reserved.start());
2135 // We'll re-use the same region whether the alloc region will
2136 // require BOT updates or not and, if it doesn't, then a non-young
2137 // region will complain that it cannot support allocations without
2138 // BOT updates. So we'll tag the dummy region as young to avoid that.
2139 dummy_region->set_young();
2140 // Make sure it's full.
2141 dummy_region->set_top(dummy_region->end());
2142 G1AllocRegion::setup(this, dummy_region);
2143
2144 init_mutator_alloc_region();
2145
2146 // Do create of the monitoring and management support so that
2147 // values in the heap have been properly initialized.
2148 _g1mm = new G1MonitoringSupport(this);
2149
2150 G1StringDedup::initialize();
2151
2152 return JNI_OK;
2153 }
2154
2155 void G1CollectedHeap::stop() {
2156 #if 0
2157 // Stopping concurrent worker threads is currently disabled until
2158 // some bugs in concurrent mark has been resolve. Without fixing
2159 // those bugs first we risk haning during VM exit when trying to
2160 // stop these threads.
2161
2162 // Abort any ongoing concurrent root region scanning and stop all
2163 // concurrent threads. We do this to make sure these threads do
2164 // not continue to execute and access resources (e.g. gclog_or_tty)
2165 // that are destroyed during shutdown.
2166 _cm->root_regions()->abort();
2167 _cm->root_regions()->wait_until_scan_finished();
2168 stop_conc_gc_threads();
2169 #endif
2170 }
2171
2172 size_t G1CollectedHeap::conservative_max_heap_alignment() {
2173 return HeapRegion::max_region_size();
2174 }
2175
2176 void G1CollectedHeap::ref_processing_init() {
2177 // Reference processing in G1 currently works as follows:
2178 //
2179 // * There are two reference processor instances. One is
2180 // used to record and process discovered references
2181 // during concurrent marking; the other is used to
2182 // record and process references during STW pauses
2183 // (both full and incremental).
2184 // * Both ref processors need to 'span' the entire heap as
2185 // the regions in the collection set may be dotted around.
2186 //
2187 // * For the concurrent marking ref processor:
2188 // * Reference discovery is enabled at initial marking.
2189 // * Reference discovery is disabled and the discovered
2190 // references processed etc during remarking.
2191 // * Reference discovery is MT (see below).
2192 // * Reference discovery requires a barrier (see below).
2193 // * Reference processing may or may not be MT
2194 // (depending on the value of ParallelRefProcEnabled
2195 // and ParallelGCThreads).
2196 // * A full GC disables reference discovery by the CM
2197 // ref processor and abandons any entries on it's
2198 // discovered lists.
2199 //
2200 // * For the STW processor:
2201 // * Non MT discovery is enabled at the start of a full GC.
2202 // * Processing and enqueueing during a full GC is non-MT.
2203 // * During a full GC, references are processed after marking.
2204 //
2205 // * Discovery (may or may not be MT) is enabled at the start
2206 // of an incremental evacuation pause.
2207 // * References are processed near the end of a STW evacuation pause.
2208 // * For both types of GC:
2209 // * Discovery is atomic - i.e. not concurrent.
2210 // * Reference discovery will not need a barrier.
2211
2212 SharedHeap::ref_processing_init();
2213 MemRegion mr = reserved_region();
2214
2215 // Concurrent Mark ref processor
2216 _ref_processor_cm =
2217 new ReferenceProcessor(mr, // span
2218 ParallelRefProcEnabled && (ParallelGCThreads > 1),
2219 // mt processing
2220 (int) ParallelGCThreads,
2221 // degree of mt processing
2222 (ParallelGCThreads > 1) || (ConcGCThreads > 1),
2223 // mt discovery
2224 (int) MAX2(ParallelGCThreads, ConcGCThreads),
2225 // degree of mt discovery
2226 false,
2227 // Reference discovery is not atomic
2228 &_is_alive_closure_cm,
2229 // is alive closure
2230 // (for efficiency/performance)
2231 true);
2232 // Setting next fields of discovered
2233 // lists requires a barrier.
2234
2235 // STW ref processor
2236 _ref_processor_stw =
2237 new ReferenceProcessor(mr, // span
2238 ParallelRefProcEnabled && (ParallelGCThreads > 1),
2239 // mt processing
2240 MAX2((int)ParallelGCThreads, 1),
2241 // degree of mt processing
2242 (ParallelGCThreads > 1),
2243 // mt discovery
2244 MAX2((int)ParallelGCThreads, 1),
2245 // degree of mt discovery
2246 true,
2247 // Reference discovery is atomic
2248 &_is_alive_closure_stw,
2249 // is alive closure
2250 // (for efficiency/performance)
2251 false);
2252 // Setting next fields of discovered
2253 // lists does not require a barrier.
2254 }
2255
2256 size_t G1CollectedHeap::capacity() const {
2257 return _g1_committed.byte_size();
2258 }
2259
2260 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) {
2261 assert(!hr->continuesHumongous(), "pre-condition");
2262 hr->reset_gc_time_stamp();
2263 if (hr->startsHumongous()) {
2264 uint first_index = hr->hrs_index() + 1;
2265 uint last_index = hr->last_hc_index();
2266 for (uint i = first_index; i < last_index; i += 1) {
2267 HeapRegion* chr = region_at(i);
2268 assert(chr->continuesHumongous(), "sanity");
2269 chr->reset_gc_time_stamp();
2270 }
2271 }
2272 }
2273
2274 #ifndef PRODUCT
2275 class CheckGCTimeStampsHRClosure : public HeapRegionClosure {
2276 private:
2277 unsigned _gc_time_stamp;
2278 bool _failures;
2279
2280 public:
2281 CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) :
2282 _gc_time_stamp(gc_time_stamp), _failures(false) { }
2283
2284 virtual bool doHeapRegion(HeapRegion* hr) {
2285 unsigned region_gc_time_stamp = hr->get_gc_time_stamp();
2286 if (_gc_time_stamp != region_gc_time_stamp) {
2287 gclog_or_tty->print_cr("Region "HR_FORMAT" has GC time stamp = %d, "
2288 "expected %d", HR_FORMAT_PARAMS(hr),
2289 region_gc_time_stamp, _gc_time_stamp);
2290 _failures = true;
2291 }
2292 return false;
2293 }
2294
2295 bool failures() { return _failures; }
2296 };
2297
2298 void G1CollectedHeap::check_gc_time_stamps() {
2299 CheckGCTimeStampsHRClosure cl(_gc_time_stamp);
2300 heap_region_iterate(&cl);
2301 guarantee(!cl.failures(), "all GC time stamps should have been reset");
2302 }
2303 #endif // PRODUCT
2304
2305 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl,
2306 DirtyCardQueue* into_cset_dcq,
2307 bool concurrent,
2308 uint worker_i) {
2309 // Clean cards in the hot card cache
2310 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
2311 hot_card_cache->drain(worker_i, g1_rem_set(), into_cset_dcq);
2312
2313 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2314 int n_completed_buffers = 0;
2315 while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) {
2316 n_completed_buffers++;
2317 }
2318 g1_policy()->phase_times()->record_update_rs_processed_buffers(worker_i, n_completed_buffers);
2319 dcqs.clear_n_completed_buffers();
2320 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!");
2321 }
2322
2323
2324 // Computes the sum of the storage used by the various regions.
2325
2326 size_t G1CollectedHeap::used() const {
2327 assert(Heap_lock->owner() != NULL,
2328 "Should be owned on this thread's behalf.");
2329 size_t result = _summary_bytes_used;
2330 // Read only once in case it is set to NULL concurrently
2331 HeapRegion* hr = _mutator_alloc_region.get();
2332 if (hr != NULL)
2333 result += hr->used();
2334 return result;
2335 }
2336
2337 size_t G1CollectedHeap::used_unlocked() const {
2338 size_t result = _summary_bytes_used;
2339 return result;
2340 }
2341
2342 class SumUsedClosure: public HeapRegionClosure {
2343 size_t _used;
2344 public:
2345 SumUsedClosure() : _used(0) {}
2346 bool doHeapRegion(HeapRegion* r) {
2347 if (!r->continuesHumongous()) {
2348 _used += r->used();
2349 }
2350 return false;
2351 }
2352 size_t result() { return _used; }
2353 };
2354
2355 size_t G1CollectedHeap::recalculate_used() const {
2356 double recalculate_used_start = os::elapsedTime();
2357
2358 SumUsedClosure blk;
2359 heap_region_iterate(&blk);
2360
2361 g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0);
2362 return blk.result();
2363 }
2364
2365 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
2366 switch (cause) {
2367 case GCCause::_gc_locker: return GCLockerInvokesConcurrent;
2368 case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent;
2369 case GCCause::_g1_humongous_allocation: return true;
2370 default: return false;
2371 }
2372 }
2373
2374 #ifndef PRODUCT
2375 void G1CollectedHeap::allocate_dummy_regions() {
2376 // Let's fill up most of the region
2377 size_t word_size = HeapRegion::GrainWords - 1024;
2378 // And as a result the region we'll allocate will be humongous.
2379 guarantee(isHumongous(word_size), "sanity");
2380
2381 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
2382 // Let's use the existing mechanism for the allocation
2383 HeapWord* dummy_obj = humongous_obj_allocate(word_size);
2384 if (dummy_obj != NULL) {
2385 MemRegion mr(dummy_obj, word_size);
2386 CollectedHeap::fill_with_object(mr);
2387 } else {
2388 // If we can't allocate once, we probably cannot allocate
2389 // again. Let's get out of the loop.
2390 break;
2391 }
2392 }
2393 }
2394 #endif // !PRODUCT
2395
2396 void G1CollectedHeap::increment_old_marking_cycles_started() {
2397 assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
2398 _old_marking_cycles_started == _old_marking_cycles_completed + 1,
2399 err_msg("Wrong marking cycle count (started: %d, completed: %d)",
2400 _old_marking_cycles_started, _old_marking_cycles_completed));
2401
2402 _old_marking_cycles_started++;
2403 }
2404
2405 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) {
2406 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
2407
2408 // We assume that if concurrent == true, then the caller is a
2409 // concurrent thread that was joined the Suspendible Thread
2410 // Set. If there's ever a cheap way to check this, we should add an
2411 // assert here.
2412
2413 // Given that this method is called at the end of a Full GC or of a
2414 // concurrent cycle, and those can be nested (i.e., a Full GC can
2415 // interrupt a concurrent cycle), the number of full collections
2416 // completed should be either one (in the case where there was no
2417 // nesting) or two (when a Full GC interrupted a concurrent cycle)
2418 // behind the number of full collections started.
2419
2420 // This is the case for the inner caller, i.e. a Full GC.
2421 assert(concurrent ||
2422 (_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
2423 (_old_marking_cycles_started == _old_marking_cycles_completed + 2),
2424 err_msg("for inner caller (Full GC): _old_marking_cycles_started = %u "
2425 "is inconsistent with _old_marking_cycles_completed = %u",
2426 _old_marking_cycles_started, _old_marking_cycles_completed));
2427
2428 // This is the case for the outer caller, i.e. the concurrent cycle.
2429 assert(!concurrent ||
2430 (_old_marking_cycles_started == _old_marking_cycles_completed + 1),
2431 err_msg("for outer caller (concurrent cycle): "
2432 "_old_marking_cycles_started = %u "
2433 "is inconsistent with _old_marking_cycles_completed = %u",
2434 _old_marking_cycles_started, _old_marking_cycles_completed));
2435
2436 _old_marking_cycles_completed += 1;
2437
2438 // We need to clear the "in_progress" flag in the CM thread before
2439 // we wake up any waiters (especially when ExplicitInvokesConcurrent
2440 // is set) so that if a waiter requests another System.gc() it doesn't
2441 // incorrectly see that a marking cycle is still in progress.
2442 if (concurrent) {
2443 _cmThread->clear_in_progress();
2444 }
2445
2446 // This notify_all() will ensure that a thread that called
2447 // System.gc() with (with ExplicitGCInvokesConcurrent set or not)
2448 // and it's waiting for a full GC to finish will be woken up. It is
2449 // waiting in VM_G1IncCollectionPause::doit_epilogue().
2450 FullGCCount_lock->notify_all();
2451 }
2452
2453 void G1CollectedHeap::register_concurrent_cycle_start(const Ticks& start_time) {
2454 _concurrent_cycle_started = true;
2455 _gc_timer_cm->register_gc_start(start_time);
2456
2457 _gc_tracer_cm->report_gc_start(gc_cause(), _gc_timer_cm->gc_start());
2458 trace_heap_before_gc(_gc_tracer_cm);
2459 }
2460
2461 void G1CollectedHeap::register_concurrent_cycle_end() {
2462 if (_concurrent_cycle_started) {
2463 if (_cm->has_aborted()) {
2464 _gc_tracer_cm->report_concurrent_mode_failure();
2465 }
2466
2467 _gc_timer_cm->register_gc_end();
2468 _gc_tracer_cm->report_gc_end(_gc_timer_cm->gc_end(), _gc_timer_cm->time_partitions());
2469
2470 _concurrent_cycle_started = false;
2471 }
2472 }
2473
2474 void G1CollectedHeap::trace_heap_after_concurrent_cycle() {
2475 if (_concurrent_cycle_started) {
2476 trace_heap_after_gc(_gc_tracer_cm);
2477 }
2478 }
2479
2480 G1YCType G1CollectedHeap::yc_type() {
2481 bool is_young = g1_policy()->gcs_are_young();
2482 bool is_initial_mark = g1_policy()->during_initial_mark_pause();
2483 bool is_during_mark = mark_in_progress();
2484
2485 if (is_initial_mark) {
2486 return InitialMark;
2487 } else if (is_during_mark) {
2488 return DuringMark;
2489 } else if (is_young) {
2490 return Normal;
2491 } else {
2492 return Mixed;
2493 }
2494 }
2495
2496 void G1CollectedHeap::collect(GCCause::Cause cause) {
2497 assert_heap_not_locked();
2498
2499 unsigned int gc_count_before;
2500 unsigned int old_marking_count_before;
2501 bool retry_gc;
2502
2503 do {
2504 retry_gc = false;
2505
2506 {
2507 MutexLocker ml(Heap_lock);
2508
2509 // Read the GC count while holding the Heap_lock
2510 gc_count_before = total_collections();
2511 old_marking_count_before = _old_marking_cycles_started;
2512 }
2513
2514 if (should_do_concurrent_full_gc(cause)) {
2515 // Schedule an initial-mark evacuation pause that will start a
2516 // concurrent cycle. We're setting word_size to 0 which means that
2517 // we are not requesting a post-GC allocation.
2518 VM_G1IncCollectionPause op(gc_count_before,
2519 0, /* word_size */
2520 true, /* should_initiate_conc_mark */
2521 g1_policy()->max_pause_time_ms(),
2522 cause);
2523
2524 VMThread::execute(&op);
2525 if (!op.pause_succeeded()) {
2526 if (old_marking_count_before == _old_marking_cycles_started) {
2527 retry_gc = op.should_retry_gc();
2528 } else {
2529 // A Full GC happened while we were trying to schedule the
2530 // initial-mark GC. No point in starting a new cycle given
2531 // that the whole heap was collected anyway.
2532 }
2533
2534 if (retry_gc) {
2535 if (GC_locker::is_active_and_needs_gc()) {
2536 GC_locker::stall_until_clear();
2537 }
2538 }
2539 }
2540 } else {
2541 if (cause == GCCause::_gc_locker
2542 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2543
2544 // Schedule a standard evacuation pause. We're setting word_size
2545 // to 0 which means that we are not requesting a post-GC allocation.
2546 VM_G1IncCollectionPause op(gc_count_before,
2547 0, /* word_size */
2548 false, /* should_initiate_conc_mark */
2549 g1_policy()->max_pause_time_ms(),
2550 cause);
2551 VMThread::execute(&op);
2552 } else {
2553 // Schedule a Full GC.
2554 VM_G1CollectFull op(gc_count_before, old_marking_count_before, cause);
2555 VMThread::execute(&op);
2556 }
2557 }
2558 } while (retry_gc);
2559 }
2560
2561 bool G1CollectedHeap::is_in(const void* p) const {
2562 if (_g1_committed.contains(p)) {
2563 // Given that we know that p is in the committed space,
2564 // heap_region_containing_raw() should successfully
2565 // return the containing region.
2566 HeapRegion* hr = heap_region_containing_raw(p);
2567 return hr->is_in(p);
2568 } else {
2569 return false;
2570 }
2571 }
2572
2573 // Iteration functions.
2574
2575 // Iterates an OopClosure over all ref-containing fields of objects
2576 // within a HeapRegion.
2577
2578 class IterateOopClosureRegionClosure: public HeapRegionClosure {
2579 MemRegion _mr;
2580 ExtendedOopClosure* _cl;
2581 public:
2582 IterateOopClosureRegionClosure(MemRegion mr, ExtendedOopClosure* cl)
2583 : _mr(mr), _cl(cl) {}
2584 bool doHeapRegion(HeapRegion* r) {
2585 if (!r->continuesHumongous()) {
2586 r->oop_iterate(_cl);
2587 }
2588 return false;
2589 }
2590 };
2591
2592 void G1CollectedHeap::oop_iterate(ExtendedOopClosure* cl) {
2593 IterateOopClosureRegionClosure blk(_g1_committed, cl);
2594 heap_region_iterate(&blk);
2595 }
2596
2597 void G1CollectedHeap::oop_iterate(MemRegion mr, ExtendedOopClosure* cl) {
2598 IterateOopClosureRegionClosure blk(mr, cl);
2599 heap_region_iterate(&blk);
2600 }
2601
2602 // Iterates an ObjectClosure over all objects within a HeapRegion.
2603
2604 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2605 ObjectClosure* _cl;
2606 public:
2607 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2608 bool doHeapRegion(HeapRegion* r) {
2609 if (! r->continuesHumongous()) {
2610 r->object_iterate(_cl);
2611 }
2612 return false;
2613 }
2614 };
2615
2616 void G1CollectedHeap::object_iterate(ObjectClosure* cl) {
2617 IterateObjectClosureRegionClosure blk(cl);
2618 heap_region_iterate(&blk);
2619 }
2620
2621 // Calls a SpaceClosure on a HeapRegion.
2622
2623 class SpaceClosureRegionClosure: public HeapRegionClosure {
2624 SpaceClosure* _cl;
2625 public:
2626 SpaceClosureRegionClosure(SpaceClosure* cl) : _cl(cl) {}
2627 bool doHeapRegion(HeapRegion* r) {
2628 _cl->do_space(r);
2629 return false;
2630 }
2631 };
2632
2633 void G1CollectedHeap::space_iterate(SpaceClosure* cl) {
2634 SpaceClosureRegionClosure blk(cl);
2635 heap_region_iterate(&blk);
2636 }
2637
2638 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2639 _hrs.iterate(cl);
2640 }
2641
2642 void
2643 G1CollectedHeap::heap_region_par_iterate_chunked(HeapRegionClosure* cl,
2644 uint worker_id,
2645 uint no_of_par_workers,
2646 jint claim_value) {
2647 const uint regions = n_regions();
2648 const uint max_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
2649 no_of_par_workers :
2650 1);
2651 assert(UseDynamicNumberOfGCThreads ||
2652 no_of_par_workers == workers()->total_workers(),
2653 "Non dynamic should use fixed number of workers");
2654 // try to spread out the starting points of the workers
2655 const HeapRegion* start_hr =
2656 start_region_for_worker(worker_id, no_of_par_workers);
2657 const uint start_index = start_hr->hrs_index();
2658
2659 // each worker will actually look at all regions
2660 for (uint count = 0; count < regions; ++count) {
2661 const uint index = (start_index + count) % regions;
2662 assert(0 <= index && index < regions, "sanity");
2663 HeapRegion* r = region_at(index);
2664 // we'll ignore "continues humongous" regions (we'll process them
2665 // when we come across their corresponding "start humongous"
2666 // region) and regions already claimed
2667 if (r->claim_value() == claim_value || r->continuesHumongous()) {
2668 continue;
2669 }
2670 // OK, try to claim it
2671 if (r->claimHeapRegion(claim_value)) {
2672 // success!
2673 assert(!r->continuesHumongous(), "sanity");
2674 if (r->startsHumongous()) {
2675 // If the region is "starts humongous" we'll iterate over its
2676 // "continues humongous" first; in fact we'll do them
2677 // first. The order is important. In on case, calling the
2678 // closure on the "starts humongous" region might de-allocate
2679 // and clear all its "continues humongous" regions and, as a
2680 // result, we might end up processing them twice. So, we'll do
2681 // them first (notice: most closures will ignore them anyway) and
2682 // then we'll do the "starts humongous" region.
2683 for (uint ch_index = index + 1; ch_index < regions; ++ch_index) {
2684 HeapRegion* chr = region_at(ch_index);
2685
2686 // if the region has already been claimed or it's not
2687 // "continues humongous" we're done
2688 if (chr->claim_value() == claim_value ||
2689 !chr->continuesHumongous()) {
2690 break;
2691 }
2692
2693 // No one should have claimed it directly. We can given
2694 // that we claimed its "starts humongous" region.
2695 assert(chr->claim_value() != claim_value, "sanity");
2696 assert(chr->humongous_start_region() == r, "sanity");
2697
2698 if (chr->claimHeapRegion(claim_value)) {
2699 // we should always be able to claim it; no one else should
2700 // be trying to claim this region
2701
2702 bool res2 = cl->doHeapRegion(chr);
2703 assert(!res2, "Should not abort");
2704
2705 // Right now, this holds (i.e., no closure that actually
2706 // does something with "continues humongous" regions
2707 // clears them). We might have to weaken it in the future,
2708 // but let's leave these two asserts here for extra safety.
2709 assert(chr->continuesHumongous(), "should still be the case");
2710 assert(chr->humongous_start_region() == r, "sanity");
2711 } else {
2712 guarantee(false, "we should not reach here");
2713 }
2714 }
2715 }
2716
2717 assert(!r->continuesHumongous(), "sanity");
2718 bool res = cl->doHeapRegion(r);
2719 assert(!res, "Should not abort");
2720 }
2721 }
2722 }
2723
2724 class ResetClaimValuesClosure: public HeapRegionClosure {
2725 public:
2726 bool doHeapRegion(HeapRegion* r) {
2727 r->set_claim_value(HeapRegion::InitialClaimValue);
2728 return false;
2729 }
2730 };
2731
2732 void G1CollectedHeap::reset_heap_region_claim_values() {
2733 ResetClaimValuesClosure blk;
2734 heap_region_iterate(&blk);
2735 }
2736
2737 void G1CollectedHeap::reset_cset_heap_region_claim_values() {
2738 ResetClaimValuesClosure blk;
2739 collection_set_iterate(&blk);
2740 }
2741
2742 #ifdef ASSERT
2743 // This checks whether all regions in the heap have the correct claim
2744 // value. I also piggy-backed on this a check to ensure that the
2745 // humongous_start_region() information on "continues humongous"
2746 // regions is correct.
2747
2748 class CheckClaimValuesClosure : public HeapRegionClosure {
2749 private:
2750 jint _claim_value;
2751 uint _failures;
2752 HeapRegion* _sh_region;
2753
2754 public:
2755 CheckClaimValuesClosure(jint claim_value) :
2756 _claim_value(claim_value), _failures(0), _sh_region(NULL) { }
2757 bool doHeapRegion(HeapRegion* r) {
2758 if (r->claim_value() != _claim_value) {
2759 gclog_or_tty->print_cr("Region " HR_FORMAT ", "
2760 "claim value = %d, should be %d",
2761 HR_FORMAT_PARAMS(r),
2762 r->claim_value(), _claim_value);
2763 ++_failures;
2764 }
2765 if (!r->isHumongous()) {
2766 _sh_region = NULL;
2767 } else if (r->startsHumongous()) {
2768 _sh_region = r;
2769 } else if (r->continuesHumongous()) {
2770 if (r->humongous_start_region() != _sh_region) {
2771 gclog_or_tty->print_cr("Region " HR_FORMAT ", "
2772 "HS = "PTR_FORMAT", should be "PTR_FORMAT,
2773 HR_FORMAT_PARAMS(r),
2774 r->humongous_start_region(),
2775 _sh_region);
2776 ++_failures;
2777 }
2778 }
2779 return false;
2780 }
2781 uint failures() { return _failures; }
2782 };
2783
2784 bool G1CollectedHeap::check_heap_region_claim_values(jint claim_value) {
2785 CheckClaimValuesClosure cl(claim_value);
2786 heap_region_iterate(&cl);
2787 return cl.failures() == 0;
2788 }
2789
2790 class CheckClaimValuesInCSetHRClosure: public HeapRegionClosure {
2791 private:
2792 jint _claim_value;
2793 uint _failures;
2794
2795 public:
2796 CheckClaimValuesInCSetHRClosure(jint claim_value) :
2797 _claim_value(claim_value), _failures(0) { }
2798
2799 uint failures() { return _failures; }
2800
2801 bool doHeapRegion(HeapRegion* hr) {
2802 assert(hr->in_collection_set(), "how?");
2803 assert(!hr->isHumongous(), "H-region in CSet");
2804 if (hr->claim_value() != _claim_value) {
2805 gclog_or_tty->print_cr("CSet Region " HR_FORMAT ", "
2806 "claim value = %d, should be %d",
2807 HR_FORMAT_PARAMS(hr),
2808 hr->claim_value(), _claim_value);
2809 _failures += 1;
2810 }
2811 return false;
2812 }
2813 };
2814
2815 bool G1CollectedHeap::check_cset_heap_region_claim_values(jint claim_value) {
2816 CheckClaimValuesInCSetHRClosure cl(claim_value);
2817 collection_set_iterate(&cl);
2818 return cl.failures() == 0;
2819 }
2820 #endif // ASSERT
2821
2822 // Clear the cached CSet starting regions and (more importantly)
2823 // the time stamps. Called when we reset the GC time stamp.
2824 void G1CollectedHeap::clear_cset_start_regions() {
2825 assert(_worker_cset_start_region != NULL, "sanity");
2826 assert(_worker_cset_start_region_time_stamp != NULL, "sanity");
2827
2828 int n_queues = MAX2((int)ParallelGCThreads, 1);
2829 for (int i = 0; i < n_queues; i++) {
2830 _worker_cset_start_region[i] = NULL;
2831 _worker_cset_start_region_time_stamp[i] = 0;
2832 }
2833 }
2834
2835 // Given the id of a worker, obtain or calculate a suitable
2836 // starting region for iterating over the current collection set.
2837 HeapRegion* G1CollectedHeap::start_cset_region_for_worker(uint worker_i) {
2838 assert(get_gc_time_stamp() > 0, "should have been updated by now");
2839
2840 HeapRegion* result = NULL;
2841 unsigned gc_time_stamp = get_gc_time_stamp();
2842
2843 if (_worker_cset_start_region_time_stamp[worker_i] == gc_time_stamp) {
2844 // Cached starting region for current worker was set
2845 // during the current pause - so it's valid.
2846 // Note: the cached starting heap region may be NULL
2847 // (when the collection set is empty).
2848 result = _worker_cset_start_region[worker_i];
2849 assert(result == NULL || result->in_collection_set(), "sanity");
2850 return result;
2851 }
2852
2853 // The cached entry was not valid so let's calculate
2854 // a suitable starting heap region for this worker.
2855
2856 // We want the parallel threads to start their collection
2857 // set iteration at different collection set regions to
2858 // avoid contention.
2859 // If we have:
2860 // n collection set regions
2861 // p threads
2862 // Then thread t will start at region floor ((t * n) / p)
2863
2864 result = g1_policy()->collection_set();
2865 if (G1CollectedHeap::use_parallel_gc_threads()) {
2866 uint cs_size = g1_policy()->cset_region_length();
2867 uint active_workers = workers()->active_workers();
2868 assert(UseDynamicNumberOfGCThreads ||
2869 active_workers == workers()->total_workers(),
2870 "Unless dynamic should use total workers");
2871
2872 uint end_ind = (cs_size * worker_i) / active_workers;
2873 uint start_ind = 0;
2874
2875 if (worker_i > 0 &&
2876 _worker_cset_start_region_time_stamp[worker_i - 1] == gc_time_stamp) {
2877 // Previous workers starting region is valid
2878 // so let's iterate from there
2879 start_ind = (cs_size * (worker_i - 1)) / active_workers;
2880 result = _worker_cset_start_region[worker_i - 1];
2881 }
2882
2883 for (uint i = start_ind; i < end_ind; i++) {
2884 result = result->next_in_collection_set();
2885 }
2886 }
2887
2888 // Note: the calculated starting heap region may be NULL
2889 // (when the collection set is empty).
2890 assert(result == NULL || result->in_collection_set(), "sanity");
2891 assert(_worker_cset_start_region_time_stamp[worker_i] != gc_time_stamp,
2892 "should be updated only once per pause");
2893 _worker_cset_start_region[worker_i] = result;
2894 OrderAccess::storestore();
2895 _worker_cset_start_region_time_stamp[worker_i] = gc_time_stamp;
2896 return result;
2897 }
2898
2899 HeapRegion* G1CollectedHeap::start_region_for_worker(uint worker_i,
2900 uint no_of_par_workers) {
2901 uint worker_num =
2902 G1CollectedHeap::use_parallel_gc_threads() ? no_of_par_workers : 1U;
2903 assert(UseDynamicNumberOfGCThreads ||
2904 no_of_par_workers == workers()->total_workers(),
2905 "Non dynamic should use fixed number of workers");
2906 const uint start_index = n_regions() * worker_i / worker_num;
2907 return region_at(start_index);
2908 }
2909
2910 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) {
2911 HeapRegion* r = g1_policy()->collection_set();
2912 while (r != NULL) {
2913 HeapRegion* next = r->next_in_collection_set();
2914 if (cl->doHeapRegion(r)) {
2915 cl->incomplete();
2916 return;
2917 }
2918 r = next;
2919 }
2920 }
2921
2922 void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r,
2923 HeapRegionClosure *cl) {
2924 if (r == NULL) {
2925 // The CSet is empty so there's nothing to do.
2926 return;
2927 }
2928
2929 assert(r->in_collection_set(),
2930 "Start region must be a member of the collection set.");
2931 HeapRegion* cur = r;
2932 while (cur != NULL) {
2933 HeapRegion* next = cur->next_in_collection_set();
2934 if (cl->doHeapRegion(cur) && false) {
2935 cl->incomplete();
2936 return;
2937 }
2938 cur = next;
2939 }
2940 cur = g1_policy()->collection_set();
2941 while (cur != r) {
2942 HeapRegion* next = cur->next_in_collection_set();
2943 if (cl->doHeapRegion(cur) && false) {
2944 cl->incomplete();
2945 return;
2946 }
2947 cur = next;
2948 }
2949 }
2950
2951 CompactibleSpace* G1CollectedHeap::first_compactible_space() {
2952 return n_regions() > 0 ? region_at(0) : NULL;
2953 }
2954
2955
2956 Space* G1CollectedHeap::space_containing(const void* addr) const {
2957 return heap_region_containing(addr);
2958 }
2959
2960 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2961 Space* sp = space_containing(addr);
2962 return sp->block_start(addr);
2963 }
2964
2965 size_t G1CollectedHeap::block_size(const HeapWord* addr) const {
2966 Space* sp = space_containing(addr);
2967 return sp->block_size(addr);
2968 }
2969
2970 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2971 Space* sp = space_containing(addr);
2972 return sp->block_is_obj(addr);
2973 }
2974
2975 bool G1CollectedHeap::supports_tlab_allocation() const {
2976 return true;
2977 }
2978
2979 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
2980 return (_g1_policy->young_list_target_length() - young_list()->survivor_length()) * HeapRegion::GrainBytes;
2981 }
2982
2983 size_t G1CollectedHeap::tlab_used(Thread* ignored) const {
2984 return young_list()->eden_used_bytes();
2985 }
2986
2987 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size
2988 // must be smaller than the humongous object limit.
2989 size_t G1CollectedHeap::max_tlab_size() const {
2990 return align_size_down(_humongous_object_threshold_in_words - 1, MinObjAlignment);
2991 }
2992
2993 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
2994 // Return the remaining space in the cur alloc region, but not less than
2995 // the min TLAB size.
2996
2997 // Also, this value can be at most the humongous object threshold,
2998 // since we can't allow tlabs to grow big enough to accommodate
2999 // humongous objects.
3000
3001 HeapRegion* hr = _mutator_alloc_region.get();
3002 size_t max_tlab = max_tlab_size() * wordSize;
3003 if (hr == NULL) {
3004 return max_tlab;
3005 } else {
3006 return MIN2(MAX2(hr->free(), (size_t) MinTLABSize), max_tlab);
3007 }
3008 }
3009
3010 size_t G1CollectedHeap::max_capacity() const {
3011 return _g1_reserved.byte_size();
3012 }
3013
3014 jlong G1CollectedHeap::millis_since_last_gc() {
3015 // assert(false, "NYI");
3016 return 0;
3017 }
3018
3019 void G1CollectedHeap::prepare_for_verify() {
3020 if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) {
3021 ensure_parsability(false);
3022 }
3023 g1_rem_set()->prepare_for_verify();
3024 }
3025
3026 bool G1CollectedHeap::allocated_since_marking(oop obj, HeapRegion* hr,
3027 VerifyOption vo) {
3028 switch (vo) {
3029 case VerifyOption_G1UsePrevMarking:
3030 return hr->obj_allocated_since_prev_marking(obj);
3031 case VerifyOption_G1UseNextMarking:
3032 return hr->obj_allocated_since_next_marking(obj);
3033 case VerifyOption_G1UseMarkWord:
3034 return false;
3035 default:
3036 ShouldNotReachHere();
3037 }
3038 return false; // keep some compilers happy
3039 }
3040
3041 HeapWord* G1CollectedHeap::top_at_mark_start(HeapRegion* hr, VerifyOption vo) {
3042 switch (vo) {
3043 case VerifyOption_G1UsePrevMarking: return hr->prev_top_at_mark_start();
3044 case VerifyOption_G1UseNextMarking: return hr->next_top_at_mark_start();
3045 case VerifyOption_G1UseMarkWord: return NULL;
3046 default: ShouldNotReachHere();
3047 }
3048 return NULL; // keep some compilers happy
3049 }
3050
3051 bool G1CollectedHeap::is_marked(oop obj, VerifyOption vo) {
3052 switch (vo) {
3053 case VerifyOption_G1UsePrevMarking: return isMarkedPrev(obj);
3054 case VerifyOption_G1UseNextMarking: return isMarkedNext(obj);
3055 case VerifyOption_G1UseMarkWord: return obj->is_gc_marked();
3056 default: ShouldNotReachHere();
3057 }
3058 return false; // keep some compilers happy
3059 }
3060
3061 const char* G1CollectedHeap::top_at_mark_start_str(VerifyOption vo) {
3062 switch (vo) {
3063 case VerifyOption_G1UsePrevMarking: return "PTAMS";
3064 case VerifyOption_G1UseNextMarking: return "NTAMS";
3065 case VerifyOption_G1UseMarkWord: return "NONE";
3066 default: ShouldNotReachHere();
3067 }
3068 return NULL; // keep some compilers happy
3069 }
3070
3071 class VerifyRootsClosure: public OopClosure {
3072 private:
3073 G1CollectedHeap* _g1h;
3074 VerifyOption _vo;
3075 bool _failures;
3076 public:
3077 // _vo == UsePrevMarking -> use "prev" marking information,
3078 // _vo == UseNextMarking -> use "next" marking information,
3079 // _vo == UseMarkWord -> use mark word from object header.
3080 VerifyRootsClosure(VerifyOption vo) :
3081 _g1h(G1CollectedHeap::heap()),
3082 _vo(vo),
3083 _failures(false) { }
3084
3085 bool failures() { return _failures; }
3086
3087 template <class T> void do_oop_nv(T* p) {
3088 T heap_oop = oopDesc::load_heap_oop(p);
3089 if (!oopDesc::is_null(heap_oop)) {
3090 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
3091 if (_g1h->is_obj_dead_cond(obj, _vo)) {
3092 gclog_or_tty->print_cr("Root location "PTR_FORMAT" "
3093 "points to dead obj "PTR_FORMAT, p, (void*) obj);
3094 if (_vo == VerifyOption_G1UseMarkWord) {
3095 gclog_or_tty->print_cr(" Mark word: "PTR_FORMAT, (void*)(obj->mark()));
3096 }
3097 obj->print_on(gclog_or_tty);
3098 _failures = true;
3099 }
3100 }
3101 }
3102
3103 void do_oop(oop* p) { do_oop_nv(p); }
3104 void do_oop(narrowOop* p) { do_oop_nv(p); }
3105 };
3106
3107 class G1VerifyCodeRootOopClosure: public OopClosure {
3108 G1CollectedHeap* _g1h;
3109 OopClosure* _root_cl;
3110 nmethod* _nm;
3111 VerifyOption _vo;
3112 bool _failures;
3113
3114 template <class T> void do_oop_work(T* p) {
3115 // First verify that this root is live
3116 _root_cl->do_oop(p);
3117
3118 if (!G1VerifyHeapRegionCodeRoots) {
3119 // We're not verifying the code roots attached to heap region.
3120 return;
3121 }
3122
3123 // Don't check the code roots during marking verification in a full GC
3124 if (_vo == VerifyOption_G1UseMarkWord) {
3125 return;
3126 }
3127
3128 // Now verify that the current nmethod (which contains p) is
3129 // in the code root list of the heap region containing the
3130 // object referenced by p.
3131
3132 T heap_oop = oopDesc::load_heap_oop(p);
3133 if (!oopDesc::is_null(heap_oop)) {
3134 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
3135
3136 // Now fetch the region containing the object
3137 HeapRegion* hr = _g1h->heap_region_containing(obj);
3138 HeapRegionRemSet* hrrs = hr->rem_set();
3139 // Verify that the strong code root list for this region
3140 // contains the nmethod
3141 if (!hrrs->strong_code_roots_list_contains(_nm)) {
3142 gclog_or_tty->print_cr("Code root location "PTR_FORMAT" "
3143 "from nmethod "PTR_FORMAT" not in strong "
3144 "code roots for region ["PTR_FORMAT","PTR_FORMAT")",
3145 p, _nm, hr->bottom(), hr->end());
3146 _failures = true;
3147 }
3148 }
3149 }
3150
3151 public:
3152 G1VerifyCodeRootOopClosure(G1CollectedHeap* g1h, OopClosure* root_cl, VerifyOption vo):
3153 _g1h(g1h), _root_cl(root_cl), _vo(vo), _nm(NULL), _failures(false) {}
3154
3155 void do_oop(oop* p) { do_oop_work(p); }
3156 void do_oop(narrowOop* p) { do_oop_work(p); }
3157
3158 void set_nmethod(nmethod* nm) { _nm = nm; }
3159 bool failures() { return _failures; }
3160 };
3161
3162 class G1VerifyCodeRootBlobClosure: public CodeBlobClosure {
3163 G1VerifyCodeRootOopClosure* _oop_cl;
3164
3165 public:
3166 G1VerifyCodeRootBlobClosure(G1VerifyCodeRootOopClosure* oop_cl):
3167 _oop_cl(oop_cl) {}
3168
3169 void do_code_blob(CodeBlob* cb) {
3170 nmethod* nm = cb->as_nmethod_or_null();
3171 if (nm != NULL) {
3172 _oop_cl->set_nmethod(nm);
3173 nm->oops_do(_oop_cl);
3174 }
3175 }
3176 };
3177
3178 class YoungRefCounterClosure : public OopClosure {
3179 G1CollectedHeap* _g1h;
3180 int _count;
3181 public:
3182 YoungRefCounterClosure(G1CollectedHeap* g1h) : _g1h(g1h), _count(0) {}
3183 void do_oop(oop* p) { if (_g1h->is_in_young(*p)) { _count++; } }
3184 void do_oop(narrowOop* p) { ShouldNotReachHere(); }
3185
3186 int count() { return _count; }
3187 void reset_count() { _count = 0; };
3188 };
3189
3190 class VerifyKlassClosure: public KlassClosure {
3191 YoungRefCounterClosure _young_ref_counter_closure;
3192 OopClosure *_oop_closure;
3193 public:
3194 VerifyKlassClosure(G1CollectedHeap* g1h, OopClosure* cl) : _young_ref_counter_closure(g1h), _oop_closure(cl) {}
3195 void do_klass(Klass* k) {
3196 k->oops_do(_oop_closure);
3197
3198 _young_ref_counter_closure.reset_count();
3199 k->oops_do(&_young_ref_counter_closure);
3200 if (_young_ref_counter_closure.count() > 0) {
3201 guarantee(k->has_modified_oops(), err_msg("Klass " PTR_FORMAT ", has young refs but is not dirty.", k));
3202 }
3203 }
3204 };
3205
3206 class VerifyLivenessOopClosure: public OopClosure {
3207 G1CollectedHeap* _g1h;
3208 VerifyOption _vo;
3209 public:
3210 VerifyLivenessOopClosure(G1CollectedHeap* g1h, VerifyOption vo):
3211 _g1h(g1h), _vo(vo)
3212 { }
3213 void do_oop(narrowOop *p) { do_oop_work(p); }
3214 void do_oop( oop *p) { do_oop_work(p); }
3215
3216 template <class T> void do_oop_work(T *p) {
3217 oop obj = oopDesc::load_decode_heap_oop(p);
3218 guarantee(obj == NULL || !_g1h->is_obj_dead_cond(obj, _vo),
3219 "Dead object referenced by a not dead object");
3220 }
3221 };
3222
3223 class VerifyObjsInRegionClosure: public ObjectClosure {
3224 private:
3225 G1CollectedHeap* _g1h;
3226 size_t _live_bytes;
3227 HeapRegion *_hr;
3228 VerifyOption _vo;
3229 public:
3230 // _vo == UsePrevMarking -> use "prev" marking information,
3231 // _vo == UseNextMarking -> use "next" marking information,
3232 // _vo == UseMarkWord -> use mark word from object header.
3233 VerifyObjsInRegionClosure(HeapRegion *hr, VerifyOption vo)
3234 : _live_bytes(0), _hr(hr), _vo(vo) {
3235 _g1h = G1CollectedHeap::heap();
3236 }
3237 void do_object(oop o) {
3238 VerifyLivenessOopClosure isLive(_g1h, _vo);
3239 assert(o != NULL, "Huh?");
3240 if (!_g1h->is_obj_dead_cond(o, _vo)) {
3241 // If the object is alive according to the mark word,
3242 // then verify that the marking information agrees.
3243 // Note we can't verify the contra-positive of the
3244 // above: if the object is dead (according to the mark
3245 // word), it may not be marked, or may have been marked
3246 // but has since became dead, or may have been allocated
3247 // since the last marking.
3248 if (_vo == VerifyOption_G1UseMarkWord) {
3249 guarantee(!_g1h->is_obj_dead(o), "mark word and concurrent mark mismatch");
3250 }
3251
3252 o->oop_iterate_no_header(&isLive);
3253 if (!_hr->obj_allocated_since_prev_marking(o)) {
3254 size_t obj_size = o->size(); // Make sure we don't overflow
3255 _live_bytes += (obj_size * HeapWordSize);
3256 }
3257 }
3258 }
3259 size_t live_bytes() { return _live_bytes; }
3260 };
3261
3262 class PrintObjsInRegionClosure : public ObjectClosure {
3263 HeapRegion *_hr;
3264 G1CollectedHeap *_g1;
3265 public:
3266 PrintObjsInRegionClosure(HeapRegion *hr) : _hr(hr) {
3267 _g1 = G1CollectedHeap::heap();
3268 };
3269
3270 void do_object(oop o) {
3271 if (o != NULL) {
3272 HeapWord *start = (HeapWord *) o;
3273 size_t word_sz = o->size();
3274 gclog_or_tty->print("\nPrinting obj "PTR_FORMAT" of size " SIZE_FORMAT
3275 " isMarkedPrev %d isMarkedNext %d isAllocSince %d\n",
3276 (void*) o, word_sz,
3277 _g1->isMarkedPrev(o),
3278 _g1->isMarkedNext(o),
3279 _hr->obj_allocated_since_prev_marking(o));
3280 HeapWord *end = start + word_sz;
3281 HeapWord *cur;
3282 int *val;
3283 for (cur = start; cur < end; cur++) {
3284 val = (int *) cur;
3285 gclog_or_tty->print("\t "PTR_FORMAT":%d\n", val, *val);
3286 }
3287 }
3288 }
3289 };
3290
3291 class VerifyRegionClosure: public HeapRegionClosure {
3292 private:
3293 bool _par;
3294 VerifyOption _vo;
3295 bool _failures;
3296 public:
3297 // _vo == UsePrevMarking -> use "prev" marking information,
3298 // _vo == UseNextMarking -> use "next" marking information,
3299 // _vo == UseMarkWord -> use mark word from object header.
3300 VerifyRegionClosure(bool par, VerifyOption vo)
3301 : _par(par),
3302 _vo(vo),
3303 _failures(false) {}
3304
3305 bool failures() {
3306 return _failures;
3307 }
3308
3309 bool doHeapRegion(HeapRegion* r) {
3310 if (!r->continuesHumongous()) {
3311 bool failures = false;
3312 r->verify(_vo, &failures);
3313 if (failures) {
3314 _failures = true;
3315 } else {
3316 VerifyObjsInRegionClosure not_dead_yet_cl(r, _vo);
3317 r->object_iterate(¬_dead_yet_cl);
3318 if (_vo != VerifyOption_G1UseNextMarking) {
3319 if (r->max_live_bytes() < not_dead_yet_cl.live_bytes()) {
3320 gclog_or_tty->print_cr("["PTR_FORMAT","PTR_FORMAT"] "
3321 "max_live_bytes "SIZE_FORMAT" "
3322 "< calculated "SIZE_FORMAT,
3323 r->bottom(), r->end(),
3324 r->max_live_bytes(),
3325 not_dead_yet_cl.live_bytes());
3326 _failures = true;
3327 }
3328 } else {
3329 // When vo == UseNextMarking we cannot currently do a sanity
3330 // check on the live bytes as the calculation has not been
3331 // finalized yet.
3332 }
3333 }
3334 }
3335 return false; // stop the region iteration if we hit a failure
3336 }
3337 };
3338
3339 // This is the task used for parallel verification of the heap regions
3340
3341 class G1ParVerifyTask: public AbstractGangTask {
3342 private:
3343 G1CollectedHeap* _g1h;
3344 VerifyOption _vo;
3345 bool _failures;
3346
3347 public:
3348 // _vo == UsePrevMarking -> use "prev" marking information,
3349 // _vo == UseNextMarking -> use "next" marking information,
3350 // _vo == UseMarkWord -> use mark word from object header.
3351 G1ParVerifyTask(G1CollectedHeap* g1h, VerifyOption vo) :
3352 AbstractGangTask("Parallel verify task"),
3353 _g1h(g1h),
3354 _vo(vo),
3355 _failures(false) { }
3356
3357 bool failures() {
3358 return _failures;
3359 }
3360
3361 void work(uint worker_id) {
3362 HandleMark hm;
3363 VerifyRegionClosure blk(true, _vo);
3364 _g1h->heap_region_par_iterate_chunked(&blk, worker_id,
3365 _g1h->workers()->active_workers(),
3366 HeapRegion::ParVerifyClaimValue);
3367 if (blk.failures()) {
3368 _failures = true;
3369 }
3370 }
3371 };
3372
3373 void G1CollectedHeap::verify(bool silent, VerifyOption vo) {
3374 if (SafepointSynchronize::is_at_safepoint()) {
3375 assert(Thread::current()->is_VM_thread(),
3376 "Expected to be executed serially by the VM thread at this point");
3377
3378 if (!silent) { gclog_or_tty->print("Roots "); }
3379 VerifyRootsClosure rootsCl(vo);
3380 VerifyKlassClosure klassCl(this, &rootsCl);
3381
3382 // We apply the relevant closures to all the oops in the
3383 // system dictionary, class loader data graph and the string table.
3384 // Don't verify the code cache here, since it's verified below.
3385 const int so = SO_AllClasses | SO_Strings;
3386
3387 // Need cleared claim bits for the strong roots processing
3388 ClassLoaderDataGraph::clear_claimed_marks();
3389
3390 process_strong_roots(true, // activate StrongRootsScope
3391 ScanningOption(so), // roots scanning options
3392 &rootsCl,
3393 &klassCl
3394 );
3395
3396 // Verify the nmethods in the code cache.
3397 G1VerifyCodeRootOopClosure codeRootsCl(this, &rootsCl, vo);
3398 G1VerifyCodeRootBlobClosure blobsCl(&codeRootsCl);
3399 CodeCache::blobs_do(&blobsCl);
3400
3401 bool failures = rootsCl.failures() || codeRootsCl.failures();
3402
3403 if (vo != VerifyOption_G1UseMarkWord) {
3404 // If we're verifying during a full GC then the region sets
3405 // will have been torn down at the start of the GC. Therefore
3406 // verifying the region sets will fail. So we only verify
3407 // the region sets when not in a full GC.
3408 if (!silent) { gclog_or_tty->print("HeapRegionSets "); }
3409 verify_region_sets();
3410 }
3411
3412 if (!silent) { gclog_or_tty->print("HeapRegions "); }
3413 if (GCParallelVerificationEnabled && ParallelGCThreads > 1) {
3414 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3415 "sanity check");
3416
3417 G1ParVerifyTask task(this, vo);
3418 assert(UseDynamicNumberOfGCThreads ||
3419 workers()->active_workers() == workers()->total_workers(),
3420 "If not dynamic should be using all the workers");
3421 int n_workers = workers()->active_workers();
3422 set_par_threads(n_workers);
3423 workers()->run_task(&task);
3424 set_par_threads(0);
3425 if (task.failures()) {
3426 failures = true;
3427 }
3428
3429 // Checks that the expected amount of parallel work was done.
3430 // The implication is that n_workers is > 0.
3431 assert(check_heap_region_claim_values(HeapRegion::ParVerifyClaimValue),
3432 "sanity check");
3433
3434 reset_heap_region_claim_values();
3435
3436 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3437 "sanity check");
3438 } else {
3439 VerifyRegionClosure blk(false, vo);
3440 heap_region_iterate(&blk);
3441 if (blk.failures()) {
3442 failures = true;
3443 }
3444 }
3445 if (!silent) gclog_or_tty->print("RemSet ");
3446 rem_set()->verify();
3447
3448 if (G1StringDedup::is_enabled()) {
3449 if (!silent) gclog_or_tty->print("StrDedup ");
3450 G1StringDedup::verify();
3451 }
3452
3453 if (failures) {
3454 gclog_or_tty->print_cr("Heap:");
3455 // It helps to have the per-region information in the output to
3456 // help us track down what went wrong. This is why we call
3457 // print_extended_on() instead of print_on().
3458 print_extended_on(gclog_or_tty);
3459 gclog_or_tty->print_cr("");
3460 #ifndef PRODUCT
3461 if (VerifyDuringGC && G1VerifyDuringGCPrintReachable) {
3462 concurrent_mark()->print_reachable("at-verification-failure",
3463 vo, false /* all */);
3464 }
3465 #endif
3466 gclog_or_tty->flush();
3467 }
3468 guarantee(!failures, "there should not have been any failures");
3469 } else {
3470 if (!silent) {
3471 gclog_or_tty->print("(SKIPPING Roots, HeapRegionSets, HeapRegions, RemSet");
3472 if (G1StringDedup::is_enabled()) {
3473 gclog_or_tty->print(", StrDedup");
3474 }
3475 gclog_or_tty->print(") ");
3476 }
3477 }
3478 }
3479
3480 void G1CollectedHeap::verify(bool silent) {
3481 verify(silent, VerifyOption_G1UsePrevMarking);
3482 }
3483
3484 double G1CollectedHeap::verify(bool guard, const char* msg) {
3485 double verify_time_ms = 0.0;
3486
3487 if (guard && total_collections() >= VerifyGCStartAt) {
3488 double verify_start = os::elapsedTime();
3489 HandleMark hm; // Discard invalid handles created during verification
3490 prepare_for_verify();
3491 Universe::verify(VerifyOption_G1UsePrevMarking, msg);
3492 verify_time_ms = (os::elapsedTime() - verify_start) * 1000;
3493 }
3494
3495 return verify_time_ms;
3496 }
3497
3498 void G1CollectedHeap::verify_before_gc() {
3499 double verify_time_ms = verify(VerifyBeforeGC, " VerifyBeforeGC:");
3500 g1_policy()->phase_times()->record_verify_before_time_ms(verify_time_ms);
3501 }
3502
3503 void G1CollectedHeap::verify_after_gc() {
3504 double verify_time_ms = verify(VerifyAfterGC, " VerifyAfterGC:");
3505 g1_policy()->phase_times()->record_verify_after_time_ms(verify_time_ms);
3506 }
3507
3508 class PrintRegionClosure: public HeapRegionClosure {
3509 outputStream* _st;
3510 public:
3511 PrintRegionClosure(outputStream* st) : _st(st) {}
3512 bool doHeapRegion(HeapRegion* r) {
3513 r->print_on(_st);
3514 return false;
3515 }
3516 };
3517
3518 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
3519 const HeapRegion* hr,
3520 const VerifyOption vo) const {
3521 switch (vo) {
3522 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr);
3523 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr);
3524 case VerifyOption_G1UseMarkWord: return !obj->is_gc_marked();
3525 default: ShouldNotReachHere();
3526 }
3527 return false; // keep some compilers happy
3528 }
3529
3530 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
3531 const VerifyOption vo) const {
3532 switch (vo) {
3533 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj);
3534 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj);
3535 case VerifyOption_G1UseMarkWord: return !obj->is_gc_marked();
3536 default: ShouldNotReachHere();
3537 }
3538 return false; // keep some compilers happy
3539 }
3540
3541 void G1CollectedHeap::print_on(outputStream* st) const {
3542 st->print(" %-20s", "garbage-first heap");
3543 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
3544 capacity()/K, used_unlocked()/K);
3545 st->print(" [" INTPTR_FORMAT ", " INTPTR_FORMAT ", " INTPTR_FORMAT ")",
3546 _g1_storage.low_boundary(),
3547 _g1_storage.high(),
3548 _g1_storage.high_boundary());
3549 st->cr();
3550 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
3551 uint young_regions = _young_list->length();
3552 st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
3553 (size_t) young_regions * HeapRegion::GrainBytes / K);
3554 uint survivor_regions = g1_policy()->recorded_survivor_regions();
3555 st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
3556 (size_t) survivor_regions * HeapRegion::GrainBytes / K);
3557 st->cr();
3558 MetaspaceAux::print_on(st);
3559 }
3560
3561 void G1CollectedHeap::print_extended_on(outputStream* st) const {
3562 print_on(st);
3563
3564 // Print the per-region information.
3565 st->cr();
3566 st->print_cr("Heap Regions: (Y=young(eden), SU=young(survivor), "
3567 "HS=humongous(starts), HC=humongous(continues), "
3568 "CS=collection set, F=free, TS=gc time stamp, "
3569 "PTAMS=previous top-at-mark-start, "
3570 "NTAMS=next top-at-mark-start)");
3571 PrintRegionClosure blk(st);
3572 heap_region_iterate(&blk);
3573 }
3574
3575 void G1CollectedHeap::print_on_error(outputStream* st) const {
3576 this->CollectedHeap::print_on_error(st);
3577
3578 if (_cm != NULL) {
3579 st->cr();
3580 _cm->print_on_error(st);
3581 }
3582 }
3583
3584 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
3585 if (G1CollectedHeap::use_parallel_gc_threads()) {
3586 workers()->print_worker_threads_on(st);
3587 }
3588 _cmThread->print_on(st);
3589 st->cr();
3590 _cm->print_worker_threads_on(st);
3591 _cg1r->print_worker_threads_on(st);
3592 if (G1StringDedup::is_enabled()) {
3593 G1StringDedup::print_worker_threads_on(st);
3594 }
3595 }
3596
3597 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
3598 if (G1CollectedHeap::use_parallel_gc_threads()) {
3599 workers()->threads_do(tc);
3600 }
3601 tc->do_thread(_cmThread);
3602 _cg1r->threads_do(tc);
3603 if (G1StringDedup::is_enabled()) {
3604 G1StringDedup::threads_do(tc);
3605 }
3606 }
3607
3608 void G1CollectedHeap::print_tracing_info() const {
3609 // We'll overload this to mean "trace GC pause statistics."
3610 if (TraceGen0Time || TraceGen1Time) {
3611 // The "G1CollectorPolicy" is keeping track of these stats, so delegate
3612 // to that.
3613 g1_policy()->print_tracing_info();
3614 }
3615 if (G1SummarizeRSetStats) {
3616 g1_rem_set()->print_summary_info();
3617 }
3618 if (G1SummarizeConcMark) {
3619 concurrent_mark()->print_summary_info();
3620 }
3621 g1_policy()->print_yg_surv_rate_info();
3622 SpecializationStats::print();
3623 }
3624
3625 #ifndef PRODUCT
3626 // Helpful for debugging RSet issues.
3627
3628 class PrintRSetsClosure : public HeapRegionClosure {
3629 private:
3630 const char* _msg;
3631 size_t _occupied_sum;
3632
3633 public:
3634 bool doHeapRegion(HeapRegion* r) {
3635 HeapRegionRemSet* hrrs = r->rem_set();
3636 size_t occupied = hrrs->occupied();
3637 _occupied_sum += occupied;
3638
3639 gclog_or_tty->print_cr("Printing RSet for region "HR_FORMAT,
3640 HR_FORMAT_PARAMS(r));
3641 if (occupied == 0) {
3642 gclog_or_tty->print_cr(" RSet is empty");
3643 } else {
3644 hrrs->print();
3645 }
3646 gclog_or_tty->print_cr("----------");
3647 return false;
3648 }
3649
3650 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
3651 gclog_or_tty->cr();
3652 gclog_or_tty->print_cr("========================================");
3653 gclog_or_tty->print_cr(msg);
3654 gclog_or_tty->cr();
3655 }
3656
3657 ~PrintRSetsClosure() {
3658 gclog_or_tty->print_cr("Occupied Sum: "SIZE_FORMAT, _occupied_sum);
3659 gclog_or_tty->print_cr("========================================");
3660 gclog_or_tty->cr();
3661 }
3662 };
3663
3664 void G1CollectedHeap::print_cset_rsets() {
3665 PrintRSetsClosure cl("Printing CSet RSets");
3666 collection_set_iterate(&cl);
3667 }
3668
3669 void G1CollectedHeap::print_all_rsets() {
3670 PrintRSetsClosure cl("Printing All RSets");;
3671 heap_region_iterate(&cl);
3672 }
3673 #endif // PRODUCT
3674
3675 G1CollectedHeap* G1CollectedHeap::heap() {
3676 assert(_sh->kind() == CollectedHeap::G1CollectedHeap,
3677 "not a garbage-first heap");
3678 return _g1h;
3679 }
3680
3681 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) {
3682 // always_do_update_barrier = false;
3683 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
3684 // Fill TLAB's and such
3685 accumulate_statistics_all_tlabs();
3686 ensure_parsability(true);
3687
3688 if (G1SummarizeRSetStats && (G1SummarizeRSetStatsPeriod > 0) &&
3689 (total_collections() % G1SummarizeRSetStatsPeriod == 0)) {
3690 g1_rem_set()->print_periodic_summary_info("Before GC RS summary");
3691 }
3692 }
3693
3694 void G1CollectedHeap::gc_epilogue(bool full /* Ignored */) {
3695
3696 if (G1SummarizeRSetStats &&
3697 (G1SummarizeRSetStatsPeriod > 0) &&
3698 // we are at the end of the GC. Total collections has already been increased.
3699 ((total_collections() - 1) % G1SummarizeRSetStatsPeriod == 0)) {
3700 g1_rem_set()->print_periodic_summary_info("After GC RS summary");
3701 }
3702
3703 // FIXME: what is this about?
3704 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
3705 // is set.
3706 COMPILER2_PRESENT(assert(DerivedPointerTable::is_empty(),
3707 "derived pointer present"));
3708 // always_do_update_barrier = true;
3709
3710 resize_all_tlabs();
3711
3712 // We have just completed a GC. Update the soft reference
3713 // policy with the new heap occupancy
3714 Universe::update_heap_info_at_gc();
3715 }
3716
3717 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
3718 unsigned int gc_count_before,
3719 bool* succeeded,
3720 GCCause::Cause gc_cause) {
3721 assert_heap_not_locked_and_not_at_safepoint();
3722 g1_policy()->record_stop_world_start();
3723 VM_G1IncCollectionPause op(gc_count_before,
3724 word_size,
3725 false, /* should_initiate_conc_mark */
3726 g1_policy()->max_pause_time_ms(),
3727 gc_cause);
3728 VMThread::execute(&op);
3729
3730 HeapWord* result = op.result();
3731 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
3732 assert(result == NULL || ret_succeeded,
3733 "the result should be NULL if the VM did not succeed");
3734 *succeeded = ret_succeeded;
3735
3736 assert_heap_not_locked();
3737 return result;
3738 }
3739
3740 void
3741 G1CollectedHeap::doConcurrentMark() {
3742 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
3743 if (!_cmThread->in_progress()) {
3744 _cmThread->set_started();
3745 CGC_lock->notify();
3746 }
3747 }
3748
3749 size_t G1CollectedHeap::pending_card_num() {
3750 size_t extra_cards = 0;
3751 JavaThread *curr = Threads::first();
3752 while (curr != NULL) {
3753 DirtyCardQueue& dcq = curr->dirty_card_queue();
3754 extra_cards += dcq.size();
3755 curr = curr->next();
3756 }
3757 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
3758 size_t buffer_size = dcqs.buffer_size();
3759 size_t buffer_num = dcqs.completed_buffers_num();
3760
3761 // PtrQueueSet::buffer_size() and PtrQueue:size() return sizes
3762 // in bytes - not the number of 'entries'. We need to convert
3763 // into a number of cards.
3764 return (buffer_size * buffer_num + extra_cards) / oopSize;
3765 }
3766
3767 size_t G1CollectedHeap::cards_scanned() {
3768 return g1_rem_set()->cardsScanned();
3769 }
3770
3771 void
3772 G1CollectedHeap::setup_surviving_young_words() {
3773 assert(_surviving_young_words == NULL, "pre-condition");
3774 uint array_length = g1_policy()->young_cset_region_length();
3775 _surviving_young_words = NEW_C_HEAP_ARRAY(size_t, (size_t) array_length, mtGC);
3776 if (_surviving_young_words == NULL) {
3777 vm_exit_out_of_memory(sizeof(size_t) * array_length, OOM_MALLOC_ERROR,
3778 "Not enough space for young surv words summary.");
3779 }
3780 memset(_surviving_young_words, 0, (size_t) array_length * sizeof(size_t));
3781 #ifdef ASSERT
3782 for (uint i = 0; i < array_length; ++i) {
3783 assert( _surviving_young_words[i] == 0, "memset above" );
3784 }
3785 #endif // !ASSERT
3786 }
3787
3788 void
3789 G1CollectedHeap::update_surviving_young_words(size_t* surv_young_words) {
3790 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
3791 uint array_length = g1_policy()->young_cset_region_length();
3792 for (uint i = 0; i < array_length; ++i) {
3793 _surviving_young_words[i] += surv_young_words[i];
3794 }
3795 }
3796
3797 void
3798 G1CollectedHeap::cleanup_surviving_young_words() {
3799 guarantee( _surviving_young_words != NULL, "pre-condition" );
3800 FREE_C_HEAP_ARRAY(size_t, _surviving_young_words, mtGC);
3801 _surviving_young_words = NULL;
3802 }
3803
3804 #ifdef ASSERT
3805 class VerifyCSetClosure: public HeapRegionClosure {
3806 public:
3807 bool doHeapRegion(HeapRegion* hr) {
3808 // Here we check that the CSet region's RSet is ready for parallel
3809 // iteration. The fields that we'll verify are only manipulated
3810 // when the region is part of a CSet and is collected. Afterwards,
3811 // we reset these fields when we clear the region's RSet (when the
3812 // region is freed) so they are ready when the region is
3813 // re-allocated. The only exception to this is if there's an
3814 // evacuation failure and instead of freeing the region we leave
3815 // it in the heap. In that case, we reset these fields during
3816 // evacuation failure handling.
3817 guarantee(hr->rem_set()->verify_ready_for_par_iteration(), "verification");
3818
3819 // Here's a good place to add any other checks we'd like to
3820 // perform on CSet regions.
3821 return false;
3822 }
3823 };
3824 #endif // ASSERT
3825
3826 #if TASKQUEUE_STATS
3827 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
3828 st->print_raw_cr("GC Task Stats");
3829 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
3830 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
3831 }
3832
3833 void G1CollectedHeap::print_taskqueue_stats(outputStream* const st) const {
3834 print_taskqueue_stats_hdr(st);
3835
3836 TaskQueueStats totals;
3837 const int n = workers() != NULL ? workers()->total_workers() : 1;
3838 for (int i = 0; i < n; ++i) {
3839 st->print("%3d ", i); task_queue(i)->stats.print(st); st->cr();
3840 totals += task_queue(i)->stats;
3841 }
3842 st->print_raw("tot "); totals.print(st); st->cr();
3843
3844 DEBUG_ONLY(totals.verify());
3845 }
3846
3847 void G1CollectedHeap::reset_taskqueue_stats() {
3848 const int n = workers() != NULL ? workers()->total_workers() : 1;
3849 for (int i = 0; i < n; ++i) {
3850 task_queue(i)->stats.reset();
3851 }
3852 }
3853 #endif // TASKQUEUE_STATS
3854
3855 void G1CollectedHeap::log_gc_header() {
3856 if (!G1Log::fine()) {
3857 return;
3858 }
3859
3860 gclog_or_tty->date_stamp(PrintGCDateStamps);
3861 gclog_or_tty->stamp(PrintGCTimeStamps);
3862
3863 GCCauseString gc_cause_str = GCCauseString("GC pause", gc_cause())
3864 .append(g1_policy()->gcs_are_young() ? "(young)" : "(mixed)")
3865 .append(g1_policy()->during_initial_mark_pause() ? " (initial-mark)" : "");
3866
3867 gclog_or_tty->print("[%s", (const char*)gc_cause_str);
3868 }
3869
3870 void G1CollectedHeap::log_gc_footer(double pause_time_sec) {
3871 if (!G1Log::fine()) {
3872 return;
3873 }
3874
3875 if (G1Log::finer()) {
3876 if (evacuation_failed()) {
3877 gclog_or_tty->print(" (to-space exhausted)");
3878 }
3879 gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec);
3880 g1_policy()->phase_times()->note_gc_end();
3881 g1_policy()->phase_times()->print(pause_time_sec);
3882 g1_policy()->print_detailed_heap_transition();
3883 } else {
3884 if (evacuation_failed()) {
3885 gclog_or_tty->print("--");
3886 }
3887 g1_policy()->print_heap_transition();
3888 gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec);
3889 }
3890 gclog_or_tty->flush();
3891 }
3892
3893 bool
3894 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
3895 assert_at_safepoint(true /* should_be_vm_thread */);
3896 guarantee(!is_gc_active(), "collection is not reentrant");
3897
3898 if (GC_locker::check_active_before_gc()) {
3899 return false;
3900 }
3901
3902 _gc_timer_stw->register_gc_start();
3903
3904 _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start());
3905
3906 SvcGCMarker sgcm(SvcGCMarker::MINOR);
3907 ResourceMark rm;
3908
3909 print_heap_before_gc();
3910 trace_heap_before_gc(_gc_tracer_stw);
3911
3912 verify_region_sets_optional();
3913 verify_dirty_young_regions();
3914
3915 // This call will decide whether this pause is an initial-mark
3916 // pause. If it is, during_initial_mark_pause() will return true
3917 // for the duration of this pause.
3918 g1_policy()->decide_on_conc_mark_initiation();
3919
3920 // We do not allow initial-mark to be piggy-backed on a mixed GC.
3921 assert(!g1_policy()->during_initial_mark_pause() ||
3922 g1_policy()->gcs_are_young(), "sanity");
3923
3924 // We also do not allow mixed GCs during marking.
3925 assert(!mark_in_progress() || g1_policy()->gcs_are_young(), "sanity");
3926
3927 // Record whether this pause is an initial mark. When the current
3928 // thread has completed its logging output and it's safe to signal
3929 // the CM thread, the flag's value in the policy has been reset.
3930 bool should_start_conc_mark = g1_policy()->during_initial_mark_pause();
3931
3932 // Inner scope for scope based logging, timers, and stats collection
3933 {
3934 EvacuationInfo evacuation_info;
3935
3936 if (g1_policy()->during_initial_mark_pause()) {
3937 // We are about to start a marking cycle, so we increment the
3938 // full collection counter.
3939 increment_old_marking_cycles_started();
3940 register_concurrent_cycle_start(_gc_timer_stw->gc_start());
3941 }
3942
3943 _gc_tracer_stw->report_yc_type(yc_type());
3944
3945 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
3946
3947 int active_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
3948 workers()->active_workers() : 1);
3949 double pause_start_sec = os::elapsedTime();
3950 g1_policy()->phase_times()->note_gc_start(active_workers);
3951 log_gc_header();
3952
3953 TraceCollectorStats tcs(g1mm()->incremental_collection_counters());
3954 TraceMemoryManagerStats tms(false /* fullGC */, gc_cause());
3955
3956 // If the secondary_free_list is not empty, append it to the
3957 // free_list. No need to wait for the cleanup operation to finish;
3958 // the region allocation code will check the secondary_free_list
3959 // and wait if necessary. If the G1StressConcRegionFreeing flag is
3960 // set, skip this step so that the region allocation code has to
3961 // get entries from the secondary_free_list.
3962 if (!G1StressConcRegionFreeing) {
3963 append_secondary_free_list_if_not_empty_with_lock();
3964 }
3965
3966 assert(check_young_list_well_formed(), "young list should be well formed");
3967 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3968 "sanity check");
3969
3970 // Don't dynamically change the number of GC threads this early. A value of
3971 // 0 is used to indicate serial work. When parallel work is done,
3972 // it will be set.
3973
3974 { // Call to jvmpi::post_class_unload_events must occur outside of active GC
3975 IsGCActiveMark x;
3976
3977 gc_prologue(false);
3978 increment_total_collections(false /* full gc */);
3979 increment_gc_time_stamp();
3980
3981 verify_before_gc();
3982
3983 COMPILER2_PRESENT(DerivedPointerTable::clear());
3984
3985 // Please see comment in g1CollectedHeap.hpp and
3986 // G1CollectedHeap::ref_processing_init() to see how
3987 // reference processing currently works in G1.
3988
3989 // Enable discovery in the STW reference processor
3990 ref_processor_stw()->enable_discovery(true /*verify_disabled*/,
3991 true /*verify_no_refs*/);
3992
3993 {
3994 // We want to temporarily turn off discovery by the
3995 // CM ref processor, if necessary, and turn it back on
3996 // on again later if we do. Using a scoped
3997 // NoRefDiscovery object will do this.
3998 NoRefDiscovery no_cm_discovery(ref_processor_cm());
3999
4000 // Forget the current alloc region (we might even choose it to be part
4001 // of the collection set!).
4002 release_mutator_alloc_region();
4003
4004 // We should call this after we retire the mutator alloc
4005 // region(s) so that all the ALLOC / RETIRE events are generated
4006 // before the start GC event.
4007 _hr_printer.start_gc(false /* full */, (size_t) total_collections());
4008
4009 // This timing is only used by the ergonomics to handle our pause target.
4010 // It is unclear why this should not include the full pause. We will
4011 // investigate this in CR 7178365.
4012 //
4013 // Preserving the old comment here if that helps the investigation:
4014 //
4015 // The elapsed time induced by the start time below deliberately elides
4016 // the possible verification above.
4017 double sample_start_time_sec = os::elapsedTime();
4018
4019 #if YOUNG_LIST_VERBOSE
4020 gclog_or_tty->print_cr("\nBefore recording pause start.\nYoung_list:");
4021 _young_list->print();
4022 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
4023 #endif // YOUNG_LIST_VERBOSE
4024
4025 g1_policy()->record_collection_pause_start(sample_start_time_sec);
4026
4027 double scan_wait_start = os::elapsedTime();
4028 // We have to wait until the CM threads finish scanning the
4029 // root regions as it's the only way to ensure that all the
4030 // objects on them have been correctly scanned before we start
4031 // moving them during the GC.
4032 bool waited = _cm->root_regions()->wait_until_scan_finished();
4033 double wait_time_ms = 0.0;
4034 if (waited) {
4035 double scan_wait_end = os::elapsedTime();
4036 wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
4037 }
4038 g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms);
4039
4040 #if YOUNG_LIST_VERBOSE
4041 gclog_or_tty->print_cr("\nAfter recording pause start.\nYoung_list:");
4042 _young_list->print();
4043 #endif // YOUNG_LIST_VERBOSE
4044
4045 if (g1_policy()->during_initial_mark_pause()) {
4046 concurrent_mark()->checkpointRootsInitialPre();
4047 }
4048
4049 #if YOUNG_LIST_VERBOSE
4050 gclog_or_tty->print_cr("\nBefore choosing collection set.\nYoung_list:");
4051 _young_list->print();
4052 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
4053 #endif // YOUNG_LIST_VERBOSE
4054
4055 g1_policy()->finalize_cset(target_pause_time_ms, evacuation_info);
4056
4057 _cm->note_start_of_gc();
4058 // We should not verify the per-thread SATB buffers given that
4059 // we have not filtered them yet (we'll do so during the
4060 // GC). We also call this after finalize_cset() to
4061 // ensure that the CSet has been finalized.
4062 _cm->verify_no_cset_oops(true /* verify_stacks */,
4063 true /* verify_enqueued_buffers */,
4064 false /* verify_thread_buffers */,
4065 true /* verify_fingers */);
4066
4067 if (_hr_printer.is_active()) {
4068 HeapRegion* hr = g1_policy()->collection_set();
4069 while (hr != NULL) {
4070 G1HRPrinter::RegionType type;
4071 if (!hr->is_young()) {
4072 type = G1HRPrinter::Old;
4073 } else if (hr->is_survivor()) {
4074 type = G1HRPrinter::Survivor;
4075 } else {
4076 type = G1HRPrinter::Eden;
4077 }
4078 _hr_printer.cset(hr);
4079 hr = hr->next_in_collection_set();
4080 }
4081 }
4082
4083 #ifdef ASSERT
4084 VerifyCSetClosure cl;
4085 collection_set_iterate(&cl);
4086 #endif // ASSERT
4087
4088 setup_surviving_young_words();
4089
4090 // Initialize the GC alloc regions.
4091 init_gc_alloc_regions(evacuation_info);
4092
4093 // Actually do the work...
4094 evacuate_collection_set(evacuation_info);
4095
4096 // We do this to mainly verify the per-thread SATB buffers
4097 // (which have been filtered by now) since we didn't verify
4098 // them earlier. No point in re-checking the stacks / enqueued
4099 // buffers given that the CSet has not changed since last time
4100 // we checked.
4101 _cm->verify_no_cset_oops(false /* verify_stacks */,
4102 false /* verify_enqueued_buffers */,
4103 true /* verify_thread_buffers */,
4104 true /* verify_fingers */);
4105
4106 free_collection_set(g1_policy()->collection_set(), evacuation_info);
4107 g1_policy()->clear_collection_set();
4108
4109 cleanup_surviving_young_words();
4110
4111 // Start a new incremental collection set for the next pause.
4112 g1_policy()->start_incremental_cset_building();
4113
4114 clear_cset_fast_test();
4115
4116 _young_list->reset_sampled_info();
4117
4118 // Don't check the whole heap at this point as the
4119 // GC alloc regions from this pause have been tagged
4120 // as survivors and moved on to the survivor list.
4121 // Survivor regions will fail the !is_young() check.
4122 assert(check_young_list_empty(false /* check_heap */),
4123 "young list should be empty");
4124
4125 #if YOUNG_LIST_VERBOSE
4126 gclog_or_tty->print_cr("Before recording survivors.\nYoung List:");
4127 _young_list->print();
4128 #endif // YOUNG_LIST_VERBOSE
4129
4130 g1_policy()->record_survivor_regions(_young_list->survivor_length(),
4131 _young_list->first_survivor_region(),
4132 _young_list->last_survivor_region());
4133
4134 _young_list->reset_auxilary_lists();
4135
4136 if (evacuation_failed()) {
4137 _summary_bytes_used = recalculate_used();
4138 uint n_queues = MAX2((int)ParallelGCThreads, 1);
4139 for (uint i = 0; i < n_queues; i++) {
4140 if (_evacuation_failed_info_array[i].has_failed()) {
4141 _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]);
4142 }
4143 }
4144 } else {
4145 // The "used" of the the collection set have already been subtracted
4146 // when they were freed. Add in the bytes evacuated.
4147 _summary_bytes_used += g1_policy()->bytes_copied_during_gc();
4148 }
4149
4150 if (g1_policy()->during_initial_mark_pause()) {
4151 // We have to do this before we notify the CM threads that
4152 // they can start working to make sure that all the
4153 // appropriate initialization is done on the CM object.
4154 concurrent_mark()->checkpointRootsInitialPost();
4155 set_marking_started();
4156 // Note that we don't actually trigger the CM thread at
4157 // this point. We do that later when we're sure that
4158 // the current thread has completed its logging output.
4159 }
4160
4161 allocate_dummy_regions();
4162
4163 #if YOUNG_LIST_VERBOSE
4164 gclog_or_tty->print_cr("\nEnd of the pause.\nYoung_list:");
4165 _young_list->print();
4166 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
4167 #endif // YOUNG_LIST_VERBOSE
4168
4169 init_mutator_alloc_region();
4170
4171 {
4172 size_t expand_bytes = g1_policy()->expansion_amount();
4173 if (expand_bytes > 0) {
4174 size_t bytes_before = capacity();
4175 // No need for an ergo verbose message here,
4176 // expansion_amount() does this when it returns a value > 0.
4177 if (!expand(expand_bytes)) {
4178 // We failed to expand the heap so let's verify that
4179 // committed/uncommitted amount match the backing store
4180 assert(capacity() == _g1_storage.committed_size(), "committed size mismatch");
4181 assert(max_capacity() == _g1_storage.reserved_size(), "reserved size mismatch");
4182 }
4183 }
4184 }
4185
4186 // We redo the verification but now wrt to the new CSet which
4187 // has just got initialized after the previous CSet was freed.
4188 _cm->verify_no_cset_oops(true /* verify_stacks */,
4189 true /* verify_enqueued_buffers */,
4190 true /* verify_thread_buffers */,
4191 true /* verify_fingers */);
4192 _cm->note_end_of_gc();
4193
4194 // This timing is only used by the ergonomics to handle our pause target.
4195 // It is unclear why this should not include the full pause. We will
4196 // investigate this in CR 7178365.
4197 double sample_end_time_sec = os::elapsedTime();
4198 double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
4199 g1_policy()->record_collection_pause_end(pause_time_ms, evacuation_info);
4200
4201 MemoryService::track_memory_usage();
4202
4203 // In prepare_for_verify() below we'll need to scan the deferred
4204 // update buffers to bring the RSets up-to-date if
4205 // G1HRRSFlushLogBuffersOnVerify has been set. While scanning
4206 // the update buffers we'll probably need to scan cards on the
4207 // regions we just allocated to (i.e., the GC alloc
4208 // regions). However, during the last GC we called
4209 // set_saved_mark() on all the GC alloc regions, so card
4210 // scanning might skip the [saved_mark_word()...top()] area of
4211 // those regions (i.e., the area we allocated objects into
4212 // during the last GC). But it shouldn't. Given that
4213 // saved_mark_word() is conditional on whether the GC time stamp
4214 // on the region is current or not, by incrementing the GC time
4215 // stamp here we invalidate all the GC time stamps on all the
4216 // regions and saved_mark_word() will simply return top() for
4217 // all the regions. This is a nicer way of ensuring this rather
4218 // than iterating over the regions and fixing them. In fact, the
4219 // GC time stamp increment here also ensures that
4220 // saved_mark_word() will return top() between pauses, i.e.,
4221 // during concurrent refinement. So we don't need the
4222 // is_gc_active() check to decided which top to use when
4223 // scanning cards (see CR 7039627).
4224 increment_gc_time_stamp();
4225
4226 verify_after_gc();
4227
4228 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
4229 ref_processor_stw()->verify_no_references_recorded();
4230
4231 // CM reference discovery will be re-enabled if necessary.
4232 }
4233
4234 // We should do this after we potentially expand the heap so
4235 // that all the COMMIT events are generated before the end GC
4236 // event, and after we retire the GC alloc regions so that all
4237 // RETIRE events are generated before the end GC event.
4238 _hr_printer.end_gc(false /* full */, (size_t) total_collections());
4239
4240 if (mark_in_progress()) {
4241 concurrent_mark()->update_g1_committed();
4242 }
4243
4244 #ifdef TRACESPINNING
4245 ParallelTaskTerminator::print_termination_counts();
4246 #endif
4247
4248 gc_epilogue(false);
4249 }
4250
4251 // Print the remainder of the GC log output.
4252 log_gc_footer(os::elapsedTime() - pause_start_sec);
4253
4254 // It is not yet to safe to tell the concurrent mark to
4255 // start as we have some optional output below. We don't want the
4256 // output from the concurrent mark thread interfering with this
4257 // logging output either.
4258
4259 _hrs.verify_optional();
4260 verify_region_sets_optional();
4261
4262 TASKQUEUE_STATS_ONLY(if (ParallelGCVerbose) print_taskqueue_stats());
4263 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
4264
4265 print_heap_after_gc();
4266 trace_heap_after_gc(_gc_tracer_stw);
4267
4268 // We must call G1MonitoringSupport::update_sizes() in the same scoping level
4269 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
4270 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
4271 // before any GC notifications are raised.
4272 g1mm()->update_sizes();
4273
4274 _gc_tracer_stw->report_evacuation_info(&evacuation_info);
4275 _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold());
4276 _gc_timer_stw->register_gc_end();
4277 _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions());
4278 }
4279 // It should now be safe to tell the concurrent mark thread to start
4280 // without its logging output interfering with the logging output
4281 // that came from the pause.
4282
4283 if (should_start_conc_mark) {
4284 // CAUTION: after the doConcurrentMark() call below,
4285 // the concurrent marking thread(s) could be running
4286 // concurrently with us. Make sure that anything after
4287 // this point does not assume that we are the only GC thread
4288 // running. Note: of course, the actual marking work will
4289 // not start until the safepoint itself is released in
4290 // SuspendibleThreadSet::desynchronize().
4291 doConcurrentMark();
4292 }
4293
4294 return true;
4295 }
4296
4297 size_t G1CollectedHeap::desired_plab_sz(GCAllocPurpose purpose)
4298 {
4299 size_t gclab_word_size;
4300 switch (purpose) {
4301 case GCAllocForSurvived:
4302 gclab_word_size = _survivor_plab_stats.desired_plab_sz();
4303 break;
4304 case GCAllocForTenured:
4305 gclab_word_size = _old_plab_stats.desired_plab_sz();
4306 break;
4307 default:
4308 assert(false, "unknown GCAllocPurpose");
4309 gclab_word_size = _old_plab_stats.desired_plab_sz();
4310 break;
4311 }
4312
4313 // Prevent humongous PLAB sizes for two reasons:
4314 // * PLABs are allocated using a similar paths as oops, but should
4315 // never be in a humongous region
4316 // * Allowing humongous PLABs needlessly churns the region free lists
4317 return MIN2(_humongous_object_threshold_in_words, gclab_word_size);
4318 }
4319
4320 void G1CollectedHeap::init_mutator_alloc_region() {
4321 assert(_mutator_alloc_region.get() == NULL, "pre-condition");
4322 _mutator_alloc_region.init();
4323 }
4324
4325 void G1CollectedHeap::release_mutator_alloc_region() {
4326 _mutator_alloc_region.release();
4327 assert(_mutator_alloc_region.get() == NULL, "post-condition");
4328 }
4329
4330 void G1CollectedHeap::init_gc_alloc_regions(EvacuationInfo& evacuation_info) {
4331 assert_at_safepoint(true /* should_be_vm_thread */);
4332
4333 _survivor_gc_alloc_region.init();
4334 _old_gc_alloc_region.init();
4335 HeapRegion* retained_region = _retained_old_gc_alloc_region;
4336 _retained_old_gc_alloc_region = NULL;
4337
4338 // We will discard the current GC alloc region if:
4339 // a) it's in the collection set (it can happen!),
4340 // b) it's already full (no point in using it),
4341 // c) it's empty (this means that it was emptied during
4342 // a cleanup and it should be on the free list now), or
4343 // d) it's humongous (this means that it was emptied
4344 // during a cleanup and was added to the free list, but
4345 // has been subsequently used to allocate a humongous
4346 // object that may be less than the region size).
4347 if (retained_region != NULL &&
4348 !retained_region->in_collection_set() &&
4349 !(retained_region->top() == retained_region->end()) &&
4350 !retained_region->is_empty() &&
4351 !retained_region->isHumongous()) {
4352 retained_region->set_saved_mark();
4353 // The retained region was added to the old region set when it was
4354 // retired. We have to remove it now, since we don't allow regions
4355 // we allocate to in the region sets. We'll re-add it later, when
4356 // it's retired again.
4357 _old_set.remove(retained_region);
4358 bool during_im = g1_policy()->during_initial_mark_pause();
4359 retained_region->note_start_of_copying(during_im);
4360 _old_gc_alloc_region.set(retained_region);
4361 _hr_printer.reuse(retained_region);
4362 evacuation_info.set_alloc_regions_used_before(retained_region->used());
4363 }
4364 }
4365
4366 void G1CollectedHeap::release_gc_alloc_regions(uint no_of_gc_workers, EvacuationInfo& evacuation_info) {
4367 evacuation_info.set_allocation_regions(_survivor_gc_alloc_region.count() +
4368 _old_gc_alloc_region.count());
4369 _survivor_gc_alloc_region.release();
4370 // If we have an old GC alloc region to release, we'll save it in
4371 // _retained_old_gc_alloc_region. If we don't
4372 // _retained_old_gc_alloc_region will become NULL. This is what we
4373 // want either way so no reason to check explicitly for either
4374 // condition.
4375 _retained_old_gc_alloc_region = _old_gc_alloc_region.release();
4376
4377 if (ResizePLAB) {
4378 _survivor_plab_stats.adjust_desired_plab_sz(no_of_gc_workers);
4379 _old_plab_stats.adjust_desired_plab_sz(no_of_gc_workers);
4380 }
4381 }
4382
4383 void G1CollectedHeap::abandon_gc_alloc_regions() {
4384 assert(_survivor_gc_alloc_region.get() == NULL, "pre-condition");
4385 assert(_old_gc_alloc_region.get() == NULL, "pre-condition");
4386 _retained_old_gc_alloc_region = NULL;
4387 }
4388
4389 void G1CollectedHeap::init_for_evac_failure(OopsInHeapRegionClosure* cl) {
4390 _drain_in_progress = false;
4391 set_evac_failure_closure(cl);
4392 _evac_failure_scan_stack = new (ResourceObj::C_HEAP, mtGC) GrowableArray<oop>(40, true);
4393 }
4394
4395 void G1CollectedHeap::finalize_for_evac_failure() {
4396 assert(_evac_failure_scan_stack != NULL &&
4397 _evac_failure_scan_stack->length() == 0,
4398 "Postcondition");
4399 assert(!_drain_in_progress, "Postcondition");
4400 delete _evac_failure_scan_stack;
4401 _evac_failure_scan_stack = NULL;
4402 }
4403
4404 void G1CollectedHeap::remove_self_forwarding_pointers() {
4405 assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity");
4406
4407 double remove_self_forwards_start = os::elapsedTime();
4408
4409 G1ParRemoveSelfForwardPtrsTask rsfp_task(this);
4410
4411 if (G1CollectedHeap::use_parallel_gc_threads()) {
4412 set_par_threads();
4413 workers()->run_task(&rsfp_task);
4414 set_par_threads(0);
4415 } else {
4416 rsfp_task.work(0);
4417 }
4418
4419 assert(check_cset_heap_region_claim_values(HeapRegion::ParEvacFailureClaimValue), "sanity");
4420
4421 // Reset the claim values in the regions in the collection set.
4422 reset_cset_heap_region_claim_values();
4423
4424 assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity");
4425
4426 // Now restore saved marks, if any.
4427 assert(_objs_with_preserved_marks.size() ==
4428 _preserved_marks_of_objs.size(), "Both or none.");
4429 while (!_objs_with_preserved_marks.is_empty()) {
4430 oop obj = _objs_with_preserved_marks.pop();
4431 markOop m = _preserved_marks_of_objs.pop();
4432 obj->set_mark(m);
4433 }
4434 _objs_with_preserved_marks.clear(true);
4435 _preserved_marks_of_objs.clear(true);
4436
4437 g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0);
4438 }
4439
4440 void G1CollectedHeap::push_on_evac_failure_scan_stack(oop obj) {
4441 _evac_failure_scan_stack->push(obj);
4442 }
4443
4444 void G1CollectedHeap::drain_evac_failure_scan_stack() {
4445 assert(_evac_failure_scan_stack != NULL, "precondition");
4446
4447 while (_evac_failure_scan_stack->length() > 0) {
4448 oop obj = _evac_failure_scan_stack->pop();
4449 _evac_failure_closure->set_region(heap_region_containing(obj));
4450 obj->oop_iterate_backwards(_evac_failure_closure);
4451 }
4452 }
4453
4454 oop
4455 G1CollectedHeap::handle_evacuation_failure_par(G1ParScanThreadState* _par_scan_state,
4456 oop old) {
4457 assert(obj_in_cs(old),
4458 err_msg("obj: "PTR_FORMAT" should still be in the CSet",
4459 (HeapWord*) old));
4460 markOop m = old->mark();
4461 oop forward_ptr = old->forward_to_atomic(old);
4462 if (forward_ptr == NULL) {
4463 // Forward-to-self succeeded.
4464 assert(_par_scan_state != NULL, "par scan state");
4465 OopsInHeapRegionClosure* cl = _par_scan_state->evac_failure_closure();
4466 uint queue_num = _par_scan_state->queue_num();
4467
4468 _evacuation_failed = true;
4469 _evacuation_failed_info_array[queue_num].register_copy_failure(old->size());
4470 if (_evac_failure_closure != cl) {
4471 MutexLockerEx x(EvacFailureStack_lock, Mutex::_no_safepoint_check_flag);
4472 assert(!_drain_in_progress,
4473 "Should only be true while someone holds the lock.");
4474 // Set the global evac-failure closure to the current thread's.
4475 assert(_evac_failure_closure == NULL, "Or locking has failed.");
4476 set_evac_failure_closure(cl);
4477 // Now do the common part.
4478 handle_evacuation_failure_common(old, m);
4479 // Reset to NULL.
4480 set_evac_failure_closure(NULL);
4481 } else {
4482 // The lock is already held, and this is recursive.
4483 assert(_drain_in_progress, "This should only be the recursive case.");
4484 handle_evacuation_failure_common(old, m);
4485 }
4486 return old;
4487 } else {
4488 // Forward-to-self failed. Either someone else managed to allocate
4489 // space for this object (old != forward_ptr) or they beat us in
4490 // self-forwarding it (old == forward_ptr).
4491 assert(old == forward_ptr || !obj_in_cs(forward_ptr),
4492 err_msg("obj: "PTR_FORMAT" forwarded to: "PTR_FORMAT" "
4493 "should not be in the CSet",
4494 (HeapWord*) old, (HeapWord*) forward_ptr));
4495 return forward_ptr;
4496 }
4497 }
4498
4499 void G1CollectedHeap::handle_evacuation_failure_common(oop old, markOop m) {
4500 preserve_mark_if_necessary(old, m);
4501
4502 HeapRegion* r = heap_region_containing(old);
4503 if (!r->evacuation_failed()) {
4504 r->set_evacuation_failed(true);
4505 _hr_printer.evac_failure(r);
4506 }
4507
4508 push_on_evac_failure_scan_stack(old);
4509
4510 if (!_drain_in_progress) {
4511 // prevent recursion in copy_to_survivor_space()
4512 _drain_in_progress = true;
4513 drain_evac_failure_scan_stack();
4514 _drain_in_progress = false;
4515 }
4516 }
4517
4518 void G1CollectedHeap::preserve_mark_if_necessary(oop obj, markOop m) {
4519 assert(evacuation_failed(), "Oversaving!");
4520 // We want to call the "for_promotion_failure" version only in the
4521 // case of a promotion failure.
4522 if (m->must_be_preserved_for_promotion_failure(obj)) {
4523 _objs_with_preserved_marks.push(obj);
4524 _preserved_marks_of_objs.push(m);
4525 }
4526 }
4527
4528 HeapWord* G1CollectedHeap::par_allocate_during_gc(GCAllocPurpose purpose,
4529 size_t word_size) {
4530 if (purpose == GCAllocForSurvived) {
4531 HeapWord* result = survivor_attempt_allocation(word_size);
4532 if (result != NULL) {
4533 return result;
4534 } else {
4535 // Let's try to allocate in the old gen in case we can fit the
4536 // object there.
4537 return old_attempt_allocation(word_size);
4538 }
4539 } else {
4540 assert(purpose == GCAllocForTenured, "sanity");
4541 HeapWord* result = old_attempt_allocation(word_size);
4542 if (result != NULL) {
4543 return result;
4544 } else {
4545 // Let's try to allocate in the survivors in case we can fit the
4546 // object there.
4547 return survivor_attempt_allocation(word_size);
4548 }
4549 }
4550
4551 ShouldNotReachHere();
4552 // Trying to keep some compilers happy.
4553 return NULL;
4554 }
4555
4556 G1ParGCAllocBuffer::G1ParGCAllocBuffer(size_t gclab_word_size) :
4557 ParGCAllocBuffer(gclab_word_size), _retired(true) { }
4558
4559 void G1ParCopyHelper::mark_object(oop obj) {
4560 assert(!_g1->heap_region_containing(obj)->in_collection_set(), "should not mark objects in the CSet");
4561
4562 // We know that the object is not moving so it's safe to read its size.
4563 _cm->grayRoot(obj, (size_t) obj->size(), _worker_id);
4564 }
4565
4566 void G1ParCopyHelper::mark_forwarded_object(oop from_obj, oop to_obj) {
4567 assert(from_obj->is_forwarded(), "from obj should be forwarded");
4568 assert(from_obj->forwardee() == to_obj, "to obj should be the forwardee");
4569 assert(from_obj != to_obj, "should not be self-forwarded");
4570
4571 assert(_g1->heap_region_containing(from_obj)->in_collection_set(), "from obj should be in the CSet");
4572 assert(!_g1->heap_region_containing(to_obj)->in_collection_set(), "should not mark objects in the CSet");
4573
4574 // The object might be in the process of being copied by another
4575 // worker so we cannot trust that its to-space image is
4576 // well-formed. So we have to read its size from its from-space
4577 // image which we know should not be changing.
4578 _cm->grayRoot(to_obj, (size_t) from_obj->size(), _worker_id);
4579 }
4580
4581 template <class T>
4582 void G1ParCopyHelper::do_klass_barrier(T* p, oop new_obj) {
4583 if (_g1->heap_region_containing_raw(new_obj)->is_young()) {
4584 _scanned_klass->record_modified_oops();
4585 }
4586 }
4587
4588 template <G1Barrier barrier, bool do_mark_object>
4589 template <class T>
4590 void G1ParCopyClosure<barrier, do_mark_object>::do_oop_work(T* p) {
4591 T heap_oop = oopDesc::load_heap_oop(p);
4592
4593 if (oopDesc::is_null(heap_oop)) {
4594 return;
4595 }
4596
4597 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
4598
4599 assert(_worker_id == _par_scan_state->queue_num(), "sanity");
4600
4601 if (_g1->in_cset_fast_test(obj)) {
4602 oop forwardee;
4603 if (obj->is_forwarded()) {
4604 forwardee = obj->forwardee();
4605 } else {
4606 forwardee = _par_scan_state->copy_to_survivor_space(obj);
4607 }
4608 assert(forwardee != NULL, "forwardee should not be NULL");
4609 oopDesc::encode_store_heap_oop(p, forwardee);
4610 if (do_mark_object && forwardee != obj) {
4611 // If the object is self-forwarded we don't need to explicitly
4612 // mark it, the evacuation failure protocol will do so.
4613 mark_forwarded_object(obj, forwardee);
4614 }
4615
4616 if (barrier == G1BarrierKlass) {
4617 do_klass_barrier(p, forwardee);
4618 }
4619 } else {
4620 // The object is not in collection set. If we're a root scanning
4621 // closure during an initial mark pause (i.e. do_mark_object will
4622 // be true) then attempt to mark the object.
4623 if (do_mark_object) {
4624 mark_object(obj);
4625 }
4626 }
4627
4628 if (barrier == G1BarrierEvac) {
4629 _par_scan_state->update_rs(_from, p, _worker_id);
4630 }
4631 }
4632
4633 template void G1ParCopyClosure<G1BarrierEvac, false>::do_oop_work(oop* p);
4634 template void G1ParCopyClosure<G1BarrierEvac, false>::do_oop_work(narrowOop* p);
4635
4636 class G1ParEvacuateFollowersClosure : public VoidClosure {
4637 protected:
4638 G1CollectedHeap* _g1h;
4639 G1ParScanThreadState* _par_scan_state;
4640 RefToScanQueueSet* _queues;
4641 ParallelTaskTerminator* _terminator;
4642
4643 G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
4644 RefToScanQueueSet* queues() { return _queues; }
4645 ParallelTaskTerminator* terminator() { return _terminator; }
4646
4647 public:
4648 G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h,
4649 G1ParScanThreadState* par_scan_state,
4650 RefToScanQueueSet* queues,
4651 ParallelTaskTerminator* terminator)
4652 : _g1h(g1h), _par_scan_state(par_scan_state),
4653 _queues(queues), _terminator(terminator) {}
4654
4655 void do_void();
4656
4657 private:
4658 inline bool offer_termination();
4659 };
4660
4661 bool G1ParEvacuateFollowersClosure::offer_termination() {
4662 G1ParScanThreadState* const pss = par_scan_state();
4663 pss->start_term_time();
4664 const bool res = terminator()->offer_termination();
4665 pss->end_term_time();
4666 return res;
4667 }
4668
4669 void G1ParEvacuateFollowersClosure::do_void() {
4670 StarTask stolen_task;
4671 G1ParScanThreadState* const pss = par_scan_state();
4672 pss->trim_queue();
4673
4674 do {
4675 while (queues()->steal(pss->queue_num(), pss->hash_seed(), stolen_task)) {
4676 assert(pss->verify_task(stolen_task), "sanity");
4677 if (stolen_task.is_narrow()) {
4678 pss->deal_with_reference((narrowOop*) stolen_task);
4679 } else {
4680 pss->deal_with_reference((oop*) stolen_task);
4681 }
4682
4683 // We've just processed a reference and we might have made
4684 // available new entries on the queues. So we have to make sure
4685 // we drain the queues as necessary.
4686 pss->trim_queue();
4687 }
4688 } while (!offer_termination());
4689 }
4690
4691 class G1KlassScanClosure : public KlassClosure {
4692 G1ParCopyHelper* _closure;
4693 bool _process_only_dirty;
4694 int _count;
4695 public:
4696 G1KlassScanClosure(G1ParCopyHelper* closure, bool process_only_dirty)
4697 : _process_only_dirty(process_only_dirty), _closure(closure), _count(0) {}
4698 void do_klass(Klass* klass) {
4699 // If the klass has not been dirtied we know that there's
4700 // no references into the young gen and we can skip it.
4701 if (!_process_only_dirty || klass->has_modified_oops()) {
4702 // Clean the klass since we're going to scavenge all the metadata.
4703 klass->clear_modified_oops();
4704
4705 // Tell the closure that this klass is the Klass to scavenge
4706 // and is the one to dirty if oops are left pointing into the young gen.
4707 _closure->set_scanned_klass(klass);
4708
4709 klass->oops_do(_closure);
4710
4711 _closure->set_scanned_klass(NULL);
4712 }
4713 _count++;
4714 }
4715 };
4716
4717 class G1ParTask : public AbstractGangTask {
4718 protected:
4719 G1CollectedHeap* _g1h;
4720 RefToScanQueueSet *_queues;
4721 ParallelTaskTerminator _terminator;
4722 uint _n_workers;
4723
4724 Mutex _stats_lock;
4725 Mutex* stats_lock() { return &_stats_lock; }
4726
4727 size_t getNCards() {
4728 return (_g1h->capacity() + G1BlockOffsetSharedArray::N_bytes - 1)
4729 / G1BlockOffsetSharedArray::N_bytes;
4730 }
4731
4732 public:
4733 G1ParTask(G1CollectedHeap* g1h,
4734 RefToScanQueueSet *task_queues)
4735 : AbstractGangTask("G1 collection"),
4736 _g1h(g1h),
4737 _queues(task_queues),
4738 _terminator(0, _queues),
4739 _stats_lock(Mutex::leaf, "parallel G1 stats lock", true)
4740 {}
4741
4742 RefToScanQueueSet* queues() { return _queues; }
4743
4744 RefToScanQueue *work_queue(int i) {
4745 return queues()->queue(i);
4746 }
4747
4748 ParallelTaskTerminator* terminator() { return &_terminator; }
4749
4750 virtual void set_for_termination(int active_workers) {
4751 // This task calls set_n_termination() in par_non_clean_card_iterate_work()
4752 // in the young space (_par_seq_tasks) in the G1 heap
4753 // for SequentialSubTasksDone.
4754 // This task also uses SubTasksDone in SharedHeap and G1CollectedHeap
4755 // both of which need setting by set_n_termination().
4756 _g1h->SharedHeap::set_n_termination(active_workers);
4757 _g1h->set_n_termination(active_workers);
4758 terminator()->reset_for_reuse(active_workers);
4759 _n_workers = active_workers;
4760 }
4761
4762 void work(uint worker_id) {
4763 if (worker_id >= _n_workers) return; // no work needed this round
4764
4765 double start_time_ms = os::elapsedTime() * 1000.0;
4766 _g1h->g1_policy()->phase_times()->record_gc_worker_start_time(worker_id, start_time_ms);
4767
4768 {
4769 ResourceMark rm;
4770 HandleMark hm;
4771
4772 ReferenceProcessor* rp = _g1h->ref_processor_stw();
4773
4774 G1ParScanThreadState pss(_g1h, worker_id, rp);
4775 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, rp);
4776
4777 pss.set_evac_failure_closure(&evac_failure_cl);
4778
4779 G1ParScanExtRootClosure only_scan_root_cl(_g1h, &pss, rp);
4780 G1ParScanMetadataClosure only_scan_metadata_cl(_g1h, &pss, rp);
4781
4782 G1ParScanAndMarkExtRootClosure scan_mark_root_cl(_g1h, &pss, rp);
4783 G1ParScanAndMarkMetadataClosure scan_mark_metadata_cl(_g1h, &pss, rp);
4784
4785 bool only_young = _g1h->g1_policy()->gcs_are_young();
4786 G1KlassScanClosure scan_mark_klasses_cl_s(&scan_mark_metadata_cl, false);
4787 G1KlassScanClosure only_scan_klasses_cl_s(&only_scan_metadata_cl, only_young);
4788
4789 OopClosure* scan_root_cl = &only_scan_root_cl;
4790 G1KlassScanClosure* scan_klasses_cl = &only_scan_klasses_cl_s;
4791
4792 if (_g1h->g1_policy()->during_initial_mark_pause()) {
4793 // We also need to mark copied objects.
4794 scan_root_cl = &scan_mark_root_cl;
4795 scan_klasses_cl = &scan_mark_klasses_cl_s;
4796 }
4797
4798 G1ParPushHeapRSClosure push_heap_rs_cl(_g1h, &pss);
4799
4800 // Don't scan the scavengable methods in the code cache as part
4801 // of strong root scanning. The code roots that point into a
4802 // region in the collection set are scanned when we scan the
4803 // region's RSet.
4804 int so = SharedHeap::SO_AllClasses | SharedHeap::SO_Strings;
4805
4806 pss.start_strong_roots();
4807 _g1h->g1_process_strong_roots(/* is scavenging */ true,
4808 SharedHeap::ScanningOption(so),
4809 scan_root_cl,
4810 &push_heap_rs_cl,
4811 scan_klasses_cl,
4812 worker_id);
4813 pss.end_strong_roots();
4814
4815 {
4816 double start = os::elapsedTime();
4817 G1ParEvacuateFollowersClosure evac(_g1h, &pss, _queues, &_terminator);
4818 evac.do_void();
4819 double elapsed_ms = (os::elapsedTime()-start)*1000.0;
4820 double term_ms = pss.term_time()*1000.0;
4821 _g1h->g1_policy()->phase_times()->add_obj_copy_time(worker_id, elapsed_ms-term_ms);
4822 _g1h->g1_policy()->phase_times()->record_termination(worker_id, term_ms, pss.term_attempts());
4823 }
4824 _g1h->g1_policy()->record_thread_age_table(pss.age_table());
4825 _g1h->update_surviving_young_words(pss.surviving_young_words()+1);
4826
4827 if (ParallelGCVerbose) {
4828 MutexLocker x(stats_lock());
4829 pss.print_termination_stats(worker_id);
4830 }
4831
4832 assert(pss.refs()->is_empty(), "should be empty");
4833
4834 // Close the inner scope so that the ResourceMark and HandleMark
4835 // destructors are executed here and are included as part of the
4836 // "GC Worker Time".
4837 }
4838
4839 double end_time_ms = os::elapsedTime() * 1000.0;
4840 _g1h->g1_policy()->phase_times()->record_gc_worker_end_time(worker_id, end_time_ms);
4841 }
4842 };
4843
4844 // *** Common G1 Evacuation Stuff
4845
4846 // This method is run in a GC worker.
4847
4848 void
4849 G1CollectedHeap::
4850 g1_process_strong_roots(bool is_scavenging,
4851 ScanningOption so,
4852 OopClosure* scan_non_heap_roots,
4853 OopsInHeapRegionClosure* scan_rs,
4854 G1KlassScanClosure* scan_klasses,
4855 uint worker_i) {
4856
4857 // First scan the strong roots
4858 double ext_roots_start = os::elapsedTime();
4859 double closure_app_time_sec = 0.0;
4860
4861 BufferingOopClosure buf_scan_non_heap_roots(scan_non_heap_roots);
4862
4863 process_strong_roots(false, // no scoping; this is parallel code
4864 so,
4865 &buf_scan_non_heap_roots,
4866 scan_klasses
4867 );
4868
4869 // Now the CM ref_processor roots.
4870 if (!_process_strong_tasks->is_task_claimed(G1H_PS_refProcessor_oops_do)) {
4871 // We need to treat the discovered reference lists of the
4872 // concurrent mark ref processor as roots and keep entries
4873 // (which are added by the marking threads) on them live
4874 // until they can be processed at the end of marking.
4875 ref_processor_cm()->weak_oops_do(&buf_scan_non_heap_roots);
4876 }
4877
4878 // Finish up any enqueued closure apps (attributed as object copy time).
4879 buf_scan_non_heap_roots.done();
4880
4881 double obj_copy_time_sec = buf_scan_non_heap_roots.closure_app_seconds();
4882
4883 g1_policy()->phase_times()->record_obj_copy_time(worker_i, obj_copy_time_sec * 1000.0);
4884
4885 double ext_root_time_ms =
4886 ((os::elapsedTime() - ext_roots_start) - obj_copy_time_sec) * 1000.0;
4887
4888 g1_policy()->phase_times()->record_ext_root_scan_time(worker_i, ext_root_time_ms);
4889
4890 // During conc marking we have to filter the per-thread SATB buffers
4891 // to make sure we remove any oops into the CSet (which will show up
4892 // as implicitly live).
4893 double satb_filtering_ms = 0.0;
4894 if (!_process_strong_tasks->is_task_claimed(G1H_PS_filter_satb_buffers)) {
4895 if (mark_in_progress()) {
4896 double satb_filter_start = os::elapsedTime();
4897
4898 JavaThread::satb_mark_queue_set().filter_thread_buffers();
4899
4900 satb_filtering_ms = (os::elapsedTime() - satb_filter_start) * 1000.0;
4901 }
4902 }
4903 g1_policy()->phase_times()->record_satb_filtering_time(worker_i, satb_filtering_ms);
4904
4905 // If this is an initial mark pause, and we're not scanning
4906 // the entire code cache, we need to mark the oops in the
4907 // strong code root lists for the regions that are not in
4908 // the collection set.
4909 // Note all threads participate in this set of root tasks.
4910 double mark_strong_code_roots_ms = 0.0;
4911 if (g1_policy()->during_initial_mark_pause() && !(so & SO_AllCodeCache)) {
4912 double mark_strong_roots_start = os::elapsedTime();
4913 mark_strong_code_roots(worker_i);
4914 mark_strong_code_roots_ms = (os::elapsedTime() - mark_strong_roots_start) * 1000.0;
4915 }
4916 g1_policy()->phase_times()->record_strong_code_root_mark_time(worker_i, mark_strong_code_roots_ms);
4917
4918 // Now scan the complement of the collection set.
4919 CodeBlobToOopClosure eager_scan_code_roots(scan_non_heap_roots, true /* do_marking */);
4920 g1_rem_set()->oops_into_collection_set_do(scan_rs, &eager_scan_code_roots, worker_i);
4921
4922 _process_strong_tasks->all_tasks_completed();
4923 }
4924
4925 class G1StringSymbolTableUnlinkTask : public AbstractGangTask {
4926 private:
4927 BoolObjectClosure* _is_alive;
4928 int _initial_string_table_size;
4929 int _initial_symbol_table_size;
4930
4931 bool _process_strings;
4932 int _strings_processed;
4933 int _strings_removed;
4934
4935 bool _process_symbols;
4936 int _symbols_processed;
4937 int _symbols_removed;
4938
4939 bool _do_in_parallel;
4940 public:
4941 G1StringSymbolTableUnlinkTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols) :
4942 AbstractGangTask("Par String/Symbol table unlink"), _is_alive(is_alive),
4943 _do_in_parallel(G1CollectedHeap::use_parallel_gc_threads()),
4944 _process_strings(process_strings), _strings_processed(0), _strings_removed(0),
4945 _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0) {
4946
4947 _initial_string_table_size = StringTable::the_table()->table_size();
4948 _initial_symbol_table_size = SymbolTable::the_table()->table_size();
4949 if (process_strings) {
4950 StringTable::clear_parallel_claimed_index();
4951 }
4952 if (process_symbols) {
4953 SymbolTable::clear_parallel_claimed_index();
4954 }
4955 }
4956
4957 ~G1StringSymbolTableUnlinkTask() {
4958 guarantee(!_process_strings || !_do_in_parallel || StringTable::parallel_claimed_index() >= _initial_string_table_size,
4959 err_msg("claim value %d after unlink less than initial string table size %d",
4960 StringTable::parallel_claimed_index(), _initial_string_table_size));
4961 guarantee(!_process_symbols || !_do_in_parallel || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size,
4962 err_msg("claim value %d after unlink less than initial symbol table size %d",
4963 SymbolTable::parallel_claimed_index(), _initial_symbol_table_size));
4964 }
4965
4966 void work(uint worker_id) {
4967 if (_do_in_parallel) {
4968 int strings_processed = 0;
4969 int strings_removed = 0;
4970 int symbols_processed = 0;
4971 int symbols_removed = 0;
4972 if (_process_strings) {
4973 StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed);
4974 Atomic::add(strings_processed, &_strings_processed);
4975 Atomic::add(strings_removed, &_strings_removed);
4976 }
4977 if (_process_symbols) {
4978 SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed);
4979 Atomic::add(symbols_processed, &_symbols_processed);
4980 Atomic::add(symbols_removed, &_symbols_removed);
4981 }
4982 } else {
4983 if (_process_strings) {
4984 StringTable::unlink(_is_alive, &_strings_processed, &_strings_removed);
4985 }
4986 if (_process_symbols) {
4987 SymbolTable::unlink(&_symbols_processed, &_symbols_removed);
4988 }
4989 }
4990 }
4991
4992 size_t strings_processed() const { return (size_t)_strings_processed; }
4993 size_t strings_removed() const { return (size_t)_strings_removed; }
4994
4995 size_t symbols_processed() const { return (size_t)_symbols_processed; }
4996 size_t symbols_removed() const { return (size_t)_symbols_removed; }
4997 };
4998
4999 void G1CollectedHeap::unlink_string_and_symbol_table(BoolObjectClosure* is_alive,
5000 bool process_strings, bool process_symbols) {
5001 uint n_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
5002 _g1h->workers()->active_workers() : 1);
5003
5004 G1StringSymbolTableUnlinkTask g1_unlink_task(is_alive, process_strings, process_symbols);
5005 if (G1CollectedHeap::use_parallel_gc_threads()) {
5006 set_par_threads(n_workers);
5007 workers()->run_task(&g1_unlink_task);
5008 set_par_threads(0);
5009 } else {
5010 g1_unlink_task.work(0);
5011 }
5012 if (G1TraceStringSymbolTableScrubbing) {
5013 gclog_or_tty->print_cr("Cleaned string and symbol table, "
5014 "strings: "SIZE_FORMAT" processed, "SIZE_FORMAT" removed, "
5015 "symbols: "SIZE_FORMAT" processed, "SIZE_FORMAT" removed",
5016 g1_unlink_task.strings_processed(), g1_unlink_task.strings_removed(),
5017 g1_unlink_task.symbols_processed(), g1_unlink_task.symbols_removed());
5018 }
5019
5020 if (G1StringDedup::is_enabled()) {
5021 G1StringDedup::unlink(is_alive);
5022 }
5023 }
5024
5025 class G1RedirtyLoggedCardsTask : public AbstractGangTask {
5026 private:
5027 DirtyCardQueueSet* _queue;
5028 public:
5029 G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue) : AbstractGangTask("Redirty Cards"), _queue(queue) { }
5030
5031 virtual void work(uint worker_id) {
5032 double start_time = os::elapsedTime();
5033
5034 RedirtyLoggedCardTableEntryClosure cl;
5035 if (G1CollectedHeap::heap()->use_parallel_gc_threads()) {
5036 _queue->par_apply_closure_to_all_completed_buffers(&cl);
5037 } else {
5038 _queue->apply_closure_to_all_completed_buffers(&cl);
5039 }
5040
5041 G1GCPhaseTimes* timer = G1CollectedHeap::heap()->g1_policy()->phase_times();
5042 timer->record_redirty_logged_cards_time_ms(worker_id, (os::elapsedTime() - start_time) * 1000.0);
5043 timer->record_redirty_logged_cards_processed_cards(worker_id, cl.num_processed());
5044 }
5045 };
5046
5047 void G1CollectedHeap::redirty_logged_cards() {
5048 guarantee(G1DeferredRSUpdate, "Must only be called when using deferred RS updates.");
5049 double redirty_logged_cards_start = os::elapsedTime();
5050
5051 uint n_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
5052 _g1h->workers()->active_workers() : 1);
5053
5054 G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set());
5055 dirty_card_queue_set().reset_for_par_iteration();
5056 if (use_parallel_gc_threads()) {
5057 set_par_threads(n_workers);
5058 workers()->run_task(&redirty_task);
5059 set_par_threads(0);
5060 } else {
5061 redirty_task.work(0);
5062 }
5063
5064 DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set();
5065 dcq.merge_bufferlists(&dirty_card_queue_set());
5066 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
5067
5068 g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0);
5069 }
5070
5071 // Weak Reference Processing support
5072
5073 // An always "is_alive" closure that is used to preserve referents.
5074 // If the object is non-null then it's alive. Used in the preservation
5075 // of referent objects that are pointed to by reference objects
5076 // discovered by the CM ref processor.
5077 class G1AlwaysAliveClosure: public BoolObjectClosure {
5078 G1CollectedHeap* _g1;
5079 public:
5080 G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
5081 bool do_object_b(oop p) {
5082 if (p != NULL) {
5083 return true;
5084 }
5085 return false;
5086 }
5087 };
5088
5089 bool G1STWIsAliveClosure::do_object_b(oop p) {
5090 // An object is reachable if it is outside the collection set,
5091 // or is inside and copied.
5092 return !_g1->obj_in_cs(p) || p->is_forwarded();
5093 }
5094
5095 // Non Copying Keep Alive closure
5096 class G1KeepAliveClosure: public OopClosure {
5097 G1CollectedHeap* _g1;
5098 public:
5099 G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
5100 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
5101 void do_oop( oop* p) {
5102 oop obj = *p;
5103
5104 if (_g1->obj_in_cs(obj)) {
5105 assert( obj->is_forwarded(), "invariant" );
5106 *p = obj->forwardee();
5107 }
5108 }
5109 };
5110
5111 // Copying Keep Alive closure - can be called from both
5112 // serial and parallel code as long as different worker
5113 // threads utilize different G1ParScanThreadState instances
5114 // and different queues.
5115
5116 class G1CopyingKeepAliveClosure: public OopClosure {
5117 G1CollectedHeap* _g1h;
5118 OopClosure* _copy_non_heap_obj_cl;
5119 OopsInHeapRegionClosure* _copy_metadata_obj_cl;
5120 G1ParScanThreadState* _par_scan_state;
5121
5122 public:
5123 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
5124 OopClosure* non_heap_obj_cl,
5125 OopsInHeapRegionClosure* metadata_obj_cl,
5126 G1ParScanThreadState* pss):
5127 _g1h(g1h),
5128 _copy_non_heap_obj_cl(non_heap_obj_cl),
5129 _copy_metadata_obj_cl(metadata_obj_cl),
5130 _par_scan_state(pss)
5131 {}
5132
5133 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
5134 virtual void do_oop( oop* p) { do_oop_work(p); }
5135
5136 template <class T> void do_oop_work(T* p) {
5137 oop obj = oopDesc::load_decode_heap_oop(p);
5138
5139 if (_g1h->obj_in_cs(obj)) {
5140 // If the referent object has been forwarded (either copied
5141 // to a new location or to itself in the event of an
5142 // evacuation failure) then we need to update the reference
5143 // field and, if both reference and referent are in the G1
5144 // heap, update the RSet for the referent.
5145 //
5146 // If the referent has not been forwarded then we have to keep
5147 // it alive by policy. Therefore we have copy the referent.
5148 //
5149 // If the reference field is in the G1 heap then we can push
5150 // on the PSS queue. When the queue is drained (after each
5151 // phase of reference processing) the object and it's followers
5152 // will be copied, the reference field set to point to the
5153 // new location, and the RSet updated. Otherwise we need to
5154 // use the the non-heap or metadata closures directly to copy
5155 // the referent object and update the pointer, while avoiding
5156 // updating the RSet.
5157
5158 if (_g1h->is_in_g1_reserved(p)) {
5159 _par_scan_state->push_on_queue(p);
5160 } else {
5161 assert(!ClassLoaderDataGraph::contains((address)p),
5162 err_msg("Otherwise need to call _copy_metadata_obj_cl->do_oop(p) "
5163 PTR_FORMAT, p));
5164 _copy_non_heap_obj_cl->do_oop(p);
5165 }
5166 }
5167 }
5168 };
5169
5170 // Serial drain queue closure. Called as the 'complete_gc'
5171 // closure for each discovered list in some of the
5172 // reference processing phases.
5173
5174 class G1STWDrainQueueClosure: public VoidClosure {
5175 protected:
5176 G1CollectedHeap* _g1h;
5177 G1ParScanThreadState* _par_scan_state;
5178
5179 G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
5180
5181 public:
5182 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
5183 _g1h(g1h),
5184 _par_scan_state(pss)
5185 { }
5186
5187 void do_void() {
5188 G1ParScanThreadState* const pss = par_scan_state();
5189 pss->trim_queue();
5190 }
5191 };
5192
5193 // Parallel Reference Processing closures
5194
5195 // Implementation of AbstractRefProcTaskExecutor for parallel reference
5196 // processing during G1 evacuation pauses.
5197
5198 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
5199 private:
5200 G1CollectedHeap* _g1h;
5201 RefToScanQueueSet* _queues;
5202 FlexibleWorkGang* _workers;
5203 int _active_workers;
5204
5205 public:
5206 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
5207 FlexibleWorkGang* workers,
5208 RefToScanQueueSet *task_queues,
5209 int n_workers) :
5210 _g1h(g1h),
5211 _queues(task_queues),
5212 _workers(workers),
5213 _active_workers(n_workers)
5214 {
5215 assert(n_workers > 0, "shouldn't call this otherwise");
5216 }
5217
5218 // Executes the given task using concurrent marking worker threads.
5219 virtual void execute(ProcessTask& task);
5220 virtual void execute(EnqueueTask& task);
5221 };
5222
5223 // Gang task for possibly parallel reference processing
5224
5225 class G1STWRefProcTaskProxy: public AbstractGangTask {
5226 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
5227 ProcessTask& _proc_task;
5228 G1CollectedHeap* _g1h;
5229 RefToScanQueueSet *_task_queues;
5230 ParallelTaskTerminator* _terminator;
5231
5232 public:
5233 G1STWRefProcTaskProxy(ProcessTask& proc_task,
5234 G1CollectedHeap* g1h,
5235 RefToScanQueueSet *task_queues,
5236 ParallelTaskTerminator* terminator) :
5237 AbstractGangTask("Process reference objects in parallel"),
5238 _proc_task(proc_task),
5239 _g1h(g1h),
5240 _task_queues(task_queues),
5241 _terminator(terminator)
5242 {}
5243
5244 virtual void work(uint worker_id) {
5245 // The reference processing task executed by a single worker.
5246 ResourceMark rm;
5247 HandleMark hm;
5248
5249 G1STWIsAliveClosure is_alive(_g1h);
5250
5251 G1ParScanThreadState pss(_g1h, worker_id, NULL);
5252 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5253
5254 pss.set_evac_failure_closure(&evac_failure_cl);
5255
5256 G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL);
5257 G1ParScanMetadataClosure only_copy_metadata_cl(_g1h, &pss, NULL);
5258
5259 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5260 G1ParScanAndMarkMetadataClosure copy_mark_metadata_cl(_g1h, &pss, NULL);
5261
5262 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5263 OopsInHeapRegionClosure* copy_metadata_cl = &only_copy_metadata_cl;
5264
5265 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5266 // We also need to mark copied objects.
5267 copy_non_heap_cl = ©_mark_non_heap_cl;
5268 copy_metadata_cl = ©_mark_metadata_cl;
5269 }
5270
5271 // Keep alive closure.
5272 G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, copy_metadata_cl, &pss);
5273
5274 // Complete GC closure
5275 G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _task_queues, _terminator);
5276
5277 // Call the reference processing task's work routine.
5278 _proc_task.work(worker_id, is_alive, keep_alive, drain_queue);
5279
5280 // Note we cannot assert that the refs array is empty here as not all
5281 // of the processing tasks (specifically phase2 - pp2_work) execute
5282 // the complete_gc closure (which ordinarily would drain the queue) so
5283 // the queue may not be empty.
5284 }
5285 };
5286
5287 // Driver routine for parallel reference processing.
5288 // Creates an instance of the ref processing gang
5289 // task and has the worker threads execute it.
5290 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) {
5291 assert(_workers != NULL, "Need parallel worker threads.");
5292
5293 ParallelTaskTerminator terminator(_active_workers, _queues);
5294 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _queues, &terminator);
5295
5296 _g1h->set_par_threads(_active_workers);
5297 _workers->run_task(&proc_task_proxy);
5298 _g1h->set_par_threads(0);
5299 }
5300
5301 // Gang task for parallel reference enqueueing.
5302
5303 class G1STWRefEnqueueTaskProxy: public AbstractGangTask {
5304 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
5305 EnqueueTask& _enq_task;
5306
5307 public:
5308 G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) :
5309 AbstractGangTask("Enqueue reference objects in parallel"),
5310 _enq_task(enq_task)
5311 { }
5312
5313 virtual void work(uint worker_id) {
5314 _enq_task.work(worker_id);
5315 }
5316 };
5317
5318 // Driver routine for parallel reference enqueueing.
5319 // Creates an instance of the ref enqueueing gang
5320 // task and has the worker threads execute it.
5321
5322 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
5323 assert(_workers != NULL, "Need parallel worker threads.");
5324
5325 G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task);
5326
5327 _g1h->set_par_threads(_active_workers);
5328 _workers->run_task(&enq_task_proxy);
5329 _g1h->set_par_threads(0);
5330 }
5331
5332 // End of weak reference support closures
5333
5334 // Abstract task used to preserve (i.e. copy) any referent objects
5335 // that are in the collection set and are pointed to by reference
5336 // objects discovered by the CM ref processor.
5337
5338 class G1ParPreserveCMReferentsTask: public AbstractGangTask {
5339 protected:
5340 G1CollectedHeap* _g1h;
5341 RefToScanQueueSet *_queues;
5342 ParallelTaskTerminator _terminator;
5343 uint _n_workers;
5344
5345 public:
5346 G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h,int workers, RefToScanQueueSet *task_queues) :
5347 AbstractGangTask("ParPreserveCMReferents"),
5348 _g1h(g1h),
5349 _queues(task_queues),
5350 _terminator(workers, _queues),
5351 _n_workers(workers)
5352 { }
5353
5354 void work(uint worker_id) {
5355 ResourceMark rm;
5356 HandleMark hm;
5357
5358 G1ParScanThreadState pss(_g1h, worker_id, NULL);
5359 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5360
5361 pss.set_evac_failure_closure(&evac_failure_cl);
5362
5363 assert(pss.refs()->is_empty(), "both queue and overflow should be empty");
5364
5365
5366 G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL);
5367 G1ParScanMetadataClosure only_copy_metadata_cl(_g1h, &pss, NULL);
5368
5369 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5370 G1ParScanAndMarkMetadataClosure copy_mark_metadata_cl(_g1h, &pss, NULL);
5371
5372 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5373 OopsInHeapRegionClosure* copy_metadata_cl = &only_copy_metadata_cl;
5374
5375 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5376 // We also need to mark copied objects.
5377 copy_non_heap_cl = ©_mark_non_heap_cl;
5378 copy_metadata_cl = ©_mark_metadata_cl;
5379 }
5380
5381 // Is alive closure
5382 G1AlwaysAliveClosure always_alive(_g1h);
5383
5384 // Copying keep alive closure. Applied to referent objects that need
5385 // to be copied.
5386 G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, copy_metadata_cl, &pss);
5387
5388 ReferenceProcessor* rp = _g1h->ref_processor_cm();
5389
5390 uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q();
5391 uint stride = MIN2(MAX2(_n_workers, 1U), limit);
5392
5393 // limit is set using max_num_q() - which was set using ParallelGCThreads.
5394 // So this must be true - but assert just in case someone decides to
5395 // change the worker ids.
5396 assert(0 <= worker_id && worker_id < limit, "sanity");
5397 assert(!rp->discovery_is_atomic(), "check this code");
5398
5399 // Select discovered lists [i, i+stride, i+2*stride,...,limit)
5400 for (uint idx = worker_id; idx < limit; idx += stride) {
5401 DiscoveredList& ref_list = rp->discovered_refs()[idx];
5402
5403 DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive);
5404 while (iter.has_next()) {
5405 // Since discovery is not atomic for the CM ref processor, we
5406 // can see some null referent objects.
5407 iter.load_ptrs(DEBUG_ONLY(true));
5408 oop ref = iter.obj();
5409
5410 // This will filter nulls.
5411 if (iter.is_referent_alive()) {
5412 iter.make_referent_alive();
5413 }
5414 iter.move_to_next();
5415 }
5416 }
5417
5418 // Drain the queue - which may cause stealing
5419 G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _queues, &_terminator);
5420 drain_queue.do_void();
5421 // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure
5422 assert(pss.refs()->is_empty(), "should be");
5423 }
5424 };
5425
5426 // Weak Reference processing during an evacuation pause (part 1).
5427 void G1CollectedHeap::process_discovered_references(uint no_of_gc_workers) {
5428 double ref_proc_start = os::elapsedTime();
5429
5430 ReferenceProcessor* rp = _ref_processor_stw;
5431 assert(rp->discovery_enabled(), "should have been enabled");
5432
5433 // Any reference objects, in the collection set, that were 'discovered'
5434 // by the CM ref processor should have already been copied (either by
5435 // applying the external root copy closure to the discovered lists, or
5436 // by following an RSet entry).
5437 //
5438 // But some of the referents, that are in the collection set, that these
5439 // reference objects point to may not have been copied: the STW ref
5440 // processor would have seen that the reference object had already
5441 // been 'discovered' and would have skipped discovering the reference,
5442 // but would not have treated the reference object as a regular oop.
5443 // As a result the copy closure would not have been applied to the
5444 // referent object.
5445 //
5446 // We need to explicitly copy these referent objects - the references
5447 // will be processed at the end of remarking.
5448 //
5449 // We also need to do this copying before we process the reference
5450 // objects discovered by the STW ref processor in case one of these
5451 // referents points to another object which is also referenced by an
5452 // object discovered by the STW ref processor.
5453
5454 assert(!G1CollectedHeap::use_parallel_gc_threads() ||
5455 no_of_gc_workers == workers()->active_workers(),
5456 "Need to reset active GC workers");
5457
5458 set_par_threads(no_of_gc_workers);
5459 G1ParPreserveCMReferentsTask keep_cm_referents(this,
5460 no_of_gc_workers,
5461 _task_queues);
5462
5463 if (G1CollectedHeap::use_parallel_gc_threads()) {
5464 workers()->run_task(&keep_cm_referents);
5465 } else {
5466 keep_cm_referents.work(0);
5467 }
5468
5469 set_par_threads(0);
5470
5471 // Closure to test whether a referent is alive.
5472 G1STWIsAliveClosure is_alive(this);
5473
5474 // Even when parallel reference processing is enabled, the processing
5475 // of JNI refs is serial and performed serially by the current thread
5476 // rather than by a worker. The following PSS will be used for processing
5477 // JNI refs.
5478
5479 // Use only a single queue for this PSS.
5480 G1ParScanThreadState pss(this, 0, NULL);
5481
5482 // We do not embed a reference processor in the copying/scanning
5483 // closures while we're actually processing the discovered
5484 // reference objects.
5485 G1ParScanHeapEvacFailureClosure evac_failure_cl(this, &pss, NULL);
5486
5487 pss.set_evac_failure_closure(&evac_failure_cl);
5488
5489 assert(pss.refs()->is_empty(), "pre-condition");
5490
5491 G1ParScanExtRootClosure only_copy_non_heap_cl(this, &pss, NULL);
5492 G1ParScanMetadataClosure only_copy_metadata_cl(this, &pss, NULL);
5493
5494 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(this, &pss, NULL);
5495 G1ParScanAndMarkMetadataClosure copy_mark_metadata_cl(this, &pss, NULL);
5496
5497 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5498 OopsInHeapRegionClosure* copy_metadata_cl = &only_copy_metadata_cl;
5499
5500 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5501 // We also need to mark copied objects.
5502 copy_non_heap_cl = ©_mark_non_heap_cl;
5503 copy_metadata_cl = ©_mark_metadata_cl;
5504 }
5505
5506 // Keep alive closure.
5507 G1CopyingKeepAliveClosure keep_alive(this, copy_non_heap_cl, copy_metadata_cl, &pss);
5508
5509 // Serial Complete GC closure
5510 G1STWDrainQueueClosure drain_queue(this, &pss);
5511
5512 // Setup the soft refs policy...
5513 rp->setup_policy(false);
5514
5515 ReferenceProcessorStats stats;
5516 if (!rp->processing_is_mt()) {
5517 // Serial reference processing...
5518 stats = rp->process_discovered_references(&is_alive,
5519 &keep_alive,
5520 &drain_queue,
5521 NULL,
5522 _gc_timer_stw);
5523 } else {
5524 // Parallel reference processing
5525 assert(rp->num_q() == no_of_gc_workers, "sanity");
5526 assert(no_of_gc_workers <= rp->max_num_q(), "sanity");
5527
5528 G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers);
5529 stats = rp->process_discovered_references(&is_alive,
5530 &keep_alive,
5531 &drain_queue,
5532 &par_task_executor,
5533 _gc_timer_stw);
5534 }
5535
5536 _gc_tracer_stw->report_gc_reference_stats(stats);
5537
5538 // We have completed copying any necessary live referent objects.
5539 assert(pss.refs()->is_empty(), "both queue and overflow should be empty");
5540
5541 double ref_proc_time = os::elapsedTime() - ref_proc_start;
5542 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
5543 }
5544
5545 // Weak Reference processing during an evacuation pause (part 2).
5546 void G1CollectedHeap::enqueue_discovered_references(uint no_of_gc_workers) {
5547 double ref_enq_start = os::elapsedTime();
5548
5549 ReferenceProcessor* rp = _ref_processor_stw;
5550 assert(!rp->discovery_enabled(), "should have been disabled as part of processing");
5551
5552 // Now enqueue any remaining on the discovered lists on to
5553 // the pending list.
5554 if (!rp->processing_is_mt()) {
5555 // Serial reference processing...
5556 rp->enqueue_discovered_references();
5557 } else {
5558 // Parallel reference enqueueing
5559
5560 assert(no_of_gc_workers == workers()->active_workers(),
5561 "Need to reset active workers");
5562 assert(rp->num_q() == no_of_gc_workers, "sanity");
5563 assert(no_of_gc_workers <= rp->max_num_q(), "sanity");
5564
5565 G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers);
5566 rp->enqueue_discovered_references(&par_task_executor);
5567 }
5568
5569 rp->verify_no_references_recorded();
5570 assert(!rp->discovery_enabled(), "should have been disabled");
5571
5572 // FIXME
5573 // CM's reference processing also cleans up the string and symbol tables.
5574 // Should we do that here also? We could, but it is a serial operation
5575 // and could significantly increase the pause time.
5576
5577 double ref_enq_time = os::elapsedTime() - ref_enq_start;
5578 g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0);
5579 }
5580
5581 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info) {
5582 _expand_heap_after_alloc_failure = true;
5583 _evacuation_failed = false;
5584
5585 // Should G1EvacuationFailureALot be in effect for this GC?
5586 NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();)
5587
5588 g1_rem_set()->prepare_for_oops_into_collection_set_do();
5589
5590 // Disable the hot card cache.
5591 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
5592 hot_card_cache->reset_hot_cache_claimed_index();
5593 hot_card_cache->set_use_cache(false);
5594
5595 uint n_workers;
5596 if (G1CollectedHeap::use_parallel_gc_threads()) {
5597 n_workers =
5598 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
5599 workers()->active_workers(),
5600 Threads::number_of_non_daemon_threads());
5601 assert(UseDynamicNumberOfGCThreads ||
5602 n_workers == workers()->total_workers(),
5603 "If not dynamic should be using all the workers");
5604 workers()->set_active_workers(n_workers);
5605 set_par_threads(n_workers);
5606 } else {
5607 assert(n_par_threads() == 0,
5608 "Should be the original non-parallel value");
5609 n_workers = 1;
5610 }
5611
5612 G1ParTask g1_par_task(this, _task_queues);
5613
5614 init_for_evac_failure(NULL);
5615
5616 rem_set()->prepare_for_younger_refs_iterate(true);
5617
5618 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
5619 double start_par_time_sec = os::elapsedTime();
5620 double end_par_time_sec;
5621
5622 {
5623 StrongRootsScope srs(this);
5624
5625 if (G1CollectedHeap::use_parallel_gc_threads()) {
5626 // The individual threads will set their evac-failure closures.
5627 if (ParallelGCVerbose) G1ParScanThreadState::print_termination_stats_hdr();
5628 // These tasks use ShareHeap::_process_strong_tasks
5629 assert(UseDynamicNumberOfGCThreads ||
5630 workers()->active_workers() == workers()->total_workers(),
5631 "If not dynamic should be using all the workers");
5632 workers()->run_task(&g1_par_task);
5633 } else {
5634 g1_par_task.set_for_termination(n_workers);
5635 g1_par_task.work(0);
5636 }
5637 end_par_time_sec = os::elapsedTime();
5638
5639 // Closing the inner scope will execute the destructor
5640 // for the StrongRootsScope object. We record the current
5641 // elapsed time before closing the scope so that time
5642 // taken for the SRS destructor is NOT included in the
5643 // reported parallel time.
5644 }
5645
5646 double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0;
5647 g1_policy()->phase_times()->record_par_time(par_time_ms);
5648
5649 double code_root_fixup_time_ms =
5650 (os::elapsedTime() - end_par_time_sec) * 1000.0;
5651 g1_policy()->phase_times()->record_code_root_fixup_time(code_root_fixup_time_ms);
5652
5653 set_par_threads(0);
5654
5655 // Process any discovered reference objects - we have
5656 // to do this _before_ we retire the GC alloc regions
5657 // as we may have to copy some 'reachable' referent
5658 // objects (and their reachable sub-graphs) that were
5659 // not copied during the pause.
5660 process_discovered_references(n_workers);
5661
5662 // Weak root processing.
5663 {
5664 G1STWIsAliveClosure is_alive(this);
5665 G1KeepAliveClosure keep_alive(this);
5666 JNIHandles::weak_oops_do(&is_alive, &keep_alive);
5667 if (G1StringDedup::is_enabled()) {
5668 G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive);
5669 }
5670 }
5671
5672 release_gc_alloc_regions(n_workers, evacuation_info);
5673 g1_rem_set()->cleanup_after_oops_into_collection_set_do();
5674
5675 // Reset and re-enable the hot card cache.
5676 // Note the counts for the cards in the regions in the
5677 // collection set are reset when the collection set is freed.
5678 hot_card_cache->reset_hot_cache();
5679 hot_card_cache->set_use_cache(true);
5680
5681 // Migrate the strong code roots attached to each region in
5682 // the collection set. Ideally we would like to do this
5683 // after we have finished the scanning/evacuation of the
5684 // strong code roots for a particular heap region.
5685 migrate_strong_code_roots();
5686
5687 purge_code_root_memory();
5688
5689 if (g1_policy()->during_initial_mark_pause()) {
5690 // Reset the claim values set during marking the strong code roots
5691 reset_heap_region_claim_values();
5692 }
5693
5694 finalize_for_evac_failure();
5695
5696 if (evacuation_failed()) {
5697 remove_self_forwarding_pointers();
5698
5699 // Reset the G1EvacuationFailureALot counters and flags
5700 // Note: the values are reset only when an actual
5701 // evacuation failure occurs.
5702 NOT_PRODUCT(reset_evacuation_should_fail();)
5703 }
5704
5705 // Enqueue any remaining references remaining on the STW
5706 // reference processor's discovered lists. We need to do
5707 // this after the card table is cleaned (and verified) as
5708 // the act of enqueueing entries on to the pending list
5709 // will log these updates (and dirty their associated
5710 // cards). We need these updates logged to update any
5711 // RSets.
5712 enqueue_discovered_references(n_workers);
5713
5714 if (G1DeferredRSUpdate) {
5715 redirty_logged_cards();
5716 }
5717 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
5718 }
5719
5720 void G1CollectedHeap::free_region(HeapRegion* hr,
5721 FreeRegionList* free_list,
5722 bool par,
5723 bool locked) {
5724 assert(!hr->isHumongous(), "this is only for non-humongous regions");
5725 assert(!hr->is_empty(), "the region should not be empty");
5726 assert(free_list != NULL, "pre-condition");
5727
5728 // Clear the card counts for this region.
5729 // Note: we only need to do this if the region is not young
5730 // (since we don't refine cards in young regions).
5731 if (!hr->is_young()) {
5732 _cg1r->hot_card_cache()->reset_card_counts(hr);
5733 }
5734 hr->hr_clear(par, true /* clear_space */, locked /* locked */);
5735 free_list->add_ordered(hr);
5736 }
5737
5738 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
5739 FreeRegionList* free_list,
5740 bool par) {
5741 assert(hr->startsHumongous(), "this is only for starts humongous regions");
5742 assert(free_list != NULL, "pre-condition");
5743
5744 size_t hr_capacity = hr->capacity();
5745 // We need to read this before we make the region non-humongous,
5746 // otherwise the information will be gone.
5747 uint last_index = hr->last_hc_index();
5748 hr->set_notHumongous();
5749 free_region(hr, free_list, par);
5750
5751 uint i = hr->hrs_index() + 1;
5752 while (i < last_index) {
5753 HeapRegion* curr_hr = region_at(i);
5754 assert(curr_hr->continuesHumongous(), "invariant");
5755 curr_hr->set_notHumongous();
5756 free_region(curr_hr, free_list, par);
5757 i += 1;
5758 }
5759 }
5760
5761 void G1CollectedHeap::remove_from_old_sets(const HeapRegionSetCount& old_regions_removed,
5762 const HeapRegionSetCount& humongous_regions_removed) {
5763 if (old_regions_removed.length() > 0 || humongous_regions_removed.length() > 0) {
5764 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
5765 _old_set.bulk_remove(old_regions_removed);
5766 _humongous_set.bulk_remove(humongous_regions_removed);
5767 }
5768
5769 }
5770
5771 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) {
5772 assert(list != NULL, "list can't be null");
5773 if (!list->is_empty()) {
5774 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
5775 _free_list.add_ordered(list);
5776 }
5777 }
5778
5779 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) {
5780 assert(_summary_bytes_used >= bytes,
5781 err_msg("invariant: _summary_bytes_used: "SIZE_FORMAT" should be >= bytes: "SIZE_FORMAT,
5782 _summary_bytes_used, bytes));
5783 _summary_bytes_used -= bytes;
5784 }
5785
5786 class G1ParCleanupCTTask : public AbstractGangTask {
5787 G1SATBCardTableModRefBS* _ct_bs;
5788 G1CollectedHeap* _g1h;
5789 HeapRegion* volatile _su_head;
5790 public:
5791 G1ParCleanupCTTask(G1SATBCardTableModRefBS* ct_bs,
5792 G1CollectedHeap* g1h) :
5793 AbstractGangTask("G1 Par Cleanup CT Task"),
5794 _ct_bs(ct_bs), _g1h(g1h) { }
5795
5796 void work(uint worker_id) {
5797 HeapRegion* r;
5798 while (r = _g1h->pop_dirty_cards_region()) {
5799 clear_cards(r);
5800 }
5801 }
5802
5803 void clear_cards(HeapRegion* r) {
5804 // Cards of the survivors should have already been dirtied.
5805 if (!r->is_survivor()) {
5806 _ct_bs->clear(MemRegion(r->bottom(), r->end()));
5807 }
5808 }
5809 };
5810
5811 #ifndef PRODUCT
5812 class G1VerifyCardTableCleanup: public HeapRegionClosure {
5813 G1CollectedHeap* _g1h;
5814 G1SATBCardTableModRefBS* _ct_bs;
5815 public:
5816 G1VerifyCardTableCleanup(G1CollectedHeap* g1h, G1SATBCardTableModRefBS* ct_bs)
5817 : _g1h(g1h), _ct_bs(ct_bs) { }
5818 virtual bool doHeapRegion(HeapRegion* r) {
5819 if (r->is_survivor()) {
5820 _g1h->verify_dirty_region(r);
5821 } else {
5822 _g1h->verify_not_dirty_region(r);
5823 }
5824 return false;
5825 }
5826 };
5827
5828 void G1CollectedHeap::verify_not_dirty_region(HeapRegion* hr) {
5829 // All of the region should be clean.
5830 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
5831 MemRegion mr(hr->bottom(), hr->end());
5832 ct_bs->verify_not_dirty_region(mr);
5833 }
5834
5835 void G1CollectedHeap::verify_dirty_region(HeapRegion* hr) {
5836 // We cannot guarantee that [bottom(),end()] is dirty. Threads
5837 // dirty allocated blocks as they allocate them. The thread that
5838 // retires each region and replaces it with a new one will do a
5839 // maximal allocation to fill in [pre_dummy_top(),end()] but will
5840 // not dirty that area (one less thing to have to do while holding
5841 // a lock). So we can only verify that [bottom(),pre_dummy_top()]
5842 // is dirty.
5843 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
5844 MemRegion mr(hr->bottom(), hr->pre_dummy_top());
5845 if (hr->is_young()) {
5846 ct_bs->verify_g1_young_region(mr);
5847 } else {
5848 ct_bs->verify_dirty_region(mr);
5849 }
5850 }
5851
5852 void G1CollectedHeap::verify_dirty_young_list(HeapRegion* head) {
5853 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
5854 for (HeapRegion* hr = head; hr != NULL; hr = hr->get_next_young_region()) {
5855 verify_dirty_region(hr);
5856 }
5857 }
5858
5859 void G1CollectedHeap::verify_dirty_young_regions() {
5860 verify_dirty_young_list(_young_list->first_region());
5861 }
5862 #endif
5863
5864 void G1CollectedHeap::cleanUpCardTable() {
5865 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
5866 double start = os::elapsedTime();
5867
5868 {
5869 // Iterate over the dirty cards region list.
5870 G1ParCleanupCTTask cleanup_task(ct_bs, this);
5871
5872 if (G1CollectedHeap::use_parallel_gc_threads()) {
5873 set_par_threads();
5874 workers()->run_task(&cleanup_task);
5875 set_par_threads(0);
5876 } else {
5877 while (_dirty_cards_region_list) {
5878 HeapRegion* r = _dirty_cards_region_list;
5879 cleanup_task.clear_cards(r);
5880 _dirty_cards_region_list = r->get_next_dirty_cards_region();
5881 if (_dirty_cards_region_list == r) {
5882 // The last region.
5883 _dirty_cards_region_list = NULL;
5884 }
5885 r->set_next_dirty_cards_region(NULL);
5886 }
5887 }
5888 #ifndef PRODUCT
5889 if (G1VerifyCTCleanup || VerifyAfterGC) {
5890 G1VerifyCardTableCleanup cleanup_verifier(this, ct_bs);
5891 heap_region_iterate(&cleanup_verifier);
5892 }
5893 #endif
5894 }
5895
5896 double elapsed = os::elapsedTime() - start;
5897 g1_policy()->phase_times()->record_clear_ct_time(elapsed * 1000.0);
5898 }
5899
5900 void G1CollectedHeap::free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info) {
5901 size_t pre_used = 0;
5902 FreeRegionList local_free_list("Local List for CSet Freeing");
5903
5904 double young_time_ms = 0.0;
5905 double non_young_time_ms = 0.0;
5906
5907 // Since the collection set is a superset of the the young list,
5908 // all we need to do to clear the young list is clear its
5909 // head and length, and unlink any young regions in the code below
5910 _young_list->clear();
5911
5912 G1CollectorPolicy* policy = g1_policy();
5913
5914 double start_sec = os::elapsedTime();
5915 bool non_young = true;
5916
5917 HeapRegion* cur = cs_head;
5918 int age_bound = -1;
5919 size_t rs_lengths = 0;
5920
5921 while (cur != NULL) {
5922 assert(!is_on_master_free_list(cur), "sanity");
5923 if (non_young) {
5924 if (cur->is_young()) {
5925 double end_sec = os::elapsedTime();
5926 double elapsed_ms = (end_sec - start_sec) * 1000.0;
5927 non_young_time_ms += elapsed_ms;
5928
5929 start_sec = os::elapsedTime();
5930 non_young = false;
5931 }
5932 } else {
5933 if (!cur->is_young()) {
5934 double end_sec = os::elapsedTime();
5935 double elapsed_ms = (end_sec - start_sec) * 1000.0;
5936 young_time_ms += elapsed_ms;
5937
5938 start_sec = os::elapsedTime();
5939 non_young = true;
5940 }
5941 }
5942
5943 rs_lengths += cur->rem_set()->occupied_locked();
5944
5945 HeapRegion* next = cur->next_in_collection_set();
5946 assert(cur->in_collection_set(), "bad CS");
5947 cur->set_next_in_collection_set(NULL);
5948 cur->set_in_collection_set(false);
5949
5950 if (cur->is_young()) {
5951 int index = cur->young_index_in_cset();
5952 assert(index != -1, "invariant");
5953 assert((uint) index < policy->young_cset_region_length(), "invariant");
5954 size_t words_survived = _surviving_young_words[index];
5955 cur->record_surv_words_in_group(words_survived);
5956
5957 // At this point the we have 'popped' cur from the collection set
5958 // (linked via next_in_collection_set()) but it is still in the
5959 // young list (linked via next_young_region()). Clear the
5960 // _next_young_region field.
5961 cur->set_next_young_region(NULL);
5962 } else {
5963 int index = cur->young_index_in_cset();
5964 assert(index == -1, "invariant");
5965 }
5966
5967 assert( (cur->is_young() && cur->young_index_in_cset() > -1) ||
5968 (!cur->is_young() && cur->young_index_in_cset() == -1),
5969 "invariant" );
5970
5971 if (!cur->evacuation_failed()) {
5972 MemRegion used_mr = cur->used_region();
5973
5974 // And the region is empty.
5975 assert(!used_mr.is_empty(), "Should not have empty regions in a CS.");
5976 pre_used += cur->used();
5977 free_region(cur, &local_free_list, false /* par */, true /* locked */);
5978 } else {
5979 cur->uninstall_surv_rate_group();
5980 if (cur->is_young()) {
5981 cur->set_young_index_in_cset(-1);
5982 }
5983 cur->set_not_young();
5984 cur->set_evacuation_failed(false);
5985 // The region is now considered to be old.
5986 _old_set.add(cur);
5987 evacuation_info.increment_collectionset_used_after(cur->used());
5988 }
5989 cur = next;
5990 }
5991
5992 evacuation_info.set_regions_freed(local_free_list.length());
5993 policy->record_max_rs_lengths(rs_lengths);
5994 policy->cset_regions_freed();
5995
5996 double end_sec = os::elapsedTime();
5997 double elapsed_ms = (end_sec - start_sec) * 1000.0;
5998
5999 if (non_young) {
6000 non_young_time_ms += elapsed_ms;
6001 } else {
6002 young_time_ms += elapsed_ms;
6003 }
6004
6005 prepend_to_freelist(&local_free_list);
6006 decrement_summary_bytes(pre_used);
6007 policy->phase_times()->record_young_free_cset_time_ms(young_time_ms);
6008 policy->phase_times()->record_non_young_free_cset_time_ms(non_young_time_ms);
6009 }
6010
6011 // This routine is similar to the above but does not record
6012 // any policy statistics or update free lists; we are abandoning
6013 // the current incremental collection set in preparation of a
6014 // full collection. After the full GC we will start to build up
6015 // the incremental collection set again.
6016 // This is only called when we're doing a full collection
6017 // and is immediately followed by the tearing down of the young list.
6018
6019 void G1CollectedHeap::abandon_collection_set(HeapRegion* cs_head) {
6020 HeapRegion* cur = cs_head;
6021
6022 while (cur != NULL) {
6023 HeapRegion* next = cur->next_in_collection_set();
6024 assert(cur->in_collection_set(), "bad CS");
6025 cur->set_next_in_collection_set(NULL);
6026 cur->set_in_collection_set(false);
6027 cur->set_young_index_in_cset(-1);
6028 cur = next;
6029 }
6030 }
6031
6032 void G1CollectedHeap::set_free_regions_coming() {
6033 if (G1ConcRegionFreeingVerbose) {
6034 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
6035 "setting free regions coming");
6036 }
6037
6038 assert(!free_regions_coming(), "pre-condition");
6039 _free_regions_coming = true;
6040 }
6041
6042 void G1CollectedHeap::reset_free_regions_coming() {
6043 assert(free_regions_coming(), "pre-condition");
6044
6045 {
6046 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6047 _free_regions_coming = false;
6048 SecondaryFreeList_lock->notify_all();
6049 }
6050
6051 if (G1ConcRegionFreeingVerbose) {
6052 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
6053 "reset free regions coming");
6054 }
6055 }
6056
6057 void G1CollectedHeap::wait_while_free_regions_coming() {
6058 // Most of the time we won't have to wait, so let's do a quick test
6059 // first before we take the lock.
6060 if (!free_regions_coming()) {
6061 return;
6062 }
6063
6064 if (G1ConcRegionFreeingVerbose) {
6065 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
6066 "waiting for free regions");
6067 }
6068
6069 {
6070 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6071 while (free_regions_coming()) {
6072 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
6073 }
6074 }
6075
6076 if (G1ConcRegionFreeingVerbose) {
6077 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
6078 "done waiting for free regions");
6079 }
6080 }
6081
6082 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
6083 assert(heap_lock_held_for_gc(),
6084 "the heap lock should already be held by or for this thread");
6085 _young_list->push_region(hr);
6086 }
6087
6088 class NoYoungRegionsClosure: public HeapRegionClosure {
6089 private:
6090 bool _success;
6091 public:
6092 NoYoungRegionsClosure() : _success(true) { }
6093 bool doHeapRegion(HeapRegion* r) {
6094 if (r->is_young()) {
6095 gclog_or_tty->print_cr("Region ["PTR_FORMAT", "PTR_FORMAT") tagged as young",
6096 r->bottom(), r->end());
6097 _success = false;
6098 }
6099 return false;
6100 }
6101 bool success() { return _success; }
6102 };
6103
6104 bool G1CollectedHeap::check_young_list_empty(bool check_heap, bool check_sample) {
6105 bool ret = _young_list->check_list_empty(check_sample);
6106
6107 if (check_heap) {
6108 NoYoungRegionsClosure closure;
6109 heap_region_iterate(&closure);
6110 ret = ret && closure.success();
6111 }
6112
6113 return ret;
6114 }
6115
6116 class TearDownRegionSetsClosure : public HeapRegionClosure {
6117 private:
6118 HeapRegionSet *_old_set;
6119
6120 public:
6121 TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { }
6122
6123 bool doHeapRegion(HeapRegion* r) {
6124 if (r->is_empty()) {
6125 // We ignore empty regions, we'll empty the free list afterwards
6126 } else if (r->is_young()) {
6127 // We ignore young regions, we'll empty the young list afterwards
6128 } else if (r->isHumongous()) {
6129 // We ignore humongous regions, we're not tearing down the
6130 // humongous region set
6131 } else {
6132 // The rest should be old
6133 _old_set->remove(r);
6134 }
6135 return false;
6136 }
6137
6138 ~TearDownRegionSetsClosure() {
6139 assert(_old_set->is_empty(), "post-condition");
6140 }
6141 };
6142
6143 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
6144 assert_at_safepoint(true /* should_be_vm_thread */);
6145
6146 if (!free_list_only) {
6147 TearDownRegionSetsClosure cl(&_old_set);
6148 heap_region_iterate(&cl);
6149
6150 // Note that emptying the _young_list is postponed and instead done as
6151 // the first step when rebuilding the regions sets again. The reason for
6152 // this is that during a full GC string deduplication needs to know if
6153 // a collected region was young or old when the full GC was initiated.
6154 }
6155 _free_list.remove_all();
6156 }
6157
6158 class RebuildRegionSetsClosure : public HeapRegionClosure {
6159 private:
6160 bool _free_list_only;
6161 HeapRegionSet* _old_set;
6162 FreeRegionList* _free_list;
6163 size_t _total_used;
6164
6165 public:
6166 RebuildRegionSetsClosure(bool free_list_only,
6167 HeapRegionSet* old_set, FreeRegionList* free_list) :
6168 _free_list_only(free_list_only),
6169 _old_set(old_set), _free_list(free_list), _total_used(0) {
6170 assert(_free_list->is_empty(), "pre-condition");
6171 if (!free_list_only) {
6172 assert(_old_set->is_empty(), "pre-condition");
6173 }
6174 }
6175
6176 bool doHeapRegion(HeapRegion* r) {
6177 if (r->continuesHumongous()) {
6178 return false;
6179 }
6180
6181 if (r->is_empty()) {
6182 // Add free regions to the free list
6183 _free_list->add_as_tail(r);
6184 } else if (!_free_list_only) {
6185 assert(!r->is_young(), "we should not come across young regions");
6186
6187 if (r->isHumongous()) {
6188 // We ignore humongous regions, we left the humongous set unchanged
6189 } else {
6190 // The rest should be old, add them to the old set
6191 _old_set->add(r);
6192 }
6193 _total_used += r->used();
6194 }
6195
6196 return false;
6197 }
6198
6199 size_t total_used() {
6200 return _total_used;
6201 }
6202 };
6203
6204 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
6205 assert_at_safepoint(true /* should_be_vm_thread */);
6206
6207 if (!free_list_only) {
6208 _young_list->empty_list();
6209 }
6210
6211 RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_free_list);
6212 heap_region_iterate(&cl);
6213
6214 if (!free_list_only) {
6215 _summary_bytes_used = cl.total_used();
6216 }
6217 assert(_summary_bytes_used == recalculate_used(),
6218 err_msg("inconsistent _summary_bytes_used, "
6219 "value: "SIZE_FORMAT" recalculated: "SIZE_FORMAT,
6220 _summary_bytes_used, recalculate_used()));
6221 }
6222
6223 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) {
6224 _refine_cte_cl->set_concurrent(concurrent);
6225 }
6226
6227 bool G1CollectedHeap::is_in_closed_subset(const void* p) const {
6228 HeapRegion* hr = heap_region_containing(p);
6229 return hr->is_in(p);
6230 }
6231
6232 // Methods for the mutator alloc region
6233
6234 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
6235 bool force) {
6236 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6237 assert(!force || g1_policy()->can_expand_young_list(),
6238 "if force is true we should be able to expand the young list");
6239 bool young_list_full = g1_policy()->is_young_list_full();
6240 if (force || !young_list_full) {
6241 HeapRegion* new_alloc_region = new_region(word_size,
6242 false /* is_old */,
6243 false /* do_expand */);
6244 if (new_alloc_region != NULL) {
6245 set_region_short_lived_locked(new_alloc_region);
6246 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Eden, young_list_full);
6247 return new_alloc_region;
6248 }
6249 }
6250 return NULL;
6251 }
6252
6253 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
6254 size_t allocated_bytes) {
6255 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6256 assert(alloc_region->is_young(), "all mutator alloc regions should be young");
6257
6258 g1_policy()->add_region_to_incremental_cset_lhs(alloc_region);
6259 _summary_bytes_used += allocated_bytes;
6260 _hr_printer.retire(alloc_region);
6261 // We update the eden sizes here, when the region is retired,
6262 // instead of when it's allocated, since this is the point that its
6263 // used space has been recored in _summary_bytes_used.
6264 g1mm()->update_eden_size();
6265 }
6266
6267 HeapRegion* MutatorAllocRegion::allocate_new_region(size_t word_size,
6268 bool force) {
6269 return _g1h->new_mutator_alloc_region(word_size, force);
6270 }
6271
6272 void G1CollectedHeap::set_par_threads() {
6273 // Don't change the number of workers. Use the value previously set
6274 // in the workgroup.
6275 assert(G1CollectedHeap::use_parallel_gc_threads(), "shouldn't be here otherwise");
6276 uint n_workers = workers()->active_workers();
6277 assert(UseDynamicNumberOfGCThreads ||
6278 n_workers == workers()->total_workers(),
6279 "Otherwise should be using the total number of workers");
6280 if (n_workers == 0) {
6281 assert(false, "Should have been set in prior evacuation pause.");
6282 n_workers = ParallelGCThreads;
6283 workers()->set_active_workers(n_workers);
6284 }
6285 set_par_threads(n_workers);
6286 }
6287
6288 void MutatorAllocRegion::retire_region(HeapRegion* alloc_region,
6289 size_t allocated_bytes) {
6290 _g1h->retire_mutator_alloc_region(alloc_region, allocated_bytes);
6291 }
6292
6293 // Methods for the GC alloc regions
6294
6295 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size,
6296 uint count,
6297 GCAllocPurpose ap) {
6298 assert(FreeList_lock->owned_by_self(), "pre-condition");
6299
6300 if (count < g1_policy()->max_regions(ap)) {
6301 bool survivor = (ap == GCAllocForSurvived);
6302 HeapRegion* new_alloc_region = new_region(word_size,
6303 !survivor,
6304 true /* do_expand */);
6305 if (new_alloc_region != NULL) {
6306 // We really only need to do this for old regions given that we
6307 // should never scan survivors. But it doesn't hurt to do it
6308 // for survivors too.
6309 new_alloc_region->set_saved_mark();
6310 if (survivor) {
6311 new_alloc_region->set_survivor();
6312 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Survivor);
6313 } else {
6314 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Old);
6315 }
6316 bool during_im = g1_policy()->during_initial_mark_pause();
6317 new_alloc_region->note_start_of_copying(during_im);
6318 return new_alloc_region;
6319 } else {
6320 g1_policy()->note_alloc_region_limit_reached(ap);
6321 }
6322 }
6323 return NULL;
6324 }
6325
6326 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
6327 size_t allocated_bytes,
6328 GCAllocPurpose ap) {
6329 bool during_im = g1_policy()->during_initial_mark_pause();
6330 alloc_region->note_end_of_copying(during_im);
6331 g1_policy()->record_bytes_copied_during_gc(allocated_bytes);
6332 if (ap == GCAllocForSurvived) {
6333 young_list()->add_survivor_region(alloc_region);
6334 } else {
6335 _old_set.add(alloc_region);
6336 }
6337 _hr_printer.retire(alloc_region);
6338 }
6339
6340 HeapRegion* SurvivorGCAllocRegion::allocate_new_region(size_t word_size,
6341 bool force) {
6342 assert(!force, "not supported for GC alloc regions");
6343 return _g1h->new_gc_alloc_region(word_size, count(), GCAllocForSurvived);
6344 }
6345
6346 void SurvivorGCAllocRegion::retire_region(HeapRegion* alloc_region,
6347 size_t allocated_bytes) {
6348 _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes,
6349 GCAllocForSurvived);
6350 }
6351
6352 HeapRegion* OldGCAllocRegion::allocate_new_region(size_t word_size,
6353 bool force) {
6354 assert(!force, "not supported for GC alloc regions");
6355 return _g1h->new_gc_alloc_region(word_size, count(), GCAllocForTenured);
6356 }
6357
6358 void OldGCAllocRegion::retire_region(HeapRegion* alloc_region,
6359 size_t allocated_bytes) {
6360 _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes,
6361 GCAllocForTenured);
6362 }
6363 // Heap region set verification
6364
6365 class VerifyRegionListsClosure : public HeapRegionClosure {
6366 private:
6367 HeapRegionSet* _old_set;
6368 HeapRegionSet* _humongous_set;
6369 FreeRegionList* _free_list;
6370
6371 public:
6372 HeapRegionSetCount _old_count;
6373 HeapRegionSetCount _humongous_count;
6374 HeapRegionSetCount _free_count;
6375
6376 VerifyRegionListsClosure(HeapRegionSet* old_set,
6377 HeapRegionSet* humongous_set,
6378 FreeRegionList* free_list) :
6379 _old_set(old_set), _humongous_set(humongous_set), _free_list(free_list),
6380 _old_count(), _humongous_count(), _free_count(){ }
6381
6382 bool doHeapRegion(HeapRegion* hr) {
6383 if (hr->continuesHumongous()) {
6384 return false;
6385 }
6386
6387 if (hr->is_young()) {
6388 // TODO
6389 } else if (hr->startsHumongous()) {
6390 assert(hr->containing_set() == _humongous_set, err_msg("Heap region %u is starts humongous but not in humongous set.", hr->hrs_index()));
6391 _humongous_count.increment(1u, hr->capacity());
6392 } else if (hr->is_empty()) {
6393 assert(hr->containing_set() == _free_list, err_msg("Heap region %u is empty but not on the free list.", hr->hrs_index()));
6394 _free_count.increment(1u, hr->capacity());
6395 } else {
6396 assert(hr->containing_set() == _old_set, err_msg("Heap region %u is old but not in the old set.", hr->hrs_index()));
6397 _old_count.increment(1u, hr->capacity());
6398 }
6399 return false;
6400 }
6401
6402 void verify_counts(HeapRegionSet* old_set, HeapRegionSet* humongous_set, FreeRegionList* free_list) {
6403 guarantee(old_set->length() == _old_count.length(), err_msg("Old set count mismatch. Expected %u, actual %u.", old_set->length(), _old_count.length()));
6404 guarantee(old_set->total_capacity_bytes() == _old_count.capacity(), err_msg("Old set capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
6405 old_set->total_capacity_bytes(), _old_count.capacity()));
6406
6407 guarantee(humongous_set->length() == _humongous_count.length(), err_msg("Hum set count mismatch. Expected %u, actual %u.", humongous_set->length(), _humongous_count.length()));
6408 guarantee(humongous_set->total_capacity_bytes() == _humongous_count.capacity(), err_msg("Hum set capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
6409 humongous_set->total_capacity_bytes(), _humongous_count.capacity()));
6410
6411 guarantee(free_list->length() == _free_count.length(), err_msg("Free list count mismatch. Expected %u, actual %u.", free_list->length(), _free_count.length()));
6412 guarantee(free_list->total_capacity_bytes() == _free_count.capacity(), err_msg("Free list capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
6413 free_list->total_capacity_bytes(), _free_count.capacity()));
6414 }
6415 };
6416
6417 HeapRegion* G1CollectedHeap::new_heap_region(uint hrs_index,
6418 HeapWord* bottom) {
6419 HeapWord* end = bottom + HeapRegion::GrainWords;
6420 MemRegion mr(bottom, end);
6421 assert(_g1_reserved.contains(mr), "invariant");
6422 // This might return NULL if the allocation fails
6423 return new HeapRegion(hrs_index, _bot_shared, mr);
6424 }
6425
6426 void G1CollectedHeap::verify_region_sets() {
6427 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6428
6429 // First, check the explicit lists.
6430 _free_list.verify_list();
6431 {
6432 // Given that a concurrent operation might be adding regions to
6433 // the secondary free list we have to take the lock before
6434 // verifying it.
6435 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6436 _secondary_free_list.verify_list();
6437 }
6438
6439 // If a concurrent region freeing operation is in progress it will
6440 // be difficult to correctly attributed any free regions we come
6441 // across to the correct free list given that they might belong to
6442 // one of several (free_list, secondary_free_list, any local lists,
6443 // etc.). So, if that's the case we will skip the rest of the
6444 // verification operation. Alternatively, waiting for the concurrent
6445 // operation to complete will have a non-trivial effect on the GC's
6446 // operation (no concurrent operation will last longer than the
6447 // interval between two calls to verification) and it might hide
6448 // any issues that we would like to catch during testing.
6449 if (free_regions_coming()) {
6450 return;
6451 }
6452
6453 // Make sure we append the secondary_free_list on the free_list so
6454 // that all free regions we will come across can be safely
6455 // attributed to the free_list.
6456 append_secondary_free_list_if_not_empty_with_lock();
6457
6458 // Finally, make sure that the region accounting in the lists is
6459 // consistent with what we see in the heap.
6460
6461 VerifyRegionListsClosure cl(&_old_set, &_humongous_set, &_free_list);
6462 heap_region_iterate(&cl);
6463 cl.verify_counts(&_old_set, &_humongous_set, &_free_list);
6464 }
6465
6466 // Optimized nmethod scanning
6467
6468 class RegisterNMethodOopClosure: public OopClosure {
6469 G1CollectedHeap* _g1h;
6470 nmethod* _nm;
6471
6472 template <class T> void do_oop_work(T* p) {
6473 T heap_oop = oopDesc::load_heap_oop(p);
6474 if (!oopDesc::is_null(heap_oop)) {
6475 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
6476 HeapRegion* hr = _g1h->heap_region_containing(obj);
6477 assert(!hr->continuesHumongous(),
6478 err_msg("trying to add code root "PTR_FORMAT" in continuation of humongous region "HR_FORMAT
6479 " starting at "HR_FORMAT,
6480 _nm, HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())));
6481
6482 // HeapRegion::add_strong_code_root() avoids adding duplicate
6483 // entries but having duplicates is OK since we "mark" nmethods
6484 // as visited when we scan the strong code root lists during the GC.
6485 hr->add_strong_code_root(_nm);
6486 assert(hr->rem_set()->strong_code_roots_list_contains(_nm),
6487 err_msg("failed to add code root "PTR_FORMAT" to remembered set of region "HR_FORMAT,
6488 _nm, HR_FORMAT_PARAMS(hr)));
6489 }
6490 }
6491
6492 public:
6493 RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
6494 _g1h(g1h), _nm(nm) {}
6495
6496 void do_oop(oop* p) { do_oop_work(p); }
6497 void do_oop(narrowOop* p) { do_oop_work(p); }
6498 };
6499
6500 class UnregisterNMethodOopClosure: public OopClosure {
6501 G1CollectedHeap* _g1h;
6502 nmethod* _nm;
6503
6504 template <class T> void do_oop_work(T* p) {
6505 T heap_oop = oopDesc::load_heap_oop(p);
6506 if (!oopDesc::is_null(heap_oop)) {
6507 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
6508 HeapRegion* hr = _g1h->heap_region_containing(obj);
6509 assert(!hr->continuesHumongous(),
6510 err_msg("trying to remove code root "PTR_FORMAT" in continuation of humongous region "HR_FORMAT
6511 " starting at "HR_FORMAT,
6512 _nm, HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())));
6513
6514 hr->remove_strong_code_root(_nm);
6515 assert(!hr->rem_set()->strong_code_roots_list_contains(_nm),
6516 err_msg("failed to remove code root "PTR_FORMAT" of region "HR_FORMAT,
6517 _nm, HR_FORMAT_PARAMS(hr)));
6518 }
6519 }
6520
6521 public:
6522 UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
6523 _g1h(g1h), _nm(nm) {}
6524
6525 void do_oop(oop* p) { do_oop_work(p); }
6526 void do_oop(narrowOop* p) { do_oop_work(p); }
6527 };
6528
6529 void G1CollectedHeap::register_nmethod(nmethod* nm) {
6530 CollectedHeap::register_nmethod(nm);
6531
6532 guarantee(nm != NULL, "sanity");
6533 RegisterNMethodOopClosure reg_cl(this, nm);
6534 nm->oops_do(®_cl);
6535 }
6536
6537 void G1CollectedHeap::unregister_nmethod(nmethod* nm) {
6538 CollectedHeap::unregister_nmethod(nm);
6539
6540 guarantee(nm != NULL, "sanity");
6541 UnregisterNMethodOopClosure reg_cl(this, nm);
6542 nm->oops_do(®_cl, true);
6543 }
6544
6545 class MigrateCodeRootsHeapRegionClosure: public HeapRegionClosure {
6546 public:
6547 bool doHeapRegion(HeapRegion *hr) {
6548 assert(!hr->isHumongous(),
6549 err_msg("humongous region "HR_FORMAT" should not have been added to collection set",
6550 HR_FORMAT_PARAMS(hr)));
6551 hr->migrate_strong_code_roots();
6552 return false;
6553 }
6554 };
6555
6556 void G1CollectedHeap::migrate_strong_code_roots() {
6557 MigrateCodeRootsHeapRegionClosure cl;
6558 double migrate_start = os::elapsedTime();
6559 collection_set_iterate(&cl);
6560 double migration_time_ms = (os::elapsedTime() - migrate_start) * 1000.0;
6561 g1_policy()->phase_times()->record_strong_code_root_migration_time(migration_time_ms);
6562 }
6563
6564 void G1CollectedHeap::purge_code_root_memory() {
6565 double purge_start = os::elapsedTime();
6566 G1CodeRootSet::purge_chunks(G1CodeRootsChunkCacheKeepPercent);
6567 double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0;
6568 g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms);
6569 }
6570
6571 // Mark all the code roots that point into regions *not* in the
6572 // collection set.
6573 //
6574 // Note we do not want to use a "marking" CodeBlobToOopClosure while
6575 // walking the the code roots lists of regions not in the collection
6576 // set. Suppose we have an nmethod (M) that points to objects in two
6577 // separate regions - one in the collection set (R1) and one not (R2).
6578 // Using a "marking" CodeBlobToOopClosure here would result in "marking"
6579 // nmethod M when walking the code roots for R1. When we come to scan
6580 // the code roots for R2, we would see that M is already marked and it
6581 // would be skipped and the objects in R2 that are referenced from M
6582 // would not be evacuated.
6583
6584 class MarkStrongCodeRootCodeBlobClosure: public CodeBlobClosure {
6585
6586 class MarkStrongCodeRootOopClosure: public OopClosure {
6587 ConcurrentMark* _cm;
6588 HeapRegion* _hr;
6589 uint _worker_id;
6590
6591 template <class T> void do_oop_work(T* p) {
6592 T heap_oop = oopDesc::load_heap_oop(p);
6593 if (!oopDesc::is_null(heap_oop)) {
6594 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
6595 // Only mark objects in the region (which is assumed
6596 // to be not in the collection set).
6597 if (_hr->is_in(obj)) {
6598 _cm->grayRoot(obj, (size_t) obj->size(), _worker_id);
6599 }
6600 }
6601 }
6602
6603 public:
6604 MarkStrongCodeRootOopClosure(ConcurrentMark* cm, HeapRegion* hr, uint worker_id) :
6605 _cm(cm), _hr(hr), _worker_id(worker_id) {
6606 assert(!_hr->in_collection_set(), "sanity");
6607 }
6608
6609 void do_oop(narrowOop* p) { do_oop_work(p); }
6610 void do_oop(oop* p) { do_oop_work(p); }
6611 };
6612
6613 MarkStrongCodeRootOopClosure _oop_cl;
6614
6615 public:
6616 MarkStrongCodeRootCodeBlobClosure(ConcurrentMark* cm, HeapRegion* hr, uint worker_id):
6617 _oop_cl(cm, hr, worker_id) {}
6618
6619 void do_code_blob(CodeBlob* cb) {
6620 nmethod* nm = (cb == NULL) ? NULL : cb->as_nmethod_or_null();
6621 if (nm != NULL) {
6622 nm->oops_do(&_oop_cl);
6623 }
6624 }
6625 };
6626
6627 class MarkStrongCodeRootsHRClosure: public HeapRegionClosure {
6628 G1CollectedHeap* _g1h;
6629 uint _worker_id;
6630
6631 public:
6632 MarkStrongCodeRootsHRClosure(G1CollectedHeap* g1h, uint worker_id) :
6633 _g1h(g1h), _worker_id(worker_id) {}
6634
6635 bool doHeapRegion(HeapRegion *hr) {
6636 HeapRegionRemSet* hrrs = hr->rem_set();
6637 if (hr->continuesHumongous()) {
6638 // Code roots should never be attached to a continuation of a humongous region
6639 assert(hrrs->strong_code_roots_list_length() == 0,
6640 err_msg("code roots should never be attached to continuations of humongous region "HR_FORMAT
6641 " starting at "HR_FORMAT", but has "SIZE_FORMAT,
6642 HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()),
6643 hrrs->strong_code_roots_list_length()));
6644 return false;
6645 }
6646
6647 if (hr->in_collection_set()) {
6648 // Don't mark code roots into regions in the collection set here.
6649 // They will be marked when we scan them.
6650 return false;
6651 }
6652
6653 MarkStrongCodeRootCodeBlobClosure cb_cl(_g1h->concurrent_mark(), hr, _worker_id);
6654 hr->strong_code_roots_do(&cb_cl);
6655 return false;
6656 }
6657 };
6658
6659 void G1CollectedHeap::mark_strong_code_roots(uint worker_id) {
6660 MarkStrongCodeRootsHRClosure cl(this, worker_id);
6661 if (G1CollectedHeap::use_parallel_gc_threads()) {
6662 heap_region_par_iterate_chunked(&cl,
6663 worker_id,
6664 workers()->active_workers(),
6665 HeapRegion::ParMarkRootClaimValue);
6666 } else {
6667 heap_region_iterate(&cl);
6668 }
6669 }
6670
6671 class RebuildStrongCodeRootClosure: public CodeBlobClosure {
6672 G1CollectedHeap* _g1h;
6673
6674 public:
6675 RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) :
6676 _g1h(g1h) {}
6677
6678 void do_code_blob(CodeBlob* cb) {
6679 nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL;
6680 if (nm == NULL) {
6681 return;
6682 }
6683
6684 if (ScavengeRootsInCode && nm->detect_scavenge_root_oops()) {
6685 _g1h->register_nmethod(nm);
6686 }
6687 }
6688 };
6689
6690 void G1CollectedHeap::rebuild_strong_code_roots() {
6691 RebuildStrongCodeRootClosure blob_cl(this);
6692 CodeCache::blobs_do(&blob_cl);
6693 }