1 /*
2 * Copyright (c) 2001, 2012, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "code/icBuffer.hpp"
27 #include "gc_implementation/g1/bufferingOopClosure.hpp"
28 #include "gc_implementation/g1/concurrentG1Refine.hpp"
29 #include "gc_implementation/g1/concurrentG1RefineThread.hpp"
30 #include "gc_implementation/g1/concurrentMarkThread.inline.hpp"
31 #include "gc_implementation/g1/g1AllocRegion.inline.hpp"
32 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
33 #include "gc_implementation/g1/g1CollectorPolicy.hpp"
34 #include "gc_implementation/g1/g1ErgoVerbose.hpp"
35 #include "gc_implementation/g1/g1EvacFailure.hpp"
36 #include "gc_implementation/g1/g1Log.hpp"
37 #include "gc_implementation/g1/g1MarkSweep.hpp"
38 #include "gc_implementation/g1/g1OopClosures.inline.hpp"
39 #include "gc_implementation/g1/g1RemSet.inline.hpp"
40 #include "gc_implementation/g1/heapRegion.inline.hpp"
41 #include "gc_implementation/g1/heapRegionRemSet.hpp"
42 #include "gc_implementation/g1/heapRegionSeq.inline.hpp"
43 #include "gc_implementation/g1/vm_operations_g1.hpp"
44 #include "gc_implementation/shared/isGCActiveMark.hpp"
45 #include "memory/gcLocker.inline.hpp"
46 #include "memory/genOopClosures.inline.hpp"
47 #include "memory/generationSpec.hpp"
48 #include "memory/referenceProcessor.hpp"
49 #include "oops/oop.inline.hpp"
50 #include "oops/oop.pcgc.inline.hpp"
51 #include "runtime/aprofiler.hpp"
52 #include "runtime/vmThread.hpp"
53
54 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;
55
56 // turn it on so that the contents of the young list (scan-only /
57 // to-be-collected) are printed at "strategic" points before / during
58 // / after the collection --- this is useful for debugging
59 #define YOUNG_LIST_VERBOSE 0
60 // CURRENT STATUS
61 // This file is under construction. Search for "FIXME".
62
63 // INVARIANTS/NOTES
64 //
65 // All allocation activity covered by the G1CollectedHeap interface is
66 // serialized by acquiring the HeapLock. This happens in mem_allocate
67 // and allocate_new_tlab, which are the "entry" points to the
68 // allocation code from the rest of the JVM. (Note that this does not
69 // apply to TLAB allocation, which is not part of this interface: it
70 // is done by clients of this interface.)
71
72 // Notes on implementation of parallelism in different tasks.
73 //
74 // G1ParVerifyTask uses heap_region_par_iterate_chunked() for parallelism.
75 // The number of GC workers is passed to heap_region_par_iterate_chunked().
76 // It does use run_task() which sets _n_workers in the task.
77 // G1ParTask executes g1_process_strong_roots() ->
78 // SharedHeap::process_strong_roots() which calls eventuall to
79 // CardTableModRefBS::par_non_clean_card_iterate_work() which uses
80 // SequentialSubTasksDone. SharedHeap::process_strong_roots() also
81 // directly uses SubTasksDone (_process_strong_tasks field in SharedHeap).
82 //
83
84 // Local to this file.
85
86 class RefineCardTableEntryClosure: public CardTableEntryClosure {
87 SuspendibleThreadSet* _sts;
88 G1RemSet* _g1rs;
89 ConcurrentG1Refine* _cg1r;
90 bool _concurrent;
91 public:
92 RefineCardTableEntryClosure(SuspendibleThreadSet* sts,
93 G1RemSet* g1rs,
94 ConcurrentG1Refine* cg1r) :
95 _sts(sts), _g1rs(g1rs), _cg1r(cg1r), _concurrent(true)
96 {}
97 bool do_card_ptr(jbyte* card_ptr, int worker_i) {
98 bool oops_into_cset = _g1rs->concurrentRefineOneCard(card_ptr, worker_i, false);
99 // This path is executed by the concurrent refine or mutator threads,
100 // concurrently, and so we do not care if card_ptr contains references
101 // that point into the collection set.
102 assert(!oops_into_cset, "should be");
103
104 if (_concurrent && _sts->should_yield()) {
105 // Caller will actually yield.
106 return false;
107 }
108 // Otherwise, we finished successfully; return true.
109 return true;
110 }
111 void set_concurrent(bool b) { _concurrent = b; }
112 };
113
114
115 class ClearLoggedCardTableEntryClosure: public CardTableEntryClosure {
116 int _calls;
117 G1CollectedHeap* _g1h;
118 CardTableModRefBS* _ctbs;
119 int _histo[256];
120 public:
121 ClearLoggedCardTableEntryClosure() :
122 _calls(0)
123 {
124 _g1h = G1CollectedHeap::heap();
125 _ctbs = (CardTableModRefBS*)_g1h->barrier_set();
126 for (int i = 0; i < 256; i++) _histo[i] = 0;
127 }
128 bool do_card_ptr(jbyte* card_ptr, int worker_i) {
129 if (_g1h->is_in_reserved(_ctbs->addr_for(card_ptr))) {
130 _calls++;
131 unsigned char* ujb = (unsigned char*)card_ptr;
132 int ind = (int)(*ujb);
133 _histo[ind]++;
134 *card_ptr = -1;
135 }
136 return true;
137 }
138 int calls() { return _calls; }
139 void print_histo() {
140 gclog_or_tty->print_cr("Card table value histogram:");
141 for (int i = 0; i < 256; i++) {
142 if (_histo[i] != 0) {
143 gclog_or_tty->print_cr(" %d: %d", i, _histo[i]);
144 }
145 }
146 }
147 };
148
149 class RedirtyLoggedCardTableEntryClosure: public CardTableEntryClosure {
150 int _calls;
151 G1CollectedHeap* _g1h;
152 CardTableModRefBS* _ctbs;
153 public:
154 RedirtyLoggedCardTableEntryClosure() :
155 _calls(0)
156 {
157 _g1h = G1CollectedHeap::heap();
158 _ctbs = (CardTableModRefBS*)_g1h->barrier_set();
159 }
160 bool do_card_ptr(jbyte* card_ptr, int worker_i) {
161 if (_g1h->is_in_reserved(_ctbs->addr_for(card_ptr))) {
162 _calls++;
163 *card_ptr = 0;
164 }
165 return true;
166 }
167 int calls() { return _calls; }
168 };
169
170 class RedirtyLoggedCardTableEntryFastClosure : public CardTableEntryClosure {
171 public:
172 bool do_card_ptr(jbyte* card_ptr, int worker_i) {
173 *card_ptr = CardTableModRefBS::dirty_card_val();
174 return true;
175 }
176 };
177
178 YoungList::YoungList(G1CollectedHeap* g1h) :
179 _g1h(g1h), _head(NULL), _length(0), _last_sampled_rs_lengths(0),
180 _survivor_head(NULL), _survivor_tail(NULL), _survivor_length(0) {
181 guarantee(check_list_empty(false), "just making sure...");
182 }
183
184 void YoungList::push_region(HeapRegion *hr) {
185 assert(!hr->is_young(), "should not already be young");
186 assert(hr->get_next_young_region() == NULL, "cause it should!");
187
188 hr->set_next_young_region(_head);
189 _head = hr;
190
191 _g1h->g1_policy()->set_region_eden(hr, (int) _length);
192 ++_length;
193 }
194
195 void YoungList::add_survivor_region(HeapRegion* hr) {
196 assert(hr->is_survivor(), "should be flagged as survivor region");
197 assert(hr->get_next_young_region() == NULL, "cause it should!");
198
199 hr->set_next_young_region(_survivor_head);
200 if (_survivor_head == NULL) {
201 _survivor_tail = hr;
202 }
203 _survivor_head = hr;
204 ++_survivor_length;
205 }
206
207 void YoungList::empty_list(HeapRegion* list) {
208 while (list != NULL) {
209 HeapRegion* next = list->get_next_young_region();
210 list->set_next_young_region(NULL);
211 list->uninstall_surv_rate_group();
212 list->set_not_young();
213 list = next;
214 }
215 }
216
217 void YoungList::empty_list() {
218 assert(check_list_well_formed(), "young list should be well formed");
219
220 empty_list(_head);
221 _head = NULL;
222 _length = 0;
223
224 empty_list(_survivor_head);
225 _survivor_head = NULL;
226 _survivor_tail = NULL;
227 _survivor_length = 0;
228
229 _last_sampled_rs_lengths = 0;
230
231 assert(check_list_empty(false), "just making sure...");
232 }
233
234 bool YoungList::check_list_well_formed() {
235 bool ret = true;
236
237 uint length = 0;
238 HeapRegion* curr = _head;
239 HeapRegion* last = NULL;
240 while (curr != NULL) {
241 if (!curr->is_young()) {
242 gclog_or_tty->print_cr("### YOUNG REGION "PTR_FORMAT"-"PTR_FORMAT" "
243 "incorrectly tagged (y: %d, surv: %d)",
244 curr->bottom(), curr->end(),
245 curr->is_young(), curr->is_survivor());
246 ret = false;
247 }
248 ++length;
249 last = curr;
250 curr = curr->get_next_young_region();
251 }
252 ret = ret && (length == _length);
253
254 if (!ret) {
255 gclog_or_tty->print_cr("### YOUNG LIST seems not well formed!");
256 gclog_or_tty->print_cr("### list has %u entries, _length is %u",
257 length, _length);
258 }
259
260 return ret;
261 }
262
263 bool YoungList::check_list_empty(bool check_sample) {
264 bool ret = true;
265
266 if (_length != 0) {
267 gclog_or_tty->print_cr("### YOUNG LIST should have 0 length, not %u",
268 _length);
269 ret = false;
270 }
271 if (check_sample && _last_sampled_rs_lengths != 0) {
272 gclog_or_tty->print_cr("### YOUNG LIST has non-zero last sampled RS lengths");
273 ret = false;
274 }
275 if (_head != NULL) {
276 gclog_or_tty->print_cr("### YOUNG LIST does not have a NULL head");
277 ret = false;
278 }
279 if (!ret) {
280 gclog_or_tty->print_cr("### YOUNG LIST does not seem empty");
281 }
282
283 return ret;
284 }
285
286 void
287 YoungList::rs_length_sampling_init() {
288 _sampled_rs_lengths = 0;
289 _curr = _head;
290 }
291
292 bool
293 YoungList::rs_length_sampling_more() {
294 return _curr != NULL;
295 }
296
297 void
298 YoungList::rs_length_sampling_next() {
299 assert( _curr != NULL, "invariant" );
300 size_t rs_length = _curr->rem_set()->occupied();
301
302 _sampled_rs_lengths += rs_length;
303
304 // The current region may not yet have been added to the
305 // incremental collection set (it gets added when it is
306 // retired as the current allocation region).
307 if (_curr->in_collection_set()) {
308 // Update the collection set policy information for this region
309 _g1h->g1_policy()->update_incremental_cset_info(_curr, rs_length);
310 }
311
312 _curr = _curr->get_next_young_region();
313 if (_curr == NULL) {
314 _last_sampled_rs_lengths = _sampled_rs_lengths;
315 // gclog_or_tty->print_cr("last sampled RS lengths = %d", _last_sampled_rs_lengths);
316 }
317 }
318
319 void
320 YoungList::reset_auxilary_lists() {
321 guarantee( is_empty(), "young list should be empty" );
322 assert(check_list_well_formed(), "young list should be well formed");
323
324 // Add survivor regions to SurvRateGroup.
325 _g1h->g1_policy()->note_start_adding_survivor_regions();
326 _g1h->g1_policy()->finished_recalculating_age_indexes(true /* is_survivors */);
327
328 int young_index_in_cset = 0;
329 for (HeapRegion* curr = _survivor_head;
330 curr != NULL;
331 curr = curr->get_next_young_region()) {
332 _g1h->g1_policy()->set_region_survivor(curr, young_index_in_cset);
333
334 // The region is a non-empty survivor so let's add it to
335 // the incremental collection set for the next evacuation
336 // pause.
337 _g1h->g1_policy()->add_region_to_incremental_cset_rhs(curr);
338 young_index_in_cset += 1;
339 }
340 assert((uint) young_index_in_cset == _survivor_length, "post-condition");
341 _g1h->g1_policy()->note_stop_adding_survivor_regions();
342
343 _head = _survivor_head;
344 _length = _survivor_length;
345 if (_survivor_head != NULL) {
346 assert(_survivor_tail != NULL, "cause it shouldn't be");
347 assert(_survivor_length > 0, "invariant");
348 _survivor_tail->set_next_young_region(NULL);
349 }
350
351 // Don't clear the survivor list handles until the start of
352 // the next evacuation pause - we need it in order to re-tag
353 // the survivor regions from this evacuation pause as 'young'
354 // at the start of the next.
355
356 _g1h->g1_policy()->finished_recalculating_age_indexes(false /* is_survivors */);
357
358 assert(check_list_well_formed(), "young list should be well formed");
359 }
360
361 void YoungList::print() {
362 HeapRegion* lists[] = {_head, _survivor_head};
363 const char* names[] = {"YOUNG", "SURVIVOR"};
364
365 for (unsigned int list = 0; list < ARRAY_SIZE(lists); ++list) {
366 gclog_or_tty->print_cr("%s LIST CONTENTS", names[list]);
367 HeapRegion *curr = lists[list];
368 if (curr == NULL)
369 gclog_or_tty->print_cr(" empty");
370 while (curr != NULL) {
371 gclog_or_tty->print_cr(" "HR_FORMAT", P: "PTR_FORMAT "N: "PTR_FORMAT", age: %4d",
372 HR_FORMAT_PARAMS(curr),
373 curr->prev_top_at_mark_start(),
374 curr->next_top_at_mark_start(),
375 curr->age_in_surv_rate_group_cond());
376 curr = curr->get_next_young_region();
377 }
378 }
379
380 gclog_or_tty->print_cr("");
381 }
382
383 void G1CollectedHeap::push_dirty_cards_region(HeapRegion* hr)
384 {
385 // Claim the right to put the region on the dirty cards region list
386 // by installing a self pointer.
387 HeapRegion* next = hr->get_next_dirty_cards_region();
388 if (next == NULL) {
389 HeapRegion* res = (HeapRegion*)
390 Atomic::cmpxchg_ptr(hr, hr->next_dirty_cards_region_addr(),
391 NULL);
392 if (res == NULL) {
393 HeapRegion* head;
394 do {
395 // Put the region to the dirty cards region list.
396 head = _dirty_cards_region_list;
397 next = (HeapRegion*)
398 Atomic::cmpxchg_ptr(hr, &_dirty_cards_region_list, head);
399 if (next == head) {
400 assert(hr->get_next_dirty_cards_region() == hr,
401 "hr->get_next_dirty_cards_region() != hr");
402 if (next == NULL) {
403 // The last region in the list points to itself.
404 hr->set_next_dirty_cards_region(hr);
405 } else {
406 hr->set_next_dirty_cards_region(next);
407 }
408 }
409 } while (next != head);
410 }
411 }
412 }
413
414 HeapRegion* G1CollectedHeap::pop_dirty_cards_region()
415 {
416 HeapRegion* head;
417 HeapRegion* hr;
418 do {
419 head = _dirty_cards_region_list;
420 if (head == NULL) {
421 return NULL;
422 }
423 HeapRegion* new_head = head->get_next_dirty_cards_region();
424 if (head == new_head) {
425 // The last region.
426 new_head = NULL;
427 }
428 hr = (HeapRegion*)Atomic::cmpxchg_ptr(new_head, &_dirty_cards_region_list,
429 head);
430 } while (hr != head);
431 assert(hr != NULL, "invariant");
432 hr->set_next_dirty_cards_region(NULL);
433 return hr;
434 }
435
436 void G1CollectedHeap::stop_conc_gc_threads() {
437 _cg1r->stop();
438 _cmThread->stop();
439 }
440
441 #ifdef ASSERT
442 // A region is added to the collection set as it is retired
443 // so an address p can point to a region which will be in the
444 // collection set but has not yet been retired. This method
445 // therefore is only accurate during a GC pause after all
446 // regions have been retired. It is used for debugging
447 // to check if an nmethod has references to objects that can
448 // be move during a partial collection. Though it can be
449 // inaccurate, it is sufficient for G1 because the conservative
450 // implementation of is_scavengable() for G1 will indicate that
451 // all nmethods must be scanned during a partial collection.
452 bool G1CollectedHeap::is_in_partial_collection(const void* p) {
453 HeapRegion* hr = heap_region_containing(p);
454 return hr != NULL && hr->in_collection_set();
455 }
456 #endif
457
458 // Returns true if the reference points to an object that
459 // can move in an incremental collecction.
460 bool G1CollectedHeap::is_scavengable(const void* p) {
461 G1CollectedHeap* g1h = G1CollectedHeap::heap();
462 G1CollectorPolicy* g1p = g1h->g1_policy();
463 HeapRegion* hr = heap_region_containing(p);
464 if (hr == NULL) {
465 // perm gen (or null)
466 return false;
467 } else {
468 return !hr->isHumongous();
469 }
470 }
471
472 void G1CollectedHeap::check_ct_logs_at_safepoint() {
473 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
474 CardTableModRefBS* ct_bs = (CardTableModRefBS*)barrier_set();
475
476 // Count the dirty cards at the start.
477 CountNonCleanMemRegionClosure count1(this);
478 ct_bs->mod_card_iterate(&count1);
479 int orig_count = count1.n();
480
481 // First clear the logged cards.
482 ClearLoggedCardTableEntryClosure clear;
483 dcqs.set_closure(&clear);
484 dcqs.apply_closure_to_all_completed_buffers();
485 dcqs.iterate_closure_all_threads(false);
486 clear.print_histo();
487
488 // Now ensure that there's no dirty cards.
489 CountNonCleanMemRegionClosure count2(this);
490 ct_bs->mod_card_iterate(&count2);
491 if (count2.n() != 0) {
492 gclog_or_tty->print_cr("Card table has %d entries; %d originally",
493 count2.n(), orig_count);
494 }
495 guarantee(count2.n() == 0, "Card table should be clean.");
496
497 RedirtyLoggedCardTableEntryClosure redirty;
498 JavaThread::dirty_card_queue_set().set_closure(&redirty);
499 dcqs.apply_closure_to_all_completed_buffers();
500 dcqs.iterate_closure_all_threads(false);
501 gclog_or_tty->print_cr("Log entries = %d, dirty cards = %d.",
502 clear.calls(), orig_count);
503 guarantee(redirty.calls() == clear.calls(),
504 "Or else mechanism is broken.");
505
506 CountNonCleanMemRegionClosure count3(this);
507 ct_bs->mod_card_iterate(&count3);
508 if (count3.n() != orig_count) {
509 gclog_or_tty->print_cr("Should have restored them all: orig = %d, final = %d.",
510 orig_count, count3.n());
511 guarantee(count3.n() >= orig_count, "Should have restored them all.");
512 }
513
514 JavaThread::dirty_card_queue_set().set_closure(_refine_cte_cl);
515 }
516
517 // Private class members.
518
519 G1CollectedHeap* G1CollectedHeap::_g1h;
520
521 // Private methods.
522
523 HeapRegion*
524 G1CollectedHeap::new_region_try_secondary_free_list() {
525 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
526 while (!_secondary_free_list.is_empty() || free_regions_coming()) {
527 if (!_secondary_free_list.is_empty()) {
528 if (G1ConcRegionFreeingVerbose) {
529 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
530 "secondary_free_list has %u entries",
531 _secondary_free_list.length());
532 }
533 // It looks as if there are free regions available on the
534 // secondary_free_list. Let's move them to the free_list and try
535 // again to allocate from it.
536 append_secondary_free_list();
537
538 assert(!_free_list.is_empty(), "if the secondary_free_list was not "
539 "empty we should have moved at least one entry to the free_list");
540 HeapRegion* res = _free_list.remove_head();
541 if (G1ConcRegionFreeingVerbose) {
542 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
543 "allocated "HR_FORMAT" from secondary_free_list",
544 HR_FORMAT_PARAMS(res));
545 }
546 return res;
547 }
548
549 // Wait here until we get notifed either when (a) there are no
550 // more free regions coming or (b) some regions have been moved on
551 // the secondary_free_list.
552 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
553 }
554
555 if (G1ConcRegionFreeingVerbose) {
556 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
557 "could not allocate from secondary_free_list");
558 }
559 return NULL;
560 }
561
562 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool do_expand) {
563 assert(!isHumongous(word_size) || word_size <= HeapRegion::GrainWords,
564 "the only time we use this to allocate a humongous region is "
565 "when we are allocating a single humongous region");
566
567 HeapRegion* res;
568 if (G1StressConcRegionFreeing) {
569 if (!_secondary_free_list.is_empty()) {
570 if (G1ConcRegionFreeingVerbose) {
571 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
572 "forced to look at the secondary_free_list");
573 }
574 res = new_region_try_secondary_free_list();
575 if (res != NULL) {
576 return res;
577 }
578 }
579 }
580 res = _free_list.remove_head_or_null();
581 if (res == NULL) {
582 if (G1ConcRegionFreeingVerbose) {
583 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
584 "res == NULL, trying the secondary_free_list");
585 }
586 res = new_region_try_secondary_free_list();
587 }
588 if (res == NULL && do_expand && _expand_heap_after_alloc_failure) {
589 // Currently, only attempts to allocate GC alloc regions set
590 // do_expand to true. So, we should only reach here during a
591 // safepoint. If this assumption changes we might have to
592 // reconsider the use of _expand_heap_after_alloc_failure.
593 assert(SafepointSynchronize::is_at_safepoint(), "invariant");
594
595 ergo_verbose1(ErgoHeapSizing,
596 "attempt heap expansion",
597 ergo_format_reason("region allocation request failed")
598 ergo_format_byte("allocation request"),
599 word_size * HeapWordSize);
600 if (expand(word_size * HeapWordSize)) {
601 // Given that expand() succeeded in expanding the heap, and we
602 // always expand the heap by an amount aligned to the heap
603 // region size, the free list should in theory not be empty. So
604 // it would probably be OK to use remove_head(). But the extra
605 // check for NULL is unlikely to be a performance issue here (we
606 // just expanded the heap!) so let's just be conservative and
607 // use remove_head_or_null().
608 res = _free_list.remove_head_or_null();
609 } else {
610 _expand_heap_after_alloc_failure = false;
611 }
612 }
613 return res;
614 }
615
616 uint G1CollectedHeap::humongous_obj_allocate_find_first(uint num_regions,
617 size_t word_size) {
618 assert(isHumongous(word_size), "word_size should be humongous");
619 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
620
621 uint first = G1_NULL_HRS_INDEX;
622 if (num_regions == 1) {
623 // Only one region to allocate, no need to go through the slower
624 // path. The caller will attempt the expasion if this fails, so
625 // let's not try to expand here too.
626 HeapRegion* hr = new_region(word_size, false /* do_expand */);
627 if (hr != NULL) {
628 first = hr->hrs_index();
629 } else {
630 first = G1_NULL_HRS_INDEX;
631 }
632 } else {
633 // We can't allocate humongous regions while cleanupComplete() is
634 // running, since some of the regions we find to be empty might not
635 // yet be added to the free list and it is not straightforward to
636 // know which list they are on so that we can remove them. Note
637 // that we only need to do this if we need to allocate more than
638 // one region to satisfy the current humongous allocation
639 // request. If we are only allocating one region we use the common
640 // region allocation code (see above).
641 wait_while_free_regions_coming();
642 append_secondary_free_list_if_not_empty_with_lock();
643
644 if (free_regions() >= num_regions) {
645 first = _hrs.find_contiguous(num_regions);
646 if (first != G1_NULL_HRS_INDEX) {
647 for (uint i = first; i < first + num_regions; ++i) {
648 HeapRegion* hr = region_at(i);
649 assert(hr->is_empty(), "sanity");
650 assert(is_on_master_free_list(hr), "sanity");
651 hr->set_pending_removal(true);
652 }
653 _free_list.remove_all_pending(num_regions);
654 }
655 }
656 }
657 return first;
658 }
659
660 HeapWord*
661 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first,
662 uint num_regions,
663 size_t word_size) {
664 assert(first != G1_NULL_HRS_INDEX, "pre-condition");
665 assert(isHumongous(word_size), "word_size should be humongous");
666 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
667
668 // Index of last region in the series + 1.
669 uint last = first + num_regions;
670
671 // We need to initialize the region(s) we just discovered. This is
672 // a bit tricky given that it can happen concurrently with
673 // refinement threads refining cards on these regions and
674 // potentially wanting to refine the BOT as they are scanning
675 // those cards (this can happen shortly after a cleanup; see CR
676 // 6991377). So we have to set up the region(s) carefully and in
677 // a specific order.
678
679 // The word size sum of all the regions we will allocate.
680 size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords;
681 assert(word_size <= word_size_sum, "sanity");
682
683 // This will be the "starts humongous" region.
684 HeapRegion* first_hr = region_at(first);
685 // The header of the new object will be placed at the bottom of
686 // the first region.
687 HeapWord* new_obj = first_hr->bottom();
688 // This will be the new end of the first region in the series that
689 // should also match the end of the last region in the seriers.
690 HeapWord* new_end = new_obj + word_size_sum;
691 // This will be the new top of the first region that will reflect
692 // this allocation.
693 HeapWord* new_top = new_obj + word_size;
694
695 // First, we need to zero the header of the space that we will be
696 // allocating. When we update top further down, some refinement
697 // threads might try to scan the region. By zeroing the header we
698 // ensure that any thread that will try to scan the region will
699 // come across the zero klass word and bail out.
700 //
701 // NOTE: It would not have been correct to have used
702 // CollectedHeap::fill_with_object() and make the space look like
703 // an int array. The thread that is doing the allocation will
704 // later update the object header to a potentially different array
705 // type and, for a very short period of time, the klass and length
706 // fields will be inconsistent. This could cause a refinement
707 // thread to calculate the object size incorrectly.
708 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
709
710 // We will set up the first region as "starts humongous". This
711 // will also update the BOT covering all the regions to reflect
712 // that there is a single object that starts at the bottom of the
713 // first region.
714 first_hr->set_startsHumongous(new_top, new_end);
715
716 // Then, if there are any, we will set up the "continues
717 // humongous" regions.
718 HeapRegion* hr = NULL;
719 for (uint i = first + 1; i < last; ++i) {
720 hr = region_at(i);
721 hr->set_continuesHumongous(first_hr);
722 }
723 // If we have "continues humongous" regions (hr != NULL), then the
724 // end of the last one should match new_end.
725 assert(hr == NULL || hr->end() == new_end, "sanity");
726
727 // Up to this point no concurrent thread would have been able to
728 // do any scanning on any region in this series. All the top
729 // fields still point to bottom, so the intersection between
730 // [bottom,top] and [card_start,card_end] will be empty. Before we
731 // update the top fields, we'll do a storestore to make sure that
732 // no thread sees the update to top before the zeroing of the
733 // object header and the BOT initialization.
734 OrderAccess::storestore();
735
736 // Now that the BOT and the object header have been initialized,
737 // we can update top of the "starts humongous" region.
738 assert(first_hr->bottom() < new_top && new_top <= first_hr->end(),
739 "new_top should be in this region");
740 first_hr->set_top(new_top);
741 if (_hr_printer.is_active()) {
742 HeapWord* bottom = first_hr->bottom();
743 HeapWord* end = first_hr->orig_end();
744 if ((first + 1) == last) {
745 // the series has a single humongous region
746 _hr_printer.alloc(G1HRPrinter::SingleHumongous, first_hr, new_top);
747 } else {
748 // the series has more than one humongous regions
749 _hr_printer.alloc(G1HRPrinter::StartsHumongous, first_hr, end);
750 }
751 }
752
753 // Now, we will update the top fields of the "continues humongous"
754 // regions. The reason we need to do this is that, otherwise,
755 // these regions would look empty and this will confuse parts of
756 // G1. For example, the code that looks for a consecutive number
757 // of empty regions will consider them empty and try to
758 // re-allocate them. We can extend is_empty() to also include
759 // !continuesHumongous(), but it is easier to just update the top
760 // fields here. The way we set top for all regions (i.e., top ==
761 // end for all regions but the last one, top == new_top for the
762 // last one) is actually used when we will free up the humongous
763 // region in free_humongous_region().
764 hr = NULL;
765 for (uint i = first + 1; i < last; ++i) {
766 hr = region_at(i);
767 if ((i + 1) == last) {
768 // last continues humongous region
769 assert(hr->bottom() < new_top && new_top <= hr->end(),
770 "new_top should fall on this region");
771 hr->set_top(new_top);
772 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, new_top);
773 } else {
774 // not last one
775 assert(new_top > hr->end(), "new_top should be above this region");
776 hr->set_top(hr->end());
777 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, hr->end());
778 }
779 }
780 // If we have continues humongous regions (hr != NULL), then the
781 // end of the last one should match new_end and its top should
782 // match new_top.
783 assert(hr == NULL ||
784 (hr->end() == new_end && hr->top() == new_top), "sanity");
785
786 assert(first_hr->used() == word_size * HeapWordSize, "invariant");
787 _summary_bytes_used += first_hr->used();
788 _humongous_set.add(first_hr);
789
790 return new_obj;
791 }
792
793 // If could fit into free regions w/o expansion, try.
794 // Otherwise, if can expand, do so.
795 // Otherwise, if using ex regions might help, try with ex given back.
796 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size) {
797 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
798
799 verify_region_sets_optional();
800
801 size_t word_size_rounded = round_to(word_size, HeapRegion::GrainWords);
802 uint num_regions = (uint) (word_size_rounded / HeapRegion::GrainWords);
803 uint x_num = expansion_regions();
804 uint fs = _hrs.free_suffix();
805 uint first = humongous_obj_allocate_find_first(num_regions, word_size);
806 if (first == G1_NULL_HRS_INDEX) {
807 // The only thing we can do now is attempt expansion.
808 if (fs + x_num >= num_regions) {
809 // If the number of regions we're trying to allocate for this
810 // object is at most the number of regions in the free suffix,
811 // then the call to humongous_obj_allocate_find_first() above
812 // should have succeeded and we wouldn't be here.
813 //
814 // We should only be trying to expand when the free suffix is
815 // not sufficient for the object _and_ we have some expansion
816 // room available.
817 assert(num_regions > fs, "earlier allocation should have succeeded");
818
819 ergo_verbose1(ErgoHeapSizing,
820 "attempt heap expansion",
821 ergo_format_reason("humongous allocation request failed")
822 ergo_format_byte("allocation request"),
823 word_size * HeapWordSize);
824 if (expand((num_regions - fs) * HeapRegion::GrainBytes)) {
825 // Even though the heap was expanded, it might not have
826 // reached the desired size. So, we cannot assume that the
827 // allocation will succeed.
828 first = humongous_obj_allocate_find_first(num_regions, word_size);
829 }
830 }
831 }
832
833 HeapWord* result = NULL;
834 if (first != G1_NULL_HRS_INDEX) {
835 result =
836 humongous_obj_allocate_initialize_regions(first, num_regions, word_size);
837 assert(result != NULL, "it should always return a valid result");
838
839 // A successful humongous object allocation changes the used space
840 // information of the old generation so we need to recalculate the
841 // sizes and update the jstat counters here.
842 g1mm()->update_sizes();
843 }
844
845 verify_region_sets_optional();
846
847 return result;
848 }
849
850 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) {
851 assert_heap_not_locked_and_not_at_safepoint();
852 assert(!isHumongous(word_size), "we do not allow humongous TLABs");
853
854 unsigned int dummy_gc_count_before;
855 return attempt_allocation(word_size, &dummy_gc_count_before);
856 }
857
858 HeapWord*
859 G1CollectedHeap::mem_allocate(size_t word_size,
860 bool* gc_overhead_limit_was_exceeded) {
861 assert_heap_not_locked_and_not_at_safepoint();
862
863 // Loop until the allocation is satisified, or unsatisfied after GC.
864 for (int try_count = 1; /* we'll return */; try_count += 1) {
865 unsigned int gc_count_before;
866
867 HeapWord* result = NULL;
868 if (!isHumongous(word_size)) {
869 result = attempt_allocation(word_size, &gc_count_before);
870 } else {
871 result = attempt_allocation_humongous(word_size, &gc_count_before);
872 }
873 if (result != NULL) {
874 return result;
875 }
876
877 // Create the garbage collection operation...
878 VM_G1CollectForAllocation op(gc_count_before, word_size);
879 // ...and get the VM thread to execute it.
880 VMThread::execute(&op);
881
882 if (op.prologue_succeeded() && op.pause_succeeded()) {
883 // If the operation was successful we'll return the result even
884 // if it is NULL. If the allocation attempt failed immediately
885 // after a Full GC, it's unlikely we'll be able to allocate now.
886 HeapWord* result = op.result();
887 if (result != NULL && !isHumongous(word_size)) {
888 // Allocations that take place on VM operations do not do any
889 // card dirtying and we have to do it here. We only have to do
890 // this for non-humongous allocations, though.
891 dirty_young_block(result, word_size);
892 }
893 return result;
894 } else {
895 assert(op.result() == NULL,
896 "the result should be NULL if the VM op did not succeed");
897 }
898
899 // Give a warning if we seem to be looping forever.
900 if ((QueuedAllocationWarningCount > 0) &&
901 (try_count % QueuedAllocationWarningCount == 0)) {
902 warning("G1CollectedHeap::mem_allocate retries %d times", try_count);
903 }
904 }
905
906 ShouldNotReachHere();
907 return NULL;
908 }
909
910 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size,
911 unsigned int *gc_count_before_ret) {
912 // Make sure you read the note in attempt_allocation_humongous().
913
914 assert_heap_not_locked_and_not_at_safepoint();
915 assert(!isHumongous(word_size), "attempt_allocation_slow() should not "
916 "be called for humongous allocation requests");
917
918 // We should only get here after the first-level allocation attempt
919 // (attempt_allocation()) failed to allocate.
920
921 // We will loop until a) we manage to successfully perform the
922 // allocation or b) we successfully schedule a collection which
923 // fails to perform the allocation. b) is the only case when we'll
924 // return NULL.
925 HeapWord* result = NULL;
926 for (int try_count = 1; /* we'll return */; try_count += 1) {
927 bool should_try_gc;
928 unsigned int gc_count_before;
929
930 {
931 MutexLockerEx x(Heap_lock);
932
933 result = _mutator_alloc_region.attempt_allocation_locked(word_size,
934 false /* bot_updates */);
935 if (result != NULL) {
936 return result;
937 }
938
939 // If we reach here, attempt_allocation_locked() above failed to
940 // allocate a new region. So the mutator alloc region should be NULL.
941 assert(_mutator_alloc_region.get() == NULL, "only way to get here");
942
943 if (GC_locker::is_active_and_needs_gc()) {
944 if (g1_policy()->can_expand_young_list()) {
945 // No need for an ergo verbose message here,
946 // can_expand_young_list() does this when it returns true.
947 result = _mutator_alloc_region.attempt_allocation_force(word_size,
948 false /* bot_updates */);
949 if (result != NULL) {
950 return result;
951 }
952 }
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 if (should_try_gc) {
962 bool succeeded;
963 result = do_collection_pause(word_size, gc_count_before, &succeeded);
964 if (result != NULL) {
965 assert(succeeded, "only way to get back a non-NULL result");
966 return result;
967 }
968
969 if (succeeded) {
970 // If we get here we successfully scheduled a collection which
971 // failed to allocate. No point in trying to allocate
972 // further. We'll just return NULL.
973 MutexLockerEx x(Heap_lock);
974 *gc_count_before_ret = total_collections();
975 return NULL;
976 }
977 } else {
978 GC_locker::stall_until_clear();
979 }
980
981 // We can reach here if we were unsuccessul in scheduling a
982 // collection (because another thread beat us to it) or if we were
983 // stalled due to the GC locker. In either can we should retry the
984 // allocation attempt in case another thread successfully
985 // performed a collection and reclaimed enough space. We do the
986 // first attempt (without holding the Heap_lock) here and the
987 // follow-on attempt will be at the start of the next loop
988 // iteration (after taking the Heap_lock).
989 result = _mutator_alloc_region.attempt_allocation(word_size,
990 false /* bot_updates */);
991 if (result != NULL) {
992 return result;
993 }
994
995 // Give a warning if we seem to be looping forever.
996 if ((QueuedAllocationWarningCount > 0) &&
997 (try_count % QueuedAllocationWarningCount == 0)) {
998 warning("G1CollectedHeap::attempt_allocation_slow() "
999 "retries %d times", try_count);
1000 }
1001 }
1002
1003 ShouldNotReachHere();
1004 return NULL;
1005 }
1006
1007 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size,
1008 unsigned int * gc_count_before_ret) {
1009 // The structure of this method has a lot of similarities to
1010 // attempt_allocation_slow(). The reason these two were not merged
1011 // into a single one is that such a method would require several "if
1012 // allocation is not humongous do this, otherwise do that"
1013 // conditional paths which would obscure its flow. In fact, an early
1014 // version of this code did use a unified method which was harder to
1015 // follow and, as a result, it had subtle bugs that were hard to
1016 // track down. So keeping these two methods separate allows each to
1017 // be more readable. It will be good to keep these two in sync as
1018 // much as possible.
1019
1020 assert_heap_not_locked_and_not_at_safepoint();
1021 assert(isHumongous(word_size), "attempt_allocation_humongous() "
1022 "should only be called for humongous allocations");
1023
1024 // Humongous objects can exhaust the heap quickly, so we should check if we
1025 // need to start a marking cycle at each humongous object allocation. We do
1026 // the check before we do the actual allocation. The reason for doing it
1027 // before the allocation is that we avoid having to keep track of the newly
1028 // allocated memory while we do a GC.
1029 if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation",
1030 word_size)) {
1031 collect(GCCause::_g1_humongous_allocation);
1032 }
1033
1034 // We will loop until a) we manage to successfully perform the
1035 // allocation or b) we successfully schedule a collection which
1036 // fails to perform the allocation. b) is the only case when we'll
1037 // return NULL.
1038 HeapWord* result = NULL;
1039 for (int try_count = 1; /* we'll return */; try_count += 1) {
1040 bool should_try_gc;
1041 unsigned int gc_count_before;
1042
1043 {
1044 MutexLockerEx x(Heap_lock);
1045
1046 // Given that humongous objects are not allocated in young
1047 // regions, we'll first try to do the allocation without doing a
1048 // collection hoping that there's enough space in the heap.
1049 result = humongous_obj_allocate(word_size);
1050 if (result != NULL) {
1051 return result;
1052 }
1053
1054 if (GC_locker::is_active_and_needs_gc()) {
1055 should_try_gc = false;
1056 } else {
1057 // Read the GC count while still holding the Heap_lock.
1058 gc_count_before = total_collections();
1059 should_try_gc = true;
1060 }
1061 }
1062
1063 if (should_try_gc) {
1064 // If we failed to allocate the humongous object, we should try to
1065 // do a collection pause (if we're allowed) in case it reclaims
1066 // enough space for the allocation to succeed after the pause.
1067
1068 bool succeeded;
1069 result = do_collection_pause(word_size, gc_count_before, &succeeded);
1070 if (result != NULL) {
1071 assert(succeeded, "only way to get back a non-NULL result");
1072 return result;
1073 }
1074
1075 if (succeeded) {
1076 // If we get here we successfully scheduled a collection which
1077 // failed to allocate. No point in trying to allocate
1078 // further. We'll just return NULL.
1079 MutexLockerEx x(Heap_lock);
1080 *gc_count_before_ret = total_collections();
1081 return NULL;
1082 }
1083 } else {
1084 GC_locker::stall_until_clear();
1085 }
1086
1087 // We can reach here if we were unsuccessul in scheduling a
1088 // collection (because another thread beat us to it) or if we were
1089 // stalled due to the GC locker. In either can we should retry the
1090 // allocation attempt in case another thread successfully
1091 // performed a collection and reclaimed enough space. Give a
1092 // warning if we seem to be looping forever.
1093
1094 if ((QueuedAllocationWarningCount > 0) &&
1095 (try_count % QueuedAllocationWarningCount == 0)) {
1096 warning("G1CollectedHeap::attempt_allocation_humongous() "
1097 "retries %d times", try_count);
1098 }
1099 }
1100
1101 ShouldNotReachHere();
1102 return NULL;
1103 }
1104
1105 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
1106 bool expect_null_mutator_alloc_region) {
1107 assert_at_safepoint(true /* should_be_vm_thread */);
1108 assert(_mutator_alloc_region.get() == NULL ||
1109 !expect_null_mutator_alloc_region,
1110 "the current alloc region was unexpectedly found to be non-NULL");
1111
1112 if (!isHumongous(word_size)) {
1113 return _mutator_alloc_region.attempt_allocation_locked(word_size,
1114 false /* bot_updates */);
1115 } else {
1116 HeapWord* result = humongous_obj_allocate(word_size);
1117 if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) {
1118 g1_policy()->set_initiate_conc_mark_if_possible();
1119 }
1120 return result;
1121 }
1122
1123 ShouldNotReachHere();
1124 }
1125
1126 class PostMCRemSetClearClosure: public HeapRegionClosure {
1127 ModRefBarrierSet* _mr_bs;
1128 public:
1129 PostMCRemSetClearClosure(ModRefBarrierSet* mr_bs) : _mr_bs(mr_bs) {}
1130 bool doHeapRegion(HeapRegion* r) {
1131 r->reset_gc_time_stamp();
1132 if (r->continuesHumongous())
1133 return false;
1134 HeapRegionRemSet* hrrs = r->rem_set();
1135 if (hrrs != NULL) hrrs->clear();
1136 // You might think here that we could clear just the cards
1137 // corresponding to the used region. But no: if we leave a dirty card
1138 // in a region we might allocate into, then it would prevent that card
1139 // from being enqueued, and cause it to be missed.
1140 // Re: the performance cost: we shouldn't be doing full GC anyway!
1141 _mr_bs->clear(MemRegion(r->bottom(), r->end()));
1142 return false;
1143 }
1144 };
1145
1146
1147 class PostMCRemSetInvalidateClosure: public HeapRegionClosure {
1148 ModRefBarrierSet* _mr_bs;
1149 public:
1150 PostMCRemSetInvalidateClosure(ModRefBarrierSet* mr_bs) : _mr_bs(mr_bs) {}
1151 bool doHeapRegion(HeapRegion* r) {
1152 if (r->continuesHumongous()) return false;
1153 if (r->used_region().word_size() != 0) {
1154 _mr_bs->invalidate(r->used_region(), true /*whole heap*/);
1155 }
1156 return false;
1157 }
1158 };
1159
1160 class RebuildRSOutOfRegionClosure: public HeapRegionClosure {
1161 G1CollectedHeap* _g1h;
1162 UpdateRSOopClosure _cl;
1163 int _worker_i;
1164 public:
1165 RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, int worker_i = 0) :
1166 _cl(g1->g1_rem_set(), worker_i),
1167 _worker_i(worker_i),
1168 _g1h(g1)
1169 { }
1170
1171 bool doHeapRegion(HeapRegion* r) {
1172 if (!r->continuesHumongous()) {
1173 _cl.set_from(r);
1174 r->oop_iterate(&_cl);
1175 }
1176 return false;
1177 }
1178 };
1179
1180 class ParRebuildRSTask: public AbstractGangTask {
1181 G1CollectedHeap* _g1;
1182 public:
1183 ParRebuildRSTask(G1CollectedHeap* g1)
1184 : AbstractGangTask("ParRebuildRSTask"),
1185 _g1(g1)
1186 { }
1187
1188 void work(uint worker_id) {
1189 RebuildRSOutOfRegionClosure rebuild_rs(_g1, worker_id);
1190 _g1->heap_region_par_iterate_chunked(&rebuild_rs, worker_id,
1191 _g1->workers()->active_workers(),
1192 HeapRegion::RebuildRSClaimValue);
1193 }
1194 };
1195
1196 class PostCompactionPrinterClosure: public HeapRegionClosure {
1197 private:
1198 G1HRPrinter* _hr_printer;
1199 public:
1200 bool doHeapRegion(HeapRegion* hr) {
1201 assert(!hr->is_young(), "not expecting to find young regions");
1202 // We only generate output for non-empty regions.
1203 if (!hr->is_empty()) {
1204 if (!hr->isHumongous()) {
1205 _hr_printer->post_compaction(hr, G1HRPrinter::Old);
1206 } else if (hr->startsHumongous()) {
1207 if (hr->capacity() == HeapRegion::GrainBytes) {
1208 // single humongous region
1209 _hr_printer->post_compaction(hr, G1HRPrinter::SingleHumongous);
1210 } else {
1211 _hr_printer->post_compaction(hr, G1HRPrinter::StartsHumongous);
1212 }
1213 } else {
1214 assert(hr->continuesHumongous(), "only way to get here");
1215 _hr_printer->post_compaction(hr, G1HRPrinter::ContinuesHumongous);
1216 }
1217 }
1218 return false;
1219 }
1220
1221 PostCompactionPrinterClosure(G1HRPrinter* hr_printer)
1222 : _hr_printer(hr_printer) { }
1223 };
1224
1225 bool G1CollectedHeap::do_collection(bool explicit_gc,
1226 bool clear_all_soft_refs,
1227 size_t word_size) {
1228 assert_at_safepoint(true /* should_be_vm_thread */);
1229
1230 if (GC_locker::check_active_before_gc()) {
1231 return false;
1232 }
1233
1234 SvcGCMarker sgcm(SvcGCMarker::FULL);
1235 ResourceMark rm;
1236
1237 print_heap_before_gc();
1238
1239 HRSPhaseSetter x(HRSPhaseFullGC);
1240 verify_region_sets_optional();
1241
1242 const bool do_clear_all_soft_refs = clear_all_soft_refs ||
1243 collector_policy()->should_clear_all_soft_refs();
1244
1245 ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy());
1246
1247 {
1248 IsGCActiveMark x;
1249
1250 // Timing
1251 assert(gc_cause() != GCCause::_java_lang_system_gc || explicit_gc, "invariant");
1252 gclog_or_tty->date_stamp(G1Log::fine() && PrintGCDateStamps);
1253 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
1254
1255 TraceTime t(GCCauseString("Full GC", gc_cause()), G1Log::fine(), true, gclog_or_tty);
1256 TraceCollectorStats tcs(g1mm()->full_collection_counters());
1257 TraceMemoryManagerStats tms(true /* fullGC */, gc_cause());
1258
1259 double start = os::elapsedTime();
1260 g1_policy()->record_full_collection_start();
1261
1262 // Note: When we have a more flexible GC logging framework that
1263 // allows us to add optional attributes to a GC log record we
1264 // could consider timing and reporting how long we wait in the
1265 // following two methods.
1266 wait_while_free_regions_coming();
1267 // If we start the compaction before the CM threads finish
1268 // scanning the root regions we might trip them over as we'll
1269 // be moving objects / updating references. So let's wait until
1270 // they are done. By telling them to abort, they should complete
1271 // early.
1272 _cm->root_regions()->abort();
1273 _cm->root_regions()->wait_until_scan_finished();
1274 append_secondary_free_list_if_not_empty_with_lock();
1275
1276 gc_prologue(true);
1277 increment_total_collections(true /* full gc */);
1278
1279 size_t g1h_prev_used = used();
1280 assert(used() == recalculate_used(), "Should be equal");
1281
1282 if (VerifyBeforeGC && total_collections() >= VerifyGCStartAt) {
1283 HandleMark hm; // Discard invalid handles created during verification
1284 gclog_or_tty->print(" VerifyBeforeGC:");
1285 prepare_for_verify();
1286 Universe::verify(/* silent */ false,
1287 /* option */ VerifyOption_G1UsePrevMarking);
1288
1289 }
1290 pre_full_gc_dump();
1291
1292 COMPILER2_PRESENT(DerivedPointerTable::clear());
1293
1294 // Disable discovery and empty the discovered lists
1295 // for the CM ref processor.
1296 ref_processor_cm()->disable_discovery();
1297 ref_processor_cm()->abandon_partial_discovery();
1298 ref_processor_cm()->verify_no_references_recorded();
1299
1300 // Abandon current iterations of concurrent marking and concurrent
1301 // refinement, if any are in progress. We have to do this before
1302 // wait_until_scan_finished() below.
1303 concurrent_mark()->abort();
1304
1305 // Make sure we'll choose a new allocation region afterwards.
1306 release_mutator_alloc_region();
1307 abandon_gc_alloc_regions();
1308 g1_rem_set()->cleanupHRRS();
1309
1310 // We should call this after we retire any currently active alloc
1311 // regions so that all the ALLOC / RETIRE events are generated
1312 // before the start GC event.
1313 _hr_printer.start_gc(true /* full */, (size_t) total_collections());
1314
1315 // We may have added regions to the current incremental collection
1316 // set between the last GC or pause and now. We need to clear the
1317 // incremental collection set and then start rebuilding it afresh
1318 // after this full GC.
1319 abandon_collection_set(g1_policy()->inc_cset_head());
1320 g1_policy()->clear_incremental_cset();
1321 g1_policy()->stop_incremental_cset_building();
1322
1323 tear_down_region_sets(false /* free_list_only */);
1324 g1_policy()->set_gcs_are_young(true);
1325
1326 // See the comments in g1CollectedHeap.hpp and
1327 // G1CollectedHeap::ref_processing_init() about
1328 // how reference processing currently works in G1.
1329
1330 // Temporarily make discovery by the STW ref processor single threaded (non-MT).
1331 ReferenceProcessorMTDiscoveryMutator stw_rp_disc_ser(ref_processor_stw(), false);
1332
1333 // Temporarily clear the STW ref processor's _is_alive_non_header field.
1334 ReferenceProcessorIsAliveMutator stw_rp_is_alive_null(ref_processor_stw(), NULL);
1335
1336 ref_processor_stw()->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/);
1337 ref_processor_stw()->setup_policy(do_clear_all_soft_refs);
1338
1339 // Do collection work
1340 {
1341 HandleMark hm; // Discard invalid handles created during gc
1342 G1MarkSweep::invoke_at_safepoint(ref_processor_stw(), do_clear_all_soft_refs);
1343 }
1344
1345 assert(free_regions() == 0, "we should not have added any free regions");
1346 rebuild_region_sets(false /* free_list_only */);
1347
1348 // Enqueue any discovered reference objects that have
1349 // not been removed from the discovered lists.
1350 ref_processor_stw()->enqueue_discovered_references();
1351
1352 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
1353
1354 MemoryService::track_memory_usage();
1355
1356 if (VerifyAfterGC && total_collections() >= VerifyGCStartAt) {
1357 HandleMark hm; // Discard invalid handles created during verification
1358 gclog_or_tty->print(" VerifyAfterGC:");
1359 prepare_for_verify();
1360 Universe::verify(/* silent */ false,
1361 /* option */ VerifyOption_G1UsePrevMarking);
1362
1363 }
1364
1365 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
1366 ref_processor_stw()->verify_no_references_recorded();
1367
1368 // Note: since we've just done a full GC, concurrent
1369 // marking is no longer active. Therefore we need not
1370 // re-enable reference discovery for the CM ref processor.
1371 // That will be done at the start of the next marking cycle.
1372 assert(!ref_processor_cm()->discovery_enabled(), "Postcondition");
1373 ref_processor_cm()->verify_no_references_recorded();
1374
1375 reset_gc_time_stamp();
1376 // Since everything potentially moved, we will clear all remembered
1377 // sets, and clear all cards. Later we will rebuild remebered
1378 // sets. We will also reset the GC time stamps of the regions.
1379 PostMCRemSetClearClosure rs_clear(mr_bs());
1380 heap_region_iterate(&rs_clear);
1381
1382 // Resize the heap if necessary.
1383 resize_if_necessary_after_full_collection(explicit_gc ? 0 : word_size);
1384
1385 if (_hr_printer.is_active()) {
1386 // We should do this after we potentially resize the heap so
1387 // that all the COMMIT / UNCOMMIT events are generated before
1388 // the end GC event.
1389
1390 PostCompactionPrinterClosure cl(hr_printer());
1391 heap_region_iterate(&cl);
1392
1393 _hr_printer.end_gc(true /* full */, (size_t) total_collections());
1394 }
1395
1396 if (_cg1r->use_cache()) {
1397 _cg1r->clear_and_record_card_counts();
1398 _cg1r->clear_hot_cache();
1399 }
1400
1401 // Rebuild remembered sets of all regions.
1402 if (G1CollectedHeap::use_parallel_gc_threads()) {
1403 uint n_workers =
1404 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
1405 workers()->active_workers(),
1406 Threads::number_of_non_daemon_threads());
1407 assert(UseDynamicNumberOfGCThreads ||
1408 n_workers == workers()->total_workers(),
1409 "If not dynamic should be using all the workers");
1410 workers()->set_active_workers(n_workers);
1411 // Set parallel threads in the heap (_n_par_threads) only
1412 // before a parallel phase and always reset it to 0 after
1413 // the phase so that the number of parallel threads does
1414 // no get carried forward to a serial phase where there
1415 // may be code that is "possibly_parallel".
1416 set_par_threads(n_workers);
1417
1418 ParRebuildRSTask rebuild_rs_task(this);
1419 assert(check_heap_region_claim_values(
1420 HeapRegion::InitialClaimValue), "sanity check");
1421 assert(UseDynamicNumberOfGCThreads ||
1422 workers()->active_workers() == workers()->total_workers(),
1423 "Unless dynamic should use total workers");
1424 // Use the most recent number of active workers
1425 assert(workers()->active_workers() > 0,
1426 "Active workers not properly set");
1427 set_par_threads(workers()->active_workers());
1428 workers()->run_task(&rebuild_rs_task);
1429 set_par_threads(0);
1430 assert(check_heap_region_claim_values(
1431 HeapRegion::RebuildRSClaimValue), "sanity check");
1432 reset_heap_region_claim_values();
1433 } else {
1434 RebuildRSOutOfRegionClosure rebuild_rs(this);
1435 heap_region_iterate(&rebuild_rs);
1436 }
1437
1438 if (G1Log::fine()) {
1439 print_size_transition(gclog_or_tty, g1h_prev_used, used(), capacity());
1440 }
1441
1442 if (true) { // FIXME
1443 // Ask the permanent generation to adjust size for full collections
1444 perm()->compute_new_size();
1445 }
1446
1447 // Start a new incremental collection set for the next pause
1448 assert(g1_policy()->collection_set() == NULL, "must be");
1449 g1_policy()->start_incremental_cset_building();
1450
1451 // Clear the _cset_fast_test bitmap in anticipation of adding
1452 // regions to the incremental collection set for the next
1453 // evacuation pause.
1454 clear_cset_fast_test();
1455
1456 init_mutator_alloc_region();
1457
1458 double end = os::elapsedTime();
1459 g1_policy()->record_full_collection_end();
1460
1461 #ifdef TRACESPINNING
1462 ParallelTaskTerminator::print_termination_counts();
1463 #endif
1464
1465 gc_epilogue(true);
1466
1467 // Discard all rset updates
1468 JavaThread::dirty_card_queue_set().abandon_logs();
1469 assert(!G1DeferredRSUpdate
1470 || (G1DeferredRSUpdate && (dirty_card_queue_set().completed_buffers_num() == 0)), "Should not be any");
1471 }
1472
1473 _young_list->reset_sampled_info();
1474 // At this point there should be no regions in the
1475 // entire heap tagged as young.
1476 assert( check_young_list_empty(true /* check_heap */),
1477 "young list should be empty at this point");
1478
1479 // Update the number of full collections that have been completed.
1480 increment_full_collections_completed(false /* concurrent */);
1481
1482 _hrs.verify_optional();
1483 verify_region_sets_optional();
1484
1485 print_heap_after_gc();
1486 g1mm()->update_sizes();
1487 post_full_gc_dump();
1488
1489 return true;
1490 }
1491
1492 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
1493 // do_collection() will return whether it succeeded in performing
1494 // the GC. Currently, there is no facility on the
1495 // do_full_collection() API to notify the caller than the collection
1496 // did not succeed (e.g., because it was locked out by the GC
1497 // locker). So, right now, we'll ignore the return value.
1498 bool dummy = do_collection(true, /* explicit_gc */
1499 clear_all_soft_refs,
1500 0 /* word_size */);
1501 }
1502
1503 // This code is mostly copied from TenuredGeneration.
1504 void
1505 G1CollectedHeap::
1506 resize_if_necessary_after_full_collection(size_t word_size) {
1507 assert(MinHeapFreeRatio <= MaxHeapFreeRatio, "sanity check");
1508
1509 // Include the current allocation, if any, and bytes that will be
1510 // pre-allocated to support collections, as "used".
1511 const size_t used_after_gc = used();
1512 const size_t capacity_after_gc = capacity();
1513 const size_t free_after_gc = capacity_after_gc - used_after_gc;
1514
1515 // This is enforced in arguments.cpp.
1516 assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
1517 "otherwise the code below doesn't make sense");
1518
1519 // We don't have floating point command-line arguments
1520 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
1521 const double maximum_used_percentage = 1.0 - minimum_free_percentage;
1522 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
1523 const double minimum_used_percentage = 1.0 - maximum_free_percentage;
1524
1525 const size_t min_heap_size = collector_policy()->min_heap_byte_size();
1526 const size_t max_heap_size = collector_policy()->max_heap_byte_size();
1527
1528 // We have to be careful here as these two calculations can overflow
1529 // 32-bit size_t's.
1530 double used_after_gc_d = (double) used_after_gc;
1531 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
1532 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
1533
1534 // Let's make sure that they are both under the max heap size, which
1535 // by default will make them fit into a size_t.
1536 double desired_capacity_upper_bound = (double) max_heap_size;
1537 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
1538 desired_capacity_upper_bound);
1539 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
1540 desired_capacity_upper_bound);
1541
1542 // We can now safely turn them into size_t's.
1543 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
1544 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
1545
1546 // This assert only makes sense here, before we adjust them
1547 // with respect to the min and max heap size.
1548 assert(minimum_desired_capacity <= maximum_desired_capacity,
1549 err_msg("minimum_desired_capacity = "SIZE_FORMAT", "
1550 "maximum_desired_capacity = "SIZE_FORMAT,
1551 minimum_desired_capacity, maximum_desired_capacity));
1552
1553 // Should not be greater than the heap max size. No need to adjust
1554 // it with respect to the heap min size as it's a lower bound (i.e.,
1555 // we'll try to make the capacity larger than it, not smaller).
1556 minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size);
1557 // Should not be less than the heap min size. No need to adjust it
1558 // with respect to the heap max size as it's an upper bound (i.e.,
1559 // we'll try to make the capacity smaller than it, not greater).
1560 maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size);
1561
1562 if (capacity_after_gc < minimum_desired_capacity) {
1563 // Don't expand unless it's significant
1564 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
1565 ergo_verbose4(ErgoHeapSizing,
1566 "attempt heap expansion",
1567 ergo_format_reason("capacity lower than "
1568 "min desired capacity after Full GC")
1569 ergo_format_byte("capacity")
1570 ergo_format_byte("occupancy")
1571 ergo_format_byte_perc("min desired capacity"),
1572 capacity_after_gc, used_after_gc,
1573 minimum_desired_capacity, (double) MinHeapFreeRatio);
1574 expand(expand_bytes);
1575
1576 // No expansion, now see if we want to shrink
1577 } else if (capacity_after_gc > maximum_desired_capacity) {
1578 // Capacity too large, compute shrinking size
1579 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
1580 ergo_verbose4(ErgoHeapSizing,
1581 "attempt heap shrinking",
1582 ergo_format_reason("capacity higher than "
1583 "max desired capacity after Full GC")
1584 ergo_format_byte("capacity")
1585 ergo_format_byte("occupancy")
1586 ergo_format_byte_perc("max desired capacity"),
1587 capacity_after_gc, used_after_gc,
1588 maximum_desired_capacity, (double) MaxHeapFreeRatio);
1589 shrink(shrink_bytes);
1590 }
1591 }
1592
1593
1594 HeapWord*
1595 G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
1596 bool* succeeded) {
1597 assert_at_safepoint(true /* should_be_vm_thread */);
1598
1599 *succeeded = true;
1600 // Let's attempt the allocation first.
1601 HeapWord* result =
1602 attempt_allocation_at_safepoint(word_size,
1603 false /* expect_null_mutator_alloc_region */);
1604 if (result != NULL) {
1605 assert(*succeeded, "sanity");
1606 return result;
1607 }
1608
1609 // In a G1 heap, we're supposed to keep allocation from failing by
1610 // incremental pauses. Therefore, at least for now, we'll favor
1611 // expansion over collection. (This might change in the future if we can
1612 // do something smarter than full collection to satisfy a failed alloc.)
1613 result = expand_and_allocate(word_size);
1614 if (result != NULL) {
1615 assert(*succeeded, "sanity");
1616 return result;
1617 }
1618
1619 // Expansion didn't work, we'll try to do a Full GC.
1620 bool gc_succeeded = do_collection(false, /* explicit_gc */
1621 false, /* clear_all_soft_refs */
1622 word_size);
1623 if (!gc_succeeded) {
1624 *succeeded = false;
1625 return NULL;
1626 }
1627
1628 // Retry the allocation
1629 result = attempt_allocation_at_safepoint(word_size,
1630 true /* expect_null_mutator_alloc_region */);
1631 if (result != NULL) {
1632 assert(*succeeded, "sanity");
1633 return result;
1634 }
1635
1636 // Then, try a Full GC that will collect all soft references.
1637 gc_succeeded = do_collection(false, /* explicit_gc */
1638 true, /* clear_all_soft_refs */
1639 word_size);
1640 if (!gc_succeeded) {
1641 *succeeded = false;
1642 return NULL;
1643 }
1644
1645 // Retry the allocation once more
1646 result = attempt_allocation_at_safepoint(word_size,
1647 true /* expect_null_mutator_alloc_region */);
1648 if (result != NULL) {
1649 assert(*succeeded, "sanity");
1650 return result;
1651 }
1652
1653 assert(!collector_policy()->should_clear_all_soft_refs(),
1654 "Flag should have been handled and cleared prior to this point");
1655
1656 // What else? We might try synchronous finalization later. If the total
1657 // space available is large enough for the allocation, then a more
1658 // complete compaction phase than we've tried so far might be
1659 // appropriate.
1660 assert(*succeeded, "sanity");
1661 return NULL;
1662 }
1663
1664 // Attempting to expand the heap sufficiently
1665 // to support an allocation of the given "word_size". If
1666 // successful, perform the allocation and return the address of the
1667 // allocated block, or else "NULL".
1668
1669 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size) {
1670 assert_at_safepoint(true /* should_be_vm_thread */);
1671
1672 verify_region_sets_optional();
1673
1674 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
1675 ergo_verbose1(ErgoHeapSizing,
1676 "attempt heap expansion",
1677 ergo_format_reason("allocation request failed")
1678 ergo_format_byte("allocation request"),
1679 word_size * HeapWordSize);
1680 if (expand(expand_bytes)) {
1681 _hrs.verify_optional();
1682 verify_region_sets_optional();
1683 return attempt_allocation_at_safepoint(word_size,
1684 false /* expect_null_mutator_alloc_region */);
1685 }
1686 return NULL;
1687 }
1688
1689 void G1CollectedHeap::update_committed_space(HeapWord* old_end,
1690 HeapWord* new_end) {
1691 assert(old_end != new_end, "don't call this otherwise");
1692 assert((HeapWord*) _g1_storage.high() == new_end, "invariant");
1693
1694 // Update the committed mem region.
1695 _g1_committed.set_end(new_end);
1696 // Tell the card table about the update.
1697 Universe::heap()->barrier_set()->resize_covered_region(_g1_committed);
1698 // Tell the BOT about the update.
1699 _bot_shared->resize(_g1_committed.word_size());
1700 }
1701
1702 bool G1CollectedHeap::expand(size_t expand_bytes) {
1703 size_t old_mem_size = _g1_storage.committed_size();
1704 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
1705 aligned_expand_bytes = align_size_up(aligned_expand_bytes,
1706 HeapRegion::GrainBytes);
1707 ergo_verbose2(ErgoHeapSizing,
1708 "expand the heap",
1709 ergo_format_byte("requested expansion amount")
1710 ergo_format_byte("attempted expansion amount"),
1711 expand_bytes, aligned_expand_bytes);
1712
1713 // First commit the memory.
1714 HeapWord* old_end = (HeapWord*) _g1_storage.high();
1715 bool successful = _g1_storage.expand_by(aligned_expand_bytes);
1716 if (successful) {
1717 // Then propagate this update to the necessary data structures.
1718 HeapWord* new_end = (HeapWord*) _g1_storage.high();
1719 update_committed_space(old_end, new_end);
1720
1721 FreeRegionList expansion_list("Local Expansion List");
1722 MemRegion mr = _hrs.expand_by(old_end, new_end, &expansion_list);
1723 assert(mr.start() == old_end, "post-condition");
1724 // mr might be a smaller region than what was requested if
1725 // expand_by() was unable to allocate the HeapRegion instances
1726 assert(mr.end() <= new_end, "post-condition");
1727
1728 size_t actual_expand_bytes = mr.byte_size();
1729 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
1730 assert(actual_expand_bytes == expansion_list.total_capacity_bytes(),
1731 "post-condition");
1732 if (actual_expand_bytes < aligned_expand_bytes) {
1733 // We could not expand _hrs to the desired size. In this case we
1734 // need to shrink the committed space accordingly.
1735 assert(mr.end() < new_end, "invariant");
1736
1737 size_t diff_bytes = aligned_expand_bytes - actual_expand_bytes;
1738 // First uncommit the memory.
1739 _g1_storage.shrink_by(diff_bytes);
1740 // Then propagate this update to the necessary data structures.
1741 update_committed_space(new_end, mr.end());
1742 }
1743 _free_list.add_as_tail(&expansion_list);
1744
1745 if (_hr_printer.is_active()) {
1746 HeapWord* curr = mr.start();
1747 while (curr < mr.end()) {
1748 HeapWord* curr_end = curr + HeapRegion::GrainWords;
1749 _hr_printer.commit(curr, curr_end);
1750 curr = curr_end;
1751 }
1752 assert(curr == mr.end(), "post-condition");
1753 }
1754 g1_policy()->record_new_heap_size(n_regions());
1755 } else {
1756 ergo_verbose0(ErgoHeapSizing,
1757 "did not expand the heap",
1758 ergo_format_reason("heap expansion operation failed"));
1759 // The expansion of the virtual storage space was unsuccessful.
1760 // Let's see if it was because we ran out of swap.
1761 if (G1ExitOnExpansionFailure &&
1762 _g1_storage.uncommitted_size() >= aligned_expand_bytes) {
1763 // We had head room...
1764 vm_exit_out_of_memory(aligned_expand_bytes, "G1 heap expansion");
1765 }
1766 }
1767 return successful;
1768 }
1769
1770 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
1771 size_t old_mem_size = _g1_storage.committed_size();
1772 size_t aligned_shrink_bytes =
1773 ReservedSpace::page_align_size_down(shrink_bytes);
1774 aligned_shrink_bytes = align_size_down(aligned_shrink_bytes,
1775 HeapRegion::GrainBytes);
1776 uint num_regions_deleted = 0;
1777 MemRegion mr = _hrs.shrink_by(aligned_shrink_bytes, &num_regions_deleted);
1778 HeapWord* old_end = (HeapWord*) _g1_storage.high();
1779 assert(mr.end() == old_end, "post-condition");
1780
1781 ergo_verbose3(ErgoHeapSizing,
1782 "shrink the heap",
1783 ergo_format_byte("requested shrinking amount")
1784 ergo_format_byte("aligned shrinking amount")
1785 ergo_format_byte("attempted shrinking amount"),
1786 shrink_bytes, aligned_shrink_bytes, mr.byte_size());
1787 if (mr.byte_size() > 0) {
1788 if (_hr_printer.is_active()) {
1789 HeapWord* curr = mr.end();
1790 while (curr > mr.start()) {
1791 HeapWord* curr_end = curr;
1792 curr -= HeapRegion::GrainWords;
1793 _hr_printer.uncommit(curr, curr_end);
1794 }
1795 assert(curr == mr.start(), "post-condition");
1796 }
1797
1798 _g1_storage.shrink_by(mr.byte_size());
1799 HeapWord* new_end = (HeapWord*) _g1_storage.high();
1800 assert(mr.start() == new_end, "post-condition");
1801
1802 _expansion_regions += num_regions_deleted;
1803 update_committed_space(old_end, new_end);
1804 HeapRegionRemSet::shrink_heap(n_regions());
1805 g1_policy()->record_new_heap_size(n_regions());
1806 } else {
1807 ergo_verbose0(ErgoHeapSizing,
1808 "did not shrink the heap",
1809 ergo_format_reason("heap shrinking operation failed"));
1810 }
1811 }
1812
1813 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1814 verify_region_sets_optional();
1815
1816 // We should only reach here at the end of a Full GC which means we
1817 // should not not be holding to any GC alloc regions. The method
1818 // below will make sure of that and do any remaining clean up.
1819 abandon_gc_alloc_regions();
1820
1821 // Instead of tearing down / rebuilding the free lists here, we
1822 // could instead use the remove_all_pending() method on free_list to
1823 // remove only the ones that we need to remove.
1824 tear_down_region_sets(true /* free_list_only */);
1825 shrink_helper(shrink_bytes);
1826 rebuild_region_sets(true /* free_list_only */);
1827
1828 _hrs.verify_optional();
1829 verify_region_sets_optional();
1830 }
1831
1832 // Public methods.
1833
1834 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away
1835 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
1836 #endif // _MSC_VER
1837
1838
1839 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* policy_) :
1840 SharedHeap(policy_),
1841 _g1_policy(policy_),
1842 _dirty_card_queue_set(false),
1843 _into_cset_dirty_card_queue_set(false),
1844 _is_alive_closure_cm(this),
1845 _is_alive_closure_stw(this),
1846 _ref_processor_cm(NULL),
1847 _ref_processor_stw(NULL),
1848 _process_strong_tasks(new SubTasksDone(G1H_PS_NumElements)),
1849 _bot_shared(NULL),
1850 _objs_with_preserved_marks(NULL), _preserved_marks_of_objs(NULL),
1851 _evac_failure_scan_stack(NULL) ,
1852 _mark_in_progress(false),
1853 _cg1r(NULL), _summary_bytes_used(0),
1854 _g1mm(NULL),
1855 _refine_cte_cl(NULL),
1856 _full_collection(false),
1857 _free_list("Master Free List"),
1858 _secondary_free_list("Secondary Free List"),
1859 _old_set("Old Set"),
1860 _humongous_set("Master Humongous Set"),
1861 _free_regions_coming(false),
1862 _young_list(new YoungList(this)),
1863 _gc_time_stamp(0),
1864 _retained_old_gc_alloc_region(NULL),
1865 _expand_heap_after_alloc_failure(true),
1866 _surviving_young_words(NULL),
1867 _full_collections_completed(0),
1868 _in_cset_fast_test(NULL),
1869 _in_cset_fast_test_base(NULL),
1870 _dirty_cards_region_list(NULL),
1871 _worker_cset_start_region(NULL),
1872 _worker_cset_start_region_time_stamp(NULL) {
1873 _g1h = this; // To catch bugs.
1874 if (_process_strong_tasks == NULL || !_process_strong_tasks->valid()) {
1875 vm_exit_during_initialization("Failed necessary allocation.");
1876 }
1877
1878 _humongous_object_threshold_in_words = HeapRegion::GrainWords / 2;
1879
1880 int n_queues = MAX2((int)ParallelGCThreads, 1);
1881 _task_queues = new RefToScanQueueSet(n_queues);
1882
1883 int n_rem_sets = HeapRegionRemSet::num_par_rem_sets();
1884 assert(n_rem_sets > 0, "Invariant.");
1885
1886 HeapRegionRemSetIterator** iter_arr =
1887 NEW_C_HEAP_ARRAY(HeapRegionRemSetIterator*, n_queues);
1888 for (int i = 0; i < n_queues; i++) {
1889 iter_arr[i] = new HeapRegionRemSetIterator();
1890 }
1891 _rem_set_iterator = iter_arr;
1892
1893 _worker_cset_start_region = NEW_C_HEAP_ARRAY(HeapRegion*, n_queues);
1894 _worker_cset_start_region_time_stamp = NEW_C_HEAP_ARRAY(unsigned int, n_queues);
1895
1896 for (int i = 0; i < n_queues; i++) {
1897 RefToScanQueue* q = new RefToScanQueue();
1898 q->initialize();
1899 _task_queues->register_queue(i, q);
1900 }
1901
1902 clear_cset_start_regions();
1903
1904 guarantee(_task_queues != NULL, "task_queues allocation failure.");
1905 }
1906
1907 jint G1CollectedHeap::initialize() {
1908 CollectedHeap::pre_initialize();
1909 os::enable_vtime();
1910
1911 G1Log::init();
1912
1913 // Necessary to satisfy locking discipline assertions.
1914
1915 MutexLocker x(Heap_lock);
1916
1917 // We have to initialize the printer before committing the heap, as
1918 // it will be used then.
1919 _hr_printer.set_active(G1PrintHeapRegions);
1920
1921 // While there are no constraints in the GC code that HeapWordSize
1922 // be any particular value, there are multiple other areas in the
1923 // system which believe this to be true (e.g. oop->object_size in some
1924 // cases incorrectly returns the size in wordSize units rather than
1925 // HeapWordSize).
1926 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
1927
1928 size_t init_byte_size = collector_policy()->initial_heap_byte_size();
1929 size_t max_byte_size = collector_policy()->max_heap_byte_size();
1930
1931 // Ensure that the sizes are properly aligned.
1932 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
1933 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
1934
1935 _cg1r = new ConcurrentG1Refine();
1936
1937 // Reserve the maximum.
1938 PermanentGenerationSpec* pgs = collector_policy()->permanent_generation();
1939 // Includes the perm-gen.
1940
1941 // When compressed oops are enabled, the preferred heap base
1942 // is calculated by subtracting the requested size from the
1943 // 32Gb boundary and using the result as the base address for
1944 // heap reservation. If the requested size is not aligned to
1945 // HeapRegion::GrainBytes (i.e. the alignment that is passed
1946 // into the ReservedHeapSpace constructor) then the actual
1947 // base of the reserved heap may end up differing from the
1948 // address that was requested (i.e. the preferred heap base).
1949 // If this happens then we could end up using a non-optimal
1950 // compressed oops mode.
1951
1952 // Since max_byte_size is aligned to the size of a heap region (checked
1953 // above), we also need to align the perm gen size as it might not be.
1954 const size_t total_reserved = max_byte_size +
1955 align_size_up(pgs->max_size(), HeapRegion::GrainBytes);
1956 Universe::check_alignment(total_reserved, HeapRegion::GrainBytes, "g1 heap and perm");
1957
1958 char* addr = Universe::preferred_heap_base(total_reserved, Universe::UnscaledNarrowOop);
1959
1960 ReservedHeapSpace heap_rs(total_reserved, HeapRegion::GrainBytes,
1961 UseLargePages, addr);
1962
1963 if (UseCompressedOops) {
1964 if (addr != NULL && !heap_rs.is_reserved()) {
1965 // Failed to reserve at specified address - the requested memory
1966 // region is taken already, for example, by 'java' launcher.
1967 // Try again to reserver heap higher.
1968 addr = Universe::preferred_heap_base(total_reserved, Universe::ZeroBasedNarrowOop);
1969
1970 ReservedHeapSpace heap_rs0(total_reserved, HeapRegion::GrainBytes,
1971 UseLargePages, addr);
1972
1973 if (addr != NULL && !heap_rs0.is_reserved()) {
1974 // Failed to reserve at specified address again - give up.
1975 addr = Universe::preferred_heap_base(total_reserved, Universe::HeapBasedNarrowOop);
1976 assert(addr == NULL, "");
1977
1978 ReservedHeapSpace heap_rs1(total_reserved, HeapRegion::GrainBytes,
1979 UseLargePages, addr);
1980 heap_rs = heap_rs1;
1981 } else {
1982 heap_rs = heap_rs0;
1983 }
1984 }
1985 }
1986
1987 if (!heap_rs.is_reserved()) {
1988 vm_exit_during_initialization("Could not reserve enough space for object heap");
1989 return JNI_ENOMEM;
1990 }
1991
1992 // It is important to do this in a way such that concurrent readers can't
1993 // temporarily think somethings in the heap. (I've actually seen this
1994 // happen in asserts: DLD.)
1995 _reserved.set_word_size(0);
1996 _reserved.set_start((HeapWord*)heap_rs.base());
1997 _reserved.set_end((HeapWord*)(heap_rs.base() + heap_rs.size()));
1998
1999 _expansion_regions = (uint) (max_byte_size / HeapRegion::GrainBytes);
2000
2001 // Create the gen rem set (and barrier set) for the entire reserved region.
2002 _rem_set = collector_policy()->create_rem_set(_reserved, 2);
2003 set_barrier_set(rem_set()->bs());
2004 if (barrier_set()->is_a(BarrierSet::ModRef)) {
2005 _mr_bs = (ModRefBarrierSet*)_barrier_set;
2006 } else {
2007 vm_exit_during_initialization("G1 requires a mod ref bs.");
2008 return JNI_ENOMEM;
2009 }
2010
2011 // Also create a G1 rem set.
2012 if (mr_bs()->is_a(BarrierSet::CardTableModRef)) {
2013 _g1_rem_set = new G1RemSet(this, (CardTableModRefBS*)mr_bs());
2014 } else {
2015 vm_exit_during_initialization("G1 requires a cardtable mod ref bs.");
2016 return JNI_ENOMEM;
2017 }
2018
2019 // Carve out the G1 part of the heap.
2020
2021 ReservedSpace g1_rs = heap_rs.first_part(max_byte_size);
2022 _g1_reserved = MemRegion((HeapWord*)g1_rs.base(),
2023 g1_rs.size()/HeapWordSize);
2024 ReservedSpace perm_gen_rs = heap_rs.last_part(max_byte_size);
2025
2026 _perm_gen = pgs->init(perm_gen_rs, pgs->init_size(), rem_set());
2027
2028 _g1_storage.initialize(g1_rs, 0);
2029 _g1_committed = MemRegion((HeapWord*)_g1_storage.low(), (size_t) 0);
2030 _hrs.initialize((HeapWord*) _g1_reserved.start(),
2031 (HeapWord*) _g1_reserved.end(),
2032 _expansion_regions);
2033
2034 // 6843694 - ensure that the maximum region index can fit
2035 // in the remembered set structures.
2036 const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
2037 guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
2038
2039 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
2040 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
2041 guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
2042 "too many cards per region");
2043
2044 HeapRegionSet::set_unrealistically_long_length(max_regions() + 1);
2045
2046 _bot_shared = new G1BlockOffsetSharedArray(_reserved,
2047 heap_word_size(init_byte_size));
2048
2049 _g1h = this;
2050
2051 _in_cset_fast_test_length = max_regions();
2052 _in_cset_fast_test_base =
2053 NEW_C_HEAP_ARRAY(bool, (size_t) _in_cset_fast_test_length);
2054
2055 // We're biasing _in_cset_fast_test to avoid subtracting the
2056 // beginning of the heap every time we want to index; basically
2057 // it's the same with what we do with the card table.
2058 _in_cset_fast_test = _in_cset_fast_test_base -
2059 ((uintx) _g1_reserved.start() >> HeapRegion::LogOfHRGrainBytes);
2060
2061 // Clear the _cset_fast_test bitmap in anticipation of adding
2062 // regions to the incremental collection set for the first
2063 // evacuation pause.
2064 clear_cset_fast_test();
2065
2066 // Create the ConcurrentMark data structure and thread.
2067 // (Must do this late, so that "max_regions" is defined.)
2068 _cm = new ConcurrentMark(heap_rs, max_regions());
2069 _cmThread = _cm->cmThread();
2070
2071 // Initialize the from_card cache structure of HeapRegionRemSet.
2072 HeapRegionRemSet::init_heap(max_regions());
2073
2074 // Now expand into the initial heap size.
2075 if (!expand(init_byte_size)) {
2076 vm_exit_during_initialization("Failed to allocate initial heap.");
2077 return JNI_ENOMEM;
2078 }
2079
2080 // Perform any initialization actions delegated to the policy.
2081 g1_policy()->init();
2082
2083 _refine_cte_cl =
2084 new RefineCardTableEntryClosure(ConcurrentG1RefineThread::sts(),
2085 g1_rem_set(),
2086 concurrent_g1_refine());
2087 JavaThread::dirty_card_queue_set().set_closure(_refine_cte_cl);
2088
2089 JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon,
2090 SATB_Q_FL_lock,
2091 G1SATBProcessCompletedThreshold,
2092 Shared_SATB_Q_lock);
2093
2094 JavaThread::dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
2095 DirtyCardQ_FL_lock,
2096 concurrent_g1_refine()->yellow_zone(),
2097 concurrent_g1_refine()->red_zone(),
2098 Shared_DirtyCardQ_lock);
2099
2100 if (G1DeferredRSUpdate) {
2101 dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
2102 DirtyCardQ_FL_lock,
2103 -1, // never trigger processing
2104 -1, // no limit on length
2105 Shared_DirtyCardQ_lock,
2106 &JavaThread::dirty_card_queue_set());
2107 }
2108
2109 // Initialize the card queue set used to hold cards containing
2110 // references into the collection set.
2111 _into_cset_dirty_card_queue_set.initialize(DirtyCardQ_CBL_mon,
2112 DirtyCardQ_FL_lock,
2113 -1, // never trigger processing
2114 -1, // no limit on length
2115 Shared_DirtyCardQ_lock,
2116 &JavaThread::dirty_card_queue_set());
2117
2118 // In case we're keeping closure specialization stats, initialize those
2119 // counts and that mechanism.
2120 SpecializationStats::clear();
2121
2122 // Do later initialization work for concurrent refinement.
2123 _cg1r->init();
2124
2125 // Here we allocate the dummy full region that is required by the
2126 // G1AllocRegion class. If we don't pass an address in the reserved
2127 // space here, lots of asserts fire.
2128
2129 HeapRegion* dummy_region = new_heap_region(0 /* index of bottom region */,
2130 _g1_reserved.start());
2131 // We'll re-use the same region whether the alloc region will
2132 // require BOT updates or not and, if it doesn't, then a non-young
2133 // region will complain that it cannot support allocations without
2134 // BOT updates. So we'll tag the dummy region as young to avoid that.
2135 dummy_region->set_young();
2136 // Make sure it's full.
2137 dummy_region->set_top(dummy_region->end());
2138 G1AllocRegion::setup(this, dummy_region);
2139
2140 init_mutator_alloc_region();
2141
2142 // Do create of the monitoring and management support so that
2143 // values in the heap have been properly initialized.
2144 _g1mm = new G1MonitoringSupport(this);
2145
2146 return JNI_OK;
2147 }
2148
2149 void G1CollectedHeap::ref_processing_init() {
2150 // Reference processing in G1 currently works as follows:
2151 //
2152 // * There are two reference processor instances. One is
2153 // used to record and process discovered references
2154 // during concurrent marking; the other is used to
2155 // record and process references during STW pauses
2156 // (both full and incremental).
2157 // * Both ref processors need to 'span' the entire heap as
2158 // the regions in the collection set may be dotted around.
2159 //
2160 // * For the concurrent marking ref processor:
2161 // * Reference discovery is enabled at initial marking.
2162 // * Reference discovery is disabled and the discovered
2163 // references processed etc during remarking.
2164 // * Reference discovery is MT (see below).
2165 // * Reference discovery requires a barrier (see below).
2166 // * Reference processing may or may not be MT
2167 // (depending on the value of ParallelRefProcEnabled
2168 // and ParallelGCThreads).
2169 // * A full GC disables reference discovery by the CM
2170 // ref processor and abandons any entries on it's
2171 // discovered lists.
2172 //
2173 // * For the STW processor:
2174 // * Non MT discovery is enabled at the start of a full GC.
2175 // * Processing and enqueueing during a full GC is non-MT.
2176 // * During a full GC, references are processed after marking.
2177 //
2178 // * Discovery (may or may not be MT) is enabled at the start
2179 // of an incremental evacuation pause.
2180 // * References are processed near the end of a STW evacuation pause.
2181 // * For both types of GC:
2182 // * Discovery is atomic - i.e. not concurrent.
2183 // * Reference discovery will not need a barrier.
2184
2185 SharedHeap::ref_processing_init();
2186 MemRegion mr = reserved_region();
2187
2188 // Concurrent Mark ref processor
2189 _ref_processor_cm =
2190 new ReferenceProcessor(mr, // span
2191 ParallelRefProcEnabled && (ParallelGCThreads > 1),
2192 // mt processing
2193 (int) ParallelGCThreads,
2194 // degree of mt processing
2195 (ParallelGCThreads > 1) || (ConcGCThreads > 1),
2196 // mt discovery
2197 (int) MAX2(ParallelGCThreads, ConcGCThreads),
2198 // degree of mt discovery
2199 false,
2200 // Reference discovery is not atomic
2201 &_is_alive_closure_cm,
2202 // is alive closure
2203 // (for efficiency/performance)
2204 true);
2205 // Setting next fields of discovered
2206 // lists requires a barrier.
2207
2208 // STW ref processor
2209 _ref_processor_stw =
2210 new ReferenceProcessor(mr, // span
2211 ParallelRefProcEnabled && (ParallelGCThreads > 1),
2212 // mt processing
2213 MAX2((int)ParallelGCThreads, 1),
2214 // degree of mt processing
2215 (ParallelGCThreads > 1),
2216 // mt discovery
2217 MAX2((int)ParallelGCThreads, 1),
2218 // degree of mt discovery
2219 true,
2220 // Reference discovery is atomic
2221 &_is_alive_closure_stw,
2222 // is alive closure
2223 // (for efficiency/performance)
2224 false);
2225 // Setting next fields of discovered
2226 // lists requires a barrier.
2227 }
2228
2229 size_t G1CollectedHeap::capacity() const {
2230 return _g1_committed.byte_size();
2231 }
2232
2233 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl,
2234 DirtyCardQueue* into_cset_dcq,
2235 bool concurrent,
2236 int worker_i) {
2237 // Clean cards in the hot card cache
2238 concurrent_g1_refine()->clean_up_cache(worker_i, g1_rem_set(), into_cset_dcq);
2239
2240 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2241 int n_completed_buffers = 0;
2242 while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) {
2243 n_completed_buffers++;
2244 }
2245 g1_policy()->record_update_rs_processed_buffers(worker_i,
2246 (double) n_completed_buffers);
2247 dcqs.clear_n_completed_buffers();
2248 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!");
2249 }
2250
2251
2252 // Computes the sum of the storage used by the various regions.
2253
2254 size_t G1CollectedHeap::used() const {
2255 assert(Heap_lock->owner() != NULL,
2256 "Should be owned on this thread's behalf.");
2257 size_t result = _summary_bytes_used;
2258 // Read only once in case it is set to NULL concurrently
2259 HeapRegion* hr = _mutator_alloc_region.get();
2260 if (hr != NULL)
2261 result += hr->used();
2262 return result;
2263 }
2264
2265 size_t G1CollectedHeap::used_unlocked() const {
2266 size_t result = _summary_bytes_used;
2267 return result;
2268 }
2269
2270 class SumUsedClosure: public HeapRegionClosure {
2271 size_t _used;
2272 public:
2273 SumUsedClosure() : _used(0) {}
2274 bool doHeapRegion(HeapRegion* r) {
2275 if (!r->continuesHumongous()) {
2276 _used += r->used();
2277 }
2278 return false;
2279 }
2280 size_t result() { return _used; }
2281 };
2282
2283 size_t G1CollectedHeap::recalculate_used() const {
2284 SumUsedClosure blk;
2285 heap_region_iterate(&blk);
2286 return blk.result();
2287 }
2288
2289 size_t G1CollectedHeap::unsafe_max_alloc() {
2290 if (free_regions() > 0) return HeapRegion::GrainBytes;
2291 // otherwise, is there space in the current allocation region?
2292
2293 // We need to store the current allocation region in a local variable
2294 // here. The problem is that this method doesn't take any locks and
2295 // there may be other threads which overwrite the current allocation
2296 // region field. attempt_allocation(), for example, sets it to NULL
2297 // and this can happen *after* the NULL check here but before the call
2298 // to free(), resulting in a SIGSEGV. Note that this doesn't appear
2299 // to be a problem in the optimized build, since the two loads of the
2300 // current allocation region field are optimized away.
2301 HeapRegion* hr = _mutator_alloc_region.get();
2302 if (hr == NULL) {
2303 return 0;
2304 }
2305 return hr->free();
2306 }
2307
2308 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
2309 switch (cause) {
2310 case GCCause::_gc_locker: return GCLockerInvokesConcurrent;
2311 case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent;
2312 case GCCause::_g1_humongous_allocation: return true;
2313 default: return false;
2314 }
2315 }
2316
2317 #ifndef PRODUCT
2318 void G1CollectedHeap::allocate_dummy_regions() {
2319 // Let's fill up most of the region
2320 size_t word_size = HeapRegion::GrainWords - 1024;
2321 // And as a result the region we'll allocate will be humongous.
2322 guarantee(isHumongous(word_size), "sanity");
2323
2324 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
2325 // Let's use the existing mechanism for the allocation
2326 HeapWord* dummy_obj = humongous_obj_allocate(word_size);
2327 if (dummy_obj != NULL) {
2328 MemRegion mr(dummy_obj, word_size);
2329 CollectedHeap::fill_with_object(mr);
2330 } else {
2331 // If we can't allocate once, we probably cannot allocate
2332 // again. Let's get out of the loop.
2333 break;
2334 }
2335 }
2336 }
2337 #endif // !PRODUCT
2338
2339 void G1CollectedHeap::increment_full_collections_completed(bool concurrent) {
2340 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
2341
2342 // We assume that if concurrent == true, then the caller is a
2343 // concurrent thread that was joined the Suspendible Thread
2344 // Set. If there's ever a cheap way to check this, we should add an
2345 // assert here.
2346
2347 // We have already incremented _total_full_collections at the start
2348 // of the GC, so total_full_collections() represents how many full
2349 // collections have been started.
2350 unsigned int full_collections_started = total_full_collections();
2351
2352 // Given that this method is called at the end of a Full GC or of a
2353 // concurrent cycle, and those can be nested (i.e., a Full GC can
2354 // interrupt a concurrent cycle), the number of full collections
2355 // completed should be either one (in the case where there was no
2356 // nesting) or two (when a Full GC interrupted a concurrent cycle)
2357 // behind the number of full collections started.
2358
2359 // This is the case for the inner caller, i.e. a Full GC.
2360 assert(concurrent ||
2361 (full_collections_started == _full_collections_completed + 1) ||
2362 (full_collections_started == _full_collections_completed + 2),
2363 err_msg("for inner caller (Full GC): full_collections_started = %u "
2364 "is inconsistent with _full_collections_completed = %u",
2365 full_collections_started, _full_collections_completed));
2366
2367 // This is the case for the outer caller, i.e. the concurrent cycle.
2368 assert(!concurrent ||
2369 (full_collections_started == _full_collections_completed + 1),
2370 err_msg("for outer caller (concurrent cycle): "
2371 "full_collections_started = %u "
2372 "is inconsistent with _full_collections_completed = %u",
2373 full_collections_started, _full_collections_completed));
2374
2375 _full_collections_completed += 1;
2376
2377 // We need to clear the "in_progress" flag in the CM thread before
2378 // we wake up any waiters (especially when ExplicitInvokesConcurrent
2379 // is set) so that if a waiter requests another System.gc() it doesn't
2380 // incorrectly see that a marking cyle is still in progress.
2381 if (concurrent) {
2382 _cmThread->clear_in_progress();
2383 }
2384
2385 // This notify_all() will ensure that a thread that called
2386 // System.gc() with (with ExplicitGCInvokesConcurrent set or not)
2387 // and it's waiting for a full GC to finish will be woken up. It is
2388 // waiting in VM_G1IncCollectionPause::doit_epilogue().
2389 FullGCCount_lock->notify_all();
2390 }
2391
2392 void G1CollectedHeap::collect_as_vm_thread(GCCause::Cause cause) {
2393 assert_at_safepoint(true /* should_be_vm_thread */);
2394 GCCauseSetter gcs(this, cause);
2395 switch (cause) {
2396 case GCCause::_heap_inspection:
2397 case GCCause::_heap_dump: {
2398 HandleMark hm;
2399 do_full_collection(false); // don't clear all soft refs
2400 break;
2401 }
2402 default: // XXX FIX ME
2403 ShouldNotReachHere(); // Unexpected use of this function
2404 }
2405 }
2406
2407 void G1CollectedHeap::collect(GCCause::Cause cause) {
2408 assert_heap_not_locked();
2409
2410 unsigned int gc_count_before;
2411 unsigned int full_gc_count_before;
2412 bool retry_gc;
2413
2414 do {
2415 retry_gc = false;
2416
2417 {
2418 MutexLocker ml(Heap_lock);
2419
2420 // Read the GC count while holding the Heap_lock
2421 gc_count_before = total_collections();
2422 full_gc_count_before = total_full_collections();
2423 }
2424
2425 if (should_do_concurrent_full_gc(cause)) {
2426 // Schedule an initial-mark evacuation pause that will start a
2427 // concurrent cycle. We're setting word_size to 0 which means that
2428 // we are not requesting a post-GC allocation.
2429 VM_G1IncCollectionPause op(gc_count_before,
2430 0, /* word_size */
2431 true, /* should_initiate_conc_mark */
2432 g1_policy()->max_pause_time_ms(),
2433 cause);
2434
2435 VMThread::execute(&op);
2436 if (!op.pause_succeeded()) {
2437 if (full_gc_count_before == total_full_collections()) {
2438 retry_gc = op.should_retry_gc();
2439 } else {
2440 // A Full GC happened while we were trying to schedule the
2441 // initial-mark GC. No point in starting a new cycle given
2442 // that the whole heap was collected anyway.
2443 }
2444
2445 if (retry_gc) {
2446 if (GC_locker::is_active_and_needs_gc()) {
2447 GC_locker::stall_until_clear();
2448 }
2449 }
2450 }
2451 } else {
2452 if (cause == GCCause::_gc_locker
2453 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2454
2455 // Schedule a standard evacuation pause. We're setting word_size
2456 // to 0 which means that we are not requesting a post-GC allocation.
2457 VM_G1IncCollectionPause op(gc_count_before,
2458 0, /* word_size */
2459 false, /* should_initiate_conc_mark */
2460 g1_policy()->max_pause_time_ms(),
2461 cause);
2462 VMThread::execute(&op);
2463 } else {
2464 // Schedule a Full GC.
2465 VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause);
2466 VMThread::execute(&op);
2467 }
2468 }
2469 } while (retry_gc);
2470 }
2471
2472 bool G1CollectedHeap::is_in(const void* p) const {
2473 if (_g1_committed.contains(p)) {
2474 // Given that we know that p is in the committed space,
2475 // heap_region_containing_raw() should successfully
2476 // return the containing region.
2477 HeapRegion* hr = heap_region_containing_raw(p);
2478 return hr->is_in(p);
2479 } else {
2480 return _perm_gen->as_gen()->is_in(p);
2481 }
2482 }
2483
2484 // Iteration functions.
2485
2486 // Iterates an OopClosure over all ref-containing fields of objects
2487 // within a HeapRegion.
2488
2489 class IterateOopClosureRegionClosure: public HeapRegionClosure {
2490 MemRegion _mr;
2491 OopClosure* _cl;
2492 public:
2493 IterateOopClosureRegionClosure(MemRegion mr, OopClosure* cl)
2494 : _mr(mr), _cl(cl) {}
2495 bool doHeapRegion(HeapRegion* r) {
2496 if (! r->continuesHumongous()) {
2497 r->oop_iterate(_cl);
2498 }
2499 return false;
2500 }
2501 };
2502
2503 void G1CollectedHeap::oop_iterate(OopClosure* cl, bool do_perm) {
2504 IterateOopClosureRegionClosure blk(_g1_committed, cl);
2505 heap_region_iterate(&blk);
2506 if (do_perm) {
2507 perm_gen()->oop_iterate(cl);
2508 }
2509 }
2510
2511 void G1CollectedHeap::oop_iterate(MemRegion mr, OopClosure* cl, bool do_perm) {
2512 IterateOopClosureRegionClosure blk(mr, cl);
2513 heap_region_iterate(&blk);
2514 if (do_perm) {
2515 perm_gen()->oop_iterate(cl);
2516 }
2517 }
2518
2519 // Iterates an ObjectClosure over all objects within a HeapRegion.
2520
2521 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2522 ObjectClosure* _cl;
2523 public:
2524 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2525 bool doHeapRegion(HeapRegion* r) {
2526 if (! r->continuesHumongous()) {
2527 r->object_iterate(_cl);
2528 }
2529 return false;
2530 }
2531 };
2532
2533 void G1CollectedHeap::object_iterate(ObjectClosure* cl, bool do_perm) {
2534 IterateObjectClosureRegionClosure blk(cl);
2535 heap_region_iterate(&blk);
2536 if (do_perm) {
2537 perm_gen()->object_iterate(cl);
2538 }
2539 }
2540
2541 void G1CollectedHeap::object_iterate_since_last_GC(ObjectClosure* cl) {
2542 // FIXME: is this right?
2543 guarantee(false, "object_iterate_since_last_GC not supported by G1 heap");
2544 }
2545
2546 // Calls a SpaceClosure on a HeapRegion.
2547
2548 class SpaceClosureRegionClosure: public HeapRegionClosure {
2549 SpaceClosure* _cl;
2550 public:
2551 SpaceClosureRegionClosure(SpaceClosure* cl) : _cl(cl) {}
2552 bool doHeapRegion(HeapRegion* r) {
2553 _cl->do_space(r);
2554 return false;
2555 }
2556 };
2557
2558 void G1CollectedHeap::space_iterate(SpaceClosure* cl) {
2559 SpaceClosureRegionClosure blk(cl);
2560 heap_region_iterate(&blk);
2561 }
2562
2563 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2564 _hrs.iterate(cl);
2565 }
2566
2567 void G1CollectedHeap::heap_region_iterate_from(HeapRegion* r,
2568 HeapRegionClosure* cl) const {
2569 _hrs.iterate_from(r, cl);
2570 }
2571
2572 void
2573 G1CollectedHeap::heap_region_par_iterate_chunked(HeapRegionClosure* cl,
2574 uint worker,
2575 uint no_of_par_workers,
2576 jint claim_value) {
2577 const uint regions = n_regions();
2578 const uint max_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
2579 no_of_par_workers :
2580 1);
2581 assert(UseDynamicNumberOfGCThreads ||
2582 no_of_par_workers == workers()->total_workers(),
2583 "Non dynamic should use fixed number of workers");
2584 // try to spread out the starting points of the workers
2585 const uint start_index = regions / max_workers * worker;
2586
2587 // each worker will actually look at all regions
2588 for (uint count = 0; count < regions; ++count) {
2589 const uint index = (start_index + count) % regions;
2590 assert(0 <= index && index < regions, "sanity");
2591 HeapRegion* r = region_at(index);
2592 // we'll ignore "continues humongous" regions (we'll process them
2593 // when we come across their corresponding "start humongous"
2594 // region) and regions already claimed
2595 if (r->claim_value() == claim_value || r->continuesHumongous()) {
2596 continue;
2597 }
2598 // OK, try to claim it
2599 if (r->claimHeapRegion(claim_value)) {
2600 // success!
2601 assert(!r->continuesHumongous(), "sanity");
2602 if (r->startsHumongous()) {
2603 // If the region is "starts humongous" we'll iterate over its
2604 // "continues humongous" first; in fact we'll do them
2605 // first. The order is important. In on case, calling the
2606 // closure on the "starts humongous" region might de-allocate
2607 // and clear all its "continues humongous" regions and, as a
2608 // result, we might end up processing them twice. So, we'll do
2609 // them first (notice: most closures will ignore them anyway) and
2610 // then we'll do the "starts humongous" region.
2611 for (uint ch_index = index + 1; ch_index < regions; ++ch_index) {
2612 HeapRegion* chr = region_at(ch_index);
2613
2614 // if the region has already been claimed or it's not
2615 // "continues humongous" we're done
2616 if (chr->claim_value() == claim_value ||
2617 !chr->continuesHumongous()) {
2618 break;
2619 }
2620
2621 // Noone should have claimed it directly. We can given
2622 // that we claimed its "starts humongous" region.
2623 assert(chr->claim_value() != claim_value, "sanity");
2624 assert(chr->humongous_start_region() == r, "sanity");
2625
2626 if (chr->claimHeapRegion(claim_value)) {
2627 // we should always be able to claim it; noone else should
2628 // be trying to claim this region
2629
2630 bool res2 = cl->doHeapRegion(chr);
2631 assert(!res2, "Should not abort");
2632
2633 // Right now, this holds (i.e., no closure that actually
2634 // does something with "continues humongous" regions
2635 // clears them). We might have to weaken it in the future,
2636 // but let's leave these two asserts here for extra safety.
2637 assert(chr->continuesHumongous(), "should still be the case");
2638 assert(chr->humongous_start_region() == r, "sanity");
2639 } else {
2640 guarantee(false, "we should not reach here");
2641 }
2642 }
2643 }
2644
2645 assert(!r->continuesHumongous(), "sanity");
2646 bool res = cl->doHeapRegion(r);
2647 assert(!res, "Should not abort");
2648 }
2649 }
2650 }
2651
2652 class ResetClaimValuesClosure: public HeapRegionClosure {
2653 public:
2654 bool doHeapRegion(HeapRegion* r) {
2655 r->set_claim_value(HeapRegion::InitialClaimValue);
2656 return false;
2657 }
2658 };
2659
2660 void G1CollectedHeap::reset_heap_region_claim_values() {
2661 ResetClaimValuesClosure blk;
2662 heap_region_iterate(&blk);
2663 }
2664
2665 void G1CollectedHeap::reset_cset_heap_region_claim_values() {
2666 ResetClaimValuesClosure blk;
2667 collection_set_iterate(&blk);
2668 }
2669
2670 #ifdef ASSERT
2671 // This checks whether all regions in the heap have the correct claim
2672 // value. I also piggy-backed on this a check to ensure that the
2673 // humongous_start_region() information on "continues humongous"
2674 // regions is correct.
2675
2676 class CheckClaimValuesClosure : public HeapRegionClosure {
2677 private:
2678 jint _claim_value;
2679 uint _failures;
2680 HeapRegion* _sh_region;
2681
2682 public:
2683 CheckClaimValuesClosure(jint claim_value) :
2684 _claim_value(claim_value), _failures(0), _sh_region(NULL) { }
2685 bool doHeapRegion(HeapRegion* r) {
2686 if (r->claim_value() != _claim_value) {
2687 gclog_or_tty->print_cr("Region " HR_FORMAT ", "
2688 "claim value = %d, should be %d",
2689 HR_FORMAT_PARAMS(r),
2690 r->claim_value(), _claim_value);
2691 ++_failures;
2692 }
2693 if (!r->isHumongous()) {
2694 _sh_region = NULL;
2695 } else if (r->startsHumongous()) {
2696 _sh_region = r;
2697 } else if (r->continuesHumongous()) {
2698 if (r->humongous_start_region() != _sh_region) {
2699 gclog_or_tty->print_cr("Region " HR_FORMAT ", "
2700 "HS = "PTR_FORMAT", should be "PTR_FORMAT,
2701 HR_FORMAT_PARAMS(r),
2702 r->humongous_start_region(),
2703 _sh_region);
2704 ++_failures;
2705 }
2706 }
2707 return false;
2708 }
2709 uint failures() { return _failures; }
2710 };
2711
2712 bool G1CollectedHeap::check_heap_region_claim_values(jint claim_value) {
2713 CheckClaimValuesClosure cl(claim_value);
2714 heap_region_iterate(&cl);
2715 return cl.failures() == 0;
2716 }
2717
2718 class CheckClaimValuesInCSetHRClosure: public HeapRegionClosure {
2719 private:
2720 jint _claim_value;
2721 uint _failures;
2722
2723 public:
2724 CheckClaimValuesInCSetHRClosure(jint claim_value) :
2725 _claim_value(claim_value), _failures(0) { }
2726
2727 uint failures() { return _failures; }
2728
2729 bool doHeapRegion(HeapRegion* hr) {
2730 assert(hr->in_collection_set(), "how?");
2731 assert(!hr->isHumongous(), "H-region in CSet");
2732 if (hr->claim_value() != _claim_value) {
2733 gclog_or_tty->print_cr("CSet Region " HR_FORMAT ", "
2734 "claim value = %d, should be %d",
2735 HR_FORMAT_PARAMS(hr),
2736 hr->claim_value(), _claim_value);
2737 _failures += 1;
2738 }
2739 return false;
2740 }
2741 };
2742
2743 bool G1CollectedHeap::check_cset_heap_region_claim_values(jint claim_value) {
2744 CheckClaimValuesInCSetHRClosure cl(claim_value);
2745 collection_set_iterate(&cl);
2746 return cl.failures() == 0;
2747 }
2748 #endif // ASSERT
2749
2750 // Clear the cached CSet starting regions and (more importantly)
2751 // the time stamps. Called when we reset the GC time stamp.
2752 void G1CollectedHeap::clear_cset_start_regions() {
2753 assert(_worker_cset_start_region != NULL, "sanity");
2754 assert(_worker_cset_start_region_time_stamp != NULL, "sanity");
2755
2756 int n_queues = MAX2((int)ParallelGCThreads, 1);
2757 for (int i = 0; i < n_queues; i++) {
2758 _worker_cset_start_region[i] = NULL;
2759 _worker_cset_start_region_time_stamp[i] = 0;
2760 }
2761 }
2762
2763 // Given the id of a worker, obtain or calculate a suitable
2764 // starting region for iterating over the current collection set.
2765 HeapRegion* G1CollectedHeap::start_cset_region_for_worker(int worker_i) {
2766 assert(get_gc_time_stamp() > 0, "should have been updated by now");
2767
2768 HeapRegion* result = NULL;
2769 unsigned gc_time_stamp = get_gc_time_stamp();
2770
2771 if (_worker_cset_start_region_time_stamp[worker_i] == gc_time_stamp) {
2772 // Cached starting region for current worker was set
2773 // during the current pause - so it's valid.
2774 // Note: the cached starting heap region may be NULL
2775 // (when the collection set is empty).
2776 result = _worker_cset_start_region[worker_i];
2777 assert(result == NULL || result->in_collection_set(), "sanity");
2778 return result;
2779 }
2780
2781 // The cached entry was not valid so let's calculate
2782 // a suitable starting heap region for this worker.
2783
2784 // We want the parallel threads to start their collection
2785 // set iteration at different collection set regions to
2786 // avoid contention.
2787 // If we have:
2788 // n collection set regions
2789 // p threads
2790 // Then thread t will start at region floor ((t * n) / p)
2791
2792 result = g1_policy()->collection_set();
2793 if (G1CollectedHeap::use_parallel_gc_threads()) {
2794 uint cs_size = g1_policy()->cset_region_length();
2795 uint active_workers = workers()->active_workers();
2796 assert(UseDynamicNumberOfGCThreads ||
2797 active_workers == workers()->total_workers(),
2798 "Unless dynamic should use total workers");
2799
2800 uint end_ind = (cs_size * worker_i) / active_workers;
2801 uint start_ind = 0;
2802
2803 if (worker_i > 0 &&
2804 _worker_cset_start_region_time_stamp[worker_i - 1] == gc_time_stamp) {
2805 // Previous workers starting region is valid
2806 // so let's iterate from there
2807 start_ind = (cs_size * (worker_i - 1)) / active_workers;
2808 result = _worker_cset_start_region[worker_i - 1];
2809 }
2810
2811 for (uint i = start_ind; i < end_ind; i++) {
2812 result = result->next_in_collection_set();
2813 }
2814 }
2815
2816 // Note: the calculated starting heap region may be NULL
2817 // (when the collection set is empty).
2818 assert(result == NULL || result->in_collection_set(), "sanity");
2819 assert(_worker_cset_start_region_time_stamp[worker_i] != gc_time_stamp,
2820 "should be updated only once per pause");
2821 _worker_cset_start_region[worker_i] = result;
2822 OrderAccess::storestore();
2823 _worker_cset_start_region_time_stamp[worker_i] = gc_time_stamp;
2824 return result;
2825 }
2826
2827 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) {
2828 HeapRegion* r = g1_policy()->collection_set();
2829 while (r != NULL) {
2830 HeapRegion* next = r->next_in_collection_set();
2831 if (cl->doHeapRegion(r)) {
2832 cl->incomplete();
2833 return;
2834 }
2835 r = next;
2836 }
2837 }
2838
2839 void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r,
2840 HeapRegionClosure *cl) {
2841 if (r == NULL) {
2842 // The CSet is empty so there's nothing to do.
2843 return;
2844 }
2845
2846 assert(r->in_collection_set(),
2847 "Start region must be a member of the collection set.");
2848 HeapRegion* cur = r;
2849 while (cur != NULL) {
2850 HeapRegion* next = cur->next_in_collection_set();
2851 if (cl->doHeapRegion(cur) && false) {
2852 cl->incomplete();
2853 return;
2854 }
2855 cur = next;
2856 }
2857 cur = g1_policy()->collection_set();
2858 while (cur != r) {
2859 HeapRegion* next = cur->next_in_collection_set();
2860 if (cl->doHeapRegion(cur) && false) {
2861 cl->incomplete();
2862 return;
2863 }
2864 cur = next;
2865 }
2866 }
2867
2868 CompactibleSpace* G1CollectedHeap::first_compactible_space() {
2869 return n_regions() > 0 ? region_at(0) : NULL;
2870 }
2871
2872
2873 Space* G1CollectedHeap::space_containing(const void* addr) const {
2874 Space* res = heap_region_containing(addr);
2875 if (res == NULL)
2876 res = perm_gen()->space_containing(addr);
2877 return res;
2878 }
2879
2880 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2881 Space* sp = space_containing(addr);
2882 if (sp != NULL) {
2883 return sp->block_start(addr);
2884 }
2885 return NULL;
2886 }
2887
2888 size_t G1CollectedHeap::block_size(const HeapWord* addr) const {
2889 Space* sp = space_containing(addr);
2890 assert(sp != NULL, "block_size of address outside of heap");
2891 return sp->block_size(addr);
2892 }
2893
2894 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2895 Space* sp = space_containing(addr);
2896 return sp->block_is_obj(addr);
2897 }
2898
2899 bool G1CollectedHeap::supports_tlab_allocation() const {
2900 return true;
2901 }
2902
2903 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
2904 return HeapRegion::GrainBytes;
2905 }
2906
2907 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
2908 // Return the remaining space in the cur alloc region, but not less than
2909 // the min TLAB size.
2910
2911 // Also, this value can be at most the humongous object threshold,
2912 // since we can't allow tlabs to grow big enough to accomodate
2913 // humongous objects.
2914
2915 HeapRegion* hr = _mutator_alloc_region.get();
2916 size_t max_tlab_size = _humongous_object_threshold_in_words * wordSize;
2917 if (hr == NULL) {
2918 return max_tlab_size;
2919 } else {
2920 return MIN2(MAX2(hr->free(), (size_t) MinTLABSize), max_tlab_size);
2921 }
2922 }
2923
2924 size_t G1CollectedHeap::max_capacity() const {
2925 return _g1_reserved.byte_size();
2926 }
2927
2928 jlong G1CollectedHeap::millis_since_last_gc() {
2929 // assert(false, "NYI");
2930 return 0;
2931 }
2932
2933 void G1CollectedHeap::prepare_for_verify() {
2934 if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) {
2935 ensure_parsability(false);
2936 }
2937 g1_rem_set()->prepare_for_verify();
2938 }
2939
2940 class VerifyLivenessOopClosure: public OopClosure {
2941 G1CollectedHeap* _g1h;
2942 VerifyOption _vo;
2943 public:
2944 VerifyLivenessOopClosure(G1CollectedHeap* g1h, VerifyOption vo):
2945 _g1h(g1h), _vo(vo)
2946 { }
2947 void do_oop(narrowOop *p) { do_oop_work(p); }
2948 void do_oop( oop *p) { do_oop_work(p); }
2949
2950 template <class T> void do_oop_work(T *p) {
2951 oop obj = oopDesc::load_decode_heap_oop(p);
2952 guarantee(obj == NULL || !_g1h->is_obj_dead_cond(obj, _vo),
2953 "Dead object referenced by a not dead object");
2954 }
2955 };
2956
2957 class VerifyObjsInRegionClosure: public ObjectClosure {
2958 private:
2959 G1CollectedHeap* _g1h;
2960 size_t _live_bytes;
2961 HeapRegion *_hr;
2962 VerifyOption _vo;
2963 public:
2964 // _vo == UsePrevMarking -> use "prev" marking information,
2965 // _vo == UseNextMarking -> use "next" marking information,
2966 // _vo == UseMarkWord -> use mark word from object header.
2967 VerifyObjsInRegionClosure(HeapRegion *hr, VerifyOption vo)
2968 : _live_bytes(0), _hr(hr), _vo(vo) {
2969 _g1h = G1CollectedHeap::heap();
2970 }
2971 void do_object(oop o) {
2972 VerifyLivenessOopClosure isLive(_g1h, _vo);
2973 assert(o != NULL, "Huh?");
2974 if (!_g1h->is_obj_dead_cond(o, _vo)) {
2975 // If the object is alive according to the mark word,
2976 // then verify that the marking information agrees.
2977 // Note we can't verify the contra-positive of the
2978 // above: if the object is dead (according to the mark
2979 // word), it may not be marked, or may have been marked
2980 // but has since became dead, or may have been allocated
2981 // since the last marking.
2982 if (_vo == VerifyOption_G1UseMarkWord) {
2983 guarantee(!_g1h->is_obj_dead(o), "mark word and concurrent mark mismatch");
2984 }
2985
2986 o->oop_iterate(&isLive);
2987 if (!_hr->obj_allocated_since_prev_marking(o)) {
2988 size_t obj_size = o->size(); // Make sure we don't overflow
2989 _live_bytes += (obj_size * HeapWordSize);
2990 }
2991 }
2992 }
2993 size_t live_bytes() { return _live_bytes; }
2994 };
2995
2996 class PrintObjsInRegionClosure : public ObjectClosure {
2997 HeapRegion *_hr;
2998 G1CollectedHeap *_g1;
2999 public:
3000 PrintObjsInRegionClosure(HeapRegion *hr) : _hr(hr) {
3001 _g1 = G1CollectedHeap::heap();
3002 };
3003
3004 void do_object(oop o) {
3005 if (o != NULL) {
3006 HeapWord *start = (HeapWord *) o;
3007 size_t word_sz = o->size();
3008 gclog_or_tty->print("\nPrinting obj "PTR_FORMAT" of size " SIZE_FORMAT
3009 " isMarkedPrev %d isMarkedNext %d isAllocSince %d\n",
3010 (void*) o, word_sz,
3011 _g1->isMarkedPrev(o),
3012 _g1->isMarkedNext(o),
3013 _hr->obj_allocated_since_prev_marking(o));
3014 HeapWord *end = start + word_sz;
3015 HeapWord *cur;
3016 int *val;
3017 for (cur = start; cur < end; cur++) {
3018 val = (int *) cur;
3019 gclog_or_tty->print("\t "PTR_FORMAT":"PTR_FORMAT"\n", val, *val);
3020 }
3021 }
3022 }
3023 };
3024
3025 class VerifyRegionClosure: public HeapRegionClosure {
3026 private:
3027 bool _par;
3028 VerifyOption _vo;
3029 bool _failures;
3030 public:
3031 // _vo == UsePrevMarking -> use "prev" marking information,
3032 // _vo == UseNextMarking -> use "next" marking information,
3033 // _vo == UseMarkWord -> use mark word from object header.
3034 VerifyRegionClosure(bool par, VerifyOption vo)
3035 : _par(par),
3036 _vo(vo),
3037 _failures(false) {}
3038
3039 bool failures() {
3040 return _failures;
3041 }
3042
3043 bool doHeapRegion(HeapRegion* r) {
3044 guarantee(_par || r->claim_value() == HeapRegion::InitialClaimValue,
3045 "Should be unclaimed at verify points.");
3046 if (!r->continuesHumongous()) {
3047 bool failures = false;
3048 r->verify(_vo, &failures);
3049 if (failures) {
3050 _failures = true;
3051 } else {
3052 VerifyObjsInRegionClosure not_dead_yet_cl(r, _vo);
3053 r->object_iterate(¬_dead_yet_cl);
3054 if (_vo != VerifyOption_G1UseNextMarking) {
3055 if (r->max_live_bytes() < not_dead_yet_cl.live_bytes()) {
3056 gclog_or_tty->print_cr("["PTR_FORMAT","PTR_FORMAT"] "
3057 "max_live_bytes "SIZE_FORMAT" "
3058 "< calculated "SIZE_FORMAT,
3059 r->bottom(), r->end(),
3060 r->max_live_bytes(),
3061 not_dead_yet_cl.live_bytes());
3062 _failures = true;
3063 }
3064 } else {
3065 // When vo == UseNextMarking we cannot currently do a sanity
3066 // check on the live bytes as the calculation has not been
3067 // finalized yet.
3068 }
3069 }
3070 }
3071 return false; // stop the region iteration if we hit a failure
3072 }
3073 };
3074
3075 class VerifyRootsClosure: public OopsInGenClosure {
3076 private:
3077 G1CollectedHeap* _g1h;
3078 VerifyOption _vo;
3079 bool _failures;
3080 public:
3081 // _vo == UsePrevMarking -> use "prev" marking information,
3082 // _vo == UseNextMarking -> use "next" marking information,
3083 // _vo == UseMarkWord -> use mark word from object header.
3084 VerifyRootsClosure(VerifyOption vo) :
3085 _g1h(G1CollectedHeap::heap()),
3086 _vo(vo),
3087 _failures(false) { }
3088
3089 bool failures() { return _failures; }
3090
3091 template <class T> void do_oop_nv(T* p) {
3092 T heap_oop = oopDesc::load_heap_oop(p);
3093 if (!oopDesc::is_null(heap_oop)) {
3094 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
3095 if (_g1h->is_obj_dead_cond(obj, _vo)) {
3096 gclog_or_tty->print_cr("Root location "PTR_FORMAT" "
3097 "points to dead obj "PTR_FORMAT, p, (void*) obj);
3098 if (_vo == VerifyOption_G1UseMarkWord) {
3099 gclog_or_tty->print_cr(" Mark word: "PTR_FORMAT, (void*)(obj->mark()));
3100 }
3101 obj->print_on(gclog_or_tty);
3102 _failures = true;
3103 }
3104 }
3105 }
3106
3107 void do_oop(oop* p) { do_oop_nv(p); }
3108 void do_oop(narrowOop* p) { do_oop_nv(p); }
3109 };
3110
3111 // This is the task used for parallel heap verification.
3112
3113 class G1ParVerifyTask: public AbstractGangTask {
3114 private:
3115 G1CollectedHeap* _g1h;
3116 VerifyOption _vo;
3117 bool _failures;
3118
3119 public:
3120 // _vo == UsePrevMarking -> use "prev" marking information,
3121 // _vo == UseNextMarking -> use "next" marking information,
3122 // _vo == UseMarkWord -> use mark word from object header.
3123 G1ParVerifyTask(G1CollectedHeap* g1h, VerifyOption vo) :
3124 AbstractGangTask("Parallel verify task"),
3125 _g1h(g1h),
3126 _vo(vo),
3127 _failures(false) { }
3128
3129 bool failures() {
3130 return _failures;
3131 }
3132
3133 void work(uint worker_id) {
3134 HandleMark hm;
3135 VerifyRegionClosure blk(true, _vo);
3136 _g1h->heap_region_par_iterate_chunked(&blk, worker_id,
3137 _g1h->workers()->active_workers(),
3138 HeapRegion::ParVerifyClaimValue);
3139 if (blk.failures()) {
3140 _failures = true;
3141 }
3142 }
3143 };
3144
3145 void G1CollectedHeap::verify(bool silent) {
3146 verify(silent, VerifyOption_G1UsePrevMarking);
3147 }
3148
3149 void G1CollectedHeap::verify(bool silent,
3150 VerifyOption vo) {
3151 if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) {
3152 if (!silent) { gclog_or_tty->print("Roots (excluding permgen) "); }
3153 VerifyRootsClosure rootsCl(vo);
3154
3155 assert(Thread::current()->is_VM_thread(),
3156 "Expected to be executed serially by the VM thread at this point");
3157
3158 CodeBlobToOopClosure blobsCl(&rootsCl, /*do_marking=*/ false);
3159
3160 // We apply the relevant closures to all the oops in the
3161 // system dictionary, the string table and the code cache.
3162 const int so = SO_AllClasses | SO_Strings | SO_CodeCache;
3163
3164 process_strong_roots(true, // activate StrongRootsScope
3165 true, // we set "collecting perm gen" to true,
3166 // so we don't reset the dirty cards in the perm gen.
3167 ScanningOption(so), // roots scanning options
3168 &rootsCl,
3169 &blobsCl,
3170 &rootsCl);
3171
3172 // If we're verifying after the marking phase of a Full GC then we can't
3173 // treat the perm gen as roots into the G1 heap. Some of the objects in
3174 // the perm gen may be dead and hence not marked. If one of these dead
3175 // objects is considered to be a root then we may end up with a false
3176 // "Root location <x> points to dead ob <y>" failure.
3177 if (vo != VerifyOption_G1UseMarkWord) {
3178 // Since we used "collecting_perm_gen" == true above, we will not have
3179 // checked the refs from perm into the G1-collected heap. We check those
3180 // references explicitly below. Whether the relevant cards are dirty
3181 // is checked further below in the rem set verification.
3182 if (!silent) { gclog_or_tty->print("Permgen roots "); }
3183 perm_gen()->oop_iterate(&rootsCl);
3184 }
3185 bool failures = rootsCl.failures();
3186
3187 if (vo != VerifyOption_G1UseMarkWord) {
3188 // If we're verifying during a full GC then the region sets
3189 // will have been torn down at the start of the GC. Therefore
3190 // verifying the region sets will fail. So we only verify
3191 // the region sets when not in a full GC.
3192 if (!silent) { gclog_or_tty->print("HeapRegionSets "); }
3193 verify_region_sets();
3194 }
3195
3196 if (!silent) { gclog_or_tty->print("HeapRegions "); }
3197 if (GCParallelVerificationEnabled && ParallelGCThreads > 1) {
3198 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3199 "sanity check");
3200
3201 G1ParVerifyTask task(this, vo);
3202 assert(UseDynamicNumberOfGCThreads ||
3203 workers()->active_workers() == workers()->total_workers(),
3204 "If not dynamic should be using all the workers");
3205 int n_workers = workers()->active_workers();
3206 set_par_threads(n_workers);
3207 workers()->run_task(&task);
3208 set_par_threads(0);
3209 if (task.failures()) {
3210 failures = true;
3211 }
3212
3213 // Checks that the expected amount of parallel work was done.
3214 // The implication is that n_workers is > 0.
3215 assert(check_heap_region_claim_values(HeapRegion::ParVerifyClaimValue),
3216 "sanity check");
3217
3218 reset_heap_region_claim_values();
3219
3220 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3221 "sanity check");
3222 } else {
3223 VerifyRegionClosure blk(false, vo);
3224 heap_region_iterate(&blk);
3225 if (blk.failures()) {
3226 failures = true;
3227 }
3228 }
3229 if (!silent) gclog_or_tty->print("RemSet ");
3230 rem_set()->verify();
3231
3232 if (failures) {
3233 gclog_or_tty->print_cr("Heap:");
3234 // It helps to have the per-region information in the output to
3235 // help us track down what went wrong. This is why we call
3236 // print_extended_on() instead of print_on().
3237 print_extended_on(gclog_or_tty);
3238 gclog_or_tty->print_cr("");
3239 #ifndef PRODUCT
3240 if (VerifyDuringGC && G1VerifyDuringGCPrintReachable) {
3241 concurrent_mark()->print_reachable("at-verification-failure",
3242 vo, false /* all */);
3243 }
3244 #endif
3245 gclog_or_tty->flush();
3246 }
3247 guarantee(!failures, "there should not have been any failures");
3248 } else {
3249 if (!silent) gclog_or_tty->print("(SKIPPING roots, heapRegions, remset) ");
3250 }
3251 }
3252
3253 class PrintRegionClosure: public HeapRegionClosure {
3254 outputStream* _st;
3255 public:
3256 PrintRegionClosure(outputStream* st) : _st(st) {}
3257 bool doHeapRegion(HeapRegion* r) {
3258 r->print_on(_st);
3259 return false;
3260 }
3261 };
3262
3263 void G1CollectedHeap::print_on(outputStream* st) const {
3264 st->print(" %-20s", "garbage-first heap");
3265 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
3266 capacity()/K, used_unlocked()/K);
3267 st->print(" [" INTPTR_FORMAT ", " INTPTR_FORMAT ", " INTPTR_FORMAT ")",
3268 _g1_storage.low_boundary(),
3269 _g1_storage.high(),
3270 _g1_storage.high_boundary());
3271 st->cr();
3272 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
3273 uint young_regions = _young_list->length();
3274 st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
3275 (size_t) young_regions * HeapRegion::GrainBytes / K);
3276 uint survivor_regions = g1_policy()->recorded_survivor_regions();
3277 st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
3278 (size_t) survivor_regions * HeapRegion::GrainBytes / K);
3279 st->cr();
3280 perm()->as_gen()->print_on(st);
3281 }
3282
3283 void G1CollectedHeap::print_extended_on(outputStream* st) const {
3284 print_on(st);
3285
3286 // Print the per-region information.
3287 st->cr();
3288 st->print_cr("Heap Regions: (Y=young(eden), SU=young(survivor), "
3289 "HS=humongous(starts), HC=humongous(continues), "
3290 "CS=collection set, F=free, TS=gc time stamp, "
3291 "PTAMS=previous top-at-mark-start, "
3292 "NTAMS=next top-at-mark-start)");
3293 PrintRegionClosure blk(st);
3294 heap_region_iterate(&blk);
3295 }
3296
3297 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
3298 if (G1CollectedHeap::use_parallel_gc_threads()) {
3299 workers()->print_worker_threads_on(st);
3300 }
3301 _cmThread->print_on(st);
3302 st->cr();
3303 _cm->print_worker_threads_on(st);
3304 _cg1r->print_worker_threads_on(st);
3305 st->cr();
3306 }
3307
3308 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
3309 if (G1CollectedHeap::use_parallel_gc_threads()) {
3310 workers()->threads_do(tc);
3311 }
3312 tc->do_thread(_cmThread);
3313 _cg1r->threads_do(tc);
3314 }
3315
3316 void G1CollectedHeap::print_tracing_info() const {
3317 // We'll overload this to mean "trace GC pause statistics."
3318 if (TraceGen0Time || TraceGen1Time) {
3319 // The "G1CollectorPolicy" is keeping track of these stats, so delegate
3320 // to that.
3321 g1_policy()->print_tracing_info();
3322 }
3323 if (G1SummarizeRSetStats) {
3324 g1_rem_set()->print_summary_info();
3325 }
3326 if (G1SummarizeConcMark) {
3327 concurrent_mark()->print_summary_info();
3328 }
3329 g1_policy()->print_yg_surv_rate_info();
3330 SpecializationStats::print();
3331 }
3332
3333 #ifndef PRODUCT
3334 // Helpful for debugging RSet issues.
3335
3336 class PrintRSetsClosure : public HeapRegionClosure {
3337 private:
3338 const char* _msg;
3339 size_t _occupied_sum;
3340
3341 public:
3342 bool doHeapRegion(HeapRegion* r) {
3343 HeapRegionRemSet* hrrs = r->rem_set();
3344 size_t occupied = hrrs->occupied();
3345 _occupied_sum += occupied;
3346
3347 gclog_or_tty->print_cr("Printing RSet for region "HR_FORMAT,
3348 HR_FORMAT_PARAMS(r));
3349 if (occupied == 0) {
3350 gclog_or_tty->print_cr(" RSet is empty");
3351 } else {
3352 hrrs->print();
3353 }
3354 gclog_or_tty->print_cr("----------");
3355 return false;
3356 }
3357
3358 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
3359 gclog_or_tty->cr();
3360 gclog_or_tty->print_cr("========================================");
3361 gclog_or_tty->print_cr(msg);
3362 gclog_or_tty->cr();
3363 }
3364
3365 ~PrintRSetsClosure() {
3366 gclog_or_tty->print_cr("Occupied Sum: "SIZE_FORMAT, _occupied_sum);
3367 gclog_or_tty->print_cr("========================================");
3368 gclog_or_tty->cr();
3369 }
3370 };
3371
3372 void G1CollectedHeap::print_cset_rsets() {
3373 PrintRSetsClosure cl("Printing CSet RSets");
3374 collection_set_iterate(&cl);
3375 }
3376
3377 void G1CollectedHeap::print_all_rsets() {
3378 PrintRSetsClosure cl("Printing All RSets");;
3379 heap_region_iterate(&cl);
3380 }
3381 #endif // PRODUCT
3382
3383 G1CollectedHeap* G1CollectedHeap::heap() {
3384 assert(_sh->kind() == CollectedHeap::G1CollectedHeap,
3385 "not a garbage-first heap");
3386 return _g1h;
3387 }
3388
3389 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) {
3390 // always_do_update_barrier = false;
3391 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
3392 // Call allocation profiler
3393 AllocationProfiler::iterate_since_last_gc();
3394 // Fill TLAB's and such
3395 ensure_parsability(true);
3396 }
3397
3398 void G1CollectedHeap::gc_epilogue(bool full /* Ignored */) {
3399 // FIXME: what is this about?
3400 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
3401 // is set.
3402 COMPILER2_PRESENT(assert(DerivedPointerTable::is_empty(),
3403 "derived pointer present"));
3404 // always_do_update_barrier = true;
3405
3406 // We have just completed a GC. Update the soft reference
3407 // policy with the new heap occupancy
3408 Universe::update_heap_info_at_gc();
3409 }
3410
3411 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
3412 unsigned int gc_count_before,
3413 bool* succeeded) {
3414 assert_heap_not_locked_and_not_at_safepoint();
3415 g1_policy()->record_stop_world_start();
3416 VM_G1IncCollectionPause op(gc_count_before,
3417 word_size,
3418 false, /* should_initiate_conc_mark */
3419 g1_policy()->max_pause_time_ms(),
3420 GCCause::_g1_inc_collection_pause);
3421 VMThread::execute(&op);
3422
3423 HeapWord* result = op.result();
3424 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
3425 assert(result == NULL || ret_succeeded,
3426 "the result should be NULL if the VM did not succeed");
3427 *succeeded = ret_succeeded;
3428
3429 assert_heap_not_locked();
3430 return result;
3431 }
3432
3433 void
3434 G1CollectedHeap::doConcurrentMark() {
3435 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
3436 if (!_cmThread->in_progress()) {
3437 _cmThread->set_started();
3438 CGC_lock->notify();
3439 }
3440 }
3441
3442 size_t G1CollectedHeap::pending_card_num() {
3443 size_t extra_cards = 0;
3444 JavaThread *curr = Threads::first();
3445 while (curr != NULL) {
3446 DirtyCardQueue& dcq = curr->dirty_card_queue();
3447 extra_cards += dcq.size();
3448 curr = curr->next();
3449 }
3450 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
3451 size_t buffer_size = dcqs.buffer_size();
3452 size_t buffer_num = dcqs.completed_buffers_num();
3453 return buffer_size * buffer_num + extra_cards;
3454 }
3455
3456 size_t G1CollectedHeap::max_pending_card_num() {
3457 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
3458 size_t buffer_size = dcqs.buffer_size();
3459 size_t buffer_num = dcqs.completed_buffers_num();
3460 int thread_num = Threads::number_of_threads();
3461 return (buffer_num + thread_num) * buffer_size;
3462 }
3463
3464 size_t G1CollectedHeap::cards_scanned() {
3465 return g1_rem_set()->cardsScanned();
3466 }
3467
3468 void
3469 G1CollectedHeap::setup_surviving_young_words() {
3470 assert(_surviving_young_words == NULL, "pre-condition");
3471 uint array_length = g1_policy()->young_cset_region_length();
3472 _surviving_young_words = NEW_C_HEAP_ARRAY(size_t, (size_t) array_length);
3473 if (_surviving_young_words == NULL) {
3474 vm_exit_out_of_memory(sizeof(size_t) * array_length,
3475 "Not enough space for young surv words summary.");
3476 }
3477 memset(_surviving_young_words, 0, (size_t) array_length * sizeof(size_t));
3478 #ifdef ASSERT
3479 for (uint i = 0; i < array_length; ++i) {
3480 assert( _surviving_young_words[i] == 0, "memset above" );
3481 }
3482 #endif // !ASSERT
3483 }
3484
3485 void
3486 G1CollectedHeap::update_surviving_young_words(size_t* surv_young_words) {
3487 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
3488 uint array_length = g1_policy()->young_cset_region_length();
3489 for (uint i = 0; i < array_length; ++i) {
3490 _surviving_young_words[i] += surv_young_words[i];
3491 }
3492 }
3493
3494 void
3495 G1CollectedHeap::cleanup_surviving_young_words() {
3496 guarantee( _surviving_young_words != NULL, "pre-condition" );
3497 FREE_C_HEAP_ARRAY(size_t, _surviving_young_words);
3498 _surviving_young_words = NULL;
3499 }
3500
3501 #ifdef ASSERT
3502 class VerifyCSetClosure: public HeapRegionClosure {
3503 public:
3504 bool doHeapRegion(HeapRegion* hr) {
3505 // Here we check that the CSet region's RSet is ready for parallel
3506 // iteration. The fields that we'll verify are only manipulated
3507 // when the region is part of a CSet and is collected. Afterwards,
3508 // we reset these fields when we clear the region's RSet (when the
3509 // region is freed) so they are ready when the region is
3510 // re-allocated. The only exception to this is if there's an
3511 // evacuation failure and instead of freeing the region we leave
3512 // it in the heap. In that case, we reset these fields during
3513 // evacuation failure handling.
3514 guarantee(hr->rem_set()->verify_ready_for_par_iteration(), "verification");
3515
3516 // Here's a good place to add any other checks we'd like to
3517 // perform on CSet regions.
3518 return false;
3519 }
3520 };
3521 #endif // ASSERT
3522
3523 #if TASKQUEUE_STATS
3524 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
3525 st->print_raw_cr("GC Task Stats");
3526 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
3527 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
3528 }
3529
3530 void G1CollectedHeap::print_taskqueue_stats(outputStream* const st) const {
3531 print_taskqueue_stats_hdr(st);
3532
3533 TaskQueueStats totals;
3534 const int n = workers() != NULL ? workers()->total_workers() : 1;
3535 for (int i = 0; i < n; ++i) {
3536 st->print("%3d ", i); task_queue(i)->stats.print(st); st->cr();
3537 totals += task_queue(i)->stats;
3538 }
3539 st->print_raw("tot "); totals.print(st); st->cr();
3540
3541 DEBUG_ONLY(totals.verify());
3542 }
3543
3544 void G1CollectedHeap::reset_taskqueue_stats() {
3545 const int n = workers() != NULL ? workers()->total_workers() : 1;
3546 for (int i = 0; i < n; ++i) {
3547 task_queue(i)->stats.reset();
3548 }
3549 }
3550 #endif // TASKQUEUE_STATS
3551
3552 bool
3553 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
3554 assert_at_safepoint(true /* should_be_vm_thread */);
3555 guarantee(!is_gc_active(), "collection is not reentrant");
3556
3557 if (GC_locker::check_active_before_gc()) {
3558 return false;
3559 }
3560
3561 SvcGCMarker sgcm(SvcGCMarker::MINOR);
3562 ResourceMark rm;
3563
3564 print_heap_before_gc();
3565
3566 HRSPhaseSetter x(HRSPhaseEvacuation);
3567 verify_region_sets_optional();
3568 verify_dirty_young_regions();
3569
3570 // This call will decide whether this pause is an initial-mark
3571 // pause. If it is, during_initial_mark_pause() will return true
3572 // for the duration of this pause.
3573 g1_policy()->decide_on_conc_mark_initiation();
3574
3575 // We do not allow initial-mark to be piggy-backed on a mixed GC.
3576 assert(!g1_policy()->during_initial_mark_pause() ||
3577 g1_policy()->gcs_are_young(), "sanity");
3578
3579 // We also do not allow mixed GCs during marking.
3580 assert(!mark_in_progress() || g1_policy()->gcs_are_young(), "sanity");
3581
3582 // Record whether this pause is an initial mark. When the current
3583 // thread has completed its logging output and it's safe to signal
3584 // the CM thread, the flag's value in the policy has been reset.
3585 bool should_start_conc_mark = g1_policy()->during_initial_mark_pause();
3586
3587 // Inner scope for scope based logging, timers, and stats collection
3588 {
3589 if (g1_policy()->during_initial_mark_pause()) {
3590 // We are about to start a marking cycle, so we increment the
3591 // full collection counter.
3592 increment_total_full_collections();
3593 }
3594 // if the log level is "finer" is on, we'll print long statistics information
3595 // in the collector policy code, so let's not print this as the output
3596 // is messy if we do.
3597 gclog_or_tty->date_stamp(G1Log::fine() && PrintGCDateStamps);
3598 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
3599
3600 GCCauseString gc_cause_str = GCCauseString("GC pause", gc_cause())
3601 .append(g1_policy()->gcs_are_young() ? " (young)" : " (mixed)")
3602 .append(g1_policy()->during_initial_mark_pause() ? " (initial-mark)" : "");
3603 TraceTime t(gc_cause_str, G1Log::fine() && !G1Log::finer(), true, gclog_or_tty);
3604
3605 TraceCollectorStats tcs(g1mm()->incremental_collection_counters());
3606 TraceMemoryManagerStats tms(false /* fullGC */, gc_cause());
3607
3608 // If the secondary_free_list is not empty, append it to the
3609 // free_list. No need to wait for the cleanup operation to finish;
3610 // the region allocation code will check the secondary_free_list
3611 // and wait if necessary. If the G1StressConcRegionFreeing flag is
3612 // set, skip this step so that the region allocation code has to
3613 // get entries from the secondary_free_list.
3614 if (!G1StressConcRegionFreeing) {
3615 append_secondary_free_list_if_not_empty_with_lock();
3616 }
3617
3618 assert(check_young_list_well_formed(),
3619 "young list should be well formed");
3620
3621 // Don't dynamically change the number of GC threads this early. A value of
3622 // 0 is used to indicate serial work. When parallel work is done,
3623 // it will be set.
3624
3625 { // Call to jvmpi::post_class_unload_events must occur outside of active GC
3626 IsGCActiveMark x;
3627
3628 gc_prologue(false);
3629 increment_total_collections(false /* full gc */);
3630 increment_gc_time_stamp();
3631
3632 if (VerifyBeforeGC && total_collections() >= VerifyGCStartAt) {
3633 HandleMark hm; // Discard invalid handles created during verification
3634 gclog_or_tty->print(" VerifyBeforeGC:");
3635 prepare_for_verify();
3636 Universe::verify(/* silent */ false,
3637 /* option */ VerifyOption_G1UsePrevMarking);
3638 }
3639
3640 COMPILER2_PRESENT(DerivedPointerTable::clear());
3641
3642 // Please see comment in g1CollectedHeap.hpp and
3643 // G1CollectedHeap::ref_processing_init() to see how
3644 // reference processing currently works in G1.
3645
3646 // Enable discovery in the STW reference processor
3647 ref_processor_stw()->enable_discovery(true /*verify_disabled*/,
3648 true /*verify_no_refs*/);
3649
3650 {
3651 // We want to temporarily turn off discovery by the
3652 // CM ref processor, if necessary, and turn it back on
3653 // on again later if we do. Using a scoped
3654 // NoRefDiscovery object will do this.
3655 NoRefDiscovery no_cm_discovery(ref_processor_cm());
3656
3657 // Forget the current alloc region (we might even choose it to be part
3658 // of the collection set!).
3659 release_mutator_alloc_region();
3660
3661 // We should call this after we retire the mutator alloc
3662 // region(s) so that all the ALLOC / RETIRE events are generated
3663 // before the start GC event.
3664 _hr_printer.start_gc(false /* full */, (size_t) total_collections());
3665
3666 // The elapsed time induced by the start time below deliberately elides
3667 // the possible verification above.
3668 double start_time_sec = os::elapsedTime();
3669 size_t start_used_bytes = used();
3670
3671 #if YOUNG_LIST_VERBOSE
3672 gclog_or_tty->print_cr("\nBefore recording pause start.\nYoung_list:");
3673 _young_list->print();
3674 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3675 #endif // YOUNG_LIST_VERBOSE
3676
3677 g1_policy()->record_collection_pause_start(start_time_sec,
3678 start_used_bytes);
3679
3680 double scan_wait_start = os::elapsedTime();
3681 // We have to wait until the CM threads finish scanning the
3682 // root regions as it's the only way to ensure that all the
3683 // objects on them have been correctly scanned before we start
3684 // moving them during the GC.
3685 bool waited = _cm->root_regions()->wait_until_scan_finished();
3686 if (waited) {
3687 double scan_wait_end = os::elapsedTime();
3688 double wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
3689 g1_policy()->record_root_region_scan_wait_time(wait_time_ms);
3690 }
3691
3692 #if YOUNG_LIST_VERBOSE
3693 gclog_or_tty->print_cr("\nAfter recording pause start.\nYoung_list:");
3694 _young_list->print();
3695 #endif // YOUNG_LIST_VERBOSE
3696
3697 if (g1_policy()->during_initial_mark_pause()) {
3698 concurrent_mark()->checkpointRootsInitialPre();
3699 }
3700 perm_gen()->save_marks();
3701
3702 #if YOUNG_LIST_VERBOSE
3703 gclog_or_tty->print_cr("\nBefore choosing collection set.\nYoung_list:");
3704 _young_list->print();
3705 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3706 #endif // YOUNG_LIST_VERBOSE
3707
3708 g1_policy()->finalize_cset(target_pause_time_ms);
3709
3710 _cm->note_start_of_gc();
3711 // We should not verify the per-thread SATB buffers given that
3712 // we have not filtered them yet (we'll do so during the
3713 // GC). We also call this after finalize_cset() to
3714 // ensure that the CSet has been finalized.
3715 _cm->verify_no_cset_oops(true /* verify_stacks */,
3716 true /* verify_enqueued_buffers */,
3717 false /* verify_thread_buffers */,
3718 true /* verify_fingers */);
3719
3720 if (_hr_printer.is_active()) {
3721 HeapRegion* hr = g1_policy()->collection_set();
3722 while (hr != NULL) {
3723 G1HRPrinter::RegionType type;
3724 if (!hr->is_young()) {
3725 type = G1HRPrinter::Old;
3726 } else if (hr->is_survivor()) {
3727 type = G1HRPrinter::Survivor;
3728 } else {
3729 type = G1HRPrinter::Eden;
3730 }
3731 _hr_printer.cset(hr);
3732 hr = hr->next_in_collection_set();
3733 }
3734 }
3735
3736 #ifdef ASSERT
3737 VerifyCSetClosure cl;
3738 collection_set_iterate(&cl);
3739 #endif // ASSERT
3740
3741 setup_surviving_young_words();
3742
3743 // Initialize the GC alloc regions.
3744 init_gc_alloc_regions();
3745
3746 // Actually do the work...
3747 evacuate_collection_set();
3748
3749 // We do this to mainly verify the per-thread SATB buffers
3750 // (which have been filtered by now) since we didn't verify
3751 // them earlier. No point in re-checking the stacks / enqueued
3752 // buffers given that the CSet has not changed since last time
3753 // we checked.
3754 _cm->verify_no_cset_oops(false /* verify_stacks */,
3755 false /* verify_enqueued_buffers */,
3756 true /* verify_thread_buffers */,
3757 true /* verify_fingers */);
3758
3759 free_collection_set(g1_policy()->collection_set());
3760 g1_policy()->clear_collection_set();
3761
3762 cleanup_surviving_young_words();
3763
3764 // Start a new incremental collection set for the next pause.
3765 g1_policy()->start_incremental_cset_building();
3766
3767 // Clear the _cset_fast_test bitmap in anticipation of adding
3768 // regions to the incremental collection set for the next
3769 // evacuation pause.
3770 clear_cset_fast_test();
3771
3772 _young_list->reset_sampled_info();
3773
3774 // Don't check the whole heap at this point as the
3775 // GC alloc regions from this pause have been tagged
3776 // as survivors and moved on to the survivor list.
3777 // Survivor regions will fail the !is_young() check.
3778 assert(check_young_list_empty(false /* check_heap */),
3779 "young list should be empty");
3780
3781 #if YOUNG_LIST_VERBOSE
3782 gclog_or_tty->print_cr("Before recording survivors.\nYoung List:");
3783 _young_list->print();
3784 #endif // YOUNG_LIST_VERBOSE
3785
3786 g1_policy()->record_survivor_regions(_young_list->survivor_length(),
3787 _young_list->first_survivor_region(),
3788 _young_list->last_survivor_region());
3789
3790 _young_list->reset_auxilary_lists();
3791
3792 if (evacuation_failed()) {
3793 _summary_bytes_used = recalculate_used();
3794 } else {
3795 // The "used" of the the collection set have already been subtracted
3796 // when they were freed. Add in the bytes evacuated.
3797 _summary_bytes_used += g1_policy()->bytes_copied_during_gc();
3798 }
3799
3800 if (g1_policy()->during_initial_mark_pause()) {
3801 // We have to do this before we notify the CM threads that
3802 // they can start working to make sure that all the
3803 // appropriate initialization is done on the CM object.
3804 concurrent_mark()->checkpointRootsInitialPost();
3805 set_marking_started();
3806 // Note that we don't actually trigger the CM thread at
3807 // this point. We do that later when we're sure that
3808 // the current thread has completed its logging output.
3809 }
3810
3811 allocate_dummy_regions();
3812
3813 #if YOUNG_LIST_VERBOSE
3814 gclog_or_tty->print_cr("\nEnd of the pause.\nYoung_list:");
3815 _young_list->print();
3816 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3817 #endif // YOUNG_LIST_VERBOSE
3818
3819 init_mutator_alloc_region();
3820
3821 {
3822 size_t expand_bytes = g1_policy()->expansion_amount();
3823 if (expand_bytes > 0) {
3824 size_t bytes_before = capacity();
3825 // No need for an ergo verbose message here,
3826 // expansion_amount() does this when it returns a value > 0.
3827 if (!expand(expand_bytes)) {
3828 // We failed to expand the heap so let's verify that
3829 // committed/uncommitted amount match the backing store
3830 assert(capacity() == _g1_storage.committed_size(), "committed size mismatch");
3831 assert(max_capacity() == _g1_storage.reserved_size(), "reserved size mismatch");
3832 }
3833 }
3834 }
3835
3836 // We redo the verificaiton but now wrt to the new CSet which
3837 // has just got initialized after the previous CSet was freed.
3838 _cm->verify_no_cset_oops(true /* verify_stacks */,
3839 true /* verify_enqueued_buffers */,
3840 true /* verify_thread_buffers */,
3841 true /* verify_fingers */);
3842 _cm->note_end_of_gc();
3843
3844 double end_time_sec = os::elapsedTime();
3845 double pause_time_ms = (end_time_sec - start_time_sec) * MILLIUNITS;
3846 g1_policy()->record_pause_time_ms(pause_time_ms);
3847 int active_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
3848 workers()->active_workers() : 1);
3849 g1_policy()->record_collection_pause_end(active_workers);
3850
3851 MemoryService::track_memory_usage();
3852
3853 // In prepare_for_verify() below we'll need to scan the deferred
3854 // update buffers to bring the RSets up-to-date if
3855 // G1HRRSFlushLogBuffersOnVerify has been set. While scanning
3856 // the update buffers we'll probably need to scan cards on the
3857 // regions we just allocated to (i.e., the GC alloc
3858 // regions). However, during the last GC we called
3859 // set_saved_mark() on all the GC alloc regions, so card
3860 // scanning might skip the [saved_mark_word()...top()] area of
3861 // those regions (i.e., the area we allocated objects into
3862 // during the last GC). But it shouldn't. Given that
3863 // saved_mark_word() is conditional on whether the GC time stamp
3864 // on the region is current or not, by incrementing the GC time
3865 // stamp here we invalidate all the GC time stamps on all the
3866 // regions and saved_mark_word() will simply return top() for
3867 // all the regions. This is a nicer way of ensuring this rather
3868 // than iterating over the regions and fixing them. In fact, the
3869 // GC time stamp increment here also ensures that
3870 // saved_mark_word() will return top() between pauses, i.e.,
3871 // during concurrent refinement. So we don't need the
3872 // is_gc_active() check to decided which top to use when
3873 // scanning cards (see CR 7039627).
3874 increment_gc_time_stamp();
3875
3876 if (VerifyAfterGC && total_collections() >= VerifyGCStartAt) {
3877 HandleMark hm; // Discard invalid handles created during verification
3878 gclog_or_tty->print(" VerifyAfterGC:");
3879 prepare_for_verify();
3880 Universe::verify(/* silent */ false,
3881 /* option */ VerifyOption_G1UsePrevMarking);
3882 }
3883
3884 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
3885 ref_processor_stw()->verify_no_references_recorded();
3886
3887 // CM reference discovery will be re-enabled if necessary.
3888 }
3889
3890 // We should do this after we potentially expand the heap so
3891 // that all the COMMIT events are generated before the end GC
3892 // event, and after we retire the GC alloc regions so that all
3893 // RETIRE events are generated before the end GC event.
3894 _hr_printer.end_gc(false /* full */, (size_t) total_collections());
3895
3896 // We have to do this after we decide whether to expand the heap or not.
3897 g1_policy()->print_heap_transition();
3898
3899 if (mark_in_progress()) {
3900 concurrent_mark()->update_g1_committed();
3901 }
3902
3903 #ifdef TRACESPINNING
3904 ParallelTaskTerminator::print_termination_counts();
3905 #endif
3906
3907 gc_epilogue(false);
3908 }
3909
3910 if (ExitAfterGCNum > 0 && total_collections() == ExitAfterGCNum) {
3911 gclog_or_tty->print_cr("Stopping after GC #%d", ExitAfterGCNum);
3912 print_tracing_info();
3913 vm_exit(-1);
3914 }
3915 }
3916
3917 // The closing of the inner scope, immediately above, will complete
3918 // logging at the "fine" level. The record_collection_pause_end() call
3919 // above will complete logging at the "finer" level.
3920 //
3921 // It is not yet to safe, however, to tell the concurrent mark to
3922 // start as we have some optional output below. We don't want the
3923 // output from the concurrent mark thread interfering with this
3924 // logging output either.
3925
3926 _hrs.verify_optional();
3927 verify_region_sets_optional();
3928
3929 TASKQUEUE_STATS_ONLY(if (ParallelGCVerbose) print_taskqueue_stats());
3930 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
3931
3932 print_heap_after_gc();
3933 g1mm()->update_sizes();
3934
3935 if (G1SummarizeRSetStats &&
3936 (G1SummarizeRSetStatsPeriod > 0) &&
3937 (total_collections() % G1SummarizeRSetStatsPeriod == 0)) {
3938 g1_rem_set()->print_summary_info();
3939 }
3940
3941 // It should now be safe to tell the concurrent mark thread to start
3942 // without its logging output interfering with the logging output
3943 // that came from the pause.
3944
3945 if (should_start_conc_mark) {
3946 // CAUTION: after the doConcurrentMark() call below,
3947 // the concurrent marking thread(s) could be running
3948 // concurrently with us. Make sure that anything after
3949 // this point does not assume that we are the only GC thread
3950 // running. Note: of course, the actual marking work will
3951 // not start until the safepoint itself is released in
3952 // ConcurrentGCThread::safepoint_desynchronize().
3953 doConcurrentMark();
3954 }
3955
3956 return true;
3957 }
3958
3959 size_t G1CollectedHeap::desired_plab_sz(GCAllocPurpose purpose)
3960 {
3961 size_t gclab_word_size;
3962 switch (purpose) {
3963 case GCAllocForSurvived:
3964 gclab_word_size = YoungPLABSize;
3965 break;
3966 case GCAllocForTenured:
3967 gclab_word_size = OldPLABSize;
3968 break;
3969 default:
3970 assert(false, "unknown GCAllocPurpose");
3971 gclab_word_size = OldPLABSize;
3972 break;
3973 }
3974 return gclab_word_size;
3975 }
3976
3977 void G1CollectedHeap::init_mutator_alloc_region() {
3978 assert(_mutator_alloc_region.get() == NULL, "pre-condition");
3979 _mutator_alloc_region.init();
3980 }
3981
3982 void G1CollectedHeap::release_mutator_alloc_region() {
3983 _mutator_alloc_region.release();
3984 assert(_mutator_alloc_region.get() == NULL, "post-condition");
3985 }
3986
3987 void G1CollectedHeap::init_gc_alloc_regions() {
3988 assert_at_safepoint(true /* should_be_vm_thread */);
3989
3990 _survivor_gc_alloc_region.init();
3991 _old_gc_alloc_region.init();
3992 HeapRegion* retained_region = _retained_old_gc_alloc_region;
3993 _retained_old_gc_alloc_region = NULL;
3994
3995 // We will discard the current GC alloc region if:
3996 // a) it's in the collection set (it can happen!),
3997 // b) it's already full (no point in using it),
3998 // c) it's empty (this means that it was emptied during
3999 // a cleanup and it should be on the free list now), or
4000 // d) it's humongous (this means that it was emptied
4001 // during a cleanup and was added to the free list, but
4002 // has been subseqently used to allocate a humongous
4003 // object that may be less than the region size).
4004 if (retained_region != NULL &&
4005 !retained_region->in_collection_set() &&
4006 !(retained_region->top() == retained_region->end()) &&
4007 !retained_region->is_empty() &&
4008 !retained_region->isHumongous()) {
4009 retained_region->set_saved_mark();
4010 // The retained region was added to the old region set when it was
4011 // retired. We have to remove it now, since we don't allow regions
4012 // we allocate to in the region sets. We'll re-add it later, when
4013 // it's retired again.
4014 _old_set.remove(retained_region);
4015 bool during_im = g1_policy()->during_initial_mark_pause();
4016 retained_region->note_start_of_copying(during_im);
4017 _old_gc_alloc_region.set(retained_region);
4018 _hr_printer.reuse(retained_region);
4019 }
4020 }
4021
4022 void G1CollectedHeap::release_gc_alloc_regions() {
4023 _survivor_gc_alloc_region.release();
4024 // If we have an old GC alloc region to release, we'll save it in
4025 // _retained_old_gc_alloc_region. If we don't
4026 // _retained_old_gc_alloc_region will become NULL. This is what we
4027 // want either way so no reason to check explicitly for either
4028 // condition.
4029 _retained_old_gc_alloc_region = _old_gc_alloc_region.release();
4030 }
4031
4032 void G1CollectedHeap::abandon_gc_alloc_regions() {
4033 assert(_survivor_gc_alloc_region.get() == NULL, "pre-condition");
4034 assert(_old_gc_alloc_region.get() == NULL, "pre-condition");
4035 _retained_old_gc_alloc_region = NULL;
4036 }
4037
4038 void G1CollectedHeap::init_for_evac_failure(OopsInHeapRegionClosure* cl) {
4039 _drain_in_progress = false;
4040 set_evac_failure_closure(cl);
4041 _evac_failure_scan_stack = new (ResourceObj::C_HEAP) GrowableArray<oop>(40, true);
4042 }
4043
4044 void G1CollectedHeap::finalize_for_evac_failure() {
4045 assert(_evac_failure_scan_stack != NULL &&
4046 _evac_failure_scan_stack->length() == 0,
4047 "Postcondition");
4048 assert(!_drain_in_progress, "Postcondition");
4049 delete _evac_failure_scan_stack;
4050 _evac_failure_scan_stack = NULL;
4051 }
4052
4053 void G1CollectedHeap::remove_self_forwarding_pointers() {
4054 assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity");
4055
4056 G1ParRemoveSelfForwardPtrsTask rsfp_task(this);
4057
4058 if (G1CollectedHeap::use_parallel_gc_threads()) {
4059 set_par_threads();
4060 workers()->run_task(&rsfp_task);
4061 set_par_threads(0);
4062 } else {
4063 rsfp_task.work(0);
4064 }
4065
4066 assert(check_cset_heap_region_claim_values(HeapRegion::ParEvacFailureClaimValue), "sanity");
4067
4068 // Reset the claim values in the regions in the collection set.
4069 reset_cset_heap_region_claim_values();
4070
4071 assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity");
4072
4073 // Now restore saved marks, if any.
4074 if (_objs_with_preserved_marks != NULL) {
4075 assert(_preserved_marks_of_objs != NULL, "Both or none.");
4076 guarantee(_objs_with_preserved_marks->length() ==
4077 _preserved_marks_of_objs->length(), "Both or none.");
4078 for (int i = 0; i < _objs_with_preserved_marks->length(); i++) {
4079 oop obj = _objs_with_preserved_marks->at(i);
4080 markOop m = _preserved_marks_of_objs->at(i);
4081 obj->set_mark(m);
4082 }
4083
4084 // Delete the preserved marks growable arrays (allocated on the C heap).
4085 delete _objs_with_preserved_marks;
4086 delete _preserved_marks_of_objs;
4087 _objs_with_preserved_marks = NULL;
4088 _preserved_marks_of_objs = NULL;
4089 }
4090 }
4091
4092 void G1CollectedHeap::push_on_evac_failure_scan_stack(oop obj) {
4093 _evac_failure_scan_stack->push(obj);
4094 }
4095
4096 void G1CollectedHeap::drain_evac_failure_scan_stack() {
4097 assert(_evac_failure_scan_stack != NULL, "precondition");
4098
4099 while (_evac_failure_scan_stack->length() > 0) {
4100 oop obj = _evac_failure_scan_stack->pop();
4101 _evac_failure_closure->set_region(heap_region_containing(obj));
4102 obj->oop_iterate_backwards(_evac_failure_closure);
4103 }
4104 }
4105
4106 oop
4107 G1CollectedHeap::handle_evacuation_failure_par(OopsInHeapRegionClosure* cl,
4108 oop old) {
4109 assert(obj_in_cs(old),
4110 err_msg("obj: "PTR_FORMAT" should still be in the CSet",
4111 (HeapWord*) old));
4112 markOop m = old->mark();
4113 oop forward_ptr = old->forward_to_atomic(old);
4114 if (forward_ptr == NULL) {
4115 // Forward-to-self succeeded.
4116
4117 if (_evac_failure_closure != cl) {
4118 MutexLockerEx x(EvacFailureStack_lock, Mutex::_no_safepoint_check_flag);
4119 assert(!_drain_in_progress,
4120 "Should only be true while someone holds the lock.");
4121 // Set the global evac-failure closure to the current thread's.
4122 assert(_evac_failure_closure == NULL, "Or locking has failed.");
4123 set_evac_failure_closure(cl);
4124 // Now do the common part.
4125 handle_evacuation_failure_common(old, m);
4126 // Reset to NULL.
4127 set_evac_failure_closure(NULL);
4128 } else {
4129 // The lock is already held, and this is recursive.
4130 assert(_drain_in_progress, "This should only be the recursive case.");
4131 handle_evacuation_failure_common(old, m);
4132 }
4133 return old;
4134 } else {
4135 // Forward-to-self failed. Either someone else managed to allocate
4136 // space for this object (old != forward_ptr) or they beat us in
4137 // self-forwarding it (old == forward_ptr).
4138 assert(old == forward_ptr || !obj_in_cs(forward_ptr),
4139 err_msg("obj: "PTR_FORMAT" forwarded to: "PTR_FORMAT" "
4140 "should not be in the CSet",
4141 (HeapWord*) old, (HeapWord*) forward_ptr));
4142 return forward_ptr;
4143 }
4144 }
4145
4146 void G1CollectedHeap::handle_evacuation_failure_common(oop old, markOop m) {
4147 set_evacuation_failed(true);
4148
4149 preserve_mark_if_necessary(old, m);
4150
4151 HeapRegion* r = heap_region_containing(old);
4152 if (!r->evacuation_failed()) {
4153 r->set_evacuation_failed(true);
4154 _hr_printer.evac_failure(r);
4155 }
4156
4157 push_on_evac_failure_scan_stack(old);
4158
4159 if (!_drain_in_progress) {
4160 // prevent recursion in copy_to_survivor_space()
4161 _drain_in_progress = true;
4162 drain_evac_failure_scan_stack();
4163 _drain_in_progress = false;
4164 }
4165 }
4166
4167 void G1CollectedHeap::preserve_mark_if_necessary(oop obj, markOop m) {
4168 assert(evacuation_failed(), "Oversaving!");
4169 // We want to call the "for_promotion_failure" version only in the
4170 // case of a promotion failure.
4171 if (m->must_be_preserved_for_promotion_failure(obj)) {
4172 if (_objs_with_preserved_marks == NULL) {
4173 assert(_preserved_marks_of_objs == NULL, "Both or none.");
4174 _objs_with_preserved_marks =
4175 new (ResourceObj::C_HEAP) GrowableArray<oop>(40, true);
4176 _preserved_marks_of_objs =
4177 new (ResourceObj::C_HEAP) GrowableArray<markOop>(40, true);
4178 }
4179 _objs_with_preserved_marks->push(obj);
4180 _preserved_marks_of_objs->push(m);
4181 }
4182 }
4183
4184 HeapWord* G1CollectedHeap::par_allocate_during_gc(GCAllocPurpose purpose,
4185 size_t word_size) {
4186 if (purpose == GCAllocForSurvived) {
4187 HeapWord* result = survivor_attempt_allocation(word_size);
4188 if (result != NULL) {
4189 return result;
4190 } else {
4191 // Let's try to allocate in the old gen in case we can fit the
4192 // object there.
4193 return old_attempt_allocation(word_size);
4194 }
4195 } else {
4196 assert(purpose == GCAllocForTenured, "sanity");
4197 HeapWord* result = old_attempt_allocation(word_size);
4198 if (result != NULL) {
4199 return result;
4200 } else {
4201 // Let's try to allocate in the survivors in case we can fit the
4202 // object there.
4203 return survivor_attempt_allocation(word_size);
4204 }
4205 }
4206
4207 ShouldNotReachHere();
4208 // Trying to keep some compilers happy.
4209 return NULL;
4210 }
4211
4212 G1ParGCAllocBuffer::G1ParGCAllocBuffer(size_t gclab_word_size) :
4213 ParGCAllocBuffer(gclab_word_size), _retired(false) { }
4214
4215 G1ParScanThreadState::G1ParScanThreadState(G1CollectedHeap* g1h, uint queue_num)
4216 : _g1h(g1h),
4217 _refs(g1h->task_queue(queue_num)),
4218 _dcq(&g1h->dirty_card_queue_set()),
4219 _ct_bs((CardTableModRefBS*)_g1h->barrier_set()),
4220 _g1_rem(g1h->g1_rem_set()),
4221 _hash_seed(17), _queue_num(queue_num),
4222 _term_attempts(0),
4223 _surviving_alloc_buffer(g1h->desired_plab_sz(GCAllocForSurvived)),
4224 _tenured_alloc_buffer(g1h->desired_plab_sz(GCAllocForTenured)),
4225 _age_table(false),
4226 _strong_roots_time(0), _term_time(0),
4227 _alloc_buffer_waste(0), _undo_waste(0) {
4228 // we allocate G1YoungSurvRateNumRegions plus one entries, since
4229 // we "sacrifice" entry 0 to keep track of surviving bytes for
4230 // non-young regions (where the age is -1)
4231 // We also add a few elements at the beginning and at the end in
4232 // an attempt to eliminate cache contention
4233 uint real_length = 1 + _g1h->g1_policy()->young_cset_region_length();
4234 uint array_length = PADDING_ELEM_NUM +
4235 real_length +
4236 PADDING_ELEM_NUM;
4237 _surviving_young_words_base = NEW_C_HEAP_ARRAY(size_t, array_length);
4238 if (_surviving_young_words_base == NULL)
4239 vm_exit_out_of_memory(array_length * sizeof(size_t),
4240 "Not enough space for young surv histo.");
4241 _surviving_young_words = _surviving_young_words_base + PADDING_ELEM_NUM;
4242 memset(_surviving_young_words, 0, (size_t) real_length * sizeof(size_t));
4243
4244 _alloc_buffers[GCAllocForSurvived] = &_surviving_alloc_buffer;
4245 _alloc_buffers[GCAllocForTenured] = &_tenured_alloc_buffer;
4246
4247 _start = os::elapsedTime();
4248 }
4249
4250 void
4251 G1ParScanThreadState::print_termination_stats_hdr(outputStream* const st)
4252 {
4253 st->print_raw_cr("GC Termination Stats");
4254 st->print_raw_cr(" elapsed --strong roots-- -------termination-------"
4255 " ------waste (KiB)------");
4256 st->print_raw_cr("thr ms ms % ms % attempts"
4257 " total alloc undo");
4258 st->print_raw_cr("--- --------- --------- ------ --------- ------ --------"
4259 " ------- ------- -------");
4260 }
4261
4262 void
4263 G1ParScanThreadState::print_termination_stats(int i,
4264 outputStream* const st) const
4265 {
4266 const double elapsed_ms = elapsed_time() * 1000.0;
4267 const double s_roots_ms = strong_roots_time() * 1000.0;
4268 const double term_ms = term_time() * 1000.0;
4269 st->print_cr("%3d %9.2f %9.2f %6.2f "
4270 "%9.2f %6.2f " SIZE_FORMAT_W(8) " "
4271 SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7),
4272 i, elapsed_ms, s_roots_ms, s_roots_ms * 100 / elapsed_ms,
4273 term_ms, term_ms * 100 / elapsed_ms, term_attempts(),
4274 (alloc_buffer_waste() + undo_waste()) * HeapWordSize / K,
4275 alloc_buffer_waste() * HeapWordSize / K,
4276 undo_waste() * HeapWordSize / K);
4277 }
4278
4279 #ifdef ASSERT
4280 bool G1ParScanThreadState::verify_ref(narrowOop* ref) const {
4281 assert(ref != NULL, "invariant");
4282 assert(UseCompressedOops, "sanity");
4283 assert(!has_partial_array_mask(ref), err_msg("ref=" PTR_FORMAT, ref));
4284 oop p = oopDesc::load_decode_heap_oop(ref);
4285 assert(_g1h->is_in_g1_reserved(p),
4286 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p)));
4287 return true;
4288 }
4289
4290 bool G1ParScanThreadState::verify_ref(oop* ref) const {
4291 assert(ref != NULL, "invariant");
4292 if (has_partial_array_mask(ref)) {
4293 // Must be in the collection set--it's already been copied.
4294 oop p = clear_partial_array_mask(ref);
4295 assert(_g1h->obj_in_cs(p),
4296 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p)));
4297 } else {
4298 oop p = oopDesc::load_decode_heap_oop(ref);
4299 assert(_g1h->is_in_g1_reserved(p),
4300 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p)));
4301 }
4302 return true;
4303 }
4304
4305 bool G1ParScanThreadState::verify_task(StarTask ref) const {
4306 if (ref.is_narrow()) {
4307 return verify_ref((narrowOop*) ref);
4308 } else {
4309 return verify_ref((oop*) ref);
4310 }
4311 }
4312 #endif // ASSERT
4313
4314 void G1ParScanThreadState::trim_queue() {
4315 assert(_evac_cl != NULL, "not set");
4316 assert(_evac_failure_cl != NULL, "not set");
4317 assert(_partial_scan_cl != NULL, "not set");
4318
4319 StarTask ref;
4320 do {
4321 // Drain the overflow stack first, so other threads can steal.
4322 while (refs()->pop_overflow(ref)) {
4323 deal_with_reference(ref);
4324 }
4325
4326 while (refs()->pop_local(ref)) {
4327 deal_with_reference(ref);
4328 }
4329 } while (!refs()->is_empty());
4330 }
4331
4332 G1ParClosureSuper::G1ParClosureSuper(G1CollectedHeap* g1,
4333 G1ParScanThreadState* par_scan_state) :
4334 _g1(g1), _g1_rem(_g1->g1_rem_set()), _cm(_g1->concurrent_mark()),
4335 _par_scan_state(par_scan_state),
4336 _worker_id(par_scan_state->queue_num()),
4337 _during_initial_mark(_g1->g1_policy()->during_initial_mark_pause()),
4338 _mark_in_progress(_g1->mark_in_progress()) { }
4339
4340 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object>
4341 void G1ParCopyClosure<do_gen_barrier, barrier, do_mark_object>::mark_object(oop obj) {
4342 #ifdef ASSERT
4343 HeapRegion* hr = _g1->heap_region_containing(obj);
4344 assert(hr != NULL, "sanity");
4345 assert(!hr->in_collection_set(), "should not mark objects in the CSet");
4346 #endif // ASSERT
4347
4348 // We know that the object is not moving so it's safe to read its size.
4349 _cm->grayRoot(obj, (size_t) obj->size(), _worker_id);
4350 }
4351
4352 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object>
4353 void G1ParCopyClosure<do_gen_barrier, barrier, do_mark_object>
4354 ::mark_forwarded_object(oop from_obj, oop to_obj) {
4355 #ifdef ASSERT
4356 assert(from_obj->is_forwarded(), "from obj should be forwarded");
4357 assert(from_obj->forwardee() == to_obj, "to obj should be the forwardee");
4358 assert(from_obj != to_obj, "should not be self-forwarded");
4359
4360 HeapRegion* from_hr = _g1->heap_region_containing(from_obj);
4361 assert(from_hr != NULL, "sanity");
4362 assert(from_hr->in_collection_set(), "from obj should be in the CSet");
4363
4364 HeapRegion* to_hr = _g1->heap_region_containing(to_obj);
4365 assert(to_hr != NULL, "sanity");
4366 assert(!to_hr->in_collection_set(), "should not mark objects in the CSet");
4367 #endif // ASSERT
4368
4369 // The object might be in the process of being copied by another
4370 // worker so we cannot trust that its to-space image is
4371 // well-formed. So we have to read its size from its from-space
4372 // image which we know should not be changing.
4373 _cm->grayRoot(to_obj, (size_t) from_obj->size(), _worker_id);
4374 }
4375
4376 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object>
4377 oop G1ParCopyClosure<do_gen_barrier, barrier, do_mark_object>
4378 ::copy_to_survivor_space(oop old) {
4379 size_t word_sz = old->size();
4380 HeapRegion* from_region = _g1->heap_region_containing_raw(old);
4381 // +1 to make the -1 indexes valid...
4382 int young_index = from_region->young_index_in_cset()+1;
4383 assert( (from_region->is_young() && young_index > 0) ||
4384 (!from_region->is_young() && young_index == 0), "invariant" );
4385 G1CollectorPolicy* g1p = _g1->g1_policy();
4386 markOop m = old->mark();
4387 int age = m->has_displaced_mark_helper() ? m->displaced_mark_helper()->age()
4388 : m->age();
4389 GCAllocPurpose alloc_purpose = g1p->evacuation_destination(from_region, age,
4390 word_sz);
4391 HeapWord* obj_ptr = _par_scan_state->allocate(alloc_purpose, word_sz);
4392 oop obj = oop(obj_ptr);
4393
4394 if (obj_ptr == NULL) {
4395 // This will either forward-to-self, or detect that someone else has
4396 // installed a forwarding pointer.
4397 OopsInHeapRegionClosure* cl = _par_scan_state->evac_failure_closure();
4398 return _g1->handle_evacuation_failure_par(cl, old);
4399 }
4400
4401 // We're going to allocate linearly, so might as well prefetch ahead.
4402 Prefetch::write(obj_ptr, PrefetchCopyIntervalInBytes);
4403
4404 oop forward_ptr = old->forward_to_atomic(obj);
4405 if (forward_ptr == NULL) {
4406 Copy::aligned_disjoint_words((HeapWord*) old, obj_ptr, word_sz);
4407 if (g1p->track_object_age(alloc_purpose)) {
4408 // We could simply do obj->incr_age(). However, this causes a
4409 // performance issue. obj->incr_age() will first check whether
4410 // the object has a displaced mark by checking its mark word;
4411 // getting the mark word from the new location of the object
4412 // stalls. So, given that we already have the mark word and we
4413 // are about to install it anyway, it's better to increase the
4414 // age on the mark word, when the object does not have a
4415 // displaced mark word. We're not expecting many objects to have
4416 // a displaced marked word, so that case is not optimized
4417 // further (it could be...) and we simply call obj->incr_age().
4418
4419 if (m->has_displaced_mark_helper()) {
4420 // in this case, we have to install the mark word first,
4421 // otherwise obj looks to be forwarded (the old mark word,
4422 // which contains the forward pointer, was copied)
4423 obj->set_mark(m);
4424 obj->incr_age();
4425 } else {
4426 m = m->incr_age();
4427 obj->set_mark(m);
4428 }
4429 _par_scan_state->age_table()->add(obj, word_sz);
4430 } else {
4431 obj->set_mark(m);
4432 }
4433
4434 size_t* surv_young_words = _par_scan_state->surviving_young_words();
4435 surv_young_words[young_index] += word_sz;
4436
4437 if (obj->is_objArray() && arrayOop(obj)->length() >= ParGCArrayScanChunk) {
4438 // We keep track of the next start index in the length field of
4439 // the to-space object. The actual length can be found in the
4440 // length field of the from-space object.
4441 arrayOop(obj)->set_length(0);
4442 oop* old_p = set_partial_array_mask(old);
4443 _par_scan_state->push_on_queue(old_p);
4444 } else {
4445 // No point in using the slower heap_region_containing() method,
4446 // given that we know obj is in the heap.
4447 _scanner.set_region(_g1->heap_region_containing_raw(obj));
4448 obj->oop_iterate_backwards(&_scanner);
4449 }
4450 } else {
4451 _par_scan_state->undo_allocation(alloc_purpose, obj_ptr, word_sz);
4452 obj = forward_ptr;
4453 }
4454 return obj;
4455 }
4456
4457 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object>
4458 template <class T>
4459 void G1ParCopyClosure<do_gen_barrier, barrier, do_mark_object>
4460 ::do_oop_work(T* p) {
4461 oop obj = oopDesc::load_decode_heap_oop(p);
4462 assert(barrier != G1BarrierRS || obj != NULL,
4463 "Precondition: G1BarrierRS implies obj is non-NULL");
4464
4465 assert(_worker_id == _par_scan_state->queue_num(), "sanity");
4466
4467 // here the null check is implicit in the cset_fast_test() test
4468 if (_g1->in_cset_fast_test(obj)) {
4469 oop forwardee;
4470 if (obj->is_forwarded()) {
4471 forwardee = obj->forwardee();
4472 } else {
4473 forwardee = copy_to_survivor_space(obj);
4474 }
4475 assert(forwardee != NULL, "forwardee should not be NULL");
4476 oopDesc::encode_store_heap_oop(p, forwardee);
4477 if (do_mark_object && forwardee != obj) {
4478 // If the object is self-forwarded we don't need to explicitly
4479 // mark it, the evacuation failure protocol will do so.
4480 mark_forwarded_object(obj, forwardee);
4481 }
4482
4483 // When scanning the RS, we only care about objs in CS.
4484 if (barrier == G1BarrierRS) {
4485 _par_scan_state->update_rs(_from, p, _worker_id);
4486 }
4487 } else {
4488 // The object is not in collection set. If we're a root scanning
4489 // closure during an initial mark pause (i.e. do_mark_object will
4490 // be true) then attempt to mark the object.
4491 if (do_mark_object && _g1->is_in_g1_reserved(obj)) {
4492 mark_object(obj);
4493 }
4494 }
4495
4496 if (barrier == G1BarrierEvac && obj != NULL) {
4497 _par_scan_state->update_rs(_from, p, _worker_id);
4498 }
4499
4500 if (do_gen_barrier && obj != NULL) {
4501 par_do_barrier(p);
4502 }
4503 }
4504
4505 template void G1ParCopyClosure<false, G1BarrierEvac, false>::do_oop_work(oop* p);
4506 template void G1ParCopyClosure<false, G1BarrierEvac, false>::do_oop_work(narrowOop* p);
4507
4508 template <class T> void G1ParScanPartialArrayClosure::do_oop_nv(T* p) {
4509 assert(has_partial_array_mask(p), "invariant");
4510 oop from_obj = clear_partial_array_mask(p);
4511
4512 assert(Universe::heap()->is_in_reserved(from_obj), "must be in heap.");
4513 assert(from_obj->is_objArray(), "must be obj array");
4514 objArrayOop from_obj_array = objArrayOop(from_obj);
4515 // The from-space object contains the real length.
4516 int length = from_obj_array->length();
4517
4518 assert(from_obj->is_forwarded(), "must be forwarded");
4519 oop to_obj = from_obj->forwardee();
4520 assert(from_obj != to_obj, "should not be chunking self-forwarded objects");
4521 objArrayOop to_obj_array = objArrayOop(to_obj);
4522 // We keep track of the next start index in the length field of the
4523 // to-space object.
4524 int next_index = to_obj_array->length();
4525 assert(0 <= next_index && next_index < length,
4526 err_msg("invariant, next index: %d, length: %d", next_index, length));
4527
4528 int start = next_index;
4529 int end = length;
4530 int remainder = end - start;
4531 // We'll try not to push a range that's smaller than ParGCArrayScanChunk.
4532 if (remainder > 2 * ParGCArrayScanChunk) {
4533 end = start + ParGCArrayScanChunk;
4534 to_obj_array->set_length(end);
4535 // Push the remainder before we process the range in case another
4536 // worker has run out of things to do and can steal it.
4537 oop* from_obj_p = set_partial_array_mask(from_obj);
4538 _par_scan_state->push_on_queue(from_obj_p);
4539 } else {
4540 assert(length == end, "sanity");
4541 // We'll process the final range for this object. Restore the length
4542 // so that the heap remains parsable in case of evacuation failure.
4543 to_obj_array->set_length(end);
4544 }
4545 _scanner.set_region(_g1->heap_region_containing_raw(to_obj));
4546 // Process indexes [start,end). It will also process the header
4547 // along with the first chunk (i.e., the chunk with start == 0).
4548 // Note that at this point the length field of to_obj_array is not
4549 // correct given that we are using it to keep track of the next
4550 // start index. oop_iterate_range() (thankfully!) ignores the length
4551 // field and only relies on the start / end parameters. It does
4552 // however return the size of the object which will be incorrect. So
4553 // we have to ignore it even if we wanted to use it.
4554 to_obj_array->oop_iterate_range(&_scanner, start, end);
4555 }
4556
4557 class G1ParEvacuateFollowersClosure : public VoidClosure {
4558 protected:
4559 G1CollectedHeap* _g1h;
4560 G1ParScanThreadState* _par_scan_state;
4561 RefToScanQueueSet* _queues;
4562 ParallelTaskTerminator* _terminator;
4563
4564 G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
4565 RefToScanQueueSet* queues() { return _queues; }
4566 ParallelTaskTerminator* terminator() { return _terminator; }
4567
4568 public:
4569 G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h,
4570 G1ParScanThreadState* par_scan_state,
4571 RefToScanQueueSet* queues,
4572 ParallelTaskTerminator* terminator)
4573 : _g1h(g1h), _par_scan_state(par_scan_state),
4574 _queues(queues), _terminator(terminator) {}
4575
4576 void do_void();
4577
4578 private:
4579 inline bool offer_termination();
4580 };
4581
4582 bool G1ParEvacuateFollowersClosure::offer_termination() {
4583 G1ParScanThreadState* const pss = par_scan_state();
4584 pss->start_term_time();
4585 const bool res = terminator()->offer_termination();
4586 pss->end_term_time();
4587 return res;
4588 }
4589
4590 void G1ParEvacuateFollowersClosure::do_void() {
4591 StarTask stolen_task;
4592 G1ParScanThreadState* const pss = par_scan_state();
4593 pss->trim_queue();
4594
4595 do {
4596 while (queues()->steal(pss->queue_num(), pss->hash_seed(), stolen_task)) {
4597 assert(pss->verify_task(stolen_task), "sanity");
4598 if (stolen_task.is_narrow()) {
4599 pss->deal_with_reference((narrowOop*) stolen_task);
4600 } else {
4601 pss->deal_with_reference((oop*) stolen_task);
4602 }
4603
4604 // We've just processed a reference and we might have made
4605 // available new entries on the queues. So we have to make sure
4606 // we drain the queues as necessary.
4607 pss->trim_queue();
4608 }
4609 } while (!offer_termination());
4610
4611 pss->retire_alloc_buffers();
4612 }
4613
4614 class G1ParTask : public AbstractGangTask {
4615 protected:
4616 G1CollectedHeap* _g1h;
4617 RefToScanQueueSet *_queues;
4618 ParallelTaskTerminator _terminator;
4619 uint _n_workers;
4620
4621 Mutex _stats_lock;
4622 Mutex* stats_lock() { return &_stats_lock; }
4623
4624 size_t getNCards() {
4625 return (_g1h->capacity() + G1BlockOffsetSharedArray::N_bytes - 1)
4626 / G1BlockOffsetSharedArray::N_bytes;
4627 }
4628
4629 public:
4630 G1ParTask(G1CollectedHeap* g1h,
4631 RefToScanQueueSet *task_queues)
4632 : AbstractGangTask("G1 collection"),
4633 _g1h(g1h),
4634 _queues(task_queues),
4635 _terminator(0, _queues),
4636 _stats_lock(Mutex::leaf, "parallel G1 stats lock", true)
4637 {}
4638
4639 RefToScanQueueSet* queues() { return _queues; }
4640
4641 RefToScanQueue *work_queue(int i) {
4642 return queues()->queue(i);
4643 }
4644
4645 ParallelTaskTerminator* terminator() { return &_terminator; }
4646
4647 virtual void set_for_termination(int active_workers) {
4648 // This task calls set_n_termination() in par_non_clean_card_iterate_work()
4649 // in the young space (_par_seq_tasks) in the G1 heap
4650 // for SequentialSubTasksDone.
4651 // This task also uses SubTasksDone in SharedHeap and G1CollectedHeap
4652 // both of which need setting by set_n_termination().
4653 _g1h->SharedHeap::set_n_termination(active_workers);
4654 _g1h->set_n_termination(active_workers);
4655 terminator()->reset_for_reuse(active_workers);
4656 _n_workers = active_workers;
4657 }
4658
4659 void work(uint worker_id) {
4660 if (worker_id >= _n_workers) return; // no work needed this round
4661
4662 double start_time_ms = os::elapsedTime() * 1000.0;
4663 _g1h->g1_policy()->record_gc_worker_start_time(worker_id, start_time_ms);
4664
4665 {
4666 ResourceMark rm;
4667 HandleMark hm;
4668
4669 ReferenceProcessor* rp = _g1h->ref_processor_stw();
4670
4671 G1ParScanThreadState pss(_g1h, worker_id);
4672 G1ParScanHeapEvacClosure scan_evac_cl(_g1h, &pss, rp);
4673 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, rp);
4674 G1ParScanPartialArrayClosure partial_scan_cl(_g1h, &pss, rp);
4675
4676 pss.set_evac_closure(&scan_evac_cl);
4677 pss.set_evac_failure_closure(&evac_failure_cl);
4678 pss.set_partial_scan_closure(&partial_scan_cl);
4679
4680 G1ParScanExtRootClosure only_scan_root_cl(_g1h, &pss, rp);
4681 G1ParScanPermClosure only_scan_perm_cl(_g1h, &pss, rp);
4682
4683 G1ParScanAndMarkExtRootClosure scan_mark_root_cl(_g1h, &pss, rp);
4684 G1ParScanAndMarkPermClosure scan_mark_perm_cl(_g1h, &pss, rp);
4685
4686 OopClosure* scan_root_cl = &only_scan_root_cl;
4687 OopsInHeapRegionClosure* scan_perm_cl = &only_scan_perm_cl;
4688
4689 if (_g1h->g1_policy()->during_initial_mark_pause()) {
4690 // We also need to mark copied objects.
4691 scan_root_cl = &scan_mark_root_cl;
4692 scan_perm_cl = &scan_mark_perm_cl;
4693 }
4694
4695 G1ParPushHeapRSClosure push_heap_rs_cl(_g1h, &pss);
4696
4697 pss.start_strong_roots();
4698 _g1h->g1_process_strong_roots(/* not collecting perm */ false,
4699 SharedHeap::SO_AllClasses,
4700 scan_root_cl,
4701 &push_heap_rs_cl,
4702 scan_perm_cl,
4703 worker_id);
4704 pss.end_strong_roots();
4705
4706 {
4707 double start = os::elapsedTime();
4708 G1ParEvacuateFollowersClosure evac(_g1h, &pss, _queues, &_terminator);
4709 evac.do_void();
4710 double elapsed_ms = (os::elapsedTime()-start)*1000.0;
4711 double term_ms = pss.term_time()*1000.0;
4712 _g1h->g1_policy()->record_obj_copy_time(worker_id, elapsed_ms-term_ms);
4713 _g1h->g1_policy()->record_termination(worker_id, term_ms, pss.term_attempts());
4714 }
4715 _g1h->g1_policy()->record_thread_age_table(pss.age_table());
4716 _g1h->update_surviving_young_words(pss.surviving_young_words()+1);
4717
4718 // Clean up any par-expanded rem sets.
4719 HeapRegionRemSet::par_cleanup();
4720
4721 if (ParallelGCVerbose) {
4722 MutexLocker x(stats_lock());
4723 pss.print_termination_stats(worker_id);
4724 }
4725
4726 assert(pss.refs()->is_empty(), "should be empty");
4727
4728 // Close the inner scope so that the ResourceMark and HandleMark
4729 // destructors are executed here and are included as part of the
4730 // "GC Worker Time".
4731 }
4732
4733 double end_time_ms = os::elapsedTime() * 1000.0;
4734 _g1h->g1_policy()->record_gc_worker_end_time(worker_id, end_time_ms);
4735 }
4736 };
4737
4738 // *** Common G1 Evacuation Stuff
4739
4740 // Closures that support the filtering of CodeBlobs scanned during
4741 // external root scanning.
4742
4743 // Closure applied to reference fields in code blobs (specifically nmethods)
4744 // to determine whether an nmethod contains references that point into
4745 // the collection set. Used as a predicate when walking code roots so
4746 // that only nmethods that point into the collection set are added to the
4747 // 'marked' list.
4748
4749 class G1FilteredCodeBlobToOopClosure : public CodeBlobToOopClosure {
4750
4751 class G1PointsIntoCSOopClosure : public OopClosure {
4752 G1CollectedHeap* _g1;
4753 bool _points_into_cs;
4754 public:
4755 G1PointsIntoCSOopClosure(G1CollectedHeap* g1) :
4756 _g1(g1), _points_into_cs(false) { }
4757
4758 bool points_into_cs() const { return _points_into_cs; }
4759
4760 template <class T>
4761 void do_oop_nv(T* p) {
4762 if (!_points_into_cs) {
4763 T heap_oop = oopDesc::load_heap_oop(p);
4764 if (!oopDesc::is_null(heap_oop) &&
4765 _g1->in_cset_fast_test(oopDesc::decode_heap_oop_not_null(heap_oop))) {
4766 _points_into_cs = true;
4767 }
4768 }
4769 }
4770
4771 virtual void do_oop(oop* p) { do_oop_nv(p); }
4772 virtual void do_oop(narrowOop* p) { do_oop_nv(p); }
4773 };
4774
4775 G1CollectedHeap* _g1;
4776
4777 public:
4778 G1FilteredCodeBlobToOopClosure(G1CollectedHeap* g1, OopClosure* cl) :
4779 CodeBlobToOopClosure(cl, true), _g1(g1) { }
4780
4781 virtual void do_code_blob(CodeBlob* cb) {
4782 nmethod* nm = cb->as_nmethod_or_null();
4783 if (nm != NULL && !(nm->test_oops_do_mark())) {
4784 G1PointsIntoCSOopClosure predicate_cl(_g1);
4785 nm->oops_do(&predicate_cl);
4786
4787 if (predicate_cl.points_into_cs()) {
4788 // At least one of the reference fields or the oop relocations
4789 // in the nmethod points into the collection set. We have to
4790 // 'mark' this nmethod.
4791 // Note: Revisit the following if CodeBlobToOopClosure::do_code_blob()
4792 // or MarkingCodeBlobClosure::do_code_blob() change.
4793 if (!nm->test_set_oops_do_mark()) {
4794 do_newly_marked_nmethod(nm);
4795 }
4796 }
4797 }
4798 }
4799 };
4800
4801 // This method is run in a GC worker.
4802
4803 void
4804 G1CollectedHeap::
4805 g1_process_strong_roots(bool collecting_perm_gen,
4806 ScanningOption so,
4807 OopClosure* scan_non_heap_roots,
4808 OopsInHeapRegionClosure* scan_rs,
4809 OopsInGenClosure* scan_perm,
4810 int worker_i) {
4811
4812 // First scan the strong roots, including the perm gen.
4813 double ext_roots_start = os::elapsedTime();
4814 double closure_app_time_sec = 0.0;
4815
4816 BufferingOopClosure buf_scan_non_heap_roots(scan_non_heap_roots);
4817 BufferingOopsInGenClosure buf_scan_perm(scan_perm);
4818 buf_scan_perm.set_generation(perm_gen());
4819
4820 // Walk the code cache w/o buffering, because StarTask cannot handle
4821 // unaligned oop locations.
4822 G1FilteredCodeBlobToOopClosure eager_scan_code_roots(this, scan_non_heap_roots);
4823
4824 process_strong_roots(false, // no scoping; this is parallel code
4825 collecting_perm_gen, so,
4826 &buf_scan_non_heap_roots,
4827 &eager_scan_code_roots,
4828 &buf_scan_perm);
4829
4830 // Now the CM ref_processor roots.
4831 if (!_process_strong_tasks->is_task_claimed(G1H_PS_refProcessor_oops_do)) {
4832 // We need to treat the discovered reference lists of the
4833 // concurrent mark ref processor as roots and keep entries
4834 // (which are added by the marking threads) on them live
4835 // until they can be processed at the end of marking.
4836 ref_processor_cm()->weak_oops_do(&buf_scan_non_heap_roots);
4837 }
4838
4839 // Finish up any enqueued closure apps (attributed as object copy time).
4840 buf_scan_non_heap_roots.done();
4841 buf_scan_perm.done();
4842
4843 double ext_roots_end = os::elapsedTime();
4844
4845 g1_policy()->reset_obj_copy_time(worker_i);
4846 double obj_copy_time_sec = buf_scan_perm.closure_app_seconds() +
4847 buf_scan_non_heap_roots.closure_app_seconds();
4848 g1_policy()->record_obj_copy_time(worker_i, obj_copy_time_sec * 1000.0);
4849
4850 double ext_root_time_ms =
4851 ((ext_roots_end - ext_roots_start) - obj_copy_time_sec) * 1000.0;
4852
4853 g1_policy()->record_ext_root_scan_time(worker_i, ext_root_time_ms);
4854
4855 // During conc marking we have to filter the per-thread SATB buffers
4856 // to make sure we remove any oops into the CSet (which will show up
4857 // as implicitly live).
4858 if (!_process_strong_tasks->is_task_claimed(G1H_PS_filter_satb_buffers)) {
4859 if (mark_in_progress()) {
4860 JavaThread::satb_mark_queue_set().filter_thread_buffers();
4861 }
4862 }
4863 double satb_filtering_ms = (os::elapsedTime() - ext_roots_end) * 1000.0;
4864 g1_policy()->record_satb_filtering_time(worker_i, satb_filtering_ms);
4865
4866 // Now scan the complement of the collection set.
4867 if (scan_rs != NULL) {
4868 g1_rem_set()->oops_into_collection_set_do(scan_rs, worker_i);
4869 }
4870
4871 _process_strong_tasks->all_tasks_completed();
4872 }
4873
4874 void
4875 G1CollectedHeap::g1_process_weak_roots(OopClosure* root_closure,
4876 OopClosure* non_root_closure) {
4877 CodeBlobToOopClosure roots_in_blobs(root_closure, /*do_marking=*/ false);
4878 SharedHeap::process_weak_roots(root_closure, &roots_in_blobs, non_root_closure);
4879 }
4880
4881 // Weak Reference Processing support
4882
4883 // An always "is_alive" closure that is used to preserve referents.
4884 // If the object is non-null then it's alive. Used in the preservation
4885 // of referent objects that are pointed to by reference objects
4886 // discovered by the CM ref processor.
4887 class G1AlwaysAliveClosure: public BoolObjectClosure {
4888 G1CollectedHeap* _g1;
4889 public:
4890 G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
4891 void do_object(oop p) { assert(false, "Do not call."); }
4892 bool do_object_b(oop p) {
4893 if (p != NULL) {
4894 return true;
4895 }
4896 return false;
4897 }
4898 };
4899
4900 bool G1STWIsAliveClosure::do_object_b(oop p) {
4901 // An object is reachable if it is outside the collection set,
4902 // or is inside and copied.
4903 return !_g1->obj_in_cs(p) || p->is_forwarded();
4904 }
4905
4906 // Non Copying Keep Alive closure
4907 class G1KeepAliveClosure: public OopClosure {
4908 G1CollectedHeap* _g1;
4909 public:
4910 G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
4911 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
4912 void do_oop( oop* p) {
4913 oop obj = *p;
4914
4915 if (_g1->obj_in_cs(obj)) {
4916 assert( obj->is_forwarded(), "invariant" );
4917 *p = obj->forwardee();
4918 }
4919 }
4920 };
4921
4922 // Copying Keep Alive closure - can be called from both
4923 // serial and parallel code as long as different worker
4924 // threads utilize different G1ParScanThreadState instances
4925 // and different queues.
4926
4927 class G1CopyingKeepAliveClosure: public OopClosure {
4928 G1CollectedHeap* _g1h;
4929 OopClosure* _copy_non_heap_obj_cl;
4930 OopsInHeapRegionClosure* _copy_perm_obj_cl;
4931 G1ParScanThreadState* _par_scan_state;
4932
4933 public:
4934 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
4935 OopClosure* non_heap_obj_cl,
4936 OopsInHeapRegionClosure* perm_obj_cl,
4937 G1ParScanThreadState* pss):
4938 _g1h(g1h),
4939 _copy_non_heap_obj_cl(non_heap_obj_cl),
4940 _copy_perm_obj_cl(perm_obj_cl),
4941 _par_scan_state(pss)
4942 {}
4943
4944 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
4945 virtual void do_oop( oop* p) { do_oop_work(p); }
4946
4947 template <class T> void do_oop_work(T* p) {
4948 oop obj = oopDesc::load_decode_heap_oop(p);
4949
4950 if (_g1h->obj_in_cs(obj)) {
4951 // If the referent object has been forwarded (either copied
4952 // to a new location or to itself in the event of an
4953 // evacuation failure) then we need to update the reference
4954 // field and, if both reference and referent are in the G1
4955 // heap, update the RSet for the referent.
4956 //
4957 // If the referent has not been forwarded then we have to keep
4958 // it alive by policy. Therefore we have copy the referent.
4959 //
4960 // If the reference field is in the G1 heap then we can push
4961 // on the PSS queue. When the queue is drained (after each
4962 // phase of reference processing) the object and it's followers
4963 // will be copied, the reference field set to point to the
4964 // new location, and the RSet updated. Otherwise we need to
4965 // use the the non-heap or perm closures directly to copy
4966 // the refernt object and update the pointer, while avoiding
4967 // updating the RSet.
4968
4969 if (_g1h->is_in_g1_reserved(p)) {
4970 _par_scan_state->push_on_queue(p);
4971 } else {
4972 // The reference field is not in the G1 heap.
4973 if (_g1h->perm_gen()->is_in(p)) {
4974 _copy_perm_obj_cl->do_oop(p);
4975 } else {
4976 _copy_non_heap_obj_cl->do_oop(p);
4977 }
4978 }
4979 }
4980 }
4981 };
4982
4983 // Serial drain queue closure. Called as the 'complete_gc'
4984 // closure for each discovered list in some of the
4985 // reference processing phases.
4986
4987 class G1STWDrainQueueClosure: public VoidClosure {
4988 protected:
4989 G1CollectedHeap* _g1h;
4990 G1ParScanThreadState* _par_scan_state;
4991
4992 G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
4993
4994 public:
4995 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
4996 _g1h(g1h),
4997 _par_scan_state(pss)
4998 { }
4999
5000 void do_void() {
5001 G1ParScanThreadState* const pss = par_scan_state();
5002 pss->trim_queue();
5003 }
5004 };
5005
5006 // Parallel Reference Processing closures
5007
5008 // Implementation of AbstractRefProcTaskExecutor for parallel reference
5009 // processing during G1 evacuation pauses.
5010
5011 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
5012 private:
5013 G1CollectedHeap* _g1h;
5014 RefToScanQueueSet* _queues;
5015 FlexibleWorkGang* _workers;
5016 int _active_workers;
5017
5018 public:
5019 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
5020 FlexibleWorkGang* workers,
5021 RefToScanQueueSet *task_queues,
5022 int n_workers) :
5023 _g1h(g1h),
5024 _queues(task_queues),
5025 _workers(workers),
5026 _active_workers(n_workers)
5027 {
5028 assert(n_workers > 0, "shouldn't call this otherwise");
5029 }
5030
5031 // Executes the given task using concurrent marking worker threads.
5032 virtual void execute(ProcessTask& task);
5033 virtual void execute(EnqueueTask& task);
5034 };
5035
5036 // Gang task for possibly parallel reference processing
5037
5038 class G1STWRefProcTaskProxy: public AbstractGangTask {
5039 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
5040 ProcessTask& _proc_task;
5041 G1CollectedHeap* _g1h;
5042 RefToScanQueueSet *_task_queues;
5043 ParallelTaskTerminator* _terminator;
5044
5045 public:
5046 G1STWRefProcTaskProxy(ProcessTask& proc_task,
5047 G1CollectedHeap* g1h,
5048 RefToScanQueueSet *task_queues,
5049 ParallelTaskTerminator* terminator) :
5050 AbstractGangTask("Process reference objects in parallel"),
5051 _proc_task(proc_task),
5052 _g1h(g1h),
5053 _task_queues(task_queues),
5054 _terminator(terminator)
5055 {}
5056
5057 virtual void work(uint worker_id) {
5058 // The reference processing task executed by a single worker.
5059 ResourceMark rm;
5060 HandleMark hm;
5061
5062 G1STWIsAliveClosure is_alive(_g1h);
5063
5064 G1ParScanThreadState pss(_g1h, worker_id);
5065
5066 G1ParScanHeapEvacClosure scan_evac_cl(_g1h, &pss, NULL);
5067 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5068 G1ParScanPartialArrayClosure partial_scan_cl(_g1h, &pss, NULL);
5069
5070 pss.set_evac_closure(&scan_evac_cl);
5071 pss.set_evac_failure_closure(&evac_failure_cl);
5072 pss.set_partial_scan_closure(&partial_scan_cl);
5073
5074 G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL);
5075 G1ParScanPermClosure only_copy_perm_cl(_g1h, &pss, NULL);
5076
5077 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5078 G1ParScanAndMarkPermClosure copy_mark_perm_cl(_g1h, &pss, NULL);
5079
5080 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5081 OopsInHeapRegionClosure* copy_perm_cl = &only_copy_perm_cl;
5082
5083 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5084 // We also need to mark copied objects.
5085 copy_non_heap_cl = ©_mark_non_heap_cl;
5086 copy_perm_cl = ©_mark_perm_cl;
5087 }
5088
5089 // Keep alive closure.
5090 G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, copy_perm_cl, &pss);
5091
5092 // Complete GC closure
5093 G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _task_queues, _terminator);
5094
5095 // Call the reference processing task's work routine.
5096 _proc_task.work(worker_id, is_alive, keep_alive, drain_queue);
5097
5098 // Note we cannot assert that the refs array is empty here as not all
5099 // of the processing tasks (specifically phase2 - pp2_work) execute
5100 // the complete_gc closure (which ordinarily would drain the queue) so
5101 // the queue may not be empty.
5102 }
5103 };
5104
5105 // Driver routine for parallel reference processing.
5106 // Creates an instance of the ref processing gang
5107 // task and has the worker threads execute it.
5108 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) {
5109 assert(_workers != NULL, "Need parallel worker threads.");
5110
5111 ParallelTaskTerminator terminator(_active_workers, _queues);
5112 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _queues, &terminator);
5113
5114 _g1h->set_par_threads(_active_workers);
5115 _workers->run_task(&proc_task_proxy);
5116 _g1h->set_par_threads(0);
5117 }
5118
5119 // Gang task for parallel reference enqueueing.
5120
5121 class G1STWRefEnqueueTaskProxy: public AbstractGangTask {
5122 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
5123 EnqueueTask& _enq_task;
5124
5125 public:
5126 G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) :
5127 AbstractGangTask("Enqueue reference objects in parallel"),
5128 _enq_task(enq_task)
5129 { }
5130
5131 virtual void work(uint worker_id) {
5132 _enq_task.work(worker_id);
5133 }
5134 };
5135
5136 // Driver routine for parallel reference enqueing.
5137 // Creates an instance of the ref enqueueing gang
5138 // task and has the worker threads execute it.
5139
5140 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
5141 assert(_workers != NULL, "Need parallel worker threads.");
5142
5143 G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task);
5144
5145 _g1h->set_par_threads(_active_workers);
5146 _workers->run_task(&enq_task_proxy);
5147 _g1h->set_par_threads(0);
5148 }
5149
5150 // End of weak reference support closures
5151
5152 // Abstract task used to preserve (i.e. copy) any referent objects
5153 // that are in the collection set and are pointed to by reference
5154 // objects discovered by the CM ref processor.
5155
5156 class G1ParPreserveCMReferentsTask: public AbstractGangTask {
5157 protected:
5158 G1CollectedHeap* _g1h;
5159 RefToScanQueueSet *_queues;
5160 ParallelTaskTerminator _terminator;
5161 uint _n_workers;
5162
5163 public:
5164 G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h,int workers, RefToScanQueueSet *task_queues) :
5165 AbstractGangTask("ParPreserveCMReferents"),
5166 _g1h(g1h),
5167 _queues(task_queues),
5168 _terminator(workers, _queues),
5169 _n_workers(workers)
5170 { }
5171
5172 void work(uint worker_id) {
5173 ResourceMark rm;
5174 HandleMark hm;
5175
5176 G1ParScanThreadState pss(_g1h, worker_id);
5177 G1ParScanHeapEvacClosure scan_evac_cl(_g1h, &pss, NULL);
5178 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5179 G1ParScanPartialArrayClosure partial_scan_cl(_g1h, &pss, NULL);
5180
5181 pss.set_evac_closure(&scan_evac_cl);
5182 pss.set_evac_failure_closure(&evac_failure_cl);
5183 pss.set_partial_scan_closure(&partial_scan_cl);
5184
5185 assert(pss.refs()->is_empty(), "both queue and overflow should be empty");
5186
5187
5188 G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL);
5189 G1ParScanPermClosure only_copy_perm_cl(_g1h, &pss, NULL);
5190
5191 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5192 G1ParScanAndMarkPermClosure copy_mark_perm_cl(_g1h, &pss, NULL);
5193
5194 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5195 OopsInHeapRegionClosure* copy_perm_cl = &only_copy_perm_cl;
5196
5197 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5198 // We also need to mark copied objects.
5199 copy_non_heap_cl = ©_mark_non_heap_cl;
5200 copy_perm_cl = ©_mark_perm_cl;
5201 }
5202
5203 // Is alive closure
5204 G1AlwaysAliveClosure always_alive(_g1h);
5205
5206 // Copying keep alive closure. Applied to referent objects that need
5207 // to be copied.
5208 G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, copy_perm_cl, &pss);
5209
5210 ReferenceProcessor* rp = _g1h->ref_processor_cm();
5211
5212 uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q();
5213 uint stride = MIN2(MAX2(_n_workers, 1U), limit);
5214
5215 // limit is set using max_num_q() - which was set using ParallelGCThreads.
5216 // So this must be true - but assert just in case someone decides to
5217 // change the worker ids.
5218 assert(0 <= worker_id && worker_id < limit, "sanity");
5219 assert(!rp->discovery_is_atomic(), "check this code");
5220
5221 // Select discovered lists [i, i+stride, i+2*stride,...,limit)
5222 for (uint idx = worker_id; idx < limit; idx += stride) {
5223 DiscoveredList& ref_list = rp->discovered_refs()[idx];
5224
5225 DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive);
5226 while (iter.has_next()) {
5227 // Since discovery is not atomic for the CM ref processor, we
5228 // can see some null referent objects.
5229 iter.load_ptrs(DEBUG_ONLY(true));
5230 oop ref = iter.obj();
5231
5232 // This will filter nulls.
5233 if (iter.is_referent_alive()) {
5234 iter.make_referent_alive();
5235 }
5236 iter.move_to_next();
5237 }
5238 }
5239
5240 // Drain the queue - which may cause stealing
5241 G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _queues, &_terminator);
5242 drain_queue.do_void();
5243 // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure
5244 assert(pss.refs()->is_empty(), "should be");
5245 }
5246 };
5247
5248 // Weak Reference processing during an evacuation pause (part 1).
5249 void G1CollectedHeap::process_discovered_references() {
5250 double ref_proc_start = os::elapsedTime();
5251
5252 ReferenceProcessor* rp = _ref_processor_stw;
5253 assert(rp->discovery_enabled(), "should have been enabled");
5254
5255 // Any reference objects, in the collection set, that were 'discovered'
5256 // by the CM ref processor should have already been copied (either by
5257 // applying the external root copy closure to the discovered lists, or
5258 // by following an RSet entry).
5259 //
5260 // But some of the referents, that are in the collection set, that these
5261 // reference objects point to may not have been copied: the STW ref
5262 // processor would have seen that the reference object had already
5263 // been 'discovered' and would have skipped discovering the reference,
5264 // but would not have treated the reference object as a regular oop.
5265 // As a reult the copy closure would not have been applied to the
5266 // referent object.
5267 //
5268 // We need to explicitly copy these referent objects - the references
5269 // will be processed at the end of remarking.
5270 //
5271 // We also need to do this copying before we process the reference
5272 // objects discovered by the STW ref processor in case one of these
5273 // referents points to another object which is also referenced by an
5274 // object discovered by the STW ref processor.
5275
5276 uint active_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
5277 workers()->active_workers() : 1);
5278
5279 assert(!G1CollectedHeap::use_parallel_gc_threads() ||
5280 active_workers == workers()->active_workers(),
5281 "Need to reset active_workers");
5282
5283 set_par_threads(active_workers);
5284 G1ParPreserveCMReferentsTask keep_cm_referents(this, active_workers, _task_queues);
5285
5286 if (G1CollectedHeap::use_parallel_gc_threads()) {
5287 workers()->run_task(&keep_cm_referents);
5288 } else {
5289 keep_cm_referents.work(0);
5290 }
5291
5292 set_par_threads(0);
5293
5294 // Closure to test whether a referent is alive.
5295 G1STWIsAliveClosure is_alive(this);
5296
5297 // Even when parallel reference processing is enabled, the processing
5298 // of JNI refs is serial and performed serially by the current thread
5299 // rather than by a worker. The following PSS will be used for processing
5300 // JNI refs.
5301
5302 // Use only a single queue for this PSS.
5303 G1ParScanThreadState pss(this, 0);
5304
5305 // We do not embed a reference processor in the copying/scanning
5306 // closures while we're actually processing the discovered
5307 // reference objects.
5308 G1ParScanHeapEvacClosure scan_evac_cl(this, &pss, NULL);
5309 G1ParScanHeapEvacFailureClosure evac_failure_cl(this, &pss, NULL);
5310 G1ParScanPartialArrayClosure partial_scan_cl(this, &pss, NULL);
5311
5312 pss.set_evac_closure(&scan_evac_cl);
5313 pss.set_evac_failure_closure(&evac_failure_cl);
5314 pss.set_partial_scan_closure(&partial_scan_cl);
5315
5316 assert(pss.refs()->is_empty(), "pre-condition");
5317
5318 G1ParScanExtRootClosure only_copy_non_heap_cl(this, &pss, NULL);
5319 G1ParScanPermClosure only_copy_perm_cl(this, &pss, NULL);
5320
5321 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(this, &pss, NULL);
5322 G1ParScanAndMarkPermClosure copy_mark_perm_cl(this, &pss, NULL);
5323
5324 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5325 OopsInHeapRegionClosure* copy_perm_cl = &only_copy_perm_cl;
5326
5327 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5328 // We also need to mark copied objects.
5329 copy_non_heap_cl = ©_mark_non_heap_cl;
5330 copy_perm_cl = ©_mark_perm_cl;
5331 }
5332
5333 // Keep alive closure.
5334 G1CopyingKeepAliveClosure keep_alive(this, copy_non_heap_cl, copy_perm_cl, &pss);
5335
5336 // Serial Complete GC closure
5337 G1STWDrainQueueClosure drain_queue(this, &pss);
5338
5339 // Setup the soft refs policy...
5340 rp->setup_policy(false);
5341
5342 if (!rp->processing_is_mt()) {
5343 // Serial reference processing...
5344 rp->process_discovered_references(&is_alive,
5345 &keep_alive,
5346 &drain_queue,
5347 NULL);
5348 } else {
5349 // Parallel reference processing
5350 assert(rp->num_q() == active_workers, "sanity");
5351 assert(active_workers <= rp->max_num_q(), "sanity");
5352
5353 G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, active_workers);
5354 rp->process_discovered_references(&is_alive, &keep_alive, &drain_queue, &par_task_executor);
5355 }
5356
5357 // We have completed copying any necessary live referent objects
5358 // (that were not copied during the actual pause) so we can
5359 // retire any active alloc buffers
5360 pss.retire_alloc_buffers();
5361 assert(pss.refs()->is_empty(), "both queue and overflow should be empty");
5362
5363 double ref_proc_time = os::elapsedTime() - ref_proc_start;
5364 g1_policy()->record_ref_proc_time(ref_proc_time * 1000.0);
5365 }
5366
5367 // Weak Reference processing during an evacuation pause (part 2).
5368 void G1CollectedHeap::enqueue_discovered_references() {
5369 double ref_enq_start = os::elapsedTime();
5370
5371 ReferenceProcessor* rp = _ref_processor_stw;
5372 assert(!rp->discovery_enabled(), "should have been disabled as part of processing");
5373
5374 // Now enqueue any remaining on the discovered lists on to
5375 // the pending list.
5376 if (!rp->processing_is_mt()) {
5377 // Serial reference processing...
5378 rp->enqueue_discovered_references();
5379 } else {
5380 // Parallel reference enqueuing
5381
5382 uint active_workers = (ParallelGCThreads > 0 ? workers()->active_workers() : 1);
5383 assert(active_workers == workers()->active_workers(),
5384 "Need to reset active_workers");
5385 assert(rp->num_q() == active_workers, "sanity");
5386 assert(active_workers <= rp->max_num_q(), "sanity");
5387
5388 G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, active_workers);
5389 rp->enqueue_discovered_references(&par_task_executor);
5390 }
5391
5392 rp->verify_no_references_recorded();
5393 assert(!rp->discovery_enabled(), "should have been disabled");
5394
5395 // FIXME
5396 // CM's reference processing also cleans up the string and symbol tables.
5397 // Should we do that here also? We could, but it is a serial operation
5398 // and could signicantly increase the pause time.
5399
5400 double ref_enq_time = os::elapsedTime() - ref_enq_start;
5401 g1_policy()->record_ref_enq_time(ref_enq_time * 1000.0);
5402 }
5403
5404 void G1CollectedHeap::evacuate_collection_set() {
5405 _expand_heap_after_alloc_failure = true;
5406 set_evacuation_failed(false);
5407
5408 g1_rem_set()->prepare_for_oops_into_collection_set_do();
5409 concurrent_g1_refine()->set_use_cache(false);
5410 concurrent_g1_refine()->clear_hot_cache_claimed_index();
5411
5412 uint n_workers;
5413 if (G1CollectedHeap::use_parallel_gc_threads()) {
5414 n_workers =
5415 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
5416 workers()->active_workers(),
5417 Threads::number_of_non_daemon_threads());
5418 assert(UseDynamicNumberOfGCThreads ||
5419 n_workers == workers()->total_workers(),
5420 "If not dynamic should be using all the workers");
5421 workers()->set_active_workers(n_workers);
5422 set_par_threads(n_workers);
5423 } else {
5424 assert(n_par_threads() == 0,
5425 "Should be the original non-parallel value");
5426 n_workers = 1;
5427 }
5428
5429 G1ParTask g1_par_task(this, _task_queues);
5430
5431 init_for_evac_failure(NULL);
5432
5433 rem_set()->prepare_for_younger_refs_iterate(true);
5434
5435 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
5436 double start_par_time_sec = os::elapsedTime();
5437 double end_par_time_sec;
5438
5439 {
5440 StrongRootsScope srs(this);
5441
5442 if (G1CollectedHeap::use_parallel_gc_threads()) {
5443 // The individual threads will set their evac-failure closures.
5444 if (ParallelGCVerbose) G1ParScanThreadState::print_termination_stats_hdr();
5445 // These tasks use ShareHeap::_process_strong_tasks
5446 assert(UseDynamicNumberOfGCThreads ||
5447 workers()->active_workers() == workers()->total_workers(),
5448 "If not dynamic should be using all the workers");
5449 workers()->run_task(&g1_par_task);
5450 } else {
5451 g1_par_task.set_for_termination(n_workers);
5452 g1_par_task.work(0);
5453 }
5454 end_par_time_sec = os::elapsedTime();
5455
5456 // Closing the inner scope will execute the destructor
5457 // for the StrongRootsScope object. We record the current
5458 // elapsed time before closing the scope so that time
5459 // taken for the SRS destructor is NOT included in the
5460 // reported parallel time.
5461 }
5462
5463 double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0;
5464 g1_policy()->record_par_time(par_time_ms);
5465
5466 double code_root_fixup_time_ms =
5467 (os::elapsedTime() - end_par_time_sec) * 1000.0;
5468 g1_policy()->record_code_root_fixup_time(code_root_fixup_time_ms);
5469
5470 set_par_threads(0);
5471
5472 // Process any discovered reference objects - we have
5473 // to do this _before_ we retire the GC alloc regions
5474 // as we may have to copy some 'reachable' referent
5475 // objects (and their reachable sub-graphs) that were
5476 // not copied during the pause.
5477 process_discovered_references();
5478
5479 // Weak root processing.
5480 // Note: when JSR 292 is enabled and code blobs can contain
5481 // non-perm oops then we will need to process the code blobs
5482 // here too.
5483 {
5484 G1STWIsAliveClosure is_alive(this);
5485 G1KeepAliveClosure keep_alive(this);
5486 JNIHandles::weak_oops_do(&is_alive, &keep_alive);
5487 }
5488
5489 release_gc_alloc_regions();
5490 g1_rem_set()->cleanup_after_oops_into_collection_set_do();
5491
5492 concurrent_g1_refine()->clear_hot_cache();
5493 concurrent_g1_refine()->set_use_cache(true);
5494
5495 finalize_for_evac_failure();
5496
5497 if (evacuation_failed()) {
5498 remove_self_forwarding_pointers();
5499 if (G1Log::finer()) {
5500 gclog_or_tty->print(" (to-space exhausted)");
5501 } else if (G1Log::fine()) {
5502 gclog_or_tty->print("--");
5503 }
5504 }
5505
5506 // Enqueue any remaining references remaining on the STW
5507 // reference processor's discovered lists. We need to do
5508 // this after the card table is cleaned (and verified) as
5509 // the act of enqueuing entries on to the pending list
5510 // will log these updates (and dirty their associated
5511 // cards). We need these updates logged to update any
5512 // RSets.
5513 enqueue_discovered_references();
5514
5515 if (G1DeferredRSUpdate) {
5516 RedirtyLoggedCardTableEntryFastClosure redirty;
5517 dirty_card_queue_set().set_closure(&redirty);
5518 dirty_card_queue_set().apply_closure_to_all_completed_buffers();
5519
5520 DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set();
5521 dcq.merge_bufferlists(&dirty_card_queue_set());
5522 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
5523 }
5524 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
5525 }
5526
5527 void G1CollectedHeap::free_region_if_empty(HeapRegion* hr,
5528 size_t* pre_used,
5529 FreeRegionList* free_list,
5530 OldRegionSet* old_proxy_set,
5531 HumongousRegionSet* humongous_proxy_set,
5532 HRRSCleanupTask* hrrs_cleanup_task,
5533 bool par) {
5534 if (hr->used() > 0 && hr->max_live_bytes() == 0 && !hr->is_young()) {
5535 if (hr->isHumongous()) {
5536 assert(hr->startsHumongous(), "we should only see starts humongous");
5537 free_humongous_region(hr, pre_used, free_list, humongous_proxy_set, par);
5538 } else {
5539 _old_set.remove_with_proxy(hr, old_proxy_set);
5540 free_region(hr, pre_used, free_list, par);
5541 }
5542 } else {
5543 hr->rem_set()->do_cleanup_work(hrrs_cleanup_task);
5544 }
5545 }
5546
5547 void G1CollectedHeap::free_region(HeapRegion* hr,
5548 size_t* pre_used,
5549 FreeRegionList* free_list,
5550 bool par) {
5551 assert(!hr->isHumongous(), "this is only for non-humongous regions");
5552 assert(!hr->is_empty(), "the region should not be empty");
5553 assert(free_list != NULL, "pre-condition");
5554
5555 *pre_used += hr->used();
5556 hr->hr_clear(par, true /* clear_space */);
5557 free_list->add_as_head(hr);
5558 }
5559
5560 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
5561 size_t* pre_used,
5562 FreeRegionList* free_list,
5563 HumongousRegionSet* humongous_proxy_set,
5564 bool par) {
5565 assert(hr->startsHumongous(), "this is only for starts humongous regions");
5566 assert(free_list != NULL, "pre-condition");
5567 assert(humongous_proxy_set != NULL, "pre-condition");
5568
5569 size_t hr_used = hr->used();
5570 size_t hr_capacity = hr->capacity();
5571 size_t hr_pre_used = 0;
5572 _humongous_set.remove_with_proxy(hr, humongous_proxy_set);
5573 hr->set_notHumongous();
5574 free_region(hr, &hr_pre_used, free_list, par);
5575
5576 uint i = hr->hrs_index() + 1;
5577 uint num = 1;
5578 while (i < n_regions()) {
5579 HeapRegion* curr_hr = region_at(i);
5580 if (!curr_hr->continuesHumongous()) {
5581 break;
5582 }
5583 curr_hr->set_notHumongous();
5584 free_region(curr_hr, &hr_pre_used, free_list, par);
5585 num += 1;
5586 i += 1;
5587 }
5588 assert(hr_pre_used == hr_used,
5589 err_msg("hr_pre_used: "SIZE_FORMAT" and hr_used: "SIZE_FORMAT" "
5590 "should be the same", hr_pre_used, hr_used));
5591 *pre_used += hr_pre_used;
5592 }
5593
5594 void G1CollectedHeap::update_sets_after_freeing_regions(size_t pre_used,
5595 FreeRegionList* free_list,
5596 OldRegionSet* old_proxy_set,
5597 HumongousRegionSet* humongous_proxy_set,
5598 bool par) {
5599 if (pre_used > 0) {
5600 Mutex* lock = (par) ? ParGCRareEvent_lock : NULL;
5601 MutexLockerEx x(lock, Mutex::_no_safepoint_check_flag);
5602 assert(_summary_bytes_used >= pre_used,
5603 err_msg("invariant: _summary_bytes_used: "SIZE_FORMAT" "
5604 "should be >= pre_used: "SIZE_FORMAT,
5605 _summary_bytes_used, pre_used));
5606 _summary_bytes_used -= pre_used;
5607 }
5608 if (free_list != NULL && !free_list->is_empty()) {
5609 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
5610 _free_list.add_as_head(free_list);
5611 }
5612 if (old_proxy_set != NULL && !old_proxy_set->is_empty()) {
5613 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
5614 _old_set.update_from_proxy(old_proxy_set);
5615 }
5616 if (humongous_proxy_set != NULL && !humongous_proxy_set->is_empty()) {
5617 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
5618 _humongous_set.update_from_proxy(humongous_proxy_set);
5619 }
5620 }
5621
5622 class G1ParCleanupCTTask : public AbstractGangTask {
5623 CardTableModRefBS* _ct_bs;
5624 G1CollectedHeap* _g1h;
5625 HeapRegion* volatile _su_head;
5626 public:
5627 G1ParCleanupCTTask(CardTableModRefBS* ct_bs,
5628 G1CollectedHeap* g1h) :
5629 AbstractGangTask("G1 Par Cleanup CT Task"),
5630 _ct_bs(ct_bs), _g1h(g1h) { }
5631
5632 void work(uint worker_id) {
5633 HeapRegion* r;
5634 while (r = _g1h->pop_dirty_cards_region()) {
5635 clear_cards(r);
5636 }
5637 }
5638
5639 void clear_cards(HeapRegion* r) {
5640 // Cards of the survivors should have already been dirtied.
5641 if (!r->is_survivor()) {
5642 _ct_bs->clear(MemRegion(r->bottom(), r->end()));
5643 }
5644 }
5645 };
5646
5647 #ifndef PRODUCT
5648 class G1VerifyCardTableCleanup: public HeapRegionClosure {
5649 G1CollectedHeap* _g1h;
5650 CardTableModRefBS* _ct_bs;
5651 public:
5652 G1VerifyCardTableCleanup(G1CollectedHeap* g1h, CardTableModRefBS* ct_bs)
5653 : _g1h(g1h), _ct_bs(ct_bs) { }
5654 virtual bool doHeapRegion(HeapRegion* r) {
5655 if (r->is_survivor()) {
5656 _g1h->verify_dirty_region(r);
5657 } else {
5658 _g1h->verify_not_dirty_region(r);
5659 }
5660 return false;
5661 }
5662 };
5663
5664 void G1CollectedHeap::verify_not_dirty_region(HeapRegion* hr) {
5665 // All of the region should be clean.
5666 CardTableModRefBS* ct_bs = (CardTableModRefBS*)barrier_set();
5667 MemRegion mr(hr->bottom(), hr->end());
5668 ct_bs->verify_not_dirty_region(mr);
5669 }
5670
5671 void G1CollectedHeap::verify_dirty_region(HeapRegion* hr) {
5672 // We cannot guarantee that [bottom(),end()] is dirty. Threads
5673 // dirty allocated blocks as they allocate them. The thread that
5674 // retires each region and replaces it with a new one will do a
5675 // maximal allocation to fill in [pre_dummy_top(),end()] but will
5676 // not dirty that area (one less thing to have to do while holding
5677 // a lock). So we can only verify that [bottom(),pre_dummy_top()]
5678 // is dirty.
5679 CardTableModRefBS* ct_bs = (CardTableModRefBS*) barrier_set();
5680 MemRegion mr(hr->bottom(), hr->pre_dummy_top());
5681 ct_bs->verify_dirty_region(mr);
5682 }
5683
5684 void G1CollectedHeap::verify_dirty_young_list(HeapRegion* head) {
5685 CardTableModRefBS* ct_bs = (CardTableModRefBS*) barrier_set();
5686 for (HeapRegion* hr = head; hr != NULL; hr = hr->get_next_young_region()) {
5687 verify_dirty_region(hr);
5688 }
5689 }
5690
5691 void G1CollectedHeap::verify_dirty_young_regions() {
5692 verify_dirty_young_list(_young_list->first_region());
5693 verify_dirty_young_list(_young_list->first_survivor_region());
5694 }
5695 #endif
5696
5697 void G1CollectedHeap::cleanUpCardTable() {
5698 CardTableModRefBS* ct_bs = (CardTableModRefBS*) (barrier_set());
5699 double start = os::elapsedTime();
5700
5701 {
5702 // Iterate over the dirty cards region list.
5703 G1ParCleanupCTTask cleanup_task(ct_bs, this);
5704
5705 if (G1CollectedHeap::use_parallel_gc_threads()) {
5706 set_par_threads();
5707 workers()->run_task(&cleanup_task);
5708 set_par_threads(0);
5709 } else {
5710 while (_dirty_cards_region_list) {
5711 HeapRegion* r = _dirty_cards_region_list;
5712 cleanup_task.clear_cards(r);
5713 _dirty_cards_region_list = r->get_next_dirty_cards_region();
5714 if (_dirty_cards_region_list == r) {
5715 // The last region.
5716 _dirty_cards_region_list = NULL;
5717 }
5718 r->set_next_dirty_cards_region(NULL);
5719 }
5720 }
5721 #ifndef PRODUCT
5722 if (G1VerifyCTCleanup || VerifyAfterGC) {
5723 G1VerifyCardTableCleanup cleanup_verifier(this, ct_bs);
5724 heap_region_iterate(&cleanup_verifier);
5725 }
5726 #endif
5727 }
5728
5729 double elapsed = os::elapsedTime() - start;
5730 g1_policy()->record_clear_ct_time(elapsed * 1000.0);
5731 }
5732
5733 void G1CollectedHeap::free_collection_set(HeapRegion* cs_head) {
5734 size_t pre_used = 0;
5735 FreeRegionList local_free_list("Local List for CSet Freeing");
5736
5737 double young_time_ms = 0.0;
5738 double non_young_time_ms = 0.0;
5739
5740 // Since the collection set is a superset of the the young list,
5741 // all we need to do to clear the young list is clear its
5742 // head and length, and unlink any young regions in the code below
5743 _young_list->clear();
5744
5745 G1CollectorPolicy* policy = g1_policy();
5746
5747 double start_sec = os::elapsedTime();
5748 bool non_young = true;
5749
5750 HeapRegion* cur = cs_head;
5751 int age_bound = -1;
5752 size_t rs_lengths = 0;
5753
5754 while (cur != NULL) {
5755 assert(!is_on_master_free_list(cur), "sanity");
5756 if (non_young) {
5757 if (cur->is_young()) {
5758 double end_sec = os::elapsedTime();
5759 double elapsed_ms = (end_sec - start_sec) * 1000.0;
5760 non_young_time_ms += elapsed_ms;
5761
5762 start_sec = os::elapsedTime();
5763 non_young = false;
5764 }
5765 } else {
5766 if (!cur->is_young()) {
5767 double end_sec = os::elapsedTime();
5768 double elapsed_ms = (end_sec - start_sec) * 1000.0;
5769 young_time_ms += elapsed_ms;
5770
5771 start_sec = os::elapsedTime();
5772 non_young = true;
5773 }
5774 }
5775
5776 rs_lengths += cur->rem_set()->occupied();
5777
5778 HeapRegion* next = cur->next_in_collection_set();
5779 assert(cur->in_collection_set(), "bad CS");
5780 cur->set_next_in_collection_set(NULL);
5781 cur->set_in_collection_set(false);
5782
5783 if (cur->is_young()) {
5784 int index = cur->young_index_in_cset();
5785 assert(index != -1, "invariant");
5786 assert((uint) index < policy->young_cset_region_length(), "invariant");
5787 size_t words_survived = _surviving_young_words[index];
5788 cur->record_surv_words_in_group(words_survived);
5789
5790 // At this point the we have 'popped' cur from the collection set
5791 // (linked via next_in_collection_set()) but it is still in the
5792 // young list (linked via next_young_region()). Clear the
5793 // _next_young_region field.
5794 cur->set_next_young_region(NULL);
5795 } else {
5796 int index = cur->young_index_in_cset();
5797 assert(index == -1, "invariant");
5798 }
5799
5800 assert( (cur->is_young() && cur->young_index_in_cset() > -1) ||
5801 (!cur->is_young() && cur->young_index_in_cset() == -1),
5802 "invariant" );
5803
5804 if (!cur->evacuation_failed()) {
5805 MemRegion used_mr = cur->used_region();
5806
5807 // And the region is empty.
5808 assert(!used_mr.is_empty(), "Should not have empty regions in a CS.");
5809 free_region(cur, &pre_used, &local_free_list, false /* par */);
5810 } else {
5811 cur->uninstall_surv_rate_group();
5812 if (cur->is_young()) {
5813 cur->set_young_index_in_cset(-1);
5814 }
5815 cur->set_not_young();
5816 cur->set_evacuation_failed(false);
5817 // The region is now considered to be old.
5818 _old_set.add(cur);
5819 }
5820 cur = next;
5821 }
5822
5823 policy->record_max_rs_lengths(rs_lengths);
5824 policy->cset_regions_freed();
5825
5826 double end_sec = os::elapsedTime();
5827 double elapsed_ms = (end_sec - start_sec) * 1000.0;
5828
5829 if (non_young) {
5830 non_young_time_ms += elapsed_ms;
5831 } else {
5832 young_time_ms += elapsed_ms;
5833 }
5834
5835 update_sets_after_freeing_regions(pre_used, &local_free_list,
5836 NULL /* old_proxy_set */,
5837 NULL /* humongous_proxy_set */,
5838 false /* par */);
5839 policy->record_young_free_cset_time_ms(young_time_ms);
5840 policy->record_non_young_free_cset_time_ms(non_young_time_ms);
5841 }
5842
5843 // This routine is similar to the above but does not record
5844 // any policy statistics or update free lists; we are abandoning
5845 // the current incremental collection set in preparation of a
5846 // full collection. After the full GC we will start to build up
5847 // the incremental collection set again.
5848 // This is only called when we're doing a full collection
5849 // and is immediately followed by the tearing down of the young list.
5850
5851 void G1CollectedHeap::abandon_collection_set(HeapRegion* cs_head) {
5852 HeapRegion* cur = cs_head;
5853
5854 while (cur != NULL) {
5855 HeapRegion* next = cur->next_in_collection_set();
5856 assert(cur->in_collection_set(), "bad CS");
5857 cur->set_next_in_collection_set(NULL);
5858 cur->set_in_collection_set(false);
5859 cur->set_young_index_in_cset(-1);
5860 cur = next;
5861 }
5862 }
5863
5864 void G1CollectedHeap::set_free_regions_coming() {
5865 if (G1ConcRegionFreeingVerbose) {
5866 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
5867 "setting free regions coming");
5868 }
5869
5870 assert(!free_regions_coming(), "pre-condition");
5871 _free_regions_coming = true;
5872 }
5873
5874 void G1CollectedHeap::reset_free_regions_coming() {
5875 assert(free_regions_coming(), "pre-condition");
5876
5877 {
5878 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
5879 _free_regions_coming = false;
5880 SecondaryFreeList_lock->notify_all();
5881 }
5882
5883 if (G1ConcRegionFreeingVerbose) {
5884 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
5885 "reset free regions coming");
5886 }
5887 }
5888
5889 void G1CollectedHeap::wait_while_free_regions_coming() {
5890 // Most of the time we won't have to wait, so let's do a quick test
5891 // first before we take the lock.
5892 if (!free_regions_coming()) {
5893 return;
5894 }
5895
5896 if (G1ConcRegionFreeingVerbose) {
5897 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
5898 "waiting for free regions");
5899 }
5900
5901 {
5902 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
5903 while (free_regions_coming()) {
5904 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
5905 }
5906 }
5907
5908 if (G1ConcRegionFreeingVerbose) {
5909 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
5910 "done waiting for free regions");
5911 }
5912 }
5913
5914 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
5915 assert(heap_lock_held_for_gc(),
5916 "the heap lock should already be held by or for this thread");
5917 _young_list->push_region(hr);
5918 }
5919
5920 class NoYoungRegionsClosure: public HeapRegionClosure {
5921 private:
5922 bool _success;
5923 public:
5924 NoYoungRegionsClosure() : _success(true) { }
5925 bool doHeapRegion(HeapRegion* r) {
5926 if (r->is_young()) {
5927 gclog_or_tty->print_cr("Region ["PTR_FORMAT", "PTR_FORMAT") tagged as young",
5928 r->bottom(), r->end());
5929 _success = false;
5930 }
5931 return false;
5932 }
5933 bool success() { return _success; }
5934 };
5935
5936 bool G1CollectedHeap::check_young_list_empty(bool check_heap, bool check_sample) {
5937 bool ret = _young_list->check_list_empty(check_sample);
5938
5939 if (check_heap) {
5940 NoYoungRegionsClosure closure;
5941 heap_region_iterate(&closure);
5942 ret = ret && closure.success();
5943 }
5944
5945 return ret;
5946 }
5947
5948 class TearDownRegionSetsClosure : public HeapRegionClosure {
5949 private:
5950 OldRegionSet *_old_set;
5951
5952 public:
5953 TearDownRegionSetsClosure(OldRegionSet* old_set) : _old_set(old_set) { }
5954
5955 bool doHeapRegion(HeapRegion* r) {
5956 if (r->is_empty()) {
5957 // We ignore empty regions, we'll empty the free list afterwards
5958 } else if (r->is_young()) {
5959 // We ignore young regions, we'll empty the young list afterwards
5960 } else if (r->isHumongous()) {
5961 // We ignore humongous regions, we're not tearing down the
5962 // humongous region set
5963 } else {
5964 // The rest should be old
5965 _old_set->remove(r);
5966 }
5967 return false;
5968 }
5969
5970 ~TearDownRegionSetsClosure() {
5971 assert(_old_set->is_empty(), "post-condition");
5972 }
5973 };
5974
5975 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
5976 assert_at_safepoint(true /* should_be_vm_thread */);
5977
5978 if (!free_list_only) {
5979 TearDownRegionSetsClosure cl(&_old_set);
5980 heap_region_iterate(&cl);
5981
5982 // Need to do this after the heap iteration to be able to
5983 // recognize the young regions and ignore them during the iteration.
5984 _young_list->empty_list();
5985 }
5986 _free_list.remove_all();
5987 }
5988
5989 class RebuildRegionSetsClosure : public HeapRegionClosure {
5990 private:
5991 bool _free_list_only;
5992 OldRegionSet* _old_set;
5993 FreeRegionList* _free_list;
5994 size_t _total_used;
5995
5996 public:
5997 RebuildRegionSetsClosure(bool free_list_only,
5998 OldRegionSet* old_set, FreeRegionList* free_list) :
5999 _free_list_only(free_list_only),
6000 _old_set(old_set), _free_list(free_list), _total_used(0) {
6001 assert(_free_list->is_empty(), "pre-condition");
6002 if (!free_list_only) {
6003 assert(_old_set->is_empty(), "pre-condition");
6004 }
6005 }
6006
6007 bool doHeapRegion(HeapRegion* r) {
6008 if (r->continuesHumongous()) {
6009 return false;
6010 }
6011
6012 if (r->is_empty()) {
6013 // Add free regions to the free list
6014 _free_list->add_as_tail(r);
6015 } else if (!_free_list_only) {
6016 assert(!r->is_young(), "we should not come across young regions");
6017
6018 if (r->isHumongous()) {
6019 // We ignore humongous regions, we left the humongous set unchanged
6020 } else {
6021 // The rest should be old, add them to the old set
6022 _old_set->add(r);
6023 }
6024 _total_used += r->used();
6025 }
6026
6027 return false;
6028 }
6029
6030 size_t total_used() {
6031 return _total_used;
6032 }
6033 };
6034
6035 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
6036 assert_at_safepoint(true /* should_be_vm_thread */);
6037
6038 RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_free_list);
6039 heap_region_iterate(&cl);
6040
6041 if (!free_list_only) {
6042 _summary_bytes_used = cl.total_used();
6043 }
6044 assert(_summary_bytes_used == recalculate_used(),
6045 err_msg("inconsistent _summary_bytes_used, "
6046 "value: "SIZE_FORMAT" recalculated: "SIZE_FORMAT,
6047 _summary_bytes_used, recalculate_used()));
6048 }
6049
6050 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) {
6051 _refine_cte_cl->set_concurrent(concurrent);
6052 }
6053
6054 bool G1CollectedHeap::is_in_closed_subset(const void* p) const {
6055 HeapRegion* hr = heap_region_containing(p);
6056 if (hr == NULL) {
6057 return is_in_permanent(p);
6058 } else {
6059 return hr->is_in(p);
6060 }
6061 }
6062
6063 // Methods for the mutator alloc region
6064
6065 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
6066 bool force) {
6067 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6068 assert(!force || g1_policy()->can_expand_young_list(),
6069 "if force is true we should be able to expand the young list");
6070 bool young_list_full = g1_policy()->is_young_list_full();
6071 if (force || !young_list_full) {
6072 HeapRegion* new_alloc_region = new_region(word_size,
6073 false /* do_expand */);
6074 if (new_alloc_region != NULL) {
6075 set_region_short_lived_locked(new_alloc_region);
6076 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Eden, young_list_full);
6077 return new_alloc_region;
6078 }
6079 }
6080 return NULL;
6081 }
6082
6083 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
6084 size_t allocated_bytes) {
6085 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6086 assert(alloc_region->is_young(), "all mutator alloc regions should be young");
6087
6088 g1_policy()->add_region_to_incremental_cset_lhs(alloc_region);
6089 _summary_bytes_used += allocated_bytes;
6090 _hr_printer.retire(alloc_region);
6091 // We update the eden sizes here, when the region is retired,
6092 // instead of when it's allocated, since this is the point that its
6093 // used space has been recored in _summary_bytes_used.
6094 g1mm()->update_eden_size();
6095 }
6096
6097 HeapRegion* MutatorAllocRegion::allocate_new_region(size_t word_size,
6098 bool force) {
6099 return _g1h->new_mutator_alloc_region(word_size, force);
6100 }
6101
6102 void G1CollectedHeap::set_par_threads() {
6103 // Don't change the number of workers. Use the value previously set
6104 // in the workgroup.
6105 assert(G1CollectedHeap::use_parallel_gc_threads(), "shouldn't be here otherwise");
6106 uint n_workers = workers()->active_workers();
6107 assert(UseDynamicNumberOfGCThreads ||
6108 n_workers == workers()->total_workers(),
6109 "Otherwise should be using the total number of workers");
6110 if (n_workers == 0) {
6111 assert(false, "Should have been set in prior evacuation pause.");
6112 n_workers = ParallelGCThreads;
6113 workers()->set_active_workers(n_workers);
6114 }
6115 set_par_threads(n_workers);
6116 }
6117
6118 void MutatorAllocRegion::retire_region(HeapRegion* alloc_region,
6119 size_t allocated_bytes) {
6120 _g1h->retire_mutator_alloc_region(alloc_region, allocated_bytes);
6121 }
6122
6123 // Methods for the GC alloc regions
6124
6125 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size,
6126 uint count,
6127 GCAllocPurpose ap) {
6128 assert(FreeList_lock->owned_by_self(), "pre-condition");
6129
6130 if (count < g1_policy()->max_regions(ap)) {
6131 HeapRegion* new_alloc_region = new_region(word_size,
6132 true /* do_expand */);
6133 if (new_alloc_region != NULL) {
6134 // We really only need to do this for old regions given that we
6135 // should never scan survivors. But it doesn't hurt to do it
6136 // for survivors too.
6137 new_alloc_region->set_saved_mark();
6138 if (ap == GCAllocForSurvived) {
6139 new_alloc_region->set_survivor();
6140 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Survivor);
6141 } else {
6142 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Old);
6143 }
6144 bool during_im = g1_policy()->during_initial_mark_pause();
6145 new_alloc_region->note_start_of_copying(during_im);
6146 return new_alloc_region;
6147 } else {
6148 g1_policy()->note_alloc_region_limit_reached(ap);
6149 }
6150 }
6151 return NULL;
6152 }
6153
6154 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
6155 size_t allocated_bytes,
6156 GCAllocPurpose ap) {
6157 bool during_im = g1_policy()->during_initial_mark_pause();
6158 alloc_region->note_end_of_copying(during_im);
6159 g1_policy()->record_bytes_copied_during_gc(allocated_bytes);
6160 if (ap == GCAllocForSurvived) {
6161 young_list()->add_survivor_region(alloc_region);
6162 } else {
6163 _old_set.add(alloc_region);
6164 }
6165 _hr_printer.retire(alloc_region);
6166 }
6167
6168 HeapRegion* SurvivorGCAllocRegion::allocate_new_region(size_t word_size,
6169 bool force) {
6170 assert(!force, "not supported for GC alloc regions");
6171 return _g1h->new_gc_alloc_region(word_size, count(), GCAllocForSurvived);
6172 }
6173
6174 void SurvivorGCAllocRegion::retire_region(HeapRegion* alloc_region,
6175 size_t allocated_bytes) {
6176 _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes,
6177 GCAllocForSurvived);
6178 }
6179
6180 HeapRegion* OldGCAllocRegion::allocate_new_region(size_t word_size,
6181 bool force) {
6182 assert(!force, "not supported for GC alloc regions");
6183 return _g1h->new_gc_alloc_region(word_size, count(), GCAllocForTenured);
6184 }
6185
6186 void OldGCAllocRegion::retire_region(HeapRegion* alloc_region,
6187 size_t allocated_bytes) {
6188 _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes,
6189 GCAllocForTenured);
6190 }
6191 // Heap region set verification
6192
6193 class VerifyRegionListsClosure : public HeapRegionClosure {
6194 private:
6195 FreeRegionList* _free_list;
6196 OldRegionSet* _old_set;
6197 HumongousRegionSet* _humongous_set;
6198 uint _region_count;
6199
6200 public:
6201 VerifyRegionListsClosure(OldRegionSet* old_set,
6202 HumongousRegionSet* humongous_set,
6203 FreeRegionList* free_list) :
6204 _old_set(old_set), _humongous_set(humongous_set),
6205 _free_list(free_list), _region_count(0) { }
6206
6207 uint region_count() { return _region_count; }
6208
6209 bool doHeapRegion(HeapRegion* hr) {
6210 _region_count += 1;
6211
6212 if (hr->continuesHumongous()) {
6213 return false;
6214 }
6215
6216 if (hr->is_young()) {
6217 // TODO
6218 } else if (hr->startsHumongous()) {
6219 _humongous_set->verify_next_region(hr);
6220 } else if (hr->is_empty()) {
6221 _free_list->verify_next_region(hr);
6222 } else {
6223 _old_set->verify_next_region(hr);
6224 }
6225 return false;
6226 }
6227 };
6228
6229 HeapRegion* G1CollectedHeap::new_heap_region(uint hrs_index,
6230 HeapWord* bottom) {
6231 HeapWord* end = bottom + HeapRegion::GrainWords;
6232 MemRegion mr(bottom, end);
6233 assert(_g1_reserved.contains(mr), "invariant");
6234 // This might return NULL if the allocation fails
6235 return new HeapRegion(hrs_index, _bot_shared, mr, true /* is_zeroed */);
6236 }
6237
6238 void G1CollectedHeap::verify_region_sets() {
6239 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6240
6241 // First, check the explicit lists.
6242 _free_list.verify();
6243 {
6244 // Given that a concurrent operation might be adding regions to
6245 // the secondary free list we have to take the lock before
6246 // verifying it.
6247 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6248 _secondary_free_list.verify();
6249 }
6250 _old_set.verify();
6251 _humongous_set.verify();
6252
6253 // If a concurrent region freeing operation is in progress it will
6254 // be difficult to correctly attributed any free regions we come
6255 // across to the correct free list given that they might belong to
6256 // one of several (free_list, secondary_free_list, any local lists,
6257 // etc.). So, if that's the case we will skip the rest of the
6258 // verification operation. Alternatively, waiting for the concurrent
6259 // operation to complete will have a non-trivial effect on the GC's
6260 // operation (no concurrent operation will last longer than the
6261 // interval between two calls to verification) and it might hide
6262 // any issues that we would like to catch during testing.
6263 if (free_regions_coming()) {
6264 return;
6265 }
6266
6267 // Make sure we append the secondary_free_list on the free_list so
6268 // that all free regions we will come across can be safely
6269 // attributed to the free_list.
6270 append_secondary_free_list_if_not_empty_with_lock();
6271
6272 // Finally, make sure that the region accounting in the lists is
6273 // consistent with what we see in the heap.
6274 _old_set.verify_start();
6275 _humongous_set.verify_start();
6276 _free_list.verify_start();
6277
6278 VerifyRegionListsClosure cl(&_old_set, &_humongous_set, &_free_list);
6279 heap_region_iterate(&cl);
6280
6281 _old_set.verify_end();
6282 _humongous_set.verify_end();
6283 _free_list.verify_end();
6284 }