1 /*
2 * Copyright (c) 2001, 2013, 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/g1GCPhaseTimes.hpp"
37 #include "gc_implementation/g1/g1Log.hpp"
38 #include "gc_implementation/g1/g1MarkSweep.hpp"
39 #include "gc_implementation/g1/g1OopClosures.inline.hpp"
40 #include "gc_implementation/g1/g1RemSet.inline.hpp"
41 #include "gc_implementation/g1/g1YCTypes.hpp"
42 #include "gc_implementation/g1/heapRegion.inline.hpp"
43 #include "gc_implementation/g1/heapRegionRemSet.hpp"
44 #include "gc_implementation/g1/heapRegionSeq.inline.hpp"
45 #include "gc_implementation/g1/vm_operations_g1.hpp"
46 #include "gc_implementation/shared/gcHeapSummary.hpp"
47 #include "gc_implementation/shared/gcTimer.hpp"
48 #include "gc_implementation/shared/gcTrace.hpp"
49 #include "gc_implementation/shared/gcTraceTime.hpp"
50 #include "gc_implementation/shared/isGCActiveMark.hpp"
51 #include "memory/gcLocker.inline.hpp"
52 #include "memory/genOopClosures.inline.hpp"
53 #include "memory/generationSpec.hpp"
54 #include "memory/referenceProcessor.hpp"
55 #include "oops/oop.inline.hpp"
56 #include "oops/oop.pcgc.inline.hpp"
57 #include "runtime/aprofiler.hpp"
58 #include "runtime/vmThread.hpp"
59
60 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;
61
62 // turn it on so that the contents of the young list (scan-only /
63 // to-be-collected) are printed at "strategic" points before / during
64 // / after the collection --- this is useful for debugging
65 #define YOUNG_LIST_VERBOSE 0
66 // CURRENT STATUS
67 // This file is under construction. Search for "FIXME".
68
69 // INVARIANTS/NOTES
70 //
71 // All allocation activity covered by the G1CollectedHeap interface is
72 // serialized by acquiring the HeapLock. This happens in mem_allocate
73 // and allocate_new_tlab, which are the "entry" points to the
74 // allocation code from the rest of the JVM. (Note that this does not
75 // apply to TLAB allocation, which is not part of this interface: it
76 // is done by clients of this interface.)
77
78 // Notes on implementation of parallelism in different tasks.
79 //
80 // G1ParVerifyTask uses heap_region_par_iterate_chunked() for parallelism.
81 // The number of GC workers is passed to heap_region_par_iterate_chunked().
82 // It does use run_task() which sets _n_workers in the task.
83 // G1ParTask executes g1_process_strong_roots() ->
84 // SharedHeap::process_strong_roots() which calls eventually to
85 // CardTableModRefBS::par_non_clean_card_iterate_work() which uses
86 // SequentialSubTasksDone. SharedHeap::process_strong_roots() also
87 // directly uses SubTasksDone (_process_strong_tasks field in SharedHeap).
88 //
89
90 // Local to this file.
91
92 class RefineCardTableEntryClosure: public CardTableEntryClosure {
93 SuspendibleThreadSet* _sts;
94 G1RemSet* _g1rs;
95 ConcurrentG1Refine* _cg1r;
96 bool _concurrent;
97 public:
98 RefineCardTableEntryClosure(SuspendibleThreadSet* sts,
99 G1RemSet* g1rs,
100 ConcurrentG1Refine* cg1r) :
101 _sts(sts), _g1rs(g1rs), _cg1r(cg1r), _concurrent(true)
102 {}
103 bool do_card_ptr(jbyte* card_ptr, int worker_i) {
104 bool oops_into_cset = _g1rs->refine_card(card_ptr, worker_i, false);
105 // This path is executed by the concurrent refine or mutator threads,
106 // concurrently, and so we do not care if card_ptr contains references
107 // that point into the collection set.
108 assert(!oops_into_cset, "should be");
109
110 if (_concurrent && _sts->should_yield()) {
111 // Caller will actually yield.
112 return false;
113 }
114 // Otherwise, we finished successfully; return true.
115 return true;
116 }
117 void set_concurrent(bool b) { _concurrent = b; }
118 };
119
120
121 class ClearLoggedCardTableEntryClosure: public CardTableEntryClosure {
122 int _calls;
123 G1CollectedHeap* _g1h;
124 CardTableModRefBS* _ctbs;
125 int _histo[256];
126 public:
127 ClearLoggedCardTableEntryClosure() :
128 _calls(0)
129 {
130 _g1h = G1CollectedHeap::heap();
131 _ctbs = (CardTableModRefBS*)_g1h->barrier_set();
132 for (int i = 0; i < 256; i++) _histo[i] = 0;
133 }
134 bool do_card_ptr(jbyte* card_ptr, int worker_i) {
135 if (_g1h->is_in_reserved(_ctbs->addr_for(card_ptr))) {
136 _calls++;
137 unsigned char* ujb = (unsigned char*)card_ptr;
138 int ind = (int)(*ujb);
139 _histo[ind]++;
140 *card_ptr = -1;
141 }
142 return true;
143 }
144 int calls() { return _calls; }
145 void print_histo() {
146 gclog_or_tty->print_cr("Card table value histogram:");
147 for (int i = 0; i < 256; i++) {
148 if (_histo[i] != 0) {
149 gclog_or_tty->print_cr(" %d: %d", i, _histo[i]);
150 }
151 }
152 }
153 };
154
155 class RedirtyLoggedCardTableEntryClosure: public CardTableEntryClosure {
156 int _calls;
157 G1CollectedHeap* _g1h;
158 CardTableModRefBS* _ctbs;
159 public:
160 RedirtyLoggedCardTableEntryClosure() :
161 _calls(0)
162 {
163 _g1h = G1CollectedHeap::heap();
164 _ctbs = (CardTableModRefBS*)_g1h->barrier_set();
165 }
166 bool do_card_ptr(jbyte* card_ptr, int worker_i) {
167 if (_g1h->is_in_reserved(_ctbs->addr_for(card_ptr))) {
168 _calls++;
169 *card_ptr = 0;
170 }
171 return true;
172 }
173 int calls() { return _calls; }
174 };
175
176 class RedirtyLoggedCardTableEntryFastClosure : public CardTableEntryClosure {
177 public:
178 bool do_card_ptr(jbyte* card_ptr, int worker_i) {
179 *card_ptr = CardTableModRefBS::dirty_card_val();
180 return true;
181 }
182 };
183
184 YoungList::YoungList(G1CollectedHeap* g1h) :
185 _g1h(g1h), _head(NULL), _length(0), _last_sampled_rs_lengths(0),
186 _survivor_head(NULL), _survivor_tail(NULL), _survivor_length(0) {
187 guarantee(check_list_empty(false), "just making sure...");
188 }
189
190 void YoungList::push_region(HeapRegion *hr) {
191 assert(!hr->is_young(), "should not already be young");
192 assert(hr->get_next_young_region() == NULL, "cause it should!");
193
194 hr->set_next_young_region(_head);
195 _head = hr;
196
197 _g1h->g1_policy()->set_region_eden(hr, (int) _length);
198 ++_length;
199 }
200
201 void YoungList::add_survivor_region(HeapRegion* hr) {
202 assert(hr->is_survivor(), "should be flagged as survivor region");
203 assert(hr->get_next_young_region() == NULL, "cause it should!");
204
205 hr->set_next_young_region(_survivor_head);
206 if (_survivor_head == NULL) {
207 _survivor_tail = hr;
208 }
209 _survivor_head = hr;
210 ++_survivor_length;
211 }
212
213 void YoungList::empty_list(HeapRegion* list) {
214 while (list != NULL) {
215 HeapRegion* next = list->get_next_young_region();
216 list->set_next_young_region(NULL);
217 list->uninstall_surv_rate_group();
218 list->set_not_young();
219 list = next;
220 }
221 }
222
223 void YoungList::empty_list() {
224 assert(check_list_well_formed(), "young list should be well formed");
225
226 empty_list(_head);
227 _head = NULL;
228 _length = 0;
229
230 empty_list(_survivor_head);
231 _survivor_head = NULL;
232 _survivor_tail = NULL;
233 _survivor_length = 0;
234
235 _last_sampled_rs_lengths = 0;
236
237 assert(check_list_empty(false), "just making sure...");
238 }
239
240 bool YoungList::check_list_well_formed() {
241 bool ret = true;
242
243 uint length = 0;
244 HeapRegion* curr = _head;
245 HeapRegion* last = NULL;
246 while (curr != NULL) {
247 if (!curr->is_young()) {
248 gclog_or_tty->print_cr("### YOUNG REGION "PTR_FORMAT"-"PTR_FORMAT" "
249 "incorrectly tagged (y: %d, surv: %d)",
250 curr->bottom(), curr->end(),
251 curr->is_young(), curr->is_survivor());
252 ret = false;
253 }
254 ++length;
255 last = curr;
256 curr = curr->get_next_young_region();
257 }
258 ret = ret && (length == _length);
259
260 if (!ret) {
261 gclog_or_tty->print_cr("### YOUNG LIST seems not well formed!");
262 gclog_or_tty->print_cr("### list has %u entries, _length is %u",
263 length, _length);
264 }
265
266 return ret;
267 }
268
269 bool YoungList::check_list_empty(bool check_sample) {
270 bool ret = true;
271
272 if (_length != 0) {
273 gclog_or_tty->print_cr("### YOUNG LIST should have 0 length, not %u",
274 _length);
275 ret = false;
276 }
277 if (check_sample && _last_sampled_rs_lengths != 0) {
278 gclog_or_tty->print_cr("### YOUNG LIST has non-zero last sampled RS lengths");
279 ret = false;
280 }
281 if (_head != NULL) {
282 gclog_or_tty->print_cr("### YOUNG LIST does not have a NULL head");
283 ret = false;
284 }
285 if (!ret) {
286 gclog_or_tty->print_cr("### YOUNG LIST does not seem empty");
287 }
288
289 return ret;
290 }
291
292 void
293 YoungList::rs_length_sampling_init() {
294 _sampled_rs_lengths = 0;
295 _curr = _head;
296 }
297
298 bool
299 YoungList::rs_length_sampling_more() {
300 return _curr != NULL;
301 }
302
303 void
304 YoungList::rs_length_sampling_next() {
305 assert( _curr != NULL, "invariant" );
306 size_t rs_length = _curr->rem_set()->occupied();
307
308 _sampled_rs_lengths += rs_length;
309
310 // The current region may not yet have been added to the
311 // incremental collection set (it gets added when it is
312 // retired as the current allocation region).
313 if (_curr->in_collection_set()) {
314 // Update the collection set policy information for this region
315 _g1h->g1_policy()->update_incremental_cset_info(_curr, rs_length);
316 }
317
318 _curr = _curr->get_next_young_region();
319 if (_curr == NULL) {
320 _last_sampled_rs_lengths = _sampled_rs_lengths;
321 // gclog_or_tty->print_cr("last sampled RS lengths = %d", _last_sampled_rs_lengths);
322 }
323 }
324
325 void
326 YoungList::reset_auxilary_lists() {
327 guarantee( is_empty(), "young list should be empty" );
328 assert(check_list_well_formed(), "young list should be well formed");
329
330 // Add survivor regions to SurvRateGroup.
331 _g1h->g1_policy()->note_start_adding_survivor_regions();
332 _g1h->g1_policy()->finished_recalculating_age_indexes(true /* is_survivors */);
333
334 int young_index_in_cset = 0;
335 for (HeapRegion* curr = _survivor_head;
336 curr != NULL;
337 curr = curr->get_next_young_region()) {
338 _g1h->g1_policy()->set_region_survivor(curr, young_index_in_cset);
339
340 // The region is a non-empty survivor so let's add it to
341 // the incremental collection set for the next evacuation
342 // pause.
343 _g1h->g1_policy()->add_region_to_incremental_cset_rhs(curr);
344 young_index_in_cset += 1;
345 }
346 assert((uint) young_index_in_cset == _survivor_length, "post-condition");
347 _g1h->g1_policy()->note_stop_adding_survivor_regions();
348
349 _head = _survivor_head;
350 _length = _survivor_length;
351 if (_survivor_head != NULL) {
352 assert(_survivor_tail != NULL, "cause it shouldn't be");
353 assert(_survivor_length > 0, "invariant");
354 _survivor_tail->set_next_young_region(NULL);
355 }
356
357 // Don't clear the survivor list handles until the start of
358 // the next evacuation pause - we need it in order to re-tag
359 // the survivor regions from this evacuation pause as 'young'
360 // at the start of the next.
361
362 _g1h->g1_policy()->finished_recalculating_age_indexes(false /* is_survivors */);
363
364 assert(check_list_well_formed(), "young list should be well formed");
365 }
366
367 void YoungList::print() {
368 HeapRegion* lists[] = {_head, _survivor_head};
369 const char* names[] = {"YOUNG", "SURVIVOR"};
370
371 for (unsigned int list = 0; list < ARRAY_SIZE(lists); ++list) {
372 gclog_or_tty->print_cr("%s LIST CONTENTS", names[list]);
373 HeapRegion *curr = lists[list];
374 if (curr == NULL)
375 gclog_or_tty->print_cr(" empty");
376 while (curr != NULL) {
377 gclog_or_tty->print_cr(" "HR_FORMAT", P: "PTR_FORMAT "N: "PTR_FORMAT", age: %4d",
378 HR_FORMAT_PARAMS(curr),
379 curr->prev_top_at_mark_start(),
380 curr->next_top_at_mark_start(),
381 curr->age_in_surv_rate_group_cond());
382 curr = curr->get_next_young_region();
383 }
384 }
385
386 gclog_or_tty->print_cr("");
387 }
388
389 void G1CollectedHeap::push_dirty_cards_region(HeapRegion* hr)
390 {
391 // Claim the right to put the region on the dirty cards region list
392 // by installing a self pointer.
393 HeapRegion* next = hr->get_next_dirty_cards_region();
394 if (next == NULL) {
395 HeapRegion* res = (HeapRegion*)
396 Atomic::cmpxchg_ptr(hr, hr->next_dirty_cards_region_addr(),
397 NULL);
398 if (res == NULL) {
399 HeapRegion* head;
400 do {
401 // Put the region to the dirty cards region list.
402 head = _dirty_cards_region_list;
403 next = (HeapRegion*)
404 Atomic::cmpxchg_ptr(hr, &_dirty_cards_region_list, head);
405 if (next == head) {
406 assert(hr->get_next_dirty_cards_region() == hr,
407 "hr->get_next_dirty_cards_region() != hr");
408 if (next == NULL) {
409 // The last region in the list points to itself.
410 hr->set_next_dirty_cards_region(hr);
411 } else {
412 hr->set_next_dirty_cards_region(next);
413 }
414 }
415 } while (next != head);
416 }
417 }
418 }
419
420 HeapRegion* G1CollectedHeap::pop_dirty_cards_region()
421 {
422 HeapRegion* head;
423 HeapRegion* hr;
424 do {
425 head = _dirty_cards_region_list;
426 if (head == NULL) {
427 return NULL;
428 }
429 HeapRegion* new_head = head->get_next_dirty_cards_region();
430 if (head == new_head) {
431 // The last region.
432 new_head = NULL;
433 }
434 hr = (HeapRegion*)Atomic::cmpxchg_ptr(new_head, &_dirty_cards_region_list,
435 head);
436 } while (hr != head);
437 assert(hr != NULL, "invariant");
438 hr->set_next_dirty_cards_region(NULL);
439 return hr;
440 }
441
442 void G1CollectedHeap::stop_conc_gc_threads() {
443 _cg1r->stop();
444 _cmThread->stop();
445 }
446
447 #ifdef ASSERT
448 // A region is added to the collection set as it is retired
449 // so an address p can point to a region which will be in the
450 // collection set but has not yet been retired. This method
451 // therefore is only accurate during a GC pause after all
452 // regions have been retired. It is used for debugging
453 // to check if an nmethod has references to objects that can
454 // be move during a partial collection. Though it can be
455 // inaccurate, it is sufficient for G1 because the conservative
456 // implementation of is_scavengable() for G1 will indicate that
457 // all nmethods must be scanned during a partial collection.
458 bool G1CollectedHeap::is_in_partial_collection(const void* p) {
459 HeapRegion* hr = heap_region_containing(p);
460 return hr != NULL && hr->in_collection_set();
461 }
462 #endif
463
464 // Returns true if the reference points to an object that
465 // can move in an incremental collection.
466 bool G1CollectedHeap::is_scavengable(const void* p) {
467 G1CollectedHeap* g1h = G1CollectedHeap::heap();
468 G1CollectorPolicy* g1p = g1h->g1_policy();
469 HeapRegion* hr = heap_region_containing(p);
470 if (hr == NULL) {
471 // perm gen (or null)
472 return false;
473 } else {
474 return !hr->isHumongous();
475 }
476 }
477
478 void G1CollectedHeap::check_ct_logs_at_safepoint() {
479 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
480 CardTableModRefBS* ct_bs = (CardTableModRefBS*)barrier_set();
481
482 // Count the dirty cards at the start.
483 CountNonCleanMemRegionClosure count1(this);
484 ct_bs->mod_card_iterate(&count1);
485 int orig_count = count1.n();
486
487 // First clear the logged cards.
488 ClearLoggedCardTableEntryClosure clear;
489 dcqs.set_closure(&clear);
490 dcqs.apply_closure_to_all_completed_buffers();
491 dcqs.iterate_closure_all_threads(false);
492 clear.print_histo();
493
494 // Now ensure that there's no dirty cards.
495 CountNonCleanMemRegionClosure count2(this);
496 ct_bs->mod_card_iterate(&count2);
497 if (count2.n() != 0) {
498 gclog_or_tty->print_cr("Card table has %d entries; %d originally",
499 count2.n(), orig_count);
500 }
501 guarantee(count2.n() == 0, "Card table should be clean.");
502
503 RedirtyLoggedCardTableEntryClosure redirty;
504 JavaThread::dirty_card_queue_set().set_closure(&redirty);
505 dcqs.apply_closure_to_all_completed_buffers();
506 dcqs.iterate_closure_all_threads(false);
507 gclog_or_tty->print_cr("Log entries = %d, dirty cards = %d.",
508 clear.calls(), orig_count);
509 guarantee(redirty.calls() == clear.calls(),
510 "Or else mechanism is broken.");
511
512 CountNonCleanMemRegionClosure count3(this);
513 ct_bs->mod_card_iterate(&count3);
514 if (count3.n() != orig_count) {
515 gclog_or_tty->print_cr("Should have restored them all: orig = %d, final = %d.",
516 orig_count, count3.n());
517 guarantee(count3.n() >= orig_count, "Should have restored them all.");
518 }
519
520 JavaThread::dirty_card_queue_set().set_closure(_refine_cte_cl);
521 }
522
523 // Private class members.
524
525 G1CollectedHeap* G1CollectedHeap::_g1h;
526
527 // Private methods.
528
529 HeapRegion*
530 G1CollectedHeap::new_region_try_secondary_free_list() {
531 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
532 while (!_secondary_free_list.is_empty() || free_regions_coming()) {
533 if (!_secondary_free_list.is_empty()) {
534 if (G1ConcRegionFreeingVerbose) {
535 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
536 "secondary_free_list has %u entries",
537 _secondary_free_list.length());
538 }
539 // It looks as if there are free regions available on the
540 // secondary_free_list. Let's move them to the free_list and try
541 // again to allocate from it.
542 append_secondary_free_list();
543
544 assert(!_free_list.is_empty(), "if the secondary_free_list was not "
545 "empty we should have moved at least one entry to the free_list");
546 HeapRegion* res = _free_list.remove_head();
547 if (G1ConcRegionFreeingVerbose) {
548 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
549 "allocated "HR_FORMAT" from secondary_free_list",
550 HR_FORMAT_PARAMS(res));
551 }
552 return res;
553 }
554
555 // Wait here until we get notified either when (a) there are no
556 // more free regions coming or (b) some regions have been moved on
557 // the secondary_free_list.
558 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
559 }
560
561 if (G1ConcRegionFreeingVerbose) {
562 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
563 "could not allocate from secondary_free_list");
564 }
565 return NULL;
566 }
567
568 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool do_expand) {
569 assert(!isHumongous(word_size) || word_size <= HeapRegion::GrainWords,
570 "the only time we use this to allocate a humongous region is "
571 "when we are allocating a single humongous region");
572
573 HeapRegion* res;
574 if (G1StressConcRegionFreeing) {
575 if (!_secondary_free_list.is_empty()) {
576 if (G1ConcRegionFreeingVerbose) {
577 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
578 "forced to look at the secondary_free_list");
579 }
580 res = new_region_try_secondary_free_list();
581 if (res != NULL) {
582 return res;
583 }
584 }
585 }
586 res = _free_list.remove_head_or_null();
587 if (res == NULL) {
588 if (G1ConcRegionFreeingVerbose) {
589 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
590 "res == NULL, trying the secondary_free_list");
591 }
592 res = new_region_try_secondary_free_list();
593 }
594 if (res == NULL && do_expand && _expand_heap_after_alloc_failure) {
595 // Currently, only attempts to allocate GC alloc regions set
596 // do_expand to true. So, we should only reach here during a
597 // safepoint. If this assumption changes we might have to
598 // reconsider the use of _expand_heap_after_alloc_failure.
599 assert(SafepointSynchronize::is_at_safepoint(), "invariant");
600
601 ergo_verbose1(ErgoHeapSizing,
602 "attempt heap expansion",
603 ergo_format_reason("region allocation request failed")
604 ergo_format_byte("allocation request"),
605 word_size * HeapWordSize);
606 if (expand(word_size * HeapWordSize)) {
607 // Given that expand() succeeded in expanding the heap, and we
608 // always expand the heap by an amount aligned to the heap
609 // region size, the free list should in theory not be empty. So
610 // it would probably be OK to use remove_head(). But the extra
611 // check for NULL is unlikely to be a performance issue here (we
612 // just expanded the heap!) so let's just be conservative and
613 // use remove_head_or_null().
614 res = _free_list.remove_head_or_null();
615 } else {
616 _expand_heap_after_alloc_failure = false;
617 }
618 }
619 return res;
620 }
621
622 uint G1CollectedHeap::humongous_obj_allocate_find_first(uint num_regions,
623 size_t word_size) {
624 assert(isHumongous(word_size), "word_size should be humongous");
625 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
626
627 uint first = G1_NULL_HRS_INDEX;
628 if (num_regions == 1) {
629 // Only one region to allocate, no need to go through the slower
630 // path. The caller will attempt the expansion if this fails, so
631 // let's not try to expand here too.
632 HeapRegion* hr = new_region(word_size, false /* do_expand */);
633 if (hr != NULL) {
634 first = hr->hrs_index();
635 } else {
636 first = G1_NULL_HRS_INDEX;
637 }
638 } else {
639 // We can't allocate humongous regions while cleanupComplete() is
640 // running, since some of the regions we find to be empty might not
641 // yet be added to the free list and it is not straightforward to
642 // know which list they are on so that we can remove them. Note
643 // that we only need to do this if we need to allocate more than
644 // one region to satisfy the current humongous allocation
645 // request. If we are only allocating one region we use the common
646 // region allocation code (see above).
647 wait_while_free_regions_coming();
648 append_secondary_free_list_if_not_empty_with_lock();
649
650 if (free_regions() >= num_regions) {
651 first = _hrs.find_contiguous(num_regions);
652 if (first != G1_NULL_HRS_INDEX) {
653 for (uint i = first; i < first + num_regions; ++i) {
654 HeapRegion* hr = region_at(i);
655 assert(hr->is_empty(), "sanity");
656 assert(is_on_master_free_list(hr), "sanity");
657 hr->set_pending_removal(true);
658 }
659 _free_list.remove_all_pending(num_regions);
660 }
661 }
662 }
663 return first;
664 }
665
666 HeapWord*
667 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first,
668 uint num_regions,
669 size_t word_size) {
670 assert(first != G1_NULL_HRS_INDEX, "pre-condition");
671 assert(isHumongous(word_size), "word_size should be humongous");
672 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
673
674 // Index of last region in the series + 1.
675 uint last = first + num_regions;
676
677 // We need to initialize the region(s) we just discovered. This is
678 // a bit tricky given that it can happen concurrently with
679 // refinement threads refining cards on these regions and
680 // potentially wanting to refine the BOT as they are scanning
681 // those cards (this can happen shortly after a cleanup; see CR
682 // 6991377). So we have to set up the region(s) carefully and in
683 // a specific order.
684
685 // The word size sum of all the regions we will allocate.
686 size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords;
687 assert(word_size <= word_size_sum, "sanity");
688
689 // This will be the "starts humongous" region.
690 HeapRegion* first_hr = region_at(first);
691 // The header of the new object will be placed at the bottom of
692 // the first region.
693 HeapWord* new_obj = first_hr->bottom();
694 // This will be the new end of the first region in the series that
695 // should also match the end of the last region in the series.
696 HeapWord* new_end = new_obj + word_size_sum;
697 // This will be the new top of the first region that will reflect
698 // this allocation.
699 HeapWord* new_top = new_obj + word_size;
700
701 // First, we need to zero the header of the space that we will be
702 // allocating. When we update top further down, some refinement
703 // threads might try to scan the region. By zeroing the header we
704 // ensure that any thread that will try to scan the region will
705 // come across the zero klass word and bail out.
706 //
707 // NOTE: It would not have been correct to have used
708 // CollectedHeap::fill_with_object() and make the space look like
709 // an int array. The thread that is doing the allocation will
710 // later update the object header to a potentially different array
711 // type and, for a very short period of time, the klass and length
712 // fields will be inconsistent. This could cause a refinement
713 // thread to calculate the object size incorrectly.
714 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
715
716 // We will set up the first region as "starts humongous". This
717 // will also update the BOT covering all the regions to reflect
718 // that there is a single object that starts at the bottom of the
719 // first region.
720 first_hr->set_startsHumongous(new_top, new_end);
721
722 // Then, if there are any, we will set up the "continues
723 // humongous" regions.
724 HeapRegion* hr = NULL;
725 for (uint i = first + 1; i < last; ++i) {
726 hr = region_at(i);
727 hr->set_continuesHumongous(first_hr);
728 }
729 // If we have "continues humongous" regions (hr != NULL), then the
730 // end of the last one should match new_end.
731 assert(hr == NULL || hr->end() == new_end, "sanity");
732
733 // Up to this point no concurrent thread would have been able to
734 // do any scanning on any region in this series. All the top
735 // fields still point to bottom, so the intersection between
736 // [bottom,top] and [card_start,card_end] will be empty. Before we
737 // update the top fields, we'll do a storestore to make sure that
738 // no thread sees the update to top before the zeroing of the
739 // object header and the BOT initialization.
740 OrderAccess::storestore();
741
742 // Now that the BOT and the object header have been initialized,
743 // we can update top of the "starts humongous" region.
744 assert(first_hr->bottom() < new_top && new_top <= first_hr->end(),
745 "new_top should be in this region");
746 first_hr->set_top(new_top);
747 if (_hr_printer.is_active()) {
748 HeapWord* bottom = first_hr->bottom();
749 HeapWord* end = first_hr->orig_end();
750 if ((first + 1) == last) {
751 // the series has a single humongous region
752 _hr_printer.alloc(G1HRPrinter::SingleHumongous, first_hr, new_top);
753 } else {
754 // the series has more than one humongous regions
755 _hr_printer.alloc(G1HRPrinter::StartsHumongous, first_hr, end);
756 }
757 }
758
759 // Now, we will update the top fields of the "continues humongous"
760 // regions. The reason we need to do this is that, otherwise,
761 // these regions would look empty and this will confuse parts of
762 // G1. For example, the code that looks for a consecutive number
763 // of empty regions will consider them empty and try to
764 // re-allocate them. We can extend is_empty() to also include
765 // !continuesHumongous(), but it is easier to just update the top
766 // fields here. The way we set top for all regions (i.e., top ==
767 // end for all regions but the last one, top == new_top for the
768 // last one) is actually used when we will free up the humongous
769 // region in free_humongous_region().
770 hr = NULL;
771 for (uint i = first + 1; i < last; ++i) {
772 hr = region_at(i);
773 if ((i + 1) == last) {
774 // last continues humongous region
775 assert(hr->bottom() < new_top && new_top <= hr->end(),
776 "new_top should fall on this region");
777 hr->set_top(new_top);
778 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, new_top);
779 } else {
780 // not last one
781 assert(new_top > hr->end(), "new_top should be above this region");
782 hr->set_top(hr->end());
783 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, hr->end());
784 }
785 }
786 // If we have continues humongous regions (hr != NULL), then the
787 // end of the last one should match new_end and its top should
788 // match new_top.
789 assert(hr == NULL ||
790 (hr->end() == new_end && hr->top() == new_top), "sanity");
791
792 assert(first_hr->used() == word_size * HeapWordSize, "invariant");
793 _summary_bytes_used += first_hr->used();
794 _humongous_set.add(first_hr);
795
796 return new_obj;
797 }
798
799 // If could fit into free regions w/o expansion, try.
800 // Otherwise, if can expand, do so.
801 // Otherwise, if using ex regions might help, try with ex given back.
802 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size) {
803 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
804
805 verify_region_sets_optional();
806
807 size_t word_size_rounded = round_to(word_size, HeapRegion::GrainWords);
808 uint num_regions = (uint) (word_size_rounded / HeapRegion::GrainWords);
809 uint x_num = expansion_regions();
810 uint fs = _hrs.free_suffix();
811 uint first = humongous_obj_allocate_find_first(num_regions, word_size);
812 if (first == G1_NULL_HRS_INDEX) {
813 // The only thing we can do now is attempt expansion.
814 if (fs + x_num >= num_regions) {
815 // If the number of regions we're trying to allocate for this
816 // object is at most the number of regions in the free suffix,
817 // then the call to humongous_obj_allocate_find_first() above
818 // should have succeeded and we wouldn't be here.
819 //
820 // We should only be trying to expand when the free suffix is
821 // not sufficient for the object _and_ we have some expansion
822 // room available.
823 assert(num_regions > fs, "earlier allocation should have succeeded");
824
825 ergo_verbose1(ErgoHeapSizing,
826 "attempt heap expansion",
827 ergo_format_reason("humongous allocation request failed")
828 ergo_format_byte("allocation request"),
829 word_size * HeapWordSize);
830 if (expand((num_regions - fs) * HeapRegion::GrainBytes)) {
831 // Even though the heap was expanded, it might not have
832 // reached the desired size. So, we cannot assume that the
833 // allocation will succeed.
834 first = humongous_obj_allocate_find_first(num_regions, word_size);
835 }
836 }
837 }
838
839 HeapWord* result = NULL;
840 if (first != G1_NULL_HRS_INDEX) {
841 result =
842 humongous_obj_allocate_initialize_regions(first, num_regions, word_size);
843 assert(result != NULL, "it should always return a valid result");
844
845 // A successful humongous object allocation changes the used space
846 // information of the old generation so we need to recalculate the
847 // sizes and update the jstat counters here.
848 g1mm()->update_sizes();
849 }
850
851 verify_region_sets_optional();
852
853 return result;
854 }
855
856 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) {
857 assert_heap_not_locked_and_not_at_safepoint();
858 assert(!isHumongous(word_size), "we do not allow humongous TLABs");
859
860 unsigned int dummy_gc_count_before;
861 return attempt_allocation(word_size, &dummy_gc_count_before);
862 }
863
864 HeapWord*
865 G1CollectedHeap::mem_allocate(size_t word_size,
866 bool* gc_overhead_limit_was_exceeded) {
867 assert_heap_not_locked_and_not_at_safepoint();
868
869 // Loop until the allocation is satisfied, or unsatisfied after GC.
870 for (int try_count = 1; /* we'll return */; try_count += 1) {
871 unsigned int gc_count_before;
872
873 HeapWord* result = NULL;
874 if (!isHumongous(word_size)) {
875 result = attempt_allocation(word_size, &gc_count_before);
876 } else {
877 result = attempt_allocation_humongous(word_size, &gc_count_before);
878 }
879 if (result != NULL) {
880 return result;
881 }
882
883 // Create the garbage collection operation...
884 VM_G1CollectForAllocation op(gc_count_before, word_size);
885 // ...and get the VM thread to execute it.
886 VMThread::execute(&op);
887
888 if (op.prologue_succeeded() && op.pause_succeeded()) {
889 // If the operation was successful we'll return the result even
890 // if it is NULL. If the allocation attempt failed immediately
891 // after a Full GC, it's unlikely we'll be able to allocate now.
892 HeapWord* result = op.result();
893 if (result != NULL && !isHumongous(word_size)) {
894 // Allocations that take place on VM operations do not do any
895 // card dirtying and we have to do it here. We only have to do
896 // this for non-humongous allocations, though.
897 dirty_young_block(result, word_size);
898 }
899 return result;
900 } else {
901 assert(op.result() == NULL,
902 "the result should be NULL if the VM op did not succeed");
903 }
904
905 // Give a warning if we seem to be looping forever.
906 if ((QueuedAllocationWarningCount > 0) &&
907 (try_count % QueuedAllocationWarningCount == 0)) {
908 warning("G1CollectedHeap::mem_allocate retries %d times", try_count);
909 }
910 }
911
912 ShouldNotReachHere();
913 return NULL;
914 }
915
916 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size,
917 unsigned int *gc_count_before_ret) {
918 // Make sure you read the note in attempt_allocation_humongous().
919
920 assert_heap_not_locked_and_not_at_safepoint();
921 assert(!isHumongous(word_size), "attempt_allocation_slow() should not "
922 "be called for humongous allocation requests");
923
924 // We should only get here after the first-level allocation attempt
925 // (attempt_allocation()) failed to allocate.
926
927 // We will loop until a) we manage to successfully perform the
928 // allocation or b) we successfully schedule a collection which
929 // fails to perform the allocation. b) is the only case when we'll
930 // return NULL.
931 HeapWord* result = NULL;
932 for (int try_count = 1; /* we'll return */; try_count += 1) {
933 bool should_try_gc;
934 unsigned int gc_count_before;
935
936 {
937 MutexLockerEx x(Heap_lock);
938
939 result = _mutator_alloc_region.attempt_allocation_locked(word_size,
940 false /* bot_updates */);
941 if (result != NULL) {
942 return result;
943 }
944
945 // If we reach here, attempt_allocation_locked() above failed to
946 // allocate a new region. So the mutator alloc region should be NULL.
947 assert(_mutator_alloc_region.get() == NULL, "only way to get here");
948
949 if (GC_locker::is_active_and_needs_gc()) {
950 if (g1_policy()->can_expand_young_list()) {
951 // No need for an ergo verbose message here,
952 // can_expand_young_list() does this when it returns true.
953 result = _mutator_alloc_region.attempt_allocation_force(word_size,
954 false /* bot_updates */);
955 if (result != NULL) {
956 return result;
957 }
958 }
959 should_try_gc = false;
960 } else {
961 // The GCLocker may not be active but the GCLocker initiated
962 // GC may not yet have been performed (GCLocker::needs_gc()
963 // returns true). In this case we do not try this GC and
964 // wait until the GCLocker initiated GC is performed, and
965 // then retry the allocation.
966 if (GC_locker::needs_gc()) {
967 should_try_gc = false;
968 } else {
969 // Read the GC count while still holding the Heap_lock.
970 gc_count_before = total_collections();
971 should_try_gc = true;
972 }
973 }
974 }
975
976 if (should_try_gc) {
977 bool succeeded;
978 result = do_collection_pause(word_size, gc_count_before, &succeeded);
979 if (result != NULL) {
980 assert(succeeded, "only way to get back a non-NULL result");
981 return result;
982 }
983
984 if (succeeded) {
985 // If we get here we successfully scheduled a collection which
986 // failed to allocate. No point in trying to allocate
987 // further. We'll just return NULL.
988 MutexLockerEx x(Heap_lock);
989 *gc_count_before_ret = total_collections();
990 return NULL;
991 }
992 } else {
993 // The GCLocker is either active or the GCLocker initiated
994 // GC has not yet been performed. Stall until it is and
995 // then retry the allocation.
996 GC_locker::stall_until_clear();
997 }
998
999 // We can reach here if we were unsuccessful in scheduling a
1000 // collection (because another thread beat us to it) or if we were
1001 // stalled due to the GC locker. In either can we should retry the
1002 // allocation attempt in case another thread successfully
1003 // performed a collection and reclaimed enough space. We do the
1004 // first attempt (without holding the Heap_lock) here and the
1005 // follow-on attempt will be at the start of the next loop
1006 // iteration (after taking the Heap_lock).
1007 result = _mutator_alloc_region.attempt_allocation(word_size,
1008 false /* bot_updates */);
1009 if (result != NULL) {
1010 return result;
1011 }
1012
1013 // Give a warning if we seem to be looping forever.
1014 if ((QueuedAllocationWarningCount > 0) &&
1015 (try_count % QueuedAllocationWarningCount == 0)) {
1016 warning("G1CollectedHeap::attempt_allocation_slow() "
1017 "retries %d times", try_count);
1018 }
1019 }
1020
1021 ShouldNotReachHere();
1022 return NULL;
1023 }
1024
1025 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size,
1026 unsigned int * gc_count_before_ret) {
1027 // The structure of this method has a lot of similarities to
1028 // attempt_allocation_slow(). The reason these two were not merged
1029 // into a single one is that such a method would require several "if
1030 // allocation is not humongous do this, otherwise do that"
1031 // conditional paths which would obscure its flow. In fact, an early
1032 // version of this code did use a unified method which was harder to
1033 // follow and, as a result, it had subtle bugs that were hard to
1034 // track down. So keeping these two methods separate allows each to
1035 // be more readable. It will be good to keep these two in sync as
1036 // much as possible.
1037
1038 assert_heap_not_locked_and_not_at_safepoint();
1039 assert(isHumongous(word_size), "attempt_allocation_humongous() "
1040 "should only be called for humongous allocations");
1041
1042 // Humongous objects can exhaust the heap quickly, so we should check if we
1043 // need to start a marking cycle at each humongous object allocation. We do
1044 // the check before we do the actual allocation. The reason for doing it
1045 // before the allocation is that we avoid having to keep track of the newly
1046 // allocated memory while we do a GC.
1047 if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation",
1048 word_size)) {
1049 collect(GCCause::_g1_humongous_allocation);
1050 }
1051
1052 // We will loop until a) we manage to successfully perform the
1053 // allocation or b) we successfully schedule a collection which
1054 // fails to perform the allocation. b) is the only case when we'll
1055 // return NULL.
1056 HeapWord* result = NULL;
1057 for (int try_count = 1; /* we'll return */; try_count += 1) {
1058 bool should_try_gc;
1059 unsigned int gc_count_before;
1060
1061 {
1062 MutexLockerEx x(Heap_lock);
1063
1064 // Given that humongous objects are not allocated in young
1065 // regions, we'll first try to do the allocation without doing a
1066 // collection hoping that there's enough space in the heap.
1067 result = humongous_obj_allocate(word_size);
1068 if (result != NULL) {
1069 return result;
1070 }
1071
1072 if (GC_locker::is_active_and_needs_gc()) {
1073 should_try_gc = false;
1074 } else {
1075 // The GCLocker may not be active but the GCLocker initiated
1076 // GC may not yet have been performed (GCLocker::needs_gc()
1077 // returns true). In this case we do not try this GC and
1078 // wait until the GCLocker initiated GC is performed, and
1079 // then retry the allocation.
1080 if (GC_locker::needs_gc()) {
1081 should_try_gc = false;
1082 } else {
1083 // Read the GC count while still holding the Heap_lock.
1084 gc_count_before = total_collections();
1085 should_try_gc = true;
1086 }
1087 }
1088 }
1089
1090 if (should_try_gc) {
1091 // If we failed to allocate the humongous object, we should try to
1092 // do a collection pause (if we're allowed) in case it reclaims
1093 // enough space for the allocation to succeed after the pause.
1094
1095 bool succeeded;
1096 result = do_collection_pause(word_size, gc_count_before, &succeeded);
1097 if (result != NULL) {
1098 assert(succeeded, "only way to get back a non-NULL result");
1099 return result;
1100 }
1101
1102 if (succeeded) {
1103 // If we get here we successfully scheduled a collection which
1104 // failed to allocate. No point in trying to allocate
1105 // further. We'll just return NULL.
1106 MutexLockerEx x(Heap_lock);
1107 *gc_count_before_ret = total_collections();
1108 return NULL;
1109 }
1110 } else {
1111 // The GCLocker is either active or the GCLocker initiated
1112 // GC has not yet been performed. Stall until it is and
1113 // then retry the allocation.
1114 GC_locker::stall_until_clear();
1115 }
1116
1117 // We can reach here if we were unsuccessful in scheduling a
1118 // collection (because another thread beat us to it) or if we were
1119 // stalled due to the GC locker. In either can we should retry the
1120 // allocation attempt in case another thread successfully
1121 // performed a collection and reclaimed enough space. Give a
1122 // warning if we seem to be looping forever.
1123
1124 if ((QueuedAllocationWarningCount > 0) &&
1125 (try_count % QueuedAllocationWarningCount == 0)) {
1126 warning("G1CollectedHeap::attempt_allocation_humongous() "
1127 "retries %d times", try_count);
1128 }
1129 }
1130
1131 ShouldNotReachHere();
1132 return NULL;
1133 }
1134
1135 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
1136 bool expect_null_mutator_alloc_region) {
1137 assert_at_safepoint(true /* should_be_vm_thread */);
1138 assert(_mutator_alloc_region.get() == NULL ||
1139 !expect_null_mutator_alloc_region,
1140 "the current alloc region was unexpectedly found to be non-NULL");
1141
1142 if (!isHumongous(word_size)) {
1143 return _mutator_alloc_region.attempt_allocation_locked(word_size,
1144 false /* bot_updates */);
1145 } else {
1146 HeapWord* result = humongous_obj_allocate(word_size);
1147 if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) {
1148 g1_policy()->set_initiate_conc_mark_if_possible();
1149 }
1150 return result;
1151 }
1152
1153 ShouldNotReachHere();
1154 }
1155
1156 class PostMCRemSetClearClosure: public HeapRegionClosure {
1157 G1CollectedHeap* _g1h;
1158 ModRefBarrierSet* _mr_bs;
1159 public:
1160 PostMCRemSetClearClosure(G1CollectedHeap* g1h, ModRefBarrierSet* mr_bs) :
1161 _g1h(g1h), _mr_bs(mr_bs) { }
1162 bool doHeapRegion(HeapRegion* r) {
1163 if (r->continuesHumongous()) {
1164 return false;
1165 }
1166 _g1h->reset_gc_time_stamps(r);
1167 HeapRegionRemSet* hrrs = r->rem_set();
1168 if (hrrs != NULL) hrrs->clear();
1169 // You might think here that we could clear just the cards
1170 // corresponding to the used region. But no: if we leave a dirty card
1171 // in a region we might allocate into, then it would prevent that card
1172 // from being enqueued, and cause it to be missed.
1173 // Re: the performance cost: we shouldn't be doing full GC anyway!
1174 _mr_bs->clear(MemRegion(r->bottom(), r->end()));
1175 return false;
1176 }
1177 };
1178
1179 void G1CollectedHeap::clear_rsets_post_compaction() {
1180 PostMCRemSetClearClosure rs_clear(this, mr_bs());
1181 heap_region_iterate(&rs_clear);
1182 }
1183
1184 class RebuildRSOutOfRegionClosure: public HeapRegionClosure {
1185 G1CollectedHeap* _g1h;
1186 UpdateRSOopClosure _cl;
1187 int _worker_i;
1188 public:
1189 RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, int worker_i = 0) :
1190 _cl(g1->g1_rem_set(), worker_i),
1191 _worker_i(worker_i),
1192 _g1h(g1)
1193 { }
1194
1195 bool doHeapRegion(HeapRegion* r) {
1196 if (!r->continuesHumongous()) {
1197 _cl.set_from(r);
1198 r->oop_iterate(&_cl);
1199 }
1200 return false;
1201 }
1202 };
1203
1204 class ParRebuildRSTask: public AbstractGangTask {
1205 G1CollectedHeap* _g1;
1206 public:
1207 ParRebuildRSTask(G1CollectedHeap* g1)
1208 : AbstractGangTask("ParRebuildRSTask"),
1209 _g1(g1)
1210 { }
1211
1212 void work(uint worker_id) {
1213 RebuildRSOutOfRegionClosure rebuild_rs(_g1, worker_id);
1214 _g1->heap_region_par_iterate_chunked(&rebuild_rs, worker_id,
1215 _g1->workers()->active_workers(),
1216 HeapRegion::RebuildRSClaimValue);
1217 }
1218 };
1219
1220 class PostCompactionPrinterClosure: public HeapRegionClosure {
1221 private:
1222 G1HRPrinter* _hr_printer;
1223 public:
1224 bool doHeapRegion(HeapRegion* hr) {
1225 assert(!hr->is_young(), "not expecting to find young regions");
1226 // We only generate output for non-empty regions.
1227 if (!hr->is_empty()) {
1228 if (!hr->isHumongous()) {
1229 _hr_printer->post_compaction(hr, G1HRPrinter::Old);
1230 } else if (hr->startsHumongous()) {
1231 if (hr->region_num() == 1) {
1232 // single humongous region
1233 _hr_printer->post_compaction(hr, G1HRPrinter::SingleHumongous);
1234 } else {
1235 _hr_printer->post_compaction(hr, G1HRPrinter::StartsHumongous);
1236 }
1237 } else {
1238 assert(hr->continuesHumongous(), "only way to get here");
1239 _hr_printer->post_compaction(hr, G1HRPrinter::ContinuesHumongous);
1240 }
1241 }
1242 return false;
1243 }
1244
1245 PostCompactionPrinterClosure(G1HRPrinter* hr_printer)
1246 : _hr_printer(hr_printer) { }
1247 };
1248
1249 void G1CollectedHeap::print_hrs_post_compaction() {
1250 PostCompactionPrinterClosure cl(hr_printer());
1251 heap_region_iterate(&cl);
1252 }
1253
1254 double G1CollectedHeap::verify(bool guard, const char* msg) {
1255 double verify_time_ms = 0.0;
1256
1257 if (guard && total_collections() >= VerifyGCStartAt) {
1258 double verify_start = os::elapsedTime();
1259 HandleMark hm; // Discard invalid handles created during verification
1260 gclog_or_tty->print(msg);
1261 prepare_for_verify();
1262 Universe::verify(false /* silent */, VerifyOption_G1UsePrevMarking);
1263 verify_time_ms = (os::elapsedTime() - verify_start) * 1000;
1264 }
1265
1266 return verify_time_ms;
1267 }
1268
1269 void G1CollectedHeap::verify_before_gc() {
1270 double verify_time_ms = verify(VerifyBeforeGC, " VerifyBeforeGC:");
1271 g1_policy()->phase_times()->record_verify_before_time_ms(verify_time_ms);
1272 }
1273
1274 void G1CollectedHeap::verify_after_gc() {
1275 double verify_time_ms = verify(VerifyAfterGC, " VerifyAfterGC:");
1276 g1_policy()->phase_times()->record_verify_after_time_ms(verify_time_ms);
1277 }
1278
1279 bool G1CollectedHeap::do_collection(bool explicit_gc,
1280 bool clear_all_soft_refs,
1281 size_t word_size) {
1282 assert_at_safepoint(true /* should_be_vm_thread */);
1283
1284 if (GC_locker::check_active_before_gc()) {
1285 return false;
1286 }
1287
1288 STWGCTimer* gc_timer = G1MarkSweep::gc_timer();
1289 gc_timer->register_gc_start(os::elapsed_counter());
1290
1291 SerialOldTracer* gc_tracer = G1MarkSweep::gc_tracer();
1292 gc_tracer->report_gc_start(gc_cause(), gc_timer->gc_start());
1293
1294 SvcGCMarker sgcm(SvcGCMarker::FULL);
1295 ResourceMark rm;
1296
1297 print_heap_before_gc();
1298 trace_heap_before_gc(gc_tracer);
1299
1300 HRSPhaseSetter x(HRSPhaseFullGC);
1301 verify_region_sets_optional();
1302
1303 const bool do_clear_all_soft_refs = clear_all_soft_refs ||
1304 collector_policy()->should_clear_all_soft_refs();
1305
1306 ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy());
1307
1308 {
1309 IsGCActiveMark x;
1310
1311 // Timing
1312 assert(gc_cause() != GCCause::_java_lang_system_gc || explicit_gc, "invariant");
1313 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
1314
1315 {
1316 GCTraceTime t(GCCauseString("Full GC", gc_cause()), G1Log::fine(), true, NULL);
1317 TraceCollectorStats tcs(g1mm()->full_collection_counters());
1318 TraceMemoryManagerStats tms(true /* fullGC */, gc_cause());
1319
1320 double start = os::elapsedTime();
1321 g1_policy()->record_full_collection_start();
1322
1323 // Note: When we have a more flexible GC logging framework that
1324 // allows us to add optional attributes to a GC log record we
1325 // could consider timing and reporting how long we wait in the
1326 // following two methods.
1327 wait_while_free_regions_coming();
1328 // If we start the compaction before the CM threads finish
1329 // scanning the root regions we might trip them over as we'll
1330 // be moving objects / updating references. So let's wait until
1331 // they are done. By telling them to abort, they should complete
1332 // early.
1333 _cm->root_regions()->abort();
1334 _cm->root_regions()->wait_until_scan_finished();
1335 append_secondary_free_list_if_not_empty_with_lock();
1336
1337 gc_prologue(true);
1338 increment_total_collections(true /* full gc */);
1339 increment_old_marking_cycles_started();
1340
1341 assert(used() == recalculate_used(), "Should be equal");
1342
1343 verify_before_gc();
1344
1345 pre_full_gc_dump(gc_timer);
1346
1347 COMPILER2_PRESENT(DerivedPointerTable::clear());
1348
1349 // Disable discovery and empty the discovered lists
1350 // for the CM ref processor.
1351 ref_processor_cm()->disable_discovery();
1352 ref_processor_cm()->abandon_partial_discovery();
1353 ref_processor_cm()->verify_no_references_recorded();
1354
1355 // Abandon current iterations of concurrent marking and concurrent
1356 // refinement, if any are in progress. We have to do this before
1357 // wait_until_scan_finished() below.
1358 concurrent_mark()->abort();
1359
1360 // Make sure we'll choose a new allocation region afterwards.
1361 release_mutator_alloc_region();
1362 abandon_gc_alloc_regions();
1363 g1_rem_set()->cleanupHRRS();
1364
1365 // We should call this after we retire any currently active alloc
1366 // regions so that all the ALLOC / RETIRE events are generated
1367 // before the start GC event.
1368 _hr_printer.start_gc(true /* full */, (size_t) total_collections());
1369
1370 // We may have added regions to the current incremental collection
1371 // set between the last GC or pause and now. We need to clear the
1372 // incremental collection set and then start rebuilding it afresh
1373 // after this full GC.
1374 abandon_collection_set(g1_policy()->inc_cset_head());
1375 g1_policy()->clear_incremental_cset();
1376 g1_policy()->stop_incremental_cset_building();
1377
1378 tear_down_region_sets(false /* free_list_only */);
1379 g1_policy()->set_gcs_are_young(true);
1380
1381 // See the comments in g1CollectedHeap.hpp and
1382 // G1CollectedHeap::ref_processing_init() about
1383 // how reference processing currently works in G1.
1384
1385 // Temporarily make discovery by the STW ref processor single threaded (non-MT).
1386 ReferenceProcessorMTDiscoveryMutator stw_rp_disc_ser(ref_processor_stw(), false);
1387
1388 // Temporarily clear the STW ref processor's _is_alive_non_header field.
1389 ReferenceProcessorIsAliveMutator stw_rp_is_alive_null(ref_processor_stw(), NULL);
1390
1391 ref_processor_stw()->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/);
1392 ref_processor_stw()->setup_policy(do_clear_all_soft_refs);
1393
1394 // Do collection work
1395 {
1396 HandleMark hm; // Discard invalid handles created during gc
1397 G1MarkSweep::invoke_at_safepoint(ref_processor_stw(), do_clear_all_soft_refs);
1398 }
1399
1400 assert(free_regions() == 0, "we should not have added any free regions");
1401 rebuild_region_sets(false /* free_list_only */);
1402
1403 // Enqueue any discovered reference objects that have
1404 // not been removed from the discovered lists.
1405 ref_processor_stw()->enqueue_discovered_references();
1406
1407 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
1408
1409 MemoryService::track_memory_usage();
1410
1411 verify_after_gc();
1412
1413 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
1414 ref_processor_stw()->verify_no_references_recorded();
1415
1416 // Note: since we've just done a full GC, concurrent
1417 // marking is no longer active. Therefore we need not
1418 // re-enable reference discovery for the CM ref processor.
1419 // That will be done at the start of the next marking cycle.
1420 assert(!ref_processor_cm()->discovery_enabled(), "Postcondition");
1421 ref_processor_cm()->verify_no_references_recorded();
1422
1423 reset_gc_time_stamp();
1424 // Since everything potentially moved, we will clear all remembered
1425 // sets, and clear all cards. Later we will rebuild remembered
1426 // sets. We will also reset the GC time stamps of the regions.
1427 clear_rsets_post_compaction();
1428 check_gc_time_stamps();
1429
1430 // Resize the heap if necessary.
1431 resize_if_necessary_after_full_collection(explicit_gc ? 0 : word_size);
1432
1433 if (_hr_printer.is_active()) {
1434 // We should do this after we potentially resize the heap so
1435 // that all the COMMIT / UNCOMMIT events are generated before
1436 // the end GC event.
1437
1438 print_hrs_post_compaction();
1439 _hr_printer.end_gc(true /* full */, (size_t) total_collections());
1440 }
1441
1442 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
1443 if (hot_card_cache->use_cache()) {
1444 hot_card_cache->reset_card_counts();
1445 hot_card_cache->reset_hot_cache();
1446 }
1447
1448 // Rebuild remembered sets of all regions.
1449 if (G1CollectedHeap::use_parallel_gc_threads()) {
1450 uint n_workers =
1451 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
1452 workers()->active_workers(),
1453 Threads::number_of_non_daemon_threads());
1454 assert(UseDynamicNumberOfGCThreads ||
1455 n_workers == workers()->total_workers(),
1456 "If not dynamic should be using all the workers");
1457 workers()->set_active_workers(n_workers);
1458 // Set parallel threads in the heap (_n_par_threads) only
1459 // before a parallel phase and always reset it to 0 after
1460 // the phase so that the number of parallel threads does
1461 // no get carried forward to a serial phase where there
1462 // may be code that is "possibly_parallel".
1463 set_par_threads(n_workers);
1464
1465 ParRebuildRSTask rebuild_rs_task(this);
1466 assert(check_heap_region_claim_values(
1467 HeapRegion::InitialClaimValue), "sanity check");
1468 assert(UseDynamicNumberOfGCThreads ||
1469 workers()->active_workers() == workers()->total_workers(),
1470 "Unless dynamic should use total workers");
1471 // Use the most recent number of active workers
1472 assert(workers()->active_workers() > 0,
1473 "Active workers not properly set");
1474 set_par_threads(workers()->active_workers());
1475 workers()->run_task(&rebuild_rs_task);
1476 set_par_threads(0);
1477 assert(check_heap_region_claim_values(
1478 HeapRegion::RebuildRSClaimValue), "sanity check");
1479 reset_heap_region_claim_values();
1480 } else {
1481 RebuildRSOutOfRegionClosure rebuild_rs(this);
1482 heap_region_iterate(&rebuild_rs);
1483 }
1484
1485 if (true) { // FIXME
1486 // Ask the permanent generation to adjust size for full collections
1487 perm()->compute_new_size();
1488 }
1489
1490 #ifdef TRACESPINNING
1491 ParallelTaskTerminator::print_termination_counts();
1492 #endif
1493
1494 // Discard all rset updates
1495 JavaThread::dirty_card_queue_set().abandon_logs();
1496 assert(!G1DeferredRSUpdate
1497 || (G1DeferredRSUpdate &&
1498 (dirty_card_queue_set().completed_buffers_num() == 0)), "Should not be any");
1499
1500 _young_list->reset_sampled_info();
1501 // At this point there should be no regions in the
1502 // entire heap tagged as young.
1503 assert(check_young_list_empty(true /* check_heap */),
1504 "young list should be empty at this point");
1505
1506 // Update the number of full collections that have been completed.
1507 increment_old_marking_cycles_completed(false /* concurrent */);
1508
1509 _hrs.verify_optional();
1510 verify_region_sets_optional();
1511
1512 // Start a new incremental collection set for the next pause
1513 assert(g1_policy()->collection_set() == NULL, "must be");
1514 g1_policy()->start_incremental_cset_building();
1515
1516 // Clear the _cset_fast_test bitmap in anticipation of adding
1517 // regions to the incremental collection set for the next
1518 // evacuation pause.
1519 clear_cset_fast_test();
1520
1521 init_mutator_alloc_region();
1522
1523 double end = os::elapsedTime();
1524 g1_policy()->record_full_collection_end();
1525
1526 if (G1Log::fine()) {
1527 g1_policy()->print_heap_transition();
1528 }
1529
1530 // We must call G1MonitoringSupport::update_sizes() in the same scoping level
1531 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
1532 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
1533 // before any GC notifications are raised.
1534 g1mm()->update_sizes();
1535
1536 gc_epilogue(true);
1537 }
1538
1539 if (G1Log::finer()) {
1540 g1_policy()->print_detailed_heap_transition();
1541 }
1542
1543 print_heap_after_gc();
1544 trace_heap_after_gc(gc_tracer);
1545
1546 post_full_gc_dump(gc_timer);
1547 }
1548
1549 gc_timer->register_gc_end(os::elapsed_counter());
1550
1551 gc_tracer->report_gc_end(gc_timer->gc_end(), gc_timer->time_partitions());
1552
1553 return true;
1554 }
1555
1556 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
1557 // do_collection() will return whether it succeeded in performing
1558 // the GC. Currently, there is no facility on the
1559 // do_full_collection() API to notify the caller than the collection
1560 // did not succeed (e.g., because it was locked out by the GC
1561 // locker). So, right now, we'll ignore the return value.
1562 bool dummy = do_collection(true, /* explicit_gc */
1563 clear_all_soft_refs,
1564 0 /* word_size */);
1565 }
1566
1567 // This code is mostly copied from TenuredGeneration.
1568 void
1569 G1CollectedHeap::
1570 resize_if_necessary_after_full_collection(size_t word_size) {
1571 assert(MinHeapFreeRatio <= MaxHeapFreeRatio, "sanity check");
1572
1573 // Include the current allocation, if any, and bytes that will be
1574 // pre-allocated to support collections, as "used".
1575 const size_t used_after_gc = used();
1576 const size_t capacity_after_gc = capacity();
1577 const size_t free_after_gc = capacity_after_gc - used_after_gc;
1578
1579 // This is enforced in arguments.cpp.
1580 assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
1581 "otherwise the code below doesn't make sense");
1582
1583 // We don't have floating point command-line arguments
1584 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
1585 const double maximum_used_percentage = 1.0 - minimum_free_percentage;
1586 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
1587 const double minimum_used_percentage = 1.0 - maximum_free_percentage;
1588
1589 const size_t min_heap_size = collector_policy()->min_heap_byte_size();
1590 const size_t max_heap_size = collector_policy()->max_heap_byte_size();
1591
1592 // We have to be careful here as these two calculations can overflow
1593 // 32-bit size_t's.
1594 double used_after_gc_d = (double) used_after_gc;
1595 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
1596 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
1597
1598 // Let's make sure that they are both under the max heap size, which
1599 // by default will make them fit into a size_t.
1600 double desired_capacity_upper_bound = (double) max_heap_size;
1601 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
1602 desired_capacity_upper_bound);
1603 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
1604 desired_capacity_upper_bound);
1605
1606 // We can now safely turn them into size_t's.
1607 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
1608 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
1609
1610 // This assert only makes sense here, before we adjust them
1611 // with respect to the min and max heap size.
1612 assert(minimum_desired_capacity <= maximum_desired_capacity,
1613 err_msg("minimum_desired_capacity = "SIZE_FORMAT", "
1614 "maximum_desired_capacity = "SIZE_FORMAT,
1615 minimum_desired_capacity, maximum_desired_capacity));
1616
1617 // Should not be greater than the heap max size. No need to adjust
1618 // it with respect to the heap min size as it's a lower bound (i.e.,
1619 // we'll try to make the capacity larger than it, not smaller).
1620 minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size);
1621 // Should not be less than the heap min size. No need to adjust it
1622 // with respect to the heap max size as it's an upper bound (i.e.,
1623 // we'll try to make the capacity smaller than it, not greater).
1624 maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size);
1625
1626 if (capacity_after_gc < minimum_desired_capacity) {
1627 // Don't expand unless it's significant
1628 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
1629 ergo_verbose4(ErgoHeapSizing,
1630 "attempt heap expansion",
1631 ergo_format_reason("capacity lower than "
1632 "min desired capacity after Full GC")
1633 ergo_format_byte("capacity")
1634 ergo_format_byte("occupancy")
1635 ergo_format_byte_perc("min desired capacity"),
1636 capacity_after_gc, used_after_gc,
1637 minimum_desired_capacity, (double) MinHeapFreeRatio);
1638 expand(expand_bytes);
1639
1640 // No expansion, now see if we want to shrink
1641 } else if (capacity_after_gc > maximum_desired_capacity) {
1642 // Capacity too large, compute shrinking size
1643 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
1644 ergo_verbose4(ErgoHeapSizing,
1645 "attempt heap shrinking",
1646 ergo_format_reason("capacity higher than "
1647 "max desired capacity after Full GC")
1648 ergo_format_byte("capacity")
1649 ergo_format_byte("occupancy")
1650 ergo_format_byte_perc("max desired capacity"),
1651 capacity_after_gc, used_after_gc,
1652 maximum_desired_capacity, (double) MaxHeapFreeRatio);
1653 shrink(shrink_bytes);
1654 }
1655 }
1656
1657
1658 HeapWord*
1659 G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
1660 bool* succeeded) {
1661 assert_at_safepoint(true /* should_be_vm_thread */);
1662
1663 *succeeded = true;
1664 // Let's attempt the allocation first.
1665 HeapWord* result =
1666 attempt_allocation_at_safepoint(word_size,
1667 false /* expect_null_mutator_alloc_region */);
1668 if (result != NULL) {
1669 assert(*succeeded, "sanity");
1670 return result;
1671 }
1672
1673 // In a G1 heap, we're supposed to keep allocation from failing by
1674 // incremental pauses. Therefore, at least for now, we'll favor
1675 // expansion over collection. (This might change in the future if we can
1676 // do something smarter than full collection to satisfy a failed alloc.)
1677 result = expand_and_allocate(word_size);
1678 if (result != NULL) {
1679 assert(*succeeded, "sanity");
1680 return result;
1681 }
1682
1683 // Expansion didn't work, we'll try to do a Full GC.
1684 bool gc_succeeded = do_collection(false, /* explicit_gc */
1685 false, /* clear_all_soft_refs */
1686 word_size);
1687 if (!gc_succeeded) {
1688 *succeeded = false;
1689 return NULL;
1690 }
1691
1692 // Retry the allocation
1693 result = attempt_allocation_at_safepoint(word_size,
1694 true /* expect_null_mutator_alloc_region */);
1695 if (result != NULL) {
1696 assert(*succeeded, "sanity");
1697 return result;
1698 }
1699
1700 // Then, try a Full GC that will collect all soft references.
1701 gc_succeeded = do_collection(false, /* explicit_gc */
1702 true, /* clear_all_soft_refs */
1703 word_size);
1704 if (!gc_succeeded) {
1705 *succeeded = false;
1706 return NULL;
1707 }
1708
1709 // Retry the allocation once more
1710 result = attempt_allocation_at_safepoint(word_size,
1711 true /* expect_null_mutator_alloc_region */);
1712 if (result != NULL) {
1713 assert(*succeeded, "sanity");
1714 return result;
1715 }
1716
1717 assert(!collector_policy()->should_clear_all_soft_refs(),
1718 "Flag should have been handled and cleared prior to this point");
1719
1720 // What else? We might try synchronous finalization later. If the total
1721 // space available is large enough for the allocation, then a more
1722 // complete compaction phase than we've tried so far might be
1723 // appropriate.
1724 assert(*succeeded, "sanity");
1725 return NULL;
1726 }
1727
1728 // Attempting to expand the heap sufficiently
1729 // to support an allocation of the given "word_size". If
1730 // successful, perform the allocation and return the address of the
1731 // allocated block, or else "NULL".
1732
1733 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size) {
1734 assert_at_safepoint(true /* should_be_vm_thread */);
1735
1736 verify_region_sets_optional();
1737
1738 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
1739 ergo_verbose1(ErgoHeapSizing,
1740 "attempt heap expansion",
1741 ergo_format_reason("allocation request failed")
1742 ergo_format_byte("allocation request"),
1743 word_size * HeapWordSize);
1744 if (expand(expand_bytes)) {
1745 _hrs.verify_optional();
1746 verify_region_sets_optional();
1747 return attempt_allocation_at_safepoint(word_size,
1748 false /* expect_null_mutator_alloc_region */);
1749 }
1750 return NULL;
1751 }
1752
1753 void G1CollectedHeap::update_committed_space(HeapWord* old_end,
1754 HeapWord* new_end) {
1755 assert(old_end != new_end, "don't call this otherwise");
1756 assert((HeapWord*) _g1_storage.high() == new_end, "invariant");
1757
1758 // Update the committed mem region.
1759 _g1_committed.set_end(new_end);
1760 // Tell the card table about the update.
1761 Universe::heap()->barrier_set()->resize_covered_region(_g1_committed);
1762 // Tell the BOT about the update.
1763 _bot_shared->resize(_g1_committed.word_size());
1764 // Tell the hot card cache about the update
1765 _cg1r->hot_card_cache()->resize_card_counts(capacity());
1766 }
1767
1768 bool G1CollectedHeap::expand(size_t expand_bytes) {
1769 size_t old_mem_size = _g1_storage.committed_size();
1770 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
1771 aligned_expand_bytes = align_size_up(aligned_expand_bytes,
1772 HeapRegion::GrainBytes);
1773 ergo_verbose2(ErgoHeapSizing,
1774 "expand the heap",
1775 ergo_format_byte("requested expansion amount")
1776 ergo_format_byte("attempted expansion amount"),
1777 expand_bytes, aligned_expand_bytes);
1778
1779 // First commit the memory.
1780 HeapWord* old_end = (HeapWord*) _g1_storage.high();
1781 bool successful = _g1_storage.expand_by(aligned_expand_bytes);
1782 if (successful) {
1783 // Then propagate this update to the necessary data structures.
1784 HeapWord* new_end = (HeapWord*) _g1_storage.high();
1785 update_committed_space(old_end, new_end);
1786
1787 FreeRegionList expansion_list("Local Expansion List");
1788 MemRegion mr = _hrs.expand_by(old_end, new_end, &expansion_list);
1789 assert(mr.start() == old_end, "post-condition");
1790 // mr might be a smaller region than what was requested if
1791 // expand_by() was unable to allocate the HeapRegion instances
1792 assert(mr.end() <= new_end, "post-condition");
1793
1794 size_t actual_expand_bytes = mr.byte_size();
1795 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
1796 assert(actual_expand_bytes == expansion_list.total_capacity_bytes(),
1797 "post-condition");
1798 if (actual_expand_bytes < aligned_expand_bytes) {
1799 // We could not expand _hrs to the desired size. In this case we
1800 // need to shrink the committed space accordingly.
1801 assert(mr.end() < new_end, "invariant");
1802
1803 size_t diff_bytes = aligned_expand_bytes - actual_expand_bytes;
1804 // First uncommit the memory.
1805 _g1_storage.shrink_by(diff_bytes);
1806 // Then propagate this update to the necessary data structures.
1807 update_committed_space(new_end, mr.end());
1808 }
1809 _free_list.add_as_tail(&expansion_list);
1810
1811 if (_hr_printer.is_active()) {
1812 HeapWord* curr = mr.start();
1813 while (curr < mr.end()) {
1814 HeapWord* curr_end = curr + HeapRegion::GrainWords;
1815 _hr_printer.commit(curr, curr_end);
1816 curr = curr_end;
1817 }
1818 assert(curr == mr.end(), "post-condition");
1819 }
1820 g1_policy()->record_new_heap_size(n_regions());
1821 } else {
1822 ergo_verbose0(ErgoHeapSizing,
1823 "did not expand the heap",
1824 ergo_format_reason("heap expansion operation failed"));
1825 // The expansion of the virtual storage space was unsuccessful.
1826 // Let's see if it was because we ran out of swap.
1827 if (G1ExitOnExpansionFailure &&
1828 _g1_storage.uncommitted_size() >= aligned_expand_bytes) {
1829 // We had head room...
1830 vm_exit_out_of_memory(aligned_expand_bytes, "G1 heap expansion");
1831 }
1832 }
1833 return successful;
1834 }
1835
1836 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
1837 size_t old_mem_size = _g1_storage.committed_size();
1838 size_t aligned_shrink_bytes =
1839 ReservedSpace::page_align_size_down(shrink_bytes);
1840 aligned_shrink_bytes = align_size_down(aligned_shrink_bytes,
1841 HeapRegion::GrainBytes);
1842 uint num_regions_deleted = 0;
1843 MemRegion mr = _hrs.shrink_by(aligned_shrink_bytes, &num_regions_deleted);
1844 HeapWord* old_end = (HeapWord*) _g1_storage.high();
1845 assert(mr.end() == old_end, "post-condition");
1846
1847 ergo_verbose3(ErgoHeapSizing,
1848 "shrink the heap",
1849 ergo_format_byte("requested shrinking amount")
1850 ergo_format_byte("aligned shrinking amount")
1851 ergo_format_byte("attempted shrinking amount"),
1852 shrink_bytes, aligned_shrink_bytes, mr.byte_size());
1853 if (mr.byte_size() > 0) {
1854 if (_hr_printer.is_active()) {
1855 HeapWord* curr = mr.end();
1856 while (curr > mr.start()) {
1857 HeapWord* curr_end = curr;
1858 curr -= HeapRegion::GrainWords;
1859 _hr_printer.uncommit(curr, curr_end);
1860 }
1861 assert(curr == mr.start(), "post-condition");
1862 }
1863
1864 _g1_storage.shrink_by(mr.byte_size());
1865 HeapWord* new_end = (HeapWord*) _g1_storage.high();
1866 assert(mr.start() == new_end, "post-condition");
1867
1868 _expansion_regions += num_regions_deleted;
1869 update_committed_space(old_end, new_end);
1870 HeapRegionRemSet::shrink_heap(n_regions());
1871 g1_policy()->record_new_heap_size(n_regions());
1872 } else {
1873 ergo_verbose0(ErgoHeapSizing,
1874 "did not shrink the heap",
1875 ergo_format_reason("heap shrinking operation failed"));
1876 }
1877 }
1878
1879 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1880 verify_region_sets_optional();
1881
1882 // We should only reach here at the end of a Full GC which means we
1883 // should not not be holding to any GC alloc regions. The method
1884 // below will make sure of that and do any remaining clean up.
1885 abandon_gc_alloc_regions();
1886
1887 // Instead of tearing down / rebuilding the free lists here, we
1888 // could instead use the remove_all_pending() method on free_list to
1889 // remove only the ones that we need to remove.
1890 tear_down_region_sets(true /* free_list_only */);
1891 shrink_helper(shrink_bytes);
1892 rebuild_region_sets(true /* free_list_only */);
1893
1894 _hrs.verify_optional();
1895 verify_region_sets_optional();
1896 }
1897
1898 // Public methods.
1899
1900 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away
1901 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
1902 #endif // _MSC_VER
1903
1904
1905 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* policy_) :
1906 SharedHeap(policy_),
1907 _g1_policy(policy_),
1908 _dirty_card_queue_set(false),
1909 _into_cset_dirty_card_queue_set(false),
1910 _is_alive_closure_cm(this),
1911 _is_alive_closure_stw(this),
1912 _ref_processor_cm(NULL),
1913 _ref_processor_stw(NULL),
1914 _process_strong_tasks(new SubTasksDone(G1H_PS_NumElements)),
1915 _bot_shared(NULL),
1916 _evac_failure_scan_stack(NULL),
1917 _mark_in_progress(false),
1918 _cg1r(NULL), _summary_bytes_used(0),
1919 _g1mm(NULL),
1920 _refine_cte_cl(NULL),
1921 _full_collection(false),
1922 _free_list("Master Free List"),
1923 _secondary_free_list("Secondary Free List"),
1924 _old_set("Old Set"),
1925 _humongous_set("Master Humongous Set"),
1926 _free_regions_coming(false),
1927 _young_list(new YoungList(this)),
1928 _gc_time_stamp(0),
1929 _retained_old_gc_alloc_region(NULL),
1930 _survivor_plab_stats(YoungPLABSize, PLABWeight),
1931 _old_plab_stats(OldPLABSize, PLABWeight),
1932 _expand_heap_after_alloc_failure(true),
1933 _surviving_young_words(NULL),
1934 _old_marking_cycles_started(0),
1935 _old_marking_cycles_completed(0),
1936 _concurrent_cycle_started(false),
1937 _in_cset_fast_test(NULL),
1938 _in_cset_fast_test_base(NULL),
1939 _dirty_cards_region_list(NULL),
1940 _worker_cset_start_region(NULL),
1941 _worker_cset_start_region_time_stamp(NULL),
1942 _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()),
1943 _gc_timer_cm(new (ResourceObj::C_HEAP, mtGC) ConcurrentGCTimer()),
1944 _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()),
1945 _gc_tracer_cm(new (ResourceObj::C_HEAP, mtGC) G1OldTracer()) {
1946
1947 _g1h = this;
1948 if (_process_strong_tasks == NULL || !_process_strong_tasks->valid()) {
1949 vm_exit_during_initialization("Failed necessary allocation.");
1950 }
1951
1952 _humongous_object_threshold_in_words = HeapRegion::GrainWords / 2;
1953
1954 int n_queues = MAX2((int)ParallelGCThreads, 1);
1955 _task_queues = new RefToScanQueueSet(n_queues);
1956
1957 int n_rem_sets = HeapRegionRemSet::num_par_rem_sets();
1958 assert(n_rem_sets > 0, "Invariant.");
1959
1960 HeapRegionRemSetIterator** iter_arr = NEW_C_HEAP_ARRAY(HeapRegionRemSetIterator*, n_queues, mtGC);
1961 _worker_cset_start_region = NEW_C_HEAP_ARRAY(HeapRegion*, n_queues, mtGC);
1962 _worker_cset_start_region_time_stamp = NEW_C_HEAP_ARRAY(unsigned int, n_queues, mtGC);
1963 _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC);
1964
1965 for (int i = 0; i < n_queues; i++) {
1966 RefToScanQueue* q = new RefToScanQueue();
1967 q->initialize();
1968 _task_queues->register_queue(i, q);
1969 iter_arr[i] = new HeapRegionRemSetIterator();
1970 ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo();
1971 }
1972 _rem_set_iterator = iter_arr;
1973
1974 clear_cset_start_regions();
1975
1976 // Initialize the G1EvacuationFailureALot counters and flags.
1977 NOT_PRODUCT(reset_evacuation_should_fail();)
1978
1979 guarantee(_task_queues != NULL, "task_queues allocation failure.");
1980 }
1981
1982 jint G1CollectedHeap::initialize() {
1983 CollectedHeap::pre_initialize();
1984 os::enable_vtime();
1985
1986 G1Log::init();
1987
1988 // Necessary to satisfy locking discipline assertions.
1989
1990 MutexLocker x(Heap_lock);
1991
1992 // We have to initialize the printer before committing the heap, as
1993 // it will be used then.
1994 _hr_printer.set_active(G1PrintHeapRegions);
1995
1996 // While there are no constraints in the GC code that HeapWordSize
1997 // be any particular value, there are multiple other areas in the
1998 // system which believe this to be true (e.g. oop->object_size in some
1999 // cases incorrectly returns the size in wordSize units rather than
2000 // HeapWordSize).
2001 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
2002
2003 size_t init_byte_size = collector_policy()->initial_heap_byte_size();
2004 size_t max_byte_size = collector_policy()->max_heap_byte_size();
2005
2006 // Ensure that the sizes are properly aligned.
2007 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
2008 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
2009
2010 _cg1r = new ConcurrentG1Refine(this);
2011
2012 // Reserve the maximum.
2013 PermanentGenerationSpec* pgs = collector_policy()->permanent_generation();
2014 // Includes the perm-gen.
2015
2016 // When compressed oops are enabled, the preferred heap base
2017 // is calculated by subtracting the requested size from the
2018 // 32Gb boundary and using the result as the base address for
2019 // heap reservation. If the requested size is not aligned to
2020 // HeapRegion::GrainBytes (i.e. the alignment that is passed
2021 // into the ReservedHeapSpace constructor) then the actual
2022 // base of the reserved heap may end up differing from the
2023 // address that was requested (i.e. the preferred heap base).
2024 // If this happens then we could end up using a non-optimal
2025 // compressed oops mode.
2026
2027 // Since max_byte_size is aligned to the size of a heap region (checked
2028 // above), we also need to align the perm gen size as it might not be.
2029 size_t total_reserved = 0;
2030
2031 total_reserved = add_and_check_overflow(total_reserved, max_byte_size);
2032 size_t pg_max_size = (size_t) align_size_up(pgs->max_size(), HeapRegion::GrainBytes);
2033 total_reserved = add_and_check_overflow(total_reserved, pg_max_size);
2034
2035 Universe::check_alignment(total_reserved, HeapRegion::GrainBytes, "g1 heap and perm");
2036
2037 char* addr = Universe::preferred_heap_base(total_reserved, Universe::UnscaledNarrowOop);
2038
2039 ReservedHeapSpace heap_rs(total_reserved, HeapRegion::GrainBytes,
2040 UseLargePages, addr);
2041
2042 if (UseCompressedOops) {
2043 if (addr != NULL && !heap_rs.is_reserved()) {
2044 // Failed to reserve at specified address - the requested memory
2045 // region is taken already, for example, by 'java' launcher.
2046 // Try again to reserver heap higher.
2047 addr = Universe::preferred_heap_base(total_reserved, Universe::ZeroBasedNarrowOop);
2048
2049 ReservedHeapSpace heap_rs0(total_reserved, HeapRegion::GrainBytes,
2050 UseLargePages, addr);
2051
2052 if (addr != NULL && !heap_rs0.is_reserved()) {
2053 // Failed to reserve at specified address again - give up.
2054 addr = Universe::preferred_heap_base(total_reserved, Universe::HeapBasedNarrowOop);
2055 assert(addr == NULL, "");
2056
2057 ReservedHeapSpace heap_rs1(total_reserved, HeapRegion::GrainBytes,
2058 UseLargePages, addr);
2059 heap_rs = heap_rs1;
2060 } else {
2061 heap_rs = heap_rs0;
2062 }
2063 }
2064 }
2065
2066 if (!heap_rs.is_reserved()) {
2067 vm_exit_during_initialization("Could not reserve enough space for object heap");
2068 return JNI_ENOMEM;
2069 }
2070
2071 // It is important to do this in a way such that concurrent readers can't
2072 // temporarily think something is in the heap. (I've actually seen this
2073 // happen in asserts: DLD.)
2074 _reserved.set_word_size(0);
2075 _reserved.set_start((HeapWord*)heap_rs.base());
2076 _reserved.set_end((HeapWord*)(heap_rs.base() + heap_rs.size()));
2077
2078 _expansion_regions = (uint) (max_byte_size / HeapRegion::GrainBytes);
2079
2080 // Create the gen rem set (and barrier set) for the entire reserved region.
2081 _rem_set = collector_policy()->create_rem_set(_reserved, 2);
2082 set_barrier_set(rem_set()->bs());
2083 if (barrier_set()->is_a(BarrierSet::ModRef)) {
2084 _mr_bs = (ModRefBarrierSet*)_barrier_set;
2085 } else {
2086 vm_exit_during_initialization("G1 requires a mod ref bs.");
2087 return JNI_ENOMEM;
2088 }
2089
2090 // Also create a G1 rem set.
2091 if (mr_bs()->is_a(BarrierSet::CardTableModRef)) {
2092 _g1_rem_set = new G1RemSet(this, (CardTableModRefBS*)mr_bs());
2093 } else {
2094 vm_exit_during_initialization("G1 requires a cardtable mod ref bs.");
2095 return JNI_ENOMEM;
2096 }
2097
2098 // Carve out the G1 part of the heap.
2099
2100 ReservedSpace g1_rs = heap_rs.first_part(max_byte_size);
2101 _g1_reserved = MemRegion((HeapWord*)g1_rs.base(),
2102 g1_rs.size()/HeapWordSize);
2103 ReservedSpace perm_gen_rs = heap_rs.last_part(max_byte_size);
2104
2105 _perm_gen = pgs->init(perm_gen_rs, pgs->init_size(), rem_set());
2106
2107 _g1_storage.initialize(g1_rs, 0);
2108 _g1_committed = MemRegion((HeapWord*)_g1_storage.low(), (size_t) 0);
2109 _hrs.initialize((HeapWord*) _g1_reserved.start(),
2110 (HeapWord*) _g1_reserved.end(),
2111 _expansion_regions);
2112
2113 // Do later initialization work for concurrent refinement.
2114 _cg1r->init();
2115
2116 // 6843694 - ensure that the maximum region index can fit
2117 // in the remembered set structures.
2118 const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
2119 guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
2120
2121 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
2122 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
2123 guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
2124 "too many cards per region");
2125
2126 HeapRegionSet::set_unrealistically_long_length(max_regions() + 1);
2127
2128 _bot_shared = new G1BlockOffsetSharedArray(_reserved,
2129 heap_word_size(init_byte_size));
2130
2131 _g1h = this;
2132
2133 _in_cset_fast_test_length = max_regions();
2134 _in_cset_fast_test_base =
2135 NEW_C_HEAP_ARRAY(bool, (size_t) _in_cset_fast_test_length, mtGC);
2136
2137 // We're biasing _in_cset_fast_test to avoid subtracting the
2138 // beginning of the heap every time we want to index; basically
2139 // it's the same with what we do with the card table.
2140 _in_cset_fast_test = _in_cset_fast_test_base -
2141 ((uintx) _g1_reserved.start() >> HeapRegion::LogOfHRGrainBytes);
2142
2143 // Clear the _cset_fast_test bitmap in anticipation of adding
2144 // regions to the incremental collection set for the first
2145 // evacuation pause.
2146 clear_cset_fast_test();
2147
2148 // Create the ConcurrentMark data structure and thread.
2149 // (Must do this late, so that "max_regions" is defined.)
2150 _cm = new ConcurrentMark(heap_rs, max_regions());
2151 _cmThread = _cm->cmThread();
2152
2153 // Initialize the from_card cache structure of HeapRegionRemSet.
2154 HeapRegionRemSet::init_heap(max_regions());
2155
2156 // Now expand into the initial heap size.
2157 if (!expand(init_byte_size)) {
2158 vm_exit_during_initialization("Failed to allocate initial heap.");
2159 return JNI_ENOMEM;
2160 }
2161
2162 // Perform any initialization actions delegated to the policy.
2163 g1_policy()->init();
2164
2165 _refine_cte_cl =
2166 new RefineCardTableEntryClosure(ConcurrentG1RefineThread::sts(),
2167 g1_rem_set(),
2168 concurrent_g1_refine());
2169 JavaThread::dirty_card_queue_set().set_closure(_refine_cte_cl);
2170
2171 JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon,
2172 SATB_Q_FL_lock,
2173 G1SATBProcessCompletedThreshold,
2174 Shared_SATB_Q_lock);
2175
2176 JavaThread::dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
2177 DirtyCardQ_FL_lock,
2178 concurrent_g1_refine()->yellow_zone(),
2179 concurrent_g1_refine()->red_zone(),
2180 Shared_DirtyCardQ_lock);
2181
2182 if (G1DeferredRSUpdate) {
2183 dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
2184 DirtyCardQ_FL_lock,
2185 -1, // never trigger processing
2186 -1, // no limit on length
2187 Shared_DirtyCardQ_lock,
2188 &JavaThread::dirty_card_queue_set());
2189 }
2190
2191 // Initialize the card queue set used to hold cards containing
2192 // references into the collection set.
2193 _into_cset_dirty_card_queue_set.initialize(DirtyCardQ_CBL_mon,
2194 DirtyCardQ_FL_lock,
2195 -1, // never trigger processing
2196 -1, // no limit on length
2197 Shared_DirtyCardQ_lock,
2198 &JavaThread::dirty_card_queue_set());
2199
2200 // In case we're keeping closure specialization stats, initialize those
2201 // counts and that mechanism.
2202 SpecializationStats::clear();
2203
2204 // Here we allocate the dummy full region that is required by the
2205 // G1AllocRegion class. If we don't pass an address in the reserved
2206 // space here, lots of asserts fire.
2207
2208 HeapRegion* dummy_region = new_heap_region(0 /* index of bottom region */,
2209 _g1_reserved.start());
2210 // We'll re-use the same region whether the alloc region will
2211 // require BOT updates or not and, if it doesn't, then a non-young
2212 // region will complain that it cannot support allocations without
2213 // BOT updates. So we'll tag the dummy region as young to avoid that.
2214 dummy_region->set_young();
2215 // Make sure it's full.
2216 dummy_region->set_top(dummy_region->end());
2217 G1AllocRegion::setup(this, dummy_region);
2218
2219 init_mutator_alloc_region();
2220
2221 // Do create of the monitoring and management support so that
2222 // values in the heap have been properly initialized.
2223 _g1mm = new G1MonitoringSupport(this);
2224
2225 return JNI_OK;
2226 }
2227
2228 void G1CollectedHeap::ref_processing_init() {
2229 // Reference processing in G1 currently works as follows:
2230 //
2231 // * There are two reference processor instances. One is
2232 // used to record and process discovered references
2233 // during concurrent marking; the other is used to
2234 // record and process references during STW pauses
2235 // (both full and incremental).
2236 // * Both ref processors need to 'span' the entire heap as
2237 // the regions in the collection set may be dotted around.
2238 //
2239 // * For the concurrent marking ref processor:
2240 // * Reference discovery is enabled at initial marking.
2241 // * Reference discovery is disabled and the discovered
2242 // references processed etc during remarking.
2243 // * Reference discovery is MT (see below).
2244 // * Reference discovery requires a barrier (see below).
2245 // * Reference processing may or may not be MT
2246 // (depending on the value of ParallelRefProcEnabled
2247 // and ParallelGCThreads).
2248 // * A full GC disables reference discovery by the CM
2249 // ref processor and abandons any entries on it's
2250 // discovered lists.
2251 //
2252 // * For the STW processor:
2253 // * Non MT discovery is enabled at the start of a full GC.
2254 // * Processing and enqueueing during a full GC is non-MT.
2255 // * During a full GC, references are processed after marking.
2256 //
2257 // * Discovery (may or may not be MT) is enabled at the start
2258 // of an incremental evacuation pause.
2259 // * References are processed near the end of a STW evacuation pause.
2260 // * For both types of GC:
2261 // * Discovery is atomic - i.e. not concurrent.
2262 // * Reference discovery will not need a barrier.
2263
2264 SharedHeap::ref_processing_init();
2265 MemRegion mr = reserved_region();
2266
2267 // Concurrent Mark ref processor
2268 _ref_processor_cm =
2269 new ReferenceProcessor(mr, // span
2270 ParallelRefProcEnabled && (ParallelGCThreads > 1),
2271 // mt processing
2272 (int) ParallelGCThreads,
2273 // degree of mt processing
2274 (ParallelGCThreads > 1) || (ConcGCThreads > 1),
2275 // mt discovery
2276 (int) MAX2(ParallelGCThreads, ConcGCThreads),
2277 // degree of mt discovery
2278 false,
2279 // Reference discovery is not atomic
2280 &_is_alive_closure_cm,
2281 // is alive closure
2282 // (for efficiency/performance)
2283 true);
2284 // Setting next fields of discovered
2285 // lists requires a barrier.
2286
2287 // STW ref processor
2288 _ref_processor_stw =
2289 new ReferenceProcessor(mr, // span
2290 ParallelRefProcEnabled && (ParallelGCThreads > 1),
2291 // mt processing
2292 MAX2((int)ParallelGCThreads, 1),
2293 // degree of mt processing
2294 (ParallelGCThreads > 1),
2295 // mt discovery
2296 MAX2((int)ParallelGCThreads, 1),
2297 // degree of mt discovery
2298 true,
2299 // Reference discovery is atomic
2300 &_is_alive_closure_stw,
2301 // is alive closure
2302 // (for efficiency/performance)
2303 false);
2304 // Setting next fields of discovered
2305 // lists requires a barrier.
2306 }
2307
2308 size_t G1CollectedHeap::capacity() const {
2309 return _g1_committed.byte_size();
2310 }
2311
2312 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) {
2313 assert(!hr->continuesHumongous(), "pre-condition");
2314 hr->reset_gc_time_stamp();
2315 if (hr->startsHumongous()) {
2316 uint first_index = hr->hrs_index() + 1;
2317 uint last_index = hr->last_hc_index();
2318 for (uint i = first_index; i < last_index; i += 1) {
2319 HeapRegion* chr = region_at(i);
2320 assert(chr->continuesHumongous(), "sanity");
2321 chr->reset_gc_time_stamp();
2322 }
2323 }
2324 }
2325
2326 #ifndef PRODUCT
2327 class CheckGCTimeStampsHRClosure : public HeapRegionClosure {
2328 private:
2329 unsigned _gc_time_stamp;
2330 bool _failures;
2331
2332 public:
2333 CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) :
2334 _gc_time_stamp(gc_time_stamp), _failures(false) { }
2335
2336 virtual bool doHeapRegion(HeapRegion* hr) {
2337 unsigned region_gc_time_stamp = hr->get_gc_time_stamp();
2338 if (_gc_time_stamp != region_gc_time_stamp) {
2339 gclog_or_tty->print_cr("Region "HR_FORMAT" has GC time stamp = %d, "
2340 "expected %d", HR_FORMAT_PARAMS(hr),
2341 region_gc_time_stamp, _gc_time_stamp);
2342 _failures = true;
2343 }
2344 return false;
2345 }
2346
2347 bool failures() { return _failures; }
2348 };
2349
2350 void G1CollectedHeap::check_gc_time_stamps() {
2351 CheckGCTimeStampsHRClosure cl(_gc_time_stamp);
2352 heap_region_iterate(&cl);
2353 guarantee(!cl.failures(), "all GC time stamps should have been reset");
2354 }
2355 #endif // PRODUCT
2356
2357 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl,
2358 DirtyCardQueue* into_cset_dcq,
2359 bool concurrent,
2360 int worker_i) {
2361 // Clean cards in the hot card cache
2362 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
2363 hot_card_cache->drain(worker_i, g1_rem_set(), into_cset_dcq);
2364
2365 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2366 int n_completed_buffers = 0;
2367 while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) {
2368 n_completed_buffers++;
2369 }
2370 g1_policy()->phase_times()->record_update_rs_processed_buffers(worker_i, n_completed_buffers);
2371 dcqs.clear_n_completed_buffers();
2372 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!");
2373 }
2374
2375
2376 // Computes the sum of the storage used by the various regions.
2377
2378 size_t G1CollectedHeap::used() const {
2379 assert(Heap_lock->owner() != NULL,
2380 "Should be owned on this thread's behalf.");
2381 size_t result = _summary_bytes_used;
2382 // Read only once in case it is set to NULL concurrently
2383 HeapRegion* hr = _mutator_alloc_region.get();
2384 if (hr != NULL)
2385 result += hr->used();
2386 return result;
2387 }
2388
2389 size_t G1CollectedHeap::used_unlocked() const {
2390 size_t result = _summary_bytes_used;
2391 return result;
2392 }
2393
2394 class SumUsedClosure: public HeapRegionClosure {
2395 size_t _used;
2396 public:
2397 SumUsedClosure() : _used(0) {}
2398 bool doHeapRegion(HeapRegion* r) {
2399 if (!r->continuesHumongous()) {
2400 _used += r->used();
2401 }
2402 return false;
2403 }
2404 size_t result() { return _used; }
2405 };
2406
2407 size_t G1CollectedHeap::recalculate_used() const {
2408 SumUsedClosure blk;
2409 heap_region_iterate(&blk);
2410 return blk.result();
2411 }
2412
2413 size_t G1CollectedHeap::unsafe_max_alloc() {
2414 if (free_regions() > 0) return HeapRegion::GrainBytes;
2415 // otherwise, is there space in the current allocation region?
2416
2417 // We need to store the current allocation region in a local variable
2418 // here. The problem is that this method doesn't take any locks and
2419 // there may be other threads which overwrite the current allocation
2420 // region field. attempt_allocation(), for example, sets it to NULL
2421 // and this can happen *after* the NULL check here but before the call
2422 // to free(), resulting in a SIGSEGV. Note that this doesn't appear
2423 // to be a problem in the optimized build, since the two loads of the
2424 // current allocation region field are optimized away.
2425 HeapRegion* hr = _mutator_alloc_region.get();
2426 if (hr == NULL) {
2427 return 0;
2428 }
2429 return hr->free();
2430 }
2431
2432 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
2433 switch (cause) {
2434 case GCCause::_gc_locker: return GCLockerInvokesConcurrent;
2435 case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent;
2436 case GCCause::_g1_humongous_allocation: return true;
2437 default: return false;
2438 }
2439 }
2440
2441 #ifndef PRODUCT
2442 void G1CollectedHeap::allocate_dummy_regions() {
2443 // Let's fill up most of the region
2444 size_t word_size = HeapRegion::GrainWords - 1024;
2445 // And as a result the region we'll allocate will be humongous.
2446 guarantee(isHumongous(word_size), "sanity");
2447
2448 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
2449 // Let's use the existing mechanism for the allocation
2450 HeapWord* dummy_obj = humongous_obj_allocate(word_size);
2451 if (dummy_obj != NULL) {
2452 MemRegion mr(dummy_obj, word_size);
2453 CollectedHeap::fill_with_object(mr);
2454 } else {
2455 // If we can't allocate once, we probably cannot allocate
2456 // again. Let's get out of the loop.
2457 break;
2458 }
2459 }
2460 }
2461 #endif // !PRODUCT
2462
2463 void G1CollectedHeap::increment_old_marking_cycles_started() {
2464 assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
2465 _old_marking_cycles_started == _old_marking_cycles_completed + 1,
2466 err_msg("Wrong marking cycle count (started: %d, completed: %d)",
2467 _old_marking_cycles_started, _old_marking_cycles_completed));
2468
2469 _old_marking_cycles_started++;
2470 }
2471
2472 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) {
2473 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
2474
2475 // We assume that if concurrent == true, then the caller is a
2476 // concurrent thread that was joined the Suspendible Thread
2477 // Set. If there's ever a cheap way to check this, we should add an
2478 // assert here.
2479
2480 // Given that this method is called at the end of a Full GC or of a
2481 // concurrent cycle, and those can be nested (i.e., a Full GC can
2482 // interrupt a concurrent cycle), the number of full collections
2483 // completed should be either one (in the case where there was no
2484 // nesting) or two (when a Full GC interrupted a concurrent cycle)
2485 // behind the number of full collections started.
2486
2487 // This is the case for the inner caller, i.e. a Full GC.
2488 assert(concurrent ||
2489 (_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
2490 (_old_marking_cycles_started == _old_marking_cycles_completed + 2),
2491 err_msg("for inner caller (Full GC): _old_marking_cycles_started = %u "
2492 "is inconsistent with _old_marking_cycles_completed = %u",
2493 _old_marking_cycles_started, _old_marking_cycles_completed));
2494
2495 // This is the case for the outer caller, i.e. the concurrent cycle.
2496 assert(!concurrent ||
2497 (_old_marking_cycles_started == _old_marking_cycles_completed + 1),
2498 err_msg("for outer caller (concurrent cycle): "
2499 "_old_marking_cycles_started = %u "
2500 "is inconsistent with _old_marking_cycles_completed = %u",
2501 _old_marking_cycles_started, _old_marking_cycles_completed));
2502
2503 _old_marking_cycles_completed += 1;
2504
2505 // We need to clear the "in_progress" flag in the CM thread before
2506 // we wake up any waiters (especially when ExplicitInvokesConcurrent
2507 // is set) so that if a waiter requests another System.gc() it doesn't
2508 // incorrectly see that a marking cycle is still in progress.
2509 if (concurrent) {
2510 _cmThread->clear_in_progress();
2511 }
2512
2513 // This notify_all() will ensure that a thread that called
2514 // System.gc() with (with ExplicitGCInvokesConcurrent set or not)
2515 // and it's waiting for a full GC to finish will be woken up. It is
2516 // waiting in VM_G1IncCollectionPause::doit_epilogue().
2517 FullGCCount_lock->notify_all();
2518 }
2519
2520 void G1CollectedHeap::register_concurrent_cycle_start(jlong start_time) {
2521 _concurrent_cycle_started = true;
2522 _gc_timer_cm->register_gc_start(start_time);
2523
2524 _gc_tracer_cm->report_gc_start(gc_cause(), _gc_timer_cm->gc_start());
2525 trace_heap_before_gc(_gc_tracer_cm);
2526 }
2527
2528 void G1CollectedHeap::register_concurrent_cycle_end() {
2529 if (_concurrent_cycle_started) {
2530 _gc_timer_cm->register_gc_end(os::elapsed_counter());
2531
2532 if (_cm->has_aborted()) {
2533 _gc_tracer_cm->report_concurrent_mode_failure();
2534 }
2535 _gc_tracer_cm->report_gc_end(_gc_timer_cm->gc_end(), _gc_timer_cm->time_partitions());
2536
2537 _concurrent_cycle_started = false;
2538 }
2539 }
2540
2541 void G1CollectedHeap::trace_heap_after_concurrent_cycle() {
2542 if (_concurrent_cycle_started) {
2543 trace_heap_after_gc(_gc_tracer_cm);
2544 }
2545 }
2546
2547 G1YCType G1CollectedHeap::yc_type() {
2548 bool is_young = g1_policy()->gcs_are_young();
2549 bool is_initial_mark = g1_policy()->during_initial_mark_pause();
2550 bool is_during_mark = mark_in_progress();
2551
2552 if (is_initial_mark) {
2553 return InitialMark;
2554 } else if (is_during_mark) {
2555 return DuringMark;
2556 } else if (is_young) {
2557 return Normal;
2558 } else {
2559 return Mixed;
2560 }
2561 }
2562
2563 void G1CollectedHeap::collect_as_vm_thread(GCCause::Cause cause) {
2564 assert_at_safepoint(true /* should_be_vm_thread */);
2565 GCCauseSetter gcs(this, cause);
2566 switch (cause) {
2567 case GCCause::_heap_inspection:
2568 case GCCause::_heap_dump: {
2569 HandleMark hm;
2570 do_full_collection(false); // don't clear all soft refs
2571 break;
2572 }
2573 default: // XXX FIX ME
2574 ShouldNotReachHere(); // Unexpected use of this function
2575 }
2576 }
2577
2578 void G1CollectedHeap::collect(GCCause::Cause cause) {
2579 assert_heap_not_locked();
2580
2581 unsigned int gc_count_before;
2582 unsigned int old_marking_count_before;
2583 bool retry_gc;
2584
2585 do {
2586 retry_gc = false;
2587
2588 {
2589 MutexLocker ml(Heap_lock);
2590
2591 // Read the GC count while holding the Heap_lock
2592 gc_count_before = total_collections();
2593 old_marking_count_before = _old_marking_cycles_started;
2594 }
2595
2596 if (should_do_concurrent_full_gc(cause)) {
2597 // Schedule an initial-mark evacuation pause that will start a
2598 // concurrent cycle. We're setting word_size to 0 which means that
2599 // we are not requesting a post-GC allocation.
2600 VM_G1IncCollectionPause op(gc_count_before,
2601 0, /* word_size */
2602 true, /* should_initiate_conc_mark */
2603 g1_policy()->max_pause_time_ms(),
2604 cause);
2605
2606 VMThread::execute(&op);
2607 if (!op.pause_succeeded()) {
2608 if (old_marking_count_before == _old_marking_cycles_started) {
2609 retry_gc = op.should_retry_gc();
2610 } else {
2611 // A Full GC happened while we were trying to schedule the
2612 // initial-mark GC. No point in starting a new cycle given
2613 // that the whole heap was collected anyway.
2614 }
2615
2616 if (retry_gc) {
2617 if (GC_locker::is_active_and_needs_gc()) {
2618 GC_locker::stall_until_clear();
2619 }
2620 }
2621 }
2622 } else {
2623 if (cause == GCCause::_gc_locker
2624 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2625
2626 // Schedule a standard evacuation pause. We're setting word_size
2627 // to 0 which means that we are not requesting a post-GC allocation.
2628 VM_G1IncCollectionPause op(gc_count_before,
2629 0, /* word_size */
2630 false, /* should_initiate_conc_mark */
2631 g1_policy()->max_pause_time_ms(),
2632 cause);
2633 VMThread::execute(&op);
2634 } else {
2635 // Schedule a Full GC.
2636 VM_G1CollectFull op(gc_count_before, old_marking_count_before, cause);
2637 VMThread::execute(&op);
2638 }
2639 }
2640 } while (retry_gc);
2641 }
2642
2643 bool G1CollectedHeap::is_in(const void* p) const {
2644 if (_g1_committed.contains(p)) {
2645 // Given that we know that p is in the committed space,
2646 // heap_region_containing_raw() should successfully
2647 // return the containing region.
2648 HeapRegion* hr = heap_region_containing_raw(p);
2649 return hr->is_in(p);
2650 } else {
2651 return _perm_gen->as_gen()->is_in(p);
2652 }
2653 }
2654
2655 // Iteration functions.
2656
2657 // Iterates an OopClosure over all ref-containing fields of objects
2658 // within a HeapRegion.
2659
2660 class IterateOopClosureRegionClosure: public HeapRegionClosure {
2661 MemRegion _mr;
2662 OopClosure* _cl;
2663 public:
2664 IterateOopClosureRegionClosure(MemRegion mr, OopClosure* cl)
2665 : _mr(mr), _cl(cl) {}
2666 bool doHeapRegion(HeapRegion* r) {
2667 if (!r->continuesHumongous()) {
2668 r->oop_iterate(_cl);
2669 }
2670 return false;
2671 }
2672 };
2673
2674 void G1CollectedHeap::oop_iterate(OopClosure* cl, bool do_perm) {
2675 IterateOopClosureRegionClosure blk(_g1_committed, cl);
2676 heap_region_iterate(&blk);
2677 if (do_perm) {
2678 perm_gen()->oop_iterate(cl);
2679 }
2680 }
2681
2682 void G1CollectedHeap::oop_iterate(MemRegion mr, OopClosure* cl, bool do_perm) {
2683 IterateOopClosureRegionClosure blk(mr, cl);
2684 heap_region_iterate(&blk);
2685 if (do_perm) {
2686 perm_gen()->oop_iterate(cl);
2687 }
2688 }
2689
2690 // Iterates an ObjectClosure over all objects within a HeapRegion.
2691
2692 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2693 ObjectClosure* _cl;
2694 public:
2695 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2696 bool doHeapRegion(HeapRegion* r) {
2697 if (! r->continuesHumongous()) {
2698 r->object_iterate(_cl);
2699 }
2700 return false;
2701 }
2702 };
2703
2704 void G1CollectedHeap::object_iterate(ObjectClosure* cl, bool do_perm) {
2705 IterateObjectClosureRegionClosure blk(cl);
2706 heap_region_iterate(&blk);
2707 if (do_perm) {
2708 perm_gen()->object_iterate(cl);
2709 }
2710 }
2711
2712 void G1CollectedHeap::object_iterate_since_last_GC(ObjectClosure* cl) {
2713 // FIXME: is this right?
2714 guarantee(false, "object_iterate_since_last_GC not supported by G1 heap");
2715 }
2716
2717 // Calls a SpaceClosure on a HeapRegion.
2718
2719 class SpaceClosureRegionClosure: public HeapRegionClosure {
2720 SpaceClosure* _cl;
2721 public:
2722 SpaceClosureRegionClosure(SpaceClosure* cl) : _cl(cl) {}
2723 bool doHeapRegion(HeapRegion* r) {
2724 _cl->do_space(r);
2725 return false;
2726 }
2727 };
2728
2729 void G1CollectedHeap::space_iterate(SpaceClosure* cl) {
2730 SpaceClosureRegionClosure blk(cl);
2731 heap_region_iterate(&blk);
2732 }
2733
2734 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2735 _hrs.iterate(cl);
2736 }
2737
2738 void
2739 G1CollectedHeap::heap_region_par_iterate_chunked(HeapRegionClosure* cl,
2740 uint worker_id,
2741 uint no_of_par_workers,
2742 jint claim_value) {
2743 const uint regions = n_regions();
2744 const uint max_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
2745 no_of_par_workers :
2746 1);
2747 assert(UseDynamicNumberOfGCThreads ||
2748 no_of_par_workers == workers()->total_workers(),
2749 "Non dynamic should use fixed number of workers");
2750 // try to spread out the starting points of the workers
2751 const HeapRegion* start_hr =
2752 start_region_for_worker(worker_id, no_of_par_workers);
2753 const uint start_index = start_hr->hrs_index();
2754
2755 // each worker will actually look at all regions
2756 for (uint count = 0; count < regions; ++count) {
2757 const uint index = (start_index + count) % regions;
2758 assert(0 <= index && index < regions, "sanity");
2759 HeapRegion* r = region_at(index);
2760 // we'll ignore "continues humongous" regions (we'll process them
2761 // when we come across their corresponding "start humongous"
2762 // region) and regions already claimed
2763 if (r->claim_value() == claim_value || r->continuesHumongous()) {
2764 continue;
2765 }
2766 // OK, try to claim it
2767 if (r->claimHeapRegion(claim_value)) {
2768 // success!
2769 assert(!r->continuesHumongous(), "sanity");
2770 if (r->startsHumongous()) {
2771 // If the region is "starts humongous" we'll iterate over its
2772 // "continues humongous" first; in fact we'll do them
2773 // first. The order is important. In on case, calling the
2774 // closure on the "starts humongous" region might de-allocate
2775 // and clear all its "continues humongous" regions and, as a
2776 // result, we might end up processing them twice. So, we'll do
2777 // them first (notice: most closures will ignore them anyway) and
2778 // then we'll do the "starts humongous" region.
2779 for (uint ch_index = index + 1; ch_index < regions; ++ch_index) {
2780 HeapRegion* chr = region_at(ch_index);
2781
2782 // if the region has already been claimed or it's not
2783 // "continues humongous" we're done
2784 if (chr->claim_value() == claim_value ||
2785 !chr->continuesHumongous()) {
2786 break;
2787 }
2788
2789 // Noone should have claimed it directly. We can given
2790 // that we claimed its "starts humongous" region.
2791 assert(chr->claim_value() != claim_value, "sanity");
2792 assert(chr->humongous_start_region() == r, "sanity");
2793
2794 if (chr->claimHeapRegion(claim_value)) {
2795 // we should always be able to claim it; noone else should
2796 // be trying to claim this region
2797
2798 bool res2 = cl->doHeapRegion(chr);
2799 assert(!res2, "Should not abort");
2800
2801 // Right now, this holds (i.e., no closure that actually
2802 // does something with "continues humongous" regions
2803 // clears them). We might have to weaken it in the future,
2804 // but let's leave these two asserts here for extra safety.
2805 assert(chr->continuesHumongous(), "should still be the case");
2806 assert(chr->humongous_start_region() == r, "sanity");
2807 } else {
2808 guarantee(false, "we should not reach here");
2809 }
2810 }
2811 }
2812
2813 assert(!r->continuesHumongous(), "sanity");
2814 bool res = cl->doHeapRegion(r);
2815 assert(!res, "Should not abort");
2816 }
2817 }
2818 }
2819
2820 class ResetClaimValuesClosure: public HeapRegionClosure {
2821 public:
2822 bool doHeapRegion(HeapRegion* r) {
2823 r->set_claim_value(HeapRegion::InitialClaimValue);
2824 return false;
2825 }
2826 };
2827
2828 void G1CollectedHeap::reset_heap_region_claim_values() {
2829 ResetClaimValuesClosure blk;
2830 heap_region_iterate(&blk);
2831 }
2832
2833 void G1CollectedHeap::reset_cset_heap_region_claim_values() {
2834 ResetClaimValuesClosure blk;
2835 collection_set_iterate(&blk);
2836 }
2837
2838 #ifdef ASSERT
2839 // This checks whether all regions in the heap have the correct claim
2840 // value. I also piggy-backed on this a check to ensure that the
2841 // humongous_start_region() information on "continues humongous"
2842 // regions is correct.
2843
2844 class CheckClaimValuesClosure : public HeapRegionClosure {
2845 private:
2846 jint _claim_value;
2847 uint _failures;
2848 HeapRegion* _sh_region;
2849
2850 public:
2851 CheckClaimValuesClosure(jint claim_value) :
2852 _claim_value(claim_value), _failures(0), _sh_region(NULL) { }
2853 bool doHeapRegion(HeapRegion* r) {
2854 if (r->claim_value() != _claim_value) {
2855 gclog_or_tty->print_cr("Region " HR_FORMAT ", "
2856 "claim value = %d, should be %d",
2857 HR_FORMAT_PARAMS(r),
2858 r->claim_value(), _claim_value);
2859 ++_failures;
2860 }
2861 if (!r->isHumongous()) {
2862 _sh_region = NULL;
2863 } else if (r->startsHumongous()) {
2864 _sh_region = r;
2865 } else if (r->continuesHumongous()) {
2866 if (r->humongous_start_region() != _sh_region) {
2867 gclog_or_tty->print_cr("Region " HR_FORMAT ", "
2868 "HS = "PTR_FORMAT", should be "PTR_FORMAT,
2869 HR_FORMAT_PARAMS(r),
2870 r->humongous_start_region(),
2871 _sh_region);
2872 ++_failures;
2873 }
2874 }
2875 return false;
2876 }
2877 uint failures() { return _failures; }
2878 };
2879
2880 bool G1CollectedHeap::check_heap_region_claim_values(jint claim_value) {
2881 CheckClaimValuesClosure cl(claim_value);
2882 heap_region_iterate(&cl);
2883 return cl.failures() == 0;
2884 }
2885
2886 class CheckClaimValuesInCSetHRClosure: public HeapRegionClosure {
2887 private:
2888 jint _claim_value;
2889 uint _failures;
2890
2891 public:
2892 CheckClaimValuesInCSetHRClosure(jint claim_value) :
2893 _claim_value(claim_value), _failures(0) { }
2894
2895 uint failures() { return _failures; }
2896
2897 bool doHeapRegion(HeapRegion* hr) {
2898 assert(hr->in_collection_set(), "how?");
2899 assert(!hr->isHumongous(), "H-region in CSet");
2900 if (hr->claim_value() != _claim_value) {
2901 gclog_or_tty->print_cr("CSet Region " HR_FORMAT ", "
2902 "claim value = %d, should be %d",
2903 HR_FORMAT_PARAMS(hr),
2904 hr->claim_value(), _claim_value);
2905 _failures += 1;
2906 }
2907 return false;
2908 }
2909 };
2910
2911 bool G1CollectedHeap::check_cset_heap_region_claim_values(jint claim_value) {
2912 CheckClaimValuesInCSetHRClosure cl(claim_value);
2913 collection_set_iterate(&cl);
2914 return cl.failures() == 0;
2915 }
2916 #endif // ASSERT
2917
2918 // Clear the cached CSet starting regions and (more importantly)
2919 // the time stamps. Called when we reset the GC time stamp.
2920 void G1CollectedHeap::clear_cset_start_regions() {
2921 assert(_worker_cset_start_region != NULL, "sanity");
2922 assert(_worker_cset_start_region_time_stamp != NULL, "sanity");
2923
2924 int n_queues = MAX2((int)ParallelGCThreads, 1);
2925 for (int i = 0; i < n_queues; i++) {
2926 _worker_cset_start_region[i] = NULL;
2927 _worker_cset_start_region_time_stamp[i] = 0;
2928 }
2929 }
2930
2931 // Given the id of a worker, obtain or calculate a suitable
2932 // starting region for iterating over the current collection set.
2933 HeapRegion* G1CollectedHeap::start_cset_region_for_worker(int worker_i) {
2934 assert(get_gc_time_stamp() > 0, "should have been updated by now");
2935
2936 HeapRegion* result = NULL;
2937 unsigned gc_time_stamp = get_gc_time_stamp();
2938
2939 if (_worker_cset_start_region_time_stamp[worker_i] == gc_time_stamp) {
2940 // Cached starting region for current worker was set
2941 // during the current pause - so it's valid.
2942 // Note: the cached starting heap region may be NULL
2943 // (when the collection set is empty).
2944 result = _worker_cset_start_region[worker_i];
2945 assert(result == NULL || result->in_collection_set(), "sanity");
2946 return result;
2947 }
2948
2949 // The cached entry was not valid so let's calculate
2950 // a suitable starting heap region for this worker.
2951
2952 // We want the parallel threads to start their collection
2953 // set iteration at different collection set regions to
2954 // avoid contention.
2955 // If we have:
2956 // n collection set regions
2957 // p threads
2958 // Then thread t will start at region floor ((t * n) / p)
2959
2960 result = g1_policy()->collection_set();
2961 if (G1CollectedHeap::use_parallel_gc_threads()) {
2962 uint cs_size = g1_policy()->cset_region_length();
2963 uint active_workers = workers()->active_workers();
2964 assert(UseDynamicNumberOfGCThreads ||
2965 active_workers == workers()->total_workers(),
2966 "Unless dynamic should use total workers");
2967
2968 uint end_ind = (cs_size * worker_i) / active_workers;
2969 uint start_ind = 0;
2970
2971 if (worker_i > 0 &&
2972 _worker_cset_start_region_time_stamp[worker_i - 1] == gc_time_stamp) {
2973 // Previous workers starting region is valid
2974 // so let's iterate from there
2975 start_ind = (cs_size * (worker_i - 1)) / active_workers;
2976 result = _worker_cset_start_region[worker_i - 1];
2977 }
2978
2979 for (uint i = start_ind; i < end_ind; i++) {
2980 result = result->next_in_collection_set();
2981 }
2982 }
2983
2984 // Note: the calculated starting heap region may be NULL
2985 // (when the collection set is empty).
2986 assert(result == NULL || result->in_collection_set(), "sanity");
2987 assert(_worker_cset_start_region_time_stamp[worker_i] != gc_time_stamp,
2988 "should be updated only once per pause");
2989 _worker_cset_start_region[worker_i] = result;
2990 OrderAccess::storestore();
2991 _worker_cset_start_region_time_stamp[worker_i] = gc_time_stamp;
2992 return result;
2993 }
2994
2995 HeapRegion* G1CollectedHeap::start_region_for_worker(uint worker_i,
2996 uint no_of_par_workers) {
2997 uint worker_num =
2998 G1CollectedHeap::use_parallel_gc_threads() ? no_of_par_workers : 1U;
2999 assert(UseDynamicNumberOfGCThreads ||
3000 no_of_par_workers == workers()->total_workers(),
3001 "Non dynamic should use fixed number of workers");
3002 const uint start_index = n_regions() * worker_i / worker_num;
3003 return region_at(start_index);
3004 }
3005
3006 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) {
3007 HeapRegion* r = g1_policy()->collection_set();
3008 while (r != NULL) {
3009 HeapRegion* next = r->next_in_collection_set();
3010 if (cl->doHeapRegion(r)) {
3011 cl->incomplete();
3012 return;
3013 }
3014 r = next;
3015 }
3016 }
3017
3018 void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r,
3019 HeapRegionClosure *cl) {
3020 if (r == NULL) {
3021 // The CSet is empty so there's nothing to do.
3022 return;
3023 }
3024
3025 assert(r->in_collection_set(),
3026 "Start region must be a member of the collection set.");
3027 HeapRegion* cur = r;
3028 while (cur != NULL) {
3029 HeapRegion* next = cur->next_in_collection_set();
3030 if (cl->doHeapRegion(cur) && false) {
3031 cl->incomplete();
3032 return;
3033 }
3034 cur = next;
3035 }
3036 cur = g1_policy()->collection_set();
3037 while (cur != r) {
3038 HeapRegion* next = cur->next_in_collection_set();
3039 if (cl->doHeapRegion(cur) && false) {
3040 cl->incomplete();
3041 return;
3042 }
3043 cur = next;
3044 }
3045 }
3046
3047 CompactibleSpace* G1CollectedHeap::first_compactible_space() {
3048 return n_regions() > 0 ? region_at(0) : NULL;
3049 }
3050
3051
3052 Space* G1CollectedHeap::space_containing(const void* addr) const {
3053 Space* res = heap_region_containing(addr);
3054 if (res == NULL)
3055 res = perm_gen()->space_containing(addr);
3056 return res;
3057 }
3058
3059 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
3060 Space* sp = space_containing(addr);
3061 if (sp != NULL) {
3062 return sp->block_start(addr);
3063 }
3064 return NULL;
3065 }
3066
3067 size_t G1CollectedHeap::block_size(const HeapWord* addr) const {
3068 Space* sp = space_containing(addr);
3069 assert(sp != NULL, "block_size of address outside of heap");
3070 return sp->block_size(addr);
3071 }
3072
3073 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
3074 Space* sp = space_containing(addr);
3075 return sp->block_is_obj(addr);
3076 }
3077
3078 bool G1CollectedHeap::supports_tlab_allocation() const {
3079 return true;
3080 }
3081
3082 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
3083 return HeapRegion::GrainBytes;
3084 }
3085
3086 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
3087 // Return the remaining space in the cur alloc region, but not less than
3088 // the min TLAB size.
3089
3090 // Also, this value can be at most the humongous object threshold,
3091 // since we can't allow tlabs to grow big enough to accommodate
3092 // humongous objects.
3093
3094 HeapRegion* hr = _mutator_alloc_region.get();
3095 size_t max_tlab_size = _humongous_object_threshold_in_words * wordSize;
3096 if (hr == NULL) {
3097 return max_tlab_size;
3098 } else {
3099 return MIN2(MAX2(hr->free(), (size_t) MinTLABSize), max_tlab_size);
3100 }
3101 }
3102
3103 size_t G1CollectedHeap::max_capacity() const {
3104 return _g1_reserved.byte_size();
3105 }
3106
3107 jlong G1CollectedHeap::millis_since_last_gc() {
3108 // assert(false, "NYI");
3109 return 0;
3110 }
3111
3112 void G1CollectedHeap::prepare_for_verify() {
3113 if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) {
3114 ensure_parsability(false);
3115 }
3116 g1_rem_set()->prepare_for_verify();
3117 }
3118
3119 bool G1CollectedHeap::allocated_since_marking(oop obj, HeapRegion* hr,
3120 VerifyOption vo) {
3121 switch (vo) {
3122 case VerifyOption_G1UsePrevMarking:
3123 return hr->obj_allocated_since_prev_marking(obj);
3124 case VerifyOption_G1UseNextMarking:
3125 return hr->obj_allocated_since_next_marking(obj);
3126 case VerifyOption_G1UseMarkWord:
3127 return false;
3128 default:
3129 ShouldNotReachHere();
3130 }
3131 return false; // keep some compilers happy
3132 }
3133
3134 HeapWord* G1CollectedHeap::top_at_mark_start(HeapRegion* hr, VerifyOption vo) {
3135 switch (vo) {
3136 case VerifyOption_G1UsePrevMarking: return hr->prev_top_at_mark_start();
3137 case VerifyOption_G1UseNextMarking: return hr->next_top_at_mark_start();
3138 case VerifyOption_G1UseMarkWord: return NULL;
3139 default: ShouldNotReachHere();
3140 }
3141 return NULL; // keep some compilers happy
3142 }
3143
3144 bool G1CollectedHeap::is_marked(oop obj, VerifyOption vo) {
3145 switch (vo) {
3146 case VerifyOption_G1UsePrevMarking: return isMarkedPrev(obj);
3147 case VerifyOption_G1UseNextMarking: return isMarkedNext(obj);
3148 case VerifyOption_G1UseMarkWord: return obj->is_gc_marked();
3149 default: ShouldNotReachHere();
3150 }
3151 return false; // keep some compilers happy
3152 }
3153
3154 const char* G1CollectedHeap::top_at_mark_start_str(VerifyOption vo) {
3155 switch (vo) {
3156 case VerifyOption_G1UsePrevMarking: return "PTAMS";
3157 case VerifyOption_G1UseNextMarking: return "NTAMS";
3158 case VerifyOption_G1UseMarkWord: return "NONE";
3159 default: ShouldNotReachHere();
3160 }
3161 return NULL; // keep some compilers happy
3162 }
3163
3164 class VerifyLivenessOopClosure: public OopClosure {
3165 G1CollectedHeap* _g1h;
3166 VerifyOption _vo;
3167 public:
3168 VerifyLivenessOopClosure(G1CollectedHeap* g1h, VerifyOption vo):
3169 _g1h(g1h), _vo(vo)
3170 { }
3171 void do_oop(narrowOop *p) { do_oop_work(p); }
3172 void do_oop( oop *p) { do_oop_work(p); }
3173
3174 template <class T> void do_oop_work(T *p) {
3175 oop obj = oopDesc::load_decode_heap_oop(p);
3176 guarantee(obj == NULL || !_g1h->is_obj_dead_cond(obj, _vo),
3177 "Dead object referenced by a not dead object");
3178 }
3179 };
3180
3181 class VerifyObjsInRegionClosure: public ObjectClosure {
3182 private:
3183 G1CollectedHeap* _g1h;
3184 size_t _live_bytes;
3185 HeapRegion *_hr;
3186 VerifyOption _vo;
3187 public:
3188 // _vo == UsePrevMarking -> use "prev" marking information,
3189 // _vo == UseNextMarking -> use "next" marking information,
3190 // _vo == UseMarkWord -> use mark word from object header.
3191 VerifyObjsInRegionClosure(HeapRegion *hr, VerifyOption vo)
3192 : _live_bytes(0), _hr(hr), _vo(vo) {
3193 _g1h = G1CollectedHeap::heap();
3194 }
3195 void do_object(oop o) {
3196 VerifyLivenessOopClosure isLive(_g1h, _vo);
3197 assert(o != NULL, "Huh?");
3198 if (!_g1h->is_obj_dead_cond(o, _vo)) {
3199 // If the object is alive according to the mark word,
3200 // then verify that the marking information agrees.
3201 // Note we can't verify the contra-positive of the
3202 // above: if the object is dead (according to the mark
3203 // word), it may not be marked, or may have been marked
3204 // but has since became dead, or may have been allocated
3205 // since the last marking.
3206 if (_vo == VerifyOption_G1UseMarkWord) {
3207 guarantee(!_g1h->is_obj_dead(o), "mark word and concurrent mark mismatch");
3208 }
3209
3210 o->oop_iterate(&isLive);
3211 if (!_hr->obj_allocated_since_prev_marking(o)) {
3212 size_t obj_size = o->size(); // Make sure we don't overflow
3213 _live_bytes += (obj_size * HeapWordSize);
3214 }
3215 }
3216 }
3217 size_t live_bytes() { return _live_bytes; }
3218 };
3219
3220 class PrintObjsInRegionClosure : public ObjectClosure {
3221 HeapRegion *_hr;
3222 G1CollectedHeap *_g1;
3223 public:
3224 PrintObjsInRegionClosure(HeapRegion *hr) : _hr(hr) {
3225 _g1 = G1CollectedHeap::heap();
3226 };
3227
3228 void do_object(oop o) {
3229 if (o != NULL) {
3230 HeapWord *start = (HeapWord *) o;
3231 size_t word_sz = o->size();
3232 gclog_or_tty->print("\nPrinting obj "PTR_FORMAT" of size " SIZE_FORMAT
3233 " isMarkedPrev %d isMarkedNext %d isAllocSince %d\n",
3234 (void*) o, word_sz,
3235 _g1->isMarkedPrev(o),
3236 _g1->isMarkedNext(o),
3237 _hr->obj_allocated_since_prev_marking(o));
3238 HeapWord *end = start + word_sz;
3239 HeapWord *cur;
3240 int *val;
3241 for (cur = start; cur < end; cur++) {
3242 val = (int *) cur;
3243 gclog_or_tty->print("\t "PTR_FORMAT":"PTR_FORMAT"\n", val, *val);
3244 }
3245 }
3246 }
3247 };
3248
3249 class VerifyRegionClosure: public HeapRegionClosure {
3250 private:
3251 bool _par;
3252 VerifyOption _vo;
3253 bool _failures;
3254 public:
3255 // _vo == UsePrevMarking -> use "prev" marking information,
3256 // _vo == UseNextMarking -> use "next" marking information,
3257 // _vo == UseMarkWord -> use mark word from object header.
3258 VerifyRegionClosure(bool par, VerifyOption vo)
3259 : _par(par),
3260 _vo(vo),
3261 _failures(false) {}
3262
3263 bool failures() {
3264 return _failures;
3265 }
3266
3267 bool doHeapRegion(HeapRegion* r) {
3268 if (!r->continuesHumongous()) {
3269 bool failures = false;
3270 r->verify(_vo, &failures);
3271 if (failures) {
3272 _failures = true;
3273 } else {
3274 VerifyObjsInRegionClosure not_dead_yet_cl(r, _vo);
3275 r->object_iterate(¬_dead_yet_cl);
3276 if (_vo != VerifyOption_G1UseNextMarking) {
3277 if (r->max_live_bytes() < not_dead_yet_cl.live_bytes()) {
3278 gclog_or_tty->print_cr("["PTR_FORMAT","PTR_FORMAT"] "
3279 "max_live_bytes "SIZE_FORMAT" "
3280 "< calculated "SIZE_FORMAT,
3281 r->bottom(), r->end(),
3282 r->max_live_bytes(),
3283 not_dead_yet_cl.live_bytes());
3284 _failures = true;
3285 }
3286 } else {
3287 // When vo == UseNextMarking we cannot currently do a sanity
3288 // check on the live bytes as the calculation has not been
3289 // finalized yet.
3290 }
3291 }
3292 }
3293 return false; // stop the region iteration if we hit a failure
3294 }
3295 };
3296
3297 class VerifyRootsClosure: public OopsInGenClosure {
3298 private:
3299 G1CollectedHeap* _g1h;
3300 VerifyOption _vo;
3301 bool _failures;
3302 public:
3303 // _vo == UsePrevMarking -> use "prev" marking information,
3304 // _vo == UseNextMarking -> use "next" marking information,
3305 // _vo == UseMarkWord -> use mark word from object header.
3306 VerifyRootsClosure(VerifyOption vo) :
3307 _g1h(G1CollectedHeap::heap()),
3308 _vo(vo),
3309 _failures(false) { }
3310
3311 bool failures() { return _failures; }
3312
3313 template <class T> void do_oop_nv(T* p) {
3314 T heap_oop = oopDesc::load_heap_oop(p);
3315 if (!oopDesc::is_null(heap_oop)) {
3316 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
3317 if (_g1h->is_obj_dead_cond(obj, _vo)) {
3318 gclog_or_tty->print_cr("Root location "PTR_FORMAT" "
3319 "points to dead obj "PTR_FORMAT, p, (void*) obj);
3320 if (_vo == VerifyOption_G1UseMarkWord) {
3321 gclog_or_tty->print_cr(" Mark word: "PTR_FORMAT, (void*)(obj->mark()));
3322 }
3323 obj->print_on(gclog_or_tty);
3324 _failures = true;
3325 }
3326 }
3327 }
3328
3329 void do_oop(oop* p) { do_oop_nv(p); }
3330 void do_oop(narrowOop* p) { do_oop_nv(p); }
3331 };
3332
3333 // This is the task used for parallel heap verification.
3334
3335 class G1ParVerifyTask: public AbstractGangTask {
3336 private:
3337 G1CollectedHeap* _g1h;
3338 VerifyOption _vo;
3339 bool _failures;
3340
3341 public:
3342 // _vo == UsePrevMarking -> use "prev" marking information,
3343 // _vo == UseNextMarking -> use "next" marking information,
3344 // _vo == UseMarkWord -> use mark word from object header.
3345 G1ParVerifyTask(G1CollectedHeap* g1h, VerifyOption vo) :
3346 AbstractGangTask("Parallel verify task"),
3347 _g1h(g1h),
3348 _vo(vo),
3349 _failures(false) { }
3350
3351 bool failures() {
3352 return _failures;
3353 }
3354
3355 void work(uint worker_id) {
3356 HandleMark hm;
3357 VerifyRegionClosure blk(true, _vo);
3358 _g1h->heap_region_par_iterate_chunked(&blk, worker_id,
3359 _g1h->workers()->active_workers(),
3360 HeapRegion::ParVerifyClaimValue);
3361 if (blk.failures()) {
3362 _failures = true;
3363 }
3364 }
3365 };
3366
3367 void G1CollectedHeap::verify(bool silent) {
3368 verify(silent, VerifyOption_G1UsePrevMarking);
3369 }
3370
3371 void G1CollectedHeap::verify(bool silent,
3372 VerifyOption vo) {
3373 if (SafepointSynchronize::is_at_safepoint()) {
3374 if (!silent) { gclog_or_tty->print("Roots (excluding permgen) "); }
3375 VerifyRootsClosure rootsCl(vo);
3376
3377 assert(Thread::current()->is_VM_thread(),
3378 "Expected to be executed serially by the VM thread at this point");
3379
3380 CodeBlobToOopClosure blobsCl(&rootsCl, /*do_marking=*/ false);
3381
3382 // We apply the relevant closures to all the oops in the
3383 // system dictionary, the string table and the code cache.
3384 const int so = SO_AllClasses | SO_Strings | SO_CodeCache;
3385
3386 process_strong_roots(true, // activate StrongRootsScope
3387 true, // we set "collecting perm gen" to true,
3388 // so we don't reset the dirty cards in the perm gen.
3389 ScanningOption(so), // roots scanning options
3390 &rootsCl,
3391 &blobsCl,
3392 &rootsCl);
3393
3394 // If we're verifying after the marking phase of a Full GC then we can't
3395 // treat the perm gen as roots into the G1 heap. Some of the objects in
3396 // the perm gen may be dead and hence not marked. If one of these dead
3397 // objects is considered to be a root then we may end up with a false
3398 // "Root location <x> points to dead ob <y>" failure.
3399 if (vo != VerifyOption_G1UseMarkWord) {
3400 // Since we used "collecting_perm_gen" == true above, we will not have
3401 // checked the refs from perm into the G1-collected heap. We check those
3402 // references explicitly below. Whether the relevant cards are dirty
3403 // is checked further below in the rem set verification.
3404 if (!silent) { gclog_or_tty->print("Permgen roots "); }
3405 perm_gen()->oop_iterate(&rootsCl);
3406 }
3407 bool failures = rootsCl.failures();
3408
3409 if (vo != VerifyOption_G1UseMarkWord) {
3410 // If we're verifying during a full GC then the region sets
3411 // will have been torn down at the start of the GC. Therefore
3412 // verifying the region sets will fail. So we only verify
3413 // the region sets when not in a full GC.
3414 if (!silent) { gclog_or_tty->print("HeapRegionSets "); }
3415 verify_region_sets();
3416 }
3417
3418 if (!silent) { gclog_or_tty->print("HeapRegions "); }
3419 if (GCParallelVerificationEnabled && ParallelGCThreads > 1) {
3420 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3421 "sanity check");
3422
3423 G1ParVerifyTask task(this, vo);
3424 assert(UseDynamicNumberOfGCThreads ||
3425 workers()->active_workers() == workers()->total_workers(),
3426 "If not dynamic should be using all the workers");
3427 int n_workers = workers()->active_workers();
3428 set_par_threads(n_workers);
3429 workers()->run_task(&task);
3430 set_par_threads(0);
3431 if (task.failures()) {
3432 failures = true;
3433 }
3434
3435 // Checks that the expected amount of parallel work was done.
3436 // The implication is that n_workers is > 0.
3437 assert(check_heap_region_claim_values(HeapRegion::ParVerifyClaimValue),
3438 "sanity check");
3439
3440 reset_heap_region_claim_values();
3441
3442 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3443 "sanity check");
3444 } else {
3445 VerifyRegionClosure blk(false, vo);
3446 heap_region_iterate(&blk);
3447 if (blk.failures()) {
3448 failures = true;
3449 }
3450 }
3451 if (!silent) gclog_or_tty->print("RemSet ");
3452 rem_set()->verify();
3453
3454 if (failures) {
3455 gclog_or_tty->print_cr("Heap:");
3456 // It helps to have the per-region information in the output to
3457 // help us track down what went wrong. This is why we call
3458 // print_extended_on() instead of print_on().
3459 print_extended_on(gclog_or_tty);
3460 gclog_or_tty->print_cr("");
3461 #ifndef PRODUCT
3462 if (VerifyDuringGC && G1VerifyDuringGCPrintReachable) {
3463 concurrent_mark()->print_reachable("at-verification-failure",
3464 vo, false /* all */);
3465 }
3466 #endif
3467 gclog_or_tty->flush();
3468 }
3469 guarantee(!failures, "there should not have been any failures");
3470 } else {
3471 if (!silent)
3472 gclog_or_tty->print("(SKIPPING roots, heapRegionSets, heapRegions, remset) ");
3473 }
3474 }
3475
3476 class PrintRegionClosure: public HeapRegionClosure {
3477 outputStream* _st;
3478 public:
3479 PrintRegionClosure(outputStream* st) : _st(st) {}
3480 bool doHeapRegion(HeapRegion* r) {
3481 r->print_on(_st);
3482 return false;
3483 }
3484 };
3485
3486 void G1CollectedHeap::print_on(outputStream* st) const {
3487 st->print(" %-20s", "garbage-first heap");
3488 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
3489 capacity()/K, used_unlocked()/K);
3490 st->print(" [" INTPTR_FORMAT ", " INTPTR_FORMAT ", " INTPTR_FORMAT ")",
3491 _g1_storage.low_boundary(),
3492 _g1_storage.high(),
3493 _g1_storage.high_boundary());
3494 st->cr();
3495 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
3496 uint young_regions = _young_list->length();
3497 st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
3498 (size_t) young_regions * HeapRegion::GrainBytes / K);
3499 uint survivor_regions = g1_policy()->recorded_survivor_regions();
3500 st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
3501 (size_t) survivor_regions * HeapRegion::GrainBytes / K);
3502 st->cr();
3503 perm()->as_gen()->print_on(st);
3504 }
3505
3506 void G1CollectedHeap::print_extended_on(outputStream* st) const {
3507 print_on(st);
3508
3509 // Print the per-region information.
3510 st->cr();
3511 st->print_cr("Heap Regions: (Y=young(eden), SU=young(survivor), "
3512 "HS=humongous(starts), HC=humongous(continues), "
3513 "CS=collection set, F=free, TS=gc time stamp, "
3514 "PTAMS=previous top-at-mark-start, "
3515 "NTAMS=next top-at-mark-start)");
3516 PrintRegionClosure blk(st);
3517 heap_region_iterate(&blk);
3518 }
3519
3520 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
3521 if (G1CollectedHeap::use_parallel_gc_threads()) {
3522 workers()->print_worker_threads_on(st);
3523 }
3524 _cmThread->print_on(st);
3525 st->cr();
3526 _cm->print_worker_threads_on(st);
3527 _cg1r->print_worker_threads_on(st);
3528 st->cr();
3529 }
3530
3531 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
3532 if (G1CollectedHeap::use_parallel_gc_threads()) {
3533 workers()->threads_do(tc);
3534 }
3535 tc->do_thread(_cmThread);
3536 _cg1r->threads_do(tc);
3537 }
3538
3539 void G1CollectedHeap::print_tracing_info() const {
3540 // We'll overload this to mean "trace GC pause statistics."
3541 if (TraceGen0Time || TraceGen1Time) {
3542 // The "G1CollectorPolicy" is keeping track of these stats, so delegate
3543 // to that.
3544 g1_policy()->print_tracing_info();
3545 }
3546 if (G1SummarizeRSetStats) {
3547 g1_rem_set()->print_summary_info();
3548 }
3549 if (G1SummarizeConcMark) {
3550 concurrent_mark()->print_summary_info();
3551 }
3552 g1_policy()->print_yg_surv_rate_info();
3553 SpecializationStats::print();
3554 }
3555
3556 #ifndef PRODUCT
3557 // Helpful for debugging RSet issues.
3558
3559 class PrintRSetsClosure : public HeapRegionClosure {
3560 private:
3561 const char* _msg;
3562 size_t _occupied_sum;
3563
3564 public:
3565 bool doHeapRegion(HeapRegion* r) {
3566 HeapRegionRemSet* hrrs = r->rem_set();
3567 size_t occupied = hrrs->occupied();
3568 _occupied_sum += occupied;
3569
3570 gclog_or_tty->print_cr("Printing RSet for region "HR_FORMAT,
3571 HR_FORMAT_PARAMS(r));
3572 if (occupied == 0) {
3573 gclog_or_tty->print_cr(" RSet is empty");
3574 } else {
3575 hrrs->print();
3576 }
3577 gclog_or_tty->print_cr("----------");
3578 return false;
3579 }
3580
3581 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
3582 gclog_or_tty->cr();
3583 gclog_or_tty->print_cr("========================================");
3584 gclog_or_tty->print_cr(msg);
3585 gclog_or_tty->cr();
3586 }
3587
3588 ~PrintRSetsClosure() {
3589 gclog_or_tty->print_cr("Occupied Sum: "SIZE_FORMAT, _occupied_sum);
3590 gclog_or_tty->print_cr("========================================");
3591 gclog_or_tty->cr();
3592 }
3593 };
3594
3595 void G1CollectedHeap::print_cset_rsets() {
3596 PrintRSetsClosure cl("Printing CSet RSets");
3597 collection_set_iterate(&cl);
3598 }
3599
3600 void G1CollectedHeap::print_all_rsets() {
3601 PrintRSetsClosure cl("Printing All RSets");;
3602 heap_region_iterate(&cl);
3603 }
3604 #endif // PRODUCT
3605
3606 G1CollectedHeap* G1CollectedHeap::heap() {
3607 assert(_sh->kind() == CollectedHeap::G1CollectedHeap,
3608 "not a garbage-first heap");
3609 return _g1h;
3610 }
3611
3612 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) {
3613 // always_do_update_barrier = false;
3614 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
3615 // Call allocation profiler
3616 AllocationProfiler::iterate_since_last_gc();
3617 // Fill TLAB's and such
3618 ensure_parsability(true);
3619 }
3620
3621 void G1CollectedHeap::gc_epilogue(bool full /* Ignored */) {
3622 // FIXME: what is this about?
3623 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
3624 // is set.
3625 COMPILER2_PRESENT(assert(DerivedPointerTable::is_empty(),
3626 "derived pointer present"));
3627 // always_do_update_barrier = true;
3628
3629 // We have just completed a GC. Update the soft reference
3630 // policy with the new heap occupancy
3631 Universe::update_heap_info_at_gc();
3632 }
3633
3634 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
3635 unsigned int gc_count_before,
3636 bool* succeeded) {
3637 assert_heap_not_locked_and_not_at_safepoint();
3638 g1_policy()->record_stop_world_start();
3639 VM_G1IncCollectionPause op(gc_count_before,
3640 word_size,
3641 false, /* should_initiate_conc_mark */
3642 g1_policy()->max_pause_time_ms(),
3643 GCCause::_g1_inc_collection_pause);
3644 VMThread::execute(&op);
3645
3646 HeapWord* result = op.result();
3647 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
3648 assert(result == NULL || ret_succeeded,
3649 "the result should be NULL if the VM did not succeed");
3650 *succeeded = ret_succeeded;
3651
3652 assert_heap_not_locked();
3653 return result;
3654 }
3655
3656 void
3657 G1CollectedHeap::doConcurrentMark() {
3658 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
3659 if (!_cmThread->in_progress()) {
3660 _cmThread->set_started();
3661 CGC_lock->notify();
3662 }
3663 }
3664
3665 size_t G1CollectedHeap::pending_card_num() {
3666 size_t extra_cards = 0;
3667 JavaThread *curr = Threads::first();
3668 while (curr != NULL) {
3669 DirtyCardQueue& dcq = curr->dirty_card_queue();
3670 extra_cards += dcq.size();
3671 curr = curr->next();
3672 }
3673 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
3674 size_t buffer_size = dcqs.buffer_size();
3675 size_t buffer_num = dcqs.completed_buffers_num();
3676
3677 // PtrQueueSet::buffer_size() and PtrQueue:size() return sizes
3678 // in bytes - not the number of 'entries'. We need to convert
3679 // into a number of cards.
3680 return (buffer_size * buffer_num + extra_cards) / oopSize;
3681 }
3682
3683 size_t G1CollectedHeap::cards_scanned() {
3684 return g1_rem_set()->cardsScanned();
3685 }
3686
3687 void
3688 G1CollectedHeap::setup_surviving_young_words() {
3689 assert(_surviving_young_words == NULL, "pre-condition");
3690 uint array_length = g1_policy()->young_cset_region_length();
3691 _surviving_young_words = NEW_C_HEAP_ARRAY(size_t, (size_t) array_length, mtGC);
3692 if (_surviving_young_words == NULL) {
3693 vm_exit_out_of_memory(sizeof(size_t) * array_length,
3694 "Not enough space for young surv words summary.");
3695 }
3696 memset(_surviving_young_words, 0, (size_t) array_length * sizeof(size_t));
3697 #ifdef ASSERT
3698 for (uint i = 0; i < array_length; ++i) {
3699 assert( _surviving_young_words[i] == 0, "memset above" );
3700 }
3701 #endif // !ASSERT
3702 }
3703
3704 void
3705 G1CollectedHeap::update_surviving_young_words(size_t* surv_young_words) {
3706 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
3707 uint array_length = g1_policy()->young_cset_region_length();
3708 for (uint i = 0; i < array_length; ++i) {
3709 _surviving_young_words[i] += surv_young_words[i];
3710 }
3711 }
3712
3713 void
3714 G1CollectedHeap::cleanup_surviving_young_words() {
3715 guarantee( _surviving_young_words != NULL, "pre-condition" );
3716 FREE_C_HEAP_ARRAY(size_t, _surviving_young_words, mtGC);
3717 _surviving_young_words = NULL;
3718 }
3719
3720 #ifdef ASSERT
3721 class VerifyCSetClosure: public HeapRegionClosure {
3722 public:
3723 bool doHeapRegion(HeapRegion* hr) {
3724 // Here we check that the CSet region's RSet is ready for parallel
3725 // iteration. The fields that we'll verify are only manipulated
3726 // when the region is part of a CSet and is collected. Afterwards,
3727 // we reset these fields when we clear the region's RSet (when the
3728 // region is freed) so they are ready when the region is
3729 // re-allocated. The only exception to this is if there's an
3730 // evacuation failure and instead of freeing the region we leave
3731 // it in the heap. In that case, we reset these fields during
3732 // evacuation failure handling.
3733 guarantee(hr->rem_set()->verify_ready_for_par_iteration(), "verification");
3734
3735 // Here's a good place to add any other checks we'd like to
3736 // perform on CSet regions.
3737 return false;
3738 }
3739 };
3740 #endif // ASSERT
3741
3742 #if TASKQUEUE_STATS
3743 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
3744 st->print_raw_cr("GC Task Stats");
3745 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
3746 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
3747 }
3748
3749 void G1CollectedHeap::print_taskqueue_stats(outputStream* const st) const {
3750 print_taskqueue_stats_hdr(st);
3751
3752 TaskQueueStats totals;
3753 const int n = workers() != NULL ? workers()->total_workers() : 1;
3754 for (int i = 0; i < n; ++i) {
3755 st->print("%3d ", i); task_queue(i)->stats.print(st); st->cr();
3756 totals += task_queue(i)->stats;
3757 }
3758 st->print_raw("tot "); totals.print(st); st->cr();
3759
3760 DEBUG_ONLY(totals.verify());
3761 }
3762
3763 void G1CollectedHeap::reset_taskqueue_stats() {
3764 const int n = workers() != NULL ? workers()->total_workers() : 1;
3765 for (int i = 0; i < n; ++i) {
3766 task_queue(i)->stats.reset();
3767 }
3768 }
3769 #endif // TASKQUEUE_STATS
3770
3771 void G1CollectedHeap::log_gc_header() {
3772 if (!G1Log::fine()) {
3773 return;
3774 }
3775
3776 gclog_or_tty->date_stamp(PrintGCDateStamps);
3777 gclog_or_tty->stamp(PrintGCTimeStamps);
3778
3779 GCCauseString gc_cause_str = GCCauseString("GC pause", gc_cause())
3780 .append(g1_policy()->gcs_are_young() ? " (young)" : " (mixed)")
3781 .append(g1_policy()->during_initial_mark_pause() ? " (initial-mark)" : "");
3782
3783 gclog_or_tty->print("[%s", (const char*)gc_cause_str);
3784 }
3785
3786 void G1CollectedHeap::log_gc_footer(double pause_time_sec) {
3787 if (!G1Log::fine()) {
3788 return;
3789 }
3790
3791 if (G1Log::finer()) {
3792 if (evacuation_failed()) {
3793 gclog_or_tty->print(" (to-space exhausted)");
3794 }
3795 gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec);
3796 g1_policy()->phase_times()->note_gc_end();
3797 g1_policy()->phase_times()->print(pause_time_sec);
3798 g1_policy()->print_detailed_heap_transition();
3799 } else {
3800 if (evacuation_failed()) {
3801 gclog_or_tty->print("--");
3802 }
3803 g1_policy()->print_heap_transition();
3804 gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec);
3805 }
3806 gclog_or_tty->flush();
3807 }
3808
3809 bool
3810 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
3811 assert_at_safepoint(true /* should_be_vm_thread */);
3812 guarantee(!is_gc_active(), "collection is not reentrant");
3813
3814 if (GC_locker::check_active_before_gc()) {
3815 return false;
3816 }
3817
3818 _gc_timer_stw->register_gc_start(os::elapsed_counter());
3819
3820 _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start());
3821
3822 SvcGCMarker sgcm(SvcGCMarker::MINOR);
3823 ResourceMark rm;
3824
3825 print_heap_before_gc();
3826 trace_heap_before_gc(_gc_tracer_stw);
3827
3828 HRSPhaseSetter x(HRSPhaseEvacuation);
3829 verify_region_sets_optional();
3830 verify_dirty_young_regions();
3831
3832 // This call will decide whether this pause is an initial-mark
3833 // pause. If it is, during_initial_mark_pause() will return true
3834 // for the duration of this pause.
3835 g1_policy()->decide_on_conc_mark_initiation();
3836
3837 // We do not allow initial-mark to be piggy-backed on a mixed GC.
3838 assert(!g1_policy()->during_initial_mark_pause() ||
3839 g1_policy()->gcs_are_young(), "sanity");
3840
3841 // We also do not allow mixed GCs during marking.
3842 assert(!mark_in_progress() || g1_policy()->gcs_are_young(), "sanity");
3843
3844 // Record whether this pause is an initial mark. When the current
3845 // thread has completed its logging output and it's safe to signal
3846 // the CM thread, the flag's value in the policy has been reset.
3847 bool should_start_conc_mark = g1_policy()->during_initial_mark_pause();
3848
3849 // Inner scope for scope based logging, timers, and stats collection
3850 {
3851 EvacuationInfo evacuation_info;
3852
3853 if (g1_policy()->during_initial_mark_pause()) {
3854 // We are about to start a marking cycle, so we increment the
3855 // full collection counter.
3856 increment_old_marking_cycles_started();
3857 register_concurrent_cycle_start(_gc_timer_stw->gc_start());
3858 }
3859
3860 _gc_tracer_stw->report_yc_type(yc_type());
3861
3862 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
3863
3864 int active_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
3865 workers()->active_workers() : 1);
3866 double pause_start_sec = os::elapsedTime();
3867 g1_policy()->phase_times()->note_gc_start(active_workers);
3868 log_gc_header();
3869
3870 TraceCollectorStats tcs(g1mm()->incremental_collection_counters());
3871 TraceMemoryManagerStats tms(false /* fullGC */, gc_cause());
3872
3873 // If the secondary_free_list is not empty, append it to the
3874 // free_list. No need to wait for the cleanup operation to finish;
3875 // the region allocation code will check the secondary_free_list
3876 // and wait if necessary. If the G1StressConcRegionFreeing flag is
3877 // set, skip this step so that the region allocation code has to
3878 // get entries from the secondary_free_list.
3879 if (!G1StressConcRegionFreeing) {
3880 append_secondary_free_list_if_not_empty_with_lock();
3881 }
3882
3883 assert(check_young_list_well_formed(),
3884 "young list should be well formed");
3885
3886 // Don't dynamically change the number of GC threads this early. A value of
3887 // 0 is used to indicate serial work. When parallel work is done,
3888 // it will be set.
3889
3890 { // Call to jvmpi::post_class_unload_events must occur outside of active GC
3891 IsGCActiveMark x;
3892
3893 gc_prologue(false);
3894 increment_total_collections(false /* full gc */);
3895 increment_gc_time_stamp();
3896
3897 verify_before_gc();
3898
3899 COMPILER2_PRESENT(DerivedPointerTable::clear());
3900
3901 // Please see comment in g1CollectedHeap.hpp and
3902 // G1CollectedHeap::ref_processing_init() to see how
3903 // reference processing currently works in G1.
3904
3905 // Enable discovery in the STW reference processor
3906 ref_processor_stw()->enable_discovery(true /*verify_disabled*/,
3907 true /*verify_no_refs*/);
3908
3909 {
3910 // We want to temporarily turn off discovery by the
3911 // CM ref processor, if necessary, and turn it back on
3912 // on again later if we do. Using a scoped
3913 // NoRefDiscovery object will do this.
3914 NoRefDiscovery no_cm_discovery(ref_processor_cm());
3915
3916 // Forget the current alloc region (we might even choose it to be part
3917 // of the collection set!).
3918 release_mutator_alloc_region();
3919
3920 // We should call this after we retire the mutator alloc
3921 // region(s) so that all the ALLOC / RETIRE events are generated
3922 // before the start GC event.
3923 _hr_printer.start_gc(false /* full */, (size_t) total_collections());
3924
3925 // This timing is only used by the ergonomics to handle our pause target.
3926 // It is unclear why this should not include the full pause. We will
3927 // investigate this in CR 7178365.
3928 //
3929 // Preserving the old comment here if that helps the investigation:
3930 //
3931 // The elapsed time induced by the start time below deliberately elides
3932 // the possible verification above.
3933 double sample_start_time_sec = os::elapsedTime();
3934
3935 #if YOUNG_LIST_VERBOSE
3936 gclog_or_tty->print_cr("\nBefore recording pause start.\nYoung_list:");
3937 _young_list->print();
3938 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3939 #endif // YOUNG_LIST_VERBOSE
3940
3941 g1_policy()->record_collection_pause_start(sample_start_time_sec);
3942
3943 double scan_wait_start = os::elapsedTime();
3944 // We have to wait until the CM threads finish scanning the
3945 // root regions as it's the only way to ensure that all the
3946 // objects on them have been correctly scanned before we start
3947 // moving them during the GC.
3948 bool waited = _cm->root_regions()->wait_until_scan_finished();
3949 double wait_time_ms = 0.0;
3950 if (waited) {
3951 double scan_wait_end = os::elapsedTime();
3952 wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
3953 }
3954 g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms);
3955
3956 #if YOUNG_LIST_VERBOSE
3957 gclog_or_tty->print_cr("\nAfter recording pause start.\nYoung_list:");
3958 _young_list->print();
3959 #endif // YOUNG_LIST_VERBOSE
3960
3961 if (g1_policy()->during_initial_mark_pause()) {
3962 concurrent_mark()->checkpointRootsInitialPre();
3963 }
3964 perm_gen()->save_marks();
3965
3966 #if YOUNG_LIST_VERBOSE
3967 gclog_or_tty->print_cr("\nBefore choosing collection set.\nYoung_list:");
3968 _young_list->print();
3969 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3970 #endif // YOUNG_LIST_VERBOSE
3971
3972 g1_policy()->finalize_cset(target_pause_time_ms, evacuation_info);
3973
3974 _cm->note_start_of_gc();
3975 // We should not verify the per-thread SATB buffers given that
3976 // we have not filtered them yet (we'll do so during the
3977 // GC). We also call this after finalize_cset() to
3978 // ensure that the CSet has been finalized.
3979 _cm->verify_no_cset_oops(true /* verify_stacks */,
3980 true /* verify_enqueued_buffers */,
3981 false /* verify_thread_buffers */,
3982 true /* verify_fingers */);
3983
3984 if (_hr_printer.is_active()) {
3985 HeapRegion* hr = g1_policy()->collection_set();
3986 while (hr != NULL) {
3987 G1HRPrinter::RegionType type;
3988 if (!hr->is_young()) {
3989 type = G1HRPrinter::Old;
3990 } else if (hr->is_survivor()) {
3991 type = G1HRPrinter::Survivor;
3992 } else {
3993 type = G1HRPrinter::Eden;
3994 }
3995 _hr_printer.cset(hr);
3996 hr = hr->next_in_collection_set();
3997 }
3998 }
3999
4000 #ifdef ASSERT
4001 VerifyCSetClosure cl;
4002 collection_set_iterate(&cl);
4003 #endif // ASSERT
4004
4005 setup_surviving_young_words();
4006
4007 // Initialize the GC alloc regions.
4008 init_gc_alloc_regions(evacuation_info);
4009
4010 // Actually do the work...
4011 evacuate_collection_set(evacuation_info);
4012
4013 // We do this to mainly verify the per-thread SATB buffers
4014 // (which have been filtered by now) since we didn't verify
4015 // them earlier. No point in re-checking the stacks / enqueued
4016 // buffers given that the CSet has not changed since last time
4017 // we checked.
4018 _cm->verify_no_cset_oops(false /* verify_stacks */,
4019 false /* verify_enqueued_buffers */,
4020 true /* verify_thread_buffers */,
4021 true /* verify_fingers */);
4022
4023 free_collection_set(g1_policy()->collection_set(), evacuation_info);
4024 g1_policy()->clear_collection_set();
4025
4026 cleanup_surviving_young_words();
4027
4028 // Start a new incremental collection set for the next pause.
4029 g1_policy()->start_incremental_cset_building();
4030
4031 // Clear the _cset_fast_test bitmap in anticipation of adding
4032 // regions to the incremental collection set for the next
4033 // evacuation pause.
4034 clear_cset_fast_test();
4035
4036 _young_list->reset_sampled_info();
4037
4038 // Don't check the whole heap at this point as the
4039 // GC alloc regions from this pause have been tagged
4040 // as survivors and moved on to the survivor list.
4041 // Survivor regions will fail the !is_young() check.
4042 assert(check_young_list_empty(false /* check_heap */),
4043 "young list should be empty");
4044
4045 #if YOUNG_LIST_VERBOSE
4046 gclog_or_tty->print_cr("Before recording survivors.\nYoung List:");
4047 _young_list->print();
4048 #endif // YOUNG_LIST_VERBOSE
4049
4050 g1_policy()->record_survivor_regions(_young_list->survivor_length(),
4051 _young_list->first_survivor_region(),
4052 _young_list->last_survivor_region());
4053
4054 _young_list->reset_auxilary_lists();
4055
4056 if (evacuation_failed()) {
4057 _summary_bytes_used = recalculate_used();
4058 uint n_queues = MAX2((int)ParallelGCThreads, 1);
4059 for (uint i = 0; i < n_queues; i++) {
4060 if (_evacuation_failed_info_array[i].has_failed()) {
4061 _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]);
4062 }
4063 }
4064 } else {
4065 // The "used" of the the collection set have already been subtracted
4066 // when they were freed. Add in the bytes evacuated.
4067 _summary_bytes_used += g1_policy()->bytes_copied_during_gc();
4068 }
4069
4070 if (g1_policy()->during_initial_mark_pause()) {
4071 // We have to do this before we notify the CM threads that
4072 // they can start working to make sure that all the
4073 // appropriate initialization is done on the CM object.
4074 concurrent_mark()->checkpointRootsInitialPost();
4075 set_marking_started();
4076 // Note that we don't actually trigger the CM thread at
4077 // this point. We do that later when we're sure that
4078 // the current thread has completed its logging output.
4079 }
4080
4081 allocate_dummy_regions();
4082
4083 #if YOUNG_LIST_VERBOSE
4084 gclog_or_tty->print_cr("\nEnd of the pause.\nYoung_list:");
4085 _young_list->print();
4086 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
4087 #endif // YOUNG_LIST_VERBOSE
4088
4089 init_mutator_alloc_region();
4090
4091 {
4092 size_t expand_bytes = g1_policy()->expansion_amount();
4093 if (expand_bytes > 0) {
4094 size_t bytes_before = capacity();
4095 // No need for an ergo verbose message here,
4096 // expansion_amount() does this when it returns a value > 0.
4097 if (!expand(expand_bytes)) {
4098 // We failed to expand the heap so let's verify that
4099 // committed/uncommitted amount match the backing store
4100 assert(capacity() == _g1_storage.committed_size(), "committed size mismatch");
4101 assert(max_capacity() == _g1_storage.reserved_size(), "reserved size mismatch");
4102 }
4103 }
4104 }
4105
4106 // We redo the verification but now wrt to the new CSet which
4107 // has just got initialized after the previous CSet was freed.
4108 _cm->verify_no_cset_oops(true /* verify_stacks */,
4109 true /* verify_enqueued_buffers */,
4110 true /* verify_thread_buffers */,
4111 true /* verify_fingers */);
4112 _cm->note_end_of_gc();
4113
4114 // This timing is only used by the ergonomics to handle our pause target.
4115 // It is unclear why this should not include the full pause. We will
4116 // investigate this in CR 7178365.
4117 double sample_end_time_sec = os::elapsedTime();
4118 double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
4119 g1_policy()->record_collection_pause_end(pause_time_ms, evacuation_info);
4120
4121 MemoryService::track_memory_usage();
4122
4123 // In prepare_for_verify() below we'll need to scan the deferred
4124 // update buffers to bring the RSets up-to-date if
4125 // G1HRRSFlushLogBuffersOnVerify has been set. While scanning
4126 // the update buffers we'll probably need to scan cards on the
4127 // regions we just allocated to (i.e., the GC alloc
4128 // regions). However, during the last GC we called
4129 // set_saved_mark() on all the GC alloc regions, so card
4130 // scanning might skip the [saved_mark_word()...top()] area of
4131 // those regions (i.e., the area we allocated objects into
4132 // during the last GC). But it shouldn't. Given that
4133 // saved_mark_word() is conditional on whether the GC time stamp
4134 // on the region is current or not, by incrementing the GC time
4135 // stamp here we invalidate all the GC time stamps on all the
4136 // regions and saved_mark_word() will simply return top() for
4137 // all the regions. This is a nicer way of ensuring this rather
4138 // than iterating over the regions and fixing them. In fact, the
4139 // GC time stamp increment here also ensures that
4140 // saved_mark_word() will return top() between pauses, i.e.,
4141 // during concurrent refinement. So we don't need the
4142 // is_gc_active() check to decided which top to use when
4143 // scanning cards (see CR 7039627).
4144 increment_gc_time_stamp();
4145
4146 verify_after_gc();
4147
4148 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
4149 ref_processor_stw()->verify_no_references_recorded();
4150
4151 // CM reference discovery will be re-enabled if necessary.
4152 }
4153
4154 // We should do this after we potentially expand the heap so
4155 // that all the COMMIT events are generated before the end GC
4156 // event, and after we retire the GC alloc regions so that all
4157 // RETIRE events are generated before the end GC event.
4158 _hr_printer.end_gc(false /* full */, (size_t) total_collections());
4159
4160 if (mark_in_progress()) {
4161 concurrent_mark()->update_g1_committed();
4162 }
4163
4164 #ifdef TRACESPINNING
4165 ParallelTaskTerminator::print_termination_counts();
4166 #endif
4167
4168 gc_epilogue(false);
4169 }
4170
4171 // Print the remainder of the GC log output.
4172 log_gc_footer(os::elapsedTime() - pause_start_sec);
4173
4174 // It is not yet to safe to tell the concurrent mark to
4175 // start as we have some optional output below. We don't want the
4176 // output from the concurrent mark thread interfering with this
4177 // logging output either.
4178
4179 _hrs.verify_optional();
4180 verify_region_sets_optional();
4181
4182 TASKQUEUE_STATS_ONLY(if (ParallelGCVerbose) print_taskqueue_stats());
4183 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
4184
4185 print_heap_after_gc();
4186 trace_heap_after_gc(_gc_tracer_stw);
4187
4188 // We must call G1MonitoringSupport::update_sizes() in the same scoping level
4189 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
4190 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
4191 // before any GC notifications are raised.
4192 g1mm()->update_sizes();
4193
4194 _gc_tracer_stw->report_evacuation_info(&evacuation_info);
4195 _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold());
4196 _gc_timer_stw->register_gc_end(os::elapsed_counter());
4197 _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions());
4198 }
4199
4200 if (G1SummarizeRSetStats &&
4201 (G1SummarizeRSetStatsPeriod > 0) &&
4202 (total_collections() % G1SummarizeRSetStatsPeriod == 0)) {
4203 g1_rem_set()->print_summary_info();
4204 }
4205 // It should now be safe to tell the concurrent mark thread to start
4206 // without its logging output interfering with the logging output
4207 // that came from the pause.
4208
4209 if (should_start_conc_mark) {
4210 // CAUTION: after the doConcurrentMark() call below,
4211 // the concurrent marking thread(s) could be running
4212 // concurrently with us. Make sure that anything after
4213 // this point does not assume that we are the only GC thread
4214 // running. Note: of course, the actual marking work will
4215 // not start until the safepoint itself is released in
4216 // ConcurrentGCThread::safepoint_desynchronize().
4217 doConcurrentMark();
4218 }
4219
4220 return true;
4221 }
4222
4223 size_t G1CollectedHeap::desired_plab_sz(GCAllocPurpose purpose)
4224 {
4225 size_t gclab_word_size;
4226 switch (purpose) {
4227 case GCAllocForSurvived:
4228 gclab_word_size = _survivor_plab_stats.desired_plab_sz();
4229 break;
4230 case GCAllocForTenured:
4231 gclab_word_size = _old_plab_stats.desired_plab_sz();
4232 break;
4233 default:
4234 assert(false, "unknown GCAllocPurpose");
4235 gclab_word_size = _old_plab_stats.desired_plab_sz();
4236 break;
4237 }
4238
4239 // Prevent humongous PLAB sizes for two reasons:
4240 // * PLABs are allocated using a similar paths as oops, but should
4241 // never be in a humongous region
4242 // * Allowing humongous PLABs needlessly churns the region free lists
4243 return MIN2(_humongous_object_threshold_in_words, gclab_word_size);
4244 }
4245
4246 void G1CollectedHeap::init_mutator_alloc_region() {
4247 assert(_mutator_alloc_region.get() == NULL, "pre-condition");
4248 _mutator_alloc_region.init();
4249 }
4250
4251 void G1CollectedHeap::release_mutator_alloc_region() {
4252 _mutator_alloc_region.release();
4253 assert(_mutator_alloc_region.get() == NULL, "post-condition");
4254 }
4255
4256 void G1CollectedHeap::init_gc_alloc_regions(EvacuationInfo& evacuation_info) {
4257 assert_at_safepoint(true /* should_be_vm_thread */);
4258
4259 _survivor_gc_alloc_region.init();
4260 _old_gc_alloc_region.init();
4261 HeapRegion* retained_region = _retained_old_gc_alloc_region;
4262 _retained_old_gc_alloc_region = NULL;
4263
4264 // We will discard the current GC alloc region if:
4265 // a) it's in the collection set (it can happen!),
4266 // b) it's already full (no point in using it),
4267 // c) it's empty (this means that it was emptied during
4268 // a cleanup and it should be on the free list now), or
4269 // d) it's humongous (this means that it was emptied
4270 // during a cleanup and was added to the free list, but
4271 // has been subsequently used to allocate a humongous
4272 // object that may be less than the region size).
4273 if (retained_region != NULL &&
4274 !retained_region->in_collection_set() &&
4275 !(retained_region->top() == retained_region->end()) &&
4276 !retained_region->is_empty() &&
4277 !retained_region->isHumongous()) {
4278 retained_region->set_saved_mark();
4279 // The retained region was added to the old region set when it was
4280 // retired. We have to remove it now, since we don't allow regions
4281 // we allocate to in the region sets. We'll re-add it later, when
4282 // it's retired again.
4283 _old_set.remove(retained_region);
4284 bool during_im = g1_policy()->during_initial_mark_pause();
4285 retained_region->note_start_of_copying(during_im);
4286 _old_gc_alloc_region.set(retained_region);
4287 _hr_printer.reuse(retained_region);
4288 evacuation_info.set_alloc_regions_used_before(retained_region->used());
4289 }
4290 }
4291
4292 void G1CollectedHeap::release_gc_alloc_regions(uint no_of_gc_workers, EvacuationInfo& evacuation_info) {
4293 evacuation_info.set_allocation_regions(_survivor_gc_alloc_region.count() +
4294 _old_gc_alloc_region.count());
4295 _survivor_gc_alloc_region.release();
4296 // If we have an old GC alloc region to release, we'll save it in
4297 // _retained_old_gc_alloc_region. If we don't
4298 // _retained_old_gc_alloc_region will become NULL. This is what we
4299 // want either way so no reason to check explicitly for either
4300 // condition.
4301 _retained_old_gc_alloc_region = _old_gc_alloc_region.release();
4302
4303 if (ResizePLAB) {
4304 _survivor_plab_stats.adjust_desired_plab_sz(no_of_gc_workers);
4305 _old_plab_stats.adjust_desired_plab_sz(no_of_gc_workers);
4306 }
4307 }
4308
4309 void G1CollectedHeap::abandon_gc_alloc_regions() {
4310 assert(_survivor_gc_alloc_region.get() == NULL, "pre-condition");
4311 assert(_old_gc_alloc_region.get() == NULL, "pre-condition");
4312 _retained_old_gc_alloc_region = NULL;
4313 }
4314
4315 void G1CollectedHeap::init_for_evac_failure(OopsInHeapRegionClosure* cl) {
4316 _drain_in_progress = false;
4317 set_evac_failure_closure(cl);
4318 _evac_failure_scan_stack = new (ResourceObj::C_HEAP, mtGC) GrowableArray<oop>(40, true);
4319 }
4320
4321 void G1CollectedHeap::finalize_for_evac_failure() {
4322 assert(_evac_failure_scan_stack != NULL &&
4323 _evac_failure_scan_stack->length() == 0,
4324 "Postcondition");
4325 assert(!_drain_in_progress, "Postcondition");
4326 delete _evac_failure_scan_stack;
4327 _evac_failure_scan_stack = NULL;
4328 }
4329
4330 void G1CollectedHeap::remove_self_forwarding_pointers() {
4331 assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity");
4332
4333 G1ParRemoveSelfForwardPtrsTask rsfp_task(this);
4334
4335 if (G1CollectedHeap::use_parallel_gc_threads()) {
4336 set_par_threads();
4337 workers()->run_task(&rsfp_task);
4338 set_par_threads(0);
4339 } else {
4340 rsfp_task.work(0);
4341 }
4342
4343 assert(check_cset_heap_region_claim_values(HeapRegion::ParEvacFailureClaimValue), "sanity");
4344
4345 // Reset the claim values in the regions in the collection set.
4346 reset_cset_heap_region_claim_values();
4347
4348 assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity");
4349
4350 // Now restore saved marks, if any.
4351 assert(_objs_with_preserved_marks.size() ==
4352 _preserved_marks_of_objs.size(), "Both or none.");
4353 while (!_objs_with_preserved_marks.is_empty()) {
4354 oop obj = _objs_with_preserved_marks.pop();
4355 markOop m = _preserved_marks_of_objs.pop();
4356 obj->set_mark(m);
4357 }
4358 _objs_with_preserved_marks.clear(true);
4359 _preserved_marks_of_objs.clear(true);
4360 }
4361
4362 void G1CollectedHeap::push_on_evac_failure_scan_stack(oop obj) {
4363 _evac_failure_scan_stack->push(obj);
4364 }
4365
4366 void G1CollectedHeap::drain_evac_failure_scan_stack() {
4367 assert(_evac_failure_scan_stack != NULL, "precondition");
4368
4369 while (_evac_failure_scan_stack->length() > 0) {
4370 oop obj = _evac_failure_scan_stack->pop();
4371 _evac_failure_closure->set_region(heap_region_containing(obj));
4372 obj->oop_iterate_backwards(_evac_failure_closure);
4373 }
4374 }
4375
4376 oop
4377 G1CollectedHeap::handle_evacuation_failure_par(G1ParScanThreadState* _par_scan_state,
4378 oop old) {
4379 assert(obj_in_cs(old),
4380 err_msg("obj: "PTR_FORMAT" should still be in the CSet",
4381 (HeapWord*) old));
4382 markOop m = old->mark();
4383 oop forward_ptr = old->forward_to_atomic(old);
4384 if (forward_ptr == NULL) {
4385 // Forward-to-self succeeded.
4386 assert(_par_scan_state != NULL, "par scan state");
4387 OopsInHeapRegionClosure* cl = _par_scan_state->evac_failure_closure();
4388 uint queue_num = _par_scan_state->queue_num();
4389
4390 _evacuation_failed = true;
4391 _evacuation_failed_info_array[queue_num].register_copy_failure(old->size());
4392 if (_evac_failure_closure != cl) {
4393 MutexLockerEx x(EvacFailureStack_lock, Mutex::_no_safepoint_check_flag);
4394 assert(!_drain_in_progress,
4395 "Should only be true while someone holds the lock.");
4396 // Set the global evac-failure closure to the current thread's.
4397 assert(_evac_failure_closure == NULL, "Or locking has failed.");
4398 set_evac_failure_closure(cl);
4399 // Now do the common part.
4400 handle_evacuation_failure_common(old, m);
4401 // Reset to NULL.
4402 set_evac_failure_closure(NULL);
4403 } else {
4404 // The lock is already held, and this is recursive.
4405 assert(_drain_in_progress, "This should only be the recursive case.");
4406 handle_evacuation_failure_common(old, m);
4407 }
4408 return old;
4409 } else {
4410 // Forward-to-self failed. Either someone else managed to allocate
4411 // space for this object (old != forward_ptr) or they beat us in
4412 // self-forwarding it (old == forward_ptr).
4413 assert(old == forward_ptr || !obj_in_cs(forward_ptr),
4414 err_msg("obj: "PTR_FORMAT" forwarded to: "PTR_FORMAT" "
4415 "should not be in the CSet",
4416 (HeapWord*) old, (HeapWord*) forward_ptr));
4417 return forward_ptr;
4418 }
4419 }
4420
4421 void G1CollectedHeap::handle_evacuation_failure_common(oop old, markOop m) {
4422 preserve_mark_if_necessary(old, m);
4423
4424 HeapRegion* r = heap_region_containing(old);
4425 if (!r->evacuation_failed()) {
4426 r->set_evacuation_failed(true);
4427 _hr_printer.evac_failure(r);
4428 }
4429
4430 push_on_evac_failure_scan_stack(old);
4431
4432 if (!_drain_in_progress) {
4433 // prevent recursion in copy_to_survivor_space()
4434 _drain_in_progress = true;
4435 drain_evac_failure_scan_stack();
4436 _drain_in_progress = false;
4437 }
4438 }
4439
4440 void G1CollectedHeap::preserve_mark_if_necessary(oop obj, markOop m) {
4441 assert(evacuation_failed(), "Oversaving!");
4442 // We want to call the "for_promotion_failure" version only in the
4443 // case of a promotion failure.
4444 if (m->must_be_preserved_for_promotion_failure(obj)) {
4445 _objs_with_preserved_marks.push(obj);
4446 _preserved_marks_of_objs.push(m);
4447 }
4448 }
4449
4450 HeapWord* G1CollectedHeap::par_allocate_during_gc(GCAllocPurpose purpose,
4451 size_t word_size) {
4452 if (purpose == GCAllocForSurvived) {
4453 HeapWord* result = survivor_attempt_allocation(word_size);
4454 if (result != NULL) {
4455 return result;
4456 } else {
4457 // Let's try to allocate in the old gen in case we can fit the
4458 // object there.
4459 return old_attempt_allocation(word_size);
4460 }
4461 } else {
4462 assert(purpose == GCAllocForTenured, "sanity");
4463 HeapWord* result = old_attempt_allocation(word_size);
4464 if (result != NULL) {
4465 return result;
4466 } else {
4467 // Let's try to allocate in the survivors in case we can fit the
4468 // object there.
4469 return survivor_attempt_allocation(word_size);
4470 }
4471 }
4472
4473 ShouldNotReachHere();
4474 // Trying to keep some compilers happy.
4475 return NULL;
4476 }
4477
4478 G1ParGCAllocBuffer::G1ParGCAllocBuffer(size_t gclab_word_size) :
4479 ParGCAllocBuffer(gclab_word_size), _retired(false) { }
4480
4481 G1ParScanThreadState::G1ParScanThreadState(G1CollectedHeap* g1h, uint queue_num)
4482 : _g1h(g1h),
4483 _refs(g1h->task_queue(queue_num)),
4484 _dcq(&g1h->dirty_card_queue_set()),
4485 _ct_bs((CardTableModRefBS*)_g1h->barrier_set()),
4486 _g1_rem(g1h->g1_rem_set()),
4487 _hash_seed(17), _queue_num(queue_num),
4488 _term_attempts(0),
4489 _surviving_alloc_buffer(g1h->desired_plab_sz(GCAllocForSurvived)),
4490 _tenured_alloc_buffer(g1h->desired_plab_sz(GCAllocForTenured)),
4491 _age_table(false),
4492 _strong_roots_time(0), _term_time(0),
4493 _alloc_buffer_waste(0), _undo_waste(0) {
4494 // we allocate G1YoungSurvRateNumRegions plus one entries, since
4495 // we "sacrifice" entry 0 to keep track of surviving bytes for
4496 // non-young regions (where the age is -1)
4497 // We also add a few elements at the beginning and at the end in
4498 // an attempt to eliminate cache contention
4499 uint real_length = 1 + _g1h->g1_policy()->young_cset_region_length();
4500 uint array_length = PADDING_ELEM_NUM +
4501 real_length +
4502 PADDING_ELEM_NUM;
4503 _surviving_young_words_base = NEW_C_HEAP_ARRAY(size_t, array_length, mtGC);
4504 if (_surviving_young_words_base == NULL)
4505 vm_exit_out_of_memory(array_length * sizeof(size_t),
4506 "Not enough space for young surv histo.");
4507 _surviving_young_words = _surviving_young_words_base + PADDING_ELEM_NUM;
4508 memset(_surviving_young_words, 0, (size_t) real_length * sizeof(size_t));
4509
4510 _alloc_buffers[GCAllocForSurvived] = &_surviving_alloc_buffer;
4511 _alloc_buffers[GCAllocForTenured] = &_tenured_alloc_buffer;
4512
4513 _start = os::elapsedTime();
4514 }
4515
4516 void
4517 G1ParScanThreadState::print_termination_stats_hdr(outputStream* const st)
4518 {
4519 st->print_raw_cr("GC Termination Stats");
4520 st->print_raw_cr(" elapsed --strong roots-- -------termination-------"
4521 " ------waste (KiB)------");
4522 st->print_raw_cr("thr ms ms % ms % attempts"
4523 " total alloc undo");
4524 st->print_raw_cr("--- --------- --------- ------ --------- ------ --------"
4525 " ------- ------- -------");
4526 }
4527
4528 void
4529 G1ParScanThreadState::print_termination_stats(int i,
4530 outputStream* const st) const
4531 {
4532 const double elapsed_ms = elapsed_time() * 1000.0;
4533 const double s_roots_ms = strong_roots_time() * 1000.0;
4534 const double term_ms = term_time() * 1000.0;
4535 st->print_cr("%3d %9.2f %9.2f %6.2f "
4536 "%9.2f %6.2f " SIZE_FORMAT_W(8) " "
4537 SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7),
4538 i, elapsed_ms, s_roots_ms, s_roots_ms * 100 / elapsed_ms,
4539 term_ms, term_ms * 100 / elapsed_ms, term_attempts(),
4540 (alloc_buffer_waste() + undo_waste()) * HeapWordSize / K,
4541 alloc_buffer_waste() * HeapWordSize / K,
4542 undo_waste() * HeapWordSize / K);
4543 }
4544
4545 #ifdef ASSERT
4546 bool G1ParScanThreadState::verify_ref(narrowOop* ref) const {
4547 assert(ref != NULL, "invariant");
4548 assert(UseCompressedOops, "sanity");
4549 assert(!has_partial_array_mask(ref), err_msg("ref=" PTR_FORMAT, ref));
4550 oop p = oopDesc::load_decode_heap_oop(ref);
4551 assert(_g1h->is_in_g1_reserved(p),
4552 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p)));
4553 return true;
4554 }
4555
4556 bool G1ParScanThreadState::verify_ref(oop* ref) const {
4557 assert(ref != NULL, "invariant");
4558 if (has_partial_array_mask(ref)) {
4559 // Must be in the collection set--it's already been copied.
4560 oop p = clear_partial_array_mask(ref);
4561 assert(_g1h->obj_in_cs(p),
4562 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p)));
4563 } else {
4564 oop p = oopDesc::load_decode_heap_oop(ref);
4565 assert(_g1h->is_in_g1_reserved(p),
4566 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p)));
4567 }
4568 return true;
4569 }
4570
4571 bool G1ParScanThreadState::verify_task(StarTask ref) const {
4572 if (ref.is_narrow()) {
4573 return verify_ref((narrowOop*) ref);
4574 } else {
4575 return verify_ref((oop*) ref);
4576 }
4577 }
4578 #endif // ASSERT
4579
4580 void G1ParScanThreadState::trim_queue() {
4581 assert(_evac_cl != NULL, "not set");
4582 assert(_evac_failure_cl != NULL, "not set");
4583 assert(_partial_scan_cl != NULL, "not set");
4584
4585 StarTask ref;
4586 do {
4587 // Drain the overflow stack first, so other threads can steal.
4588 while (refs()->pop_overflow(ref)) {
4589 deal_with_reference(ref);
4590 }
4591
4592 while (refs()->pop_local(ref)) {
4593 deal_with_reference(ref);
4594 }
4595 } while (!refs()->is_empty());
4596 }
4597
4598 G1ParClosureSuper::G1ParClosureSuper(G1CollectedHeap* g1,
4599 G1ParScanThreadState* par_scan_state) :
4600 _g1(g1), _g1_rem(_g1->g1_rem_set()), _cm(_g1->concurrent_mark()),
4601 _par_scan_state(par_scan_state),
4602 _worker_id(par_scan_state->queue_num()),
4603 _during_initial_mark(_g1->g1_policy()->during_initial_mark_pause()),
4604 _mark_in_progress(_g1->mark_in_progress()) { }
4605
4606 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object>
4607 void G1ParCopyClosure<do_gen_barrier, barrier, do_mark_object>::mark_object(oop obj) {
4608 #ifdef ASSERT
4609 HeapRegion* hr = _g1->heap_region_containing(obj);
4610 assert(hr != NULL, "sanity");
4611 assert(!hr->in_collection_set(), "should not mark objects in the CSet");
4612 #endif // ASSERT
4613
4614 // We know that the object is not moving so it's safe to read its size.
4615 _cm->grayRoot(obj, (size_t) obj->size(), _worker_id);
4616 }
4617
4618 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object>
4619 void G1ParCopyClosure<do_gen_barrier, barrier, do_mark_object>
4620 ::mark_forwarded_object(oop from_obj, oop to_obj) {
4621 #ifdef ASSERT
4622 assert(from_obj->is_forwarded(), "from obj should be forwarded");
4623 assert(from_obj->forwardee() == to_obj, "to obj should be the forwardee");
4624 assert(from_obj != to_obj, "should not be self-forwarded");
4625
4626 HeapRegion* from_hr = _g1->heap_region_containing(from_obj);
4627 assert(from_hr != NULL, "sanity");
4628 assert(from_hr->in_collection_set(), "from obj should be in the CSet");
4629
4630 HeapRegion* to_hr = _g1->heap_region_containing(to_obj);
4631 assert(to_hr != NULL, "sanity");
4632 assert(!to_hr->in_collection_set(), "should not mark objects in the CSet");
4633 #endif // ASSERT
4634
4635 // The object might be in the process of being copied by another
4636 // worker so we cannot trust that its to-space image is
4637 // well-formed. So we have to read its size from its from-space
4638 // image which we know should not be changing.
4639 _cm->grayRoot(to_obj, (size_t) from_obj->size(), _worker_id);
4640 }
4641
4642 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object>
4643 oop G1ParCopyClosure<do_gen_barrier, barrier, do_mark_object>
4644 ::copy_to_survivor_space(oop old) {
4645 size_t word_sz = old->size();
4646 HeapRegion* from_region = _g1->heap_region_containing_raw(old);
4647 // +1 to make the -1 indexes valid...
4648 int young_index = from_region->young_index_in_cset()+1;
4649 assert( (from_region->is_young() && young_index > 0) ||
4650 (!from_region->is_young() && young_index == 0), "invariant" );
4651 G1CollectorPolicy* g1p = _g1->g1_policy();
4652 markOop m = old->mark();
4653 int age = m->has_displaced_mark_helper() ? m->displaced_mark_helper()->age()
4654 : m->age();
4655 GCAllocPurpose alloc_purpose = g1p->evacuation_destination(from_region, age,
4656 word_sz);
4657 HeapWord* obj_ptr = _par_scan_state->allocate(alloc_purpose, word_sz);
4658 #ifndef PRODUCT
4659 // Should this evacuation fail?
4660 if (_g1->evacuation_should_fail()) {
4661 if (obj_ptr != NULL) {
4662 _par_scan_state->undo_allocation(alloc_purpose, obj_ptr, word_sz);
4663 obj_ptr = NULL;
4664 }
4665 }
4666 #endif // !PRODUCT
4667
4668 if (obj_ptr == NULL) {
4669 // This will either forward-to-self, or detect that someone else has
4670 // installed a forwarding pointer.
4671 return _g1->handle_evacuation_failure_par(_par_scan_state, old);
4672 }
4673
4674 oop obj = oop(obj_ptr);
4675
4676 // We're going to allocate linearly, so might as well prefetch ahead.
4677 Prefetch::write(obj_ptr, PrefetchCopyIntervalInBytes);
4678
4679 oop forward_ptr = old->forward_to_atomic(obj);
4680 if (forward_ptr == NULL) {
4681 Copy::aligned_disjoint_words((HeapWord*) old, obj_ptr, word_sz);
4682 if (g1p->track_object_age(alloc_purpose)) {
4683 // We could simply do obj->incr_age(). However, this causes a
4684 // performance issue. obj->incr_age() will first check whether
4685 // the object has a displaced mark by checking its mark word;
4686 // getting the mark word from the new location of the object
4687 // stalls. So, given that we already have the mark word and we
4688 // are about to install it anyway, it's better to increase the
4689 // age on the mark word, when the object does not have a
4690 // displaced mark word. We're not expecting many objects to have
4691 // a displaced marked word, so that case is not optimized
4692 // further (it could be...) and we simply call obj->incr_age().
4693
4694 if (m->has_displaced_mark_helper()) {
4695 // in this case, we have to install the mark word first,
4696 // otherwise obj looks to be forwarded (the old mark word,
4697 // which contains the forward pointer, was copied)
4698 obj->set_mark(m);
4699 obj->incr_age();
4700 } else {
4701 m = m->incr_age();
4702 obj->set_mark(m);
4703 }
4704 _par_scan_state->age_table()->add(obj, word_sz);
4705 } else {
4706 obj->set_mark(m);
4707 }
4708
4709 size_t* surv_young_words = _par_scan_state->surviving_young_words();
4710 surv_young_words[young_index] += word_sz;
4711
4712 if (obj->is_objArray() && arrayOop(obj)->length() >= ParGCArrayScanChunk) {
4713 // We keep track of the next start index in the length field of
4714 // the to-space object. The actual length can be found in the
4715 // length field of the from-space object.
4716 arrayOop(obj)->set_length(0);
4717 oop* old_p = set_partial_array_mask(old);
4718 _par_scan_state->push_on_queue(old_p);
4719 } else {
4720 // No point in using the slower heap_region_containing() method,
4721 // given that we know obj is in the heap.
4722 _scanner.set_region(_g1->heap_region_containing_raw(obj));
4723 obj->oop_iterate_backwards(&_scanner);
4724 }
4725 } else {
4726 _par_scan_state->undo_allocation(alloc_purpose, obj_ptr, word_sz);
4727 obj = forward_ptr;
4728 }
4729 return obj;
4730 }
4731
4732 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object>
4733 template <class T>
4734 void G1ParCopyClosure<do_gen_barrier, barrier, do_mark_object>
4735 ::do_oop_work(T* p) {
4736 oop obj = oopDesc::load_decode_heap_oop(p);
4737 assert(barrier != G1BarrierRS || obj != NULL,
4738 "Precondition: G1BarrierRS implies obj is non-NULL");
4739
4740 assert(_worker_id == _par_scan_state->queue_num(), "sanity");
4741
4742 // here the null check is implicit in the cset_fast_test() test
4743 if (_g1->in_cset_fast_test(obj)) {
4744 oop forwardee;
4745 if (obj->is_forwarded()) {
4746 forwardee = obj->forwardee();
4747 } else {
4748 forwardee = copy_to_survivor_space(obj);
4749 }
4750 assert(forwardee != NULL, "forwardee should not be NULL");
4751 oopDesc::encode_store_heap_oop(p, forwardee);
4752 if (do_mark_object && forwardee != obj) {
4753 // If the object is self-forwarded we don't need to explicitly
4754 // mark it, the evacuation failure protocol will do so.
4755 mark_forwarded_object(obj, forwardee);
4756 }
4757
4758 // When scanning the RS, we only care about objs in CS.
4759 if (barrier == G1BarrierRS) {
4760 _par_scan_state->update_rs(_from, p, _worker_id);
4761 }
4762 } else {
4763 // The object is not in collection set. If we're a root scanning
4764 // closure during an initial mark pause (i.e. do_mark_object will
4765 // be true) then attempt to mark the object.
4766 if (do_mark_object && _g1->is_in_g1_reserved(obj)) {
4767 mark_object(obj);
4768 }
4769 }
4770
4771 if (barrier == G1BarrierEvac && obj != NULL) {
4772 _par_scan_state->update_rs(_from, p, _worker_id);
4773 }
4774
4775 if (do_gen_barrier && obj != NULL) {
4776 par_do_barrier(p);
4777 }
4778 }
4779
4780 template void G1ParCopyClosure<false, G1BarrierEvac, false>::do_oop_work(oop* p);
4781 template void G1ParCopyClosure<false, G1BarrierEvac, false>::do_oop_work(narrowOop* p);
4782
4783 template <class T> void G1ParScanPartialArrayClosure::do_oop_nv(T* p) {
4784 assert(has_partial_array_mask(p), "invariant");
4785 oop from_obj = clear_partial_array_mask(p);
4786
4787 assert(Universe::heap()->is_in_reserved(from_obj), "must be in heap.");
4788 assert(from_obj->is_objArray(), "must be obj array");
4789 objArrayOop from_obj_array = objArrayOop(from_obj);
4790 // The from-space object contains the real length.
4791 int length = from_obj_array->length();
4792
4793 assert(from_obj->is_forwarded(), "must be forwarded");
4794 oop to_obj = from_obj->forwardee();
4795 assert(from_obj != to_obj, "should not be chunking self-forwarded objects");
4796 objArrayOop to_obj_array = objArrayOop(to_obj);
4797 // We keep track of the next start index in the length field of the
4798 // to-space object.
4799 int next_index = to_obj_array->length();
4800 assert(0 <= next_index && next_index < length,
4801 err_msg("invariant, next index: %d, length: %d", next_index, length));
4802
4803 int start = next_index;
4804 int end = length;
4805 int remainder = end - start;
4806 // We'll try not to push a range that's smaller than ParGCArrayScanChunk.
4807 if (remainder > 2 * ParGCArrayScanChunk) {
4808 end = start + ParGCArrayScanChunk;
4809 to_obj_array->set_length(end);
4810 // Push the remainder before we process the range in case another
4811 // worker has run out of things to do and can steal it.
4812 oop* from_obj_p = set_partial_array_mask(from_obj);
4813 _par_scan_state->push_on_queue(from_obj_p);
4814 } else {
4815 assert(length == end, "sanity");
4816 // We'll process the final range for this object. Restore the length
4817 // so that the heap remains parsable in case of evacuation failure.
4818 to_obj_array->set_length(end);
4819 }
4820 _scanner.set_region(_g1->heap_region_containing_raw(to_obj));
4821 // Process indexes [start,end). It will also process the header
4822 // along with the first chunk (i.e., the chunk with start == 0).
4823 // Note that at this point the length field of to_obj_array is not
4824 // correct given that we are using it to keep track of the next
4825 // start index. oop_iterate_range() (thankfully!) ignores the length
4826 // field and only relies on the start / end parameters. It does
4827 // however return the size of the object which will be incorrect. So
4828 // we have to ignore it even if we wanted to use it.
4829 to_obj_array->oop_iterate_range(&_scanner, start, end);
4830 }
4831
4832 class G1ParEvacuateFollowersClosure : public VoidClosure {
4833 protected:
4834 G1CollectedHeap* _g1h;
4835 G1ParScanThreadState* _par_scan_state;
4836 RefToScanQueueSet* _queues;
4837 ParallelTaskTerminator* _terminator;
4838
4839 G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
4840 RefToScanQueueSet* queues() { return _queues; }
4841 ParallelTaskTerminator* terminator() { return _terminator; }
4842
4843 public:
4844 G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h,
4845 G1ParScanThreadState* par_scan_state,
4846 RefToScanQueueSet* queues,
4847 ParallelTaskTerminator* terminator)
4848 : _g1h(g1h), _par_scan_state(par_scan_state),
4849 _queues(queues), _terminator(terminator) {}
4850
4851 void do_void();
4852
4853 private:
4854 inline bool offer_termination();
4855 };
4856
4857 bool G1ParEvacuateFollowersClosure::offer_termination() {
4858 G1ParScanThreadState* const pss = par_scan_state();
4859 pss->start_term_time();
4860 const bool res = terminator()->offer_termination();
4861 pss->end_term_time();
4862 return res;
4863 }
4864
4865 void G1ParEvacuateFollowersClosure::do_void() {
4866 StarTask stolen_task;
4867 G1ParScanThreadState* const pss = par_scan_state();
4868 pss->trim_queue();
4869
4870 do {
4871 while (queues()->steal(pss->queue_num(), pss->hash_seed(), stolen_task)) {
4872 assert(pss->verify_task(stolen_task), "sanity");
4873 if (stolen_task.is_narrow()) {
4874 pss->deal_with_reference((narrowOop*) stolen_task);
4875 } else {
4876 pss->deal_with_reference((oop*) stolen_task);
4877 }
4878
4879 // We've just processed a reference and we might have made
4880 // available new entries on the queues. So we have to make sure
4881 // we drain the queues as necessary.
4882 pss->trim_queue();
4883 }
4884 } while (!offer_termination());
4885
4886 pss->retire_alloc_buffers();
4887 }
4888
4889 class G1ParTask : public AbstractGangTask {
4890 protected:
4891 G1CollectedHeap* _g1h;
4892 RefToScanQueueSet *_queues;
4893 ParallelTaskTerminator _terminator;
4894 uint _n_workers;
4895
4896 Mutex _stats_lock;
4897 Mutex* stats_lock() { return &_stats_lock; }
4898
4899 size_t getNCards() {
4900 return (_g1h->capacity() + G1BlockOffsetSharedArray::N_bytes - 1)
4901 / G1BlockOffsetSharedArray::N_bytes;
4902 }
4903
4904 public:
4905 G1ParTask(G1CollectedHeap* g1h,
4906 RefToScanQueueSet *task_queues)
4907 : AbstractGangTask("G1 collection"),
4908 _g1h(g1h),
4909 _queues(task_queues),
4910 _terminator(0, _queues),
4911 _stats_lock(Mutex::leaf, "parallel G1 stats lock", true)
4912 {}
4913
4914 RefToScanQueueSet* queues() { return _queues; }
4915
4916 RefToScanQueue *work_queue(int i) {
4917 return queues()->queue(i);
4918 }
4919
4920 ParallelTaskTerminator* terminator() { return &_terminator; }
4921
4922 virtual void set_for_termination(int active_workers) {
4923 // This task calls set_n_termination() in par_non_clean_card_iterate_work()
4924 // in the young space (_par_seq_tasks) in the G1 heap
4925 // for SequentialSubTasksDone.
4926 // This task also uses SubTasksDone in SharedHeap and G1CollectedHeap
4927 // both of which need setting by set_n_termination().
4928 _g1h->SharedHeap::set_n_termination(active_workers);
4929 _g1h->set_n_termination(active_workers);
4930 terminator()->reset_for_reuse(active_workers);
4931 _n_workers = active_workers;
4932 }
4933
4934 void work(uint worker_id) {
4935 if (worker_id >= _n_workers) return; // no work needed this round
4936
4937 double start_time_ms = os::elapsedTime() * 1000.0;
4938 _g1h->g1_policy()->phase_times()->record_gc_worker_start_time(worker_id, start_time_ms);
4939
4940 {
4941 ResourceMark rm;
4942 HandleMark hm;
4943
4944 ReferenceProcessor* rp = _g1h->ref_processor_stw();
4945
4946 G1ParScanThreadState pss(_g1h, worker_id);
4947 G1ParScanHeapEvacClosure scan_evac_cl(_g1h, &pss, rp);
4948 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, rp);
4949 G1ParScanPartialArrayClosure partial_scan_cl(_g1h, &pss, rp);
4950
4951 pss.set_evac_closure(&scan_evac_cl);
4952 pss.set_evac_failure_closure(&evac_failure_cl);
4953 pss.set_partial_scan_closure(&partial_scan_cl);
4954
4955 G1ParScanExtRootClosure only_scan_root_cl(_g1h, &pss, rp);
4956 G1ParScanPermClosure only_scan_perm_cl(_g1h, &pss, rp);
4957
4958 G1ParScanAndMarkExtRootClosure scan_mark_root_cl(_g1h, &pss, rp);
4959 G1ParScanAndMarkPermClosure scan_mark_perm_cl(_g1h, &pss, rp);
4960
4961 OopClosure* scan_root_cl = &only_scan_root_cl;
4962 OopsInHeapRegionClosure* scan_perm_cl = &only_scan_perm_cl;
4963
4964 if (_g1h->g1_policy()->during_initial_mark_pause()) {
4965 // We also need to mark copied objects.
4966 scan_root_cl = &scan_mark_root_cl;
4967 scan_perm_cl = &scan_mark_perm_cl;
4968 }
4969
4970 G1ParPushHeapRSClosure push_heap_rs_cl(_g1h, &pss);
4971
4972 pss.start_strong_roots();
4973 _g1h->g1_process_strong_roots(/* not collecting perm */ false,
4974 SharedHeap::SO_AllClasses,
4975 scan_root_cl,
4976 &push_heap_rs_cl,
4977 scan_perm_cl,
4978 worker_id);
4979 pss.end_strong_roots();
4980
4981 {
4982 double start = os::elapsedTime();
4983 G1ParEvacuateFollowersClosure evac(_g1h, &pss, _queues, &_terminator);
4984 evac.do_void();
4985 double elapsed_ms = (os::elapsedTime()-start)*1000.0;
4986 double term_ms = pss.term_time()*1000.0;
4987 _g1h->g1_policy()->phase_times()->add_obj_copy_time(worker_id, elapsed_ms-term_ms);
4988 _g1h->g1_policy()->phase_times()->record_termination(worker_id, term_ms, pss.term_attempts());
4989 }
4990 _g1h->g1_policy()->record_thread_age_table(pss.age_table());
4991 _g1h->update_surviving_young_words(pss.surviving_young_words()+1);
4992
4993 if (ParallelGCVerbose) {
4994 MutexLocker x(stats_lock());
4995 pss.print_termination_stats(worker_id);
4996 }
4997
4998 assert(pss.refs()->is_empty(), "should be empty");
4999
5000 // Close the inner scope so that the ResourceMark and HandleMark
5001 // destructors are executed here and are included as part of the
5002 // "GC Worker Time".
5003 }
5004
5005 double end_time_ms = os::elapsedTime() * 1000.0;
5006 _g1h->g1_policy()->phase_times()->record_gc_worker_end_time(worker_id, end_time_ms);
5007 }
5008 };
5009
5010 // *** Common G1 Evacuation Stuff
5011
5012 // Closures that support the filtering of CodeBlobs scanned during
5013 // external root scanning.
5014
5015 // Closure applied to reference fields in code blobs (specifically nmethods)
5016 // to determine whether an nmethod contains references that point into
5017 // the collection set. Used as a predicate when walking code roots so
5018 // that only nmethods that point into the collection set are added to the
5019 // 'marked' list.
5020
5021 class G1FilteredCodeBlobToOopClosure : public CodeBlobToOopClosure {
5022
5023 class G1PointsIntoCSOopClosure : public OopClosure {
5024 G1CollectedHeap* _g1;
5025 bool _points_into_cs;
5026 public:
5027 G1PointsIntoCSOopClosure(G1CollectedHeap* g1) :
5028 _g1(g1), _points_into_cs(false) { }
5029
5030 bool points_into_cs() const { return _points_into_cs; }
5031
5032 template <class T>
5033 void do_oop_nv(T* p) {
5034 if (!_points_into_cs) {
5035 T heap_oop = oopDesc::load_heap_oop(p);
5036 if (!oopDesc::is_null(heap_oop) &&
5037 _g1->in_cset_fast_test(oopDesc::decode_heap_oop_not_null(heap_oop))) {
5038 _points_into_cs = true;
5039 }
5040 }
5041 }
5042
5043 virtual void do_oop(oop* p) { do_oop_nv(p); }
5044 virtual void do_oop(narrowOop* p) { do_oop_nv(p); }
5045 };
5046
5047 G1CollectedHeap* _g1;
5048
5049 public:
5050 G1FilteredCodeBlobToOopClosure(G1CollectedHeap* g1, OopClosure* cl) :
5051 CodeBlobToOopClosure(cl, true), _g1(g1) { }
5052
5053 virtual void do_code_blob(CodeBlob* cb) {
5054 nmethod* nm = cb->as_nmethod_or_null();
5055 if (nm != NULL && !(nm->test_oops_do_mark())) {
5056 G1PointsIntoCSOopClosure predicate_cl(_g1);
5057 nm->oops_do(&predicate_cl);
5058
5059 if (predicate_cl.points_into_cs()) {
5060 // At least one of the reference fields or the oop relocations
5061 // in the nmethod points into the collection set. We have to
5062 // 'mark' this nmethod.
5063 // Note: Revisit the following if CodeBlobToOopClosure::do_code_blob()
5064 // or MarkingCodeBlobClosure::do_code_blob() change.
5065 if (!nm->test_set_oops_do_mark()) {
5066 do_newly_marked_nmethod(nm);
5067 }
5068 }
5069 }
5070 }
5071 };
5072
5073 // This method is run in a GC worker.
5074
5075 void
5076 G1CollectedHeap::
5077 g1_process_strong_roots(bool collecting_perm_gen,
5078 ScanningOption so,
5079 OopClosure* scan_non_heap_roots,
5080 OopsInHeapRegionClosure* scan_rs,
5081 OopsInGenClosure* scan_perm,
5082 int worker_i) {
5083
5084 // First scan the strong roots, including the perm gen.
5085 double ext_roots_start = os::elapsedTime();
5086 double closure_app_time_sec = 0.0;
5087
5088 BufferingOopClosure buf_scan_non_heap_roots(scan_non_heap_roots);
5089 BufferingOopsInGenClosure buf_scan_perm(scan_perm);
5090 buf_scan_perm.set_generation(perm_gen());
5091
5092 // Walk the code cache w/o buffering, because StarTask cannot handle
5093 // unaligned oop locations.
5094 G1FilteredCodeBlobToOopClosure eager_scan_code_roots(this, scan_non_heap_roots);
5095
5096 process_strong_roots(false, // no scoping; this is parallel code
5097 collecting_perm_gen, so,
5098 &buf_scan_non_heap_roots,
5099 &eager_scan_code_roots,
5100 &buf_scan_perm);
5101
5102 // Now the CM ref_processor roots.
5103 if (!_process_strong_tasks->is_task_claimed(G1H_PS_refProcessor_oops_do)) {
5104 // We need to treat the discovered reference lists of the
5105 // concurrent mark ref processor as roots and keep entries
5106 // (which are added by the marking threads) on them live
5107 // until they can be processed at the end of marking.
5108 ref_processor_cm()->weak_oops_do(&buf_scan_non_heap_roots);
5109 }
5110
5111 // Finish up any enqueued closure apps (attributed as object copy time).
5112 buf_scan_non_heap_roots.done();
5113 buf_scan_perm.done();
5114
5115 double obj_copy_time_sec = buf_scan_perm.closure_app_seconds() +
5116 buf_scan_non_heap_roots.closure_app_seconds();
5117 g1_policy()->phase_times()->record_obj_copy_time(worker_i, obj_copy_time_sec * 1000.0);
5118
5119 double ext_root_time_ms =
5120 ((os::elapsedTime() - ext_roots_start) - obj_copy_time_sec) * 1000.0;
5121
5122 g1_policy()->phase_times()->record_ext_root_scan_time(worker_i, ext_root_time_ms);
5123
5124 // During conc marking we have to filter the per-thread SATB buffers
5125 // to make sure we remove any oops into the CSet (which will show up
5126 // as implicitly live).
5127 double satb_filtering_ms = 0.0;
5128 if (!_process_strong_tasks->is_task_claimed(G1H_PS_filter_satb_buffers)) {
5129 if (mark_in_progress()) {
5130 double satb_filter_start = os::elapsedTime();
5131
5132 JavaThread::satb_mark_queue_set().filter_thread_buffers();
5133
5134 satb_filtering_ms = (os::elapsedTime() - satb_filter_start) * 1000.0;
5135 }
5136 }
5137 g1_policy()->phase_times()->record_satb_filtering_time(worker_i, satb_filtering_ms);
5138
5139 // Now scan the complement of the collection set.
5140 if (scan_rs != NULL) {
5141 g1_rem_set()->oops_into_collection_set_do(scan_rs, worker_i);
5142 }
5143
5144 _process_strong_tasks->all_tasks_completed();
5145 }
5146
5147 void
5148 G1CollectedHeap::g1_process_weak_roots(OopClosure* root_closure,
5149 OopClosure* non_root_closure) {
5150 CodeBlobToOopClosure roots_in_blobs(root_closure, /*do_marking=*/ false);
5151 SharedHeap::process_weak_roots(root_closure, &roots_in_blobs, non_root_closure);
5152 }
5153
5154 // Weak Reference Processing support
5155
5156 // An always "is_alive" closure that is used to preserve referents.
5157 // If the object is non-null then it's alive. Used in the preservation
5158 // of referent objects that are pointed to by reference objects
5159 // discovered by the CM ref processor.
5160 class G1AlwaysAliveClosure: public BoolObjectClosure {
5161 G1CollectedHeap* _g1;
5162 public:
5163 G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
5164 void do_object(oop p) { assert(false, "Do not call."); }
5165 bool do_object_b(oop p) {
5166 if (p != NULL) {
5167 return true;
5168 }
5169 return false;
5170 }
5171 };
5172
5173 bool G1STWIsAliveClosure::do_object_b(oop p) {
5174 // An object is reachable if it is outside the collection set,
5175 // or is inside and copied.
5176 return !_g1->obj_in_cs(p) || p->is_forwarded();
5177 }
5178
5179 // Non Copying Keep Alive closure
5180 class G1KeepAliveClosure: public OopClosure {
5181 G1CollectedHeap* _g1;
5182 public:
5183 G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
5184 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
5185 void do_oop( oop* p) {
5186 oop obj = *p;
5187
5188 if (_g1->obj_in_cs(obj)) {
5189 assert( obj->is_forwarded(), "invariant" );
5190 *p = obj->forwardee();
5191 }
5192 }
5193 };
5194
5195 // Copying Keep Alive closure - can be called from both
5196 // serial and parallel code as long as different worker
5197 // threads utilize different G1ParScanThreadState instances
5198 // and different queues.
5199
5200 class G1CopyingKeepAliveClosure: public OopClosure {
5201 G1CollectedHeap* _g1h;
5202 OopClosure* _copy_non_heap_obj_cl;
5203 OopsInHeapRegionClosure* _copy_perm_obj_cl;
5204 G1ParScanThreadState* _par_scan_state;
5205
5206 public:
5207 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
5208 OopClosure* non_heap_obj_cl,
5209 OopsInHeapRegionClosure* perm_obj_cl,
5210 G1ParScanThreadState* pss):
5211 _g1h(g1h),
5212 _copy_non_heap_obj_cl(non_heap_obj_cl),
5213 _copy_perm_obj_cl(perm_obj_cl),
5214 _par_scan_state(pss)
5215 {}
5216
5217 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
5218 virtual void do_oop( oop* p) { do_oop_work(p); }
5219
5220 template <class T> void do_oop_work(T* p) {
5221 oop obj = oopDesc::load_decode_heap_oop(p);
5222
5223 if (_g1h->obj_in_cs(obj)) {
5224 // If the referent object has been forwarded (either copied
5225 // to a new location or to itself in the event of an
5226 // evacuation failure) then we need to update the reference
5227 // field and, if both reference and referent are in the G1
5228 // heap, update the RSet for the referent.
5229 //
5230 // If the referent has not been forwarded then we have to keep
5231 // it alive by policy. Therefore we have copy the referent.
5232 //
5233 // If the reference field is in the G1 heap then we can push
5234 // on the PSS queue. When the queue is drained (after each
5235 // phase of reference processing) the object and it's followers
5236 // will be copied, the reference field set to point to the
5237 // new location, and the RSet updated. Otherwise we need to
5238 // use the the non-heap or perm closures directly to copy
5239 // the referent object and update the pointer, while avoiding
5240 // updating the RSet.
5241
5242 if (_g1h->is_in_g1_reserved(p)) {
5243 _par_scan_state->push_on_queue(p);
5244 } else {
5245 // The reference field is not in the G1 heap.
5246 if (_g1h->perm_gen()->is_in(p)) {
5247 _copy_perm_obj_cl->do_oop(p);
5248 } else {
5249 _copy_non_heap_obj_cl->do_oop(p);
5250 }
5251 }
5252 }
5253 }
5254 };
5255
5256 // Serial drain queue closure. Called as the 'complete_gc'
5257 // closure for each discovered list in some of the
5258 // reference processing phases.
5259
5260 class G1STWDrainQueueClosure: public VoidClosure {
5261 protected:
5262 G1CollectedHeap* _g1h;
5263 G1ParScanThreadState* _par_scan_state;
5264
5265 G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
5266
5267 public:
5268 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
5269 _g1h(g1h),
5270 _par_scan_state(pss)
5271 { }
5272
5273 void do_void() {
5274 G1ParScanThreadState* const pss = par_scan_state();
5275 pss->trim_queue();
5276 }
5277 };
5278
5279 // Parallel Reference Processing closures
5280
5281 // Implementation of AbstractRefProcTaskExecutor for parallel reference
5282 // processing during G1 evacuation pauses.
5283
5284 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
5285 private:
5286 G1CollectedHeap* _g1h;
5287 RefToScanQueueSet* _queues;
5288 FlexibleWorkGang* _workers;
5289 int _active_workers;
5290
5291 public:
5292 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
5293 FlexibleWorkGang* workers,
5294 RefToScanQueueSet *task_queues,
5295 int n_workers) :
5296 _g1h(g1h),
5297 _queues(task_queues),
5298 _workers(workers),
5299 _active_workers(n_workers)
5300 {
5301 assert(n_workers > 0, "shouldn't call this otherwise");
5302 }
5303
5304 // Executes the given task using concurrent marking worker threads.
5305 virtual void execute(ProcessTask& task);
5306 virtual void execute(EnqueueTask& task);
5307 };
5308
5309 // Gang task for possibly parallel reference processing
5310
5311 class G1STWRefProcTaskProxy: public AbstractGangTask {
5312 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
5313 ProcessTask& _proc_task;
5314 G1CollectedHeap* _g1h;
5315 RefToScanQueueSet *_task_queues;
5316 ParallelTaskTerminator* _terminator;
5317
5318 public:
5319 G1STWRefProcTaskProxy(ProcessTask& proc_task,
5320 G1CollectedHeap* g1h,
5321 RefToScanQueueSet *task_queues,
5322 ParallelTaskTerminator* terminator) :
5323 AbstractGangTask("Process reference objects in parallel"),
5324 _proc_task(proc_task),
5325 _g1h(g1h),
5326 _task_queues(task_queues),
5327 _terminator(terminator)
5328 {}
5329
5330 virtual void work(uint worker_id) {
5331 // The reference processing task executed by a single worker.
5332 ResourceMark rm;
5333 HandleMark hm;
5334
5335 G1STWIsAliveClosure is_alive(_g1h);
5336
5337 G1ParScanThreadState pss(_g1h, worker_id);
5338
5339 G1ParScanHeapEvacClosure scan_evac_cl(_g1h, &pss, NULL);
5340 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5341 G1ParScanPartialArrayClosure partial_scan_cl(_g1h, &pss, NULL);
5342
5343 pss.set_evac_closure(&scan_evac_cl);
5344 pss.set_evac_failure_closure(&evac_failure_cl);
5345 pss.set_partial_scan_closure(&partial_scan_cl);
5346
5347 G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL);
5348 G1ParScanPermClosure only_copy_perm_cl(_g1h, &pss, NULL);
5349
5350 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5351 G1ParScanAndMarkPermClosure copy_mark_perm_cl(_g1h, &pss, NULL);
5352
5353 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5354 OopsInHeapRegionClosure* copy_perm_cl = &only_copy_perm_cl;
5355
5356 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5357 // We also need to mark copied objects.
5358 copy_non_heap_cl = ©_mark_non_heap_cl;
5359 copy_perm_cl = ©_mark_perm_cl;
5360 }
5361
5362 // Keep alive closure.
5363 G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, copy_perm_cl, &pss);
5364
5365 // Complete GC closure
5366 G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _task_queues, _terminator);
5367
5368 // Call the reference processing task's work routine.
5369 _proc_task.work(worker_id, is_alive, keep_alive, drain_queue);
5370
5371 // Note we cannot assert that the refs array is empty here as not all
5372 // of the processing tasks (specifically phase2 - pp2_work) execute
5373 // the complete_gc closure (which ordinarily would drain the queue) so
5374 // the queue may not be empty.
5375 }
5376 };
5377
5378 // Driver routine for parallel reference processing.
5379 // Creates an instance of the ref processing gang
5380 // task and has the worker threads execute it.
5381 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) {
5382 assert(_workers != NULL, "Need parallel worker threads.");
5383
5384 ParallelTaskTerminator terminator(_active_workers, _queues);
5385 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _queues, &terminator);
5386
5387 _g1h->set_par_threads(_active_workers);
5388 _workers->run_task(&proc_task_proxy);
5389 _g1h->set_par_threads(0);
5390 }
5391
5392 // Gang task for parallel reference enqueueing.
5393
5394 class G1STWRefEnqueueTaskProxy: public AbstractGangTask {
5395 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
5396 EnqueueTask& _enq_task;
5397
5398 public:
5399 G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) :
5400 AbstractGangTask("Enqueue reference objects in parallel"),
5401 _enq_task(enq_task)
5402 { }
5403
5404 virtual void work(uint worker_id) {
5405 _enq_task.work(worker_id);
5406 }
5407 };
5408
5409 // Driver routine for parallel reference enqueueing.
5410 // Creates an instance of the ref enqueueing gang
5411 // task and has the worker threads execute it.
5412
5413 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
5414 assert(_workers != NULL, "Need parallel worker threads.");
5415
5416 G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task);
5417
5418 _g1h->set_par_threads(_active_workers);
5419 _workers->run_task(&enq_task_proxy);
5420 _g1h->set_par_threads(0);
5421 }
5422
5423 // End of weak reference support closures
5424
5425 // Abstract task used to preserve (i.e. copy) any referent objects
5426 // that are in the collection set and are pointed to by reference
5427 // objects discovered by the CM ref processor.
5428
5429 class G1ParPreserveCMReferentsTask: public AbstractGangTask {
5430 protected:
5431 G1CollectedHeap* _g1h;
5432 RefToScanQueueSet *_queues;
5433 ParallelTaskTerminator _terminator;
5434 uint _n_workers;
5435
5436 public:
5437 G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h,int workers, RefToScanQueueSet *task_queues) :
5438 AbstractGangTask("ParPreserveCMReferents"),
5439 _g1h(g1h),
5440 _queues(task_queues),
5441 _terminator(workers, _queues),
5442 _n_workers(workers)
5443 { }
5444
5445 void work(uint worker_id) {
5446 ResourceMark rm;
5447 HandleMark hm;
5448
5449 G1ParScanThreadState pss(_g1h, worker_id);
5450 G1ParScanHeapEvacClosure scan_evac_cl(_g1h, &pss, NULL);
5451 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5452 G1ParScanPartialArrayClosure partial_scan_cl(_g1h, &pss, NULL);
5453
5454 pss.set_evac_closure(&scan_evac_cl);
5455 pss.set_evac_failure_closure(&evac_failure_cl);
5456 pss.set_partial_scan_closure(&partial_scan_cl);
5457
5458 assert(pss.refs()->is_empty(), "both queue and overflow should be empty");
5459
5460
5461 G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL);
5462 G1ParScanPermClosure only_copy_perm_cl(_g1h, &pss, NULL);
5463
5464 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5465 G1ParScanAndMarkPermClosure copy_mark_perm_cl(_g1h, &pss, NULL);
5466
5467 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5468 OopsInHeapRegionClosure* copy_perm_cl = &only_copy_perm_cl;
5469
5470 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5471 // We also need to mark copied objects.
5472 copy_non_heap_cl = ©_mark_non_heap_cl;
5473 copy_perm_cl = ©_mark_perm_cl;
5474 }
5475
5476 // Is alive closure
5477 G1AlwaysAliveClosure always_alive(_g1h);
5478
5479 // Copying keep alive closure. Applied to referent objects that need
5480 // to be copied.
5481 G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, copy_perm_cl, &pss);
5482
5483 ReferenceProcessor* rp = _g1h->ref_processor_cm();
5484
5485 uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q();
5486 uint stride = MIN2(MAX2(_n_workers, 1U), limit);
5487
5488 // limit is set using max_num_q() - which was set using ParallelGCThreads.
5489 // So this must be true - but assert just in case someone decides to
5490 // change the worker ids.
5491 assert(0 <= worker_id && worker_id < limit, "sanity");
5492 assert(!rp->discovery_is_atomic(), "check this code");
5493
5494 // Select discovered lists [i, i+stride, i+2*stride,...,limit)
5495 for (uint idx = worker_id; idx < limit; idx += stride) {
5496 DiscoveredList& ref_list = rp->discovered_refs()[idx];
5497
5498 DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive);
5499 while (iter.has_next()) {
5500 // Since discovery is not atomic for the CM ref processor, we
5501 // can see some null referent objects.
5502 iter.load_ptrs(DEBUG_ONLY(true));
5503 oop ref = iter.obj();
5504
5505 // This will filter nulls.
5506 if (iter.is_referent_alive()) {
5507 iter.make_referent_alive();
5508 }
5509 iter.move_to_next();
5510 }
5511 }
5512
5513 // Drain the queue - which may cause stealing
5514 G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _queues, &_terminator);
5515 drain_queue.do_void();
5516 // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure
5517 assert(pss.refs()->is_empty(), "should be");
5518 }
5519 };
5520
5521 // Weak Reference processing during an evacuation pause (part 1).
5522 void G1CollectedHeap::process_discovered_references(uint no_of_gc_workers) {
5523 double ref_proc_start = os::elapsedTime();
5524
5525 ReferenceProcessor* rp = _ref_processor_stw;
5526 assert(rp->discovery_enabled(), "should have been enabled");
5527
5528 // Any reference objects, in the collection set, that were 'discovered'
5529 // by the CM ref processor should have already been copied (either by
5530 // applying the external root copy closure to the discovered lists, or
5531 // by following an RSet entry).
5532 //
5533 // But some of the referents, that are in the collection set, that these
5534 // reference objects point to may not have been copied: the STW ref
5535 // processor would have seen that the reference object had already
5536 // been 'discovered' and would have skipped discovering the reference,
5537 // but would not have treated the reference object as a regular oop.
5538 // As a result the copy closure would not have been applied to the
5539 // referent object.
5540 //
5541 // We need to explicitly copy these referent objects - the references
5542 // will be processed at the end of remarking.
5543 //
5544 // We also need to do this copying before we process the reference
5545 // objects discovered by the STW ref processor in case one of these
5546 // referents points to another object which is also referenced by an
5547 // object discovered by the STW ref processor.
5548
5549 assert(!G1CollectedHeap::use_parallel_gc_threads() ||
5550 no_of_gc_workers == workers()->active_workers(),
5551 "Need to reset active GC workers");
5552
5553 set_par_threads(no_of_gc_workers);
5554 G1ParPreserveCMReferentsTask keep_cm_referents(this,
5555 no_of_gc_workers,
5556 _task_queues);
5557
5558 if (G1CollectedHeap::use_parallel_gc_threads()) {
5559 workers()->run_task(&keep_cm_referents);
5560 } else {
5561 keep_cm_referents.work(0);
5562 }
5563
5564 set_par_threads(0);
5565
5566 // Closure to test whether a referent is alive.
5567 G1STWIsAliveClosure is_alive(this);
5568
5569 // Even when parallel reference processing is enabled, the processing
5570 // of JNI refs is serial and performed serially by the current thread
5571 // rather than by a worker. The following PSS will be used for processing
5572 // JNI refs.
5573
5574 // Use only a single queue for this PSS.
5575 G1ParScanThreadState pss(this, 0);
5576
5577 // We do not embed a reference processor in the copying/scanning
5578 // closures while we're actually processing the discovered
5579 // reference objects.
5580 G1ParScanHeapEvacClosure scan_evac_cl(this, &pss, NULL);
5581 G1ParScanHeapEvacFailureClosure evac_failure_cl(this, &pss, NULL);
5582 G1ParScanPartialArrayClosure partial_scan_cl(this, &pss, NULL);
5583
5584 pss.set_evac_closure(&scan_evac_cl);
5585 pss.set_evac_failure_closure(&evac_failure_cl);
5586 pss.set_partial_scan_closure(&partial_scan_cl);
5587
5588 assert(pss.refs()->is_empty(), "pre-condition");
5589
5590 G1ParScanExtRootClosure only_copy_non_heap_cl(this, &pss, NULL);
5591 G1ParScanPermClosure only_copy_perm_cl(this, &pss, NULL);
5592
5593 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(this, &pss, NULL);
5594 G1ParScanAndMarkPermClosure copy_mark_perm_cl(this, &pss, NULL);
5595
5596 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5597 OopsInHeapRegionClosure* copy_perm_cl = &only_copy_perm_cl;
5598
5599 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5600 // We also need to mark copied objects.
5601 copy_non_heap_cl = ©_mark_non_heap_cl;
5602 copy_perm_cl = ©_mark_perm_cl;
5603 }
5604
5605 // Keep alive closure.
5606 G1CopyingKeepAliveClosure keep_alive(this, copy_non_heap_cl, copy_perm_cl, &pss);
5607
5608 // Serial Complete GC closure
5609 G1STWDrainQueueClosure drain_queue(this, &pss);
5610
5611 // Setup the soft refs policy...
5612 rp->setup_policy(false);
5613
5614 ReferenceProcessorStats stats;
5615 if (!rp->processing_is_mt()) {
5616 // Serial reference processing...
5617 stats = rp->process_discovered_references(&is_alive,
5618 &keep_alive,
5619 &drain_queue,
5620 NULL,
5621 _gc_timer_stw);
5622 } else {
5623 // Parallel reference processing
5624 assert(rp->num_q() == no_of_gc_workers, "sanity");
5625 assert(no_of_gc_workers <= rp->max_num_q(), "sanity");
5626
5627 G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers);
5628 stats = rp->process_discovered_references(&is_alive,
5629 &keep_alive,
5630 &drain_queue,
5631 &par_task_executor,
5632 _gc_timer_stw);
5633 }
5634
5635 _gc_tracer_stw->report_gc_reference_stats(stats);
5636 // We have completed copying any necessary live referent objects
5637 // (that were not copied during the actual pause) so we can
5638 // retire any active alloc buffers
5639 pss.retire_alloc_buffers();
5640 assert(pss.refs()->is_empty(), "both queue and overflow should be empty");
5641
5642 double ref_proc_time = os::elapsedTime() - ref_proc_start;
5643 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
5644 }
5645
5646 // Weak Reference processing during an evacuation pause (part 2).
5647 void G1CollectedHeap::enqueue_discovered_references(uint no_of_gc_workers) {
5648 double ref_enq_start = os::elapsedTime();
5649
5650 ReferenceProcessor* rp = _ref_processor_stw;
5651 assert(!rp->discovery_enabled(), "should have been disabled as part of processing");
5652
5653 // Now enqueue any remaining on the discovered lists on to
5654 // the pending list.
5655 if (!rp->processing_is_mt()) {
5656 // Serial reference processing...
5657 rp->enqueue_discovered_references();
5658 } else {
5659 // Parallel reference enqueueing
5660
5661 assert(no_of_gc_workers == workers()->active_workers(),
5662 "Need to reset active workers");
5663 assert(rp->num_q() == no_of_gc_workers, "sanity");
5664 assert(no_of_gc_workers <= rp->max_num_q(), "sanity");
5665
5666 G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers);
5667 rp->enqueue_discovered_references(&par_task_executor);
5668 }
5669
5670 rp->verify_no_references_recorded();
5671 assert(!rp->discovery_enabled(), "should have been disabled");
5672
5673 // FIXME
5674 // CM's reference processing also cleans up the string and symbol tables.
5675 // Should we do that here also? We could, but it is a serial operation
5676 // and could significantly increase the pause time.
5677
5678 double ref_enq_time = os::elapsedTime() - ref_enq_start;
5679 g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0);
5680 }
5681
5682 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info) {
5683 _expand_heap_after_alloc_failure = true;
5684 _evacuation_failed = false;
5685
5686 // Should G1EvacuationFailureALot be in effect for this GC?
5687 NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();)
5688
5689 g1_rem_set()->prepare_for_oops_into_collection_set_do();
5690
5691 // Disable the hot card cache.
5692 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
5693 hot_card_cache->reset_hot_cache_claimed_index();
5694 hot_card_cache->set_use_cache(false);
5695
5696 uint n_workers;
5697 if (G1CollectedHeap::use_parallel_gc_threads()) {
5698 n_workers =
5699 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
5700 workers()->active_workers(),
5701 Threads::number_of_non_daemon_threads());
5702 assert(UseDynamicNumberOfGCThreads ||
5703 n_workers == workers()->total_workers(),
5704 "If not dynamic should be using all the workers");
5705 workers()->set_active_workers(n_workers);
5706 set_par_threads(n_workers);
5707 } else {
5708 assert(n_par_threads() == 0,
5709 "Should be the original non-parallel value");
5710 n_workers = 1;
5711 }
5712
5713 G1ParTask g1_par_task(this, _task_queues);
5714
5715 init_for_evac_failure(NULL);
5716
5717 rem_set()->prepare_for_younger_refs_iterate(true);
5718
5719 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
5720 double start_par_time_sec = os::elapsedTime();
5721 double end_par_time_sec;
5722
5723 {
5724 StrongRootsScope srs(this);
5725
5726 if (G1CollectedHeap::use_parallel_gc_threads()) {
5727 // The individual threads will set their evac-failure closures.
5728 if (ParallelGCVerbose) G1ParScanThreadState::print_termination_stats_hdr();
5729 // These tasks use ShareHeap::_process_strong_tasks
5730 assert(UseDynamicNumberOfGCThreads ||
5731 workers()->active_workers() == workers()->total_workers(),
5732 "If not dynamic should be using all the workers");
5733 workers()->run_task(&g1_par_task);
5734 } else {
5735 g1_par_task.set_for_termination(n_workers);
5736 g1_par_task.work(0);
5737 }
5738 end_par_time_sec = os::elapsedTime();
5739
5740 // Closing the inner scope will execute the destructor
5741 // for the StrongRootsScope object. We record the current
5742 // elapsed time before closing the scope so that time
5743 // taken for the SRS destructor is NOT included in the
5744 // reported parallel time.
5745 }
5746
5747 double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0;
5748 g1_policy()->phase_times()->record_par_time(par_time_ms);
5749
5750 double code_root_fixup_time_ms =
5751 (os::elapsedTime() - end_par_time_sec) * 1000.0;
5752 g1_policy()->phase_times()->record_code_root_fixup_time(code_root_fixup_time_ms);
5753
5754 set_par_threads(0);
5755
5756 // Process any discovered reference objects - we have
5757 // to do this _before_ we retire the GC alloc regions
5758 // as we may have to copy some 'reachable' referent
5759 // objects (and their reachable sub-graphs) that were
5760 // not copied during the pause.
5761 process_discovered_references(n_workers);
5762
5763 // Weak root processing.
5764 // Note: when JSR 292 is enabled and code blobs can contain
5765 // non-perm oops then we will need to process the code blobs
5766 // here too.
5767 {
5768 G1STWIsAliveClosure is_alive(this);
5769 G1KeepAliveClosure keep_alive(this);
5770 JNIHandles::weak_oops_do(&is_alive, &keep_alive);
5771 }
5772
5773 release_gc_alloc_regions(n_workers, evacuation_info);
5774 g1_rem_set()->cleanup_after_oops_into_collection_set_do();
5775
5776 // Reset and re-enable the hot card cache.
5777 // Note the counts for the cards in the regions in the
5778 // collection set are reset when the collection set is freed.
5779 hot_card_cache->reset_hot_cache();
5780 hot_card_cache->set_use_cache(true);
5781
5782 finalize_for_evac_failure();
5783
5784 if (evacuation_failed()) {
5785 remove_self_forwarding_pointers();
5786
5787 // Reset the G1EvacuationFailureALot counters and flags
5788 // Note: the values are reset only when an actual
5789 // evacuation failure occurs.
5790 NOT_PRODUCT(reset_evacuation_should_fail();)
5791 }
5792
5793 // Enqueue any remaining references remaining on the STW
5794 // reference processor's discovered lists. We need to do
5795 // this after the card table is cleaned (and verified) as
5796 // the act of enqueueing entries on to the pending list
5797 // will log these updates (and dirty their associated
5798 // cards). We need these updates logged to update any
5799 // RSets.
5800 enqueue_discovered_references(n_workers);
5801
5802 if (G1DeferredRSUpdate) {
5803 RedirtyLoggedCardTableEntryFastClosure redirty;
5804 dirty_card_queue_set().set_closure(&redirty);
5805 dirty_card_queue_set().apply_closure_to_all_completed_buffers();
5806
5807 DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set();
5808 dcq.merge_bufferlists(&dirty_card_queue_set());
5809 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
5810 }
5811 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
5812 }
5813
5814 void G1CollectedHeap::free_region_if_empty(HeapRegion* hr,
5815 size_t* pre_used,
5816 FreeRegionList* free_list,
5817 OldRegionSet* old_proxy_set,
5818 HumongousRegionSet* humongous_proxy_set,
5819 HRRSCleanupTask* hrrs_cleanup_task,
5820 bool par) {
5821 if (hr->used() > 0 && hr->max_live_bytes() == 0 && !hr->is_young()) {
5822 if (hr->isHumongous()) {
5823 assert(hr->startsHumongous(), "we should only see starts humongous");
5824 free_humongous_region(hr, pre_used, free_list, humongous_proxy_set, par);
5825 } else {
5826 _old_set.remove_with_proxy(hr, old_proxy_set);
5827 free_region(hr, pre_used, free_list, par);
5828 }
5829 } else {
5830 hr->rem_set()->do_cleanup_work(hrrs_cleanup_task);
5831 }
5832 }
5833
5834 void G1CollectedHeap::free_region(HeapRegion* hr,
5835 size_t* pre_used,
5836 FreeRegionList* free_list,
5837 bool par) {
5838 assert(!hr->isHumongous(), "this is only for non-humongous regions");
5839 assert(!hr->is_empty(), "the region should not be empty");
5840 assert(free_list != NULL, "pre-condition");
5841
5842 // Clear the card counts for this region.
5843 // Note: we only need to do this if the region is not young
5844 // (since we don't refine cards in young regions).
5845 if (!hr->is_young()) {
5846 _cg1r->hot_card_cache()->reset_card_counts(hr);
5847 }
5848 *pre_used += hr->used();
5849 hr->hr_clear(par, true /* clear_space */);
5850 free_list->add_as_head(hr);
5851 }
5852
5853 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
5854 size_t* pre_used,
5855 FreeRegionList* free_list,
5856 HumongousRegionSet* humongous_proxy_set,
5857 bool par) {
5858 assert(hr->startsHumongous(), "this is only for starts humongous regions");
5859 assert(free_list != NULL, "pre-condition");
5860 assert(humongous_proxy_set != NULL, "pre-condition");
5861
5862 size_t hr_used = hr->used();
5863 size_t hr_capacity = hr->capacity();
5864 size_t hr_pre_used = 0;
5865 _humongous_set.remove_with_proxy(hr, humongous_proxy_set);
5866 // We need to read this before we make the region non-humongous,
5867 // otherwise the information will be gone.
5868 uint last_index = hr->last_hc_index();
5869 hr->set_notHumongous();
5870 free_region(hr, &hr_pre_used, free_list, par);
5871
5872 uint i = hr->hrs_index() + 1;
5873 while (i < last_index) {
5874 HeapRegion* curr_hr = region_at(i);
5875 assert(curr_hr->continuesHumongous(), "invariant");
5876 curr_hr->set_notHumongous();
5877 free_region(curr_hr, &hr_pre_used, free_list, par);
5878 i += 1;
5879 }
5880 assert(hr_pre_used == hr_used,
5881 err_msg("hr_pre_used: "SIZE_FORMAT" and hr_used: "SIZE_FORMAT" "
5882 "should be the same", hr_pre_used, hr_used));
5883 *pre_used += hr_pre_used;
5884 }
5885
5886 void G1CollectedHeap::update_sets_after_freeing_regions(size_t pre_used,
5887 FreeRegionList* free_list,
5888 OldRegionSet* old_proxy_set,
5889 HumongousRegionSet* humongous_proxy_set,
5890 bool par) {
5891 if (pre_used > 0) {
5892 Mutex* lock = (par) ? ParGCRareEvent_lock : NULL;
5893 MutexLockerEx x(lock, Mutex::_no_safepoint_check_flag);
5894 assert(_summary_bytes_used >= pre_used,
5895 err_msg("invariant: _summary_bytes_used: "SIZE_FORMAT" "
5896 "should be >= pre_used: "SIZE_FORMAT,
5897 _summary_bytes_used, pre_used));
5898 _summary_bytes_used -= pre_used;
5899 }
5900 if (free_list != NULL && !free_list->is_empty()) {
5901 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
5902 _free_list.add_as_head(free_list);
5903 }
5904 if (old_proxy_set != NULL && !old_proxy_set->is_empty()) {
5905 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
5906 _old_set.update_from_proxy(old_proxy_set);
5907 }
5908 if (humongous_proxy_set != NULL && !humongous_proxy_set->is_empty()) {
5909 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
5910 _humongous_set.update_from_proxy(humongous_proxy_set);
5911 }
5912 }
5913
5914 class G1ParCleanupCTTask : public AbstractGangTask {
5915 CardTableModRefBS* _ct_bs;
5916 G1CollectedHeap* _g1h;
5917 HeapRegion* volatile _su_head;
5918 public:
5919 G1ParCleanupCTTask(CardTableModRefBS* ct_bs,
5920 G1CollectedHeap* g1h) :
5921 AbstractGangTask("G1 Par Cleanup CT Task"),
5922 _ct_bs(ct_bs), _g1h(g1h) { }
5923
5924 void work(uint worker_id) {
5925 HeapRegion* r;
5926 while (r = _g1h->pop_dirty_cards_region()) {
5927 clear_cards(r);
5928 }
5929 }
5930
5931 void clear_cards(HeapRegion* r) {
5932 // Cards of the survivors should have already been dirtied.
5933 if (!r->is_survivor()) {
5934 _ct_bs->clear(MemRegion(r->bottom(), r->end()));
5935 }
5936 }
5937 };
5938
5939 #ifndef PRODUCT
5940 class G1VerifyCardTableCleanup: public HeapRegionClosure {
5941 G1CollectedHeap* _g1h;
5942 CardTableModRefBS* _ct_bs;
5943 public:
5944 G1VerifyCardTableCleanup(G1CollectedHeap* g1h, CardTableModRefBS* ct_bs)
5945 : _g1h(g1h), _ct_bs(ct_bs) { }
5946 virtual bool doHeapRegion(HeapRegion* r) {
5947 if (r->is_survivor()) {
5948 _g1h->verify_dirty_region(r);
5949 } else {
5950 _g1h->verify_not_dirty_region(r);
5951 }
5952 return false;
5953 }
5954 };
5955
5956 void G1CollectedHeap::verify_not_dirty_region(HeapRegion* hr) {
5957 // All of the region should be clean.
5958 CardTableModRefBS* ct_bs = (CardTableModRefBS*)barrier_set();
5959 MemRegion mr(hr->bottom(), hr->end());
5960 ct_bs->verify_not_dirty_region(mr);
5961 }
5962
5963 void G1CollectedHeap::verify_dirty_region(HeapRegion* hr) {
5964 // We cannot guarantee that [bottom(),end()] is dirty. Threads
5965 // dirty allocated blocks as they allocate them. The thread that
5966 // retires each region and replaces it with a new one will do a
5967 // maximal allocation to fill in [pre_dummy_top(),end()] but will
5968 // not dirty that area (one less thing to have to do while holding
5969 // a lock). So we can only verify that [bottom(),pre_dummy_top()]
5970 // is dirty.
5971 CardTableModRefBS* ct_bs = (CardTableModRefBS*) barrier_set();
5972 MemRegion mr(hr->bottom(), hr->pre_dummy_top());
5973 ct_bs->verify_dirty_region(mr);
5974 }
5975
5976 void G1CollectedHeap::verify_dirty_young_list(HeapRegion* head) {
5977 CardTableModRefBS* ct_bs = (CardTableModRefBS*) barrier_set();
5978 for (HeapRegion* hr = head; hr != NULL; hr = hr->get_next_young_region()) {
5979 verify_dirty_region(hr);
5980 }
5981 }
5982
5983 void G1CollectedHeap::verify_dirty_young_regions() {
5984 verify_dirty_young_list(_young_list->first_region());
5985 }
5986 #endif
5987
5988 void G1CollectedHeap::cleanUpCardTable() {
5989 CardTableModRefBS* ct_bs = (CardTableModRefBS*) (barrier_set());
5990 double start = os::elapsedTime();
5991
5992 {
5993 // Iterate over the dirty cards region list.
5994 G1ParCleanupCTTask cleanup_task(ct_bs, this);
5995
5996 if (G1CollectedHeap::use_parallel_gc_threads()) {
5997 set_par_threads();
5998 workers()->run_task(&cleanup_task);
5999 set_par_threads(0);
6000 } else {
6001 while (_dirty_cards_region_list) {
6002 HeapRegion* r = _dirty_cards_region_list;
6003 cleanup_task.clear_cards(r);
6004 _dirty_cards_region_list = r->get_next_dirty_cards_region();
6005 if (_dirty_cards_region_list == r) {
6006 // The last region.
6007 _dirty_cards_region_list = NULL;
6008 }
6009 r->set_next_dirty_cards_region(NULL);
6010 }
6011 }
6012 #ifndef PRODUCT
6013 if (G1VerifyCTCleanup || VerifyAfterGC) {
6014 G1VerifyCardTableCleanup cleanup_verifier(this, ct_bs);
6015 heap_region_iterate(&cleanup_verifier);
6016 }
6017 #endif
6018 }
6019
6020 double elapsed = os::elapsedTime() - start;
6021 g1_policy()->phase_times()->record_clear_ct_time(elapsed * 1000.0);
6022 }
6023
6024 void G1CollectedHeap::free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info) {
6025 size_t pre_used = 0;
6026 FreeRegionList local_free_list("Local List for CSet Freeing");
6027
6028 double young_time_ms = 0.0;
6029 double non_young_time_ms = 0.0;
6030
6031 // Since the collection set is a superset of the the young list,
6032 // all we need to do to clear the young list is clear its
6033 // head and length, and unlink any young regions in the code below
6034 _young_list->clear();
6035
6036 G1CollectorPolicy* policy = g1_policy();
6037
6038 double start_sec = os::elapsedTime();
6039 bool non_young = true;
6040
6041 HeapRegion* cur = cs_head;
6042 int age_bound = -1;
6043 size_t rs_lengths = 0;
6044
6045 while (cur != NULL) {
6046 assert(!is_on_master_free_list(cur), "sanity");
6047 if (non_young) {
6048 if (cur->is_young()) {
6049 double end_sec = os::elapsedTime();
6050 double elapsed_ms = (end_sec - start_sec) * 1000.0;
6051 non_young_time_ms += elapsed_ms;
6052
6053 start_sec = os::elapsedTime();
6054 non_young = false;
6055 }
6056 } else {
6057 if (!cur->is_young()) {
6058 double end_sec = os::elapsedTime();
6059 double elapsed_ms = (end_sec - start_sec) * 1000.0;
6060 young_time_ms += elapsed_ms;
6061
6062 start_sec = os::elapsedTime();
6063 non_young = true;
6064 }
6065 }
6066
6067 rs_lengths += cur->rem_set()->occupied();
6068
6069 HeapRegion* next = cur->next_in_collection_set();
6070 assert(cur->in_collection_set(), "bad CS");
6071 cur->set_next_in_collection_set(NULL);
6072 cur->set_in_collection_set(false);
6073
6074 if (cur->is_young()) {
6075 int index = cur->young_index_in_cset();
6076 assert(index != -1, "invariant");
6077 assert((uint) index < policy->young_cset_region_length(), "invariant");
6078 size_t words_survived = _surviving_young_words[index];
6079 cur->record_surv_words_in_group(words_survived);
6080
6081 // At this point the we have 'popped' cur from the collection set
6082 // (linked via next_in_collection_set()) but it is still in the
6083 // young list (linked via next_young_region()). Clear the
6084 // _next_young_region field.
6085 cur->set_next_young_region(NULL);
6086 } else {
6087 int index = cur->young_index_in_cset();
6088 assert(index == -1, "invariant");
6089 }
6090
6091 assert( (cur->is_young() && cur->young_index_in_cset() > -1) ||
6092 (!cur->is_young() && cur->young_index_in_cset() == -1),
6093 "invariant" );
6094
6095 if (!cur->evacuation_failed()) {
6096 MemRegion used_mr = cur->used_region();
6097
6098 // And the region is empty.
6099 assert(!used_mr.is_empty(), "Should not have empty regions in a CS.");
6100 free_region(cur, &pre_used, &local_free_list, false /* par */);
6101 } else {
6102 cur->uninstall_surv_rate_group();
6103 if (cur->is_young()) {
6104 cur->set_young_index_in_cset(-1);
6105 }
6106 cur->set_not_young();
6107 cur->set_evacuation_failed(false);
6108 // The region is now considered to be old.
6109 _old_set.add(cur);
6110 evacuation_info.increment_collectionset_used_after(cur->used());
6111 }
6112 cur = next;
6113 }
6114
6115 evacuation_info.set_regions_freed(local_free_list.length());
6116 policy->record_max_rs_lengths(rs_lengths);
6117 policy->cset_regions_freed();
6118
6119 double end_sec = os::elapsedTime();
6120 double elapsed_ms = (end_sec - start_sec) * 1000.0;
6121
6122 if (non_young) {
6123 non_young_time_ms += elapsed_ms;
6124 } else {
6125 young_time_ms += elapsed_ms;
6126 }
6127
6128 update_sets_after_freeing_regions(pre_used, &local_free_list,
6129 NULL /* old_proxy_set */,
6130 NULL /* humongous_proxy_set */,
6131 false /* par */);
6132 policy->phase_times()->record_young_free_cset_time_ms(young_time_ms);
6133 policy->phase_times()->record_non_young_free_cset_time_ms(non_young_time_ms);
6134 }
6135
6136 // This routine is similar to the above but does not record
6137 // any policy statistics or update free lists; we are abandoning
6138 // the current incremental collection set in preparation of a
6139 // full collection. After the full GC we will start to build up
6140 // the incremental collection set again.
6141 // This is only called when we're doing a full collection
6142 // and is immediately followed by the tearing down of the young list.
6143
6144 void G1CollectedHeap::abandon_collection_set(HeapRegion* cs_head) {
6145 HeapRegion* cur = cs_head;
6146
6147 while (cur != NULL) {
6148 HeapRegion* next = cur->next_in_collection_set();
6149 assert(cur->in_collection_set(), "bad CS");
6150 cur->set_next_in_collection_set(NULL);
6151 cur->set_in_collection_set(false);
6152 cur->set_young_index_in_cset(-1);
6153 cur = next;
6154 }
6155 }
6156
6157 void G1CollectedHeap::set_free_regions_coming() {
6158 if (G1ConcRegionFreeingVerbose) {
6159 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
6160 "setting free regions coming");
6161 }
6162
6163 assert(!free_regions_coming(), "pre-condition");
6164 _free_regions_coming = true;
6165 }
6166
6167 void G1CollectedHeap::reset_free_regions_coming() {
6168 assert(free_regions_coming(), "pre-condition");
6169
6170 {
6171 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6172 _free_regions_coming = false;
6173 SecondaryFreeList_lock->notify_all();
6174 }
6175
6176 if (G1ConcRegionFreeingVerbose) {
6177 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
6178 "reset free regions coming");
6179 }
6180 }
6181
6182 void G1CollectedHeap::wait_while_free_regions_coming() {
6183 // Most of the time we won't have to wait, so let's do a quick test
6184 // first before we take the lock.
6185 if (!free_regions_coming()) {
6186 return;
6187 }
6188
6189 if (G1ConcRegionFreeingVerbose) {
6190 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
6191 "waiting for free regions");
6192 }
6193
6194 {
6195 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6196 while (free_regions_coming()) {
6197 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
6198 }
6199 }
6200
6201 if (G1ConcRegionFreeingVerbose) {
6202 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
6203 "done waiting for free regions");
6204 }
6205 }
6206
6207 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
6208 assert(heap_lock_held_for_gc(),
6209 "the heap lock should already be held by or for this thread");
6210 _young_list->push_region(hr);
6211 }
6212
6213 class NoYoungRegionsClosure: public HeapRegionClosure {
6214 private:
6215 bool _success;
6216 public:
6217 NoYoungRegionsClosure() : _success(true) { }
6218 bool doHeapRegion(HeapRegion* r) {
6219 if (r->is_young()) {
6220 gclog_or_tty->print_cr("Region ["PTR_FORMAT", "PTR_FORMAT") tagged as young",
6221 r->bottom(), r->end());
6222 _success = false;
6223 }
6224 return false;
6225 }
6226 bool success() { return _success; }
6227 };
6228
6229 bool G1CollectedHeap::check_young_list_empty(bool check_heap, bool check_sample) {
6230 bool ret = _young_list->check_list_empty(check_sample);
6231
6232 if (check_heap) {
6233 NoYoungRegionsClosure closure;
6234 heap_region_iterate(&closure);
6235 ret = ret && closure.success();
6236 }
6237
6238 return ret;
6239 }
6240
6241 class TearDownRegionSetsClosure : public HeapRegionClosure {
6242 private:
6243 OldRegionSet *_old_set;
6244
6245 public:
6246 TearDownRegionSetsClosure(OldRegionSet* old_set) : _old_set(old_set) { }
6247
6248 bool doHeapRegion(HeapRegion* r) {
6249 if (r->is_empty()) {
6250 // We ignore empty regions, we'll empty the free list afterwards
6251 } else if (r->is_young()) {
6252 // We ignore young regions, we'll empty the young list afterwards
6253 } else if (r->isHumongous()) {
6254 // We ignore humongous regions, we're not tearing down the
6255 // humongous region set
6256 } else {
6257 // The rest should be old
6258 _old_set->remove(r);
6259 }
6260 return false;
6261 }
6262
6263 ~TearDownRegionSetsClosure() {
6264 assert(_old_set->is_empty(), "post-condition");
6265 }
6266 };
6267
6268 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
6269 assert_at_safepoint(true /* should_be_vm_thread */);
6270
6271 if (!free_list_only) {
6272 TearDownRegionSetsClosure cl(&_old_set);
6273 heap_region_iterate(&cl);
6274
6275 // Need to do this after the heap iteration to be able to
6276 // recognize the young regions and ignore them during the iteration.
6277 _young_list->empty_list();
6278 }
6279 _free_list.remove_all();
6280 }
6281
6282 class RebuildRegionSetsClosure : public HeapRegionClosure {
6283 private:
6284 bool _free_list_only;
6285 OldRegionSet* _old_set;
6286 FreeRegionList* _free_list;
6287 size_t _total_used;
6288
6289 public:
6290 RebuildRegionSetsClosure(bool free_list_only,
6291 OldRegionSet* old_set, FreeRegionList* free_list) :
6292 _free_list_only(free_list_only),
6293 _old_set(old_set), _free_list(free_list), _total_used(0) {
6294 assert(_free_list->is_empty(), "pre-condition");
6295 if (!free_list_only) {
6296 assert(_old_set->is_empty(), "pre-condition");
6297 }
6298 }
6299
6300 bool doHeapRegion(HeapRegion* r) {
6301 if (r->continuesHumongous()) {
6302 return false;
6303 }
6304
6305 if (r->is_empty()) {
6306 // Add free regions to the free list
6307 _free_list->add_as_tail(r);
6308 } else if (!_free_list_only) {
6309 assert(!r->is_young(), "we should not come across young regions");
6310
6311 if (r->isHumongous()) {
6312 // We ignore humongous regions, we left the humongous set unchanged
6313 } else {
6314 // The rest should be old, add them to the old set
6315 _old_set->add(r);
6316 }
6317 _total_used += r->used();
6318 }
6319
6320 return false;
6321 }
6322
6323 size_t total_used() {
6324 return _total_used;
6325 }
6326 };
6327
6328 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
6329 assert_at_safepoint(true /* should_be_vm_thread */);
6330
6331 RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_free_list);
6332 heap_region_iterate(&cl);
6333
6334 if (!free_list_only) {
6335 _summary_bytes_used = cl.total_used();
6336 }
6337 assert(_summary_bytes_used == recalculate_used(),
6338 err_msg("inconsistent _summary_bytes_used, "
6339 "value: "SIZE_FORMAT" recalculated: "SIZE_FORMAT,
6340 _summary_bytes_used, recalculate_used()));
6341 }
6342
6343 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) {
6344 _refine_cte_cl->set_concurrent(concurrent);
6345 }
6346
6347 bool G1CollectedHeap::is_in_closed_subset(const void* p) const {
6348 HeapRegion* hr = heap_region_containing(p);
6349 if (hr == NULL) {
6350 return is_in_permanent(p);
6351 } else {
6352 return hr->is_in(p);
6353 }
6354 }
6355
6356 // Methods for the mutator alloc region
6357
6358 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
6359 bool force) {
6360 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6361 assert(!force || g1_policy()->can_expand_young_list(),
6362 "if force is true we should be able to expand the young list");
6363 bool young_list_full = g1_policy()->is_young_list_full();
6364 if (force || !young_list_full) {
6365 HeapRegion* new_alloc_region = new_region(word_size,
6366 false /* do_expand */);
6367 if (new_alloc_region != NULL) {
6368 set_region_short_lived_locked(new_alloc_region);
6369 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Eden, young_list_full);
6370 return new_alloc_region;
6371 }
6372 }
6373 return NULL;
6374 }
6375
6376 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
6377 size_t allocated_bytes) {
6378 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6379 assert(alloc_region->is_young(), "all mutator alloc regions should be young");
6380
6381 g1_policy()->add_region_to_incremental_cset_lhs(alloc_region);
6382 _summary_bytes_used += allocated_bytes;
6383 _hr_printer.retire(alloc_region);
6384 // We update the eden sizes here, when the region is retired,
6385 // instead of when it's allocated, since this is the point that its
6386 // used space has been recored in _summary_bytes_used.
6387 g1mm()->update_eden_size();
6388 }
6389
6390 HeapRegion* MutatorAllocRegion::allocate_new_region(size_t word_size,
6391 bool force) {
6392 return _g1h->new_mutator_alloc_region(word_size, force);
6393 }
6394
6395 void G1CollectedHeap::set_par_threads() {
6396 // Don't change the number of workers. Use the value previously set
6397 // in the workgroup.
6398 assert(G1CollectedHeap::use_parallel_gc_threads(), "shouldn't be here otherwise");
6399 uint n_workers = workers()->active_workers();
6400 assert(UseDynamicNumberOfGCThreads ||
6401 n_workers == workers()->total_workers(),
6402 "Otherwise should be using the total number of workers");
6403 if (n_workers == 0) {
6404 assert(false, "Should have been set in prior evacuation pause.");
6405 n_workers = ParallelGCThreads;
6406 workers()->set_active_workers(n_workers);
6407 }
6408 set_par_threads(n_workers);
6409 }
6410
6411 void MutatorAllocRegion::retire_region(HeapRegion* alloc_region,
6412 size_t allocated_bytes) {
6413 _g1h->retire_mutator_alloc_region(alloc_region, allocated_bytes);
6414 }
6415
6416 // Methods for the GC alloc regions
6417
6418 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size,
6419 uint count,
6420 GCAllocPurpose ap) {
6421 assert(FreeList_lock->owned_by_self(), "pre-condition");
6422
6423 if (count < g1_policy()->max_regions(ap)) {
6424 HeapRegion* new_alloc_region = new_region(word_size,
6425 true /* do_expand */);
6426 if (new_alloc_region != NULL) {
6427 // We really only need to do this for old regions given that we
6428 // should never scan survivors. But it doesn't hurt to do it
6429 // for survivors too.
6430 new_alloc_region->set_saved_mark();
6431 if (ap == GCAllocForSurvived) {
6432 new_alloc_region->set_survivor();
6433 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Survivor);
6434 } else {
6435 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Old);
6436 }
6437 bool during_im = g1_policy()->during_initial_mark_pause();
6438 new_alloc_region->note_start_of_copying(during_im);
6439 return new_alloc_region;
6440 } else {
6441 g1_policy()->note_alloc_region_limit_reached(ap);
6442 }
6443 }
6444 return NULL;
6445 }
6446
6447 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
6448 size_t allocated_bytes,
6449 GCAllocPurpose ap) {
6450 bool during_im = g1_policy()->during_initial_mark_pause();
6451 alloc_region->note_end_of_copying(during_im);
6452 g1_policy()->record_bytes_copied_during_gc(allocated_bytes);
6453 if (ap == GCAllocForSurvived) {
6454 young_list()->add_survivor_region(alloc_region);
6455 } else {
6456 _old_set.add(alloc_region);
6457 }
6458 _hr_printer.retire(alloc_region);
6459 }
6460
6461 HeapRegion* SurvivorGCAllocRegion::allocate_new_region(size_t word_size,
6462 bool force) {
6463 assert(!force, "not supported for GC alloc regions");
6464 return _g1h->new_gc_alloc_region(word_size, count(), GCAllocForSurvived);
6465 }
6466
6467 void SurvivorGCAllocRegion::retire_region(HeapRegion* alloc_region,
6468 size_t allocated_bytes) {
6469 _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes,
6470 GCAllocForSurvived);
6471 }
6472
6473 HeapRegion* OldGCAllocRegion::allocate_new_region(size_t word_size,
6474 bool force) {
6475 assert(!force, "not supported for GC alloc regions");
6476 return _g1h->new_gc_alloc_region(word_size, count(), GCAllocForTenured);
6477 }
6478
6479 void OldGCAllocRegion::retire_region(HeapRegion* alloc_region,
6480 size_t allocated_bytes) {
6481 _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes,
6482 GCAllocForTenured);
6483 }
6484 // Heap region set verification
6485
6486 class VerifyRegionListsClosure : public HeapRegionClosure {
6487 private:
6488 FreeRegionList* _free_list;
6489 OldRegionSet* _old_set;
6490 HumongousRegionSet* _humongous_set;
6491 uint _region_count;
6492
6493 public:
6494 VerifyRegionListsClosure(OldRegionSet* old_set,
6495 HumongousRegionSet* humongous_set,
6496 FreeRegionList* free_list) :
6497 _old_set(old_set), _humongous_set(humongous_set),
6498 _free_list(free_list), _region_count(0) { }
6499
6500 uint region_count() { return _region_count; }
6501
6502 bool doHeapRegion(HeapRegion* hr) {
6503 _region_count += 1;
6504
6505 if (hr->continuesHumongous()) {
6506 return false;
6507 }
6508
6509 if (hr->is_young()) {
6510 // TODO
6511 } else if (hr->startsHumongous()) {
6512 _humongous_set->verify_next_region(hr);
6513 } else if (hr->is_empty()) {
6514 _free_list->verify_next_region(hr);
6515 } else {
6516 _old_set->verify_next_region(hr);
6517 }
6518 return false;
6519 }
6520 };
6521
6522 HeapRegion* G1CollectedHeap::new_heap_region(uint hrs_index,
6523 HeapWord* bottom) {
6524 HeapWord* end = bottom + HeapRegion::GrainWords;
6525 MemRegion mr(bottom, end);
6526 assert(_g1_reserved.contains(mr), "invariant");
6527 // This might return NULL if the allocation fails
6528 return new HeapRegion(hrs_index, _bot_shared, mr, true /* is_zeroed */);
6529 }
6530
6531 void G1CollectedHeap::verify_region_sets() {
6532 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6533
6534 // First, check the explicit lists.
6535 _free_list.verify();
6536 {
6537 // Given that a concurrent operation might be adding regions to
6538 // the secondary free list we have to take the lock before
6539 // verifying it.
6540 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6541 _secondary_free_list.verify();
6542 }
6543 _old_set.verify();
6544 _humongous_set.verify();
6545
6546 // If a concurrent region freeing operation is in progress it will
6547 // be difficult to correctly attributed any free regions we come
6548 // across to the correct free list given that they might belong to
6549 // one of several (free_list, secondary_free_list, any local lists,
6550 // etc.). So, if that's the case we will skip the rest of the
6551 // verification operation. Alternatively, waiting for the concurrent
6552 // operation to complete will have a non-trivial effect on the GC's
6553 // operation (no concurrent operation will last longer than the
6554 // interval between two calls to verification) and it might hide
6555 // any issues that we would like to catch during testing.
6556 if (free_regions_coming()) {
6557 return;
6558 }
6559
6560 // Make sure we append the secondary_free_list on the free_list so
6561 // that all free regions we will come across can be safely
6562 // attributed to the free_list.
6563 append_secondary_free_list_if_not_empty_with_lock();
6564
6565 // Finally, make sure that the region accounting in the lists is
6566 // consistent with what we see in the heap.
6567 _old_set.verify_start();
6568 _humongous_set.verify_start();
6569 _free_list.verify_start();
6570
6571 VerifyRegionListsClosure cl(&_old_set, &_humongous_set, &_free_list);
6572 heap_region_iterate(&cl);
6573
6574 _old_set.verify_end();
6575 _humongous_set.verify_end();
6576 _free_list.verify_end();
6577 }