1 /*
2 * Copyright (c) 2001, 2012, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "code/icBuffer.hpp"
27 #include "gc_implementation/g1/bufferingOopClosure.hpp"
28 #include "gc_implementation/g1/concurrentG1Refine.hpp"
29 #include "gc_implementation/g1/concurrentG1RefineThread.hpp"
30 #include "gc_implementation/g1/concurrentMarkThread.inline.hpp"
31 #include "gc_implementation/g1/g1AllocRegion.inline.hpp"
32 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
33 #include "gc_implementation/g1/g1CollectorPolicy.hpp"
34 #include "gc_implementation/g1/g1ErgoVerbose.hpp"
35 #include "gc_implementation/g1/g1EvacFailure.hpp"
36 #include "gc_implementation/g1/g1Log.hpp"
37 #include "gc_implementation/g1/g1MarkSweep.hpp"
38 #include "gc_implementation/g1/g1OopClosures.inline.hpp"
39 #include "gc_implementation/g1/g1RemSet.inline.hpp"
40 #include "gc_implementation/g1/heapRegion.inline.hpp"
41 #include "gc_implementation/g1/heapRegionRemSet.hpp"
42 #include "gc_implementation/g1/heapRegionSeq.inline.hpp"
43 #include "gc_implementation/g1/vm_operations_g1.hpp"
44 #include "gc_implementation/shared/isGCActiveMark.hpp"
45 #include "memory/gcLocker.inline.hpp"
46 #include "memory/genOopClosures.inline.hpp"
47 #include "memory/generationSpec.hpp"
48 #include "memory/referenceProcessor.hpp"
49 #include "oops/oop.inline.hpp"
50 #include "oops/oop.pcgc.inline.hpp"
51 #include "runtime/aprofiler.hpp"
52 #include "runtime/vmThread.hpp"
53
54 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;
55
56 // turn it on so that the contents of the young list (scan-only /
57 // to-be-collected) are printed at "strategic" points before / during
58 // / after the collection --- this is useful for debugging
59 #define YOUNG_LIST_VERBOSE 0
60 // CURRENT STATUS
61 // This file is under construction. Search for "FIXME".
62
63 // INVARIANTS/NOTES
64 //
65 // All allocation activity covered by the G1CollectedHeap interface is
66 // serialized by acquiring the HeapLock. This happens in mem_allocate
67 // and allocate_new_tlab, which are the "entry" points to the
68 // allocation code from the rest of the JVM. (Note that this does not
69 // apply to TLAB allocation, which is not part of this interface: it
70 // is done by clients of this interface.)
71
72 // Notes on implementation of parallelism in different tasks.
73 //
74 // G1ParVerifyTask uses heap_region_par_iterate_chunked() for parallelism.
75 // The number of GC workers is passed to heap_region_par_iterate_chunked().
76 // It does use run_task() which sets _n_workers in the task.
77 // G1ParTask executes g1_process_strong_roots() ->
78 // SharedHeap::process_strong_roots() which calls eventuall to
79 // CardTableModRefBS::par_non_clean_card_iterate_work() which uses
80 // SequentialSubTasksDone. SharedHeap::process_strong_roots() also
81 // directly uses SubTasksDone (_process_strong_tasks field in SharedHeap).
82 //
83
84 // Local to this file.
85
86 class RefineCardTableEntryClosure: public CardTableEntryClosure {
87 SuspendibleThreadSet* _sts;
88 G1RemSet* _g1rs;
89 ConcurrentG1Refine* _cg1r;
90 bool _concurrent;
91 public:
92 RefineCardTableEntryClosure(SuspendibleThreadSet* sts,
93 G1RemSet* g1rs,
94 ConcurrentG1Refine* cg1r) :
95 _sts(sts), _g1rs(g1rs), _cg1r(cg1r), _concurrent(true)
96 {}
97 bool do_card_ptr(jbyte* card_ptr, int worker_i) {
98 bool oops_into_cset = _g1rs->concurrentRefineOneCard(card_ptr, worker_i, false);
99 // This path is executed by the concurrent refine or mutator threads,
100 // concurrently, and so we do not care if card_ptr contains references
101 // that point into the collection set.
102 assert(!oops_into_cset, "should be");
103
104 if (_concurrent && _sts->should_yield()) {
105 // Caller will actually yield.
106 return false;
107 }
108 // Otherwise, we finished successfully; return true.
109 return true;
110 }
111 void set_concurrent(bool b) { _concurrent = b; }
112 };
113
114
115 class ClearLoggedCardTableEntryClosure: public CardTableEntryClosure {
116 int _calls;
117 G1CollectedHeap* _g1h;
118 CardTableModRefBS* _ctbs;
119 int _histo[256];
120 public:
121 ClearLoggedCardTableEntryClosure() :
122 _calls(0)
123 {
124 _g1h = G1CollectedHeap::heap();
125 _ctbs = (CardTableModRefBS*)_g1h->barrier_set();
126 for (int i = 0; i < 256; i++) _histo[i] = 0;
127 }
128 bool do_card_ptr(jbyte* card_ptr, int worker_i) {
129 if (_g1h->is_in_reserved(_ctbs->addr_for(card_ptr))) {
130 _calls++;
131 unsigned char* ujb = (unsigned char*)card_ptr;
132 int ind = (int)(*ujb);
133 _histo[ind]++;
134 *card_ptr = -1;
135 }
136 return true;
137 }
138 int calls() { return _calls; }
139 void print_histo() {
140 gclog_or_tty->print_cr("Card table value histogram:");
141 for (int i = 0; i < 256; i++) {
142 if (_histo[i] != 0) {
143 gclog_or_tty->print_cr(" %d: %d", i, _histo[i]);
144 }
145 }
146 }
147 };
148
149 class RedirtyLoggedCardTableEntryClosure: public CardTableEntryClosure {
150 int _calls;
151 G1CollectedHeap* _g1h;
152 CardTableModRefBS* _ctbs;
153 public:
154 RedirtyLoggedCardTableEntryClosure() :
155 _calls(0)
156 {
157 _g1h = G1CollectedHeap::heap();
158 _ctbs = (CardTableModRefBS*)_g1h->barrier_set();
159 }
160 bool do_card_ptr(jbyte* card_ptr, int worker_i) {
161 if (_g1h->is_in_reserved(_ctbs->addr_for(card_ptr))) {
162 _calls++;
163 *card_ptr = 0;
164 }
165 return true;
166 }
167 int calls() { return _calls; }
168 };
169
170 class RedirtyLoggedCardTableEntryFastClosure : public CardTableEntryClosure {
171 public:
172 bool do_card_ptr(jbyte* card_ptr, int worker_i) {
173 *card_ptr = CardTableModRefBS::dirty_card_val();
174 return true;
175 }
176 };
177
178 YoungList::YoungList(G1CollectedHeap* g1h) :
179 _g1h(g1h), _head(NULL), _length(0), _last_sampled_rs_lengths(0),
180 _survivor_head(NULL), _survivor_tail(NULL), _survivor_length(0) {
181 guarantee(check_list_empty(false), "just making sure...");
182 }
183
184 void YoungList::push_region(HeapRegion *hr) {
185 assert(!hr->is_young(), "should not already be young");
186 assert(hr->get_next_young_region() == NULL, "cause it should!");
187
188 hr->set_next_young_region(_head);
189 _head = hr;
190
191 _g1h->g1_policy()->set_region_eden(hr, (int) _length);
192 ++_length;
193 }
194
195 void YoungList::add_survivor_region(HeapRegion* hr) {
196 assert(hr->is_survivor(), "should be flagged as survivor region");
197 assert(hr->get_next_young_region() == NULL, "cause it should!");
198
199 hr->set_next_young_region(_survivor_head);
200 if (_survivor_head == NULL) {
201 _survivor_tail = hr;
202 }
203 _survivor_head = hr;
204 ++_survivor_length;
205 }
206
207 void YoungList::empty_list(HeapRegion* list) {
208 while (list != NULL) {
209 HeapRegion* next = list->get_next_young_region();
210 list->set_next_young_region(NULL);
211 list->uninstall_surv_rate_group();
212 list->set_not_young();
213 list = next;
214 }
215 }
216
217 void YoungList::empty_list() {
218 assert(check_list_well_formed(), "young list should be well formed");
219
220 empty_list(_head);
221 _head = NULL;
222 _length = 0;
223
224 empty_list(_survivor_head);
225 _survivor_head = NULL;
226 _survivor_tail = NULL;
227 _survivor_length = 0;
228
229 _last_sampled_rs_lengths = 0;
230
231 assert(check_list_empty(false), "just making sure...");
232 }
233
234 bool YoungList::check_list_well_formed() {
235 bool ret = true;
236
237 uint length = 0;
238 HeapRegion* curr = _head;
239 HeapRegion* last = NULL;
240 while (curr != NULL) {
241 if (!curr->is_young()) {
242 gclog_or_tty->print_cr("### YOUNG REGION "PTR_FORMAT"-"PTR_FORMAT" "
243 "incorrectly tagged (y: %d, surv: %d)",
244 curr->bottom(), curr->end(),
245 curr->is_young(), curr->is_survivor());
246 ret = false;
247 }
248 ++length;
249 last = curr;
250 curr = curr->get_next_young_region();
251 }
252 ret = ret && (length == _length);
253
254 if (!ret) {
255 gclog_or_tty->print_cr("### YOUNG LIST seems not well formed!");
256 gclog_or_tty->print_cr("### list has %u entries, _length is %u",
257 length, _length);
258 }
259
260 return ret;
261 }
262
263 bool YoungList::check_list_empty(bool check_sample) {
264 bool ret = true;
265
266 if (_length != 0) {
267 gclog_or_tty->print_cr("### YOUNG LIST should have 0 length, not %u",
268 _length);
269 ret = false;
270 }
271 if (check_sample && _last_sampled_rs_lengths != 0) {
272 gclog_or_tty->print_cr("### YOUNG LIST has non-zero last sampled RS lengths");
273 ret = false;
274 }
275 if (_head != NULL) {
276 gclog_or_tty->print_cr("### YOUNG LIST does not have a NULL head");
277 ret = false;
278 }
279 if (!ret) {
280 gclog_or_tty->print_cr("### YOUNG LIST does not seem empty");
281 }
282
283 return ret;
284 }
285
286 void
287 YoungList::rs_length_sampling_init() {
288 _sampled_rs_lengths = 0;
289 _curr = _head;
290 }
291
292 bool
293 YoungList::rs_length_sampling_more() {
294 return _curr != NULL;
295 }
296
297 void
298 YoungList::rs_length_sampling_next() {
299 assert( _curr != NULL, "invariant" );
300 size_t rs_length = _curr->rem_set()->occupied();
301
302 _sampled_rs_lengths += rs_length;
303
304 // The current region may not yet have been added to the
305 // incremental collection set (it gets added when it is
306 // retired as the current allocation region).
307 if (_curr->in_collection_set()) {
308 // Update the collection set policy information for this region
309 _g1h->g1_policy()->update_incremental_cset_info(_curr, rs_length);
310 }
311
312 _curr = _curr->get_next_young_region();
313 if (_curr == NULL) {
314 _last_sampled_rs_lengths = _sampled_rs_lengths;
315 // gclog_or_tty->print_cr("last sampled RS lengths = %d", _last_sampled_rs_lengths);
316 }
317 }
318
319 void
320 YoungList::reset_auxilary_lists() {
321 guarantee( is_empty(), "young list should be empty" );
322 assert(check_list_well_formed(), "young list should be well formed");
323
324 // Add survivor regions to SurvRateGroup.
325 _g1h->g1_policy()->note_start_adding_survivor_regions();
326 _g1h->g1_policy()->finished_recalculating_age_indexes(true /* is_survivors */);
327
328 int young_index_in_cset = 0;
329 for (HeapRegion* curr = _survivor_head;
330 curr != NULL;
331 curr = curr->get_next_young_region()) {
332 _g1h->g1_policy()->set_region_survivor(curr, young_index_in_cset);
333
334 // The region is a non-empty survivor so let's add it to
335 // the incremental collection set for the next evacuation
336 // pause.
337 _g1h->g1_policy()->add_region_to_incremental_cset_rhs(curr);
338 young_index_in_cset += 1;
339 }
340 assert((uint) young_index_in_cset == _survivor_length, "post-condition");
341 _g1h->g1_policy()->note_stop_adding_survivor_regions();
342
343 _head = _survivor_head;
344 _length = _survivor_length;
345 if (_survivor_head != NULL) {
346 assert(_survivor_tail != NULL, "cause it shouldn't be");
347 assert(_survivor_length > 0, "invariant");
348 _survivor_tail->set_next_young_region(NULL);
349 }
350
351 // Don't clear the survivor list handles until the start of
352 // the next evacuation pause - we need it in order to re-tag
353 // the survivor regions from this evacuation pause as 'young'
354 // at the start of the next.
355
356 _g1h->g1_policy()->finished_recalculating_age_indexes(false /* is_survivors */);
357
358 assert(check_list_well_formed(), "young list should be well formed");
359 }
360
361 void YoungList::print() {
362 HeapRegion* lists[] = {_head, _survivor_head};
363 const char* names[] = {"YOUNG", "SURVIVOR"};
364
365 for (unsigned int list = 0; list < ARRAY_SIZE(lists); ++list) {
366 gclog_or_tty->print_cr("%s LIST CONTENTS", names[list]);
367 HeapRegion *curr = lists[list];
368 if (curr == NULL)
369 gclog_or_tty->print_cr(" empty");
370 while (curr != NULL) {
371 gclog_or_tty->print_cr(" [%08x-%08x], t: %08x, P: %08x, N: %08x, C: %08x, "
372 "age: %4d, y: %d, surv: %d",
373 curr->bottom(), curr->end(),
374 curr->top(),
375 curr->prev_top_at_mark_start(),
376 curr->next_top_at_mark_start(),
377 curr->top_at_conc_mark_count(),
378 curr->age_in_surv_rate_group_cond(),
379 curr->is_young(),
380 curr->is_survivor());
381 curr = curr->get_next_young_region();
382 }
383 }
384
385 gclog_or_tty->print_cr("");
386 }
387
388 void G1CollectedHeap::push_dirty_cards_region(HeapRegion* hr)
389 {
390 // Claim the right to put the region on the dirty cards region list
391 // by installing a self pointer.
392 HeapRegion* next = hr->get_next_dirty_cards_region();
393 if (next == NULL) {
394 HeapRegion* res = (HeapRegion*)
395 Atomic::cmpxchg_ptr(hr, hr->next_dirty_cards_region_addr(),
396 NULL);
397 if (res == NULL) {
398 HeapRegion* head;
399 do {
400 // Put the region to the dirty cards region list.
401 head = _dirty_cards_region_list;
402 next = (HeapRegion*)
403 Atomic::cmpxchg_ptr(hr, &_dirty_cards_region_list, head);
404 if (next == head) {
405 assert(hr->get_next_dirty_cards_region() == hr,
406 "hr->get_next_dirty_cards_region() != hr");
407 if (next == NULL) {
408 // The last region in the list points to itself.
409 hr->set_next_dirty_cards_region(hr);
410 } else {
411 hr->set_next_dirty_cards_region(next);
412 }
413 }
414 } while (next != head);
415 }
416 }
417 }
418
419 HeapRegion* G1CollectedHeap::pop_dirty_cards_region()
420 {
421 HeapRegion* head;
422 HeapRegion* hr;
423 do {
424 head = _dirty_cards_region_list;
425 if (head == NULL) {
426 return NULL;
427 }
428 HeapRegion* new_head = head->get_next_dirty_cards_region();
429 if (head == new_head) {
430 // The last region.
431 new_head = NULL;
432 }
433 hr = (HeapRegion*)Atomic::cmpxchg_ptr(new_head, &_dirty_cards_region_list,
434 head);
435 } while (hr != head);
436 assert(hr != NULL, "invariant");
437 hr->set_next_dirty_cards_region(NULL);
438 return hr;
439 }
440
441 void G1CollectedHeap::stop_conc_gc_threads() {
442 _cg1r->stop();
443 _cmThread->stop();
444 }
445
446 #ifdef ASSERT
447 // A region is added to the collection set as it is retired
448 // so an address p can point to a region which will be in the
449 // collection set but has not yet been retired. This method
450 // therefore is only accurate during a GC pause after all
451 // regions have been retired. It is used for debugging
452 // to check if an nmethod has references to objects that can
453 // be move during a partial collection. Though it can be
454 // inaccurate, it is sufficient for G1 because the conservative
455 // implementation of is_scavengable() for G1 will indicate that
456 // all nmethods must be scanned during a partial collection.
457 bool G1CollectedHeap::is_in_partial_collection(const void* p) {
458 HeapRegion* hr = heap_region_containing(p);
459 return hr != NULL && hr->in_collection_set();
460 }
461 #endif
462
463 // Returns true if the reference points to an object that
464 // can move in an incremental collecction.
465 bool G1CollectedHeap::is_scavengable(const void* p) {
466 G1CollectedHeap* g1h = G1CollectedHeap::heap();
467 G1CollectorPolicy* g1p = g1h->g1_policy();
468 HeapRegion* hr = heap_region_containing(p);
469 if (hr == NULL) {
470 // perm gen (or null)
471 return false;
472 } else {
473 return !hr->isHumongous();
474 }
475 }
476
477 void G1CollectedHeap::check_ct_logs_at_safepoint() {
478 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
479 CardTableModRefBS* ct_bs = (CardTableModRefBS*)barrier_set();
480
481 // Count the dirty cards at the start.
482 CountNonCleanMemRegionClosure count1(this);
483 ct_bs->mod_card_iterate(&count1);
484 int orig_count = count1.n();
485
486 // First clear the logged cards.
487 ClearLoggedCardTableEntryClosure clear;
488 dcqs.set_closure(&clear);
489 dcqs.apply_closure_to_all_completed_buffers();
490 dcqs.iterate_closure_all_threads(false);
491 clear.print_histo();
492
493 // Now ensure that there's no dirty cards.
494 CountNonCleanMemRegionClosure count2(this);
495 ct_bs->mod_card_iterate(&count2);
496 if (count2.n() != 0) {
497 gclog_or_tty->print_cr("Card table has %d entries; %d originally",
498 count2.n(), orig_count);
499 }
500 guarantee(count2.n() == 0, "Card table should be clean.");
501
502 RedirtyLoggedCardTableEntryClosure redirty;
503 JavaThread::dirty_card_queue_set().set_closure(&redirty);
504 dcqs.apply_closure_to_all_completed_buffers();
505 dcqs.iterate_closure_all_threads(false);
506 gclog_or_tty->print_cr("Log entries = %d, dirty cards = %d.",
507 clear.calls(), orig_count);
508 guarantee(redirty.calls() == clear.calls(),
509 "Or else mechanism is broken.");
510
511 CountNonCleanMemRegionClosure count3(this);
512 ct_bs->mod_card_iterate(&count3);
513 if (count3.n() != orig_count) {
514 gclog_or_tty->print_cr("Should have restored them all: orig = %d, final = %d.",
515 orig_count, count3.n());
516 guarantee(count3.n() >= orig_count, "Should have restored them all.");
517 }
518
519 JavaThread::dirty_card_queue_set().set_closure(_refine_cte_cl);
520 }
521
522 // Private class members.
523
524 G1CollectedHeap* G1CollectedHeap::_g1h;
525
526 // Private methods.
527
528 HeapRegion*
529 G1CollectedHeap::new_region_try_secondary_free_list() {
530 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
531 while (!_secondary_free_list.is_empty() || free_regions_coming()) {
532 if (!_secondary_free_list.is_empty()) {
533 if (G1ConcRegionFreeingVerbose) {
534 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
535 "secondary_free_list has %u entries",
536 _secondary_free_list.length());
537 }
538 // It looks as if there are free regions available on the
539 // secondary_free_list. Let's move them to the free_list and try
540 // again to allocate from it.
541 append_secondary_free_list();
542
543 assert(!_free_list.is_empty(), "if the secondary_free_list was not "
544 "empty we should have moved at least one entry to the free_list");
545 HeapRegion* res = _free_list.remove_head();
546 if (G1ConcRegionFreeingVerbose) {
547 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
548 "allocated "HR_FORMAT" from secondary_free_list",
549 HR_FORMAT_PARAMS(res));
550 }
551 return res;
552 }
553
554 // Wait here until we get notifed either when (a) there are no
555 // more free regions coming or (b) some regions have been moved on
556 // the secondary_free_list.
557 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
558 }
559
560 if (G1ConcRegionFreeingVerbose) {
561 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
562 "could not allocate from secondary_free_list");
563 }
564 return NULL;
565 }
566
567 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool do_expand) {
568 assert(!isHumongous(word_size) || word_size <= HeapRegion::GrainWords,
569 "the only time we use this to allocate a humongous region is "
570 "when we are allocating a single humongous region");
571
572 HeapRegion* res;
573 if (G1StressConcRegionFreeing) {
574 if (!_secondary_free_list.is_empty()) {
575 if (G1ConcRegionFreeingVerbose) {
576 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
577 "forced to look at the secondary_free_list");
578 }
579 res = new_region_try_secondary_free_list();
580 if (res != NULL) {
581 return res;
582 }
583 }
584 }
585 res = _free_list.remove_head_or_null();
586 if (res == NULL) {
587 if (G1ConcRegionFreeingVerbose) {
588 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
589 "res == NULL, trying the secondary_free_list");
590 }
591 res = new_region_try_secondary_free_list();
592 }
593 if (res == NULL && do_expand && _expand_heap_after_alloc_failure) {
594 // Currently, only attempts to allocate GC alloc regions set
595 // do_expand to true. So, we should only reach here during a
596 // safepoint. If this assumption changes we might have to
597 // reconsider the use of _expand_heap_after_alloc_failure.
598 assert(SafepointSynchronize::is_at_safepoint(), "invariant");
599
600 ergo_verbose1(ErgoHeapSizing,
601 "attempt heap expansion",
602 ergo_format_reason("region allocation request failed")
603 ergo_format_byte("allocation request"),
604 word_size * HeapWordSize);
605 if (expand(word_size * HeapWordSize)) {
606 // Given that expand() succeeded in expanding the heap, and we
607 // always expand the heap by an amount aligned to the heap
608 // region size, the free list should in theory not be empty. So
609 // it would probably be OK to use remove_head(). But the extra
610 // check for NULL is unlikely to be a performance issue here (we
611 // just expanded the heap!) so let's just be conservative and
612 // use remove_head_or_null().
613 res = _free_list.remove_head_or_null();
614 } else {
615 _expand_heap_after_alloc_failure = false;
616 }
617 }
618 return res;
619 }
620
621 uint G1CollectedHeap::humongous_obj_allocate_find_first(uint num_regions,
622 size_t word_size) {
623 assert(isHumongous(word_size), "word_size should be humongous");
624 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
625
626 uint first = G1_NULL_HRS_INDEX;
627 if (num_regions == 1) {
628 // Only one region to allocate, no need to go through the slower
629 // path. The caller will attempt the expasion if this fails, so
630 // let's not try to expand here too.
631 HeapRegion* hr = new_region(word_size, false /* do_expand */);
632 if (hr != NULL) {
633 first = hr->hrs_index();
634 } else {
635 first = G1_NULL_HRS_INDEX;
636 }
637 } else {
638 // We can't allocate humongous regions while cleanupComplete() is
639 // running, since some of the regions we find to be empty might not
640 // yet be added to the free list and it is not straightforward to
641 // know which list they are on so that we can remove them. Note
642 // that we only need to do this if we need to allocate more than
643 // one region to satisfy the current humongous allocation
644 // request. If we are only allocating one region we use the common
645 // region allocation code (see above).
646 wait_while_free_regions_coming();
647 append_secondary_free_list_if_not_empty_with_lock();
648
649 if (free_regions() >= num_regions) {
650 first = _hrs.find_contiguous(num_regions);
651 if (first != G1_NULL_HRS_INDEX) {
652 for (uint i = first; i < first + num_regions; ++i) {
653 HeapRegion* hr = region_at(i);
654 assert(hr->is_empty(), "sanity");
655 assert(is_on_master_free_list(hr), "sanity");
656 hr->set_pending_removal(true);
657 }
658 _free_list.remove_all_pending(num_regions);
659 }
660 }
661 }
662 return first;
663 }
664
665 HeapWord*
666 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first,
667 uint num_regions,
668 size_t word_size) {
669 assert(first != G1_NULL_HRS_INDEX, "pre-condition");
670 assert(isHumongous(word_size), "word_size should be humongous");
671 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
672
673 // Index of last region in the series + 1.
674 uint last = first + num_regions;
675
676 // We need to initialize the region(s) we just discovered. This is
677 // a bit tricky given that it can happen concurrently with
678 // refinement threads refining cards on these regions and
679 // potentially wanting to refine the BOT as they are scanning
680 // those cards (this can happen shortly after a cleanup; see CR
681 // 6991377). So we have to set up the region(s) carefully and in
682 // a specific order.
683
684 // The word size sum of all the regions we will allocate.
685 size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords;
686 assert(word_size <= word_size_sum, "sanity");
687
688 // This will be the "starts humongous" region.
689 HeapRegion* first_hr = region_at(first);
690 // The header of the new object will be placed at the bottom of
691 // the first region.
692 HeapWord* new_obj = first_hr->bottom();
693 // This will be the new end of the first region in the series that
694 // should also match the end of the last region in the seriers.
695 HeapWord* new_end = new_obj + word_size_sum;
696 // This will be the new top of the first region that will reflect
697 // this allocation.
698 HeapWord* new_top = new_obj + word_size;
699
700 // First, we need to zero the header of the space that we will be
701 // allocating. When we update top further down, some refinement
702 // threads might try to scan the region. By zeroing the header we
703 // ensure that any thread that will try to scan the region will
704 // come across the zero klass word and bail out.
705 //
706 // NOTE: It would not have been correct to have used
707 // CollectedHeap::fill_with_object() and make the space look like
708 // an int array. The thread that is doing the allocation will
709 // later update the object header to a potentially different array
710 // type and, for a very short period of time, the klass and length
711 // fields will be inconsistent. This could cause a refinement
712 // thread to calculate the object size incorrectly.
713 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
714
715 // We will set up the first region as "starts humongous". This
716 // will also update the BOT covering all the regions to reflect
717 // that there is a single object that starts at the bottom of the
718 // first region.
719 first_hr->set_startsHumongous(new_top, new_end);
720
721 // Then, if there are any, we will set up the "continues
722 // humongous" regions.
723 HeapRegion* hr = NULL;
724 for (uint i = first + 1; i < last; ++i) {
725 hr = region_at(i);
726 hr->set_continuesHumongous(first_hr);
727 }
728 // If we have "continues humongous" regions (hr != NULL), then the
729 // end of the last one should match new_end.
730 assert(hr == NULL || hr->end() == new_end, "sanity");
731
732 // Up to this point no concurrent thread would have been able to
733 // do any scanning on any region in this series. All the top
734 // fields still point to bottom, so the intersection between
735 // [bottom,top] and [card_start,card_end] will be empty. Before we
736 // update the top fields, we'll do a storestore to make sure that
737 // no thread sees the update to top before the zeroing of the
738 // object header and the BOT initialization.
739 OrderAccess::storestore();
740
741 // Now that the BOT and the object header have been initialized,
742 // we can update top of the "starts humongous" region.
743 assert(first_hr->bottom() < new_top && new_top <= first_hr->end(),
744 "new_top should be in this region");
745 first_hr->set_top(new_top);
746 if (_hr_printer.is_active()) {
747 HeapWord* bottom = first_hr->bottom();
748 HeapWord* end = first_hr->orig_end();
749 if ((first + 1) == last) {
750 // the series has a single humongous region
751 _hr_printer.alloc(G1HRPrinter::SingleHumongous, first_hr, new_top);
752 } else {
753 // the series has more than one humongous regions
754 _hr_printer.alloc(G1HRPrinter::StartsHumongous, first_hr, end);
755 }
756 }
757
758 // Now, we will update the top fields of the "continues humongous"
759 // regions. The reason we need to do this is that, otherwise,
760 // these regions would look empty and this will confuse parts of
761 // G1. For example, the code that looks for a consecutive number
762 // of empty regions will consider them empty and try to
763 // re-allocate them. We can extend is_empty() to also include
764 // !continuesHumongous(), but it is easier to just update the top
765 // fields here. The way we set top for all regions (i.e., top ==
766 // end for all regions but the last one, top == new_top for the
767 // last one) is actually used when we will free up the humongous
768 // region in free_humongous_region().
769 hr = NULL;
770 for (uint i = first + 1; i < last; ++i) {
771 hr = region_at(i);
772 if ((i + 1) == last) {
773 // last continues humongous region
774 assert(hr->bottom() < new_top && new_top <= hr->end(),
775 "new_top should fall on this region");
776 hr->set_top(new_top);
777 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, new_top);
778 } else {
779 // not last one
780 assert(new_top > hr->end(), "new_top should be above this region");
781 hr->set_top(hr->end());
782 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, hr->end());
783 }
784 }
785 // If we have continues humongous regions (hr != NULL), then the
786 // end of the last one should match new_end and its top should
787 // match new_top.
788 assert(hr == NULL ||
789 (hr->end() == new_end && hr->top() == new_top), "sanity");
790
791 assert(first_hr->used() == word_size * HeapWordSize, "invariant");
792 _summary_bytes_used += first_hr->used();
793 _humongous_set.add(first_hr);
794
795 return new_obj;
796 }
797
798 // If could fit into free regions w/o expansion, try.
799 // Otherwise, if can expand, do so.
800 // Otherwise, if using ex regions might help, try with ex given back.
801 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size) {
802 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
803
804 verify_region_sets_optional();
805
806 size_t word_size_rounded = round_to(word_size, HeapRegion::GrainWords);
807 uint num_regions = (uint) (word_size_rounded / HeapRegion::GrainWords);
808 uint x_num = expansion_regions();
809 uint fs = _hrs.free_suffix();
810 uint first = humongous_obj_allocate_find_first(num_regions, word_size);
811 if (first == G1_NULL_HRS_INDEX) {
812 // The only thing we can do now is attempt expansion.
813 if (fs + x_num >= num_regions) {
814 // If the number of regions we're trying to allocate for this
815 // object is at most the number of regions in the free suffix,
816 // then the call to humongous_obj_allocate_find_first() above
817 // should have succeeded and we wouldn't be here.
818 //
819 // We should only be trying to expand when the free suffix is
820 // not sufficient for the object _and_ we have some expansion
821 // room available.
822 assert(num_regions > fs, "earlier allocation should have succeeded");
823
824 ergo_verbose1(ErgoHeapSizing,
825 "attempt heap expansion",
826 ergo_format_reason("humongous allocation request failed")
827 ergo_format_byte("allocation request"),
828 word_size * HeapWordSize);
829 if (expand((num_regions - fs) * HeapRegion::GrainBytes)) {
830 // Even though the heap was expanded, it might not have
831 // reached the desired size. So, we cannot assume that the
832 // allocation will succeed.
833 first = humongous_obj_allocate_find_first(num_regions, word_size);
834 }
835 }
836 }
837
838 HeapWord* result = NULL;
839 if (first != G1_NULL_HRS_INDEX) {
840 result =
841 humongous_obj_allocate_initialize_regions(first, num_regions, word_size);
842 assert(result != NULL, "it should always return a valid result");
843
844 // A successful humongous object allocation changes the used space
845 // information of the old generation so we need to recalculate the
846 // sizes and update the jstat counters here.
847 g1mm()->update_sizes();
848 }
849
850 verify_region_sets_optional();
851
852 return result;
853 }
854
855 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) {
856 assert_heap_not_locked_and_not_at_safepoint();
857 assert(!isHumongous(word_size), "we do not allow humongous TLABs");
858
859 unsigned int dummy_gc_count_before;
860 return attempt_allocation(word_size, &dummy_gc_count_before);
861 }
862
863 HeapWord*
864 G1CollectedHeap::mem_allocate(size_t word_size,
865 bool* gc_overhead_limit_was_exceeded) {
866 assert_heap_not_locked_and_not_at_safepoint();
867
868 // Loop until the allocation is satisified, or unsatisfied after GC.
869 for (int try_count = 1; /* we'll return */; try_count += 1) {
870 unsigned int gc_count_before;
871
872 HeapWord* result = NULL;
873 if (!isHumongous(word_size)) {
874 result = attempt_allocation(word_size, &gc_count_before);
875 } else {
876 result = attempt_allocation_humongous(word_size, &gc_count_before);
877 }
878 if (result != NULL) {
879 return result;
880 }
881
882 // Create the garbage collection operation...
883 VM_G1CollectForAllocation op(gc_count_before, word_size);
884 // ...and get the VM thread to execute it.
885 VMThread::execute(&op);
886
887 if (op.prologue_succeeded() && op.pause_succeeded()) {
888 // If the operation was successful we'll return the result even
889 // if it is NULL. If the allocation attempt failed immediately
890 // after a Full GC, it's unlikely we'll be able to allocate now.
891 HeapWord* result = op.result();
892 if (result != NULL && !isHumongous(word_size)) {
893 // Allocations that take place on VM operations do not do any
894 // card dirtying and we have to do it here. We only have to do
895 // this for non-humongous allocations, though.
896 dirty_young_block(result, word_size);
897 }
898 return result;
899 } else {
900 assert(op.result() == NULL,
901 "the result should be NULL if the VM op did not succeed");
902 }
903
904 // Give a warning if we seem to be looping forever.
905 if ((QueuedAllocationWarningCount > 0) &&
906 (try_count % QueuedAllocationWarningCount == 0)) {
907 warning("G1CollectedHeap::mem_allocate retries %d times", try_count);
908 }
909 }
910
911 ShouldNotReachHere();
912 return NULL;
913 }
914
915 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size,
916 unsigned int *gc_count_before_ret) {
917 // Make sure you read the note in attempt_allocation_humongous().
918
919 assert_heap_not_locked_and_not_at_safepoint();
920 assert(!isHumongous(word_size), "attempt_allocation_slow() should not "
921 "be called for humongous allocation requests");
922
923 // We should only get here after the first-level allocation attempt
924 // (attempt_allocation()) failed to allocate.
925
926 // We will loop until a) we manage to successfully perform the
927 // allocation or b) we successfully schedule a collection which
928 // fails to perform the allocation. b) is the only case when we'll
929 // return NULL.
930 HeapWord* result = NULL;
931 for (int try_count = 1; /* we'll return */; try_count += 1) {
932 bool should_try_gc;
933 unsigned int gc_count_before;
934
935 {
936 MutexLockerEx x(Heap_lock);
937
938 result = _mutator_alloc_region.attempt_allocation_locked(word_size,
939 false /* bot_updates */);
940 if (result != NULL) {
941 return result;
942 }
943
944 // If we reach here, attempt_allocation_locked() above failed to
945 // allocate a new region. So the mutator alloc region should be NULL.
946 assert(_mutator_alloc_region.get() == NULL, "only way to get here");
947
948 if (GC_locker::is_active_and_needs_gc()) {
949 if (g1_policy()->can_expand_young_list()) {
950 // No need for an ergo verbose message here,
951 // can_expand_young_list() does this when it returns true.
952 result = _mutator_alloc_region.attempt_allocation_force(word_size,
953 false /* bot_updates */);
954 if (result != NULL) {
955 return result;
956 }
957 }
958 should_try_gc = false;
959 } else {
960 // Read the GC count while still holding the Heap_lock.
961 gc_count_before = total_collections();
962 should_try_gc = true;
963 }
964 }
965
966 if (should_try_gc) {
967 bool succeeded;
968 result = do_collection_pause(word_size, gc_count_before, &succeeded);
969 if (result != NULL) {
970 assert(succeeded, "only way to get back a non-NULL result");
971 return result;
972 }
973
974 if (succeeded) {
975 // If we get here we successfully scheduled a collection which
976 // failed to allocate. No point in trying to allocate
977 // further. We'll just return NULL.
978 MutexLockerEx x(Heap_lock);
979 *gc_count_before_ret = total_collections();
980 return NULL;
981 }
982 } else {
983 GC_locker::stall_until_clear();
984 }
985
986 // We can reach here if we were unsuccessul in scheduling a
987 // collection (because another thread beat us to it) or if we were
988 // stalled due to the GC locker. In either can we should retry the
989 // allocation attempt in case another thread successfully
990 // performed a collection and reclaimed enough space. We do the
991 // first attempt (without holding the Heap_lock) here and the
992 // follow-on attempt will be at the start of the next loop
993 // iteration (after taking the Heap_lock).
994 result = _mutator_alloc_region.attempt_allocation(word_size,
995 false /* bot_updates */);
996 if (result != NULL) {
997 return result;
998 }
999
1000 // Give a warning if we seem to be looping forever.
1001 if ((QueuedAllocationWarningCount > 0) &&
1002 (try_count % QueuedAllocationWarningCount == 0)) {
1003 warning("G1CollectedHeap::attempt_allocation_slow() "
1004 "retries %d times", try_count);
1005 }
1006 }
1007
1008 ShouldNotReachHere();
1009 return NULL;
1010 }
1011
1012 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size,
1013 unsigned int * gc_count_before_ret) {
1014 // The structure of this method has a lot of similarities to
1015 // attempt_allocation_slow(). The reason these two were not merged
1016 // into a single one is that such a method would require several "if
1017 // allocation is not humongous do this, otherwise do that"
1018 // conditional paths which would obscure its flow. In fact, an early
1019 // version of this code did use a unified method which was harder to
1020 // follow and, as a result, it had subtle bugs that were hard to
1021 // track down. So keeping these two methods separate allows each to
1022 // be more readable. It will be good to keep these two in sync as
1023 // much as possible.
1024
1025 assert_heap_not_locked_and_not_at_safepoint();
1026 assert(isHumongous(word_size), "attempt_allocation_humongous() "
1027 "should only be called for humongous allocations");
1028
1029 // Humongous objects can exhaust the heap quickly, so we should check if we
1030 // need to start a marking cycle at each humongous object allocation. We do
1031 // the check before we do the actual allocation. The reason for doing it
1032 // before the allocation is that we avoid having to keep track of the newly
1033 // allocated memory while we do a GC.
1034 if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation",
1035 word_size)) {
1036 collect(GCCause::_g1_humongous_allocation);
1037 }
1038
1039 // We will loop until a) we manage to successfully perform the
1040 // allocation or b) we successfully schedule a collection which
1041 // fails to perform the allocation. b) is the only case when we'll
1042 // return NULL.
1043 HeapWord* result = NULL;
1044 for (int try_count = 1; /* we'll return */; try_count += 1) {
1045 bool should_try_gc;
1046 unsigned int gc_count_before;
1047
1048 {
1049 MutexLockerEx x(Heap_lock);
1050
1051 // Given that humongous objects are not allocated in young
1052 // regions, we'll first try to do the allocation without doing a
1053 // collection hoping that there's enough space in the heap.
1054 result = humongous_obj_allocate(word_size);
1055 if (result != NULL) {
1056 return result;
1057 }
1058
1059 if (GC_locker::is_active_and_needs_gc()) {
1060 should_try_gc = false;
1061 } else {
1062 // Read the GC count while still holding the Heap_lock.
1063 gc_count_before = total_collections();
1064 should_try_gc = true;
1065 }
1066 }
1067
1068 if (should_try_gc) {
1069 // If we failed to allocate the humongous object, we should try to
1070 // do a collection pause (if we're allowed) in case it reclaims
1071 // enough space for the allocation to succeed after the pause.
1072
1073 bool succeeded;
1074 result = do_collection_pause(word_size, gc_count_before, &succeeded);
1075 if (result != NULL) {
1076 assert(succeeded, "only way to get back a non-NULL result");
1077 return result;
1078 }
1079
1080 if (succeeded) {
1081 // If we get here we successfully scheduled a collection which
1082 // failed to allocate. No point in trying to allocate
1083 // further. We'll just return NULL.
1084 MutexLockerEx x(Heap_lock);
1085 *gc_count_before_ret = total_collections();
1086 return NULL;
1087 }
1088 } else {
1089 GC_locker::stall_until_clear();
1090 }
1091
1092 // We can reach here if we were unsuccessul in scheduling a
1093 // collection (because another thread beat us to it) or if we were
1094 // stalled due to the GC locker. In either can we should retry the
1095 // allocation attempt in case another thread successfully
1096 // performed a collection and reclaimed enough space. Give a
1097 // warning if we seem to be looping forever.
1098
1099 if ((QueuedAllocationWarningCount > 0) &&
1100 (try_count % QueuedAllocationWarningCount == 0)) {
1101 warning("G1CollectedHeap::attempt_allocation_humongous() "
1102 "retries %d times", try_count);
1103 }
1104 }
1105
1106 ShouldNotReachHere();
1107 return NULL;
1108 }
1109
1110 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
1111 bool expect_null_mutator_alloc_region) {
1112 assert_at_safepoint(true /* should_be_vm_thread */);
1113 assert(_mutator_alloc_region.get() == NULL ||
1114 !expect_null_mutator_alloc_region,
1115 "the current alloc region was unexpectedly found to be non-NULL");
1116
1117 if (!isHumongous(word_size)) {
1118 return _mutator_alloc_region.attempt_allocation_locked(word_size,
1119 false /* bot_updates */);
1120 } else {
1121 HeapWord* result = humongous_obj_allocate(word_size);
1122 if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) {
1123 g1_policy()->set_initiate_conc_mark_if_possible();
1124 }
1125 return result;
1126 }
1127
1128 ShouldNotReachHere();
1129 }
1130
1131 class PostMCRemSetClearClosure: public HeapRegionClosure {
1132 ModRefBarrierSet* _mr_bs;
1133 public:
1134 PostMCRemSetClearClosure(ModRefBarrierSet* mr_bs) : _mr_bs(mr_bs) {}
1135 bool doHeapRegion(HeapRegion* r) {
1136 r->reset_gc_time_stamp();
1137 if (r->continuesHumongous())
1138 return false;
1139 HeapRegionRemSet* hrrs = r->rem_set();
1140 if (hrrs != NULL) hrrs->clear();
1141 // You might think here that we could clear just the cards
1142 // corresponding to the used region. But no: if we leave a dirty card
1143 // in a region we might allocate into, then it would prevent that card
1144 // from being enqueued, and cause it to be missed.
1145 // Re: the performance cost: we shouldn't be doing full GC anyway!
1146 _mr_bs->clear(MemRegion(r->bottom(), r->end()));
1147 return false;
1148 }
1149 };
1150
1151
1152 class PostMCRemSetInvalidateClosure: public HeapRegionClosure {
1153 ModRefBarrierSet* _mr_bs;
1154 public:
1155 PostMCRemSetInvalidateClosure(ModRefBarrierSet* mr_bs) : _mr_bs(mr_bs) {}
1156 bool doHeapRegion(HeapRegion* r) {
1157 if (r->continuesHumongous()) return false;
1158 if (r->used_region().word_size() != 0) {
1159 _mr_bs->invalidate(r->used_region(), true /*whole heap*/);
1160 }
1161 return false;
1162 }
1163 };
1164
1165 class RebuildRSOutOfRegionClosure: public HeapRegionClosure {
1166 G1CollectedHeap* _g1h;
1167 UpdateRSOopClosure _cl;
1168 int _worker_i;
1169 public:
1170 RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, int worker_i = 0) :
1171 _cl(g1->g1_rem_set(), worker_i),
1172 _worker_i(worker_i),
1173 _g1h(g1)
1174 { }
1175
1176 bool doHeapRegion(HeapRegion* r) {
1177 if (!r->continuesHumongous()) {
1178 _cl.set_from(r);
1179 r->oop_iterate(&_cl);
1180 }
1181 return false;
1182 }
1183 };
1184
1185 class ParRebuildRSTask: public AbstractGangTask {
1186 G1CollectedHeap* _g1;
1187 public:
1188 ParRebuildRSTask(G1CollectedHeap* g1)
1189 : AbstractGangTask("ParRebuildRSTask"),
1190 _g1(g1)
1191 { }
1192
1193 void work(uint worker_id) {
1194 RebuildRSOutOfRegionClosure rebuild_rs(_g1, worker_id);
1195 _g1->heap_region_par_iterate_chunked(&rebuild_rs, worker_id,
1196 _g1->workers()->active_workers(),
1197 HeapRegion::RebuildRSClaimValue);
1198 }
1199 };
1200
1201 class PostCompactionPrinterClosure: public HeapRegionClosure {
1202 private:
1203 G1HRPrinter* _hr_printer;
1204 public:
1205 bool doHeapRegion(HeapRegion* hr) {
1206 assert(!hr->is_young(), "not expecting to find young regions");
1207 // We only generate output for non-empty regions.
1208 if (!hr->is_empty()) {
1209 if (!hr->isHumongous()) {
1210 _hr_printer->post_compaction(hr, G1HRPrinter::Old);
1211 } else if (hr->startsHumongous()) {
1212 if (hr->capacity() == HeapRegion::GrainBytes) {
1213 // single humongous region
1214 _hr_printer->post_compaction(hr, G1HRPrinter::SingleHumongous);
1215 } else {
1216 _hr_printer->post_compaction(hr, G1HRPrinter::StartsHumongous);
1217 }
1218 } else {
1219 assert(hr->continuesHumongous(), "only way to get here");
1220 _hr_printer->post_compaction(hr, G1HRPrinter::ContinuesHumongous);
1221 }
1222 }
1223 return false;
1224 }
1225
1226 PostCompactionPrinterClosure(G1HRPrinter* hr_printer)
1227 : _hr_printer(hr_printer) { }
1228 };
1229
1230 bool G1CollectedHeap::do_collection(bool explicit_gc,
1231 bool clear_all_soft_refs,
1232 size_t word_size) {
1233 assert_at_safepoint(true /* should_be_vm_thread */);
1234
1235 if (GC_locker::check_active_before_gc()) {
1236 return false;
1237 }
1238
1239 SvcGCMarker sgcm(SvcGCMarker::FULL);
1240 ResourceMark rm;
1241
1242 print_heap_before_gc();
1243
1244 HRSPhaseSetter x(HRSPhaseFullGC);
1245 verify_region_sets_optional();
1246
1247 const bool do_clear_all_soft_refs = clear_all_soft_refs ||
1248 collector_policy()->should_clear_all_soft_refs();
1249
1250 ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy());
1251
1252 {
1253 IsGCActiveMark x;
1254
1255 // Timing
1256 bool system_gc = (gc_cause() == GCCause::_java_lang_system_gc);
1257 assert(!system_gc || explicit_gc, "invariant");
1258 gclog_or_tty->date_stamp(G1Log::fine() && PrintGCDateStamps);
1259 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
1260 TraceTime t(system_gc ? "Full GC (System.gc())" : "Full GC",
1261 G1Log::fine(), true, gclog_or_tty);
1262
1263 TraceCollectorStats tcs(g1mm()->full_collection_counters());
1264 TraceMemoryManagerStats tms(true /* fullGC */, gc_cause());
1265
1266 double start = os::elapsedTime();
1267 g1_policy()->record_full_collection_start();
1268
1269 // Note: When we have a more flexible GC logging framework that
1270 // allows us to add optional attributes to a GC log record we
1271 // could consider timing and reporting how long we wait in the
1272 // following two methods.
1273 wait_while_free_regions_coming();
1274 // If we start the compaction before the CM threads finish
1275 // scanning the root regions we might trip them over as we'll
1276 // be moving objects / updating references. So let's wait until
1277 // they are done. By telling them to abort, they should complete
1278 // early.
1279 _cm->root_regions()->abort();
1280 _cm->root_regions()->wait_until_scan_finished();
1281 append_secondary_free_list_if_not_empty_with_lock();
1282
1283 gc_prologue(true);
1284 increment_total_collections(true /* full gc */);
1285
1286 size_t g1h_prev_used = used();
1287 assert(used() == recalculate_used(), "Should be equal");
1288
1289 if (VerifyBeforeGC && total_collections() >= VerifyGCStartAt) {
1290 HandleMark hm; // Discard invalid handles created during verification
1291 gclog_or_tty->print(" VerifyBeforeGC:");
1292 prepare_for_verify();
1293 Universe::verify(/* silent */ false,
1294 /* option */ VerifyOption_G1UsePrevMarking);
1295
1296 }
1297 pre_full_gc_dump();
1298
1299 COMPILER2_PRESENT(DerivedPointerTable::clear());
1300
1301 // Disable discovery and empty the discovered lists
1302 // for the CM ref processor.
1303 ref_processor_cm()->disable_discovery();
1304 ref_processor_cm()->abandon_partial_discovery();
1305 ref_processor_cm()->verify_no_references_recorded();
1306
1307 // Abandon current iterations of concurrent marking and concurrent
1308 // refinement, if any are in progress. We have to do this before
1309 // wait_until_scan_finished() below.
1310 concurrent_mark()->abort();
1311
1312 // Make sure we'll choose a new allocation region afterwards.
1313 release_mutator_alloc_region();
1314 abandon_gc_alloc_regions();
1315 g1_rem_set()->cleanupHRRS();
1316
1317 // We should call this after we retire any currently active alloc
1318 // regions so that all the ALLOC / RETIRE events are generated
1319 // before the start GC event.
1320 _hr_printer.start_gc(true /* full */, (size_t) total_collections());
1321
1322 // We may have added regions to the current incremental collection
1323 // set between the last GC or pause and now. We need to clear the
1324 // incremental collection set and then start rebuilding it afresh
1325 // after this full GC.
1326 abandon_collection_set(g1_policy()->inc_cset_head());
1327 g1_policy()->clear_incremental_cset();
1328 g1_policy()->stop_incremental_cset_building();
1329
1330 tear_down_region_sets(false /* free_list_only */);
1331 g1_policy()->set_gcs_are_young(true);
1332
1333 // See the comments in g1CollectedHeap.hpp and
1334 // G1CollectedHeap::ref_processing_init() about
1335 // how reference processing currently works in G1.
1336
1337 // Temporarily make discovery by the STW ref processor single threaded (non-MT).
1338 ReferenceProcessorMTDiscoveryMutator stw_rp_disc_ser(ref_processor_stw(), false);
1339
1340 // Temporarily clear the STW ref processor's _is_alive_non_header field.
1341 ReferenceProcessorIsAliveMutator stw_rp_is_alive_null(ref_processor_stw(), NULL);
1342
1343 ref_processor_stw()->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/);
1344 ref_processor_stw()->setup_policy(do_clear_all_soft_refs);
1345
1346 // Do collection work
1347 {
1348 HandleMark hm; // Discard invalid handles created during gc
1349 G1MarkSweep::invoke_at_safepoint(ref_processor_stw(), do_clear_all_soft_refs);
1350 }
1351
1352 assert(free_regions() == 0, "we should not have added any free regions");
1353 rebuild_region_sets(false /* free_list_only */);
1354
1355 // Enqueue any discovered reference objects that have
1356 // not been removed from the discovered lists.
1357 ref_processor_stw()->enqueue_discovered_references();
1358
1359 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
1360
1361 MemoryService::track_memory_usage();
1362
1363 if (VerifyAfterGC && total_collections() >= VerifyGCStartAt) {
1364 HandleMark hm; // Discard invalid handles created during verification
1365 gclog_or_tty->print(" VerifyAfterGC:");
1366 prepare_for_verify();
1367 Universe::verify(/* silent */ false,
1368 /* option */ VerifyOption_G1UsePrevMarking);
1369
1370 }
1371
1372 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
1373 ref_processor_stw()->verify_no_references_recorded();
1374
1375 // Note: since we've just done a full GC, concurrent
1376 // marking is no longer active. Therefore we need not
1377 // re-enable reference discovery for the CM ref processor.
1378 // That will be done at the start of the next marking cycle.
1379 assert(!ref_processor_cm()->discovery_enabled(), "Postcondition");
1380 ref_processor_cm()->verify_no_references_recorded();
1381
1382 reset_gc_time_stamp();
1383 // Since everything potentially moved, we will clear all remembered
1384 // sets, and clear all cards. Later we will rebuild remebered
1385 // sets. We will also reset the GC time stamps of the regions.
1386 PostMCRemSetClearClosure rs_clear(mr_bs());
1387 heap_region_iterate(&rs_clear);
1388
1389 // Resize the heap if necessary.
1390 resize_if_necessary_after_full_collection(explicit_gc ? 0 : word_size);
1391
1392 if (_hr_printer.is_active()) {
1393 // We should do this after we potentially resize the heap so
1394 // that all the COMMIT / UNCOMMIT events are generated before
1395 // the end GC event.
1396
1397 PostCompactionPrinterClosure cl(hr_printer());
1398 heap_region_iterate(&cl);
1399
1400 _hr_printer.end_gc(true /* full */, (size_t) total_collections());
1401 }
1402
1403 if (_cg1r->use_cache()) {
1404 _cg1r->clear_and_record_card_counts();
1405 _cg1r->clear_hot_cache();
1406 }
1407
1408 // Rebuild remembered sets of all regions.
1409 if (G1CollectedHeap::use_parallel_gc_threads()) {
1410 uint n_workers =
1411 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
1412 workers()->active_workers(),
1413 Threads::number_of_non_daemon_threads());
1414 assert(UseDynamicNumberOfGCThreads ||
1415 n_workers == workers()->total_workers(),
1416 "If not dynamic should be using all the workers");
1417 workers()->set_active_workers(n_workers);
1418 // Set parallel threads in the heap (_n_par_threads) only
1419 // before a parallel phase and always reset it to 0 after
1420 // the phase so that the number of parallel threads does
1421 // no get carried forward to a serial phase where there
1422 // may be code that is "possibly_parallel".
1423 set_par_threads(n_workers);
1424
1425 ParRebuildRSTask rebuild_rs_task(this);
1426 assert(check_heap_region_claim_values(
1427 HeapRegion::InitialClaimValue), "sanity check");
1428 assert(UseDynamicNumberOfGCThreads ||
1429 workers()->active_workers() == workers()->total_workers(),
1430 "Unless dynamic should use total workers");
1431 // Use the most recent number of active workers
1432 assert(workers()->active_workers() > 0,
1433 "Active workers not properly set");
1434 set_par_threads(workers()->active_workers());
1435 workers()->run_task(&rebuild_rs_task);
1436 set_par_threads(0);
1437 assert(check_heap_region_claim_values(
1438 HeapRegion::RebuildRSClaimValue), "sanity check");
1439 reset_heap_region_claim_values();
1440 } else {
1441 RebuildRSOutOfRegionClosure rebuild_rs(this);
1442 heap_region_iterate(&rebuild_rs);
1443 }
1444
1445 if (G1Log::fine()) {
1446 print_size_transition(gclog_or_tty, g1h_prev_used, used(), capacity());
1447 }
1448
1449 if (true) { // FIXME
1450 // Ask the permanent generation to adjust size for full collections
1451 perm()->compute_new_size();
1452 }
1453
1454 // Start a new incremental collection set for the next pause
1455 assert(g1_policy()->collection_set() == NULL, "must be");
1456 g1_policy()->start_incremental_cset_building();
1457
1458 // Clear the _cset_fast_test bitmap in anticipation of adding
1459 // regions to the incremental collection set for the next
1460 // evacuation pause.
1461 clear_cset_fast_test();
1462
1463 init_mutator_alloc_region();
1464
1465 double end = os::elapsedTime();
1466 g1_policy()->record_full_collection_end();
1467
1468 #ifdef TRACESPINNING
1469 ParallelTaskTerminator::print_termination_counts();
1470 #endif
1471
1472 gc_epilogue(true);
1473
1474 // Discard all rset updates
1475 JavaThread::dirty_card_queue_set().abandon_logs();
1476 assert(!G1DeferredRSUpdate
1477 || (G1DeferredRSUpdate && (dirty_card_queue_set().completed_buffers_num() == 0)), "Should not be any");
1478 }
1479
1480 _young_list->reset_sampled_info();
1481 // At this point there should be no regions in the
1482 // entire heap tagged as young.
1483 assert( check_young_list_empty(true /* check_heap */),
1484 "young list should be empty at this point");
1485
1486 // Update the number of full collections that have been completed.
1487 increment_full_collections_completed(false /* concurrent */);
1488
1489 _hrs.verify_optional();
1490 verify_region_sets_optional();
1491
1492 print_heap_after_gc();
1493 g1mm()->update_sizes();
1494 post_full_gc_dump();
1495
1496 return true;
1497 }
1498
1499 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
1500 // do_collection() will return whether it succeeded in performing
1501 // the GC. Currently, there is no facility on the
1502 // do_full_collection() API to notify the caller than the collection
1503 // did not succeed (e.g., because it was locked out by the GC
1504 // locker). So, right now, we'll ignore the return value.
1505 bool dummy = do_collection(true, /* explicit_gc */
1506 clear_all_soft_refs,
1507 0 /* word_size */);
1508 }
1509
1510 // This code is mostly copied from TenuredGeneration.
1511 void
1512 G1CollectedHeap::
1513 resize_if_necessary_after_full_collection(size_t word_size) {
1514 assert(MinHeapFreeRatio <= MaxHeapFreeRatio, "sanity check");
1515
1516 // Include the current allocation, if any, and bytes that will be
1517 // pre-allocated to support collections, as "used".
1518 const size_t used_after_gc = used();
1519 const size_t capacity_after_gc = capacity();
1520 const size_t free_after_gc = capacity_after_gc - used_after_gc;
1521
1522 // This is enforced in arguments.cpp.
1523 assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
1524 "otherwise the code below doesn't make sense");
1525
1526 // We don't have floating point command-line arguments
1527 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
1528 const double maximum_used_percentage = 1.0 - minimum_free_percentage;
1529 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
1530 const double minimum_used_percentage = 1.0 - maximum_free_percentage;
1531
1532 const size_t min_heap_size = collector_policy()->min_heap_byte_size();
1533 const size_t max_heap_size = collector_policy()->max_heap_byte_size();
1534
1535 // We have to be careful here as these two calculations can overflow
1536 // 32-bit size_t's.
1537 double used_after_gc_d = (double) used_after_gc;
1538 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
1539 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
1540
1541 // Let's make sure that they are both under the max heap size, which
1542 // by default will make them fit into a size_t.
1543 double desired_capacity_upper_bound = (double) max_heap_size;
1544 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
1545 desired_capacity_upper_bound);
1546 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
1547 desired_capacity_upper_bound);
1548
1549 // We can now safely turn them into size_t's.
1550 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
1551 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
1552
1553 // This assert only makes sense here, before we adjust them
1554 // with respect to the min and max heap size.
1555 assert(minimum_desired_capacity <= maximum_desired_capacity,
1556 err_msg("minimum_desired_capacity = "SIZE_FORMAT", "
1557 "maximum_desired_capacity = "SIZE_FORMAT,
1558 minimum_desired_capacity, maximum_desired_capacity));
1559
1560 // Should not be greater than the heap max size. No need to adjust
1561 // it with respect to the heap min size as it's a lower bound (i.e.,
1562 // we'll try to make the capacity larger than it, not smaller).
1563 minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size);
1564 // Should not be less than the heap min size. No need to adjust it
1565 // with respect to the heap max size as it's an upper bound (i.e.,
1566 // we'll try to make the capacity smaller than it, not greater).
1567 maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size);
1568
1569 if (capacity_after_gc < minimum_desired_capacity) {
1570 // Don't expand unless it's significant
1571 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
1572 ergo_verbose4(ErgoHeapSizing,
1573 "attempt heap expansion",
1574 ergo_format_reason("capacity lower than "
1575 "min desired capacity after Full GC")
1576 ergo_format_byte("capacity")
1577 ergo_format_byte("occupancy")
1578 ergo_format_byte_perc("min desired capacity"),
1579 capacity_after_gc, used_after_gc,
1580 minimum_desired_capacity, (double) MinHeapFreeRatio);
1581 expand(expand_bytes);
1582
1583 // No expansion, now see if we want to shrink
1584 } else if (capacity_after_gc > maximum_desired_capacity) {
1585 // Capacity too large, compute shrinking size
1586 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
1587 ergo_verbose4(ErgoHeapSizing,
1588 "attempt heap shrinking",
1589 ergo_format_reason("capacity higher than "
1590 "max desired capacity after Full GC")
1591 ergo_format_byte("capacity")
1592 ergo_format_byte("occupancy")
1593 ergo_format_byte_perc("max desired capacity"),
1594 capacity_after_gc, used_after_gc,
1595 maximum_desired_capacity, (double) MaxHeapFreeRatio);
1596 shrink(shrink_bytes);
1597 }
1598 }
1599
1600
1601 HeapWord*
1602 G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
1603 bool* succeeded) {
1604 assert_at_safepoint(true /* should_be_vm_thread */);
1605
1606 *succeeded = true;
1607 // Let's attempt the allocation first.
1608 HeapWord* result =
1609 attempt_allocation_at_safepoint(word_size,
1610 false /* expect_null_mutator_alloc_region */);
1611 if (result != NULL) {
1612 assert(*succeeded, "sanity");
1613 return result;
1614 }
1615
1616 // In a G1 heap, we're supposed to keep allocation from failing by
1617 // incremental pauses. Therefore, at least for now, we'll favor
1618 // expansion over collection. (This might change in the future if we can
1619 // do something smarter than full collection to satisfy a failed alloc.)
1620 result = expand_and_allocate(word_size);
1621 if (result != NULL) {
1622 assert(*succeeded, "sanity");
1623 return result;
1624 }
1625
1626 // Expansion didn't work, we'll try to do a Full GC.
1627 bool gc_succeeded = do_collection(false, /* explicit_gc */
1628 false, /* clear_all_soft_refs */
1629 word_size);
1630 if (!gc_succeeded) {
1631 *succeeded = false;
1632 return NULL;
1633 }
1634
1635 // Retry the allocation
1636 result = attempt_allocation_at_safepoint(word_size,
1637 true /* expect_null_mutator_alloc_region */);
1638 if (result != NULL) {
1639 assert(*succeeded, "sanity");
1640 return result;
1641 }
1642
1643 // Then, try a Full GC that will collect all soft references.
1644 gc_succeeded = do_collection(false, /* explicit_gc */
1645 true, /* clear_all_soft_refs */
1646 word_size);
1647 if (!gc_succeeded) {
1648 *succeeded = false;
1649 return NULL;
1650 }
1651
1652 // Retry the allocation once more
1653 result = attempt_allocation_at_safepoint(word_size,
1654 true /* expect_null_mutator_alloc_region */);
1655 if (result != NULL) {
1656 assert(*succeeded, "sanity");
1657 return result;
1658 }
1659
1660 assert(!collector_policy()->should_clear_all_soft_refs(),
1661 "Flag should have been handled and cleared prior to this point");
1662
1663 // What else? We might try synchronous finalization later. If the total
1664 // space available is large enough for the allocation, then a more
1665 // complete compaction phase than we've tried so far might be
1666 // appropriate.
1667 assert(*succeeded, "sanity");
1668 return NULL;
1669 }
1670
1671 // Attempting to expand the heap sufficiently
1672 // to support an allocation of the given "word_size". If
1673 // successful, perform the allocation and return the address of the
1674 // allocated block, or else "NULL".
1675
1676 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size) {
1677 assert_at_safepoint(true /* should_be_vm_thread */);
1678
1679 verify_region_sets_optional();
1680
1681 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
1682 ergo_verbose1(ErgoHeapSizing,
1683 "attempt heap expansion",
1684 ergo_format_reason("allocation request failed")
1685 ergo_format_byte("allocation request"),
1686 word_size * HeapWordSize);
1687 if (expand(expand_bytes)) {
1688 _hrs.verify_optional();
1689 verify_region_sets_optional();
1690 return attempt_allocation_at_safepoint(word_size,
1691 false /* expect_null_mutator_alloc_region */);
1692 }
1693 return NULL;
1694 }
1695
1696 void G1CollectedHeap::update_committed_space(HeapWord* old_end,
1697 HeapWord* new_end) {
1698 assert(old_end != new_end, "don't call this otherwise");
1699 assert((HeapWord*) _g1_storage.high() == new_end, "invariant");
1700
1701 // Update the committed mem region.
1702 _g1_committed.set_end(new_end);
1703 // Tell the card table about the update.
1704 Universe::heap()->barrier_set()->resize_covered_region(_g1_committed);
1705 // Tell the BOT about the update.
1706 _bot_shared->resize(_g1_committed.word_size());
1707 }
1708
1709 bool G1CollectedHeap::expand(size_t expand_bytes) {
1710 size_t old_mem_size = _g1_storage.committed_size();
1711 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
1712 aligned_expand_bytes = align_size_up(aligned_expand_bytes,
1713 HeapRegion::GrainBytes);
1714 ergo_verbose2(ErgoHeapSizing,
1715 "expand the heap",
1716 ergo_format_byte("requested expansion amount")
1717 ergo_format_byte("attempted expansion amount"),
1718 expand_bytes, aligned_expand_bytes);
1719
1720 // First commit the memory.
1721 HeapWord* old_end = (HeapWord*) _g1_storage.high();
1722 bool successful = _g1_storage.expand_by(aligned_expand_bytes);
1723 if (successful) {
1724 // Then propagate this update to the necessary data structures.
1725 HeapWord* new_end = (HeapWord*) _g1_storage.high();
1726 update_committed_space(old_end, new_end);
1727
1728 FreeRegionList expansion_list("Local Expansion List");
1729 MemRegion mr = _hrs.expand_by(old_end, new_end, &expansion_list);
1730 assert(mr.start() == old_end, "post-condition");
1731 // mr might be a smaller region than what was requested if
1732 // expand_by() was unable to allocate the HeapRegion instances
1733 assert(mr.end() <= new_end, "post-condition");
1734
1735 size_t actual_expand_bytes = mr.byte_size();
1736 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
1737 assert(actual_expand_bytes == expansion_list.total_capacity_bytes(),
1738 "post-condition");
1739 if (actual_expand_bytes < aligned_expand_bytes) {
1740 // We could not expand _hrs to the desired size. In this case we
1741 // need to shrink the committed space accordingly.
1742 assert(mr.end() < new_end, "invariant");
1743
1744 size_t diff_bytes = aligned_expand_bytes - actual_expand_bytes;
1745 // First uncommit the memory.
1746 _g1_storage.shrink_by(diff_bytes);
1747 // Then propagate this update to the necessary data structures.
1748 update_committed_space(new_end, mr.end());
1749 }
1750 _free_list.add_as_tail(&expansion_list);
1751
1752 if (_hr_printer.is_active()) {
1753 HeapWord* curr = mr.start();
1754 while (curr < mr.end()) {
1755 HeapWord* curr_end = curr + HeapRegion::GrainWords;
1756 _hr_printer.commit(curr, curr_end);
1757 curr = curr_end;
1758 }
1759 assert(curr == mr.end(), "post-condition");
1760 }
1761 g1_policy()->record_new_heap_size(n_regions());
1762 } else {
1763 ergo_verbose0(ErgoHeapSizing,
1764 "did not expand the heap",
1765 ergo_format_reason("heap expansion operation failed"));
1766 // The expansion of the virtual storage space was unsuccessful.
1767 // Let's see if it was because we ran out of swap.
1768 if (G1ExitOnExpansionFailure &&
1769 _g1_storage.uncommitted_size() >= aligned_expand_bytes) {
1770 // We had head room...
1771 vm_exit_out_of_memory(aligned_expand_bytes, "G1 heap expansion");
1772 }
1773 }
1774 return successful;
1775 }
1776
1777 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
1778 size_t old_mem_size = _g1_storage.committed_size();
1779 size_t aligned_shrink_bytes =
1780 ReservedSpace::page_align_size_down(shrink_bytes);
1781 aligned_shrink_bytes = align_size_down(aligned_shrink_bytes,
1782 HeapRegion::GrainBytes);
1783 uint num_regions_deleted = 0;
1784 MemRegion mr = _hrs.shrink_by(aligned_shrink_bytes, &num_regions_deleted);
1785 HeapWord* old_end = (HeapWord*) _g1_storage.high();
1786 assert(mr.end() == old_end, "post-condition");
1787
1788 ergo_verbose3(ErgoHeapSizing,
1789 "shrink the heap",
1790 ergo_format_byte("requested shrinking amount")
1791 ergo_format_byte("aligned shrinking amount")
1792 ergo_format_byte("attempted shrinking amount"),
1793 shrink_bytes, aligned_shrink_bytes, mr.byte_size());
1794 if (mr.byte_size() > 0) {
1795 if (_hr_printer.is_active()) {
1796 HeapWord* curr = mr.end();
1797 while (curr > mr.start()) {
1798 HeapWord* curr_end = curr;
1799 curr -= HeapRegion::GrainWords;
1800 _hr_printer.uncommit(curr, curr_end);
1801 }
1802 assert(curr == mr.start(), "post-condition");
1803 }
1804
1805 _g1_storage.shrink_by(mr.byte_size());
1806 HeapWord* new_end = (HeapWord*) _g1_storage.high();
1807 assert(mr.start() == new_end, "post-condition");
1808
1809 _expansion_regions += num_regions_deleted;
1810 update_committed_space(old_end, new_end);
1811 HeapRegionRemSet::shrink_heap(n_regions());
1812 g1_policy()->record_new_heap_size(n_regions());
1813 } else {
1814 ergo_verbose0(ErgoHeapSizing,
1815 "did not shrink the heap",
1816 ergo_format_reason("heap shrinking operation failed"));
1817 }
1818 }
1819
1820 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1821 verify_region_sets_optional();
1822
1823 // We should only reach here at the end of a Full GC which means we
1824 // should not not be holding to any GC alloc regions. The method
1825 // below will make sure of that and do any remaining clean up.
1826 abandon_gc_alloc_regions();
1827
1828 // Instead of tearing down / rebuilding the free lists here, we
1829 // could instead use the remove_all_pending() method on free_list to
1830 // remove only the ones that we need to remove.
1831 tear_down_region_sets(true /* free_list_only */);
1832 shrink_helper(shrink_bytes);
1833 rebuild_region_sets(true /* free_list_only */);
1834
1835 _hrs.verify_optional();
1836 verify_region_sets_optional();
1837 }
1838
1839 // Public methods.
1840
1841 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away
1842 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
1843 #endif // _MSC_VER
1844
1845
1846 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* policy_) :
1847 SharedHeap(policy_),
1848 _g1_policy(policy_),
1849 _dirty_card_queue_set(false),
1850 _into_cset_dirty_card_queue_set(false),
1851 _is_alive_closure_cm(this),
1852 _is_alive_closure_stw(this),
1853 _ref_processor_cm(NULL),
1854 _ref_processor_stw(NULL),
1855 _process_strong_tasks(new SubTasksDone(G1H_PS_NumElements)),
1856 _bot_shared(NULL),
1857 _objs_with_preserved_marks(NULL), _preserved_marks_of_objs(NULL),
1858 _evac_failure_scan_stack(NULL) ,
1859 _mark_in_progress(false),
1860 _cg1r(NULL), _summary_bytes_used(0),
1861 _g1mm(NULL),
1862 _refine_cte_cl(NULL),
1863 _full_collection(false),
1864 _free_list("Master Free List"),
1865 _secondary_free_list("Secondary Free List"),
1866 _old_set("Old Set"),
1867 _humongous_set("Master Humongous Set"),
1868 _free_regions_coming(false),
1869 _young_list(new YoungList(this)),
1870 _gc_time_stamp(0),
1871 _retained_old_gc_alloc_region(NULL),
1872 _expand_heap_after_alloc_failure(true),
1873 _surviving_young_words(NULL),
1874 _full_collections_completed(0),
1875 _in_cset_fast_test(NULL),
1876 _in_cset_fast_test_base(NULL),
1877 _dirty_cards_region_list(NULL),
1878 _worker_cset_start_region(NULL),
1879 _worker_cset_start_region_time_stamp(NULL) {
1880 _g1h = this; // To catch bugs.
1881 if (_process_strong_tasks == NULL || !_process_strong_tasks->valid()) {
1882 vm_exit_during_initialization("Failed necessary allocation.");
1883 }
1884
1885 _humongous_object_threshold_in_words = HeapRegion::GrainWords / 2;
1886
1887 int n_queues = MAX2((int)ParallelGCThreads, 1);
1888 _task_queues = new RefToScanQueueSet(n_queues);
1889
1890 int n_rem_sets = HeapRegionRemSet::num_par_rem_sets();
1891 assert(n_rem_sets > 0, "Invariant.");
1892
1893 HeapRegionRemSetIterator** iter_arr =
1894 NEW_C_HEAP_ARRAY(HeapRegionRemSetIterator*, n_queues);
1895 for (int i = 0; i < n_queues; i++) {
1896 iter_arr[i] = new HeapRegionRemSetIterator();
1897 }
1898 _rem_set_iterator = iter_arr;
1899
1900 _worker_cset_start_region = NEW_C_HEAP_ARRAY(HeapRegion*, n_queues);
1901 _worker_cset_start_region_time_stamp = NEW_C_HEAP_ARRAY(unsigned int, n_queues);
1902
1903 for (int i = 0; i < n_queues; i++) {
1904 RefToScanQueue* q = new RefToScanQueue();
1905 q->initialize();
1906 _task_queues->register_queue(i, q);
1907 }
1908
1909 clear_cset_start_regions();
1910
1911 guarantee(_task_queues != NULL, "task_queues allocation failure.");
1912 }
1913
1914 jint G1CollectedHeap::initialize() {
1915 CollectedHeap::pre_initialize();
1916 os::enable_vtime();
1917
1918 G1Log::init();
1919
1920 // Necessary to satisfy locking discipline assertions.
1921
1922 MutexLocker x(Heap_lock);
1923
1924 // We have to initialize the printer before committing the heap, as
1925 // it will be used then.
1926 _hr_printer.set_active(G1PrintHeapRegions);
1927
1928 // While there are no constraints in the GC code that HeapWordSize
1929 // be any particular value, there are multiple other areas in the
1930 // system which believe this to be true (e.g. oop->object_size in some
1931 // cases incorrectly returns the size in wordSize units rather than
1932 // HeapWordSize).
1933 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
1934
1935 size_t init_byte_size = collector_policy()->initial_heap_byte_size();
1936 size_t max_byte_size = collector_policy()->max_heap_byte_size();
1937
1938 // Ensure that the sizes are properly aligned.
1939 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
1940 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
1941
1942 _cg1r = new ConcurrentG1Refine();
1943
1944 // Reserve the maximum.
1945 PermanentGenerationSpec* pgs = collector_policy()->permanent_generation();
1946 // Includes the perm-gen.
1947
1948 // When compressed oops are enabled, the preferred heap base
1949 // is calculated by subtracting the requested size from the
1950 // 32Gb boundary and using the result as the base address for
1951 // heap reservation. If the requested size is not aligned to
1952 // HeapRegion::GrainBytes (i.e. the alignment that is passed
1953 // into the ReservedHeapSpace constructor) then the actual
1954 // base of the reserved heap may end up differing from the
1955 // address that was requested (i.e. the preferred heap base).
1956 // If this happens then we could end up using a non-optimal
1957 // compressed oops mode.
1958
1959 // Since max_byte_size is aligned to the size of a heap region (checked
1960 // above), we also need to align the perm gen size as it might not be.
1961 const size_t total_reserved = max_byte_size +
1962 align_size_up(pgs->max_size(), HeapRegion::GrainBytes);
1963 Universe::check_alignment(total_reserved, HeapRegion::GrainBytes, "g1 heap and perm");
1964
1965 char* addr = Universe::preferred_heap_base(total_reserved, Universe::UnscaledNarrowOop);
1966
1967 ReservedHeapSpace heap_rs(total_reserved, HeapRegion::GrainBytes,
1968 UseLargePages, addr);
1969
1970 if (UseCompressedOops) {
1971 if (addr != NULL && !heap_rs.is_reserved()) {
1972 // Failed to reserve at specified address - the requested memory
1973 // region is taken already, for example, by 'java' launcher.
1974 // Try again to reserver heap higher.
1975 addr = Universe::preferred_heap_base(total_reserved, Universe::ZeroBasedNarrowOop);
1976
1977 ReservedHeapSpace heap_rs0(total_reserved, HeapRegion::GrainBytes,
1978 UseLargePages, addr);
1979
1980 if (addr != NULL && !heap_rs0.is_reserved()) {
1981 // Failed to reserve at specified address again - give up.
1982 addr = Universe::preferred_heap_base(total_reserved, Universe::HeapBasedNarrowOop);
1983 assert(addr == NULL, "");
1984
1985 ReservedHeapSpace heap_rs1(total_reserved, HeapRegion::GrainBytes,
1986 UseLargePages, addr);
1987 heap_rs = heap_rs1;
1988 } else {
1989 heap_rs = heap_rs0;
1990 }
1991 }
1992 }
1993
1994 if (!heap_rs.is_reserved()) {
1995 vm_exit_during_initialization("Could not reserve enough space for object heap");
1996 return JNI_ENOMEM;
1997 }
1998
1999 // It is important to do this in a way such that concurrent readers can't
2000 // temporarily think somethings in the heap. (I've actually seen this
2001 // happen in asserts: DLD.)
2002 _reserved.set_word_size(0);
2003 _reserved.set_start((HeapWord*)heap_rs.base());
2004 _reserved.set_end((HeapWord*)(heap_rs.base() + heap_rs.size()));
2005
2006 _expansion_regions = (uint) (max_byte_size / HeapRegion::GrainBytes);
2007
2008 // Create the gen rem set (and barrier set) for the entire reserved region.
2009 _rem_set = collector_policy()->create_rem_set(_reserved, 2);
2010 set_barrier_set(rem_set()->bs());
2011 if (barrier_set()->is_a(BarrierSet::ModRef)) {
2012 _mr_bs = (ModRefBarrierSet*)_barrier_set;
2013 } else {
2014 vm_exit_during_initialization("G1 requires a mod ref bs.");
2015 return JNI_ENOMEM;
2016 }
2017
2018 // Also create a G1 rem set.
2019 if (mr_bs()->is_a(BarrierSet::CardTableModRef)) {
2020 _g1_rem_set = new G1RemSet(this, (CardTableModRefBS*)mr_bs());
2021 } else {
2022 vm_exit_during_initialization("G1 requires a cardtable mod ref bs.");
2023 return JNI_ENOMEM;
2024 }
2025
2026 // Carve out the G1 part of the heap.
2027
2028 ReservedSpace g1_rs = heap_rs.first_part(max_byte_size);
2029 _g1_reserved = MemRegion((HeapWord*)g1_rs.base(),
2030 g1_rs.size()/HeapWordSize);
2031 ReservedSpace perm_gen_rs = heap_rs.last_part(max_byte_size);
2032
2033 _perm_gen = pgs->init(perm_gen_rs, pgs->init_size(), rem_set());
2034
2035 _g1_storage.initialize(g1_rs, 0);
2036 _g1_committed = MemRegion((HeapWord*)_g1_storage.low(), (size_t) 0);
2037 _hrs.initialize((HeapWord*) _g1_reserved.start(),
2038 (HeapWord*) _g1_reserved.end(),
2039 _expansion_regions);
2040
2041 // 6843694 - ensure that the maximum region index can fit
2042 // in the remembered set structures.
2043 const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
2044 guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
2045
2046 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
2047 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
2048 guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
2049 "too many cards per region");
2050
2051 HeapRegionSet::set_unrealistically_long_length(max_regions() + 1);
2052
2053 _bot_shared = new G1BlockOffsetSharedArray(_reserved,
2054 heap_word_size(init_byte_size));
2055
2056 _g1h = this;
2057
2058 _in_cset_fast_test_length = max_regions();
2059 _in_cset_fast_test_base =
2060 NEW_C_HEAP_ARRAY(bool, (size_t) _in_cset_fast_test_length);
2061
2062 // We're biasing _in_cset_fast_test to avoid subtracting the
2063 // beginning of the heap every time we want to index; basically
2064 // it's the same with what we do with the card table.
2065 _in_cset_fast_test = _in_cset_fast_test_base -
2066 ((uintx) _g1_reserved.start() >> HeapRegion::LogOfHRGrainBytes);
2067
2068 // Clear the _cset_fast_test bitmap in anticipation of adding
2069 // regions to the incremental collection set for the first
2070 // evacuation pause.
2071 clear_cset_fast_test();
2072
2073 // Create the ConcurrentMark data structure and thread.
2074 // (Must do this late, so that "max_regions" is defined.)
2075 _cm = new ConcurrentMark(heap_rs, max_regions());
2076 _cmThread = _cm->cmThread();
2077
2078 // Initialize the from_card cache structure of HeapRegionRemSet.
2079 HeapRegionRemSet::init_heap(max_regions());
2080
2081 // Now expand into the initial heap size.
2082 if (!expand(init_byte_size)) {
2083 vm_exit_during_initialization("Failed to allocate initial heap.");
2084 return JNI_ENOMEM;
2085 }
2086
2087 // Perform any initialization actions delegated to the policy.
2088 g1_policy()->init();
2089
2090 _refine_cte_cl =
2091 new RefineCardTableEntryClosure(ConcurrentG1RefineThread::sts(),
2092 g1_rem_set(),
2093 concurrent_g1_refine());
2094 JavaThread::dirty_card_queue_set().set_closure(_refine_cte_cl);
2095
2096 JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon,
2097 SATB_Q_FL_lock,
2098 G1SATBProcessCompletedThreshold,
2099 Shared_SATB_Q_lock);
2100
2101 JavaThread::dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
2102 DirtyCardQ_FL_lock,
2103 concurrent_g1_refine()->yellow_zone(),
2104 concurrent_g1_refine()->red_zone(),
2105 Shared_DirtyCardQ_lock);
2106
2107 if (G1DeferredRSUpdate) {
2108 dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
2109 DirtyCardQ_FL_lock,
2110 -1, // never trigger processing
2111 -1, // no limit on length
2112 Shared_DirtyCardQ_lock,
2113 &JavaThread::dirty_card_queue_set());
2114 }
2115
2116 // Initialize the card queue set used to hold cards containing
2117 // references into the collection set.
2118 _into_cset_dirty_card_queue_set.initialize(DirtyCardQ_CBL_mon,
2119 DirtyCardQ_FL_lock,
2120 -1, // never trigger processing
2121 -1, // no limit on length
2122 Shared_DirtyCardQ_lock,
2123 &JavaThread::dirty_card_queue_set());
2124
2125 // In case we're keeping closure specialization stats, initialize those
2126 // counts and that mechanism.
2127 SpecializationStats::clear();
2128
2129 // Do later initialization work for concurrent refinement.
2130 _cg1r->init();
2131
2132 // Here we allocate the dummy full region that is required by the
2133 // G1AllocRegion class. If we don't pass an address in the reserved
2134 // space here, lots of asserts fire.
2135
2136 HeapRegion* dummy_region = new_heap_region(0 /* index of bottom region */,
2137 _g1_reserved.start());
2138 // We'll re-use the same region whether the alloc region will
2139 // require BOT updates or not and, if it doesn't, then a non-young
2140 // region will complain that it cannot support allocations without
2141 // BOT updates. So we'll tag the dummy region as young to avoid that.
2142 dummy_region->set_young();
2143 // Make sure it's full.
2144 dummy_region->set_top(dummy_region->end());
2145 G1AllocRegion::setup(this, dummy_region);
2146
2147 init_mutator_alloc_region();
2148
2149 // Do create of the monitoring and management support so that
2150 // values in the heap have been properly initialized.
2151 _g1mm = new G1MonitoringSupport(this);
2152
2153 return JNI_OK;
2154 }
2155
2156 void G1CollectedHeap::ref_processing_init() {
2157 // Reference processing in G1 currently works as follows:
2158 //
2159 // * There are two reference processor instances. One is
2160 // used to record and process discovered references
2161 // during concurrent marking; the other is used to
2162 // record and process references during STW pauses
2163 // (both full and incremental).
2164 // * Both ref processors need to 'span' the entire heap as
2165 // the regions in the collection set may be dotted around.
2166 //
2167 // * For the concurrent marking ref processor:
2168 // * Reference discovery is enabled at initial marking.
2169 // * Reference discovery is disabled and the discovered
2170 // references processed etc during remarking.
2171 // * Reference discovery is MT (see below).
2172 // * Reference discovery requires a barrier (see below).
2173 // * Reference processing may or may not be MT
2174 // (depending on the value of ParallelRefProcEnabled
2175 // and ParallelGCThreads).
2176 // * A full GC disables reference discovery by the CM
2177 // ref processor and abandons any entries on it's
2178 // discovered lists.
2179 //
2180 // * For the STW processor:
2181 // * Non MT discovery is enabled at the start of a full GC.
2182 // * Processing and enqueueing during a full GC is non-MT.
2183 // * During a full GC, references are processed after marking.
2184 //
2185 // * Discovery (may or may not be MT) is enabled at the start
2186 // of an incremental evacuation pause.
2187 // * References are processed near the end of a STW evacuation pause.
2188 // * For both types of GC:
2189 // * Discovery is atomic - i.e. not concurrent.
2190 // * Reference discovery will not need a barrier.
2191
2192 SharedHeap::ref_processing_init();
2193 MemRegion mr = reserved_region();
2194
2195 // Concurrent Mark ref processor
2196 _ref_processor_cm =
2197 new ReferenceProcessor(mr, // span
2198 ParallelRefProcEnabled && (ParallelGCThreads > 1),
2199 // mt processing
2200 (int) ParallelGCThreads,
2201 // degree of mt processing
2202 (ParallelGCThreads > 1) || (ConcGCThreads > 1),
2203 // mt discovery
2204 (int) MAX2(ParallelGCThreads, ConcGCThreads),
2205 // degree of mt discovery
2206 false,
2207 // Reference discovery is not atomic
2208 &_is_alive_closure_cm,
2209 // is alive closure
2210 // (for efficiency/performance)
2211 true);
2212 // Setting next fields of discovered
2213 // lists requires a barrier.
2214
2215 // STW ref processor
2216 _ref_processor_stw =
2217 new ReferenceProcessor(mr, // span
2218 ParallelRefProcEnabled && (ParallelGCThreads > 1),
2219 // mt processing
2220 MAX2((int)ParallelGCThreads, 1),
2221 // degree of mt processing
2222 (ParallelGCThreads > 1),
2223 // mt discovery
2224 MAX2((int)ParallelGCThreads, 1),
2225 // degree of mt discovery
2226 true,
2227 // Reference discovery is atomic
2228 &_is_alive_closure_stw,
2229 // is alive closure
2230 // (for efficiency/performance)
2231 false);
2232 // Setting next fields of discovered
2233 // lists requires a barrier.
2234 }
2235
2236 size_t G1CollectedHeap::capacity() const {
2237 return _g1_committed.byte_size();
2238 }
2239
2240 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl,
2241 DirtyCardQueue* into_cset_dcq,
2242 bool concurrent,
2243 int worker_i) {
2244 // Clean cards in the hot card cache
2245 concurrent_g1_refine()->clean_up_cache(worker_i, g1_rem_set(), into_cset_dcq);
2246
2247 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2248 int n_completed_buffers = 0;
2249 while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) {
2250 n_completed_buffers++;
2251 }
2252 g1_policy()->record_update_rs_processed_buffers(worker_i,
2253 (double) n_completed_buffers);
2254 dcqs.clear_n_completed_buffers();
2255 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!");
2256 }
2257
2258
2259 // Computes the sum of the storage used by the various regions.
2260
2261 size_t G1CollectedHeap::used() const {
2262 assert(Heap_lock->owner() != NULL,
2263 "Should be owned on this thread's behalf.");
2264 size_t result = _summary_bytes_used;
2265 // Read only once in case it is set to NULL concurrently
2266 HeapRegion* hr = _mutator_alloc_region.get();
2267 if (hr != NULL)
2268 result += hr->used();
2269 return result;
2270 }
2271
2272 size_t G1CollectedHeap::used_unlocked() const {
2273 size_t result = _summary_bytes_used;
2274 return result;
2275 }
2276
2277 class SumUsedClosure: public HeapRegionClosure {
2278 size_t _used;
2279 public:
2280 SumUsedClosure() : _used(0) {}
2281 bool doHeapRegion(HeapRegion* r) {
2282 if (!r->continuesHumongous()) {
2283 _used += r->used();
2284 }
2285 return false;
2286 }
2287 size_t result() { return _used; }
2288 };
2289
2290 size_t G1CollectedHeap::recalculate_used() const {
2291 SumUsedClosure blk;
2292 heap_region_iterate(&blk);
2293 return blk.result();
2294 }
2295
2296 size_t G1CollectedHeap::unsafe_max_alloc() {
2297 if (free_regions() > 0) return HeapRegion::GrainBytes;
2298 // otherwise, is there space in the current allocation region?
2299
2300 // We need to store the current allocation region in a local variable
2301 // here. The problem is that this method doesn't take any locks and
2302 // there may be other threads which overwrite the current allocation
2303 // region field. attempt_allocation(), for example, sets it to NULL
2304 // and this can happen *after* the NULL check here but before the call
2305 // to free(), resulting in a SIGSEGV. Note that this doesn't appear
2306 // to be a problem in the optimized build, since the two loads of the
2307 // current allocation region field are optimized away.
2308 HeapRegion* hr = _mutator_alloc_region.get();
2309 if (hr == NULL) {
2310 return 0;
2311 }
2312 return hr->free();
2313 }
2314
2315 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
2316 switch (cause) {
2317 case GCCause::_gc_locker: return GCLockerInvokesConcurrent;
2318 case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent;
2319 case GCCause::_g1_humongous_allocation: return true;
2320 default: return false;
2321 }
2322 }
2323
2324 #ifndef PRODUCT
2325 void G1CollectedHeap::allocate_dummy_regions() {
2326 // Let's fill up most of the region
2327 size_t word_size = HeapRegion::GrainWords - 1024;
2328 // And as a result the region we'll allocate will be humongous.
2329 guarantee(isHumongous(word_size), "sanity");
2330
2331 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
2332 // Let's use the existing mechanism for the allocation
2333 HeapWord* dummy_obj = humongous_obj_allocate(word_size);
2334 if (dummy_obj != NULL) {
2335 MemRegion mr(dummy_obj, word_size);
2336 CollectedHeap::fill_with_object(mr);
2337 } else {
2338 // If we can't allocate once, we probably cannot allocate
2339 // again. Let's get out of the loop.
2340 break;
2341 }
2342 }
2343 }
2344 #endif // !PRODUCT
2345
2346 void G1CollectedHeap::increment_full_collections_completed(bool concurrent) {
2347 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
2348
2349 // We assume that if concurrent == true, then the caller is a
2350 // concurrent thread that was joined the Suspendible Thread
2351 // Set. If there's ever a cheap way to check this, we should add an
2352 // assert here.
2353
2354 // We have already incremented _total_full_collections at the start
2355 // of the GC, so total_full_collections() represents how many full
2356 // collections have been started.
2357 unsigned int full_collections_started = total_full_collections();
2358
2359 // Given that this method is called at the end of a Full GC or of a
2360 // concurrent cycle, and those can be nested (i.e., a Full GC can
2361 // interrupt a concurrent cycle), the number of full collections
2362 // completed should be either one (in the case where there was no
2363 // nesting) or two (when a Full GC interrupted a concurrent cycle)
2364 // behind the number of full collections started.
2365
2366 // This is the case for the inner caller, i.e. a Full GC.
2367 assert(concurrent ||
2368 (full_collections_started == _full_collections_completed + 1) ||
2369 (full_collections_started == _full_collections_completed + 2),
2370 err_msg("for inner caller (Full GC): full_collections_started = %u "
2371 "is inconsistent with _full_collections_completed = %u",
2372 full_collections_started, _full_collections_completed));
2373
2374 // This is the case for the outer caller, i.e. the concurrent cycle.
2375 assert(!concurrent ||
2376 (full_collections_started == _full_collections_completed + 1),
2377 err_msg("for outer caller (concurrent cycle): "
2378 "full_collections_started = %u "
2379 "is inconsistent with _full_collections_completed = %u",
2380 full_collections_started, _full_collections_completed));
2381
2382 _full_collections_completed += 1;
2383
2384 // We need to clear the "in_progress" flag in the CM thread before
2385 // we wake up any waiters (especially when ExplicitInvokesConcurrent
2386 // is set) so that if a waiter requests another System.gc() it doesn't
2387 // incorrectly see that a marking cyle is still in progress.
2388 if (concurrent) {
2389 _cmThread->clear_in_progress();
2390 }
2391
2392 // This notify_all() will ensure that a thread that called
2393 // System.gc() with (with ExplicitGCInvokesConcurrent set or not)
2394 // and it's waiting for a full GC to finish will be woken up. It is
2395 // waiting in VM_G1IncCollectionPause::doit_epilogue().
2396 FullGCCount_lock->notify_all();
2397 }
2398
2399 void G1CollectedHeap::collect_as_vm_thread(GCCause::Cause cause) {
2400 assert_at_safepoint(true /* should_be_vm_thread */);
2401 GCCauseSetter gcs(this, cause);
2402 switch (cause) {
2403 case GCCause::_heap_inspection:
2404 case GCCause::_heap_dump: {
2405 HandleMark hm;
2406 do_full_collection(false); // don't clear all soft refs
2407 break;
2408 }
2409 default: // XXX FIX ME
2410 ShouldNotReachHere(); // Unexpected use of this function
2411 }
2412 }
2413
2414 void G1CollectedHeap::collect(GCCause::Cause cause) {
2415 assert_heap_not_locked();
2416
2417 unsigned int gc_count_before;
2418 unsigned int full_gc_count_before;
2419 bool retry_gc;
2420
2421 do {
2422 retry_gc = false;
2423
2424 {
2425 MutexLocker ml(Heap_lock);
2426
2427 // Read the GC count while holding the Heap_lock
2428 gc_count_before = total_collections();
2429 full_gc_count_before = total_full_collections();
2430 }
2431
2432 if (should_do_concurrent_full_gc(cause)) {
2433 // Schedule an initial-mark evacuation pause that will start a
2434 // concurrent cycle. We're setting word_size to 0 which means that
2435 // we are not requesting a post-GC allocation.
2436 VM_G1IncCollectionPause op(gc_count_before,
2437 0, /* word_size */
2438 true, /* should_initiate_conc_mark */
2439 g1_policy()->max_pause_time_ms(),
2440 cause);
2441
2442 VMThread::execute(&op);
2443 if (!op.pause_succeeded()) {
2444 if (full_gc_count_before == total_full_collections()) {
2445 retry_gc = op.should_retry_gc();
2446 } else {
2447 // A Full GC happened while we were trying to schedule the
2448 // initial-mark GC. No point in starting a new cycle given
2449 // that the whole heap was collected anyway.
2450 }
2451
2452 if (retry_gc) {
2453 if (GC_locker::is_active_and_needs_gc()) {
2454 GC_locker::stall_until_clear();
2455 }
2456 }
2457 }
2458 } else {
2459 if (cause == GCCause::_gc_locker
2460 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2461
2462 // Schedule a standard evacuation pause. We're setting word_size
2463 // to 0 which means that we are not requesting a post-GC allocation.
2464 VM_G1IncCollectionPause op(gc_count_before,
2465 0, /* word_size */
2466 false, /* should_initiate_conc_mark */
2467 g1_policy()->max_pause_time_ms(),
2468 cause);
2469 VMThread::execute(&op);
2470 } else {
2471 // Schedule a Full GC.
2472 VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause);
2473 VMThread::execute(&op);
2474 }
2475 }
2476 } while (retry_gc);
2477 }
2478
2479 bool G1CollectedHeap::is_in(const void* p) const {
2480 if (_g1_committed.contains(p)) {
2481 // Given that we know that p is in the committed space,
2482 // heap_region_containing_raw() should successfully
2483 // return the containing region.
2484 HeapRegion* hr = heap_region_containing_raw(p);
2485 return hr->is_in(p);
2486 } else {
2487 return _perm_gen->as_gen()->is_in(p);
2488 }
2489 }
2490
2491 // Iteration functions.
2492
2493 // Iterates an OopClosure over all ref-containing fields of objects
2494 // within a HeapRegion.
2495
2496 class IterateOopClosureRegionClosure: public HeapRegionClosure {
2497 MemRegion _mr;
2498 OopClosure* _cl;
2499 public:
2500 IterateOopClosureRegionClosure(MemRegion mr, OopClosure* cl)
2501 : _mr(mr), _cl(cl) {}
2502 bool doHeapRegion(HeapRegion* r) {
2503 if (! r->continuesHumongous()) {
2504 r->oop_iterate(_cl);
2505 }
2506 return false;
2507 }
2508 };
2509
2510 void G1CollectedHeap::oop_iterate(OopClosure* cl, bool do_perm) {
2511 IterateOopClosureRegionClosure blk(_g1_committed, cl);
2512 heap_region_iterate(&blk);
2513 if (do_perm) {
2514 perm_gen()->oop_iterate(cl);
2515 }
2516 }
2517
2518 void G1CollectedHeap::oop_iterate(MemRegion mr, OopClosure* cl, bool do_perm) {
2519 IterateOopClosureRegionClosure blk(mr, cl);
2520 heap_region_iterate(&blk);
2521 if (do_perm) {
2522 perm_gen()->oop_iterate(cl);
2523 }
2524 }
2525
2526 // Iterates an ObjectClosure over all objects within a HeapRegion.
2527
2528 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2529 ObjectClosure* _cl;
2530 public:
2531 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2532 bool doHeapRegion(HeapRegion* r) {
2533 if (! r->continuesHumongous()) {
2534 r->object_iterate(_cl);
2535 }
2536 return false;
2537 }
2538 };
2539
2540 void G1CollectedHeap::object_iterate(ObjectClosure* cl, bool do_perm) {
2541 IterateObjectClosureRegionClosure blk(cl);
2542 heap_region_iterate(&blk);
2543 if (do_perm) {
2544 perm_gen()->object_iterate(cl);
2545 }
2546 }
2547
2548 void G1CollectedHeap::object_iterate_since_last_GC(ObjectClosure* cl) {
2549 // FIXME: is this right?
2550 guarantee(false, "object_iterate_since_last_GC not supported by G1 heap");
2551 }
2552
2553 // Calls a SpaceClosure on a HeapRegion.
2554
2555 class SpaceClosureRegionClosure: public HeapRegionClosure {
2556 SpaceClosure* _cl;
2557 public:
2558 SpaceClosureRegionClosure(SpaceClosure* cl) : _cl(cl) {}
2559 bool doHeapRegion(HeapRegion* r) {
2560 _cl->do_space(r);
2561 return false;
2562 }
2563 };
2564
2565 void G1CollectedHeap::space_iterate(SpaceClosure* cl) {
2566 SpaceClosureRegionClosure blk(cl);
2567 heap_region_iterate(&blk);
2568 }
2569
2570 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2571 _hrs.iterate(cl);
2572 }
2573
2574 void G1CollectedHeap::heap_region_iterate_from(HeapRegion* r,
2575 HeapRegionClosure* cl) const {
2576 _hrs.iterate_from(r, cl);
2577 }
2578
2579 void
2580 G1CollectedHeap::heap_region_par_iterate_chunked(HeapRegionClosure* cl,
2581 uint worker,
2582 uint no_of_par_workers,
2583 jint claim_value) {
2584 const uint regions = n_regions();
2585 const uint max_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
2586 no_of_par_workers :
2587 1);
2588 assert(UseDynamicNumberOfGCThreads ||
2589 no_of_par_workers == workers()->total_workers(),
2590 "Non dynamic should use fixed number of workers");
2591 // try to spread out the starting points of the workers
2592 const uint start_index = regions / max_workers * worker;
2593
2594 // each worker will actually look at all regions
2595 for (uint count = 0; count < regions; ++count) {
2596 const uint index = (start_index + count) % regions;
2597 assert(0 <= index && index < regions, "sanity");
2598 HeapRegion* r = region_at(index);
2599 // we'll ignore "continues humongous" regions (we'll process them
2600 // when we come across their corresponding "start humongous"
2601 // region) and regions already claimed
2602 if (r->claim_value() == claim_value || r->continuesHumongous()) {
2603 continue;
2604 }
2605 // OK, try to claim it
2606 if (r->claimHeapRegion(claim_value)) {
2607 // success!
2608 assert(!r->continuesHumongous(), "sanity");
2609 if (r->startsHumongous()) {
2610 // If the region is "starts humongous" we'll iterate over its
2611 // "continues humongous" first; in fact we'll do them
2612 // first. The order is important. In on case, calling the
2613 // closure on the "starts humongous" region might de-allocate
2614 // and clear all its "continues humongous" regions and, as a
2615 // result, we might end up processing them twice. So, we'll do
2616 // them first (notice: most closures will ignore them anyway) and
2617 // then we'll do the "starts humongous" region.
2618 for (uint ch_index = index + 1; ch_index < regions; ++ch_index) {
2619 HeapRegion* chr = region_at(ch_index);
2620
2621 // if the region has already been claimed or it's not
2622 // "continues humongous" we're done
2623 if (chr->claim_value() == claim_value ||
2624 !chr->continuesHumongous()) {
2625 break;
2626 }
2627
2628 // Noone should have claimed it directly. We can given
2629 // that we claimed its "starts humongous" region.
2630 assert(chr->claim_value() != claim_value, "sanity");
2631 assert(chr->humongous_start_region() == r, "sanity");
2632
2633 if (chr->claimHeapRegion(claim_value)) {
2634 // we should always be able to claim it; noone else should
2635 // be trying to claim this region
2636
2637 bool res2 = cl->doHeapRegion(chr);
2638 assert(!res2, "Should not abort");
2639
2640 // Right now, this holds (i.e., no closure that actually
2641 // does something with "continues humongous" regions
2642 // clears them). We might have to weaken it in the future,
2643 // but let's leave these two asserts here for extra safety.
2644 assert(chr->continuesHumongous(), "should still be the case");
2645 assert(chr->humongous_start_region() == r, "sanity");
2646 } else {
2647 guarantee(false, "we should not reach here");
2648 }
2649 }
2650 }
2651
2652 assert(!r->continuesHumongous(), "sanity");
2653 bool res = cl->doHeapRegion(r);
2654 assert(!res, "Should not abort");
2655 }
2656 }
2657 }
2658
2659 class ResetClaimValuesClosure: public HeapRegionClosure {
2660 public:
2661 bool doHeapRegion(HeapRegion* r) {
2662 r->set_claim_value(HeapRegion::InitialClaimValue);
2663 return false;
2664 }
2665 };
2666
2667 void G1CollectedHeap::reset_heap_region_claim_values() {
2668 ResetClaimValuesClosure blk;
2669 heap_region_iterate(&blk);
2670 }
2671
2672 void G1CollectedHeap::reset_cset_heap_region_claim_values() {
2673 ResetClaimValuesClosure blk;
2674 collection_set_iterate(&blk);
2675 }
2676
2677 #ifdef ASSERT
2678 // This checks whether all regions in the heap have the correct claim
2679 // value. I also piggy-backed on this a check to ensure that the
2680 // humongous_start_region() information on "continues humongous"
2681 // regions is correct.
2682
2683 class CheckClaimValuesClosure : public HeapRegionClosure {
2684 private:
2685 jint _claim_value;
2686 uint _failures;
2687 HeapRegion* _sh_region;
2688
2689 public:
2690 CheckClaimValuesClosure(jint claim_value) :
2691 _claim_value(claim_value), _failures(0), _sh_region(NULL) { }
2692 bool doHeapRegion(HeapRegion* r) {
2693 if (r->claim_value() != _claim_value) {
2694 gclog_or_tty->print_cr("Region " HR_FORMAT ", "
2695 "claim value = %d, should be %d",
2696 HR_FORMAT_PARAMS(r),
2697 r->claim_value(), _claim_value);
2698 ++_failures;
2699 }
2700 if (!r->isHumongous()) {
2701 _sh_region = NULL;
2702 } else if (r->startsHumongous()) {
2703 _sh_region = r;
2704 } else if (r->continuesHumongous()) {
2705 if (r->humongous_start_region() != _sh_region) {
2706 gclog_or_tty->print_cr("Region " HR_FORMAT ", "
2707 "HS = "PTR_FORMAT", should be "PTR_FORMAT,
2708 HR_FORMAT_PARAMS(r),
2709 r->humongous_start_region(),
2710 _sh_region);
2711 ++_failures;
2712 }
2713 }
2714 return false;
2715 }
2716 uint failures() { return _failures; }
2717 };
2718
2719 bool G1CollectedHeap::check_heap_region_claim_values(jint claim_value) {
2720 CheckClaimValuesClosure cl(claim_value);
2721 heap_region_iterate(&cl);
2722 return cl.failures() == 0;
2723 }
2724
2725 class CheckClaimValuesInCSetHRClosure: public HeapRegionClosure {
2726 private:
2727 jint _claim_value;
2728 uint _failures;
2729
2730 public:
2731 CheckClaimValuesInCSetHRClosure(jint claim_value) :
2732 _claim_value(claim_value), _failures(0) { }
2733
2734 uint failures() { return _failures; }
2735
2736 bool doHeapRegion(HeapRegion* hr) {
2737 assert(hr->in_collection_set(), "how?");
2738 assert(!hr->isHumongous(), "H-region in CSet");
2739 if (hr->claim_value() != _claim_value) {
2740 gclog_or_tty->print_cr("CSet Region " HR_FORMAT ", "
2741 "claim value = %d, should be %d",
2742 HR_FORMAT_PARAMS(hr),
2743 hr->claim_value(), _claim_value);
2744 _failures += 1;
2745 }
2746 return false;
2747 }
2748 };
2749
2750 bool G1CollectedHeap::check_cset_heap_region_claim_values(jint claim_value) {
2751 CheckClaimValuesInCSetHRClosure cl(claim_value);
2752 collection_set_iterate(&cl);
2753 return cl.failures() == 0;
2754 }
2755 #endif // ASSERT
2756
2757 // Clear the cached CSet starting regions and (more importantly)
2758 // the time stamps. Called when we reset the GC time stamp.
2759 void G1CollectedHeap::clear_cset_start_regions() {
2760 assert(_worker_cset_start_region != NULL, "sanity");
2761 assert(_worker_cset_start_region_time_stamp != NULL, "sanity");
2762
2763 int n_queues = MAX2((int)ParallelGCThreads, 1);
2764 for (int i = 0; i < n_queues; i++) {
2765 _worker_cset_start_region[i] = NULL;
2766 _worker_cset_start_region_time_stamp[i] = 0;
2767 }
2768 }
2769
2770 // Given the id of a worker, obtain or calculate a suitable
2771 // starting region for iterating over the current collection set.
2772 HeapRegion* G1CollectedHeap::start_cset_region_for_worker(int worker_i) {
2773 assert(get_gc_time_stamp() > 0, "should have been updated by now");
2774
2775 HeapRegion* result = NULL;
2776 unsigned gc_time_stamp = get_gc_time_stamp();
2777
2778 if (_worker_cset_start_region_time_stamp[worker_i] == gc_time_stamp) {
2779 // Cached starting region for current worker was set
2780 // during the current pause - so it's valid.
2781 // Note: the cached starting heap region may be NULL
2782 // (when the collection set is empty).
2783 result = _worker_cset_start_region[worker_i];
2784 assert(result == NULL || result->in_collection_set(), "sanity");
2785 return result;
2786 }
2787
2788 // The cached entry was not valid so let's calculate
2789 // a suitable starting heap region for this worker.
2790
2791 // We want the parallel threads to start their collection
2792 // set iteration at different collection set regions to
2793 // avoid contention.
2794 // If we have:
2795 // n collection set regions
2796 // p threads
2797 // Then thread t will start at region floor ((t * n) / p)
2798
2799 result = g1_policy()->collection_set();
2800 if (G1CollectedHeap::use_parallel_gc_threads()) {
2801 uint cs_size = g1_policy()->cset_region_length();
2802 uint active_workers = workers()->active_workers();
2803 assert(UseDynamicNumberOfGCThreads ||
2804 active_workers == workers()->total_workers(),
2805 "Unless dynamic should use total workers");
2806
2807 uint end_ind = (cs_size * worker_i) / active_workers;
2808 uint start_ind = 0;
2809
2810 if (worker_i > 0 &&
2811 _worker_cset_start_region_time_stamp[worker_i - 1] == gc_time_stamp) {
2812 // Previous workers starting region is valid
2813 // so let's iterate from there
2814 start_ind = (cs_size * (worker_i - 1)) / active_workers;
2815 result = _worker_cset_start_region[worker_i - 1];
2816 }
2817
2818 for (uint i = start_ind; i < end_ind; i++) {
2819 result = result->next_in_collection_set();
2820 }
2821 }
2822
2823 // Note: the calculated starting heap region may be NULL
2824 // (when the collection set is empty).
2825 assert(result == NULL || result->in_collection_set(), "sanity");
2826 assert(_worker_cset_start_region_time_stamp[worker_i] != gc_time_stamp,
2827 "should be updated only once per pause");
2828 _worker_cset_start_region[worker_i] = result;
2829 OrderAccess::storestore();
2830 _worker_cset_start_region_time_stamp[worker_i] = gc_time_stamp;
2831 return result;
2832 }
2833
2834 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) {
2835 HeapRegion* r = g1_policy()->collection_set();
2836 while (r != NULL) {
2837 HeapRegion* next = r->next_in_collection_set();
2838 if (cl->doHeapRegion(r)) {
2839 cl->incomplete();
2840 return;
2841 }
2842 r = next;
2843 }
2844 }
2845
2846 void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r,
2847 HeapRegionClosure *cl) {
2848 if (r == NULL) {
2849 // The CSet is empty so there's nothing to do.
2850 return;
2851 }
2852
2853 assert(r->in_collection_set(),
2854 "Start region must be a member of the collection set.");
2855 HeapRegion* cur = r;
2856 while (cur != NULL) {
2857 HeapRegion* next = cur->next_in_collection_set();
2858 if (cl->doHeapRegion(cur) && false) {
2859 cl->incomplete();
2860 return;
2861 }
2862 cur = next;
2863 }
2864 cur = g1_policy()->collection_set();
2865 while (cur != r) {
2866 HeapRegion* next = cur->next_in_collection_set();
2867 if (cl->doHeapRegion(cur) && false) {
2868 cl->incomplete();
2869 return;
2870 }
2871 cur = next;
2872 }
2873 }
2874
2875 CompactibleSpace* G1CollectedHeap::first_compactible_space() {
2876 return n_regions() > 0 ? region_at(0) : NULL;
2877 }
2878
2879
2880 Space* G1CollectedHeap::space_containing(const void* addr) const {
2881 Space* res = heap_region_containing(addr);
2882 if (res == NULL)
2883 res = perm_gen()->space_containing(addr);
2884 return res;
2885 }
2886
2887 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2888 Space* sp = space_containing(addr);
2889 if (sp != NULL) {
2890 return sp->block_start(addr);
2891 }
2892 return NULL;
2893 }
2894
2895 size_t G1CollectedHeap::block_size(const HeapWord* addr) const {
2896 Space* sp = space_containing(addr);
2897 assert(sp != NULL, "block_size of address outside of heap");
2898 return sp->block_size(addr);
2899 }
2900
2901 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2902 Space* sp = space_containing(addr);
2903 return sp->block_is_obj(addr);
2904 }
2905
2906 bool G1CollectedHeap::supports_tlab_allocation() const {
2907 return true;
2908 }
2909
2910 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
2911 return HeapRegion::GrainBytes;
2912 }
2913
2914 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
2915 // Return the remaining space in the cur alloc region, but not less than
2916 // the min TLAB size.
2917
2918 // Also, this value can be at most the humongous object threshold,
2919 // since we can't allow tlabs to grow big enough to accomodate
2920 // humongous objects.
2921
2922 HeapRegion* hr = _mutator_alloc_region.get();
2923 size_t max_tlab_size = _humongous_object_threshold_in_words * wordSize;
2924 if (hr == NULL) {
2925 return max_tlab_size;
2926 } else {
2927 return MIN2(MAX2(hr->free(), (size_t) MinTLABSize), max_tlab_size);
2928 }
2929 }
2930
2931 size_t G1CollectedHeap::max_capacity() const {
2932 return _g1_reserved.byte_size();
2933 }
2934
2935 jlong G1CollectedHeap::millis_since_last_gc() {
2936 // assert(false, "NYI");
2937 return 0;
2938 }
2939
2940 void G1CollectedHeap::prepare_for_verify() {
2941 if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) {
2942 ensure_parsability(false);
2943 }
2944 g1_rem_set()->prepare_for_verify();
2945 }
2946
2947 class VerifyLivenessOopClosure: public OopClosure {
2948 G1CollectedHeap* _g1h;
2949 VerifyOption _vo;
2950 public:
2951 VerifyLivenessOopClosure(G1CollectedHeap* g1h, VerifyOption vo):
2952 _g1h(g1h), _vo(vo)
2953 { }
2954 void do_oop(narrowOop *p) { do_oop_work(p); }
2955 void do_oop( oop *p) { do_oop_work(p); }
2956
2957 template <class T> void do_oop_work(T *p) {
2958 oop obj = oopDesc::load_decode_heap_oop(p);
2959 guarantee(obj == NULL || !_g1h->is_obj_dead_cond(obj, _vo),
2960 "Dead object referenced by a not dead object");
2961 }
2962 };
2963
2964 class VerifyObjsInRegionClosure: public ObjectClosure {
2965 private:
2966 G1CollectedHeap* _g1h;
2967 size_t _live_bytes;
2968 HeapRegion *_hr;
2969 VerifyOption _vo;
2970 public:
2971 // _vo == UsePrevMarking -> use "prev" marking information,
2972 // _vo == UseNextMarking -> use "next" marking information,
2973 // _vo == UseMarkWord -> use mark word from object header.
2974 VerifyObjsInRegionClosure(HeapRegion *hr, VerifyOption vo)
2975 : _live_bytes(0), _hr(hr), _vo(vo) {
2976 _g1h = G1CollectedHeap::heap();
2977 }
2978 void do_object(oop o) {
2979 VerifyLivenessOopClosure isLive(_g1h, _vo);
2980 assert(o != NULL, "Huh?");
2981 if (!_g1h->is_obj_dead_cond(o, _vo)) {
2982 // If the object is alive according to the mark word,
2983 // then verify that the marking information agrees.
2984 // Note we can't verify the contra-positive of the
2985 // above: if the object is dead (according to the mark
2986 // word), it may not be marked, or may have been marked
2987 // but has since became dead, or may have been allocated
2988 // since the last marking.
2989 if (_vo == VerifyOption_G1UseMarkWord) {
2990 guarantee(!_g1h->is_obj_dead(o), "mark word and concurrent mark mismatch");
2991 }
2992
2993 o->oop_iterate(&isLive);
2994 if (!_hr->obj_allocated_since_prev_marking(o)) {
2995 size_t obj_size = o->size(); // Make sure we don't overflow
2996 _live_bytes += (obj_size * HeapWordSize);
2997 }
2998 }
2999 }
3000 size_t live_bytes() { return _live_bytes; }
3001 };
3002
3003 class PrintObjsInRegionClosure : public ObjectClosure {
3004 HeapRegion *_hr;
3005 G1CollectedHeap *_g1;
3006 public:
3007 PrintObjsInRegionClosure(HeapRegion *hr) : _hr(hr) {
3008 _g1 = G1CollectedHeap::heap();
3009 };
3010
3011 void do_object(oop o) {
3012 if (o != NULL) {
3013 HeapWord *start = (HeapWord *) o;
3014 size_t word_sz = o->size();
3015 gclog_or_tty->print("\nPrinting obj "PTR_FORMAT" of size " SIZE_FORMAT
3016 " isMarkedPrev %d isMarkedNext %d isAllocSince %d\n",
3017 (void*) o, word_sz,
3018 _g1->isMarkedPrev(o),
3019 _g1->isMarkedNext(o),
3020 _hr->obj_allocated_since_prev_marking(o));
3021 HeapWord *end = start + word_sz;
3022 HeapWord *cur;
3023 int *val;
3024 for (cur = start; cur < end; cur++) {
3025 val = (int *) cur;
3026 gclog_or_tty->print("\t "PTR_FORMAT":"PTR_FORMAT"\n", val, *val);
3027 }
3028 }
3029 }
3030 };
3031
3032 class VerifyRegionClosure: public HeapRegionClosure {
3033 private:
3034 bool _par;
3035 VerifyOption _vo;
3036 bool _failures;
3037 public:
3038 // _vo == UsePrevMarking -> use "prev" marking information,
3039 // _vo == UseNextMarking -> use "next" marking information,
3040 // _vo == UseMarkWord -> use mark word from object header.
3041 VerifyRegionClosure(bool par, VerifyOption vo)
3042 : _par(par),
3043 _vo(vo),
3044 _failures(false) {}
3045
3046 bool failures() {
3047 return _failures;
3048 }
3049
3050 bool doHeapRegion(HeapRegion* r) {
3051 guarantee(_par || r->claim_value() == HeapRegion::InitialClaimValue,
3052 "Should be unclaimed at verify points.");
3053 if (!r->continuesHumongous()) {
3054 bool failures = false;
3055 r->verify(_vo, &failures);
3056 if (failures) {
3057 _failures = true;
3058 } else {
3059 VerifyObjsInRegionClosure not_dead_yet_cl(r, _vo);
3060 r->object_iterate(¬_dead_yet_cl);
3061 if (_vo != VerifyOption_G1UseNextMarking) {
3062 if (r->max_live_bytes() < not_dead_yet_cl.live_bytes()) {
3063 gclog_or_tty->print_cr("["PTR_FORMAT","PTR_FORMAT"] "
3064 "max_live_bytes "SIZE_FORMAT" "
3065 "< calculated "SIZE_FORMAT,
3066 r->bottom(), r->end(),
3067 r->max_live_bytes(),
3068 not_dead_yet_cl.live_bytes());
3069 _failures = true;
3070 }
3071 } else {
3072 // When vo == UseNextMarking we cannot currently do a sanity
3073 // check on the live bytes as the calculation has not been
3074 // finalized yet.
3075 }
3076 }
3077 }
3078 return false; // stop the region iteration if we hit a failure
3079 }
3080 };
3081
3082 class VerifyRootsClosure: public OopsInGenClosure {
3083 private:
3084 G1CollectedHeap* _g1h;
3085 VerifyOption _vo;
3086 bool _failures;
3087 public:
3088 // _vo == UsePrevMarking -> use "prev" marking information,
3089 // _vo == UseNextMarking -> use "next" marking information,
3090 // _vo == UseMarkWord -> use mark word from object header.
3091 VerifyRootsClosure(VerifyOption vo) :
3092 _g1h(G1CollectedHeap::heap()),
3093 _vo(vo),
3094 _failures(false) { }
3095
3096 bool failures() { return _failures; }
3097
3098 template <class T> void do_oop_nv(T* p) {
3099 T heap_oop = oopDesc::load_heap_oop(p);
3100 if (!oopDesc::is_null(heap_oop)) {
3101 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
3102 if (_g1h->is_obj_dead_cond(obj, _vo)) {
3103 gclog_or_tty->print_cr("Root location "PTR_FORMAT" "
3104 "points to dead obj "PTR_FORMAT, p, (void*) obj);
3105 if (_vo == VerifyOption_G1UseMarkWord) {
3106 gclog_or_tty->print_cr(" Mark word: "PTR_FORMAT, (void*)(obj->mark()));
3107 }
3108 obj->print_on(gclog_or_tty);
3109 _failures = true;
3110 }
3111 }
3112 }
3113
3114 void do_oop(oop* p) { do_oop_nv(p); }
3115 void do_oop(narrowOop* p) { do_oop_nv(p); }
3116 };
3117
3118 // This is the task used for parallel heap verification.
3119
3120 class G1ParVerifyTask: public AbstractGangTask {
3121 private:
3122 G1CollectedHeap* _g1h;
3123 VerifyOption _vo;
3124 bool _failures;
3125
3126 public:
3127 // _vo == UsePrevMarking -> use "prev" marking information,
3128 // _vo == UseNextMarking -> use "next" marking information,
3129 // _vo == UseMarkWord -> use mark word from object header.
3130 G1ParVerifyTask(G1CollectedHeap* g1h, VerifyOption vo) :
3131 AbstractGangTask("Parallel verify task"),
3132 _g1h(g1h),
3133 _vo(vo),
3134 _failures(false) { }
3135
3136 bool failures() {
3137 return _failures;
3138 }
3139
3140 void work(uint worker_id) {
3141 HandleMark hm;
3142 VerifyRegionClosure blk(true, _vo);
3143 _g1h->heap_region_par_iterate_chunked(&blk, worker_id,
3144 _g1h->workers()->active_workers(),
3145 HeapRegion::ParVerifyClaimValue);
3146 if (blk.failures()) {
3147 _failures = true;
3148 }
3149 }
3150 };
3151
3152 void G1CollectedHeap::verify(bool silent) {
3153 verify(silent, VerifyOption_G1UsePrevMarking);
3154 }
3155
3156 void G1CollectedHeap::verify(bool silent,
3157 VerifyOption vo) {
3158 if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) {
3159 if (!silent) { gclog_or_tty->print("Roots (excluding permgen) "); }
3160 VerifyRootsClosure rootsCl(vo);
3161
3162 assert(Thread::current()->is_VM_thread(),
3163 "Expected to be executed serially by the VM thread at this point");
3164
3165 CodeBlobToOopClosure blobsCl(&rootsCl, /*do_marking=*/ false);
3166
3167 // We apply the relevant closures to all the oops in the
3168 // system dictionary, the string table and the code cache.
3169 const int so = SO_AllClasses | SO_Strings | SO_CodeCache;
3170
3171 process_strong_roots(true, // activate StrongRootsScope
3172 true, // we set "collecting perm gen" to true,
3173 // so we don't reset the dirty cards in the perm gen.
3174 ScanningOption(so), // roots scanning options
3175 &rootsCl,
3176 &blobsCl,
3177 &rootsCl);
3178
3179 // If we're verifying after the marking phase of a Full GC then we can't
3180 // treat the perm gen as roots into the G1 heap. Some of the objects in
3181 // the perm gen may be dead and hence not marked. If one of these dead
3182 // objects is considered to be a root then we may end up with a false
3183 // "Root location <x> points to dead ob <y>" failure.
3184 if (vo != VerifyOption_G1UseMarkWord) {
3185 // Since we used "collecting_perm_gen" == true above, we will not have
3186 // checked the refs from perm into the G1-collected heap. We check those
3187 // references explicitly below. Whether the relevant cards are dirty
3188 // is checked further below in the rem set verification.
3189 if (!silent) { gclog_or_tty->print("Permgen roots "); }
3190 perm_gen()->oop_iterate(&rootsCl);
3191 }
3192 bool failures = rootsCl.failures();
3193
3194 if (vo != VerifyOption_G1UseMarkWord) {
3195 // If we're verifying during a full GC then the region sets
3196 // will have been torn down at the start of the GC. Therefore
3197 // verifying the region sets will fail. So we only verify
3198 // the region sets when not in a full GC.
3199 if (!silent) { gclog_or_tty->print("HeapRegionSets "); }
3200 verify_region_sets();
3201 }
3202
3203 if (!silent) { gclog_or_tty->print("HeapRegions "); }
3204 if (GCParallelVerificationEnabled && ParallelGCThreads > 1) {
3205 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3206 "sanity check");
3207
3208 G1ParVerifyTask task(this, vo);
3209 assert(UseDynamicNumberOfGCThreads ||
3210 workers()->active_workers() == workers()->total_workers(),
3211 "If not dynamic should be using all the workers");
3212 int n_workers = workers()->active_workers();
3213 set_par_threads(n_workers);
3214 workers()->run_task(&task);
3215 set_par_threads(0);
3216 if (task.failures()) {
3217 failures = true;
3218 }
3219
3220 // Checks that the expected amount of parallel work was done.
3221 // The implication is that n_workers is > 0.
3222 assert(check_heap_region_claim_values(HeapRegion::ParVerifyClaimValue),
3223 "sanity check");
3224
3225 reset_heap_region_claim_values();
3226
3227 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3228 "sanity check");
3229 } else {
3230 VerifyRegionClosure blk(false, vo);
3231 heap_region_iterate(&blk);
3232 if (blk.failures()) {
3233 failures = true;
3234 }
3235 }
3236 if (!silent) gclog_or_tty->print("RemSet ");
3237 rem_set()->verify();
3238
3239 if (failures) {
3240 gclog_or_tty->print_cr("Heap:");
3241 // It helps to have the per-region information in the output to
3242 // help us track down what went wrong. This is why we call
3243 // print_extended_on() instead of print_on().
3244 print_extended_on(gclog_or_tty);
3245 gclog_or_tty->print_cr("");
3246 #ifndef PRODUCT
3247 if (VerifyDuringGC && G1VerifyDuringGCPrintReachable) {
3248 concurrent_mark()->print_reachable("at-verification-failure",
3249 vo, false /* all */);
3250 }
3251 #endif
3252 gclog_or_tty->flush();
3253 }
3254 guarantee(!failures, "there should not have been any failures");
3255 } else {
3256 if (!silent) gclog_or_tty->print("(SKIPPING roots, heapRegions, remset) ");
3257 }
3258 }
3259
3260 class PrintRegionClosure: public HeapRegionClosure {
3261 outputStream* _st;
3262 public:
3263 PrintRegionClosure(outputStream* st) : _st(st) {}
3264 bool doHeapRegion(HeapRegion* r) {
3265 r->print_on(_st);
3266 return false;
3267 }
3268 };
3269
3270 void G1CollectedHeap::print_on(outputStream* st) const {
3271 st->print(" %-20s", "garbage-first heap");
3272 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
3273 capacity()/K, used_unlocked()/K);
3274 st->print(" [" INTPTR_FORMAT ", " INTPTR_FORMAT ", " INTPTR_FORMAT ")",
3275 _g1_storage.low_boundary(),
3276 _g1_storage.high(),
3277 _g1_storage.high_boundary());
3278 st->cr();
3279 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
3280 uint young_regions = _young_list->length();
3281 st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
3282 (size_t) young_regions * HeapRegion::GrainBytes / K);
3283 uint survivor_regions = g1_policy()->recorded_survivor_regions();
3284 st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
3285 (size_t) survivor_regions * HeapRegion::GrainBytes / K);
3286 st->cr();
3287 perm()->as_gen()->print_on(st);
3288 }
3289
3290 void G1CollectedHeap::print_extended_on(outputStream* st) const {
3291 print_on(st);
3292
3293 // Print the per-region information.
3294 st->cr();
3295 st->print_cr("Heap Regions: (Y=young(eden), SU=young(survivor), "
3296 "HS=humongous(starts), HC=humongous(continues), "
3297 "CS=collection set, F=free, TS=gc time stamp, "
3298 "PTAMS=previous top-at-mark-start, "
3299 "NTAMS=next top-at-mark-start)");
3300 PrintRegionClosure blk(st);
3301 heap_region_iterate(&blk);
3302 }
3303
3304 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
3305 if (G1CollectedHeap::use_parallel_gc_threads()) {
3306 workers()->print_worker_threads_on(st);
3307 }
3308 _cmThread->print_on(st);
3309 st->cr();
3310 _cm->print_worker_threads_on(st);
3311 _cg1r->print_worker_threads_on(st);
3312 st->cr();
3313 }
3314
3315 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
3316 if (G1CollectedHeap::use_parallel_gc_threads()) {
3317 workers()->threads_do(tc);
3318 }
3319 tc->do_thread(_cmThread);
3320 _cg1r->threads_do(tc);
3321 }
3322
3323 void G1CollectedHeap::print_tracing_info() const {
3324 // We'll overload this to mean "trace GC pause statistics."
3325 if (TraceGen0Time || TraceGen1Time) {
3326 // The "G1CollectorPolicy" is keeping track of these stats, so delegate
3327 // to that.
3328 g1_policy()->print_tracing_info();
3329 }
3330 if (G1SummarizeRSetStats) {
3331 g1_rem_set()->print_summary_info();
3332 }
3333 if (G1SummarizeConcMark) {
3334 concurrent_mark()->print_summary_info();
3335 }
3336 g1_policy()->print_yg_surv_rate_info();
3337 SpecializationStats::print();
3338 }
3339
3340 #ifndef PRODUCT
3341 // Helpful for debugging RSet issues.
3342
3343 class PrintRSetsClosure : public HeapRegionClosure {
3344 private:
3345 const char* _msg;
3346 size_t _occupied_sum;
3347
3348 public:
3349 bool doHeapRegion(HeapRegion* r) {
3350 HeapRegionRemSet* hrrs = r->rem_set();
3351 size_t occupied = hrrs->occupied();
3352 _occupied_sum += occupied;
3353
3354 gclog_or_tty->print_cr("Printing RSet for region "HR_FORMAT,
3355 HR_FORMAT_PARAMS(r));
3356 if (occupied == 0) {
3357 gclog_or_tty->print_cr(" RSet is empty");
3358 } else {
3359 hrrs->print();
3360 }
3361 gclog_or_tty->print_cr("----------");
3362 return false;
3363 }
3364
3365 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
3366 gclog_or_tty->cr();
3367 gclog_or_tty->print_cr("========================================");
3368 gclog_or_tty->print_cr(msg);
3369 gclog_or_tty->cr();
3370 }
3371
3372 ~PrintRSetsClosure() {
3373 gclog_or_tty->print_cr("Occupied Sum: "SIZE_FORMAT, _occupied_sum);
3374 gclog_or_tty->print_cr("========================================");
3375 gclog_or_tty->cr();
3376 }
3377 };
3378
3379 void G1CollectedHeap::print_cset_rsets() {
3380 PrintRSetsClosure cl("Printing CSet RSets");
3381 collection_set_iterate(&cl);
3382 }
3383
3384 void G1CollectedHeap::print_all_rsets() {
3385 PrintRSetsClosure cl("Printing All RSets");;
3386 heap_region_iterate(&cl);
3387 }
3388 #endif // PRODUCT
3389
3390 G1CollectedHeap* G1CollectedHeap::heap() {
3391 assert(_sh->kind() == CollectedHeap::G1CollectedHeap,
3392 "not a garbage-first heap");
3393 return _g1h;
3394 }
3395
3396 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) {
3397 // always_do_update_barrier = false;
3398 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
3399 // Call allocation profiler
3400 AllocationProfiler::iterate_since_last_gc();
3401 // Fill TLAB's and such
3402 ensure_parsability(true);
3403 }
3404
3405 void G1CollectedHeap::gc_epilogue(bool full /* Ignored */) {
3406 // FIXME: what is this about?
3407 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
3408 // is set.
3409 COMPILER2_PRESENT(assert(DerivedPointerTable::is_empty(),
3410 "derived pointer present"));
3411 // always_do_update_barrier = true;
3412
3413 // We have just completed a GC. Update the soft reference
3414 // policy with the new heap occupancy
3415 Universe::update_heap_info_at_gc();
3416 }
3417
3418 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
3419 unsigned int gc_count_before,
3420 bool* succeeded) {
3421 assert_heap_not_locked_and_not_at_safepoint();
3422 g1_policy()->record_stop_world_start();
3423 VM_G1IncCollectionPause op(gc_count_before,
3424 word_size,
3425 false, /* should_initiate_conc_mark */
3426 g1_policy()->max_pause_time_ms(),
3427 GCCause::_g1_inc_collection_pause);
3428 VMThread::execute(&op);
3429
3430 HeapWord* result = op.result();
3431 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
3432 assert(result == NULL || ret_succeeded,
3433 "the result should be NULL if the VM did not succeed");
3434 *succeeded = ret_succeeded;
3435
3436 assert_heap_not_locked();
3437 return result;
3438 }
3439
3440 void
3441 G1CollectedHeap::doConcurrentMark() {
3442 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
3443 if (!_cmThread->in_progress()) {
3444 _cmThread->set_started();
3445 CGC_lock->notify();
3446 }
3447 }
3448
3449 size_t G1CollectedHeap::pending_card_num() {
3450 size_t extra_cards = 0;
3451 JavaThread *curr = Threads::first();
3452 while (curr != NULL) {
3453 DirtyCardQueue& dcq = curr->dirty_card_queue();
3454 extra_cards += dcq.size();
3455 curr = curr->next();
3456 }
3457 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
3458 size_t buffer_size = dcqs.buffer_size();
3459 size_t buffer_num = dcqs.completed_buffers_num();
3460 return buffer_size * buffer_num + extra_cards;
3461 }
3462
3463 size_t G1CollectedHeap::max_pending_card_num() {
3464 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
3465 size_t buffer_size = dcqs.buffer_size();
3466 size_t buffer_num = dcqs.completed_buffers_num();
3467 int thread_num = Threads::number_of_threads();
3468 return (buffer_num + thread_num) * buffer_size;
3469 }
3470
3471 size_t G1CollectedHeap::cards_scanned() {
3472 return g1_rem_set()->cardsScanned();
3473 }
3474
3475 void
3476 G1CollectedHeap::setup_surviving_young_words() {
3477 assert(_surviving_young_words == NULL, "pre-condition");
3478 uint array_length = g1_policy()->young_cset_region_length();
3479 _surviving_young_words = NEW_C_HEAP_ARRAY(size_t, (size_t) array_length);
3480 if (_surviving_young_words == NULL) {
3481 vm_exit_out_of_memory(sizeof(size_t) * array_length,
3482 "Not enough space for young surv words summary.");
3483 }
3484 memset(_surviving_young_words, 0, (size_t) array_length * sizeof(size_t));
3485 #ifdef ASSERT
3486 for (uint i = 0; i < array_length; ++i) {
3487 assert( _surviving_young_words[i] == 0, "memset above" );
3488 }
3489 #endif // !ASSERT
3490 }
3491
3492 void
3493 G1CollectedHeap::update_surviving_young_words(size_t* surv_young_words) {
3494 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
3495 uint array_length = g1_policy()->young_cset_region_length();
3496 for (uint i = 0; i < array_length; ++i) {
3497 _surviving_young_words[i] += surv_young_words[i];
3498 }
3499 }
3500
3501 void
3502 G1CollectedHeap::cleanup_surviving_young_words() {
3503 guarantee( _surviving_young_words != NULL, "pre-condition" );
3504 FREE_C_HEAP_ARRAY(size_t, _surviving_young_words);
3505 _surviving_young_words = NULL;
3506 }
3507
3508 #ifdef ASSERT
3509 class VerifyCSetClosure: public HeapRegionClosure {
3510 public:
3511 bool doHeapRegion(HeapRegion* hr) {
3512 // Here we check that the CSet region's RSet is ready for parallel
3513 // iteration. The fields that we'll verify are only manipulated
3514 // when the region is part of a CSet and is collected. Afterwards,
3515 // we reset these fields when we clear the region's RSet (when the
3516 // region is freed) so they are ready when the region is
3517 // re-allocated. The only exception to this is if there's an
3518 // evacuation failure and instead of freeing the region we leave
3519 // it in the heap. In that case, we reset these fields during
3520 // evacuation failure handling.
3521 guarantee(hr->rem_set()->verify_ready_for_par_iteration(), "verification");
3522
3523 // Here's a good place to add any other checks we'd like to
3524 // perform on CSet regions.
3525 return false;
3526 }
3527 };
3528 #endif // ASSERT
3529
3530 #if TASKQUEUE_STATS
3531 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
3532 st->print_raw_cr("GC Task Stats");
3533 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
3534 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
3535 }
3536
3537 void G1CollectedHeap::print_taskqueue_stats(outputStream* const st) const {
3538 print_taskqueue_stats_hdr(st);
3539
3540 TaskQueueStats totals;
3541 const int n = workers() != NULL ? workers()->total_workers() : 1;
3542 for (int i = 0; i < n; ++i) {
3543 st->print("%3d ", i); task_queue(i)->stats.print(st); st->cr();
3544 totals += task_queue(i)->stats;
3545 }
3546 st->print_raw("tot "); totals.print(st); st->cr();
3547
3548 DEBUG_ONLY(totals.verify());
3549 }
3550
3551 void G1CollectedHeap::reset_taskqueue_stats() {
3552 const int n = workers() != NULL ? workers()->total_workers() : 1;
3553 for (int i = 0; i < n; ++i) {
3554 task_queue(i)->stats.reset();
3555 }
3556 }
3557 #endif // TASKQUEUE_STATS
3558
3559 bool
3560 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
3561 assert_at_safepoint(true /* should_be_vm_thread */);
3562 guarantee(!is_gc_active(), "collection is not reentrant");
3563
3564 if (GC_locker::check_active_before_gc()) {
3565 return false;
3566 }
3567
3568 SvcGCMarker sgcm(SvcGCMarker::MINOR);
3569 ResourceMark rm;
3570
3571 print_heap_before_gc();
3572
3573 HRSPhaseSetter x(HRSPhaseEvacuation);
3574 verify_region_sets_optional();
3575 verify_dirty_young_regions();
3576
3577 // This call will decide whether this pause is an initial-mark
3578 // pause. If it is, during_initial_mark_pause() will return true
3579 // for the duration of this pause.
3580 g1_policy()->decide_on_conc_mark_initiation();
3581
3582 // We do not allow initial-mark to be piggy-backed on a mixed GC.
3583 assert(!g1_policy()->during_initial_mark_pause() ||
3584 g1_policy()->gcs_are_young(), "sanity");
3585
3586 // We also do not allow mixed GCs during marking.
3587 assert(!mark_in_progress() || g1_policy()->gcs_are_young(), "sanity");
3588
3589 // Record whether this pause is an initial mark. When the current
3590 // thread has completed its logging output and it's safe to signal
3591 // the CM thread, the flag's value in the policy has been reset.
3592 bool should_start_conc_mark = g1_policy()->during_initial_mark_pause();
3593
3594 // Inner scope for scope based logging, timers, and stats collection
3595 {
3596 char verbose_str[128];
3597 sprintf(verbose_str, "GC pause ");
3598 if (g1_policy()->gcs_are_young()) {
3599 strcat(verbose_str, "(young)");
3600 } else {
3601 strcat(verbose_str, "(mixed)");
3602 }
3603 if (g1_policy()->during_initial_mark_pause()) {
3604 strcat(verbose_str, " (initial-mark)");
3605 // We are about to start a marking cycle, so we increment the
3606 // full collection counter.
3607 increment_total_full_collections();
3608 }
3609
3610 // if the log level is "finer" is on, we'll print long statistics information
3611 // in the collector policy code, so let's not print this as the output
3612 // is messy if we do.
3613 gclog_or_tty->date_stamp(G1Log::fine() && PrintGCDateStamps);
3614 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
3615 TraceTime t(verbose_str, G1Log::fine() && !G1Log::finer(), true, gclog_or_tty);
3616
3617 TraceCollectorStats tcs(g1mm()->incremental_collection_counters());
3618 TraceMemoryManagerStats tms(false /* fullGC */, gc_cause());
3619
3620 // If the secondary_free_list is not empty, append it to the
3621 // free_list. No need to wait for the cleanup operation to finish;
3622 // the region allocation code will check the secondary_free_list
3623 // and wait if necessary. If the G1StressConcRegionFreeing flag is
3624 // set, skip this step so that the region allocation code has to
3625 // get entries from the secondary_free_list.
3626 if (!G1StressConcRegionFreeing) {
3627 append_secondary_free_list_if_not_empty_with_lock();
3628 }
3629
3630 assert(check_young_list_well_formed(),
3631 "young list should be well formed");
3632
3633 // Don't dynamically change the number of GC threads this early. A value of
3634 // 0 is used to indicate serial work. When parallel work is done,
3635 // it will be set.
3636
3637 { // Call to jvmpi::post_class_unload_events must occur outside of active GC
3638 IsGCActiveMark x;
3639
3640 gc_prologue(false);
3641 increment_total_collections(false /* full gc */);
3642 increment_gc_time_stamp();
3643
3644 if (VerifyBeforeGC && total_collections() >= VerifyGCStartAt) {
3645 HandleMark hm; // Discard invalid handles created during verification
3646 gclog_or_tty->print(" VerifyBeforeGC:");
3647 prepare_for_verify();
3648 Universe::verify(/* silent */ false,
3649 /* option */ VerifyOption_G1UsePrevMarking);
3650 }
3651
3652 COMPILER2_PRESENT(DerivedPointerTable::clear());
3653
3654 // Please see comment in g1CollectedHeap.hpp and
3655 // G1CollectedHeap::ref_processing_init() to see how
3656 // reference processing currently works in G1.
3657
3658 // Enable discovery in the STW reference processor
3659 ref_processor_stw()->enable_discovery(true /*verify_disabled*/,
3660 true /*verify_no_refs*/);
3661
3662 {
3663 // We want to temporarily turn off discovery by the
3664 // CM ref processor, if necessary, and turn it back on
3665 // on again later if we do. Using a scoped
3666 // NoRefDiscovery object will do this.
3667 NoRefDiscovery no_cm_discovery(ref_processor_cm());
3668
3669 // Forget the current alloc region (we might even choose it to be part
3670 // of the collection set!).
3671 release_mutator_alloc_region();
3672
3673 // We should call this after we retire the mutator alloc
3674 // region(s) so that all the ALLOC / RETIRE events are generated
3675 // before the start GC event.
3676 _hr_printer.start_gc(false /* full */, (size_t) total_collections());
3677
3678 // The elapsed time induced by the start time below deliberately elides
3679 // the possible verification above.
3680 double start_time_sec = os::elapsedTime();
3681 size_t start_used_bytes = used();
3682
3683 #if YOUNG_LIST_VERBOSE
3684 gclog_or_tty->print_cr("\nBefore recording pause start.\nYoung_list:");
3685 _young_list->print();
3686 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3687 #endif // YOUNG_LIST_VERBOSE
3688
3689 g1_policy()->record_collection_pause_start(start_time_sec,
3690 start_used_bytes);
3691
3692 double scan_wait_start = os::elapsedTime();
3693 // We have to wait until the CM threads finish scanning the
3694 // root regions as it's the only way to ensure that all the
3695 // objects on them have been correctly scanned before we start
3696 // moving them during the GC.
3697 bool waited = _cm->root_regions()->wait_until_scan_finished();
3698 if (waited) {
3699 double scan_wait_end = os::elapsedTime();
3700 double wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
3701 g1_policy()->record_root_region_scan_wait_time(wait_time_ms);
3702 }
3703
3704 #if YOUNG_LIST_VERBOSE
3705 gclog_or_tty->print_cr("\nAfter recording pause start.\nYoung_list:");
3706 _young_list->print();
3707 #endif // YOUNG_LIST_VERBOSE
3708
3709 if (g1_policy()->during_initial_mark_pause()) {
3710 concurrent_mark()->checkpointRootsInitialPre();
3711 }
3712 perm_gen()->save_marks();
3713
3714 #if YOUNG_LIST_VERBOSE
3715 gclog_or_tty->print_cr("\nBefore choosing collection set.\nYoung_list:");
3716 _young_list->print();
3717 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3718 #endif // YOUNG_LIST_VERBOSE
3719
3720 g1_policy()->finalize_cset(target_pause_time_ms);
3721
3722 _cm->note_start_of_gc();
3723 // We should not verify the per-thread SATB buffers given that
3724 // we have not filtered them yet (we'll do so during the
3725 // GC). We also call this after finalize_cset() to
3726 // ensure that the CSet has been finalized.
3727 _cm->verify_no_cset_oops(true /* verify_stacks */,
3728 true /* verify_enqueued_buffers */,
3729 false /* verify_thread_buffers */,
3730 true /* verify_fingers */);
3731
3732 if (_hr_printer.is_active()) {
3733 HeapRegion* hr = g1_policy()->collection_set();
3734 while (hr != NULL) {
3735 G1HRPrinter::RegionType type;
3736 if (!hr->is_young()) {
3737 type = G1HRPrinter::Old;
3738 } else if (hr->is_survivor()) {
3739 type = G1HRPrinter::Survivor;
3740 } else {
3741 type = G1HRPrinter::Eden;
3742 }
3743 _hr_printer.cset(hr);
3744 hr = hr->next_in_collection_set();
3745 }
3746 }
3747
3748 #ifdef ASSERT
3749 VerifyCSetClosure cl;
3750 collection_set_iterate(&cl);
3751 #endif // ASSERT
3752
3753 setup_surviving_young_words();
3754
3755 // Initialize the GC alloc regions.
3756 init_gc_alloc_regions();
3757
3758 // Actually do the work...
3759 evacuate_collection_set();
3760
3761 // We do this to mainly verify the per-thread SATB buffers
3762 // (which have been filtered by now) since we didn't verify
3763 // them earlier. No point in re-checking the stacks / enqueued
3764 // buffers given that the CSet has not changed since last time
3765 // we checked.
3766 _cm->verify_no_cset_oops(false /* verify_stacks */,
3767 false /* verify_enqueued_buffers */,
3768 true /* verify_thread_buffers */,
3769 true /* verify_fingers */);
3770
3771 free_collection_set(g1_policy()->collection_set());
3772 g1_policy()->clear_collection_set();
3773
3774 cleanup_surviving_young_words();
3775
3776 // Start a new incremental collection set for the next pause.
3777 g1_policy()->start_incremental_cset_building();
3778
3779 // Clear the _cset_fast_test bitmap in anticipation of adding
3780 // regions to the incremental collection set for the next
3781 // evacuation pause.
3782 clear_cset_fast_test();
3783
3784 _young_list->reset_sampled_info();
3785
3786 // Don't check the whole heap at this point as the
3787 // GC alloc regions from this pause have been tagged
3788 // as survivors and moved on to the survivor list.
3789 // Survivor regions will fail the !is_young() check.
3790 assert(check_young_list_empty(false /* check_heap */),
3791 "young list should be empty");
3792
3793 #if YOUNG_LIST_VERBOSE
3794 gclog_or_tty->print_cr("Before recording survivors.\nYoung List:");
3795 _young_list->print();
3796 #endif // YOUNG_LIST_VERBOSE
3797
3798 g1_policy()->record_survivor_regions(_young_list->survivor_length(),
3799 _young_list->first_survivor_region(),
3800 _young_list->last_survivor_region());
3801
3802 _young_list->reset_auxilary_lists();
3803
3804 if (evacuation_failed()) {
3805 _summary_bytes_used = recalculate_used();
3806 } else {
3807 // The "used" of the the collection set have already been subtracted
3808 // when they were freed. Add in the bytes evacuated.
3809 _summary_bytes_used += g1_policy()->bytes_copied_during_gc();
3810 }
3811
3812 if (g1_policy()->during_initial_mark_pause()) {
3813 // We have to do this before we notify the CM threads that
3814 // they can start working to make sure that all the
3815 // appropriate initialization is done on the CM object.
3816 concurrent_mark()->checkpointRootsInitialPost();
3817 set_marking_started();
3818 // Note that we don't actually trigger the CM thread at
3819 // this point. We do that later when we're sure that
3820 // the current thread has completed its logging output.
3821 }
3822
3823 allocate_dummy_regions();
3824
3825 #if YOUNG_LIST_VERBOSE
3826 gclog_or_tty->print_cr("\nEnd of the pause.\nYoung_list:");
3827 _young_list->print();
3828 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3829 #endif // YOUNG_LIST_VERBOSE
3830
3831 init_mutator_alloc_region();
3832
3833 {
3834 size_t expand_bytes = g1_policy()->expansion_amount();
3835 if (expand_bytes > 0) {
3836 size_t bytes_before = capacity();
3837 // No need for an ergo verbose message here,
3838 // expansion_amount() does this when it returns a value > 0.
3839 if (!expand(expand_bytes)) {
3840 // We failed to expand the heap so let's verify that
3841 // committed/uncommitted amount match the backing store
3842 assert(capacity() == _g1_storage.committed_size(), "committed size mismatch");
3843 assert(max_capacity() == _g1_storage.reserved_size(), "reserved size mismatch");
3844 }
3845 }
3846 }
3847
3848 // We redo the verificaiton but now wrt to the new CSet which
3849 // has just got initialized after the previous CSet was freed.
3850 _cm->verify_no_cset_oops(true /* verify_stacks */,
3851 true /* verify_enqueued_buffers */,
3852 true /* verify_thread_buffers */,
3853 true /* verify_fingers */);
3854 _cm->note_end_of_gc();
3855
3856 double end_time_sec = os::elapsedTime();
3857 double pause_time_ms = (end_time_sec - start_time_sec) * MILLIUNITS;
3858 g1_policy()->record_pause_time_ms(pause_time_ms);
3859 int active_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
3860 workers()->active_workers() : 1);
3861 g1_policy()->record_collection_pause_end(active_workers);
3862
3863 MemoryService::track_memory_usage();
3864
3865 // In prepare_for_verify() below we'll need to scan the deferred
3866 // update buffers to bring the RSets up-to-date if
3867 // G1HRRSFlushLogBuffersOnVerify has been set. While scanning
3868 // the update buffers we'll probably need to scan cards on the
3869 // regions we just allocated to (i.e., the GC alloc
3870 // regions). However, during the last GC we called
3871 // set_saved_mark() on all the GC alloc regions, so card
3872 // scanning might skip the [saved_mark_word()...top()] area of
3873 // those regions (i.e., the area we allocated objects into
3874 // during the last GC). But it shouldn't. Given that
3875 // saved_mark_word() is conditional on whether the GC time stamp
3876 // on the region is current or not, by incrementing the GC time
3877 // stamp here we invalidate all the GC time stamps on all the
3878 // regions and saved_mark_word() will simply return top() for
3879 // all the regions. This is a nicer way of ensuring this rather
3880 // than iterating over the regions and fixing them. In fact, the
3881 // GC time stamp increment here also ensures that
3882 // saved_mark_word() will return top() between pauses, i.e.,
3883 // during concurrent refinement. So we don't need the
3884 // is_gc_active() check to decided which top to use when
3885 // scanning cards (see CR 7039627).
3886 increment_gc_time_stamp();
3887
3888 if (VerifyAfterGC && total_collections() >= VerifyGCStartAt) {
3889 HandleMark hm; // Discard invalid handles created during verification
3890 gclog_or_tty->print(" VerifyAfterGC:");
3891 prepare_for_verify();
3892 Universe::verify(/* silent */ false,
3893 /* option */ VerifyOption_G1UsePrevMarking);
3894 }
3895
3896 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
3897 ref_processor_stw()->verify_no_references_recorded();
3898
3899 // CM reference discovery will be re-enabled if necessary.
3900 }
3901
3902 // We should do this after we potentially expand the heap so
3903 // that all the COMMIT events are generated before the end GC
3904 // event, and after we retire the GC alloc regions so that all
3905 // RETIRE events are generated before the end GC event.
3906 _hr_printer.end_gc(false /* full */, (size_t) total_collections());
3907
3908 // We have to do this after we decide whether to expand the heap or not.
3909 g1_policy()->print_heap_transition();
3910
3911 if (mark_in_progress()) {
3912 concurrent_mark()->update_g1_committed();
3913 }
3914
3915 #ifdef TRACESPINNING
3916 ParallelTaskTerminator::print_termination_counts();
3917 #endif
3918
3919 gc_epilogue(false);
3920 }
3921
3922 if (ExitAfterGCNum > 0 && total_collections() == ExitAfterGCNum) {
3923 gclog_or_tty->print_cr("Stopping after GC #%d", ExitAfterGCNum);
3924 print_tracing_info();
3925 vm_exit(-1);
3926 }
3927 }
3928
3929 // The closing of the inner scope, immediately above, will complete
3930 // logging at the "fine" level. The record_collection_pause_end() call
3931 // above will complete logging at the "finer" level.
3932 //
3933 // It is not yet to safe, however, to tell the concurrent mark to
3934 // start as we have some optional output below. We don't want the
3935 // output from the concurrent mark thread interfering with this
3936 // logging output either.
3937
3938 _hrs.verify_optional();
3939 verify_region_sets_optional();
3940
3941 TASKQUEUE_STATS_ONLY(if (ParallelGCVerbose) print_taskqueue_stats());
3942 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
3943
3944 print_heap_after_gc();
3945 g1mm()->update_sizes();
3946
3947 if (G1SummarizeRSetStats &&
3948 (G1SummarizeRSetStatsPeriod > 0) &&
3949 (total_collections() % G1SummarizeRSetStatsPeriod == 0)) {
3950 g1_rem_set()->print_summary_info();
3951 }
3952
3953 // It should now be safe to tell the concurrent mark thread to start
3954 // without its logging output interfering with the logging output
3955 // that came from the pause.
3956
3957 if (should_start_conc_mark) {
3958 // CAUTION: after the doConcurrentMark() call below,
3959 // the concurrent marking thread(s) could be running
3960 // concurrently with us. Make sure that anything after
3961 // this point does not assume that we are the only GC thread
3962 // running. Note: of course, the actual marking work will
3963 // not start until the safepoint itself is released in
3964 // ConcurrentGCThread::safepoint_desynchronize().
3965 doConcurrentMark();
3966 }
3967
3968 return true;
3969 }
3970
3971 size_t G1CollectedHeap::desired_plab_sz(GCAllocPurpose purpose)
3972 {
3973 size_t gclab_word_size;
3974 switch (purpose) {
3975 case GCAllocForSurvived:
3976 gclab_word_size = YoungPLABSize;
3977 break;
3978 case GCAllocForTenured:
3979 gclab_word_size = OldPLABSize;
3980 break;
3981 default:
3982 assert(false, "unknown GCAllocPurpose");
3983 gclab_word_size = OldPLABSize;
3984 break;
3985 }
3986 return gclab_word_size;
3987 }
3988
3989 void G1CollectedHeap::init_mutator_alloc_region() {
3990 assert(_mutator_alloc_region.get() == NULL, "pre-condition");
3991 _mutator_alloc_region.init();
3992 }
3993
3994 void G1CollectedHeap::release_mutator_alloc_region() {
3995 _mutator_alloc_region.release();
3996 assert(_mutator_alloc_region.get() == NULL, "post-condition");
3997 }
3998
3999 void G1CollectedHeap::init_gc_alloc_regions() {
4000 assert_at_safepoint(true /* should_be_vm_thread */);
4001
4002 _survivor_gc_alloc_region.init();
4003 _old_gc_alloc_region.init();
4004 HeapRegion* retained_region = _retained_old_gc_alloc_region;
4005 _retained_old_gc_alloc_region = NULL;
4006
4007 // We will discard the current GC alloc region if:
4008 // a) it's in the collection set (it can happen!),
4009 // b) it's already full (no point in using it),
4010 // c) it's empty (this means that it was emptied during
4011 // a cleanup and it should be on the free list now), or
4012 // d) it's humongous (this means that it was emptied
4013 // during a cleanup and was added to the free list, but
4014 // has been subseqently used to allocate a humongous
4015 // object that may be less than the region size).
4016 if (retained_region != NULL &&
4017 !retained_region->in_collection_set() &&
4018 !(retained_region->top() == retained_region->end()) &&
4019 !retained_region->is_empty() &&
4020 !retained_region->isHumongous()) {
4021 retained_region->set_saved_mark();
4022 // The retained region was added to the old region set when it was
4023 // retired. We have to remove it now, since we don't allow regions
4024 // we allocate to in the region sets. We'll re-add it later, when
4025 // it's retired again.
4026 _old_set.remove(retained_region);
4027 bool during_im = g1_policy()->during_initial_mark_pause();
4028 retained_region->note_start_of_copying(during_im);
4029 _old_gc_alloc_region.set(retained_region);
4030 _hr_printer.reuse(retained_region);
4031 }
4032 }
4033
4034 void G1CollectedHeap::release_gc_alloc_regions() {
4035 _survivor_gc_alloc_region.release();
4036 // If we have an old GC alloc region to release, we'll save it in
4037 // _retained_old_gc_alloc_region. If we don't
4038 // _retained_old_gc_alloc_region will become NULL. This is what we
4039 // want either way so no reason to check explicitly for either
4040 // condition.
4041 _retained_old_gc_alloc_region = _old_gc_alloc_region.release();
4042 }
4043
4044 void G1CollectedHeap::abandon_gc_alloc_regions() {
4045 assert(_survivor_gc_alloc_region.get() == NULL, "pre-condition");
4046 assert(_old_gc_alloc_region.get() == NULL, "pre-condition");
4047 _retained_old_gc_alloc_region = NULL;
4048 }
4049
4050 void G1CollectedHeap::init_for_evac_failure(OopsInHeapRegionClosure* cl) {
4051 _drain_in_progress = false;
4052 set_evac_failure_closure(cl);
4053 _evac_failure_scan_stack = new (ResourceObj::C_HEAP) GrowableArray<oop>(40, true);
4054 }
4055
4056 void G1CollectedHeap::finalize_for_evac_failure() {
4057 assert(_evac_failure_scan_stack != NULL &&
4058 _evac_failure_scan_stack->length() == 0,
4059 "Postcondition");
4060 assert(!_drain_in_progress, "Postcondition");
4061 delete _evac_failure_scan_stack;
4062 _evac_failure_scan_stack = NULL;
4063 }
4064
4065 void G1CollectedHeap::remove_self_forwarding_pointers() {
4066 assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity");
4067
4068 G1ParRemoveSelfForwardPtrsTask rsfp_task(this);
4069
4070 if (G1CollectedHeap::use_parallel_gc_threads()) {
4071 set_par_threads();
4072 workers()->run_task(&rsfp_task);
4073 set_par_threads(0);
4074 } else {
4075 rsfp_task.work(0);
4076 }
4077
4078 assert(check_cset_heap_region_claim_values(HeapRegion::ParEvacFailureClaimValue), "sanity");
4079
4080 // Reset the claim values in the regions in the collection set.
4081 reset_cset_heap_region_claim_values();
4082
4083 assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity");
4084
4085 // Now restore saved marks, if any.
4086 if (_objs_with_preserved_marks != NULL) {
4087 assert(_preserved_marks_of_objs != NULL, "Both or none.");
4088 guarantee(_objs_with_preserved_marks->length() ==
4089 _preserved_marks_of_objs->length(), "Both or none.");
4090 for (int i = 0; i < _objs_with_preserved_marks->length(); i++) {
4091 oop obj = _objs_with_preserved_marks->at(i);
4092 markOop m = _preserved_marks_of_objs->at(i);
4093 obj->set_mark(m);
4094 }
4095
4096 // Delete the preserved marks growable arrays (allocated on the C heap).
4097 delete _objs_with_preserved_marks;
4098 delete _preserved_marks_of_objs;
4099 _objs_with_preserved_marks = NULL;
4100 _preserved_marks_of_objs = NULL;
4101 }
4102 }
4103
4104 void G1CollectedHeap::push_on_evac_failure_scan_stack(oop obj) {
4105 _evac_failure_scan_stack->push(obj);
4106 }
4107
4108 void G1CollectedHeap::drain_evac_failure_scan_stack() {
4109 assert(_evac_failure_scan_stack != NULL, "precondition");
4110
4111 while (_evac_failure_scan_stack->length() > 0) {
4112 oop obj = _evac_failure_scan_stack->pop();
4113 _evac_failure_closure->set_region(heap_region_containing(obj));
4114 obj->oop_iterate_backwards(_evac_failure_closure);
4115 }
4116 }
4117
4118 oop
4119 G1CollectedHeap::handle_evacuation_failure_par(OopsInHeapRegionClosure* cl,
4120 oop old) {
4121 assert(obj_in_cs(old),
4122 err_msg("obj: "PTR_FORMAT" should still be in the CSet",
4123 (HeapWord*) old));
4124 markOop m = old->mark();
4125 oop forward_ptr = old->forward_to_atomic(old);
4126 if (forward_ptr == NULL) {
4127 // Forward-to-self succeeded.
4128
4129 if (_evac_failure_closure != cl) {
4130 MutexLockerEx x(EvacFailureStack_lock, Mutex::_no_safepoint_check_flag);
4131 assert(!_drain_in_progress,
4132 "Should only be true while someone holds the lock.");
4133 // Set the global evac-failure closure to the current thread's.
4134 assert(_evac_failure_closure == NULL, "Or locking has failed.");
4135 set_evac_failure_closure(cl);
4136 // Now do the common part.
4137 handle_evacuation_failure_common(old, m);
4138 // Reset to NULL.
4139 set_evac_failure_closure(NULL);
4140 } else {
4141 // The lock is already held, and this is recursive.
4142 assert(_drain_in_progress, "This should only be the recursive case.");
4143 handle_evacuation_failure_common(old, m);
4144 }
4145 return old;
4146 } else {
4147 // Forward-to-self failed. Either someone else managed to allocate
4148 // space for this object (old != forward_ptr) or they beat us in
4149 // self-forwarding it (old == forward_ptr).
4150 assert(old == forward_ptr || !obj_in_cs(forward_ptr),
4151 err_msg("obj: "PTR_FORMAT" forwarded to: "PTR_FORMAT" "
4152 "should not be in the CSet",
4153 (HeapWord*) old, (HeapWord*) forward_ptr));
4154 return forward_ptr;
4155 }
4156 }
4157
4158 void G1CollectedHeap::handle_evacuation_failure_common(oop old, markOop m) {
4159 set_evacuation_failed(true);
4160
4161 preserve_mark_if_necessary(old, m);
4162
4163 HeapRegion* r = heap_region_containing(old);
4164 if (!r->evacuation_failed()) {
4165 r->set_evacuation_failed(true);
4166 _hr_printer.evac_failure(r);
4167 }
4168
4169 push_on_evac_failure_scan_stack(old);
4170
4171 if (!_drain_in_progress) {
4172 // prevent recursion in copy_to_survivor_space()
4173 _drain_in_progress = true;
4174 drain_evac_failure_scan_stack();
4175 _drain_in_progress = false;
4176 }
4177 }
4178
4179 void G1CollectedHeap::preserve_mark_if_necessary(oop obj, markOop m) {
4180 assert(evacuation_failed(), "Oversaving!");
4181 // We want to call the "for_promotion_failure" version only in the
4182 // case of a promotion failure.
4183 if (m->must_be_preserved_for_promotion_failure(obj)) {
4184 if (_objs_with_preserved_marks == NULL) {
4185 assert(_preserved_marks_of_objs == NULL, "Both or none.");
4186 _objs_with_preserved_marks =
4187 new (ResourceObj::C_HEAP) GrowableArray<oop>(40, true);
4188 _preserved_marks_of_objs =
4189 new (ResourceObj::C_HEAP) GrowableArray<markOop>(40, true);
4190 }
4191 _objs_with_preserved_marks->push(obj);
4192 _preserved_marks_of_objs->push(m);
4193 }
4194 }
4195
4196 HeapWord* G1CollectedHeap::par_allocate_during_gc(GCAllocPurpose purpose,
4197 size_t word_size) {
4198 if (purpose == GCAllocForSurvived) {
4199 HeapWord* result = survivor_attempt_allocation(word_size);
4200 if (result != NULL) {
4201 return result;
4202 } else {
4203 // Let's try to allocate in the old gen in case we can fit the
4204 // object there.
4205 return old_attempt_allocation(word_size);
4206 }
4207 } else {
4208 assert(purpose == GCAllocForTenured, "sanity");
4209 HeapWord* result = old_attempt_allocation(word_size);
4210 if (result != NULL) {
4211 return result;
4212 } else {
4213 // Let's try to allocate in the survivors in case we can fit the
4214 // object there.
4215 return survivor_attempt_allocation(word_size);
4216 }
4217 }
4218
4219 ShouldNotReachHere();
4220 // Trying to keep some compilers happy.
4221 return NULL;
4222 }
4223
4224 G1ParGCAllocBuffer::G1ParGCAllocBuffer(size_t gclab_word_size) :
4225 ParGCAllocBuffer(gclab_word_size), _retired(false) { }
4226
4227 G1ParScanThreadState::G1ParScanThreadState(G1CollectedHeap* g1h, uint queue_num)
4228 : _g1h(g1h),
4229 _refs(g1h->task_queue(queue_num)),
4230 _dcq(&g1h->dirty_card_queue_set()),
4231 _ct_bs((CardTableModRefBS*)_g1h->barrier_set()),
4232 _g1_rem(g1h->g1_rem_set()),
4233 _hash_seed(17), _queue_num(queue_num),
4234 _term_attempts(0),
4235 _surviving_alloc_buffer(g1h->desired_plab_sz(GCAllocForSurvived)),
4236 _tenured_alloc_buffer(g1h->desired_plab_sz(GCAllocForTenured)),
4237 _age_table(false),
4238 _strong_roots_time(0), _term_time(0),
4239 _alloc_buffer_waste(0), _undo_waste(0) {
4240 // we allocate G1YoungSurvRateNumRegions plus one entries, since
4241 // we "sacrifice" entry 0 to keep track of surviving bytes for
4242 // non-young regions (where the age is -1)
4243 // We also add a few elements at the beginning and at the end in
4244 // an attempt to eliminate cache contention
4245 uint real_length = 1 + _g1h->g1_policy()->young_cset_region_length();
4246 uint array_length = PADDING_ELEM_NUM +
4247 real_length +
4248 PADDING_ELEM_NUM;
4249 _surviving_young_words_base = NEW_C_HEAP_ARRAY(size_t, array_length);
4250 if (_surviving_young_words_base == NULL)
4251 vm_exit_out_of_memory(array_length * sizeof(size_t),
4252 "Not enough space for young surv histo.");
4253 _surviving_young_words = _surviving_young_words_base + PADDING_ELEM_NUM;
4254 memset(_surviving_young_words, 0, (size_t) real_length * sizeof(size_t));
4255
4256 _alloc_buffers[GCAllocForSurvived] = &_surviving_alloc_buffer;
4257 _alloc_buffers[GCAllocForTenured] = &_tenured_alloc_buffer;
4258
4259 _start = os::elapsedTime();
4260 }
4261
4262 void
4263 G1ParScanThreadState::print_termination_stats_hdr(outputStream* const st)
4264 {
4265 st->print_raw_cr("GC Termination Stats");
4266 st->print_raw_cr(" elapsed --strong roots-- -------termination-------"
4267 " ------waste (KiB)------");
4268 st->print_raw_cr("thr ms ms % ms % attempts"
4269 " total alloc undo");
4270 st->print_raw_cr("--- --------- --------- ------ --------- ------ --------"
4271 " ------- ------- -------");
4272 }
4273
4274 void
4275 G1ParScanThreadState::print_termination_stats(int i,
4276 outputStream* const st) const
4277 {
4278 const double elapsed_ms = elapsed_time() * 1000.0;
4279 const double s_roots_ms = strong_roots_time() * 1000.0;
4280 const double term_ms = term_time() * 1000.0;
4281 st->print_cr("%3d %9.2f %9.2f %6.2f "
4282 "%9.2f %6.2f " SIZE_FORMAT_W(8) " "
4283 SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7),
4284 i, elapsed_ms, s_roots_ms, s_roots_ms * 100 / elapsed_ms,
4285 term_ms, term_ms * 100 / elapsed_ms, term_attempts(),
4286 (alloc_buffer_waste() + undo_waste()) * HeapWordSize / K,
4287 alloc_buffer_waste() * HeapWordSize / K,
4288 undo_waste() * HeapWordSize / K);
4289 }
4290
4291 #ifdef ASSERT
4292 bool G1ParScanThreadState::verify_ref(narrowOop* ref) const {
4293 assert(ref != NULL, "invariant");
4294 assert(UseCompressedOops, "sanity");
4295 assert(!has_partial_array_mask(ref), err_msg("ref=" PTR_FORMAT, ref));
4296 oop p = oopDesc::load_decode_heap_oop(ref);
4297 assert(_g1h->is_in_g1_reserved(p),
4298 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p)));
4299 return true;
4300 }
4301
4302 bool G1ParScanThreadState::verify_ref(oop* ref) const {
4303 assert(ref != NULL, "invariant");
4304 if (has_partial_array_mask(ref)) {
4305 // Must be in the collection set--it's already been copied.
4306 oop p = clear_partial_array_mask(ref);
4307 assert(_g1h->obj_in_cs(p),
4308 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p)));
4309 } else {
4310 oop p = oopDesc::load_decode_heap_oop(ref);
4311 assert(_g1h->is_in_g1_reserved(p),
4312 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p)));
4313 }
4314 return true;
4315 }
4316
4317 bool G1ParScanThreadState::verify_task(StarTask ref) const {
4318 if (ref.is_narrow()) {
4319 return verify_ref((narrowOop*) ref);
4320 } else {
4321 return verify_ref((oop*) ref);
4322 }
4323 }
4324 #endif // ASSERT
4325
4326 void G1ParScanThreadState::trim_queue() {
4327 assert(_evac_cl != NULL, "not set");
4328 assert(_evac_failure_cl != NULL, "not set");
4329 assert(_partial_scan_cl != NULL, "not set");
4330
4331 StarTask ref;
4332 do {
4333 // Drain the overflow stack first, so other threads can steal.
4334 while (refs()->pop_overflow(ref)) {
4335 deal_with_reference(ref);
4336 }
4337
4338 while (refs()->pop_local(ref)) {
4339 deal_with_reference(ref);
4340 }
4341 } while (!refs()->is_empty());
4342 }
4343
4344 G1ParClosureSuper::G1ParClosureSuper(G1CollectedHeap* g1,
4345 G1ParScanThreadState* par_scan_state) :
4346 _g1(g1), _g1_rem(_g1->g1_rem_set()), _cm(_g1->concurrent_mark()),
4347 _par_scan_state(par_scan_state),
4348 _worker_id(par_scan_state->queue_num()),
4349 _during_initial_mark(_g1->g1_policy()->during_initial_mark_pause()),
4350 _mark_in_progress(_g1->mark_in_progress()) { }
4351
4352 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object>
4353 void G1ParCopyClosure<do_gen_barrier, barrier, do_mark_object>::mark_object(oop obj) {
4354 #ifdef ASSERT
4355 HeapRegion* hr = _g1->heap_region_containing(obj);
4356 assert(hr != NULL, "sanity");
4357 assert(!hr->in_collection_set(), "should not mark objects in the CSet");
4358 #endif // ASSERT
4359
4360 // We know that the object is not moving so it's safe to read its size.
4361 _cm->grayRoot(obj, (size_t) obj->size(), _worker_id);
4362 }
4363
4364 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object>
4365 void G1ParCopyClosure<do_gen_barrier, barrier, do_mark_object>
4366 ::mark_forwarded_object(oop from_obj, oop to_obj) {
4367 #ifdef ASSERT
4368 assert(from_obj->is_forwarded(), "from obj should be forwarded");
4369 assert(from_obj->forwardee() == to_obj, "to obj should be the forwardee");
4370 assert(from_obj != to_obj, "should not be self-forwarded");
4371
4372 HeapRegion* from_hr = _g1->heap_region_containing(from_obj);
4373 assert(from_hr != NULL, "sanity");
4374 assert(from_hr->in_collection_set(), "from obj should be in the CSet");
4375
4376 HeapRegion* to_hr = _g1->heap_region_containing(to_obj);
4377 assert(to_hr != NULL, "sanity");
4378 assert(!to_hr->in_collection_set(), "should not mark objects in the CSet");
4379 #endif // ASSERT
4380
4381 // The object might be in the process of being copied by another
4382 // worker so we cannot trust that its to-space image is
4383 // well-formed. So we have to read its size from its from-space
4384 // image which we know should not be changing.
4385 _cm->grayRoot(to_obj, (size_t) from_obj->size(), _worker_id);
4386 }
4387
4388 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object>
4389 oop G1ParCopyClosure<do_gen_barrier, barrier, do_mark_object>
4390 ::copy_to_survivor_space(oop old) {
4391 size_t word_sz = old->size();
4392 HeapRegion* from_region = _g1->heap_region_containing_raw(old);
4393 // +1 to make the -1 indexes valid...
4394 int young_index = from_region->young_index_in_cset()+1;
4395 assert( (from_region->is_young() && young_index > 0) ||
4396 (!from_region->is_young() && young_index == 0), "invariant" );
4397 G1CollectorPolicy* g1p = _g1->g1_policy();
4398 markOop m = old->mark();
4399 int age = m->has_displaced_mark_helper() ? m->displaced_mark_helper()->age()
4400 : m->age();
4401 GCAllocPurpose alloc_purpose = g1p->evacuation_destination(from_region, age,
4402 word_sz);
4403 HeapWord* obj_ptr = _par_scan_state->allocate(alloc_purpose, word_sz);
4404 oop obj = oop(obj_ptr);
4405
4406 if (obj_ptr == NULL) {
4407 // This will either forward-to-self, or detect that someone else has
4408 // installed a forwarding pointer.
4409 OopsInHeapRegionClosure* cl = _par_scan_state->evac_failure_closure();
4410 return _g1->handle_evacuation_failure_par(cl, old);
4411 }
4412
4413 // We're going to allocate linearly, so might as well prefetch ahead.
4414 Prefetch::write(obj_ptr, PrefetchCopyIntervalInBytes);
4415
4416 oop forward_ptr = old->forward_to_atomic(obj);
4417 if (forward_ptr == NULL) {
4418 Copy::aligned_disjoint_words((HeapWord*) old, obj_ptr, word_sz);
4419 if (g1p->track_object_age(alloc_purpose)) {
4420 // We could simply do obj->incr_age(). However, this causes a
4421 // performance issue. obj->incr_age() will first check whether
4422 // the object has a displaced mark by checking its mark word;
4423 // getting the mark word from the new location of the object
4424 // stalls. So, given that we already have the mark word and we
4425 // are about to install it anyway, it's better to increase the
4426 // age on the mark word, when the object does not have a
4427 // displaced mark word. We're not expecting many objects to have
4428 // a displaced marked word, so that case is not optimized
4429 // further (it could be...) and we simply call obj->incr_age().
4430
4431 if (m->has_displaced_mark_helper()) {
4432 // in this case, we have to install the mark word first,
4433 // otherwise obj looks to be forwarded (the old mark word,
4434 // which contains the forward pointer, was copied)
4435 obj->set_mark(m);
4436 obj->incr_age();
4437 } else {
4438 m = m->incr_age();
4439 obj->set_mark(m);
4440 }
4441 _par_scan_state->age_table()->add(obj, word_sz);
4442 } else {
4443 obj->set_mark(m);
4444 }
4445
4446 size_t* surv_young_words = _par_scan_state->surviving_young_words();
4447 surv_young_words[young_index] += word_sz;
4448
4449 if (obj->is_objArray() && arrayOop(obj)->length() >= ParGCArrayScanChunk) {
4450 // We keep track of the next start index in the length field of
4451 // the to-space object. The actual length can be found in the
4452 // length field of the from-space object.
4453 arrayOop(obj)->set_length(0);
4454 oop* old_p = set_partial_array_mask(old);
4455 _par_scan_state->push_on_queue(old_p);
4456 } else {
4457 // No point in using the slower heap_region_containing() method,
4458 // given that we know obj is in the heap.
4459 _scanner.set_region(_g1->heap_region_containing_raw(obj));
4460 obj->oop_iterate_backwards(&_scanner);
4461 }
4462 } else {
4463 _par_scan_state->undo_allocation(alloc_purpose, obj_ptr, word_sz);
4464 obj = forward_ptr;
4465 }
4466 return obj;
4467 }
4468
4469 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object>
4470 template <class T>
4471 void G1ParCopyClosure<do_gen_barrier, barrier, do_mark_object>
4472 ::do_oop_work(T* p) {
4473 oop obj = oopDesc::load_decode_heap_oop(p);
4474 assert(barrier != G1BarrierRS || obj != NULL,
4475 "Precondition: G1BarrierRS implies obj is non-NULL");
4476
4477 assert(_worker_id == _par_scan_state->queue_num(), "sanity");
4478
4479 // here the null check is implicit in the cset_fast_test() test
4480 if (_g1->in_cset_fast_test(obj)) {
4481 oop forwardee;
4482 if (obj->is_forwarded()) {
4483 forwardee = obj->forwardee();
4484 } else {
4485 forwardee = copy_to_survivor_space(obj);
4486 }
4487 assert(forwardee != NULL, "forwardee should not be NULL");
4488 oopDesc::encode_store_heap_oop(p, forwardee);
4489 if (do_mark_object && forwardee != obj) {
4490 // If the object is self-forwarded we don't need to explicitly
4491 // mark it, the evacuation failure protocol will do so.
4492 mark_forwarded_object(obj, forwardee);
4493 }
4494
4495 // When scanning the RS, we only care about objs in CS.
4496 if (barrier == G1BarrierRS) {
4497 _par_scan_state->update_rs(_from, p, _worker_id);
4498 }
4499 } else {
4500 // The object is not in collection set. If we're a root scanning
4501 // closure during an initial mark pause (i.e. do_mark_object will
4502 // be true) then attempt to mark the object.
4503 if (do_mark_object && _g1->is_in_g1_reserved(obj)) {
4504 mark_object(obj);
4505 }
4506 }
4507
4508 if (barrier == G1BarrierEvac && obj != NULL) {
4509 _par_scan_state->update_rs(_from, p, _worker_id);
4510 }
4511
4512 if (do_gen_barrier && obj != NULL) {
4513 par_do_barrier(p);
4514 }
4515 }
4516
4517 template void G1ParCopyClosure<false, G1BarrierEvac, false>::do_oop_work(oop* p);
4518 template void G1ParCopyClosure<false, G1BarrierEvac, false>::do_oop_work(narrowOop* p);
4519
4520 template <class T> void G1ParScanPartialArrayClosure::do_oop_nv(T* p) {
4521 assert(has_partial_array_mask(p), "invariant");
4522 oop from_obj = clear_partial_array_mask(p);
4523
4524 assert(Universe::heap()->is_in_reserved(from_obj), "must be in heap.");
4525 assert(from_obj->is_objArray(), "must be obj array");
4526 objArrayOop from_obj_array = objArrayOop(from_obj);
4527 // The from-space object contains the real length.
4528 int length = from_obj_array->length();
4529
4530 assert(from_obj->is_forwarded(), "must be forwarded");
4531 oop to_obj = from_obj->forwardee();
4532 assert(from_obj != to_obj, "should not be chunking self-forwarded objects");
4533 objArrayOop to_obj_array = objArrayOop(to_obj);
4534 // We keep track of the next start index in the length field of the
4535 // to-space object.
4536 int next_index = to_obj_array->length();
4537 assert(0 <= next_index && next_index < length,
4538 err_msg("invariant, next index: %d, length: %d", next_index, length));
4539
4540 int start = next_index;
4541 int end = length;
4542 int remainder = end - start;
4543 // We'll try not to push a range that's smaller than ParGCArrayScanChunk.
4544 if (remainder > 2 * ParGCArrayScanChunk) {
4545 end = start + ParGCArrayScanChunk;
4546 to_obj_array->set_length(end);
4547 // Push the remainder before we process the range in case another
4548 // worker has run out of things to do and can steal it.
4549 oop* from_obj_p = set_partial_array_mask(from_obj);
4550 _par_scan_state->push_on_queue(from_obj_p);
4551 } else {
4552 assert(length == end, "sanity");
4553 // We'll process the final range for this object. Restore the length
4554 // so that the heap remains parsable in case of evacuation failure.
4555 to_obj_array->set_length(end);
4556 }
4557 _scanner.set_region(_g1->heap_region_containing_raw(to_obj));
4558 // Process indexes [start,end). It will also process the header
4559 // along with the first chunk (i.e., the chunk with start == 0).
4560 // Note that at this point the length field of to_obj_array is not
4561 // correct given that we are using it to keep track of the next
4562 // start index. oop_iterate_range() (thankfully!) ignores the length
4563 // field and only relies on the start / end parameters. It does
4564 // however return the size of the object which will be incorrect. So
4565 // we have to ignore it even if we wanted to use it.
4566 to_obj_array->oop_iterate_range(&_scanner, start, end);
4567 }
4568
4569 class G1ParEvacuateFollowersClosure : public VoidClosure {
4570 protected:
4571 G1CollectedHeap* _g1h;
4572 G1ParScanThreadState* _par_scan_state;
4573 RefToScanQueueSet* _queues;
4574 ParallelTaskTerminator* _terminator;
4575
4576 G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
4577 RefToScanQueueSet* queues() { return _queues; }
4578 ParallelTaskTerminator* terminator() { return _terminator; }
4579
4580 public:
4581 G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h,
4582 G1ParScanThreadState* par_scan_state,
4583 RefToScanQueueSet* queues,
4584 ParallelTaskTerminator* terminator)
4585 : _g1h(g1h), _par_scan_state(par_scan_state),
4586 _queues(queues), _terminator(terminator) {}
4587
4588 void do_void();
4589
4590 private:
4591 inline bool offer_termination();
4592 };
4593
4594 bool G1ParEvacuateFollowersClosure::offer_termination() {
4595 G1ParScanThreadState* const pss = par_scan_state();
4596 pss->start_term_time();
4597 const bool res = terminator()->offer_termination();
4598 pss->end_term_time();
4599 return res;
4600 }
4601
4602 void G1ParEvacuateFollowersClosure::do_void() {
4603 StarTask stolen_task;
4604 G1ParScanThreadState* const pss = par_scan_state();
4605 pss->trim_queue();
4606
4607 do {
4608 while (queues()->steal(pss->queue_num(), pss->hash_seed(), stolen_task)) {
4609 assert(pss->verify_task(stolen_task), "sanity");
4610 if (stolen_task.is_narrow()) {
4611 pss->deal_with_reference((narrowOop*) stolen_task);
4612 } else {
4613 pss->deal_with_reference((oop*) stolen_task);
4614 }
4615
4616 // We've just processed a reference and we might have made
4617 // available new entries on the queues. So we have to make sure
4618 // we drain the queues as necessary.
4619 pss->trim_queue();
4620 }
4621 } while (!offer_termination());
4622
4623 pss->retire_alloc_buffers();
4624 }
4625
4626 class G1ParTask : public AbstractGangTask {
4627 protected:
4628 G1CollectedHeap* _g1h;
4629 RefToScanQueueSet *_queues;
4630 ParallelTaskTerminator _terminator;
4631 uint _n_workers;
4632
4633 Mutex _stats_lock;
4634 Mutex* stats_lock() { return &_stats_lock; }
4635
4636 size_t getNCards() {
4637 return (_g1h->capacity() + G1BlockOffsetSharedArray::N_bytes - 1)
4638 / G1BlockOffsetSharedArray::N_bytes;
4639 }
4640
4641 public:
4642 G1ParTask(G1CollectedHeap* g1h,
4643 RefToScanQueueSet *task_queues)
4644 : AbstractGangTask("G1 collection"),
4645 _g1h(g1h),
4646 _queues(task_queues),
4647 _terminator(0, _queues),
4648 _stats_lock(Mutex::leaf, "parallel G1 stats lock", true)
4649 {}
4650
4651 RefToScanQueueSet* queues() { return _queues; }
4652
4653 RefToScanQueue *work_queue(int i) {
4654 return queues()->queue(i);
4655 }
4656
4657 ParallelTaskTerminator* terminator() { return &_terminator; }
4658
4659 virtual void set_for_termination(int active_workers) {
4660 // This task calls set_n_termination() in par_non_clean_card_iterate_work()
4661 // in the young space (_par_seq_tasks) in the G1 heap
4662 // for SequentialSubTasksDone.
4663 // This task also uses SubTasksDone in SharedHeap and G1CollectedHeap
4664 // both of which need setting by set_n_termination().
4665 _g1h->SharedHeap::set_n_termination(active_workers);
4666 _g1h->set_n_termination(active_workers);
4667 terminator()->reset_for_reuse(active_workers);
4668 _n_workers = active_workers;
4669 }
4670
4671 void work(uint worker_id) {
4672 if (worker_id >= _n_workers) return; // no work needed this round
4673
4674 double start_time_ms = os::elapsedTime() * 1000.0;
4675 _g1h->g1_policy()->record_gc_worker_start_time(worker_id, start_time_ms);
4676
4677 {
4678 ResourceMark rm;
4679 HandleMark hm;
4680
4681 ReferenceProcessor* rp = _g1h->ref_processor_stw();
4682
4683 G1ParScanThreadState pss(_g1h, worker_id);
4684 G1ParScanHeapEvacClosure scan_evac_cl(_g1h, &pss, rp);
4685 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, rp);
4686 G1ParScanPartialArrayClosure partial_scan_cl(_g1h, &pss, rp);
4687
4688 pss.set_evac_closure(&scan_evac_cl);
4689 pss.set_evac_failure_closure(&evac_failure_cl);
4690 pss.set_partial_scan_closure(&partial_scan_cl);
4691
4692 G1ParScanExtRootClosure only_scan_root_cl(_g1h, &pss, rp);
4693 G1ParScanPermClosure only_scan_perm_cl(_g1h, &pss, rp);
4694
4695 G1ParScanAndMarkExtRootClosure scan_mark_root_cl(_g1h, &pss, rp);
4696 G1ParScanAndMarkPermClosure scan_mark_perm_cl(_g1h, &pss, rp);
4697
4698 OopClosure* scan_root_cl = &only_scan_root_cl;
4699 OopsInHeapRegionClosure* scan_perm_cl = &only_scan_perm_cl;
4700
4701 if (_g1h->g1_policy()->during_initial_mark_pause()) {
4702 // We also need to mark copied objects.
4703 scan_root_cl = &scan_mark_root_cl;
4704 scan_perm_cl = &scan_mark_perm_cl;
4705 }
4706
4707 G1ParPushHeapRSClosure push_heap_rs_cl(_g1h, &pss);
4708
4709 pss.start_strong_roots();
4710 _g1h->g1_process_strong_roots(/* not collecting perm */ false,
4711 SharedHeap::SO_AllClasses,
4712 scan_root_cl,
4713 &push_heap_rs_cl,
4714 scan_perm_cl,
4715 worker_id);
4716 pss.end_strong_roots();
4717
4718 {
4719 double start = os::elapsedTime();
4720 G1ParEvacuateFollowersClosure evac(_g1h, &pss, _queues, &_terminator);
4721 evac.do_void();
4722 double elapsed_ms = (os::elapsedTime()-start)*1000.0;
4723 double term_ms = pss.term_time()*1000.0;
4724 _g1h->g1_policy()->record_obj_copy_time(worker_id, elapsed_ms-term_ms);
4725 _g1h->g1_policy()->record_termination(worker_id, term_ms, pss.term_attempts());
4726 }
4727 _g1h->g1_policy()->record_thread_age_table(pss.age_table());
4728 _g1h->update_surviving_young_words(pss.surviving_young_words()+1);
4729
4730 // Clean up any par-expanded rem sets.
4731 HeapRegionRemSet::par_cleanup();
4732
4733 if (ParallelGCVerbose) {
4734 MutexLocker x(stats_lock());
4735 pss.print_termination_stats(worker_id);
4736 }
4737
4738 assert(pss.refs()->is_empty(), "should be empty");
4739
4740 // Close the inner scope so that the ResourceMark and HandleMark
4741 // destructors are executed here and are included as part of the
4742 // "GC Worker Time".
4743 }
4744
4745 double end_time_ms = os::elapsedTime() * 1000.0;
4746 _g1h->g1_policy()->record_gc_worker_end_time(worker_id, end_time_ms);
4747 }
4748 };
4749
4750 // *** Common G1 Evacuation Stuff
4751
4752 // Closures that support the filtering of CodeBlobs scanned during
4753 // external root scanning.
4754
4755 // Closure applied to reference fields in code blobs (specifically nmethods)
4756 // to determine whether an nmethod contains references that point into
4757 // the collection set. Used as a predicate when walking code roots so
4758 // that only nmethods that point into the collection set are added to the
4759 // 'marked' list.
4760
4761 class G1FilteredCodeBlobToOopClosure : public CodeBlobToOopClosure {
4762
4763 class G1PointsIntoCSOopClosure : public OopClosure {
4764 G1CollectedHeap* _g1;
4765 bool _points_into_cs;
4766 public:
4767 G1PointsIntoCSOopClosure(G1CollectedHeap* g1) :
4768 _g1(g1), _points_into_cs(false) { }
4769
4770 bool points_into_cs() const { return _points_into_cs; }
4771
4772 template <class T>
4773 void do_oop_nv(T* p) {
4774 if (!_points_into_cs) {
4775 T heap_oop = oopDesc::load_heap_oop(p);
4776 if (!oopDesc::is_null(heap_oop) &&
4777 _g1->in_cset_fast_test(oopDesc::decode_heap_oop_not_null(heap_oop))) {
4778 _points_into_cs = true;
4779 }
4780 }
4781 }
4782
4783 virtual void do_oop(oop* p) { do_oop_nv(p); }
4784 virtual void do_oop(narrowOop* p) { do_oop_nv(p); }
4785 };
4786
4787 G1CollectedHeap* _g1;
4788
4789 public:
4790 G1FilteredCodeBlobToOopClosure(G1CollectedHeap* g1, OopClosure* cl) :
4791 CodeBlobToOopClosure(cl, true), _g1(g1) { }
4792
4793 virtual void do_code_blob(CodeBlob* cb) {
4794 nmethod* nm = cb->as_nmethod_or_null();
4795 if (nm != NULL && !(nm->test_oops_do_mark())) {
4796 G1PointsIntoCSOopClosure predicate_cl(_g1);
4797 nm->oops_do(&predicate_cl);
4798
4799 if (predicate_cl.points_into_cs()) {
4800 // At least one of the reference fields or the oop relocations
4801 // in the nmethod points into the collection set. We have to
4802 // 'mark' this nmethod.
4803 // Note: Revisit the following if CodeBlobToOopClosure::do_code_blob()
4804 // or MarkingCodeBlobClosure::do_code_blob() change.
4805 if (!nm->test_set_oops_do_mark()) {
4806 do_newly_marked_nmethod(nm);
4807 }
4808 }
4809 }
4810 }
4811 };
4812
4813 // This method is run in a GC worker.
4814
4815 void
4816 G1CollectedHeap::
4817 g1_process_strong_roots(bool collecting_perm_gen,
4818 ScanningOption so,
4819 OopClosure* scan_non_heap_roots,
4820 OopsInHeapRegionClosure* scan_rs,
4821 OopsInGenClosure* scan_perm,
4822 int worker_i) {
4823
4824 // First scan the strong roots, including the perm gen.
4825 double ext_roots_start = os::elapsedTime();
4826 double closure_app_time_sec = 0.0;
4827
4828 BufferingOopClosure buf_scan_non_heap_roots(scan_non_heap_roots);
4829 BufferingOopsInGenClosure buf_scan_perm(scan_perm);
4830 buf_scan_perm.set_generation(perm_gen());
4831
4832 // Walk the code cache w/o buffering, because StarTask cannot handle
4833 // unaligned oop locations.
4834 G1FilteredCodeBlobToOopClosure eager_scan_code_roots(this, scan_non_heap_roots);
4835
4836 process_strong_roots(false, // no scoping; this is parallel code
4837 collecting_perm_gen, so,
4838 &buf_scan_non_heap_roots,
4839 &eager_scan_code_roots,
4840 &buf_scan_perm);
4841
4842 // Now the CM ref_processor roots.
4843 if (!_process_strong_tasks->is_task_claimed(G1H_PS_refProcessor_oops_do)) {
4844 // We need to treat the discovered reference lists of the
4845 // concurrent mark ref processor as roots and keep entries
4846 // (which are added by the marking threads) on them live
4847 // until they can be processed at the end of marking.
4848 ref_processor_cm()->weak_oops_do(&buf_scan_non_heap_roots);
4849 }
4850
4851 // Finish up any enqueued closure apps (attributed as object copy time).
4852 buf_scan_non_heap_roots.done();
4853 buf_scan_perm.done();
4854
4855 double ext_roots_end = os::elapsedTime();
4856
4857 g1_policy()->reset_obj_copy_time(worker_i);
4858 double obj_copy_time_sec = buf_scan_perm.closure_app_seconds() +
4859 buf_scan_non_heap_roots.closure_app_seconds();
4860 g1_policy()->record_obj_copy_time(worker_i, obj_copy_time_sec * 1000.0);
4861
4862 double ext_root_time_ms =
4863 ((ext_roots_end - ext_roots_start) - obj_copy_time_sec) * 1000.0;
4864
4865 g1_policy()->record_ext_root_scan_time(worker_i, ext_root_time_ms);
4866
4867 // During conc marking we have to filter the per-thread SATB buffers
4868 // to make sure we remove any oops into the CSet (which will show up
4869 // as implicitly live).
4870 if (!_process_strong_tasks->is_task_claimed(G1H_PS_filter_satb_buffers)) {
4871 if (mark_in_progress()) {
4872 JavaThread::satb_mark_queue_set().filter_thread_buffers();
4873 }
4874 }
4875 double satb_filtering_ms = (os::elapsedTime() - ext_roots_end) * 1000.0;
4876 g1_policy()->record_satb_filtering_time(worker_i, satb_filtering_ms);
4877
4878 // Now scan the complement of the collection set.
4879 if (scan_rs != NULL) {
4880 g1_rem_set()->oops_into_collection_set_do(scan_rs, worker_i);
4881 }
4882
4883 _process_strong_tasks->all_tasks_completed();
4884 }
4885
4886 void
4887 G1CollectedHeap::g1_process_weak_roots(OopClosure* root_closure,
4888 OopClosure* non_root_closure) {
4889 CodeBlobToOopClosure roots_in_blobs(root_closure, /*do_marking=*/ false);
4890 SharedHeap::process_weak_roots(root_closure, &roots_in_blobs, non_root_closure);
4891 }
4892
4893 // Weak Reference Processing support
4894
4895 // An always "is_alive" closure that is used to preserve referents.
4896 // If the object is non-null then it's alive. Used in the preservation
4897 // of referent objects that are pointed to by reference objects
4898 // discovered by the CM ref processor.
4899 class G1AlwaysAliveClosure: public BoolObjectClosure {
4900 G1CollectedHeap* _g1;
4901 public:
4902 G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
4903 void do_object(oop p) { assert(false, "Do not call."); }
4904 bool do_object_b(oop p) {
4905 if (p != NULL) {
4906 return true;
4907 }
4908 return false;
4909 }
4910 };
4911
4912 bool G1STWIsAliveClosure::do_object_b(oop p) {
4913 // An object is reachable if it is outside the collection set,
4914 // or is inside and copied.
4915 return !_g1->obj_in_cs(p) || p->is_forwarded();
4916 }
4917
4918 // Non Copying Keep Alive closure
4919 class G1KeepAliveClosure: public OopClosure {
4920 G1CollectedHeap* _g1;
4921 public:
4922 G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
4923 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
4924 void do_oop( oop* p) {
4925 oop obj = *p;
4926
4927 if (_g1->obj_in_cs(obj)) {
4928 assert( obj->is_forwarded(), "invariant" );
4929 *p = obj->forwardee();
4930 }
4931 }
4932 };
4933
4934 // Copying Keep Alive closure - can be called from both
4935 // serial and parallel code as long as different worker
4936 // threads utilize different G1ParScanThreadState instances
4937 // and different queues.
4938
4939 class G1CopyingKeepAliveClosure: public OopClosure {
4940 G1CollectedHeap* _g1h;
4941 OopClosure* _copy_non_heap_obj_cl;
4942 OopsInHeapRegionClosure* _copy_perm_obj_cl;
4943 G1ParScanThreadState* _par_scan_state;
4944
4945 public:
4946 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
4947 OopClosure* non_heap_obj_cl,
4948 OopsInHeapRegionClosure* perm_obj_cl,
4949 G1ParScanThreadState* pss):
4950 _g1h(g1h),
4951 _copy_non_heap_obj_cl(non_heap_obj_cl),
4952 _copy_perm_obj_cl(perm_obj_cl),
4953 _par_scan_state(pss)
4954 {}
4955
4956 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
4957 virtual void do_oop( oop* p) { do_oop_work(p); }
4958
4959 template <class T> void do_oop_work(T* p) {
4960 oop obj = oopDesc::load_decode_heap_oop(p);
4961
4962 if (_g1h->obj_in_cs(obj)) {
4963 // If the referent object has been forwarded (either copied
4964 // to a new location or to itself in the event of an
4965 // evacuation failure) then we need to update the reference
4966 // field and, if both reference and referent are in the G1
4967 // heap, update the RSet for the referent.
4968 //
4969 // If the referent has not been forwarded then we have to keep
4970 // it alive by policy. Therefore we have copy the referent.
4971 //
4972 // If the reference field is in the G1 heap then we can push
4973 // on the PSS queue. When the queue is drained (after each
4974 // phase of reference processing) the object and it's followers
4975 // will be copied, the reference field set to point to the
4976 // new location, and the RSet updated. Otherwise we need to
4977 // use the the non-heap or perm closures directly to copy
4978 // the refernt object and update the pointer, while avoiding
4979 // updating the RSet.
4980
4981 if (_g1h->is_in_g1_reserved(p)) {
4982 _par_scan_state->push_on_queue(p);
4983 } else {
4984 // The reference field is not in the G1 heap.
4985 if (_g1h->perm_gen()->is_in(p)) {
4986 _copy_perm_obj_cl->do_oop(p);
4987 } else {
4988 _copy_non_heap_obj_cl->do_oop(p);
4989 }
4990 }
4991 }
4992 }
4993 };
4994
4995 // Serial drain queue closure. Called as the 'complete_gc'
4996 // closure for each discovered list in some of the
4997 // reference processing phases.
4998
4999 class G1STWDrainQueueClosure: public VoidClosure {
5000 protected:
5001 G1CollectedHeap* _g1h;
5002 G1ParScanThreadState* _par_scan_state;
5003
5004 G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
5005
5006 public:
5007 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
5008 _g1h(g1h),
5009 _par_scan_state(pss)
5010 { }
5011
5012 void do_void() {
5013 G1ParScanThreadState* const pss = par_scan_state();
5014 pss->trim_queue();
5015 }
5016 };
5017
5018 // Parallel Reference Processing closures
5019
5020 // Implementation of AbstractRefProcTaskExecutor for parallel reference
5021 // processing during G1 evacuation pauses.
5022
5023 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
5024 private:
5025 G1CollectedHeap* _g1h;
5026 RefToScanQueueSet* _queues;
5027 FlexibleWorkGang* _workers;
5028 int _active_workers;
5029
5030 public:
5031 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
5032 FlexibleWorkGang* workers,
5033 RefToScanQueueSet *task_queues,
5034 int n_workers) :
5035 _g1h(g1h),
5036 _queues(task_queues),
5037 _workers(workers),
5038 _active_workers(n_workers)
5039 {
5040 assert(n_workers > 0, "shouldn't call this otherwise");
5041 }
5042
5043 // Executes the given task using concurrent marking worker threads.
5044 virtual void execute(ProcessTask& task);
5045 virtual void execute(EnqueueTask& task);
5046 };
5047
5048 // Gang task for possibly parallel reference processing
5049
5050 class G1STWRefProcTaskProxy: public AbstractGangTask {
5051 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
5052 ProcessTask& _proc_task;
5053 G1CollectedHeap* _g1h;
5054 RefToScanQueueSet *_task_queues;
5055 ParallelTaskTerminator* _terminator;
5056
5057 public:
5058 G1STWRefProcTaskProxy(ProcessTask& proc_task,
5059 G1CollectedHeap* g1h,
5060 RefToScanQueueSet *task_queues,
5061 ParallelTaskTerminator* terminator) :
5062 AbstractGangTask("Process reference objects in parallel"),
5063 _proc_task(proc_task),
5064 _g1h(g1h),
5065 _task_queues(task_queues),
5066 _terminator(terminator)
5067 {}
5068
5069 virtual void work(uint worker_id) {
5070 // The reference processing task executed by a single worker.
5071 ResourceMark rm;
5072 HandleMark hm;
5073
5074 G1STWIsAliveClosure is_alive(_g1h);
5075
5076 G1ParScanThreadState pss(_g1h, worker_id);
5077
5078 G1ParScanHeapEvacClosure scan_evac_cl(_g1h, &pss, NULL);
5079 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5080 G1ParScanPartialArrayClosure partial_scan_cl(_g1h, &pss, NULL);
5081
5082 pss.set_evac_closure(&scan_evac_cl);
5083 pss.set_evac_failure_closure(&evac_failure_cl);
5084 pss.set_partial_scan_closure(&partial_scan_cl);
5085
5086 G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL);
5087 G1ParScanPermClosure only_copy_perm_cl(_g1h, &pss, NULL);
5088
5089 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5090 G1ParScanAndMarkPermClosure copy_mark_perm_cl(_g1h, &pss, NULL);
5091
5092 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5093 OopsInHeapRegionClosure* copy_perm_cl = &only_copy_perm_cl;
5094
5095 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5096 // We also need to mark copied objects.
5097 copy_non_heap_cl = ©_mark_non_heap_cl;
5098 copy_perm_cl = ©_mark_perm_cl;
5099 }
5100
5101 // Keep alive closure.
5102 G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, copy_perm_cl, &pss);
5103
5104 // Complete GC closure
5105 G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _task_queues, _terminator);
5106
5107 // Call the reference processing task's work routine.
5108 _proc_task.work(worker_id, is_alive, keep_alive, drain_queue);
5109
5110 // Note we cannot assert that the refs array is empty here as not all
5111 // of the processing tasks (specifically phase2 - pp2_work) execute
5112 // the complete_gc closure (which ordinarily would drain the queue) so
5113 // the queue may not be empty.
5114 }
5115 };
5116
5117 // Driver routine for parallel reference processing.
5118 // Creates an instance of the ref processing gang
5119 // task and has the worker threads execute it.
5120 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) {
5121 assert(_workers != NULL, "Need parallel worker threads.");
5122
5123 ParallelTaskTerminator terminator(_active_workers, _queues);
5124 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _queues, &terminator);
5125
5126 _g1h->set_par_threads(_active_workers);
5127 _workers->run_task(&proc_task_proxy);
5128 _g1h->set_par_threads(0);
5129 }
5130
5131 // Gang task for parallel reference enqueueing.
5132
5133 class G1STWRefEnqueueTaskProxy: public AbstractGangTask {
5134 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
5135 EnqueueTask& _enq_task;
5136
5137 public:
5138 G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) :
5139 AbstractGangTask("Enqueue reference objects in parallel"),
5140 _enq_task(enq_task)
5141 { }
5142
5143 virtual void work(uint worker_id) {
5144 _enq_task.work(worker_id);
5145 }
5146 };
5147
5148 // Driver routine for parallel reference enqueing.
5149 // Creates an instance of the ref enqueueing gang
5150 // task and has the worker threads execute it.
5151
5152 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
5153 assert(_workers != NULL, "Need parallel worker threads.");
5154
5155 G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task);
5156
5157 _g1h->set_par_threads(_active_workers);
5158 _workers->run_task(&enq_task_proxy);
5159 _g1h->set_par_threads(0);
5160 }
5161
5162 // End of weak reference support closures
5163
5164 // Abstract task used to preserve (i.e. copy) any referent objects
5165 // that are in the collection set and are pointed to by reference
5166 // objects discovered by the CM ref processor.
5167
5168 class G1ParPreserveCMReferentsTask: public AbstractGangTask {
5169 protected:
5170 G1CollectedHeap* _g1h;
5171 RefToScanQueueSet *_queues;
5172 ParallelTaskTerminator _terminator;
5173 uint _n_workers;
5174
5175 public:
5176 G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h,int workers, RefToScanQueueSet *task_queues) :
5177 AbstractGangTask("ParPreserveCMReferents"),
5178 _g1h(g1h),
5179 _queues(task_queues),
5180 _terminator(workers, _queues),
5181 _n_workers(workers)
5182 { }
5183
5184 void work(uint worker_id) {
5185 ResourceMark rm;
5186 HandleMark hm;
5187
5188 G1ParScanThreadState pss(_g1h, worker_id);
5189 G1ParScanHeapEvacClosure scan_evac_cl(_g1h, &pss, NULL);
5190 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5191 G1ParScanPartialArrayClosure partial_scan_cl(_g1h, &pss, NULL);
5192
5193 pss.set_evac_closure(&scan_evac_cl);
5194 pss.set_evac_failure_closure(&evac_failure_cl);
5195 pss.set_partial_scan_closure(&partial_scan_cl);
5196
5197 assert(pss.refs()->is_empty(), "both queue and overflow should be empty");
5198
5199
5200 G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL);
5201 G1ParScanPermClosure only_copy_perm_cl(_g1h, &pss, NULL);
5202
5203 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5204 G1ParScanAndMarkPermClosure copy_mark_perm_cl(_g1h, &pss, NULL);
5205
5206 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5207 OopsInHeapRegionClosure* copy_perm_cl = &only_copy_perm_cl;
5208
5209 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5210 // We also need to mark copied objects.
5211 copy_non_heap_cl = ©_mark_non_heap_cl;
5212 copy_perm_cl = ©_mark_perm_cl;
5213 }
5214
5215 // Is alive closure
5216 G1AlwaysAliveClosure always_alive(_g1h);
5217
5218 // Copying keep alive closure. Applied to referent objects that need
5219 // to be copied.
5220 G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, copy_perm_cl, &pss);
5221
5222 ReferenceProcessor* rp = _g1h->ref_processor_cm();
5223
5224 uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q();
5225 uint stride = MIN2(MAX2(_n_workers, 1U), limit);
5226
5227 // limit is set using max_num_q() - which was set using ParallelGCThreads.
5228 // So this must be true - but assert just in case someone decides to
5229 // change the worker ids.
5230 assert(0 <= worker_id && worker_id < limit, "sanity");
5231 assert(!rp->discovery_is_atomic(), "check this code");
5232
5233 // Select discovered lists [i, i+stride, i+2*stride,...,limit)
5234 for (uint idx = worker_id; idx < limit; idx += stride) {
5235 DiscoveredList& ref_list = rp->discovered_refs()[idx];
5236
5237 DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive);
5238 while (iter.has_next()) {
5239 // Since discovery is not atomic for the CM ref processor, we
5240 // can see some null referent objects.
5241 iter.load_ptrs(DEBUG_ONLY(true));
5242 oop ref = iter.obj();
5243
5244 // This will filter nulls.
5245 if (iter.is_referent_alive()) {
5246 iter.make_referent_alive();
5247 }
5248 iter.move_to_next();
5249 }
5250 }
5251
5252 // Drain the queue - which may cause stealing
5253 G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _queues, &_terminator);
5254 drain_queue.do_void();
5255 // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure
5256 assert(pss.refs()->is_empty(), "should be");
5257 }
5258 };
5259
5260 // Weak Reference processing during an evacuation pause (part 1).
5261 void G1CollectedHeap::process_discovered_references() {
5262 double ref_proc_start = os::elapsedTime();
5263
5264 ReferenceProcessor* rp = _ref_processor_stw;
5265 assert(rp->discovery_enabled(), "should have been enabled");
5266
5267 // Any reference objects, in the collection set, that were 'discovered'
5268 // by the CM ref processor should have already been copied (either by
5269 // applying the external root copy closure to the discovered lists, or
5270 // by following an RSet entry).
5271 //
5272 // But some of the referents, that are in the collection set, that these
5273 // reference objects point to may not have been copied: the STW ref
5274 // processor would have seen that the reference object had already
5275 // been 'discovered' and would have skipped discovering the reference,
5276 // but would not have treated the reference object as a regular oop.
5277 // As a reult the copy closure would not have been applied to the
5278 // referent object.
5279 //
5280 // We need to explicitly copy these referent objects - the references
5281 // will be processed at the end of remarking.
5282 //
5283 // We also need to do this copying before we process the reference
5284 // objects discovered by the STW ref processor in case one of these
5285 // referents points to another object which is also referenced by an
5286 // object discovered by the STW ref processor.
5287
5288 uint active_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
5289 workers()->active_workers() : 1);
5290
5291 assert(!G1CollectedHeap::use_parallel_gc_threads() ||
5292 active_workers == workers()->active_workers(),
5293 "Need to reset active_workers");
5294
5295 set_par_threads(active_workers);
5296 G1ParPreserveCMReferentsTask keep_cm_referents(this, active_workers, _task_queues);
5297
5298 if (G1CollectedHeap::use_parallel_gc_threads()) {
5299 workers()->run_task(&keep_cm_referents);
5300 } else {
5301 keep_cm_referents.work(0);
5302 }
5303
5304 set_par_threads(0);
5305
5306 // Closure to test whether a referent is alive.
5307 G1STWIsAliveClosure is_alive(this);
5308
5309 // Even when parallel reference processing is enabled, the processing
5310 // of JNI refs is serial and performed serially by the current thread
5311 // rather than by a worker. The following PSS will be used for processing
5312 // JNI refs.
5313
5314 // Use only a single queue for this PSS.
5315 G1ParScanThreadState pss(this, 0);
5316
5317 // We do not embed a reference processor in the copying/scanning
5318 // closures while we're actually processing the discovered
5319 // reference objects.
5320 G1ParScanHeapEvacClosure scan_evac_cl(this, &pss, NULL);
5321 G1ParScanHeapEvacFailureClosure evac_failure_cl(this, &pss, NULL);
5322 G1ParScanPartialArrayClosure partial_scan_cl(this, &pss, NULL);
5323
5324 pss.set_evac_closure(&scan_evac_cl);
5325 pss.set_evac_failure_closure(&evac_failure_cl);
5326 pss.set_partial_scan_closure(&partial_scan_cl);
5327
5328 assert(pss.refs()->is_empty(), "pre-condition");
5329
5330 G1ParScanExtRootClosure only_copy_non_heap_cl(this, &pss, NULL);
5331 G1ParScanPermClosure only_copy_perm_cl(this, &pss, NULL);
5332
5333 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(this, &pss, NULL);
5334 G1ParScanAndMarkPermClosure copy_mark_perm_cl(this, &pss, NULL);
5335
5336 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5337 OopsInHeapRegionClosure* copy_perm_cl = &only_copy_perm_cl;
5338
5339 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5340 // We also need to mark copied objects.
5341 copy_non_heap_cl = ©_mark_non_heap_cl;
5342 copy_perm_cl = ©_mark_perm_cl;
5343 }
5344
5345 // Keep alive closure.
5346 G1CopyingKeepAliveClosure keep_alive(this, copy_non_heap_cl, copy_perm_cl, &pss);
5347
5348 // Serial Complete GC closure
5349 G1STWDrainQueueClosure drain_queue(this, &pss);
5350
5351 // Setup the soft refs policy...
5352 rp->setup_policy(false);
5353
5354 if (!rp->processing_is_mt()) {
5355 // Serial reference processing...
5356 rp->process_discovered_references(&is_alive,
5357 &keep_alive,
5358 &drain_queue,
5359 NULL);
5360 } else {
5361 // Parallel reference processing
5362 assert(rp->num_q() == active_workers, "sanity");
5363 assert(active_workers <= rp->max_num_q(), "sanity");
5364
5365 G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, active_workers);
5366 rp->process_discovered_references(&is_alive, &keep_alive, &drain_queue, &par_task_executor);
5367 }
5368
5369 // We have completed copying any necessary live referent objects
5370 // (that were not copied during the actual pause) so we can
5371 // retire any active alloc buffers
5372 pss.retire_alloc_buffers();
5373 assert(pss.refs()->is_empty(), "both queue and overflow should be empty");
5374
5375 double ref_proc_time = os::elapsedTime() - ref_proc_start;
5376 g1_policy()->record_ref_proc_time(ref_proc_time * 1000.0);
5377 }
5378
5379 // Weak Reference processing during an evacuation pause (part 2).
5380 void G1CollectedHeap::enqueue_discovered_references() {
5381 double ref_enq_start = os::elapsedTime();
5382
5383 ReferenceProcessor* rp = _ref_processor_stw;
5384 assert(!rp->discovery_enabled(), "should have been disabled as part of processing");
5385
5386 // Now enqueue any remaining on the discovered lists on to
5387 // the pending list.
5388 if (!rp->processing_is_mt()) {
5389 // Serial reference processing...
5390 rp->enqueue_discovered_references();
5391 } else {
5392 // Parallel reference enqueuing
5393
5394 uint active_workers = (ParallelGCThreads > 0 ? workers()->active_workers() : 1);
5395 assert(active_workers == workers()->active_workers(),
5396 "Need to reset active_workers");
5397 assert(rp->num_q() == active_workers, "sanity");
5398 assert(active_workers <= rp->max_num_q(), "sanity");
5399
5400 G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, active_workers);
5401 rp->enqueue_discovered_references(&par_task_executor);
5402 }
5403
5404 rp->verify_no_references_recorded();
5405 assert(!rp->discovery_enabled(), "should have been disabled");
5406
5407 // FIXME
5408 // CM's reference processing also cleans up the string and symbol tables.
5409 // Should we do that here also? We could, but it is a serial operation
5410 // and could signicantly increase the pause time.
5411
5412 double ref_enq_time = os::elapsedTime() - ref_enq_start;
5413 g1_policy()->record_ref_enq_time(ref_enq_time * 1000.0);
5414 }
5415
5416 void G1CollectedHeap::evacuate_collection_set() {
5417 _expand_heap_after_alloc_failure = true;
5418 set_evacuation_failed(false);
5419
5420 g1_rem_set()->prepare_for_oops_into_collection_set_do();
5421 concurrent_g1_refine()->set_use_cache(false);
5422 concurrent_g1_refine()->clear_hot_cache_claimed_index();
5423
5424 uint n_workers;
5425 if (G1CollectedHeap::use_parallel_gc_threads()) {
5426 n_workers =
5427 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
5428 workers()->active_workers(),
5429 Threads::number_of_non_daemon_threads());
5430 assert(UseDynamicNumberOfGCThreads ||
5431 n_workers == workers()->total_workers(),
5432 "If not dynamic should be using all the workers");
5433 workers()->set_active_workers(n_workers);
5434 set_par_threads(n_workers);
5435 } else {
5436 assert(n_par_threads() == 0,
5437 "Should be the original non-parallel value");
5438 n_workers = 1;
5439 }
5440
5441 G1ParTask g1_par_task(this, _task_queues);
5442
5443 init_for_evac_failure(NULL);
5444
5445 rem_set()->prepare_for_younger_refs_iterate(true);
5446
5447 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
5448 double start_par_time_sec = os::elapsedTime();
5449 double end_par_time_sec;
5450
5451 {
5452 StrongRootsScope srs(this);
5453
5454 if (G1CollectedHeap::use_parallel_gc_threads()) {
5455 // The individual threads will set their evac-failure closures.
5456 if (ParallelGCVerbose) G1ParScanThreadState::print_termination_stats_hdr();
5457 // These tasks use ShareHeap::_process_strong_tasks
5458 assert(UseDynamicNumberOfGCThreads ||
5459 workers()->active_workers() == workers()->total_workers(),
5460 "If not dynamic should be using all the workers");
5461 workers()->run_task(&g1_par_task);
5462 } else {
5463 g1_par_task.set_for_termination(n_workers);
5464 g1_par_task.work(0);
5465 }
5466 end_par_time_sec = os::elapsedTime();
5467
5468 // Closing the inner scope will execute the destructor
5469 // for the StrongRootsScope object. We record the current
5470 // elapsed time before closing the scope so that time
5471 // taken for the SRS destructor is NOT included in the
5472 // reported parallel time.
5473 }
5474
5475 double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0;
5476 g1_policy()->record_par_time(par_time_ms);
5477
5478 double code_root_fixup_time_ms =
5479 (os::elapsedTime() - end_par_time_sec) * 1000.0;
5480 g1_policy()->record_code_root_fixup_time(code_root_fixup_time_ms);
5481
5482 set_par_threads(0);
5483
5484 // Process any discovered reference objects - we have
5485 // to do this _before_ we retire the GC alloc regions
5486 // as we may have to copy some 'reachable' referent
5487 // objects (and their reachable sub-graphs) that were
5488 // not copied during the pause.
5489 process_discovered_references();
5490
5491 // Weak root processing.
5492 // Note: when JSR 292 is enabled and code blobs can contain
5493 // non-perm oops then we will need to process the code blobs
5494 // here too.
5495 {
5496 G1STWIsAliveClosure is_alive(this);
5497 G1KeepAliveClosure keep_alive(this);
5498 JNIHandles::weak_oops_do(&is_alive, &keep_alive);
5499 }
5500
5501 release_gc_alloc_regions();
5502 g1_rem_set()->cleanup_after_oops_into_collection_set_do();
5503
5504 concurrent_g1_refine()->clear_hot_cache();
5505 concurrent_g1_refine()->set_use_cache(true);
5506
5507 finalize_for_evac_failure();
5508
5509 if (evacuation_failed()) {
5510 remove_self_forwarding_pointers();
5511 if (G1Log::finer()) {
5512 gclog_or_tty->print(" (to-space exhausted)");
5513 } else if (G1Log::fine()) {
5514 gclog_or_tty->print("--");
5515 }
5516 }
5517
5518 // Enqueue any remaining references remaining on the STW
5519 // reference processor's discovered lists. We need to do
5520 // this after the card table is cleaned (and verified) as
5521 // the act of enqueuing entries on to the pending list
5522 // will log these updates (and dirty their associated
5523 // cards). We need these updates logged to update any
5524 // RSets.
5525 enqueue_discovered_references();
5526
5527 if (G1DeferredRSUpdate) {
5528 RedirtyLoggedCardTableEntryFastClosure redirty;
5529 dirty_card_queue_set().set_closure(&redirty);
5530 dirty_card_queue_set().apply_closure_to_all_completed_buffers();
5531
5532 DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set();
5533 dcq.merge_bufferlists(&dirty_card_queue_set());
5534 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
5535 }
5536 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
5537 }
5538
5539 void G1CollectedHeap::free_region_if_empty(HeapRegion* hr,
5540 size_t* pre_used,
5541 FreeRegionList* free_list,
5542 OldRegionSet* old_proxy_set,
5543 HumongousRegionSet* humongous_proxy_set,
5544 HRRSCleanupTask* hrrs_cleanup_task,
5545 bool par) {
5546 if (hr->used() > 0 && hr->max_live_bytes() == 0 && !hr->is_young()) {
5547 if (hr->isHumongous()) {
5548 assert(hr->startsHumongous(), "we should only see starts humongous");
5549 free_humongous_region(hr, pre_used, free_list, humongous_proxy_set, par);
5550 } else {
5551 _old_set.remove_with_proxy(hr, old_proxy_set);
5552 free_region(hr, pre_used, free_list, par);
5553 }
5554 } else {
5555 hr->rem_set()->do_cleanup_work(hrrs_cleanup_task);
5556 }
5557 }
5558
5559 void G1CollectedHeap::free_region(HeapRegion* hr,
5560 size_t* pre_used,
5561 FreeRegionList* free_list,
5562 bool par) {
5563 assert(!hr->isHumongous(), "this is only for non-humongous regions");
5564 assert(!hr->is_empty(), "the region should not be empty");
5565 assert(free_list != NULL, "pre-condition");
5566
5567 *pre_used += hr->used();
5568 hr->hr_clear(par, true /* clear_space */);
5569 free_list->add_as_head(hr);
5570 }
5571
5572 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
5573 size_t* pre_used,
5574 FreeRegionList* free_list,
5575 HumongousRegionSet* humongous_proxy_set,
5576 bool par) {
5577 assert(hr->startsHumongous(), "this is only for starts humongous regions");
5578 assert(free_list != NULL, "pre-condition");
5579 assert(humongous_proxy_set != NULL, "pre-condition");
5580
5581 size_t hr_used = hr->used();
5582 size_t hr_capacity = hr->capacity();
5583 size_t hr_pre_used = 0;
5584 _humongous_set.remove_with_proxy(hr, humongous_proxy_set);
5585 hr->set_notHumongous();
5586 free_region(hr, &hr_pre_used, free_list, par);
5587
5588 uint i = hr->hrs_index() + 1;
5589 uint num = 1;
5590 while (i < n_regions()) {
5591 HeapRegion* curr_hr = region_at(i);
5592 if (!curr_hr->continuesHumongous()) {
5593 break;
5594 }
5595 curr_hr->set_notHumongous();
5596 free_region(curr_hr, &hr_pre_used, free_list, par);
5597 num += 1;
5598 i += 1;
5599 }
5600 assert(hr_pre_used == hr_used,
5601 err_msg("hr_pre_used: "SIZE_FORMAT" and hr_used: "SIZE_FORMAT" "
5602 "should be the same", hr_pre_used, hr_used));
5603 *pre_used += hr_pre_used;
5604 }
5605
5606 void G1CollectedHeap::update_sets_after_freeing_regions(size_t pre_used,
5607 FreeRegionList* free_list,
5608 OldRegionSet* old_proxy_set,
5609 HumongousRegionSet* humongous_proxy_set,
5610 bool par) {
5611 if (pre_used > 0) {
5612 Mutex* lock = (par) ? ParGCRareEvent_lock : NULL;
5613 MutexLockerEx x(lock, Mutex::_no_safepoint_check_flag);
5614 assert(_summary_bytes_used >= pre_used,
5615 err_msg("invariant: _summary_bytes_used: "SIZE_FORMAT" "
5616 "should be >= pre_used: "SIZE_FORMAT,
5617 _summary_bytes_used, pre_used));
5618 _summary_bytes_used -= pre_used;
5619 }
5620 if (free_list != NULL && !free_list->is_empty()) {
5621 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
5622 _free_list.add_as_head(free_list);
5623 }
5624 if (old_proxy_set != NULL && !old_proxy_set->is_empty()) {
5625 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
5626 _old_set.update_from_proxy(old_proxy_set);
5627 }
5628 if (humongous_proxy_set != NULL && !humongous_proxy_set->is_empty()) {
5629 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
5630 _humongous_set.update_from_proxy(humongous_proxy_set);
5631 }
5632 }
5633
5634 class G1ParCleanupCTTask : public AbstractGangTask {
5635 CardTableModRefBS* _ct_bs;
5636 G1CollectedHeap* _g1h;
5637 HeapRegion* volatile _su_head;
5638 public:
5639 G1ParCleanupCTTask(CardTableModRefBS* ct_bs,
5640 G1CollectedHeap* g1h) :
5641 AbstractGangTask("G1 Par Cleanup CT Task"),
5642 _ct_bs(ct_bs), _g1h(g1h) { }
5643
5644 void work(uint worker_id) {
5645 HeapRegion* r;
5646 while (r = _g1h->pop_dirty_cards_region()) {
5647 clear_cards(r);
5648 }
5649 }
5650
5651 void clear_cards(HeapRegion* r) {
5652 // Cards of the survivors should have already been dirtied.
5653 if (!r->is_survivor()) {
5654 _ct_bs->clear(MemRegion(r->bottom(), r->end()));
5655 }
5656 }
5657 };
5658
5659 #ifndef PRODUCT
5660 class G1VerifyCardTableCleanup: public HeapRegionClosure {
5661 G1CollectedHeap* _g1h;
5662 CardTableModRefBS* _ct_bs;
5663 public:
5664 G1VerifyCardTableCleanup(G1CollectedHeap* g1h, CardTableModRefBS* ct_bs)
5665 : _g1h(g1h), _ct_bs(ct_bs) { }
5666 virtual bool doHeapRegion(HeapRegion* r) {
5667 if (r->is_survivor()) {
5668 _g1h->verify_dirty_region(r);
5669 } else {
5670 _g1h->verify_not_dirty_region(r);
5671 }
5672 return false;
5673 }
5674 };
5675
5676 void G1CollectedHeap::verify_not_dirty_region(HeapRegion* hr) {
5677 // All of the region should be clean.
5678 CardTableModRefBS* ct_bs = (CardTableModRefBS*)barrier_set();
5679 MemRegion mr(hr->bottom(), hr->end());
5680 ct_bs->verify_not_dirty_region(mr);
5681 }
5682
5683 void G1CollectedHeap::verify_dirty_region(HeapRegion* hr) {
5684 // We cannot guarantee that [bottom(),end()] is dirty. Threads
5685 // dirty allocated blocks as they allocate them. The thread that
5686 // retires each region and replaces it with a new one will do a
5687 // maximal allocation to fill in [pre_dummy_top(),end()] but will
5688 // not dirty that area (one less thing to have to do while holding
5689 // a lock). So we can only verify that [bottom(),pre_dummy_top()]
5690 // is dirty.
5691 CardTableModRefBS* ct_bs = (CardTableModRefBS*) barrier_set();
5692 MemRegion mr(hr->bottom(), hr->pre_dummy_top());
5693 ct_bs->verify_dirty_region(mr);
5694 }
5695
5696 void G1CollectedHeap::verify_dirty_young_list(HeapRegion* head) {
5697 CardTableModRefBS* ct_bs = (CardTableModRefBS*) barrier_set();
5698 for (HeapRegion* hr = head; hr != NULL; hr = hr->get_next_young_region()) {
5699 verify_dirty_region(hr);
5700 }
5701 }
5702
5703 void G1CollectedHeap::verify_dirty_young_regions() {
5704 verify_dirty_young_list(_young_list->first_region());
5705 verify_dirty_young_list(_young_list->first_survivor_region());
5706 }
5707 #endif
5708
5709 void G1CollectedHeap::cleanUpCardTable() {
5710 CardTableModRefBS* ct_bs = (CardTableModRefBS*) (barrier_set());
5711 double start = os::elapsedTime();
5712
5713 {
5714 // Iterate over the dirty cards region list.
5715 G1ParCleanupCTTask cleanup_task(ct_bs, this);
5716
5717 if (G1CollectedHeap::use_parallel_gc_threads()) {
5718 set_par_threads();
5719 workers()->run_task(&cleanup_task);
5720 set_par_threads(0);
5721 } else {
5722 while (_dirty_cards_region_list) {
5723 HeapRegion* r = _dirty_cards_region_list;
5724 cleanup_task.clear_cards(r);
5725 _dirty_cards_region_list = r->get_next_dirty_cards_region();
5726 if (_dirty_cards_region_list == r) {
5727 // The last region.
5728 _dirty_cards_region_list = NULL;
5729 }
5730 r->set_next_dirty_cards_region(NULL);
5731 }
5732 }
5733 #ifndef PRODUCT
5734 if (G1VerifyCTCleanup || VerifyAfterGC) {
5735 G1VerifyCardTableCleanup cleanup_verifier(this, ct_bs);
5736 heap_region_iterate(&cleanup_verifier);
5737 }
5738 #endif
5739 }
5740
5741 double elapsed = os::elapsedTime() - start;
5742 g1_policy()->record_clear_ct_time(elapsed * 1000.0);
5743 }
5744
5745 void G1CollectedHeap::free_collection_set(HeapRegion* cs_head) {
5746 size_t pre_used = 0;
5747 FreeRegionList local_free_list("Local List for CSet Freeing");
5748
5749 double young_time_ms = 0.0;
5750 double non_young_time_ms = 0.0;
5751
5752 // Since the collection set is a superset of the the young list,
5753 // all we need to do to clear the young list is clear its
5754 // head and length, and unlink any young regions in the code below
5755 _young_list->clear();
5756
5757 G1CollectorPolicy* policy = g1_policy();
5758
5759 double start_sec = os::elapsedTime();
5760 bool non_young = true;
5761
5762 HeapRegion* cur = cs_head;
5763 int age_bound = -1;
5764 size_t rs_lengths = 0;
5765
5766 while (cur != NULL) {
5767 assert(!is_on_master_free_list(cur), "sanity");
5768 if (non_young) {
5769 if (cur->is_young()) {
5770 double end_sec = os::elapsedTime();
5771 double elapsed_ms = (end_sec - start_sec) * 1000.0;
5772 non_young_time_ms += elapsed_ms;
5773
5774 start_sec = os::elapsedTime();
5775 non_young = false;
5776 }
5777 } else {
5778 if (!cur->is_young()) {
5779 double end_sec = os::elapsedTime();
5780 double elapsed_ms = (end_sec - start_sec) * 1000.0;
5781 young_time_ms += elapsed_ms;
5782
5783 start_sec = os::elapsedTime();
5784 non_young = true;
5785 }
5786 }
5787
5788 rs_lengths += cur->rem_set()->occupied();
5789
5790 HeapRegion* next = cur->next_in_collection_set();
5791 assert(cur->in_collection_set(), "bad CS");
5792 cur->set_next_in_collection_set(NULL);
5793 cur->set_in_collection_set(false);
5794
5795 if (cur->is_young()) {
5796 int index = cur->young_index_in_cset();
5797 assert(index != -1, "invariant");
5798 assert((uint) index < policy->young_cset_region_length(), "invariant");
5799 size_t words_survived = _surviving_young_words[index];
5800 cur->record_surv_words_in_group(words_survived);
5801
5802 // At this point the we have 'popped' cur from the collection set
5803 // (linked via next_in_collection_set()) but it is still in the
5804 // young list (linked via next_young_region()). Clear the
5805 // _next_young_region field.
5806 cur->set_next_young_region(NULL);
5807 } else {
5808 int index = cur->young_index_in_cset();
5809 assert(index == -1, "invariant");
5810 }
5811
5812 assert( (cur->is_young() && cur->young_index_in_cset() > -1) ||
5813 (!cur->is_young() && cur->young_index_in_cset() == -1),
5814 "invariant" );
5815
5816 if (!cur->evacuation_failed()) {
5817 MemRegion used_mr = cur->used_region();
5818
5819 // And the region is empty.
5820 assert(!used_mr.is_empty(), "Should not have empty regions in a CS.");
5821 free_region(cur, &pre_used, &local_free_list, false /* par */);
5822 } else {
5823 cur->uninstall_surv_rate_group();
5824 if (cur->is_young()) {
5825 cur->set_young_index_in_cset(-1);
5826 }
5827 cur->set_not_young();
5828 cur->set_evacuation_failed(false);
5829 // The region is now considered to be old.
5830 _old_set.add(cur);
5831 }
5832 cur = next;
5833 }
5834
5835 policy->record_max_rs_lengths(rs_lengths);
5836 policy->cset_regions_freed();
5837
5838 double end_sec = os::elapsedTime();
5839 double elapsed_ms = (end_sec - start_sec) * 1000.0;
5840
5841 if (non_young) {
5842 non_young_time_ms += elapsed_ms;
5843 } else {
5844 young_time_ms += elapsed_ms;
5845 }
5846
5847 update_sets_after_freeing_regions(pre_used, &local_free_list,
5848 NULL /* old_proxy_set */,
5849 NULL /* humongous_proxy_set */,
5850 false /* par */);
5851 policy->record_young_free_cset_time_ms(young_time_ms);
5852 policy->record_non_young_free_cset_time_ms(non_young_time_ms);
5853 }
5854
5855 // This routine is similar to the above but does not record
5856 // any policy statistics or update free lists; we are abandoning
5857 // the current incremental collection set in preparation of a
5858 // full collection. After the full GC we will start to build up
5859 // the incremental collection set again.
5860 // This is only called when we're doing a full collection
5861 // and is immediately followed by the tearing down of the young list.
5862
5863 void G1CollectedHeap::abandon_collection_set(HeapRegion* cs_head) {
5864 HeapRegion* cur = cs_head;
5865
5866 while (cur != NULL) {
5867 HeapRegion* next = cur->next_in_collection_set();
5868 assert(cur->in_collection_set(), "bad CS");
5869 cur->set_next_in_collection_set(NULL);
5870 cur->set_in_collection_set(false);
5871 cur->set_young_index_in_cset(-1);
5872 cur = next;
5873 }
5874 }
5875
5876 void G1CollectedHeap::set_free_regions_coming() {
5877 if (G1ConcRegionFreeingVerbose) {
5878 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
5879 "setting free regions coming");
5880 }
5881
5882 assert(!free_regions_coming(), "pre-condition");
5883 _free_regions_coming = true;
5884 }
5885
5886 void G1CollectedHeap::reset_free_regions_coming() {
5887 assert(free_regions_coming(), "pre-condition");
5888
5889 {
5890 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
5891 _free_regions_coming = false;
5892 SecondaryFreeList_lock->notify_all();
5893 }
5894
5895 if (G1ConcRegionFreeingVerbose) {
5896 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
5897 "reset free regions coming");
5898 }
5899 }
5900
5901 void G1CollectedHeap::wait_while_free_regions_coming() {
5902 // Most of the time we won't have to wait, so let's do a quick test
5903 // first before we take the lock.
5904 if (!free_regions_coming()) {
5905 return;
5906 }
5907
5908 if (G1ConcRegionFreeingVerbose) {
5909 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
5910 "waiting for free regions");
5911 }
5912
5913 {
5914 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
5915 while (free_regions_coming()) {
5916 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
5917 }
5918 }
5919
5920 if (G1ConcRegionFreeingVerbose) {
5921 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
5922 "done waiting for free regions");
5923 }
5924 }
5925
5926 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
5927 assert(heap_lock_held_for_gc(),
5928 "the heap lock should already be held by or for this thread");
5929 _young_list->push_region(hr);
5930 }
5931
5932 class NoYoungRegionsClosure: public HeapRegionClosure {
5933 private:
5934 bool _success;
5935 public:
5936 NoYoungRegionsClosure() : _success(true) { }
5937 bool doHeapRegion(HeapRegion* r) {
5938 if (r->is_young()) {
5939 gclog_or_tty->print_cr("Region ["PTR_FORMAT", "PTR_FORMAT") tagged as young",
5940 r->bottom(), r->end());
5941 _success = false;
5942 }
5943 return false;
5944 }
5945 bool success() { return _success; }
5946 };
5947
5948 bool G1CollectedHeap::check_young_list_empty(bool check_heap, bool check_sample) {
5949 bool ret = _young_list->check_list_empty(check_sample);
5950
5951 if (check_heap) {
5952 NoYoungRegionsClosure closure;
5953 heap_region_iterate(&closure);
5954 ret = ret && closure.success();
5955 }
5956
5957 return ret;
5958 }
5959
5960 class TearDownRegionSetsClosure : public HeapRegionClosure {
5961 private:
5962 OldRegionSet *_old_set;
5963
5964 public:
5965 TearDownRegionSetsClosure(OldRegionSet* old_set) : _old_set(old_set) { }
5966
5967 bool doHeapRegion(HeapRegion* r) {
5968 if (r->is_empty()) {
5969 // We ignore empty regions, we'll empty the free list afterwards
5970 } else if (r->is_young()) {
5971 // We ignore young regions, we'll empty the young list afterwards
5972 } else if (r->isHumongous()) {
5973 // We ignore humongous regions, we're not tearing down the
5974 // humongous region set
5975 } else {
5976 // The rest should be old
5977 _old_set->remove(r);
5978 }
5979 return false;
5980 }
5981
5982 ~TearDownRegionSetsClosure() {
5983 assert(_old_set->is_empty(), "post-condition");
5984 }
5985 };
5986
5987 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
5988 assert_at_safepoint(true /* should_be_vm_thread */);
5989
5990 if (!free_list_only) {
5991 TearDownRegionSetsClosure cl(&_old_set);
5992 heap_region_iterate(&cl);
5993
5994 // Need to do this after the heap iteration to be able to
5995 // recognize the young regions and ignore them during the iteration.
5996 _young_list->empty_list();
5997 }
5998 _free_list.remove_all();
5999 }
6000
6001 class RebuildRegionSetsClosure : public HeapRegionClosure {
6002 private:
6003 bool _free_list_only;
6004 OldRegionSet* _old_set;
6005 FreeRegionList* _free_list;
6006 size_t _total_used;
6007
6008 public:
6009 RebuildRegionSetsClosure(bool free_list_only,
6010 OldRegionSet* old_set, FreeRegionList* free_list) :
6011 _free_list_only(free_list_only),
6012 _old_set(old_set), _free_list(free_list), _total_used(0) {
6013 assert(_free_list->is_empty(), "pre-condition");
6014 if (!free_list_only) {
6015 assert(_old_set->is_empty(), "pre-condition");
6016 }
6017 }
6018
6019 bool doHeapRegion(HeapRegion* r) {
6020 if (r->continuesHumongous()) {
6021 return false;
6022 }
6023
6024 if (r->is_empty()) {
6025 // Add free regions to the free list
6026 _free_list->add_as_tail(r);
6027 } else if (!_free_list_only) {
6028 assert(!r->is_young(), "we should not come across young regions");
6029
6030 if (r->isHumongous()) {
6031 // We ignore humongous regions, we left the humongous set unchanged
6032 } else {
6033 // The rest should be old, add them to the old set
6034 _old_set->add(r);
6035 }
6036 _total_used += r->used();
6037 }
6038
6039 return false;
6040 }
6041
6042 size_t total_used() {
6043 return _total_used;
6044 }
6045 };
6046
6047 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
6048 assert_at_safepoint(true /* should_be_vm_thread */);
6049
6050 RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_free_list);
6051 heap_region_iterate(&cl);
6052
6053 if (!free_list_only) {
6054 _summary_bytes_used = cl.total_used();
6055 }
6056 assert(_summary_bytes_used == recalculate_used(),
6057 err_msg("inconsistent _summary_bytes_used, "
6058 "value: "SIZE_FORMAT" recalculated: "SIZE_FORMAT,
6059 _summary_bytes_used, recalculate_used()));
6060 }
6061
6062 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) {
6063 _refine_cte_cl->set_concurrent(concurrent);
6064 }
6065
6066 bool G1CollectedHeap::is_in_closed_subset(const void* p) const {
6067 HeapRegion* hr = heap_region_containing(p);
6068 if (hr == NULL) {
6069 return is_in_permanent(p);
6070 } else {
6071 return hr->is_in(p);
6072 }
6073 }
6074
6075 // Methods for the mutator alloc region
6076
6077 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
6078 bool force) {
6079 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6080 assert(!force || g1_policy()->can_expand_young_list(),
6081 "if force is true we should be able to expand the young list");
6082 bool young_list_full = g1_policy()->is_young_list_full();
6083 if (force || !young_list_full) {
6084 HeapRegion* new_alloc_region = new_region(word_size,
6085 false /* do_expand */);
6086 if (new_alloc_region != NULL) {
6087 set_region_short_lived_locked(new_alloc_region);
6088 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Eden, young_list_full);
6089 return new_alloc_region;
6090 }
6091 }
6092 return NULL;
6093 }
6094
6095 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
6096 size_t allocated_bytes) {
6097 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6098 assert(alloc_region->is_young(), "all mutator alloc regions should be young");
6099
6100 g1_policy()->add_region_to_incremental_cset_lhs(alloc_region);
6101 _summary_bytes_used += allocated_bytes;
6102 _hr_printer.retire(alloc_region);
6103 // We update the eden sizes here, when the region is retired,
6104 // instead of when it's allocated, since this is the point that its
6105 // used space has been recored in _summary_bytes_used.
6106 g1mm()->update_eden_size();
6107 }
6108
6109 HeapRegion* MutatorAllocRegion::allocate_new_region(size_t word_size,
6110 bool force) {
6111 return _g1h->new_mutator_alloc_region(word_size, force);
6112 }
6113
6114 void G1CollectedHeap::set_par_threads() {
6115 // Don't change the number of workers. Use the value previously set
6116 // in the workgroup.
6117 assert(G1CollectedHeap::use_parallel_gc_threads(), "shouldn't be here otherwise");
6118 uint n_workers = workers()->active_workers();
6119 assert(UseDynamicNumberOfGCThreads ||
6120 n_workers == workers()->total_workers(),
6121 "Otherwise should be using the total number of workers");
6122 if (n_workers == 0) {
6123 assert(false, "Should have been set in prior evacuation pause.");
6124 n_workers = ParallelGCThreads;
6125 workers()->set_active_workers(n_workers);
6126 }
6127 set_par_threads(n_workers);
6128 }
6129
6130 void MutatorAllocRegion::retire_region(HeapRegion* alloc_region,
6131 size_t allocated_bytes) {
6132 _g1h->retire_mutator_alloc_region(alloc_region, allocated_bytes);
6133 }
6134
6135 // Methods for the GC alloc regions
6136
6137 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size,
6138 uint count,
6139 GCAllocPurpose ap) {
6140 assert(FreeList_lock->owned_by_self(), "pre-condition");
6141
6142 if (count < g1_policy()->max_regions(ap)) {
6143 HeapRegion* new_alloc_region = new_region(word_size,
6144 true /* do_expand */);
6145 if (new_alloc_region != NULL) {
6146 // We really only need to do this for old regions given that we
6147 // should never scan survivors. But it doesn't hurt to do it
6148 // for survivors too.
6149 new_alloc_region->set_saved_mark();
6150 if (ap == GCAllocForSurvived) {
6151 new_alloc_region->set_survivor();
6152 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Survivor);
6153 } else {
6154 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Old);
6155 }
6156 bool during_im = g1_policy()->during_initial_mark_pause();
6157 new_alloc_region->note_start_of_copying(during_im);
6158 return new_alloc_region;
6159 } else {
6160 g1_policy()->note_alloc_region_limit_reached(ap);
6161 }
6162 }
6163 return NULL;
6164 }
6165
6166 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
6167 size_t allocated_bytes,
6168 GCAllocPurpose ap) {
6169 bool during_im = g1_policy()->during_initial_mark_pause();
6170 alloc_region->note_end_of_copying(during_im);
6171 g1_policy()->record_bytes_copied_during_gc(allocated_bytes);
6172 if (ap == GCAllocForSurvived) {
6173 young_list()->add_survivor_region(alloc_region);
6174 } else {
6175 _old_set.add(alloc_region);
6176 }
6177 _hr_printer.retire(alloc_region);
6178 }
6179
6180 HeapRegion* SurvivorGCAllocRegion::allocate_new_region(size_t word_size,
6181 bool force) {
6182 assert(!force, "not supported for GC alloc regions");
6183 return _g1h->new_gc_alloc_region(word_size, count(), GCAllocForSurvived);
6184 }
6185
6186 void SurvivorGCAllocRegion::retire_region(HeapRegion* alloc_region,
6187 size_t allocated_bytes) {
6188 _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes,
6189 GCAllocForSurvived);
6190 }
6191
6192 HeapRegion* OldGCAllocRegion::allocate_new_region(size_t word_size,
6193 bool force) {
6194 assert(!force, "not supported for GC alloc regions");
6195 return _g1h->new_gc_alloc_region(word_size, count(), GCAllocForTenured);
6196 }
6197
6198 void OldGCAllocRegion::retire_region(HeapRegion* alloc_region,
6199 size_t allocated_bytes) {
6200 _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes,
6201 GCAllocForTenured);
6202 }
6203 // Heap region set verification
6204
6205 class VerifyRegionListsClosure : public HeapRegionClosure {
6206 private:
6207 FreeRegionList* _free_list;
6208 OldRegionSet* _old_set;
6209 HumongousRegionSet* _humongous_set;
6210 uint _region_count;
6211
6212 public:
6213 VerifyRegionListsClosure(OldRegionSet* old_set,
6214 HumongousRegionSet* humongous_set,
6215 FreeRegionList* free_list) :
6216 _old_set(old_set), _humongous_set(humongous_set),
6217 _free_list(free_list), _region_count(0) { }
6218
6219 uint region_count() { return _region_count; }
6220
6221 bool doHeapRegion(HeapRegion* hr) {
6222 _region_count += 1;
6223
6224 if (hr->continuesHumongous()) {
6225 return false;
6226 }
6227
6228 if (hr->is_young()) {
6229 // TODO
6230 } else if (hr->startsHumongous()) {
6231 _humongous_set->verify_next_region(hr);
6232 } else if (hr->is_empty()) {
6233 _free_list->verify_next_region(hr);
6234 } else {
6235 _old_set->verify_next_region(hr);
6236 }
6237 return false;
6238 }
6239 };
6240
6241 HeapRegion* G1CollectedHeap::new_heap_region(uint hrs_index,
6242 HeapWord* bottom) {
6243 HeapWord* end = bottom + HeapRegion::GrainWords;
6244 MemRegion mr(bottom, end);
6245 assert(_g1_reserved.contains(mr), "invariant");
6246 // This might return NULL if the allocation fails
6247 return new HeapRegion(hrs_index, _bot_shared, mr, true /* is_zeroed */);
6248 }
6249
6250 void G1CollectedHeap::verify_region_sets() {
6251 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6252
6253 // First, check the explicit lists.
6254 _free_list.verify();
6255 {
6256 // Given that a concurrent operation might be adding regions to
6257 // the secondary free list we have to take the lock before
6258 // verifying it.
6259 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6260 _secondary_free_list.verify();
6261 }
6262 _old_set.verify();
6263 _humongous_set.verify();
6264
6265 // If a concurrent region freeing operation is in progress it will
6266 // be difficult to correctly attributed any free regions we come
6267 // across to the correct free list given that they might belong to
6268 // one of several (free_list, secondary_free_list, any local lists,
6269 // etc.). So, if that's the case we will skip the rest of the
6270 // verification operation. Alternatively, waiting for the concurrent
6271 // operation to complete will have a non-trivial effect on the GC's
6272 // operation (no concurrent operation will last longer than the
6273 // interval between two calls to verification) and it might hide
6274 // any issues that we would like to catch during testing.
6275 if (free_regions_coming()) {
6276 return;
6277 }
6278
6279 // Make sure we append the secondary_free_list on the free_list so
6280 // that all free regions we will come across can be safely
6281 // attributed to the free_list.
6282 append_secondary_free_list_if_not_empty_with_lock();
6283
6284 // Finally, make sure that the region accounting in the lists is
6285 // consistent with what we see in the heap.
6286 _old_set.verify_start();
6287 _humongous_set.verify_start();
6288 _free_list.verify_start();
6289
6290 VerifyRegionListsClosure cl(&_old_set, &_humongous_set, &_free_list);
6291 heap_region_iterate(&cl);
6292
6293 _old_set.verify_end();
6294 _humongous_set.verify_end();
6295 _free_list.verify_end();
6296 }