rev 2891 : 7120038: G1: ParallelGCThreads==0 is broken
Summary: Running G1 with ParallelGCThreads==0 results in various crashes and asserts. Most of these are caused by unguarded references to the worker threads array or an incorrect number of active workers.
Reviewed-by:
1 /*
2 * Copyright (c) 2001, 2011, 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/g1MarkSweep.hpp"
36 #include "gc_implementation/g1/g1OopClosures.inline.hpp"
37 #include "gc_implementation/g1/g1RemSet.inline.hpp"
38 #include "gc_implementation/g1/heapRegionRemSet.hpp"
39 #include "gc_implementation/g1/heapRegionSeq.inline.hpp"
40 #include "gc_implementation/g1/vm_operations_g1.hpp"
41 #include "gc_implementation/shared/isGCActiveMark.hpp"
42 #include "memory/gcLocker.inline.hpp"
43 #include "memory/genOopClosures.inline.hpp"
44 #include "memory/generationSpec.hpp"
45 #include "memory/referenceProcessor.hpp"
46 #include "oops/oop.inline.hpp"
47 #include "oops/oop.pcgc.inline.hpp"
48 #include "runtime/aprofiler.hpp"
49 #include "runtime/vmThread.hpp"
50
51 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;
52
53 // turn it on so that the contents of the young list (scan-only /
54 // to-be-collected) are printed at "strategic" points before / during
55 // / after the collection --- this is useful for debugging
56 #define YOUNG_LIST_VERBOSE 0
57 // CURRENT STATUS
58 // This file is under construction. Search for "FIXME".
59
60 // INVARIANTS/NOTES
61 //
62 // All allocation activity covered by the G1CollectedHeap interface is
63 // serialized by acquiring the HeapLock. This happens in mem_allocate
64 // and allocate_new_tlab, which are the "entry" points to the
65 // allocation code from the rest of the JVM. (Note that this does not
66 // apply to TLAB allocation, which is not part of this interface: it
67 // is done by clients of this interface.)
68
69 // Notes on implementation of parallelism in different tasks.
70 //
71 // G1ParVerifyTask uses heap_region_par_iterate_chunked() for parallelism.
72 // The number of GC workers is passed to heap_region_par_iterate_chunked().
73 // It does use run_task() which sets _n_workers in the task.
74 // G1ParTask executes g1_process_strong_roots() ->
75 // SharedHeap::process_strong_roots() which calls eventuall to
76 // CardTableModRefBS::par_non_clean_card_iterate_work() which uses
77 // SequentialSubTasksDone. SharedHeap::process_strong_roots() also
78 // directly uses SubTasksDone (_process_strong_tasks field in SharedHeap).
79 //
80
81 // Local to this file.
82
83 class RefineCardTableEntryClosure: public CardTableEntryClosure {
84 SuspendibleThreadSet* _sts;
85 G1RemSet* _g1rs;
86 ConcurrentG1Refine* _cg1r;
87 bool _concurrent;
88 public:
89 RefineCardTableEntryClosure(SuspendibleThreadSet* sts,
90 G1RemSet* g1rs,
91 ConcurrentG1Refine* cg1r) :
92 _sts(sts), _g1rs(g1rs), _cg1r(cg1r), _concurrent(true)
93 {}
94 bool do_card_ptr(jbyte* card_ptr, int worker_i) {
95 bool oops_into_cset = _g1rs->concurrentRefineOneCard(card_ptr, worker_i, false);
96 // This path is executed by the concurrent refine or mutator threads,
97 // concurrently, and so we do not care if card_ptr contains references
98 // that point into the collection set.
99 assert(!oops_into_cset, "should be");
100
101 if (_concurrent && _sts->should_yield()) {
102 // Caller will actually yield.
103 return false;
104 }
105 // Otherwise, we finished successfully; return true.
106 return true;
107 }
108 void set_concurrent(bool b) { _concurrent = b; }
109 };
110
111
112 class ClearLoggedCardTableEntryClosure: public CardTableEntryClosure {
113 int _calls;
114 G1CollectedHeap* _g1h;
115 CardTableModRefBS* _ctbs;
116 int _histo[256];
117 public:
118 ClearLoggedCardTableEntryClosure() :
119 _calls(0)
120 {
121 _g1h = G1CollectedHeap::heap();
122 _ctbs = (CardTableModRefBS*)_g1h->barrier_set();
123 for (int i = 0; i < 256; i++) _histo[i] = 0;
124 }
125 bool do_card_ptr(jbyte* card_ptr, int worker_i) {
126 if (_g1h->is_in_reserved(_ctbs->addr_for(card_ptr))) {
127 _calls++;
128 unsigned char* ujb = (unsigned char*)card_ptr;
129 int ind = (int)(*ujb);
130 _histo[ind]++;
131 *card_ptr = -1;
132 }
133 return true;
134 }
135 int calls() { return _calls; }
136 void print_histo() {
137 gclog_or_tty->print_cr("Card table value histogram:");
138 for (int i = 0; i < 256; i++) {
139 if (_histo[i] != 0) {
140 gclog_or_tty->print_cr(" %d: %d", i, _histo[i]);
141 }
142 }
143 }
144 };
145
146 class RedirtyLoggedCardTableEntryClosure: public CardTableEntryClosure {
147 int _calls;
148 G1CollectedHeap* _g1h;
149 CardTableModRefBS* _ctbs;
150 public:
151 RedirtyLoggedCardTableEntryClosure() :
152 _calls(0)
153 {
154 _g1h = G1CollectedHeap::heap();
155 _ctbs = (CardTableModRefBS*)_g1h->barrier_set();
156 }
157 bool do_card_ptr(jbyte* card_ptr, int worker_i) {
158 if (_g1h->is_in_reserved(_ctbs->addr_for(card_ptr))) {
159 _calls++;
160 *card_ptr = 0;
161 }
162 return true;
163 }
164 int calls() { return _calls; }
165 };
166
167 class RedirtyLoggedCardTableEntryFastClosure : public CardTableEntryClosure {
168 public:
169 bool do_card_ptr(jbyte* card_ptr, int worker_i) {
170 *card_ptr = CardTableModRefBS::dirty_card_val();
171 return true;
172 }
173 };
174
175 YoungList::YoungList(G1CollectedHeap* g1h)
176 : _g1h(g1h), _head(NULL),
177 _length(0),
178 _last_sampled_rs_lengths(0),
179 _survivor_head(NULL), _survivor_tail(NULL), _survivor_length(0)
180 {
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 size_t 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 %d entries, _length is %d",
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 %d",
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((size_t) young_index_in_cset == _survivor_length,
341 "post-condition");
342 _g1h->g1_policy()->note_stop_adding_survivor_regions();
343
344 _head = _survivor_head;
345 _length = _survivor_length;
346 if (_survivor_head != NULL) {
347 assert(_survivor_tail != NULL, "cause it shouldn't be");
348 assert(_survivor_length > 0, "invariant");
349 _survivor_tail->set_next_young_region(NULL);
350 }
351
352 // Don't clear the survivor list handles until the start of
353 // the next evacuation pause - we need it in order to re-tag
354 // the survivor regions from this evacuation pause as 'young'
355 // at the start of the next.
356
357 _g1h->g1_policy()->finished_recalculating_age_indexes(false /* is_survivors */);
358
359 assert(check_list_well_formed(), "young list should be well formed");
360 }
361
362 void YoungList::print() {
363 HeapRegion* lists[] = {_head, _survivor_head};
364 const char* names[] = {"YOUNG", "SURVIVOR"};
365
366 for (unsigned int list = 0; list < ARRAY_SIZE(lists); ++list) {
367 gclog_or_tty->print_cr("%s LIST CONTENTS", names[list]);
368 HeapRegion *curr = lists[list];
369 if (curr == NULL)
370 gclog_or_tty->print_cr(" empty");
371 while (curr != NULL) {
372 gclog_or_tty->print_cr(" [%08x-%08x], t: %08x, P: %08x, N: %08x, C: %08x, "
373 "age: %4d, y: %d, surv: %d",
374 curr->bottom(), curr->end(),
375 curr->top(),
376 curr->prev_top_at_mark_start(),
377 curr->next_top_at_mark_start(),
378 curr->top_at_conc_mark_count(),
379 curr->age_in_surv_rate_group_cond(),
380 curr->is_young(),
381 curr->is_survivor());
382 curr = curr->get_next_young_region();
383 }
384 }
385
386 gclog_or_tty->print_cr("");
387 }
388
389 void G1CollectedHeap::push_dirty_cards_region(HeapRegion* hr)
390 {
391 // Claim the right to put the region on the dirty cards region list
392 // by installing a self pointer.
393 HeapRegion* next = hr->get_next_dirty_cards_region();
394 if (next == NULL) {
395 HeapRegion* res = (HeapRegion*)
396 Atomic::cmpxchg_ptr(hr, hr->next_dirty_cards_region_addr(),
397 NULL);
398 if (res == NULL) {
399 HeapRegion* head;
400 do {
401 // Put the region to the dirty cards region list.
402 head = _dirty_cards_region_list;
403 next = (HeapRegion*)
404 Atomic::cmpxchg_ptr(hr, &_dirty_cards_region_list, head);
405 if (next == head) {
406 assert(hr->get_next_dirty_cards_region() == hr,
407 "hr->get_next_dirty_cards_region() != hr");
408 if (next == NULL) {
409 // The last region in the list points to itself.
410 hr->set_next_dirty_cards_region(hr);
411 } else {
412 hr->set_next_dirty_cards_region(next);
413 }
414 }
415 } while (next != head);
416 }
417 }
418 }
419
420 HeapRegion* G1CollectedHeap::pop_dirty_cards_region()
421 {
422 HeapRegion* head;
423 HeapRegion* hr;
424 do {
425 head = _dirty_cards_region_list;
426 if (head == NULL) {
427 return NULL;
428 }
429 HeapRegion* new_head = head->get_next_dirty_cards_region();
430 if (head == new_head) {
431 // The last region.
432 new_head = NULL;
433 }
434 hr = (HeapRegion*)Atomic::cmpxchg_ptr(new_head, &_dirty_cards_region_list,
435 head);
436 } while (hr != head);
437 assert(hr != NULL, "invariant");
438 hr->set_next_dirty_cards_region(NULL);
439 return hr;
440 }
441
442 void G1CollectedHeap::stop_conc_gc_threads() {
443 _cg1r->stop();
444 _cmThread->stop();
445 }
446
447 #ifdef ASSERT
448 // A region is added to the collection set as it is retired
449 // so an address p can point to a region which will be in the
450 // collection set but has not yet been retired. This method
451 // therefore is only accurate during a GC pause after all
452 // regions have been retired. It is used for debugging
453 // to check if an nmethod has references to objects that can
454 // be move during a partial collection. Though it can be
455 // inaccurate, it is sufficient for G1 because the conservative
456 // implementation of is_scavengable() for G1 will indicate that
457 // all nmethods must be scanned during a partial collection.
458 bool G1CollectedHeap::is_in_partial_collection(const void* p) {
459 HeapRegion* hr = heap_region_containing(p);
460 return hr != NULL && hr->in_collection_set();
461 }
462 #endif
463
464 // Returns true if the reference points to an object that
465 // can move in an incremental collecction.
466 bool G1CollectedHeap::is_scavengable(const void* p) {
467 G1CollectedHeap* g1h = G1CollectedHeap::heap();
468 G1CollectorPolicy* g1p = g1h->g1_policy();
469 HeapRegion* hr = heap_region_containing(p);
470 if (hr == NULL) {
471 // perm gen (or null)
472 return false;
473 } else {
474 return !hr->isHumongous();
475 }
476 }
477
478 void G1CollectedHeap::check_ct_logs_at_safepoint() {
479 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
480 CardTableModRefBS* ct_bs = (CardTableModRefBS*)barrier_set();
481
482 // Count the dirty cards at the start.
483 CountNonCleanMemRegionClosure count1(this);
484 ct_bs->mod_card_iterate(&count1);
485 int orig_count = count1.n();
486
487 // First clear the logged cards.
488 ClearLoggedCardTableEntryClosure clear;
489 dcqs.set_closure(&clear);
490 dcqs.apply_closure_to_all_completed_buffers();
491 dcqs.iterate_closure_all_threads(false);
492 clear.print_histo();
493
494 // Now ensure that there's no dirty cards.
495 CountNonCleanMemRegionClosure count2(this);
496 ct_bs->mod_card_iterate(&count2);
497 if (count2.n() != 0) {
498 gclog_or_tty->print_cr("Card table has %d entries; %d originally",
499 count2.n(), orig_count);
500 }
501 guarantee(count2.n() == 0, "Card table should be clean.");
502
503 RedirtyLoggedCardTableEntryClosure redirty;
504 JavaThread::dirty_card_queue_set().set_closure(&redirty);
505 dcqs.apply_closure_to_all_completed_buffers();
506 dcqs.iterate_closure_all_threads(false);
507 gclog_or_tty->print_cr("Log entries = %d, dirty cards = %d.",
508 clear.calls(), orig_count);
509 guarantee(redirty.calls() == clear.calls(),
510 "Or else mechanism is broken.");
511
512 CountNonCleanMemRegionClosure count3(this);
513 ct_bs->mod_card_iterate(&count3);
514 if (count3.n() != orig_count) {
515 gclog_or_tty->print_cr("Should have restored them all: orig = %d, final = %d.",
516 orig_count, count3.n());
517 guarantee(count3.n() >= orig_count, "Should have restored them all.");
518 }
519
520 JavaThread::dirty_card_queue_set().set_closure(_refine_cte_cl);
521 }
522
523 // Private class members.
524
525 G1CollectedHeap* G1CollectedHeap::_g1h;
526
527 // Private methods.
528
529 HeapRegion*
530 G1CollectedHeap::new_region_try_secondary_free_list() {
531 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
532 while (!_secondary_free_list.is_empty() || free_regions_coming()) {
533 if (!_secondary_free_list.is_empty()) {
534 if (G1ConcRegionFreeingVerbose) {
535 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
536 "secondary_free_list has "SIZE_FORMAT" entries",
537 _secondary_free_list.length());
538 }
539 // It looks as if there are free regions available on the
540 // secondary_free_list. Let's move them to the free_list and try
541 // again to allocate from it.
542 append_secondary_free_list();
543
544 assert(!_free_list.is_empty(), "if the secondary_free_list was not "
545 "empty we should have moved at least one entry to the free_list");
546 HeapRegion* res = _free_list.remove_head();
547 if (G1ConcRegionFreeingVerbose) {
548 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
549 "allocated "HR_FORMAT" from secondary_free_list",
550 HR_FORMAT_PARAMS(res));
551 }
552 return res;
553 }
554
555 // Wait here until we get notifed either when (a) there are no
556 // more free regions coming or (b) some regions have been moved on
557 // the secondary_free_list.
558 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
559 }
560
561 if (G1ConcRegionFreeingVerbose) {
562 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
563 "could not allocate from secondary_free_list");
564 }
565 return NULL;
566 }
567
568 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool do_expand) {
569 assert(!isHumongous(word_size) || word_size <= HeapRegion::GrainWords,
570 "the only time we use this to allocate a humongous region is "
571 "when we are allocating a single humongous region");
572
573 HeapRegion* res;
574 if (G1StressConcRegionFreeing) {
575 if (!_secondary_free_list.is_empty()) {
576 if (G1ConcRegionFreeingVerbose) {
577 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
578 "forced to look at the secondary_free_list");
579 }
580 res = new_region_try_secondary_free_list();
581 if (res != NULL) {
582 return res;
583 }
584 }
585 }
586 res = _free_list.remove_head_or_null();
587 if (res == NULL) {
588 if (G1ConcRegionFreeingVerbose) {
589 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
590 "res == NULL, trying the secondary_free_list");
591 }
592 res = new_region_try_secondary_free_list();
593 }
594 if (res == NULL && do_expand) {
595 ergo_verbose1(ErgoHeapSizing,
596 "attempt heap expansion",
597 ergo_format_reason("region allocation request failed")
598 ergo_format_byte("allocation request"),
599 word_size * HeapWordSize);
600 if (expand(word_size * HeapWordSize)) {
601 // Even though the heap was expanded, it might not have reached
602 // the desired size. So, we cannot assume that the allocation
603 // will succeed.
604 res = _free_list.remove_head_or_null();
605 }
606 }
607 return res;
608 }
609
610 size_t G1CollectedHeap::humongous_obj_allocate_find_first(size_t num_regions,
611 size_t word_size) {
612 assert(isHumongous(word_size), "word_size should be humongous");
613 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
614
615 size_t first = G1_NULL_HRS_INDEX;
616 if (num_regions == 1) {
617 // Only one region to allocate, no need to go through the slower
618 // path. The caller will attempt the expasion if this fails, so
619 // let's not try to expand here too.
620 HeapRegion* hr = new_region(word_size, false /* do_expand */);
621 if (hr != NULL) {
622 first = hr->hrs_index();
623 } else {
624 first = G1_NULL_HRS_INDEX;
625 }
626 } else {
627 // We can't allocate humongous regions while cleanupComplete() is
628 // running, since some of the regions we find to be empty might not
629 // yet be added to the free list and it is not straightforward to
630 // know which list they are on so that we can remove them. Note
631 // that we only need to do this if we need to allocate more than
632 // one region to satisfy the current humongous allocation
633 // request. If we are only allocating one region we use the common
634 // region allocation code (see above).
635 wait_while_free_regions_coming();
636 append_secondary_free_list_if_not_empty_with_lock();
637
638 if (free_regions() >= num_regions) {
639 first = _hrs.find_contiguous(num_regions);
640 if (first != G1_NULL_HRS_INDEX) {
641 for (size_t i = first; i < first + num_regions; ++i) {
642 HeapRegion* hr = region_at(i);
643 assert(hr->is_empty(), "sanity");
644 assert(is_on_master_free_list(hr), "sanity");
645 hr->set_pending_removal(true);
646 }
647 _free_list.remove_all_pending(num_regions);
648 }
649 }
650 }
651 return first;
652 }
653
654 HeapWord*
655 G1CollectedHeap::humongous_obj_allocate_initialize_regions(size_t first,
656 size_t num_regions,
657 size_t word_size) {
658 assert(first != G1_NULL_HRS_INDEX, "pre-condition");
659 assert(isHumongous(word_size), "word_size should be humongous");
660 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
661
662 // Index of last region in the series + 1.
663 size_t last = first + num_regions;
664
665 // We need to initialize the region(s) we just discovered. This is
666 // a bit tricky given that it can happen concurrently with
667 // refinement threads refining cards on these regions and
668 // potentially wanting to refine the BOT as they are scanning
669 // those cards (this can happen shortly after a cleanup; see CR
670 // 6991377). So we have to set up the region(s) carefully and in
671 // a specific order.
672
673 // The word size sum of all the regions we will allocate.
674 size_t word_size_sum = num_regions * HeapRegion::GrainWords;
675 assert(word_size <= word_size_sum, "sanity");
676
677 // This will be the "starts humongous" region.
678 HeapRegion* first_hr = region_at(first);
679 // The header of the new object will be placed at the bottom of
680 // the first region.
681 HeapWord* new_obj = first_hr->bottom();
682 // This will be the new end of the first region in the series that
683 // should also match the end of the last region in the seriers.
684 HeapWord* new_end = new_obj + word_size_sum;
685 // This will be the new top of the first region that will reflect
686 // this allocation.
687 HeapWord* new_top = new_obj + word_size;
688
689 // First, we need to zero the header of the space that we will be
690 // allocating. When we update top further down, some refinement
691 // threads might try to scan the region. By zeroing the header we
692 // ensure that any thread that will try to scan the region will
693 // come across the zero klass word and bail out.
694 //
695 // NOTE: It would not have been correct to have used
696 // CollectedHeap::fill_with_object() and make the space look like
697 // an int array. The thread that is doing the allocation will
698 // later update the object header to a potentially different array
699 // type and, for a very short period of time, the klass and length
700 // fields will be inconsistent. This could cause a refinement
701 // thread to calculate the object size incorrectly.
702 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
703
704 // We will set up the first region as "starts humongous". This
705 // will also update the BOT covering all the regions to reflect
706 // that there is a single object that starts at the bottom of the
707 // first region.
708 first_hr->set_startsHumongous(new_top, new_end);
709
710 // Then, if there are any, we will set up the "continues
711 // humongous" regions.
712 HeapRegion* hr = NULL;
713 for (size_t i = first + 1; i < last; ++i) {
714 hr = region_at(i);
715 hr->set_continuesHumongous(first_hr);
716 }
717 // If we have "continues humongous" regions (hr != NULL), then the
718 // end of the last one should match new_end.
719 assert(hr == NULL || hr->end() == new_end, "sanity");
720
721 // Up to this point no concurrent thread would have been able to
722 // do any scanning on any region in this series. All the top
723 // fields still point to bottom, so the intersection between
724 // [bottom,top] and [card_start,card_end] will be empty. Before we
725 // update the top fields, we'll do a storestore to make sure that
726 // no thread sees the update to top before the zeroing of the
727 // object header and the BOT initialization.
728 OrderAccess::storestore();
729
730 // Now that the BOT and the object header have been initialized,
731 // we can update top of the "starts humongous" region.
732 assert(first_hr->bottom() < new_top && new_top <= first_hr->end(),
733 "new_top should be in this region");
734 first_hr->set_top(new_top);
735 if (_hr_printer.is_active()) {
736 HeapWord* bottom = first_hr->bottom();
737 HeapWord* end = first_hr->orig_end();
738 if ((first + 1) == last) {
739 // the series has a single humongous region
740 _hr_printer.alloc(G1HRPrinter::SingleHumongous, first_hr, new_top);
741 } else {
742 // the series has more than one humongous regions
743 _hr_printer.alloc(G1HRPrinter::StartsHumongous, first_hr, end);
744 }
745 }
746
747 // Now, we will update the top fields of the "continues humongous"
748 // regions. The reason we need to do this is that, otherwise,
749 // these regions would look empty and this will confuse parts of
750 // G1. For example, the code that looks for a consecutive number
751 // of empty regions will consider them empty and try to
752 // re-allocate them. We can extend is_empty() to also include
753 // !continuesHumongous(), but it is easier to just update the top
754 // fields here. The way we set top for all regions (i.e., top ==
755 // end for all regions but the last one, top == new_top for the
756 // last one) is actually used when we will free up the humongous
757 // region in free_humongous_region().
758 hr = NULL;
759 for (size_t i = first + 1; i < last; ++i) {
760 hr = region_at(i);
761 if ((i + 1) == last) {
762 // last continues humongous region
763 assert(hr->bottom() < new_top && new_top <= hr->end(),
764 "new_top should fall on this region");
765 hr->set_top(new_top);
766 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, new_top);
767 } else {
768 // not last one
769 assert(new_top > hr->end(), "new_top should be above this region");
770 hr->set_top(hr->end());
771 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, hr->end());
772 }
773 }
774 // If we have continues humongous regions (hr != NULL), then the
775 // end of the last one should match new_end and its top should
776 // match new_top.
777 assert(hr == NULL ||
778 (hr->end() == new_end && hr->top() == new_top), "sanity");
779
780 assert(first_hr->used() == word_size * HeapWordSize, "invariant");
781 _summary_bytes_used += first_hr->used();
782 _humongous_set.add(first_hr);
783
784 return new_obj;
785 }
786
787 // If could fit into free regions w/o expansion, try.
788 // Otherwise, if can expand, do so.
789 // Otherwise, if using ex regions might help, try with ex given back.
790 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size) {
791 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
792
793 verify_region_sets_optional();
794
795 size_t num_regions =
796 round_to(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords;
797 size_t x_size = expansion_regions();
798 size_t fs = _hrs.free_suffix();
799 size_t first = humongous_obj_allocate_find_first(num_regions, word_size);
800 if (first == G1_NULL_HRS_INDEX) {
801 // The only thing we can do now is attempt expansion.
802 if (fs + x_size >= num_regions) {
803 // If the number of regions we're trying to allocate for this
804 // object is at most the number of regions in the free suffix,
805 // then the call to humongous_obj_allocate_find_first() above
806 // should have succeeded and we wouldn't be here.
807 //
808 // We should only be trying to expand when the free suffix is
809 // not sufficient for the object _and_ we have some expansion
810 // room available.
811 assert(num_regions > fs, "earlier allocation should have succeeded");
812
813 ergo_verbose1(ErgoHeapSizing,
814 "attempt heap expansion",
815 ergo_format_reason("humongous allocation request failed")
816 ergo_format_byte("allocation request"),
817 word_size * HeapWordSize);
818 if (expand((num_regions - fs) * HeapRegion::GrainBytes)) {
819 // Even though the heap was expanded, it might not have
820 // reached the desired size. So, we cannot assume that the
821 // allocation will succeed.
822 first = humongous_obj_allocate_find_first(num_regions, word_size);
823 }
824 }
825 }
826
827 HeapWord* result = NULL;
828 if (first != G1_NULL_HRS_INDEX) {
829 result =
830 humongous_obj_allocate_initialize_regions(first, num_regions, word_size);
831 assert(result != NULL, "it should always return a valid result");
832
833 // A successful humongous object allocation changes the used space
834 // information of the old generation so we need to recalculate the
835 // sizes and update the jstat counters here.
836 g1mm()->update_sizes();
837 }
838
839 verify_region_sets_optional();
840
841 return result;
842 }
843
844 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) {
845 assert_heap_not_locked_and_not_at_safepoint();
846 assert(!isHumongous(word_size), "we do not allow humongous TLABs");
847
848 unsigned int dummy_gc_count_before;
849 return attempt_allocation(word_size, &dummy_gc_count_before);
850 }
851
852 HeapWord*
853 G1CollectedHeap::mem_allocate(size_t word_size,
854 bool* gc_overhead_limit_was_exceeded) {
855 assert_heap_not_locked_and_not_at_safepoint();
856
857 // Loop until the allocation is satisified, or unsatisfied after GC.
858 for (int try_count = 1; /* we'll return */; try_count += 1) {
859 unsigned int gc_count_before;
860
861 HeapWord* result = NULL;
862 if (!isHumongous(word_size)) {
863 result = attempt_allocation(word_size, &gc_count_before);
864 } else {
865 result = attempt_allocation_humongous(word_size, &gc_count_before);
866 }
867 if (result != NULL) {
868 return result;
869 }
870
871 // Create the garbage collection operation...
872 VM_G1CollectForAllocation op(gc_count_before, word_size);
873 // ...and get the VM thread to execute it.
874 VMThread::execute(&op);
875
876 if (op.prologue_succeeded() && op.pause_succeeded()) {
877 // If the operation was successful we'll return the result even
878 // if it is NULL. If the allocation attempt failed immediately
879 // after a Full GC, it's unlikely we'll be able to allocate now.
880 HeapWord* result = op.result();
881 if (result != NULL && !isHumongous(word_size)) {
882 // Allocations that take place on VM operations do not do any
883 // card dirtying and we have to do it here. We only have to do
884 // this for non-humongous allocations, though.
885 dirty_young_block(result, word_size);
886 }
887 return result;
888 } else {
889 assert(op.result() == NULL,
890 "the result should be NULL if the VM op did not succeed");
891 }
892
893 // Give a warning if we seem to be looping forever.
894 if ((QueuedAllocationWarningCount > 0) &&
895 (try_count % QueuedAllocationWarningCount == 0)) {
896 warning("G1CollectedHeap::mem_allocate retries %d times", try_count);
897 }
898 }
899
900 ShouldNotReachHere();
901 return NULL;
902 }
903
904 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size,
905 unsigned int *gc_count_before_ret) {
906 // Make sure you read the note in attempt_allocation_humongous().
907
908 assert_heap_not_locked_and_not_at_safepoint();
909 assert(!isHumongous(word_size), "attempt_allocation_slow() should not "
910 "be called for humongous allocation requests");
911
912 // We should only get here after the first-level allocation attempt
913 // (attempt_allocation()) failed to allocate.
914
915 // We will loop until a) we manage to successfully perform the
916 // allocation or b) we successfully schedule a collection which
917 // fails to perform the allocation. b) is the only case when we'll
918 // return NULL.
919 HeapWord* result = NULL;
920 for (int try_count = 1; /* we'll return */; try_count += 1) {
921 bool should_try_gc;
922 unsigned int gc_count_before;
923
924 {
925 MutexLockerEx x(Heap_lock);
926
927 result = _mutator_alloc_region.attempt_allocation_locked(word_size,
928 false /* bot_updates */);
929 if (result != NULL) {
930 return result;
931 }
932
933 // If we reach here, attempt_allocation_locked() above failed to
934 // allocate a new region. So the mutator alloc region should be NULL.
935 assert(_mutator_alloc_region.get() == NULL, "only way to get here");
936
937 if (GC_locker::is_active_and_needs_gc()) {
938 if (g1_policy()->can_expand_young_list()) {
939 // No need for an ergo verbose message here,
940 // can_expand_young_list() does this when it returns true.
941 result = _mutator_alloc_region.attempt_allocation_force(word_size,
942 false /* bot_updates */);
943 if (result != NULL) {
944 return result;
945 }
946 }
947 should_try_gc = false;
948 } else {
949 // Read the GC count while still holding the Heap_lock.
950 gc_count_before = SharedHeap::heap()->total_collections();
951 should_try_gc = true;
952 }
953 }
954
955 if (should_try_gc) {
956 bool succeeded;
957 result = do_collection_pause(word_size, gc_count_before, &succeeded);
958 if (result != NULL) {
959 assert(succeeded, "only way to get back a non-NULL result");
960 return result;
961 }
962
963 if (succeeded) {
964 // If we get here we successfully scheduled a collection which
965 // failed to allocate. No point in trying to allocate
966 // further. We'll just return NULL.
967 MutexLockerEx x(Heap_lock);
968 *gc_count_before_ret = SharedHeap::heap()->total_collections();
969 return NULL;
970 }
971 } else {
972 GC_locker::stall_until_clear();
973 }
974
975 // We can reach here if we were unsuccessul in scheduling a
976 // collection (because another thread beat us to it) or if we were
977 // stalled due to the GC locker. In either can we should retry the
978 // allocation attempt in case another thread successfully
979 // performed a collection and reclaimed enough space. We do the
980 // first attempt (without holding the Heap_lock) here and the
981 // follow-on attempt will be at the start of the next loop
982 // iteration (after taking the Heap_lock).
983 result = _mutator_alloc_region.attempt_allocation(word_size,
984 false /* bot_updates */);
985 if (result != NULL ){
986 return result;
987 }
988
989 // Give a warning if we seem to be looping forever.
990 if ((QueuedAllocationWarningCount > 0) &&
991 (try_count % QueuedAllocationWarningCount == 0)) {
992 warning("G1CollectedHeap::attempt_allocation_slow() "
993 "retries %d times", try_count);
994 }
995 }
996
997 ShouldNotReachHere();
998 return NULL;
999 }
1000
1001 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size,
1002 unsigned int * gc_count_before_ret) {
1003 // The structure of this method has a lot of similarities to
1004 // attempt_allocation_slow(). The reason these two were not merged
1005 // into a single one is that such a method would require several "if
1006 // allocation is not humongous do this, otherwise do that"
1007 // conditional paths which would obscure its flow. In fact, an early
1008 // version of this code did use a unified method which was harder to
1009 // follow and, as a result, it had subtle bugs that were hard to
1010 // track down. So keeping these two methods separate allows each to
1011 // be more readable. It will be good to keep these two in sync as
1012 // much as possible.
1013
1014 assert_heap_not_locked_and_not_at_safepoint();
1015 assert(isHumongous(word_size), "attempt_allocation_humongous() "
1016 "should only be called for humongous allocations");
1017
1018 // We will loop until a) we manage to successfully perform the
1019 // allocation or b) we successfully schedule a collection which
1020 // fails to perform the allocation. b) is the only case when we'll
1021 // return NULL.
1022 HeapWord* result = NULL;
1023 for (int try_count = 1; /* we'll return */; try_count += 1) {
1024 bool should_try_gc;
1025 unsigned int gc_count_before;
1026
1027 {
1028 MutexLockerEx x(Heap_lock);
1029
1030 // Given that humongous objects are not allocated in young
1031 // regions, we'll first try to do the allocation without doing a
1032 // collection hoping that there's enough space in the heap.
1033 result = humongous_obj_allocate(word_size);
1034 if (result != NULL) {
1035 return result;
1036 }
1037
1038 if (GC_locker::is_active_and_needs_gc()) {
1039 should_try_gc = false;
1040 } else {
1041 // Read the GC count while still holding the Heap_lock.
1042 gc_count_before = SharedHeap::heap()->total_collections();
1043 should_try_gc = true;
1044 }
1045 }
1046
1047 if (should_try_gc) {
1048 // If we failed to allocate the humongous object, we should try to
1049 // do a collection pause (if we're allowed) in case it reclaims
1050 // enough space for the allocation to succeed after the pause.
1051
1052 bool succeeded;
1053 result = do_collection_pause(word_size, gc_count_before, &succeeded);
1054 if (result != NULL) {
1055 assert(succeeded, "only way to get back a non-NULL result");
1056 return result;
1057 }
1058
1059 if (succeeded) {
1060 // If we get here we successfully scheduled a collection which
1061 // failed to allocate. No point in trying to allocate
1062 // further. We'll just return NULL.
1063 MutexLockerEx x(Heap_lock);
1064 *gc_count_before_ret = SharedHeap::heap()->total_collections();
1065 return NULL;
1066 }
1067 } else {
1068 GC_locker::stall_until_clear();
1069 }
1070
1071 // We can reach here if we were unsuccessul in scheduling a
1072 // collection (because another thread beat us to it) or if we were
1073 // stalled due to the GC locker. In either can we should retry the
1074 // allocation attempt in case another thread successfully
1075 // performed a collection and reclaimed enough space. Give a
1076 // warning if we seem to be looping forever.
1077
1078 if ((QueuedAllocationWarningCount > 0) &&
1079 (try_count % QueuedAllocationWarningCount == 0)) {
1080 warning("G1CollectedHeap::attempt_allocation_humongous() "
1081 "retries %d times", try_count);
1082 }
1083 }
1084
1085 ShouldNotReachHere();
1086 return NULL;
1087 }
1088
1089 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
1090 bool expect_null_mutator_alloc_region) {
1091 assert_at_safepoint(true /* should_be_vm_thread */);
1092 assert(_mutator_alloc_region.get() == NULL ||
1093 !expect_null_mutator_alloc_region,
1094 "the current alloc region was unexpectedly found to be non-NULL");
1095
1096 if (!isHumongous(word_size)) {
1097 return _mutator_alloc_region.attempt_allocation_locked(word_size,
1098 false /* bot_updates */);
1099 } else {
1100 return humongous_obj_allocate(word_size);
1101 }
1102
1103 ShouldNotReachHere();
1104 }
1105
1106 class PostMCRemSetClearClosure: public HeapRegionClosure {
1107 ModRefBarrierSet* _mr_bs;
1108 public:
1109 PostMCRemSetClearClosure(ModRefBarrierSet* mr_bs) : _mr_bs(mr_bs) {}
1110 bool doHeapRegion(HeapRegion* r) {
1111 r->reset_gc_time_stamp();
1112 if (r->continuesHumongous())
1113 return false;
1114 HeapRegionRemSet* hrrs = r->rem_set();
1115 if (hrrs != NULL) hrrs->clear();
1116 // You might think here that we could clear just the cards
1117 // corresponding to the used region. But no: if we leave a dirty card
1118 // in a region we might allocate into, then it would prevent that card
1119 // from being enqueued, and cause it to be missed.
1120 // Re: the performance cost: we shouldn't be doing full GC anyway!
1121 _mr_bs->clear(MemRegion(r->bottom(), r->end()));
1122 return false;
1123 }
1124 };
1125
1126
1127 class PostMCRemSetInvalidateClosure: public HeapRegionClosure {
1128 ModRefBarrierSet* _mr_bs;
1129 public:
1130 PostMCRemSetInvalidateClosure(ModRefBarrierSet* mr_bs) : _mr_bs(mr_bs) {}
1131 bool doHeapRegion(HeapRegion* r) {
1132 if (r->continuesHumongous()) return false;
1133 if (r->used_region().word_size() != 0) {
1134 _mr_bs->invalidate(r->used_region(), true /*whole heap*/);
1135 }
1136 return false;
1137 }
1138 };
1139
1140 class RebuildRSOutOfRegionClosure: public HeapRegionClosure {
1141 G1CollectedHeap* _g1h;
1142 UpdateRSOopClosure _cl;
1143 int _worker_i;
1144 public:
1145 RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, int worker_i = 0) :
1146 _cl(g1->g1_rem_set(), worker_i),
1147 _worker_i(worker_i),
1148 _g1h(g1)
1149 { }
1150
1151 bool doHeapRegion(HeapRegion* r) {
1152 if (!r->continuesHumongous()) {
1153 _cl.set_from(r);
1154 r->oop_iterate(&_cl);
1155 }
1156 return false;
1157 }
1158 };
1159
1160 class ParRebuildRSTask: public AbstractGangTask {
1161 G1CollectedHeap* _g1;
1162 public:
1163 ParRebuildRSTask(G1CollectedHeap* g1)
1164 : AbstractGangTask("ParRebuildRSTask"),
1165 _g1(g1)
1166 { }
1167
1168 void work(int i) {
1169 RebuildRSOutOfRegionClosure rebuild_rs(_g1, i);
1170 _g1->heap_region_par_iterate_chunked(&rebuild_rs, i,
1171 _g1->workers()->active_workers(),
1172 HeapRegion::RebuildRSClaimValue);
1173 }
1174 };
1175
1176 class PostCompactionPrinterClosure: public HeapRegionClosure {
1177 private:
1178 G1HRPrinter* _hr_printer;
1179 public:
1180 bool doHeapRegion(HeapRegion* hr) {
1181 assert(!hr->is_young(), "not expecting to find young regions");
1182 // We only generate output for non-empty regions.
1183 if (!hr->is_empty()) {
1184 if (!hr->isHumongous()) {
1185 _hr_printer->post_compaction(hr, G1HRPrinter::Old);
1186 } else if (hr->startsHumongous()) {
1187 if (hr->capacity() == HeapRegion::GrainBytes) {
1188 // single humongous region
1189 _hr_printer->post_compaction(hr, G1HRPrinter::SingleHumongous);
1190 } else {
1191 _hr_printer->post_compaction(hr, G1HRPrinter::StartsHumongous);
1192 }
1193 } else {
1194 assert(hr->continuesHumongous(), "only way to get here");
1195 _hr_printer->post_compaction(hr, G1HRPrinter::ContinuesHumongous);
1196 }
1197 }
1198 return false;
1199 }
1200
1201 PostCompactionPrinterClosure(G1HRPrinter* hr_printer)
1202 : _hr_printer(hr_printer) { }
1203 };
1204
1205 bool G1CollectedHeap::do_collection(bool explicit_gc,
1206 bool clear_all_soft_refs,
1207 size_t word_size) {
1208 assert_at_safepoint(true /* should_be_vm_thread */);
1209
1210 if (GC_locker::check_active_before_gc()) {
1211 return false;
1212 }
1213
1214 SvcGCMarker sgcm(SvcGCMarker::FULL);
1215 ResourceMark rm;
1216
1217 if (PrintHeapAtGC) {
1218 Universe::print_heap_before_gc();
1219 }
1220
1221 HRSPhaseSetter x(HRSPhaseFullGC);
1222 verify_region_sets_optional();
1223
1224 const bool do_clear_all_soft_refs = clear_all_soft_refs ||
1225 collector_policy()->should_clear_all_soft_refs();
1226
1227 ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy());
1228
1229 {
1230 IsGCActiveMark x;
1231
1232 // Timing
1233 bool system_gc = (gc_cause() == GCCause::_java_lang_system_gc);
1234 assert(!system_gc || explicit_gc, "invariant");
1235 gclog_or_tty->date_stamp(PrintGC && PrintGCDateStamps);
1236 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty);
1237 TraceTime t(system_gc ? "Full GC (System.gc())" : "Full GC",
1238 PrintGC, true, gclog_or_tty);
1239
1240 TraceCollectorStats tcs(g1mm()->full_collection_counters());
1241 TraceMemoryManagerStats tms(true /* fullGC */, gc_cause());
1242
1243 double start = os::elapsedTime();
1244 g1_policy()->record_full_collection_start();
1245
1246 wait_while_free_regions_coming();
1247 append_secondary_free_list_if_not_empty_with_lock();
1248
1249 gc_prologue(true);
1250 increment_total_collections(true /* full gc */);
1251
1252 size_t g1h_prev_used = used();
1253 assert(used() == recalculate_used(), "Should be equal");
1254
1255 if (VerifyBeforeGC && total_collections() >= VerifyGCStartAt) {
1256 HandleMark hm; // Discard invalid handles created during verification
1257 gclog_or_tty->print(" VerifyBeforeGC:");
1258 prepare_for_verify();
1259 Universe::verify(/* allow dirty */ true,
1260 /* silent */ false,
1261 /* option */ VerifyOption_G1UsePrevMarking);
1262
1263 }
1264 pre_full_gc_dump();
1265
1266 COMPILER2_PRESENT(DerivedPointerTable::clear());
1267
1268 // Disable discovery and empty the discovered lists
1269 // for the CM ref processor.
1270 ref_processor_cm()->disable_discovery();
1271 ref_processor_cm()->abandon_partial_discovery();
1272 ref_processor_cm()->verify_no_references_recorded();
1273
1274 // Abandon current iterations of concurrent marking and concurrent
1275 // refinement, if any are in progress.
1276 concurrent_mark()->abort();
1277
1278 // Make sure we'll choose a new allocation region afterwards.
1279 release_mutator_alloc_region();
1280 abandon_gc_alloc_regions();
1281 g1_rem_set()->cleanupHRRS();
1282
1283 // We should call this after we retire any currently active alloc
1284 // regions so that all the ALLOC / RETIRE events are generated
1285 // before the start GC event.
1286 _hr_printer.start_gc(true /* full */, (size_t) total_collections());
1287
1288 // We may have added regions to the current incremental collection
1289 // set between the last GC or pause and now. We need to clear the
1290 // incremental collection set and then start rebuilding it afresh
1291 // after this full GC.
1292 abandon_collection_set(g1_policy()->inc_cset_head());
1293 g1_policy()->clear_incremental_cset();
1294 g1_policy()->stop_incremental_cset_building();
1295
1296 tear_down_region_sets(false /* free_list_only */);
1297 g1_policy()->set_full_young_gcs(true);
1298
1299 // See the comments in g1CollectedHeap.hpp and
1300 // G1CollectedHeap::ref_processing_init() about
1301 // how reference processing currently works in G1.
1302
1303 // Temporarily make discovery by the STW ref processor single threaded (non-MT).
1304 ReferenceProcessorMTDiscoveryMutator stw_rp_disc_ser(ref_processor_stw(), false);
1305
1306 // Temporarily clear the STW ref processor's _is_alive_non_header field.
1307 ReferenceProcessorIsAliveMutator stw_rp_is_alive_null(ref_processor_stw(), NULL);
1308
1309 ref_processor_stw()->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/);
1310 ref_processor_stw()->setup_policy(do_clear_all_soft_refs);
1311
1312 // Do collection work
1313 {
1314 HandleMark hm; // Discard invalid handles created during gc
1315 G1MarkSweep::invoke_at_safepoint(ref_processor_stw(), do_clear_all_soft_refs);
1316 }
1317
1318 assert(free_regions() == 0, "we should not have added any free regions");
1319 rebuild_region_sets(false /* free_list_only */);
1320
1321 // Enqueue any discovered reference objects that have
1322 // not been removed from the discovered lists.
1323 ref_processor_stw()->enqueue_discovered_references();
1324
1325 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
1326
1327 MemoryService::track_memory_usage();
1328
1329 if (VerifyAfterGC && total_collections() >= VerifyGCStartAt) {
1330 HandleMark hm; // Discard invalid handles created during verification
1331 gclog_or_tty->print(" VerifyAfterGC:");
1332 prepare_for_verify();
1333 Universe::verify(/* allow dirty */ false,
1334 /* silent */ false,
1335 /* option */ VerifyOption_G1UsePrevMarking);
1336
1337 }
1338
1339 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
1340 ref_processor_stw()->verify_no_references_recorded();
1341
1342 // Note: since we've just done a full GC, concurrent
1343 // marking is no longer active. Therefore we need not
1344 // re-enable reference discovery for the CM ref processor.
1345 // That will be done at the start of the next marking cycle.
1346 assert(!ref_processor_cm()->discovery_enabled(), "Postcondition");
1347 ref_processor_cm()->verify_no_references_recorded();
1348
1349 reset_gc_time_stamp();
1350 // Since everything potentially moved, we will clear all remembered
1351 // sets, and clear all cards. Later we will rebuild remebered
1352 // sets. We will also reset the GC time stamps of the regions.
1353 PostMCRemSetClearClosure rs_clear(mr_bs());
1354 heap_region_iterate(&rs_clear);
1355
1356 // Resize the heap if necessary.
1357 resize_if_necessary_after_full_collection(explicit_gc ? 0 : word_size);
1358
1359 if (_hr_printer.is_active()) {
1360 // We should do this after we potentially resize the heap so
1361 // that all the COMMIT / UNCOMMIT events are generated before
1362 // the end GC event.
1363
1364 PostCompactionPrinterClosure cl(hr_printer());
1365 heap_region_iterate(&cl);
1366
1367 _hr_printer.end_gc(true /* full */, (size_t) total_collections());
1368 }
1369
1370 if (_cg1r->use_cache()) {
1371 _cg1r->clear_and_record_card_counts();
1372 _cg1r->clear_hot_cache();
1373 }
1374
1375 // Rebuild remembered sets of all regions.
1376 if (G1CollectedHeap::use_parallel_gc_threads()) {
1377 int n_workers =
1378 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
1379 workers()->active_workers(),
1380 Threads::number_of_non_daemon_threads());
1381 assert(UseDynamicNumberOfGCThreads ||
1382 n_workers == workers()->total_workers(),
1383 "If not dynamic should be using all the workers");
1384 workers()->set_active_workers(n_workers);
1385 // Set parallel threads in the heap (_n_par_threads) only
1386 // before a parallel phase and always reset it to 0 after
1387 // the phase so that the number of parallel threads does
1388 // no get carried forward to a serial phase where there
1389 // may be code that is "possibly_parallel".
1390 set_par_threads(n_workers);
1391
1392 ParRebuildRSTask rebuild_rs_task(this);
1393 assert(check_heap_region_claim_values(
1394 HeapRegion::InitialClaimValue), "sanity check");
1395 assert(UseDynamicNumberOfGCThreads ||
1396 workers()->active_workers() == workers()->total_workers(),
1397 "Unless dynamic should use total workers");
1398 // Use the most recent number of active workers
1399 assert(workers()->active_workers() > 0,
1400 "Active workers not properly set");
1401 set_par_threads(workers()->active_workers());
1402 workers()->run_task(&rebuild_rs_task);
1403 set_par_threads(0);
1404 assert(check_heap_region_claim_values(
1405 HeapRegion::RebuildRSClaimValue), "sanity check");
1406 reset_heap_region_claim_values();
1407 } else {
1408 RebuildRSOutOfRegionClosure rebuild_rs(this);
1409 heap_region_iterate(&rebuild_rs);
1410 }
1411
1412 if (PrintGC) {
1413 print_size_transition(gclog_or_tty, g1h_prev_used, used(), capacity());
1414 }
1415
1416 if (true) { // FIXME
1417 // Ask the permanent generation to adjust size for full collections
1418 perm()->compute_new_size();
1419 }
1420
1421 // Start a new incremental collection set for the next pause
1422 assert(g1_policy()->collection_set() == NULL, "must be");
1423 g1_policy()->start_incremental_cset_building();
1424
1425 // Clear the _cset_fast_test bitmap in anticipation of adding
1426 // regions to the incremental collection set for the next
1427 // evacuation pause.
1428 clear_cset_fast_test();
1429
1430 init_mutator_alloc_region();
1431
1432 double end = os::elapsedTime();
1433 g1_policy()->record_full_collection_end();
1434
1435 #ifdef TRACESPINNING
1436 ParallelTaskTerminator::print_termination_counts();
1437 #endif
1438
1439 gc_epilogue(true);
1440
1441 // Discard all rset updates
1442 JavaThread::dirty_card_queue_set().abandon_logs();
1443 assert(!G1DeferredRSUpdate
1444 || (G1DeferredRSUpdate && (dirty_card_queue_set().completed_buffers_num() == 0)), "Should not be any");
1445 }
1446
1447 _young_list->reset_sampled_info();
1448 // At this point there should be no regions in the
1449 // entire heap tagged as young.
1450 assert( check_young_list_empty(true /* check_heap */),
1451 "young list should be empty at this point");
1452
1453 // Update the number of full collections that have been completed.
1454 increment_full_collections_completed(false /* concurrent */);
1455
1456 _hrs.verify_optional();
1457 verify_region_sets_optional();
1458
1459 if (PrintHeapAtGC) {
1460 Universe::print_heap_after_gc();
1461 }
1462 g1mm()->update_sizes();
1463 post_full_gc_dump();
1464
1465 return true;
1466 }
1467
1468 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
1469 // do_collection() will return whether it succeeded in performing
1470 // the GC. Currently, there is no facility on the
1471 // do_full_collection() API to notify the caller than the collection
1472 // did not succeed (e.g., because it was locked out by the GC
1473 // locker). So, right now, we'll ignore the return value.
1474 bool dummy = do_collection(true, /* explicit_gc */
1475 clear_all_soft_refs,
1476 0 /* word_size */);
1477 }
1478
1479 // This code is mostly copied from TenuredGeneration.
1480 void
1481 G1CollectedHeap::
1482 resize_if_necessary_after_full_collection(size_t word_size) {
1483 assert(MinHeapFreeRatio <= MaxHeapFreeRatio, "sanity check");
1484
1485 // Include the current allocation, if any, and bytes that will be
1486 // pre-allocated to support collections, as "used".
1487 const size_t used_after_gc = used();
1488 const size_t capacity_after_gc = capacity();
1489 const size_t free_after_gc = capacity_after_gc - used_after_gc;
1490
1491 // This is enforced in arguments.cpp.
1492 assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
1493 "otherwise the code below doesn't make sense");
1494
1495 // We don't have floating point command-line arguments
1496 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
1497 const double maximum_used_percentage = 1.0 - minimum_free_percentage;
1498 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
1499 const double minimum_used_percentage = 1.0 - maximum_free_percentage;
1500
1501 const size_t min_heap_size = collector_policy()->min_heap_byte_size();
1502 const size_t max_heap_size = collector_policy()->max_heap_byte_size();
1503
1504 // We have to be careful here as these two calculations can overflow
1505 // 32-bit size_t's.
1506 double used_after_gc_d = (double) used_after_gc;
1507 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
1508 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
1509
1510 // Let's make sure that they are both under the max heap size, which
1511 // by default will make them fit into a size_t.
1512 double desired_capacity_upper_bound = (double) max_heap_size;
1513 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
1514 desired_capacity_upper_bound);
1515 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
1516 desired_capacity_upper_bound);
1517
1518 // We can now safely turn them into size_t's.
1519 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
1520 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
1521
1522 // This assert only makes sense here, before we adjust them
1523 // with respect to the min and max heap size.
1524 assert(minimum_desired_capacity <= maximum_desired_capacity,
1525 err_msg("minimum_desired_capacity = "SIZE_FORMAT", "
1526 "maximum_desired_capacity = "SIZE_FORMAT,
1527 minimum_desired_capacity, maximum_desired_capacity));
1528
1529 // Should not be greater than the heap max size. No need to adjust
1530 // it with respect to the heap min size as it's a lower bound (i.e.,
1531 // we'll try to make the capacity larger than it, not smaller).
1532 minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size);
1533 // Should not be less than the heap min size. No need to adjust it
1534 // with respect to the heap max size as it's an upper bound (i.e.,
1535 // we'll try to make the capacity smaller than it, not greater).
1536 maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size);
1537
1538 if (capacity_after_gc < minimum_desired_capacity) {
1539 // Don't expand unless it's significant
1540 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
1541 ergo_verbose4(ErgoHeapSizing,
1542 "attempt heap expansion",
1543 ergo_format_reason("capacity lower than "
1544 "min desired capacity after Full GC")
1545 ergo_format_byte("capacity")
1546 ergo_format_byte("occupancy")
1547 ergo_format_byte_perc("min desired capacity"),
1548 capacity_after_gc, used_after_gc,
1549 minimum_desired_capacity, (double) MinHeapFreeRatio);
1550 expand(expand_bytes);
1551
1552 // No expansion, now see if we want to shrink
1553 } else if (capacity_after_gc > maximum_desired_capacity) {
1554 // Capacity too large, compute shrinking size
1555 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
1556 ergo_verbose4(ErgoHeapSizing,
1557 "attempt heap shrinking",
1558 ergo_format_reason("capacity higher than "
1559 "max desired capacity after Full GC")
1560 ergo_format_byte("capacity")
1561 ergo_format_byte("occupancy")
1562 ergo_format_byte_perc("max desired capacity"),
1563 capacity_after_gc, used_after_gc,
1564 maximum_desired_capacity, (double) MaxHeapFreeRatio);
1565 shrink(shrink_bytes);
1566 }
1567 }
1568
1569
1570 HeapWord*
1571 G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
1572 bool* succeeded) {
1573 assert_at_safepoint(true /* should_be_vm_thread */);
1574
1575 *succeeded = true;
1576 // Let's attempt the allocation first.
1577 HeapWord* result =
1578 attempt_allocation_at_safepoint(word_size,
1579 false /* expect_null_mutator_alloc_region */);
1580 if (result != NULL) {
1581 assert(*succeeded, "sanity");
1582 return result;
1583 }
1584
1585 // In a G1 heap, we're supposed to keep allocation from failing by
1586 // incremental pauses. Therefore, at least for now, we'll favor
1587 // expansion over collection. (This might change in the future if we can
1588 // do something smarter than full collection to satisfy a failed alloc.)
1589 result = expand_and_allocate(word_size);
1590 if (result != NULL) {
1591 assert(*succeeded, "sanity");
1592 return result;
1593 }
1594
1595 // Expansion didn't work, we'll try to do a Full GC.
1596 bool gc_succeeded = do_collection(false, /* explicit_gc */
1597 false, /* clear_all_soft_refs */
1598 word_size);
1599 if (!gc_succeeded) {
1600 *succeeded = false;
1601 return NULL;
1602 }
1603
1604 // Retry the allocation
1605 result = attempt_allocation_at_safepoint(word_size,
1606 true /* expect_null_mutator_alloc_region */);
1607 if (result != NULL) {
1608 assert(*succeeded, "sanity");
1609 return result;
1610 }
1611
1612 // Then, try a Full GC that will collect all soft references.
1613 gc_succeeded = do_collection(false, /* explicit_gc */
1614 true, /* clear_all_soft_refs */
1615 word_size);
1616 if (!gc_succeeded) {
1617 *succeeded = false;
1618 return NULL;
1619 }
1620
1621 // Retry the allocation once more
1622 result = attempt_allocation_at_safepoint(word_size,
1623 true /* expect_null_mutator_alloc_region */);
1624 if (result != NULL) {
1625 assert(*succeeded, "sanity");
1626 return result;
1627 }
1628
1629 assert(!collector_policy()->should_clear_all_soft_refs(),
1630 "Flag should have been handled and cleared prior to this point");
1631
1632 // What else? We might try synchronous finalization later. If the total
1633 // space available is large enough for the allocation, then a more
1634 // complete compaction phase than we've tried so far might be
1635 // appropriate.
1636 assert(*succeeded, "sanity");
1637 return NULL;
1638 }
1639
1640 // Attempting to expand the heap sufficiently
1641 // to support an allocation of the given "word_size". If
1642 // successful, perform the allocation and return the address of the
1643 // allocated block, or else "NULL".
1644
1645 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size) {
1646 assert_at_safepoint(true /* should_be_vm_thread */);
1647
1648 verify_region_sets_optional();
1649
1650 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
1651 ergo_verbose1(ErgoHeapSizing,
1652 "attempt heap expansion",
1653 ergo_format_reason("allocation request failed")
1654 ergo_format_byte("allocation request"),
1655 word_size * HeapWordSize);
1656 if (expand(expand_bytes)) {
1657 _hrs.verify_optional();
1658 verify_region_sets_optional();
1659 return attempt_allocation_at_safepoint(word_size,
1660 false /* expect_null_mutator_alloc_region */);
1661 }
1662 return NULL;
1663 }
1664
1665 void G1CollectedHeap::update_committed_space(HeapWord* old_end,
1666 HeapWord* new_end) {
1667 assert(old_end != new_end, "don't call this otherwise");
1668 assert((HeapWord*) _g1_storage.high() == new_end, "invariant");
1669
1670 // Update the committed mem region.
1671 _g1_committed.set_end(new_end);
1672 // Tell the card table about the update.
1673 Universe::heap()->barrier_set()->resize_covered_region(_g1_committed);
1674 // Tell the BOT about the update.
1675 _bot_shared->resize(_g1_committed.word_size());
1676 }
1677
1678 bool G1CollectedHeap::expand(size_t expand_bytes) {
1679 size_t old_mem_size = _g1_storage.committed_size();
1680 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
1681 aligned_expand_bytes = align_size_up(aligned_expand_bytes,
1682 HeapRegion::GrainBytes);
1683 ergo_verbose2(ErgoHeapSizing,
1684 "expand the heap",
1685 ergo_format_byte("requested expansion amount")
1686 ergo_format_byte("attempted expansion amount"),
1687 expand_bytes, aligned_expand_bytes);
1688
1689 // First commit the memory.
1690 HeapWord* old_end = (HeapWord*) _g1_storage.high();
1691 bool successful = _g1_storage.expand_by(aligned_expand_bytes);
1692 if (successful) {
1693 // Then propagate this update to the necessary data structures.
1694 HeapWord* new_end = (HeapWord*) _g1_storage.high();
1695 update_committed_space(old_end, new_end);
1696
1697 FreeRegionList expansion_list("Local Expansion List");
1698 MemRegion mr = _hrs.expand_by(old_end, new_end, &expansion_list);
1699 assert(mr.start() == old_end, "post-condition");
1700 // mr might be a smaller region than what was requested if
1701 // expand_by() was unable to allocate the HeapRegion instances
1702 assert(mr.end() <= new_end, "post-condition");
1703
1704 size_t actual_expand_bytes = mr.byte_size();
1705 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
1706 assert(actual_expand_bytes == expansion_list.total_capacity_bytes(),
1707 "post-condition");
1708 if (actual_expand_bytes < aligned_expand_bytes) {
1709 // We could not expand _hrs to the desired size. In this case we
1710 // need to shrink the committed space accordingly.
1711 assert(mr.end() < new_end, "invariant");
1712
1713 size_t diff_bytes = aligned_expand_bytes - actual_expand_bytes;
1714 // First uncommit the memory.
1715 _g1_storage.shrink_by(diff_bytes);
1716 // Then propagate this update to the necessary data structures.
1717 update_committed_space(new_end, mr.end());
1718 }
1719 _free_list.add_as_tail(&expansion_list);
1720
1721 if (_hr_printer.is_active()) {
1722 HeapWord* curr = mr.start();
1723 while (curr < mr.end()) {
1724 HeapWord* curr_end = curr + HeapRegion::GrainWords;
1725 _hr_printer.commit(curr, curr_end);
1726 curr = curr_end;
1727 }
1728 assert(curr == mr.end(), "post-condition");
1729 }
1730 g1_policy()->record_new_heap_size(n_regions());
1731 } else {
1732 ergo_verbose0(ErgoHeapSizing,
1733 "did not expand the heap",
1734 ergo_format_reason("heap expansion operation failed"));
1735 // The expansion of the virtual storage space was unsuccessful.
1736 // Let's see if it was because we ran out of swap.
1737 if (G1ExitOnExpansionFailure &&
1738 _g1_storage.uncommitted_size() >= aligned_expand_bytes) {
1739 // We had head room...
1740 vm_exit_out_of_memory(aligned_expand_bytes, "G1 heap expansion");
1741 }
1742 }
1743 return successful;
1744 }
1745
1746 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
1747 size_t old_mem_size = _g1_storage.committed_size();
1748 size_t aligned_shrink_bytes =
1749 ReservedSpace::page_align_size_down(shrink_bytes);
1750 aligned_shrink_bytes = align_size_down(aligned_shrink_bytes,
1751 HeapRegion::GrainBytes);
1752 size_t num_regions_deleted = 0;
1753 MemRegion mr = _hrs.shrink_by(aligned_shrink_bytes, &num_regions_deleted);
1754 HeapWord* old_end = (HeapWord*) _g1_storage.high();
1755 assert(mr.end() == old_end, "post-condition");
1756
1757 ergo_verbose3(ErgoHeapSizing,
1758 "shrink the heap",
1759 ergo_format_byte("requested shrinking amount")
1760 ergo_format_byte("aligned shrinking amount")
1761 ergo_format_byte("attempted shrinking amount"),
1762 shrink_bytes, aligned_shrink_bytes, mr.byte_size());
1763 if (mr.byte_size() > 0) {
1764 if (_hr_printer.is_active()) {
1765 HeapWord* curr = mr.end();
1766 while (curr > mr.start()) {
1767 HeapWord* curr_end = curr;
1768 curr -= HeapRegion::GrainWords;
1769 _hr_printer.uncommit(curr, curr_end);
1770 }
1771 assert(curr == mr.start(), "post-condition");
1772 }
1773
1774 _g1_storage.shrink_by(mr.byte_size());
1775 HeapWord* new_end = (HeapWord*) _g1_storage.high();
1776 assert(mr.start() == new_end, "post-condition");
1777
1778 _expansion_regions += num_regions_deleted;
1779 update_committed_space(old_end, new_end);
1780 HeapRegionRemSet::shrink_heap(n_regions());
1781 g1_policy()->record_new_heap_size(n_regions());
1782 } else {
1783 ergo_verbose0(ErgoHeapSizing,
1784 "did not shrink the heap",
1785 ergo_format_reason("heap shrinking operation failed"));
1786 }
1787 }
1788
1789 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1790 verify_region_sets_optional();
1791
1792 // We should only reach here at the end of a Full GC which means we
1793 // should not not be holding to any GC alloc regions. The method
1794 // below will make sure of that and do any remaining clean up.
1795 abandon_gc_alloc_regions();
1796
1797 // Instead of tearing down / rebuilding the free lists here, we
1798 // could instead use the remove_all_pending() method on free_list to
1799 // remove only the ones that we need to remove.
1800 tear_down_region_sets(true /* free_list_only */);
1801 shrink_helper(shrink_bytes);
1802 rebuild_region_sets(true /* free_list_only */);
1803
1804 _hrs.verify_optional();
1805 verify_region_sets_optional();
1806 }
1807
1808 // Public methods.
1809
1810 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away
1811 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
1812 #endif // _MSC_VER
1813
1814
1815 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* policy_) :
1816 SharedHeap(policy_),
1817 _g1_policy(policy_),
1818 _dirty_card_queue_set(false),
1819 _into_cset_dirty_card_queue_set(false),
1820 _is_alive_closure_cm(this),
1821 _is_alive_closure_stw(this),
1822 _ref_processor_cm(NULL),
1823 _ref_processor_stw(NULL),
1824 _process_strong_tasks(new SubTasksDone(G1H_PS_NumElements)),
1825 _bot_shared(NULL),
1826 _objs_with_preserved_marks(NULL), _preserved_marks_of_objs(NULL),
1827 _evac_failure_scan_stack(NULL) ,
1828 _mark_in_progress(false),
1829 _cg1r(NULL), _summary_bytes_used(0),
1830 _g1mm(NULL),
1831 _refine_cte_cl(NULL),
1832 _full_collection(false),
1833 _free_list("Master Free List"),
1834 _secondary_free_list("Secondary Free List"),
1835 _old_set("Old Set"),
1836 _humongous_set("Master Humongous Set"),
1837 _free_regions_coming(false),
1838 _young_list(new YoungList(this)),
1839 _gc_time_stamp(0),
1840 _retained_old_gc_alloc_region(NULL),
1841 _surviving_young_words(NULL),
1842 _full_collections_completed(0),
1843 _in_cset_fast_test(NULL),
1844 _in_cset_fast_test_base(NULL),
1845 _dirty_cards_region_list(NULL) {
1846 _g1h = this; // To catch bugs.
1847 if (_process_strong_tasks == NULL || !_process_strong_tasks->valid()) {
1848 vm_exit_during_initialization("Failed necessary allocation.");
1849 }
1850
1851 _humongous_object_threshold_in_words = HeapRegion::GrainWords / 2;
1852
1853 int n_queues = MAX2((int)ParallelGCThreads, 1);
1854 _task_queues = new RefToScanQueueSet(n_queues);
1855
1856 int n_rem_sets = HeapRegionRemSet::num_par_rem_sets();
1857 assert(n_rem_sets > 0, "Invariant.");
1858
1859 HeapRegionRemSetIterator** iter_arr =
1860 NEW_C_HEAP_ARRAY(HeapRegionRemSetIterator*, n_queues);
1861 for (int i = 0; i < n_queues; i++) {
1862 iter_arr[i] = new HeapRegionRemSetIterator();
1863 }
1864 _rem_set_iterator = iter_arr;
1865
1866 for (int i = 0; i < n_queues; i++) {
1867 RefToScanQueue* q = new RefToScanQueue();
1868 q->initialize();
1869 _task_queues->register_queue(i, q);
1870 }
1871
1872 guarantee(_task_queues != NULL, "task_queues allocation failure.");
1873 }
1874
1875 jint G1CollectedHeap::initialize() {
1876 CollectedHeap::pre_initialize();
1877 os::enable_vtime();
1878
1879 // Necessary to satisfy locking discipline assertions.
1880
1881 MutexLocker x(Heap_lock);
1882
1883 // We have to initialize the printer before committing the heap, as
1884 // it will be used then.
1885 _hr_printer.set_active(G1PrintHeapRegions);
1886
1887 // While there are no constraints in the GC code that HeapWordSize
1888 // be any particular value, there are multiple other areas in the
1889 // system which believe this to be true (e.g. oop->object_size in some
1890 // cases incorrectly returns the size in wordSize units rather than
1891 // HeapWordSize).
1892 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
1893
1894 size_t init_byte_size = collector_policy()->initial_heap_byte_size();
1895 size_t max_byte_size = collector_policy()->max_heap_byte_size();
1896
1897 // Ensure that the sizes are properly aligned.
1898 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
1899 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
1900
1901 _cg1r = new ConcurrentG1Refine();
1902
1903 // Reserve the maximum.
1904 PermanentGenerationSpec* pgs = collector_policy()->permanent_generation();
1905 // Includes the perm-gen.
1906
1907 // When compressed oops are enabled, the preferred heap base
1908 // is calculated by subtracting the requested size from the
1909 // 32Gb boundary and using the result as the base address for
1910 // heap reservation. If the requested size is not aligned to
1911 // HeapRegion::GrainBytes (i.e. the alignment that is passed
1912 // into the ReservedHeapSpace constructor) then the actual
1913 // base of the reserved heap may end up differing from the
1914 // address that was requested (i.e. the preferred heap base).
1915 // If this happens then we could end up using a non-optimal
1916 // compressed oops mode.
1917
1918 // Since max_byte_size is aligned to the size of a heap region (checked
1919 // above), we also need to align the perm gen size as it might not be.
1920 const size_t total_reserved = max_byte_size +
1921 align_size_up(pgs->max_size(), HeapRegion::GrainBytes);
1922 Universe::check_alignment(total_reserved, HeapRegion::GrainBytes, "g1 heap and perm");
1923
1924 char* addr = Universe::preferred_heap_base(total_reserved, Universe::UnscaledNarrowOop);
1925
1926 ReservedHeapSpace heap_rs(total_reserved, HeapRegion::GrainBytes,
1927 UseLargePages, addr);
1928
1929 if (UseCompressedOops) {
1930 if (addr != NULL && !heap_rs.is_reserved()) {
1931 // Failed to reserve at specified address - the requested memory
1932 // region is taken already, for example, by 'java' launcher.
1933 // Try again to reserver heap higher.
1934 addr = Universe::preferred_heap_base(total_reserved, Universe::ZeroBasedNarrowOop);
1935
1936 ReservedHeapSpace heap_rs0(total_reserved, HeapRegion::GrainBytes,
1937 UseLargePages, addr);
1938
1939 if (addr != NULL && !heap_rs0.is_reserved()) {
1940 // Failed to reserve at specified address again - give up.
1941 addr = Universe::preferred_heap_base(total_reserved, Universe::HeapBasedNarrowOop);
1942 assert(addr == NULL, "");
1943
1944 ReservedHeapSpace heap_rs1(total_reserved, HeapRegion::GrainBytes,
1945 UseLargePages, addr);
1946 heap_rs = heap_rs1;
1947 } else {
1948 heap_rs = heap_rs0;
1949 }
1950 }
1951 }
1952
1953 if (!heap_rs.is_reserved()) {
1954 vm_exit_during_initialization("Could not reserve enough space for object heap");
1955 return JNI_ENOMEM;
1956 }
1957
1958 // It is important to do this in a way such that concurrent readers can't
1959 // temporarily think somethings in the heap. (I've actually seen this
1960 // happen in asserts: DLD.)
1961 _reserved.set_word_size(0);
1962 _reserved.set_start((HeapWord*)heap_rs.base());
1963 _reserved.set_end((HeapWord*)(heap_rs.base() + heap_rs.size()));
1964
1965 _expansion_regions = max_byte_size/HeapRegion::GrainBytes;
1966
1967 // Create the gen rem set (and barrier set) for the entire reserved region.
1968 _rem_set = collector_policy()->create_rem_set(_reserved, 2);
1969 set_barrier_set(rem_set()->bs());
1970 if (barrier_set()->is_a(BarrierSet::ModRef)) {
1971 _mr_bs = (ModRefBarrierSet*)_barrier_set;
1972 } else {
1973 vm_exit_during_initialization("G1 requires a mod ref bs.");
1974 return JNI_ENOMEM;
1975 }
1976
1977 // Also create a G1 rem set.
1978 if (mr_bs()->is_a(BarrierSet::CardTableModRef)) {
1979 _g1_rem_set = new G1RemSet(this, (CardTableModRefBS*)mr_bs());
1980 } else {
1981 vm_exit_during_initialization("G1 requires a cardtable mod ref bs.");
1982 return JNI_ENOMEM;
1983 }
1984
1985 // Carve out the G1 part of the heap.
1986
1987 ReservedSpace g1_rs = heap_rs.first_part(max_byte_size);
1988 _g1_reserved = MemRegion((HeapWord*)g1_rs.base(),
1989 g1_rs.size()/HeapWordSize);
1990 ReservedSpace perm_gen_rs = heap_rs.last_part(max_byte_size);
1991
1992 _perm_gen = pgs->init(perm_gen_rs, pgs->init_size(), rem_set());
1993
1994 _g1_storage.initialize(g1_rs, 0);
1995 _g1_committed = MemRegion((HeapWord*)_g1_storage.low(), (size_t) 0);
1996 _hrs.initialize((HeapWord*) _g1_reserved.start(),
1997 (HeapWord*) _g1_reserved.end(),
1998 _expansion_regions);
1999
2000 // 6843694 - ensure that the maximum region index can fit
2001 // in the remembered set structures.
2002 const size_t max_region_idx = ((size_t)1 << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
2003 guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
2004
2005 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
2006 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
2007 guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
2008 "too many cards per region");
2009
2010 HeapRegionSet::set_unrealistically_long_length(max_regions() + 1);
2011
2012 _bot_shared = new G1BlockOffsetSharedArray(_reserved,
2013 heap_word_size(init_byte_size));
2014
2015 _g1h = this;
2016
2017 _in_cset_fast_test_length = max_regions();
2018 _in_cset_fast_test_base = NEW_C_HEAP_ARRAY(bool, _in_cset_fast_test_length);
2019
2020 // We're biasing _in_cset_fast_test to avoid subtracting the
2021 // beginning of the heap every time we want to index; basically
2022 // it's the same with what we do with the card table.
2023 _in_cset_fast_test = _in_cset_fast_test_base -
2024 ((size_t) _g1_reserved.start() >> HeapRegion::LogOfHRGrainBytes);
2025
2026 // Clear the _cset_fast_test bitmap in anticipation of adding
2027 // regions to the incremental collection set for the first
2028 // evacuation pause.
2029 clear_cset_fast_test();
2030
2031 // Create the ConcurrentMark data structure and thread.
2032 // (Must do this late, so that "max_regions" is defined.)
2033 _cm = new ConcurrentMark(heap_rs, (int) max_regions());
2034 _cmThread = _cm->cmThread();
2035
2036 // Initialize the from_card cache structure of HeapRegionRemSet.
2037 HeapRegionRemSet::init_heap(max_regions());
2038
2039 // Now expand into the initial heap size.
2040 if (!expand(init_byte_size)) {
2041 vm_exit_during_initialization("Failed to allocate initial heap.");
2042 return JNI_ENOMEM;
2043 }
2044
2045 // Perform any initialization actions delegated to the policy.
2046 g1_policy()->init();
2047
2048 _refine_cte_cl =
2049 new RefineCardTableEntryClosure(ConcurrentG1RefineThread::sts(),
2050 g1_rem_set(),
2051 concurrent_g1_refine());
2052 JavaThread::dirty_card_queue_set().set_closure(_refine_cte_cl);
2053
2054 JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon,
2055 SATB_Q_FL_lock,
2056 G1SATBProcessCompletedThreshold,
2057 Shared_SATB_Q_lock);
2058
2059 JavaThread::dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
2060 DirtyCardQ_FL_lock,
2061 concurrent_g1_refine()->yellow_zone(),
2062 concurrent_g1_refine()->red_zone(),
2063 Shared_DirtyCardQ_lock);
2064
2065 if (G1DeferredRSUpdate) {
2066 dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
2067 DirtyCardQ_FL_lock,
2068 -1, // never trigger processing
2069 -1, // no limit on length
2070 Shared_DirtyCardQ_lock,
2071 &JavaThread::dirty_card_queue_set());
2072 }
2073
2074 // Initialize the card queue set used to hold cards containing
2075 // references into the collection set.
2076 _into_cset_dirty_card_queue_set.initialize(DirtyCardQ_CBL_mon,
2077 DirtyCardQ_FL_lock,
2078 -1, // never trigger processing
2079 -1, // no limit on length
2080 Shared_DirtyCardQ_lock,
2081 &JavaThread::dirty_card_queue_set());
2082
2083 // In case we're keeping closure specialization stats, initialize those
2084 // counts and that mechanism.
2085 SpecializationStats::clear();
2086
2087 // Do later initialization work for concurrent refinement.
2088 _cg1r->init();
2089
2090 // Here we allocate the dummy full region that is required by the
2091 // G1AllocRegion class. If we don't pass an address in the reserved
2092 // space here, lots of asserts fire.
2093
2094 HeapRegion* dummy_region = new_heap_region(0 /* index of bottom region */,
2095 _g1_reserved.start());
2096 // We'll re-use the same region whether the alloc region will
2097 // require BOT updates or not and, if it doesn't, then a non-young
2098 // region will complain that it cannot support allocations without
2099 // BOT updates. So we'll tag the dummy region as young to avoid that.
2100 dummy_region->set_young();
2101 // Make sure it's full.
2102 dummy_region->set_top(dummy_region->end());
2103 G1AllocRegion::setup(this, dummy_region);
2104
2105 init_mutator_alloc_region();
2106
2107 // Do create of the monitoring and management support so that
2108 // values in the heap have been properly initialized.
2109 _g1mm = new G1MonitoringSupport(this);
2110
2111 return JNI_OK;
2112 }
2113
2114 void G1CollectedHeap::ref_processing_init() {
2115 // Reference processing in G1 currently works as follows:
2116 //
2117 // * There are two reference processor instances. One is
2118 // used to record and process discovered references
2119 // during concurrent marking; the other is used to
2120 // record and process references during STW pauses
2121 // (both full and incremental).
2122 // * Both ref processors need to 'span' the entire heap as
2123 // the regions in the collection set may be dotted around.
2124 //
2125 // * For the concurrent marking ref processor:
2126 // * Reference discovery is enabled at initial marking.
2127 // * Reference discovery is disabled and the discovered
2128 // references processed etc during remarking.
2129 // * Reference discovery is MT (see below).
2130 // * Reference discovery requires a barrier (see below).
2131 // * Reference processing may or may not be MT
2132 // (depending on the value of ParallelRefProcEnabled
2133 // and ParallelGCThreads).
2134 // * A full GC disables reference discovery by the CM
2135 // ref processor and abandons any entries on it's
2136 // discovered lists.
2137 //
2138 // * For the STW processor:
2139 // * Non MT discovery is enabled at the start of a full GC.
2140 // * Processing and enqueueing during a full GC is non-MT.
2141 // * During a full GC, references are processed after marking.
2142 //
2143 // * Discovery (may or may not be MT) is enabled at the start
2144 // of an incremental evacuation pause.
2145 // * References are processed near the end of a STW evacuation pause.
2146 // * For both types of GC:
2147 // * Discovery is atomic - i.e. not concurrent.
2148 // * Reference discovery will not need a barrier.
2149
2150 SharedHeap::ref_processing_init();
2151 MemRegion mr = reserved_region();
2152
2153 // Concurrent Mark ref processor
2154 _ref_processor_cm =
2155 new ReferenceProcessor(mr, // span
2156 ParallelRefProcEnabled && (ParallelGCThreads > 1),
2157 // mt processing
2158 (int) ParallelGCThreads,
2159 // degree of mt processing
2160 (ParallelGCThreads > 1) || (ConcGCThreads > 1),
2161 // mt discovery
2162 (int) MAX2(ParallelGCThreads, ConcGCThreads),
2163 // degree of mt discovery
2164 false,
2165 // Reference discovery is not atomic
2166 &_is_alive_closure_cm,
2167 // is alive closure
2168 // (for efficiency/performance)
2169 true);
2170 // Setting next fields of discovered
2171 // lists requires a barrier.
2172
2173 // STW ref processor
2174 _ref_processor_stw =
2175 new ReferenceProcessor(mr, // span
2176 ParallelRefProcEnabled && (ParallelGCThreads > 1),
2177 // mt processing
2178 MAX2((int)ParallelGCThreads, 1),
2179 // degree of mt processing
2180 (ParallelGCThreads > 1),
2181 // mt discovery
2182 MAX2((int)ParallelGCThreads, 1),
2183 // degree of mt discovery
2184 true,
2185 // Reference discovery is atomic
2186 &_is_alive_closure_stw,
2187 // is alive closure
2188 // (for efficiency/performance)
2189 false);
2190 // Setting next fields of discovered
2191 // lists requires a barrier.
2192 }
2193
2194 size_t G1CollectedHeap::capacity() const {
2195 return _g1_committed.byte_size();
2196 }
2197
2198 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl,
2199 DirtyCardQueue* into_cset_dcq,
2200 bool concurrent,
2201 int worker_i) {
2202 // Clean cards in the hot card cache
2203 concurrent_g1_refine()->clean_up_cache(worker_i, g1_rem_set(), into_cset_dcq);
2204
2205 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2206 int n_completed_buffers = 0;
2207 while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) {
2208 n_completed_buffers++;
2209 }
2210 g1_policy()->record_update_rs_processed_buffers(worker_i,
2211 (double) n_completed_buffers);
2212 dcqs.clear_n_completed_buffers();
2213 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!");
2214 }
2215
2216
2217 // Computes the sum of the storage used by the various regions.
2218
2219 size_t G1CollectedHeap::used() const {
2220 assert(Heap_lock->owner() != NULL,
2221 "Should be owned on this thread's behalf.");
2222 size_t result = _summary_bytes_used;
2223 // Read only once in case it is set to NULL concurrently
2224 HeapRegion* hr = _mutator_alloc_region.get();
2225 if (hr != NULL)
2226 result += hr->used();
2227 return result;
2228 }
2229
2230 size_t G1CollectedHeap::used_unlocked() const {
2231 size_t result = _summary_bytes_used;
2232 return result;
2233 }
2234
2235 class SumUsedClosure: public HeapRegionClosure {
2236 size_t _used;
2237 public:
2238 SumUsedClosure() : _used(0) {}
2239 bool doHeapRegion(HeapRegion* r) {
2240 if (!r->continuesHumongous()) {
2241 _used += r->used();
2242 }
2243 return false;
2244 }
2245 size_t result() { return _used; }
2246 };
2247
2248 size_t G1CollectedHeap::recalculate_used() const {
2249 SumUsedClosure blk;
2250 heap_region_iterate(&blk);
2251 return blk.result();
2252 }
2253
2254 size_t G1CollectedHeap::unsafe_max_alloc() {
2255 if (free_regions() > 0) return HeapRegion::GrainBytes;
2256 // otherwise, is there space in the current allocation region?
2257
2258 // We need to store the current allocation region in a local variable
2259 // here. The problem is that this method doesn't take any locks and
2260 // there may be other threads which overwrite the current allocation
2261 // region field. attempt_allocation(), for example, sets it to NULL
2262 // and this can happen *after* the NULL check here but before the call
2263 // to free(), resulting in a SIGSEGV. Note that this doesn't appear
2264 // to be a problem in the optimized build, since the two loads of the
2265 // current allocation region field are optimized away.
2266 HeapRegion* hr = _mutator_alloc_region.get();
2267 if (hr == NULL) {
2268 return 0;
2269 }
2270 return hr->free();
2271 }
2272
2273 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
2274 return
2275 ((cause == GCCause::_gc_locker && GCLockerInvokesConcurrent) ||
2276 (cause == GCCause::_java_lang_system_gc && ExplicitGCInvokesConcurrent));
2277 }
2278
2279 #ifndef PRODUCT
2280 void G1CollectedHeap::allocate_dummy_regions() {
2281 // Let's fill up most of the region
2282 size_t word_size = HeapRegion::GrainWords - 1024;
2283 // And as a result the region we'll allocate will be humongous.
2284 guarantee(isHumongous(word_size), "sanity");
2285
2286 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
2287 // Let's use the existing mechanism for the allocation
2288 HeapWord* dummy_obj = humongous_obj_allocate(word_size);
2289 if (dummy_obj != NULL) {
2290 MemRegion mr(dummy_obj, word_size);
2291 CollectedHeap::fill_with_object(mr);
2292 } else {
2293 // If we can't allocate once, we probably cannot allocate
2294 // again. Let's get out of the loop.
2295 break;
2296 }
2297 }
2298 }
2299 #endif // !PRODUCT
2300
2301 void G1CollectedHeap::increment_full_collections_completed(bool concurrent) {
2302 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
2303
2304 // We assume that if concurrent == true, then the caller is a
2305 // concurrent thread that was joined the Suspendible Thread
2306 // Set. If there's ever a cheap way to check this, we should add an
2307 // assert here.
2308
2309 // We have already incremented _total_full_collections at the start
2310 // of the GC, so total_full_collections() represents how many full
2311 // collections have been started.
2312 unsigned int full_collections_started = total_full_collections();
2313
2314 // Given that this method is called at the end of a Full GC or of a
2315 // concurrent cycle, and those can be nested (i.e., a Full GC can
2316 // interrupt a concurrent cycle), the number of full collections
2317 // completed should be either one (in the case where there was no
2318 // nesting) or two (when a Full GC interrupted a concurrent cycle)
2319 // behind the number of full collections started.
2320
2321 // This is the case for the inner caller, i.e. a Full GC.
2322 assert(concurrent ||
2323 (full_collections_started == _full_collections_completed + 1) ||
2324 (full_collections_started == _full_collections_completed + 2),
2325 err_msg("for inner caller (Full GC): full_collections_started = %u "
2326 "is inconsistent with _full_collections_completed = %u",
2327 full_collections_started, _full_collections_completed));
2328
2329 // This is the case for the outer caller, i.e. the concurrent cycle.
2330 assert(!concurrent ||
2331 (full_collections_started == _full_collections_completed + 1),
2332 err_msg("for outer caller (concurrent cycle): "
2333 "full_collections_started = %u "
2334 "is inconsistent with _full_collections_completed = %u",
2335 full_collections_started, _full_collections_completed));
2336
2337 _full_collections_completed += 1;
2338
2339 // We need to clear the "in_progress" flag in the CM thread before
2340 // we wake up any waiters (especially when ExplicitInvokesConcurrent
2341 // is set) so that if a waiter requests another System.gc() it doesn't
2342 // incorrectly see that a marking cyle is still in progress.
2343 if (concurrent) {
2344 _cmThread->clear_in_progress();
2345 }
2346
2347 // This notify_all() will ensure that a thread that called
2348 // System.gc() with (with ExplicitGCInvokesConcurrent set or not)
2349 // and it's waiting for a full GC to finish will be woken up. It is
2350 // waiting in VM_G1IncCollectionPause::doit_epilogue().
2351 FullGCCount_lock->notify_all();
2352 }
2353
2354 void G1CollectedHeap::collect_as_vm_thread(GCCause::Cause cause) {
2355 assert_at_safepoint(true /* should_be_vm_thread */);
2356 GCCauseSetter gcs(this, cause);
2357 switch (cause) {
2358 case GCCause::_heap_inspection:
2359 case GCCause::_heap_dump: {
2360 HandleMark hm;
2361 do_full_collection(false); // don't clear all soft refs
2362 break;
2363 }
2364 default: // XXX FIX ME
2365 ShouldNotReachHere(); // Unexpected use of this function
2366 }
2367 }
2368
2369 void G1CollectedHeap::collect(GCCause::Cause cause) {
2370 // The caller doesn't have the Heap_lock
2371 assert(!Heap_lock->owned_by_self(), "this thread should not own the Heap_lock");
2372
2373 unsigned int gc_count_before;
2374 unsigned int full_gc_count_before;
2375 {
2376 MutexLocker ml(Heap_lock);
2377
2378 // Read the GC count while holding the Heap_lock
2379 gc_count_before = SharedHeap::heap()->total_collections();
2380 full_gc_count_before = SharedHeap::heap()->total_full_collections();
2381 }
2382
2383 if (should_do_concurrent_full_gc(cause)) {
2384 // Schedule an initial-mark evacuation pause that will start a
2385 // concurrent cycle. We're setting word_size to 0 which means that
2386 // we are not requesting a post-GC allocation.
2387 VM_G1IncCollectionPause op(gc_count_before,
2388 0, /* word_size */
2389 true, /* should_initiate_conc_mark */
2390 g1_policy()->max_pause_time_ms(),
2391 cause);
2392 VMThread::execute(&op);
2393 } else {
2394 if (cause == GCCause::_gc_locker
2395 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2396
2397 // Schedule a standard evacuation pause. We're setting word_size
2398 // to 0 which means that we are not requesting a post-GC allocation.
2399 VM_G1IncCollectionPause op(gc_count_before,
2400 0, /* word_size */
2401 false, /* should_initiate_conc_mark */
2402 g1_policy()->max_pause_time_ms(),
2403 cause);
2404 VMThread::execute(&op);
2405 } else {
2406 // Schedule a Full GC.
2407 VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause);
2408 VMThread::execute(&op);
2409 }
2410 }
2411 }
2412
2413 bool G1CollectedHeap::is_in(const void* p) const {
2414 HeapRegion* hr = _hrs.addr_to_region((HeapWord*) p);
2415 if (hr != NULL) {
2416 return hr->is_in(p);
2417 } else {
2418 return _perm_gen->as_gen()->is_in(p);
2419 }
2420 }
2421
2422 // Iteration functions.
2423
2424 // Iterates an OopClosure over all ref-containing fields of objects
2425 // within a HeapRegion.
2426
2427 class IterateOopClosureRegionClosure: public HeapRegionClosure {
2428 MemRegion _mr;
2429 OopClosure* _cl;
2430 public:
2431 IterateOopClosureRegionClosure(MemRegion mr, OopClosure* cl)
2432 : _mr(mr), _cl(cl) {}
2433 bool doHeapRegion(HeapRegion* r) {
2434 if (! r->continuesHumongous()) {
2435 r->oop_iterate(_cl);
2436 }
2437 return false;
2438 }
2439 };
2440
2441 void G1CollectedHeap::oop_iterate(OopClosure* cl, bool do_perm) {
2442 IterateOopClosureRegionClosure blk(_g1_committed, cl);
2443 heap_region_iterate(&blk);
2444 if (do_perm) {
2445 perm_gen()->oop_iterate(cl);
2446 }
2447 }
2448
2449 void G1CollectedHeap::oop_iterate(MemRegion mr, OopClosure* cl, bool do_perm) {
2450 IterateOopClosureRegionClosure blk(mr, cl);
2451 heap_region_iterate(&blk);
2452 if (do_perm) {
2453 perm_gen()->oop_iterate(cl);
2454 }
2455 }
2456
2457 // Iterates an ObjectClosure over all objects within a HeapRegion.
2458
2459 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2460 ObjectClosure* _cl;
2461 public:
2462 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2463 bool doHeapRegion(HeapRegion* r) {
2464 if (! r->continuesHumongous()) {
2465 r->object_iterate(_cl);
2466 }
2467 return false;
2468 }
2469 };
2470
2471 void G1CollectedHeap::object_iterate(ObjectClosure* cl, bool do_perm) {
2472 IterateObjectClosureRegionClosure blk(cl);
2473 heap_region_iterate(&blk);
2474 if (do_perm) {
2475 perm_gen()->object_iterate(cl);
2476 }
2477 }
2478
2479 void G1CollectedHeap::object_iterate_since_last_GC(ObjectClosure* cl) {
2480 // FIXME: is this right?
2481 guarantee(false, "object_iterate_since_last_GC not supported by G1 heap");
2482 }
2483
2484 // Calls a SpaceClosure on a HeapRegion.
2485
2486 class SpaceClosureRegionClosure: public HeapRegionClosure {
2487 SpaceClosure* _cl;
2488 public:
2489 SpaceClosureRegionClosure(SpaceClosure* cl) : _cl(cl) {}
2490 bool doHeapRegion(HeapRegion* r) {
2491 _cl->do_space(r);
2492 return false;
2493 }
2494 };
2495
2496 void G1CollectedHeap::space_iterate(SpaceClosure* cl) {
2497 SpaceClosureRegionClosure blk(cl);
2498 heap_region_iterate(&blk);
2499 }
2500
2501 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2502 _hrs.iterate(cl);
2503 }
2504
2505 void G1CollectedHeap::heap_region_iterate_from(HeapRegion* r,
2506 HeapRegionClosure* cl) const {
2507 _hrs.iterate_from(r, cl);
2508 }
2509
2510 void
2511 G1CollectedHeap::heap_region_par_iterate_chunked(HeapRegionClosure* cl,
2512 int worker,
2513 int no_of_par_workers,
2514 jint claim_value) {
2515 const size_t regions = n_regions();
2516 const size_t max_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
2517 no_of_par_workers :
2518 1);
2519 assert(UseDynamicNumberOfGCThreads ||
2520 no_of_par_workers == workers()->total_workers(),
2521 "Non dynamic should use fixed number of workers");
2522 // try to spread out the starting points of the workers
2523 const size_t start_index = regions / max_workers * (size_t) worker;
2524
2525 // each worker will actually look at all regions
2526 for (size_t count = 0; count < regions; ++count) {
2527 const size_t index = (start_index + count) % regions;
2528 assert(0 <= index && index < regions, "sanity");
2529 HeapRegion* r = region_at(index);
2530 // we'll ignore "continues humongous" regions (we'll process them
2531 // when we come across their corresponding "start humongous"
2532 // region) and regions already claimed
2533 if (r->claim_value() == claim_value || r->continuesHumongous()) {
2534 continue;
2535 }
2536 // OK, try to claim it
2537 if (r->claimHeapRegion(claim_value)) {
2538 // success!
2539 assert(!r->continuesHumongous(), "sanity");
2540 if (r->startsHumongous()) {
2541 // If the region is "starts humongous" we'll iterate over its
2542 // "continues humongous" first; in fact we'll do them
2543 // first. The order is important. In on case, calling the
2544 // closure on the "starts humongous" region might de-allocate
2545 // and clear all its "continues humongous" regions and, as a
2546 // result, we might end up processing them twice. So, we'll do
2547 // them first (notice: most closures will ignore them anyway) and
2548 // then we'll do the "starts humongous" region.
2549 for (size_t ch_index = index + 1; ch_index < regions; ++ch_index) {
2550 HeapRegion* chr = region_at(ch_index);
2551
2552 // if the region has already been claimed or it's not
2553 // "continues humongous" we're done
2554 if (chr->claim_value() == claim_value ||
2555 !chr->continuesHumongous()) {
2556 break;
2557 }
2558
2559 // Noone should have claimed it directly. We can given
2560 // that we claimed its "starts humongous" region.
2561 assert(chr->claim_value() != claim_value, "sanity");
2562 assert(chr->humongous_start_region() == r, "sanity");
2563
2564 if (chr->claimHeapRegion(claim_value)) {
2565 // we should always be able to claim it; noone else should
2566 // be trying to claim this region
2567
2568 bool res2 = cl->doHeapRegion(chr);
2569 assert(!res2, "Should not abort");
2570
2571 // Right now, this holds (i.e., no closure that actually
2572 // does something with "continues humongous" regions
2573 // clears them). We might have to weaken it in the future,
2574 // but let's leave these two asserts here for extra safety.
2575 assert(chr->continuesHumongous(), "should still be the case");
2576 assert(chr->humongous_start_region() == r, "sanity");
2577 } else {
2578 guarantee(false, "we should not reach here");
2579 }
2580 }
2581 }
2582
2583 assert(!r->continuesHumongous(), "sanity");
2584 bool res = cl->doHeapRegion(r);
2585 assert(!res, "Should not abort");
2586 }
2587 }
2588 }
2589
2590 class ResetClaimValuesClosure: public HeapRegionClosure {
2591 public:
2592 bool doHeapRegion(HeapRegion* r) {
2593 r->set_claim_value(HeapRegion::InitialClaimValue);
2594 return false;
2595 }
2596 };
2597
2598 void
2599 G1CollectedHeap::reset_heap_region_claim_values() {
2600 ResetClaimValuesClosure blk;
2601 heap_region_iterate(&blk);
2602 }
2603
2604 #ifdef ASSERT
2605 // This checks whether all regions in the heap have the correct claim
2606 // value. I also piggy-backed on this a check to ensure that the
2607 // humongous_start_region() information on "continues humongous"
2608 // regions is correct.
2609
2610 class CheckClaimValuesClosure : public HeapRegionClosure {
2611 private:
2612 jint _claim_value;
2613 size_t _failures;
2614 HeapRegion* _sh_region;
2615 public:
2616 CheckClaimValuesClosure(jint claim_value) :
2617 _claim_value(claim_value), _failures(0), _sh_region(NULL) { }
2618 bool doHeapRegion(HeapRegion* r) {
2619 if (r->claim_value() != _claim_value) {
2620 gclog_or_tty->print_cr("Region " HR_FORMAT ", "
2621 "claim value = %d, should be %d",
2622 HR_FORMAT_PARAMS(r),
2623 r->claim_value(), _claim_value);
2624 ++_failures;
2625 }
2626 if (!r->isHumongous()) {
2627 _sh_region = NULL;
2628 } else if (r->startsHumongous()) {
2629 _sh_region = r;
2630 } else if (r->continuesHumongous()) {
2631 if (r->humongous_start_region() != _sh_region) {
2632 gclog_or_tty->print_cr("Region " HR_FORMAT ", "
2633 "HS = "PTR_FORMAT", should be "PTR_FORMAT,
2634 HR_FORMAT_PARAMS(r),
2635 r->humongous_start_region(),
2636 _sh_region);
2637 ++_failures;
2638 }
2639 }
2640 return false;
2641 }
2642 size_t failures() {
2643 return _failures;
2644 }
2645 };
2646
2647 bool G1CollectedHeap::check_heap_region_claim_values(jint claim_value) {
2648 CheckClaimValuesClosure cl(claim_value);
2649 heap_region_iterate(&cl);
2650 return cl.failures() == 0;
2651 }
2652
2653 class CheckClaimValuesInCSetHRClosure: public HeapRegionClosure {
2654 jint _claim_value;
2655 size_t _failures;
2656
2657 public:
2658 CheckClaimValuesInCSetHRClosure(jint claim_value) :
2659 _claim_value(claim_value),
2660 _failures(0) { }
2661
2662 size_t failures() {
2663 return _failures;
2664 }
2665
2666 bool doHeapRegion(HeapRegion* hr) {
2667 assert(hr->in_collection_set(), "how?");
2668 assert(!hr->isHumongous(), "H-region in CSet");
2669 if (hr->claim_value() != _claim_value) {
2670 gclog_or_tty->print_cr("CSet Region " HR_FORMAT ", "
2671 "claim value = %d, should be %d",
2672 HR_FORMAT_PARAMS(hr),
2673 hr->claim_value(), _claim_value);
2674 _failures += 1;
2675 }
2676 return false;
2677 }
2678 };
2679
2680 bool G1CollectedHeap::check_cset_heap_region_claim_values(jint claim_value) {
2681 CheckClaimValuesInCSetHRClosure cl(claim_value);
2682 collection_set_iterate(&cl);
2683 return cl.failures() == 0;
2684 }
2685 #endif // ASSERT
2686
2687 // We want the parallel threads to start their collection
2688 // set iteration at different collection set regions to
2689 // avoid contention.
2690 // If we have:
2691 // n collection set regions
2692 // p threads
2693 // Then thread t will start at region t * floor (n/p)
2694
2695 HeapRegion* G1CollectedHeap::start_cset_region_for_worker(int worker_i) {
2696 HeapRegion* result = g1_policy()->collection_set();
2697 if (G1CollectedHeap::use_parallel_gc_threads()) {
2698 size_t cs_size = g1_policy()->cset_region_length();
2699 int n_workers = workers()->total_workers();
2700 size_t cs_spans = cs_size / n_workers;
2701 size_t ind = cs_spans * worker_i;
2702 for (size_t i = 0; i < ind; i++) {
2703 result = result->next_in_collection_set();
2704 }
2705 }
2706 return result;
2707 }
2708
2709 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) {
2710 HeapRegion* r = g1_policy()->collection_set();
2711 while (r != NULL) {
2712 HeapRegion* next = r->next_in_collection_set();
2713 if (cl->doHeapRegion(r)) {
2714 cl->incomplete();
2715 return;
2716 }
2717 r = next;
2718 }
2719 }
2720
2721 void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r,
2722 HeapRegionClosure *cl) {
2723 if (r == NULL) {
2724 // The CSet is empty so there's nothing to do.
2725 return;
2726 }
2727
2728 assert(r->in_collection_set(),
2729 "Start region must be a member of the collection set.");
2730 HeapRegion* cur = r;
2731 while (cur != NULL) {
2732 HeapRegion* next = cur->next_in_collection_set();
2733 if (cl->doHeapRegion(cur) && false) {
2734 cl->incomplete();
2735 return;
2736 }
2737 cur = next;
2738 }
2739 cur = g1_policy()->collection_set();
2740 while (cur != r) {
2741 HeapRegion* next = cur->next_in_collection_set();
2742 if (cl->doHeapRegion(cur) && false) {
2743 cl->incomplete();
2744 return;
2745 }
2746 cur = next;
2747 }
2748 }
2749
2750 CompactibleSpace* G1CollectedHeap::first_compactible_space() {
2751 return n_regions() > 0 ? region_at(0) : NULL;
2752 }
2753
2754
2755 Space* G1CollectedHeap::space_containing(const void* addr) const {
2756 Space* res = heap_region_containing(addr);
2757 if (res == NULL)
2758 res = perm_gen()->space_containing(addr);
2759 return res;
2760 }
2761
2762 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2763 Space* sp = space_containing(addr);
2764 if (sp != NULL) {
2765 return sp->block_start(addr);
2766 }
2767 return NULL;
2768 }
2769
2770 size_t G1CollectedHeap::block_size(const HeapWord* addr) const {
2771 Space* sp = space_containing(addr);
2772 assert(sp != NULL, "block_size of address outside of heap");
2773 return sp->block_size(addr);
2774 }
2775
2776 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2777 Space* sp = space_containing(addr);
2778 return sp->block_is_obj(addr);
2779 }
2780
2781 bool G1CollectedHeap::supports_tlab_allocation() const {
2782 return true;
2783 }
2784
2785 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
2786 return HeapRegion::GrainBytes;
2787 }
2788
2789 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
2790 // Return the remaining space in the cur alloc region, but not less than
2791 // the min TLAB size.
2792
2793 // Also, this value can be at most the humongous object threshold,
2794 // since we can't allow tlabs to grow big enough to accomodate
2795 // humongous objects.
2796
2797 HeapRegion* hr = _mutator_alloc_region.get();
2798 size_t max_tlab_size = _humongous_object_threshold_in_words * wordSize;
2799 if (hr == NULL) {
2800 return max_tlab_size;
2801 } else {
2802 return MIN2(MAX2(hr->free(), (size_t) MinTLABSize), max_tlab_size);
2803 }
2804 }
2805
2806 size_t G1CollectedHeap::max_capacity() const {
2807 return _g1_reserved.byte_size();
2808 }
2809
2810 jlong G1CollectedHeap::millis_since_last_gc() {
2811 // assert(false, "NYI");
2812 return 0;
2813 }
2814
2815 void G1CollectedHeap::prepare_for_verify() {
2816 if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) {
2817 ensure_parsability(false);
2818 }
2819 g1_rem_set()->prepare_for_verify();
2820 }
2821
2822 class VerifyLivenessOopClosure: public OopClosure {
2823 G1CollectedHeap* _g1h;
2824 VerifyOption _vo;
2825 public:
2826 VerifyLivenessOopClosure(G1CollectedHeap* g1h, VerifyOption vo):
2827 _g1h(g1h), _vo(vo)
2828 { }
2829 void do_oop(narrowOop *p) { do_oop_work(p); }
2830 void do_oop( oop *p) { do_oop_work(p); }
2831
2832 template <class T> void do_oop_work(T *p) {
2833 oop obj = oopDesc::load_decode_heap_oop(p);
2834 guarantee(obj == NULL || !_g1h->is_obj_dead_cond(obj, _vo),
2835 "Dead object referenced by a not dead object");
2836 }
2837 };
2838
2839 class VerifyObjsInRegionClosure: public ObjectClosure {
2840 private:
2841 G1CollectedHeap* _g1h;
2842 size_t _live_bytes;
2843 HeapRegion *_hr;
2844 VerifyOption _vo;
2845 public:
2846 // _vo == UsePrevMarking -> use "prev" marking information,
2847 // _vo == UseNextMarking -> use "next" marking information,
2848 // _vo == UseMarkWord -> use mark word from object header.
2849 VerifyObjsInRegionClosure(HeapRegion *hr, VerifyOption vo)
2850 : _live_bytes(0), _hr(hr), _vo(vo) {
2851 _g1h = G1CollectedHeap::heap();
2852 }
2853 void do_object(oop o) {
2854 VerifyLivenessOopClosure isLive(_g1h, _vo);
2855 assert(o != NULL, "Huh?");
2856 if (!_g1h->is_obj_dead_cond(o, _vo)) {
2857 // If the object is alive according to the mark word,
2858 // then verify that the marking information agrees.
2859 // Note we can't verify the contra-positive of the
2860 // above: if the object is dead (according to the mark
2861 // word), it may not be marked, or may have been marked
2862 // but has since became dead, or may have been allocated
2863 // since the last marking.
2864 if (_vo == VerifyOption_G1UseMarkWord) {
2865 guarantee(!_g1h->is_obj_dead(o), "mark word and concurrent mark mismatch");
2866 }
2867
2868 o->oop_iterate(&isLive);
2869 if (!_hr->obj_allocated_since_prev_marking(o)) {
2870 size_t obj_size = o->size(); // Make sure we don't overflow
2871 _live_bytes += (obj_size * HeapWordSize);
2872 }
2873 }
2874 }
2875 size_t live_bytes() { return _live_bytes; }
2876 };
2877
2878 class PrintObjsInRegionClosure : public ObjectClosure {
2879 HeapRegion *_hr;
2880 G1CollectedHeap *_g1;
2881 public:
2882 PrintObjsInRegionClosure(HeapRegion *hr) : _hr(hr) {
2883 _g1 = G1CollectedHeap::heap();
2884 };
2885
2886 void do_object(oop o) {
2887 if (o != NULL) {
2888 HeapWord *start = (HeapWord *) o;
2889 size_t word_sz = o->size();
2890 gclog_or_tty->print("\nPrinting obj "PTR_FORMAT" of size " SIZE_FORMAT
2891 " isMarkedPrev %d isMarkedNext %d isAllocSince %d\n",
2892 (void*) o, word_sz,
2893 _g1->isMarkedPrev(o),
2894 _g1->isMarkedNext(o),
2895 _hr->obj_allocated_since_prev_marking(o));
2896 HeapWord *end = start + word_sz;
2897 HeapWord *cur;
2898 int *val;
2899 for (cur = start; cur < end; cur++) {
2900 val = (int *) cur;
2901 gclog_or_tty->print("\t "PTR_FORMAT":"PTR_FORMAT"\n", val, *val);
2902 }
2903 }
2904 }
2905 };
2906
2907 class VerifyRegionClosure: public HeapRegionClosure {
2908 private:
2909 bool _allow_dirty;
2910 bool _par;
2911 VerifyOption _vo;
2912 bool _failures;
2913 public:
2914 // _vo == UsePrevMarking -> use "prev" marking information,
2915 // _vo == UseNextMarking -> use "next" marking information,
2916 // _vo == UseMarkWord -> use mark word from object header.
2917 VerifyRegionClosure(bool allow_dirty, bool par, VerifyOption vo)
2918 : _allow_dirty(allow_dirty),
2919 _par(par),
2920 _vo(vo),
2921 _failures(false) {}
2922
2923 bool failures() {
2924 return _failures;
2925 }
2926
2927 bool doHeapRegion(HeapRegion* r) {
2928 guarantee(_par || r->claim_value() == HeapRegion::InitialClaimValue,
2929 "Should be unclaimed at verify points.");
2930 if (!r->continuesHumongous()) {
2931 bool failures = false;
2932 r->verify(_allow_dirty, _vo, &failures);
2933 if (failures) {
2934 _failures = true;
2935 } else {
2936 VerifyObjsInRegionClosure not_dead_yet_cl(r, _vo);
2937 r->object_iterate(¬_dead_yet_cl);
2938 if (r->max_live_bytes() < not_dead_yet_cl.live_bytes()) {
2939 gclog_or_tty->print_cr("["PTR_FORMAT","PTR_FORMAT"] "
2940 "max_live_bytes "SIZE_FORMAT" "
2941 "< calculated "SIZE_FORMAT,
2942 r->bottom(), r->end(),
2943 r->max_live_bytes(),
2944 not_dead_yet_cl.live_bytes());
2945 _failures = true;
2946 }
2947 }
2948 }
2949 return false; // stop the region iteration if we hit a failure
2950 }
2951 };
2952
2953 class VerifyRootsClosure: public OopsInGenClosure {
2954 private:
2955 G1CollectedHeap* _g1h;
2956 VerifyOption _vo;
2957 bool _failures;
2958 public:
2959 // _vo == UsePrevMarking -> use "prev" marking information,
2960 // _vo == UseNextMarking -> use "next" marking information,
2961 // _vo == UseMarkWord -> use mark word from object header.
2962 VerifyRootsClosure(VerifyOption vo) :
2963 _g1h(G1CollectedHeap::heap()),
2964 _vo(vo),
2965 _failures(false) { }
2966
2967 bool failures() { return _failures; }
2968
2969 template <class T> void do_oop_nv(T* p) {
2970 T heap_oop = oopDesc::load_heap_oop(p);
2971 if (!oopDesc::is_null(heap_oop)) {
2972 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
2973 if (_g1h->is_obj_dead_cond(obj, _vo)) {
2974 gclog_or_tty->print_cr("Root location "PTR_FORMAT" "
2975 "points to dead obj "PTR_FORMAT, p, (void*) obj);
2976 if (_vo == VerifyOption_G1UseMarkWord) {
2977 gclog_or_tty->print_cr(" Mark word: "PTR_FORMAT, (void*)(obj->mark()));
2978 }
2979 obj->print_on(gclog_or_tty);
2980 _failures = true;
2981 }
2982 }
2983 }
2984
2985 void do_oop(oop* p) { do_oop_nv(p); }
2986 void do_oop(narrowOop* p) { do_oop_nv(p); }
2987 };
2988
2989 // This is the task used for parallel heap verification.
2990
2991 class G1ParVerifyTask: public AbstractGangTask {
2992 private:
2993 G1CollectedHeap* _g1h;
2994 bool _allow_dirty;
2995 VerifyOption _vo;
2996 bool _failures;
2997
2998 public:
2999 // _vo == UsePrevMarking -> use "prev" marking information,
3000 // _vo == UseNextMarking -> use "next" marking information,
3001 // _vo == UseMarkWord -> use mark word from object header.
3002 G1ParVerifyTask(G1CollectedHeap* g1h, bool allow_dirty, VerifyOption vo) :
3003 AbstractGangTask("Parallel verify task"),
3004 _g1h(g1h),
3005 _allow_dirty(allow_dirty),
3006 _vo(vo),
3007 _failures(false) { }
3008
3009 bool failures() {
3010 return _failures;
3011 }
3012
3013 void work(int worker_i) {
3014 HandleMark hm;
3015 VerifyRegionClosure blk(_allow_dirty, true, _vo);
3016 _g1h->heap_region_par_iterate_chunked(&blk, worker_i,
3017 _g1h->workers()->active_workers(),
3018 HeapRegion::ParVerifyClaimValue);
3019 if (blk.failures()) {
3020 _failures = true;
3021 }
3022 }
3023 };
3024
3025 void G1CollectedHeap::verify(bool allow_dirty, bool silent) {
3026 verify(allow_dirty, silent, VerifyOption_G1UsePrevMarking);
3027 }
3028
3029 void G1CollectedHeap::verify(bool allow_dirty,
3030 bool silent,
3031 VerifyOption vo) {
3032 if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) {
3033 if (!silent) { gclog_or_tty->print("Roots (excluding permgen) "); }
3034 VerifyRootsClosure rootsCl(vo);
3035
3036 assert(Thread::current()->is_VM_thread(),
3037 "Expected to be executed serially by the VM thread at this point");
3038
3039 CodeBlobToOopClosure blobsCl(&rootsCl, /*do_marking=*/ false);
3040
3041 // We apply the relevant closures to all the oops in the
3042 // system dictionary, the string table and the code cache.
3043 const int so = SharedHeap::SO_AllClasses | SharedHeap::SO_Strings | SharedHeap::SO_CodeCache;
3044
3045 process_strong_roots(true, // activate StrongRootsScope
3046 true, // we set "collecting perm gen" to true,
3047 // so we don't reset the dirty cards in the perm gen.
3048 SharedHeap::ScanningOption(so), // roots scanning options
3049 &rootsCl,
3050 &blobsCl,
3051 &rootsCl);
3052
3053 // If we're verifying after the marking phase of a Full GC then we can't
3054 // treat the perm gen as roots into the G1 heap. Some of the objects in
3055 // the perm gen may be dead and hence not marked. If one of these dead
3056 // objects is considered to be a root then we may end up with a false
3057 // "Root location <x> points to dead ob <y>" failure.
3058 if (vo != VerifyOption_G1UseMarkWord) {
3059 // Since we used "collecting_perm_gen" == true above, we will not have
3060 // checked the refs from perm into the G1-collected heap. We check those
3061 // references explicitly below. Whether the relevant cards are dirty
3062 // is checked further below in the rem set verification.
3063 if (!silent) { gclog_or_tty->print("Permgen roots "); }
3064 perm_gen()->oop_iterate(&rootsCl);
3065 }
3066 bool failures = rootsCl.failures();
3067
3068 if (vo != VerifyOption_G1UseMarkWord) {
3069 // If we're verifying during a full GC then the region sets
3070 // will have been torn down at the start of the GC. Therefore
3071 // verifying the region sets will fail. So we only verify
3072 // the region sets when not in a full GC.
3073 if (!silent) { gclog_or_tty->print("HeapRegionSets "); }
3074 verify_region_sets();
3075 }
3076
3077 if (!silent) { gclog_or_tty->print("HeapRegions "); }
3078 if (GCParallelVerificationEnabled && ParallelGCThreads > 1) {
3079 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3080 "sanity check");
3081
3082 G1ParVerifyTask task(this, allow_dirty, vo);
3083 assert(UseDynamicNumberOfGCThreads ||
3084 workers()->active_workers() == workers()->total_workers(),
3085 "If not dynamic should be using all the workers");
3086 int n_workers = workers()->active_workers();
3087 set_par_threads(n_workers);
3088 workers()->run_task(&task);
3089 set_par_threads(0);
3090 if (task.failures()) {
3091 failures = true;
3092 }
3093
3094 // Checks that the expected amount of parallel work was done.
3095 // The implication is that n_workers is > 0.
3096 assert(check_heap_region_claim_values(HeapRegion::ParVerifyClaimValue),
3097 "sanity check");
3098
3099 reset_heap_region_claim_values();
3100
3101 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3102 "sanity check");
3103 } else {
3104 VerifyRegionClosure blk(allow_dirty, false, vo);
3105 heap_region_iterate(&blk);
3106 if (blk.failures()) {
3107 failures = true;
3108 }
3109 }
3110 if (!silent) gclog_or_tty->print("RemSet ");
3111 rem_set()->verify();
3112
3113 if (failures) {
3114 gclog_or_tty->print_cr("Heap:");
3115 // It helps to have the per-region information in the output to
3116 // help us track down what went wrong. This is why we call
3117 // print_extended_on() instead of print_on().
3118 print_extended_on(gclog_or_tty);
3119 gclog_or_tty->print_cr("");
3120 #ifndef PRODUCT
3121 if (VerifyDuringGC && G1VerifyDuringGCPrintReachable) {
3122 concurrent_mark()->print_reachable("at-verification-failure",
3123 vo, false /* all */);
3124 }
3125 #endif
3126 gclog_or_tty->flush();
3127 }
3128 guarantee(!failures, "there should not have been any failures");
3129 } else {
3130 if (!silent) gclog_or_tty->print("(SKIPPING roots, heapRegions, remset) ");
3131 }
3132 }
3133
3134 class PrintRegionClosure: public HeapRegionClosure {
3135 outputStream* _st;
3136 public:
3137 PrintRegionClosure(outputStream* st) : _st(st) {}
3138 bool doHeapRegion(HeapRegion* r) {
3139 r->print_on(_st);
3140 return false;
3141 }
3142 };
3143
3144 void G1CollectedHeap::print_on(outputStream* st) const {
3145 st->print(" %-20s", "garbage-first heap");
3146 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
3147 capacity()/K, used_unlocked()/K);
3148 st->print(" [" INTPTR_FORMAT ", " INTPTR_FORMAT ", " INTPTR_FORMAT ")",
3149 _g1_storage.low_boundary(),
3150 _g1_storage.high(),
3151 _g1_storage.high_boundary());
3152 st->cr();
3153 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
3154 size_t young_regions = _young_list->length();
3155 st->print(SIZE_FORMAT " young (" SIZE_FORMAT "K), ",
3156 young_regions, young_regions * HeapRegion::GrainBytes / K);
3157 size_t survivor_regions = g1_policy()->recorded_survivor_regions();
3158 st->print(SIZE_FORMAT " survivors (" SIZE_FORMAT "K)",
3159 survivor_regions, survivor_regions * HeapRegion::GrainBytes / K);
3160 st->cr();
3161 perm()->as_gen()->print_on(st);
3162 }
3163
3164 void G1CollectedHeap::print_extended_on(outputStream* st) const {
3165 print_on(st);
3166
3167 // Print the per-region information.
3168 st->cr();
3169 st->print_cr("Heap Regions: (Y=young(eden), SU=young(survivor), HS=humongous(starts), HC=humongous(continues), CS=collection set, F=free, TS=gc time stamp, PTAMS=previous top-at-mark-start, NTAMS=next top-at-mark-start)");
3170 PrintRegionClosure blk(st);
3171 heap_region_iterate(&blk);
3172 }
3173
3174 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
3175 if (G1CollectedHeap::use_parallel_gc_threads()) {
3176 workers()->print_worker_threads_on(st);
3177 }
3178 _cmThread->print_on(st);
3179 st->cr();
3180 _cm->print_worker_threads_on(st);
3181 _cg1r->print_worker_threads_on(st);
3182 st->cr();
3183 }
3184
3185 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
3186 if (G1CollectedHeap::use_parallel_gc_threads()) {
3187 workers()->threads_do(tc);
3188 }
3189 tc->do_thread(_cmThread);
3190 _cg1r->threads_do(tc);
3191 }
3192
3193 void G1CollectedHeap::print_tracing_info() const {
3194 // We'll overload this to mean "trace GC pause statistics."
3195 if (TraceGen0Time || TraceGen1Time) {
3196 // The "G1CollectorPolicy" is keeping track of these stats, so delegate
3197 // to that.
3198 g1_policy()->print_tracing_info();
3199 }
3200 if (G1SummarizeRSetStats) {
3201 g1_rem_set()->print_summary_info();
3202 }
3203 if (G1SummarizeConcMark) {
3204 concurrent_mark()->print_summary_info();
3205 }
3206 g1_policy()->print_yg_surv_rate_info();
3207 SpecializationStats::print();
3208 }
3209
3210 #ifndef PRODUCT
3211 // Helpful for debugging RSet issues.
3212
3213 class PrintRSetsClosure : public HeapRegionClosure {
3214 private:
3215 const char* _msg;
3216 size_t _occupied_sum;
3217
3218 public:
3219 bool doHeapRegion(HeapRegion* r) {
3220 HeapRegionRemSet* hrrs = r->rem_set();
3221 size_t occupied = hrrs->occupied();
3222 _occupied_sum += occupied;
3223
3224 gclog_or_tty->print_cr("Printing RSet for region "HR_FORMAT,
3225 HR_FORMAT_PARAMS(r));
3226 if (occupied == 0) {
3227 gclog_or_tty->print_cr(" RSet is empty");
3228 } else {
3229 hrrs->print();
3230 }
3231 gclog_or_tty->print_cr("----------");
3232 return false;
3233 }
3234
3235 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
3236 gclog_or_tty->cr();
3237 gclog_or_tty->print_cr("========================================");
3238 gclog_or_tty->print_cr(msg);
3239 gclog_or_tty->cr();
3240 }
3241
3242 ~PrintRSetsClosure() {
3243 gclog_or_tty->print_cr("Occupied Sum: "SIZE_FORMAT, _occupied_sum);
3244 gclog_or_tty->print_cr("========================================");
3245 gclog_or_tty->cr();
3246 }
3247 };
3248
3249 void G1CollectedHeap::print_cset_rsets() {
3250 PrintRSetsClosure cl("Printing CSet RSets");
3251 collection_set_iterate(&cl);
3252 }
3253
3254 void G1CollectedHeap::print_all_rsets() {
3255 PrintRSetsClosure cl("Printing All RSets");;
3256 heap_region_iterate(&cl);
3257 }
3258 #endif // PRODUCT
3259
3260 G1CollectedHeap* G1CollectedHeap::heap() {
3261 assert(_sh->kind() == CollectedHeap::G1CollectedHeap,
3262 "not a garbage-first heap");
3263 return _g1h;
3264 }
3265
3266 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) {
3267 // always_do_update_barrier = false;
3268 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
3269 // Call allocation profiler
3270 AllocationProfiler::iterate_since_last_gc();
3271 // Fill TLAB's and such
3272 ensure_parsability(true);
3273 }
3274
3275 void G1CollectedHeap::gc_epilogue(bool full /* Ignored */) {
3276 // FIXME: what is this about?
3277 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
3278 // is set.
3279 COMPILER2_PRESENT(assert(DerivedPointerTable::is_empty(),
3280 "derived pointer present"));
3281 // always_do_update_barrier = true;
3282
3283 // We have just completed a GC. Update the soft reference
3284 // policy with the new heap occupancy
3285 Universe::update_heap_info_at_gc();
3286 }
3287
3288 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
3289 unsigned int gc_count_before,
3290 bool* succeeded) {
3291 assert_heap_not_locked_and_not_at_safepoint();
3292 g1_policy()->record_stop_world_start();
3293 VM_G1IncCollectionPause op(gc_count_before,
3294 word_size,
3295 false, /* should_initiate_conc_mark */
3296 g1_policy()->max_pause_time_ms(),
3297 GCCause::_g1_inc_collection_pause);
3298 VMThread::execute(&op);
3299
3300 HeapWord* result = op.result();
3301 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
3302 assert(result == NULL || ret_succeeded,
3303 "the result should be NULL if the VM did not succeed");
3304 *succeeded = ret_succeeded;
3305
3306 assert_heap_not_locked();
3307 return result;
3308 }
3309
3310 void
3311 G1CollectedHeap::doConcurrentMark() {
3312 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
3313 if (!_cmThread->in_progress()) {
3314 _cmThread->set_started();
3315 CGC_lock->notify();
3316 }
3317 }
3318
3319 double G1CollectedHeap::predict_region_elapsed_time_ms(HeapRegion *hr,
3320 bool young) {
3321 return _g1_policy->predict_region_elapsed_time_ms(hr, young);
3322 }
3323
3324 void G1CollectedHeap::check_if_region_is_too_expensive(double
3325 predicted_time_ms) {
3326 _g1_policy->check_if_region_is_too_expensive(predicted_time_ms);
3327 }
3328
3329 size_t G1CollectedHeap::pending_card_num() {
3330 size_t extra_cards = 0;
3331 JavaThread *curr = Threads::first();
3332 while (curr != NULL) {
3333 DirtyCardQueue& dcq = curr->dirty_card_queue();
3334 extra_cards += dcq.size();
3335 curr = curr->next();
3336 }
3337 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
3338 size_t buffer_size = dcqs.buffer_size();
3339 size_t buffer_num = dcqs.completed_buffers_num();
3340 return buffer_size * buffer_num + extra_cards;
3341 }
3342
3343 size_t G1CollectedHeap::max_pending_card_num() {
3344 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
3345 size_t buffer_size = dcqs.buffer_size();
3346 size_t buffer_num = dcqs.completed_buffers_num();
3347 int thread_num = Threads::number_of_threads();
3348 return (buffer_num + thread_num) * buffer_size;
3349 }
3350
3351 size_t G1CollectedHeap::cards_scanned() {
3352 return g1_rem_set()->cardsScanned();
3353 }
3354
3355 void
3356 G1CollectedHeap::setup_surviving_young_words() {
3357 guarantee( _surviving_young_words == NULL, "pre-condition" );
3358 size_t array_length = g1_policy()->young_cset_region_length();
3359 _surviving_young_words = NEW_C_HEAP_ARRAY(size_t, array_length);
3360 if (_surviving_young_words == NULL) {
3361 vm_exit_out_of_memory(sizeof(size_t) * array_length,
3362 "Not enough space for young surv words summary.");
3363 }
3364 memset(_surviving_young_words, 0, array_length * sizeof(size_t));
3365 #ifdef ASSERT
3366 for (size_t i = 0; i < array_length; ++i) {
3367 assert( _surviving_young_words[i] == 0, "memset above" );
3368 }
3369 #endif // !ASSERT
3370 }
3371
3372 void
3373 G1CollectedHeap::update_surviving_young_words(size_t* surv_young_words) {
3374 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
3375 size_t array_length = g1_policy()->young_cset_region_length();
3376 for (size_t i = 0; i < array_length; ++i)
3377 _surviving_young_words[i] += surv_young_words[i];
3378 }
3379
3380 void
3381 G1CollectedHeap::cleanup_surviving_young_words() {
3382 guarantee( _surviving_young_words != NULL, "pre-condition" );
3383 FREE_C_HEAP_ARRAY(size_t, _surviving_young_words);
3384 _surviving_young_words = NULL;
3385 }
3386
3387 #ifdef ASSERT
3388 class VerifyCSetClosure: public HeapRegionClosure {
3389 public:
3390 bool doHeapRegion(HeapRegion* hr) {
3391 // Here we check that the CSet region's RSet is ready for parallel
3392 // iteration. The fields that we'll verify are only manipulated
3393 // when the region is part of a CSet and is collected. Afterwards,
3394 // we reset these fields when we clear the region's RSet (when the
3395 // region is freed) so they are ready when the region is
3396 // re-allocated. The only exception to this is if there's an
3397 // evacuation failure and instead of freeing the region we leave
3398 // it in the heap. In that case, we reset these fields during
3399 // evacuation failure handling.
3400 guarantee(hr->rem_set()->verify_ready_for_par_iteration(), "verification");
3401
3402 // Here's a good place to add any other checks we'd like to
3403 // perform on CSet regions.
3404 return false;
3405 }
3406 };
3407 #endif // ASSERT
3408
3409 #if TASKQUEUE_STATS
3410 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
3411 st->print_raw_cr("GC Task Stats");
3412 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
3413 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
3414 }
3415
3416 void G1CollectedHeap::print_taskqueue_stats(outputStream* const st) const {
3417 print_taskqueue_stats_hdr(st);
3418
3419 TaskQueueStats totals;
3420 const int n = workers() != NULL ? workers()->total_workers() : 1;
3421 for (int i = 0; i < n; ++i) {
3422 st->print("%3d ", i); task_queue(i)->stats.print(st); st->cr();
3423 totals += task_queue(i)->stats;
3424 }
3425 st->print_raw("tot "); totals.print(st); st->cr();
3426
3427 DEBUG_ONLY(totals.verify());
3428 }
3429
3430 void G1CollectedHeap::reset_taskqueue_stats() {
3431 const int n = workers() != NULL ? workers()->total_workers() : 1;
3432 for (int i = 0; i < n; ++i) {
3433 task_queue(i)->stats.reset();
3434 }
3435 }
3436 #endif // TASKQUEUE_STATS
3437
3438 bool
3439 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
3440 assert_at_safepoint(true /* should_be_vm_thread */);
3441 guarantee(!is_gc_active(), "collection is not reentrant");
3442
3443 if (GC_locker::check_active_before_gc()) {
3444 return false;
3445 }
3446
3447 SvcGCMarker sgcm(SvcGCMarker::MINOR);
3448 ResourceMark rm;
3449
3450 if (PrintHeapAtGC) {
3451 Universe::print_heap_before_gc();
3452 }
3453
3454 HRSPhaseSetter x(HRSPhaseEvacuation);
3455 verify_region_sets_optional();
3456 verify_dirty_young_regions();
3457
3458 {
3459 // This call will decide whether this pause is an initial-mark
3460 // pause. If it is, during_initial_mark_pause() will return true
3461 // for the duration of this pause.
3462 g1_policy()->decide_on_conc_mark_initiation();
3463
3464 // We do not allow initial-mark to be piggy-backed on a
3465 // partially-young GC.
3466 assert(!g1_policy()->during_initial_mark_pause() ||
3467 g1_policy()->full_young_gcs(), "sanity");
3468
3469 // We also do not allow partially-young GCs during marking.
3470 assert(!mark_in_progress() || g1_policy()->full_young_gcs(), "sanity");
3471
3472 char verbose_str[128];
3473 sprintf(verbose_str, "GC pause ");
3474 if (g1_policy()->full_young_gcs()) {
3475 strcat(verbose_str, "(young)");
3476 } else {
3477 strcat(verbose_str, "(partial)");
3478 }
3479 if (g1_policy()->during_initial_mark_pause()) {
3480 strcat(verbose_str, " (initial-mark)");
3481 // We are about to start a marking cycle, so we increment the
3482 // full collection counter.
3483 increment_total_full_collections();
3484 }
3485
3486 // if PrintGCDetails is on, we'll print long statistics information
3487 // in the collector policy code, so let's not print this as the output
3488 // is messy if we do.
3489 gclog_or_tty->date_stamp(PrintGC && PrintGCDateStamps);
3490 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty);
3491 TraceTime t(verbose_str, PrintGC && !PrintGCDetails, true, gclog_or_tty);
3492
3493 TraceCollectorStats tcs(g1mm()->incremental_collection_counters());
3494 TraceMemoryManagerStats tms(false /* fullGC */, gc_cause());
3495
3496 // If the secondary_free_list is not empty, append it to the
3497 // free_list. No need to wait for the cleanup operation to finish;
3498 // the region allocation code will check the secondary_free_list
3499 // and wait if necessary. If the G1StressConcRegionFreeing flag is
3500 // set, skip this step so that the region allocation code has to
3501 // get entries from the secondary_free_list.
3502 if (!G1StressConcRegionFreeing) {
3503 append_secondary_free_list_if_not_empty_with_lock();
3504 }
3505
3506 assert(check_young_list_well_formed(),
3507 "young list should be well formed");
3508
3509 // Don't dynamically change the number of GC threads this early. A value of
3510 // 0 is used to indicate serial work. When parallel work is done,
3511 // it will be set.
3512
3513 { // Call to jvmpi::post_class_unload_events must occur outside of active GC
3514 IsGCActiveMark x;
3515
3516 gc_prologue(false);
3517 increment_total_collections(false /* full gc */);
3518 increment_gc_time_stamp();
3519
3520 if (VerifyBeforeGC && total_collections() >= VerifyGCStartAt) {
3521 HandleMark hm; // Discard invalid handles created during verification
3522 gclog_or_tty->print(" VerifyBeforeGC:");
3523 prepare_for_verify();
3524 Universe::verify(/* allow dirty */ false,
3525 /* silent */ false,
3526 /* option */ VerifyOption_G1UsePrevMarking);
3527
3528 }
3529
3530 COMPILER2_PRESENT(DerivedPointerTable::clear());
3531
3532 // Please see comment in g1CollectedHeap.hpp and
3533 // G1CollectedHeap::ref_processing_init() to see how
3534 // reference processing currently works in G1.
3535
3536 // Enable discovery in the STW reference processor
3537 ref_processor_stw()->enable_discovery(true /*verify_disabled*/,
3538 true /*verify_no_refs*/);
3539
3540 {
3541 // We want to temporarily turn off discovery by the
3542 // CM ref processor, if necessary, and turn it back on
3543 // on again later if we do. Using a scoped
3544 // NoRefDiscovery object will do this.
3545 NoRefDiscovery no_cm_discovery(ref_processor_cm());
3546
3547 // Forget the current alloc region (we might even choose it to be part
3548 // of the collection set!).
3549 release_mutator_alloc_region();
3550
3551 // We should call this after we retire the mutator alloc
3552 // region(s) so that all the ALLOC / RETIRE events are generated
3553 // before the start GC event.
3554 _hr_printer.start_gc(false /* full */, (size_t) total_collections());
3555
3556 // The elapsed time induced by the start time below deliberately elides
3557 // the possible verification above.
3558 double start_time_sec = os::elapsedTime();
3559 size_t start_used_bytes = used();
3560
3561 #if YOUNG_LIST_VERBOSE
3562 gclog_or_tty->print_cr("\nBefore recording pause start.\nYoung_list:");
3563 _young_list->print();
3564 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3565 #endif // YOUNG_LIST_VERBOSE
3566
3567 g1_policy()->record_collection_pause_start(start_time_sec,
3568 start_used_bytes);
3569
3570 #if YOUNG_LIST_VERBOSE
3571 gclog_or_tty->print_cr("\nAfter recording pause start.\nYoung_list:");
3572 _young_list->print();
3573 #endif // YOUNG_LIST_VERBOSE
3574
3575 if (g1_policy()->during_initial_mark_pause()) {
3576 concurrent_mark()->checkpointRootsInitialPre();
3577 }
3578 perm_gen()->save_marks();
3579
3580 // We must do this before any possible evacuation that should propagate
3581 // marks.
3582 if (mark_in_progress()) {
3583 double start_time_sec = os::elapsedTime();
3584
3585 _cm->drainAllSATBBuffers();
3586 double finish_mark_ms = (os::elapsedTime() - start_time_sec) * 1000.0;
3587 g1_policy()->record_satb_drain_time(finish_mark_ms);
3588 }
3589 // Record the number of elements currently on the mark stack, so we
3590 // only iterate over these. (Since evacuation may add to the mark
3591 // stack, doing more exposes race conditions.) If no mark is in
3592 // progress, this will be zero.
3593 _cm->set_oops_do_bound();
3594
3595 if (mark_in_progress()) {
3596 concurrent_mark()->newCSet();
3597 }
3598
3599 #if YOUNG_LIST_VERBOSE
3600 gclog_or_tty->print_cr("\nBefore choosing collection set.\nYoung_list:");
3601 _young_list->print();
3602 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3603 #endif // YOUNG_LIST_VERBOSE
3604
3605 g1_policy()->choose_collection_set(target_pause_time_ms);
3606
3607 if (_hr_printer.is_active()) {
3608 HeapRegion* hr = g1_policy()->collection_set();
3609 while (hr != NULL) {
3610 G1HRPrinter::RegionType type;
3611 if (!hr->is_young()) {
3612 type = G1HRPrinter::Old;
3613 } else if (hr->is_survivor()) {
3614 type = G1HRPrinter::Survivor;
3615 } else {
3616 type = G1HRPrinter::Eden;
3617 }
3618 _hr_printer.cset(hr);
3619 hr = hr->next_in_collection_set();
3620 }
3621 }
3622
3623 // We have chosen the complete collection set. If marking is
3624 // active then, we clear the region fields of any of the
3625 // concurrent marking tasks whose region fields point into
3626 // the collection set as these values will become stale. This
3627 // will cause the owning marking threads to claim a new region
3628 // when marking restarts.
3629 if (mark_in_progress()) {
3630 concurrent_mark()->reset_active_task_region_fields_in_cset();
3631 }
3632
3633 #ifdef ASSERT
3634 VerifyCSetClosure cl;
3635 collection_set_iterate(&cl);
3636 #endif // ASSERT
3637
3638 setup_surviving_young_words();
3639
3640 // Initialize the GC alloc regions.
3641 init_gc_alloc_regions();
3642
3643 // Actually do the work...
3644 evacuate_collection_set();
3645
3646 free_collection_set(g1_policy()->collection_set());
3647 g1_policy()->clear_collection_set();
3648
3649 cleanup_surviving_young_words();
3650
3651 // Start a new incremental collection set for the next pause.
3652 g1_policy()->start_incremental_cset_building();
3653
3654 // Clear the _cset_fast_test bitmap in anticipation of adding
3655 // regions to the incremental collection set for the next
3656 // evacuation pause.
3657 clear_cset_fast_test();
3658
3659 _young_list->reset_sampled_info();
3660
3661 // Don't check the whole heap at this point as the
3662 // GC alloc regions from this pause have been tagged
3663 // as survivors and moved on to the survivor list.
3664 // Survivor regions will fail the !is_young() check.
3665 assert(check_young_list_empty(false /* check_heap */),
3666 "young list should be empty");
3667
3668 #if YOUNG_LIST_VERBOSE
3669 gclog_or_tty->print_cr("Before recording survivors.\nYoung List:");
3670 _young_list->print();
3671 #endif // YOUNG_LIST_VERBOSE
3672
3673 g1_policy()->record_survivor_regions(_young_list->survivor_length(),
3674 _young_list->first_survivor_region(),
3675 _young_list->last_survivor_region());
3676
3677 _young_list->reset_auxilary_lists();
3678
3679 if (evacuation_failed()) {
3680 _summary_bytes_used = recalculate_used();
3681 } else {
3682 // The "used" of the the collection set have already been subtracted
3683 // when they were freed. Add in the bytes evacuated.
3684 _summary_bytes_used += g1_policy()->bytes_copied_during_gc();
3685 }
3686
3687 if (g1_policy()->during_initial_mark_pause()) {
3688 concurrent_mark()->checkpointRootsInitialPost();
3689 set_marking_started();
3690 // CAUTION: after the doConcurrentMark() call below,
3691 // the concurrent marking thread(s) could be running
3692 // concurrently with us. Make sure that anything after
3693 // this point does not assume that we are the only GC thread
3694 // running. Note: of course, the actual marking work will
3695 // not start until the safepoint itself is released in
3696 // ConcurrentGCThread::safepoint_desynchronize().
3697 doConcurrentMark();
3698 }
3699
3700 allocate_dummy_regions();
3701
3702 #if YOUNG_LIST_VERBOSE
3703 gclog_or_tty->print_cr("\nEnd of the pause.\nYoung_list:");
3704 _young_list->print();
3705 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3706 #endif // YOUNG_LIST_VERBOSE
3707
3708 init_mutator_alloc_region();
3709
3710 {
3711 size_t expand_bytes = g1_policy()->expansion_amount();
3712 if (expand_bytes > 0) {
3713 size_t bytes_before = capacity();
3714 if (!expand(expand_bytes)) {
3715 // We failed to expand the heap so let's verify that
3716 // committed/uncommitted amount match the backing store
3717 assert(capacity() == _g1_storage.committed_size(), "committed size mismatch");
3718 assert(max_capacity() == _g1_storage.reserved_size(), "reserved size mismatch");
3719 }
3720 }
3721 }
3722
3723 double end_time_sec = os::elapsedTime();
3724 double pause_time_ms = (end_time_sec - start_time_sec) * MILLIUNITS;
3725 g1_policy()->record_pause_time_ms(pause_time_ms);
3726 int active_gc_threads = workers()->active_workers();
3727 g1_policy()->record_collection_pause_end(active_gc_threads);
3728
3729 MemoryService::track_memory_usage();
3730
3731 // In prepare_for_verify() below we'll need to scan the deferred
3732 // update buffers to bring the RSets up-to-date if
3733 // G1HRRSFlushLogBuffersOnVerify has been set. While scanning
3734 // the update buffers we'll probably need to scan cards on the
3735 // regions we just allocated to (i.e., the GC alloc
3736 // regions). However, during the last GC we called
3737 // set_saved_mark() on all the GC alloc regions, so card
3738 // scanning might skip the [saved_mark_word()...top()] area of
3739 // those regions (i.e., the area we allocated objects into
3740 // during the last GC). But it shouldn't. Given that
3741 // saved_mark_word() is conditional on whether the GC time stamp
3742 // on the region is current or not, by incrementing the GC time
3743 // stamp here we invalidate all the GC time stamps on all the
3744 // regions and saved_mark_word() will simply return top() for
3745 // all the regions. This is a nicer way of ensuring this rather
3746 // than iterating over the regions and fixing them. In fact, the
3747 // GC time stamp increment here also ensures that
3748 // saved_mark_word() will return top() between pauses, i.e.,
3749 // during concurrent refinement. So we don't need the
3750 // is_gc_active() check to decided which top to use when
3751 // scanning cards (see CR 7039627).
3752 increment_gc_time_stamp();
3753
3754 if (VerifyAfterGC && total_collections() >= VerifyGCStartAt) {
3755 HandleMark hm; // Discard invalid handles created during verification
3756 gclog_or_tty->print(" VerifyAfterGC:");
3757 prepare_for_verify();
3758 Universe::verify(/* allow dirty */ true,
3759 /* silent */ false,
3760 /* option */ VerifyOption_G1UsePrevMarking);
3761 }
3762
3763 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
3764 ref_processor_stw()->verify_no_references_recorded();
3765
3766 // CM reference discovery will be re-enabled if necessary.
3767 }
3768
3769 {
3770 size_t expand_bytes = g1_policy()->expansion_amount();
3771 if (expand_bytes > 0) {
3772 size_t bytes_before = capacity();
3773 // No need for an ergo verbose message here,
3774 // expansion_amount() does this when it returns a value > 0.
3775 if (!expand(expand_bytes)) {
3776 // We failed to expand the heap so let's verify that
3777 // committed/uncommitted amount match the backing store
3778 assert(capacity() == _g1_storage.committed_size(), "committed size mismatch");
3779 assert(max_capacity() == _g1_storage.reserved_size(), "reserved size mismatch");
3780 }
3781 }
3782 }
3783
3784 // We should do this after we potentially expand the heap so
3785 // that all the COMMIT events are generated before the end GC
3786 // event, and after we retire the GC alloc regions so that all
3787 // RETIRE events are generated before the end GC event.
3788 _hr_printer.end_gc(false /* full */, (size_t) total_collections());
3789
3790 // We have to do this after we decide whether to expand the heap or not.
3791 g1_policy()->print_heap_transition();
3792
3793 if (mark_in_progress()) {
3794 concurrent_mark()->update_g1_committed();
3795 }
3796
3797 #ifdef TRACESPINNING
3798 ParallelTaskTerminator::print_termination_counts();
3799 #endif
3800
3801 gc_epilogue(false);
3802 }
3803
3804 if (ExitAfterGCNum > 0 && total_collections() == ExitAfterGCNum) {
3805 gclog_or_tty->print_cr("Stopping after GC #%d", ExitAfterGCNum);
3806 print_tracing_info();
3807 vm_exit(-1);
3808 }
3809 }
3810
3811 _hrs.verify_optional();
3812 verify_region_sets_optional();
3813
3814 TASKQUEUE_STATS_ONLY(if (ParallelGCVerbose) print_taskqueue_stats());
3815 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
3816
3817 if (PrintHeapAtGC) {
3818 Universe::print_heap_after_gc();
3819 }
3820 g1mm()->update_sizes();
3821
3822 if (G1SummarizeRSetStats &&
3823 (G1SummarizeRSetStatsPeriod > 0) &&
3824 (total_collections() % G1SummarizeRSetStatsPeriod == 0)) {
3825 g1_rem_set()->print_summary_info();
3826 }
3827
3828 return true;
3829 }
3830
3831 size_t G1CollectedHeap::desired_plab_sz(GCAllocPurpose purpose)
3832 {
3833 size_t gclab_word_size;
3834 switch (purpose) {
3835 case GCAllocForSurvived:
3836 gclab_word_size = YoungPLABSize;
3837 break;
3838 case GCAllocForTenured:
3839 gclab_word_size = OldPLABSize;
3840 break;
3841 default:
3842 assert(false, "unknown GCAllocPurpose");
3843 gclab_word_size = OldPLABSize;
3844 break;
3845 }
3846 return gclab_word_size;
3847 }
3848
3849 void G1CollectedHeap::init_mutator_alloc_region() {
3850 assert(_mutator_alloc_region.get() == NULL, "pre-condition");
3851 _mutator_alloc_region.init();
3852 }
3853
3854 void G1CollectedHeap::release_mutator_alloc_region() {
3855 _mutator_alloc_region.release();
3856 assert(_mutator_alloc_region.get() == NULL, "post-condition");
3857 }
3858
3859 void G1CollectedHeap::init_gc_alloc_regions() {
3860 assert_at_safepoint(true /* should_be_vm_thread */);
3861
3862 _survivor_gc_alloc_region.init();
3863 _old_gc_alloc_region.init();
3864 HeapRegion* retained_region = _retained_old_gc_alloc_region;
3865 _retained_old_gc_alloc_region = NULL;
3866
3867 // We will discard the current GC alloc region if:
3868 // a) it's in the collection set (it can happen!),
3869 // b) it's already full (no point in using it),
3870 // c) it's empty (this means that it was emptied during
3871 // a cleanup and it should be on the free list now), or
3872 // d) it's humongous (this means that it was emptied
3873 // during a cleanup and was added to the free list, but
3874 // has been subseqently used to allocate a humongous
3875 // object that may be less than the region size).
3876 if (retained_region != NULL &&
3877 !retained_region->in_collection_set() &&
3878 !(retained_region->top() == retained_region->end()) &&
3879 !retained_region->is_empty() &&
3880 !retained_region->isHumongous()) {
3881 retained_region->set_saved_mark();
3882 // The retained region was added to the old region set when it was
3883 // retired. We have to remove it now, since we don't allow regions
3884 // we allocate to in the region sets. We'll re-add it later, when
3885 // it's retired again.
3886 _old_set.remove(retained_region);
3887 _old_gc_alloc_region.set(retained_region);
3888 _hr_printer.reuse(retained_region);
3889 }
3890 }
3891
3892 void G1CollectedHeap::release_gc_alloc_regions() {
3893 _survivor_gc_alloc_region.release();
3894 // If we have an old GC alloc region to release, we'll save it in
3895 // _retained_old_gc_alloc_region. If we don't
3896 // _retained_old_gc_alloc_region will become NULL. This is what we
3897 // want either way so no reason to check explicitly for either
3898 // condition.
3899 _retained_old_gc_alloc_region = _old_gc_alloc_region.release();
3900 }
3901
3902 void G1CollectedHeap::abandon_gc_alloc_regions() {
3903 assert(_survivor_gc_alloc_region.get() == NULL, "pre-condition");
3904 assert(_old_gc_alloc_region.get() == NULL, "pre-condition");
3905 _retained_old_gc_alloc_region = NULL;
3906 }
3907
3908 void G1CollectedHeap::init_for_evac_failure(OopsInHeapRegionClosure* cl) {
3909 _drain_in_progress = false;
3910 set_evac_failure_closure(cl);
3911 _evac_failure_scan_stack = new (ResourceObj::C_HEAP) GrowableArray<oop>(40, true);
3912 }
3913
3914 void G1CollectedHeap::finalize_for_evac_failure() {
3915 assert(_evac_failure_scan_stack != NULL &&
3916 _evac_failure_scan_stack->length() == 0,
3917 "Postcondition");
3918 assert(!_drain_in_progress, "Postcondition");
3919 delete _evac_failure_scan_stack;
3920 _evac_failure_scan_stack = NULL;
3921 }
3922
3923 class UpdateRSetDeferred : public OopsInHeapRegionClosure {
3924 private:
3925 G1CollectedHeap* _g1;
3926 DirtyCardQueue *_dcq;
3927 CardTableModRefBS* _ct_bs;
3928
3929 public:
3930 UpdateRSetDeferred(G1CollectedHeap* g1, DirtyCardQueue* dcq) :
3931 _g1(g1), _ct_bs((CardTableModRefBS*)_g1->barrier_set()), _dcq(dcq) {}
3932
3933 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
3934 virtual void do_oop( oop* p) { do_oop_work(p); }
3935 template <class T> void do_oop_work(T* p) {
3936 assert(_from->is_in_reserved(p), "paranoia");
3937 if (!_from->is_in_reserved(oopDesc::load_decode_heap_oop(p)) &&
3938 !_from->is_survivor()) {
3939 size_t card_index = _ct_bs->index_for(p);
3940 if (_ct_bs->mark_card_deferred(card_index)) {
3941 _dcq->enqueue((jbyte*)_ct_bs->byte_for_index(card_index));
3942 }
3943 }
3944 }
3945 };
3946
3947 class RemoveSelfPointerClosure: public ObjectClosure {
3948 private:
3949 G1CollectedHeap* _g1;
3950 ConcurrentMark* _cm;
3951 HeapRegion* _hr;
3952 size_t _prev_marked_bytes;
3953 size_t _next_marked_bytes;
3954 OopsInHeapRegionClosure *_cl;
3955 public:
3956 RemoveSelfPointerClosure(G1CollectedHeap* g1, HeapRegion* hr,
3957 OopsInHeapRegionClosure* cl) :
3958 _g1(g1), _hr(hr), _cm(_g1->concurrent_mark()), _prev_marked_bytes(0),
3959 _next_marked_bytes(0), _cl(cl) {}
3960
3961 size_t prev_marked_bytes() { return _prev_marked_bytes; }
3962 size_t next_marked_bytes() { return _next_marked_bytes; }
3963
3964 // <original comment>
3965 // The original idea here was to coalesce evacuated and dead objects.
3966 // However that caused complications with the block offset table (BOT).
3967 // In particular if there were two TLABs, one of them partially refined.
3968 // |----- TLAB_1--------|----TLAB_2-~~~(partially refined part)~~~|
3969 // The BOT entries of the unrefined part of TLAB_2 point to the start
3970 // of TLAB_2. If the last object of the TLAB_1 and the first object
3971 // of TLAB_2 are coalesced, then the cards of the unrefined part
3972 // would point into middle of the filler object.
3973 // The current approach is to not coalesce and leave the BOT contents intact.
3974 // </original comment>
3975 //
3976 // We now reset the BOT when we start the object iteration over the
3977 // region and refine its entries for every object we come across. So
3978 // the above comment is not really relevant and we should be able
3979 // to coalesce dead objects if we want to.
3980 void do_object(oop obj) {
3981 HeapWord* obj_addr = (HeapWord*) obj;
3982 assert(_hr->is_in(obj_addr), "sanity");
3983 size_t obj_size = obj->size();
3984 _hr->update_bot_for_object(obj_addr, obj_size);
3985 if (obj->is_forwarded() && obj->forwardee() == obj) {
3986 // The object failed to move.
3987 assert(!_g1->is_obj_dead(obj), "We should not be preserving dead objs.");
3988 _cm->markPrev(obj);
3989 assert(_cm->isPrevMarked(obj), "Should be marked!");
3990 _prev_marked_bytes += (obj_size * HeapWordSize);
3991 if (_g1->mark_in_progress() && !_g1->is_obj_ill(obj)) {
3992 _cm->markAndGrayObjectIfNecessary(obj);
3993 }
3994 obj->set_mark(markOopDesc::prototype());
3995 // While we were processing RSet buffers during the
3996 // collection, we actually didn't scan any cards on the
3997 // collection set, since we didn't want to update remebered
3998 // sets with entries that point into the collection set, given
3999 // that live objects fromthe collection set are about to move
4000 // and such entries will be stale very soon. This change also
4001 // dealt with a reliability issue which involved scanning a
4002 // card in the collection set and coming across an array that
4003 // was being chunked and looking malformed. The problem is
4004 // that, if evacuation fails, we might have remembered set
4005 // entries missing given that we skipped cards on the
4006 // collection set. So, we'll recreate such entries now.
4007 obj->oop_iterate(_cl);
4008 assert(_cm->isPrevMarked(obj), "Should be marked!");
4009 } else {
4010 // The object has been either evacuated or is dead. Fill it with a
4011 // dummy object.
4012 MemRegion mr((HeapWord*)obj, obj_size);
4013 CollectedHeap::fill_with_object(mr);
4014 _cm->clearRangeBothMaps(mr);
4015 }
4016 }
4017 };
4018
4019 void G1CollectedHeap::remove_self_forwarding_pointers() {
4020 UpdateRSetImmediate immediate_update(_g1h->g1_rem_set());
4021 DirtyCardQueue dcq(&_g1h->dirty_card_queue_set());
4022 UpdateRSetDeferred deferred_update(_g1h, &dcq);
4023 OopsInHeapRegionClosure *cl;
4024 if (G1DeferredRSUpdate) {
4025 cl = &deferred_update;
4026 } else {
4027 cl = &immediate_update;
4028 }
4029 HeapRegion* cur = g1_policy()->collection_set();
4030 while (cur != NULL) {
4031 assert(g1_policy()->assertMarkedBytesDataOK(), "Should be!");
4032 assert(!cur->isHumongous(), "sanity");
4033
4034 if (cur->evacuation_failed()) {
4035 assert(cur->in_collection_set(), "bad CS");
4036 RemoveSelfPointerClosure rspc(_g1h, cur, cl);
4037
4038 // In the common case we make sure that this is done when the
4039 // region is freed so that it is "ready-to-go" when it's
4040 // re-allocated. However, when evacuation failure happens, a
4041 // region will remain in the heap and might ultimately be added
4042 // to a CSet in the future. So we have to be careful here and
4043 // make sure the region's RSet is ready for parallel iteration
4044 // whenever this might be required in the future.
4045 cur->rem_set()->reset_for_par_iteration();
4046 cur->reset_bot();
4047 cl->set_region(cur);
4048 cur->object_iterate(&rspc);
4049
4050 // A number of manipulations to make the TAMS be the current top,
4051 // and the marked bytes be the ones observed in the iteration.
4052 if (_g1h->concurrent_mark()->at_least_one_mark_complete()) {
4053 // The comments below are the postconditions achieved by the
4054 // calls. Note especially the last such condition, which says that
4055 // the count of marked bytes has been properly restored.
4056 cur->note_start_of_marking(false);
4057 // _next_top_at_mark_start == top, _next_marked_bytes == 0
4058 cur->add_to_marked_bytes(rspc.prev_marked_bytes());
4059 // _next_marked_bytes == prev_marked_bytes.
4060 cur->note_end_of_marking();
4061 // _prev_top_at_mark_start == top(),
4062 // _prev_marked_bytes == prev_marked_bytes
4063 }
4064 // If there is no mark in progress, we modified the _next variables
4065 // above needlessly, but harmlessly.
4066 if (_g1h->mark_in_progress()) {
4067 cur->note_start_of_marking(false);
4068 // _next_top_at_mark_start == top, _next_marked_bytes == 0
4069 // _next_marked_bytes == next_marked_bytes.
4070 }
4071 }
4072 cur = cur->next_in_collection_set();
4073 }
4074 assert(g1_policy()->assertMarkedBytesDataOK(), "Should be!");
4075
4076 // Now restore saved marks, if any.
4077 if (_objs_with_preserved_marks != NULL) {
4078 assert(_preserved_marks_of_objs != NULL, "Both or none.");
4079 guarantee(_objs_with_preserved_marks->length() ==
4080 _preserved_marks_of_objs->length(), "Both or none.");
4081 for (int i = 0; i < _objs_with_preserved_marks->length(); i++) {
4082 oop obj = _objs_with_preserved_marks->at(i);
4083 markOop m = _preserved_marks_of_objs->at(i);
4084 obj->set_mark(m);
4085 }
4086 // Delete the preserved marks growable arrays (allocated on the C heap).
4087 delete _objs_with_preserved_marks;
4088 delete _preserved_marks_of_objs;
4089 _objs_with_preserved_marks = NULL;
4090 _preserved_marks_of_objs = NULL;
4091 }
4092 }
4093
4094 void G1CollectedHeap::push_on_evac_failure_scan_stack(oop obj) {
4095 _evac_failure_scan_stack->push(obj);
4096 }
4097
4098 void G1CollectedHeap::drain_evac_failure_scan_stack() {
4099 assert(_evac_failure_scan_stack != NULL, "precondition");
4100
4101 while (_evac_failure_scan_stack->length() > 0) {
4102 oop obj = _evac_failure_scan_stack->pop();
4103 _evac_failure_closure->set_region(heap_region_containing(obj));
4104 obj->oop_iterate_backwards(_evac_failure_closure);
4105 }
4106 }
4107
4108 oop
4109 G1CollectedHeap::handle_evacuation_failure_par(OopsInHeapRegionClosure* cl,
4110 oop old,
4111 bool should_mark_root) {
4112 assert(obj_in_cs(old),
4113 err_msg("obj: "PTR_FORMAT" should still be in the CSet",
4114 (HeapWord*) old));
4115 markOop m = old->mark();
4116 oop forward_ptr = old->forward_to_atomic(old);
4117 if (forward_ptr == NULL) {
4118 // Forward-to-self succeeded.
4119
4120 // should_mark_root will be true when this routine is called
4121 // from a root scanning closure during an initial mark pause.
4122 // In this case the thread that succeeds in self-forwarding the
4123 // object is also responsible for marking the object.
4124 if (should_mark_root) {
4125 assert(!oopDesc::is_null(old), "shouldn't be");
4126 _cm->grayRoot(old);
4127 }
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 #ifndef PRODUCT
4225 bool GCLabBitMapClosure::do_bit(size_t offset) {
4226 HeapWord* addr = _bitmap->offsetToHeapWord(offset);
4227 guarantee(_cm->isMarked(oop(addr)), "it should be!");
4228 return true;
4229 }
4230 #endif // PRODUCT
4231
4232 G1ParGCAllocBuffer::G1ParGCAllocBuffer(size_t gclab_word_size) :
4233 ParGCAllocBuffer(gclab_word_size),
4234 _should_mark_objects(false),
4235 _bitmap(G1CollectedHeap::heap()->reserved_region().start(), gclab_word_size),
4236 _retired(false)
4237 {
4238 //_should_mark_objects is set to true when G1ParCopyHelper needs to
4239 // mark the forwarded location of an evacuated object.
4240 // We set _should_mark_objects to true if marking is active, i.e. when we
4241 // need to propagate a mark, or during an initial mark pause, i.e. when we
4242 // need to mark objects immediately reachable by the roots.
4243 if (G1CollectedHeap::heap()->mark_in_progress() ||
4244 G1CollectedHeap::heap()->g1_policy()->during_initial_mark_pause()) {
4245 _should_mark_objects = true;
4246 }
4247 }
4248
4249 G1ParScanThreadState::G1ParScanThreadState(G1CollectedHeap* g1h, int queue_num)
4250 : _g1h(g1h),
4251 _refs(g1h->task_queue(queue_num)),
4252 _dcq(&g1h->dirty_card_queue_set()),
4253 _ct_bs((CardTableModRefBS*)_g1h->barrier_set()),
4254 _g1_rem(g1h->g1_rem_set()),
4255 _hash_seed(17), _queue_num(queue_num),
4256 _term_attempts(0),
4257 _surviving_alloc_buffer(g1h->desired_plab_sz(GCAllocForSurvived)),
4258 _tenured_alloc_buffer(g1h->desired_plab_sz(GCAllocForTenured)),
4259 _age_table(false),
4260 _strong_roots_time(0), _term_time(0),
4261 _alloc_buffer_waste(0), _undo_waste(0)
4262 {
4263 // we allocate G1YoungSurvRateNumRegions plus one entries, since
4264 // we "sacrifice" entry 0 to keep track of surviving bytes for
4265 // non-young regions (where the age is -1)
4266 // We also add a few elements at the beginning and at the end in
4267 // an attempt to eliminate cache contention
4268 size_t real_length = 1 + _g1h->g1_policy()->young_cset_region_length();
4269 size_t array_length = PADDING_ELEM_NUM +
4270 real_length +
4271 PADDING_ELEM_NUM;
4272 _surviving_young_words_base = NEW_C_HEAP_ARRAY(size_t, array_length);
4273 if (_surviving_young_words_base == NULL)
4274 vm_exit_out_of_memory(array_length * sizeof(size_t),
4275 "Not enough space for young surv histo.");
4276 _surviving_young_words = _surviving_young_words_base + PADDING_ELEM_NUM;
4277 memset(_surviving_young_words, 0, real_length * sizeof(size_t));
4278
4279 _alloc_buffers[GCAllocForSurvived] = &_surviving_alloc_buffer;
4280 _alloc_buffers[GCAllocForTenured] = &_tenured_alloc_buffer;
4281
4282 _start = os::elapsedTime();
4283 }
4284
4285 void
4286 G1ParScanThreadState::print_termination_stats_hdr(outputStream* const st)
4287 {
4288 st->print_raw_cr("GC Termination Stats");
4289 st->print_raw_cr(" elapsed --strong roots-- -------termination-------"
4290 " ------waste (KiB)------");
4291 st->print_raw_cr("thr ms ms % ms % attempts"
4292 " total alloc undo");
4293 st->print_raw_cr("--- --------- --------- ------ --------- ------ --------"
4294 " ------- ------- -------");
4295 }
4296
4297 void
4298 G1ParScanThreadState::print_termination_stats(int i,
4299 outputStream* const st) const
4300 {
4301 const double elapsed_ms = elapsed_time() * 1000.0;
4302 const double s_roots_ms = strong_roots_time() * 1000.0;
4303 const double term_ms = term_time() * 1000.0;
4304 st->print_cr("%3d %9.2f %9.2f %6.2f "
4305 "%9.2f %6.2f " SIZE_FORMAT_W(8) " "
4306 SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7),
4307 i, elapsed_ms, s_roots_ms, s_roots_ms * 100 / elapsed_ms,
4308 term_ms, term_ms * 100 / elapsed_ms, term_attempts(),
4309 (alloc_buffer_waste() + undo_waste()) * HeapWordSize / K,
4310 alloc_buffer_waste() * HeapWordSize / K,
4311 undo_waste() * HeapWordSize / K);
4312 }
4313
4314 #ifdef ASSERT
4315 bool G1ParScanThreadState::verify_ref(narrowOop* ref) const {
4316 assert(ref != NULL, "invariant");
4317 assert(UseCompressedOops, "sanity");
4318 assert(!has_partial_array_mask(ref), err_msg("ref=" PTR_FORMAT, ref));
4319 oop p = oopDesc::load_decode_heap_oop(ref);
4320 assert(_g1h->is_in_g1_reserved(p),
4321 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p)));
4322 return true;
4323 }
4324
4325 bool G1ParScanThreadState::verify_ref(oop* ref) const {
4326 assert(ref != NULL, "invariant");
4327 if (has_partial_array_mask(ref)) {
4328 // Must be in the collection set--it's already been copied.
4329 oop p = clear_partial_array_mask(ref);
4330 assert(_g1h->obj_in_cs(p),
4331 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p)));
4332 } else {
4333 oop p = oopDesc::load_decode_heap_oop(ref);
4334 assert(_g1h->is_in_g1_reserved(p),
4335 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p)));
4336 }
4337 return true;
4338 }
4339
4340 bool G1ParScanThreadState::verify_task(StarTask ref) const {
4341 if (ref.is_narrow()) {
4342 return verify_ref((narrowOop*) ref);
4343 } else {
4344 return verify_ref((oop*) ref);
4345 }
4346 }
4347 #endif // ASSERT
4348
4349 void G1ParScanThreadState::trim_queue() {
4350 assert(_evac_cl != NULL, "not set");
4351 assert(_evac_failure_cl != NULL, "not set");
4352 assert(_partial_scan_cl != NULL, "not set");
4353
4354 StarTask ref;
4355 do {
4356 // Drain the overflow stack first, so other threads can steal.
4357 while (refs()->pop_overflow(ref)) {
4358 deal_with_reference(ref);
4359 }
4360
4361 while (refs()->pop_local(ref)) {
4362 deal_with_reference(ref);
4363 }
4364 } while (!refs()->is_empty());
4365 }
4366
4367 G1ParClosureSuper::G1ParClosureSuper(G1CollectedHeap* g1, G1ParScanThreadState* par_scan_state) :
4368 _g1(g1), _g1_rem(_g1->g1_rem_set()), _cm(_g1->concurrent_mark()),
4369 _par_scan_state(par_scan_state),
4370 _during_initial_mark(_g1->g1_policy()->during_initial_mark_pause()),
4371 _mark_in_progress(_g1->mark_in_progress()) { }
4372
4373 template <class T> void G1ParCopyHelper::mark_object(T* p) {
4374 // This is called from do_oop_work for objects that are not
4375 // in the collection set. Objects in the collection set
4376 // are marked after they have been evacuated.
4377
4378 T heap_oop = oopDesc::load_heap_oop(p);
4379 if (!oopDesc::is_null(heap_oop)) {
4380 oop obj = oopDesc::decode_heap_oop(heap_oop);
4381 HeapWord* addr = (HeapWord*)obj;
4382 if (_g1->is_in_g1_reserved(addr)) {
4383 _cm->grayRoot(oop(addr));
4384 }
4385 }
4386 }
4387
4388 oop G1ParCopyHelper::copy_to_survivor_space(oop old, bool should_mark_root,
4389 bool should_mark_copy) {
4390 size_t word_sz = old->size();
4391 HeapRegion* from_region = _g1->heap_region_containing_raw(old);
4392 // +1 to make the -1 indexes valid...
4393 int young_index = from_region->young_index_in_cset()+1;
4394 assert( (from_region->is_young() && young_index > 0) ||
4395 (!from_region->is_young() && young_index == 0), "invariant" );
4396 G1CollectorPolicy* g1p = _g1->g1_policy();
4397 markOop m = old->mark();
4398 int age = m->has_displaced_mark_helper() ? m->displaced_mark_helper()->age()
4399 : m->age();
4400 GCAllocPurpose alloc_purpose = g1p->evacuation_destination(from_region, age,
4401 word_sz);
4402 HeapWord* obj_ptr = _par_scan_state->allocate(alloc_purpose, word_sz);
4403 oop obj = oop(obj_ptr);
4404
4405 if (obj_ptr == NULL) {
4406 // This will either forward-to-self, or detect that someone else has
4407 // installed a forwarding pointer.
4408 OopsInHeapRegionClosure* cl = _par_scan_state->evac_failure_closure();
4409 return _g1->handle_evacuation_failure_par(cl, old, should_mark_root);
4410 }
4411
4412 // We're going to allocate linearly, so might as well prefetch ahead.
4413 Prefetch::write(obj_ptr, PrefetchCopyIntervalInBytes);
4414
4415 oop forward_ptr = old->forward_to_atomic(obj);
4416 if (forward_ptr == NULL) {
4417 Copy::aligned_disjoint_words((HeapWord*) old, obj_ptr, word_sz);
4418 if (g1p->track_object_age(alloc_purpose)) {
4419 // We could simply do obj->incr_age(). However, this causes a
4420 // performance issue. obj->incr_age() will first check whether
4421 // the object has a displaced mark by checking its mark word;
4422 // getting the mark word from the new location of the object
4423 // stalls. So, given that we already have the mark word and we
4424 // are about to install it anyway, it's better to increase the
4425 // age on the mark word, when the object does not have a
4426 // displaced mark word. We're not expecting many objects to have
4427 // a displaced marked word, so that case is not optimized
4428 // further (it could be...) and we simply call obj->incr_age().
4429
4430 if (m->has_displaced_mark_helper()) {
4431 // in this case, we have to install the mark word first,
4432 // otherwise obj looks to be forwarded (the old mark word,
4433 // which contains the forward pointer, was copied)
4434 obj->set_mark(m);
4435 obj->incr_age();
4436 } else {
4437 m = m->incr_age();
4438 obj->set_mark(m);
4439 }
4440 _par_scan_state->age_table()->add(obj, word_sz);
4441 } else {
4442 obj->set_mark(m);
4443 }
4444
4445 // Mark the evacuated object or propagate "next" mark bit
4446 if (should_mark_copy) {
4447 if (!use_local_bitmaps ||
4448 !_par_scan_state->alloc_buffer(alloc_purpose)->mark(obj_ptr)) {
4449 // if we couldn't mark it on the local bitmap (this happens when
4450 // the object was not allocated in the GCLab), we have to bite
4451 // the bullet and do the standard parallel mark
4452 _cm->markAndGrayObjectIfNecessary(obj);
4453 }
4454
4455 if (_g1->isMarkedNext(old)) {
4456 // Unmark the object's old location so that marking
4457 // doesn't think the old object is alive.
4458 _cm->nextMarkBitMap()->parClear((HeapWord*)old);
4459 }
4460 }
4461
4462 size_t* surv_young_words = _par_scan_state->surviving_young_words();
4463 surv_young_words[young_index] += word_sz;
4464
4465 if (obj->is_objArray() && arrayOop(obj)->length() >= ParGCArrayScanChunk) {
4466 arrayOop(old)->set_length(0);
4467 oop* old_p = set_partial_array_mask(old);
4468 _par_scan_state->push_on_queue(old_p);
4469 } else {
4470 // No point in using the slower heap_region_containing() method,
4471 // given that we know obj is in the heap.
4472 _scanner->set_region(_g1->heap_region_containing_raw(obj));
4473 obj->oop_iterate_backwards(_scanner);
4474 }
4475 } else {
4476 _par_scan_state->undo_allocation(alloc_purpose, obj_ptr, word_sz);
4477 obj = forward_ptr;
4478 }
4479 return obj;
4480 }
4481
4482 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object>
4483 template <class T>
4484 void G1ParCopyClosure<do_gen_barrier, barrier, do_mark_object>
4485 ::do_oop_work(T* p) {
4486 oop obj = oopDesc::load_decode_heap_oop(p);
4487 assert(barrier != G1BarrierRS || obj != NULL,
4488 "Precondition: G1BarrierRS implies obj is nonNull");
4489
4490 // Marking:
4491 // If the object is in the collection set, then the thread
4492 // that copies the object should mark, or propagate the
4493 // mark to, the evacuated object.
4494 // If the object is not in the collection set then we
4495 // should call the mark_object() method depending on the
4496 // value of the template parameter do_mark_object (which will
4497 // be true for root scanning closures during an initial mark
4498 // pause).
4499 // The mark_object() method first checks whether the object
4500 // is marked and, if not, attempts to mark the object.
4501
4502 // here the null check is implicit in the cset_fast_test() test
4503 if (_g1->in_cset_fast_test(obj)) {
4504 if (obj->is_forwarded()) {
4505 oopDesc::encode_store_heap_oop(p, obj->forwardee());
4506 // If we are a root scanning closure during an initial
4507 // mark pause (i.e. do_mark_object will be true) then
4508 // we also need to handle marking of roots in the
4509 // event of an evacuation failure. In the event of an
4510 // evacuation failure, the object is forwarded to itself
4511 // and not copied. For root-scanning closures, the
4512 // object would be marked after a successful self-forward
4513 // but an object could be pointed to by both a root and non
4514 // root location and be self-forwarded by a non-root-scanning
4515 // closure. Therefore we also have to attempt to mark the
4516 // self-forwarded root object here.
4517 if (do_mark_object && obj->forwardee() == obj) {
4518 mark_object(p);
4519 }
4520 } else {
4521 // During an initial mark pause, objects that are pointed to
4522 // by the roots need to be marked - even in the event of an
4523 // evacuation failure. We pass the template parameter
4524 // do_mark_object (which is true for root scanning closures
4525 // during an initial mark pause) to copy_to_survivor_space
4526 // which will pass it on to the evacuation failure handling
4527 // code. The thread that successfully self-forwards a root
4528 // object to itself is responsible for marking the object.
4529 bool should_mark_root = do_mark_object;
4530
4531 // We need to mark the copied object if we're a root scanning
4532 // closure during an initial mark pause (i.e. do_mark_object
4533 // will be true), or the object is already marked and we need
4534 // to propagate the mark to the evacuated copy.
4535 bool should_mark_copy = do_mark_object ||
4536 _during_initial_mark ||
4537 (_mark_in_progress && !_g1->is_obj_ill(obj));
4538
4539 oop copy_oop = copy_to_survivor_space(obj, should_mark_root,
4540 should_mark_copy);
4541 oopDesc::encode_store_heap_oop(p, copy_oop);
4542 }
4543 // When scanning the RS, we only care about objs in CS.
4544 if (barrier == G1BarrierRS) {
4545 _par_scan_state->update_rs(_from, p, _par_scan_state->queue_num());
4546 }
4547 } else {
4548 // The object is not in collection set. If we're a root scanning
4549 // closure during an initial mark pause (i.e. do_mark_object will
4550 // be true) then attempt to mark the object.
4551 if (do_mark_object) {
4552 mark_object(p);
4553 }
4554 }
4555
4556 if (barrier == G1BarrierEvac && obj != NULL) {
4557 _par_scan_state->update_rs(_from, p, _par_scan_state->queue_num());
4558 }
4559
4560 if (do_gen_barrier && obj != NULL) {
4561 par_do_barrier(p);
4562 }
4563 }
4564
4565 template void G1ParCopyClosure<false, G1BarrierEvac, false>::do_oop_work(oop* p);
4566 template void G1ParCopyClosure<false, G1BarrierEvac, false>::do_oop_work(narrowOop* p);
4567
4568 template <class T> void G1ParScanPartialArrayClosure::do_oop_nv(T* p) {
4569 assert(has_partial_array_mask(p), "invariant");
4570 oop old = clear_partial_array_mask(p);
4571 assert(old->is_objArray(), "must be obj array");
4572 assert(old->is_forwarded(), "must be forwarded");
4573 assert(Universe::heap()->is_in_reserved(old), "must be in heap.");
4574
4575 objArrayOop obj = objArrayOop(old->forwardee());
4576 assert((void*)old != (void*)old->forwardee(), "self forwarding here?");
4577 // Process ParGCArrayScanChunk elements now
4578 // and push the remainder back onto queue
4579 int start = arrayOop(old)->length();
4580 int end = obj->length();
4581 int remainder = end - start;
4582 assert(start <= end, "just checking");
4583 if (remainder > 2 * ParGCArrayScanChunk) {
4584 // Test above combines last partial chunk with a full chunk
4585 end = start + ParGCArrayScanChunk;
4586 arrayOop(old)->set_length(end);
4587 // Push remainder.
4588 oop* old_p = set_partial_array_mask(old);
4589 assert(arrayOop(old)->length() < obj->length(), "Empty push?");
4590 _par_scan_state->push_on_queue(old_p);
4591 } else {
4592 // Restore length so that the heap remains parsable in
4593 // case of evacuation failure.
4594 arrayOop(old)->set_length(end);
4595 }
4596 _scanner.set_region(_g1->heap_region_containing_raw(obj));
4597 // process our set of indices (include header in first chunk)
4598 obj->oop_iterate_range(&_scanner, start, end);
4599 }
4600
4601 class G1ParEvacuateFollowersClosure : public VoidClosure {
4602 protected:
4603 G1CollectedHeap* _g1h;
4604 G1ParScanThreadState* _par_scan_state;
4605 RefToScanQueueSet* _queues;
4606 ParallelTaskTerminator* _terminator;
4607
4608 G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
4609 RefToScanQueueSet* queues() { return _queues; }
4610 ParallelTaskTerminator* terminator() { return _terminator; }
4611
4612 public:
4613 G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h,
4614 G1ParScanThreadState* par_scan_state,
4615 RefToScanQueueSet* queues,
4616 ParallelTaskTerminator* terminator)
4617 : _g1h(g1h), _par_scan_state(par_scan_state),
4618 _queues(queues), _terminator(terminator) {}
4619
4620 void do_void();
4621
4622 private:
4623 inline bool offer_termination();
4624 };
4625
4626 bool G1ParEvacuateFollowersClosure::offer_termination() {
4627 G1ParScanThreadState* const pss = par_scan_state();
4628 pss->start_term_time();
4629 const bool res = terminator()->offer_termination();
4630 pss->end_term_time();
4631 return res;
4632 }
4633
4634 void G1ParEvacuateFollowersClosure::do_void() {
4635 StarTask stolen_task;
4636 G1ParScanThreadState* const pss = par_scan_state();
4637 pss->trim_queue();
4638
4639 do {
4640 while (queues()->steal(pss->queue_num(), pss->hash_seed(), stolen_task)) {
4641 assert(pss->verify_task(stolen_task), "sanity");
4642 if (stolen_task.is_narrow()) {
4643 pss->deal_with_reference((narrowOop*) stolen_task);
4644 } else {
4645 pss->deal_with_reference((oop*) stolen_task);
4646 }
4647
4648 // We've just processed a reference and we might have made
4649 // available new entries on the queues. So we have to make sure
4650 // we drain the queues as necessary.
4651 pss->trim_queue();
4652 }
4653 } while (!offer_termination());
4654
4655 pss->retire_alloc_buffers();
4656 }
4657
4658 class G1ParTask : public AbstractGangTask {
4659 protected:
4660 G1CollectedHeap* _g1h;
4661 RefToScanQueueSet *_queues;
4662 ParallelTaskTerminator _terminator;
4663 int _n_workers;
4664
4665 Mutex _stats_lock;
4666 Mutex* stats_lock() { return &_stats_lock; }
4667
4668 size_t getNCards() {
4669 return (_g1h->capacity() + G1BlockOffsetSharedArray::N_bytes - 1)
4670 / G1BlockOffsetSharedArray::N_bytes;
4671 }
4672
4673 public:
4674 G1ParTask(G1CollectedHeap* g1h,
4675 RefToScanQueueSet *task_queues)
4676 : AbstractGangTask("G1 collection"),
4677 _g1h(g1h),
4678 _queues(task_queues),
4679 _terminator(0, _queues),
4680 _stats_lock(Mutex::leaf, "parallel G1 stats lock", true)
4681 {}
4682
4683 RefToScanQueueSet* queues() { return _queues; }
4684
4685 RefToScanQueue *work_queue(int i) {
4686 return queues()->queue(i);
4687 }
4688
4689 ParallelTaskTerminator* terminator() { return &_terminator; }
4690
4691 virtual void set_for_termination(int active_workers) {
4692 // This task calls set_n_termination() in par_non_clean_card_iterate_work()
4693 // in the young space (_par_seq_tasks) in the G1 heap
4694 // for SequentialSubTasksDone.
4695 // This task also uses SubTasksDone in SharedHeap and G1CollectedHeap
4696 // both of which need setting by set_n_termination().
4697 _g1h->SharedHeap::set_n_termination(active_workers);
4698 _g1h->set_n_termination(active_workers);
4699 terminator()->reset_for_reuse(active_workers);
4700 _n_workers = active_workers;
4701 }
4702
4703 void work(int i) {
4704 if (i >= _n_workers) return; // no work needed this round
4705
4706 double start_time_ms = os::elapsedTime() * 1000.0;
4707 _g1h->g1_policy()->record_gc_worker_start_time(i, start_time_ms);
4708
4709 ResourceMark rm;
4710 HandleMark hm;
4711
4712 ReferenceProcessor* rp = _g1h->ref_processor_stw();
4713
4714 G1ParScanThreadState pss(_g1h, i);
4715 G1ParScanHeapEvacClosure scan_evac_cl(_g1h, &pss, rp);
4716 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, rp);
4717 G1ParScanPartialArrayClosure partial_scan_cl(_g1h, &pss, rp);
4718
4719 pss.set_evac_closure(&scan_evac_cl);
4720 pss.set_evac_failure_closure(&evac_failure_cl);
4721 pss.set_partial_scan_closure(&partial_scan_cl);
4722
4723 G1ParScanExtRootClosure only_scan_root_cl(_g1h, &pss, rp);
4724 G1ParScanPermClosure only_scan_perm_cl(_g1h, &pss, rp);
4725
4726 G1ParScanAndMarkExtRootClosure scan_mark_root_cl(_g1h, &pss, rp);
4727 G1ParScanAndMarkPermClosure scan_mark_perm_cl(_g1h, &pss, rp);
4728
4729 OopClosure* scan_root_cl = &only_scan_root_cl;
4730 OopsInHeapRegionClosure* scan_perm_cl = &only_scan_perm_cl;
4731
4732 if (_g1h->g1_policy()->during_initial_mark_pause()) {
4733 // We also need to mark copied objects.
4734 scan_root_cl = &scan_mark_root_cl;
4735 scan_perm_cl = &scan_mark_perm_cl;
4736 }
4737
4738 G1ParPushHeapRSClosure push_heap_rs_cl(_g1h, &pss);
4739
4740 pss.start_strong_roots();
4741 _g1h->g1_process_strong_roots(/* not collecting perm */ false,
4742 SharedHeap::SO_AllClasses,
4743 scan_root_cl,
4744 &push_heap_rs_cl,
4745 scan_perm_cl,
4746 i);
4747 pss.end_strong_roots();
4748
4749 {
4750 double start = os::elapsedTime();
4751 G1ParEvacuateFollowersClosure evac(_g1h, &pss, _queues, &_terminator);
4752 evac.do_void();
4753 double elapsed_ms = (os::elapsedTime()-start)*1000.0;
4754 double term_ms = pss.term_time()*1000.0;
4755 _g1h->g1_policy()->record_obj_copy_time(i, elapsed_ms-term_ms);
4756 _g1h->g1_policy()->record_termination(i, term_ms, pss.term_attempts());
4757 }
4758 _g1h->g1_policy()->record_thread_age_table(pss.age_table());
4759 _g1h->update_surviving_young_words(pss.surviving_young_words()+1);
4760
4761 // Clean up any par-expanded rem sets.
4762 HeapRegionRemSet::par_cleanup();
4763
4764 if (ParallelGCVerbose) {
4765 MutexLocker x(stats_lock());
4766 pss.print_termination_stats(i);
4767 }
4768
4769 assert(pss.refs()->is_empty(), "should be empty");
4770 double end_time_ms = os::elapsedTime() * 1000.0;
4771 _g1h->g1_policy()->record_gc_worker_end_time(i, end_time_ms);
4772 }
4773 };
4774
4775 // *** Common G1 Evacuation Stuff
4776
4777 // This method is run in a GC worker.
4778
4779 void
4780 G1CollectedHeap::
4781 g1_process_strong_roots(bool collecting_perm_gen,
4782 SharedHeap::ScanningOption so,
4783 OopClosure* scan_non_heap_roots,
4784 OopsInHeapRegionClosure* scan_rs,
4785 OopsInGenClosure* scan_perm,
4786 int worker_i) {
4787
4788 // First scan the strong roots, including the perm gen.
4789 double ext_roots_start = os::elapsedTime();
4790 double closure_app_time_sec = 0.0;
4791
4792 BufferingOopClosure buf_scan_non_heap_roots(scan_non_heap_roots);
4793 BufferingOopsInGenClosure buf_scan_perm(scan_perm);
4794 buf_scan_perm.set_generation(perm_gen());
4795
4796 // Walk the code cache w/o buffering, because StarTask cannot handle
4797 // unaligned oop locations.
4798 CodeBlobToOopClosure eager_scan_code_roots(scan_non_heap_roots, /*do_marking=*/ true);
4799
4800 process_strong_roots(false, // no scoping; this is parallel code
4801 collecting_perm_gen, so,
4802 &buf_scan_non_heap_roots,
4803 &eager_scan_code_roots,
4804 &buf_scan_perm);
4805
4806 // Now the CM ref_processor roots.
4807 if (!_process_strong_tasks->is_task_claimed(G1H_PS_refProcessor_oops_do)) {
4808 // We need to treat the discovered reference lists of the
4809 // concurrent mark ref processor as roots and keep entries
4810 // (which are added by the marking threads) on them live
4811 // until they can be processed at the end of marking.
4812 ref_processor_cm()->weak_oops_do(&buf_scan_non_heap_roots);
4813 }
4814
4815 // Finish up any enqueued closure apps (attributed as object copy time).
4816 buf_scan_non_heap_roots.done();
4817 buf_scan_perm.done();
4818
4819 double ext_roots_end = os::elapsedTime();
4820
4821 g1_policy()->reset_obj_copy_time(worker_i);
4822 double obj_copy_time_sec = buf_scan_perm.closure_app_seconds() +
4823 buf_scan_non_heap_roots.closure_app_seconds();
4824 g1_policy()->record_obj_copy_time(worker_i, obj_copy_time_sec * 1000.0);
4825
4826 double ext_root_time_ms =
4827 ((ext_roots_end - ext_roots_start) - obj_copy_time_sec) * 1000.0;
4828
4829 g1_policy()->record_ext_root_scan_time(worker_i, ext_root_time_ms);
4830
4831 // Scan strong roots in mark stack.
4832 if (!_process_strong_tasks->is_task_claimed(G1H_PS_mark_stack_oops_do)) {
4833 concurrent_mark()->oops_do(scan_non_heap_roots);
4834 }
4835 double mark_stack_scan_ms = (os::elapsedTime() - ext_roots_end) * 1000.0;
4836 g1_policy()->record_mark_stack_scan_time(worker_i, mark_stack_scan_ms);
4837
4838 // Now scan the complement of the collection set.
4839 if (scan_rs != NULL) {
4840 g1_rem_set()->oops_into_collection_set_do(scan_rs, worker_i);
4841 }
4842
4843 _process_strong_tasks->all_tasks_completed();
4844 }
4845
4846 void
4847 G1CollectedHeap::g1_process_weak_roots(OopClosure* root_closure,
4848 OopClosure* non_root_closure) {
4849 CodeBlobToOopClosure roots_in_blobs(root_closure, /*do_marking=*/ false);
4850 SharedHeap::process_weak_roots(root_closure, &roots_in_blobs, non_root_closure);
4851 }
4852
4853 // Weak Reference Processing support
4854
4855 // An always "is_alive" closure that is used to preserve referents.
4856 // If the object is non-null then it's alive. Used in the preservation
4857 // of referent objects that are pointed to by reference objects
4858 // discovered by the CM ref processor.
4859 class G1AlwaysAliveClosure: public BoolObjectClosure {
4860 G1CollectedHeap* _g1;
4861 public:
4862 G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
4863 void do_object(oop p) { assert(false, "Do not call."); }
4864 bool do_object_b(oop p) {
4865 if (p != NULL) {
4866 return true;
4867 }
4868 return false;
4869 }
4870 };
4871
4872 bool G1STWIsAliveClosure::do_object_b(oop p) {
4873 // An object is reachable if it is outside the collection set,
4874 // or is inside and copied.
4875 return !_g1->obj_in_cs(p) || p->is_forwarded();
4876 }
4877
4878 // Non Copying Keep Alive closure
4879 class G1KeepAliveClosure: public OopClosure {
4880 G1CollectedHeap* _g1;
4881 public:
4882 G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
4883 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
4884 void do_oop( oop* p) {
4885 oop obj = *p;
4886
4887 if (_g1->obj_in_cs(obj)) {
4888 assert( obj->is_forwarded(), "invariant" );
4889 *p = obj->forwardee();
4890 }
4891 }
4892 };
4893
4894 // Copying Keep Alive closure - can be called from both
4895 // serial and parallel code as long as different worker
4896 // threads utilize different G1ParScanThreadState instances
4897 // and different queues.
4898
4899 class G1CopyingKeepAliveClosure: public OopClosure {
4900 G1CollectedHeap* _g1h;
4901 OopClosure* _copy_non_heap_obj_cl;
4902 OopsInHeapRegionClosure* _copy_perm_obj_cl;
4903 G1ParScanThreadState* _par_scan_state;
4904
4905 public:
4906 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
4907 OopClosure* non_heap_obj_cl,
4908 OopsInHeapRegionClosure* perm_obj_cl,
4909 G1ParScanThreadState* pss):
4910 _g1h(g1h),
4911 _copy_non_heap_obj_cl(non_heap_obj_cl),
4912 _copy_perm_obj_cl(perm_obj_cl),
4913 _par_scan_state(pss)
4914 {}
4915
4916 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
4917 virtual void do_oop( oop* p) { do_oop_work(p); }
4918
4919 template <class T> void do_oop_work(T* p) {
4920 oop obj = oopDesc::load_decode_heap_oop(p);
4921
4922 if (_g1h->obj_in_cs(obj)) {
4923 // If the referent object has been forwarded (either copied
4924 // to a new location or to itself in the event of an
4925 // evacuation failure) then we need to update the reference
4926 // field and, if both reference and referent are in the G1
4927 // heap, update the RSet for the referent.
4928 //
4929 // If the referent has not been forwarded then we have to keep
4930 // it alive by policy. Therefore we have copy the referent.
4931 //
4932 // If the reference field is in the G1 heap then we can push
4933 // on the PSS queue. When the queue is drained (after each
4934 // phase of reference processing) the object and it's followers
4935 // will be copied, the reference field set to point to the
4936 // new location, and the RSet updated. Otherwise we need to
4937 // use the the non-heap or perm closures directly to copy
4938 // the refernt object and update the pointer, while avoiding
4939 // updating the RSet.
4940
4941 if (_g1h->is_in_g1_reserved(p)) {
4942 _par_scan_state->push_on_queue(p);
4943 } else {
4944 // The reference field is not in the G1 heap.
4945 if (_g1h->perm_gen()->is_in(p)) {
4946 _copy_perm_obj_cl->do_oop(p);
4947 } else {
4948 _copy_non_heap_obj_cl->do_oop(p);
4949 }
4950 }
4951 }
4952 }
4953 };
4954
4955 // Serial drain queue closure. Called as the 'complete_gc'
4956 // closure for each discovered list in some of the
4957 // reference processing phases.
4958
4959 class G1STWDrainQueueClosure: public VoidClosure {
4960 protected:
4961 G1CollectedHeap* _g1h;
4962 G1ParScanThreadState* _par_scan_state;
4963
4964 G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
4965
4966 public:
4967 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
4968 _g1h(g1h),
4969 _par_scan_state(pss)
4970 { }
4971
4972 void do_void() {
4973 G1ParScanThreadState* const pss = par_scan_state();
4974 pss->trim_queue();
4975 }
4976 };
4977
4978 // Parallel Reference Processing closures
4979
4980 // Implementation of AbstractRefProcTaskExecutor for parallel reference
4981 // processing during G1 evacuation pauses.
4982
4983 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
4984 private:
4985 G1CollectedHeap* _g1h;
4986 RefToScanQueueSet* _queues;
4987 FlexibleWorkGang* _workers;
4988 int _active_workers;
4989
4990 public:
4991 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
4992 FlexibleWorkGang* workers,
4993 RefToScanQueueSet *task_queues,
4994 int n_workers) :
4995 _g1h(g1h),
4996 _queues(task_queues),
4997 _workers(workers),
4998 _active_workers(n_workers)
4999 {
5000 assert(n_workers > 0, "shouldn't call this otherwise");
5001 }
5002
5003 // Executes the given task using concurrent marking worker threads.
5004 virtual void execute(ProcessTask& task);
5005 virtual void execute(EnqueueTask& task);
5006 };
5007
5008 // Gang task for possibly parallel reference processing
5009
5010 class G1STWRefProcTaskProxy: public AbstractGangTask {
5011 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
5012 ProcessTask& _proc_task;
5013 G1CollectedHeap* _g1h;
5014 RefToScanQueueSet *_task_queues;
5015 ParallelTaskTerminator* _terminator;
5016
5017 public:
5018 G1STWRefProcTaskProxy(ProcessTask& proc_task,
5019 G1CollectedHeap* g1h,
5020 RefToScanQueueSet *task_queues,
5021 ParallelTaskTerminator* terminator) :
5022 AbstractGangTask("Process reference objects in parallel"),
5023 _proc_task(proc_task),
5024 _g1h(g1h),
5025 _task_queues(task_queues),
5026 _terminator(terminator)
5027 {}
5028
5029 virtual void work(int i) {
5030 // The reference processing task executed by a single worker.
5031 ResourceMark rm;
5032 HandleMark hm;
5033
5034 G1STWIsAliveClosure is_alive(_g1h);
5035
5036 G1ParScanThreadState pss(_g1h, i);
5037
5038 G1ParScanHeapEvacClosure scan_evac_cl(_g1h, &pss, NULL);
5039 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5040 G1ParScanPartialArrayClosure partial_scan_cl(_g1h, &pss, NULL);
5041
5042 pss.set_evac_closure(&scan_evac_cl);
5043 pss.set_evac_failure_closure(&evac_failure_cl);
5044 pss.set_partial_scan_closure(&partial_scan_cl);
5045
5046 G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL);
5047 G1ParScanPermClosure only_copy_perm_cl(_g1h, &pss, NULL);
5048
5049 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5050 G1ParScanAndMarkPermClosure copy_mark_perm_cl(_g1h, &pss, NULL);
5051
5052 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5053 OopsInHeapRegionClosure* copy_perm_cl = &only_copy_perm_cl;
5054
5055 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5056 // We also need to mark copied objects.
5057 copy_non_heap_cl = ©_mark_non_heap_cl;
5058 copy_perm_cl = ©_mark_perm_cl;
5059 }
5060
5061 // Keep alive closure.
5062 G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, copy_perm_cl, &pss);
5063
5064 // Complete GC closure
5065 G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _task_queues, _terminator);
5066
5067 // Call the reference processing task's work routine.
5068 _proc_task.work(i, is_alive, keep_alive, drain_queue);
5069
5070 // Note we cannot assert that the refs array is empty here as not all
5071 // of the processing tasks (specifically phase2 - pp2_work) execute
5072 // the complete_gc closure (which ordinarily would drain the queue) so
5073 // the queue may not be empty.
5074 }
5075 };
5076
5077 // Driver routine for parallel reference processing.
5078 // Creates an instance of the ref processing gang
5079 // task and has the worker threads execute it.
5080 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) {
5081 assert(_workers != NULL, "Need parallel worker threads.");
5082
5083 ParallelTaskTerminator terminator(_active_workers, _queues);
5084 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _queues, &terminator);
5085
5086 _g1h->set_par_threads(_active_workers);
5087 _workers->run_task(&proc_task_proxy);
5088 _g1h->set_par_threads(0);
5089 }
5090
5091 // Gang task for parallel reference enqueueing.
5092
5093 class G1STWRefEnqueueTaskProxy: public AbstractGangTask {
5094 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
5095 EnqueueTask& _enq_task;
5096
5097 public:
5098 G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) :
5099 AbstractGangTask("Enqueue reference objects in parallel"),
5100 _enq_task(enq_task)
5101 { }
5102
5103 virtual void work(int i) {
5104 _enq_task.work(i);
5105 }
5106 };
5107
5108 // Driver routine for parallel reference enqueing.
5109 // Creates an instance of the ref enqueueing gang
5110 // task and has the worker threads execute it.
5111
5112 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
5113 assert(_workers != NULL, "Need parallel worker threads.");
5114
5115 G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task);
5116
5117 _g1h->set_par_threads(_active_workers);
5118 _workers->run_task(&enq_task_proxy);
5119 _g1h->set_par_threads(0);
5120 }
5121
5122 // End of weak reference support closures
5123
5124 // Abstract task used to preserve (i.e. copy) any referent objects
5125 // that are in the collection set and are pointed to by reference
5126 // objects discovered by the CM ref processor.
5127
5128 class G1ParPreserveCMReferentsTask: public AbstractGangTask {
5129 protected:
5130 G1CollectedHeap* _g1h;
5131 RefToScanQueueSet *_queues;
5132 ParallelTaskTerminator _terminator;
5133 int _n_workers;
5134
5135 public:
5136 G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h,int workers, RefToScanQueueSet *task_queues) :
5137 AbstractGangTask("ParPreserveCMReferents"),
5138 _g1h(g1h),
5139 _queues(task_queues),
5140 _terminator(workers, _queues),
5141 _n_workers(workers)
5142 { }
5143
5144 void work(int i) {
5145 ResourceMark rm;
5146 HandleMark hm;
5147
5148 G1ParScanThreadState pss(_g1h, i);
5149 G1ParScanHeapEvacClosure scan_evac_cl(_g1h, &pss, NULL);
5150 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5151 G1ParScanPartialArrayClosure partial_scan_cl(_g1h, &pss, NULL);
5152
5153 pss.set_evac_closure(&scan_evac_cl);
5154 pss.set_evac_failure_closure(&evac_failure_cl);
5155 pss.set_partial_scan_closure(&partial_scan_cl);
5156
5157 assert(pss.refs()->is_empty(), "both queue and overflow should be empty");
5158
5159
5160 G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL);
5161 G1ParScanPermClosure only_copy_perm_cl(_g1h, &pss, NULL);
5162
5163 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5164 G1ParScanAndMarkPermClosure copy_mark_perm_cl(_g1h, &pss, NULL);
5165
5166 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5167 OopsInHeapRegionClosure* copy_perm_cl = &only_copy_perm_cl;
5168
5169 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5170 // We also need to mark copied objects.
5171 copy_non_heap_cl = ©_mark_non_heap_cl;
5172 copy_perm_cl = ©_mark_perm_cl;
5173 }
5174
5175 // Is alive closure
5176 G1AlwaysAliveClosure always_alive(_g1h);
5177
5178 // Copying keep alive closure. Applied to referent objects that need
5179 // to be copied.
5180 G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, copy_perm_cl, &pss);
5181
5182 ReferenceProcessor* rp = _g1h->ref_processor_cm();
5183
5184 int limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q();
5185 int stride = MIN2(MAX2(_n_workers, 1), limit);
5186
5187 // limit is set using max_num_q() - which was set using ParallelGCThreads.
5188 // So this must be true - but assert just in case someone decides to
5189 // change the worker ids.
5190 assert(0 <= i && i < limit, "sanity");
5191 assert(!rp->discovery_is_atomic(), "check this code");
5192
5193 // Select discovered lists [i, i+stride, i+2*stride,...,limit)
5194 for (int idx = i; idx < limit; idx += stride) {
5195 DiscoveredList& ref_list = rp->discovered_refs()[idx];
5196
5197 DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive);
5198 while (iter.has_next()) {
5199 // Since discovery is not atomic for the CM ref processor, we
5200 // can see some null referent objects.
5201 iter.load_ptrs(DEBUG_ONLY(true));
5202 oop ref = iter.obj();
5203
5204 // This will filter nulls.
5205 if (iter.is_referent_alive()) {
5206 iter.make_referent_alive();
5207 }
5208 iter.move_to_next();
5209 }
5210 }
5211
5212 // Drain the queue - which may cause stealing
5213 G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _queues, &_terminator);
5214 drain_queue.do_void();
5215 // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure
5216 assert(pss.refs()->is_empty(), "should be");
5217 }
5218 };
5219
5220 // Weak Reference processing during an evacuation pause (part 1).
5221 void G1CollectedHeap::process_discovered_references() {
5222 double ref_proc_start = os::elapsedTime();
5223
5224 ReferenceProcessor* rp = _ref_processor_stw;
5225 assert(rp->discovery_enabled(), "should have been enabled");
5226
5227 // Any reference objects, in the collection set, that were 'discovered'
5228 // by the CM ref processor should have already been copied (either by
5229 // applying the external root copy closure to the discovered lists, or
5230 // by following an RSet entry).
5231 //
5232 // But some of the referents, that are in the collection set, that these
5233 // reference objects point to may not have been copied: the STW ref
5234 // processor would have seen that the reference object had already
5235 // been 'discovered' and would have skipped discovering the reference,
5236 // but would not have treated the reference object as a regular oop.
5237 // As a reult the copy closure would not have been applied to the
5238 // referent object.
5239 //
5240 // We need to explicitly copy these referent objects - the references
5241 // will be processed at the end of remarking.
5242 //
5243 // We also need to do this copying before we process the reference
5244 // objects discovered by the STW ref processor in case one of these
5245 // referents points to another object which is also referenced by an
5246 // object discovered by the STW ref processor.
5247
5248 int active_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
5249 workers()->active_workers() : 1);
5250
5251 assert(active_workers == workers()->active_workers(),
5252 "Need to reset active_workers");
5253 set_par_threads(active_workers);
5254 G1ParPreserveCMReferentsTask keep_cm_referents(this, active_workers, _task_queues);
5255
5256 if (G1CollectedHeap::use_parallel_gc_threads()) {
5257 workers()->run_task(&keep_cm_referents);
5258 } else {
5259 keep_cm_referents.work(0);
5260 }
5261
5262 set_par_threads(0);
5263
5264 // Closure to test whether a referent is alive.
5265 G1STWIsAliveClosure is_alive(this);
5266
5267 // Even when parallel reference processing is enabled, the processing
5268 // of JNI refs is serial and performed serially by the current thread
5269 // rather than by a worker. The following PSS will be used for processing
5270 // JNI refs.
5271
5272 // Use only a single queue for this PSS.
5273 G1ParScanThreadState pss(this, 0);
5274
5275 // We do not embed a reference processor in the copying/scanning
5276 // closures while we're actually processing the discovered
5277 // reference objects.
5278 G1ParScanHeapEvacClosure scan_evac_cl(this, &pss, NULL);
5279 G1ParScanHeapEvacFailureClosure evac_failure_cl(this, &pss, NULL);
5280 G1ParScanPartialArrayClosure partial_scan_cl(this, &pss, NULL);
5281
5282 pss.set_evac_closure(&scan_evac_cl);
5283 pss.set_evac_failure_closure(&evac_failure_cl);
5284 pss.set_partial_scan_closure(&partial_scan_cl);
5285
5286 assert(pss.refs()->is_empty(), "pre-condition");
5287
5288 G1ParScanExtRootClosure only_copy_non_heap_cl(this, &pss, NULL);
5289 G1ParScanPermClosure only_copy_perm_cl(this, &pss, NULL);
5290
5291 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(this, &pss, NULL);
5292 G1ParScanAndMarkPermClosure copy_mark_perm_cl(this, &pss, NULL);
5293
5294 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5295 OopsInHeapRegionClosure* copy_perm_cl = &only_copy_perm_cl;
5296
5297 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5298 // We also need to mark copied objects.
5299 copy_non_heap_cl = ©_mark_non_heap_cl;
5300 copy_perm_cl = ©_mark_perm_cl;
5301 }
5302
5303 // Keep alive closure.
5304 G1CopyingKeepAliveClosure keep_alive(this, copy_non_heap_cl, copy_perm_cl, &pss);
5305
5306 // Serial Complete GC closure
5307 G1STWDrainQueueClosure drain_queue(this, &pss);
5308
5309 // Setup the soft refs policy...
5310 rp->setup_policy(false);
5311
5312 if (!rp->processing_is_mt()) {
5313 // Serial reference processing...
5314 rp->process_discovered_references(&is_alive,
5315 &keep_alive,
5316 &drain_queue,
5317 NULL);
5318 } else {
5319 // Parallel reference processing
5320 assert(rp->num_q() == active_workers, "sanity");
5321 assert(active_workers <= rp->max_num_q(), "sanity");
5322
5323 G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, active_workers);
5324 rp->process_discovered_references(&is_alive, &keep_alive, &drain_queue, &par_task_executor);
5325 }
5326
5327 // We have completed copying any necessary live referent objects
5328 // (that were not copied during the actual pause) so we can
5329 // retire any active alloc buffers
5330 pss.retire_alloc_buffers();
5331 assert(pss.refs()->is_empty(), "both queue and overflow should be empty");
5332
5333 double ref_proc_time = os::elapsedTime() - ref_proc_start;
5334 g1_policy()->record_ref_proc_time(ref_proc_time * 1000.0);
5335 }
5336
5337 // Weak Reference processing during an evacuation pause (part 2).
5338 void G1CollectedHeap::enqueue_discovered_references() {
5339 double ref_enq_start = os::elapsedTime();
5340
5341 ReferenceProcessor* rp = _ref_processor_stw;
5342 assert(!rp->discovery_enabled(), "should have been disabled as part of processing");
5343
5344 // Now enqueue any remaining on the discovered lists on to
5345 // the pending list.
5346 if (!rp->processing_is_mt()) {
5347 // Serial reference processing...
5348 rp->enqueue_discovered_references();
5349 } else {
5350 // Parallel reference enqueuing
5351
5352 int active_workers = (ParallelGCThreads > 0 ? workers()->active_workers() : 1);
5353 assert(active_workers == workers()->active_workers(),
5354 "Need to reset active_workers");
5355 assert(rp->num_q() == active_workers, "sanity");
5356 assert(active_workers <= rp->max_num_q(), "sanity");
5357
5358 G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, active_workers);
5359 rp->enqueue_discovered_references(&par_task_executor);
5360 }
5361
5362 rp->verify_no_references_recorded();
5363 assert(!rp->discovery_enabled(), "should have been disabled");
5364
5365 // FIXME
5366 // CM's reference processing also cleans up the string and symbol tables.
5367 // Should we do that here also? We could, but it is a serial operation
5368 // and could signicantly increase the pause time.
5369
5370 double ref_enq_time = os::elapsedTime() - ref_enq_start;
5371 g1_policy()->record_ref_enq_time(ref_enq_time * 1000.0);
5372 }
5373
5374 void G1CollectedHeap::evacuate_collection_set() {
5375 set_evacuation_failed(false);
5376
5377 g1_rem_set()->prepare_for_oops_into_collection_set_do();
5378 concurrent_g1_refine()->set_use_cache(false);
5379 concurrent_g1_refine()->clear_hot_cache_claimed_index();
5380
5381 int n_workers;
5382 if (G1CollectedHeap::use_parallel_gc_threads()) {
5383 n_workers =
5384 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
5385 workers()->active_workers(),
5386 Threads::number_of_non_daemon_threads());
5387 assert(UseDynamicNumberOfGCThreads ||
5388 n_workers == workers()->total_workers(),
5389 "If not dynamic should be using all the workers");
5390 set_par_threads(n_workers);
5391 } else {
5392 assert(n_par_threads() == 0,
5393 "Should be the original non-parallel value");
5394 n_workers = 1;
5395 }
5396 workers()->set_active_workers(n_workers);
5397
5398 G1ParTask g1_par_task(this, _task_queues);
5399
5400 init_for_evac_failure(NULL);
5401
5402 rem_set()->prepare_for_younger_refs_iterate(true);
5403
5404 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
5405 double start_par = os::elapsedTime();
5406
5407 if (G1CollectedHeap::use_parallel_gc_threads()) {
5408 // The individual threads will set their evac-failure closures.
5409 StrongRootsScope srs(this);
5410 if (ParallelGCVerbose) G1ParScanThreadState::print_termination_stats_hdr();
5411 // These tasks use ShareHeap::_process_strong_tasks
5412 assert(UseDynamicNumberOfGCThreads ||
5413 workers()->active_workers() == workers()->total_workers(),
5414 "If not dynamic should be using all the workers");
5415 workers()->run_task(&g1_par_task);
5416 } else {
5417 StrongRootsScope srs(this);
5418 g1_par_task.work(0);
5419 }
5420
5421 double par_time = (os::elapsedTime() - start_par) * 1000.0;
5422 g1_policy()->record_par_time(par_time);
5423
5424 set_par_threads(0);
5425
5426 // Process any discovered reference objects - we have
5427 // to do this _before_ we retire the GC alloc regions
5428 // as we may have to copy some 'reachable' referent
5429 // objects (and their reachable sub-graphs) that were
5430 // not copied during the pause.
5431 process_discovered_references();
5432
5433 // Weak root processing.
5434 // Note: when JSR 292 is enabled and code blobs can contain
5435 // non-perm oops then we will need to process the code blobs
5436 // here too.
5437 {
5438 G1STWIsAliveClosure is_alive(this);
5439 G1KeepAliveClosure keep_alive(this);
5440 JNIHandles::weak_oops_do(&is_alive, &keep_alive);
5441 }
5442
5443 release_gc_alloc_regions();
5444 g1_rem_set()->cleanup_after_oops_into_collection_set_do();
5445
5446 concurrent_g1_refine()->clear_hot_cache();
5447 concurrent_g1_refine()->set_use_cache(true);
5448
5449 finalize_for_evac_failure();
5450
5451 // Must do this before clearing the per-region evac-failure flags
5452 // (which is currently done when we free the collection set).
5453 // We also only do this if marking is actually in progress and so
5454 // have to do this before we set the mark_in_progress flag at the
5455 // end of an initial mark pause.
5456 concurrent_mark()->complete_marking_in_collection_set();
5457
5458 if (evacuation_failed()) {
5459 remove_self_forwarding_pointers();
5460 if (PrintGCDetails) {
5461 gclog_or_tty->print(" (to-space overflow)");
5462 } else if (PrintGC) {
5463 gclog_or_tty->print("--");
5464 }
5465 }
5466
5467 // Enqueue any remaining references remaining on the STW
5468 // reference processor's discovered lists. We need to do
5469 // this after the card table is cleaned (and verified) as
5470 // the act of enqueuing entries on to the pending list
5471 // will log these updates (and dirty their associated
5472 // cards). We need these updates logged to update any
5473 // RSets.
5474 enqueue_discovered_references();
5475
5476 if (G1DeferredRSUpdate) {
5477 RedirtyLoggedCardTableEntryFastClosure redirty;
5478 dirty_card_queue_set().set_closure(&redirty);
5479 dirty_card_queue_set().apply_closure_to_all_completed_buffers();
5480
5481 DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set();
5482 dcq.merge_bufferlists(&dirty_card_queue_set());
5483 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
5484 }
5485 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
5486 }
5487
5488 void G1CollectedHeap::free_region_if_empty(HeapRegion* hr,
5489 size_t* pre_used,
5490 FreeRegionList* free_list,
5491 OldRegionSet* old_proxy_set,
5492 HumongousRegionSet* humongous_proxy_set,
5493 HRRSCleanupTask* hrrs_cleanup_task,
5494 bool par) {
5495 if (hr->used() > 0 && hr->max_live_bytes() == 0 && !hr->is_young()) {
5496 if (hr->isHumongous()) {
5497 assert(hr->startsHumongous(), "we should only see starts humongous");
5498 free_humongous_region(hr, pre_used, free_list, humongous_proxy_set, par);
5499 } else {
5500 _old_set.remove_with_proxy(hr, old_proxy_set);
5501 free_region(hr, pre_used, free_list, par);
5502 }
5503 } else {
5504 hr->rem_set()->do_cleanup_work(hrrs_cleanup_task);
5505 }
5506 }
5507
5508 void G1CollectedHeap::free_region(HeapRegion* hr,
5509 size_t* pre_used,
5510 FreeRegionList* free_list,
5511 bool par) {
5512 assert(!hr->isHumongous(), "this is only for non-humongous regions");
5513 assert(!hr->is_empty(), "the region should not be empty");
5514 assert(free_list != NULL, "pre-condition");
5515
5516 *pre_used += hr->used();
5517 hr->hr_clear(par, true /* clear_space */);
5518 free_list->add_as_head(hr);
5519 }
5520
5521 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
5522 size_t* pre_used,
5523 FreeRegionList* free_list,
5524 HumongousRegionSet* humongous_proxy_set,
5525 bool par) {
5526 assert(hr->startsHumongous(), "this is only for starts humongous regions");
5527 assert(free_list != NULL, "pre-condition");
5528 assert(humongous_proxy_set != NULL, "pre-condition");
5529
5530 size_t hr_used = hr->used();
5531 size_t hr_capacity = hr->capacity();
5532 size_t hr_pre_used = 0;
5533 _humongous_set.remove_with_proxy(hr, humongous_proxy_set);
5534 hr->set_notHumongous();
5535 free_region(hr, &hr_pre_used, free_list, par);
5536
5537 size_t i = hr->hrs_index() + 1;
5538 size_t num = 1;
5539 while (i < n_regions()) {
5540 HeapRegion* curr_hr = region_at(i);
5541 if (!curr_hr->continuesHumongous()) {
5542 break;
5543 }
5544 curr_hr->set_notHumongous();
5545 free_region(curr_hr, &hr_pre_used, free_list, par);
5546 num += 1;
5547 i += 1;
5548 }
5549 assert(hr_pre_used == hr_used,
5550 err_msg("hr_pre_used: "SIZE_FORMAT" and hr_used: "SIZE_FORMAT" "
5551 "should be the same", hr_pre_used, hr_used));
5552 *pre_used += hr_pre_used;
5553 }
5554
5555 void G1CollectedHeap::update_sets_after_freeing_regions(size_t pre_used,
5556 FreeRegionList* free_list,
5557 OldRegionSet* old_proxy_set,
5558 HumongousRegionSet* humongous_proxy_set,
5559 bool par) {
5560 if (pre_used > 0) {
5561 Mutex* lock = (par) ? ParGCRareEvent_lock : NULL;
5562 MutexLockerEx x(lock, Mutex::_no_safepoint_check_flag);
5563 assert(_summary_bytes_used >= pre_used,
5564 err_msg("invariant: _summary_bytes_used: "SIZE_FORMAT" "
5565 "should be >= pre_used: "SIZE_FORMAT,
5566 _summary_bytes_used, pre_used));
5567 _summary_bytes_used -= pre_used;
5568 }
5569 if (free_list != NULL && !free_list->is_empty()) {
5570 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
5571 _free_list.add_as_head(free_list);
5572 }
5573 if (old_proxy_set != NULL && !old_proxy_set->is_empty()) {
5574 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
5575 _old_set.update_from_proxy(old_proxy_set);
5576 }
5577 if (humongous_proxy_set != NULL && !humongous_proxy_set->is_empty()) {
5578 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
5579 _humongous_set.update_from_proxy(humongous_proxy_set);
5580 }
5581 }
5582
5583 class G1ParCleanupCTTask : public AbstractGangTask {
5584 CardTableModRefBS* _ct_bs;
5585 G1CollectedHeap* _g1h;
5586 HeapRegion* volatile _su_head;
5587 public:
5588 G1ParCleanupCTTask(CardTableModRefBS* ct_bs,
5589 G1CollectedHeap* g1h) :
5590 AbstractGangTask("G1 Par Cleanup CT Task"),
5591 _ct_bs(ct_bs), _g1h(g1h) { }
5592
5593 void work(int i) {
5594 HeapRegion* r;
5595 while (r = _g1h->pop_dirty_cards_region()) {
5596 clear_cards(r);
5597 }
5598 }
5599
5600 void clear_cards(HeapRegion* r) {
5601 // Cards of the survivors should have already been dirtied.
5602 if (!r->is_survivor()) {
5603 _ct_bs->clear(MemRegion(r->bottom(), r->end()));
5604 }
5605 }
5606 };
5607
5608 #ifndef PRODUCT
5609 class G1VerifyCardTableCleanup: public HeapRegionClosure {
5610 G1CollectedHeap* _g1h;
5611 CardTableModRefBS* _ct_bs;
5612 public:
5613 G1VerifyCardTableCleanup(G1CollectedHeap* g1h, CardTableModRefBS* ct_bs)
5614 : _g1h(g1h), _ct_bs(ct_bs) { }
5615 virtual bool doHeapRegion(HeapRegion* r) {
5616 if (r->is_survivor()) {
5617 _g1h->verify_dirty_region(r);
5618 } else {
5619 _g1h->verify_not_dirty_region(r);
5620 }
5621 return false;
5622 }
5623 };
5624
5625 void G1CollectedHeap::verify_not_dirty_region(HeapRegion* hr) {
5626 // All of the region should be clean.
5627 CardTableModRefBS* ct_bs = (CardTableModRefBS*)barrier_set();
5628 MemRegion mr(hr->bottom(), hr->end());
5629 ct_bs->verify_not_dirty_region(mr);
5630 }
5631
5632 void G1CollectedHeap::verify_dirty_region(HeapRegion* hr) {
5633 // We cannot guarantee that [bottom(),end()] is dirty. Threads
5634 // dirty allocated blocks as they allocate them. The thread that
5635 // retires each region and replaces it with a new one will do a
5636 // maximal allocation to fill in [pre_dummy_top(),end()] but will
5637 // not dirty that area (one less thing to have to do while holding
5638 // a lock). So we can only verify that [bottom(),pre_dummy_top()]
5639 // is dirty.
5640 CardTableModRefBS* ct_bs = (CardTableModRefBS*) barrier_set();
5641 MemRegion mr(hr->bottom(), hr->pre_dummy_top());
5642 ct_bs->verify_dirty_region(mr);
5643 }
5644
5645 void G1CollectedHeap::verify_dirty_young_list(HeapRegion* head) {
5646 CardTableModRefBS* ct_bs = (CardTableModRefBS*) barrier_set();
5647 for (HeapRegion* hr = head; hr != NULL; hr = hr->get_next_young_region()) {
5648 verify_dirty_region(hr);
5649 }
5650 }
5651
5652 void G1CollectedHeap::verify_dirty_young_regions() {
5653 verify_dirty_young_list(_young_list->first_region());
5654 verify_dirty_young_list(_young_list->first_survivor_region());
5655 }
5656 #endif
5657
5658 void G1CollectedHeap::cleanUpCardTable() {
5659 CardTableModRefBS* ct_bs = (CardTableModRefBS*) (barrier_set());
5660 double start = os::elapsedTime();
5661
5662 {
5663 // Iterate over the dirty cards region list.
5664 G1ParCleanupCTTask cleanup_task(ct_bs, this);
5665
5666 if (ParallelGCThreads > 0) {
5667 set_par_threads(workers()->total_workers());
5668 workers()->run_task(&cleanup_task);
5669 set_par_threads(0);
5670 } else {
5671 while (_dirty_cards_region_list) {
5672 HeapRegion* r = _dirty_cards_region_list;
5673 cleanup_task.clear_cards(r);
5674 _dirty_cards_region_list = r->get_next_dirty_cards_region();
5675 if (_dirty_cards_region_list == r) {
5676 // The last region.
5677 _dirty_cards_region_list = NULL;
5678 }
5679 r->set_next_dirty_cards_region(NULL);
5680 }
5681 }
5682 #ifndef PRODUCT
5683 if (G1VerifyCTCleanup || VerifyAfterGC) {
5684 G1VerifyCardTableCleanup cleanup_verifier(this, ct_bs);
5685 heap_region_iterate(&cleanup_verifier);
5686 }
5687 #endif
5688 }
5689
5690 double elapsed = os::elapsedTime() - start;
5691 g1_policy()->record_clear_ct_time(elapsed * 1000.0);
5692 }
5693
5694 void G1CollectedHeap::free_collection_set(HeapRegion* cs_head) {
5695 size_t pre_used = 0;
5696 FreeRegionList local_free_list("Local List for CSet Freeing");
5697
5698 double young_time_ms = 0.0;
5699 double non_young_time_ms = 0.0;
5700
5701 // Since the collection set is a superset of the the young list,
5702 // all we need to do to clear the young list is clear its
5703 // head and length, and unlink any young regions in the code below
5704 _young_list->clear();
5705
5706 G1CollectorPolicy* policy = g1_policy();
5707
5708 double start_sec = os::elapsedTime();
5709 bool non_young = true;
5710
5711 HeapRegion* cur = cs_head;
5712 int age_bound = -1;
5713 size_t rs_lengths = 0;
5714
5715 while (cur != NULL) {
5716 assert(!is_on_master_free_list(cur), "sanity");
5717 if (non_young) {
5718 if (cur->is_young()) {
5719 double end_sec = os::elapsedTime();
5720 double elapsed_ms = (end_sec - start_sec) * 1000.0;
5721 non_young_time_ms += elapsed_ms;
5722
5723 start_sec = os::elapsedTime();
5724 non_young = false;
5725 }
5726 } else {
5727 if (!cur->is_young()) {
5728 double end_sec = os::elapsedTime();
5729 double elapsed_ms = (end_sec - start_sec) * 1000.0;
5730 young_time_ms += elapsed_ms;
5731
5732 start_sec = os::elapsedTime();
5733 non_young = true;
5734 }
5735 }
5736
5737 rs_lengths += cur->rem_set()->occupied();
5738
5739 HeapRegion* next = cur->next_in_collection_set();
5740 assert(cur->in_collection_set(), "bad CS");
5741 cur->set_next_in_collection_set(NULL);
5742 cur->set_in_collection_set(false);
5743
5744 if (cur->is_young()) {
5745 int index = cur->young_index_in_cset();
5746 assert(index != -1, "invariant");
5747 assert((size_t) index < policy->young_cset_region_length(), "invariant");
5748 size_t words_survived = _surviving_young_words[index];
5749 cur->record_surv_words_in_group(words_survived);
5750
5751 // At this point the we have 'popped' cur from the collection set
5752 // (linked via next_in_collection_set()) but it is still in the
5753 // young list (linked via next_young_region()). Clear the
5754 // _next_young_region field.
5755 cur->set_next_young_region(NULL);
5756 } else {
5757 int index = cur->young_index_in_cset();
5758 assert(index == -1, "invariant");
5759 }
5760
5761 assert( (cur->is_young() && cur->young_index_in_cset() > -1) ||
5762 (!cur->is_young() && cur->young_index_in_cset() == -1),
5763 "invariant" );
5764
5765 if (!cur->evacuation_failed()) {
5766 MemRegion used_mr = cur->used_region();
5767
5768 // And the region is empty.
5769 assert(!used_mr.is_empty(), "Should not have empty regions in a CS.");
5770
5771 // If marking is in progress then clear any objects marked in
5772 // the current region. Note mark_in_progress() returns false,
5773 // even during an initial mark pause, until the set_marking_started()
5774 // call which takes place later in the pause.
5775 if (mark_in_progress()) {
5776 assert(!g1_policy()->during_initial_mark_pause(), "sanity");
5777 _cm->nextMarkBitMap()->clearRange(used_mr);
5778 }
5779
5780 free_region(cur, &pre_used, &local_free_list, false /* par */);
5781 } else {
5782 cur->uninstall_surv_rate_group();
5783 if (cur->is_young()) {
5784 cur->set_young_index_in_cset(-1);
5785 }
5786 cur->set_not_young();
5787 cur->set_evacuation_failed(false);
5788 // The region is now considered to be old.
5789 _old_set.add(cur);
5790 }
5791 cur = next;
5792 }
5793
5794 policy->record_max_rs_lengths(rs_lengths);
5795 policy->cset_regions_freed();
5796
5797 double end_sec = os::elapsedTime();
5798 double elapsed_ms = (end_sec - start_sec) * 1000.0;
5799
5800 if (non_young) {
5801 non_young_time_ms += elapsed_ms;
5802 } else {
5803 young_time_ms += elapsed_ms;
5804 }
5805
5806 update_sets_after_freeing_regions(pre_used, &local_free_list,
5807 NULL /* old_proxy_set */,
5808 NULL /* humongous_proxy_set */,
5809 false /* par */);
5810 policy->record_young_free_cset_time_ms(young_time_ms);
5811 policy->record_non_young_free_cset_time_ms(non_young_time_ms);
5812 }
5813
5814 // This routine is similar to the above but does not record
5815 // any policy statistics or update free lists; we are abandoning
5816 // the current incremental collection set in preparation of a
5817 // full collection. After the full GC we will start to build up
5818 // the incremental collection set again.
5819 // This is only called when we're doing a full collection
5820 // and is immediately followed by the tearing down of the young list.
5821
5822 void G1CollectedHeap::abandon_collection_set(HeapRegion* cs_head) {
5823 HeapRegion* cur = cs_head;
5824
5825 while (cur != NULL) {
5826 HeapRegion* next = cur->next_in_collection_set();
5827 assert(cur->in_collection_set(), "bad CS");
5828 cur->set_next_in_collection_set(NULL);
5829 cur->set_in_collection_set(false);
5830 cur->set_young_index_in_cset(-1);
5831 cur = next;
5832 }
5833 }
5834
5835 void G1CollectedHeap::set_free_regions_coming() {
5836 if (G1ConcRegionFreeingVerbose) {
5837 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
5838 "setting free regions coming");
5839 }
5840
5841 assert(!free_regions_coming(), "pre-condition");
5842 _free_regions_coming = true;
5843 }
5844
5845 void G1CollectedHeap::reset_free_regions_coming() {
5846 {
5847 assert(free_regions_coming(), "pre-condition");
5848 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
5849 _free_regions_coming = false;
5850 SecondaryFreeList_lock->notify_all();
5851 }
5852
5853 if (G1ConcRegionFreeingVerbose) {
5854 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
5855 "reset free regions coming");
5856 }
5857 }
5858
5859 void G1CollectedHeap::wait_while_free_regions_coming() {
5860 // Most of the time we won't have to wait, so let's do a quick test
5861 // first before we take the lock.
5862 if (!free_regions_coming()) {
5863 return;
5864 }
5865
5866 if (G1ConcRegionFreeingVerbose) {
5867 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
5868 "waiting for free regions");
5869 }
5870
5871 {
5872 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
5873 while (free_regions_coming()) {
5874 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
5875 }
5876 }
5877
5878 if (G1ConcRegionFreeingVerbose) {
5879 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
5880 "done waiting for free regions");
5881 }
5882 }
5883
5884 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
5885 assert(heap_lock_held_for_gc(),
5886 "the heap lock should already be held by or for this thread");
5887 _young_list->push_region(hr);
5888 }
5889
5890 class NoYoungRegionsClosure: public HeapRegionClosure {
5891 private:
5892 bool _success;
5893 public:
5894 NoYoungRegionsClosure() : _success(true) { }
5895 bool doHeapRegion(HeapRegion* r) {
5896 if (r->is_young()) {
5897 gclog_or_tty->print_cr("Region ["PTR_FORMAT", "PTR_FORMAT") tagged as young",
5898 r->bottom(), r->end());
5899 _success = false;
5900 }
5901 return false;
5902 }
5903 bool success() { return _success; }
5904 };
5905
5906 bool G1CollectedHeap::check_young_list_empty(bool check_heap, bool check_sample) {
5907 bool ret = _young_list->check_list_empty(check_sample);
5908
5909 if (check_heap) {
5910 NoYoungRegionsClosure closure;
5911 heap_region_iterate(&closure);
5912 ret = ret && closure.success();
5913 }
5914
5915 return ret;
5916 }
5917
5918 class TearDownRegionSetsClosure : public HeapRegionClosure {
5919 private:
5920 OldRegionSet *_old_set;
5921
5922 public:
5923 TearDownRegionSetsClosure(OldRegionSet* old_set) : _old_set(old_set) { }
5924
5925 bool doHeapRegion(HeapRegion* r) {
5926 if (r->is_empty()) {
5927 // We ignore empty regions, we'll empty the free list afterwards
5928 } else if (r->is_young()) {
5929 // We ignore young regions, we'll empty the young list afterwards
5930 } else if (r->isHumongous()) {
5931 // We ignore humongous regions, we're not tearing down the
5932 // humongous region set
5933 } else {
5934 // The rest should be old
5935 _old_set->remove(r);
5936 }
5937 return false;
5938 }
5939
5940 ~TearDownRegionSetsClosure() {
5941 assert(_old_set->is_empty(), "post-condition");
5942 }
5943 };
5944
5945 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
5946 assert_at_safepoint(true /* should_be_vm_thread */);
5947
5948 if (!free_list_only) {
5949 TearDownRegionSetsClosure cl(&_old_set);
5950 heap_region_iterate(&cl);
5951
5952 // Need to do this after the heap iteration to be able to
5953 // recognize the young regions and ignore them during the iteration.
5954 _young_list->empty_list();
5955 }
5956 _free_list.remove_all();
5957 }
5958
5959 class RebuildRegionSetsClosure : public HeapRegionClosure {
5960 private:
5961 bool _free_list_only;
5962 OldRegionSet* _old_set;
5963 FreeRegionList* _free_list;
5964 size_t _total_used;
5965
5966 public:
5967 RebuildRegionSetsClosure(bool free_list_only,
5968 OldRegionSet* old_set, FreeRegionList* free_list) :
5969 _free_list_only(free_list_only),
5970 _old_set(old_set), _free_list(free_list), _total_used(0) {
5971 assert(_free_list->is_empty(), "pre-condition");
5972 if (!free_list_only) {
5973 assert(_old_set->is_empty(), "pre-condition");
5974 }
5975 }
5976
5977 bool doHeapRegion(HeapRegion* r) {
5978 if (r->continuesHumongous()) {
5979 return false;
5980 }
5981
5982 if (r->is_empty()) {
5983 // Add free regions to the free list
5984 _free_list->add_as_tail(r);
5985 } else if (!_free_list_only) {
5986 assert(!r->is_young(), "we should not come across young regions");
5987
5988 if (r->isHumongous()) {
5989 // We ignore humongous regions, we left the humongous set unchanged
5990 } else {
5991 // The rest should be old, add them to the old set
5992 _old_set->add(r);
5993 }
5994 _total_used += r->used();
5995 }
5996
5997 return false;
5998 }
5999
6000 size_t total_used() {
6001 return _total_used;
6002 }
6003 };
6004
6005 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
6006 assert_at_safepoint(true /* should_be_vm_thread */);
6007
6008 RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_free_list);
6009 heap_region_iterate(&cl);
6010
6011 if (!free_list_only) {
6012 _summary_bytes_used = cl.total_used();
6013 }
6014 assert(_summary_bytes_used == recalculate_used(),
6015 err_msg("inconsistent _summary_bytes_used, "
6016 "value: "SIZE_FORMAT" recalculated: "SIZE_FORMAT,
6017 _summary_bytes_used, recalculate_used()));
6018 }
6019
6020 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) {
6021 _refine_cte_cl->set_concurrent(concurrent);
6022 }
6023
6024 bool G1CollectedHeap::is_in_closed_subset(const void* p) const {
6025 HeapRegion* hr = heap_region_containing(p);
6026 if (hr == NULL) {
6027 return is_in_permanent(p);
6028 } else {
6029 return hr->is_in(p);
6030 }
6031 }
6032
6033 // Methods for the mutator alloc region
6034
6035 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
6036 bool force) {
6037 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6038 assert(!force || g1_policy()->can_expand_young_list(),
6039 "if force is true we should be able to expand the young list");
6040 bool young_list_full = g1_policy()->is_young_list_full();
6041 if (force || !young_list_full) {
6042 HeapRegion* new_alloc_region = new_region(word_size,
6043 false /* do_expand */);
6044 if (new_alloc_region != NULL) {
6045 set_region_short_lived_locked(new_alloc_region);
6046 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Eden, young_list_full);
6047 return new_alloc_region;
6048 }
6049 }
6050 return NULL;
6051 }
6052
6053 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
6054 size_t allocated_bytes) {
6055 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6056 assert(alloc_region->is_young(), "all mutator alloc regions should be young");
6057
6058 g1_policy()->add_region_to_incremental_cset_lhs(alloc_region);
6059 _summary_bytes_used += allocated_bytes;
6060 _hr_printer.retire(alloc_region);
6061 // We update the eden sizes here, when the region is retired,
6062 // instead of when it's allocated, since this is the point that its
6063 // used space has been recored in _summary_bytes_used.
6064 g1mm()->update_eden_size();
6065 }
6066
6067 HeapRegion* MutatorAllocRegion::allocate_new_region(size_t word_size,
6068 bool force) {
6069 return _g1h->new_mutator_alloc_region(word_size, force);
6070 }
6071
6072 void G1CollectedHeap::set_par_threads() {
6073 // Don't change the number of workers. Use the value previously set
6074 // in the workgroup.
6075 int n_workers = workers()->active_workers();
6076 assert(UseDynamicNumberOfGCThreads ||
6077 n_workers == workers()->total_workers(),
6078 "Otherwise should be using the total number of workers");
6079 if (n_workers == 0) {
6080 assert(false, "Should have been set in prior evacuation pause.");
6081 n_workers = ParallelGCThreads;
6082 workers()->set_active_workers(n_workers);
6083 }
6084 set_par_threads(n_workers);
6085 }
6086
6087 void MutatorAllocRegion::retire_region(HeapRegion* alloc_region,
6088 size_t allocated_bytes) {
6089 _g1h->retire_mutator_alloc_region(alloc_region, allocated_bytes);
6090 }
6091
6092 // Methods for the GC alloc regions
6093
6094 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size,
6095 size_t count,
6096 GCAllocPurpose ap) {
6097 assert(FreeList_lock->owned_by_self(), "pre-condition");
6098
6099 if (count < g1_policy()->max_regions(ap)) {
6100 HeapRegion* new_alloc_region = new_region(word_size,
6101 true /* do_expand */);
6102 if (new_alloc_region != NULL) {
6103 // We really only need to do this for old regions given that we
6104 // should never scan survivors. But it doesn't hurt to do it
6105 // for survivors too.
6106 new_alloc_region->set_saved_mark();
6107 if (ap == GCAllocForSurvived) {
6108 new_alloc_region->set_survivor();
6109 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Survivor);
6110 } else {
6111 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Old);
6112 }
6113 return new_alloc_region;
6114 } else {
6115 g1_policy()->note_alloc_region_limit_reached(ap);
6116 }
6117 }
6118 return NULL;
6119 }
6120
6121 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
6122 size_t allocated_bytes,
6123 GCAllocPurpose ap) {
6124 alloc_region->note_end_of_copying();
6125 g1_policy()->record_bytes_copied_during_gc(allocated_bytes);
6126 if (ap == GCAllocForSurvived) {
6127 young_list()->add_survivor_region(alloc_region);
6128 } else {
6129 _old_set.add(alloc_region);
6130 }
6131 _hr_printer.retire(alloc_region);
6132 }
6133
6134 HeapRegion* SurvivorGCAllocRegion::allocate_new_region(size_t word_size,
6135 bool force) {
6136 assert(!force, "not supported for GC alloc regions");
6137 return _g1h->new_gc_alloc_region(word_size, count(), GCAllocForSurvived);
6138 }
6139
6140 void SurvivorGCAllocRegion::retire_region(HeapRegion* alloc_region,
6141 size_t allocated_bytes) {
6142 _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes,
6143 GCAllocForSurvived);
6144 }
6145
6146 HeapRegion* OldGCAllocRegion::allocate_new_region(size_t word_size,
6147 bool force) {
6148 assert(!force, "not supported for GC alloc regions");
6149 return _g1h->new_gc_alloc_region(word_size, count(), GCAllocForTenured);
6150 }
6151
6152 void OldGCAllocRegion::retire_region(HeapRegion* alloc_region,
6153 size_t allocated_bytes) {
6154 _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes,
6155 GCAllocForTenured);
6156 }
6157 // Heap region set verification
6158
6159 class VerifyRegionListsClosure : public HeapRegionClosure {
6160 private:
6161 FreeRegionList* _free_list;
6162 OldRegionSet* _old_set;
6163 HumongousRegionSet* _humongous_set;
6164 size_t _region_count;
6165
6166 public:
6167 VerifyRegionListsClosure(OldRegionSet* old_set,
6168 HumongousRegionSet* humongous_set,
6169 FreeRegionList* free_list) :
6170 _old_set(old_set), _humongous_set(humongous_set),
6171 _free_list(free_list), _region_count(0) { }
6172
6173 size_t region_count() { return _region_count; }
6174
6175 bool doHeapRegion(HeapRegion* hr) {
6176 _region_count += 1;
6177
6178 if (hr->continuesHumongous()) {
6179 return false;
6180 }
6181
6182 if (hr->is_young()) {
6183 // TODO
6184 } else if (hr->startsHumongous()) {
6185 _humongous_set->verify_next_region(hr);
6186 } else if (hr->is_empty()) {
6187 _free_list->verify_next_region(hr);
6188 } else {
6189 _old_set->verify_next_region(hr);
6190 }
6191 return false;
6192 }
6193 };
6194
6195 HeapRegion* G1CollectedHeap::new_heap_region(size_t hrs_index,
6196 HeapWord* bottom) {
6197 HeapWord* end = bottom + HeapRegion::GrainWords;
6198 MemRegion mr(bottom, end);
6199 assert(_g1_reserved.contains(mr), "invariant");
6200 // This might return NULL if the allocation fails
6201 return new HeapRegion(hrs_index, _bot_shared, mr, true /* is_zeroed */);
6202 }
6203
6204 void G1CollectedHeap::verify_region_sets() {
6205 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6206
6207 // First, check the explicit lists.
6208 _free_list.verify();
6209 {
6210 // Given that a concurrent operation might be adding regions to
6211 // the secondary free list we have to take the lock before
6212 // verifying it.
6213 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6214 _secondary_free_list.verify();
6215 }
6216 _old_set.verify();
6217 _humongous_set.verify();
6218
6219 // If a concurrent region freeing operation is in progress it will
6220 // be difficult to correctly attributed any free regions we come
6221 // across to the correct free list given that they might belong to
6222 // one of several (free_list, secondary_free_list, any local lists,
6223 // etc.). So, if that's the case we will skip the rest of the
6224 // verification operation. Alternatively, waiting for the concurrent
6225 // operation to complete will have a non-trivial effect on the GC's
6226 // operation (no concurrent operation will last longer than the
6227 // interval between two calls to verification) and it might hide
6228 // any issues that we would like to catch during testing.
6229 if (free_regions_coming()) {
6230 return;
6231 }
6232
6233 // Make sure we append the secondary_free_list on the free_list so
6234 // that all free regions we will come across can be safely
6235 // attributed to the free_list.
6236 append_secondary_free_list_if_not_empty_with_lock();
6237
6238 // Finally, make sure that the region accounting in the lists is
6239 // consistent with what we see in the heap.
6240 _old_set.verify_start();
6241 _humongous_set.verify_start();
6242 _free_list.verify_start();
6243
6244 VerifyRegionListsClosure cl(&_old_set, &_humongous_set, &_free_list);
6245 heap_region_iterate(&cl);
6246
6247 _old_set.verify_end();
6248 _humongous_set.verify_end();
6249 _free_list.verify_end();
6250 }
--- EOF ---