1 /*
2 * Copyright (c) 2001, 2012, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "code/icBuffer.hpp"
27 #include "gc_implementation/g1/bufferingOopClosure.hpp"
28 #include "gc_implementation/g1/concurrentG1Refine.hpp"
29 #include "gc_implementation/g1/concurrentG1RefineThread.hpp"
30 #include "gc_implementation/g1/concurrentMarkThread.inline.hpp"
31 #include "gc_implementation/g1/g1AllocRegion.inline.hpp"
32 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
33 #include "gc_implementation/g1/g1CollectorPolicy.hpp"
34 #include "gc_implementation/g1/g1ErgoVerbose.hpp"
35 #include "gc_implementation/g1/g1EvacFailure.hpp"
36 #include "gc_implementation/g1/g1GCPhaseTimes.hpp"
37 #include "gc_implementation/g1/g1Log.hpp"
38 #include "gc_implementation/g1/g1MarkSweep.hpp"
39 #include "gc_implementation/g1/g1OopClosures.inline.hpp"
40 #include "gc_implementation/g1/g1RemSet.inline.hpp"
41 #include "gc_implementation/g1/heapRegion.inline.hpp"
42 #include "gc_implementation/g1/heapRegionRemSet.hpp"
43 #include "gc_implementation/g1/heapRegionSeq.inline.hpp"
44 #include "gc_implementation/g1/vm_operations_g1.hpp"
45 #include "gc_implementation/shared/isGCActiveMark.hpp"
46 #include "memory/gcLocker.inline.hpp"
47 #include "memory/genOopClosures.inline.hpp"
48 #include "memory/generationSpec.hpp"
49 #include "memory/referenceProcessor.hpp"
50 #include "oops/oop.inline.hpp"
51 #include "oops/oop.pcgc.inline.hpp"
52 #include "runtime/aprofiler.hpp"
53 #include "runtime/vmThread.hpp"
54
55 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;
56
57 // turn it on so that the contents of the young list (scan-only /
58 // to-be-collected) are printed at "strategic" points before / during
59 // / after the collection --- this is useful for debugging
60 #define YOUNG_LIST_VERBOSE 0
61 // CURRENT STATUS
62 // This file is under construction. Search for "FIXME".
63
64 // INVARIANTS/NOTES
65 //
66 // All allocation activity covered by the G1CollectedHeap interface is
67 // serialized by acquiring the HeapLock. This happens in mem_allocate
68 // and allocate_new_tlab, which are the "entry" points to the
69 // allocation code from the rest of the JVM. (Note that this does not
70 // apply to TLAB allocation, which is not part of this interface: it
71 // is done by clients of this interface.)
72
73 // Notes on implementation of parallelism in different tasks.
74 //
75 // G1ParVerifyTask uses heap_region_par_iterate_chunked() for parallelism.
76 // The number of GC workers is passed to heap_region_par_iterate_chunked().
77 // It does use run_task() which sets _n_workers in the task.
78 // G1ParTask executes g1_process_strong_roots() ->
79 // SharedHeap::process_strong_roots() which calls eventuall to
80 // CardTableModRefBS::par_non_clean_card_iterate_work() which uses
81 // SequentialSubTasksDone. SharedHeap::process_strong_roots() also
82 // directly uses SubTasksDone (_process_strong_tasks field in SharedHeap).
83 //
84
85 // Local to this file.
86
87 class RefineCardTableEntryClosure: public CardTableEntryClosure {
88 SuspendibleThreadSet* _sts;
89 G1RemSet* _g1rs;
90 ConcurrentG1Refine* _cg1r;
91 bool _concurrent;
92 public:
93 RefineCardTableEntryClosure(SuspendibleThreadSet* sts,
94 G1RemSet* g1rs,
95 ConcurrentG1Refine* cg1r) :
96 _sts(sts), _g1rs(g1rs), _cg1r(cg1r), _concurrent(true)
97 {}
98 bool do_card_ptr(jbyte* card_ptr, int worker_i) {
99 bool oops_into_cset = _g1rs->concurrentRefineOneCard(card_ptr, worker_i, false);
100 // This path is executed by the concurrent refine or mutator threads,
101 // concurrently, and so we do not care if card_ptr contains references
102 // that point into the collection set.
103 assert(!oops_into_cset, "should be");
104
105 if (_concurrent && _sts->should_yield()) {
106 // Caller will actually yield.
107 return false;
108 }
109 // Otherwise, we finished successfully; return true.
110 return true;
111 }
112 void set_concurrent(bool b) { _concurrent = b; }
113 };
114
115
116 class ClearLoggedCardTableEntryClosure: public CardTableEntryClosure {
117 int _calls;
118 G1CollectedHeap* _g1h;
119 CardTableModRefBS* _ctbs;
120 int _histo[256];
121 public:
122 ClearLoggedCardTableEntryClosure() :
123 _calls(0)
124 {
125 _g1h = G1CollectedHeap::heap();
126 _ctbs = (CardTableModRefBS*)_g1h->barrier_set();
127 for (int i = 0; i < 256; i++) _histo[i] = 0;
128 }
129 bool do_card_ptr(jbyte* card_ptr, int worker_i) {
130 if (_g1h->is_in_reserved(_ctbs->addr_for(card_ptr))) {
131 _calls++;
132 unsigned char* ujb = (unsigned char*)card_ptr;
133 int ind = (int)(*ujb);
134 _histo[ind]++;
135 *card_ptr = -1;
136 }
137 return true;
138 }
139 int calls() { return _calls; }
140 void print_histo() {
141 gclog_or_tty->print_cr("Card table value histogram:");
142 for (int i = 0; i < 256; i++) {
143 if (_histo[i] != 0) {
144 gclog_or_tty->print_cr(" %d: %d", i, _histo[i]);
145 }
146 }
147 }
148 };
149
150 class RedirtyLoggedCardTableEntryClosure: public CardTableEntryClosure {
151 int _calls;
152 G1CollectedHeap* _g1h;
153 CardTableModRefBS* _ctbs;
154 public:
155 RedirtyLoggedCardTableEntryClosure() :
156 _calls(0)
157 {
158 _g1h = G1CollectedHeap::heap();
159 _ctbs = (CardTableModRefBS*)_g1h->barrier_set();
160 }
161 bool do_card_ptr(jbyte* card_ptr, int worker_i) {
162 if (_g1h->is_in_reserved(_ctbs->addr_for(card_ptr))) {
163 _calls++;
164 *card_ptr = 0;
165 }
166 return true;
167 }
168 int calls() { return _calls; }
169 };
170
171 class RedirtyLoggedCardTableEntryFastClosure : public CardTableEntryClosure {
172 public:
173 bool do_card_ptr(jbyte* card_ptr, int worker_i) {
174 *card_ptr = CardTableModRefBS::dirty_card_val();
175 return true;
176 }
177 };
178
179 YoungList::YoungList(G1CollectedHeap* g1h) :
180 _g1h(g1h), _head(NULL), _length(0), _last_sampled_rs_lengths(0),
181 _survivor_head(NULL), _survivor_tail(NULL), _survivor_length(0) {
182 guarantee(check_list_empty(false), "just making sure...");
183 }
184
185 void YoungList::push_region(HeapRegion *hr) {
186 assert(!hr->is_young(), "should not already be young");
187 assert(hr->get_next_young_region() == NULL, "cause it should!");
188
189 hr->set_next_young_region(_head);
190 _head = hr;
191
192 _g1h->g1_policy()->set_region_eden(hr, (int) _length);
193 ++_length;
194 }
195
196 void YoungList::add_survivor_region(HeapRegion* hr) {
197 assert(hr->is_survivor(), "should be flagged as survivor region");
198 assert(hr->get_next_young_region() == NULL, "cause it should!");
199
200 hr->set_next_young_region(_survivor_head);
201 if (_survivor_head == NULL) {
202 _survivor_tail = hr;
203 }
204 _survivor_head = hr;
205 ++_survivor_length;
206 }
207
208 void YoungList::empty_list(HeapRegion* list) {
209 while (list != NULL) {
210 HeapRegion* next = list->get_next_young_region();
211 list->set_next_young_region(NULL);
212 list->uninstall_surv_rate_group();
213 list->set_not_young();
214 list = next;
215 }
216 }
217
218 void YoungList::empty_list() {
219 assert(check_list_well_formed(), "young list should be well formed");
220
221 empty_list(_head);
222 _head = NULL;
223 _length = 0;
224
225 empty_list(_survivor_head);
226 _survivor_head = NULL;
227 _survivor_tail = NULL;
228 _survivor_length = 0;
229
230 _last_sampled_rs_lengths = 0;
231
232 assert(check_list_empty(false), "just making sure...");
233 }
234
235 bool YoungList::check_list_well_formed() {
236 bool ret = true;
237
238 uint length = 0;
239 HeapRegion* curr = _head;
240 HeapRegion* last = NULL;
241 while (curr != NULL) {
242 if (!curr->is_young()) {
243 gclog_or_tty->print_cr("### YOUNG REGION "PTR_FORMAT"-"PTR_FORMAT" "
244 "incorrectly tagged (y: %d, surv: %d)",
245 curr->bottom(), curr->end(),
246 curr->is_young(), curr->is_survivor());
247 ret = false;
248 }
249 ++length;
250 last = curr;
251 curr = curr->get_next_young_region();
252 }
253 ret = ret && (length == _length);
254
255 if (!ret) {
256 gclog_or_tty->print_cr("### YOUNG LIST seems not well formed!");
257 gclog_or_tty->print_cr("### list has %u entries, _length is %u",
258 length, _length);
259 }
260
261 return ret;
262 }
263
264 bool YoungList::check_list_empty(bool check_sample) {
265 bool ret = true;
266
267 if (_length != 0) {
268 gclog_or_tty->print_cr("### YOUNG LIST should have 0 length, not %u",
269 _length);
270 ret = false;
271 }
272 if (check_sample && _last_sampled_rs_lengths != 0) {
273 gclog_or_tty->print_cr("### YOUNG LIST has non-zero last sampled RS lengths");
274 ret = false;
275 }
276 if (_head != NULL) {
277 gclog_or_tty->print_cr("### YOUNG LIST does not have a NULL head");
278 ret = false;
279 }
280 if (!ret) {
281 gclog_or_tty->print_cr("### YOUNG LIST does not seem empty");
282 }
283
284 return ret;
285 }
286
287 void
288 YoungList::rs_length_sampling_init() {
289 _sampled_rs_lengths = 0;
290 _curr = _head;
291 }
292
293 bool
294 YoungList::rs_length_sampling_more() {
295 return _curr != NULL;
296 }
297
298 void
299 YoungList::rs_length_sampling_next() {
300 assert( _curr != NULL, "invariant" );
301 size_t rs_length = _curr->rem_set()->occupied();
302
303 _sampled_rs_lengths += rs_length;
304
305 // The current region may not yet have been added to the
306 // incremental collection set (it gets added when it is
307 // retired as the current allocation region).
308 if (_curr->in_collection_set()) {
309 // Update the collection set policy information for this region
310 _g1h->g1_policy()->update_incremental_cset_info(_curr, rs_length);
311 }
312
313 _curr = _curr->get_next_young_region();
314 if (_curr == NULL) {
315 _last_sampled_rs_lengths = _sampled_rs_lengths;
316 // gclog_or_tty->print_cr("last sampled RS lengths = %d", _last_sampled_rs_lengths);
317 }
318 }
319
320 void
321 YoungList::reset_auxilary_lists() {
322 guarantee( is_empty(), "young list should be empty" );
323 assert(check_list_well_formed(), "young list should be well formed");
324
325 // Add survivor regions to SurvRateGroup.
326 _g1h->g1_policy()->note_start_adding_survivor_regions();
327 _g1h->g1_policy()->finished_recalculating_age_indexes(true /* is_survivors */);
328
329 int young_index_in_cset = 0;
330 for (HeapRegion* curr = _survivor_head;
331 curr != NULL;
332 curr = curr->get_next_young_region()) {
333 _g1h->g1_policy()->set_region_survivor(curr, young_index_in_cset);
334
335 // The region is a non-empty survivor so let's add it to
336 // the incremental collection set for the next evacuation
337 // pause.
338 _g1h->g1_policy()->add_region_to_incremental_cset_rhs(curr);
339 young_index_in_cset += 1;
340 }
341 assert((uint) young_index_in_cset == _survivor_length, "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(" "HR_FORMAT", P: "PTR_FORMAT "N: "PTR_FORMAT", age: %4d",
373 HR_FORMAT_PARAMS(curr),
374 curr->prev_top_at_mark_start(),
375 curr->next_top_at_mark_start(),
376 curr->age_in_surv_rate_group_cond());
377 curr = curr->get_next_young_region();
378 }
379 }
380
381 gclog_or_tty->print_cr("");
382 }
383
384 void G1CollectedHeap::push_dirty_cards_region(HeapRegion* hr)
385 {
386 // Claim the right to put the region on the dirty cards region list
387 // by installing a self pointer.
388 HeapRegion* next = hr->get_next_dirty_cards_region();
389 if (next == NULL) {
390 HeapRegion* res = (HeapRegion*)
391 Atomic::cmpxchg_ptr(hr, hr->next_dirty_cards_region_addr(),
392 NULL);
393 if (res == NULL) {
394 HeapRegion* head;
395 do {
396 // Put the region to the dirty cards region list.
397 head = _dirty_cards_region_list;
398 next = (HeapRegion*)
399 Atomic::cmpxchg_ptr(hr, &_dirty_cards_region_list, head);
400 if (next == head) {
401 assert(hr->get_next_dirty_cards_region() == hr,
402 "hr->get_next_dirty_cards_region() != hr");
403 if (next == NULL) {
404 // The last region in the list points to itself.
405 hr->set_next_dirty_cards_region(hr);
406 } else {
407 hr->set_next_dirty_cards_region(next);
408 }
409 }
410 } while (next != head);
411 }
412 }
413 }
414
415 HeapRegion* G1CollectedHeap::pop_dirty_cards_region()
416 {
417 HeapRegion* head;
418 HeapRegion* hr;
419 do {
420 head = _dirty_cards_region_list;
421 if (head == NULL) {
422 return NULL;
423 }
424 HeapRegion* new_head = head->get_next_dirty_cards_region();
425 if (head == new_head) {
426 // The last region.
427 new_head = NULL;
428 }
429 hr = (HeapRegion*)Atomic::cmpxchg_ptr(new_head, &_dirty_cards_region_list,
430 head);
431 } while (hr != head);
432 assert(hr != NULL, "invariant");
433 hr->set_next_dirty_cards_region(NULL);
434 return hr;
435 }
436
437 void G1CollectedHeap::stop_conc_gc_threads() {
438 _cg1r->stop();
439 _cmThread->stop();
440 }
441
442 #ifdef ASSERT
443 // A region is added to the collection set as it is retired
444 // so an address p can point to a region which will be in the
445 // collection set but has not yet been retired. This method
446 // therefore is only accurate during a GC pause after all
447 // regions have been retired. It is used for debugging
448 // to check if an nmethod has references to objects that can
449 // be move during a partial collection. Though it can be
450 // inaccurate, it is sufficient for G1 because the conservative
451 // implementation of is_scavengable() for G1 will indicate that
452 // all nmethods must be scanned during a partial collection.
453 bool G1CollectedHeap::is_in_partial_collection(const void* p) {
454 HeapRegion* hr = heap_region_containing(p);
455 return hr != NULL && hr->in_collection_set();
456 }
457 #endif
458
459 // Returns true if the reference points to an object that
460 // can move in an incremental collecction.
461 bool G1CollectedHeap::is_scavengable(const void* p) {
462 G1CollectedHeap* g1h = G1CollectedHeap::heap();
463 G1CollectorPolicy* g1p = g1h->g1_policy();
464 HeapRegion* hr = heap_region_containing(p);
465 if (hr == NULL) {
466 // perm gen (or null)
467 return false;
468 } else {
469 return !hr->isHumongous();
470 }
471 }
472
473 void G1CollectedHeap::check_ct_logs_at_safepoint() {
474 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
475 CardTableModRefBS* ct_bs = (CardTableModRefBS*)barrier_set();
476
477 // Count the dirty cards at the start.
478 CountNonCleanMemRegionClosure count1(this);
479 ct_bs->mod_card_iterate(&count1);
480 int orig_count = count1.n();
481
482 // First clear the logged cards.
483 ClearLoggedCardTableEntryClosure clear;
484 dcqs.set_closure(&clear);
485 dcqs.apply_closure_to_all_completed_buffers();
486 dcqs.iterate_closure_all_threads(false);
487 clear.print_histo();
488
489 // Now ensure that there's no dirty cards.
490 CountNonCleanMemRegionClosure count2(this);
491 ct_bs->mod_card_iterate(&count2);
492 if (count2.n() != 0) {
493 gclog_or_tty->print_cr("Card table has %d entries; %d originally",
494 count2.n(), orig_count);
495 }
496 guarantee(count2.n() == 0, "Card table should be clean.");
497
498 RedirtyLoggedCardTableEntryClosure redirty;
499 JavaThread::dirty_card_queue_set().set_closure(&redirty);
500 dcqs.apply_closure_to_all_completed_buffers();
501 dcqs.iterate_closure_all_threads(false);
502 gclog_or_tty->print_cr("Log entries = %d, dirty cards = %d.",
503 clear.calls(), orig_count);
504 guarantee(redirty.calls() == clear.calls(),
505 "Or else mechanism is broken.");
506
507 CountNonCleanMemRegionClosure count3(this);
508 ct_bs->mod_card_iterate(&count3);
509 if (count3.n() != orig_count) {
510 gclog_or_tty->print_cr("Should have restored them all: orig = %d, final = %d.",
511 orig_count, count3.n());
512 guarantee(count3.n() >= orig_count, "Should have restored them all.");
513 }
514
515 JavaThread::dirty_card_queue_set().set_closure(_refine_cte_cl);
516 }
517
518 // Private class members.
519
520 G1CollectedHeap* G1CollectedHeap::_g1h;
521
522 // Private methods.
523
524 HeapRegion*
525 G1CollectedHeap::new_region_try_secondary_free_list() {
526 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
527 while (!_secondary_free_list.is_empty() || free_regions_coming()) {
528 if (!_secondary_free_list.is_empty()) {
529 if (G1ConcRegionFreeingVerbose) {
530 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
531 "secondary_free_list has %u entries",
532 _secondary_free_list.length());
533 }
534 // It looks as if there are free regions available on the
535 // secondary_free_list. Let's move them to the free_list and try
536 // again to allocate from it.
537 append_secondary_free_list();
538
539 assert(!_free_list.is_empty(), "if the secondary_free_list was not "
540 "empty we should have moved at least one entry to the free_list");
541 HeapRegion* res = _free_list.remove_head();
542 if (G1ConcRegionFreeingVerbose) {
543 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
544 "allocated "HR_FORMAT" from secondary_free_list",
545 HR_FORMAT_PARAMS(res));
546 }
547 return res;
548 }
549
550 // Wait here until we get notifed either when (a) there are no
551 // more free regions coming or (b) some regions have been moved on
552 // the secondary_free_list.
553 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
554 }
555
556 if (G1ConcRegionFreeingVerbose) {
557 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
558 "could not allocate from secondary_free_list");
559 }
560 return NULL;
561 }
562
563 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool do_expand) {
564 assert(!isHumongous(word_size) || word_size <= HeapRegion::GrainWords,
565 "the only time we use this to allocate a humongous region is "
566 "when we are allocating a single humongous region");
567
568 HeapRegion* res;
569 if (G1StressConcRegionFreeing) {
570 if (!_secondary_free_list.is_empty()) {
571 if (G1ConcRegionFreeingVerbose) {
572 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
573 "forced to look at the secondary_free_list");
574 }
575 res = new_region_try_secondary_free_list();
576 if (res != NULL) {
577 return res;
578 }
579 }
580 }
581 res = _free_list.remove_head_or_null();
582 if (res == NULL) {
583 if (G1ConcRegionFreeingVerbose) {
584 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
585 "res == NULL, trying the secondary_free_list");
586 }
587 res = new_region_try_secondary_free_list();
588 }
589 if (res == NULL && do_expand && _expand_heap_after_alloc_failure) {
590 // Currently, only attempts to allocate GC alloc regions set
591 // do_expand to true. So, we should only reach here during a
592 // safepoint. If this assumption changes we might have to
593 // reconsider the use of _expand_heap_after_alloc_failure.
594 assert(SafepointSynchronize::is_at_safepoint(), "invariant");
595
596 ergo_verbose1(ErgoHeapSizing,
597 "attempt heap expansion",
598 ergo_format_reason("region allocation request failed")
599 ergo_format_byte("allocation request"),
600 word_size * HeapWordSize);
601 if (expand(word_size * HeapWordSize)) {
602 // Given that expand() succeeded in expanding the heap, and we
603 // always expand the heap by an amount aligned to the heap
604 // region size, the free list should in theory not be empty. So
605 // it would probably be OK to use remove_head(). But the extra
606 // check for NULL is unlikely to be a performance issue here (we
607 // just expanded the heap!) so let's just be conservative and
608 // use remove_head_or_null().
609 res = _free_list.remove_head_or_null();
610 } else {
611 _expand_heap_after_alloc_failure = false;
612 }
613 }
614 return res;
615 }
616
617 uint G1CollectedHeap::humongous_obj_allocate_find_first(uint num_regions,
618 size_t word_size) {
619 assert(isHumongous(word_size), "word_size should be humongous");
620 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
621
622 uint first = G1_NULL_HRS_INDEX;
623 if (num_regions == 1) {
624 // Only one region to allocate, no need to go through the slower
625 // path. The caller will attempt the expasion if this fails, so
626 // let's not try to expand here too.
627 HeapRegion* hr = new_region(word_size, false /* do_expand */);
628 if (hr != NULL) {
629 first = hr->hrs_index();
630 } else {
631 first = G1_NULL_HRS_INDEX;
632 }
633 } else {
634 // We can't allocate humongous regions while cleanupComplete() is
635 // running, since some of the regions we find to be empty might not
636 // yet be added to the free list and it is not straightforward to
637 // know which list they are on so that we can remove them. Note
638 // that we only need to do this if we need to allocate more than
639 // one region to satisfy the current humongous allocation
640 // request. If we are only allocating one region we use the common
641 // region allocation code (see above).
642 wait_while_free_regions_coming();
643 append_secondary_free_list_if_not_empty_with_lock();
644
645 if (free_regions() >= num_regions) {
646 first = _hrs.find_contiguous(num_regions);
647 if (first != G1_NULL_HRS_INDEX) {
648 for (uint i = first; i < first + num_regions; ++i) {
649 HeapRegion* hr = region_at(i);
650 assert(hr->is_empty(), "sanity");
651 assert(is_on_master_free_list(hr), "sanity");
652 hr->set_pending_removal(true);
653 }
654 _free_list.remove_all_pending(num_regions);
655 }
656 }
657 }
658 return first;
659 }
660
661 HeapWord*
662 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first,
663 uint num_regions,
664 size_t word_size) {
665 assert(first != G1_NULL_HRS_INDEX, "pre-condition");
666 assert(isHumongous(word_size), "word_size should be humongous");
667 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
668
669 // Index of last region in the series + 1.
670 uint last = first + num_regions;
671
672 // We need to initialize the region(s) we just discovered. This is
673 // a bit tricky given that it can happen concurrently with
674 // refinement threads refining cards on these regions and
675 // potentially wanting to refine the BOT as they are scanning
676 // those cards (this can happen shortly after a cleanup; see CR
677 // 6991377). So we have to set up the region(s) carefully and in
678 // a specific order.
679
680 // The word size sum of all the regions we will allocate.
681 size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords;
682 assert(word_size <= word_size_sum, "sanity");
683
684 // This will be the "starts humongous" region.
685 HeapRegion* first_hr = region_at(first);
686 // The header of the new object will be placed at the bottom of
687 // the first region.
688 HeapWord* new_obj = first_hr->bottom();
689 // This will be the new end of the first region in the series that
690 // should also match the end of the last region in the seriers.
691 HeapWord* new_end = new_obj + word_size_sum;
692 // This will be the new top of the first region that will reflect
693 // this allocation.
694 HeapWord* new_top = new_obj + word_size;
695
696 // First, we need to zero the header of the space that we will be
697 // allocating. When we update top further down, some refinement
698 // threads might try to scan the region. By zeroing the header we
699 // ensure that any thread that will try to scan the region will
700 // come across the zero klass word and bail out.
701 //
702 // NOTE: It would not have been correct to have used
703 // CollectedHeap::fill_with_object() and make the space look like
704 // an int array. The thread that is doing the allocation will
705 // later update the object header to a potentially different array
706 // type and, for a very short period of time, the klass and length
707 // fields will be inconsistent. This could cause a refinement
708 // thread to calculate the object size incorrectly.
709 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
710
711 // We will set up the first region as "starts humongous". This
712 // will also update the BOT covering all the regions to reflect
713 // that there is a single object that starts at the bottom of the
714 // first region.
715 first_hr->set_startsHumongous(new_top, new_end);
716
717 // Then, if there are any, we will set up the "continues
718 // humongous" regions.
719 HeapRegion* hr = NULL;
720 for (uint i = first + 1; i < last; ++i) {
721 hr = region_at(i);
722 hr->set_continuesHumongous(first_hr);
723 }
724 // If we have "continues humongous" regions (hr != NULL), then the
725 // end of the last one should match new_end.
726 assert(hr == NULL || hr->end() == new_end, "sanity");
727
728 // Up to this point no concurrent thread would have been able to
729 // do any scanning on any region in this series. All the top
730 // fields still point to bottom, so the intersection between
731 // [bottom,top] and [card_start,card_end] will be empty. Before we
732 // update the top fields, we'll do a storestore to make sure that
733 // no thread sees the update to top before the zeroing of the
734 // object header and the BOT initialization.
735 OrderAccess::storestore();
736
737 // Now that the BOT and the object header have been initialized,
738 // we can update top of the "starts humongous" region.
739 assert(first_hr->bottom() < new_top && new_top <= first_hr->end(),
740 "new_top should be in this region");
741 first_hr->set_top(new_top);
742 if (_hr_printer.is_active()) {
743 HeapWord* bottom = first_hr->bottom();
744 HeapWord* end = first_hr->orig_end();
745 if ((first + 1) == last) {
746 // the series has a single humongous region
747 _hr_printer.alloc(G1HRPrinter::SingleHumongous, first_hr, new_top);
748 } else {
749 // the series has more than one humongous regions
750 _hr_printer.alloc(G1HRPrinter::StartsHumongous, first_hr, end);
751 }
752 }
753
754 // Now, we will update the top fields of the "continues humongous"
755 // regions. The reason we need to do this is that, otherwise,
756 // these regions would look empty and this will confuse parts of
757 // G1. For example, the code that looks for a consecutive number
758 // of empty regions will consider them empty and try to
759 // re-allocate them. We can extend is_empty() to also include
760 // !continuesHumongous(), but it is easier to just update the top
761 // fields here. The way we set top for all regions (i.e., top ==
762 // end for all regions but the last one, top == new_top for the
763 // last one) is actually used when we will free up the humongous
764 // region in free_humongous_region().
765 hr = NULL;
766 for (uint i = first + 1; i < last; ++i) {
767 hr = region_at(i);
768 if ((i + 1) == last) {
769 // last continues humongous region
770 assert(hr->bottom() < new_top && new_top <= hr->end(),
771 "new_top should fall on this region");
772 hr->set_top(new_top);
773 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, new_top);
774 } else {
775 // not last one
776 assert(new_top > hr->end(), "new_top should be above this region");
777 hr->set_top(hr->end());
778 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, hr->end());
779 }
780 }
781 // If we have continues humongous regions (hr != NULL), then the
782 // end of the last one should match new_end and its top should
783 // match new_top.
784 assert(hr == NULL ||
785 (hr->end() == new_end && hr->top() == new_top), "sanity");
786
787 assert(first_hr->used() == word_size * HeapWordSize, "invariant");
788 _summary_bytes_used += first_hr->used();
789 _humongous_set.add(first_hr);
790
791 return new_obj;
792 }
793
794 // If could fit into free regions w/o expansion, try.
795 // Otherwise, if can expand, do so.
796 // Otherwise, if using ex regions might help, try with ex given back.
797 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size) {
798 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
799
800 verify_region_sets_optional();
801
802 size_t word_size_rounded = round_to(word_size, HeapRegion::GrainWords);
803 uint num_regions = (uint) (word_size_rounded / HeapRegion::GrainWords);
804 uint x_num = expansion_regions();
805 uint fs = _hrs.free_suffix();
806 uint first = humongous_obj_allocate_find_first(num_regions, word_size);
807 if (first == G1_NULL_HRS_INDEX) {
808 // The only thing we can do now is attempt expansion.
809 if (fs + x_num >= num_regions) {
810 // If the number of regions we're trying to allocate for this
811 // object is at most the number of regions in the free suffix,
812 // then the call to humongous_obj_allocate_find_first() above
813 // should have succeeded and we wouldn't be here.
814 //
815 // We should only be trying to expand when the free suffix is
816 // not sufficient for the object _and_ we have some expansion
817 // room available.
818 assert(num_regions > fs, "earlier allocation should have succeeded");
819
820 ergo_verbose1(ErgoHeapSizing,
821 "attempt heap expansion",
822 ergo_format_reason("humongous allocation request failed")
823 ergo_format_byte("allocation request"),
824 word_size * HeapWordSize);
825 if (expand((num_regions - fs) * HeapRegion::GrainBytes)) {
826 // Even though the heap was expanded, it might not have
827 // reached the desired size. So, we cannot assume that the
828 // allocation will succeed.
829 first = humongous_obj_allocate_find_first(num_regions, word_size);
830 }
831 }
832 }
833
834 HeapWord* result = NULL;
835 if (first != G1_NULL_HRS_INDEX) {
836 result =
837 humongous_obj_allocate_initialize_regions(first, num_regions, word_size);
838 assert(result != NULL, "it should always return a valid result");
839
840 // A successful humongous object allocation changes the used space
841 // information of the old generation so we need to recalculate the
842 // sizes and update the jstat counters here.
843 g1mm()->update_sizes();
844 }
845
846 verify_region_sets_optional();
847
848 return result;
849 }
850
851 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) {
852 assert_heap_not_locked_and_not_at_safepoint();
853 assert(!isHumongous(word_size), "we do not allow humongous TLABs");
854
855 unsigned int dummy_gc_count_before;
856 return attempt_allocation(word_size, &dummy_gc_count_before);
857 }
858
859 HeapWord*
860 G1CollectedHeap::mem_allocate(size_t word_size,
861 bool* gc_overhead_limit_was_exceeded) {
862 assert_heap_not_locked_and_not_at_safepoint();
863
864 // Loop until the allocation is satisified, or unsatisfied after GC.
865 for (int try_count = 1; /* we'll return */; try_count += 1) {
866 unsigned int gc_count_before;
867
868 HeapWord* result = NULL;
869 if (!isHumongous(word_size)) {
870 result = attempt_allocation(word_size, &gc_count_before);
871 } else {
872 result = attempt_allocation_humongous(word_size, &gc_count_before);
873 }
874 if (result != NULL) {
875 return result;
876 }
877
878 // Create the garbage collection operation...
879 VM_G1CollectForAllocation op(gc_count_before, word_size);
880 // ...and get the VM thread to execute it.
881 VMThread::execute(&op);
882
883 if (op.prologue_succeeded() && op.pause_succeeded()) {
884 // If the operation was successful we'll return the result even
885 // if it is NULL. If the allocation attempt failed immediately
886 // after a Full GC, it's unlikely we'll be able to allocate now.
887 HeapWord* result = op.result();
888 if (result != NULL && !isHumongous(word_size)) {
889 // Allocations that take place on VM operations do not do any
890 // card dirtying and we have to do it here. We only have to do
891 // this for non-humongous allocations, though.
892 dirty_young_block(result, word_size);
893 }
894 return result;
895 } else {
896 assert(op.result() == NULL,
897 "the result should be NULL if the VM op did not succeed");
898 }
899
900 // Give a warning if we seem to be looping forever.
901 if ((QueuedAllocationWarningCount > 0) &&
902 (try_count % QueuedAllocationWarningCount == 0)) {
903 warning("G1CollectedHeap::mem_allocate retries %d times", try_count);
904 }
905 }
906
907 ShouldNotReachHere();
908 return NULL;
909 }
910
911 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size,
912 unsigned int *gc_count_before_ret) {
913 // Make sure you read the note in attempt_allocation_humongous().
914
915 assert_heap_not_locked_and_not_at_safepoint();
916 assert(!isHumongous(word_size), "attempt_allocation_slow() should not "
917 "be called for humongous allocation requests");
918
919 // We should only get here after the first-level allocation attempt
920 // (attempt_allocation()) failed to allocate.
921
922 // We will loop until a) we manage to successfully perform the
923 // allocation or b) we successfully schedule a collection which
924 // fails to perform the allocation. b) is the only case when we'll
925 // return NULL.
926 HeapWord* result = NULL;
927 for (int try_count = 1; /* we'll return */; try_count += 1) {
928 bool should_try_gc;
929 unsigned int gc_count_before;
930
931 {
932 MutexLockerEx x(Heap_lock);
933
934 result = _mutator_alloc_region.attempt_allocation_locked(word_size,
935 false /* bot_updates */);
936 if (result != NULL) {
937 return result;
938 }
939
940 // If we reach here, attempt_allocation_locked() above failed to
941 // allocate a new region. So the mutator alloc region should be NULL.
942 assert(_mutator_alloc_region.get() == NULL, "only way to get here");
943
944 if (GC_locker::is_active_and_needs_gc()) {
945 if (g1_policy()->can_expand_young_list()) {
946 // No need for an ergo verbose message here,
947 // can_expand_young_list() does this when it returns true.
948 result = _mutator_alloc_region.attempt_allocation_force(word_size,
949 false /* bot_updates */);
950 if (result != NULL) {
951 return result;
952 }
953 }
954 should_try_gc = false;
955 } else {
956 // The GCLocker may not be active but the GCLocker initiated
957 // GC may not yet have been performed (GCLocker::needs_gc()
958 // returns true). In this case we do not try this GC and
959 // wait until the GCLocker initiated GC is performed, and
960 // then retry the allocation.
961 if (GC_locker::needs_gc()) {
962 should_try_gc = false;
963 } else {
964 // Read the GC count while still holding the Heap_lock.
965 gc_count_before = total_collections();
966 should_try_gc = true;
967 }
968 }
969 }
970
971 if (should_try_gc) {
972 bool succeeded;
973 result = do_collection_pause(word_size, gc_count_before, &succeeded);
974 if (result != NULL) {
975 assert(succeeded, "only way to get back a non-NULL result");
976 return result;
977 }
978
979 if (succeeded) {
980 // If we get here we successfully scheduled a collection which
981 // failed to allocate. No point in trying to allocate
982 // further. We'll just return NULL.
983 MutexLockerEx x(Heap_lock);
984 *gc_count_before_ret = total_collections();
985 return NULL;
986 }
987 } else {
988 // The GCLocker is either active or the GCLocker initiated
989 // GC has not yet been performed. Stall until it is and
990 // then retry the allocation.
991 GC_locker::stall_until_clear();
992 }
993
994 // We can reach here if we were unsuccessul in scheduling a
995 // collection (because another thread beat us to it) or if we were
996 // stalled due to the GC locker. In either can we should retry the
997 // allocation attempt in case another thread successfully
998 // performed a collection and reclaimed enough space. We do the
999 // first attempt (without holding the Heap_lock) here and the
1000 // follow-on attempt will be at the start of the next loop
1001 // iteration (after taking the Heap_lock).
1002 result = _mutator_alloc_region.attempt_allocation(word_size,
1003 false /* bot_updates */);
1004 if (result != NULL) {
1005 return result;
1006 }
1007
1008 // Give a warning if we seem to be looping forever.
1009 if ((QueuedAllocationWarningCount > 0) &&
1010 (try_count % QueuedAllocationWarningCount == 0)) {
1011 warning("G1CollectedHeap::attempt_allocation_slow() "
1012 "retries %d times", try_count);
1013 }
1014 }
1015
1016 ShouldNotReachHere();
1017 return NULL;
1018 }
1019
1020 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size,
1021 unsigned int * gc_count_before_ret) {
1022 // The structure of this method has a lot of similarities to
1023 // attempt_allocation_slow(). The reason these two were not merged
1024 // into a single one is that such a method would require several "if
1025 // allocation is not humongous do this, otherwise do that"
1026 // conditional paths which would obscure its flow. In fact, an early
1027 // version of this code did use a unified method which was harder to
1028 // follow and, as a result, it had subtle bugs that were hard to
1029 // track down. So keeping these two methods separate allows each to
1030 // be more readable. It will be good to keep these two in sync as
1031 // much as possible.
1032
1033 assert_heap_not_locked_and_not_at_safepoint();
1034 assert(isHumongous(word_size), "attempt_allocation_humongous() "
1035 "should only be called for humongous allocations");
1036
1037 // Humongous objects can exhaust the heap quickly, so we should check if we
1038 // need to start a marking cycle at each humongous object allocation. We do
1039 // the check before we do the actual allocation. The reason for doing it
1040 // before the allocation is that we avoid having to keep track of the newly
1041 // allocated memory while we do a GC.
1042 if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation",
1043 word_size)) {
1044 collect(GCCause::_g1_humongous_allocation);
1045 }
1046
1047 // We will loop until a) we manage to successfully perform the
1048 // allocation or b) we successfully schedule a collection which
1049 // fails to perform the allocation. b) is the only case when we'll
1050 // return NULL.
1051 HeapWord* result = NULL;
1052 for (int try_count = 1; /* we'll return */; try_count += 1) {
1053 bool should_try_gc;
1054 unsigned int gc_count_before;
1055
1056 {
1057 MutexLockerEx x(Heap_lock);
1058
1059 // Given that humongous objects are not allocated in young
1060 // regions, we'll first try to do the allocation without doing a
1061 // collection hoping that there's enough space in the heap.
1062 result = humongous_obj_allocate(word_size);
1063 if (result != NULL) {
1064 return result;
1065 }
1066
1067 if (GC_locker::is_active_and_needs_gc()) {
1068 should_try_gc = false;
1069 } else {
1070 // The GCLocker may not be active but the GCLocker initiated
1071 // GC may not yet have been performed (GCLocker::needs_gc()
1072 // returns true). In this case we do not try this GC and
1073 // wait until the GCLocker initiated GC is performed, and
1074 // then retry the allocation.
1075 if (GC_locker::needs_gc()) {
1076 should_try_gc = false;
1077 } else {
1078 // Read the GC count while still holding the Heap_lock.
1079 gc_count_before = total_collections();
1080 should_try_gc = true;
1081 }
1082 }
1083 }
1084
1085 if (should_try_gc) {
1086 // If we failed to allocate the humongous object, we should try to
1087 // do a collection pause (if we're allowed) in case it reclaims
1088 // enough space for the allocation to succeed after the pause.
1089
1090 bool succeeded;
1091 result = do_collection_pause(word_size, gc_count_before, &succeeded);
1092 if (result != NULL) {
1093 assert(succeeded, "only way to get back a non-NULL result");
1094 return result;
1095 }
1096
1097 if (succeeded) {
1098 // If we get here we successfully scheduled a collection which
1099 // failed to allocate. No point in trying to allocate
1100 // further. We'll just return NULL.
1101 MutexLockerEx x(Heap_lock);
1102 *gc_count_before_ret = total_collections();
1103 return NULL;
1104 }
1105 } else {
1106 // The GCLocker is either active or the GCLocker initiated
1107 // GC has not yet been performed. Stall until it is and
1108 // then retry the allocation.
1109 GC_locker::stall_until_clear();
1110 }
1111
1112 // We can reach here if we were unsuccessul in scheduling a
1113 // collection (because another thread beat us to it) or if we were
1114 // stalled due to the GC locker. In either can we should retry the
1115 // allocation attempt in case another thread successfully
1116 // performed a collection and reclaimed enough space. Give a
1117 // warning if we seem to be looping forever.
1118
1119 if ((QueuedAllocationWarningCount > 0) &&
1120 (try_count % QueuedAllocationWarningCount == 0)) {
1121 warning("G1CollectedHeap::attempt_allocation_humongous() "
1122 "retries %d times", try_count);
1123 }
1124 }
1125
1126 ShouldNotReachHere();
1127 return NULL;
1128 }
1129
1130 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
1131 bool expect_null_mutator_alloc_region) {
1132 assert_at_safepoint(true /* should_be_vm_thread */);
1133 assert(_mutator_alloc_region.get() == NULL ||
1134 !expect_null_mutator_alloc_region,
1135 "the current alloc region was unexpectedly found to be non-NULL");
1136
1137 if (!isHumongous(word_size)) {
1138 return _mutator_alloc_region.attempt_allocation_locked(word_size,
1139 false /* bot_updates */);
1140 } else {
1141 HeapWord* result = humongous_obj_allocate(word_size);
1142 if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) {
1143 g1_policy()->set_initiate_conc_mark_if_possible();
1144 }
1145 return result;
1146 }
1147
1148 ShouldNotReachHere();
1149 }
1150
1151 class PostMCRemSetClearClosure: public HeapRegionClosure {
1152 ModRefBarrierSet* _mr_bs;
1153 public:
1154 PostMCRemSetClearClosure(ModRefBarrierSet* mr_bs) : _mr_bs(mr_bs) {}
1155 bool doHeapRegion(HeapRegion* r) {
1156 r->reset_gc_time_stamp();
1157 if (r->continuesHumongous())
1158 return false;
1159 HeapRegionRemSet* hrrs = r->rem_set();
1160 if (hrrs != NULL) hrrs->clear();
1161 // You might think here that we could clear just the cards
1162 // corresponding to the used region. But no: if we leave a dirty card
1163 // in a region we might allocate into, then it would prevent that card
1164 // from being enqueued, and cause it to be missed.
1165 // Re: the performance cost: we shouldn't be doing full GC anyway!
1166 _mr_bs->clear(MemRegion(r->bottom(), r->end()));
1167 return false;
1168 }
1169 };
1170
1171
1172 class PostMCRemSetInvalidateClosure: public HeapRegionClosure {
1173 ModRefBarrierSet* _mr_bs;
1174 public:
1175 PostMCRemSetInvalidateClosure(ModRefBarrierSet* mr_bs) : _mr_bs(mr_bs) {}
1176 bool doHeapRegion(HeapRegion* r) {
1177 if (r->continuesHumongous()) return false;
1178 if (r->used_region().word_size() != 0) {
1179 _mr_bs->invalidate(r->used_region(), true /*whole heap*/);
1180 }
1181 return false;
1182 }
1183 };
1184
1185 class RebuildRSOutOfRegionClosure: public HeapRegionClosure {
1186 G1CollectedHeap* _g1h;
1187 UpdateRSOopClosure _cl;
1188 int _worker_i;
1189 public:
1190 RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, int worker_i = 0) :
1191 _cl(g1->g1_rem_set(), worker_i),
1192 _worker_i(worker_i),
1193 _g1h(g1)
1194 { }
1195
1196 bool doHeapRegion(HeapRegion* r) {
1197 if (!r->continuesHumongous()) {
1198 _cl.set_from(r);
1199 r->oop_iterate(&_cl);
1200 }
1201 return false;
1202 }
1203 };
1204
1205 class ParRebuildRSTask: public AbstractGangTask {
1206 G1CollectedHeap* _g1;
1207 public:
1208 ParRebuildRSTask(G1CollectedHeap* g1)
1209 : AbstractGangTask("ParRebuildRSTask"),
1210 _g1(g1)
1211 { }
1212
1213 void work(uint worker_id) {
1214 RebuildRSOutOfRegionClosure rebuild_rs(_g1, worker_id);
1215 _g1->heap_region_par_iterate_chunked(&rebuild_rs, worker_id,
1216 _g1->workers()->active_workers(),
1217 HeapRegion::RebuildRSClaimValue);
1218 }
1219 };
1220
1221 class PostCompactionPrinterClosure: public HeapRegionClosure {
1222 private:
1223 G1HRPrinter* _hr_printer;
1224 public:
1225 bool doHeapRegion(HeapRegion* hr) {
1226 assert(!hr->is_young(), "not expecting to find young regions");
1227 // We only generate output for non-empty regions.
1228 if (!hr->is_empty()) {
1229 if (!hr->isHumongous()) {
1230 _hr_printer->post_compaction(hr, G1HRPrinter::Old);
1231 } else if (hr->startsHumongous()) {
1232 if (hr->capacity() == HeapRegion::GrainBytes) {
1233 // single humongous region
1234 _hr_printer->post_compaction(hr, G1HRPrinter::SingleHumongous);
1235 } else {
1236 _hr_printer->post_compaction(hr, G1HRPrinter::StartsHumongous);
1237 }
1238 } else {
1239 assert(hr->continuesHumongous(), "only way to get here");
1240 _hr_printer->post_compaction(hr, G1HRPrinter::ContinuesHumongous);
1241 }
1242 }
1243 return false;
1244 }
1245
1246 PostCompactionPrinterClosure(G1HRPrinter* hr_printer)
1247 : _hr_printer(hr_printer) { }
1248 };
1249
1250 bool G1CollectedHeap::do_collection(bool explicit_gc,
1251 bool clear_all_soft_refs,
1252 size_t word_size) {
1253 assert_at_safepoint(true /* should_be_vm_thread */);
1254
1255 if (GC_locker::check_active_before_gc()) {
1256 return false;
1257 }
1258
1259 SvcGCMarker sgcm(SvcGCMarker::FULL);
1260 ResourceMark rm;
1261
1262 print_heap_before_gc();
1263
1264 HRSPhaseSetter x(HRSPhaseFullGC);
1265 verify_region_sets_optional();
1266
1267 const bool do_clear_all_soft_refs = clear_all_soft_refs ||
1268 collector_policy()->should_clear_all_soft_refs();
1269
1270 ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy());
1271
1272 {
1273 IsGCActiveMark x;
1274
1275 // Timing
1276 assert(gc_cause() != GCCause::_java_lang_system_gc || explicit_gc, "invariant");
1277 gclog_or_tty->date_stamp(G1Log::fine() && PrintGCDateStamps);
1278 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
1279
1280 TraceTime t(GCCauseString("Full GC", gc_cause()), G1Log::fine(), true, gclog_or_tty);
1281 TraceCollectorStats tcs(g1mm()->full_collection_counters());
1282 TraceMemoryManagerStats tms(true /* fullGC */, gc_cause());
1283
1284 double start = os::elapsedTime();
1285 g1_policy()->record_full_collection_start();
1286
1287 // Note: When we have a more flexible GC logging framework that
1288 // allows us to add optional attributes to a GC log record we
1289 // could consider timing and reporting how long we wait in the
1290 // following two methods.
1291 wait_while_free_regions_coming();
1292 // If we start the compaction before the CM threads finish
1293 // scanning the root regions we might trip them over as we'll
1294 // be moving objects / updating references. So let's wait until
1295 // they are done. By telling them to abort, they should complete
1296 // early.
1297 _cm->root_regions()->abort();
1298 _cm->root_regions()->wait_until_scan_finished();
1299 append_secondary_free_list_if_not_empty_with_lock();
1300
1301 gc_prologue(true);
1302 increment_total_collections(true /* full gc */);
1303 increment_old_marking_cycles_started();
1304
1305 size_t g1h_prev_used = used();
1306 assert(used() == recalculate_used(), "Should be equal");
1307
1308 if (VerifyBeforeGC && total_collections() >= VerifyGCStartAt) {
1309 HandleMark hm; // Discard invalid handles created during verification
1310 gclog_or_tty->print(" VerifyBeforeGC:");
1311 prepare_for_verify();
1312 Universe::verify(/* silent */ false,
1313 /* option */ VerifyOption_G1UsePrevMarking);
1314
1315 }
1316 pre_full_gc_dump();
1317
1318 COMPILER2_PRESENT(DerivedPointerTable::clear());
1319
1320 // Disable discovery and empty the discovered lists
1321 // for the CM ref processor.
1322 ref_processor_cm()->disable_discovery();
1323 ref_processor_cm()->abandon_partial_discovery();
1324 ref_processor_cm()->verify_no_references_recorded();
1325
1326 // Abandon current iterations of concurrent marking and concurrent
1327 // refinement, if any are in progress. We have to do this before
1328 // wait_until_scan_finished() below.
1329 concurrent_mark()->abort();
1330
1331 // Make sure we'll choose a new allocation region afterwards.
1332 release_mutator_alloc_region();
1333 abandon_gc_alloc_regions();
1334 g1_rem_set()->cleanupHRRS();
1335
1336 // We should call this after we retire any currently active alloc
1337 // regions so that all the ALLOC / RETIRE events are generated
1338 // before the start GC event.
1339 _hr_printer.start_gc(true /* full */, (size_t) total_collections());
1340
1341 // We may have added regions to the current incremental collection
1342 // set between the last GC or pause and now. We need to clear the
1343 // incremental collection set and then start rebuilding it afresh
1344 // after this full GC.
1345 abandon_collection_set(g1_policy()->inc_cset_head());
1346 g1_policy()->clear_incremental_cset();
1347 g1_policy()->stop_incremental_cset_building();
1348
1349 tear_down_region_sets(false /* free_list_only */);
1350 g1_policy()->set_gcs_are_young(true);
1351
1352 // See the comments in g1CollectedHeap.hpp and
1353 // G1CollectedHeap::ref_processing_init() about
1354 // how reference processing currently works in G1.
1355
1356 // Temporarily make discovery by the STW ref processor single threaded (non-MT).
1357 ReferenceProcessorMTDiscoveryMutator stw_rp_disc_ser(ref_processor_stw(), false);
1358
1359 // Temporarily clear the STW ref processor's _is_alive_non_header field.
1360 ReferenceProcessorIsAliveMutator stw_rp_is_alive_null(ref_processor_stw(), NULL);
1361
1362 ref_processor_stw()->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/);
1363 ref_processor_stw()->setup_policy(do_clear_all_soft_refs);
1364
1365 // Do collection work
1366 {
1367 HandleMark hm; // Discard invalid handles created during gc
1368 G1MarkSweep::invoke_at_safepoint(ref_processor_stw(), do_clear_all_soft_refs);
1369 }
1370
1371 assert(free_regions() == 0, "we should not have added any free regions");
1372 rebuild_region_sets(false /* free_list_only */);
1373
1374 // Enqueue any discovered reference objects that have
1375 // not been removed from the discovered lists.
1376 ref_processor_stw()->enqueue_discovered_references();
1377
1378 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
1379
1380 MemoryService::track_memory_usage();
1381
1382 if (VerifyAfterGC && total_collections() >= VerifyGCStartAt) {
1383 HandleMark hm; // Discard invalid handles created during verification
1384 gclog_or_tty->print(" VerifyAfterGC:");
1385 prepare_for_verify();
1386 Universe::verify(/* silent */ false,
1387 /* option */ VerifyOption_G1UsePrevMarking);
1388
1389 }
1390
1391 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
1392 ref_processor_stw()->verify_no_references_recorded();
1393
1394 // Note: since we've just done a full GC, concurrent
1395 // marking is no longer active. Therefore we need not
1396 // re-enable reference discovery for the CM ref processor.
1397 // That will be done at the start of the next marking cycle.
1398 assert(!ref_processor_cm()->discovery_enabled(), "Postcondition");
1399 ref_processor_cm()->verify_no_references_recorded();
1400
1401 reset_gc_time_stamp();
1402 // Since everything potentially moved, we will clear all remembered
1403 // sets, and clear all cards. Later we will rebuild remebered
1404 // sets. We will also reset the GC time stamps of the regions.
1405 PostMCRemSetClearClosure rs_clear(mr_bs());
1406 heap_region_iterate(&rs_clear);
1407
1408 // Resize the heap if necessary.
1409 resize_if_necessary_after_full_collection(explicit_gc ? 0 : word_size);
1410
1411 if (_hr_printer.is_active()) {
1412 // We should do this after we potentially resize the heap so
1413 // that all the COMMIT / UNCOMMIT events are generated before
1414 // the end GC event.
1415
1416 PostCompactionPrinterClosure cl(hr_printer());
1417 heap_region_iterate(&cl);
1418
1419 _hr_printer.end_gc(true /* full */, (size_t) total_collections());
1420 }
1421
1422 if (_cg1r->use_cache()) {
1423 _cg1r->clear_and_record_card_counts();
1424 _cg1r->clear_hot_cache();
1425 }
1426
1427 // Rebuild remembered sets of all regions.
1428 if (G1CollectedHeap::use_parallel_gc_threads()) {
1429 uint n_workers =
1430 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
1431 workers()->active_workers(),
1432 Threads::number_of_non_daemon_threads());
1433 assert(UseDynamicNumberOfGCThreads ||
1434 n_workers == workers()->total_workers(),
1435 "If not dynamic should be using all the workers");
1436 workers()->set_active_workers(n_workers);
1437 // Set parallel threads in the heap (_n_par_threads) only
1438 // before a parallel phase and always reset it to 0 after
1439 // the phase so that the number of parallel threads does
1440 // no get carried forward to a serial phase where there
1441 // may be code that is "possibly_parallel".
1442 set_par_threads(n_workers);
1443
1444 ParRebuildRSTask rebuild_rs_task(this);
1445 assert(check_heap_region_claim_values(
1446 HeapRegion::InitialClaimValue), "sanity check");
1447 assert(UseDynamicNumberOfGCThreads ||
1448 workers()->active_workers() == workers()->total_workers(),
1449 "Unless dynamic should use total workers");
1450 // Use the most recent number of active workers
1451 assert(workers()->active_workers() > 0,
1452 "Active workers not properly set");
1453 set_par_threads(workers()->active_workers());
1454 workers()->run_task(&rebuild_rs_task);
1455 set_par_threads(0);
1456 assert(check_heap_region_claim_values(
1457 HeapRegion::RebuildRSClaimValue), "sanity check");
1458 reset_heap_region_claim_values();
1459 } else {
1460 RebuildRSOutOfRegionClosure rebuild_rs(this);
1461 heap_region_iterate(&rebuild_rs);
1462 }
1463
1464 if (G1Log::fine()) {
1465 print_size_transition(gclog_or_tty, g1h_prev_used, used(), capacity());
1466 }
1467
1468 if (true) { // FIXME
1469 // Ask the permanent generation to adjust size for full collections
1470 perm()->compute_new_size();
1471 }
1472
1473 // Start a new incremental collection set for the next pause
1474 assert(g1_policy()->collection_set() == NULL, "must be");
1475 g1_policy()->start_incremental_cset_building();
1476
1477 // Clear the _cset_fast_test bitmap in anticipation of adding
1478 // regions to the incremental collection set for the next
1479 // evacuation pause.
1480 clear_cset_fast_test();
1481
1482 init_mutator_alloc_region();
1483
1484 double end = os::elapsedTime();
1485 g1_policy()->record_full_collection_end();
1486
1487 #ifdef TRACESPINNING
1488 ParallelTaskTerminator::print_termination_counts();
1489 #endif
1490
1491 gc_epilogue(true);
1492
1493 // Discard all rset updates
1494 JavaThread::dirty_card_queue_set().abandon_logs();
1495 assert(!G1DeferredRSUpdate
1496 || (G1DeferredRSUpdate && (dirty_card_queue_set().completed_buffers_num() == 0)), "Should not be any");
1497
1498 _young_list->reset_sampled_info();
1499 // At this point there should be no regions in the
1500 // entire heap tagged as young.
1501 assert( check_young_list_empty(true /* check_heap */),
1502 "young list should be empty at this point");
1503
1504 // Update the number of full collections that have been completed.
1505 increment_old_marking_cycles_completed(false /* concurrent */);
1506
1507 _hrs.verify_optional();
1508 verify_region_sets_optional();
1509
1510 print_heap_after_gc();
1511
1512 // We must call G1MonitoringSupport::update_sizes() in the same scoping level
1513 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
1514 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
1515 // before any GC notifications are raised.
1516 g1mm()->update_sizes();
1517 }
1518
1519 post_full_gc_dump();
1520
1521 return true;
1522 }
1523
1524 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
1525 // do_collection() will return whether it succeeded in performing
1526 // the GC. Currently, there is no facility on the
1527 // do_full_collection() API to notify the caller than the collection
1528 // did not succeed (e.g., because it was locked out by the GC
1529 // locker). So, right now, we'll ignore the return value.
1530 bool dummy = do_collection(true, /* explicit_gc */
1531 clear_all_soft_refs,
1532 0 /* word_size */);
1533 }
1534
1535 // This code is mostly copied from TenuredGeneration.
1536 void
1537 G1CollectedHeap::
1538 resize_if_necessary_after_full_collection(size_t word_size) {
1539 assert(MinHeapFreeRatio <= MaxHeapFreeRatio, "sanity check");
1540
1541 // Include the current allocation, if any, and bytes that will be
1542 // pre-allocated to support collections, as "used".
1543 const size_t used_after_gc = used();
1544 const size_t capacity_after_gc = capacity();
1545 const size_t free_after_gc = capacity_after_gc - used_after_gc;
1546
1547 // This is enforced in arguments.cpp.
1548 assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
1549 "otherwise the code below doesn't make sense");
1550
1551 // We don't have floating point command-line arguments
1552 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
1553 const double maximum_used_percentage = 1.0 - minimum_free_percentage;
1554 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
1555 const double minimum_used_percentage = 1.0 - maximum_free_percentage;
1556
1557 const size_t min_heap_size = collector_policy()->min_heap_byte_size();
1558 const size_t max_heap_size = collector_policy()->max_heap_byte_size();
1559
1560 // We have to be careful here as these two calculations can overflow
1561 // 32-bit size_t's.
1562 double used_after_gc_d = (double) used_after_gc;
1563 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
1564 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
1565
1566 // Let's make sure that they are both under the max heap size, which
1567 // by default will make them fit into a size_t.
1568 double desired_capacity_upper_bound = (double) max_heap_size;
1569 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
1570 desired_capacity_upper_bound);
1571 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
1572 desired_capacity_upper_bound);
1573
1574 // We can now safely turn them into size_t's.
1575 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
1576 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
1577
1578 // This assert only makes sense here, before we adjust them
1579 // with respect to the min and max heap size.
1580 assert(minimum_desired_capacity <= maximum_desired_capacity,
1581 err_msg("minimum_desired_capacity = "SIZE_FORMAT", "
1582 "maximum_desired_capacity = "SIZE_FORMAT,
1583 minimum_desired_capacity, maximum_desired_capacity));
1584
1585 // Should not be greater than the heap max size. No need to adjust
1586 // it with respect to the heap min size as it's a lower bound (i.e.,
1587 // we'll try to make the capacity larger than it, not smaller).
1588 minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size);
1589 // Should not be less than the heap min size. No need to adjust it
1590 // with respect to the heap max size as it's an upper bound (i.e.,
1591 // we'll try to make the capacity smaller than it, not greater).
1592 maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size);
1593
1594 if (capacity_after_gc < minimum_desired_capacity) {
1595 // Don't expand unless it's significant
1596 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
1597 ergo_verbose4(ErgoHeapSizing,
1598 "attempt heap expansion",
1599 ergo_format_reason("capacity lower than "
1600 "min desired capacity after Full GC")
1601 ergo_format_byte("capacity")
1602 ergo_format_byte("occupancy")
1603 ergo_format_byte_perc("min desired capacity"),
1604 capacity_after_gc, used_after_gc,
1605 minimum_desired_capacity, (double) MinHeapFreeRatio);
1606 expand(expand_bytes);
1607
1608 // No expansion, now see if we want to shrink
1609 } else if (capacity_after_gc > maximum_desired_capacity) {
1610 // Capacity too large, compute shrinking size
1611 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
1612 ergo_verbose4(ErgoHeapSizing,
1613 "attempt heap shrinking",
1614 ergo_format_reason("capacity higher than "
1615 "max desired capacity after Full GC")
1616 ergo_format_byte("capacity")
1617 ergo_format_byte("occupancy")
1618 ergo_format_byte_perc("max desired capacity"),
1619 capacity_after_gc, used_after_gc,
1620 maximum_desired_capacity, (double) MaxHeapFreeRatio);
1621 shrink(shrink_bytes);
1622 }
1623 }
1624
1625
1626 HeapWord*
1627 G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
1628 bool* succeeded) {
1629 assert_at_safepoint(true /* should_be_vm_thread */);
1630
1631 *succeeded = true;
1632 // Let's attempt the allocation first.
1633 HeapWord* result =
1634 attempt_allocation_at_safepoint(word_size,
1635 false /* expect_null_mutator_alloc_region */);
1636 if (result != NULL) {
1637 assert(*succeeded, "sanity");
1638 return result;
1639 }
1640
1641 // In a G1 heap, we're supposed to keep allocation from failing by
1642 // incremental pauses. Therefore, at least for now, we'll favor
1643 // expansion over collection. (This might change in the future if we can
1644 // do something smarter than full collection to satisfy a failed alloc.)
1645 result = expand_and_allocate(word_size);
1646 if (result != NULL) {
1647 assert(*succeeded, "sanity");
1648 return result;
1649 }
1650
1651 // Expansion didn't work, we'll try to do a Full GC.
1652 bool gc_succeeded = do_collection(false, /* explicit_gc */
1653 false, /* clear_all_soft_refs */
1654 word_size);
1655 if (!gc_succeeded) {
1656 *succeeded = false;
1657 return NULL;
1658 }
1659
1660 // Retry the allocation
1661 result = attempt_allocation_at_safepoint(word_size,
1662 true /* expect_null_mutator_alloc_region */);
1663 if (result != NULL) {
1664 assert(*succeeded, "sanity");
1665 return result;
1666 }
1667
1668 // Then, try a Full GC that will collect all soft references.
1669 gc_succeeded = do_collection(false, /* explicit_gc */
1670 true, /* clear_all_soft_refs */
1671 word_size);
1672 if (!gc_succeeded) {
1673 *succeeded = false;
1674 return NULL;
1675 }
1676
1677 // Retry the allocation once more
1678 result = attempt_allocation_at_safepoint(word_size,
1679 true /* expect_null_mutator_alloc_region */);
1680 if (result != NULL) {
1681 assert(*succeeded, "sanity");
1682 return result;
1683 }
1684
1685 assert(!collector_policy()->should_clear_all_soft_refs(),
1686 "Flag should have been handled and cleared prior to this point");
1687
1688 // What else? We might try synchronous finalization later. If the total
1689 // space available is large enough for the allocation, then a more
1690 // complete compaction phase than we've tried so far might be
1691 // appropriate.
1692 assert(*succeeded, "sanity");
1693 return NULL;
1694 }
1695
1696 // Attempting to expand the heap sufficiently
1697 // to support an allocation of the given "word_size". If
1698 // successful, perform the allocation and return the address of the
1699 // allocated block, or else "NULL".
1700
1701 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size) {
1702 assert_at_safepoint(true /* should_be_vm_thread */);
1703
1704 verify_region_sets_optional();
1705
1706 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
1707 ergo_verbose1(ErgoHeapSizing,
1708 "attempt heap expansion",
1709 ergo_format_reason("allocation request failed")
1710 ergo_format_byte("allocation request"),
1711 word_size * HeapWordSize);
1712 if (expand(expand_bytes)) {
1713 _hrs.verify_optional();
1714 verify_region_sets_optional();
1715 return attempt_allocation_at_safepoint(word_size,
1716 false /* expect_null_mutator_alloc_region */);
1717 }
1718 return NULL;
1719 }
1720
1721 void G1CollectedHeap::update_committed_space(HeapWord* old_end,
1722 HeapWord* new_end) {
1723 assert(old_end != new_end, "don't call this otherwise");
1724 assert((HeapWord*) _g1_storage.high() == new_end, "invariant");
1725
1726 // Update the committed mem region.
1727 _g1_committed.set_end(new_end);
1728 // Tell the card table about the update.
1729 Universe::heap()->barrier_set()->resize_covered_region(_g1_committed);
1730 // Tell the BOT about the update.
1731 _bot_shared->resize(_g1_committed.word_size());
1732 }
1733
1734 bool G1CollectedHeap::expand(size_t expand_bytes) {
1735 size_t old_mem_size = _g1_storage.committed_size();
1736 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
1737 aligned_expand_bytes = align_size_up(aligned_expand_bytes,
1738 HeapRegion::GrainBytes);
1739 ergo_verbose2(ErgoHeapSizing,
1740 "expand the heap",
1741 ergo_format_byte("requested expansion amount")
1742 ergo_format_byte("attempted expansion amount"),
1743 expand_bytes, aligned_expand_bytes);
1744
1745 // First commit the memory.
1746 HeapWord* old_end = (HeapWord*) _g1_storage.high();
1747 bool successful = _g1_storage.expand_by(aligned_expand_bytes);
1748 if (successful) {
1749 // Then propagate this update to the necessary data structures.
1750 HeapWord* new_end = (HeapWord*) _g1_storage.high();
1751 update_committed_space(old_end, new_end);
1752
1753 FreeRegionList expansion_list("Local Expansion List");
1754 MemRegion mr = _hrs.expand_by(old_end, new_end, &expansion_list);
1755 assert(mr.start() == old_end, "post-condition");
1756 // mr might be a smaller region than what was requested if
1757 // expand_by() was unable to allocate the HeapRegion instances
1758 assert(mr.end() <= new_end, "post-condition");
1759
1760 size_t actual_expand_bytes = mr.byte_size();
1761 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
1762 assert(actual_expand_bytes == expansion_list.total_capacity_bytes(),
1763 "post-condition");
1764 if (actual_expand_bytes < aligned_expand_bytes) {
1765 // We could not expand _hrs to the desired size. In this case we
1766 // need to shrink the committed space accordingly.
1767 assert(mr.end() < new_end, "invariant");
1768
1769 size_t diff_bytes = aligned_expand_bytes - actual_expand_bytes;
1770 // First uncommit the memory.
1771 _g1_storage.shrink_by(diff_bytes);
1772 // Then propagate this update to the necessary data structures.
1773 update_committed_space(new_end, mr.end());
1774 }
1775 _free_list.add_as_tail(&expansion_list);
1776
1777 if (_hr_printer.is_active()) {
1778 HeapWord* curr = mr.start();
1779 while (curr < mr.end()) {
1780 HeapWord* curr_end = curr + HeapRegion::GrainWords;
1781 _hr_printer.commit(curr, curr_end);
1782 curr = curr_end;
1783 }
1784 assert(curr == mr.end(), "post-condition");
1785 }
1786 g1_policy()->record_new_heap_size(n_regions());
1787 } else {
1788 ergo_verbose0(ErgoHeapSizing,
1789 "did not expand the heap",
1790 ergo_format_reason("heap expansion operation failed"));
1791 // The expansion of the virtual storage space was unsuccessful.
1792 // Let's see if it was because we ran out of swap.
1793 if (G1ExitOnExpansionFailure &&
1794 _g1_storage.uncommitted_size() >= aligned_expand_bytes) {
1795 // We had head room...
1796 vm_exit_out_of_memory(aligned_expand_bytes, "G1 heap expansion");
1797 }
1798 }
1799 return successful;
1800 }
1801
1802 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
1803 size_t old_mem_size = _g1_storage.committed_size();
1804 size_t aligned_shrink_bytes =
1805 ReservedSpace::page_align_size_down(shrink_bytes);
1806 aligned_shrink_bytes = align_size_down(aligned_shrink_bytes,
1807 HeapRegion::GrainBytes);
1808 uint num_regions_deleted = 0;
1809 MemRegion mr = _hrs.shrink_by(aligned_shrink_bytes, &num_regions_deleted);
1810 HeapWord* old_end = (HeapWord*) _g1_storage.high();
1811 assert(mr.end() == old_end, "post-condition");
1812
1813 ergo_verbose3(ErgoHeapSizing,
1814 "shrink the heap",
1815 ergo_format_byte("requested shrinking amount")
1816 ergo_format_byte("aligned shrinking amount")
1817 ergo_format_byte("attempted shrinking amount"),
1818 shrink_bytes, aligned_shrink_bytes, mr.byte_size());
1819 if (mr.byte_size() > 0) {
1820 if (_hr_printer.is_active()) {
1821 HeapWord* curr = mr.end();
1822 while (curr > mr.start()) {
1823 HeapWord* curr_end = curr;
1824 curr -= HeapRegion::GrainWords;
1825 _hr_printer.uncommit(curr, curr_end);
1826 }
1827 assert(curr == mr.start(), "post-condition");
1828 }
1829
1830 _g1_storage.shrink_by(mr.byte_size());
1831 HeapWord* new_end = (HeapWord*) _g1_storage.high();
1832 assert(mr.start() == new_end, "post-condition");
1833
1834 _expansion_regions += num_regions_deleted;
1835 update_committed_space(old_end, new_end);
1836 HeapRegionRemSet::shrink_heap(n_regions());
1837 g1_policy()->record_new_heap_size(n_regions());
1838 } else {
1839 ergo_verbose0(ErgoHeapSizing,
1840 "did not shrink the heap",
1841 ergo_format_reason("heap shrinking operation failed"));
1842 }
1843 }
1844
1845 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1846 verify_region_sets_optional();
1847
1848 // We should only reach here at the end of a Full GC which means we
1849 // should not not be holding to any GC alloc regions. The method
1850 // below will make sure of that and do any remaining clean up.
1851 abandon_gc_alloc_regions();
1852
1853 // Instead of tearing down / rebuilding the free lists here, we
1854 // could instead use the remove_all_pending() method on free_list to
1855 // remove only the ones that we need to remove.
1856 tear_down_region_sets(true /* free_list_only */);
1857 shrink_helper(shrink_bytes);
1858 rebuild_region_sets(true /* free_list_only */);
1859
1860 _hrs.verify_optional();
1861 verify_region_sets_optional();
1862 }
1863
1864 // Public methods.
1865
1866 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away
1867 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
1868 #endif // _MSC_VER
1869
1870
1871 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* policy_) :
1872 SharedHeap(policy_),
1873 _g1_policy(policy_),
1874 _dirty_card_queue_set(false),
1875 _into_cset_dirty_card_queue_set(false),
1876 _is_alive_closure_cm(this),
1877 _is_alive_closure_stw(this),
1878 _ref_processor_cm(NULL),
1879 _ref_processor_stw(NULL),
1880 _process_strong_tasks(new SubTasksDone(G1H_PS_NumElements)),
1881 _bot_shared(NULL),
1882 _objs_with_preserved_marks(NULL), _preserved_marks_of_objs(NULL),
1883 _evac_failure_scan_stack(NULL) ,
1884 _mark_in_progress(false),
1885 _cg1r(NULL), _summary_bytes_used(0),
1886 _g1mm(NULL),
1887 _refine_cte_cl(NULL),
1888 _full_collection(false),
1889 _free_list("Master Free List"),
1890 _secondary_free_list("Secondary Free List"),
1891 _old_set("Old Set"),
1892 _humongous_set("Master Humongous Set"),
1893 _free_regions_coming(false),
1894 _young_list(new YoungList(this)),
1895 _gc_time_stamp(0),
1896 _retained_old_gc_alloc_region(NULL),
1897 _expand_heap_after_alloc_failure(true),
1898 _surviving_young_words(NULL),
1899 _old_marking_cycles_started(0),
1900 _old_marking_cycles_completed(0),
1901 _in_cset_fast_test(NULL),
1902 _in_cset_fast_test_base(NULL),
1903 _dirty_cards_region_list(NULL),
1904 _worker_cset_start_region(NULL),
1905 _worker_cset_start_region_time_stamp(NULL) {
1906 _g1h = this; // To catch bugs.
1907 if (_process_strong_tasks == NULL || !_process_strong_tasks->valid()) {
1908 vm_exit_during_initialization("Failed necessary allocation.");
1909 }
1910
1911 _humongous_object_threshold_in_words = HeapRegion::GrainWords / 2;
1912
1913 int n_queues = MAX2((int)ParallelGCThreads, 1);
1914 _task_queues = new RefToScanQueueSet(n_queues);
1915
1916 int n_rem_sets = HeapRegionRemSet::num_par_rem_sets();
1917 assert(n_rem_sets > 0, "Invariant.");
1918
1919 HeapRegionRemSetIterator** iter_arr =
1920 NEW_C_HEAP_ARRAY(HeapRegionRemSetIterator*, n_queues, mtGC);
1921 for (int i = 0; i < n_queues; i++) {
1922 iter_arr[i] = new HeapRegionRemSetIterator();
1923 }
1924 _rem_set_iterator = iter_arr;
1925
1926 _worker_cset_start_region = NEW_C_HEAP_ARRAY(HeapRegion*, n_queues, mtGC);
1927 _worker_cset_start_region_time_stamp = NEW_C_HEAP_ARRAY(unsigned int, n_queues, mtGC);
1928
1929 for (int i = 0; i < n_queues; i++) {
1930 RefToScanQueue* q = new RefToScanQueue();
1931 q->initialize();
1932 _task_queues->register_queue(i, q);
1933 }
1934
1935 clear_cset_start_regions();
1936
1937 guarantee(_task_queues != NULL, "task_queues allocation failure.");
1938 }
1939
1940 jint G1CollectedHeap::initialize() {
1941 CollectedHeap::pre_initialize();
1942 os::enable_vtime();
1943
1944 G1Log::init();
1945
1946 // Necessary to satisfy locking discipline assertions.
1947
1948 MutexLocker x(Heap_lock);
1949
1950 // We have to initialize the printer before committing the heap, as
1951 // it will be used then.
1952 _hr_printer.set_active(G1PrintHeapRegions);
1953
1954 // While there are no constraints in the GC code that HeapWordSize
1955 // be any particular value, there are multiple other areas in the
1956 // system which believe this to be true (e.g. oop->object_size in some
1957 // cases incorrectly returns the size in wordSize units rather than
1958 // HeapWordSize).
1959 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
1960
1961 size_t init_byte_size = collector_policy()->initial_heap_byte_size();
1962 size_t max_byte_size = collector_policy()->max_heap_byte_size();
1963
1964 // Ensure that the sizes are properly aligned.
1965 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
1966 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
1967
1968 _cg1r = new ConcurrentG1Refine();
1969
1970 // Reserve the maximum.
1971 PermanentGenerationSpec* pgs = collector_policy()->permanent_generation();
1972 // Includes the perm-gen.
1973
1974 // When compressed oops are enabled, the preferred heap base
1975 // is calculated by subtracting the requested size from the
1976 // 32Gb boundary and using the result as the base address for
1977 // heap reservation. If the requested size is not aligned to
1978 // HeapRegion::GrainBytes (i.e. the alignment that is passed
1979 // into the ReservedHeapSpace constructor) then the actual
1980 // base of the reserved heap may end up differing from the
1981 // address that was requested (i.e. the preferred heap base).
1982 // If this happens then we could end up using a non-optimal
1983 // compressed oops mode.
1984
1985 // Since max_byte_size is aligned to the size of a heap region (checked
1986 // above), we also need to align the perm gen size as it might not be.
1987 const size_t total_reserved = max_byte_size +
1988 align_size_up(pgs->max_size(), HeapRegion::GrainBytes);
1989 Universe::check_alignment(total_reserved, HeapRegion::GrainBytes, "g1 heap and perm");
1990
1991 char* addr = Universe::preferred_heap_base(total_reserved, Universe::UnscaledNarrowOop);
1992
1993 ReservedHeapSpace heap_rs(total_reserved, HeapRegion::GrainBytes,
1994 UseLargePages, addr);
1995
1996 if (UseCompressedOops) {
1997 if (addr != NULL && !heap_rs.is_reserved()) {
1998 // Failed to reserve at specified address - the requested memory
1999 // region is taken already, for example, by 'java' launcher.
2000 // Try again to reserver heap higher.
2001 addr = Universe::preferred_heap_base(total_reserved, Universe::ZeroBasedNarrowOop);
2002
2003 ReservedHeapSpace heap_rs0(total_reserved, HeapRegion::GrainBytes,
2004 UseLargePages, addr);
2005
2006 if (addr != NULL && !heap_rs0.is_reserved()) {
2007 // Failed to reserve at specified address again - give up.
2008 addr = Universe::preferred_heap_base(total_reserved, Universe::HeapBasedNarrowOop);
2009 assert(addr == NULL, "");
2010
2011 ReservedHeapSpace heap_rs1(total_reserved, HeapRegion::GrainBytes,
2012 UseLargePages, addr);
2013 heap_rs = heap_rs1;
2014 } else {
2015 heap_rs = heap_rs0;
2016 }
2017 }
2018 }
2019
2020 if (!heap_rs.is_reserved()) {
2021 vm_exit_during_initialization("Could not reserve enough space for object heap");
2022 return JNI_ENOMEM;
2023 }
2024
2025 // It is important to do this in a way such that concurrent readers can't
2026 // temporarily think somethings in the heap. (I've actually seen this
2027 // happen in asserts: DLD.)
2028 _reserved.set_word_size(0);
2029 _reserved.set_start((HeapWord*)heap_rs.base());
2030 _reserved.set_end((HeapWord*)(heap_rs.base() + heap_rs.size()));
2031
2032 _expansion_regions = (uint) (max_byte_size / HeapRegion::GrainBytes);
2033
2034 // Create the gen rem set (and barrier set) for the entire reserved region.
2035 _rem_set = collector_policy()->create_rem_set(_reserved, 2);
2036 set_barrier_set(rem_set()->bs());
2037 if (barrier_set()->is_a(BarrierSet::ModRef)) {
2038 _mr_bs = (ModRefBarrierSet*)_barrier_set;
2039 } else {
2040 vm_exit_during_initialization("G1 requires a mod ref bs.");
2041 return JNI_ENOMEM;
2042 }
2043
2044 // Also create a G1 rem set.
2045 if (mr_bs()->is_a(BarrierSet::CardTableModRef)) {
2046 _g1_rem_set = new G1RemSet(this, (CardTableModRefBS*)mr_bs());
2047 } else {
2048 vm_exit_during_initialization("G1 requires a cardtable mod ref bs.");
2049 return JNI_ENOMEM;
2050 }
2051
2052 // Carve out the G1 part of the heap.
2053
2054 ReservedSpace g1_rs = heap_rs.first_part(max_byte_size);
2055 _g1_reserved = MemRegion((HeapWord*)g1_rs.base(),
2056 g1_rs.size()/HeapWordSize);
2057 ReservedSpace perm_gen_rs = heap_rs.last_part(max_byte_size);
2058
2059 _perm_gen = pgs->init(perm_gen_rs, pgs->init_size(), rem_set());
2060
2061 _g1_storage.initialize(g1_rs, 0);
2062 _g1_committed = MemRegion((HeapWord*)_g1_storage.low(), (size_t) 0);
2063 _hrs.initialize((HeapWord*) _g1_reserved.start(),
2064 (HeapWord*) _g1_reserved.end(),
2065 _expansion_regions);
2066
2067 // 6843694 - ensure that the maximum region index can fit
2068 // in the remembered set structures.
2069 const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
2070 guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
2071
2072 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
2073 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
2074 guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
2075 "too many cards per region");
2076
2077 HeapRegionSet::set_unrealistically_long_length(max_regions() + 1);
2078
2079 _bot_shared = new G1BlockOffsetSharedArray(_reserved,
2080 heap_word_size(init_byte_size));
2081
2082 _g1h = this;
2083
2084 _in_cset_fast_test_length = max_regions();
2085 _in_cset_fast_test_base =
2086 NEW_C_HEAP_ARRAY(bool, (size_t) _in_cset_fast_test_length, mtGC);
2087
2088 // We're biasing _in_cset_fast_test to avoid subtracting the
2089 // beginning of the heap every time we want to index; basically
2090 // it's the same with what we do with the card table.
2091 _in_cset_fast_test = _in_cset_fast_test_base -
2092 ((uintx) _g1_reserved.start() >> HeapRegion::LogOfHRGrainBytes);
2093
2094 // Clear the _cset_fast_test bitmap in anticipation of adding
2095 // regions to the incremental collection set for the first
2096 // evacuation pause.
2097 clear_cset_fast_test();
2098
2099 // Create the ConcurrentMark data structure and thread.
2100 // (Must do this late, so that "max_regions" is defined.)
2101 _cm = new ConcurrentMark(heap_rs, max_regions());
2102 _cmThread = _cm->cmThread();
2103
2104 // Initialize the from_card cache structure of HeapRegionRemSet.
2105 HeapRegionRemSet::init_heap(max_regions());
2106
2107 // Now expand into the initial heap size.
2108 if (!expand(init_byte_size)) {
2109 vm_exit_during_initialization("Failed to allocate initial heap.");
2110 return JNI_ENOMEM;
2111 }
2112
2113 // Perform any initialization actions delegated to the policy.
2114 g1_policy()->init();
2115
2116 _refine_cte_cl =
2117 new RefineCardTableEntryClosure(ConcurrentG1RefineThread::sts(),
2118 g1_rem_set(),
2119 concurrent_g1_refine());
2120 JavaThread::dirty_card_queue_set().set_closure(_refine_cte_cl);
2121
2122 JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon,
2123 SATB_Q_FL_lock,
2124 G1SATBProcessCompletedThreshold,
2125 Shared_SATB_Q_lock);
2126
2127 JavaThread::dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
2128 DirtyCardQ_FL_lock,
2129 concurrent_g1_refine()->yellow_zone(),
2130 concurrent_g1_refine()->red_zone(),
2131 Shared_DirtyCardQ_lock);
2132
2133 if (G1DeferredRSUpdate) {
2134 dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
2135 DirtyCardQ_FL_lock,
2136 -1, // never trigger processing
2137 -1, // no limit on length
2138 Shared_DirtyCardQ_lock,
2139 &JavaThread::dirty_card_queue_set());
2140 }
2141
2142 // Initialize the card queue set used to hold cards containing
2143 // references into the collection set.
2144 _into_cset_dirty_card_queue_set.initialize(DirtyCardQ_CBL_mon,
2145 DirtyCardQ_FL_lock,
2146 -1, // never trigger processing
2147 -1, // no limit on length
2148 Shared_DirtyCardQ_lock,
2149 &JavaThread::dirty_card_queue_set());
2150
2151 // In case we're keeping closure specialization stats, initialize those
2152 // counts and that mechanism.
2153 SpecializationStats::clear();
2154
2155 // Do later initialization work for concurrent refinement.
2156 _cg1r->init();
2157
2158 // Here we allocate the dummy full region that is required by the
2159 // G1AllocRegion class. If we don't pass an address in the reserved
2160 // space here, lots of asserts fire.
2161
2162 HeapRegion* dummy_region = new_heap_region(0 /* index of bottom region */,
2163 _g1_reserved.start());
2164 // We'll re-use the same region whether the alloc region will
2165 // require BOT updates or not and, if it doesn't, then a non-young
2166 // region will complain that it cannot support allocations without
2167 // BOT updates. So we'll tag the dummy region as young to avoid that.
2168 dummy_region->set_young();
2169 // Make sure it's full.
2170 dummy_region->set_top(dummy_region->end());
2171 G1AllocRegion::setup(this, dummy_region);
2172
2173 init_mutator_alloc_region();
2174
2175 // Do create of the monitoring and management support so that
2176 // values in the heap have been properly initialized.
2177 _g1mm = new G1MonitoringSupport(this);
2178
2179 return JNI_OK;
2180 }
2181
2182 void G1CollectedHeap::ref_processing_init() {
2183 // Reference processing in G1 currently works as follows:
2184 //
2185 // * There are two reference processor instances. One is
2186 // used to record and process discovered references
2187 // during concurrent marking; the other is used to
2188 // record and process references during STW pauses
2189 // (both full and incremental).
2190 // * Both ref processors need to 'span' the entire heap as
2191 // the regions in the collection set may be dotted around.
2192 //
2193 // * For the concurrent marking ref processor:
2194 // * Reference discovery is enabled at initial marking.
2195 // * Reference discovery is disabled and the discovered
2196 // references processed etc during remarking.
2197 // * Reference discovery is MT (see below).
2198 // * Reference discovery requires a barrier (see below).
2199 // * Reference processing may or may not be MT
2200 // (depending on the value of ParallelRefProcEnabled
2201 // and ParallelGCThreads).
2202 // * A full GC disables reference discovery by the CM
2203 // ref processor and abandons any entries on it's
2204 // discovered lists.
2205 //
2206 // * For the STW processor:
2207 // * Non MT discovery is enabled at the start of a full GC.
2208 // * Processing and enqueueing during a full GC is non-MT.
2209 // * During a full GC, references are processed after marking.
2210 //
2211 // * Discovery (may or may not be MT) is enabled at the start
2212 // of an incremental evacuation pause.
2213 // * References are processed near the end of a STW evacuation pause.
2214 // * For both types of GC:
2215 // * Discovery is atomic - i.e. not concurrent.
2216 // * Reference discovery will not need a barrier.
2217
2218 SharedHeap::ref_processing_init();
2219 MemRegion mr = reserved_region();
2220
2221 // Concurrent Mark ref processor
2222 _ref_processor_cm =
2223 new ReferenceProcessor(mr, // span
2224 ParallelRefProcEnabled && (ParallelGCThreads > 1),
2225 // mt processing
2226 (int) ParallelGCThreads,
2227 // degree of mt processing
2228 (ParallelGCThreads > 1) || (ConcGCThreads > 1),
2229 // mt discovery
2230 (int) MAX2(ParallelGCThreads, ConcGCThreads),
2231 // degree of mt discovery
2232 false,
2233 // Reference discovery is not atomic
2234 &_is_alive_closure_cm,
2235 // is alive closure
2236 // (for efficiency/performance)
2237 true);
2238 // Setting next fields of discovered
2239 // lists requires a barrier.
2240
2241 // STW ref processor
2242 _ref_processor_stw =
2243 new ReferenceProcessor(mr, // span
2244 ParallelRefProcEnabled && (ParallelGCThreads > 1),
2245 // mt processing
2246 MAX2((int)ParallelGCThreads, 1),
2247 // degree of mt processing
2248 (ParallelGCThreads > 1),
2249 // mt discovery
2250 MAX2((int)ParallelGCThreads, 1),
2251 // degree of mt discovery
2252 true,
2253 // Reference discovery is atomic
2254 &_is_alive_closure_stw,
2255 // is alive closure
2256 // (for efficiency/performance)
2257 false);
2258 // Setting next fields of discovered
2259 // lists requires a barrier.
2260 }
2261
2262 size_t G1CollectedHeap::capacity() const {
2263 return _g1_committed.byte_size();
2264 }
2265
2266 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl,
2267 DirtyCardQueue* into_cset_dcq,
2268 bool concurrent,
2269 int worker_i) {
2270 // Clean cards in the hot card cache
2271 concurrent_g1_refine()->clean_up_cache(worker_i, g1_rem_set(), into_cset_dcq);
2272
2273 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2274 int n_completed_buffers = 0;
2275 while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) {
2276 n_completed_buffers++;
2277 }
2278 g1_policy()->phase_times()->record_update_rs_processed_buffers(worker_i,
2279 (double) n_completed_buffers);
2280 dcqs.clear_n_completed_buffers();
2281 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!");
2282 }
2283
2284
2285 // Computes the sum of the storage used by the various regions.
2286
2287 size_t G1CollectedHeap::used() const {
2288 assert(Heap_lock->owner() != NULL,
2289 "Should be owned on this thread's behalf.");
2290 size_t result = _summary_bytes_used;
2291 // Read only once in case it is set to NULL concurrently
2292 HeapRegion* hr = _mutator_alloc_region.get();
2293 if (hr != NULL)
2294 result += hr->used();
2295 return result;
2296 }
2297
2298 size_t G1CollectedHeap::used_unlocked() const {
2299 size_t result = _summary_bytes_used;
2300 return result;
2301 }
2302
2303 class SumUsedClosure: public HeapRegionClosure {
2304 size_t _used;
2305 public:
2306 SumUsedClosure() : _used(0) {}
2307 bool doHeapRegion(HeapRegion* r) {
2308 if (!r->continuesHumongous()) {
2309 _used += r->used();
2310 }
2311 return false;
2312 }
2313 size_t result() { return _used; }
2314 };
2315
2316 size_t G1CollectedHeap::recalculate_used() const {
2317 SumUsedClosure blk;
2318 heap_region_iterate(&blk);
2319 return blk.result();
2320 }
2321
2322 size_t G1CollectedHeap::unsafe_max_alloc() {
2323 if (free_regions() > 0) return HeapRegion::GrainBytes;
2324 // otherwise, is there space in the current allocation region?
2325
2326 // We need to store the current allocation region in a local variable
2327 // here. The problem is that this method doesn't take any locks and
2328 // there may be other threads which overwrite the current allocation
2329 // region field. attempt_allocation(), for example, sets it to NULL
2330 // and this can happen *after* the NULL check here but before the call
2331 // to free(), resulting in a SIGSEGV. Note that this doesn't appear
2332 // to be a problem in the optimized build, since the two loads of the
2333 // current allocation region field are optimized away.
2334 HeapRegion* hr = _mutator_alloc_region.get();
2335 if (hr == NULL) {
2336 return 0;
2337 }
2338 return hr->free();
2339 }
2340
2341 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
2342 switch (cause) {
2343 case GCCause::_gc_locker: return GCLockerInvokesConcurrent;
2344 case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent;
2345 case GCCause::_g1_humongous_allocation: return true;
2346 default: return false;
2347 }
2348 }
2349
2350 #ifndef PRODUCT
2351 void G1CollectedHeap::allocate_dummy_regions() {
2352 // Let's fill up most of the region
2353 size_t word_size = HeapRegion::GrainWords - 1024;
2354 // And as a result the region we'll allocate will be humongous.
2355 guarantee(isHumongous(word_size), "sanity");
2356
2357 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
2358 // Let's use the existing mechanism for the allocation
2359 HeapWord* dummy_obj = humongous_obj_allocate(word_size);
2360 if (dummy_obj != NULL) {
2361 MemRegion mr(dummy_obj, word_size);
2362 CollectedHeap::fill_with_object(mr);
2363 } else {
2364 // If we can't allocate once, we probably cannot allocate
2365 // again. Let's get out of the loop.
2366 break;
2367 }
2368 }
2369 }
2370 #endif // !PRODUCT
2371
2372 void G1CollectedHeap::increment_old_marking_cycles_started() {
2373 assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
2374 _old_marking_cycles_started == _old_marking_cycles_completed + 1,
2375 err_msg("Wrong marking cycle count (started: %d, completed: %d)",
2376 _old_marking_cycles_started, _old_marking_cycles_completed));
2377
2378 _old_marking_cycles_started++;
2379 }
2380
2381 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) {
2382 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
2383
2384 // We assume that if concurrent == true, then the caller is a
2385 // concurrent thread that was joined the Suspendible Thread
2386 // Set. If there's ever a cheap way to check this, we should add an
2387 // assert here.
2388
2389 // Given that this method is called at the end of a Full GC or of a
2390 // concurrent cycle, and those can be nested (i.e., a Full GC can
2391 // interrupt a concurrent cycle), the number of full collections
2392 // completed should be either one (in the case where there was no
2393 // nesting) or two (when a Full GC interrupted a concurrent cycle)
2394 // behind the number of full collections started.
2395
2396 // This is the case for the inner caller, i.e. a Full GC.
2397 assert(concurrent ||
2398 (_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
2399 (_old_marking_cycles_started == _old_marking_cycles_completed + 2),
2400 err_msg("for inner caller (Full GC): _old_marking_cycles_started = %u "
2401 "is inconsistent with _old_marking_cycles_completed = %u",
2402 _old_marking_cycles_started, _old_marking_cycles_completed));
2403
2404 // This is the case for the outer caller, i.e. the concurrent cycle.
2405 assert(!concurrent ||
2406 (_old_marking_cycles_started == _old_marking_cycles_completed + 1),
2407 err_msg("for outer caller (concurrent cycle): "
2408 "_old_marking_cycles_started = %u "
2409 "is inconsistent with _old_marking_cycles_completed = %u",
2410 _old_marking_cycles_started, _old_marking_cycles_completed));
2411
2412 _old_marking_cycles_completed += 1;
2413
2414 // We need to clear the "in_progress" flag in the CM thread before
2415 // we wake up any waiters (especially when ExplicitInvokesConcurrent
2416 // is set) so that if a waiter requests another System.gc() it doesn't
2417 // incorrectly see that a marking cyle is still in progress.
2418 if (concurrent) {
2419 _cmThread->clear_in_progress();
2420 }
2421
2422 // This notify_all() will ensure that a thread that called
2423 // System.gc() with (with ExplicitGCInvokesConcurrent set or not)
2424 // and it's waiting for a full GC to finish will be woken up. It is
2425 // waiting in VM_G1IncCollectionPause::doit_epilogue().
2426 FullGCCount_lock->notify_all();
2427 }
2428
2429 void G1CollectedHeap::collect_as_vm_thread(GCCause::Cause cause) {
2430 assert_at_safepoint(true /* should_be_vm_thread */);
2431 GCCauseSetter gcs(this, cause);
2432 switch (cause) {
2433 case GCCause::_heap_inspection:
2434 case GCCause::_heap_dump: {
2435 HandleMark hm;
2436 do_full_collection(false); // don't clear all soft refs
2437 break;
2438 }
2439 default: // XXX FIX ME
2440 ShouldNotReachHere(); // Unexpected use of this function
2441 }
2442 }
2443
2444 void G1CollectedHeap::collect(GCCause::Cause cause) {
2445 assert_heap_not_locked();
2446
2447 unsigned int gc_count_before;
2448 unsigned int old_marking_count_before;
2449 bool retry_gc;
2450
2451 do {
2452 retry_gc = false;
2453
2454 {
2455 MutexLocker ml(Heap_lock);
2456
2457 // Read the GC count while holding the Heap_lock
2458 gc_count_before = total_collections();
2459 old_marking_count_before = _old_marking_cycles_started;
2460 }
2461
2462 if (should_do_concurrent_full_gc(cause)) {
2463 // Schedule an initial-mark evacuation pause that will start a
2464 // concurrent cycle. We're setting word_size to 0 which means that
2465 // we are not requesting a post-GC allocation.
2466 VM_G1IncCollectionPause op(gc_count_before,
2467 0, /* word_size */
2468 true, /* should_initiate_conc_mark */
2469 g1_policy()->max_pause_time_ms(),
2470 cause);
2471
2472 VMThread::execute(&op);
2473 if (!op.pause_succeeded()) {
2474 if (old_marking_count_before == _old_marking_cycles_started) {
2475 retry_gc = op.should_retry_gc();
2476 } else {
2477 // A Full GC happened while we were trying to schedule the
2478 // initial-mark GC. No point in starting a new cycle given
2479 // that the whole heap was collected anyway.
2480 }
2481
2482 if (retry_gc) {
2483 if (GC_locker::is_active_and_needs_gc()) {
2484 GC_locker::stall_until_clear();
2485 }
2486 }
2487 }
2488 } else {
2489 if (cause == GCCause::_gc_locker
2490 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2491
2492 // Schedule a standard evacuation pause. We're setting word_size
2493 // to 0 which means that we are not requesting a post-GC allocation.
2494 VM_G1IncCollectionPause op(gc_count_before,
2495 0, /* word_size */
2496 false, /* should_initiate_conc_mark */
2497 g1_policy()->max_pause_time_ms(),
2498 cause);
2499 VMThread::execute(&op);
2500 } else {
2501 // Schedule a Full GC.
2502 VM_G1CollectFull op(gc_count_before, old_marking_count_before, cause);
2503 VMThread::execute(&op);
2504 }
2505 }
2506 } while (retry_gc);
2507 }
2508
2509 bool G1CollectedHeap::is_in(const void* p) const {
2510 if (_g1_committed.contains(p)) {
2511 // Given that we know that p is in the committed space,
2512 // heap_region_containing_raw() should successfully
2513 // return the containing region.
2514 HeapRegion* hr = heap_region_containing_raw(p);
2515 return hr->is_in(p);
2516 } else {
2517 return _perm_gen->as_gen()->is_in(p);
2518 }
2519 }
2520
2521 // Iteration functions.
2522
2523 // Iterates an OopClosure over all ref-containing fields of objects
2524 // within a HeapRegion.
2525
2526 class IterateOopClosureRegionClosure: public HeapRegionClosure {
2527 MemRegion _mr;
2528 OopClosure* _cl;
2529 public:
2530 IterateOopClosureRegionClosure(MemRegion mr, OopClosure* cl)
2531 : _mr(mr), _cl(cl) {}
2532 bool doHeapRegion(HeapRegion* r) {
2533 if (! r->continuesHumongous()) {
2534 r->oop_iterate(_cl);
2535 }
2536 return false;
2537 }
2538 };
2539
2540 void G1CollectedHeap::oop_iterate(OopClosure* cl, bool do_perm) {
2541 IterateOopClosureRegionClosure blk(_g1_committed, cl);
2542 heap_region_iterate(&blk);
2543 if (do_perm) {
2544 perm_gen()->oop_iterate(cl);
2545 }
2546 }
2547
2548 void G1CollectedHeap::oop_iterate(MemRegion mr, OopClosure* cl, bool do_perm) {
2549 IterateOopClosureRegionClosure blk(mr, cl);
2550 heap_region_iterate(&blk);
2551 if (do_perm) {
2552 perm_gen()->oop_iterate(cl);
2553 }
2554 }
2555
2556 // Iterates an ObjectClosure over all objects within a HeapRegion.
2557
2558 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2559 ObjectClosure* _cl;
2560 public:
2561 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2562 bool doHeapRegion(HeapRegion* r) {
2563 if (! r->continuesHumongous()) {
2564 r->object_iterate(_cl);
2565 }
2566 return false;
2567 }
2568 };
2569
2570 void G1CollectedHeap::object_iterate(ObjectClosure* cl, bool do_perm) {
2571 IterateObjectClosureRegionClosure blk(cl);
2572 heap_region_iterate(&blk);
2573 if (do_perm) {
2574 perm_gen()->object_iterate(cl);
2575 }
2576 }
2577
2578 void G1CollectedHeap::object_iterate_since_last_GC(ObjectClosure* cl) {
2579 // FIXME: is this right?
2580 guarantee(false, "object_iterate_since_last_GC not supported by G1 heap");
2581 }
2582
2583 // Calls a SpaceClosure on a HeapRegion.
2584
2585 class SpaceClosureRegionClosure: public HeapRegionClosure {
2586 SpaceClosure* _cl;
2587 public:
2588 SpaceClosureRegionClosure(SpaceClosure* cl) : _cl(cl) {}
2589 bool doHeapRegion(HeapRegion* r) {
2590 _cl->do_space(r);
2591 return false;
2592 }
2593 };
2594
2595 void G1CollectedHeap::space_iterate(SpaceClosure* cl) {
2596 SpaceClosureRegionClosure blk(cl);
2597 heap_region_iterate(&blk);
2598 }
2599
2600 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2601 _hrs.iterate(cl);
2602 }
2603
2604 void G1CollectedHeap::heap_region_iterate_from(HeapRegion* r,
2605 HeapRegionClosure* cl) const {
2606 _hrs.iterate_from(r, cl);
2607 }
2608
2609 void
2610 G1CollectedHeap::heap_region_par_iterate_chunked(HeapRegionClosure* cl,
2611 uint worker,
2612 uint no_of_par_workers,
2613 jint claim_value) {
2614 const uint regions = n_regions();
2615 const uint max_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
2616 no_of_par_workers :
2617 1);
2618 assert(UseDynamicNumberOfGCThreads ||
2619 no_of_par_workers == workers()->total_workers(),
2620 "Non dynamic should use fixed number of workers");
2621 // try to spread out the starting points of the workers
2622 const uint start_index = regions / max_workers * worker;
2623
2624 // each worker will actually look at all regions
2625 for (uint count = 0; count < regions; ++count) {
2626 const uint index = (start_index + count) % regions;
2627 assert(0 <= index && index < regions, "sanity");
2628 HeapRegion* r = region_at(index);
2629 // we'll ignore "continues humongous" regions (we'll process them
2630 // when we come across their corresponding "start humongous"
2631 // region) and regions already claimed
2632 if (r->claim_value() == claim_value || r->continuesHumongous()) {
2633 continue;
2634 }
2635 // OK, try to claim it
2636 if (r->claimHeapRegion(claim_value)) {
2637 // success!
2638 assert(!r->continuesHumongous(), "sanity");
2639 if (r->startsHumongous()) {
2640 // If the region is "starts humongous" we'll iterate over its
2641 // "continues humongous" first; in fact we'll do them
2642 // first. The order is important. In on case, calling the
2643 // closure on the "starts humongous" region might de-allocate
2644 // and clear all its "continues humongous" regions and, as a
2645 // result, we might end up processing them twice. So, we'll do
2646 // them first (notice: most closures will ignore them anyway) and
2647 // then we'll do the "starts humongous" region.
2648 for (uint ch_index = index + 1; ch_index < regions; ++ch_index) {
2649 HeapRegion* chr = region_at(ch_index);
2650
2651 // if the region has already been claimed or it's not
2652 // "continues humongous" we're done
2653 if (chr->claim_value() == claim_value ||
2654 !chr->continuesHumongous()) {
2655 break;
2656 }
2657
2658 // Noone should have claimed it directly. We can given
2659 // that we claimed its "starts humongous" region.
2660 assert(chr->claim_value() != claim_value, "sanity");
2661 assert(chr->humongous_start_region() == r, "sanity");
2662
2663 if (chr->claimHeapRegion(claim_value)) {
2664 // we should always be able to claim it; noone else should
2665 // be trying to claim this region
2666
2667 bool res2 = cl->doHeapRegion(chr);
2668 assert(!res2, "Should not abort");
2669
2670 // Right now, this holds (i.e., no closure that actually
2671 // does something with "continues humongous" regions
2672 // clears them). We might have to weaken it in the future,
2673 // but let's leave these two asserts here for extra safety.
2674 assert(chr->continuesHumongous(), "should still be the case");
2675 assert(chr->humongous_start_region() == r, "sanity");
2676 } else {
2677 guarantee(false, "we should not reach here");
2678 }
2679 }
2680 }
2681
2682 assert(!r->continuesHumongous(), "sanity");
2683 bool res = cl->doHeapRegion(r);
2684 assert(!res, "Should not abort");
2685 }
2686 }
2687 }
2688
2689 class ResetClaimValuesClosure: public HeapRegionClosure {
2690 public:
2691 bool doHeapRegion(HeapRegion* r) {
2692 r->set_claim_value(HeapRegion::InitialClaimValue);
2693 return false;
2694 }
2695 };
2696
2697 void G1CollectedHeap::reset_heap_region_claim_values() {
2698 ResetClaimValuesClosure blk;
2699 heap_region_iterate(&blk);
2700 }
2701
2702 void G1CollectedHeap::reset_cset_heap_region_claim_values() {
2703 ResetClaimValuesClosure blk;
2704 collection_set_iterate(&blk);
2705 }
2706
2707 #ifdef ASSERT
2708 // This checks whether all regions in the heap have the correct claim
2709 // value. I also piggy-backed on this a check to ensure that the
2710 // humongous_start_region() information on "continues humongous"
2711 // regions is correct.
2712
2713 class CheckClaimValuesClosure : public HeapRegionClosure {
2714 private:
2715 jint _claim_value;
2716 uint _failures;
2717 HeapRegion* _sh_region;
2718
2719 public:
2720 CheckClaimValuesClosure(jint claim_value) :
2721 _claim_value(claim_value), _failures(0), _sh_region(NULL) { }
2722 bool doHeapRegion(HeapRegion* r) {
2723 if (r->claim_value() != _claim_value) {
2724 gclog_or_tty->print_cr("Region " HR_FORMAT ", "
2725 "claim value = %d, should be %d",
2726 HR_FORMAT_PARAMS(r),
2727 r->claim_value(), _claim_value);
2728 ++_failures;
2729 }
2730 if (!r->isHumongous()) {
2731 _sh_region = NULL;
2732 } else if (r->startsHumongous()) {
2733 _sh_region = r;
2734 } else if (r->continuesHumongous()) {
2735 if (r->humongous_start_region() != _sh_region) {
2736 gclog_or_tty->print_cr("Region " HR_FORMAT ", "
2737 "HS = "PTR_FORMAT", should be "PTR_FORMAT,
2738 HR_FORMAT_PARAMS(r),
2739 r->humongous_start_region(),
2740 _sh_region);
2741 ++_failures;
2742 }
2743 }
2744 return false;
2745 }
2746 uint failures() { return _failures; }
2747 };
2748
2749 bool G1CollectedHeap::check_heap_region_claim_values(jint claim_value) {
2750 CheckClaimValuesClosure cl(claim_value);
2751 heap_region_iterate(&cl);
2752 return cl.failures() == 0;
2753 }
2754
2755 class CheckClaimValuesInCSetHRClosure: public HeapRegionClosure {
2756 private:
2757 jint _claim_value;
2758 uint _failures;
2759
2760 public:
2761 CheckClaimValuesInCSetHRClosure(jint claim_value) :
2762 _claim_value(claim_value), _failures(0) { }
2763
2764 uint failures() { return _failures; }
2765
2766 bool doHeapRegion(HeapRegion* hr) {
2767 assert(hr->in_collection_set(), "how?");
2768 assert(!hr->isHumongous(), "H-region in CSet");
2769 if (hr->claim_value() != _claim_value) {
2770 gclog_or_tty->print_cr("CSet Region " HR_FORMAT ", "
2771 "claim value = %d, should be %d",
2772 HR_FORMAT_PARAMS(hr),
2773 hr->claim_value(), _claim_value);
2774 _failures += 1;
2775 }
2776 return false;
2777 }
2778 };
2779
2780 bool G1CollectedHeap::check_cset_heap_region_claim_values(jint claim_value) {
2781 CheckClaimValuesInCSetHRClosure cl(claim_value);
2782 collection_set_iterate(&cl);
2783 return cl.failures() == 0;
2784 }
2785 #endif // ASSERT
2786
2787 // Clear the cached CSet starting regions and (more importantly)
2788 // the time stamps. Called when we reset the GC time stamp.
2789 void G1CollectedHeap::clear_cset_start_regions() {
2790 assert(_worker_cset_start_region != NULL, "sanity");
2791 assert(_worker_cset_start_region_time_stamp != NULL, "sanity");
2792
2793 int n_queues = MAX2((int)ParallelGCThreads, 1);
2794 for (int i = 0; i < n_queues; i++) {
2795 _worker_cset_start_region[i] = NULL;
2796 _worker_cset_start_region_time_stamp[i] = 0;
2797 }
2798 }
2799
2800 // Given the id of a worker, obtain or calculate a suitable
2801 // starting region for iterating over the current collection set.
2802 HeapRegion* G1CollectedHeap::start_cset_region_for_worker(int worker_i) {
2803 assert(get_gc_time_stamp() > 0, "should have been updated by now");
2804
2805 HeapRegion* result = NULL;
2806 unsigned gc_time_stamp = get_gc_time_stamp();
2807
2808 if (_worker_cset_start_region_time_stamp[worker_i] == gc_time_stamp) {
2809 // Cached starting region for current worker was set
2810 // during the current pause - so it's valid.
2811 // Note: the cached starting heap region may be NULL
2812 // (when the collection set is empty).
2813 result = _worker_cset_start_region[worker_i];
2814 assert(result == NULL || result->in_collection_set(), "sanity");
2815 return result;
2816 }
2817
2818 // The cached entry was not valid so let's calculate
2819 // a suitable starting heap region for this worker.
2820
2821 // We want the parallel threads to start their collection
2822 // set iteration at different collection set regions to
2823 // avoid contention.
2824 // If we have:
2825 // n collection set regions
2826 // p threads
2827 // Then thread t will start at region floor ((t * n) / p)
2828
2829 result = g1_policy()->collection_set();
2830 if (G1CollectedHeap::use_parallel_gc_threads()) {
2831 uint cs_size = g1_policy()->cset_region_length();
2832 uint active_workers = workers()->active_workers();
2833 assert(UseDynamicNumberOfGCThreads ||
2834 active_workers == workers()->total_workers(),
2835 "Unless dynamic should use total workers");
2836
2837 uint end_ind = (cs_size * worker_i) / active_workers;
2838 uint start_ind = 0;
2839
2840 if (worker_i > 0 &&
2841 _worker_cset_start_region_time_stamp[worker_i - 1] == gc_time_stamp) {
2842 // Previous workers starting region is valid
2843 // so let's iterate from there
2844 start_ind = (cs_size * (worker_i - 1)) / active_workers;
2845 result = _worker_cset_start_region[worker_i - 1];
2846 }
2847
2848 for (uint i = start_ind; i < end_ind; i++) {
2849 result = result->next_in_collection_set();
2850 }
2851 }
2852
2853 // Note: the calculated starting heap region may be NULL
2854 // (when the collection set is empty).
2855 assert(result == NULL || result->in_collection_set(), "sanity");
2856 assert(_worker_cset_start_region_time_stamp[worker_i] != gc_time_stamp,
2857 "should be updated only once per pause");
2858 _worker_cset_start_region[worker_i] = result;
2859 OrderAccess::storestore();
2860 _worker_cset_start_region_time_stamp[worker_i] = gc_time_stamp;
2861 return result;
2862 }
2863
2864 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) {
2865 HeapRegion* r = g1_policy()->collection_set();
2866 while (r != NULL) {
2867 HeapRegion* next = r->next_in_collection_set();
2868 if (cl->doHeapRegion(r)) {
2869 cl->incomplete();
2870 return;
2871 }
2872 r = next;
2873 }
2874 }
2875
2876 void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r,
2877 HeapRegionClosure *cl) {
2878 if (r == NULL) {
2879 // The CSet is empty so there's nothing to do.
2880 return;
2881 }
2882
2883 assert(r->in_collection_set(),
2884 "Start region must be a member of the collection set.");
2885 HeapRegion* cur = r;
2886 while (cur != NULL) {
2887 HeapRegion* next = cur->next_in_collection_set();
2888 if (cl->doHeapRegion(cur) && false) {
2889 cl->incomplete();
2890 return;
2891 }
2892 cur = next;
2893 }
2894 cur = g1_policy()->collection_set();
2895 while (cur != r) {
2896 HeapRegion* next = cur->next_in_collection_set();
2897 if (cl->doHeapRegion(cur) && false) {
2898 cl->incomplete();
2899 return;
2900 }
2901 cur = next;
2902 }
2903 }
2904
2905 CompactibleSpace* G1CollectedHeap::first_compactible_space() {
2906 return n_regions() > 0 ? region_at(0) : NULL;
2907 }
2908
2909
2910 Space* G1CollectedHeap::space_containing(const void* addr) const {
2911 Space* res = heap_region_containing(addr);
2912 if (res == NULL)
2913 res = perm_gen()->space_containing(addr);
2914 return res;
2915 }
2916
2917 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2918 Space* sp = space_containing(addr);
2919 if (sp != NULL) {
2920 return sp->block_start(addr);
2921 }
2922 return NULL;
2923 }
2924
2925 size_t G1CollectedHeap::block_size(const HeapWord* addr) const {
2926 Space* sp = space_containing(addr);
2927 assert(sp != NULL, "block_size of address outside of heap");
2928 return sp->block_size(addr);
2929 }
2930
2931 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2932 Space* sp = space_containing(addr);
2933 return sp->block_is_obj(addr);
2934 }
2935
2936 bool G1CollectedHeap::supports_tlab_allocation() const {
2937 return true;
2938 }
2939
2940 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
2941 return HeapRegion::GrainBytes;
2942 }
2943
2944 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
2945 // Return the remaining space in the cur alloc region, but not less than
2946 // the min TLAB size.
2947
2948 // Also, this value can be at most the humongous object threshold,
2949 // since we can't allow tlabs to grow big enough to accomodate
2950 // humongous objects.
2951
2952 HeapRegion* hr = _mutator_alloc_region.get();
2953 size_t max_tlab_size = _humongous_object_threshold_in_words * wordSize;
2954 if (hr == NULL) {
2955 return max_tlab_size;
2956 } else {
2957 return MIN2(MAX2(hr->free(), (size_t) MinTLABSize), max_tlab_size);
2958 }
2959 }
2960
2961 size_t G1CollectedHeap::max_capacity() const {
2962 return _g1_reserved.byte_size();
2963 }
2964
2965 jlong G1CollectedHeap::millis_since_last_gc() {
2966 // assert(false, "NYI");
2967 return 0;
2968 }
2969
2970 void G1CollectedHeap::prepare_for_verify() {
2971 if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) {
2972 ensure_parsability(false);
2973 }
2974 g1_rem_set()->prepare_for_verify();
2975 }
2976
2977 class VerifyLivenessOopClosure: public OopClosure {
2978 G1CollectedHeap* _g1h;
2979 VerifyOption _vo;
2980 public:
2981 VerifyLivenessOopClosure(G1CollectedHeap* g1h, VerifyOption vo):
2982 _g1h(g1h), _vo(vo)
2983 { }
2984 void do_oop(narrowOop *p) { do_oop_work(p); }
2985 void do_oop( oop *p) { do_oop_work(p); }
2986
2987 template <class T> void do_oop_work(T *p) {
2988 oop obj = oopDesc::load_decode_heap_oop(p);
2989 guarantee(obj == NULL || !_g1h->is_obj_dead_cond(obj, _vo),
2990 "Dead object referenced by a not dead object");
2991 }
2992 };
2993
2994 class VerifyObjsInRegionClosure: public ObjectClosure {
2995 private:
2996 G1CollectedHeap* _g1h;
2997 size_t _live_bytes;
2998 HeapRegion *_hr;
2999 VerifyOption _vo;
3000 public:
3001 // _vo == UsePrevMarking -> use "prev" marking information,
3002 // _vo == UseNextMarking -> use "next" marking information,
3003 // _vo == UseMarkWord -> use mark word from object header.
3004 VerifyObjsInRegionClosure(HeapRegion *hr, VerifyOption vo)
3005 : _live_bytes(0), _hr(hr), _vo(vo) {
3006 _g1h = G1CollectedHeap::heap();
3007 }
3008 void do_object(oop o) {
3009 VerifyLivenessOopClosure isLive(_g1h, _vo);
3010 assert(o != NULL, "Huh?");
3011 if (!_g1h->is_obj_dead_cond(o, _vo)) {
3012 // If the object is alive according to the mark word,
3013 // then verify that the marking information agrees.
3014 // Note we can't verify the contra-positive of the
3015 // above: if the object is dead (according to the mark
3016 // word), it may not be marked, or may have been marked
3017 // but has since became dead, or may have been allocated
3018 // since the last marking.
3019 if (_vo == VerifyOption_G1UseMarkWord) {
3020 guarantee(!_g1h->is_obj_dead(o), "mark word and concurrent mark mismatch");
3021 }
3022
3023 o->oop_iterate(&isLive);
3024 if (!_hr->obj_allocated_since_prev_marking(o)) {
3025 size_t obj_size = o->size(); // Make sure we don't overflow
3026 _live_bytes += (obj_size * HeapWordSize);
3027 }
3028 }
3029 }
3030 size_t live_bytes() { return _live_bytes; }
3031 };
3032
3033 class PrintObjsInRegionClosure : public ObjectClosure {
3034 HeapRegion *_hr;
3035 G1CollectedHeap *_g1;
3036 public:
3037 PrintObjsInRegionClosure(HeapRegion *hr) : _hr(hr) {
3038 _g1 = G1CollectedHeap::heap();
3039 };
3040
3041 void do_object(oop o) {
3042 if (o != NULL) {
3043 HeapWord *start = (HeapWord *) o;
3044 size_t word_sz = o->size();
3045 gclog_or_tty->print("\nPrinting obj "PTR_FORMAT" of size " SIZE_FORMAT
3046 " isMarkedPrev %d isMarkedNext %d isAllocSince %d\n",
3047 (void*) o, word_sz,
3048 _g1->isMarkedPrev(o),
3049 _g1->isMarkedNext(o),
3050 _hr->obj_allocated_since_prev_marking(o));
3051 HeapWord *end = start + word_sz;
3052 HeapWord *cur;
3053 int *val;
3054 for (cur = start; cur < end; cur++) {
3055 val = (int *) cur;
3056 gclog_or_tty->print("\t "PTR_FORMAT":"PTR_FORMAT"\n", val, *val);
3057 }
3058 }
3059 }
3060 };
3061
3062 class VerifyRegionClosure: public HeapRegionClosure {
3063 private:
3064 bool _par;
3065 VerifyOption _vo;
3066 bool _failures;
3067 public:
3068 // _vo == UsePrevMarking -> use "prev" marking information,
3069 // _vo == UseNextMarking -> use "next" marking information,
3070 // _vo == UseMarkWord -> use mark word from object header.
3071 VerifyRegionClosure(bool par, VerifyOption vo)
3072 : _par(par),
3073 _vo(vo),
3074 _failures(false) {}
3075
3076 bool failures() {
3077 return _failures;
3078 }
3079
3080 bool doHeapRegion(HeapRegion* r) {
3081 guarantee(_par || r->claim_value() == HeapRegion::InitialClaimValue,
3082 "Should be unclaimed at verify points.");
3083 if (!r->continuesHumongous()) {
3084 bool failures = false;
3085 r->verify(_vo, &failures);
3086 if (failures) {
3087 _failures = true;
3088 } else {
3089 VerifyObjsInRegionClosure not_dead_yet_cl(r, _vo);
3090 r->object_iterate(¬_dead_yet_cl);
3091 if (_vo != VerifyOption_G1UseNextMarking) {
3092 if (r->max_live_bytes() < not_dead_yet_cl.live_bytes()) {
3093 gclog_or_tty->print_cr("["PTR_FORMAT","PTR_FORMAT"] "
3094 "max_live_bytes "SIZE_FORMAT" "
3095 "< calculated "SIZE_FORMAT,
3096 r->bottom(), r->end(),
3097 r->max_live_bytes(),
3098 not_dead_yet_cl.live_bytes());
3099 _failures = true;
3100 }
3101 } else {
3102 // When vo == UseNextMarking we cannot currently do a sanity
3103 // check on the live bytes as the calculation has not been
3104 // finalized yet.
3105 }
3106 }
3107 }
3108 return false; // stop the region iteration if we hit a failure
3109 }
3110 };
3111
3112 class VerifyRootsClosure: public OopsInGenClosure {
3113 private:
3114 G1CollectedHeap* _g1h;
3115 VerifyOption _vo;
3116 bool _failures;
3117 public:
3118 // _vo == UsePrevMarking -> use "prev" marking information,
3119 // _vo == UseNextMarking -> use "next" marking information,
3120 // _vo == UseMarkWord -> use mark word from object header.
3121 VerifyRootsClosure(VerifyOption vo) :
3122 _g1h(G1CollectedHeap::heap()),
3123 _vo(vo),
3124 _failures(false) { }
3125
3126 bool failures() { return _failures; }
3127
3128 template <class T> void do_oop_nv(T* p) {
3129 T heap_oop = oopDesc::load_heap_oop(p);
3130 if (!oopDesc::is_null(heap_oop)) {
3131 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
3132 if (_g1h->is_obj_dead_cond(obj, _vo)) {
3133 gclog_or_tty->print_cr("Root location "PTR_FORMAT" "
3134 "points to dead obj "PTR_FORMAT, p, (void*) obj);
3135 if (_vo == VerifyOption_G1UseMarkWord) {
3136 gclog_or_tty->print_cr(" Mark word: "PTR_FORMAT, (void*)(obj->mark()));
3137 }
3138 obj->print_on(gclog_or_tty);
3139 _failures = true;
3140 }
3141 }
3142 }
3143
3144 void do_oop(oop* p) { do_oop_nv(p); }
3145 void do_oop(narrowOop* p) { do_oop_nv(p); }
3146 };
3147
3148 // This is the task used for parallel heap verification.
3149
3150 class G1ParVerifyTask: public AbstractGangTask {
3151 private:
3152 G1CollectedHeap* _g1h;
3153 VerifyOption _vo;
3154 bool _failures;
3155
3156 public:
3157 // _vo == UsePrevMarking -> use "prev" marking information,
3158 // _vo == UseNextMarking -> use "next" marking information,
3159 // _vo == UseMarkWord -> use mark word from object header.
3160 G1ParVerifyTask(G1CollectedHeap* g1h, VerifyOption vo) :
3161 AbstractGangTask("Parallel verify task"),
3162 _g1h(g1h),
3163 _vo(vo),
3164 _failures(false) { }
3165
3166 bool failures() {
3167 return _failures;
3168 }
3169
3170 void work(uint worker_id) {
3171 HandleMark hm;
3172 VerifyRegionClosure blk(true, _vo);
3173 _g1h->heap_region_par_iterate_chunked(&blk, worker_id,
3174 _g1h->workers()->active_workers(),
3175 HeapRegion::ParVerifyClaimValue);
3176 if (blk.failures()) {
3177 _failures = true;
3178 }
3179 }
3180 };
3181
3182 void G1CollectedHeap::verify(bool silent) {
3183 verify(silent, VerifyOption_G1UsePrevMarking);
3184 }
3185
3186 void G1CollectedHeap::verify(bool silent,
3187 VerifyOption vo) {
3188 if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) {
3189 if (!silent) { gclog_or_tty->print("Roots (excluding permgen) "); }
3190 VerifyRootsClosure rootsCl(vo);
3191
3192 assert(Thread::current()->is_VM_thread(),
3193 "Expected to be executed serially by the VM thread at this point");
3194
3195 CodeBlobToOopClosure blobsCl(&rootsCl, /*do_marking=*/ false);
3196
3197 // We apply the relevant closures to all the oops in the
3198 // system dictionary, the string table and the code cache.
3199 const int so = SO_AllClasses | SO_Strings | SO_CodeCache;
3200
3201 process_strong_roots(true, // activate StrongRootsScope
3202 true, // we set "collecting perm gen" to true,
3203 // so we don't reset the dirty cards in the perm gen.
3204 ScanningOption(so), // roots scanning options
3205 &rootsCl,
3206 &blobsCl,
3207 &rootsCl);
3208
3209 // If we're verifying after the marking phase of a Full GC then we can't
3210 // treat the perm gen as roots into the G1 heap. Some of the objects in
3211 // the perm gen may be dead and hence not marked. If one of these dead
3212 // objects is considered to be a root then we may end up with a false
3213 // "Root location <x> points to dead ob <y>" failure.
3214 if (vo != VerifyOption_G1UseMarkWord) {
3215 // Since we used "collecting_perm_gen" == true above, we will not have
3216 // checked the refs from perm into the G1-collected heap. We check those
3217 // references explicitly below. Whether the relevant cards are dirty
3218 // is checked further below in the rem set verification.
3219 if (!silent) { gclog_or_tty->print("Permgen roots "); }
3220 perm_gen()->oop_iterate(&rootsCl);
3221 }
3222 bool failures = rootsCl.failures();
3223
3224 if (vo != VerifyOption_G1UseMarkWord) {
3225 // If we're verifying during a full GC then the region sets
3226 // will have been torn down at the start of the GC. Therefore
3227 // verifying the region sets will fail. So we only verify
3228 // the region sets when not in a full GC.
3229 if (!silent) { gclog_or_tty->print("HeapRegionSets "); }
3230 verify_region_sets();
3231 }
3232
3233 if (!silent) { gclog_or_tty->print("HeapRegions "); }
3234 if (GCParallelVerificationEnabled && ParallelGCThreads > 1) {
3235 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3236 "sanity check");
3237
3238 G1ParVerifyTask task(this, vo);
3239 assert(UseDynamicNumberOfGCThreads ||
3240 workers()->active_workers() == workers()->total_workers(),
3241 "If not dynamic should be using all the workers");
3242 int n_workers = workers()->active_workers();
3243 set_par_threads(n_workers);
3244 workers()->run_task(&task);
3245 set_par_threads(0);
3246 if (task.failures()) {
3247 failures = true;
3248 }
3249
3250 // Checks that the expected amount of parallel work was done.
3251 // The implication is that n_workers is > 0.
3252 assert(check_heap_region_claim_values(HeapRegion::ParVerifyClaimValue),
3253 "sanity check");
3254
3255 reset_heap_region_claim_values();
3256
3257 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3258 "sanity check");
3259 } else {
3260 VerifyRegionClosure blk(false, vo);
3261 heap_region_iterate(&blk);
3262 if (blk.failures()) {
3263 failures = true;
3264 }
3265 }
3266 if (!silent) gclog_or_tty->print("RemSet ");
3267 rem_set()->verify();
3268
3269 if (failures) {
3270 gclog_or_tty->print_cr("Heap:");
3271 // It helps to have the per-region information in the output to
3272 // help us track down what went wrong. This is why we call
3273 // print_extended_on() instead of print_on().
3274 print_extended_on(gclog_or_tty);
3275 gclog_or_tty->print_cr("");
3276 #ifndef PRODUCT
3277 if (VerifyDuringGC && G1VerifyDuringGCPrintReachable) {
3278 concurrent_mark()->print_reachable("at-verification-failure",
3279 vo, false /* all */);
3280 }
3281 #endif
3282 gclog_or_tty->flush();
3283 }
3284 guarantee(!failures, "there should not have been any failures");
3285 } else {
3286 if (!silent) gclog_or_tty->print("(SKIPPING roots, heapRegions, remset) ");
3287 }
3288 }
3289
3290 class PrintRegionClosure: public HeapRegionClosure {
3291 outputStream* _st;
3292 public:
3293 PrintRegionClosure(outputStream* st) : _st(st) {}
3294 bool doHeapRegion(HeapRegion* r) {
3295 r->print_on(_st);
3296 return false;
3297 }
3298 };
3299
3300 void G1CollectedHeap::print_on(outputStream* st) const {
3301 st->print(" %-20s", "garbage-first heap");
3302 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
3303 capacity()/K, used_unlocked()/K);
3304 st->print(" [" INTPTR_FORMAT ", " INTPTR_FORMAT ", " INTPTR_FORMAT ")",
3305 _g1_storage.low_boundary(),
3306 _g1_storage.high(),
3307 _g1_storage.high_boundary());
3308 st->cr();
3309 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
3310 uint young_regions = _young_list->length();
3311 st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
3312 (size_t) young_regions * HeapRegion::GrainBytes / K);
3313 uint survivor_regions = g1_policy()->recorded_survivor_regions();
3314 st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
3315 (size_t) survivor_regions * HeapRegion::GrainBytes / K);
3316 st->cr();
3317 perm()->as_gen()->print_on(st);
3318 }
3319
3320 void G1CollectedHeap::print_extended_on(outputStream* st) const {
3321 print_on(st);
3322
3323 // Print the per-region information.
3324 st->cr();
3325 st->print_cr("Heap Regions: (Y=young(eden), SU=young(survivor), "
3326 "HS=humongous(starts), HC=humongous(continues), "
3327 "CS=collection set, F=free, TS=gc time stamp, "
3328 "PTAMS=previous top-at-mark-start, "
3329 "NTAMS=next top-at-mark-start)");
3330 PrintRegionClosure blk(st);
3331 heap_region_iterate(&blk);
3332 }
3333
3334 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
3335 if (G1CollectedHeap::use_parallel_gc_threads()) {
3336 workers()->print_worker_threads_on(st);
3337 }
3338 _cmThread->print_on(st);
3339 st->cr();
3340 _cm->print_worker_threads_on(st);
3341 _cg1r->print_worker_threads_on(st);
3342 st->cr();
3343 }
3344
3345 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
3346 if (G1CollectedHeap::use_parallel_gc_threads()) {
3347 workers()->threads_do(tc);
3348 }
3349 tc->do_thread(_cmThread);
3350 _cg1r->threads_do(tc);
3351 }
3352
3353 void G1CollectedHeap::print_tracing_info() const {
3354 // We'll overload this to mean "trace GC pause statistics."
3355 if (TraceGen0Time || TraceGen1Time) {
3356 // The "G1CollectorPolicy" is keeping track of these stats, so delegate
3357 // to that.
3358 g1_policy()->print_tracing_info();
3359 }
3360 if (G1SummarizeRSetStats) {
3361 g1_rem_set()->print_summary_info();
3362 }
3363 if (G1SummarizeConcMark) {
3364 concurrent_mark()->print_summary_info();
3365 }
3366 g1_policy()->print_yg_surv_rate_info();
3367 SpecializationStats::print();
3368 }
3369
3370 #ifndef PRODUCT
3371 // Helpful for debugging RSet issues.
3372
3373 class PrintRSetsClosure : public HeapRegionClosure {
3374 private:
3375 const char* _msg;
3376 size_t _occupied_sum;
3377
3378 public:
3379 bool doHeapRegion(HeapRegion* r) {
3380 HeapRegionRemSet* hrrs = r->rem_set();
3381 size_t occupied = hrrs->occupied();
3382 _occupied_sum += occupied;
3383
3384 gclog_or_tty->print_cr("Printing RSet for region "HR_FORMAT,
3385 HR_FORMAT_PARAMS(r));
3386 if (occupied == 0) {
3387 gclog_or_tty->print_cr(" RSet is empty");
3388 } else {
3389 hrrs->print();
3390 }
3391 gclog_or_tty->print_cr("----------");
3392 return false;
3393 }
3394
3395 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
3396 gclog_or_tty->cr();
3397 gclog_or_tty->print_cr("========================================");
3398 gclog_or_tty->print_cr(msg);
3399 gclog_or_tty->cr();
3400 }
3401
3402 ~PrintRSetsClosure() {
3403 gclog_or_tty->print_cr("Occupied Sum: "SIZE_FORMAT, _occupied_sum);
3404 gclog_or_tty->print_cr("========================================");
3405 gclog_or_tty->cr();
3406 }
3407 };
3408
3409 void G1CollectedHeap::print_cset_rsets() {
3410 PrintRSetsClosure cl("Printing CSet RSets");
3411 collection_set_iterate(&cl);
3412 }
3413
3414 void G1CollectedHeap::print_all_rsets() {
3415 PrintRSetsClosure cl("Printing All RSets");;
3416 heap_region_iterate(&cl);
3417 }
3418 #endif // PRODUCT
3419
3420 G1CollectedHeap* G1CollectedHeap::heap() {
3421 assert(_sh->kind() == CollectedHeap::G1CollectedHeap,
3422 "not a garbage-first heap");
3423 return _g1h;
3424 }
3425
3426 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) {
3427 // always_do_update_barrier = false;
3428 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
3429 // Call allocation profiler
3430 AllocationProfiler::iterate_since_last_gc();
3431 // Fill TLAB's and such
3432 ensure_parsability(true);
3433 }
3434
3435 void G1CollectedHeap::gc_epilogue(bool full /* Ignored */) {
3436 // FIXME: what is this about?
3437 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
3438 // is set.
3439 COMPILER2_PRESENT(assert(DerivedPointerTable::is_empty(),
3440 "derived pointer present"));
3441 // always_do_update_barrier = true;
3442
3443 // We have just completed a GC. Update the soft reference
3444 // policy with the new heap occupancy
3445 Universe::update_heap_info_at_gc();
3446 }
3447
3448 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
3449 unsigned int gc_count_before,
3450 bool* succeeded) {
3451 assert_heap_not_locked_and_not_at_safepoint();
3452 g1_policy()->record_stop_world_start();
3453 VM_G1IncCollectionPause op(gc_count_before,
3454 word_size,
3455 false, /* should_initiate_conc_mark */
3456 g1_policy()->max_pause_time_ms(),
3457 GCCause::_g1_inc_collection_pause);
3458 VMThread::execute(&op);
3459
3460 HeapWord* result = op.result();
3461 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
3462 assert(result == NULL || ret_succeeded,
3463 "the result should be NULL if the VM did not succeed");
3464 *succeeded = ret_succeeded;
3465
3466 assert_heap_not_locked();
3467 return result;
3468 }
3469
3470 void
3471 G1CollectedHeap::doConcurrentMark() {
3472 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
3473 if (!_cmThread->in_progress()) {
3474 _cmThread->set_started();
3475 CGC_lock->notify();
3476 }
3477 }
3478
3479 size_t G1CollectedHeap::pending_card_num() {
3480 size_t extra_cards = 0;
3481 JavaThread *curr = Threads::first();
3482 while (curr != NULL) {
3483 DirtyCardQueue& dcq = curr->dirty_card_queue();
3484 extra_cards += dcq.size();
3485 curr = curr->next();
3486 }
3487 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
3488 size_t buffer_size = dcqs.buffer_size();
3489 size_t buffer_num = dcqs.completed_buffers_num();
3490 return buffer_size * buffer_num + extra_cards;
3491 }
3492
3493 size_t G1CollectedHeap::max_pending_card_num() {
3494 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
3495 size_t buffer_size = dcqs.buffer_size();
3496 size_t buffer_num = dcqs.completed_buffers_num();
3497 int thread_num = Threads::number_of_threads();
3498 return (buffer_num + thread_num) * buffer_size;
3499 }
3500
3501 size_t G1CollectedHeap::cards_scanned() {
3502 return g1_rem_set()->cardsScanned();
3503 }
3504
3505 void
3506 G1CollectedHeap::setup_surviving_young_words() {
3507 assert(_surviving_young_words == NULL, "pre-condition");
3508 uint array_length = g1_policy()->young_cset_region_length();
3509 _surviving_young_words = NEW_C_HEAP_ARRAY(size_t, (size_t) array_length, mtGC);
3510 if (_surviving_young_words == NULL) {
3511 vm_exit_out_of_memory(sizeof(size_t) * array_length,
3512 "Not enough space for young surv words summary.");
3513 }
3514 memset(_surviving_young_words, 0, (size_t) array_length * sizeof(size_t));
3515 #ifdef ASSERT
3516 for (uint i = 0; i < array_length; ++i) {
3517 assert( _surviving_young_words[i] == 0, "memset above" );
3518 }
3519 #endif // !ASSERT
3520 }
3521
3522 void
3523 G1CollectedHeap::update_surviving_young_words(size_t* surv_young_words) {
3524 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
3525 uint array_length = g1_policy()->young_cset_region_length();
3526 for (uint i = 0; i < array_length; ++i) {
3527 _surviving_young_words[i] += surv_young_words[i];
3528 }
3529 }
3530
3531 void
3532 G1CollectedHeap::cleanup_surviving_young_words() {
3533 guarantee( _surviving_young_words != NULL, "pre-condition" );
3534 FREE_C_HEAP_ARRAY(size_t, _surviving_young_words, mtGC);
3535 _surviving_young_words = NULL;
3536 }
3537
3538 #ifdef ASSERT
3539 class VerifyCSetClosure: public HeapRegionClosure {
3540 public:
3541 bool doHeapRegion(HeapRegion* hr) {
3542 // Here we check that the CSet region's RSet is ready for parallel
3543 // iteration. The fields that we'll verify are only manipulated
3544 // when the region is part of a CSet and is collected. Afterwards,
3545 // we reset these fields when we clear the region's RSet (when the
3546 // region is freed) so they are ready when the region is
3547 // re-allocated. The only exception to this is if there's an
3548 // evacuation failure and instead of freeing the region we leave
3549 // it in the heap. In that case, we reset these fields during
3550 // evacuation failure handling.
3551 guarantee(hr->rem_set()->verify_ready_for_par_iteration(), "verification");
3552
3553 // Here's a good place to add any other checks we'd like to
3554 // perform on CSet regions.
3555 return false;
3556 }
3557 };
3558 #endif // ASSERT
3559
3560 #if TASKQUEUE_STATS
3561 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
3562 st->print_raw_cr("GC Task Stats");
3563 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
3564 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
3565 }
3566
3567 void G1CollectedHeap::print_taskqueue_stats(outputStream* const st) const {
3568 print_taskqueue_stats_hdr(st);
3569
3570 TaskQueueStats totals;
3571 const int n = workers() != NULL ? workers()->total_workers() : 1;
3572 for (int i = 0; i < n; ++i) {
3573 st->print("%3d ", i); task_queue(i)->stats.print(st); st->cr();
3574 totals += task_queue(i)->stats;
3575 }
3576 st->print_raw("tot "); totals.print(st); st->cr();
3577
3578 DEBUG_ONLY(totals.verify());
3579 }
3580
3581 void G1CollectedHeap::reset_taskqueue_stats() {
3582 const int n = workers() != NULL ? workers()->total_workers() : 1;
3583 for (int i = 0; i < n; ++i) {
3584 task_queue(i)->stats.reset();
3585 }
3586 }
3587 #endif // TASKQUEUE_STATS
3588
3589 bool
3590 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
3591 assert_at_safepoint(true /* should_be_vm_thread */);
3592 guarantee(!is_gc_active(), "collection is not reentrant");
3593
3594 if (GC_locker::check_active_before_gc()) {
3595 return false;
3596 }
3597
3598 SvcGCMarker sgcm(SvcGCMarker::MINOR);
3599 ResourceMark rm;
3600
3601 print_heap_before_gc();
3602
3603 HRSPhaseSetter x(HRSPhaseEvacuation);
3604 verify_region_sets_optional();
3605 verify_dirty_young_regions();
3606
3607 // This call will decide whether this pause is an initial-mark
3608 // pause. If it is, during_initial_mark_pause() will return true
3609 // for the duration of this pause.
3610 g1_policy()->decide_on_conc_mark_initiation();
3611
3612 // We do not allow initial-mark to be piggy-backed on a mixed GC.
3613 assert(!g1_policy()->during_initial_mark_pause() ||
3614 g1_policy()->gcs_are_young(), "sanity");
3615
3616 // We also do not allow mixed GCs during marking.
3617 assert(!mark_in_progress() || g1_policy()->gcs_are_young(), "sanity");
3618
3619 // Record whether this pause is an initial mark. When the current
3620 // thread has completed its logging output and it's safe to signal
3621 // the CM thread, the flag's value in the policy has been reset.
3622 bool should_start_conc_mark = g1_policy()->during_initial_mark_pause();
3623
3624 // Inner scope for scope based logging, timers, and stats collection
3625 {
3626 if (g1_policy()->during_initial_mark_pause()) {
3627 // We are about to start a marking cycle, so we increment the
3628 // full collection counter.
3629 increment_old_marking_cycles_started();
3630 }
3631 // if the log level is "finer" is on, we'll print long statistics information
3632 // in the collector policy code, so let's not print this as the output
3633 // is messy if we do.
3634 gclog_or_tty->date_stamp(G1Log::fine() && PrintGCDateStamps);
3635 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
3636
3637 int active_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
3638 workers()->active_workers() : 1);
3639 g1_policy()->phase_times()->note_gc_start(os::elapsedTime(), active_workers,
3640 g1_policy()->gcs_are_young(), g1_policy()->during_initial_mark_pause(), gc_cause());
3641
3642 TraceCollectorStats tcs(g1mm()->incremental_collection_counters());
3643 TraceMemoryManagerStats tms(false /* fullGC */, gc_cause());
3644
3645 // If the secondary_free_list is not empty, append it to the
3646 // free_list. No need to wait for the cleanup operation to finish;
3647 // the region allocation code will check the secondary_free_list
3648 // and wait if necessary. If the G1StressConcRegionFreeing flag is
3649 // set, skip this step so that the region allocation code has to
3650 // get entries from the secondary_free_list.
3651 if (!G1StressConcRegionFreeing) {
3652 append_secondary_free_list_if_not_empty_with_lock();
3653 }
3654
3655 assert(check_young_list_well_formed(),
3656 "young list should be well formed");
3657
3658 // Don't dynamically change the number of GC threads this early. A value of
3659 // 0 is used to indicate serial work. When parallel work is done,
3660 // it will be set.
3661
3662 { // Call to jvmpi::post_class_unload_events must occur outside of active GC
3663 IsGCActiveMark x;
3664
3665 gc_prologue(false);
3666 increment_total_collections(false /* full gc */);
3667 increment_gc_time_stamp();
3668
3669 if (VerifyBeforeGC && total_collections() >= VerifyGCStartAt) {
3670 HandleMark hm; // Discard invalid handles created during verification
3671 gclog_or_tty->print(" VerifyBeforeGC:");
3672 prepare_for_verify();
3673 Universe::verify(/* silent */ false,
3674 /* option */ VerifyOption_G1UsePrevMarking);
3675 }
3676
3677 COMPILER2_PRESENT(DerivedPointerTable::clear());
3678
3679 // Please see comment in g1CollectedHeap.hpp and
3680 // G1CollectedHeap::ref_processing_init() to see how
3681 // reference processing currently works in G1.
3682
3683 // Enable discovery in the STW reference processor
3684 ref_processor_stw()->enable_discovery(true /*verify_disabled*/,
3685 true /*verify_no_refs*/);
3686
3687 {
3688 // We want to temporarily turn off discovery by the
3689 // CM ref processor, if necessary, and turn it back on
3690 // on again later if we do. Using a scoped
3691 // NoRefDiscovery object will do this.
3692 NoRefDiscovery no_cm_discovery(ref_processor_cm());
3693
3694 // Forget the current alloc region (we might even choose it to be part
3695 // of the collection set!).
3696 release_mutator_alloc_region();
3697
3698 // We should call this after we retire the mutator alloc
3699 // region(s) so that all the ALLOC / RETIRE events are generated
3700 // before the start GC event.
3701 _hr_printer.start_gc(false /* full */, (size_t) total_collections());
3702
3703 // This timing is only used by the ergonomics to handle our pause target.
3704 // It is unclear why this should not include the full pause. We will
3705 // investigate this in CR 7178365.
3706 //
3707 // Preserving the old comment here if that helps the investigation:
3708 //
3709 // The elapsed time induced by the start time below deliberately elides
3710 // the possible verification above.
3711 double sample_start_time_sec = os::elapsedTime();
3712 size_t start_used_bytes = used();
3713
3714 #if YOUNG_LIST_VERBOSE
3715 gclog_or_tty->print_cr("\nBefore recording pause start.\nYoung_list:");
3716 _young_list->print();
3717 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3718 #endif // YOUNG_LIST_VERBOSE
3719
3720 g1_policy()->record_collection_pause_start(sample_start_time_sec,
3721 start_used_bytes);
3722
3723 double scan_wait_start = os::elapsedTime();
3724 // We have to wait until the CM threads finish scanning the
3725 // root regions as it's the only way to ensure that all the
3726 // objects on them have been correctly scanned before we start
3727 // moving them during the GC.
3728 bool waited = _cm->root_regions()->wait_until_scan_finished();
3729 double wait_time_ms = 0.0;
3730 if (waited) {
3731 double scan_wait_end = os::elapsedTime();
3732 wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
3733 }
3734 g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms);
3735
3736 #if YOUNG_LIST_VERBOSE
3737 gclog_or_tty->print_cr("\nAfter recording pause start.\nYoung_list:");
3738 _young_list->print();
3739 #endif // YOUNG_LIST_VERBOSE
3740
3741 if (g1_policy()->during_initial_mark_pause()) {
3742 concurrent_mark()->checkpointRootsInitialPre();
3743 }
3744 perm_gen()->save_marks();
3745
3746 #if YOUNG_LIST_VERBOSE
3747 gclog_or_tty->print_cr("\nBefore choosing collection set.\nYoung_list:");
3748 _young_list->print();
3749 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3750 #endif // YOUNG_LIST_VERBOSE
3751
3752 g1_policy()->finalize_cset(target_pause_time_ms);
3753
3754 _cm->note_start_of_gc();
3755 // We should not verify the per-thread SATB buffers given that
3756 // we have not filtered them yet (we'll do so during the
3757 // GC). We also call this after finalize_cset() to
3758 // ensure that the CSet has been finalized.
3759 _cm->verify_no_cset_oops(true /* verify_stacks */,
3760 true /* verify_enqueued_buffers */,
3761 false /* verify_thread_buffers */,
3762 true /* verify_fingers */);
3763
3764 if (_hr_printer.is_active()) {
3765 HeapRegion* hr = g1_policy()->collection_set();
3766 while (hr != NULL) {
3767 G1HRPrinter::RegionType type;
3768 if (!hr->is_young()) {
3769 type = G1HRPrinter::Old;
3770 } else if (hr->is_survivor()) {
3771 type = G1HRPrinter::Survivor;
3772 } else {
3773 type = G1HRPrinter::Eden;
3774 }
3775 _hr_printer.cset(hr);
3776 hr = hr->next_in_collection_set();
3777 }
3778 }
3779
3780 #ifdef ASSERT
3781 VerifyCSetClosure cl;
3782 collection_set_iterate(&cl);
3783 #endif // ASSERT
3784
3785 setup_surviving_young_words();
3786
3787 // Initialize the GC alloc regions.
3788 init_gc_alloc_regions();
3789
3790 // Actually do the work...
3791 evacuate_collection_set();
3792
3793 // We do this to mainly verify the per-thread SATB buffers
3794 // (which have been filtered by now) since we didn't verify
3795 // them earlier. No point in re-checking the stacks / enqueued
3796 // buffers given that the CSet has not changed since last time
3797 // we checked.
3798 _cm->verify_no_cset_oops(false /* verify_stacks */,
3799 false /* verify_enqueued_buffers */,
3800 true /* verify_thread_buffers */,
3801 true /* verify_fingers */);
3802
3803 free_collection_set(g1_policy()->collection_set());
3804 g1_policy()->clear_collection_set();
3805
3806 cleanup_surviving_young_words();
3807
3808 // Start a new incremental collection set for the next pause.
3809 g1_policy()->start_incremental_cset_building();
3810
3811 // Clear the _cset_fast_test bitmap in anticipation of adding
3812 // regions to the incremental collection set for the next
3813 // evacuation pause.
3814 clear_cset_fast_test();
3815
3816 _young_list->reset_sampled_info();
3817
3818 // Don't check the whole heap at this point as the
3819 // GC alloc regions from this pause have been tagged
3820 // as survivors and moved on to the survivor list.
3821 // Survivor regions will fail the !is_young() check.
3822 assert(check_young_list_empty(false /* check_heap */),
3823 "young list should be empty");
3824
3825 #if YOUNG_LIST_VERBOSE
3826 gclog_or_tty->print_cr("Before recording survivors.\nYoung List:");
3827 _young_list->print();
3828 #endif // YOUNG_LIST_VERBOSE
3829
3830 g1_policy()->record_survivor_regions(_young_list->survivor_length(),
3831 _young_list->first_survivor_region(),
3832 _young_list->last_survivor_region());
3833
3834 _young_list->reset_auxilary_lists();
3835
3836 if (evacuation_failed()) {
3837 _summary_bytes_used = recalculate_used();
3838 } else {
3839 // The "used" of the the collection set have already been subtracted
3840 // when they were freed. Add in the bytes evacuated.
3841 _summary_bytes_used += g1_policy()->bytes_copied_during_gc();
3842 }
3843
3844 if (g1_policy()->during_initial_mark_pause()) {
3845 // We have to do this before we notify the CM threads that
3846 // they can start working to make sure that all the
3847 // appropriate initialization is done on the CM object.
3848 concurrent_mark()->checkpointRootsInitialPost();
3849 set_marking_started();
3850 // Note that we don't actually trigger the CM thread at
3851 // this point. We do that later when we're sure that
3852 // the current thread has completed its logging output.
3853 }
3854
3855 allocate_dummy_regions();
3856
3857 #if YOUNG_LIST_VERBOSE
3858 gclog_or_tty->print_cr("\nEnd of the pause.\nYoung_list:");
3859 _young_list->print();
3860 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3861 #endif // YOUNG_LIST_VERBOSE
3862
3863 init_mutator_alloc_region();
3864
3865 {
3866 size_t expand_bytes = g1_policy()->expansion_amount();
3867 if (expand_bytes > 0) {
3868 size_t bytes_before = capacity();
3869 // No need for an ergo verbose message here,
3870 // expansion_amount() does this when it returns a value > 0.
3871 if (!expand(expand_bytes)) {
3872 // We failed to expand the heap so let's verify that
3873 // committed/uncommitted amount match the backing store
3874 assert(capacity() == _g1_storage.committed_size(), "committed size mismatch");
3875 assert(max_capacity() == _g1_storage.reserved_size(), "reserved size mismatch");
3876 }
3877 }
3878 }
3879
3880 // We redo the verificaiton but now wrt to the new CSet which
3881 // has just got initialized after the previous CSet was freed.
3882 _cm->verify_no_cset_oops(true /* verify_stacks */,
3883 true /* verify_enqueued_buffers */,
3884 true /* verify_thread_buffers */,
3885 true /* verify_fingers */);
3886 _cm->note_end_of_gc();
3887
3888 // Collect thread local data to allow the ergonomics to use
3889 // the collected information
3890 g1_policy()->phase_times()->collapse_par_times();
3891
3892 // This timing is only used by the ergonomics to handle our pause target.
3893 // It is unclear why this should not include the full pause. We will
3894 // investigate this in CR 7178365.
3895 double sample_end_time_sec = os::elapsedTime();
3896 double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
3897 g1_policy()->record_collection_pause_end(pause_time_ms);
3898
3899 MemoryService::track_memory_usage();
3900
3901 // In prepare_for_verify() below we'll need to scan the deferred
3902 // update buffers to bring the RSets up-to-date if
3903 // G1HRRSFlushLogBuffersOnVerify has been set. While scanning
3904 // the update buffers we'll probably need to scan cards on the
3905 // regions we just allocated to (i.e., the GC alloc
3906 // regions). However, during the last GC we called
3907 // set_saved_mark() on all the GC alloc regions, so card
3908 // scanning might skip the [saved_mark_word()...top()] area of
3909 // those regions (i.e., the area we allocated objects into
3910 // during the last GC). But it shouldn't. Given that
3911 // saved_mark_word() is conditional on whether the GC time stamp
3912 // on the region is current or not, by incrementing the GC time
3913 // stamp here we invalidate all the GC time stamps on all the
3914 // regions and saved_mark_word() will simply return top() for
3915 // all the regions. This is a nicer way of ensuring this rather
3916 // than iterating over the regions and fixing them. In fact, the
3917 // GC time stamp increment here also ensures that
3918 // saved_mark_word() will return top() between pauses, i.e.,
3919 // during concurrent refinement. So we don't need the
3920 // is_gc_active() check to decided which top to use when
3921 // scanning cards (see CR 7039627).
3922 increment_gc_time_stamp();
3923
3924 if (VerifyAfterGC && total_collections() >= VerifyGCStartAt) {
3925 HandleMark hm; // Discard invalid handles created during verification
3926 gclog_or_tty->print(" VerifyAfterGC:");
3927 prepare_for_verify();
3928 Universe::verify(/* silent */ false,
3929 /* option */ VerifyOption_G1UsePrevMarking);
3930 }
3931
3932 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
3933 ref_processor_stw()->verify_no_references_recorded();
3934
3935 // CM reference discovery will be re-enabled if necessary.
3936 }
3937
3938 // We should do this after we potentially expand the heap so
3939 // that all the COMMIT events are generated before the end GC
3940 // event, and after we retire the GC alloc regions so that all
3941 // RETIRE events are generated before the end GC event.
3942 _hr_printer.end_gc(false /* full */, (size_t) total_collections());
3943
3944 if (mark_in_progress()) {
3945 concurrent_mark()->update_g1_committed();
3946 }
3947
3948 #ifdef TRACESPINNING
3949 ParallelTaskTerminator::print_termination_counts();
3950 #endif
3951
3952 gc_epilogue(false);
3953
3954 g1_policy()->phase_times()->note_gc_end(os::elapsedTime());
3955
3956 // We have to do this after we decide whether to expand the heap or not.
3957 g1_policy()->print_heap_transition();
3958 }
3959
3960 // It is not yet to safe to tell the concurrent mark to
3961 // start as we have some optional output below. We don't want the
3962 // output from the concurrent mark thread interfering with this
3963 // logging output either.
3964
3965 _hrs.verify_optional();
3966 verify_region_sets_optional();
3967
3968 TASKQUEUE_STATS_ONLY(if (ParallelGCVerbose) print_taskqueue_stats());
3969 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
3970
3971 print_heap_after_gc();
3972
3973 // We must call G1MonitoringSupport::update_sizes() in the same scoping level
3974 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
3975 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
3976 // before any GC notifications are raised.
3977 g1mm()->update_sizes();
3978 }
3979
3980 if (G1SummarizeRSetStats &&
3981 (G1SummarizeRSetStatsPeriod > 0) &&
3982 (total_collections() % G1SummarizeRSetStatsPeriod == 0)) {
3983 g1_rem_set()->print_summary_info();
3984 }
3985
3986 // It should now be safe to tell the concurrent mark thread to start
3987 // without its logging output interfering with the logging output
3988 // that came from the pause.
3989
3990 if (should_start_conc_mark) {
3991 // CAUTION: after the doConcurrentMark() call below,
3992 // the concurrent marking thread(s) could be running
3993 // concurrently with us. Make sure that anything after
3994 // this point does not assume that we are the only GC thread
3995 // running. Note: of course, the actual marking work will
3996 // not start until the safepoint itself is released in
3997 // ConcurrentGCThread::safepoint_desynchronize().
3998 doConcurrentMark();
3999 }
4000
4001 return true;
4002 }
4003
4004 size_t G1CollectedHeap::desired_plab_sz(GCAllocPurpose purpose)
4005 {
4006 size_t gclab_word_size;
4007 switch (purpose) {
4008 case GCAllocForSurvived:
4009 gclab_word_size = YoungPLABSize;
4010 break;
4011 case GCAllocForTenured:
4012 gclab_word_size = OldPLABSize;
4013 break;
4014 default:
4015 assert(false, "unknown GCAllocPurpose");
4016 gclab_word_size = OldPLABSize;
4017 break;
4018 }
4019 return gclab_word_size;
4020 }
4021
4022 void G1CollectedHeap::init_mutator_alloc_region() {
4023 assert(_mutator_alloc_region.get() == NULL, "pre-condition");
4024 _mutator_alloc_region.init();
4025 }
4026
4027 void G1CollectedHeap::release_mutator_alloc_region() {
4028 _mutator_alloc_region.release();
4029 assert(_mutator_alloc_region.get() == NULL, "post-condition");
4030 }
4031
4032 void G1CollectedHeap::init_gc_alloc_regions() {
4033 assert_at_safepoint(true /* should_be_vm_thread */);
4034
4035 _survivor_gc_alloc_region.init();
4036 _old_gc_alloc_region.init();
4037 HeapRegion* retained_region = _retained_old_gc_alloc_region;
4038 _retained_old_gc_alloc_region = NULL;
4039
4040 // We will discard the current GC alloc region if:
4041 // a) it's in the collection set (it can happen!),
4042 // b) it's already full (no point in using it),
4043 // c) it's empty (this means that it was emptied during
4044 // a cleanup and it should be on the free list now), or
4045 // d) it's humongous (this means that it was emptied
4046 // during a cleanup and was added to the free list, but
4047 // has been subseqently used to allocate a humongous
4048 // object that may be less than the region size).
4049 if (retained_region != NULL &&
4050 !retained_region->in_collection_set() &&
4051 !(retained_region->top() == retained_region->end()) &&
4052 !retained_region->is_empty() &&
4053 !retained_region->isHumongous()) {
4054 retained_region->set_saved_mark();
4055 // The retained region was added to the old region set when it was
4056 // retired. We have to remove it now, since we don't allow regions
4057 // we allocate to in the region sets. We'll re-add it later, when
4058 // it's retired again.
4059 _old_set.remove(retained_region);
4060 bool during_im = g1_policy()->during_initial_mark_pause();
4061 retained_region->note_start_of_copying(during_im);
4062 _old_gc_alloc_region.set(retained_region);
4063 _hr_printer.reuse(retained_region);
4064 }
4065 }
4066
4067 void G1CollectedHeap::release_gc_alloc_regions() {
4068 _survivor_gc_alloc_region.release();
4069 // If we have an old GC alloc region to release, we'll save it in
4070 // _retained_old_gc_alloc_region. If we don't
4071 // _retained_old_gc_alloc_region will become NULL. This is what we
4072 // want either way so no reason to check explicitly for either
4073 // condition.
4074 _retained_old_gc_alloc_region = _old_gc_alloc_region.release();
4075 }
4076
4077 void G1CollectedHeap::abandon_gc_alloc_regions() {
4078 assert(_survivor_gc_alloc_region.get() == NULL, "pre-condition");
4079 assert(_old_gc_alloc_region.get() == NULL, "pre-condition");
4080 _retained_old_gc_alloc_region = NULL;
4081 }
4082
4083 void G1CollectedHeap::init_for_evac_failure(OopsInHeapRegionClosure* cl) {
4084 _drain_in_progress = false;
4085 set_evac_failure_closure(cl);
4086 _evac_failure_scan_stack = new (ResourceObj::C_HEAP, mtGC) GrowableArray<oop>(40, true);
4087 }
4088
4089 void G1CollectedHeap::finalize_for_evac_failure() {
4090 assert(_evac_failure_scan_stack != NULL &&
4091 _evac_failure_scan_stack->length() == 0,
4092 "Postcondition");
4093 assert(!_drain_in_progress, "Postcondition");
4094 delete _evac_failure_scan_stack;
4095 _evac_failure_scan_stack = NULL;
4096 }
4097
4098 void G1CollectedHeap::remove_self_forwarding_pointers() {
4099 assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity");
4100
4101 G1ParRemoveSelfForwardPtrsTask rsfp_task(this);
4102
4103 if (G1CollectedHeap::use_parallel_gc_threads()) {
4104 set_par_threads();
4105 workers()->run_task(&rsfp_task);
4106 set_par_threads(0);
4107 } else {
4108 rsfp_task.work(0);
4109 }
4110
4111 assert(check_cset_heap_region_claim_values(HeapRegion::ParEvacFailureClaimValue), "sanity");
4112
4113 // Reset the claim values in the regions in the collection set.
4114 reset_cset_heap_region_claim_values();
4115
4116 assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity");
4117
4118 // Now restore saved marks, if any.
4119 if (_objs_with_preserved_marks != NULL) {
4120 assert(_preserved_marks_of_objs != NULL, "Both or none.");
4121 guarantee(_objs_with_preserved_marks->length() ==
4122 _preserved_marks_of_objs->length(), "Both or none.");
4123 for (int i = 0; i < _objs_with_preserved_marks->length(); i++) {
4124 oop obj = _objs_with_preserved_marks->at(i);
4125 markOop m = _preserved_marks_of_objs->at(i);
4126 obj->set_mark(m);
4127 }
4128
4129 // Delete the preserved marks growable arrays (allocated on the C heap).
4130 delete _objs_with_preserved_marks;
4131 delete _preserved_marks_of_objs;
4132 _objs_with_preserved_marks = NULL;
4133 _preserved_marks_of_objs = NULL;
4134 }
4135 }
4136
4137 void G1CollectedHeap::push_on_evac_failure_scan_stack(oop obj) {
4138 _evac_failure_scan_stack->push(obj);
4139 }
4140
4141 void G1CollectedHeap::drain_evac_failure_scan_stack() {
4142 assert(_evac_failure_scan_stack != NULL, "precondition");
4143
4144 while (_evac_failure_scan_stack->length() > 0) {
4145 oop obj = _evac_failure_scan_stack->pop();
4146 _evac_failure_closure->set_region(heap_region_containing(obj));
4147 obj->oop_iterate_backwards(_evac_failure_closure);
4148 }
4149 }
4150
4151 oop
4152 G1CollectedHeap::handle_evacuation_failure_par(OopsInHeapRegionClosure* cl,
4153 oop old) {
4154 assert(obj_in_cs(old),
4155 err_msg("obj: "PTR_FORMAT" should still be in the CSet",
4156 (HeapWord*) old));
4157 markOop m = old->mark();
4158 oop forward_ptr = old->forward_to_atomic(old);
4159 if (forward_ptr == NULL) {
4160 // Forward-to-self succeeded.
4161
4162 if (_evac_failure_closure != cl) {
4163 MutexLockerEx x(EvacFailureStack_lock, Mutex::_no_safepoint_check_flag);
4164 assert(!_drain_in_progress,
4165 "Should only be true while someone holds the lock.");
4166 // Set the global evac-failure closure to the current thread's.
4167 assert(_evac_failure_closure == NULL, "Or locking has failed.");
4168 set_evac_failure_closure(cl);
4169 // Now do the common part.
4170 handle_evacuation_failure_common(old, m);
4171 // Reset to NULL.
4172 set_evac_failure_closure(NULL);
4173 } else {
4174 // The lock is already held, and this is recursive.
4175 assert(_drain_in_progress, "This should only be the recursive case.");
4176 handle_evacuation_failure_common(old, m);
4177 }
4178 return old;
4179 } else {
4180 // Forward-to-self failed. Either someone else managed to allocate
4181 // space for this object (old != forward_ptr) or they beat us in
4182 // self-forwarding it (old == forward_ptr).
4183 assert(old == forward_ptr || !obj_in_cs(forward_ptr),
4184 err_msg("obj: "PTR_FORMAT" forwarded to: "PTR_FORMAT" "
4185 "should not be in the CSet",
4186 (HeapWord*) old, (HeapWord*) forward_ptr));
4187 return forward_ptr;
4188 }
4189 }
4190
4191 void G1CollectedHeap::handle_evacuation_failure_common(oop old, markOop m) {
4192 set_evacuation_failed(true);
4193
4194 preserve_mark_if_necessary(old, m);
4195
4196 HeapRegion* r = heap_region_containing(old);
4197 if (!r->evacuation_failed()) {
4198 r->set_evacuation_failed(true);
4199 _hr_printer.evac_failure(r);
4200 }
4201
4202 push_on_evac_failure_scan_stack(old);
4203
4204 if (!_drain_in_progress) {
4205 // prevent recursion in copy_to_survivor_space()
4206 _drain_in_progress = true;
4207 drain_evac_failure_scan_stack();
4208 _drain_in_progress = false;
4209 }
4210 }
4211
4212 void G1CollectedHeap::preserve_mark_if_necessary(oop obj, markOop m) {
4213 assert(evacuation_failed(), "Oversaving!");
4214 // We want to call the "for_promotion_failure" version only in the
4215 // case of a promotion failure.
4216 if (m->must_be_preserved_for_promotion_failure(obj)) {
4217 if (_objs_with_preserved_marks == NULL) {
4218 assert(_preserved_marks_of_objs == NULL, "Both or none.");
4219 _objs_with_preserved_marks =
4220 new (ResourceObj::C_HEAP, mtGC) GrowableArray<oop>(40, true);
4221 _preserved_marks_of_objs =
4222 new (ResourceObj::C_HEAP, mtGC) GrowableArray<markOop>(40, true);
4223 }
4224 _objs_with_preserved_marks->push(obj);
4225 _preserved_marks_of_objs->push(m);
4226 }
4227 }
4228
4229 HeapWord* G1CollectedHeap::par_allocate_during_gc(GCAllocPurpose purpose,
4230 size_t word_size) {
4231 if (purpose == GCAllocForSurvived) {
4232 HeapWord* result = survivor_attempt_allocation(word_size);
4233 if (result != NULL) {
4234 return result;
4235 } else {
4236 // Let's try to allocate in the old gen in case we can fit the
4237 // object there.
4238 return old_attempt_allocation(word_size);
4239 }
4240 } else {
4241 assert(purpose == GCAllocForTenured, "sanity");
4242 HeapWord* result = old_attempt_allocation(word_size);
4243 if (result != NULL) {
4244 return result;
4245 } else {
4246 // Let's try to allocate in the survivors in case we can fit the
4247 // object there.
4248 return survivor_attempt_allocation(word_size);
4249 }
4250 }
4251
4252 ShouldNotReachHere();
4253 // Trying to keep some compilers happy.
4254 return NULL;
4255 }
4256
4257 G1ParGCAllocBuffer::G1ParGCAllocBuffer(size_t gclab_word_size) :
4258 ParGCAllocBuffer(gclab_word_size), _retired(false) { }
4259
4260 G1ParScanThreadState::G1ParScanThreadState(G1CollectedHeap* g1h, uint queue_num)
4261 : _g1h(g1h),
4262 _refs(g1h->task_queue(queue_num)),
4263 _dcq(&g1h->dirty_card_queue_set()),
4264 _ct_bs((CardTableModRefBS*)_g1h->barrier_set()),
4265 _g1_rem(g1h->g1_rem_set()),
4266 _hash_seed(17), _queue_num(queue_num),
4267 _term_attempts(0),
4268 _surviving_alloc_buffer(g1h->desired_plab_sz(GCAllocForSurvived)),
4269 _tenured_alloc_buffer(g1h->desired_plab_sz(GCAllocForTenured)),
4270 _age_table(false),
4271 _strong_roots_time(0), _term_time(0),
4272 _alloc_buffer_waste(0), _undo_waste(0) {
4273 // we allocate G1YoungSurvRateNumRegions plus one entries, since
4274 // we "sacrifice" entry 0 to keep track of surviving bytes for
4275 // non-young regions (where the age is -1)
4276 // We also add a few elements at the beginning and at the end in
4277 // an attempt to eliminate cache contention
4278 uint real_length = 1 + _g1h->g1_policy()->young_cset_region_length();
4279 uint array_length = PADDING_ELEM_NUM +
4280 real_length +
4281 PADDING_ELEM_NUM;
4282 _surviving_young_words_base = NEW_C_HEAP_ARRAY(size_t, array_length, mtGC);
4283 if (_surviving_young_words_base == NULL)
4284 vm_exit_out_of_memory(array_length * sizeof(size_t),
4285 "Not enough space for young surv histo.");
4286 _surviving_young_words = _surviving_young_words_base + PADDING_ELEM_NUM;
4287 memset(_surviving_young_words, 0, (size_t) real_length * sizeof(size_t));
4288
4289 _alloc_buffers[GCAllocForSurvived] = &_surviving_alloc_buffer;
4290 _alloc_buffers[GCAllocForTenured] = &_tenured_alloc_buffer;
4291
4292 _start = os::elapsedTime();
4293 }
4294
4295 void
4296 G1ParScanThreadState::print_termination_stats_hdr(outputStream* const st)
4297 {
4298 st->print_raw_cr("GC Termination Stats");
4299 st->print_raw_cr(" elapsed --strong roots-- -------termination-------"
4300 " ------waste (KiB)------");
4301 st->print_raw_cr("thr ms ms % ms % attempts"
4302 " total alloc undo");
4303 st->print_raw_cr("--- --------- --------- ------ --------- ------ --------"
4304 " ------- ------- -------");
4305 }
4306
4307 void
4308 G1ParScanThreadState::print_termination_stats(int i,
4309 outputStream* const st) const
4310 {
4311 const double elapsed_ms = elapsed_time() * 1000.0;
4312 const double s_roots_ms = strong_roots_time() * 1000.0;
4313 const double term_ms = term_time() * 1000.0;
4314 st->print_cr("%3d %9.2f %9.2f %6.2f "
4315 "%9.2f %6.2f " SIZE_FORMAT_W(8) " "
4316 SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7),
4317 i, elapsed_ms, s_roots_ms, s_roots_ms * 100 / elapsed_ms,
4318 term_ms, term_ms * 100 / elapsed_ms, term_attempts(),
4319 (alloc_buffer_waste() + undo_waste()) * HeapWordSize / K,
4320 alloc_buffer_waste() * HeapWordSize / K,
4321 undo_waste() * HeapWordSize / K);
4322 }
4323
4324 #ifdef ASSERT
4325 bool G1ParScanThreadState::verify_ref(narrowOop* ref) const {
4326 assert(ref != NULL, "invariant");
4327 assert(UseCompressedOops, "sanity");
4328 assert(!has_partial_array_mask(ref), err_msg("ref=" PTR_FORMAT, ref));
4329 oop p = oopDesc::load_decode_heap_oop(ref);
4330 assert(_g1h->is_in_g1_reserved(p),
4331 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p)));
4332 return true;
4333 }
4334
4335 bool G1ParScanThreadState::verify_ref(oop* ref) const {
4336 assert(ref != NULL, "invariant");
4337 if (has_partial_array_mask(ref)) {
4338 // Must be in the collection set--it's already been copied.
4339 oop p = clear_partial_array_mask(ref);
4340 assert(_g1h->obj_in_cs(p),
4341 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p)));
4342 } else {
4343 oop p = oopDesc::load_decode_heap_oop(ref);
4344 assert(_g1h->is_in_g1_reserved(p),
4345 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p)));
4346 }
4347 return true;
4348 }
4349
4350 bool G1ParScanThreadState::verify_task(StarTask ref) const {
4351 if (ref.is_narrow()) {
4352 return verify_ref((narrowOop*) ref);
4353 } else {
4354 return verify_ref((oop*) ref);
4355 }
4356 }
4357 #endif // ASSERT
4358
4359 void G1ParScanThreadState::trim_queue() {
4360 assert(_evac_cl != NULL, "not set");
4361 assert(_evac_failure_cl != NULL, "not set");
4362 assert(_partial_scan_cl != NULL, "not set");
4363
4364 StarTask ref;
4365 do {
4366 // Drain the overflow stack first, so other threads can steal.
4367 while (refs()->pop_overflow(ref)) {
4368 deal_with_reference(ref);
4369 }
4370
4371 while (refs()->pop_local(ref)) {
4372 deal_with_reference(ref);
4373 }
4374 } while (!refs()->is_empty());
4375 }
4376
4377 G1ParClosureSuper::G1ParClosureSuper(G1CollectedHeap* g1,
4378 G1ParScanThreadState* par_scan_state) :
4379 _g1(g1), _g1_rem(_g1->g1_rem_set()), _cm(_g1->concurrent_mark()),
4380 _par_scan_state(par_scan_state),
4381 _worker_id(par_scan_state->queue_num()),
4382 _during_initial_mark(_g1->g1_policy()->during_initial_mark_pause()),
4383 _mark_in_progress(_g1->mark_in_progress()) { }
4384
4385 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object>
4386 void G1ParCopyClosure<do_gen_barrier, barrier, do_mark_object>::mark_object(oop obj) {
4387 #ifdef ASSERT
4388 HeapRegion* hr = _g1->heap_region_containing(obj);
4389 assert(hr != NULL, "sanity");
4390 assert(!hr->in_collection_set(), "should not mark objects in the CSet");
4391 #endif // ASSERT
4392
4393 // We know that the object is not moving so it's safe to read its size.
4394 _cm->grayRoot(obj, (size_t) obj->size(), _worker_id);
4395 }
4396
4397 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object>
4398 void G1ParCopyClosure<do_gen_barrier, barrier, do_mark_object>
4399 ::mark_forwarded_object(oop from_obj, oop to_obj) {
4400 #ifdef ASSERT
4401 assert(from_obj->is_forwarded(), "from obj should be forwarded");
4402 assert(from_obj->forwardee() == to_obj, "to obj should be the forwardee");
4403 assert(from_obj != to_obj, "should not be self-forwarded");
4404
4405 HeapRegion* from_hr = _g1->heap_region_containing(from_obj);
4406 assert(from_hr != NULL, "sanity");
4407 assert(from_hr->in_collection_set(), "from obj should be in the CSet");
4408
4409 HeapRegion* to_hr = _g1->heap_region_containing(to_obj);
4410 assert(to_hr != NULL, "sanity");
4411 assert(!to_hr->in_collection_set(), "should not mark objects in the CSet");
4412 #endif // ASSERT
4413
4414 // The object might be in the process of being copied by another
4415 // worker so we cannot trust that its to-space image is
4416 // well-formed. So we have to read its size from its from-space
4417 // image which we know should not be changing.
4418 _cm->grayRoot(to_obj, (size_t) from_obj->size(), _worker_id);
4419 }
4420
4421 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object>
4422 oop G1ParCopyClosure<do_gen_barrier, barrier, do_mark_object>
4423 ::copy_to_survivor_space(oop old) {
4424 size_t word_sz = old->size();
4425 HeapRegion* from_region = _g1->heap_region_containing_raw(old);
4426 // +1 to make the -1 indexes valid...
4427 int young_index = from_region->young_index_in_cset()+1;
4428 assert( (from_region->is_young() && young_index > 0) ||
4429 (!from_region->is_young() && young_index == 0), "invariant" );
4430 G1CollectorPolicy* g1p = _g1->g1_policy();
4431 markOop m = old->mark();
4432 int age = m->has_displaced_mark_helper() ? m->displaced_mark_helper()->age()
4433 : m->age();
4434 GCAllocPurpose alloc_purpose = g1p->evacuation_destination(from_region, age,
4435 word_sz);
4436 HeapWord* obj_ptr = _par_scan_state->allocate(alloc_purpose, word_sz);
4437 oop obj = oop(obj_ptr);
4438
4439 if (obj_ptr == NULL) {
4440 // This will either forward-to-self, or detect that someone else has
4441 // installed a forwarding pointer.
4442 OopsInHeapRegionClosure* cl = _par_scan_state->evac_failure_closure();
4443 return _g1->handle_evacuation_failure_par(cl, old);
4444 }
4445
4446 // We're going to allocate linearly, so might as well prefetch ahead.
4447 Prefetch::write(obj_ptr, PrefetchCopyIntervalInBytes);
4448
4449 oop forward_ptr = old->forward_to_atomic(obj);
4450 if (forward_ptr == NULL) {
4451 Copy::aligned_disjoint_words((HeapWord*) old, obj_ptr, word_sz);
4452 if (g1p->track_object_age(alloc_purpose)) {
4453 // We could simply do obj->incr_age(). However, this causes a
4454 // performance issue. obj->incr_age() will first check whether
4455 // the object has a displaced mark by checking its mark word;
4456 // getting the mark word from the new location of the object
4457 // stalls. So, given that we already have the mark word and we
4458 // are about to install it anyway, it's better to increase the
4459 // age on the mark word, when the object does not have a
4460 // displaced mark word. We're not expecting many objects to have
4461 // a displaced marked word, so that case is not optimized
4462 // further (it could be...) and we simply call obj->incr_age().
4463
4464 if (m->has_displaced_mark_helper()) {
4465 // in this case, we have to install the mark word first,
4466 // otherwise obj looks to be forwarded (the old mark word,
4467 // which contains the forward pointer, was copied)
4468 obj->set_mark(m);
4469 obj->incr_age();
4470 } else {
4471 m = m->incr_age();
4472 obj->set_mark(m);
4473 }
4474 _par_scan_state->age_table()->add(obj, word_sz);
4475 } else {
4476 obj->set_mark(m);
4477 }
4478
4479 size_t* surv_young_words = _par_scan_state->surviving_young_words();
4480 surv_young_words[young_index] += word_sz;
4481
4482 if (obj->is_objArray() && arrayOop(obj)->length() >= ParGCArrayScanChunk) {
4483 // We keep track of the next start index in the length field of
4484 // the to-space object. The actual length can be found in the
4485 // length field of the from-space object.
4486 arrayOop(obj)->set_length(0);
4487 oop* old_p = set_partial_array_mask(old);
4488 _par_scan_state->push_on_queue(old_p);
4489 } else {
4490 // No point in using the slower heap_region_containing() method,
4491 // given that we know obj is in the heap.
4492 _scanner.set_region(_g1->heap_region_containing_raw(obj));
4493 obj->oop_iterate_backwards(&_scanner);
4494 }
4495 } else {
4496 _par_scan_state->undo_allocation(alloc_purpose, obj_ptr, word_sz);
4497 obj = forward_ptr;
4498 }
4499 return obj;
4500 }
4501
4502 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object>
4503 template <class T>
4504 void G1ParCopyClosure<do_gen_barrier, barrier, do_mark_object>
4505 ::do_oop_work(T* p) {
4506 oop obj = oopDesc::load_decode_heap_oop(p);
4507 assert(barrier != G1BarrierRS || obj != NULL,
4508 "Precondition: G1BarrierRS implies obj is non-NULL");
4509
4510 assert(_worker_id == _par_scan_state->queue_num(), "sanity");
4511
4512 // here the null check is implicit in the cset_fast_test() test
4513 if (_g1->in_cset_fast_test(obj)) {
4514 oop forwardee;
4515 if (obj->is_forwarded()) {
4516 forwardee = obj->forwardee();
4517 } else {
4518 forwardee = copy_to_survivor_space(obj);
4519 }
4520 assert(forwardee != NULL, "forwardee should not be NULL");
4521 oopDesc::encode_store_heap_oop(p, forwardee);
4522 if (do_mark_object && forwardee != obj) {
4523 // If the object is self-forwarded we don't need to explicitly
4524 // mark it, the evacuation failure protocol will do so.
4525 mark_forwarded_object(obj, forwardee);
4526 }
4527
4528 // When scanning the RS, we only care about objs in CS.
4529 if (barrier == G1BarrierRS) {
4530 _par_scan_state->update_rs(_from, p, _worker_id);
4531 }
4532 } else {
4533 // The object is not in collection set. If we're a root scanning
4534 // closure during an initial mark pause (i.e. do_mark_object will
4535 // be true) then attempt to mark the object.
4536 if (do_mark_object && _g1->is_in_g1_reserved(obj)) {
4537 mark_object(obj);
4538 }
4539 }
4540
4541 if (barrier == G1BarrierEvac && obj != NULL) {
4542 _par_scan_state->update_rs(_from, p, _worker_id);
4543 }
4544
4545 if (do_gen_barrier && obj != NULL) {
4546 par_do_barrier(p);
4547 }
4548 }
4549
4550 template void G1ParCopyClosure<false, G1BarrierEvac, false>::do_oop_work(oop* p);
4551 template void G1ParCopyClosure<false, G1BarrierEvac, false>::do_oop_work(narrowOop* p);
4552
4553 template <class T> void G1ParScanPartialArrayClosure::do_oop_nv(T* p) {
4554 assert(has_partial_array_mask(p), "invariant");
4555 oop from_obj = clear_partial_array_mask(p);
4556
4557 assert(Universe::heap()->is_in_reserved(from_obj), "must be in heap.");
4558 assert(from_obj->is_objArray(), "must be obj array");
4559 objArrayOop from_obj_array = objArrayOop(from_obj);
4560 // The from-space object contains the real length.
4561 int length = from_obj_array->length();
4562
4563 assert(from_obj->is_forwarded(), "must be forwarded");
4564 oop to_obj = from_obj->forwardee();
4565 assert(from_obj != to_obj, "should not be chunking self-forwarded objects");
4566 objArrayOop to_obj_array = objArrayOop(to_obj);
4567 // We keep track of the next start index in the length field of the
4568 // to-space object.
4569 int next_index = to_obj_array->length();
4570 assert(0 <= next_index && next_index < length,
4571 err_msg("invariant, next index: %d, length: %d", next_index, length));
4572
4573 int start = next_index;
4574 int end = length;
4575 int remainder = end - start;
4576 // We'll try not to push a range that's smaller than ParGCArrayScanChunk.
4577 if (remainder > 2 * ParGCArrayScanChunk) {
4578 end = start + ParGCArrayScanChunk;
4579 to_obj_array->set_length(end);
4580 // Push the remainder before we process the range in case another
4581 // worker has run out of things to do and can steal it.
4582 oop* from_obj_p = set_partial_array_mask(from_obj);
4583 _par_scan_state->push_on_queue(from_obj_p);
4584 } else {
4585 assert(length == end, "sanity");
4586 // We'll process the final range for this object. Restore the length
4587 // so that the heap remains parsable in case of evacuation failure.
4588 to_obj_array->set_length(end);
4589 }
4590 _scanner.set_region(_g1->heap_region_containing_raw(to_obj));
4591 // Process indexes [start,end). It will also process the header
4592 // along with the first chunk (i.e., the chunk with start == 0).
4593 // Note that at this point the length field of to_obj_array is not
4594 // correct given that we are using it to keep track of the next
4595 // start index. oop_iterate_range() (thankfully!) ignores the length
4596 // field and only relies on the start / end parameters. It does
4597 // however return the size of the object which will be incorrect. So
4598 // we have to ignore it even if we wanted to use it.
4599 to_obj_array->oop_iterate_range(&_scanner, start, end);
4600 }
4601
4602 class G1ParEvacuateFollowersClosure : public VoidClosure {
4603 protected:
4604 G1CollectedHeap* _g1h;
4605 G1ParScanThreadState* _par_scan_state;
4606 RefToScanQueueSet* _queues;
4607 ParallelTaskTerminator* _terminator;
4608
4609 G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
4610 RefToScanQueueSet* queues() { return _queues; }
4611 ParallelTaskTerminator* terminator() { return _terminator; }
4612
4613 public:
4614 G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h,
4615 G1ParScanThreadState* par_scan_state,
4616 RefToScanQueueSet* queues,
4617 ParallelTaskTerminator* terminator)
4618 : _g1h(g1h), _par_scan_state(par_scan_state),
4619 _queues(queues), _terminator(terminator) {}
4620
4621 void do_void();
4622
4623 private:
4624 inline bool offer_termination();
4625 };
4626
4627 bool G1ParEvacuateFollowersClosure::offer_termination() {
4628 G1ParScanThreadState* const pss = par_scan_state();
4629 pss->start_term_time();
4630 const bool res = terminator()->offer_termination();
4631 pss->end_term_time();
4632 return res;
4633 }
4634
4635 void G1ParEvacuateFollowersClosure::do_void() {
4636 StarTask stolen_task;
4637 G1ParScanThreadState* const pss = par_scan_state();
4638 pss->trim_queue();
4639
4640 do {
4641 while (queues()->steal(pss->queue_num(), pss->hash_seed(), stolen_task)) {
4642 assert(pss->verify_task(stolen_task), "sanity");
4643 if (stolen_task.is_narrow()) {
4644 pss->deal_with_reference((narrowOop*) stolen_task);
4645 } else {
4646 pss->deal_with_reference((oop*) stolen_task);
4647 }
4648
4649 // We've just processed a reference and we might have made
4650 // available new entries on the queues. So we have to make sure
4651 // we drain the queues as necessary.
4652 pss->trim_queue();
4653 }
4654 } while (!offer_termination());
4655
4656 pss->retire_alloc_buffers();
4657 }
4658
4659 class G1ParTask : public AbstractGangTask {
4660 protected:
4661 G1CollectedHeap* _g1h;
4662 RefToScanQueueSet *_queues;
4663 ParallelTaskTerminator _terminator;
4664 uint _n_workers;
4665
4666 Mutex _stats_lock;
4667 Mutex* stats_lock() { return &_stats_lock; }
4668
4669 size_t getNCards() {
4670 return (_g1h->capacity() + G1BlockOffsetSharedArray::N_bytes - 1)
4671 / G1BlockOffsetSharedArray::N_bytes;
4672 }
4673
4674 public:
4675 G1ParTask(G1CollectedHeap* g1h,
4676 RefToScanQueueSet *task_queues)
4677 : AbstractGangTask("G1 collection"),
4678 _g1h(g1h),
4679 _queues(task_queues),
4680 _terminator(0, _queues),
4681 _stats_lock(Mutex::leaf, "parallel G1 stats lock", true)
4682 {}
4683
4684 RefToScanQueueSet* queues() { return _queues; }
4685
4686 RefToScanQueue *work_queue(int i) {
4687 return queues()->queue(i);
4688 }
4689
4690 ParallelTaskTerminator* terminator() { return &_terminator; }
4691
4692 virtual void set_for_termination(int active_workers) {
4693 // This task calls set_n_termination() in par_non_clean_card_iterate_work()
4694 // in the young space (_par_seq_tasks) in the G1 heap
4695 // for SequentialSubTasksDone.
4696 // This task also uses SubTasksDone in SharedHeap and G1CollectedHeap
4697 // both of which need setting by set_n_termination().
4698 _g1h->SharedHeap::set_n_termination(active_workers);
4699 _g1h->set_n_termination(active_workers);
4700 terminator()->reset_for_reuse(active_workers);
4701 _n_workers = active_workers;
4702 }
4703
4704 void work(uint worker_id) {
4705 if (worker_id >= _n_workers) return; // no work needed this round
4706
4707 double start_time_ms = os::elapsedTime() * 1000.0;
4708 _g1h->g1_policy()->phase_times()->record_gc_worker_start_time(worker_id, start_time_ms);
4709
4710 {
4711 ResourceMark rm;
4712 HandleMark hm;
4713
4714 ReferenceProcessor* rp = _g1h->ref_processor_stw();
4715
4716 G1ParScanThreadState pss(_g1h, worker_id);
4717 G1ParScanHeapEvacClosure scan_evac_cl(_g1h, &pss, rp);
4718 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, rp);
4719 G1ParScanPartialArrayClosure partial_scan_cl(_g1h, &pss, rp);
4720
4721 pss.set_evac_closure(&scan_evac_cl);
4722 pss.set_evac_failure_closure(&evac_failure_cl);
4723 pss.set_partial_scan_closure(&partial_scan_cl);
4724
4725 G1ParScanExtRootClosure only_scan_root_cl(_g1h, &pss, rp);
4726 G1ParScanPermClosure only_scan_perm_cl(_g1h, &pss, rp);
4727
4728 G1ParScanAndMarkExtRootClosure scan_mark_root_cl(_g1h, &pss, rp);
4729 G1ParScanAndMarkPermClosure scan_mark_perm_cl(_g1h, &pss, rp);
4730
4731 OopClosure* scan_root_cl = &only_scan_root_cl;
4732 OopsInHeapRegionClosure* scan_perm_cl = &only_scan_perm_cl;
4733
4734 if (_g1h->g1_policy()->during_initial_mark_pause()) {
4735 // We also need to mark copied objects.
4736 scan_root_cl = &scan_mark_root_cl;
4737 scan_perm_cl = &scan_mark_perm_cl;
4738 }
4739
4740 G1ParPushHeapRSClosure push_heap_rs_cl(_g1h, &pss);
4741
4742 pss.start_strong_roots();
4743 _g1h->g1_process_strong_roots(/* not collecting perm */ false,
4744 SharedHeap::SO_AllClasses,
4745 scan_root_cl,
4746 &push_heap_rs_cl,
4747 scan_perm_cl,
4748 worker_id);
4749 pss.end_strong_roots();
4750
4751 {
4752 double start = os::elapsedTime();
4753 G1ParEvacuateFollowersClosure evac(_g1h, &pss, _queues, &_terminator);
4754 evac.do_void();
4755 double elapsed_ms = (os::elapsedTime()-start)*1000.0;
4756 double term_ms = pss.term_time()*1000.0;
4757 _g1h->g1_policy()->phase_times()->record_obj_copy_time(worker_id, elapsed_ms-term_ms);
4758 _g1h->g1_policy()->phase_times()->record_termination(worker_id, term_ms, pss.term_attempts());
4759 }
4760 _g1h->g1_policy()->record_thread_age_table(pss.age_table());
4761 _g1h->update_surviving_young_words(pss.surviving_young_words()+1);
4762
4763 if (ParallelGCVerbose) {
4764 MutexLocker x(stats_lock());
4765 pss.print_termination_stats(worker_id);
4766 }
4767
4768 assert(pss.refs()->is_empty(), "should be empty");
4769
4770 // Close the inner scope so that the ResourceMark and HandleMark
4771 // destructors are executed here and are included as part of the
4772 // "GC Worker Time".
4773 }
4774
4775 double end_time_ms = os::elapsedTime() * 1000.0;
4776 _g1h->g1_policy()->phase_times()->record_gc_worker_end_time(worker_id, end_time_ms);
4777 }
4778 };
4779
4780 // *** Common G1 Evacuation Stuff
4781
4782 // Closures that support the filtering of CodeBlobs scanned during
4783 // external root scanning.
4784
4785 // Closure applied to reference fields in code blobs (specifically nmethods)
4786 // to determine whether an nmethod contains references that point into
4787 // the collection set. Used as a predicate when walking code roots so
4788 // that only nmethods that point into the collection set are added to the
4789 // 'marked' list.
4790
4791 class G1FilteredCodeBlobToOopClosure : public CodeBlobToOopClosure {
4792
4793 class G1PointsIntoCSOopClosure : public OopClosure {
4794 G1CollectedHeap* _g1;
4795 bool _points_into_cs;
4796 public:
4797 G1PointsIntoCSOopClosure(G1CollectedHeap* g1) :
4798 _g1(g1), _points_into_cs(false) { }
4799
4800 bool points_into_cs() const { return _points_into_cs; }
4801
4802 template <class T>
4803 void do_oop_nv(T* p) {
4804 if (!_points_into_cs) {
4805 T heap_oop = oopDesc::load_heap_oop(p);
4806 if (!oopDesc::is_null(heap_oop) &&
4807 _g1->in_cset_fast_test(oopDesc::decode_heap_oop_not_null(heap_oop))) {
4808 _points_into_cs = true;
4809 }
4810 }
4811 }
4812
4813 virtual void do_oop(oop* p) { do_oop_nv(p); }
4814 virtual void do_oop(narrowOop* p) { do_oop_nv(p); }
4815 };
4816
4817 G1CollectedHeap* _g1;
4818
4819 public:
4820 G1FilteredCodeBlobToOopClosure(G1CollectedHeap* g1, OopClosure* cl) :
4821 CodeBlobToOopClosure(cl, true), _g1(g1) { }
4822
4823 virtual void do_code_blob(CodeBlob* cb) {
4824 nmethod* nm = cb->as_nmethod_or_null();
4825 if (nm != NULL && !(nm->test_oops_do_mark())) {
4826 G1PointsIntoCSOopClosure predicate_cl(_g1);
4827 nm->oops_do(&predicate_cl);
4828
4829 if (predicate_cl.points_into_cs()) {
4830 // At least one of the reference fields or the oop relocations
4831 // in the nmethod points into the collection set. We have to
4832 // 'mark' this nmethod.
4833 // Note: Revisit the following if CodeBlobToOopClosure::do_code_blob()
4834 // or MarkingCodeBlobClosure::do_code_blob() change.
4835 if (!nm->test_set_oops_do_mark()) {
4836 do_newly_marked_nmethod(nm);
4837 }
4838 }
4839 }
4840 }
4841 };
4842
4843 // This method is run in a GC worker.
4844
4845 void
4846 G1CollectedHeap::
4847 g1_process_strong_roots(bool collecting_perm_gen,
4848 ScanningOption so,
4849 OopClosure* scan_non_heap_roots,
4850 OopsInHeapRegionClosure* scan_rs,
4851 OopsInGenClosure* scan_perm,
4852 int worker_i) {
4853
4854 // First scan the strong roots, including the perm gen.
4855 double ext_roots_start = os::elapsedTime();
4856 double closure_app_time_sec = 0.0;
4857
4858 BufferingOopClosure buf_scan_non_heap_roots(scan_non_heap_roots);
4859 BufferingOopsInGenClosure buf_scan_perm(scan_perm);
4860 buf_scan_perm.set_generation(perm_gen());
4861
4862 // Walk the code cache w/o buffering, because StarTask cannot handle
4863 // unaligned oop locations.
4864 G1FilteredCodeBlobToOopClosure eager_scan_code_roots(this, scan_non_heap_roots);
4865
4866 process_strong_roots(false, // no scoping; this is parallel code
4867 collecting_perm_gen, so,
4868 &buf_scan_non_heap_roots,
4869 &eager_scan_code_roots,
4870 &buf_scan_perm);
4871
4872 // Now the CM ref_processor roots.
4873 if (!_process_strong_tasks->is_task_claimed(G1H_PS_refProcessor_oops_do)) {
4874 // We need to treat the discovered reference lists of the
4875 // concurrent mark ref processor as roots and keep entries
4876 // (which are added by the marking threads) on them live
4877 // until they can be processed at the end of marking.
4878 ref_processor_cm()->weak_oops_do(&buf_scan_non_heap_roots);
4879 }
4880
4881 // Finish up any enqueued closure apps (attributed as object copy time).
4882 buf_scan_non_heap_roots.done();
4883 buf_scan_perm.done();
4884
4885 double ext_roots_end = os::elapsedTime();
4886
4887 g1_policy()->phase_times()->reset_obj_copy_time(worker_i);
4888 double obj_copy_time_sec = buf_scan_perm.closure_app_seconds() +
4889 buf_scan_non_heap_roots.closure_app_seconds();
4890 g1_policy()->phase_times()->record_obj_copy_time(worker_i, obj_copy_time_sec * 1000.0);
4891
4892 double ext_root_time_ms =
4893 ((ext_roots_end - ext_roots_start) - obj_copy_time_sec) * 1000.0;
4894
4895 g1_policy()->phase_times()->record_ext_root_scan_time(worker_i, ext_root_time_ms);
4896
4897 // During conc marking we have to filter the per-thread SATB buffers
4898 // to make sure we remove any oops into the CSet (which will show up
4899 // as implicitly live).
4900 if (!_process_strong_tasks->is_task_claimed(G1H_PS_filter_satb_buffers)) {
4901 if (mark_in_progress()) {
4902 JavaThread::satb_mark_queue_set().filter_thread_buffers();
4903 }
4904 }
4905 double satb_filtering_ms = (os::elapsedTime() - ext_roots_end) * 1000.0;
4906 g1_policy()->phase_times()->record_satb_filtering_time(worker_i, satb_filtering_ms);
4907
4908 // Now scan the complement of the collection set.
4909 if (scan_rs != NULL) {
4910 g1_rem_set()->oops_into_collection_set_do(scan_rs, worker_i);
4911 }
4912
4913 _process_strong_tasks->all_tasks_completed();
4914 }
4915
4916 void
4917 G1CollectedHeap::g1_process_weak_roots(OopClosure* root_closure,
4918 OopClosure* non_root_closure) {
4919 CodeBlobToOopClosure roots_in_blobs(root_closure, /*do_marking=*/ false);
4920 SharedHeap::process_weak_roots(root_closure, &roots_in_blobs, non_root_closure);
4921 }
4922
4923 // Weak Reference Processing support
4924
4925 // An always "is_alive" closure that is used to preserve referents.
4926 // If the object is non-null then it's alive. Used in the preservation
4927 // of referent objects that are pointed to by reference objects
4928 // discovered by the CM ref processor.
4929 class G1AlwaysAliveClosure: public BoolObjectClosure {
4930 G1CollectedHeap* _g1;
4931 public:
4932 G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
4933 void do_object(oop p) { assert(false, "Do not call."); }
4934 bool do_object_b(oop p) {
4935 if (p != NULL) {
4936 return true;
4937 }
4938 return false;
4939 }
4940 };
4941
4942 bool G1STWIsAliveClosure::do_object_b(oop p) {
4943 // An object is reachable if it is outside the collection set,
4944 // or is inside and copied.
4945 return !_g1->obj_in_cs(p) || p->is_forwarded();
4946 }
4947
4948 // Non Copying Keep Alive closure
4949 class G1KeepAliveClosure: public OopClosure {
4950 G1CollectedHeap* _g1;
4951 public:
4952 G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
4953 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
4954 void do_oop( oop* p) {
4955 oop obj = *p;
4956
4957 if (_g1->obj_in_cs(obj)) {
4958 assert( obj->is_forwarded(), "invariant" );
4959 *p = obj->forwardee();
4960 }
4961 }
4962 };
4963
4964 // Copying Keep Alive closure - can be called from both
4965 // serial and parallel code as long as different worker
4966 // threads utilize different G1ParScanThreadState instances
4967 // and different queues.
4968
4969 class G1CopyingKeepAliveClosure: public OopClosure {
4970 G1CollectedHeap* _g1h;
4971 OopClosure* _copy_non_heap_obj_cl;
4972 OopsInHeapRegionClosure* _copy_perm_obj_cl;
4973 G1ParScanThreadState* _par_scan_state;
4974
4975 public:
4976 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
4977 OopClosure* non_heap_obj_cl,
4978 OopsInHeapRegionClosure* perm_obj_cl,
4979 G1ParScanThreadState* pss):
4980 _g1h(g1h),
4981 _copy_non_heap_obj_cl(non_heap_obj_cl),
4982 _copy_perm_obj_cl(perm_obj_cl),
4983 _par_scan_state(pss)
4984 {}
4985
4986 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
4987 virtual void do_oop( oop* p) { do_oop_work(p); }
4988
4989 template <class T> void do_oop_work(T* p) {
4990 oop obj = oopDesc::load_decode_heap_oop(p);
4991
4992 if (_g1h->obj_in_cs(obj)) {
4993 // If the referent object has been forwarded (either copied
4994 // to a new location or to itself in the event of an
4995 // evacuation failure) then we need to update the reference
4996 // field and, if both reference and referent are in the G1
4997 // heap, update the RSet for the referent.
4998 //
4999 // If the referent has not been forwarded then we have to keep
5000 // it alive by policy. Therefore we have copy the referent.
5001 //
5002 // If the reference field is in the G1 heap then we can push
5003 // on the PSS queue. When the queue is drained (after each
5004 // phase of reference processing) the object and it's followers
5005 // will be copied, the reference field set to point to the
5006 // new location, and the RSet updated. Otherwise we need to
5007 // use the the non-heap or perm closures directly to copy
5008 // the refernt object and update the pointer, while avoiding
5009 // updating the RSet.
5010
5011 if (_g1h->is_in_g1_reserved(p)) {
5012 _par_scan_state->push_on_queue(p);
5013 } else {
5014 // The reference field is not in the G1 heap.
5015 if (_g1h->perm_gen()->is_in(p)) {
5016 _copy_perm_obj_cl->do_oop(p);
5017 } else {
5018 _copy_non_heap_obj_cl->do_oop(p);
5019 }
5020 }
5021 }
5022 }
5023 };
5024
5025 // Serial drain queue closure. Called as the 'complete_gc'
5026 // closure for each discovered list in some of the
5027 // reference processing phases.
5028
5029 class G1STWDrainQueueClosure: public VoidClosure {
5030 protected:
5031 G1CollectedHeap* _g1h;
5032 G1ParScanThreadState* _par_scan_state;
5033
5034 G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
5035
5036 public:
5037 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
5038 _g1h(g1h),
5039 _par_scan_state(pss)
5040 { }
5041
5042 void do_void() {
5043 G1ParScanThreadState* const pss = par_scan_state();
5044 pss->trim_queue();
5045 }
5046 };
5047
5048 // Parallel Reference Processing closures
5049
5050 // Implementation of AbstractRefProcTaskExecutor for parallel reference
5051 // processing during G1 evacuation pauses.
5052
5053 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
5054 private:
5055 G1CollectedHeap* _g1h;
5056 RefToScanQueueSet* _queues;
5057 FlexibleWorkGang* _workers;
5058 int _active_workers;
5059
5060 public:
5061 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
5062 FlexibleWorkGang* workers,
5063 RefToScanQueueSet *task_queues,
5064 int n_workers) :
5065 _g1h(g1h),
5066 _queues(task_queues),
5067 _workers(workers),
5068 _active_workers(n_workers)
5069 {
5070 assert(n_workers > 0, "shouldn't call this otherwise");
5071 }
5072
5073 // Executes the given task using concurrent marking worker threads.
5074 virtual void execute(ProcessTask& task);
5075 virtual void execute(EnqueueTask& task);
5076 };
5077
5078 // Gang task for possibly parallel reference processing
5079
5080 class G1STWRefProcTaskProxy: public AbstractGangTask {
5081 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
5082 ProcessTask& _proc_task;
5083 G1CollectedHeap* _g1h;
5084 RefToScanQueueSet *_task_queues;
5085 ParallelTaskTerminator* _terminator;
5086
5087 public:
5088 G1STWRefProcTaskProxy(ProcessTask& proc_task,
5089 G1CollectedHeap* g1h,
5090 RefToScanQueueSet *task_queues,
5091 ParallelTaskTerminator* terminator) :
5092 AbstractGangTask("Process reference objects in parallel"),
5093 _proc_task(proc_task),
5094 _g1h(g1h),
5095 _task_queues(task_queues),
5096 _terminator(terminator)
5097 {}
5098
5099 virtual void work(uint worker_id) {
5100 // The reference processing task executed by a single worker.
5101 ResourceMark rm;
5102 HandleMark hm;
5103
5104 G1STWIsAliveClosure is_alive(_g1h);
5105
5106 G1ParScanThreadState pss(_g1h, worker_id);
5107
5108 G1ParScanHeapEvacClosure scan_evac_cl(_g1h, &pss, NULL);
5109 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5110 G1ParScanPartialArrayClosure partial_scan_cl(_g1h, &pss, NULL);
5111
5112 pss.set_evac_closure(&scan_evac_cl);
5113 pss.set_evac_failure_closure(&evac_failure_cl);
5114 pss.set_partial_scan_closure(&partial_scan_cl);
5115
5116 G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL);
5117 G1ParScanPermClosure only_copy_perm_cl(_g1h, &pss, NULL);
5118
5119 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5120 G1ParScanAndMarkPermClosure copy_mark_perm_cl(_g1h, &pss, NULL);
5121
5122 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5123 OopsInHeapRegionClosure* copy_perm_cl = &only_copy_perm_cl;
5124
5125 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5126 // We also need to mark copied objects.
5127 copy_non_heap_cl = ©_mark_non_heap_cl;
5128 copy_perm_cl = ©_mark_perm_cl;
5129 }
5130
5131 // Keep alive closure.
5132 G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, copy_perm_cl, &pss);
5133
5134 // Complete GC closure
5135 G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _task_queues, _terminator);
5136
5137 // Call the reference processing task's work routine.
5138 _proc_task.work(worker_id, is_alive, keep_alive, drain_queue);
5139
5140 // Note we cannot assert that the refs array is empty here as not all
5141 // of the processing tasks (specifically phase2 - pp2_work) execute
5142 // the complete_gc closure (which ordinarily would drain the queue) so
5143 // the queue may not be empty.
5144 }
5145 };
5146
5147 // Driver routine for parallel reference processing.
5148 // Creates an instance of the ref processing gang
5149 // task and has the worker threads execute it.
5150 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) {
5151 assert(_workers != NULL, "Need parallel worker threads.");
5152
5153 ParallelTaskTerminator terminator(_active_workers, _queues);
5154 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _queues, &terminator);
5155
5156 _g1h->set_par_threads(_active_workers);
5157 _workers->run_task(&proc_task_proxy);
5158 _g1h->set_par_threads(0);
5159 }
5160
5161 // Gang task for parallel reference enqueueing.
5162
5163 class G1STWRefEnqueueTaskProxy: public AbstractGangTask {
5164 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
5165 EnqueueTask& _enq_task;
5166
5167 public:
5168 G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) :
5169 AbstractGangTask("Enqueue reference objects in parallel"),
5170 _enq_task(enq_task)
5171 { }
5172
5173 virtual void work(uint worker_id) {
5174 _enq_task.work(worker_id);
5175 }
5176 };
5177
5178 // Driver routine for parallel reference enqueing.
5179 // Creates an instance of the ref enqueueing gang
5180 // task and has the worker threads execute it.
5181
5182 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
5183 assert(_workers != NULL, "Need parallel worker threads.");
5184
5185 G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task);
5186
5187 _g1h->set_par_threads(_active_workers);
5188 _workers->run_task(&enq_task_proxy);
5189 _g1h->set_par_threads(0);
5190 }
5191
5192 // End of weak reference support closures
5193
5194 // Abstract task used to preserve (i.e. copy) any referent objects
5195 // that are in the collection set and are pointed to by reference
5196 // objects discovered by the CM ref processor.
5197
5198 class G1ParPreserveCMReferentsTask: public AbstractGangTask {
5199 protected:
5200 G1CollectedHeap* _g1h;
5201 RefToScanQueueSet *_queues;
5202 ParallelTaskTerminator _terminator;
5203 uint _n_workers;
5204
5205 public:
5206 G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h,int workers, RefToScanQueueSet *task_queues) :
5207 AbstractGangTask("ParPreserveCMReferents"),
5208 _g1h(g1h),
5209 _queues(task_queues),
5210 _terminator(workers, _queues),
5211 _n_workers(workers)
5212 { }
5213
5214 void work(uint worker_id) {
5215 ResourceMark rm;
5216 HandleMark hm;
5217
5218 G1ParScanThreadState pss(_g1h, worker_id);
5219 G1ParScanHeapEvacClosure scan_evac_cl(_g1h, &pss, NULL);
5220 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5221 G1ParScanPartialArrayClosure partial_scan_cl(_g1h, &pss, NULL);
5222
5223 pss.set_evac_closure(&scan_evac_cl);
5224 pss.set_evac_failure_closure(&evac_failure_cl);
5225 pss.set_partial_scan_closure(&partial_scan_cl);
5226
5227 assert(pss.refs()->is_empty(), "both queue and overflow should be empty");
5228
5229
5230 G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL);
5231 G1ParScanPermClosure only_copy_perm_cl(_g1h, &pss, NULL);
5232
5233 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5234 G1ParScanAndMarkPermClosure copy_mark_perm_cl(_g1h, &pss, NULL);
5235
5236 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5237 OopsInHeapRegionClosure* copy_perm_cl = &only_copy_perm_cl;
5238
5239 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5240 // We also need to mark copied objects.
5241 copy_non_heap_cl = ©_mark_non_heap_cl;
5242 copy_perm_cl = ©_mark_perm_cl;
5243 }
5244
5245 // Is alive closure
5246 G1AlwaysAliveClosure always_alive(_g1h);
5247
5248 // Copying keep alive closure. Applied to referent objects that need
5249 // to be copied.
5250 G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, copy_perm_cl, &pss);
5251
5252 ReferenceProcessor* rp = _g1h->ref_processor_cm();
5253
5254 uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q();
5255 uint stride = MIN2(MAX2(_n_workers, 1U), limit);
5256
5257 // limit is set using max_num_q() - which was set using ParallelGCThreads.
5258 // So this must be true - but assert just in case someone decides to
5259 // change the worker ids.
5260 assert(0 <= worker_id && worker_id < limit, "sanity");
5261 assert(!rp->discovery_is_atomic(), "check this code");
5262
5263 // Select discovered lists [i, i+stride, i+2*stride,...,limit)
5264 for (uint idx = worker_id; idx < limit; idx += stride) {
5265 DiscoveredList& ref_list = rp->discovered_refs()[idx];
5266
5267 DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive);
5268 while (iter.has_next()) {
5269 // Since discovery is not atomic for the CM ref processor, we
5270 // can see some null referent objects.
5271 iter.load_ptrs(DEBUG_ONLY(true));
5272 oop ref = iter.obj();
5273
5274 // This will filter nulls.
5275 if (iter.is_referent_alive()) {
5276 iter.make_referent_alive();
5277 }
5278 iter.move_to_next();
5279 }
5280 }
5281
5282 // Drain the queue - which may cause stealing
5283 G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _queues, &_terminator);
5284 drain_queue.do_void();
5285 // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure
5286 assert(pss.refs()->is_empty(), "should be");
5287 }
5288 };
5289
5290 // Weak Reference processing during an evacuation pause (part 1).
5291 void G1CollectedHeap::process_discovered_references() {
5292 double ref_proc_start = os::elapsedTime();
5293
5294 ReferenceProcessor* rp = _ref_processor_stw;
5295 assert(rp->discovery_enabled(), "should have been enabled");
5296
5297 // Any reference objects, in the collection set, that were 'discovered'
5298 // by the CM ref processor should have already been copied (either by
5299 // applying the external root copy closure to the discovered lists, or
5300 // by following an RSet entry).
5301 //
5302 // But some of the referents, that are in the collection set, that these
5303 // reference objects point to may not have been copied: the STW ref
5304 // processor would have seen that the reference object had already
5305 // been 'discovered' and would have skipped discovering the reference,
5306 // but would not have treated the reference object as a regular oop.
5307 // As a reult the copy closure would not have been applied to the
5308 // referent object.
5309 //
5310 // We need to explicitly copy these referent objects - the references
5311 // will be processed at the end of remarking.
5312 //
5313 // We also need to do this copying before we process the reference
5314 // objects discovered by the STW ref processor in case one of these
5315 // referents points to another object which is also referenced by an
5316 // object discovered by the STW ref processor.
5317
5318 uint active_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
5319 workers()->active_workers() : 1);
5320
5321 assert(!G1CollectedHeap::use_parallel_gc_threads() ||
5322 active_workers == workers()->active_workers(),
5323 "Need to reset active_workers");
5324
5325 set_par_threads(active_workers);
5326 G1ParPreserveCMReferentsTask keep_cm_referents(this, active_workers, _task_queues);
5327
5328 if (G1CollectedHeap::use_parallel_gc_threads()) {
5329 workers()->run_task(&keep_cm_referents);
5330 } else {
5331 keep_cm_referents.work(0);
5332 }
5333
5334 set_par_threads(0);
5335
5336 // Closure to test whether a referent is alive.
5337 G1STWIsAliveClosure is_alive(this);
5338
5339 // Even when parallel reference processing is enabled, the processing
5340 // of JNI refs is serial and performed serially by the current thread
5341 // rather than by a worker. The following PSS will be used for processing
5342 // JNI refs.
5343
5344 // Use only a single queue for this PSS.
5345 G1ParScanThreadState pss(this, 0);
5346
5347 // We do not embed a reference processor in the copying/scanning
5348 // closures while we're actually processing the discovered
5349 // reference objects.
5350 G1ParScanHeapEvacClosure scan_evac_cl(this, &pss, NULL);
5351 G1ParScanHeapEvacFailureClosure evac_failure_cl(this, &pss, NULL);
5352 G1ParScanPartialArrayClosure partial_scan_cl(this, &pss, NULL);
5353
5354 pss.set_evac_closure(&scan_evac_cl);
5355 pss.set_evac_failure_closure(&evac_failure_cl);
5356 pss.set_partial_scan_closure(&partial_scan_cl);
5357
5358 assert(pss.refs()->is_empty(), "pre-condition");
5359
5360 G1ParScanExtRootClosure only_copy_non_heap_cl(this, &pss, NULL);
5361 G1ParScanPermClosure only_copy_perm_cl(this, &pss, NULL);
5362
5363 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(this, &pss, NULL);
5364 G1ParScanAndMarkPermClosure copy_mark_perm_cl(this, &pss, NULL);
5365
5366 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5367 OopsInHeapRegionClosure* copy_perm_cl = &only_copy_perm_cl;
5368
5369 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5370 // We also need to mark copied objects.
5371 copy_non_heap_cl = ©_mark_non_heap_cl;
5372 copy_perm_cl = ©_mark_perm_cl;
5373 }
5374
5375 // Keep alive closure.
5376 G1CopyingKeepAliveClosure keep_alive(this, copy_non_heap_cl, copy_perm_cl, &pss);
5377
5378 // Serial Complete GC closure
5379 G1STWDrainQueueClosure drain_queue(this, &pss);
5380
5381 // Setup the soft refs policy...
5382 rp->setup_policy(false);
5383
5384 if (!rp->processing_is_mt()) {
5385 // Serial reference processing...
5386 rp->process_discovered_references(&is_alive,
5387 &keep_alive,
5388 &drain_queue,
5389 NULL);
5390 } else {
5391 // Parallel reference processing
5392 assert(rp->num_q() == active_workers, "sanity");
5393 assert(active_workers <= rp->max_num_q(), "sanity");
5394
5395 G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, active_workers);
5396 rp->process_discovered_references(&is_alive, &keep_alive, &drain_queue, &par_task_executor);
5397 }
5398
5399 // We have completed copying any necessary live referent objects
5400 // (that were not copied during the actual pause) so we can
5401 // retire any active alloc buffers
5402 pss.retire_alloc_buffers();
5403 assert(pss.refs()->is_empty(), "both queue and overflow should be empty");
5404
5405 double ref_proc_time = os::elapsedTime() - ref_proc_start;
5406 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
5407 }
5408
5409 // Weak Reference processing during an evacuation pause (part 2).
5410 void G1CollectedHeap::enqueue_discovered_references() {
5411 double ref_enq_start = os::elapsedTime();
5412
5413 ReferenceProcessor* rp = _ref_processor_stw;
5414 assert(!rp->discovery_enabled(), "should have been disabled as part of processing");
5415
5416 // Now enqueue any remaining on the discovered lists on to
5417 // the pending list.
5418 if (!rp->processing_is_mt()) {
5419 // Serial reference processing...
5420 rp->enqueue_discovered_references();
5421 } else {
5422 // Parallel reference enqueuing
5423
5424 uint active_workers = (ParallelGCThreads > 0 ? workers()->active_workers() : 1);
5425 assert(active_workers == workers()->active_workers(),
5426 "Need to reset active_workers");
5427 assert(rp->num_q() == active_workers, "sanity");
5428 assert(active_workers <= rp->max_num_q(), "sanity");
5429
5430 G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, active_workers);
5431 rp->enqueue_discovered_references(&par_task_executor);
5432 }
5433
5434 rp->verify_no_references_recorded();
5435 assert(!rp->discovery_enabled(), "should have been disabled");
5436
5437 // FIXME
5438 // CM's reference processing also cleans up the string and symbol tables.
5439 // Should we do that here also? We could, but it is a serial operation
5440 // and could signicantly increase the pause time.
5441
5442 double ref_enq_time = os::elapsedTime() - ref_enq_start;
5443 g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0);
5444 }
5445
5446 void G1CollectedHeap::evacuate_collection_set() {
5447 _expand_heap_after_alloc_failure = true;
5448 set_evacuation_failed(false);
5449
5450 g1_rem_set()->prepare_for_oops_into_collection_set_do();
5451 concurrent_g1_refine()->set_use_cache(false);
5452 concurrent_g1_refine()->clear_hot_cache_claimed_index();
5453
5454 uint n_workers;
5455 if (G1CollectedHeap::use_parallel_gc_threads()) {
5456 n_workers =
5457 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
5458 workers()->active_workers(),
5459 Threads::number_of_non_daemon_threads());
5460 assert(UseDynamicNumberOfGCThreads ||
5461 n_workers == workers()->total_workers(),
5462 "If not dynamic should be using all the workers");
5463 workers()->set_active_workers(n_workers);
5464 set_par_threads(n_workers);
5465 } else {
5466 assert(n_par_threads() == 0,
5467 "Should be the original non-parallel value");
5468 n_workers = 1;
5469 }
5470
5471 G1ParTask g1_par_task(this, _task_queues);
5472
5473 init_for_evac_failure(NULL);
5474
5475 rem_set()->prepare_for_younger_refs_iterate(true);
5476
5477 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
5478 double start_par_time_sec = os::elapsedTime();
5479 double end_par_time_sec;
5480
5481 {
5482 StrongRootsScope srs(this);
5483
5484 if (G1CollectedHeap::use_parallel_gc_threads()) {
5485 // The individual threads will set their evac-failure closures.
5486 if (ParallelGCVerbose) G1ParScanThreadState::print_termination_stats_hdr();
5487 // These tasks use ShareHeap::_process_strong_tasks
5488 assert(UseDynamicNumberOfGCThreads ||
5489 workers()->active_workers() == workers()->total_workers(),
5490 "If not dynamic should be using all the workers");
5491 workers()->run_task(&g1_par_task);
5492 } else {
5493 g1_par_task.set_for_termination(n_workers);
5494 g1_par_task.work(0);
5495 }
5496 end_par_time_sec = os::elapsedTime();
5497
5498 // Closing the inner scope will execute the destructor
5499 // for the StrongRootsScope object. We record the current
5500 // elapsed time before closing the scope so that time
5501 // taken for the SRS destructor is NOT included in the
5502 // reported parallel time.
5503 }
5504
5505 double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0;
5506 g1_policy()->phase_times()->record_par_time(par_time_ms);
5507
5508 double code_root_fixup_time_ms =
5509 (os::elapsedTime() - end_par_time_sec) * 1000.0;
5510 g1_policy()->phase_times()->record_code_root_fixup_time(code_root_fixup_time_ms);
5511
5512 set_par_threads(0);
5513
5514 // Process any discovered reference objects - we have
5515 // to do this _before_ we retire the GC alloc regions
5516 // as we may have to copy some 'reachable' referent
5517 // objects (and their reachable sub-graphs) that were
5518 // not copied during the pause.
5519 process_discovered_references();
5520
5521 // Weak root processing.
5522 // Note: when JSR 292 is enabled and code blobs can contain
5523 // non-perm oops then we will need to process the code blobs
5524 // here too.
5525 {
5526 G1STWIsAliveClosure is_alive(this);
5527 G1KeepAliveClosure keep_alive(this);
5528 JNIHandles::weak_oops_do(&is_alive, &keep_alive);
5529 }
5530
5531 release_gc_alloc_regions();
5532 g1_rem_set()->cleanup_after_oops_into_collection_set_do();
5533
5534 concurrent_g1_refine()->clear_hot_cache();
5535 concurrent_g1_refine()->set_use_cache(true);
5536
5537 finalize_for_evac_failure();
5538
5539 if (evacuation_failed()) {
5540 remove_self_forwarding_pointers();
5541 if (G1Log::finer()) {
5542 gclog_or_tty->print(" (to-space exhausted)");
5543 } else if (G1Log::fine()) {
5544 gclog_or_tty->print("--");
5545 }
5546 }
5547
5548 // Enqueue any remaining references remaining on the STW
5549 // reference processor's discovered lists. We need to do
5550 // this after the card table is cleaned (and verified) as
5551 // the act of enqueuing entries on to the pending list
5552 // will log these updates (and dirty their associated
5553 // cards). We need these updates logged to update any
5554 // RSets.
5555 enqueue_discovered_references();
5556
5557 if (G1DeferredRSUpdate) {
5558 RedirtyLoggedCardTableEntryFastClosure redirty;
5559 dirty_card_queue_set().set_closure(&redirty);
5560 dirty_card_queue_set().apply_closure_to_all_completed_buffers();
5561
5562 DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set();
5563 dcq.merge_bufferlists(&dirty_card_queue_set());
5564 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
5565 }
5566 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
5567 }
5568
5569 void G1CollectedHeap::free_region_if_empty(HeapRegion* hr,
5570 size_t* pre_used,
5571 FreeRegionList* free_list,
5572 OldRegionSet* old_proxy_set,
5573 HumongousRegionSet* humongous_proxy_set,
5574 HRRSCleanupTask* hrrs_cleanup_task,
5575 bool par) {
5576 if (hr->used() > 0 && hr->max_live_bytes() == 0 && !hr->is_young()) {
5577 if (hr->isHumongous()) {
5578 assert(hr->startsHumongous(), "we should only see starts humongous");
5579 free_humongous_region(hr, pre_used, free_list, humongous_proxy_set, par);
5580 } else {
5581 _old_set.remove_with_proxy(hr, old_proxy_set);
5582 free_region(hr, pre_used, free_list, par);
5583 }
5584 } else {
5585 hr->rem_set()->do_cleanup_work(hrrs_cleanup_task);
5586 }
5587 }
5588
5589 void G1CollectedHeap::free_region(HeapRegion* hr,
5590 size_t* pre_used,
5591 FreeRegionList* free_list,
5592 bool par) {
5593 assert(!hr->isHumongous(), "this is only for non-humongous regions");
5594 assert(!hr->is_empty(), "the region should not be empty");
5595 assert(free_list != NULL, "pre-condition");
5596
5597 *pre_used += hr->used();
5598 hr->hr_clear(par, true /* clear_space */);
5599 free_list->add_as_head(hr);
5600 }
5601
5602 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
5603 size_t* pre_used,
5604 FreeRegionList* free_list,
5605 HumongousRegionSet* humongous_proxy_set,
5606 bool par) {
5607 assert(hr->startsHumongous(), "this is only for starts humongous regions");
5608 assert(free_list != NULL, "pre-condition");
5609 assert(humongous_proxy_set != NULL, "pre-condition");
5610
5611 size_t hr_used = hr->used();
5612 size_t hr_capacity = hr->capacity();
5613 size_t hr_pre_used = 0;
5614 _humongous_set.remove_with_proxy(hr, humongous_proxy_set);
5615 hr->set_notHumongous();
5616 free_region(hr, &hr_pre_used, free_list, par);
5617
5618 uint i = hr->hrs_index() + 1;
5619 uint num = 1;
5620 while (i < n_regions()) {
5621 HeapRegion* curr_hr = region_at(i);
5622 if (!curr_hr->continuesHumongous()) {
5623 break;
5624 }
5625 curr_hr->set_notHumongous();
5626 free_region(curr_hr, &hr_pre_used, free_list, par);
5627 num += 1;
5628 i += 1;
5629 }
5630 assert(hr_pre_used == hr_used,
5631 err_msg("hr_pre_used: "SIZE_FORMAT" and hr_used: "SIZE_FORMAT" "
5632 "should be the same", hr_pre_used, hr_used));
5633 *pre_used += hr_pre_used;
5634 }
5635
5636 void G1CollectedHeap::update_sets_after_freeing_regions(size_t pre_used,
5637 FreeRegionList* free_list,
5638 OldRegionSet* old_proxy_set,
5639 HumongousRegionSet* humongous_proxy_set,
5640 bool par) {
5641 if (pre_used > 0) {
5642 Mutex* lock = (par) ? ParGCRareEvent_lock : NULL;
5643 MutexLockerEx x(lock, Mutex::_no_safepoint_check_flag);
5644 assert(_summary_bytes_used >= pre_used,
5645 err_msg("invariant: _summary_bytes_used: "SIZE_FORMAT" "
5646 "should be >= pre_used: "SIZE_FORMAT,
5647 _summary_bytes_used, pre_used));
5648 _summary_bytes_used -= pre_used;
5649 }
5650 if (free_list != NULL && !free_list->is_empty()) {
5651 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
5652 _free_list.add_as_head(free_list);
5653 }
5654 if (old_proxy_set != NULL && !old_proxy_set->is_empty()) {
5655 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
5656 _old_set.update_from_proxy(old_proxy_set);
5657 }
5658 if (humongous_proxy_set != NULL && !humongous_proxy_set->is_empty()) {
5659 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
5660 _humongous_set.update_from_proxy(humongous_proxy_set);
5661 }
5662 }
5663
5664 class G1ParCleanupCTTask : public AbstractGangTask {
5665 CardTableModRefBS* _ct_bs;
5666 G1CollectedHeap* _g1h;
5667 HeapRegion* volatile _su_head;
5668 public:
5669 G1ParCleanupCTTask(CardTableModRefBS* ct_bs,
5670 G1CollectedHeap* g1h) :
5671 AbstractGangTask("G1 Par Cleanup CT Task"),
5672 _ct_bs(ct_bs), _g1h(g1h) { }
5673
5674 void work(uint worker_id) {
5675 HeapRegion* r;
5676 while (r = _g1h->pop_dirty_cards_region()) {
5677 clear_cards(r);
5678 }
5679 }
5680
5681 void clear_cards(HeapRegion* r) {
5682 // Cards of the survivors should have already been dirtied.
5683 if (!r->is_survivor()) {
5684 _ct_bs->clear(MemRegion(r->bottom(), r->end()));
5685 }
5686 }
5687 };
5688
5689 #ifndef PRODUCT
5690 class G1VerifyCardTableCleanup: public HeapRegionClosure {
5691 G1CollectedHeap* _g1h;
5692 CardTableModRefBS* _ct_bs;
5693 public:
5694 G1VerifyCardTableCleanup(G1CollectedHeap* g1h, CardTableModRefBS* ct_bs)
5695 : _g1h(g1h), _ct_bs(ct_bs) { }
5696 virtual bool doHeapRegion(HeapRegion* r) {
5697 if (r->is_survivor()) {
5698 _g1h->verify_dirty_region(r);
5699 } else {
5700 _g1h->verify_not_dirty_region(r);
5701 }
5702 return false;
5703 }
5704 };
5705
5706 void G1CollectedHeap::verify_not_dirty_region(HeapRegion* hr) {
5707 // All of the region should be clean.
5708 CardTableModRefBS* ct_bs = (CardTableModRefBS*)barrier_set();
5709 MemRegion mr(hr->bottom(), hr->end());
5710 ct_bs->verify_not_dirty_region(mr);
5711 }
5712
5713 void G1CollectedHeap::verify_dirty_region(HeapRegion* hr) {
5714 // We cannot guarantee that [bottom(),end()] is dirty. Threads
5715 // dirty allocated blocks as they allocate them. The thread that
5716 // retires each region and replaces it with a new one will do a
5717 // maximal allocation to fill in [pre_dummy_top(),end()] but will
5718 // not dirty that area (one less thing to have to do while holding
5719 // a lock). So we can only verify that [bottom(),pre_dummy_top()]
5720 // is dirty.
5721 CardTableModRefBS* ct_bs = (CardTableModRefBS*) barrier_set();
5722 MemRegion mr(hr->bottom(), hr->pre_dummy_top());
5723 ct_bs->verify_dirty_region(mr);
5724 }
5725
5726 void G1CollectedHeap::verify_dirty_young_list(HeapRegion* head) {
5727 CardTableModRefBS* ct_bs = (CardTableModRefBS*) barrier_set();
5728 for (HeapRegion* hr = head; hr != NULL; hr = hr->get_next_young_region()) {
5729 verify_dirty_region(hr);
5730 }
5731 }
5732
5733 void G1CollectedHeap::verify_dirty_young_regions() {
5734 verify_dirty_young_list(_young_list->first_region());
5735 verify_dirty_young_list(_young_list->first_survivor_region());
5736 }
5737 #endif
5738
5739 void G1CollectedHeap::cleanUpCardTable() {
5740 CardTableModRefBS* ct_bs = (CardTableModRefBS*) (barrier_set());
5741 double start = os::elapsedTime();
5742
5743 {
5744 // Iterate over the dirty cards region list.
5745 G1ParCleanupCTTask cleanup_task(ct_bs, this);
5746
5747 if (G1CollectedHeap::use_parallel_gc_threads()) {
5748 set_par_threads();
5749 workers()->run_task(&cleanup_task);
5750 set_par_threads(0);
5751 } else {
5752 while (_dirty_cards_region_list) {
5753 HeapRegion* r = _dirty_cards_region_list;
5754 cleanup_task.clear_cards(r);
5755 _dirty_cards_region_list = r->get_next_dirty_cards_region();
5756 if (_dirty_cards_region_list == r) {
5757 // The last region.
5758 _dirty_cards_region_list = NULL;
5759 }
5760 r->set_next_dirty_cards_region(NULL);
5761 }
5762 }
5763 #ifndef PRODUCT
5764 if (G1VerifyCTCleanup || VerifyAfterGC) {
5765 G1VerifyCardTableCleanup cleanup_verifier(this, ct_bs);
5766 heap_region_iterate(&cleanup_verifier);
5767 }
5768 #endif
5769 }
5770
5771 double elapsed = os::elapsedTime() - start;
5772 g1_policy()->phase_times()->record_clear_ct_time(elapsed * 1000.0);
5773 }
5774
5775 void G1CollectedHeap::free_collection_set(HeapRegion* cs_head) {
5776 size_t pre_used = 0;
5777 FreeRegionList local_free_list("Local List for CSet Freeing");
5778
5779 double young_time_ms = 0.0;
5780 double non_young_time_ms = 0.0;
5781
5782 // Since the collection set is a superset of the the young list,
5783 // all we need to do to clear the young list is clear its
5784 // head and length, and unlink any young regions in the code below
5785 _young_list->clear();
5786
5787 G1CollectorPolicy* policy = g1_policy();
5788
5789 double start_sec = os::elapsedTime();
5790 bool non_young = true;
5791
5792 HeapRegion* cur = cs_head;
5793 int age_bound = -1;
5794 size_t rs_lengths = 0;
5795
5796 while (cur != NULL) {
5797 assert(!is_on_master_free_list(cur), "sanity");
5798 if (non_young) {
5799 if (cur->is_young()) {
5800 double end_sec = os::elapsedTime();
5801 double elapsed_ms = (end_sec - start_sec) * 1000.0;
5802 non_young_time_ms += elapsed_ms;
5803
5804 start_sec = os::elapsedTime();
5805 non_young = false;
5806 }
5807 } else {
5808 if (!cur->is_young()) {
5809 double end_sec = os::elapsedTime();
5810 double elapsed_ms = (end_sec - start_sec) * 1000.0;
5811 young_time_ms += elapsed_ms;
5812
5813 start_sec = os::elapsedTime();
5814 non_young = true;
5815 }
5816 }
5817
5818 rs_lengths += cur->rem_set()->occupied();
5819
5820 HeapRegion* next = cur->next_in_collection_set();
5821 assert(cur->in_collection_set(), "bad CS");
5822 cur->set_next_in_collection_set(NULL);
5823 cur->set_in_collection_set(false);
5824
5825 if (cur->is_young()) {
5826 int index = cur->young_index_in_cset();
5827 assert(index != -1, "invariant");
5828 assert((uint) index < policy->young_cset_region_length(), "invariant");
5829 size_t words_survived = _surviving_young_words[index];
5830 cur->record_surv_words_in_group(words_survived);
5831
5832 // At this point the we have 'popped' cur from the collection set
5833 // (linked via next_in_collection_set()) but it is still in the
5834 // young list (linked via next_young_region()). Clear the
5835 // _next_young_region field.
5836 cur->set_next_young_region(NULL);
5837 } else {
5838 int index = cur->young_index_in_cset();
5839 assert(index == -1, "invariant");
5840 }
5841
5842 assert( (cur->is_young() && cur->young_index_in_cset() > -1) ||
5843 (!cur->is_young() && cur->young_index_in_cset() == -1),
5844 "invariant" );
5845
5846 if (!cur->evacuation_failed()) {
5847 MemRegion used_mr = cur->used_region();
5848
5849 // And the region is empty.
5850 assert(!used_mr.is_empty(), "Should not have empty regions in a CS.");
5851 free_region(cur, &pre_used, &local_free_list, false /* par */);
5852 } else {
5853 cur->uninstall_surv_rate_group();
5854 if (cur->is_young()) {
5855 cur->set_young_index_in_cset(-1);
5856 }
5857 cur->set_not_young();
5858 cur->set_evacuation_failed(false);
5859 // The region is now considered to be old.
5860 _old_set.add(cur);
5861 }
5862 cur = next;
5863 }
5864
5865 policy->record_max_rs_lengths(rs_lengths);
5866 policy->cset_regions_freed();
5867
5868 double end_sec = os::elapsedTime();
5869 double elapsed_ms = (end_sec - start_sec) * 1000.0;
5870
5871 if (non_young) {
5872 non_young_time_ms += elapsed_ms;
5873 } else {
5874 young_time_ms += elapsed_ms;
5875 }
5876
5877 update_sets_after_freeing_regions(pre_used, &local_free_list,
5878 NULL /* old_proxy_set */,
5879 NULL /* humongous_proxy_set */,
5880 false /* par */);
5881 policy->phase_times()->record_young_free_cset_time_ms(young_time_ms);
5882 policy->phase_times()->record_non_young_free_cset_time_ms(non_young_time_ms);
5883 }
5884
5885 // This routine is similar to the above but does not record
5886 // any policy statistics or update free lists; we are abandoning
5887 // the current incremental collection set in preparation of a
5888 // full collection. After the full GC we will start to build up
5889 // the incremental collection set again.
5890 // This is only called when we're doing a full collection
5891 // and is immediately followed by the tearing down of the young list.
5892
5893 void G1CollectedHeap::abandon_collection_set(HeapRegion* cs_head) {
5894 HeapRegion* cur = cs_head;
5895
5896 while (cur != NULL) {
5897 HeapRegion* next = cur->next_in_collection_set();
5898 assert(cur->in_collection_set(), "bad CS");
5899 cur->set_next_in_collection_set(NULL);
5900 cur->set_in_collection_set(false);
5901 cur->set_young_index_in_cset(-1);
5902 cur = next;
5903 }
5904 }
5905
5906 void G1CollectedHeap::set_free_regions_coming() {
5907 if (G1ConcRegionFreeingVerbose) {
5908 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
5909 "setting free regions coming");
5910 }
5911
5912 assert(!free_regions_coming(), "pre-condition");
5913 _free_regions_coming = true;
5914 }
5915
5916 void G1CollectedHeap::reset_free_regions_coming() {
5917 assert(free_regions_coming(), "pre-condition");
5918
5919 {
5920 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
5921 _free_regions_coming = false;
5922 SecondaryFreeList_lock->notify_all();
5923 }
5924
5925 if (G1ConcRegionFreeingVerbose) {
5926 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
5927 "reset free regions coming");
5928 }
5929 }
5930
5931 void G1CollectedHeap::wait_while_free_regions_coming() {
5932 // Most of the time we won't have to wait, so let's do a quick test
5933 // first before we take the lock.
5934 if (!free_regions_coming()) {
5935 return;
5936 }
5937
5938 if (G1ConcRegionFreeingVerbose) {
5939 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
5940 "waiting for free regions");
5941 }
5942
5943 {
5944 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
5945 while (free_regions_coming()) {
5946 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
5947 }
5948 }
5949
5950 if (G1ConcRegionFreeingVerbose) {
5951 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
5952 "done waiting for free regions");
5953 }
5954 }
5955
5956 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
5957 assert(heap_lock_held_for_gc(),
5958 "the heap lock should already be held by or for this thread");
5959 _young_list->push_region(hr);
5960 }
5961
5962 class NoYoungRegionsClosure: public HeapRegionClosure {
5963 private:
5964 bool _success;
5965 public:
5966 NoYoungRegionsClosure() : _success(true) { }
5967 bool doHeapRegion(HeapRegion* r) {
5968 if (r->is_young()) {
5969 gclog_or_tty->print_cr("Region ["PTR_FORMAT", "PTR_FORMAT") tagged as young",
5970 r->bottom(), r->end());
5971 _success = false;
5972 }
5973 return false;
5974 }
5975 bool success() { return _success; }
5976 };
5977
5978 bool G1CollectedHeap::check_young_list_empty(bool check_heap, bool check_sample) {
5979 bool ret = _young_list->check_list_empty(check_sample);
5980
5981 if (check_heap) {
5982 NoYoungRegionsClosure closure;
5983 heap_region_iterate(&closure);
5984 ret = ret && closure.success();
5985 }
5986
5987 return ret;
5988 }
5989
5990 class TearDownRegionSetsClosure : public HeapRegionClosure {
5991 private:
5992 OldRegionSet *_old_set;
5993
5994 public:
5995 TearDownRegionSetsClosure(OldRegionSet* old_set) : _old_set(old_set) { }
5996
5997 bool doHeapRegion(HeapRegion* r) {
5998 if (r->is_empty()) {
5999 // We ignore empty regions, we'll empty the free list afterwards
6000 } else if (r->is_young()) {
6001 // We ignore young regions, we'll empty the young list afterwards
6002 } else if (r->isHumongous()) {
6003 // We ignore humongous regions, we're not tearing down the
6004 // humongous region set
6005 } else {
6006 // The rest should be old
6007 _old_set->remove(r);
6008 }
6009 return false;
6010 }
6011
6012 ~TearDownRegionSetsClosure() {
6013 assert(_old_set->is_empty(), "post-condition");
6014 }
6015 };
6016
6017 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
6018 assert_at_safepoint(true /* should_be_vm_thread */);
6019
6020 if (!free_list_only) {
6021 TearDownRegionSetsClosure cl(&_old_set);
6022 heap_region_iterate(&cl);
6023
6024 // Need to do this after the heap iteration to be able to
6025 // recognize the young regions and ignore them during the iteration.
6026 _young_list->empty_list();
6027 }
6028 _free_list.remove_all();
6029 }
6030
6031 class RebuildRegionSetsClosure : public HeapRegionClosure {
6032 private:
6033 bool _free_list_only;
6034 OldRegionSet* _old_set;
6035 FreeRegionList* _free_list;
6036 size_t _total_used;
6037
6038 public:
6039 RebuildRegionSetsClosure(bool free_list_only,
6040 OldRegionSet* old_set, FreeRegionList* free_list) :
6041 _free_list_only(free_list_only),
6042 _old_set(old_set), _free_list(free_list), _total_used(0) {
6043 assert(_free_list->is_empty(), "pre-condition");
6044 if (!free_list_only) {
6045 assert(_old_set->is_empty(), "pre-condition");
6046 }
6047 }
6048
6049 bool doHeapRegion(HeapRegion* r) {
6050 if (r->continuesHumongous()) {
6051 return false;
6052 }
6053
6054 if (r->is_empty()) {
6055 // Add free regions to the free list
6056 _free_list->add_as_tail(r);
6057 } else if (!_free_list_only) {
6058 assert(!r->is_young(), "we should not come across young regions");
6059
6060 if (r->isHumongous()) {
6061 // We ignore humongous regions, we left the humongous set unchanged
6062 } else {
6063 // The rest should be old, add them to the old set
6064 _old_set->add(r);
6065 }
6066 _total_used += r->used();
6067 }
6068
6069 return false;
6070 }
6071
6072 size_t total_used() {
6073 return _total_used;
6074 }
6075 };
6076
6077 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
6078 assert_at_safepoint(true /* should_be_vm_thread */);
6079
6080 RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_free_list);
6081 heap_region_iterate(&cl);
6082
6083 if (!free_list_only) {
6084 _summary_bytes_used = cl.total_used();
6085 }
6086 assert(_summary_bytes_used == recalculate_used(),
6087 err_msg("inconsistent _summary_bytes_used, "
6088 "value: "SIZE_FORMAT" recalculated: "SIZE_FORMAT,
6089 _summary_bytes_used, recalculate_used()));
6090 }
6091
6092 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) {
6093 _refine_cte_cl->set_concurrent(concurrent);
6094 }
6095
6096 bool G1CollectedHeap::is_in_closed_subset(const void* p) const {
6097 HeapRegion* hr = heap_region_containing(p);
6098 if (hr == NULL) {
6099 return is_in_permanent(p);
6100 } else {
6101 return hr->is_in(p);
6102 }
6103 }
6104
6105 // Methods for the mutator alloc region
6106
6107 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
6108 bool force) {
6109 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6110 assert(!force || g1_policy()->can_expand_young_list(),
6111 "if force is true we should be able to expand the young list");
6112 bool young_list_full = g1_policy()->is_young_list_full();
6113 if (force || !young_list_full) {
6114 HeapRegion* new_alloc_region = new_region(word_size,
6115 false /* do_expand */);
6116 if (new_alloc_region != NULL) {
6117 set_region_short_lived_locked(new_alloc_region);
6118 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Eden, young_list_full);
6119 return new_alloc_region;
6120 }
6121 }
6122 return NULL;
6123 }
6124
6125 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
6126 size_t allocated_bytes) {
6127 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6128 assert(alloc_region->is_young(), "all mutator alloc regions should be young");
6129
6130 g1_policy()->add_region_to_incremental_cset_lhs(alloc_region);
6131 _summary_bytes_used += allocated_bytes;
6132 _hr_printer.retire(alloc_region);
6133 // We update the eden sizes here, when the region is retired,
6134 // instead of when it's allocated, since this is the point that its
6135 // used space has been recored in _summary_bytes_used.
6136 g1mm()->update_eden_size();
6137 }
6138
6139 HeapRegion* MutatorAllocRegion::allocate_new_region(size_t word_size,
6140 bool force) {
6141 return _g1h->new_mutator_alloc_region(word_size, force);
6142 }
6143
6144 void G1CollectedHeap::set_par_threads() {
6145 // Don't change the number of workers. Use the value previously set
6146 // in the workgroup.
6147 assert(G1CollectedHeap::use_parallel_gc_threads(), "shouldn't be here otherwise");
6148 uint n_workers = workers()->active_workers();
6149 assert(UseDynamicNumberOfGCThreads ||
6150 n_workers == workers()->total_workers(),
6151 "Otherwise should be using the total number of workers");
6152 if (n_workers == 0) {
6153 assert(false, "Should have been set in prior evacuation pause.");
6154 n_workers = ParallelGCThreads;
6155 workers()->set_active_workers(n_workers);
6156 }
6157 set_par_threads(n_workers);
6158 }
6159
6160 void MutatorAllocRegion::retire_region(HeapRegion* alloc_region,
6161 size_t allocated_bytes) {
6162 _g1h->retire_mutator_alloc_region(alloc_region, allocated_bytes);
6163 }
6164
6165 // Methods for the GC alloc regions
6166
6167 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size,
6168 uint count,
6169 GCAllocPurpose ap) {
6170 assert(FreeList_lock->owned_by_self(), "pre-condition");
6171
6172 if (count < g1_policy()->max_regions(ap)) {
6173 HeapRegion* new_alloc_region = new_region(word_size,
6174 true /* do_expand */);
6175 if (new_alloc_region != NULL) {
6176 // We really only need to do this for old regions given that we
6177 // should never scan survivors. But it doesn't hurt to do it
6178 // for survivors too.
6179 new_alloc_region->set_saved_mark();
6180 if (ap == GCAllocForSurvived) {
6181 new_alloc_region->set_survivor();
6182 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Survivor);
6183 } else {
6184 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Old);
6185 }
6186 bool during_im = g1_policy()->during_initial_mark_pause();
6187 new_alloc_region->note_start_of_copying(during_im);
6188 return new_alloc_region;
6189 } else {
6190 g1_policy()->note_alloc_region_limit_reached(ap);
6191 }
6192 }
6193 return NULL;
6194 }
6195
6196 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
6197 size_t allocated_bytes,
6198 GCAllocPurpose ap) {
6199 bool during_im = g1_policy()->during_initial_mark_pause();
6200 alloc_region->note_end_of_copying(during_im);
6201 g1_policy()->record_bytes_copied_during_gc(allocated_bytes);
6202 if (ap == GCAllocForSurvived) {
6203 young_list()->add_survivor_region(alloc_region);
6204 } else {
6205 _old_set.add(alloc_region);
6206 }
6207 _hr_printer.retire(alloc_region);
6208 }
6209
6210 HeapRegion* SurvivorGCAllocRegion::allocate_new_region(size_t word_size,
6211 bool force) {
6212 assert(!force, "not supported for GC alloc regions");
6213 return _g1h->new_gc_alloc_region(word_size, count(), GCAllocForSurvived);
6214 }
6215
6216 void SurvivorGCAllocRegion::retire_region(HeapRegion* alloc_region,
6217 size_t allocated_bytes) {
6218 _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes,
6219 GCAllocForSurvived);
6220 }
6221
6222 HeapRegion* OldGCAllocRegion::allocate_new_region(size_t word_size,
6223 bool force) {
6224 assert(!force, "not supported for GC alloc regions");
6225 return _g1h->new_gc_alloc_region(word_size, count(), GCAllocForTenured);
6226 }
6227
6228 void OldGCAllocRegion::retire_region(HeapRegion* alloc_region,
6229 size_t allocated_bytes) {
6230 _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes,
6231 GCAllocForTenured);
6232 }
6233 // Heap region set verification
6234
6235 class VerifyRegionListsClosure : public HeapRegionClosure {
6236 private:
6237 FreeRegionList* _free_list;
6238 OldRegionSet* _old_set;
6239 HumongousRegionSet* _humongous_set;
6240 uint _region_count;
6241
6242 public:
6243 VerifyRegionListsClosure(OldRegionSet* old_set,
6244 HumongousRegionSet* humongous_set,
6245 FreeRegionList* free_list) :
6246 _old_set(old_set), _humongous_set(humongous_set),
6247 _free_list(free_list), _region_count(0) { }
6248
6249 uint region_count() { return _region_count; }
6250
6251 bool doHeapRegion(HeapRegion* hr) {
6252 _region_count += 1;
6253
6254 if (hr->continuesHumongous()) {
6255 return false;
6256 }
6257
6258 if (hr->is_young()) {
6259 // TODO
6260 } else if (hr->startsHumongous()) {
6261 _humongous_set->verify_next_region(hr);
6262 } else if (hr->is_empty()) {
6263 _free_list->verify_next_region(hr);
6264 } else {
6265 _old_set->verify_next_region(hr);
6266 }
6267 return false;
6268 }
6269 };
6270
6271 HeapRegion* G1CollectedHeap::new_heap_region(uint hrs_index,
6272 HeapWord* bottom) {
6273 HeapWord* end = bottom + HeapRegion::GrainWords;
6274 MemRegion mr(bottom, end);
6275 assert(_g1_reserved.contains(mr), "invariant");
6276 // This might return NULL if the allocation fails
6277 return new HeapRegion(hrs_index, _bot_shared, mr, true /* is_zeroed */);
6278 }
6279
6280 void G1CollectedHeap::verify_region_sets() {
6281 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6282
6283 // First, check the explicit lists.
6284 _free_list.verify();
6285 {
6286 // Given that a concurrent operation might be adding regions to
6287 // the secondary free list we have to take the lock before
6288 // verifying it.
6289 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6290 _secondary_free_list.verify();
6291 }
6292 _old_set.verify();
6293 _humongous_set.verify();
6294
6295 // If a concurrent region freeing operation is in progress it will
6296 // be difficult to correctly attributed any free regions we come
6297 // across to the correct free list given that they might belong to
6298 // one of several (free_list, secondary_free_list, any local lists,
6299 // etc.). So, if that's the case we will skip the rest of the
6300 // verification operation. Alternatively, waiting for the concurrent
6301 // operation to complete will have a non-trivial effect on the GC's
6302 // operation (no concurrent operation will last longer than the
6303 // interval between two calls to verification) and it might hide
6304 // any issues that we would like to catch during testing.
6305 if (free_regions_coming()) {
6306 return;
6307 }
6308
6309 // Make sure we append the secondary_free_list on the free_list so
6310 // that all free regions we will come across can be safely
6311 // attributed to the free_list.
6312 append_secondary_free_list_if_not_empty_with_lock();
6313
6314 // Finally, make sure that the region accounting in the lists is
6315 // consistent with what we see in the heap.
6316 _old_set.verify_start();
6317 _humongous_set.verify_start();
6318 _free_list.verify_start();
6319
6320 VerifyRegionListsClosure cl(&_old_set, &_humongous_set, &_free_list);
6321 heap_region_iterate(&cl);
6322
6323 _old_set.verify_end();
6324 _humongous_set.verify_end();
6325 _free_list.verify_end();
6326 }