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 // null
467 assert(p == NULL, err_msg("Not NULL " PTR_FORMAT ,p));
468 return false;
469 } else {
470 return !hr->isHumongous();
471 }
472 }
473
474 void G1CollectedHeap::check_ct_logs_at_safepoint() {
475 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
476 CardTableModRefBS* ct_bs = (CardTableModRefBS*)barrier_set();
477
478 // Count the dirty cards at the start.
479 CountNonCleanMemRegionClosure count1(this);
480 ct_bs->mod_card_iterate(&count1);
481 int orig_count = count1.n();
482
483 // First clear the logged cards.
484 ClearLoggedCardTableEntryClosure clear;
485 dcqs.set_closure(&clear);
486 dcqs.apply_closure_to_all_completed_buffers();
487 dcqs.iterate_closure_all_threads(false);
488 clear.print_histo();
489
490 // Now ensure that there's no dirty cards.
491 CountNonCleanMemRegionClosure count2(this);
492 ct_bs->mod_card_iterate(&count2);
493 if (count2.n() != 0) {
494 gclog_or_tty->print_cr("Card table has %d entries; %d originally",
495 count2.n(), orig_count);
496 }
497 guarantee(count2.n() == 0, "Card table should be clean.");
498
499 RedirtyLoggedCardTableEntryClosure redirty;
500 JavaThread::dirty_card_queue_set().set_closure(&redirty);
501 dcqs.apply_closure_to_all_completed_buffers();
502 dcqs.iterate_closure_all_threads(false);
503 gclog_or_tty->print_cr("Log entries = %d, dirty cards = %d.",
504 clear.calls(), orig_count);
505 guarantee(redirty.calls() == clear.calls(),
506 "Or else mechanism is broken.");
507
508 CountNonCleanMemRegionClosure count3(this);
509 ct_bs->mod_card_iterate(&count3);
510 if (count3.n() != orig_count) {
511 gclog_or_tty->print_cr("Should have restored them all: orig = %d, final = %d.",
512 orig_count, count3.n());
513 guarantee(count3.n() >= orig_count, "Should have restored them all.");
514 }
515
516 JavaThread::dirty_card_queue_set().set_closure(_refine_cte_cl);
517 }
518
519 // Private class members.
520
521 G1CollectedHeap* G1CollectedHeap::_g1h;
522
523 // Private methods.
524
525 HeapRegion*
526 G1CollectedHeap::new_region_try_secondary_free_list() {
527 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
528 while (!_secondary_free_list.is_empty() || free_regions_coming()) {
529 if (!_secondary_free_list.is_empty()) {
530 if (G1ConcRegionFreeingVerbose) {
531 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
532 "secondary_free_list has %u entries",
533 _secondary_free_list.length());
534 }
535 // It looks as if there are free regions available on the
536 // secondary_free_list. Let's move them to the free_list and try
537 // again to allocate from it.
538 append_secondary_free_list();
539
540 assert(!_free_list.is_empty(), "if the secondary_free_list was not "
541 "empty we should have moved at least one entry to the free_list");
542 HeapRegion* res = _free_list.remove_head();
543 if (G1ConcRegionFreeingVerbose) {
544 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
545 "allocated "HR_FORMAT" from secondary_free_list",
546 HR_FORMAT_PARAMS(res));
547 }
548 return res;
549 }
550
551 // Wait here until we get notifed either when (a) there are no
552 // more free regions coming or (b) some regions have been moved on
553 // the secondary_free_list.
554 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
555 }
556
557 if (G1ConcRegionFreeingVerbose) {
558 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
559 "could not allocate from secondary_free_list");
560 }
561 return NULL;
562 }
563
564 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool do_expand) {
565 assert(!isHumongous(word_size) || word_size <= HeapRegion::GrainWords,
566 "the only time we use this to allocate a humongous region is "
567 "when we are allocating a single humongous region");
568
569 HeapRegion* res;
570 if (G1StressConcRegionFreeing) {
571 if (!_secondary_free_list.is_empty()) {
572 if (G1ConcRegionFreeingVerbose) {
573 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
574 "forced to look at the secondary_free_list");
575 }
576 res = new_region_try_secondary_free_list();
577 if (res != NULL) {
578 return res;
579 }
580 }
581 }
582 res = _free_list.remove_head_or_null();
583 if (res == NULL) {
584 if (G1ConcRegionFreeingVerbose) {
585 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
586 "res == NULL, trying the secondary_free_list");
587 }
588 res = new_region_try_secondary_free_list();
589 }
590 if (res == NULL && do_expand && _expand_heap_after_alloc_failure) {
591 // Currently, only attempts to allocate GC alloc regions set
592 // do_expand to true. So, we should only reach here during a
593 // safepoint. If this assumption changes we might have to
594 // reconsider the use of _expand_heap_after_alloc_failure.
595 assert(SafepointSynchronize::is_at_safepoint(), "invariant");
596
597 ergo_verbose1(ErgoHeapSizing,
598 "attempt heap expansion",
599 ergo_format_reason("region allocation request failed")
600 ergo_format_byte("allocation request"),
601 word_size * HeapWordSize);
602 if (expand(word_size * HeapWordSize)) {
603 // Given that expand() succeeded in expanding the heap, and we
604 // always expand the heap by an amount aligned to the heap
605 // region size, the free list should in theory not be empty. So
606 // it would probably be OK to use remove_head(). But the extra
607 // check for NULL is unlikely to be a performance issue here (we
608 // just expanded the heap!) so let's just be conservative and
609 // use remove_head_or_null().
610 res = _free_list.remove_head_or_null();
611 } else {
612 _expand_heap_after_alloc_failure = false;
613 }
614 }
615 return res;
616 }
617
618 uint G1CollectedHeap::humongous_obj_allocate_find_first(uint num_regions,
619 size_t word_size) {
620 assert(isHumongous(word_size), "word_size should be humongous");
621 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
622
623 uint first = G1_NULL_HRS_INDEX;
624 if (num_regions == 1) {
625 // Only one region to allocate, no need to go through the slower
626 // path. The caller will attempt the expasion if this fails, so
627 // let's not try to expand here too.
628 HeapRegion* hr = new_region(word_size, false /* do_expand */);
629 if (hr != NULL) {
630 first = hr->hrs_index();
631 } else {
632 first = G1_NULL_HRS_INDEX;
633 }
634 } else {
635 // We can't allocate humongous regions while cleanupComplete() is
636 // running, since some of the regions we find to be empty might not
637 // yet be added to the free list and it is not straightforward to
638 // know which list they are on so that we can remove them. Note
639 // that we only need to do this if we need to allocate more than
640 // one region to satisfy the current humongous allocation
641 // request. If we are only allocating one region we use the common
642 // region allocation code (see above).
643 wait_while_free_regions_coming();
644 append_secondary_free_list_if_not_empty_with_lock();
645
646 if (free_regions() >= num_regions) {
647 first = _hrs.find_contiguous(num_regions);
648 if (first != G1_NULL_HRS_INDEX) {
649 for (uint i = first; i < first + num_regions; ++i) {
650 HeapRegion* hr = region_at(i);
651 assert(hr->is_empty(), "sanity");
652 assert(is_on_master_free_list(hr), "sanity");
653 hr->set_pending_removal(true);
654 }
655 _free_list.remove_all_pending(num_regions);
656 }
657 }
658 }
659 return first;
660 }
661
662 HeapWord*
663 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first,
664 uint num_regions,
665 size_t word_size) {
666 assert(first != G1_NULL_HRS_INDEX, "pre-condition");
667 assert(isHumongous(word_size), "word_size should be humongous");
668 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
669
670 // Index of last region in the series + 1.
671 uint last = first + num_regions;
672
673 // We need to initialize the region(s) we just discovered. This is
674 // a bit tricky given that it can happen concurrently with
675 // refinement threads refining cards on these regions and
676 // potentially wanting to refine the BOT as they are scanning
677 // those cards (this can happen shortly after a cleanup; see CR
678 // 6991377). So we have to set up the region(s) carefully and in
679 // a specific order.
680
681 // The word size sum of all the regions we will allocate.
682 size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords;
683 assert(word_size <= word_size_sum, "sanity");
684
685 // This will be the "starts humongous" region.
686 HeapRegion* first_hr = region_at(first);
687 // The header of the new object will be placed at the bottom of
688 // the first region.
689 HeapWord* new_obj = first_hr->bottom();
690 // This will be the new end of the first region in the series that
691 // should also match the end of the last region in the seriers.
692 HeapWord* new_end = new_obj + word_size_sum;
693 // This will be the new top of the first region that will reflect
694 // this allocation.
695 HeapWord* new_top = new_obj + word_size;
696
697 // First, we need to zero the header of the space that we will be
698 // allocating. When we update top further down, some refinement
699 // threads might try to scan the region. By zeroing the header we
700 // ensure that any thread that will try to scan the region will
701 // come across the zero klass word and bail out.
702 //
703 // NOTE: It would not have been correct to have used
704 // CollectedHeap::fill_with_object() and make the space look like
705 // an int array. The thread that is doing the allocation will
706 // later update the object header to a potentially different array
707 // type and, for a very short period of time, the klass and length
708 // fields will be inconsistent. This could cause a refinement
709 // thread to calculate the object size incorrectly.
710 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
711
712 // We will set up the first region as "starts humongous". This
713 // will also update the BOT covering all the regions to reflect
714 // that there is a single object that starts at the bottom of the
715 // first region.
716 first_hr->set_startsHumongous(new_top, new_end);
717
718 // Then, if there are any, we will set up the "continues
719 // humongous" regions.
720 HeapRegion* hr = NULL;
721 for (uint i = first + 1; i < last; ++i) {
722 hr = region_at(i);
723 hr->set_continuesHumongous(first_hr);
724 }
725 // If we have "continues humongous" regions (hr != NULL), then the
726 // end of the last one should match new_end.
727 assert(hr == NULL || hr->end() == new_end, "sanity");
728
729 // Up to this point no concurrent thread would have been able to
730 // do any scanning on any region in this series. All the top
731 // fields still point to bottom, so the intersection between
732 // [bottom,top] and [card_start,card_end] will be empty. Before we
733 // update the top fields, we'll do a storestore to make sure that
734 // no thread sees the update to top before the zeroing of the
735 // object header and the BOT initialization.
736 OrderAccess::storestore();
737
738 // Now that the BOT and the object header have been initialized,
739 // we can update top of the "starts humongous" region.
740 assert(first_hr->bottom() < new_top && new_top <= first_hr->end(),
741 "new_top should be in this region");
742 first_hr->set_top(new_top);
743 if (_hr_printer.is_active()) {
744 HeapWord* bottom = first_hr->bottom();
745 HeapWord* end = first_hr->orig_end();
746 if ((first + 1) == last) {
747 // the series has a single humongous region
748 _hr_printer.alloc(G1HRPrinter::SingleHumongous, first_hr, new_top);
749 } else {
750 // the series has more than one humongous regions
751 _hr_printer.alloc(G1HRPrinter::StartsHumongous, first_hr, end);
752 }
753 }
754
755 // Now, we will update the top fields of the "continues humongous"
756 // regions. The reason we need to do this is that, otherwise,
757 // these regions would look empty and this will confuse parts of
758 // G1. For example, the code that looks for a consecutive number
759 // of empty regions will consider them empty and try to
760 // re-allocate them. We can extend is_empty() to also include
761 // !continuesHumongous(), but it is easier to just update the top
762 // fields here. The way we set top for all regions (i.e., top ==
763 // end for all regions but the last one, top == new_top for the
764 // last one) is actually used when we will free up the humongous
765 // region in free_humongous_region().
766 hr = NULL;
767 for (uint i = first + 1; i < last; ++i) {
768 hr = region_at(i);
769 if ((i + 1) == last) {
770 // last continues humongous region
771 assert(hr->bottom() < new_top && new_top <= hr->end(),
772 "new_top should fall on this region");
773 hr->set_top(new_top);
774 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, new_top);
775 } else {
776 // not last one
777 assert(new_top > hr->end(), "new_top should be above this region");
778 hr->set_top(hr->end());
779 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, hr->end());
780 }
781 }
782 // If we have continues humongous regions (hr != NULL), then the
783 // end of the last one should match new_end and its top should
784 // match new_top.
785 assert(hr == NULL ||
786 (hr->end() == new_end && hr->top() == new_top), "sanity");
787
788 assert(first_hr->used() == word_size * HeapWordSize, "invariant");
789 _summary_bytes_used += first_hr->used();
790 _humongous_set.add(first_hr);
791
792 return new_obj;
793 }
794
795 // If could fit into free regions w/o expansion, try.
796 // Otherwise, if can expand, do so.
797 // Otherwise, if using ex regions might help, try with ex given back.
798 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size) {
799 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
800
801 verify_region_sets_optional();
802
803 size_t word_size_rounded = round_to(word_size, HeapRegion::GrainWords);
804 uint num_regions = (uint) (word_size_rounded / HeapRegion::GrainWords);
805 uint x_num = expansion_regions();
806 uint fs = _hrs.free_suffix();
807 uint first = humongous_obj_allocate_find_first(num_regions, word_size);
808 if (first == G1_NULL_HRS_INDEX) {
809 // The only thing we can do now is attempt expansion.
810 if (fs + x_num >= num_regions) {
811 // If the number of regions we're trying to allocate for this
812 // object is at most the number of regions in the free suffix,
813 // then the call to humongous_obj_allocate_find_first() above
814 // should have succeeded and we wouldn't be here.
815 //
816 // We should only be trying to expand when the free suffix is
817 // not sufficient for the object _and_ we have some expansion
818 // room available.
819 assert(num_regions > fs, "earlier allocation should have succeeded");
820
821 ergo_verbose1(ErgoHeapSizing,
822 "attempt heap expansion",
823 ergo_format_reason("humongous allocation request failed")
824 ergo_format_byte("allocation request"),
825 word_size * HeapWordSize);
826 if (expand((num_regions - fs) * HeapRegion::GrainBytes)) {
827 // Even though the heap was expanded, it might not have
828 // reached the desired size. So, we cannot assume that the
829 // allocation will succeed.
830 first = humongous_obj_allocate_find_first(num_regions, word_size);
831 }
832 }
833 }
834
835 HeapWord* result = NULL;
836 if (first != G1_NULL_HRS_INDEX) {
837 result =
838 humongous_obj_allocate_initialize_regions(first, num_regions, word_size);
839 assert(result != NULL, "it should always return a valid result");
840
841 // A successful humongous object allocation changes the used space
842 // information of the old generation so we need to recalculate the
843 // sizes and update the jstat counters here.
844 g1mm()->update_sizes();
845 }
846
847 verify_region_sets_optional();
848
849 return result;
850 }
851
852 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) {
853 assert_heap_not_locked_and_not_at_safepoint();
854 assert(!isHumongous(word_size), "we do not allow humongous TLABs");
855
856 unsigned int dummy_gc_count_before;
857 return attempt_allocation(word_size, &dummy_gc_count_before);
858 }
859
860 HeapWord*
861 G1CollectedHeap::mem_allocate(size_t word_size,
862 bool* gc_overhead_limit_was_exceeded) {
863 assert_heap_not_locked_and_not_at_safepoint();
864
865 // Loop until the allocation is satisified, or unsatisfied after GC.
866 for (int try_count = 1; /* we'll return */; try_count += 1) {
867 unsigned int gc_count_before;
868
869 HeapWord* result = NULL;
870 if (!isHumongous(word_size)) {
871 result = attempt_allocation(word_size, &gc_count_before);
872 } else {
873 result = attempt_allocation_humongous(word_size, &gc_count_before);
874 }
875 if (result != NULL) {
876 return result;
877 }
878
879 // Create the garbage collection operation...
880 VM_G1CollectForAllocation op(gc_count_before, word_size);
881 // ...and get the VM thread to execute it.
882 VMThread::execute(&op);
883
884 if (op.prologue_succeeded() && op.pause_succeeded()) {
885 // If the operation was successful we'll return the result even
886 // if it is NULL. If the allocation attempt failed immediately
887 // after a Full GC, it's unlikely we'll be able to allocate now.
888 HeapWord* result = op.result();
889 if (result != NULL && !isHumongous(word_size)) {
890 // Allocations that take place on VM operations do not do any
891 // card dirtying and we have to do it here. We only have to do
892 // this for non-humongous allocations, though.
893 dirty_young_block(result, word_size);
894 }
895 return result;
896 } else {
897 assert(op.result() == NULL,
898 "the result should be NULL if the VM op did not succeed");
899 }
900
901 // Give a warning if we seem to be looping forever.
902 if ((QueuedAllocationWarningCount > 0) &&
903 (try_count % QueuedAllocationWarningCount == 0)) {
904 warning("G1CollectedHeap::mem_allocate retries %d times", try_count);
905 }
906 }
907
908 ShouldNotReachHere();
909 return NULL;
910 }
911
912 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size,
913 unsigned int *gc_count_before_ret) {
914 // Make sure you read the note in attempt_allocation_humongous().
915
916 assert_heap_not_locked_and_not_at_safepoint();
917 assert(!isHumongous(word_size), "attempt_allocation_slow() should not "
918 "be called for humongous allocation requests");
919
920 // We should only get here after the first-level allocation attempt
921 // (attempt_allocation()) failed to allocate.
922
923 // We will loop until a) we manage to successfully perform the
924 // allocation or b) we successfully schedule a collection which
925 // fails to perform the allocation. b) is the only case when we'll
926 // return NULL.
927 HeapWord* result = NULL;
928 for (int try_count = 1; /* we'll return */; try_count += 1) {
929 bool should_try_gc;
930 unsigned int gc_count_before;
931
932 {
933 MutexLockerEx x(Heap_lock);
934
935 result = _mutator_alloc_region.attempt_allocation_locked(word_size,
936 false /* bot_updates */);
937 if (result != NULL) {
938 return result;
939 }
940
941 // If we reach here, attempt_allocation_locked() above failed to
942 // allocate a new region. So the mutator alloc region should be NULL.
943 assert(_mutator_alloc_region.get() == NULL, "only way to get here");
944
945 if (GC_locker::is_active_and_needs_gc()) {
946 if (g1_policy()->can_expand_young_list()) {
947 // No need for an ergo verbose message here,
948 // can_expand_young_list() does this when it returns true.
949 result = _mutator_alloc_region.attempt_allocation_force(word_size,
950 false /* bot_updates */);
951 if (result != NULL) {
952 return result;
953 }
954 }
955 should_try_gc = false;
956 } else {
957 // The GCLocker may not be active but the GCLocker initiated
958 // GC may not yet have been performed (GCLocker::needs_gc()
959 // returns true). In this case we do not try this GC and
960 // wait until the GCLocker initiated GC is performed, and
961 // then retry the allocation.
962 if (GC_locker::needs_gc()) {
963 should_try_gc = false;
964 } else {
965 // Read the GC count while still holding the Heap_lock.
966 gc_count_before = total_collections();
967 should_try_gc = true;
968 }
969 }
970 }
971
972 if (should_try_gc) {
973 bool succeeded;
974 result = do_collection_pause(word_size, gc_count_before, &succeeded);
975 if (result != NULL) {
976 assert(succeeded, "only way to get back a non-NULL result");
977 return result;
978 }
979
980 if (succeeded) {
981 // If we get here we successfully scheduled a collection which
982 // failed to allocate. No point in trying to allocate
983 // further. We'll just return NULL.
984 MutexLockerEx x(Heap_lock);
985 *gc_count_before_ret = total_collections();
986 return NULL;
987 }
988 } else {
989 // The GCLocker is either active or the GCLocker initiated
990 // GC has not yet been performed. Stall until it is and
991 // then retry the allocation.
992 GC_locker::stall_until_clear();
993 }
994
995 // We can reach here if we were unsuccessul in scheduling a
996 // collection (because another thread beat us to it) or if we were
997 // stalled due to the GC locker. In either can we should retry the
998 // allocation attempt in case another thread successfully
999 // performed a collection and reclaimed enough space. We do the
1000 // first attempt (without holding the Heap_lock) here and the
1001 // follow-on attempt will be at the start of the next loop
1002 // iteration (after taking the Heap_lock).
1003 result = _mutator_alloc_region.attempt_allocation(word_size,
1004 false /* bot_updates */);
1005 if (result != NULL) {
1006 return result;
1007 }
1008
1009 // Give a warning if we seem to be looping forever.
1010 if ((QueuedAllocationWarningCount > 0) &&
1011 (try_count % QueuedAllocationWarningCount == 0)) {
1012 warning("G1CollectedHeap::attempt_allocation_slow() "
1013 "retries %d times", try_count);
1014 }
1015 }
1016
1017 ShouldNotReachHere();
1018 return NULL;
1019 }
1020
1021 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size,
1022 unsigned int * gc_count_before_ret) {
1023 // The structure of this method has a lot of similarities to
1024 // attempt_allocation_slow(). The reason these two were not merged
1025 // into a single one is that such a method would require several "if
1026 // allocation is not humongous do this, otherwise do that"
1027 // conditional paths which would obscure its flow. In fact, an early
1028 // version of this code did use a unified method which was harder to
1029 // follow and, as a result, it had subtle bugs that were hard to
1030 // track down. So keeping these two methods separate allows each to
1031 // be more readable. It will be good to keep these two in sync as
1032 // much as possible.
1033
1034 assert_heap_not_locked_and_not_at_safepoint();
1035 assert(isHumongous(word_size), "attempt_allocation_humongous() "
1036 "should only be called for humongous allocations");
1037
1038 // Humongous objects can exhaust the heap quickly, so we should check if we
1039 // need to start a marking cycle at each humongous object allocation. We do
1040 // the check before we do the actual allocation. The reason for doing it
1041 // before the allocation is that we avoid having to keep track of the newly
1042 // allocated memory while we do a GC.
1043 if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation",
1044 word_size)) {
1045 collect(GCCause::_g1_humongous_allocation);
1046 }
1047
1048 // We will loop until a) we manage to successfully perform the
1049 // allocation or b) we successfully schedule a collection which
1050 // fails to perform the allocation. b) is the only case when we'll
1051 // return NULL.
1052 HeapWord* result = NULL;
1053 for (int try_count = 1; /* we'll return */; try_count += 1) {
1054 bool should_try_gc;
1055 unsigned int gc_count_before;
1056
1057 {
1058 MutexLockerEx x(Heap_lock);
1059
1060 // Given that humongous objects are not allocated in young
1061 // regions, we'll first try to do the allocation without doing a
1062 // collection hoping that there's enough space in the heap.
1063 result = humongous_obj_allocate(word_size);
1064 if (result != NULL) {
1065 return result;
1066 }
1067
1068 if (GC_locker::is_active_and_needs_gc()) {
1069 should_try_gc = false;
1070 } else {
1071 // The GCLocker may not be active but the GCLocker initiated
1072 // GC may not yet have been performed (GCLocker::needs_gc()
1073 // returns true). In this case we do not try this GC and
1074 // wait until the GCLocker initiated GC is performed, and
1075 // then retry the allocation.
1076 if (GC_locker::needs_gc()) {
1077 should_try_gc = false;
1078 } else {
1079 // Read the GC count while still holding the Heap_lock.
1080 gc_count_before = total_collections();
1081 should_try_gc = true;
1082 }
1083 }
1084 }
1085
1086 if (should_try_gc) {
1087 // If we failed to allocate the humongous object, we should try to
1088 // do a collection pause (if we're allowed) in case it reclaims
1089 // enough space for the allocation to succeed after the pause.
1090
1091 bool succeeded;
1092 result = do_collection_pause(word_size, gc_count_before, &succeeded);
1093 if (result != NULL) {
1094 assert(succeeded, "only way to get back a non-NULL result");
1095 return result;
1096 }
1097
1098 if (succeeded) {
1099 // If we get here we successfully scheduled a collection which
1100 // failed to allocate. No point in trying to allocate
1101 // further. We'll just return NULL.
1102 MutexLockerEx x(Heap_lock);
1103 *gc_count_before_ret = total_collections();
1104 return NULL;
1105 }
1106 } else {
1107 // The GCLocker is either active or the GCLocker initiated
1108 // GC has not yet been performed. Stall until it is and
1109 // then retry the allocation.
1110 GC_locker::stall_until_clear();
1111 }
1112
1113 // We can reach here if we were unsuccessul in scheduling a
1114 // collection (because another thread beat us to it) or if we were
1115 // stalled due to the GC locker. In either can we should retry the
1116 // allocation attempt in case another thread successfully
1117 // performed a collection and reclaimed enough space. Give a
1118 // warning if we seem to be looping forever.
1119
1120 if ((QueuedAllocationWarningCount > 0) &&
1121 (try_count % QueuedAllocationWarningCount == 0)) {
1122 warning("G1CollectedHeap::attempt_allocation_humongous() "
1123 "retries %d times", try_count);
1124 }
1125 }
1126
1127 ShouldNotReachHere();
1128 return NULL;
1129 }
1130
1131 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
1132 bool expect_null_mutator_alloc_region) {
1133 assert_at_safepoint(true /* should_be_vm_thread */);
1134 assert(_mutator_alloc_region.get() == NULL ||
1135 !expect_null_mutator_alloc_region,
1136 "the current alloc region was unexpectedly found to be non-NULL");
1137
1138 if (!isHumongous(word_size)) {
1139 return _mutator_alloc_region.attempt_allocation_locked(word_size,
1140 false /* bot_updates */);
1141 } else {
1142 HeapWord* result = humongous_obj_allocate(word_size);
1143 if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) {
1144 g1_policy()->set_initiate_conc_mark_if_possible();
1145 }
1146 return result;
1147 }
1148
1149 ShouldNotReachHere();
1150 }
1151
1152 class PostMCRemSetClearClosure: public HeapRegionClosure {
1153 G1CollectedHeap* _g1h;
1154 ModRefBarrierSet* _mr_bs;
1155 public:
1156 PostMCRemSetClearClosure(G1CollectedHeap* g1h, ModRefBarrierSet* mr_bs) :
1157 _g1h(g1h), _mr_bs(mr_bs) { }
1158 bool doHeapRegion(HeapRegion* r) {
1159 if (r->continuesHumongous()) {
1160 return false;
1161 }
1162 _g1h->reset_gc_time_stamps(r);
1163 HeapRegionRemSet* hrrs = r->rem_set();
1164 if (hrrs != NULL) hrrs->clear();
1165 // You might think here that we could clear just the cards
1166 // corresponding to the used region. But no: if we leave a dirty card
1167 // in a region we might allocate into, then it would prevent that card
1168 // from being enqueued, and cause it to be missed.
1169 // Re: the performance cost: we shouldn't be doing full GC anyway!
1170 _mr_bs->clear(MemRegion(r->bottom(), r->end()));
1171 return false;
1172 }
1173 };
1174
1175 void G1CollectedHeap::clear_rsets_post_compaction() {
1176 PostMCRemSetClearClosure rs_clear(this, mr_bs());
1177 heap_region_iterate(&rs_clear);
1178 }
1179
1180 class RebuildRSOutOfRegionClosure: public HeapRegionClosure {
1181 G1CollectedHeap* _g1h;
1182 UpdateRSOopClosure _cl;
1183 int _worker_i;
1184 public:
1185 RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, int worker_i = 0) :
1186 _cl(g1->g1_rem_set(), worker_i),
1187 _worker_i(worker_i),
1188 _g1h(g1)
1189 { }
1190
1191 bool doHeapRegion(HeapRegion* r) {
1192 if (!r->continuesHumongous()) {
1193 _cl.set_from(r);
1194 r->oop_iterate(&_cl);
1195 }
1196 return false;
1197 }
1198 };
1199
1200 class ParRebuildRSTask: public AbstractGangTask {
1201 G1CollectedHeap* _g1;
1202 public:
1203 ParRebuildRSTask(G1CollectedHeap* g1)
1204 : AbstractGangTask("ParRebuildRSTask"),
1205 _g1(g1)
1206 { }
1207
1208 void work(uint worker_id) {
1209 RebuildRSOutOfRegionClosure rebuild_rs(_g1, worker_id);
1210 _g1->heap_region_par_iterate_chunked(&rebuild_rs, worker_id,
1211 _g1->workers()->active_workers(),
1212 HeapRegion::RebuildRSClaimValue);
1213 }
1214 };
1215
1216 class PostCompactionPrinterClosure: public HeapRegionClosure {
1217 private:
1218 G1HRPrinter* _hr_printer;
1219 public:
1220 bool doHeapRegion(HeapRegion* hr) {
1221 assert(!hr->is_young(), "not expecting to find young regions");
1222 // We only generate output for non-empty regions.
1223 if (!hr->is_empty()) {
1224 if (!hr->isHumongous()) {
1225 _hr_printer->post_compaction(hr, G1HRPrinter::Old);
1226 } else if (hr->startsHumongous()) {
1227 if (hr->region_num() == 1) {
1228 // single humongous region
1229 _hr_printer->post_compaction(hr, G1HRPrinter::SingleHumongous);
1230 } else {
1231 _hr_printer->post_compaction(hr, G1HRPrinter::StartsHumongous);
1232 }
1233 } else {
1234 assert(hr->continuesHumongous(), "only way to get here");
1235 _hr_printer->post_compaction(hr, G1HRPrinter::ContinuesHumongous);
1236 }
1237 }
1238 return false;
1239 }
1240
1241 PostCompactionPrinterClosure(G1HRPrinter* hr_printer)
1242 : _hr_printer(hr_printer) { }
1243 };
1244
1245 void G1CollectedHeap::print_hrs_post_compaction() {
1246 PostCompactionPrinterClosure cl(hr_printer());
1247 heap_region_iterate(&cl);
1248 }
1249
1250 double G1CollectedHeap::verify(bool guard, const char* msg) {
1251 double verify_time_ms = 0.0;
1252
1253 if (guard && total_collections() >= VerifyGCStartAt) {
1254 double verify_start = os::elapsedTime();
1255 HandleMark hm; // Discard invalid handles created during verification
1256 gclog_or_tty->print(msg);
1257 prepare_for_verify();
1258 Universe::verify(false /* silent */, VerifyOption_G1UsePrevMarking);
1259 verify_time_ms = (os::elapsedTime() - verify_start) * 1000;
1260 }
1261
1262 return verify_time_ms;
1263 }
1264
1265 void G1CollectedHeap::verify_before_gc() {
1266 double verify_time_ms = verify(VerifyBeforeGC, " VerifyBeforeGC:");
1267 g1_policy()->phase_times()->record_verify_before_time_ms(verify_time_ms);
1268 }
1269
1270 void G1CollectedHeap::verify_after_gc() {
1271 double verify_time_ms = verify(VerifyAfterGC, " VerifyAfterGC:");
1272 g1_policy()->phase_times()->record_verify_after_time_ms(verify_time_ms);
1273 }
1274
1275 bool G1CollectedHeap::do_collection(bool explicit_gc,
1276 bool clear_all_soft_refs,
1277 size_t word_size) {
1278 assert_at_safepoint(true /* should_be_vm_thread */);
1279
1280 if (GC_locker::check_active_before_gc()) {
1281 return false;
1282 }
1283
1284 SvcGCMarker sgcm(SvcGCMarker::FULL);
1285 ResourceMark rm;
1286
1287 print_heap_before_gc();
1288
1289 size_t metadata_prev_used = MetaspaceAux::used_in_bytes();
1290
1291 HRSPhaseSetter x(HRSPhaseFullGC);
1292 verify_region_sets_optional();
1293
1294 const bool do_clear_all_soft_refs = clear_all_soft_refs ||
1295 collector_policy()->should_clear_all_soft_refs();
1296
1297 ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy());
1298
1299 {
1300 IsGCActiveMark x;
1301
1302 // Timing
1303 assert(gc_cause() != GCCause::_java_lang_system_gc || explicit_gc, "invariant");
1304 gclog_or_tty->date_stamp(G1Log::fine() && PrintGCDateStamps);
1305 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
1306
1307 TraceTime t(GCCauseString("Full GC", gc_cause()), G1Log::fine(), true, gclog_or_tty);
1308 TraceCollectorStats tcs(g1mm()->full_collection_counters());
1309 TraceMemoryManagerStats tms(true /* fullGC */, gc_cause());
1310
1311 double start = os::elapsedTime();
1312 g1_policy()->record_full_collection_start();
1313
1314 // Note: When we have a more flexible GC logging framework that
1315 // allows us to add optional attributes to a GC log record we
1316 // could consider timing and reporting how long we wait in the
1317 // following two methods.
1318 wait_while_free_regions_coming();
1319 // If we start the compaction before the CM threads finish
1320 // scanning the root regions we might trip them over as we'll
1321 // be moving objects / updating references. So let's wait until
1322 // they are done. By telling them to abort, they should complete
1323 // early.
1324 _cm->root_regions()->abort();
1325 _cm->root_regions()->wait_until_scan_finished();
1326 append_secondary_free_list_if_not_empty_with_lock();
1327
1328 gc_prologue(true);
1329 increment_total_collections(true /* full gc */);
1330 increment_old_marking_cycles_started();
1331
1332 size_t g1h_prev_used = used();
1333 assert(used() == recalculate_used(), "Should be equal");
1334
1335 verify_before_gc();
1336
1337 pre_full_gc_dump();
1338
1339 COMPILER2_PRESENT(DerivedPointerTable::clear());
1340
1341 // Disable discovery and empty the discovered lists
1342 // for the CM ref processor.
1343 ref_processor_cm()->disable_discovery();
1344 ref_processor_cm()->abandon_partial_discovery();
1345 ref_processor_cm()->verify_no_references_recorded();
1346
1347 // Abandon current iterations of concurrent marking and concurrent
1348 // refinement, if any are in progress. We have to do this before
1349 // wait_until_scan_finished() below.
1350 concurrent_mark()->abort();
1351
1352 // Make sure we'll choose a new allocation region afterwards.
1353 release_mutator_alloc_region();
1354 abandon_gc_alloc_regions();
1355 g1_rem_set()->cleanupHRRS();
1356
1357 // We should call this after we retire any currently active alloc
1358 // regions so that all the ALLOC / RETIRE events are generated
1359 // before the start GC event.
1360 _hr_printer.start_gc(true /* full */, (size_t) total_collections());
1361
1362 // We may have added regions to the current incremental collection
1363 // set between the last GC or pause and now. We need to clear the
1364 // incremental collection set and then start rebuilding it afresh
1365 // after this full GC.
1366 abandon_collection_set(g1_policy()->inc_cset_head());
1367 g1_policy()->clear_incremental_cset();
1368 g1_policy()->stop_incremental_cset_building();
1369
1370 tear_down_region_sets(false /* free_list_only */);
1371 g1_policy()->set_gcs_are_young(true);
1372
1373 // See the comments in g1CollectedHeap.hpp and
1374 // G1CollectedHeap::ref_processing_init() about
1375 // how reference processing currently works in G1.
1376
1377 // Temporarily make discovery by the STW ref processor single threaded (non-MT).
1378 ReferenceProcessorMTDiscoveryMutator stw_rp_disc_ser(ref_processor_stw(), false);
1379
1380 // Temporarily clear the STW ref processor's _is_alive_non_header field.
1381 ReferenceProcessorIsAliveMutator stw_rp_is_alive_null(ref_processor_stw(), NULL);
1382
1383 ref_processor_stw()->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/);
1384 ref_processor_stw()->setup_policy(do_clear_all_soft_refs);
1385
1386 // Do collection work
1387 {
1388 HandleMark hm; // Discard invalid handles created during gc
1389 G1MarkSweep::invoke_at_safepoint(ref_processor_stw(), do_clear_all_soft_refs);
1390 }
1391
1392 assert(free_regions() == 0, "we should not have added any free regions");
1393 rebuild_region_sets(false /* free_list_only */);
1394
1395 // Enqueue any discovered reference objects that have
1396 // not been removed from the discovered lists.
1397 ref_processor_stw()->enqueue_discovered_references();
1398
1399 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
1400
1401 MemoryService::track_memory_usage();
1402
1403 verify_after_gc();
1404
1405 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
1406 ref_processor_stw()->verify_no_references_recorded();
1407
1408 // Delete metaspaces for unloaded class loaders and clean up loader_data graph
1409 ClassLoaderDataGraph::purge();
1410
1411 // Note: since we've just done a full GC, concurrent
1412 // marking is no longer active. Therefore we need not
1413 // re-enable reference discovery for the CM ref processor.
1414 // That will be done at the start of the next marking cycle.
1415 assert(!ref_processor_cm()->discovery_enabled(), "Postcondition");
1416 ref_processor_cm()->verify_no_references_recorded();
1417
1418 reset_gc_time_stamp();
1419 // Since everything potentially moved, we will clear all remembered
1420 // sets, and clear all cards. Later we will rebuild remebered
1421 // sets. We will also reset the GC time stamps of the regions.
1422 clear_rsets_post_compaction();
1423 check_gc_time_stamps();
1424
1425 // Resize the heap if necessary.
1426 resize_if_necessary_after_full_collection(explicit_gc ? 0 : word_size);
1427
1428 if (_hr_printer.is_active()) {
1429 // We should do this after we potentially resize the heap so
1430 // that all the COMMIT / UNCOMMIT events are generated before
1431 // the end GC event.
1432
1433 print_hrs_post_compaction();
1434 _hr_printer.end_gc(true /* full */, (size_t) total_collections());
1435 }
1436
1437 if (_cg1r->use_cache()) {
1438 _cg1r->clear_and_record_card_counts();
1439 _cg1r->clear_hot_cache();
1440 }
1441
1442 // Rebuild remembered sets of all regions.
1443 if (G1CollectedHeap::use_parallel_gc_threads()) {
1444 uint n_workers =
1445 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
1446 workers()->active_workers(),
1447 Threads::number_of_non_daemon_threads());
1448 assert(UseDynamicNumberOfGCThreads ||
1449 n_workers == workers()->total_workers(),
1450 "If not dynamic should be using all the workers");
1451 workers()->set_active_workers(n_workers);
1452 // Set parallel threads in the heap (_n_par_threads) only
1453 // before a parallel phase and always reset it to 0 after
1454 // the phase so that the number of parallel threads does
1455 // no get carried forward to a serial phase where there
1456 // may be code that is "possibly_parallel".
1457 set_par_threads(n_workers);
1458
1459 ParRebuildRSTask rebuild_rs_task(this);
1460 assert(check_heap_region_claim_values(
1461 HeapRegion::InitialClaimValue), "sanity check");
1462 assert(UseDynamicNumberOfGCThreads ||
1463 workers()->active_workers() == workers()->total_workers(),
1464 "Unless dynamic should use total workers");
1465 // Use the most recent number of active workers
1466 assert(workers()->active_workers() > 0,
1467 "Active workers not properly set");
1468 set_par_threads(workers()->active_workers());
1469 workers()->run_task(&rebuild_rs_task);
1470 set_par_threads(0);
1471 assert(check_heap_region_claim_values(
1472 HeapRegion::RebuildRSClaimValue), "sanity check");
1473 reset_heap_region_claim_values();
1474 } else {
1475 RebuildRSOutOfRegionClosure rebuild_rs(this);
1476 heap_region_iterate(&rebuild_rs);
1477 }
1478
1479 if (G1Log::fine()) {
1480 print_size_transition(gclog_or_tty, g1h_prev_used, used(), capacity());
1481 }
1482
1483 if (true) { // FIXME
1484 MetaspaceGC::compute_new_size();
1485 }
1486
1487 // Start a new incremental collection set for the next pause
1488 assert(g1_policy()->collection_set() == NULL, "must be");
1489 g1_policy()->start_incremental_cset_building();
1490
1491 // Clear the _cset_fast_test bitmap in anticipation of adding
1492 // regions to the incremental collection set for the next
1493 // evacuation pause.
1494 clear_cset_fast_test();
1495
1496 init_mutator_alloc_region();
1497
1498 double end = os::elapsedTime();
1499 g1_policy()->record_full_collection_end();
1500
1501 #ifdef TRACESPINNING
1502 ParallelTaskTerminator::print_termination_counts();
1503 #endif
1504
1505 gc_epilogue(true);
1506
1507 // Discard all rset updates
1508 JavaThread::dirty_card_queue_set().abandon_logs();
1509 assert(!G1DeferredRSUpdate
1510 || (G1DeferredRSUpdate && (dirty_card_queue_set().completed_buffers_num() == 0)), "Should not be any");
1511
1512 _young_list->reset_sampled_info();
1513 // At this point there should be no regions in the
1514 // entire heap tagged as young.
1515 assert( check_young_list_empty(true /* check_heap */),
1516 "young list should be empty at this point");
1517
1518 // Update the number of full collections that have been completed.
1519 increment_old_marking_cycles_completed(false /* concurrent */);
1520
1521 _hrs.verify_optional();
1522 verify_region_sets_optional();
1523
1524 print_heap_after_gc();
1525
1526 // We must call G1MonitoringSupport::update_sizes() in the same scoping level
1527 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
1528 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
1529 // before any GC notifications are raised.
1530 g1mm()->update_sizes();
1531 }
1532
1533 post_full_gc_dump();
1534
1535 return true;
1536 }
1537
1538 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
1539 // do_collection() will return whether it succeeded in performing
1540 // the GC. Currently, there is no facility on the
1541 // do_full_collection() API to notify the caller than the collection
1542 // did not succeed (e.g., because it was locked out by the GC
1543 // locker). So, right now, we'll ignore the return value.
1544 bool dummy = do_collection(true, /* explicit_gc */
1545 clear_all_soft_refs,
1546 0 /* word_size */);
1547 }
1548
1549 // This code is mostly copied from TenuredGeneration.
1550 void
1551 G1CollectedHeap::
1552 resize_if_necessary_after_full_collection(size_t word_size) {
1553 assert(MinHeapFreeRatio <= MaxHeapFreeRatio, "sanity check");
1554
1555 // Include the current allocation, if any, and bytes that will be
1556 // pre-allocated to support collections, as "used".
1557 const size_t used_after_gc = used();
1558 const size_t capacity_after_gc = capacity();
1559 const size_t free_after_gc = capacity_after_gc - used_after_gc;
1560
1561 // This is enforced in arguments.cpp.
1562 assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
1563 "otherwise the code below doesn't make sense");
1564
1565 // We don't have floating point command-line arguments
1566 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
1567 const double maximum_used_percentage = 1.0 - minimum_free_percentage;
1568 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
1569 const double minimum_used_percentage = 1.0 - maximum_free_percentage;
1570
1571 const size_t min_heap_size = collector_policy()->min_heap_byte_size();
1572 const size_t max_heap_size = collector_policy()->max_heap_byte_size();
1573
1574 // We have to be careful here as these two calculations can overflow
1575 // 32-bit size_t's.
1576 double used_after_gc_d = (double) used_after_gc;
1577 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
1578 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
1579
1580 // Let's make sure that they are both under the max heap size, which
1581 // by default will make them fit into a size_t.
1582 double desired_capacity_upper_bound = (double) max_heap_size;
1583 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
1584 desired_capacity_upper_bound);
1585 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
1586 desired_capacity_upper_bound);
1587
1588 // We can now safely turn them into size_t's.
1589 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
1590 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
1591
1592 // This assert only makes sense here, before we adjust them
1593 // with respect to the min and max heap size.
1594 assert(minimum_desired_capacity <= maximum_desired_capacity,
1595 err_msg("minimum_desired_capacity = "SIZE_FORMAT", "
1596 "maximum_desired_capacity = "SIZE_FORMAT,
1597 minimum_desired_capacity, maximum_desired_capacity));
1598
1599 // Should not be greater than the heap max size. No need to adjust
1600 // it with respect to the heap min size as it's a lower bound (i.e.,
1601 // we'll try to make the capacity larger than it, not smaller).
1602 minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size);
1603 // Should not be less than the heap min size. No need to adjust it
1604 // with respect to the heap max size as it's an upper bound (i.e.,
1605 // we'll try to make the capacity smaller than it, not greater).
1606 maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size);
1607
1608 if (capacity_after_gc < minimum_desired_capacity) {
1609 // Don't expand unless it's significant
1610 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
1611 ergo_verbose4(ErgoHeapSizing,
1612 "attempt heap expansion",
1613 ergo_format_reason("capacity lower than "
1614 "min desired capacity after Full GC")
1615 ergo_format_byte("capacity")
1616 ergo_format_byte("occupancy")
1617 ergo_format_byte_perc("min desired capacity"),
1618 capacity_after_gc, used_after_gc,
1619 minimum_desired_capacity, (double) MinHeapFreeRatio);
1620 expand(expand_bytes);
1621
1622 // No expansion, now see if we want to shrink
1623 } else if (capacity_after_gc > maximum_desired_capacity) {
1624 // Capacity too large, compute shrinking size
1625 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
1626 ergo_verbose4(ErgoHeapSizing,
1627 "attempt heap shrinking",
1628 ergo_format_reason("capacity higher than "
1629 "max desired capacity after Full GC")
1630 ergo_format_byte("capacity")
1631 ergo_format_byte("occupancy")
1632 ergo_format_byte_perc("max desired capacity"),
1633 capacity_after_gc, used_after_gc,
1634 maximum_desired_capacity, (double) MaxHeapFreeRatio);
1635 shrink(shrink_bytes);
1636 }
1637 }
1638
1639
1640 HeapWord*
1641 G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
1642 bool* succeeded) {
1643 assert_at_safepoint(true /* should_be_vm_thread */);
1644
1645 *succeeded = true;
1646 // Let's attempt the allocation first.
1647 HeapWord* result =
1648 attempt_allocation_at_safepoint(word_size,
1649 false /* expect_null_mutator_alloc_region */);
1650 if (result != NULL) {
1651 assert(*succeeded, "sanity");
1652 return result;
1653 }
1654
1655 // In a G1 heap, we're supposed to keep allocation from failing by
1656 // incremental pauses. Therefore, at least for now, we'll favor
1657 // expansion over collection. (This might change in the future if we can
1658 // do something smarter than full collection to satisfy a failed alloc.)
1659 result = expand_and_allocate(word_size);
1660 if (result != NULL) {
1661 assert(*succeeded, "sanity");
1662 return result;
1663 }
1664
1665 // Expansion didn't work, we'll try to do a Full GC.
1666 bool gc_succeeded = do_collection(false, /* explicit_gc */
1667 false, /* clear_all_soft_refs */
1668 word_size);
1669 if (!gc_succeeded) {
1670 *succeeded = false;
1671 return NULL;
1672 }
1673
1674 // Retry the allocation
1675 result = attempt_allocation_at_safepoint(word_size,
1676 true /* expect_null_mutator_alloc_region */);
1677 if (result != NULL) {
1678 assert(*succeeded, "sanity");
1679 return result;
1680 }
1681
1682 // Then, try a Full GC that will collect all soft references.
1683 gc_succeeded = do_collection(false, /* explicit_gc */
1684 true, /* clear_all_soft_refs */
1685 word_size);
1686 if (!gc_succeeded) {
1687 *succeeded = false;
1688 return NULL;
1689 }
1690
1691 // Retry the allocation once more
1692 result = attempt_allocation_at_safepoint(word_size,
1693 true /* expect_null_mutator_alloc_region */);
1694 if (result != NULL) {
1695 assert(*succeeded, "sanity");
1696 return result;
1697 }
1698
1699 assert(!collector_policy()->should_clear_all_soft_refs(),
1700 "Flag should have been handled and cleared prior to this point");
1701
1702 // What else? We might try synchronous finalization later. If the total
1703 // space available is large enough for the allocation, then a more
1704 // complete compaction phase than we've tried so far might be
1705 // appropriate.
1706 assert(*succeeded, "sanity");
1707 return NULL;
1708 }
1709
1710 // Attempting to expand the heap sufficiently
1711 // to support an allocation of the given "word_size". If
1712 // successful, perform the allocation and return the address of the
1713 // allocated block, or else "NULL".
1714
1715 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size) {
1716 assert_at_safepoint(true /* should_be_vm_thread */);
1717
1718 verify_region_sets_optional();
1719
1720 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
1721 ergo_verbose1(ErgoHeapSizing,
1722 "attempt heap expansion",
1723 ergo_format_reason("allocation request failed")
1724 ergo_format_byte("allocation request"),
1725 word_size * HeapWordSize);
1726 if (expand(expand_bytes)) {
1727 _hrs.verify_optional();
1728 verify_region_sets_optional();
1729 return attempt_allocation_at_safepoint(word_size,
1730 false /* expect_null_mutator_alloc_region */);
1731 }
1732 return NULL;
1733 }
1734
1735 void G1CollectedHeap::update_committed_space(HeapWord* old_end,
1736 HeapWord* new_end) {
1737 assert(old_end != new_end, "don't call this otherwise");
1738 assert((HeapWord*) _g1_storage.high() == new_end, "invariant");
1739
1740 // Update the committed mem region.
1741 _g1_committed.set_end(new_end);
1742 // Tell the card table about the update.
1743 Universe::heap()->barrier_set()->resize_covered_region(_g1_committed);
1744 // Tell the BOT about the update.
1745 _bot_shared->resize(_g1_committed.word_size());
1746 }
1747
1748 bool G1CollectedHeap::expand(size_t expand_bytes) {
1749 size_t old_mem_size = _g1_storage.committed_size();
1750 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
1751 aligned_expand_bytes = align_size_up(aligned_expand_bytes,
1752 HeapRegion::GrainBytes);
1753 ergo_verbose2(ErgoHeapSizing,
1754 "expand the heap",
1755 ergo_format_byte("requested expansion amount")
1756 ergo_format_byte("attempted expansion amount"),
1757 expand_bytes, aligned_expand_bytes);
1758
1759 // First commit the memory.
1760 HeapWord* old_end = (HeapWord*) _g1_storage.high();
1761 bool successful = _g1_storage.expand_by(aligned_expand_bytes);
1762 if (successful) {
1763 // Then propagate this update to the necessary data structures.
1764 HeapWord* new_end = (HeapWord*) _g1_storage.high();
1765 update_committed_space(old_end, new_end);
1766
1767 FreeRegionList expansion_list("Local Expansion List");
1768 MemRegion mr = _hrs.expand_by(old_end, new_end, &expansion_list);
1769 assert(mr.start() == old_end, "post-condition");
1770 // mr might be a smaller region than what was requested if
1771 // expand_by() was unable to allocate the HeapRegion instances
1772 assert(mr.end() <= new_end, "post-condition");
1773
1774 size_t actual_expand_bytes = mr.byte_size();
1775 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
1776 assert(actual_expand_bytes == expansion_list.total_capacity_bytes(),
1777 "post-condition");
1778 if (actual_expand_bytes < aligned_expand_bytes) {
1779 // We could not expand _hrs to the desired size. In this case we
1780 // need to shrink the committed space accordingly.
1781 assert(mr.end() < new_end, "invariant");
1782
1783 size_t diff_bytes = aligned_expand_bytes - actual_expand_bytes;
1784 // First uncommit the memory.
1785 _g1_storage.shrink_by(diff_bytes);
1786 // Then propagate this update to the necessary data structures.
1787 update_committed_space(new_end, mr.end());
1788 }
1789 _free_list.add_as_tail(&expansion_list);
1790
1791 if (_hr_printer.is_active()) {
1792 HeapWord* curr = mr.start();
1793 while (curr < mr.end()) {
1794 HeapWord* curr_end = curr + HeapRegion::GrainWords;
1795 _hr_printer.commit(curr, curr_end);
1796 curr = curr_end;
1797 }
1798 assert(curr == mr.end(), "post-condition");
1799 }
1800 g1_policy()->record_new_heap_size(n_regions());
1801 } else {
1802 ergo_verbose0(ErgoHeapSizing,
1803 "did not expand the heap",
1804 ergo_format_reason("heap expansion operation failed"));
1805 // The expansion of the virtual storage space was unsuccessful.
1806 // Let's see if it was because we ran out of swap.
1807 if (G1ExitOnExpansionFailure &&
1808 _g1_storage.uncommitted_size() >= aligned_expand_bytes) {
1809 // We had head room...
1810 vm_exit_out_of_memory(aligned_expand_bytes, "G1 heap expansion");
1811 }
1812 }
1813 return successful;
1814 }
1815
1816 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
1817 size_t old_mem_size = _g1_storage.committed_size();
1818 size_t aligned_shrink_bytes =
1819 ReservedSpace::page_align_size_down(shrink_bytes);
1820 aligned_shrink_bytes = align_size_down(aligned_shrink_bytes,
1821 HeapRegion::GrainBytes);
1822 uint num_regions_deleted = 0;
1823 MemRegion mr = _hrs.shrink_by(aligned_shrink_bytes, &num_regions_deleted);
1824 HeapWord* old_end = (HeapWord*) _g1_storage.high();
1825 assert(mr.end() == old_end, "post-condition");
1826
1827 ergo_verbose3(ErgoHeapSizing,
1828 "shrink the heap",
1829 ergo_format_byte("requested shrinking amount")
1830 ergo_format_byte("aligned shrinking amount")
1831 ergo_format_byte("attempted shrinking amount"),
1832 shrink_bytes, aligned_shrink_bytes, mr.byte_size());
1833 if (mr.byte_size() > 0) {
1834 if (_hr_printer.is_active()) {
1835 HeapWord* curr = mr.end();
1836 while (curr > mr.start()) {
1837 HeapWord* curr_end = curr;
1838 curr -= HeapRegion::GrainWords;
1839 _hr_printer.uncommit(curr, curr_end);
1840 }
1841 assert(curr == mr.start(), "post-condition");
1842 }
1843
1844 _g1_storage.shrink_by(mr.byte_size());
1845 HeapWord* new_end = (HeapWord*) _g1_storage.high();
1846 assert(mr.start() == new_end, "post-condition");
1847
1848 _expansion_regions += num_regions_deleted;
1849 update_committed_space(old_end, new_end);
1850 HeapRegionRemSet::shrink_heap(n_regions());
1851 g1_policy()->record_new_heap_size(n_regions());
1852 } else {
1853 ergo_verbose0(ErgoHeapSizing,
1854 "did not shrink the heap",
1855 ergo_format_reason("heap shrinking operation failed"));
1856 }
1857 }
1858
1859 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1860 verify_region_sets_optional();
1861
1862 // We should only reach here at the end of a Full GC which means we
1863 // should not not be holding to any GC alloc regions. The method
1864 // below will make sure of that and do any remaining clean up.
1865 abandon_gc_alloc_regions();
1866
1867 // Instead of tearing down / rebuilding the free lists here, we
1868 // could instead use the remove_all_pending() method on free_list to
1869 // remove only the ones that we need to remove.
1870 tear_down_region_sets(true /* free_list_only */);
1871 shrink_helper(shrink_bytes);
1872 rebuild_region_sets(true /* free_list_only */);
1873
1874 _hrs.verify_optional();
1875 verify_region_sets_optional();
1876 }
1877
1878 // Public methods.
1879
1880 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away
1881 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
1882 #endif // _MSC_VER
1883
1884
1885 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* policy_) :
1886 SharedHeap(policy_),
1887 _g1_policy(policy_),
1888 _dirty_card_queue_set(false),
1889 _into_cset_dirty_card_queue_set(false),
1890 _is_alive_closure_cm(this),
1891 _is_alive_closure_stw(this),
1892 _ref_processor_cm(NULL),
1893 _ref_processor_stw(NULL),
1894 _process_strong_tasks(new SubTasksDone(G1H_PS_NumElements)),
1895 _bot_shared(NULL),
1896 _evac_failure_scan_stack(NULL) ,
1897 _mark_in_progress(false),
1898 _cg1r(NULL), _summary_bytes_used(0),
1899 _g1mm(NULL),
1900 _refine_cte_cl(NULL),
1901 _full_collection(false),
1902 _free_list("Master Free List"),
1903 _secondary_free_list("Secondary Free List"),
1904 _old_set("Old Set"),
1905 _humongous_set("Master Humongous Set"),
1906 _free_regions_coming(false),
1907 _young_list(new YoungList(this)),
1908 _gc_time_stamp(0),
1909 _retained_old_gc_alloc_region(NULL),
1910 _survivor_plab_stats(YoungPLABSize, PLABWeight),
1911 _old_plab_stats(OldPLABSize, PLABWeight),
1912 _expand_heap_after_alloc_failure(true),
1913 _surviving_young_words(NULL),
1914 _old_marking_cycles_started(0),
1915 _old_marking_cycles_completed(0),
1916 _in_cset_fast_test(NULL),
1917 _in_cset_fast_test_base(NULL),
1918 _dirty_cards_region_list(NULL),
1919 _worker_cset_start_region(NULL),
1920 _worker_cset_start_region_time_stamp(NULL) {
1921 _g1h = this; // To catch bugs.
1922 if (_process_strong_tasks == NULL || !_process_strong_tasks->valid()) {
1923 vm_exit_during_initialization("Failed necessary allocation.");
1924 }
1925
1926 _humongous_object_threshold_in_words = HeapRegion::GrainWords / 2;
1927
1928 int n_queues = MAX2((int)ParallelGCThreads, 1);
1929 _task_queues = new RefToScanQueueSet(n_queues);
1930
1931 int n_rem_sets = HeapRegionRemSet::num_par_rem_sets();
1932 assert(n_rem_sets > 0, "Invariant.");
1933
1934 HeapRegionRemSetIterator** iter_arr =
1935 NEW_C_HEAP_ARRAY(HeapRegionRemSetIterator*, n_queues, mtGC);
1936 for (int i = 0; i < n_queues; i++) {
1937 iter_arr[i] = new HeapRegionRemSetIterator();
1938 }
1939 _rem_set_iterator = iter_arr;
1940
1941 _worker_cset_start_region = NEW_C_HEAP_ARRAY(HeapRegion*, n_queues, mtGC);
1942 _worker_cset_start_region_time_stamp = NEW_C_HEAP_ARRAY(unsigned int, n_queues, mtGC);
1943
1944 for (int i = 0; i < n_queues; i++) {
1945 RefToScanQueue* q = new RefToScanQueue();
1946 q->initialize();
1947 _task_queues->register_queue(i, q);
1948 }
1949
1950 clear_cset_start_regions();
1951
1952 // Initialize the G1EvacuationFailureALot counters and flags.
1953 NOT_PRODUCT(reset_evacuation_should_fail();)
1954
1955 guarantee(_task_queues != NULL, "task_queues allocation failure.");
1956 }
1957
1958 jint G1CollectedHeap::initialize() {
1959 CollectedHeap::pre_initialize();
1960 os::enable_vtime();
1961
1962 G1Log::init();
1963
1964 // Necessary to satisfy locking discipline assertions.
1965
1966 MutexLocker x(Heap_lock);
1967
1968 // We have to initialize the printer before committing the heap, as
1969 // it will be used then.
1970 _hr_printer.set_active(G1PrintHeapRegions);
1971
1972 // While there are no constraints in the GC code that HeapWordSize
1973 // be any particular value, there are multiple other areas in the
1974 // system which believe this to be true (e.g. oop->object_size in some
1975 // cases incorrectly returns the size in wordSize units rather than
1976 // HeapWordSize).
1977 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
1978
1979 size_t init_byte_size = collector_policy()->initial_heap_byte_size();
1980 size_t max_byte_size = collector_policy()->max_heap_byte_size();
1981
1982 // Ensure that the sizes are properly aligned.
1983 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
1984 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
1985
1986 _cg1r = new ConcurrentG1Refine();
1987
1988 // Reserve the maximum.
1989
1990 // When compressed oops are enabled, the preferred heap base
1991 // is calculated by subtracting the requested size from the
1992 // 32Gb boundary and using the result as the base address for
1993 // heap reservation. If the requested size is not aligned to
1994 // HeapRegion::GrainBytes (i.e. the alignment that is passed
1995 // into the ReservedHeapSpace constructor) then the actual
1996 // base of the reserved heap may end up differing from the
1997 // address that was requested (i.e. the preferred heap base).
1998 // If this happens then we could end up using a non-optimal
1999 // compressed oops mode.
2000
2001 // Since max_byte_size is aligned to the size of a heap region (checked
2002 // above).
2003 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
2004
2005 ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size,
2006 HeapRegion::GrainBytes);
2007
2008 // It is important to do this in a way such that concurrent readers can't
2009 // temporarily think somethings in the heap. (I've actually seen this
2010 // happen in asserts: DLD.)
2011 _reserved.set_word_size(0);
2012 _reserved.set_start((HeapWord*)heap_rs.base());
2013 _reserved.set_end((HeapWord*)(heap_rs.base() + heap_rs.size()));
2014
2015 _expansion_regions = (uint) (max_byte_size / HeapRegion::GrainBytes);
2016
2017 // Create the gen rem set (and barrier set) for the entire reserved region.
2018 _rem_set = collector_policy()->create_rem_set(_reserved, 2);
2019 set_barrier_set(rem_set()->bs());
2020 if (barrier_set()->is_a(BarrierSet::ModRef)) {
2021 _mr_bs = (ModRefBarrierSet*)_barrier_set;
2022 } else {
2023 vm_exit_during_initialization("G1 requires a mod ref bs.");
2024 return JNI_ENOMEM;
2025 }
2026
2027 // Also create a G1 rem set.
2028 if (mr_bs()->is_a(BarrierSet::CardTableModRef)) {
2029 _g1_rem_set = new G1RemSet(this, (CardTableModRefBS*)mr_bs());
2030 } else {
2031 vm_exit_during_initialization("G1 requires a cardtable mod ref bs.");
2032 return JNI_ENOMEM;
2033 }
2034
2035 // Carve out the G1 part of the heap.
2036
2037 ReservedSpace g1_rs = heap_rs.first_part(max_byte_size);
2038 _g1_reserved = MemRegion((HeapWord*)g1_rs.base(),
2039 g1_rs.size()/HeapWordSize);
2040
2041 _g1_storage.initialize(g1_rs, 0);
2042 _g1_committed = MemRegion((HeapWord*)_g1_storage.low(), (size_t) 0);
2043 _hrs.initialize((HeapWord*) _g1_reserved.start(),
2044 (HeapWord*) _g1_reserved.end(),
2045 _expansion_regions);
2046
2047 // 6843694 - ensure that the maximum region index can fit
2048 // in the remembered set structures.
2049 const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
2050 guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
2051
2052 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
2053 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
2054 guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
2055 "too many cards per region");
2056
2057 HeapRegionSet::set_unrealistically_long_length(max_regions() + 1);
2058
2059 _bot_shared = new G1BlockOffsetSharedArray(_reserved,
2060 heap_word_size(init_byte_size));
2061
2062 _g1h = this;
2063
2064 _in_cset_fast_test_length = max_regions();
2065 _in_cset_fast_test_base =
2066 NEW_C_HEAP_ARRAY(bool, (size_t) _in_cset_fast_test_length, mtGC);
2067
2068 // We're biasing _in_cset_fast_test to avoid subtracting the
2069 // beginning of the heap every time we want to index; basically
2070 // it's the same with what we do with the card table.
2071 _in_cset_fast_test = _in_cset_fast_test_base -
2072 ((uintx) _g1_reserved.start() >> HeapRegion::LogOfHRGrainBytes);
2073
2074 // Clear the _cset_fast_test bitmap in anticipation of adding
2075 // regions to the incremental collection set for the first
2076 // evacuation pause.
2077 clear_cset_fast_test();
2078
2079 // Create the ConcurrentMark data structure and thread.
2080 // (Must do this late, so that "max_regions" is defined.)
2081 _cm = new ConcurrentMark(this, heap_rs);
2082 if (_cm == NULL || !_cm->completed_initialization()) {
2083 vm_shutdown_during_initialization("Could not create/initialize ConcurrentMark");
2084 return JNI_ENOMEM;
2085 }
2086 _cmThread = _cm->cmThread();
2087
2088 // Initialize the from_card cache structure of HeapRegionRemSet.
2089 HeapRegionRemSet::init_heap(max_regions());
2090
2091 // Now expand into the initial heap size.
2092 if (!expand(init_byte_size)) {
2093 vm_shutdown_during_initialization("Failed to allocate initial heap.");
2094 return JNI_ENOMEM;
2095 }
2096
2097 // Perform any initialization actions delegated to the policy.
2098 g1_policy()->init();
2099
2100 _refine_cte_cl =
2101 new RefineCardTableEntryClosure(ConcurrentG1RefineThread::sts(),
2102 g1_rem_set(),
2103 concurrent_g1_refine());
2104 JavaThread::dirty_card_queue_set().set_closure(_refine_cte_cl);
2105
2106 JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon,
2107 SATB_Q_FL_lock,
2108 G1SATBProcessCompletedThreshold,
2109 Shared_SATB_Q_lock);
2110
2111 JavaThread::dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
2112 DirtyCardQ_FL_lock,
2113 concurrent_g1_refine()->yellow_zone(),
2114 concurrent_g1_refine()->red_zone(),
2115 Shared_DirtyCardQ_lock);
2116
2117 if (G1DeferredRSUpdate) {
2118 dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
2119 DirtyCardQ_FL_lock,
2120 -1, // never trigger processing
2121 -1, // no limit on length
2122 Shared_DirtyCardQ_lock,
2123 &JavaThread::dirty_card_queue_set());
2124 }
2125
2126 // Initialize the card queue set used to hold cards containing
2127 // references into the collection set.
2128 _into_cset_dirty_card_queue_set.initialize(DirtyCardQ_CBL_mon,
2129 DirtyCardQ_FL_lock,
2130 -1, // never trigger processing
2131 -1, // no limit on length
2132 Shared_DirtyCardQ_lock,
2133 &JavaThread::dirty_card_queue_set());
2134
2135 // In case we're keeping closure specialization stats, initialize those
2136 // counts and that mechanism.
2137 SpecializationStats::clear();
2138
2139 // Do later initialization work for concurrent refinement.
2140 _cg1r->init();
2141
2142 // Here we allocate the dummy full region that is required by the
2143 // G1AllocRegion class. If we don't pass an address in the reserved
2144 // space here, lots of asserts fire.
2145
2146 HeapRegion* dummy_region = new_heap_region(0 /* index of bottom region */,
2147 _g1_reserved.start());
2148 // We'll re-use the same region whether the alloc region will
2149 // require BOT updates or not and, if it doesn't, then a non-young
2150 // region will complain that it cannot support allocations without
2151 // BOT updates. So we'll tag the dummy region as young to avoid that.
2152 dummy_region->set_young();
2153 // Make sure it's full.
2154 dummy_region->set_top(dummy_region->end());
2155 G1AllocRegion::setup(this, dummy_region);
2156
2157 init_mutator_alloc_region();
2158
2159 // Do create of the monitoring and management support so that
2160 // values in the heap have been properly initialized.
2161 _g1mm = new G1MonitoringSupport(this);
2162
2163 return JNI_OK;
2164 }
2165
2166 void G1CollectedHeap::ref_processing_init() {
2167 // Reference processing in G1 currently works as follows:
2168 //
2169 // * There are two reference processor instances. One is
2170 // used to record and process discovered references
2171 // during concurrent marking; the other is used to
2172 // record and process references during STW pauses
2173 // (both full and incremental).
2174 // * Both ref processors need to 'span' the entire heap as
2175 // the regions in the collection set may be dotted around.
2176 //
2177 // * For the concurrent marking ref processor:
2178 // * Reference discovery is enabled at initial marking.
2179 // * Reference discovery is disabled and the discovered
2180 // references processed etc during remarking.
2181 // * Reference discovery is MT (see below).
2182 // * Reference discovery requires a barrier (see below).
2183 // * Reference processing may or may not be MT
2184 // (depending on the value of ParallelRefProcEnabled
2185 // and ParallelGCThreads).
2186 // * A full GC disables reference discovery by the CM
2187 // ref processor and abandons any entries on it's
2188 // discovered lists.
2189 //
2190 // * For the STW processor:
2191 // * Non MT discovery is enabled at the start of a full GC.
2192 // * Processing and enqueueing during a full GC is non-MT.
2193 // * During a full GC, references are processed after marking.
2194 //
2195 // * Discovery (may or may not be MT) is enabled at the start
2196 // of an incremental evacuation pause.
2197 // * References are processed near the end of a STW evacuation pause.
2198 // * For both types of GC:
2199 // * Discovery is atomic - i.e. not concurrent.
2200 // * Reference discovery will not need a barrier.
2201
2202 SharedHeap::ref_processing_init();
2203 MemRegion mr = reserved_region();
2204
2205 // Concurrent Mark ref processor
2206 _ref_processor_cm =
2207 new ReferenceProcessor(mr, // span
2208 ParallelRefProcEnabled && (ParallelGCThreads > 1),
2209 // mt processing
2210 (int) ParallelGCThreads,
2211 // degree of mt processing
2212 (ParallelGCThreads > 1) || (ConcGCThreads > 1),
2213 // mt discovery
2214 (int) MAX2(ParallelGCThreads, ConcGCThreads),
2215 // degree of mt discovery
2216 false,
2217 // Reference discovery is not atomic
2218 &_is_alive_closure_cm,
2219 // is alive closure
2220 // (for efficiency/performance)
2221 true);
2222 // Setting next fields of discovered
2223 // lists requires a barrier.
2224
2225 // STW ref processor
2226 _ref_processor_stw =
2227 new ReferenceProcessor(mr, // span
2228 ParallelRefProcEnabled && (ParallelGCThreads > 1),
2229 // mt processing
2230 MAX2((int)ParallelGCThreads, 1),
2231 // degree of mt processing
2232 (ParallelGCThreads > 1),
2233 // mt discovery
2234 MAX2((int)ParallelGCThreads, 1),
2235 // degree of mt discovery
2236 true,
2237 // Reference discovery is atomic
2238 &_is_alive_closure_stw,
2239 // is alive closure
2240 // (for efficiency/performance)
2241 false);
2242 // Setting next fields of discovered
2243 // lists requires a barrier.
2244 }
2245
2246 size_t G1CollectedHeap::capacity() const {
2247 return _g1_committed.byte_size();
2248 }
2249
2250 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) {
2251 assert(!hr->continuesHumongous(), "pre-condition");
2252 hr->reset_gc_time_stamp();
2253 if (hr->startsHumongous()) {
2254 uint first_index = hr->hrs_index() + 1;
2255 uint last_index = hr->last_hc_index();
2256 for (uint i = first_index; i < last_index; i += 1) {
2257 HeapRegion* chr = region_at(i);
2258 assert(chr->continuesHumongous(), "sanity");
2259 chr->reset_gc_time_stamp();
2260 }
2261 }
2262 }
2263
2264 #ifndef PRODUCT
2265 class CheckGCTimeStampsHRClosure : public HeapRegionClosure {
2266 private:
2267 unsigned _gc_time_stamp;
2268 bool _failures;
2269
2270 public:
2271 CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) :
2272 _gc_time_stamp(gc_time_stamp), _failures(false) { }
2273
2274 virtual bool doHeapRegion(HeapRegion* hr) {
2275 unsigned region_gc_time_stamp = hr->get_gc_time_stamp();
2276 if (_gc_time_stamp != region_gc_time_stamp) {
2277 gclog_or_tty->print_cr("Region "HR_FORMAT" has GC time stamp = %d, "
2278 "expected %d", HR_FORMAT_PARAMS(hr),
2279 region_gc_time_stamp, _gc_time_stamp);
2280 _failures = true;
2281 }
2282 return false;
2283 }
2284
2285 bool failures() { return _failures; }
2286 };
2287
2288 void G1CollectedHeap::check_gc_time_stamps() {
2289 CheckGCTimeStampsHRClosure cl(_gc_time_stamp);
2290 heap_region_iterate(&cl);
2291 guarantee(!cl.failures(), "all GC time stamps should have been reset");
2292 }
2293 #endif // PRODUCT
2294
2295 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl,
2296 DirtyCardQueue* into_cset_dcq,
2297 bool concurrent,
2298 int worker_i) {
2299 // Clean cards in the hot card cache
2300 concurrent_g1_refine()->clean_up_cache(worker_i, g1_rem_set(), into_cset_dcq);
2301
2302 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2303 int n_completed_buffers = 0;
2304 while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) {
2305 n_completed_buffers++;
2306 }
2307 g1_policy()->phase_times()->record_update_rs_processed_buffers(worker_i, n_completed_buffers);
2308 dcqs.clear_n_completed_buffers();
2309 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!");
2310 }
2311
2312
2313 // Computes the sum of the storage used by the various regions.
2314
2315 size_t G1CollectedHeap::used() const {
2316 assert(Heap_lock->owner() != NULL,
2317 "Should be owned on this thread's behalf.");
2318 size_t result = _summary_bytes_used;
2319 // Read only once in case it is set to NULL concurrently
2320 HeapRegion* hr = _mutator_alloc_region.get();
2321 if (hr != NULL)
2322 result += hr->used();
2323 return result;
2324 }
2325
2326 size_t G1CollectedHeap::used_unlocked() const {
2327 size_t result = _summary_bytes_used;
2328 return result;
2329 }
2330
2331 class SumUsedClosure: public HeapRegionClosure {
2332 size_t _used;
2333 public:
2334 SumUsedClosure() : _used(0) {}
2335 bool doHeapRegion(HeapRegion* r) {
2336 if (!r->continuesHumongous()) {
2337 _used += r->used();
2338 }
2339 return false;
2340 }
2341 size_t result() { return _used; }
2342 };
2343
2344 size_t G1CollectedHeap::recalculate_used() const {
2345 SumUsedClosure blk;
2346 heap_region_iterate(&blk);
2347 return blk.result();
2348 }
2349
2350 size_t G1CollectedHeap::unsafe_max_alloc() {
2351 if (free_regions() > 0) return HeapRegion::GrainBytes;
2352 // otherwise, is there space in the current allocation region?
2353
2354 // We need to store the current allocation region in a local variable
2355 // here. The problem is that this method doesn't take any locks and
2356 // there may be other threads which overwrite the current allocation
2357 // region field. attempt_allocation(), for example, sets it to NULL
2358 // and this can happen *after* the NULL check here but before the call
2359 // to free(), resulting in a SIGSEGV. Note that this doesn't appear
2360 // to be a problem in the optimized build, since the two loads of the
2361 // current allocation region field are optimized away.
2362 HeapRegion* hr = _mutator_alloc_region.get();
2363 if (hr == NULL) {
2364 return 0;
2365 }
2366 return hr->free();
2367 }
2368
2369 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
2370 switch (cause) {
2371 case GCCause::_gc_locker: return GCLockerInvokesConcurrent;
2372 case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent;
2373 case GCCause::_g1_humongous_allocation: return true;
2374 default: return false;
2375 }
2376 }
2377
2378 #ifndef PRODUCT
2379 void G1CollectedHeap::allocate_dummy_regions() {
2380 // Let's fill up most of the region
2381 size_t word_size = HeapRegion::GrainWords - 1024;
2382 // And as a result the region we'll allocate will be humongous.
2383 guarantee(isHumongous(word_size), "sanity");
2384
2385 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
2386 // Let's use the existing mechanism for the allocation
2387 HeapWord* dummy_obj = humongous_obj_allocate(word_size);
2388 if (dummy_obj != NULL) {
2389 MemRegion mr(dummy_obj, word_size);
2390 CollectedHeap::fill_with_object(mr);
2391 } else {
2392 // If we can't allocate once, we probably cannot allocate
2393 // again. Let's get out of the loop.
2394 break;
2395 }
2396 }
2397 }
2398 #endif // !PRODUCT
2399
2400 void G1CollectedHeap::increment_old_marking_cycles_started() {
2401 assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
2402 _old_marking_cycles_started == _old_marking_cycles_completed + 1,
2403 err_msg("Wrong marking cycle count (started: %d, completed: %d)",
2404 _old_marking_cycles_started, _old_marking_cycles_completed));
2405
2406 _old_marking_cycles_started++;
2407 }
2408
2409 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) {
2410 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
2411
2412 // We assume that if concurrent == true, then the caller is a
2413 // concurrent thread that was joined the Suspendible Thread
2414 // Set. If there's ever a cheap way to check this, we should add an
2415 // assert here.
2416
2417 // Given that this method is called at the end of a Full GC or of a
2418 // concurrent cycle, and those can be nested (i.e., a Full GC can
2419 // interrupt a concurrent cycle), the number of full collections
2420 // completed should be either one (in the case where there was no
2421 // nesting) or two (when a Full GC interrupted a concurrent cycle)
2422 // behind the number of full collections started.
2423
2424 // This is the case for the inner caller, i.e. a Full GC.
2425 assert(concurrent ||
2426 (_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
2427 (_old_marking_cycles_started == _old_marking_cycles_completed + 2),
2428 err_msg("for inner caller (Full GC): _old_marking_cycles_started = %u "
2429 "is inconsistent with _old_marking_cycles_completed = %u",
2430 _old_marking_cycles_started, _old_marking_cycles_completed));
2431
2432 // This is the case for the outer caller, i.e. the concurrent cycle.
2433 assert(!concurrent ||
2434 (_old_marking_cycles_started == _old_marking_cycles_completed + 1),
2435 err_msg("for outer caller (concurrent cycle): "
2436 "_old_marking_cycles_started = %u "
2437 "is inconsistent with _old_marking_cycles_completed = %u",
2438 _old_marking_cycles_started, _old_marking_cycles_completed));
2439
2440 _old_marking_cycles_completed += 1;
2441
2442 // We need to clear the "in_progress" flag in the CM thread before
2443 // we wake up any waiters (especially when ExplicitInvokesConcurrent
2444 // is set) so that if a waiter requests another System.gc() it doesn't
2445 // incorrectly see that a marking cyle is still in progress.
2446 if (concurrent) {
2447 _cmThread->clear_in_progress();
2448 }
2449
2450 // This notify_all() will ensure that a thread that called
2451 // System.gc() with (with ExplicitGCInvokesConcurrent set or not)
2452 // and it's waiting for a full GC to finish will be woken up. It is
2453 // waiting in VM_G1IncCollectionPause::doit_epilogue().
2454 FullGCCount_lock->notify_all();
2455 }
2456
2457 void G1CollectedHeap::collect(GCCause::Cause cause) {
2458 assert_heap_not_locked();
2459
2460 unsigned int gc_count_before;
2461 unsigned int old_marking_count_before;
2462 bool retry_gc;
2463
2464 do {
2465 retry_gc = false;
2466
2467 {
2468 MutexLocker ml(Heap_lock);
2469
2470 // Read the GC count while holding the Heap_lock
2471 gc_count_before = total_collections();
2472 old_marking_count_before = _old_marking_cycles_started;
2473 }
2474
2475 if (should_do_concurrent_full_gc(cause)) {
2476 // Schedule an initial-mark evacuation pause that will start a
2477 // concurrent cycle. We're setting word_size to 0 which means that
2478 // we are not requesting a post-GC allocation.
2479 VM_G1IncCollectionPause op(gc_count_before,
2480 0, /* word_size */
2481 true, /* should_initiate_conc_mark */
2482 g1_policy()->max_pause_time_ms(),
2483 cause);
2484
2485 VMThread::execute(&op);
2486 if (!op.pause_succeeded()) {
2487 if (old_marking_count_before == _old_marking_cycles_started) {
2488 retry_gc = op.should_retry_gc();
2489 } else {
2490 // A Full GC happened while we were trying to schedule the
2491 // initial-mark GC. No point in starting a new cycle given
2492 // that the whole heap was collected anyway.
2493 }
2494
2495 if (retry_gc) {
2496 if (GC_locker::is_active_and_needs_gc()) {
2497 GC_locker::stall_until_clear();
2498 }
2499 }
2500 }
2501 } else {
2502 if (cause == GCCause::_gc_locker
2503 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2504
2505 // Schedule a standard evacuation pause. We're setting word_size
2506 // to 0 which means that we are not requesting a post-GC allocation.
2507 VM_G1IncCollectionPause op(gc_count_before,
2508 0, /* word_size */
2509 false, /* should_initiate_conc_mark */
2510 g1_policy()->max_pause_time_ms(),
2511 cause);
2512 VMThread::execute(&op);
2513 } else {
2514 // Schedule a Full GC.
2515 VM_G1CollectFull op(gc_count_before, old_marking_count_before, cause);
2516 VMThread::execute(&op);
2517 }
2518 }
2519 } while (retry_gc);
2520 }
2521
2522 bool G1CollectedHeap::is_in(const void* p) const {
2523 if (_g1_committed.contains(p)) {
2524 // Given that we know that p is in the committed space,
2525 // heap_region_containing_raw() should successfully
2526 // return the containing region.
2527 HeapRegion* hr = heap_region_containing_raw(p);
2528 return hr->is_in(p);
2529 } else {
2530 return false;
2531 }
2532 }
2533
2534 // Iteration functions.
2535
2536 // Iterates an OopClosure over all ref-containing fields of objects
2537 // within a HeapRegion.
2538
2539 class IterateOopClosureRegionClosure: public HeapRegionClosure {
2540 MemRegion _mr;
2541 ExtendedOopClosure* _cl;
2542 public:
2543 IterateOopClosureRegionClosure(MemRegion mr, ExtendedOopClosure* cl)
2544 : _mr(mr), _cl(cl) {}
2545 bool doHeapRegion(HeapRegion* r) {
2546 if (!r->continuesHumongous()) {
2547 r->oop_iterate(_cl);
2548 }
2549 return false;
2550 }
2551 };
2552
2553 void G1CollectedHeap::oop_iterate(ExtendedOopClosure* cl) {
2554 IterateOopClosureRegionClosure blk(_g1_committed, cl);
2555 heap_region_iterate(&blk);
2556 }
2557
2558 void G1CollectedHeap::oop_iterate(MemRegion mr, ExtendedOopClosure* cl) {
2559 IterateOopClosureRegionClosure blk(mr, cl);
2560 heap_region_iterate(&blk);
2561 }
2562
2563 // Iterates an ObjectClosure over all objects within a HeapRegion.
2564
2565 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2566 ObjectClosure* _cl;
2567 public:
2568 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2569 bool doHeapRegion(HeapRegion* r) {
2570 if (! r->continuesHumongous()) {
2571 r->object_iterate(_cl);
2572 }
2573 return false;
2574 }
2575 };
2576
2577 void G1CollectedHeap::object_iterate(ObjectClosure* cl) {
2578 IterateObjectClosureRegionClosure blk(cl);
2579 heap_region_iterate(&blk);
2580 }
2581
2582 void G1CollectedHeap::object_iterate_since_last_GC(ObjectClosure* cl) {
2583 // FIXME: is this right?
2584 guarantee(false, "object_iterate_since_last_GC not supported by G1 heap");
2585 }
2586
2587 // Calls a SpaceClosure on a HeapRegion.
2588
2589 class SpaceClosureRegionClosure: public HeapRegionClosure {
2590 SpaceClosure* _cl;
2591 public:
2592 SpaceClosureRegionClosure(SpaceClosure* cl) : _cl(cl) {}
2593 bool doHeapRegion(HeapRegion* r) {
2594 _cl->do_space(r);
2595 return false;
2596 }
2597 };
2598
2599 void G1CollectedHeap::space_iterate(SpaceClosure* cl) {
2600 SpaceClosureRegionClosure blk(cl);
2601 heap_region_iterate(&blk);
2602 }
2603
2604 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2605 _hrs.iterate(cl);
2606 }
2607
2608 void
2609 G1CollectedHeap::heap_region_par_iterate_chunked(HeapRegionClosure* cl,
2610 uint worker_id,
2611 uint no_of_par_workers,
2612 jint claim_value) {
2613 const uint regions = n_regions();
2614 const uint max_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
2615 no_of_par_workers :
2616 1);
2617 assert(UseDynamicNumberOfGCThreads ||
2618 no_of_par_workers == workers()->total_workers(),
2619 "Non dynamic should use fixed number of workers");
2620 // try to spread out the starting points of the workers
2621 const HeapRegion* start_hr =
2622 start_region_for_worker(worker_id, no_of_par_workers);
2623 const uint start_index = start_hr->hrs_index();
2624
2625 // each worker will actually look at all regions
2626 for (uint count = 0; count < regions; ++count) {
2627 const uint index = (start_index + count) % regions;
2628 assert(0 <= index && index < regions, "sanity");
2629 HeapRegion* r = region_at(index);
2630 // we'll ignore "continues humongous" regions (we'll process them
2631 // when we come across their corresponding "start humongous"
2632 // region) and regions already claimed
2633 if (r->claim_value() == claim_value || r->continuesHumongous()) {
2634 continue;
2635 }
2636 // OK, try to claim it
2637 if (r->claimHeapRegion(claim_value)) {
2638 // success!
2639 assert(!r->continuesHumongous(), "sanity");
2640 if (r->startsHumongous()) {
2641 // If the region is "starts humongous" we'll iterate over its
2642 // "continues humongous" first; in fact we'll do them
2643 // first. The order is important. In on case, calling the
2644 // closure on the "starts humongous" region might de-allocate
2645 // and clear all its "continues humongous" regions and, as a
2646 // result, we might end up processing them twice. So, we'll do
2647 // them first (notice: most closures will ignore them anyway) and
2648 // then we'll do the "starts humongous" region.
2649 for (uint ch_index = index + 1; ch_index < regions; ++ch_index) {
2650 HeapRegion* chr = region_at(ch_index);
2651
2652 // if the region has already been claimed or it's not
2653 // "continues humongous" we're done
2654 if (chr->claim_value() == claim_value ||
2655 !chr->continuesHumongous()) {
2656 break;
2657 }
2658
2659 // Noone should have claimed it directly. We can given
2660 // that we claimed its "starts humongous" region.
2661 assert(chr->claim_value() != claim_value, "sanity");
2662 assert(chr->humongous_start_region() == r, "sanity");
2663
2664 if (chr->claimHeapRegion(claim_value)) {
2665 // we should always be able to claim it; noone else should
2666 // be trying to claim this region
2667
2668 bool res2 = cl->doHeapRegion(chr);
2669 assert(!res2, "Should not abort");
2670
2671 // Right now, this holds (i.e., no closure that actually
2672 // does something with "continues humongous" regions
2673 // clears them). We might have to weaken it in the future,
2674 // but let's leave these two asserts here for extra safety.
2675 assert(chr->continuesHumongous(), "should still be the case");
2676 assert(chr->humongous_start_region() == r, "sanity");
2677 } else {
2678 guarantee(false, "we should not reach here");
2679 }
2680 }
2681 }
2682
2683 assert(!r->continuesHumongous(), "sanity");
2684 bool res = cl->doHeapRegion(r);
2685 assert(!res, "Should not abort");
2686 }
2687 }
2688 }
2689
2690 class ResetClaimValuesClosure: public HeapRegionClosure {
2691 public:
2692 bool doHeapRegion(HeapRegion* r) {
2693 r->set_claim_value(HeapRegion::InitialClaimValue);
2694 return false;
2695 }
2696 };
2697
2698 void G1CollectedHeap::reset_heap_region_claim_values() {
2699 ResetClaimValuesClosure blk;
2700 heap_region_iterate(&blk);
2701 }
2702
2703 void G1CollectedHeap::reset_cset_heap_region_claim_values() {
2704 ResetClaimValuesClosure blk;
2705 collection_set_iterate(&blk);
2706 }
2707
2708 #ifdef ASSERT
2709 // This checks whether all regions in the heap have the correct claim
2710 // value. I also piggy-backed on this a check to ensure that the
2711 // humongous_start_region() information on "continues humongous"
2712 // regions is correct.
2713
2714 class CheckClaimValuesClosure : public HeapRegionClosure {
2715 private:
2716 jint _claim_value;
2717 uint _failures;
2718 HeapRegion* _sh_region;
2719
2720 public:
2721 CheckClaimValuesClosure(jint claim_value) :
2722 _claim_value(claim_value), _failures(0), _sh_region(NULL) { }
2723 bool doHeapRegion(HeapRegion* r) {
2724 if (r->claim_value() != _claim_value) {
2725 gclog_or_tty->print_cr("Region " HR_FORMAT ", "
2726 "claim value = %d, should be %d",
2727 HR_FORMAT_PARAMS(r),
2728 r->claim_value(), _claim_value);
2729 ++_failures;
2730 }
2731 if (!r->isHumongous()) {
2732 _sh_region = NULL;
2733 } else if (r->startsHumongous()) {
2734 _sh_region = r;
2735 } else if (r->continuesHumongous()) {
2736 if (r->humongous_start_region() != _sh_region) {
2737 gclog_or_tty->print_cr("Region " HR_FORMAT ", "
2738 "HS = "PTR_FORMAT", should be "PTR_FORMAT,
2739 HR_FORMAT_PARAMS(r),
2740 r->humongous_start_region(),
2741 _sh_region);
2742 ++_failures;
2743 }
2744 }
2745 return false;
2746 }
2747 uint failures() { return _failures; }
2748 };
2749
2750 bool G1CollectedHeap::check_heap_region_claim_values(jint claim_value) {
2751 CheckClaimValuesClosure cl(claim_value);
2752 heap_region_iterate(&cl);
2753 return cl.failures() == 0;
2754 }
2755
2756 class CheckClaimValuesInCSetHRClosure: public HeapRegionClosure {
2757 private:
2758 jint _claim_value;
2759 uint _failures;
2760
2761 public:
2762 CheckClaimValuesInCSetHRClosure(jint claim_value) :
2763 _claim_value(claim_value), _failures(0) { }
2764
2765 uint failures() { return _failures; }
2766
2767 bool doHeapRegion(HeapRegion* hr) {
2768 assert(hr->in_collection_set(), "how?");
2769 assert(!hr->isHumongous(), "H-region in CSet");
2770 if (hr->claim_value() != _claim_value) {
2771 gclog_or_tty->print_cr("CSet Region " HR_FORMAT ", "
2772 "claim value = %d, should be %d",
2773 HR_FORMAT_PARAMS(hr),
2774 hr->claim_value(), _claim_value);
2775 _failures += 1;
2776 }
2777 return false;
2778 }
2779 };
2780
2781 bool G1CollectedHeap::check_cset_heap_region_claim_values(jint claim_value) {
2782 CheckClaimValuesInCSetHRClosure cl(claim_value);
2783 collection_set_iterate(&cl);
2784 return cl.failures() == 0;
2785 }
2786 #endif // ASSERT
2787
2788 // Clear the cached CSet starting regions and (more importantly)
2789 // the time stamps. Called when we reset the GC time stamp.
2790 void G1CollectedHeap::clear_cset_start_regions() {
2791 assert(_worker_cset_start_region != NULL, "sanity");
2792 assert(_worker_cset_start_region_time_stamp != NULL, "sanity");
2793
2794 int n_queues = MAX2((int)ParallelGCThreads, 1);
2795 for (int i = 0; i < n_queues; i++) {
2796 _worker_cset_start_region[i] = NULL;
2797 _worker_cset_start_region_time_stamp[i] = 0;
2798 }
2799 }
2800
2801 // Given the id of a worker, obtain or calculate a suitable
2802 // starting region for iterating over the current collection set.
2803 HeapRegion* G1CollectedHeap::start_cset_region_for_worker(int worker_i) {
2804 assert(get_gc_time_stamp() > 0, "should have been updated by now");
2805
2806 HeapRegion* result = NULL;
2807 unsigned gc_time_stamp = get_gc_time_stamp();
2808
2809 if (_worker_cset_start_region_time_stamp[worker_i] == gc_time_stamp) {
2810 // Cached starting region for current worker was set
2811 // during the current pause - so it's valid.
2812 // Note: the cached starting heap region may be NULL
2813 // (when the collection set is empty).
2814 result = _worker_cset_start_region[worker_i];
2815 assert(result == NULL || result->in_collection_set(), "sanity");
2816 return result;
2817 }
2818
2819 // The cached entry was not valid so let's calculate
2820 // a suitable starting heap region for this worker.
2821
2822 // We want the parallel threads to start their collection
2823 // set iteration at different collection set regions to
2824 // avoid contention.
2825 // If we have:
2826 // n collection set regions
2827 // p threads
2828 // Then thread t will start at region floor ((t * n) / p)
2829
2830 result = g1_policy()->collection_set();
2831 if (G1CollectedHeap::use_parallel_gc_threads()) {
2832 uint cs_size = g1_policy()->cset_region_length();
2833 uint active_workers = workers()->active_workers();
2834 assert(UseDynamicNumberOfGCThreads ||
2835 active_workers == workers()->total_workers(),
2836 "Unless dynamic should use total workers");
2837
2838 uint end_ind = (cs_size * worker_i) / active_workers;
2839 uint start_ind = 0;
2840
2841 if (worker_i > 0 &&
2842 _worker_cset_start_region_time_stamp[worker_i - 1] == gc_time_stamp) {
2843 // Previous workers starting region is valid
2844 // so let's iterate from there
2845 start_ind = (cs_size * (worker_i - 1)) / active_workers;
2846 result = _worker_cset_start_region[worker_i - 1];
2847 }
2848
2849 for (uint i = start_ind; i < end_ind; i++) {
2850 result = result->next_in_collection_set();
2851 }
2852 }
2853
2854 // Note: the calculated starting heap region may be NULL
2855 // (when the collection set is empty).
2856 assert(result == NULL || result->in_collection_set(), "sanity");
2857 assert(_worker_cset_start_region_time_stamp[worker_i] != gc_time_stamp,
2858 "should be updated only once per pause");
2859 _worker_cset_start_region[worker_i] = result;
2860 OrderAccess::storestore();
2861 _worker_cset_start_region_time_stamp[worker_i] = gc_time_stamp;
2862 return result;
2863 }
2864
2865 HeapRegion* G1CollectedHeap::start_region_for_worker(uint worker_i,
2866 uint no_of_par_workers) {
2867 uint worker_num =
2868 G1CollectedHeap::use_parallel_gc_threads() ? no_of_par_workers : 1U;
2869 assert(UseDynamicNumberOfGCThreads ||
2870 no_of_par_workers == workers()->total_workers(),
2871 "Non dynamic should use fixed number of workers");
2872 const uint start_index = n_regions() * worker_i / worker_num;
2873 return region_at(start_index);
2874 }
2875
2876 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) {
2877 HeapRegion* r = g1_policy()->collection_set();
2878 while (r != NULL) {
2879 HeapRegion* next = r->next_in_collection_set();
2880 if (cl->doHeapRegion(r)) {
2881 cl->incomplete();
2882 return;
2883 }
2884 r = next;
2885 }
2886 }
2887
2888 void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r,
2889 HeapRegionClosure *cl) {
2890 if (r == NULL) {
2891 // The CSet is empty so there's nothing to do.
2892 return;
2893 }
2894
2895 assert(r->in_collection_set(),
2896 "Start region must be a member of the collection set.");
2897 HeapRegion* cur = r;
2898 while (cur != NULL) {
2899 HeapRegion* next = cur->next_in_collection_set();
2900 if (cl->doHeapRegion(cur) && false) {
2901 cl->incomplete();
2902 return;
2903 }
2904 cur = next;
2905 }
2906 cur = g1_policy()->collection_set();
2907 while (cur != r) {
2908 HeapRegion* next = cur->next_in_collection_set();
2909 if (cl->doHeapRegion(cur) && false) {
2910 cl->incomplete();
2911 return;
2912 }
2913 cur = next;
2914 }
2915 }
2916
2917 CompactibleSpace* G1CollectedHeap::first_compactible_space() {
2918 return n_regions() > 0 ? region_at(0) : NULL;
2919 }
2920
2921
2922 Space* G1CollectedHeap::space_containing(const void* addr) const {
2923 Space* res = heap_region_containing(addr);
2924 return res;
2925 }
2926
2927 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2928 Space* sp = space_containing(addr);
2929 if (sp != NULL) {
2930 return sp->block_start(addr);
2931 }
2932 return NULL;
2933 }
2934
2935 size_t G1CollectedHeap::block_size(const HeapWord* addr) const {
2936 Space* sp = space_containing(addr);
2937 assert(sp != NULL, "block_size of address outside of heap");
2938 return sp->block_size(addr);
2939 }
2940
2941 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2942 Space* sp = space_containing(addr);
2943 return sp->block_is_obj(addr);
2944 }
2945
2946 bool G1CollectedHeap::supports_tlab_allocation() const {
2947 return true;
2948 }
2949
2950 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
2951 return HeapRegion::GrainBytes;
2952 }
2953
2954 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
2955 // Return the remaining space in the cur alloc region, but not less than
2956 // the min TLAB size.
2957
2958 // Also, this value can be at most the humongous object threshold,
2959 // since we can't allow tlabs to grow big enough to accomodate
2960 // humongous objects.
2961
2962 HeapRegion* hr = _mutator_alloc_region.get();
2963 size_t max_tlab_size = _humongous_object_threshold_in_words * wordSize;
2964 if (hr == NULL) {
2965 return max_tlab_size;
2966 } else {
2967 return MIN2(MAX2(hr->free(), (size_t) MinTLABSize), max_tlab_size);
2968 }
2969 }
2970
2971 size_t G1CollectedHeap::max_capacity() const {
2972 return _g1_reserved.byte_size();
2973 }
2974
2975 jlong G1CollectedHeap::millis_since_last_gc() {
2976 // assert(false, "NYI");
2977 return 0;
2978 }
2979
2980 void G1CollectedHeap::prepare_for_verify() {
2981 if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) {
2982 ensure_parsability(false);
2983 }
2984 g1_rem_set()->prepare_for_verify();
2985 }
2986
2987 bool G1CollectedHeap::allocated_since_marking(oop obj, HeapRegion* hr,
2988 VerifyOption vo) {
2989 switch (vo) {
2990 case VerifyOption_G1UsePrevMarking:
2991 return hr->obj_allocated_since_prev_marking(obj);
2992 case VerifyOption_G1UseNextMarking:
2993 return hr->obj_allocated_since_next_marking(obj);
2994 case VerifyOption_G1UseMarkWord:
2995 return false;
2996 default:
2997 ShouldNotReachHere();
2998 }
2999 return false; // keep some compilers happy
3000 }
3001
3002 HeapWord* G1CollectedHeap::top_at_mark_start(HeapRegion* hr, VerifyOption vo) {
3003 switch (vo) {
3004 case VerifyOption_G1UsePrevMarking: return hr->prev_top_at_mark_start();
3005 case VerifyOption_G1UseNextMarking: return hr->next_top_at_mark_start();
3006 case VerifyOption_G1UseMarkWord: return NULL;
3007 default: ShouldNotReachHere();
3008 }
3009 return NULL; // keep some compilers happy
3010 }
3011
3012 bool G1CollectedHeap::is_marked(oop obj, VerifyOption vo) {
3013 switch (vo) {
3014 case VerifyOption_G1UsePrevMarking: return isMarkedPrev(obj);
3015 case VerifyOption_G1UseNextMarking: return isMarkedNext(obj);
3016 case VerifyOption_G1UseMarkWord: return obj->is_gc_marked();
3017 default: ShouldNotReachHere();
3018 }
3019 return false; // keep some compilers happy
3020 }
3021
3022 const char* G1CollectedHeap::top_at_mark_start_str(VerifyOption vo) {
3023 switch (vo) {
3024 case VerifyOption_G1UsePrevMarking: return "PTAMS";
3025 case VerifyOption_G1UseNextMarking: return "NTAMS";
3026 case VerifyOption_G1UseMarkWord: return "NONE";
3027 default: ShouldNotReachHere();
3028 }
3029 return NULL; // keep some compilers happy
3030 }
3031
3032 class VerifyLivenessOopClosure: public OopClosure {
3033 G1CollectedHeap* _g1h;
3034 VerifyOption _vo;
3035 public:
3036 VerifyLivenessOopClosure(G1CollectedHeap* g1h, VerifyOption vo):
3037 _g1h(g1h), _vo(vo)
3038 { }
3039 void do_oop(narrowOop *p) { do_oop_work(p); }
3040 void do_oop( oop *p) { do_oop_work(p); }
3041
3042 template <class T> void do_oop_work(T *p) {
3043 oop obj = oopDesc::load_decode_heap_oop(p);
3044 guarantee(obj == NULL || !_g1h->is_obj_dead_cond(obj, _vo),
3045 "Dead object referenced by a not dead object");
3046 }
3047 };
3048
3049 class VerifyObjsInRegionClosure: public ObjectClosure {
3050 private:
3051 G1CollectedHeap* _g1h;
3052 size_t _live_bytes;
3053 HeapRegion *_hr;
3054 VerifyOption _vo;
3055 public:
3056 // _vo == UsePrevMarking -> use "prev" marking information,
3057 // _vo == UseNextMarking -> use "next" marking information,
3058 // _vo == UseMarkWord -> use mark word from object header.
3059 VerifyObjsInRegionClosure(HeapRegion *hr, VerifyOption vo)
3060 : _live_bytes(0), _hr(hr), _vo(vo) {
3061 _g1h = G1CollectedHeap::heap();
3062 }
3063 void do_object(oop o) {
3064 VerifyLivenessOopClosure isLive(_g1h, _vo);
3065 assert(o != NULL, "Huh?");
3066 if (!_g1h->is_obj_dead_cond(o, _vo)) {
3067 // If the object is alive according to the mark word,
3068 // then verify that the marking information agrees.
3069 // Note we can't verify the contra-positive of the
3070 // above: if the object is dead (according to the mark
3071 // word), it may not be marked, or may have been marked
3072 // but has since became dead, or may have been allocated
3073 // since the last marking.
3074 if (_vo == VerifyOption_G1UseMarkWord) {
3075 guarantee(!_g1h->is_obj_dead(o), "mark word and concurrent mark mismatch");
3076 }
3077
3078 o->oop_iterate_no_header(&isLive);
3079 if (!_hr->obj_allocated_since_prev_marking(o)) {
3080 size_t obj_size = o->size(); // Make sure we don't overflow
3081 _live_bytes += (obj_size * HeapWordSize);
3082 }
3083 }
3084 }
3085 size_t live_bytes() { return _live_bytes; }
3086 };
3087
3088 class PrintObjsInRegionClosure : public ObjectClosure {
3089 HeapRegion *_hr;
3090 G1CollectedHeap *_g1;
3091 public:
3092 PrintObjsInRegionClosure(HeapRegion *hr) : _hr(hr) {
3093 _g1 = G1CollectedHeap::heap();
3094 };
3095
3096 void do_object(oop o) {
3097 if (o != NULL) {
3098 HeapWord *start = (HeapWord *) o;
3099 size_t word_sz = o->size();
3100 gclog_or_tty->print("\nPrinting obj "PTR_FORMAT" of size " SIZE_FORMAT
3101 " isMarkedPrev %d isMarkedNext %d isAllocSince %d\n",
3102 (void*) o, word_sz,
3103 _g1->isMarkedPrev(o),
3104 _g1->isMarkedNext(o),
3105 _hr->obj_allocated_since_prev_marking(o));
3106 HeapWord *end = start + word_sz;
3107 HeapWord *cur;
3108 int *val;
3109 for (cur = start; cur < end; cur++) {
3110 val = (int *) cur;
3111 gclog_or_tty->print("\t "PTR_FORMAT":"PTR_FORMAT"\n", val, *val);
3112 }
3113 }
3114 }
3115 };
3116
3117 class VerifyRegionClosure: public HeapRegionClosure {
3118 private:
3119 bool _par;
3120 VerifyOption _vo;
3121 bool _failures;
3122 public:
3123 // _vo == UsePrevMarking -> use "prev" marking information,
3124 // _vo == UseNextMarking -> use "next" marking information,
3125 // _vo == UseMarkWord -> use mark word from object header.
3126 VerifyRegionClosure(bool par, VerifyOption vo)
3127 : _par(par),
3128 _vo(vo),
3129 _failures(false) {}
3130
3131 bool failures() {
3132 return _failures;
3133 }
3134
3135 bool doHeapRegion(HeapRegion* r) {
3136 if (!r->continuesHumongous()) {
3137 bool failures = false;
3138 r->verify(_vo, &failures);
3139 if (failures) {
3140 _failures = true;
3141 } else {
3142 VerifyObjsInRegionClosure not_dead_yet_cl(r, _vo);
3143 r->object_iterate(¬_dead_yet_cl);
3144 if (_vo != VerifyOption_G1UseNextMarking) {
3145 if (r->max_live_bytes() < not_dead_yet_cl.live_bytes()) {
3146 gclog_or_tty->print_cr("["PTR_FORMAT","PTR_FORMAT"] "
3147 "max_live_bytes "SIZE_FORMAT" "
3148 "< calculated "SIZE_FORMAT,
3149 r->bottom(), r->end(),
3150 r->max_live_bytes(),
3151 not_dead_yet_cl.live_bytes());
3152 _failures = true;
3153 }
3154 } else {
3155 // When vo == UseNextMarking we cannot currently do a sanity
3156 // check on the live bytes as the calculation has not been
3157 // finalized yet.
3158 }
3159 }
3160 }
3161 return false; // stop the region iteration if we hit a failure
3162 }
3163 };
3164
3165 class YoungRefCounterClosure : public OopClosure {
3166 G1CollectedHeap* _g1h;
3167 int _count;
3168 public:
3169 YoungRefCounterClosure(G1CollectedHeap* g1h) : _g1h(g1h), _count(0) {}
3170 void do_oop(oop* p) { if (_g1h->is_in_young(*p)) { _count++; } }
3171 void do_oop(narrowOop* p) { ShouldNotReachHere(); }
3172
3173 int count() { return _count; }
3174 void reset_count() { _count = 0; };
3175 };
3176
3177 class VerifyKlassClosure: public KlassClosure {
3178 YoungRefCounterClosure _young_ref_counter_closure;
3179 OopClosure *_oop_closure;
3180 public:
3181 VerifyKlassClosure(G1CollectedHeap* g1h, OopClosure* cl) : _young_ref_counter_closure(g1h), _oop_closure(cl) {}
3182 void do_klass(Klass* k) {
3183 k->oops_do(_oop_closure);
3184
3185 _young_ref_counter_closure.reset_count();
3186 k->oops_do(&_young_ref_counter_closure);
3187 if (_young_ref_counter_closure.count() > 0) {
3188 guarantee(k->has_modified_oops(), err_msg("Klass %p, has young refs but is not dirty.", k));
3189 }
3190 }
3191 };
3192
3193 // TODO: VerifyRootsClosure extends OopsInGenClosure so that we can
3194 // pass it as the perm_blk to SharedHeap::process_strong_roots.
3195 // When process_strong_roots stop calling perm_blk->younger_refs_iterate
3196 // we can change this closure to extend the simpler OopClosure.
3197 class VerifyRootsClosure: public OopsInGenClosure {
3198 private:
3199 G1CollectedHeap* _g1h;
3200 VerifyOption _vo;
3201 bool _failures;
3202 public:
3203 // _vo == UsePrevMarking -> use "prev" marking information,
3204 // _vo == UseNextMarking -> use "next" marking information,
3205 // _vo == UseMarkWord -> use mark word from object header.
3206 VerifyRootsClosure(VerifyOption vo) :
3207 _g1h(G1CollectedHeap::heap()),
3208 _vo(vo),
3209 _failures(false) { }
3210
3211 bool failures() { return _failures; }
3212
3213 template <class T> void do_oop_nv(T* p) {
3214 T heap_oop = oopDesc::load_heap_oop(p);
3215 if (!oopDesc::is_null(heap_oop)) {
3216 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
3217 if (_g1h->is_obj_dead_cond(obj, _vo)) {
3218 gclog_or_tty->print_cr("Root location "PTR_FORMAT" "
3219 "points to dead obj "PTR_FORMAT, p, (void*) obj);
3220 if (_vo == VerifyOption_G1UseMarkWord) {
3221 gclog_or_tty->print_cr(" Mark word: "PTR_FORMAT, (void*)(obj->mark()));
3222 }
3223 obj->print_on(gclog_or_tty);
3224 _failures = true;
3225 }
3226 }
3227 }
3228
3229 void do_oop(oop* p) { do_oop_nv(p); }
3230 void do_oop(narrowOop* p) { do_oop_nv(p); }
3231 };
3232
3233 // This is the task used for parallel heap verification.
3234
3235 class G1ParVerifyTask: public AbstractGangTask {
3236 private:
3237 G1CollectedHeap* _g1h;
3238 VerifyOption _vo;
3239 bool _failures;
3240
3241 public:
3242 // _vo == UsePrevMarking -> use "prev" marking information,
3243 // _vo == UseNextMarking -> use "next" marking information,
3244 // _vo == UseMarkWord -> use mark word from object header.
3245 G1ParVerifyTask(G1CollectedHeap* g1h, VerifyOption vo) :
3246 AbstractGangTask("Parallel verify task"),
3247 _g1h(g1h),
3248 _vo(vo),
3249 _failures(false) { }
3250
3251 bool failures() {
3252 return _failures;
3253 }
3254
3255 void work(uint worker_id) {
3256 HandleMark hm;
3257 VerifyRegionClosure blk(true, _vo);
3258 _g1h->heap_region_par_iterate_chunked(&blk, worker_id,
3259 _g1h->workers()->active_workers(),
3260 HeapRegion::ParVerifyClaimValue);
3261 if (blk.failures()) {
3262 _failures = true;
3263 }
3264 }
3265 };
3266
3267 void G1CollectedHeap::verify(bool silent) {
3268 verify(silent, VerifyOption_G1UsePrevMarking);
3269 }
3270
3271 void G1CollectedHeap::verify(bool silent,
3272 VerifyOption vo) {
3273 if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) {
3274 if (!silent) { gclog_or_tty->print("Roots "); }
3275 VerifyRootsClosure rootsCl(vo);
3276
3277 assert(Thread::current()->is_VM_thread(),
3278 "Expected to be executed serially by the VM thread at this point");
3279
3280 CodeBlobToOopClosure blobsCl(&rootsCl, /*do_marking=*/ false);
3281 VerifyKlassClosure klassCl(this, &rootsCl);
3282
3283 // We apply the relevant closures to all the oops in the
3284 // system dictionary, the string table and the code cache.
3285 const int so = SO_AllClasses | SO_Strings | SO_CodeCache;
3286
3287 // Need cleared claim bits for the strong roots processing
3288 ClassLoaderDataGraph::clear_claimed_marks();
3289
3290 process_strong_roots(true, // activate StrongRootsScope
3291 false, // we set "is scavenging" to false,
3292 // so we don't reset the dirty cards.
3293 ScanningOption(so), // roots scanning options
3294 &rootsCl,
3295 &blobsCl,
3296 &klassCl
3297 );
3298
3299 bool failures = rootsCl.failures();
3300
3301 if (vo != VerifyOption_G1UseMarkWord) {
3302 // If we're verifying during a full GC then the region sets
3303 // will have been torn down at the start of the GC. Therefore
3304 // verifying the region sets will fail. So we only verify
3305 // the region sets when not in a full GC.
3306 if (!silent) { gclog_or_tty->print("HeapRegionSets "); }
3307 verify_region_sets();
3308 }
3309
3310 if (!silent) { gclog_or_tty->print("HeapRegions "); }
3311 if (GCParallelVerificationEnabled && ParallelGCThreads > 1) {
3312 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3313 "sanity check");
3314
3315 G1ParVerifyTask task(this, vo);
3316 assert(UseDynamicNumberOfGCThreads ||
3317 workers()->active_workers() == workers()->total_workers(),
3318 "If not dynamic should be using all the workers");
3319 int n_workers = workers()->active_workers();
3320 set_par_threads(n_workers);
3321 workers()->run_task(&task);
3322 set_par_threads(0);
3323 if (task.failures()) {
3324 failures = true;
3325 }
3326
3327 // Checks that the expected amount of parallel work was done.
3328 // The implication is that n_workers is > 0.
3329 assert(check_heap_region_claim_values(HeapRegion::ParVerifyClaimValue),
3330 "sanity check");
3331
3332 reset_heap_region_claim_values();
3333
3334 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3335 "sanity check");
3336 } else {
3337 VerifyRegionClosure blk(false, vo);
3338 heap_region_iterate(&blk);
3339 if (blk.failures()) {
3340 failures = true;
3341 }
3342 }
3343 if (!silent) gclog_or_tty->print("RemSet ");
3344 rem_set()->verify();
3345
3346 if (failures) {
3347 gclog_or_tty->print_cr("Heap:");
3348 // It helps to have the per-region information in the output to
3349 // help us track down what went wrong. This is why we call
3350 // print_extended_on() instead of print_on().
3351 print_extended_on(gclog_or_tty);
3352 gclog_or_tty->print_cr("");
3353 #ifndef PRODUCT
3354 if (VerifyDuringGC && G1VerifyDuringGCPrintReachable) {
3355 concurrent_mark()->print_reachable("at-verification-failure",
3356 vo, false /* all */);
3357 }
3358 #endif
3359 gclog_or_tty->flush();
3360 }
3361 guarantee(!failures, "there should not have been any failures");
3362 } else {
3363 if (!silent) gclog_or_tty->print("(SKIPPING roots, heapRegions, remset) ");
3364 }
3365 }
3366
3367 class PrintRegionClosure: public HeapRegionClosure {
3368 outputStream* _st;
3369 public:
3370 PrintRegionClosure(outputStream* st) : _st(st) {}
3371 bool doHeapRegion(HeapRegion* r) {
3372 r->print_on(_st);
3373 return false;
3374 }
3375 };
3376
3377 void G1CollectedHeap::print_on(outputStream* st) const {
3378 st->print(" %-20s", "garbage-first heap");
3379 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
3380 capacity()/K, used_unlocked()/K);
3381 st->print(" [" INTPTR_FORMAT ", " INTPTR_FORMAT ", " INTPTR_FORMAT ")",
3382 _g1_storage.low_boundary(),
3383 _g1_storage.high(),
3384 _g1_storage.high_boundary());
3385 st->cr();
3386 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
3387 uint young_regions = _young_list->length();
3388 st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
3389 (size_t) young_regions * HeapRegion::GrainBytes / K);
3390 uint survivor_regions = g1_policy()->recorded_survivor_regions();
3391 st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
3392 (size_t) survivor_regions * HeapRegion::GrainBytes / K);
3393 st->cr();
3394 MetaspaceAux::print_on(st);
3395 }
3396
3397 void G1CollectedHeap::print_extended_on(outputStream* st) const {
3398 print_on(st);
3399
3400 // Print the per-region information.
3401 st->cr();
3402 st->print_cr("Heap Regions: (Y=young(eden), SU=young(survivor), "
3403 "HS=humongous(starts), HC=humongous(continues), "
3404 "CS=collection set, F=free, TS=gc time stamp, "
3405 "PTAMS=previous top-at-mark-start, "
3406 "NTAMS=next top-at-mark-start)");
3407 PrintRegionClosure blk(st);
3408 heap_region_iterate(&blk);
3409 }
3410
3411 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
3412 if (G1CollectedHeap::use_parallel_gc_threads()) {
3413 workers()->print_worker_threads_on(st);
3414 }
3415 _cmThread->print_on(st);
3416 st->cr();
3417 _cm->print_worker_threads_on(st);
3418 _cg1r->print_worker_threads_on(st);
3419 }
3420
3421 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
3422 if (G1CollectedHeap::use_parallel_gc_threads()) {
3423 workers()->threads_do(tc);
3424 }
3425 tc->do_thread(_cmThread);
3426 _cg1r->threads_do(tc);
3427 }
3428
3429 void G1CollectedHeap::print_tracing_info() const {
3430 // We'll overload this to mean "trace GC pause statistics."
3431 if (TraceGen0Time || TraceGen1Time) {
3432 // The "G1CollectorPolicy" is keeping track of these stats, so delegate
3433 // to that.
3434 g1_policy()->print_tracing_info();
3435 }
3436 if (G1SummarizeRSetStats) {
3437 g1_rem_set()->print_summary_info();
3438 }
3439 if (G1SummarizeConcMark) {
3440 concurrent_mark()->print_summary_info();
3441 }
3442 g1_policy()->print_yg_surv_rate_info();
3443 SpecializationStats::print();
3444 }
3445
3446 #ifndef PRODUCT
3447 // Helpful for debugging RSet issues.
3448
3449 class PrintRSetsClosure : public HeapRegionClosure {
3450 private:
3451 const char* _msg;
3452 size_t _occupied_sum;
3453
3454 public:
3455 bool doHeapRegion(HeapRegion* r) {
3456 HeapRegionRemSet* hrrs = r->rem_set();
3457 size_t occupied = hrrs->occupied();
3458 _occupied_sum += occupied;
3459
3460 gclog_or_tty->print_cr("Printing RSet for region "HR_FORMAT,
3461 HR_FORMAT_PARAMS(r));
3462 if (occupied == 0) {
3463 gclog_or_tty->print_cr(" RSet is empty");
3464 } else {
3465 hrrs->print();
3466 }
3467 gclog_or_tty->print_cr("----------");
3468 return false;
3469 }
3470
3471 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
3472 gclog_or_tty->cr();
3473 gclog_or_tty->print_cr("========================================");
3474 gclog_or_tty->print_cr(msg);
3475 gclog_or_tty->cr();
3476 }
3477
3478 ~PrintRSetsClosure() {
3479 gclog_or_tty->print_cr("Occupied Sum: "SIZE_FORMAT, _occupied_sum);
3480 gclog_or_tty->print_cr("========================================");
3481 gclog_or_tty->cr();
3482 }
3483 };
3484
3485 void G1CollectedHeap::print_cset_rsets() {
3486 PrintRSetsClosure cl("Printing CSet RSets");
3487 collection_set_iterate(&cl);
3488 }
3489
3490 void G1CollectedHeap::print_all_rsets() {
3491 PrintRSetsClosure cl("Printing All RSets");;
3492 heap_region_iterate(&cl);
3493 }
3494 #endif // PRODUCT
3495
3496 G1CollectedHeap* G1CollectedHeap::heap() {
3497 assert(_sh->kind() == CollectedHeap::G1CollectedHeap,
3498 "not a garbage-first heap");
3499 return _g1h;
3500 }
3501
3502 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) {
3503 // always_do_update_barrier = false;
3504 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
3505 // Call allocation profiler
3506 AllocationProfiler::iterate_since_last_gc();
3507 // Fill TLAB's and such
3508 ensure_parsability(true);
3509 }
3510
3511 void G1CollectedHeap::gc_epilogue(bool full /* Ignored */) {
3512 // FIXME: what is this about?
3513 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
3514 // is set.
3515 COMPILER2_PRESENT(assert(DerivedPointerTable::is_empty(),
3516 "derived pointer present"));
3517 // always_do_update_barrier = true;
3518
3519 // We have just completed a GC. Update the soft reference
3520 // policy with the new heap occupancy
3521 Universe::update_heap_info_at_gc();
3522 }
3523
3524 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
3525 unsigned int gc_count_before,
3526 bool* succeeded) {
3527 assert_heap_not_locked_and_not_at_safepoint();
3528 g1_policy()->record_stop_world_start();
3529 VM_G1IncCollectionPause op(gc_count_before,
3530 word_size,
3531 false, /* should_initiate_conc_mark */
3532 g1_policy()->max_pause_time_ms(),
3533 GCCause::_g1_inc_collection_pause);
3534 VMThread::execute(&op);
3535
3536 HeapWord* result = op.result();
3537 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
3538 assert(result == NULL || ret_succeeded,
3539 "the result should be NULL if the VM did not succeed");
3540 *succeeded = ret_succeeded;
3541
3542 assert_heap_not_locked();
3543 return result;
3544 }
3545
3546 void
3547 G1CollectedHeap::doConcurrentMark() {
3548 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
3549 if (!_cmThread->in_progress()) {
3550 _cmThread->set_started();
3551 CGC_lock->notify();
3552 }
3553 }
3554
3555 size_t G1CollectedHeap::pending_card_num() {
3556 size_t extra_cards = 0;
3557 JavaThread *curr = Threads::first();
3558 while (curr != NULL) {
3559 DirtyCardQueue& dcq = curr->dirty_card_queue();
3560 extra_cards += dcq.size();
3561 curr = curr->next();
3562 }
3563 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
3564 size_t buffer_size = dcqs.buffer_size();
3565 size_t buffer_num = dcqs.completed_buffers_num();
3566
3567 // PtrQueueSet::buffer_size() and PtrQueue:size() return sizes
3568 // in bytes - not the number of 'entries'. We need to convert
3569 // into a number of cards.
3570 return (buffer_size * buffer_num + extra_cards) / oopSize;
3571 }
3572
3573 size_t G1CollectedHeap::cards_scanned() {
3574 return g1_rem_set()->cardsScanned();
3575 }
3576
3577 void
3578 G1CollectedHeap::setup_surviving_young_words() {
3579 assert(_surviving_young_words == NULL, "pre-condition");
3580 uint array_length = g1_policy()->young_cset_region_length();
3581 _surviving_young_words = NEW_C_HEAP_ARRAY(size_t, (size_t) array_length, mtGC);
3582 if (_surviving_young_words == NULL) {
3583 vm_exit_out_of_memory(sizeof(size_t) * array_length,
3584 "Not enough space for young surv words summary.");
3585 }
3586 memset(_surviving_young_words, 0, (size_t) array_length * sizeof(size_t));
3587 #ifdef ASSERT
3588 for (uint i = 0; i < array_length; ++i) {
3589 assert( _surviving_young_words[i] == 0, "memset above" );
3590 }
3591 #endif // !ASSERT
3592 }
3593
3594 void
3595 G1CollectedHeap::update_surviving_young_words(size_t* surv_young_words) {
3596 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
3597 uint array_length = g1_policy()->young_cset_region_length();
3598 for (uint i = 0; i < array_length; ++i) {
3599 _surviving_young_words[i] += surv_young_words[i];
3600 }
3601 }
3602
3603 void
3604 G1CollectedHeap::cleanup_surviving_young_words() {
3605 guarantee( _surviving_young_words != NULL, "pre-condition" );
3606 FREE_C_HEAP_ARRAY(size_t, _surviving_young_words, mtGC);
3607 _surviving_young_words = NULL;
3608 }
3609
3610 #ifdef ASSERT
3611 class VerifyCSetClosure: public HeapRegionClosure {
3612 public:
3613 bool doHeapRegion(HeapRegion* hr) {
3614 // Here we check that the CSet region's RSet is ready for parallel
3615 // iteration. The fields that we'll verify are only manipulated
3616 // when the region is part of a CSet and is collected. Afterwards,
3617 // we reset these fields when we clear the region's RSet (when the
3618 // region is freed) so they are ready when the region is
3619 // re-allocated. The only exception to this is if there's an
3620 // evacuation failure and instead of freeing the region we leave
3621 // it in the heap. In that case, we reset these fields during
3622 // evacuation failure handling.
3623 guarantee(hr->rem_set()->verify_ready_for_par_iteration(), "verification");
3624
3625 // Here's a good place to add any other checks we'd like to
3626 // perform on CSet regions.
3627 return false;
3628 }
3629 };
3630 #endif // ASSERT
3631
3632 #if TASKQUEUE_STATS
3633 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
3634 st->print_raw_cr("GC Task Stats");
3635 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
3636 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
3637 }
3638
3639 void G1CollectedHeap::print_taskqueue_stats(outputStream* const st) const {
3640 print_taskqueue_stats_hdr(st);
3641
3642 TaskQueueStats totals;
3643 const int n = workers() != NULL ? workers()->total_workers() : 1;
3644 for (int i = 0; i < n; ++i) {
3645 st->print("%3d ", i); task_queue(i)->stats.print(st); st->cr();
3646 totals += task_queue(i)->stats;
3647 }
3648 st->print_raw("tot "); totals.print(st); st->cr();
3649
3650 DEBUG_ONLY(totals.verify());
3651 }
3652
3653 void G1CollectedHeap::reset_taskqueue_stats() {
3654 const int n = workers() != NULL ? workers()->total_workers() : 1;
3655 for (int i = 0; i < n; ++i) {
3656 task_queue(i)->stats.reset();
3657 }
3658 }
3659 #endif // TASKQUEUE_STATS
3660
3661 void G1CollectedHeap::log_gc_header() {
3662 if (!G1Log::fine()) {
3663 return;
3664 }
3665
3666 gclog_or_tty->date_stamp(PrintGCDateStamps);
3667 gclog_or_tty->stamp(PrintGCTimeStamps);
3668
3669 GCCauseString gc_cause_str = GCCauseString("GC pause", gc_cause())
3670 .append(g1_policy()->gcs_are_young() ? "(young)" : "(mixed)")
3671 .append(g1_policy()->during_initial_mark_pause() ? " (initial-mark)" : "");
3672
3673 gclog_or_tty->print("[%s", (const char*)gc_cause_str);
3674 }
3675
3676 void G1CollectedHeap::log_gc_footer(double pause_time_sec) {
3677 if (!G1Log::fine()) {
3678 return;
3679 }
3680
3681 if (G1Log::finer()) {
3682 if (evacuation_failed()) {
3683 gclog_or_tty->print(" (to-space exhausted)");
3684 }
3685 gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec);
3686 g1_policy()->phase_times()->note_gc_end();
3687 g1_policy()->phase_times()->print(pause_time_sec);
3688 g1_policy()->print_detailed_heap_transition();
3689 } else {
3690 if (evacuation_failed()) {
3691 gclog_or_tty->print("--");
3692 }
3693 g1_policy()->print_heap_transition();
3694 gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec);
3695 }
3696 gclog_or_tty->flush();
3697 }
3698
3699 bool
3700 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
3701 assert_at_safepoint(true /* should_be_vm_thread */);
3702 guarantee(!is_gc_active(), "collection is not reentrant");
3703
3704 if (GC_locker::check_active_before_gc()) {
3705 return false;
3706 }
3707
3708 SvcGCMarker sgcm(SvcGCMarker::MINOR);
3709 ResourceMark rm;
3710
3711 print_heap_before_gc();
3712
3713 HRSPhaseSetter x(HRSPhaseEvacuation);
3714 verify_region_sets_optional();
3715 verify_dirty_young_regions();
3716
3717 // This call will decide whether this pause is an initial-mark
3718 // pause. If it is, during_initial_mark_pause() will return true
3719 // for the duration of this pause.
3720 g1_policy()->decide_on_conc_mark_initiation();
3721
3722 // We do not allow initial-mark to be piggy-backed on a mixed GC.
3723 assert(!g1_policy()->during_initial_mark_pause() ||
3724 g1_policy()->gcs_are_young(), "sanity");
3725
3726 // We also do not allow mixed GCs during marking.
3727 assert(!mark_in_progress() || g1_policy()->gcs_are_young(), "sanity");
3728
3729 // Record whether this pause is an initial mark. When the current
3730 // thread has completed its logging output and it's safe to signal
3731 // the CM thread, the flag's value in the policy has been reset.
3732 bool should_start_conc_mark = g1_policy()->during_initial_mark_pause();
3733
3734 // Inner scope for scope based logging, timers, and stats collection
3735 {
3736 if (g1_policy()->during_initial_mark_pause()) {
3737 // We are about to start a marking cycle, so we increment the
3738 // full collection counter.
3739 increment_old_marking_cycles_started();
3740 }
3741 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
3742
3743 int active_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
3744 workers()->active_workers() : 1);
3745 double pause_start_sec = os::elapsedTime();
3746 g1_policy()->phase_times()->note_gc_start(active_workers);
3747 log_gc_header();
3748
3749 TraceCollectorStats tcs(g1mm()->incremental_collection_counters());
3750 TraceMemoryManagerStats tms(false /* fullGC */, gc_cause());
3751
3752 // If the secondary_free_list is not empty, append it to the
3753 // free_list. No need to wait for the cleanup operation to finish;
3754 // the region allocation code will check the secondary_free_list
3755 // and wait if necessary. If the G1StressConcRegionFreeing flag is
3756 // set, skip this step so that the region allocation code has to
3757 // get entries from the secondary_free_list.
3758 if (!G1StressConcRegionFreeing) {
3759 append_secondary_free_list_if_not_empty_with_lock();
3760 }
3761
3762 assert(check_young_list_well_formed(),
3763 "young list should be well formed");
3764
3765 // Don't dynamically change the number of GC threads this early. A value of
3766 // 0 is used to indicate serial work. When parallel work is done,
3767 // it will be set.
3768
3769 { // Call to jvmpi::post_class_unload_events must occur outside of active GC
3770 IsGCActiveMark x;
3771
3772 gc_prologue(false);
3773 increment_total_collections(false /* full gc */);
3774 increment_gc_time_stamp();
3775
3776 verify_before_gc();
3777
3778 COMPILER2_PRESENT(DerivedPointerTable::clear());
3779
3780 // Please see comment in g1CollectedHeap.hpp and
3781 // G1CollectedHeap::ref_processing_init() to see how
3782 // reference processing currently works in G1.
3783
3784 // Enable discovery in the STW reference processor
3785 ref_processor_stw()->enable_discovery(true /*verify_disabled*/,
3786 true /*verify_no_refs*/);
3787
3788 {
3789 // We want to temporarily turn off discovery by the
3790 // CM ref processor, if necessary, and turn it back on
3791 // on again later if we do. Using a scoped
3792 // NoRefDiscovery object will do this.
3793 NoRefDiscovery no_cm_discovery(ref_processor_cm());
3794
3795 // Forget the current alloc region (we might even choose it to be part
3796 // of the collection set!).
3797 release_mutator_alloc_region();
3798
3799 // We should call this after we retire the mutator alloc
3800 // region(s) so that all the ALLOC / RETIRE events are generated
3801 // before the start GC event.
3802 _hr_printer.start_gc(false /* full */, (size_t) total_collections());
3803
3804 // This timing is only used by the ergonomics to handle our pause target.
3805 // It is unclear why this should not include the full pause. We will
3806 // investigate this in CR 7178365.
3807 //
3808 // Preserving the old comment here if that helps the investigation:
3809 //
3810 // The elapsed time induced by the start time below deliberately elides
3811 // the possible verification above.
3812 double sample_start_time_sec = os::elapsedTime();
3813 size_t start_used_bytes = used();
3814
3815 #if YOUNG_LIST_VERBOSE
3816 gclog_or_tty->print_cr("\nBefore recording pause start.\nYoung_list:");
3817 _young_list->print();
3818 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3819 #endif // YOUNG_LIST_VERBOSE
3820
3821 g1_policy()->record_collection_pause_start(sample_start_time_sec,
3822 start_used_bytes);
3823
3824 double scan_wait_start = os::elapsedTime();
3825 // We have to wait until the CM threads finish scanning the
3826 // root regions as it's the only way to ensure that all the
3827 // objects on them have been correctly scanned before we start
3828 // moving them during the GC.
3829 bool waited = _cm->root_regions()->wait_until_scan_finished();
3830 double wait_time_ms = 0.0;
3831 if (waited) {
3832 double scan_wait_end = os::elapsedTime();
3833 wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
3834 }
3835 g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms);
3836
3837 #if YOUNG_LIST_VERBOSE
3838 gclog_or_tty->print_cr("\nAfter recording pause start.\nYoung_list:");
3839 _young_list->print();
3840 #endif // YOUNG_LIST_VERBOSE
3841
3842 if (g1_policy()->during_initial_mark_pause()) {
3843 concurrent_mark()->checkpointRootsInitialPre();
3844 }
3845
3846 #if YOUNG_LIST_VERBOSE
3847 gclog_or_tty->print_cr("\nBefore choosing collection set.\nYoung_list:");
3848 _young_list->print();
3849 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3850 #endif // YOUNG_LIST_VERBOSE
3851
3852 g1_policy()->finalize_cset(target_pause_time_ms);
3853
3854 _cm->note_start_of_gc();
3855 // We should not verify the per-thread SATB buffers given that
3856 // we have not filtered them yet (we'll do so during the
3857 // GC). We also call this after finalize_cset() to
3858 // ensure that the CSet has been finalized.
3859 _cm->verify_no_cset_oops(true /* verify_stacks */,
3860 true /* verify_enqueued_buffers */,
3861 false /* verify_thread_buffers */,
3862 true /* verify_fingers */);
3863
3864 if (_hr_printer.is_active()) {
3865 HeapRegion* hr = g1_policy()->collection_set();
3866 while (hr != NULL) {
3867 G1HRPrinter::RegionType type;
3868 if (!hr->is_young()) {
3869 type = G1HRPrinter::Old;
3870 } else if (hr->is_survivor()) {
3871 type = G1HRPrinter::Survivor;
3872 } else {
3873 type = G1HRPrinter::Eden;
3874 }
3875 _hr_printer.cset(hr);
3876 hr = hr->next_in_collection_set();
3877 }
3878 }
3879
3880 #ifdef ASSERT
3881 VerifyCSetClosure cl;
3882 collection_set_iterate(&cl);
3883 #endif // ASSERT
3884
3885 setup_surviving_young_words();
3886
3887 // Initialize the GC alloc regions.
3888 init_gc_alloc_regions();
3889
3890 // Actually do the work...
3891 evacuate_collection_set();
3892
3893 // We do this to mainly verify the per-thread SATB buffers
3894 // (which have been filtered by now) since we didn't verify
3895 // them earlier. No point in re-checking the stacks / enqueued
3896 // buffers given that the CSet has not changed since last time
3897 // we checked.
3898 _cm->verify_no_cset_oops(false /* verify_stacks */,
3899 false /* verify_enqueued_buffers */,
3900 true /* verify_thread_buffers */,
3901 true /* verify_fingers */);
3902
3903 free_collection_set(g1_policy()->collection_set());
3904 g1_policy()->clear_collection_set();
3905
3906 cleanup_surviving_young_words();
3907
3908 // Start a new incremental collection set for the next pause.
3909 g1_policy()->start_incremental_cset_building();
3910
3911 // Clear the _cset_fast_test bitmap in anticipation of adding
3912 // regions to the incremental collection set for the next
3913 // evacuation pause.
3914 clear_cset_fast_test();
3915
3916 _young_list->reset_sampled_info();
3917
3918 // Don't check the whole heap at this point as the
3919 // GC alloc regions from this pause have been tagged
3920 // as survivors and moved on to the survivor list.
3921 // Survivor regions will fail the !is_young() check.
3922 assert(check_young_list_empty(false /* check_heap */),
3923 "young list should be empty");
3924
3925 #if YOUNG_LIST_VERBOSE
3926 gclog_or_tty->print_cr("Before recording survivors.\nYoung List:");
3927 _young_list->print();
3928 #endif // YOUNG_LIST_VERBOSE
3929
3930 g1_policy()->record_survivor_regions(_young_list->survivor_length(),
3931 _young_list->first_survivor_region(),
3932 _young_list->last_survivor_region());
3933
3934 _young_list->reset_auxilary_lists();
3935
3936 if (evacuation_failed()) {
3937 _summary_bytes_used = recalculate_used();
3938 } else {
3939 // The "used" of the the collection set have already been subtracted
3940 // when they were freed. Add in the bytes evacuated.
3941 _summary_bytes_used += g1_policy()->bytes_copied_during_gc();
3942 }
3943
3944 if (g1_policy()->during_initial_mark_pause()) {
3945 // We have to do this before we notify the CM threads that
3946 // they can start working to make sure that all the
3947 // appropriate initialization is done on the CM object.
3948 concurrent_mark()->checkpointRootsInitialPost();
3949 set_marking_started();
3950 // Note that we don't actually trigger the CM thread at
3951 // this point. We do that later when we're sure that
3952 // the current thread has completed its logging output.
3953 }
3954
3955 allocate_dummy_regions();
3956
3957 #if YOUNG_LIST_VERBOSE
3958 gclog_or_tty->print_cr("\nEnd of the pause.\nYoung_list:");
3959 _young_list->print();
3960 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3961 #endif // YOUNG_LIST_VERBOSE
3962
3963 init_mutator_alloc_region();
3964
3965 {
3966 size_t expand_bytes = g1_policy()->expansion_amount();
3967 if (expand_bytes > 0) {
3968 size_t bytes_before = capacity();
3969 // No need for an ergo verbose message here,
3970 // expansion_amount() does this when it returns a value > 0.
3971 if (!expand(expand_bytes)) {
3972 // We failed to expand the heap so let's verify that
3973 // committed/uncommitted amount match the backing store
3974 assert(capacity() == _g1_storage.committed_size(), "committed size mismatch");
3975 assert(max_capacity() == _g1_storage.reserved_size(), "reserved size mismatch");
3976 }
3977 }
3978 }
3979
3980 // We redo the verificaiton but now wrt to the new CSet which
3981 // has just got initialized after the previous CSet was freed.
3982 _cm->verify_no_cset_oops(true /* verify_stacks */,
3983 true /* verify_enqueued_buffers */,
3984 true /* verify_thread_buffers */,
3985 true /* verify_fingers */);
3986 _cm->note_end_of_gc();
3987
3988 // This timing is only used by the ergonomics to handle our pause target.
3989 // It is unclear why this should not include the full pause. We will
3990 // investigate this in CR 7178365.
3991 double sample_end_time_sec = os::elapsedTime();
3992 double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
3993 g1_policy()->record_collection_pause_end(pause_time_ms);
3994
3995 MemoryService::track_memory_usage();
3996
3997 // In prepare_for_verify() below we'll need to scan the deferred
3998 // update buffers to bring the RSets up-to-date if
3999 // G1HRRSFlushLogBuffersOnVerify has been set. While scanning
4000 // the update buffers we'll probably need to scan cards on the
4001 // regions we just allocated to (i.e., the GC alloc
4002 // regions). However, during the last GC we called
4003 // set_saved_mark() on all the GC alloc regions, so card
4004 // scanning might skip the [saved_mark_word()...top()] area of
4005 // those regions (i.e., the area we allocated objects into
4006 // during the last GC). But it shouldn't. Given that
4007 // saved_mark_word() is conditional on whether the GC time stamp
4008 // on the region is current or not, by incrementing the GC time
4009 // stamp here we invalidate all the GC time stamps on all the
4010 // regions and saved_mark_word() will simply return top() for
4011 // all the regions. This is a nicer way of ensuring this rather
4012 // than iterating over the regions and fixing them. In fact, the
4013 // GC time stamp increment here also ensures that
4014 // saved_mark_word() will return top() between pauses, i.e.,
4015 // during concurrent refinement. So we don't need the
4016 // is_gc_active() check to decided which top to use when
4017 // scanning cards (see CR 7039627).
4018 increment_gc_time_stamp();
4019
4020 verify_after_gc();
4021
4022 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
4023 ref_processor_stw()->verify_no_references_recorded();
4024
4025 // CM reference discovery will be re-enabled if necessary.
4026 }
4027
4028 // We should do this after we potentially expand the heap so
4029 // that all the COMMIT events are generated before the end GC
4030 // event, and after we retire the GC alloc regions so that all
4031 // RETIRE events are generated before the end GC event.
4032 _hr_printer.end_gc(false /* full */, (size_t) total_collections());
4033
4034 if (mark_in_progress()) {
4035 concurrent_mark()->update_g1_committed();
4036 }
4037
4038 #ifdef TRACESPINNING
4039 ParallelTaskTerminator::print_termination_counts();
4040 #endif
4041
4042 gc_epilogue(false);
4043 }
4044
4045 // Print the remainder of the GC log output.
4046 log_gc_footer(os::elapsedTime() - pause_start_sec);
4047
4048 // It is not yet to safe to tell the concurrent mark to
4049 // start as we have some optional output below. We don't want the
4050 // output from the concurrent mark thread interfering with this
4051 // logging output either.
4052
4053 _hrs.verify_optional();
4054 verify_region_sets_optional();
4055
4056 TASKQUEUE_STATS_ONLY(if (ParallelGCVerbose) print_taskqueue_stats());
4057 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
4058
4059 print_heap_after_gc();
4060
4061 // We must call G1MonitoringSupport::update_sizes() in the same scoping level
4062 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
4063 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
4064 // before any GC notifications are raised.
4065 g1mm()->update_sizes();
4066 }
4067
4068 if (G1SummarizeRSetStats &&
4069 (G1SummarizeRSetStatsPeriod > 0) &&
4070 (total_collections() % G1SummarizeRSetStatsPeriod == 0)) {
4071 g1_rem_set()->print_summary_info();
4072 }
4073
4074 // It should now be safe to tell the concurrent mark thread to start
4075 // without its logging output interfering with the logging output
4076 // that came from the pause.
4077
4078 if (should_start_conc_mark) {
4079 // CAUTION: after the doConcurrentMark() call below,
4080 // the concurrent marking thread(s) could be running
4081 // concurrently with us. Make sure that anything after
4082 // this point does not assume that we are the only GC thread
4083 // running. Note: of course, the actual marking work will
4084 // not start until the safepoint itself is released in
4085 // ConcurrentGCThread::safepoint_desynchronize().
4086 doConcurrentMark();
4087 }
4088
4089 return true;
4090 }
4091
4092 size_t G1CollectedHeap::desired_plab_sz(GCAllocPurpose purpose)
4093 {
4094 size_t gclab_word_size;
4095 switch (purpose) {
4096 case GCAllocForSurvived:
4097 gclab_word_size = _survivor_plab_stats.desired_plab_sz();
4098 break;
4099 case GCAllocForTenured:
4100 gclab_word_size = _old_plab_stats.desired_plab_sz();
4101 break;
4102 default:
4103 assert(false, "unknown GCAllocPurpose");
4104 gclab_word_size = _old_plab_stats.desired_plab_sz();
4105 break;
4106 }
4107
4108 // Prevent humongous PLAB sizes for two reasons:
4109 // * PLABs are allocated using a similar paths as oops, but should
4110 // never be in a humongous region
4111 // * Allowing humongous PLABs needlessly churns the region free lists
4112 return MIN2(_humongous_object_threshold_in_words, gclab_word_size);
4113 }
4114
4115 void G1CollectedHeap::init_mutator_alloc_region() {
4116 assert(_mutator_alloc_region.get() == NULL, "pre-condition");
4117 _mutator_alloc_region.init();
4118 }
4119
4120 void G1CollectedHeap::release_mutator_alloc_region() {
4121 _mutator_alloc_region.release();
4122 assert(_mutator_alloc_region.get() == NULL, "post-condition");
4123 }
4124
4125 void G1CollectedHeap::init_gc_alloc_regions() {
4126 assert_at_safepoint(true /* should_be_vm_thread */);
4127
4128 _survivor_gc_alloc_region.init();
4129 _old_gc_alloc_region.init();
4130 HeapRegion* retained_region = _retained_old_gc_alloc_region;
4131 _retained_old_gc_alloc_region = NULL;
4132
4133 // We will discard the current GC alloc region if:
4134 // a) it's in the collection set (it can happen!),
4135 // b) it's already full (no point in using it),
4136 // c) it's empty (this means that it was emptied during
4137 // a cleanup and it should be on the free list now), or
4138 // d) it's humongous (this means that it was emptied
4139 // during a cleanup and was added to the free list, but
4140 // has been subseqently used to allocate a humongous
4141 // object that may be less than the region size).
4142 if (retained_region != NULL &&
4143 !retained_region->in_collection_set() &&
4144 !(retained_region->top() == retained_region->end()) &&
4145 !retained_region->is_empty() &&
4146 !retained_region->isHumongous()) {
4147 retained_region->set_saved_mark();
4148 // The retained region was added to the old region set when it was
4149 // retired. We have to remove it now, since we don't allow regions
4150 // we allocate to in the region sets. We'll re-add it later, when
4151 // it's retired again.
4152 _old_set.remove(retained_region);
4153 bool during_im = g1_policy()->during_initial_mark_pause();
4154 retained_region->note_start_of_copying(during_im);
4155 _old_gc_alloc_region.set(retained_region);
4156 _hr_printer.reuse(retained_region);
4157 }
4158 }
4159
4160 void G1CollectedHeap::release_gc_alloc_regions(uint no_of_gc_workers) {
4161 _survivor_gc_alloc_region.release();
4162 // If we have an old GC alloc region to release, we'll save it in
4163 // _retained_old_gc_alloc_region. If we don't
4164 // _retained_old_gc_alloc_region will become NULL. This is what we
4165 // want either way so no reason to check explicitly for either
4166 // condition.
4167 _retained_old_gc_alloc_region = _old_gc_alloc_region.release();
4168
4169 if (ResizePLAB) {
4170 _survivor_plab_stats.adjust_desired_plab_sz(no_of_gc_workers);
4171 _old_plab_stats.adjust_desired_plab_sz(no_of_gc_workers);
4172 }
4173 }
4174
4175 void G1CollectedHeap::abandon_gc_alloc_regions() {
4176 assert(_survivor_gc_alloc_region.get() == NULL, "pre-condition");
4177 assert(_old_gc_alloc_region.get() == NULL, "pre-condition");
4178 _retained_old_gc_alloc_region = NULL;
4179 }
4180
4181 void G1CollectedHeap::init_for_evac_failure(OopsInHeapRegionClosure* cl) {
4182 _drain_in_progress = false;
4183 set_evac_failure_closure(cl);
4184 _evac_failure_scan_stack = new (ResourceObj::C_HEAP, mtGC) GrowableArray<oop>(40, true);
4185 }
4186
4187 void G1CollectedHeap::finalize_for_evac_failure() {
4188 assert(_evac_failure_scan_stack != NULL &&
4189 _evac_failure_scan_stack->length() == 0,
4190 "Postcondition");
4191 assert(!_drain_in_progress, "Postcondition");
4192 delete _evac_failure_scan_stack;
4193 _evac_failure_scan_stack = NULL;
4194 }
4195
4196 void G1CollectedHeap::remove_self_forwarding_pointers() {
4197 assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity");
4198
4199 G1ParRemoveSelfForwardPtrsTask rsfp_task(this);
4200
4201 if (G1CollectedHeap::use_parallel_gc_threads()) {
4202 set_par_threads();
4203 workers()->run_task(&rsfp_task);
4204 set_par_threads(0);
4205 } else {
4206 rsfp_task.work(0);
4207 }
4208
4209 assert(check_cset_heap_region_claim_values(HeapRegion::ParEvacFailureClaimValue), "sanity");
4210
4211 // Reset the claim values in the regions in the collection set.
4212 reset_cset_heap_region_claim_values();
4213
4214 assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity");
4215
4216 // Now restore saved marks, if any.
4217 assert(_objs_with_preserved_marks.size() ==
4218 _preserved_marks_of_objs.size(), "Both or none.");
4219 while (!_objs_with_preserved_marks.is_empty()) {
4220 oop obj = _objs_with_preserved_marks.pop();
4221 markOop m = _preserved_marks_of_objs.pop();
4222 obj->set_mark(m);
4223 }
4224 _objs_with_preserved_marks.clear(true);
4225 _preserved_marks_of_objs.clear(true);
4226 }
4227
4228 void G1CollectedHeap::push_on_evac_failure_scan_stack(oop obj) {
4229 _evac_failure_scan_stack->push(obj);
4230 }
4231
4232 void G1CollectedHeap::drain_evac_failure_scan_stack() {
4233 assert(_evac_failure_scan_stack != NULL, "precondition");
4234
4235 while (_evac_failure_scan_stack->length() > 0) {
4236 oop obj = _evac_failure_scan_stack->pop();
4237 _evac_failure_closure->set_region(heap_region_containing(obj));
4238 obj->oop_iterate_backwards(_evac_failure_closure);
4239 }
4240 }
4241
4242 oop
4243 G1CollectedHeap::handle_evacuation_failure_par(OopsInHeapRegionClosure* cl,
4244 oop old) {
4245 assert(obj_in_cs(old),
4246 err_msg("obj: "PTR_FORMAT" should still be in the CSet",
4247 (HeapWord*) old));
4248 markOop m = old->mark();
4249 oop forward_ptr = old->forward_to_atomic(old);
4250 if (forward_ptr == NULL) {
4251 // Forward-to-self succeeded.
4252
4253 if (_evac_failure_closure != cl) {
4254 MutexLockerEx x(EvacFailureStack_lock, Mutex::_no_safepoint_check_flag);
4255 assert(!_drain_in_progress,
4256 "Should only be true while someone holds the lock.");
4257 // Set the global evac-failure closure to the current thread's.
4258 assert(_evac_failure_closure == NULL, "Or locking has failed.");
4259 set_evac_failure_closure(cl);
4260 // Now do the common part.
4261 handle_evacuation_failure_common(old, m);
4262 // Reset to NULL.
4263 set_evac_failure_closure(NULL);
4264 } else {
4265 // The lock is already held, and this is recursive.
4266 assert(_drain_in_progress, "This should only be the recursive case.");
4267 handle_evacuation_failure_common(old, m);
4268 }
4269 return old;
4270 } else {
4271 // Forward-to-self failed. Either someone else managed to allocate
4272 // space for this object (old != forward_ptr) or they beat us in
4273 // self-forwarding it (old == forward_ptr).
4274 assert(old == forward_ptr || !obj_in_cs(forward_ptr),
4275 err_msg("obj: "PTR_FORMAT" forwarded to: "PTR_FORMAT" "
4276 "should not be in the CSet",
4277 (HeapWord*) old, (HeapWord*) forward_ptr));
4278 return forward_ptr;
4279 }
4280 }
4281
4282 void G1CollectedHeap::handle_evacuation_failure_common(oop old, markOop m) {
4283 set_evacuation_failed(true);
4284
4285 preserve_mark_if_necessary(old, m);
4286
4287 HeapRegion* r = heap_region_containing(old);
4288 if (!r->evacuation_failed()) {
4289 r->set_evacuation_failed(true);
4290 _hr_printer.evac_failure(r);
4291 }
4292
4293 push_on_evac_failure_scan_stack(old);
4294
4295 if (!_drain_in_progress) {
4296 // prevent recursion in copy_to_survivor_space()
4297 _drain_in_progress = true;
4298 drain_evac_failure_scan_stack();
4299 _drain_in_progress = false;
4300 }
4301 }
4302
4303 void G1CollectedHeap::preserve_mark_if_necessary(oop obj, markOop m) {
4304 assert(evacuation_failed(), "Oversaving!");
4305 // We want to call the "for_promotion_failure" version only in the
4306 // case of a promotion failure.
4307 if (m->must_be_preserved_for_promotion_failure(obj)) {
4308 _objs_with_preserved_marks.push(obj);
4309 _preserved_marks_of_objs.push(m);
4310 }
4311 }
4312
4313 HeapWord* G1CollectedHeap::par_allocate_during_gc(GCAllocPurpose purpose,
4314 size_t word_size) {
4315 if (purpose == GCAllocForSurvived) {
4316 HeapWord* result = survivor_attempt_allocation(word_size);
4317 if (result != NULL) {
4318 return result;
4319 } else {
4320 // Let's try to allocate in the old gen in case we can fit the
4321 // object there.
4322 return old_attempt_allocation(word_size);
4323 }
4324 } else {
4325 assert(purpose == GCAllocForTenured, "sanity");
4326 HeapWord* result = old_attempt_allocation(word_size);
4327 if (result != NULL) {
4328 return result;
4329 } else {
4330 // Let's try to allocate in the survivors in case we can fit the
4331 // object there.
4332 return survivor_attempt_allocation(word_size);
4333 }
4334 }
4335
4336 ShouldNotReachHere();
4337 // Trying to keep some compilers happy.
4338 return NULL;
4339 }
4340
4341 G1ParGCAllocBuffer::G1ParGCAllocBuffer(size_t gclab_word_size) :
4342 ParGCAllocBuffer(gclab_word_size), _retired(false) { }
4343
4344 G1ParScanThreadState::G1ParScanThreadState(G1CollectedHeap* g1h, uint queue_num)
4345 : _g1h(g1h),
4346 _refs(g1h->task_queue(queue_num)),
4347 _dcq(&g1h->dirty_card_queue_set()),
4348 _ct_bs((CardTableModRefBS*)_g1h->barrier_set()),
4349 _g1_rem(g1h->g1_rem_set()),
4350 _hash_seed(17), _queue_num(queue_num),
4351 _term_attempts(0),
4352 _surviving_alloc_buffer(g1h->desired_plab_sz(GCAllocForSurvived)),
4353 _tenured_alloc_buffer(g1h->desired_plab_sz(GCAllocForTenured)),
4354 _age_table(false),
4355 _strong_roots_time(0), _term_time(0),
4356 _alloc_buffer_waste(0), _undo_waste(0) {
4357 // we allocate G1YoungSurvRateNumRegions plus one entries, since
4358 // we "sacrifice" entry 0 to keep track of surviving bytes for
4359 // non-young regions (where the age is -1)
4360 // We also add a few elements at the beginning and at the end in
4361 // an attempt to eliminate cache contention
4362 uint real_length = 1 + _g1h->g1_policy()->young_cset_region_length();
4363 uint array_length = PADDING_ELEM_NUM +
4364 real_length +
4365 PADDING_ELEM_NUM;
4366 _surviving_young_words_base = NEW_C_HEAP_ARRAY(size_t, array_length, mtGC);
4367 if (_surviving_young_words_base == NULL)
4368 vm_exit_out_of_memory(array_length * sizeof(size_t),
4369 "Not enough space for young surv histo.");
4370 _surviving_young_words = _surviving_young_words_base + PADDING_ELEM_NUM;
4371 memset(_surviving_young_words, 0, (size_t) real_length * sizeof(size_t));
4372
4373 _alloc_buffers[GCAllocForSurvived] = &_surviving_alloc_buffer;
4374 _alloc_buffers[GCAllocForTenured] = &_tenured_alloc_buffer;
4375
4376 _start = os::elapsedTime();
4377 }
4378
4379 void
4380 G1ParScanThreadState::print_termination_stats_hdr(outputStream* const st)
4381 {
4382 st->print_raw_cr("GC Termination Stats");
4383 st->print_raw_cr(" elapsed --strong roots-- -------termination-------"
4384 " ------waste (KiB)------");
4385 st->print_raw_cr("thr ms ms % ms % attempts"
4386 " total alloc undo");
4387 st->print_raw_cr("--- --------- --------- ------ --------- ------ --------"
4388 " ------- ------- -------");
4389 }
4390
4391 void
4392 G1ParScanThreadState::print_termination_stats(int i,
4393 outputStream* const st) const
4394 {
4395 const double elapsed_ms = elapsed_time() * 1000.0;
4396 const double s_roots_ms = strong_roots_time() * 1000.0;
4397 const double term_ms = term_time() * 1000.0;
4398 st->print_cr("%3d %9.2f %9.2f %6.2f "
4399 "%9.2f %6.2f " SIZE_FORMAT_W(8) " "
4400 SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7),
4401 i, elapsed_ms, s_roots_ms, s_roots_ms * 100 / elapsed_ms,
4402 term_ms, term_ms * 100 / elapsed_ms, term_attempts(),
4403 (alloc_buffer_waste() + undo_waste()) * HeapWordSize / K,
4404 alloc_buffer_waste() * HeapWordSize / K,
4405 undo_waste() * HeapWordSize / K);
4406 }
4407
4408 #ifdef ASSERT
4409 bool G1ParScanThreadState::verify_ref(narrowOop* ref) const {
4410 assert(ref != NULL, "invariant");
4411 assert(UseCompressedOops, "sanity");
4412 assert(!has_partial_array_mask(ref), err_msg("ref=" PTR_FORMAT, ref));
4413 oop p = oopDesc::load_decode_heap_oop(ref);
4414 assert(_g1h->is_in_g1_reserved(p),
4415 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p)));
4416 return true;
4417 }
4418
4419 bool G1ParScanThreadState::verify_ref(oop* ref) const {
4420 assert(ref != NULL, "invariant");
4421 if (has_partial_array_mask(ref)) {
4422 // Must be in the collection set--it's already been copied.
4423 oop p = clear_partial_array_mask(ref);
4424 assert(_g1h->obj_in_cs(p),
4425 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p)));
4426 } else {
4427 oop p = oopDesc::load_decode_heap_oop(ref);
4428 assert(_g1h->is_in_g1_reserved(p),
4429 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p)));
4430 }
4431 return true;
4432 }
4433
4434 bool G1ParScanThreadState::verify_task(StarTask ref) const {
4435 if (ref.is_narrow()) {
4436 return verify_ref((narrowOop*) ref);
4437 } else {
4438 return verify_ref((oop*) ref);
4439 }
4440 }
4441 #endif // ASSERT
4442
4443 void G1ParScanThreadState::trim_queue() {
4444 assert(_evac_cl != NULL, "not set");
4445 assert(_evac_failure_cl != NULL, "not set");
4446 assert(_partial_scan_cl != NULL, "not set");
4447
4448 StarTask ref;
4449 do {
4450 // Drain the overflow stack first, so other threads can steal.
4451 while (refs()->pop_overflow(ref)) {
4452 deal_with_reference(ref);
4453 }
4454
4455 while (refs()->pop_local(ref)) {
4456 deal_with_reference(ref);
4457 }
4458 } while (!refs()->is_empty());
4459 }
4460
4461 G1ParClosureSuper::G1ParClosureSuper(G1CollectedHeap* g1,
4462 G1ParScanThreadState* par_scan_state) :
4463 _g1(g1), _g1_rem(_g1->g1_rem_set()), _cm(_g1->concurrent_mark()),
4464 _par_scan_state(par_scan_state),
4465 _worker_id(par_scan_state->queue_num()),
4466 _during_initial_mark(_g1->g1_policy()->during_initial_mark_pause()),
4467 _mark_in_progress(_g1->mark_in_progress()) { }
4468
4469 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object>
4470 void G1ParCopyClosure<do_gen_barrier, barrier, do_mark_object>::mark_object(oop obj) {
4471 #ifdef ASSERT
4472 HeapRegion* hr = _g1->heap_region_containing(obj);
4473 assert(hr != NULL, "sanity");
4474 assert(!hr->in_collection_set(), "should not mark objects in the CSet");
4475 #endif // ASSERT
4476
4477 // We know that the object is not moving so it's safe to read its size.
4478 _cm->grayRoot(obj, (size_t) obj->size(), _worker_id);
4479 }
4480
4481 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object>
4482 void G1ParCopyClosure<do_gen_barrier, barrier, do_mark_object>
4483 ::mark_forwarded_object(oop from_obj, oop to_obj) {
4484 #ifdef ASSERT
4485 assert(from_obj->is_forwarded(), "from obj should be forwarded");
4486 assert(from_obj->forwardee() == to_obj, "to obj should be the forwardee");
4487 assert(from_obj != to_obj, "should not be self-forwarded");
4488
4489 HeapRegion* from_hr = _g1->heap_region_containing(from_obj);
4490 assert(from_hr != NULL, "sanity");
4491 assert(from_hr->in_collection_set(), "from obj should be in the CSet");
4492
4493 HeapRegion* to_hr = _g1->heap_region_containing(to_obj);
4494 assert(to_hr != NULL, "sanity");
4495 assert(!to_hr->in_collection_set(), "should not mark objects in the CSet");
4496 #endif // ASSERT
4497
4498 // The object might be in the process of being copied by another
4499 // worker so we cannot trust that its to-space image is
4500 // well-formed. So we have to read its size from its from-space
4501 // image which we know should not be changing.
4502 _cm->grayRoot(to_obj, (size_t) from_obj->size(), _worker_id);
4503 }
4504
4505 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object>
4506 oop G1ParCopyClosure<do_gen_barrier, barrier, do_mark_object>
4507 ::copy_to_survivor_space(oop old) {
4508 size_t word_sz = old->size();
4509 HeapRegion* from_region = _g1->heap_region_containing_raw(old);
4510 // +1 to make the -1 indexes valid...
4511 int young_index = from_region->young_index_in_cset()+1;
4512 assert( (from_region->is_young() && young_index > 0) ||
4513 (!from_region->is_young() && young_index == 0), "invariant" );
4514 G1CollectorPolicy* g1p = _g1->g1_policy();
4515 markOop m = old->mark();
4516 int age = m->has_displaced_mark_helper() ? m->displaced_mark_helper()->age()
4517 : m->age();
4518 GCAllocPurpose alloc_purpose = g1p->evacuation_destination(from_region, age,
4519 word_sz);
4520 HeapWord* obj_ptr = _par_scan_state->allocate(alloc_purpose, word_sz);
4521 #ifndef PRODUCT
4522 // Should this evacuation fail?
4523 if (_g1->evacuation_should_fail()) {
4524 if (obj_ptr != NULL) {
4525 _par_scan_state->undo_allocation(alloc_purpose, obj_ptr, word_sz);
4526 obj_ptr = NULL;
4527 }
4528 }
4529 #endif // !PRODUCT
4530
4531 if (obj_ptr == NULL) {
4532 // This will either forward-to-self, or detect that someone else has
4533 // installed a forwarding pointer.
4534 OopsInHeapRegionClosure* cl = _par_scan_state->evac_failure_closure();
4535 return _g1->handle_evacuation_failure_par(cl, old);
4536 }
4537
4538 oop obj = oop(obj_ptr);
4539
4540 // We're going to allocate linearly, so might as well prefetch ahead.
4541 Prefetch::write(obj_ptr, PrefetchCopyIntervalInBytes);
4542
4543 oop forward_ptr = old->forward_to_atomic(obj);
4544 if (forward_ptr == NULL) {
4545 Copy::aligned_disjoint_words((HeapWord*) old, obj_ptr, word_sz);
4546 if (g1p->track_object_age(alloc_purpose)) {
4547 // We could simply do obj->incr_age(). However, this causes a
4548 // performance issue. obj->incr_age() will first check whether
4549 // the object has a displaced mark by checking its mark word;
4550 // getting the mark word from the new location of the object
4551 // stalls. So, given that we already have the mark word and we
4552 // are about to install it anyway, it's better to increase the
4553 // age on the mark word, when the object does not have a
4554 // displaced mark word. We're not expecting many objects to have
4555 // a displaced marked word, so that case is not optimized
4556 // further (it could be...) and we simply call obj->incr_age().
4557
4558 if (m->has_displaced_mark_helper()) {
4559 // in this case, we have to install the mark word first,
4560 // otherwise obj looks to be forwarded (the old mark word,
4561 // which contains the forward pointer, was copied)
4562 obj->set_mark(m);
4563 obj->incr_age();
4564 } else {
4565 m = m->incr_age();
4566 obj->set_mark(m);
4567 }
4568 _par_scan_state->age_table()->add(obj, word_sz);
4569 } else {
4570 obj->set_mark(m);
4571 }
4572
4573 size_t* surv_young_words = _par_scan_state->surviving_young_words();
4574 surv_young_words[young_index] += word_sz;
4575
4576 if (obj->is_objArray() && arrayOop(obj)->length() >= ParGCArrayScanChunk) {
4577 // We keep track of the next start index in the length field of
4578 // the to-space object. The actual length can be found in the
4579 // length field of the from-space object.
4580 arrayOop(obj)->set_length(0);
4581 oop* old_p = set_partial_array_mask(old);
4582 _par_scan_state->push_on_queue(old_p);
4583 } else {
4584 // No point in using the slower heap_region_containing() method,
4585 // given that we know obj is in the heap.
4586 _scanner.set_region(_g1->heap_region_containing_raw(obj));
4587 obj->oop_iterate_backwards(&_scanner);
4588 }
4589 } else {
4590 _par_scan_state->undo_allocation(alloc_purpose, obj_ptr, word_sz);
4591 obj = forward_ptr;
4592 }
4593 return obj;
4594 }
4595
4596 template <class T>
4597 void G1ParCopyHelper::do_klass_barrier(T* p, oop new_obj) {
4598 if (_g1->heap_region_containing_raw(new_obj)->is_young()) {
4599 _scanned_klass->record_modified_oops();
4600 }
4601 }
4602
4603 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object>
4604 template <class T>
4605 void G1ParCopyClosure<do_gen_barrier, barrier, do_mark_object>
4606 ::do_oop_work(T* p) {
4607 oop obj = oopDesc::load_decode_heap_oop(p);
4608 assert(barrier != G1BarrierRS || obj != NULL,
4609 "Precondition: G1BarrierRS implies obj is non-NULL");
4610
4611 assert(_worker_id == _par_scan_state->queue_num(), "sanity");
4612
4613 // here the null check is implicit in the cset_fast_test() test
4614 if (_g1->in_cset_fast_test(obj)) {
4615 oop forwardee;
4616 if (obj->is_forwarded()) {
4617 forwardee = obj->forwardee();
4618 } else {
4619 forwardee = copy_to_survivor_space(obj);
4620 }
4621 assert(forwardee != NULL, "forwardee should not be NULL");
4622 oopDesc::encode_store_heap_oop(p, forwardee);
4623 if (do_mark_object && forwardee != obj) {
4624 // If the object is self-forwarded we don't need to explicitly
4625 // mark it, the evacuation failure protocol will do so.
4626 mark_forwarded_object(obj, forwardee);
4627 }
4628
4629 // When scanning the RS, we only care about objs in CS.
4630 if (barrier == G1BarrierRS) {
4631 _par_scan_state->update_rs(_from, p, _worker_id);
4632 } else if (barrier == G1BarrierKlass) {
4633 do_klass_barrier(p, forwardee);
4634 }
4635 } else {
4636 // The object is not in collection set. If we're a root scanning
4637 // closure during an initial mark pause (i.e. do_mark_object will
4638 // be true) then attempt to mark the object.
4639 if (do_mark_object && _g1->is_in_g1_reserved(obj)) {
4640 mark_object(obj);
4641 }
4642 }
4643
4644 if (barrier == G1BarrierEvac && obj != NULL) {
4645 _par_scan_state->update_rs(_from, p, _worker_id);
4646 }
4647
4648 if (do_gen_barrier && obj != NULL) {
4649 par_do_barrier(p);
4650 }
4651 }
4652
4653 template void G1ParCopyClosure<false, G1BarrierEvac, false>::do_oop_work(oop* p);
4654 template void G1ParCopyClosure<false, G1BarrierEvac, false>::do_oop_work(narrowOop* p);
4655
4656 template <class T> void G1ParScanPartialArrayClosure::do_oop_nv(T* p) {
4657 assert(has_partial_array_mask(p), "invariant");
4658 oop from_obj = clear_partial_array_mask(p);
4659
4660 assert(Universe::heap()->is_in_reserved(from_obj), "must be in heap.");
4661 assert(from_obj->is_objArray(), "must be obj array");
4662 objArrayOop from_obj_array = objArrayOop(from_obj);
4663 // The from-space object contains the real length.
4664 int length = from_obj_array->length();
4665
4666 assert(from_obj->is_forwarded(), "must be forwarded");
4667 oop to_obj = from_obj->forwardee();
4668 assert(from_obj != to_obj, "should not be chunking self-forwarded objects");
4669 objArrayOop to_obj_array = objArrayOop(to_obj);
4670 // We keep track of the next start index in the length field of the
4671 // to-space object.
4672 int next_index = to_obj_array->length();
4673 assert(0 <= next_index && next_index < length,
4674 err_msg("invariant, next index: %d, length: %d", next_index, length));
4675
4676 int start = next_index;
4677 int end = length;
4678 int remainder = end - start;
4679 // We'll try not to push a range that's smaller than ParGCArrayScanChunk.
4680 if (remainder > 2 * ParGCArrayScanChunk) {
4681 end = start + ParGCArrayScanChunk;
4682 to_obj_array->set_length(end);
4683 // Push the remainder before we process the range in case another
4684 // worker has run out of things to do and can steal it.
4685 oop* from_obj_p = set_partial_array_mask(from_obj);
4686 _par_scan_state->push_on_queue(from_obj_p);
4687 } else {
4688 assert(length == end, "sanity");
4689 // We'll process the final range for this object. Restore the length
4690 // so that the heap remains parsable in case of evacuation failure.
4691 to_obj_array->set_length(end);
4692 }
4693 _scanner.set_region(_g1->heap_region_containing_raw(to_obj));
4694 // Process indexes [start,end). It will also process the header
4695 // along with the first chunk (i.e., the chunk with start == 0).
4696 // Note that at this point the length field of to_obj_array is not
4697 // correct given that we are using it to keep track of the next
4698 // start index. oop_iterate_range() (thankfully!) ignores the length
4699 // field and only relies on the start / end parameters. It does
4700 // however return the size of the object which will be incorrect. So
4701 // we have to ignore it even if we wanted to use it.
4702 to_obj_array->oop_iterate_range(&_scanner, start, end);
4703 }
4704
4705 class G1ParEvacuateFollowersClosure : public VoidClosure {
4706 protected:
4707 G1CollectedHeap* _g1h;
4708 G1ParScanThreadState* _par_scan_state;
4709 RefToScanQueueSet* _queues;
4710 ParallelTaskTerminator* _terminator;
4711
4712 G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
4713 RefToScanQueueSet* queues() { return _queues; }
4714 ParallelTaskTerminator* terminator() { return _terminator; }
4715
4716 public:
4717 G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h,
4718 G1ParScanThreadState* par_scan_state,
4719 RefToScanQueueSet* queues,
4720 ParallelTaskTerminator* terminator)
4721 : _g1h(g1h), _par_scan_state(par_scan_state),
4722 _queues(queues), _terminator(terminator) {}
4723
4724 void do_void();
4725
4726 private:
4727 inline bool offer_termination();
4728 };
4729
4730 bool G1ParEvacuateFollowersClosure::offer_termination() {
4731 G1ParScanThreadState* const pss = par_scan_state();
4732 pss->start_term_time();
4733 const bool res = terminator()->offer_termination();
4734 pss->end_term_time();
4735 return res;
4736 }
4737
4738 void G1ParEvacuateFollowersClosure::do_void() {
4739 StarTask stolen_task;
4740 G1ParScanThreadState* const pss = par_scan_state();
4741 pss->trim_queue();
4742
4743 do {
4744 while (queues()->steal(pss->queue_num(), pss->hash_seed(), stolen_task)) {
4745 assert(pss->verify_task(stolen_task), "sanity");
4746 if (stolen_task.is_narrow()) {
4747 pss->deal_with_reference((narrowOop*) stolen_task);
4748 } else {
4749 pss->deal_with_reference((oop*) stolen_task);
4750 }
4751
4752 // We've just processed a reference and we might have made
4753 // available new entries on the queues. So we have to make sure
4754 // we drain the queues as necessary.
4755 pss->trim_queue();
4756 }
4757 } while (!offer_termination());
4758
4759 pss->retire_alloc_buffers();
4760 }
4761
4762 class G1KlassScanClosure : public KlassClosure {
4763 G1ParCopyHelper* _closure;
4764 bool _process_only_dirty;
4765 int _count;
4766 public:
4767 G1KlassScanClosure(G1ParCopyHelper* closure, bool process_only_dirty)
4768 : _process_only_dirty(process_only_dirty), _closure(closure), _count(0) {}
4769 void do_klass(Klass* klass) {
4770 // If the klass has not been dirtied we know that there's
4771 // no references into the young gen and we can skip it.
4772 if (!_process_only_dirty || klass->has_modified_oops()) {
4773 // Clean the klass since we're going to scavenge all the metadata.
4774 klass->clear_modified_oops();
4775
4776 // Tell the closure that this klass is the Klass to scavenge
4777 // and is the one to dirty if oops are left pointing into the young gen.
4778 _closure->set_scanned_klass(klass);
4779
4780 klass->oops_do(_closure);
4781
4782 _closure->set_scanned_klass(NULL);
4783 }
4784 _count++;
4785 }
4786 };
4787
4788 class G1ParTask : public AbstractGangTask {
4789 protected:
4790 G1CollectedHeap* _g1h;
4791 RefToScanQueueSet *_queues;
4792 ParallelTaskTerminator _terminator;
4793 uint _n_workers;
4794
4795 Mutex _stats_lock;
4796 Mutex* stats_lock() { return &_stats_lock; }
4797
4798 size_t getNCards() {
4799 return (_g1h->capacity() + G1BlockOffsetSharedArray::N_bytes - 1)
4800 / G1BlockOffsetSharedArray::N_bytes;
4801 }
4802
4803 public:
4804 G1ParTask(G1CollectedHeap* g1h,
4805 RefToScanQueueSet *task_queues)
4806 : AbstractGangTask("G1 collection"),
4807 _g1h(g1h),
4808 _queues(task_queues),
4809 _terminator(0, _queues),
4810 _stats_lock(Mutex::leaf, "parallel G1 stats lock", true)
4811 {}
4812
4813 RefToScanQueueSet* queues() { return _queues; }
4814
4815 RefToScanQueue *work_queue(int i) {
4816 return queues()->queue(i);
4817 }
4818
4819 ParallelTaskTerminator* terminator() { return &_terminator; }
4820
4821 virtual void set_for_termination(int active_workers) {
4822 // This task calls set_n_termination() in par_non_clean_card_iterate_work()
4823 // in the young space (_par_seq_tasks) in the G1 heap
4824 // for SequentialSubTasksDone.
4825 // This task also uses SubTasksDone in SharedHeap and G1CollectedHeap
4826 // both of which need setting by set_n_termination().
4827 _g1h->SharedHeap::set_n_termination(active_workers);
4828 _g1h->set_n_termination(active_workers);
4829 terminator()->reset_for_reuse(active_workers);
4830 _n_workers = active_workers;
4831 }
4832
4833 void work(uint worker_id) {
4834 if (worker_id >= _n_workers) return; // no work needed this round
4835
4836 double start_time_ms = os::elapsedTime() * 1000.0;
4837 _g1h->g1_policy()->phase_times()->record_gc_worker_start_time(worker_id, start_time_ms);
4838
4839 {
4840 ResourceMark rm;
4841 HandleMark hm;
4842
4843 ReferenceProcessor* rp = _g1h->ref_processor_stw();
4844
4845 G1ParScanThreadState pss(_g1h, worker_id);
4846 G1ParScanHeapEvacClosure scan_evac_cl(_g1h, &pss, rp);
4847 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, rp);
4848 G1ParScanPartialArrayClosure partial_scan_cl(_g1h, &pss, rp);
4849
4850 pss.set_evac_closure(&scan_evac_cl);
4851 pss.set_evac_failure_closure(&evac_failure_cl);
4852 pss.set_partial_scan_closure(&partial_scan_cl);
4853
4854 G1ParScanExtRootClosure only_scan_root_cl(_g1h, &pss, rp);
4855 G1ParScanMetadataClosure only_scan_metadata_cl(_g1h, &pss, rp);
4856
4857 G1ParScanAndMarkExtRootClosure scan_mark_root_cl(_g1h, &pss, rp);
4858 G1ParScanAndMarkMetadataClosure scan_mark_metadata_cl(_g1h, &pss, rp);
4859
4860 bool only_young = _g1h->g1_policy()->gcs_are_young();
4861 G1KlassScanClosure scan_mark_klasses_cl_s(&scan_mark_metadata_cl, false);
4862 G1KlassScanClosure only_scan_klasses_cl_s(&only_scan_metadata_cl, only_young);
4863
4864 OopClosure* scan_root_cl = &only_scan_root_cl;
4865 G1KlassScanClosure* scan_klasses_cl = &only_scan_klasses_cl_s;
4866
4867 if (_g1h->g1_policy()->during_initial_mark_pause()) {
4868 // We also need to mark copied objects.
4869 scan_root_cl = &scan_mark_root_cl;
4870 scan_klasses_cl = &scan_mark_klasses_cl_s;
4871 }
4872
4873 G1ParPushHeapRSClosure push_heap_rs_cl(_g1h, &pss);
4874
4875 int so = SharedHeap::SO_AllClasses | SharedHeap::SO_Strings | SharedHeap::SO_CodeCache;
4876
4877 pss.start_strong_roots();
4878 _g1h->g1_process_strong_roots(/* is scavenging */ true,
4879 SharedHeap::ScanningOption(so),
4880 scan_root_cl,
4881 &push_heap_rs_cl,
4882 scan_klasses_cl,
4883 worker_id);
4884 pss.end_strong_roots();
4885
4886 {
4887 double start = os::elapsedTime();
4888 G1ParEvacuateFollowersClosure evac(_g1h, &pss, _queues, &_terminator);
4889 evac.do_void();
4890 double elapsed_ms = (os::elapsedTime()-start)*1000.0;
4891 double term_ms = pss.term_time()*1000.0;
4892 _g1h->g1_policy()->phase_times()->add_obj_copy_time(worker_id, elapsed_ms-term_ms);
4893 _g1h->g1_policy()->phase_times()->record_termination(worker_id, term_ms, pss.term_attempts());
4894 }
4895 _g1h->g1_policy()->record_thread_age_table(pss.age_table());
4896 _g1h->update_surviving_young_words(pss.surviving_young_words()+1);
4897
4898 if (ParallelGCVerbose) {
4899 MutexLocker x(stats_lock());
4900 pss.print_termination_stats(worker_id);
4901 }
4902
4903 assert(pss.refs()->is_empty(), "should be empty");
4904
4905 // Close the inner scope so that the ResourceMark and HandleMark
4906 // destructors are executed here and are included as part of the
4907 // "GC Worker Time".
4908 }
4909
4910 double end_time_ms = os::elapsedTime() * 1000.0;
4911 _g1h->g1_policy()->phase_times()->record_gc_worker_end_time(worker_id, end_time_ms);
4912 }
4913 };
4914
4915 // *** Common G1 Evacuation Stuff
4916
4917 // Closures that support the filtering of CodeBlobs scanned during
4918 // external root scanning.
4919
4920 // Closure applied to reference fields in code blobs (specifically nmethods)
4921 // to determine whether an nmethod contains references that point into
4922 // the collection set. Used as a predicate when walking code roots so
4923 // that only nmethods that point into the collection set are added to the
4924 // 'marked' list.
4925
4926 class G1FilteredCodeBlobToOopClosure : public CodeBlobToOopClosure {
4927
4928 class G1PointsIntoCSOopClosure : public OopClosure {
4929 G1CollectedHeap* _g1;
4930 bool _points_into_cs;
4931 public:
4932 G1PointsIntoCSOopClosure(G1CollectedHeap* g1) :
4933 _g1(g1), _points_into_cs(false) { }
4934
4935 bool points_into_cs() const { return _points_into_cs; }
4936
4937 template <class T>
4938 void do_oop_nv(T* p) {
4939 if (!_points_into_cs) {
4940 T heap_oop = oopDesc::load_heap_oop(p);
4941 if (!oopDesc::is_null(heap_oop) &&
4942 _g1->in_cset_fast_test(oopDesc::decode_heap_oop_not_null(heap_oop))) {
4943 _points_into_cs = true;
4944 }
4945 }
4946 }
4947
4948 virtual void do_oop(oop* p) { do_oop_nv(p); }
4949 virtual void do_oop(narrowOop* p) { do_oop_nv(p); }
4950 };
4951
4952 G1CollectedHeap* _g1;
4953
4954 public:
4955 G1FilteredCodeBlobToOopClosure(G1CollectedHeap* g1, OopClosure* cl) :
4956 CodeBlobToOopClosure(cl, true), _g1(g1) { }
4957
4958 virtual void do_code_blob(CodeBlob* cb) {
4959 nmethod* nm = cb->as_nmethod_or_null();
4960 if (nm != NULL && !(nm->test_oops_do_mark())) {
4961 G1PointsIntoCSOopClosure predicate_cl(_g1);
4962 nm->oops_do(&predicate_cl);
4963
4964 if (predicate_cl.points_into_cs()) {
4965 // At least one of the reference fields or the oop relocations
4966 // in the nmethod points into the collection set. We have to
4967 // 'mark' this nmethod.
4968 // Note: Revisit the following if CodeBlobToOopClosure::do_code_blob()
4969 // or MarkingCodeBlobClosure::do_code_blob() change.
4970 if (!nm->test_set_oops_do_mark()) {
4971 do_newly_marked_nmethod(nm);
4972 }
4973 }
4974 }
4975 }
4976 };
4977
4978 // This method is run in a GC worker.
4979
4980 void
4981 G1CollectedHeap::
4982 g1_process_strong_roots(bool is_scavenging,
4983 ScanningOption so,
4984 OopClosure* scan_non_heap_roots,
4985 OopsInHeapRegionClosure* scan_rs,
4986 G1KlassScanClosure* scan_klasses,
4987 int worker_i) {
4988
4989 // First scan the strong roots
4990 double ext_roots_start = os::elapsedTime();
4991 double closure_app_time_sec = 0.0;
4992
4993 BufferingOopClosure buf_scan_non_heap_roots(scan_non_heap_roots);
4994
4995 // Walk the code cache w/o buffering, because StarTask cannot handle
4996 // unaligned oop locations.
4997 G1FilteredCodeBlobToOopClosure eager_scan_code_roots(this, scan_non_heap_roots);
4998
4999 process_strong_roots(false, // no scoping; this is parallel code
5000 is_scavenging, so,
5001 &buf_scan_non_heap_roots,
5002 &eager_scan_code_roots,
5003 scan_klasses
5004 );
5005
5006 // Now the CM ref_processor roots.
5007 if (!_process_strong_tasks->is_task_claimed(G1H_PS_refProcessor_oops_do)) {
5008 // We need to treat the discovered reference lists of the
5009 // concurrent mark ref processor as roots and keep entries
5010 // (which are added by the marking threads) on them live
5011 // until they can be processed at the end of marking.
5012 ref_processor_cm()->weak_oops_do(&buf_scan_non_heap_roots);
5013 }
5014
5015 // Finish up any enqueued closure apps (attributed as object copy time).
5016 buf_scan_non_heap_roots.done();
5017
5018 double obj_copy_time_sec = buf_scan_non_heap_roots.closure_app_seconds();
5019
5020 g1_policy()->phase_times()->record_obj_copy_time(worker_i, obj_copy_time_sec * 1000.0);
5021
5022 double ext_root_time_ms =
5023 ((os::elapsedTime() - ext_roots_start) - obj_copy_time_sec) * 1000.0;
5024
5025 g1_policy()->phase_times()->record_ext_root_scan_time(worker_i, ext_root_time_ms);
5026
5027 // During conc marking we have to filter the per-thread SATB buffers
5028 // to make sure we remove any oops into the CSet (which will show up
5029 // as implicitly live).
5030 double satb_filtering_ms = 0.0;
5031 if (!_process_strong_tasks->is_task_claimed(G1H_PS_filter_satb_buffers)) {
5032 if (mark_in_progress()) {
5033 double satb_filter_start = os::elapsedTime();
5034
5035 JavaThread::satb_mark_queue_set().filter_thread_buffers();
5036
5037 satb_filtering_ms = (os::elapsedTime() - satb_filter_start) * 1000.0;
5038 }
5039 }
5040 g1_policy()->phase_times()->record_satb_filtering_time(worker_i, satb_filtering_ms);
5041
5042 // Now scan the complement of the collection set.
5043 if (scan_rs != NULL) {
5044 g1_rem_set()->oops_into_collection_set_do(scan_rs, worker_i);
5045 }
5046 _process_strong_tasks->all_tasks_completed();
5047 }
5048
5049 void
5050 G1CollectedHeap::g1_process_weak_roots(OopClosure* root_closure,
5051 OopClosure* non_root_closure) {
5052 CodeBlobToOopClosure roots_in_blobs(root_closure, /*do_marking=*/ false);
5053 SharedHeap::process_weak_roots(root_closure, &roots_in_blobs, non_root_closure);
5054 }
5055
5056 // Weak Reference Processing support
5057
5058 // An always "is_alive" closure that is used to preserve referents.
5059 // If the object is non-null then it's alive. Used in the preservation
5060 // of referent objects that are pointed to by reference objects
5061 // discovered by the CM ref processor.
5062 class G1AlwaysAliveClosure: public BoolObjectClosure {
5063 G1CollectedHeap* _g1;
5064 public:
5065 G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
5066 void do_object(oop p) { assert(false, "Do not call."); }
5067 bool do_object_b(oop p) {
5068 if (p != NULL) {
5069 return true;
5070 }
5071 return false;
5072 }
5073 };
5074
5075 bool G1STWIsAliveClosure::do_object_b(oop p) {
5076 // An object is reachable if it is outside the collection set,
5077 // or is inside and copied.
5078 return !_g1->obj_in_cs(p) || p->is_forwarded();
5079 }
5080
5081 // Non Copying Keep Alive closure
5082 class G1KeepAliveClosure: public OopClosure {
5083 G1CollectedHeap* _g1;
5084 public:
5085 G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
5086 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
5087 void do_oop( oop* p) {
5088 oop obj = *p;
5089
5090 if (_g1->obj_in_cs(obj)) {
5091 assert( obj->is_forwarded(), "invariant" );
5092 *p = obj->forwardee();
5093 }
5094 }
5095 };
5096
5097 // Copying Keep Alive closure - can be called from both
5098 // serial and parallel code as long as different worker
5099 // threads utilize different G1ParScanThreadState instances
5100 // and different queues.
5101
5102 class G1CopyingKeepAliveClosure: public OopClosure {
5103 G1CollectedHeap* _g1h;
5104 OopClosure* _copy_non_heap_obj_cl;
5105 OopsInHeapRegionClosure* _copy_metadata_obj_cl;
5106 G1ParScanThreadState* _par_scan_state;
5107
5108 public:
5109 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
5110 OopClosure* non_heap_obj_cl,
5111 OopsInHeapRegionClosure* metadata_obj_cl,
5112 G1ParScanThreadState* pss):
5113 _g1h(g1h),
5114 _copy_non_heap_obj_cl(non_heap_obj_cl),
5115 _copy_metadata_obj_cl(metadata_obj_cl),
5116 _par_scan_state(pss)
5117 {}
5118
5119 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
5120 virtual void do_oop( oop* p) { do_oop_work(p); }
5121
5122 template <class T> void do_oop_work(T* p) {
5123 oop obj = oopDesc::load_decode_heap_oop(p);
5124
5125 if (_g1h->obj_in_cs(obj)) {
5126 // If the referent object has been forwarded (either copied
5127 // to a new location or to itself in the event of an
5128 // evacuation failure) then we need to update the reference
5129 // field and, if both reference and referent are in the G1
5130 // heap, update the RSet for the referent.
5131 //
5132 // If the referent has not been forwarded then we have to keep
5133 // it alive by policy. Therefore we have copy the referent.
5134 //
5135 // If the reference field is in the G1 heap then we can push
5136 // on the PSS queue. When the queue is drained (after each
5137 // phase of reference processing) the object and it's followers
5138 // will be copied, the reference field set to point to the
5139 // new location, and the RSet updated. Otherwise we need to
5140 // use the the non-heap or metadata closures directly to copy
5141 // the refernt object and update the pointer, while avoiding
5142 // updating the RSet.
5143
5144 if (_g1h->is_in_g1_reserved(p)) {
5145 _par_scan_state->push_on_queue(p);
5146 } else {
5147 assert(!ClassLoaderDataGraph::contains((address)p),
5148 err_msg("Otherwise need to call _copy_metadata_obj_cl->do_oop(p) "
5149 PTR_FORMAT, p));
5150 _copy_non_heap_obj_cl->do_oop(p);
5151 }
5152 }
5153 }
5154 };
5155
5156 // Serial drain queue closure. Called as the 'complete_gc'
5157 // closure for each discovered list in some of the
5158 // reference processing phases.
5159
5160 class G1STWDrainQueueClosure: public VoidClosure {
5161 protected:
5162 G1CollectedHeap* _g1h;
5163 G1ParScanThreadState* _par_scan_state;
5164
5165 G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
5166
5167 public:
5168 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
5169 _g1h(g1h),
5170 _par_scan_state(pss)
5171 { }
5172
5173 void do_void() {
5174 G1ParScanThreadState* const pss = par_scan_state();
5175 pss->trim_queue();
5176 }
5177 };
5178
5179 // Parallel Reference Processing closures
5180
5181 // Implementation of AbstractRefProcTaskExecutor for parallel reference
5182 // processing during G1 evacuation pauses.
5183
5184 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
5185 private:
5186 G1CollectedHeap* _g1h;
5187 RefToScanQueueSet* _queues;
5188 FlexibleWorkGang* _workers;
5189 int _active_workers;
5190
5191 public:
5192 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
5193 FlexibleWorkGang* workers,
5194 RefToScanQueueSet *task_queues,
5195 int n_workers) :
5196 _g1h(g1h),
5197 _queues(task_queues),
5198 _workers(workers),
5199 _active_workers(n_workers)
5200 {
5201 assert(n_workers > 0, "shouldn't call this otherwise");
5202 }
5203
5204 // Executes the given task using concurrent marking worker threads.
5205 virtual void execute(ProcessTask& task);
5206 virtual void execute(EnqueueTask& task);
5207 };
5208
5209 // Gang task for possibly parallel reference processing
5210
5211 class G1STWRefProcTaskProxy: public AbstractGangTask {
5212 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
5213 ProcessTask& _proc_task;
5214 G1CollectedHeap* _g1h;
5215 RefToScanQueueSet *_task_queues;
5216 ParallelTaskTerminator* _terminator;
5217
5218 public:
5219 G1STWRefProcTaskProxy(ProcessTask& proc_task,
5220 G1CollectedHeap* g1h,
5221 RefToScanQueueSet *task_queues,
5222 ParallelTaskTerminator* terminator) :
5223 AbstractGangTask("Process reference objects in parallel"),
5224 _proc_task(proc_task),
5225 _g1h(g1h),
5226 _task_queues(task_queues),
5227 _terminator(terminator)
5228 {}
5229
5230 virtual void work(uint worker_id) {
5231 // The reference processing task executed by a single worker.
5232 ResourceMark rm;
5233 HandleMark hm;
5234
5235 G1STWIsAliveClosure is_alive(_g1h);
5236
5237 G1ParScanThreadState pss(_g1h, worker_id);
5238
5239 G1ParScanHeapEvacClosure scan_evac_cl(_g1h, &pss, NULL);
5240 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5241 G1ParScanPartialArrayClosure partial_scan_cl(_g1h, &pss, NULL);
5242
5243 pss.set_evac_closure(&scan_evac_cl);
5244 pss.set_evac_failure_closure(&evac_failure_cl);
5245 pss.set_partial_scan_closure(&partial_scan_cl);
5246
5247 G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL);
5248 G1ParScanMetadataClosure only_copy_metadata_cl(_g1h, &pss, NULL);
5249
5250 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5251 G1ParScanAndMarkMetadataClosure copy_mark_metadata_cl(_g1h, &pss, NULL);
5252
5253 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5254 OopsInHeapRegionClosure* copy_metadata_cl = &only_copy_metadata_cl;
5255
5256 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5257 // We also need to mark copied objects.
5258 copy_non_heap_cl = ©_mark_non_heap_cl;
5259 copy_metadata_cl = ©_mark_metadata_cl;
5260 }
5261
5262 // Keep alive closure.
5263 G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, copy_metadata_cl, &pss);
5264
5265 // Complete GC closure
5266 G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _task_queues, _terminator);
5267
5268 // Call the reference processing task's work routine.
5269 _proc_task.work(worker_id, is_alive, keep_alive, drain_queue);
5270
5271 // Note we cannot assert that the refs array is empty here as not all
5272 // of the processing tasks (specifically phase2 - pp2_work) execute
5273 // the complete_gc closure (which ordinarily would drain the queue) so
5274 // the queue may not be empty.
5275 }
5276 };
5277
5278 // Driver routine for parallel reference processing.
5279 // Creates an instance of the ref processing gang
5280 // task and has the worker threads execute it.
5281 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) {
5282 assert(_workers != NULL, "Need parallel worker threads.");
5283
5284 ParallelTaskTerminator terminator(_active_workers, _queues);
5285 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _queues, &terminator);
5286
5287 _g1h->set_par_threads(_active_workers);
5288 _workers->run_task(&proc_task_proxy);
5289 _g1h->set_par_threads(0);
5290 }
5291
5292 // Gang task for parallel reference enqueueing.
5293
5294 class G1STWRefEnqueueTaskProxy: public AbstractGangTask {
5295 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
5296 EnqueueTask& _enq_task;
5297
5298 public:
5299 G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) :
5300 AbstractGangTask("Enqueue reference objects in parallel"),
5301 _enq_task(enq_task)
5302 { }
5303
5304 virtual void work(uint worker_id) {
5305 _enq_task.work(worker_id);
5306 }
5307 };
5308
5309 // Driver routine for parallel reference enqueing.
5310 // Creates an instance of the ref enqueueing gang
5311 // task and has the worker threads execute it.
5312
5313 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
5314 assert(_workers != NULL, "Need parallel worker threads.");
5315
5316 G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task);
5317
5318 _g1h->set_par_threads(_active_workers);
5319 _workers->run_task(&enq_task_proxy);
5320 _g1h->set_par_threads(0);
5321 }
5322
5323 // End of weak reference support closures
5324
5325 // Abstract task used to preserve (i.e. copy) any referent objects
5326 // that are in the collection set and are pointed to by reference
5327 // objects discovered by the CM ref processor.
5328
5329 class G1ParPreserveCMReferentsTask: public AbstractGangTask {
5330 protected:
5331 G1CollectedHeap* _g1h;
5332 RefToScanQueueSet *_queues;
5333 ParallelTaskTerminator _terminator;
5334 uint _n_workers;
5335
5336 public:
5337 G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h,int workers, RefToScanQueueSet *task_queues) :
5338 AbstractGangTask("ParPreserveCMReferents"),
5339 _g1h(g1h),
5340 _queues(task_queues),
5341 _terminator(workers, _queues),
5342 _n_workers(workers)
5343 { }
5344
5345 void work(uint worker_id) {
5346 ResourceMark rm;
5347 HandleMark hm;
5348
5349 G1ParScanThreadState pss(_g1h, worker_id);
5350 G1ParScanHeapEvacClosure scan_evac_cl(_g1h, &pss, NULL);
5351 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5352 G1ParScanPartialArrayClosure partial_scan_cl(_g1h, &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(), "both queue and overflow should be empty");
5359
5360
5361 G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL);
5362 G1ParScanMetadataClosure only_copy_metadata_cl(_g1h, &pss, NULL);
5363
5364 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5365 G1ParScanAndMarkMetadataClosure copy_mark_metadata_cl(_g1h, &pss, NULL);
5366
5367 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5368 OopsInHeapRegionClosure* copy_metadata_cl = &only_copy_metadata_cl;
5369
5370 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5371 // We also need to mark copied objects.
5372 copy_non_heap_cl = ©_mark_non_heap_cl;
5373 copy_metadata_cl = ©_mark_metadata_cl;
5374 }
5375
5376 // Is alive closure
5377 G1AlwaysAliveClosure always_alive(_g1h);
5378
5379 // Copying keep alive closure. Applied to referent objects that need
5380 // to be copied.
5381 G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, copy_metadata_cl, &pss);
5382
5383 ReferenceProcessor* rp = _g1h->ref_processor_cm();
5384
5385 uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q();
5386 uint stride = MIN2(MAX2(_n_workers, 1U), limit);
5387
5388 // limit is set using max_num_q() - which was set using ParallelGCThreads.
5389 // So this must be true - but assert just in case someone decides to
5390 // change the worker ids.
5391 assert(0 <= worker_id && worker_id < limit, "sanity");
5392 assert(!rp->discovery_is_atomic(), "check this code");
5393
5394 // Select discovered lists [i, i+stride, i+2*stride,...,limit)
5395 for (uint idx = worker_id; idx < limit; idx += stride) {
5396 DiscoveredList& ref_list = rp->discovered_refs()[idx];
5397
5398 DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive);
5399 while (iter.has_next()) {
5400 // Since discovery is not atomic for the CM ref processor, we
5401 // can see some null referent objects.
5402 iter.load_ptrs(DEBUG_ONLY(true));
5403 oop ref = iter.obj();
5404
5405 // This will filter nulls.
5406 if (iter.is_referent_alive()) {
5407 iter.make_referent_alive();
5408 }
5409 iter.move_to_next();
5410 }
5411 }
5412
5413 // Drain the queue - which may cause stealing
5414 G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _queues, &_terminator);
5415 drain_queue.do_void();
5416 // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure
5417 assert(pss.refs()->is_empty(), "should be");
5418 }
5419 };
5420
5421 // Weak Reference processing during an evacuation pause (part 1).
5422 void G1CollectedHeap::process_discovered_references(uint no_of_gc_workers) {
5423 double ref_proc_start = os::elapsedTime();
5424
5425 ReferenceProcessor* rp = _ref_processor_stw;
5426 assert(rp->discovery_enabled(), "should have been enabled");
5427
5428 // Any reference objects, in the collection set, that were 'discovered'
5429 // by the CM ref processor should have already been copied (either by
5430 // applying the external root copy closure to the discovered lists, or
5431 // by following an RSet entry).
5432 //
5433 // But some of the referents, that are in the collection set, that these
5434 // reference objects point to may not have been copied: the STW ref
5435 // processor would have seen that the reference object had already
5436 // been 'discovered' and would have skipped discovering the reference,
5437 // but would not have treated the reference object as a regular oop.
5438 // As a reult the copy closure would not have been applied to the
5439 // referent object.
5440 //
5441 // We need to explicitly copy these referent objects - the references
5442 // will be processed at the end of remarking.
5443 //
5444 // We also need to do this copying before we process the reference
5445 // objects discovered by the STW ref processor in case one of these
5446 // referents points to another object which is also referenced by an
5447 // object discovered by the STW ref processor.
5448
5449 assert(!G1CollectedHeap::use_parallel_gc_threads() ||
5450 no_of_gc_workers == workers()->active_workers(),
5451 "Need to reset active GC workers");
5452
5453 set_par_threads(no_of_gc_workers);
5454 G1ParPreserveCMReferentsTask keep_cm_referents(this,
5455 no_of_gc_workers,
5456 _task_queues);
5457
5458 if (G1CollectedHeap::use_parallel_gc_threads()) {
5459 workers()->run_task(&keep_cm_referents);
5460 } else {
5461 keep_cm_referents.work(0);
5462 }
5463
5464 set_par_threads(0);
5465
5466 // Closure to test whether a referent is alive.
5467 G1STWIsAliveClosure is_alive(this);
5468
5469 // Even when parallel reference processing is enabled, the processing
5470 // of JNI refs is serial and performed serially by the current thread
5471 // rather than by a worker. The following PSS will be used for processing
5472 // JNI refs.
5473
5474 // Use only a single queue for this PSS.
5475 G1ParScanThreadState pss(this, 0);
5476
5477 // We do not embed a reference processor in the copying/scanning
5478 // closures while we're actually processing the discovered
5479 // reference objects.
5480 G1ParScanHeapEvacClosure scan_evac_cl(this, &pss, NULL);
5481 G1ParScanHeapEvacFailureClosure evac_failure_cl(this, &pss, NULL);
5482 G1ParScanPartialArrayClosure partial_scan_cl(this, &pss, NULL);
5483
5484 pss.set_evac_closure(&scan_evac_cl);
5485 pss.set_evac_failure_closure(&evac_failure_cl);
5486 pss.set_partial_scan_closure(&partial_scan_cl);
5487
5488 assert(pss.refs()->is_empty(), "pre-condition");
5489
5490 G1ParScanExtRootClosure only_copy_non_heap_cl(this, &pss, NULL);
5491 G1ParScanMetadataClosure only_copy_metadata_cl(this, &pss, NULL);
5492
5493 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(this, &pss, NULL);
5494 G1ParScanAndMarkMetadataClosure copy_mark_metadata_cl(this, &pss, NULL);
5495
5496 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5497 OopsInHeapRegionClosure* copy_metadata_cl = &only_copy_metadata_cl;
5498
5499 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5500 // We also need to mark copied objects.
5501 copy_non_heap_cl = ©_mark_non_heap_cl;
5502 copy_metadata_cl = ©_mark_metadata_cl;
5503 }
5504
5505 // Keep alive closure.
5506 G1CopyingKeepAliveClosure keep_alive(this, copy_non_heap_cl, copy_metadata_cl, &pss);
5507
5508 // Serial Complete GC closure
5509 G1STWDrainQueueClosure drain_queue(this, &pss);
5510
5511 // Setup the soft refs policy...
5512 rp->setup_policy(false);
5513
5514 if (!rp->processing_is_mt()) {
5515 // Serial reference processing...
5516 rp->process_discovered_references(&is_alive,
5517 &keep_alive,
5518 &drain_queue,
5519 NULL);
5520 } else {
5521 // Parallel reference processing
5522 assert(rp->num_q() == no_of_gc_workers, "sanity");
5523 assert(no_of_gc_workers <= rp->max_num_q(), "sanity");
5524
5525 G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers);
5526 rp->process_discovered_references(&is_alive, &keep_alive, &drain_queue, &par_task_executor);
5527 }
5528
5529 // We have completed copying any necessary live referent objects
5530 // (that were not copied during the actual pause) so we can
5531 // retire any active alloc buffers
5532 pss.retire_alloc_buffers();
5533 assert(pss.refs()->is_empty(), "both queue and overflow should be empty");
5534
5535 double ref_proc_time = os::elapsedTime() - ref_proc_start;
5536 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
5537 }
5538
5539 // Weak Reference processing during an evacuation pause (part 2).
5540 void G1CollectedHeap::enqueue_discovered_references(uint no_of_gc_workers) {
5541 double ref_enq_start = os::elapsedTime();
5542
5543 ReferenceProcessor* rp = _ref_processor_stw;
5544 assert(!rp->discovery_enabled(), "should have been disabled as part of processing");
5545
5546 // Now enqueue any remaining on the discovered lists on to
5547 // the pending list.
5548 if (!rp->processing_is_mt()) {
5549 // Serial reference processing...
5550 rp->enqueue_discovered_references();
5551 } else {
5552 // Parallel reference enqueuing
5553
5554 assert(no_of_gc_workers == workers()->active_workers(),
5555 "Need to reset active workers");
5556 assert(rp->num_q() == no_of_gc_workers, "sanity");
5557 assert(no_of_gc_workers <= rp->max_num_q(), "sanity");
5558
5559 G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers);
5560 rp->enqueue_discovered_references(&par_task_executor);
5561 }
5562
5563 rp->verify_no_references_recorded();
5564 assert(!rp->discovery_enabled(), "should have been disabled");
5565
5566 // FIXME
5567 // CM's reference processing also cleans up the string and symbol tables.
5568 // Should we do that here also? We could, but it is a serial operation
5569 // and could signicantly increase the pause time.
5570
5571 double ref_enq_time = os::elapsedTime() - ref_enq_start;
5572 g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0);
5573 }
5574
5575 void G1CollectedHeap::evacuate_collection_set() {
5576 _expand_heap_after_alloc_failure = true;
5577 set_evacuation_failed(false);
5578
5579 // Should G1EvacuationFailureALot be in effect for this GC?
5580 NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();)
5581
5582 g1_rem_set()->prepare_for_oops_into_collection_set_do();
5583 concurrent_g1_refine()->set_use_cache(false);
5584 concurrent_g1_refine()->clear_hot_cache_claimed_index();
5585
5586 uint n_workers;
5587 if (G1CollectedHeap::use_parallel_gc_threads()) {
5588 n_workers =
5589 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
5590 workers()->active_workers(),
5591 Threads::number_of_non_daemon_threads());
5592 assert(UseDynamicNumberOfGCThreads ||
5593 n_workers == workers()->total_workers(),
5594 "If not dynamic should be using all the workers");
5595 workers()->set_active_workers(n_workers);
5596 set_par_threads(n_workers);
5597 } else {
5598 assert(n_par_threads() == 0,
5599 "Should be the original non-parallel value");
5600 n_workers = 1;
5601 }
5602
5603 G1ParTask g1_par_task(this, _task_queues);
5604
5605 init_for_evac_failure(NULL);
5606
5607 rem_set()->prepare_for_younger_refs_iterate(true);
5608
5609 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
5610 double start_par_time_sec = os::elapsedTime();
5611 double end_par_time_sec;
5612
5613 {
5614 StrongRootsScope srs(this);
5615
5616 if (G1CollectedHeap::use_parallel_gc_threads()) {
5617 // The individual threads will set their evac-failure closures.
5618 if (ParallelGCVerbose) G1ParScanThreadState::print_termination_stats_hdr();
5619 // These tasks use ShareHeap::_process_strong_tasks
5620 assert(UseDynamicNumberOfGCThreads ||
5621 workers()->active_workers() == workers()->total_workers(),
5622 "If not dynamic should be using all the workers");
5623 workers()->run_task(&g1_par_task);
5624 } else {
5625 g1_par_task.set_for_termination(n_workers);
5626 g1_par_task.work(0);
5627 }
5628 end_par_time_sec = os::elapsedTime();
5629
5630 // Closing the inner scope will execute the destructor
5631 // for the StrongRootsScope object. We record the current
5632 // elapsed time before closing the scope so that time
5633 // taken for the SRS destructor is NOT included in the
5634 // reported parallel time.
5635 }
5636
5637 double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0;
5638 g1_policy()->phase_times()->record_par_time(par_time_ms);
5639
5640 double code_root_fixup_time_ms =
5641 (os::elapsedTime() - end_par_time_sec) * 1000.0;
5642 g1_policy()->phase_times()->record_code_root_fixup_time(code_root_fixup_time_ms);
5643
5644 set_par_threads(0);
5645
5646 // Process any discovered reference objects - we have
5647 // to do this _before_ we retire the GC alloc regions
5648 // as we may have to copy some 'reachable' referent
5649 // objects (and their reachable sub-graphs) that were
5650 // not copied during the pause.
5651 process_discovered_references(n_workers);
5652
5653 // Weak root processing.
5654 // Note: when JSR 292 is enabled and code blobs can contain
5655 // non-perm oops then we will need to process the code blobs
5656 // here too.
5657 {
5658 G1STWIsAliveClosure is_alive(this);
5659 G1KeepAliveClosure keep_alive(this);
5660 JNIHandles::weak_oops_do(&is_alive, &keep_alive);
5661 }
5662
5663 release_gc_alloc_regions(n_workers);
5664 g1_rem_set()->cleanup_after_oops_into_collection_set_do();
5665
5666 concurrent_g1_refine()->clear_hot_cache();
5667 concurrent_g1_refine()->set_use_cache(true);
5668
5669 finalize_for_evac_failure();
5670
5671 if (evacuation_failed()) {
5672 remove_self_forwarding_pointers();
5673
5674 // Reset the G1EvacuationFailureALot counters and flags
5675 // Note: the values are reset only when an actual
5676 // evacuation failure occurs.
5677 NOT_PRODUCT(reset_evacuation_should_fail();)
5678 }
5679
5680 // Enqueue any remaining references remaining on the STW
5681 // reference processor's discovered lists. We need to do
5682 // this after the card table is cleaned (and verified) as
5683 // the act of enqueuing entries on to the pending list
5684 // will log these updates (and dirty their associated
5685 // cards). We need these updates logged to update any
5686 // RSets.
5687 enqueue_discovered_references(n_workers);
5688
5689 if (G1DeferredRSUpdate) {
5690 RedirtyLoggedCardTableEntryFastClosure redirty;
5691 dirty_card_queue_set().set_closure(&redirty);
5692 dirty_card_queue_set().apply_closure_to_all_completed_buffers();
5693
5694 DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set();
5695 dcq.merge_bufferlists(&dirty_card_queue_set());
5696 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
5697 }
5698 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
5699 }
5700
5701 void G1CollectedHeap::free_region_if_empty(HeapRegion* hr,
5702 size_t* pre_used,
5703 FreeRegionList* free_list,
5704 OldRegionSet* old_proxy_set,
5705 HumongousRegionSet* humongous_proxy_set,
5706 HRRSCleanupTask* hrrs_cleanup_task,
5707 bool par) {
5708 if (hr->used() > 0 && hr->max_live_bytes() == 0 && !hr->is_young()) {
5709 if (hr->isHumongous()) {
5710 assert(hr->startsHumongous(), "we should only see starts humongous");
5711 free_humongous_region(hr, pre_used, free_list, humongous_proxy_set, par);
5712 } else {
5713 _old_set.remove_with_proxy(hr, old_proxy_set);
5714 free_region(hr, pre_used, free_list, par);
5715 }
5716 } else {
5717 hr->rem_set()->do_cleanup_work(hrrs_cleanup_task);
5718 }
5719 }
5720
5721 void G1CollectedHeap::free_region(HeapRegion* hr,
5722 size_t* pre_used,
5723 FreeRegionList* free_list,
5724 bool par) {
5725 assert(!hr->isHumongous(), "this is only for non-humongous regions");
5726 assert(!hr->is_empty(), "the region should not be empty");
5727 assert(free_list != NULL, "pre-condition");
5728
5729 *pre_used += hr->used();
5730 hr->hr_clear(par, true /* clear_space */);
5731 free_list->add_as_head(hr);
5732 }
5733
5734 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
5735 size_t* pre_used,
5736 FreeRegionList* free_list,
5737 HumongousRegionSet* humongous_proxy_set,
5738 bool par) {
5739 assert(hr->startsHumongous(), "this is only for starts humongous regions");
5740 assert(free_list != NULL, "pre-condition");
5741 assert(humongous_proxy_set != NULL, "pre-condition");
5742
5743 size_t hr_used = hr->used();
5744 size_t hr_capacity = hr->capacity();
5745 size_t hr_pre_used = 0;
5746 _humongous_set.remove_with_proxy(hr, humongous_proxy_set);
5747 // We need to read this before we make the region non-humongous,
5748 // otherwise the information will be gone.
5749 uint last_index = hr->last_hc_index();
5750 hr->set_notHumongous();
5751 free_region(hr, &hr_pre_used, free_list, par);
5752
5753 uint i = hr->hrs_index() + 1;
5754 while (i < last_index) {
5755 HeapRegion* curr_hr = region_at(i);
5756 assert(curr_hr->continuesHumongous(), "invariant");
5757 curr_hr->set_notHumongous();
5758 free_region(curr_hr, &hr_pre_used, free_list, par);
5759 i += 1;
5760 }
5761 assert(hr_pre_used == hr_used,
5762 err_msg("hr_pre_used: "SIZE_FORMAT" and hr_used: "SIZE_FORMAT" "
5763 "should be the same", hr_pre_used, hr_used));
5764 *pre_used += hr_pre_used;
5765 }
5766
5767 void G1CollectedHeap::update_sets_after_freeing_regions(size_t pre_used,
5768 FreeRegionList* free_list,
5769 OldRegionSet* old_proxy_set,
5770 HumongousRegionSet* humongous_proxy_set,
5771 bool par) {
5772 if (pre_used > 0) {
5773 Mutex* lock = (par) ? ParGCRareEvent_lock : NULL;
5774 MutexLockerEx x(lock, Mutex::_no_safepoint_check_flag);
5775 assert(_summary_bytes_used >= pre_used,
5776 err_msg("invariant: _summary_bytes_used: "SIZE_FORMAT" "
5777 "should be >= pre_used: "SIZE_FORMAT,
5778 _summary_bytes_used, pre_used));
5779 _summary_bytes_used -= pre_used;
5780 }
5781 if (free_list != NULL && !free_list->is_empty()) {
5782 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
5783 _free_list.add_as_head(free_list);
5784 }
5785 if (old_proxy_set != NULL && !old_proxy_set->is_empty()) {
5786 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
5787 _old_set.update_from_proxy(old_proxy_set);
5788 }
5789 if (humongous_proxy_set != NULL && !humongous_proxy_set->is_empty()) {
5790 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
5791 _humongous_set.update_from_proxy(humongous_proxy_set);
5792 }
5793 }
5794
5795 class G1ParCleanupCTTask : public AbstractGangTask {
5796 CardTableModRefBS* _ct_bs;
5797 G1CollectedHeap* _g1h;
5798 HeapRegion* volatile _su_head;
5799 public:
5800 G1ParCleanupCTTask(CardTableModRefBS* ct_bs,
5801 G1CollectedHeap* g1h) :
5802 AbstractGangTask("G1 Par Cleanup CT Task"),
5803 _ct_bs(ct_bs), _g1h(g1h) { }
5804
5805 void work(uint worker_id) {
5806 HeapRegion* r;
5807 while (r = _g1h->pop_dirty_cards_region()) {
5808 clear_cards(r);
5809 }
5810 }
5811
5812 void clear_cards(HeapRegion* r) {
5813 // Cards of the survivors should have already been dirtied.
5814 if (!r->is_survivor()) {
5815 _ct_bs->clear(MemRegion(r->bottom(), r->end()));
5816 }
5817 }
5818 };
5819
5820 #ifndef PRODUCT
5821 class G1VerifyCardTableCleanup: public HeapRegionClosure {
5822 G1CollectedHeap* _g1h;
5823 CardTableModRefBS* _ct_bs;
5824 public:
5825 G1VerifyCardTableCleanup(G1CollectedHeap* g1h, CardTableModRefBS* ct_bs)
5826 : _g1h(g1h), _ct_bs(ct_bs) { }
5827 virtual bool doHeapRegion(HeapRegion* r) {
5828 if (r->is_survivor()) {
5829 _g1h->verify_dirty_region(r);
5830 } else {
5831 _g1h->verify_not_dirty_region(r);
5832 }
5833 return false;
5834 }
5835 };
5836
5837 void G1CollectedHeap::verify_not_dirty_region(HeapRegion* hr) {
5838 // All of the region should be clean.
5839 CardTableModRefBS* ct_bs = (CardTableModRefBS*)barrier_set();
5840 MemRegion mr(hr->bottom(), hr->end());
5841 ct_bs->verify_not_dirty_region(mr);
5842 }
5843
5844 void G1CollectedHeap::verify_dirty_region(HeapRegion* hr) {
5845 // We cannot guarantee that [bottom(),end()] is dirty. Threads
5846 // dirty allocated blocks as they allocate them. The thread that
5847 // retires each region and replaces it with a new one will do a
5848 // maximal allocation to fill in [pre_dummy_top(),end()] but will
5849 // not dirty that area (one less thing to have to do while holding
5850 // a lock). So we can only verify that [bottom(),pre_dummy_top()]
5851 // is dirty.
5852 CardTableModRefBS* ct_bs = (CardTableModRefBS*) barrier_set();
5853 MemRegion mr(hr->bottom(), hr->pre_dummy_top());
5854 ct_bs->verify_dirty_region(mr);
5855 }
5856
5857 void G1CollectedHeap::verify_dirty_young_list(HeapRegion* head) {
5858 CardTableModRefBS* ct_bs = (CardTableModRefBS*) barrier_set();
5859 for (HeapRegion* hr = head; hr != NULL; hr = hr->get_next_young_region()) {
5860 verify_dirty_region(hr);
5861 }
5862 }
5863
5864 void G1CollectedHeap::verify_dirty_young_regions() {
5865 verify_dirty_young_list(_young_list->first_region());
5866 }
5867 #endif
5868
5869 void G1CollectedHeap::cleanUpCardTable() {
5870 CardTableModRefBS* ct_bs = (CardTableModRefBS*) (barrier_set());
5871 double start = os::elapsedTime();
5872
5873 {
5874 // Iterate over the dirty cards region list.
5875 G1ParCleanupCTTask cleanup_task(ct_bs, this);
5876
5877 if (G1CollectedHeap::use_parallel_gc_threads()) {
5878 set_par_threads();
5879 workers()->run_task(&cleanup_task);
5880 set_par_threads(0);
5881 } else {
5882 while (_dirty_cards_region_list) {
5883 HeapRegion* r = _dirty_cards_region_list;
5884 cleanup_task.clear_cards(r);
5885 _dirty_cards_region_list = r->get_next_dirty_cards_region();
5886 if (_dirty_cards_region_list == r) {
5887 // The last region.
5888 _dirty_cards_region_list = NULL;
5889 }
5890 r->set_next_dirty_cards_region(NULL);
5891 }
5892 }
5893 #ifndef PRODUCT
5894 if (G1VerifyCTCleanup || VerifyAfterGC) {
5895 G1VerifyCardTableCleanup cleanup_verifier(this, ct_bs);
5896 heap_region_iterate(&cleanup_verifier);
5897 }
5898 #endif
5899 }
5900
5901 double elapsed = os::elapsedTime() - start;
5902 g1_policy()->phase_times()->record_clear_ct_time(elapsed * 1000.0);
5903 }
5904
5905 void G1CollectedHeap::free_collection_set(HeapRegion* cs_head) {
5906 size_t pre_used = 0;
5907 FreeRegionList local_free_list("Local List for CSet Freeing");
5908
5909 double young_time_ms = 0.0;
5910 double non_young_time_ms = 0.0;
5911
5912 // Since the collection set is a superset of the the young list,
5913 // all we need to do to clear the young list is clear its
5914 // head and length, and unlink any young regions in the code below
5915 _young_list->clear();
5916
5917 G1CollectorPolicy* policy = g1_policy();
5918
5919 double start_sec = os::elapsedTime();
5920 bool non_young = true;
5921
5922 HeapRegion* cur = cs_head;
5923 int age_bound = -1;
5924 size_t rs_lengths = 0;
5925
5926 while (cur != NULL) {
5927 assert(!is_on_master_free_list(cur), "sanity");
5928 if (non_young) {
5929 if (cur->is_young()) {
5930 double end_sec = os::elapsedTime();
5931 double elapsed_ms = (end_sec - start_sec) * 1000.0;
5932 non_young_time_ms += elapsed_ms;
5933
5934 start_sec = os::elapsedTime();
5935 non_young = false;
5936 }
5937 } else {
5938 if (!cur->is_young()) {
5939 double end_sec = os::elapsedTime();
5940 double elapsed_ms = (end_sec - start_sec) * 1000.0;
5941 young_time_ms += elapsed_ms;
5942
5943 start_sec = os::elapsedTime();
5944 non_young = true;
5945 }
5946 }
5947
5948 rs_lengths += cur->rem_set()->occupied();
5949
5950 HeapRegion* next = cur->next_in_collection_set();
5951 assert(cur->in_collection_set(), "bad CS");
5952 cur->set_next_in_collection_set(NULL);
5953 cur->set_in_collection_set(false);
5954
5955 if (cur->is_young()) {
5956 int index = cur->young_index_in_cset();
5957 assert(index != -1, "invariant");
5958 assert((uint) index < policy->young_cset_region_length(), "invariant");
5959 size_t words_survived = _surviving_young_words[index];
5960 cur->record_surv_words_in_group(words_survived);
5961
5962 // At this point the we have 'popped' cur from the collection set
5963 // (linked via next_in_collection_set()) but it is still in the
5964 // young list (linked via next_young_region()). Clear the
5965 // _next_young_region field.
5966 cur->set_next_young_region(NULL);
5967 } else {
5968 int index = cur->young_index_in_cset();
5969 assert(index == -1, "invariant");
5970 }
5971
5972 assert( (cur->is_young() && cur->young_index_in_cset() > -1) ||
5973 (!cur->is_young() && cur->young_index_in_cset() == -1),
5974 "invariant" );
5975
5976 if (!cur->evacuation_failed()) {
5977 MemRegion used_mr = cur->used_region();
5978
5979 // And the region is empty.
5980 assert(!used_mr.is_empty(), "Should not have empty regions in a CS.");
5981 free_region(cur, &pre_used, &local_free_list, false /* par */);
5982 } else {
5983 cur->uninstall_surv_rate_group();
5984 if (cur->is_young()) {
5985 cur->set_young_index_in_cset(-1);
5986 }
5987 cur->set_not_young();
5988 cur->set_evacuation_failed(false);
5989 // The region is now considered to be old.
5990 _old_set.add(cur);
5991 }
5992 cur = next;
5993 }
5994
5995 policy->record_max_rs_lengths(rs_lengths);
5996 policy->cset_regions_freed();
5997
5998 double end_sec = os::elapsedTime();
5999 double elapsed_ms = (end_sec - start_sec) * 1000.0;
6000
6001 if (non_young) {
6002 non_young_time_ms += elapsed_ms;
6003 } else {
6004 young_time_ms += elapsed_ms;
6005 }
6006
6007 update_sets_after_freeing_regions(pre_used, &local_free_list,
6008 NULL /* old_proxy_set */,
6009 NULL /* humongous_proxy_set */,
6010 false /* par */);
6011 policy->phase_times()->record_young_free_cset_time_ms(young_time_ms);
6012 policy->phase_times()->record_non_young_free_cset_time_ms(non_young_time_ms);
6013 }
6014
6015 // This routine is similar to the above but does not record
6016 // any policy statistics or update free lists; we are abandoning
6017 // the current incremental collection set in preparation of a
6018 // full collection. After the full GC we will start to build up
6019 // the incremental collection set again.
6020 // This is only called when we're doing a full collection
6021 // and is immediately followed by the tearing down of the young list.
6022
6023 void G1CollectedHeap::abandon_collection_set(HeapRegion* cs_head) {
6024 HeapRegion* cur = cs_head;
6025
6026 while (cur != NULL) {
6027 HeapRegion* next = cur->next_in_collection_set();
6028 assert(cur->in_collection_set(), "bad CS");
6029 cur->set_next_in_collection_set(NULL);
6030 cur->set_in_collection_set(false);
6031 cur->set_young_index_in_cset(-1);
6032 cur = next;
6033 }
6034 }
6035
6036 void G1CollectedHeap::set_free_regions_coming() {
6037 if (G1ConcRegionFreeingVerbose) {
6038 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
6039 "setting free regions coming");
6040 }
6041
6042 assert(!free_regions_coming(), "pre-condition");
6043 _free_regions_coming = true;
6044 }
6045
6046 void G1CollectedHeap::reset_free_regions_coming() {
6047 assert(free_regions_coming(), "pre-condition");
6048
6049 {
6050 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6051 _free_regions_coming = false;
6052 SecondaryFreeList_lock->notify_all();
6053 }
6054
6055 if (G1ConcRegionFreeingVerbose) {
6056 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
6057 "reset free regions coming");
6058 }
6059 }
6060
6061 void G1CollectedHeap::wait_while_free_regions_coming() {
6062 // Most of the time we won't have to wait, so let's do a quick test
6063 // first before we take the lock.
6064 if (!free_regions_coming()) {
6065 return;
6066 }
6067
6068 if (G1ConcRegionFreeingVerbose) {
6069 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
6070 "waiting for free regions");
6071 }
6072
6073 {
6074 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6075 while (free_regions_coming()) {
6076 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
6077 }
6078 }
6079
6080 if (G1ConcRegionFreeingVerbose) {
6081 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
6082 "done waiting for free regions");
6083 }
6084 }
6085
6086 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
6087 assert(heap_lock_held_for_gc(),
6088 "the heap lock should already be held by or for this thread");
6089 _young_list->push_region(hr);
6090 }
6091
6092 class NoYoungRegionsClosure: public HeapRegionClosure {
6093 private:
6094 bool _success;
6095 public:
6096 NoYoungRegionsClosure() : _success(true) { }
6097 bool doHeapRegion(HeapRegion* r) {
6098 if (r->is_young()) {
6099 gclog_or_tty->print_cr("Region ["PTR_FORMAT", "PTR_FORMAT") tagged as young",
6100 r->bottom(), r->end());
6101 _success = false;
6102 }
6103 return false;
6104 }
6105 bool success() { return _success; }
6106 };
6107
6108 bool G1CollectedHeap::check_young_list_empty(bool check_heap, bool check_sample) {
6109 bool ret = _young_list->check_list_empty(check_sample);
6110
6111 if (check_heap) {
6112 NoYoungRegionsClosure closure;
6113 heap_region_iterate(&closure);
6114 ret = ret && closure.success();
6115 }
6116
6117 return ret;
6118 }
6119
6120 class TearDownRegionSetsClosure : public HeapRegionClosure {
6121 private:
6122 OldRegionSet *_old_set;
6123
6124 public:
6125 TearDownRegionSetsClosure(OldRegionSet* old_set) : _old_set(old_set) { }
6126
6127 bool doHeapRegion(HeapRegion* r) {
6128 if (r->is_empty()) {
6129 // We ignore empty regions, we'll empty the free list afterwards
6130 } else if (r->is_young()) {
6131 // We ignore young regions, we'll empty the young list afterwards
6132 } else if (r->isHumongous()) {
6133 // We ignore humongous regions, we're not tearing down the
6134 // humongous region set
6135 } else {
6136 // The rest should be old
6137 _old_set->remove(r);
6138 }
6139 return false;
6140 }
6141
6142 ~TearDownRegionSetsClosure() {
6143 assert(_old_set->is_empty(), "post-condition");
6144 }
6145 };
6146
6147 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
6148 assert_at_safepoint(true /* should_be_vm_thread */);
6149
6150 if (!free_list_only) {
6151 TearDownRegionSetsClosure cl(&_old_set);
6152 heap_region_iterate(&cl);
6153
6154 // Need to do this after the heap iteration to be able to
6155 // recognize the young regions and ignore them during the iteration.
6156 _young_list->empty_list();
6157 }
6158 _free_list.remove_all();
6159 }
6160
6161 class RebuildRegionSetsClosure : public HeapRegionClosure {
6162 private:
6163 bool _free_list_only;
6164 OldRegionSet* _old_set;
6165 FreeRegionList* _free_list;
6166 size_t _total_used;
6167
6168 public:
6169 RebuildRegionSetsClosure(bool free_list_only,
6170 OldRegionSet* old_set, FreeRegionList* free_list) :
6171 _free_list_only(free_list_only),
6172 _old_set(old_set), _free_list(free_list), _total_used(0) {
6173 assert(_free_list->is_empty(), "pre-condition");
6174 if (!free_list_only) {
6175 assert(_old_set->is_empty(), "pre-condition");
6176 }
6177 }
6178
6179 bool doHeapRegion(HeapRegion* r) {
6180 if (r->continuesHumongous()) {
6181 return false;
6182 }
6183
6184 if (r->is_empty()) {
6185 // Add free regions to the free list
6186 _free_list->add_as_tail(r);
6187 } else if (!_free_list_only) {
6188 assert(!r->is_young(), "we should not come across young regions");
6189
6190 if (r->isHumongous()) {
6191 // We ignore humongous regions, we left the humongous set unchanged
6192 } else {
6193 // The rest should be old, add them to the old set
6194 _old_set->add(r);
6195 }
6196 _total_used += r->used();
6197 }
6198
6199 return false;
6200 }
6201
6202 size_t total_used() {
6203 return _total_used;
6204 }
6205 };
6206
6207 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
6208 assert_at_safepoint(true /* should_be_vm_thread */);
6209
6210 RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_free_list);
6211 heap_region_iterate(&cl);
6212
6213 if (!free_list_only) {
6214 _summary_bytes_used = cl.total_used();
6215 }
6216 assert(_summary_bytes_used == recalculate_used(),
6217 err_msg("inconsistent _summary_bytes_used, "
6218 "value: "SIZE_FORMAT" recalculated: "SIZE_FORMAT,
6219 _summary_bytes_used, recalculate_used()));
6220 }
6221
6222 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) {
6223 _refine_cte_cl->set_concurrent(concurrent);
6224 }
6225
6226 bool G1CollectedHeap::is_in_closed_subset(const void* p) const {
6227 HeapRegion* hr = heap_region_containing(p);
6228 if (hr == NULL) {
6229 return false;
6230 } else {
6231 return hr->is_in(p);
6232 }
6233 }
6234
6235 // Methods for the mutator alloc region
6236
6237 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
6238 bool force) {
6239 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6240 assert(!force || g1_policy()->can_expand_young_list(),
6241 "if force is true we should be able to expand the young list");
6242 bool young_list_full = g1_policy()->is_young_list_full();
6243 if (force || !young_list_full) {
6244 HeapRegion* new_alloc_region = new_region(word_size,
6245 false /* do_expand */);
6246 if (new_alloc_region != NULL) {
6247 set_region_short_lived_locked(new_alloc_region);
6248 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Eden, young_list_full);
6249 return new_alloc_region;
6250 }
6251 }
6252 return NULL;
6253 }
6254
6255 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
6256 size_t allocated_bytes) {
6257 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6258 assert(alloc_region->is_young(), "all mutator alloc regions should be young");
6259
6260 g1_policy()->add_region_to_incremental_cset_lhs(alloc_region);
6261 _summary_bytes_used += allocated_bytes;
6262 _hr_printer.retire(alloc_region);
6263 // We update the eden sizes here, when the region is retired,
6264 // instead of when it's allocated, since this is the point that its
6265 // used space has been recored in _summary_bytes_used.
6266 g1mm()->update_eden_size();
6267 }
6268
6269 HeapRegion* MutatorAllocRegion::allocate_new_region(size_t word_size,
6270 bool force) {
6271 return _g1h->new_mutator_alloc_region(word_size, force);
6272 }
6273
6274 void G1CollectedHeap::set_par_threads() {
6275 // Don't change the number of workers. Use the value previously set
6276 // in the workgroup.
6277 assert(G1CollectedHeap::use_parallel_gc_threads(), "shouldn't be here otherwise");
6278 uint n_workers = workers()->active_workers();
6279 assert(UseDynamicNumberOfGCThreads ||
6280 n_workers == workers()->total_workers(),
6281 "Otherwise should be using the total number of workers");
6282 if (n_workers == 0) {
6283 assert(false, "Should have been set in prior evacuation pause.");
6284 n_workers = ParallelGCThreads;
6285 workers()->set_active_workers(n_workers);
6286 }
6287 set_par_threads(n_workers);
6288 }
6289
6290 void MutatorAllocRegion::retire_region(HeapRegion* alloc_region,
6291 size_t allocated_bytes) {
6292 _g1h->retire_mutator_alloc_region(alloc_region, allocated_bytes);
6293 }
6294
6295 // Methods for the GC alloc regions
6296
6297 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size,
6298 uint count,
6299 GCAllocPurpose ap) {
6300 assert(FreeList_lock->owned_by_self(), "pre-condition");
6301
6302 if (count < g1_policy()->max_regions(ap)) {
6303 HeapRegion* new_alloc_region = new_region(word_size,
6304 true /* do_expand */);
6305 if (new_alloc_region != NULL) {
6306 // We really only need to do this for old regions given that we
6307 // should never scan survivors. But it doesn't hurt to do it
6308 // for survivors too.
6309 new_alloc_region->set_saved_mark();
6310 if (ap == GCAllocForSurvived) {
6311 new_alloc_region->set_survivor();
6312 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Survivor);
6313 } else {
6314 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Old);
6315 }
6316 bool during_im = g1_policy()->during_initial_mark_pause();
6317 new_alloc_region->note_start_of_copying(during_im);
6318 return new_alloc_region;
6319 } else {
6320 g1_policy()->note_alloc_region_limit_reached(ap);
6321 }
6322 }
6323 return NULL;
6324 }
6325
6326 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
6327 size_t allocated_bytes,
6328 GCAllocPurpose ap) {
6329 bool during_im = g1_policy()->during_initial_mark_pause();
6330 alloc_region->note_end_of_copying(during_im);
6331 g1_policy()->record_bytes_copied_during_gc(allocated_bytes);
6332 if (ap == GCAllocForSurvived) {
6333 young_list()->add_survivor_region(alloc_region);
6334 } else {
6335 _old_set.add(alloc_region);
6336 }
6337 _hr_printer.retire(alloc_region);
6338 }
6339
6340 HeapRegion* SurvivorGCAllocRegion::allocate_new_region(size_t word_size,
6341 bool force) {
6342 assert(!force, "not supported for GC alloc regions");
6343 return _g1h->new_gc_alloc_region(word_size, count(), GCAllocForSurvived);
6344 }
6345
6346 void SurvivorGCAllocRegion::retire_region(HeapRegion* alloc_region,
6347 size_t allocated_bytes) {
6348 _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes,
6349 GCAllocForSurvived);
6350 }
6351
6352 HeapRegion* OldGCAllocRegion::allocate_new_region(size_t word_size,
6353 bool force) {
6354 assert(!force, "not supported for GC alloc regions");
6355 return _g1h->new_gc_alloc_region(word_size, count(), GCAllocForTenured);
6356 }
6357
6358 void OldGCAllocRegion::retire_region(HeapRegion* alloc_region,
6359 size_t allocated_bytes) {
6360 _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes,
6361 GCAllocForTenured);
6362 }
6363 // Heap region set verification
6364
6365 class VerifyRegionListsClosure : public HeapRegionClosure {
6366 private:
6367 FreeRegionList* _free_list;
6368 OldRegionSet* _old_set;
6369 HumongousRegionSet* _humongous_set;
6370 uint _region_count;
6371
6372 public:
6373 VerifyRegionListsClosure(OldRegionSet* old_set,
6374 HumongousRegionSet* humongous_set,
6375 FreeRegionList* free_list) :
6376 _old_set(old_set), _humongous_set(humongous_set),
6377 _free_list(free_list), _region_count(0) { }
6378
6379 uint region_count() { return _region_count; }
6380
6381 bool doHeapRegion(HeapRegion* hr) {
6382 _region_count += 1;
6383
6384 if (hr->continuesHumongous()) {
6385 return false;
6386 }
6387
6388 if (hr->is_young()) {
6389 // TODO
6390 } else if (hr->startsHumongous()) {
6391 _humongous_set->verify_next_region(hr);
6392 } else if (hr->is_empty()) {
6393 _free_list->verify_next_region(hr);
6394 } else {
6395 _old_set->verify_next_region(hr);
6396 }
6397 return false;
6398 }
6399 };
6400
6401 HeapRegion* G1CollectedHeap::new_heap_region(uint hrs_index,
6402 HeapWord* bottom) {
6403 HeapWord* end = bottom + HeapRegion::GrainWords;
6404 MemRegion mr(bottom, end);
6405 assert(_g1_reserved.contains(mr), "invariant");
6406 // This might return NULL if the allocation fails
6407 return new HeapRegion(hrs_index, _bot_shared, mr);
6408 }
6409
6410 void G1CollectedHeap::verify_region_sets() {
6411 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6412
6413 // First, check the explicit lists.
6414 _free_list.verify();
6415 {
6416 // Given that a concurrent operation might be adding regions to
6417 // the secondary free list we have to take the lock before
6418 // verifying it.
6419 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6420 _secondary_free_list.verify();
6421 }
6422 _old_set.verify();
6423 _humongous_set.verify();
6424
6425 // If a concurrent region freeing operation is in progress it will
6426 // be difficult to correctly attributed any free regions we come
6427 // across to the correct free list given that they might belong to
6428 // one of several (free_list, secondary_free_list, any local lists,
6429 // etc.). So, if that's the case we will skip the rest of the
6430 // verification operation. Alternatively, waiting for the concurrent
6431 // operation to complete will have a non-trivial effect on the GC's
6432 // operation (no concurrent operation will last longer than the
6433 // interval between two calls to verification) and it might hide
6434 // any issues that we would like to catch during testing.
6435 if (free_regions_coming()) {
6436 return;
6437 }
6438
6439 // Make sure we append the secondary_free_list on the free_list so
6440 // that all free regions we will come across can be safely
6441 // attributed to the free_list.
6442 append_secondary_free_list_if_not_empty_with_lock();
6443
6444 // Finally, make sure that the region accounting in the lists is
6445 // consistent with what we see in the heap.
6446 _old_set.verify_start();
6447 _humongous_set.verify_start();
6448 _free_list.verify_start();
6449
6450 VerifyRegionListsClosure cl(&_old_set, &_humongous_set, &_free_list);
6451 heap_region_iterate(&cl);
6452
6453 _old_set.verify_end();
6454 _humongous_set.verify_end();
6455 _free_list.verify_end();
6456 }