Tue, 01 Mar 2011 14:56:48 -0800
6627983: G1: Bad oop deference during marking
Summary: Bulk zeroing reduction didn't work with G1, because arraycopy would call pre-barriers on uninitialized oops. The solution is to have version of arraycopy stubs that don't have pre-barriers. Also refactored arraycopy stubs generation on SPARC to be more readable and reduced the number of stubs necessary in some cases.
Reviewed-by: jrose, kvn, never
1 /*
2 * Copyright (c) 2001, 2011, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
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/g1CollectedHeap.inline.hpp"
32 #include "gc_implementation/g1/g1CollectorPolicy.hpp"
33 #include "gc_implementation/g1/g1MarkSweep.hpp"
34 #include "gc_implementation/g1/g1OopClosures.inline.hpp"
35 #include "gc_implementation/g1/g1RemSet.inline.hpp"
36 #include "gc_implementation/g1/heapRegionRemSet.hpp"
37 #include "gc_implementation/g1/heapRegionSeq.inline.hpp"
38 #include "gc_implementation/g1/vm_operations_g1.hpp"
39 #include "gc_implementation/shared/isGCActiveMark.hpp"
40 #include "memory/gcLocker.inline.hpp"
41 #include "memory/genOopClosures.inline.hpp"
42 #include "memory/generationSpec.hpp"
43 #include "oops/oop.inline.hpp"
44 #include "oops/oop.pcgc.inline.hpp"
45 #include "runtime/aprofiler.hpp"
46 #include "runtime/vmThread.hpp"
48 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;
50 // turn it on so that the contents of the young list (scan-only /
51 // to-be-collected) are printed at "strategic" points before / during
52 // / after the collection --- this is useful for debugging
53 #define YOUNG_LIST_VERBOSE 0
54 // CURRENT STATUS
55 // This file is under construction. Search for "FIXME".
57 // INVARIANTS/NOTES
58 //
59 // All allocation activity covered by the G1CollectedHeap interface is
60 // serialized by acquiring the HeapLock. This happens in mem_allocate
61 // and allocate_new_tlab, which are the "entry" points to the
62 // allocation code from the rest of the JVM. (Note that this does not
63 // apply to TLAB allocation, which is not part of this interface: it
64 // is done by clients of this interface.)
66 // Local to this file.
68 class RefineCardTableEntryClosure: public CardTableEntryClosure {
69 SuspendibleThreadSet* _sts;
70 G1RemSet* _g1rs;
71 ConcurrentG1Refine* _cg1r;
72 bool _concurrent;
73 public:
74 RefineCardTableEntryClosure(SuspendibleThreadSet* sts,
75 G1RemSet* g1rs,
76 ConcurrentG1Refine* cg1r) :
77 _sts(sts), _g1rs(g1rs), _cg1r(cg1r), _concurrent(true)
78 {}
79 bool do_card_ptr(jbyte* card_ptr, int worker_i) {
80 bool oops_into_cset = _g1rs->concurrentRefineOneCard(card_ptr, worker_i, false);
81 // This path is executed by the concurrent refine or mutator threads,
82 // concurrently, and so we do not care if card_ptr contains references
83 // that point into the collection set.
84 assert(!oops_into_cset, "should be");
86 if (_concurrent && _sts->should_yield()) {
87 // Caller will actually yield.
88 return false;
89 }
90 // Otherwise, we finished successfully; return true.
91 return true;
92 }
93 void set_concurrent(bool b) { _concurrent = b; }
94 };
97 class ClearLoggedCardTableEntryClosure: public CardTableEntryClosure {
98 int _calls;
99 G1CollectedHeap* _g1h;
100 CardTableModRefBS* _ctbs;
101 int _histo[256];
102 public:
103 ClearLoggedCardTableEntryClosure() :
104 _calls(0)
105 {
106 _g1h = G1CollectedHeap::heap();
107 _ctbs = (CardTableModRefBS*)_g1h->barrier_set();
108 for (int i = 0; i < 256; i++) _histo[i] = 0;
109 }
110 bool do_card_ptr(jbyte* card_ptr, int worker_i) {
111 if (_g1h->is_in_reserved(_ctbs->addr_for(card_ptr))) {
112 _calls++;
113 unsigned char* ujb = (unsigned char*)card_ptr;
114 int ind = (int)(*ujb);
115 _histo[ind]++;
116 *card_ptr = -1;
117 }
118 return true;
119 }
120 int calls() { return _calls; }
121 void print_histo() {
122 gclog_or_tty->print_cr("Card table value histogram:");
123 for (int i = 0; i < 256; i++) {
124 if (_histo[i] != 0) {
125 gclog_or_tty->print_cr(" %d: %d", i, _histo[i]);
126 }
127 }
128 }
129 };
131 class RedirtyLoggedCardTableEntryClosure: public CardTableEntryClosure {
132 int _calls;
133 G1CollectedHeap* _g1h;
134 CardTableModRefBS* _ctbs;
135 public:
136 RedirtyLoggedCardTableEntryClosure() :
137 _calls(0)
138 {
139 _g1h = G1CollectedHeap::heap();
140 _ctbs = (CardTableModRefBS*)_g1h->barrier_set();
141 }
142 bool do_card_ptr(jbyte* card_ptr, int worker_i) {
143 if (_g1h->is_in_reserved(_ctbs->addr_for(card_ptr))) {
144 _calls++;
145 *card_ptr = 0;
146 }
147 return true;
148 }
149 int calls() { return _calls; }
150 };
152 class RedirtyLoggedCardTableEntryFastClosure : public CardTableEntryClosure {
153 public:
154 bool do_card_ptr(jbyte* card_ptr, int worker_i) {
155 *card_ptr = CardTableModRefBS::dirty_card_val();
156 return true;
157 }
158 };
160 YoungList::YoungList(G1CollectedHeap* g1h)
161 : _g1h(g1h), _head(NULL),
162 _length(0),
163 _last_sampled_rs_lengths(0),
164 _survivor_head(NULL), _survivor_tail(NULL), _survivor_length(0)
165 {
166 guarantee( check_list_empty(false), "just making sure..." );
167 }
169 void YoungList::push_region(HeapRegion *hr) {
170 assert(!hr->is_young(), "should not already be young");
171 assert(hr->get_next_young_region() == NULL, "cause it should!");
173 hr->set_next_young_region(_head);
174 _head = hr;
176 hr->set_young();
177 double yg_surv_rate = _g1h->g1_policy()->predict_yg_surv_rate((int)_length);
178 ++_length;
179 }
181 void YoungList::add_survivor_region(HeapRegion* hr) {
182 assert(hr->is_survivor(), "should be flagged as survivor region");
183 assert(hr->get_next_young_region() == NULL, "cause it should!");
185 hr->set_next_young_region(_survivor_head);
186 if (_survivor_head == NULL) {
187 _survivor_tail = hr;
188 }
189 _survivor_head = hr;
191 ++_survivor_length;
192 }
194 void YoungList::empty_list(HeapRegion* list) {
195 while (list != NULL) {
196 HeapRegion* next = list->get_next_young_region();
197 list->set_next_young_region(NULL);
198 list->uninstall_surv_rate_group();
199 list->set_not_young();
200 list = next;
201 }
202 }
204 void YoungList::empty_list() {
205 assert(check_list_well_formed(), "young list should be well formed");
207 empty_list(_head);
208 _head = NULL;
209 _length = 0;
211 empty_list(_survivor_head);
212 _survivor_head = NULL;
213 _survivor_tail = NULL;
214 _survivor_length = 0;
216 _last_sampled_rs_lengths = 0;
218 assert(check_list_empty(false), "just making sure...");
219 }
221 bool YoungList::check_list_well_formed() {
222 bool ret = true;
224 size_t length = 0;
225 HeapRegion* curr = _head;
226 HeapRegion* last = NULL;
227 while (curr != NULL) {
228 if (!curr->is_young()) {
229 gclog_or_tty->print_cr("### YOUNG REGION "PTR_FORMAT"-"PTR_FORMAT" "
230 "incorrectly tagged (y: %d, surv: %d)",
231 curr->bottom(), curr->end(),
232 curr->is_young(), curr->is_survivor());
233 ret = false;
234 }
235 ++length;
236 last = curr;
237 curr = curr->get_next_young_region();
238 }
239 ret = ret && (length == _length);
241 if (!ret) {
242 gclog_or_tty->print_cr("### YOUNG LIST seems not well formed!");
243 gclog_or_tty->print_cr("### list has %d entries, _length is %d",
244 length, _length);
245 }
247 return ret;
248 }
250 bool YoungList::check_list_empty(bool check_sample) {
251 bool ret = true;
253 if (_length != 0) {
254 gclog_or_tty->print_cr("### YOUNG LIST should have 0 length, not %d",
255 _length);
256 ret = false;
257 }
258 if (check_sample && _last_sampled_rs_lengths != 0) {
259 gclog_or_tty->print_cr("### YOUNG LIST has non-zero last sampled RS lengths");
260 ret = false;
261 }
262 if (_head != NULL) {
263 gclog_or_tty->print_cr("### YOUNG LIST does not have a NULL head");
264 ret = false;
265 }
266 if (!ret) {
267 gclog_or_tty->print_cr("### YOUNG LIST does not seem empty");
268 }
270 return ret;
271 }
273 void
274 YoungList::rs_length_sampling_init() {
275 _sampled_rs_lengths = 0;
276 _curr = _head;
277 }
279 bool
280 YoungList::rs_length_sampling_more() {
281 return _curr != NULL;
282 }
284 void
285 YoungList::rs_length_sampling_next() {
286 assert( _curr != NULL, "invariant" );
287 size_t rs_length = _curr->rem_set()->occupied();
289 _sampled_rs_lengths += rs_length;
291 // The current region may not yet have been added to the
292 // incremental collection set (it gets added when it is
293 // retired as the current allocation region).
294 if (_curr->in_collection_set()) {
295 // Update the collection set policy information for this region
296 _g1h->g1_policy()->update_incremental_cset_info(_curr, rs_length);
297 }
299 _curr = _curr->get_next_young_region();
300 if (_curr == NULL) {
301 _last_sampled_rs_lengths = _sampled_rs_lengths;
302 // gclog_or_tty->print_cr("last sampled RS lengths = %d", _last_sampled_rs_lengths);
303 }
304 }
306 void
307 YoungList::reset_auxilary_lists() {
308 guarantee( is_empty(), "young list should be empty" );
309 assert(check_list_well_formed(), "young list should be well formed");
311 // Add survivor regions to SurvRateGroup.
312 _g1h->g1_policy()->note_start_adding_survivor_regions();
313 _g1h->g1_policy()->finished_recalculating_age_indexes(true /* is_survivors */);
315 for (HeapRegion* curr = _survivor_head;
316 curr != NULL;
317 curr = curr->get_next_young_region()) {
318 _g1h->g1_policy()->set_region_survivors(curr);
320 // The region is a non-empty survivor so let's add it to
321 // the incremental collection set for the next evacuation
322 // pause.
323 _g1h->g1_policy()->add_region_to_incremental_cset_rhs(curr);
324 }
325 _g1h->g1_policy()->note_stop_adding_survivor_regions();
327 _head = _survivor_head;
328 _length = _survivor_length;
329 if (_survivor_head != NULL) {
330 assert(_survivor_tail != NULL, "cause it shouldn't be");
331 assert(_survivor_length > 0, "invariant");
332 _survivor_tail->set_next_young_region(NULL);
333 }
335 // Don't clear the survivor list handles until the start of
336 // the next evacuation pause - we need it in order to re-tag
337 // the survivor regions from this evacuation pause as 'young'
338 // at the start of the next.
340 _g1h->g1_policy()->finished_recalculating_age_indexes(false /* is_survivors */);
342 assert(check_list_well_formed(), "young list should be well formed");
343 }
345 void YoungList::print() {
346 HeapRegion* lists[] = {_head, _survivor_head};
347 const char* names[] = {"YOUNG", "SURVIVOR"};
349 for (unsigned int list = 0; list < ARRAY_SIZE(lists); ++list) {
350 gclog_or_tty->print_cr("%s LIST CONTENTS", names[list]);
351 HeapRegion *curr = lists[list];
352 if (curr == NULL)
353 gclog_or_tty->print_cr(" empty");
354 while (curr != NULL) {
355 gclog_or_tty->print_cr(" [%08x-%08x], t: %08x, P: %08x, N: %08x, C: %08x, "
356 "age: %4d, y: %d, surv: %d",
357 curr->bottom(), curr->end(),
358 curr->top(),
359 curr->prev_top_at_mark_start(),
360 curr->next_top_at_mark_start(),
361 curr->top_at_conc_mark_count(),
362 curr->age_in_surv_rate_group_cond(),
363 curr->is_young(),
364 curr->is_survivor());
365 curr = curr->get_next_young_region();
366 }
367 }
369 gclog_or_tty->print_cr("");
370 }
372 void G1CollectedHeap::push_dirty_cards_region(HeapRegion* hr)
373 {
374 // Claim the right to put the region on the dirty cards region list
375 // by installing a self pointer.
376 HeapRegion* next = hr->get_next_dirty_cards_region();
377 if (next == NULL) {
378 HeapRegion* res = (HeapRegion*)
379 Atomic::cmpxchg_ptr(hr, hr->next_dirty_cards_region_addr(),
380 NULL);
381 if (res == NULL) {
382 HeapRegion* head;
383 do {
384 // Put the region to the dirty cards region list.
385 head = _dirty_cards_region_list;
386 next = (HeapRegion*)
387 Atomic::cmpxchg_ptr(hr, &_dirty_cards_region_list, head);
388 if (next == head) {
389 assert(hr->get_next_dirty_cards_region() == hr,
390 "hr->get_next_dirty_cards_region() != hr");
391 if (next == NULL) {
392 // The last region in the list points to itself.
393 hr->set_next_dirty_cards_region(hr);
394 } else {
395 hr->set_next_dirty_cards_region(next);
396 }
397 }
398 } while (next != head);
399 }
400 }
401 }
403 HeapRegion* G1CollectedHeap::pop_dirty_cards_region()
404 {
405 HeapRegion* head;
406 HeapRegion* hr;
407 do {
408 head = _dirty_cards_region_list;
409 if (head == NULL) {
410 return NULL;
411 }
412 HeapRegion* new_head = head->get_next_dirty_cards_region();
413 if (head == new_head) {
414 // The last region.
415 new_head = NULL;
416 }
417 hr = (HeapRegion*)Atomic::cmpxchg_ptr(new_head, &_dirty_cards_region_list,
418 head);
419 } while (hr != head);
420 assert(hr != NULL, "invariant");
421 hr->set_next_dirty_cards_region(NULL);
422 return hr;
423 }
425 void G1CollectedHeap::stop_conc_gc_threads() {
426 _cg1r->stop();
427 _cmThread->stop();
428 }
430 void G1CollectedHeap::check_ct_logs_at_safepoint() {
431 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
432 CardTableModRefBS* ct_bs = (CardTableModRefBS*)barrier_set();
434 // Count the dirty cards at the start.
435 CountNonCleanMemRegionClosure count1(this);
436 ct_bs->mod_card_iterate(&count1);
437 int orig_count = count1.n();
439 // First clear the logged cards.
440 ClearLoggedCardTableEntryClosure clear;
441 dcqs.set_closure(&clear);
442 dcqs.apply_closure_to_all_completed_buffers();
443 dcqs.iterate_closure_all_threads(false);
444 clear.print_histo();
446 // Now ensure that there's no dirty cards.
447 CountNonCleanMemRegionClosure count2(this);
448 ct_bs->mod_card_iterate(&count2);
449 if (count2.n() != 0) {
450 gclog_or_tty->print_cr("Card table has %d entries; %d originally",
451 count2.n(), orig_count);
452 }
453 guarantee(count2.n() == 0, "Card table should be clean.");
455 RedirtyLoggedCardTableEntryClosure redirty;
456 JavaThread::dirty_card_queue_set().set_closure(&redirty);
457 dcqs.apply_closure_to_all_completed_buffers();
458 dcqs.iterate_closure_all_threads(false);
459 gclog_or_tty->print_cr("Log entries = %d, dirty cards = %d.",
460 clear.calls(), orig_count);
461 guarantee(redirty.calls() == clear.calls(),
462 "Or else mechanism is broken.");
464 CountNonCleanMemRegionClosure count3(this);
465 ct_bs->mod_card_iterate(&count3);
466 if (count3.n() != orig_count) {
467 gclog_or_tty->print_cr("Should have restored them all: orig = %d, final = %d.",
468 orig_count, count3.n());
469 guarantee(count3.n() >= orig_count, "Should have restored them all.");
470 }
472 JavaThread::dirty_card_queue_set().set_closure(_refine_cte_cl);
473 }
475 // Private class members.
477 G1CollectedHeap* G1CollectedHeap::_g1h;
479 // Private methods.
481 HeapRegion*
482 G1CollectedHeap::new_region_try_secondary_free_list(size_t word_size) {
483 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
484 while (!_secondary_free_list.is_empty() || free_regions_coming()) {
485 if (!_secondary_free_list.is_empty()) {
486 if (G1ConcRegionFreeingVerbose) {
487 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
488 "secondary_free_list has "SIZE_FORMAT" entries",
489 _secondary_free_list.length());
490 }
491 // It looks as if there are free regions available on the
492 // secondary_free_list. Let's move them to the free_list and try
493 // again to allocate from it.
494 append_secondary_free_list();
496 assert(!_free_list.is_empty(), "if the secondary_free_list was not "
497 "empty we should have moved at least one entry to the free_list");
498 HeapRegion* res = _free_list.remove_head();
499 if (G1ConcRegionFreeingVerbose) {
500 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
501 "allocated "HR_FORMAT" from secondary_free_list",
502 HR_FORMAT_PARAMS(res));
503 }
504 return res;
505 }
507 // Wait here until we get notifed either when (a) there are no
508 // more free regions coming or (b) some regions have been moved on
509 // the secondary_free_list.
510 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
511 }
513 if (G1ConcRegionFreeingVerbose) {
514 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
515 "could not allocate from secondary_free_list");
516 }
517 return NULL;
518 }
520 HeapRegion* G1CollectedHeap::new_region_work(size_t word_size,
521 bool do_expand) {
522 assert(!isHumongous(word_size) ||
523 word_size <= (size_t) HeapRegion::GrainWords,
524 "the only time we use this to allocate a humongous region is "
525 "when we are allocating a single humongous region");
527 HeapRegion* res;
528 if (G1StressConcRegionFreeing) {
529 if (!_secondary_free_list.is_empty()) {
530 if (G1ConcRegionFreeingVerbose) {
531 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
532 "forced to look at the secondary_free_list");
533 }
534 res = new_region_try_secondary_free_list(word_size);
535 if (res != NULL) {
536 return res;
537 }
538 }
539 }
540 res = _free_list.remove_head_or_null();
541 if (res == NULL) {
542 if (G1ConcRegionFreeingVerbose) {
543 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
544 "res == NULL, trying the secondary_free_list");
545 }
546 res = new_region_try_secondary_free_list(word_size);
547 }
548 if (res == NULL && do_expand) {
549 if (expand(word_size * HeapWordSize)) {
550 // The expansion succeeded and so we should have at least one
551 // region on the free list.
552 res = _free_list.remove_head();
553 }
554 }
555 if (res != NULL) {
556 if (G1PrintHeapRegions) {
557 gclog_or_tty->print_cr("new alloc region %d:["PTR_FORMAT","PTR_FORMAT"], "
558 "top "PTR_FORMAT, res->hrs_index(),
559 res->bottom(), res->end(), res->top());
560 }
561 }
562 return res;
563 }
565 HeapRegion* G1CollectedHeap::new_gc_alloc_region(int purpose,
566 size_t word_size) {
567 HeapRegion* alloc_region = NULL;
568 if (_gc_alloc_region_counts[purpose] < g1_policy()->max_regions(purpose)) {
569 alloc_region = new_region_work(word_size, true /* do_expand */);
570 if (purpose == GCAllocForSurvived && alloc_region != NULL) {
571 alloc_region->set_survivor();
572 }
573 ++_gc_alloc_region_counts[purpose];
574 } else {
575 g1_policy()->note_alloc_region_limit_reached(purpose);
576 }
577 return alloc_region;
578 }
580 int G1CollectedHeap::humongous_obj_allocate_find_first(size_t num_regions,
581 size_t word_size) {
582 int first = -1;
583 if (num_regions == 1) {
584 // Only one region to allocate, no need to go through the slower
585 // path. The caller will attempt the expasion if this fails, so
586 // let's not try to expand here too.
587 HeapRegion* hr = new_region_work(word_size, false /* do_expand */);
588 if (hr != NULL) {
589 first = hr->hrs_index();
590 } else {
591 first = -1;
592 }
593 } else {
594 // We can't allocate humongous regions while cleanupComplete() is
595 // running, since some of the regions we find to be empty might not
596 // yet be added to the free list and it is not straightforward to
597 // know which list they are on so that we can remove them. Note
598 // that we only need to do this if we need to allocate more than
599 // one region to satisfy the current humongous allocation
600 // request. If we are only allocating one region we use the common
601 // region allocation code (see above).
602 wait_while_free_regions_coming();
603 append_secondary_free_list_if_not_empty();
605 if (free_regions() >= num_regions) {
606 first = _hrs->find_contiguous(num_regions);
607 if (first != -1) {
608 for (int i = first; i < first + (int) num_regions; ++i) {
609 HeapRegion* hr = _hrs->at(i);
610 assert(hr->is_empty(), "sanity");
611 assert(is_on_free_list(hr), "sanity");
612 hr->set_pending_removal(true);
613 }
614 _free_list.remove_all_pending(num_regions);
615 }
616 }
617 }
618 return first;
619 }
621 // If could fit into free regions w/o expansion, try.
622 // Otherwise, if can expand, do so.
623 // Otherwise, if using ex regions might help, try with ex given back.
624 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size) {
625 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
627 verify_region_sets_optional();
629 size_t num_regions =
630 round_to(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords;
631 size_t x_size = expansion_regions();
632 size_t fs = _hrs->free_suffix();
633 int first = humongous_obj_allocate_find_first(num_regions, word_size);
634 if (first == -1) {
635 // The only thing we can do now is attempt expansion.
636 if (fs + x_size >= num_regions) {
637 // If the number of regions we're trying to allocate for this
638 // object is at most the number of regions in the free suffix,
639 // then the call to humongous_obj_allocate_find_first() above
640 // should have succeeded and we wouldn't be here.
641 //
642 // We should only be trying to expand when the free suffix is
643 // not sufficient for the object _and_ we have some expansion
644 // room available.
645 assert(num_regions > fs, "earlier allocation should have succeeded");
647 if (expand((num_regions - fs) * HeapRegion::GrainBytes)) {
648 first = humongous_obj_allocate_find_first(num_regions, word_size);
649 // If the expansion was successful then the allocation
650 // should have been successful.
651 assert(first != -1, "this should have worked");
652 }
653 }
654 }
656 if (first != -1) {
657 // Index of last region in the series + 1.
658 int last = first + (int) num_regions;
660 // We need to initialize the region(s) we just discovered. This is
661 // a bit tricky given that it can happen concurrently with
662 // refinement threads refining cards on these regions and
663 // potentially wanting to refine the BOT as they are scanning
664 // those cards (this can happen shortly after a cleanup; see CR
665 // 6991377). So we have to set up the region(s) carefully and in
666 // a specific order.
668 // The word size sum of all the regions we will allocate.
669 size_t word_size_sum = num_regions * HeapRegion::GrainWords;
670 assert(word_size <= word_size_sum, "sanity");
672 // This will be the "starts humongous" region.
673 HeapRegion* first_hr = _hrs->at(first);
674 // The header of the new object will be placed at the bottom of
675 // the first region.
676 HeapWord* new_obj = first_hr->bottom();
677 // This will be the new end of the first region in the series that
678 // should also match the end of the last region in the seriers.
679 HeapWord* new_end = new_obj + word_size_sum;
680 // This will be the new top of the first region that will reflect
681 // this allocation.
682 HeapWord* new_top = new_obj + word_size;
684 // First, we need to zero the header of the space that we will be
685 // allocating. When we update top further down, some refinement
686 // threads might try to scan the region. By zeroing the header we
687 // ensure that any thread that will try to scan the region will
688 // come across the zero klass word and bail out.
689 //
690 // NOTE: It would not have been correct to have used
691 // CollectedHeap::fill_with_object() and make the space look like
692 // an int array. The thread that is doing the allocation will
693 // later update the object header to a potentially different array
694 // type and, for a very short period of time, the klass and length
695 // fields will be inconsistent. This could cause a refinement
696 // thread to calculate the object size incorrectly.
697 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
699 // We will set up the first region as "starts humongous". This
700 // will also update the BOT covering all the regions to reflect
701 // that there is a single object that starts at the bottom of the
702 // first region.
703 first_hr->set_startsHumongous(new_top, new_end);
705 // Then, if there are any, we will set up the "continues
706 // humongous" regions.
707 HeapRegion* hr = NULL;
708 for (int i = first + 1; i < last; ++i) {
709 hr = _hrs->at(i);
710 hr->set_continuesHumongous(first_hr);
711 }
712 // If we have "continues humongous" regions (hr != NULL), then the
713 // end of the last one should match new_end.
714 assert(hr == NULL || hr->end() == new_end, "sanity");
716 // Up to this point no concurrent thread would have been able to
717 // do any scanning on any region in this series. All the top
718 // fields still point to bottom, so the intersection between
719 // [bottom,top] and [card_start,card_end] will be empty. Before we
720 // update the top fields, we'll do a storestore to make sure that
721 // no thread sees the update to top before the zeroing of the
722 // object header and the BOT initialization.
723 OrderAccess::storestore();
725 // Now that the BOT and the object header have been initialized,
726 // we can update top of the "starts humongous" region.
727 assert(first_hr->bottom() < new_top && new_top <= first_hr->end(),
728 "new_top should be in this region");
729 first_hr->set_top(new_top);
731 // Now, we will update the top fields of the "continues humongous"
732 // regions. The reason we need to do this is that, otherwise,
733 // these regions would look empty and this will confuse parts of
734 // G1. For example, the code that looks for a consecutive number
735 // of empty regions will consider them empty and try to
736 // re-allocate them. We can extend is_empty() to also include
737 // !continuesHumongous(), but it is easier to just update the top
738 // fields here. The way we set top for all regions (i.e., top ==
739 // end for all regions but the last one, top == new_top for the
740 // last one) is actually used when we will free up the humongous
741 // region in free_humongous_region().
742 hr = NULL;
743 for (int i = first + 1; i < last; ++i) {
744 hr = _hrs->at(i);
745 if ((i + 1) == last) {
746 // last continues humongous region
747 assert(hr->bottom() < new_top && new_top <= hr->end(),
748 "new_top should fall on this region");
749 hr->set_top(new_top);
750 } else {
751 // not last one
752 assert(new_top > hr->end(), "new_top should be above this region");
753 hr->set_top(hr->end());
754 }
755 }
756 // If we have continues humongous regions (hr != NULL), then the
757 // end of the last one should match new_end and its top should
758 // match new_top.
759 assert(hr == NULL ||
760 (hr->end() == new_end && hr->top() == new_top), "sanity");
762 assert(first_hr->used() == word_size * HeapWordSize, "invariant");
763 _summary_bytes_used += first_hr->used();
764 _humongous_set.add(first_hr);
766 return new_obj;
767 }
769 verify_region_sets_optional();
770 return NULL;
771 }
773 void
774 G1CollectedHeap::retire_cur_alloc_region(HeapRegion* cur_alloc_region) {
775 // Other threads might still be trying to allocate using CASes out
776 // of the region we are retiring, as they can do so without holding
777 // the Heap_lock. So we first have to make sure that noone else can
778 // allocate in it by doing a maximal allocation. Even if our CAS
779 // attempt fails a few times, we'll succeed sooner or later given
780 // that a failed CAS attempt mean that the region is getting closed
781 // to being full (someone else succeeded in allocating into it).
782 size_t free_word_size = cur_alloc_region->free() / HeapWordSize;
784 // This is the minimum free chunk we can turn into a dummy
785 // object. If the free space falls below this, then noone can
786 // allocate in this region anyway (all allocation requests will be
787 // of a size larger than this) so we won't have to perform the dummy
788 // allocation.
789 size_t min_word_size_to_fill = CollectedHeap::min_fill_size();
791 while (free_word_size >= min_word_size_to_fill) {
792 HeapWord* dummy =
793 cur_alloc_region->par_allocate_no_bot_updates(free_word_size);
794 if (dummy != NULL) {
795 // If the allocation was successful we should fill in the space.
796 CollectedHeap::fill_with_object(dummy, free_word_size);
797 break;
798 }
800 free_word_size = cur_alloc_region->free() / HeapWordSize;
801 // It's also possible that someone else beats us to the
802 // allocation and they fill up the region. In that case, we can
803 // just get out of the loop
804 }
805 assert(cur_alloc_region->free() / HeapWordSize < min_word_size_to_fill,
806 "sanity");
808 retire_cur_alloc_region_common(cur_alloc_region);
809 assert(_cur_alloc_region == NULL, "post-condition");
810 }
812 // See the comment in the .hpp file about the locking protocol and
813 // assumptions of this method (and other related ones).
814 HeapWord*
815 G1CollectedHeap::replace_cur_alloc_region_and_allocate(size_t word_size,
816 bool at_safepoint,
817 bool do_dirtying,
818 bool can_expand) {
819 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
820 assert(_cur_alloc_region == NULL,
821 "replace_cur_alloc_region_and_allocate() should only be called "
822 "after retiring the previous current alloc region");
823 assert(SafepointSynchronize::is_at_safepoint() == at_safepoint,
824 "at_safepoint and is_at_safepoint() should be a tautology");
825 assert(!can_expand || g1_policy()->can_expand_young_list(),
826 "we should not call this method with can_expand == true if "
827 "we are not allowed to expand the young gen");
829 if (can_expand || !g1_policy()->is_young_list_full()) {
830 HeapRegion* new_cur_alloc_region = new_alloc_region(word_size);
831 if (new_cur_alloc_region != NULL) {
832 assert(new_cur_alloc_region->is_empty(),
833 "the newly-allocated region should be empty, "
834 "as right now we only allocate new regions out of the free list");
835 g1_policy()->update_region_num(true /* next_is_young */);
836 set_region_short_lived_locked(new_cur_alloc_region);
838 assert(!new_cur_alloc_region->isHumongous(),
839 "Catch a regression of this bug.");
841 // We need to ensure that the stores to _cur_alloc_region and,
842 // subsequently, to top do not float above the setting of the
843 // young type.
844 OrderAccess::storestore();
846 // Now, perform the allocation out of the region we just
847 // allocated. Note that noone else can access that region at
848 // this point (as _cur_alloc_region has not been updated yet),
849 // so we can just go ahead and do the allocation without any
850 // atomics (and we expect this allocation attempt to
851 // suceeded). Given that other threads can attempt an allocation
852 // with a CAS and without needing the Heap_lock, if we assigned
853 // the new region to _cur_alloc_region before first allocating
854 // into it other threads might have filled up the new region
855 // before we got a chance to do the allocation ourselves. In
856 // that case, we would have needed to retire the region, grab a
857 // new one, and go through all this again. Allocating out of the
858 // new region before assigning it to _cur_alloc_region avoids
859 // all this.
860 HeapWord* result =
861 new_cur_alloc_region->allocate_no_bot_updates(word_size);
862 assert(result != NULL, "we just allocate out of an empty region "
863 "so allocation should have been successful");
864 assert(is_in(result), "result should be in the heap");
866 // Now make sure that the store to _cur_alloc_region does not
867 // float above the store to top.
868 OrderAccess::storestore();
869 _cur_alloc_region = new_cur_alloc_region;
871 if (!at_safepoint) {
872 Heap_lock->unlock();
873 }
875 // do the dirtying, if necessary, after we release the Heap_lock
876 if (do_dirtying) {
877 dirty_young_block(result, word_size);
878 }
879 return result;
880 }
881 }
883 assert(_cur_alloc_region == NULL, "we failed to allocate a new current "
884 "alloc region, it should still be NULL");
885 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
886 return NULL;
887 }
889 // See the comment in the .hpp file about the locking protocol and
890 // assumptions of this method (and other related ones).
891 HeapWord*
892 G1CollectedHeap::attempt_allocation_slow(size_t word_size) {
893 assert_heap_locked_and_not_at_safepoint();
894 assert(!isHumongous(word_size), "attempt_allocation_slow() should not be "
895 "used for humongous allocations");
897 // We should only reach here when we were unable to allocate
898 // otherwise. So, we should have not active current alloc region.
899 assert(_cur_alloc_region == NULL, "current alloc region should be NULL");
901 // We will loop while succeeded is false, which means that we tried
902 // to do a collection, but the VM op did not succeed. So, when we
903 // exit the loop, either one of the allocation attempts was
904 // successful, or we succeeded in doing the VM op but which was
905 // unable to allocate after the collection.
906 for (int try_count = 1; /* we'll return or break */; try_count += 1) {
907 bool succeeded = true;
909 // Every time we go round the loop we should be holding the Heap_lock.
910 assert_heap_locked();
912 if (GC_locker::is_active_and_needs_gc()) {
913 // We are locked out of GC because of the GC locker. We can
914 // allocate a new region only if we can expand the young gen.
916 if (g1_policy()->can_expand_young_list()) {
917 // Yes, we are allowed to expand the young gen. Let's try to
918 // allocate a new current alloc region.
919 HeapWord* result =
920 replace_cur_alloc_region_and_allocate(word_size,
921 false, /* at_safepoint */
922 true, /* do_dirtying */
923 true /* can_expand */);
924 if (result != NULL) {
925 assert_heap_not_locked();
926 return result;
927 }
928 }
929 // We could not expand the young gen further (or we could but we
930 // failed to allocate a new region). We'll stall until the GC
931 // locker forces a GC.
933 // If this thread is not in a jni critical section, we stall
934 // the requestor until the critical section has cleared and
935 // GC allowed. When the critical section clears, a GC is
936 // initiated by the last thread exiting the critical section; so
937 // we retry the allocation sequence from the beginning of the loop,
938 // rather than causing more, now probably unnecessary, GC attempts.
939 JavaThread* jthr = JavaThread::current();
940 assert(jthr != NULL, "sanity");
941 if (jthr->in_critical()) {
942 if (CheckJNICalls) {
943 fatal("Possible deadlock due to allocating while"
944 " in jni critical section");
945 }
946 // We are returning NULL so the protocol is that we're still
947 // holding the Heap_lock.
948 assert_heap_locked();
949 return NULL;
950 }
952 Heap_lock->unlock();
953 GC_locker::stall_until_clear();
955 // No need to relock the Heap_lock. We'll fall off to the code
956 // below the else-statement which assumes that we are not
957 // holding the Heap_lock.
958 } else {
959 // We are not locked out. So, let's try to do a GC. The VM op
960 // will retry the allocation before it completes.
962 // Read the GC count while holding the Heap_lock
963 unsigned int gc_count_before = SharedHeap::heap()->total_collections();
965 Heap_lock->unlock();
967 HeapWord* result =
968 do_collection_pause(word_size, gc_count_before, &succeeded);
969 assert_heap_not_locked();
970 if (result != NULL) {
971 assert(succeeded, "the VM op should have succeeded");
973 // Allocations that take place on VM operations do not do any
974 // card dirtying and we have to do it here.
975 dirty_young_block(result, word_size);
976 return result;
977 }
978 }
980 // Both paths that get us here from above unlock the Heap_lock.
981 assert_heap_not_locked();
983 // We can reach here when we were unsuccessful in doing a GC,
984 // because another thread beat us to it, or because we were locked
985 // out of GC due to the GC locker. In either case a new alloc
986 // region might be available so we will retry the allocation.
987 HeapWord* result = attempt_allocation(word_size);
988 if (result != NULL) {
989 assert_heap_not_locked();
990 return result;
991 }
993 // So far our attempts to allocate failed. The only time we'll go
994 // around the loop and try again is if we tried to do a GC and the
995 // VM op that we tried to schedule was not successful because
996 // another thread beat us to it. If that happened it's possible
997 // that by the time we grabbed the Heap_lock again and tried to
998 // allocate other threads filled up the young generation, which
999 // means that the allocation attempt after the GC also failed. So,
1000 // it's worth trying to schedule another GC pause.
1001 if (succeeded) {
1002 break;
1003 }
1005 // Give a warning if we seem to be looping forever.
1006 if ((QueuedAllocationWarningCount > 0) &&
1007 (try_count % QueuedAllocationWarningCount == 0)) {
1008 warning("G1CollectedHeap::attempt_allocation_slow() "
1009 "retries %d times", try_count);
1010 }
1011 }
1013 assert_heap_locked();
1014 return NULL;
1015 }
1017 // See the comment in the .hpp file about the locking protocol and
1018 // assumptions of this method (and other related ones).
1019 HeapWord*
1020 G1CollectedHeap::attempt_allocation_humongous(size_t word_size,
1021 bool at_safepoint) {
1022 // This is the method that will allocate a humongous object. All
1023 // allocation paths that attempt to allocate a humongous object
1024 // should eventually reach here. Currently, the only paths are from
1025 // mem_allocate() and attempt_allocation_at_safepoint().
1026 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
1027 assert(isHumongous(word_size), "attempt_allocation_humongous() "
1028 "should only be used for humongous allocations");
1029 assert(SafepointSynchronize::is_at_safepoint() == at_safepoint,
1030 "at_safepoint and is_at_safepoint() should be a tautology");
1032 HeapWord* result = NULL;
1034 // We will loop while succeeded is false, which means that we tried
1035 // to do a collection, but the VM op did not succeed. So, when we
1036 // exit the loop, either one of the allocation attempts was
1037 // successful, or we succeeded in doing the VM op but which was
1038 // unable to allocate after the collection.
1039 for (int try_count = 1; /* we'll return or break */; try_count += 1) {
1040 bool succeeded = true;
1042 // Given that humongous objects are not allocated in young
1043 // regions, we'll first try to do the allocation without doing a
1044 // collection hoping that there's enough space in the heap.
1045 result = humongous_obj_allocate(word_size);
1046 assert(_cur_alloc_region == NULL || !_cur_alloc_region->isHumongous(),
1047 "catch a regression of this bug.");
1048 if (result != NULL) {
1049 if (!at_safepoint) {
1050 // If we're not at a safepoint, unlock the Heap_lock.
1051 Heap_lock->unlock();
1052 }
1053 return result;
1054 }
1056 // If we failed to allocate the humongous object, we should try to
1057 // do a collection pause (if we're allowed) in case it reclaims
1058 // enough space for the allocation to succeed after the pause.
1059 if (!at_safepoint) {
1060 // Read the GC count while holding the Heap_lock
1061 unsigned int gc_count_before = SharedHeap::heap()->total_collections();
1063 // If we're allowed to do a collection we're not at a
1064 // safepoint, so it is safe to unlock the Heap_lock.
1065 Heap_lock->unlock();
1067 result = do_collection_pause(word_size, gc_count_before, &succeeded);
1068 assert_heap_not_locked();
1069 if (result != NULL) {
1070 assert(succeeded, "the VM op should have succeeded");
1071 return result;
1072 }
1074 // If we get here, the VM operation either did not succeed
1075 // (i.e., another thread beat us to it) or it succeeded but
1076 // failed to allocate the object.
1078 // If we're allowed to do a collection we're not at a
1079 // safepoint, so it is safe to lock the Heap_lock.
1080 Heap_lock->lock();
1081 }
1083 assert(result == NULL, "otherwise we should have exited the loop earlier");
1085 // So far our attempts to allocate failed. The only time we'll go
1086 // around the loop and try again is if we tried to do a GC and the
1087 // VM op that we tried to schedule was not successful because
1088 // another thread beat us to it. That way it's possible that some
1089 // space was freed up by the thread that successfully scheduled a
1090 // GC. So it's worth trying to allocate again.
1091 if (succeeded) {
1092 break;
1093 }
1095 // Give a warning if we seem to be looping forever.
1096 if ((QueuedAllocationWarningCount > 0) &&
1097 (try_count % QueuedAllocationWarningCount == 0)) {
1098 warning("G1CollectedHeap::attempt_allocation_humongous "
1099 "retries %d times", try_count);
1100 }
1101 }
1103 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
1104 return NULL;
1105 }
1107 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
1108 bool expect_null_cur_alloc_region) {
1109 assert_at_safepoint(true /* should_be_vm_thread */);
1110 assert(_cur_alloc_region == NULL || !expect_null_cur_alloc_region,
1111 err_msg("the current alloc region was unexpectedly found "
1112 "to be non-NULL, cur alloc region: "PTR_FORMAT" "
1113 "expect_null_cur_alloc_region: %d word_size: "SIZE_FORMAT,
1114 _cur_alloc_region, expect_null_cur_alloc_region, word_size));
1116 if (!isHumongous(word_size)) {
1117 if (!expect_null_cur_alloc_region) {
1118 HeapRegion* cur_alloc_region = _cur_alloc_region;
1119 if (cur_alloc_region != NULL) {
1120 // We are at a safepoint so no reason to use the MT-safe version.
1121 HeapWord* result = cur_alloc_region->allocate_no_bot_updates(word_size);
1122 if (result != NULL) {
1123 assert(is_in(result), "result should be in the heap");
1125 // We will not do any dirtying here. This is guaranteed to be
1126 // called during a safepoint and the thread that scheduled the
1127 // pause will do the dirtying if we return a non-NULL result.
1128 return result;
1129 }
1131 retire_cur_alloc_region_common(cur_alloc_region);
1132 }
1133 }
1135 assert(_cur_alloc_region == NULL,
1136 "at this point we should have no cur alloc region");
1137 return replace_cur_alloc_region_and_allocate(word_size,
1138 true, /* at_safepoint */
1139 false /* do_dirtying */,
1140 false /* can_expand */);
1141 } else {
1142 return attempt_allocation_humongous(word_size,
1143 true /* at_safepoint */);
1144 }
1146 ShouldNotReachHere();
1147 }
1149 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) {
1150 assert_heap_not_locked_and_not_at_safepoint();
1151 assert(!isHumongous(word_size), "we do not allow TLABs of humongous size");
1153 // First attempt: Try allocating out of the current alloc region
1154 // using a CAS. If that fails, take the Heap_lock and retry the
1155 // allocation, potentially replacing the current alloc region.
1156 HeapWord* result = attempt_allocation(word_size);
1157 if (result != NULL) {
1158 assert_heap_not_locked();
1159 return result;
1160 }
1162 // Second attempt: Go to the slower path where we might try to
1163 // schedule a collection.
1164 result = attempt_allocation_slow(word_size);
1165 if (result != NULL) {
1166 assert_heap_not_locked();
1167 return result;
1168 }
1170 assert_heap_locked();
1171 // Need to unlock the Heap_lock before returning.
1172 Heap_lock->unlock();
1173 return NULL;
1174 }
1176 HeapWord*
1177 G1CollectedHeap::mem_allocate(size_t word_size,
1178 bool is_noref,
1179 bool is_tlab,
1180 bool* gc_overhead_limit_was_exceeded) {
1181 assert_heap_not_locked_and_not_at_safepoint();
1182 assert(!is_tlab, "mem_allocate() this should not be called directly "
1183 "to allocate TLABs");
1185 // Loop until the allocation is satisified,
1186 // or unsatisfied after GC.
1187 for (int try_count = 1; /* we'll return */; try_count += 1) {
1188 unsigned int gc_count_before;
1189 {
1190 if (!isHumongous(word_size)) {
1191 // First attempt: Try allocating out of the current alloc region
1192 // using a CAS. If that fails, take the Heap_lock and retry the
1193 // allocation, potentially replacing the current alloc region.
1194 HeapWord* result = attempt_allocation(word_size);
1195 if (result != NULL) {
1196 assert_heap_not_locked();
1197 return result;
1198 }
1200 assert_heap_locked();
1202 // Second attempt: Go to the slower path where we might try to
1203 // schedule a collection.
1204 result = attempt_allocation_slow(word_size);
1205 if (result != NULL) {
1206 assert_heap_not_locked();
1207 return result;
1208 }
1209 } else {
1210 // attempt_allocation_humongous() requires the Heap_lock to be held.
1211 Heap_lock->lock();
1213 HeapWord* result = attempt_allocation_humongous(word_size,
1214 false /* at_safepoint */);
1215 if (result != NULL) {
1216 assert_heap_not_locked();
1217 return result;
1218 }
1219 }
1221 assert_heap_locked();
1222 // Read the gc count while the heap lock is held.
1223 gc_count_before = SharedHeap::heap()->total_collections();
1225 // Release the Heap_lock before attempting the collection.
1226 Heap_lock->unlock();
1227 }
1229 // Create the garbage collection operation...
1230 VM_G1CollectForAllocation op(gc_count_before, word_size);
1231 // ...and get the VM thread to execute it.
1232 VMThread::execute(&op);
1234 assert_heap_not_locked();
1235 if (op.prologue_succeeded() && op.pause_succeeded()) {
1236 // If the operation was successful we'll return the result even
1237 // if it is NULL. If the allocation attempt failed immediately
1238 // after a Full GC, it's unlikely we'll be able to allocate now.
1239 HeapWord* result = op.result();
1240 if (result != NULL && !isHumongous(word_size)) {
1241 // Allocations that take place on VM operations do not do any
1242 // card dirtying and we have to do it here. We only have to do
1243 // this for non-humongous allocations, though.
1244 dirty_young_block(result, word_size);
1245 }
1246 return result;
1247 } else {
1248 assert(op.result() == NULL,
1249 "the result should be NULL if the VM op did not succeed");
1250 }
1252 // Give a warning if we seem to be looping forever.
1253 if ((QueuedAllocationWarningCount > 0) &&
1254 (try_count % QueuedAllocationWarningCount == 0)) {
1255 warning("G1CollectedHeap::mem_allocate retries %d times", try_count);
1256 }
1257 }
1259 ShouldNotReachHere();
1260 }
1262 void G1CollectedHeap::abandon_cur_alloc_region() {
1263 assert_at_safepoint(true /* should_be_vm_thread */);
1265 HeapRegion* cur_alloc_region = _cur_alloc_region;
1266 if (cur_alloc_region != NULL) {
1267 assert(!cur_alloc_region->is_empty(),
1268 "the current alloc region can never be empty");
1269 assert(cur_alloc_region->is_young(),
1270 "the current alloc region should be young");
1272 retire_cur_alloc_region_common(cur_alloc_region);
1273 }
1274 assert(_cur_alloc_region == NULL, "post-condition");
1275 }
1277 void G1CollectedHeap::abandon_gc_alloc_regions() {
1278 // first, make sure that the GC alloc region list is empty (it should!)
1279 assert(_gc_alloc_region_list == NULL, "invariant");
1280 release_gc_alloc_regions(true /* totally */);
1281 }
1283 class PostMCRemSetClearClosure: public HeapRegionClosure {
1284 ModRefBarrierSet* _mr_bs;
1285 public:
1286 PostMCRemSetClearClosure(ModRefBarrierSet* mr_bs) : _mr_bs(mr_bs) {}
1287 bool doHeapRegion(HeapRegion* r) {
1288 r->reset_gc_time_stamp();
1289 if (r->continuesHumongous())
1290 return false;
1291 HeapRegionRemSet* hrrs = r->rem_set();
1292 if (hrrs != NULL) hrrs->clear();
1293 // You might think here that we could clear just the cards
1294 // corresponding to the used region. But no: if we leave a dirty card
1295 // in a region we might allocate into, then it would prevent that card
1296 // from being enqueued, and cause it to be missed.
1297 // Re: the performance cost: we shouldn't be doing full GC anyway!
1298 _mr_bs->clear(MemRegion(r->bottom(), r->end()));
1299 return false;
1300 }
1301 };
1304 class PostMCRemSetInvalidateClosure: public HeapRegionClosure {
1305 ModRefBarrierSet* _mr_bs;
1306 public:
1307 PostMCRemSetInvalidateClosure(ModRefBarrierSet* mr_bs) : _mr_bs(mr_bs) {}
1308 bool doHeapRegion(HeapRegion* r) {
1309 if (r->continuesHumongous()) return false;
1310 if (r->used_region().word_size() != 0) {
1311 _mr_bs->invalidate(r->used_region(), true /*whole heap*/);
1312 }
1313 return false;
1314 }
1315 };
1317 class RebuildRSOutOfRegionClosure: public HeapRegionClosure {
1318 G1CollectedHeap* _g1h;
1319 UpdateRSOopClosure _cl;
1320 int _worker_i;
1321 public:
1322 RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, int worker_i = 0) :
1323 _cl(g1->g1_rem_set(), worker_i),
1324 _worker_i(worker_i),
1325 _g1h(g1)
1326 { }
1328 bool doHeapRegion(HeapRegion* r) {
1329 if (!r->continuesHumongous()) {
1330 _cl.set_from(r);
1331 r->oop_iterate(&_cl);
1332 }
1333 return false;
1334 }
1335 };
1337 class ParRebuildRSTask: public AbstractGangTask {
1338 G1CollectedHeap* _g1;
1339 public:
1340 ParRebuildRSTask(G1CollectedHeap* g1)
1341 : AbstractGangTask("ParRebuildRSTask"),
1342 _g1(g1)
1343 { }
1345 void work(int i) {
1346 RebuildRSOutOfRegionClosure rebuild_rs(_g1, i);
1347 _g1->heap_region_par_iterate_chunked(&rebuild_rs, i,
1348 HeapRegion::RebuildRSClaimValue);
1349 }
1350 };
1352 bool G1CollectedHeap::do_collection(bool explicit_gc,
1353 bool clear_all_soft_refs,
1354 size_t word_size) {
1355 assert_at_safepoint(true /* should_be_vm_thread */);
1357 if (GC_locker::check_active_before_gc()) {
1358 return false;
1359 }
1361 SvcGCMarker sgcm(SvcGCMarker::FULL);
1362 ResourceMark rm;
1364 if (PrintHeapAtGC) {
1365 Universe::print_heap_before_gc();
1366 }
1368 verify_region_sets_optional();
1370 const bool do_clear_all_soft_refs = clear_all_soft_refs ||
1371 collector_policy()->should_clear_all_soft_refs();
1373 ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy());
1375 {
1376 IsGCActiveMark x;
1378 // Timing
1379 bool system_gc = (gc_cause() == GCCause::_java_lang_system_gc);
1380 assert(!system_gc || explicit_gc, "invariant");
1381 gclog_or_tty->date_stamp(PrintGC && PrintGCDateStamps);
1382 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty);
1383 TraceTime t(system_gc ? "Full GC (System.gc())" : "Full GC",
1384 PrintGC, true, gclog_or_tty);
1386 TraceMemoryManagerStats tms(true /* fullGC */);
1388 double start = os::elapsedTime();
1389 g1_policy()->record_full_collection_start();
1391 wait_while_free_regions_coming();
1392 append_secondary_free_list_if_not_empty();
1394 gc_prologue(true);
1395 increment_total_collections(true /* full gc */);
1397 size_t g1h_prev_used = used();
1398 assert(used() == recalculate_used(), "Should be equal");
1400 if (VerifyBeforeGC && total_collections() >= VerifyGCStartAt) {
1401 HandleMark hm; // Discard invalid handles created during verification
1402 prepare_for_verify();
1403 gclog_or_tty->print(" VerifyBeforeGC:");
1404 Universe::verify(true);
1405 }
1407 COMPILER2_PRESENT(DerivedPointerTable::clear());
1409 // We want to discover references, but not process them yet.
1410 // This mode is disabled in
1411 // instanceRefKlass::process_discovered_references if the
1412 // generation does some collection work, or
1413 // instanceRefKlass::enqueue_discovered_references if the
1414 // generation returns without doing any work.
1415 ref_processor()->disable_discovery();
1416 ref_processor()->abandon_partial_discovery();
1417 ref_processor()->verify_no_references_recorded();
1419 // Abandon current iterations of concurrent marking and concurrent
1420 // refinement, if any are in progress.
1421 concurrent_mark()->abort();
1423 // Make sure we'll choose a new allocation region afterwards.
1424 abandon_cur_alloc_region();
1425 abandon_gc_alloc_regions();
1426 assert(_cur_alloc_region == NULL, "Invariant.");
1427 g1_rem_set()->cleanupHRRS();
1428 tear_down_region_lists();
1430 // We may have added regions to the current incremental collection
1431 // set between the last GC or pause and now. We need to clear the
1432 // incremental collection set and then start rebuilding it afresh
1433 // after this full GC.
1434 abandon_collection_set(g1_policy()->inc_cset_head());
1435 g1_policy()->clear_incremental_cset();
1436 g1_policy()->stop_incremental_cset_building();
1438 if (g1_policy()->in_young_gc_mode()) {
1439 empty_young_list();
1440 g1_policy()->set_full_young_gcs(true);
1441 }
1443 // See the comment in G1CollectedHeap::ref_processing_init() about
1444 // how reference processing currently works in G1.
1446 // Temporarily make reference _discovery_ single threaded (non-MT).
1447 ReferenceProcessorMTMutator rp_disc_ser(ref_processor(), false);
1449 // Temporarily make refs discovery atomic
1450 ReferenceProcessorAtomicMutator rp_disc_atomic(ref_processor(), true);
1452 // Temporarily clear _is_alive_non_header
1453 ReferenceProcessorIsAliveMutator rp_is_alive_null(ref_processor(), NULL);
1455 ref_processor()->enable_discovery();
1456 ref_processor()->setup_policy(do_clear_all_soft_refs);
1458 // Do collection work
1459 {
1460 HandleMark hm; // Discard invalid handles created during gc
1461 G1MarkSweep::invoke_at_safepoint(ref_processor(), do_clear_all_soft_refs);
1462 }
1463 assert(free_regions() == 0, "we should not have added any free regions");
1464 rebuild_region_lists();
1466 _summary_bytes_used = recalculate_used();
1468 ref_processor()->enqueue_discovered_references();
1470 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
1472 MemoryService::track_memory_usage();
1474 if (VerifyAfterGC && total_collections() >= VerifyGCStartAt) {
1475 HandleMark hm; // Discard invalid handles created during verification
1476 gclog_or_tty->print(" VerifyAfterGC:");
1477 prepare_for_verify();
1478 Universe::verify(false);
1479 }
1480 NOT_PRODUCT(ref_processor()->verify_no_references_recorded());
1482 reset_gc_time_stamp();
1483 // Since everything potentially moved, we will clear all remembered
1484 // sets, and clear all cards. Later we will rebuild remebered
1485 // sets. We will also reset the GC time stamps of the regions.
1486 PostMCRemSetClearClosure rs_clear(mr_bs());
1487 heap_region_iterate(&rs_clear);
1489 // Resize the heap if necessary.
1490 resize_if_necessary_after_full_collection(explicit_gc ? 0 : word_size);
1492 if (_cg1r->use_cache()) {
1493 _cg1r->clear_and_record_card_counts();
1494 _cg1r->clear_hot_cache();
1495 }
1497 // Rebuild remembered sets of all regions.
1499 if (G1CollectedHeap::use_parallel_gc_threads()) {
1500 ParRebuildRSTask rebuild_rs_task(this);
1501 assert(check_heap_region_claim_values(
1502 HeapRegion::InitialClaimValue), "sanity check");
1503 set_par_threads(workers()->total_workers());
1504 workers()->run_task(&rebuild_rs_task);
1505 set_par_threads(0);
1506 assert(check_heap_region_claim_values(
1507 HeapRegion::RebuildRSClaimValue), "sanity check");
1508 reset_heap_region_claim_values();
1509 } else {
1510 RebuildRSOutOfRegionClosure rebuild_rs(this);
1511 heap_region_iterate(&rebuild_rs);
1512 }
1514 if (PrintGC) {
1515 print_size_transition(gclog_or_tty, g1h_prev_used, used(), capacity());
1516 }
1518 if (true) { // FIXME
1519 // Ask the permanent generation to adjust size for full collections
1520 perm()->compute_new_size();
1521 }
1523 // Start a new incremental collection set for the next pause
1524 assert(g1_policy()->collection_set() == NULL, "must be");
1525 g1_policy()->start_incremental_cset_building();
1527 // Clear the _cset_fast_test bitmap in anticipation of adding
1528 // regions to the incremental collection set for the next
1529 // evacuation pause.
1530 clear_cset_fast_test();
1532 double end = os::elapsedTime();
1533 g1_policy()->record_full_collection_end();
1535 #ifdef TRACESPINNING
1536 ParallelTaskTerminator::print_termination_counts();
1537 #endif
1539 gc_epilogue(true);
1541 // Discard all rset updates
1542 JavaThread::dirty_card_queue_set().abandon_logs();
1543 assert(!G1DeferredRSUpdate
1544 || (G1DeferredRSUpdate && (dirty_card_queue_set().completed_buffers_num() == 0)), "Should not be any");
1545 }
1547 if (g1_policy()->in_young_gc_mode()) {
1548 _young_list->reset_sampled_info();
1549 // At this point there should be no regions in the
1550 // entire heap tagged as young.
1551 assert( check_young_list_empty(true /* check_heap */),
1552 "young list should be empty at this point");
1553 }
1555 // Update the number of full collections that have been completed.
1556 increment_full_collections_completed(false /* concurrent */);
1558 verify_region_sets_optional();
1560 if (PrintHeapAtGC) {
1561 Universe::print_heap_after_gc();
1562 }
1564 return true;
1565 }
1567 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
1568 // do_collection() will return whether it succeeded in performing
1569 // the GC. Currently, there is no facility on the
1570 // do_full_collection() API to notify the caller than the collection
1571 // did not succeed (e.g., because it was locked out by the GC
1572 // locker). So, right now, we'll ignore the return value.
1573 bool dummy = do_collection(true, /* explicit_gc */
1574 clear_all_soft_refs,
1575 0 /* word_size */);
1576 }
1578 // This code is mostly copied from TenuredGeneration.
1579 void
1580 G1CollectedHeap::
1581 resize_if_necessary_after_full_collection(size_t word_size) {
1582 assert(MinHeapFreeRatio <= MaxHeapFreeRatio, "sanity check");
1584 // Include the current allocation, if any, and bytes that will be
1585 // pre-allocated to support collections, as "used".
1586 const size_t used_after_gc = used();
1587 const size_t capacity_after_gc = capacity();
1588 const size_t free_after_gc = capacity_after_gc - used_after_gc;
1590 // This is enforced in arguments.cpp.
1591 assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
1592 "otherwise the code below doesn't make sense");
1594 // We don't have floating point command-line arguments
1595 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
1596 const double maximum_used_percentage = 1.0 - minimum_free_percentage;
1597 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
1598 const double minimum_used_percentage = 1.0 - maximum_free_percentage;
1600 const size_t min_heap_size = collector_policy()->min_heap_byte_size();
1601 const size_t max_heap_size = collector_policy()->max_heap_byte_size();
1603 // We have to be careful here as these two calculations can overflow
1604 // 32-bit size_t's.
1605 double used_after_gc_d = (double) used_after_gc;
1606 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
1607 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
1609 // Let's make sure that they are both under the max heap size, which
1610 // by default will make them fit into a size_t.
1611 double desired_capacity_upper_bound = (double) max_heap_size;
1612 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
1613 desired_capacity_upper_bound);
1614 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
1615 desired_capacity_upper_bound);
1617 // We can now safely turn them into size_t's.
1618 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
1619 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
1621 // This assert only makes sense here, before we adjust them
1622 // with respect to the min and max heap size.
1623 assert(minimum_desired_capacity <= maximum_desired_capacity,
1624 err_msg("minimum_desired_capacity = "SIZE_FORMAT", "
1625 "maximum_desired_capacity = "SIZE_FORMAT,
1626 minimum_desired_capacity, maximum_desired_capacity));
1628 // Should not be greater than the heap max size. No need to adjust
1629 // it with respect to the heap min size as it's a lower bound (i.e.,
1630 // we'll try to make the capacity larger than it, not smaller).
1631 minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size);
1632 // Should not be less than the heap min size. No need to adjust it
1633 // with respect to the heap max size as it's an upper bound (i.e.,
1634 // we'll try to make the capacity smaller than it, not greater).
1635 maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size);
1637 if (PrintGC && Verbose) {
1638 const double free_percentage =
1639 (double) free_after_gc / (double) capacity_after_gc;
1640 gclog_or_tty->print_cr("Computing new size after full GC ");
1641 gclog_or_tty->print_cr(" "
1642 " minimum_free_percentage: %6.2f",
1643 minimum_free_percentage);
1644 gclog_or_tty->print_cr(" "
1645 " maximum_free_percentage: %6.2f",
1646 maximum_free_percentage);
1647 gclog_or_tty->print_cr(" "
1648 " capacity: %6.1fK"
1649 " minimum_desired_capacity: %6.1fK"
1650 " maximum_desired_capacity: %6.1fK",
1651 (double) capacity_after_gc / (double) K,
1652 (double) minimum_desired_capacity / (double) K,
1653 (double) maximum_desired_capacity / (double) K);
1654 gclog_or_tty->print_cr(" "
1655 " free_after_gc: %6.1fK"
1656 " used_after_gc: %6.1fK",
1657 (double) free_after_gc / (double) K,
1658 (double) used_after_gc / (double) K);
1659 gclog_or_tty->print_cr(" "
1660 " free_percentage: %6.2f",
1661 free_percentage);
1662 }
1663 if (capacity_after_gc < minimum_desired_capacity) {
1664 // Don't expand unless it's significant
1665 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
1666 if (expand(expand_bytes)) {
1667 if (PrintGC && Verbose) {
1668 gclog_or_tty->print_cr(" "
1669 " expanding:"
1670 " max_heap_size: %6.1fK"
1671 " minimum_desired_capacity: %6.1fK"
1672 " expand_bytes: %6.1fK",
1673 (double) max_heap_size / (double) K,
1674 (double) minimum_desired_capacity / (double) K,
1675 (double) expand_bytes / (double) K);
1676 }
1677 }
1679 // No expansion, now see if we want to shrink
1680 } else if (capacity_after_gc > maximum_desired_capacity) {
1681 // Capacity too large, compute shrinking size
1682 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
1683 shrink(shrink_bytes);
1684 if (PrintGC && Verbose) {
1685 gclog_or_tty->print_cr(" "
1686 " shrinking:"
1687 " min_heap_size: %6.1fK"
1688 " maximum_desired_capacity: %6.1fK"
1689 " shrink_bytes: %6.1fK",
1690 (double) min_heap_size / (double) K,
1691 (double) maximum_desired_capacity / (double) K,
1692 (double) shrink_bytes / (double) K);
1693 }
1694 }
1695 }
1698 HeapWord*
1699 G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
1700 bool* succeeded) {
1701 assert_at_safepoint(true /* should_be_vm_thread */);
1703 *succeeded = true;
1704 // Let's attempt the allocation first.
1705 HeapWord* result = attempt_allocation_at_safepoint(word_size,
1706 false /* expect_null_cur_alloc_region */);
1707 if (result != NULL) {
1708 assert(*succeeded, "sanity");
1709 return result;
1710 }
1712 // In a G1 heap, we're supposed to keep allocation from failing by
1713 // incremental pauses. Therefore, at least for now, we'll favor
1714 // expansion over collection. (This might change in the future if we can
1715 // do something smarter than full collection to satisfy a failed alloc.)
1716 result = expand_and_allocate(word_size);
1717 if (result != NULL) {
1718 assert(*succeeded, "sanity");
1719 return result;
1720 }
1722 // Expansion didn't work, we'll try to do a Full GC.
1723 bool gc_succeeded = do_collection(false, /* explicit_gc */
1724 false, /* clear_all_soft_refs */
1725 word_size);
1726 if (!gc_succeeded) {
1727 *succeeded = false;
1728 return NULL;
1729 }
1731 // Retry the allocation
1732 result = attempt_allocation_at_safepoint(word_size,
1733 true /* expect_null_cur_alloc_region */);
1734 if (result != NULL) {
1735 assert(*succeeded, "sanity");
1736 return result;
1737 }
1739 // Then, try a Full GC that will collect all soft references.
1740 gc_succeeded = do_collection(false, /* explicit_gc */
1741 true, /* clear_all_soft_refs */
1742 word_size);
1743 if (!gc_succeeded) {
1744 *succeeded = false;
1745 return NULL;
1746 }
1748 // Retry the allocation once more
1749 result = attempt_allocation_at_safepoint(word_size,
1750 true /* expect_null_cur_alloc_region */);
1751 if (result != NULL) {
1752 assert(*succeeded, "sanity");
1753 return result;
1754 }
1756 assert(!collector_policy()->should_clear_all_soft_refs(),
1757 "Flag should have been handled and cleared prior to this point");
1759 // What else? We might try synchronous finalization later. If the total
1760 // space available is large enough for the allocation, then a more
1761 // complete compaction phase than we've tried so far might be
1762 // appropriate.
1763 assert(*succeeded, "sanity");
1764 return NULL;
1765 }
1767 // Attempting to expand the heap sufficiently
1768 // to support an allocation of the given "word_size". If
1769 // successful, perform the allocation and return the address of the
1770 // allocated block, or else "NULL".
1772 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size) {
1773 assert_at_safepoint(true /* should_be_vm_thread */);
1775 verify_region_sets_optional();
1777 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
1778 if (expand(expand_bytes)) {
1779 verify_region_sets_optional();
1780 return attempt_allocation_at_safepoint(word_size,
1781 false /* expect_null_cur_alloc_region */);
1782 }
1783 return NULL;
1784 }
1786 bool G1CollectedHeap::expand(size_t expand_bytes) {
1787 size_t old_mem_size = _g1_storage.committed_size();
1788 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
1789 aligned_expand_bytes = align_size_up(aligned_expand_bytes,
1790 HeapRegion::GrainBytes);
1792 if (Verbose && PrintGC) {
1793 gclog_or_tty->print("Expanding garbage-first heap from %ldK by %ldK",
1794 old_mem_size/K, aligned_expand_bytes/K);
1795 }
1797 HeapWord* old_end = (HeapWord*)_g1_storage.high();
1798 bool successful = _g1_storage.expand_by(aligned_expand_bytes);
1799 if (successful) {
1800 HeapWord* new_end = (HeapWord*)_g1_storage.high();
1802 // Expand the committed region.
1803 _g1_committed.set_end(new_end);
1805 // Tell the cardtable about the expansion.
1806 Universe::heap()->barrier_set()->resize_covered_region(_g1_committed);
1808 // And the offset table as well.
1809 _bot_shared->resize(_g1_committed.word_size());
1811 expand_bytes = aligned_expand_bytes;
1812 HeapWord* base = old_end;
1814 // Create the heap regions for [old_end, new_end)
1815 while (expand_bytes > 0) {
1816 HeapWord* high = base + HeapRegion::GrainWords;
1818 // Create a new HeapRegion.
1819 MemRegion mr(base, high);
1820 bool is_zeroed = !_g1_max_committed.contains(base);
1821 HeapRegion* hr = new HeapRegion(_bot_shared, mr, is_zeroed);
1823 // Add it to the HeapRegionSeq.
1824 _hrs->insert(hr);
1825 _free_list.add_as_tail(hr);
1827 // And we used up an expansion region to create it.
1828 _expansion_regions--;
1830 expand_bytes -= HeapRegion::GrainBytes;
1831 base += HeapRegion::GrainWords;
1832 }
1833 assert(base == new_end, "sanity");
1835 // Now update max_committed if necessary.
1836 _g1_max_committed.set_end(MAX2(_g1_max_committed.end(), new_end));
1838 } else {
1839 // The expansion of the virtual storage space was unsuccessful.
1840 // Let's see if it was because we ran out of swap.
1841 if (G1ExitOnExpansionFailure &&
1842 _g1_storage.uncommitted_size() >= aligned_expand_bytes) {
1843 // We had head room...
1844 vm_exit_out_of_memory(aligned_expand_bytes, "G1 heap expansion");
1845 }
1846 }
1848 if (Verbose && PrintGC) {
1849 size_t new_mem_size = _g1_storage.committed_size();
1850 gclog_or_tty->print_cr("...%s, expanded to %ldK",
1851 (successful ? "Successful" : "Failed"),
1852 new_mem_size/K);
1853 }
1854 return successful;
1855 }
1857 void G1CollectedHeap::shrink_helper(size_t shrink_bytes)
1858 {
1859 size_t old_mem_size = _g1_storage.committed_size();
1860 size_t aligned_shrink_bytes =
1861 ReservedSpace::page_align_size_down(shrink_bytes);
1862 aligned_shrink_bytes = align_size_down(aligned_shrink_bytes,
1863 HeapRegion::GrainBytes);
1864 size_t num_regions_deleted = 0;
1865 MemRegion mr = _hrs->shrink_by(aligned_shrink_bytes, num_regions_deleted);
1867 assert(mr.end() == (HeapWord*)_g1_storage.high(), "Bad shrink!");
1868 if (mr.byte_size() > 0)
1869 _g1_storage.shrink_by(mr.byte_size());
1870 assert(mr.start() == (HeapWord*)_g1_storage.high(), "Bad shrink!");
1872 _g1_committed.set_end(mr.start());
1873 _expansion_regions += num_regions_deleted;
1875 // Tell the cardtable about it.
1876 Universe::heap()->barrier_set()->resize_covered_region(_g1_committed);
1878 // And the offset table as well.
1879 _bot_shared->resize(_g1_committed.word_size());
1881 HeapRegionRemSet::shrink_heap(n_regions());
1883 if (Verbose && PrintGC) {
1884 size_t new_mem_size = _g1_storage.committed_size();
1885 gclog_or_tty->print_cr("Shrinking garbage-first heap from %ldK by %ldK to %ldK",
1886 old_mem_size/K, aligned_shrink_bytes/K,
1887 new_mem_size/K);
1888 }
1889 }
1891 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1892 verify_region_sets_optional();
1894 release_gc_alloc_regions(true /* totally */);
1895 // Instead of tearing down / rebuilding the free lists here, we
1896 // could instead use the remove_all_pending() method on free_list to
1897 // remove only the ones that we need to remove.
1898 tear_down_region_lists(); // We will rebuild them in a moment.
1899 shrink_helper(shrink_bytes);
1900 rebuild_region_lists();
1902 verify_region_sets_optional();
1903 }
1905 // Public methods.
1907 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away
1908 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
1909 #endif // _MSC_VER
1912 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* policy_) :
1913 SharedHeap(policy_),
1914 _g1_policy(policy_),
1915 _dirty_card_queue_set(false),
1916 _into_cset_dirty_card_queue_set(false),
1917 _is_alive_closure(this),
1918 _ref_processor(NULL),
1919 _process_strong_tasks(new SubTasksDone(G1H_PS_NumElements)),
1920 _bot_shared(NULL),
1921 _objs_with_preserved_marks(NULL), _preserved_marks_of_objs(NULL),
1922 _evac_failure_scan_stack(NULL) ,
1923 _mark_in_progress(false),
1924 _cg1r(NULL), _summary_bytes_used(0),
1925 _cur_alloc_region(NULL),
1926 _refine_cte_cl(NULL),
1927 _full_collection(false),
1928 _free_list("Master Free List"),
1929 _secondary_free_list("Secondary Free List"),
1930 _humongous_set("Master Humongous Set"),
1931 _free_regions_coming(false),
1932 _young_list(new YoungList(this)),
1933 _gc_time_stamp(0),
1934 _surviving_young_words(NULL),
1935 _full_collections_completed(0),
1936 _in_cset_fast_test(NULL),
1937 _in_cset_fast_test_base(NULL),
1938 _dirty_cards_region_list(NULL) {
1939 _g1h = this; // To catch bugs.
1940 if (_process_strong_tasks == NULL || !_process_strong_tasks->valid()) {
1941 vm_exit_during_initialization("Failed necessary allocation.");
1942 }
1944 _humongous_object_threshold_in_words = HeapRegion::GrainWords / 2;
1946 int n_queues = MAX2((int)ParallelGCThreads, 1);
1947 _task_queues = new RefToScanQueueSet(n_queues);
1949 int n_rem_sets = HeapRegionRemSet::num_par_rem_sets();
1950 assert(n_rem_sets > 0, "Invariant.");
1952 HeapRegionRemSetIterator** iter_arr =
1953 NEW_C_HEAP_ARRAY(HeapRegionRemSetIterator*, n_queues);
1954 for (int i = 0; i < n_queues; i++) {
1955 iter_arr[i] = new HeapRegionRemSetIterator();
1956 }
1957 _rem_set_iterator = iter_arr;
1959 for (int i = 0; i < n_queues; i++) {
1960 RefToScanQueue* q = new RefToScanQueue();
1961 q->initialize();
1962 _task_queues->register_queue(i, q);
1963 }
1965 for (int ap = 0; ap < GCAllocPurposeCount; ++ap) {
1966 _gc_alloc_regions[ap] = NULL;
1967 _gc_alloc_region_counts[ap] = 0;
1968 _retained_gc_alloc_regions[ap] = NULL;
1969 // by default, we do not retain a GC alloc region for each ap;
1970 // we'll override this, when appropriate, below
1971 _retain_gc_alloc_region[ap] = false;
1972 }
1974 // We will try to remember the last half-full tenured region we
1975 // allocated to at the end of a collection so that we can re-use it
1976 // during the next collection.
1977 _retain_gc_alloc_region[GCAllocForTenured] = true;
1979 guarantee(_task_queues != NULL, "task_queues allocation failure.");
1980 }
1982 jint G1CollectedHeap::initialize() {
1983 CollectedHeap::pre_initialize();
1984 os::enable_vtime();
1986 // Necessary to satisfy locking discipline assertions.
1988 MutexLocker x(Heap_lock);
1990 // While there are no constraints in the GC code that HeapWordSize
1991 // be any particular value, there are multiple other areas in the
1992 // system which believe this to be true (e.g. oop->object_size in some
1993 // cases incorrectly returns the size in wordSize units rather than
1994 // HeapWordSize).
1995 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
1997 size_t init_byte_size = collector_policy()->initial_heap_byte_size();
1998 size_t max_byte_size = collector_policy()->max_heap_byte_size();
2000 // Ensure that the sizes are properly aligned.
2001 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
2002 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
2004 _cg1r = new ConcurrentG1Refine();
2006 // Reserve the maximum.
2007 PermanentGenerationSpec* pgs = collector_policy()->permanent_generation();
2008 // Includes the perm-gen.
2010 const size_t total_reserved = max_byte_size + pgs->max_size();
2011 char* addr = Universe::preferred_heap_base(total_reserved, Universe::UnscaledNarrowOop);
2013 ReservedSpace heap_rs(max_byte_size + pgs->max_size(),
2014 HeapRegion::GrainBytes,
2015 UseLargePages, addr);
2017 if (UseCompressedOops) {
2018 if (addr != NULL && !heap_rs.is_reserved()) {
2019 // Failed to reserve at specified address - the requested memory
2020 // region is taken already, for example, by 'java' launcher.
2021 // Try again to reserver heap higher.
2022 addr = Universe::preferred_heap_base(total_reserved, Universe::ZeroBasedNarrowOop);
2023 ReservedSpace heap_rs0(total_reserved, HeapRegion::GrainBytes,
2024 UseLargePages, addr);
2025 if (addr != NULL && !heap_rs0.is_reserved()) {
2026 // Failed to reserve at specified address again - give up.
2027 addr = Universe::preferred_heap_base(total_reserved, Universe::HeapBasedNarrowOop);
2028 assert(addr == NULL, "");
2029 ReservedSpace heap_rs1(total_reserved, HeapRegion::GrainBytes,
2030 UseLargePages, addr);
2031 heap_rs = heap_rs1;
2032 } else {
2033 heap_rs = heap_rs0;
2034 }
2035 }
2036 }
2038 if (!heap_rs.is_reserved()) {
2039 vm_exit_during_initialization("Could not reserve enough space for object heap");
2040 return JNI_ENOMEM;
2041 }
2043 // It is important to do this in a way such that concurrent readers can't
2044 // temporarily think somethings in the heap. (I've actually seen this
2045 // happen in asserts: DLD.)
2046 _reserved.set_word_size(0);
2047 _reserved.set_start((HeapWord*)heap_rs.base());
2048 _reserved.set_end((HeapWord*)(heap_rs.base() + heap_rs.size()));
2050 _expansion_regions = max_byte_size/HeapRegion::GrainBytes;
2052 // Create the gen rem set (and barrier set) for the entire reserved region.
2053 _rem_set = collector_policy()->create_rem_set(_reserved, 2);
2054 set_barrier_set(rem_set()->bs());
2055 if (barrier_set()->is_a(BarrierSet::ModRef)) {
2056 _mr_bs = (ModRefBarrierSet*)_barrier_set;
2057 } else {
2058 vm_exit_during_initialization("G1 requires a mod ref bs.");
2059 return JNI_ENOMEM;
2060 }
2062 // Also create a G1 rem set.
2063 if (mr_bs()->is_a(BarrierSet::CardTableModRef)) {
2064 _g1_rem_set = new G1RemSet(this, (CardTableModRefBS*)mr_bs());
2065 } else {
2066 vm_exit_during_initialization("G1 requires a cardtable mod ref bs.");
2067 return JNI_ENOMEM;
2068 }
2070 // Carve out the G1 part of the heap.
2072 ReservedSpace g1_rs = heap_rs.first_part(max_byte_size);
2073 _g1_reserved = MemRegion((HeapWord*)g1_rs.base(),
2074 g1_rs.size()/HeapWordSize);
2075 ReservedSpace perm_gen_rs = heap_rs.last_part(max_byte_size);
2077 _perm_gen = pgs->init(perm_gen_rs, pgs->init_size(), rem_set());
2079 _g1_storage.initialize(g1_rs, 0);
2080 _g1_committed = MemRegion((HeapWord*)_g1_storage.low(), (size_t) 0);
2081 _g1_max_committed = _g1_committed;
2082 _hrs = new HeapRegionSeq(_expansion_regions);
2083 guarantee(_hrs != NULL, "Couldn't allocate HeapRegionSeq");
2084 guarantee(_cur_alloc_region == NULL, "from constructor");
2086 // 6843694 - ensure that the maximum region index can fit
2087 // in the remembered set structures.
2088 const size_t max_region_idx = ((size_t)1 << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
2089 guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
2091 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
2092 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
2093 guarantee((size_t) HeapRegion::CardsPerRegion < max_cards_per_region,
2094 "too many cards per region");
2096 HeapRegionSet::set_unrealistically_long_length(max_regions() + 1);
2098 _bot_shared = new G1BlockOffsetSharedArray(_reserved,
2099 heap_word_size(init_byte_size));
2101 _g1h = this;
2103 _in_cset_fast_test_length = max_regions();
2104 _in_cset_fast_test_base = NEW_C_HEAP_ARRAY(bool, _in_cset_fast_test_length);
2106 // We're biasing _in_cset_fast_test to avoid subtracting the
2107 // beginning of the heap every time we want to index; basically
2108 // it's the same with what we do with the card table.
2109 _in_cset_fast_test = _in_cset_fast_test_base -
2110 ((size_t) _g1_reserved.start() >> HeapRegion::LogOfHRGrainBytes);
2112 // Clear the _cset_fast_test bitmap in anticipation of adding
2113 // regions to the incremental collection set for the first
2114 // evacuation pause.
2115 clear_cset_fast_test();
2117 // Create the ConcurrentMark data structure and thread.
2118 // (Must do this late, so that "max_regions" is defined.)
2119 _cm = new ConcurrentMark(heap_rs, (int) max_regions());
2120 _cmThread = _cm->cmThread();
2122 // Initialize the from_card cache structure of HeapRegionRemSet.
2123 HeapRegionRemSet::init_heap(max_regions());
2125 // Now expand into the initial heap size.
2126 if (!expand(init_byte_size)) {
2127 vm_exit_during_initialization("Failed to allocate initial heap.");
2128 return JNI_ENOMEM;
2129 }
2131 // Perform any initialization actions delegated to the policy.
2132 g1_policy()->init();
2134 g1_policy()->note_start_of_mark_thread();
2136 _refine_cte_cl =
2137 new RefineCardTableEntryClosure(ConcurrentG1RefineThread::sts(),
2138 g1_rem_set(),
2139 concurrent_g1_refine());
2140 JavaThread::dirty_card_queue_set().set_closure(_refine_cte_cl);
2142 JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon,
2143 SATB_Q_FL_lock,
2144 G1SATBProcessCompletedThreshold,
2145 Shared_SATB_Q_lock);
2147 JavaThread::dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
2148 DirtyCardQ_FL_lock,
2149 concurrent_g1_refine()->yellow_zone(),
2150 concurrent_g1_refine()->red_zone(),
2151 Shared_DirtyCardQ_lock);
2153 if (G1DeferredRSUpdate) {
2154 dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
2155 DirtyCardQ_FL_lock,
2156 -1, // never trigger processing
2157 -1, // no limit on length
2158 Shared_DirtyCardQ_lock,
2159 &JavaThread::dirty_card_queue_set());
2160 }
2162 // Initialize the card queue set used to hold cards containing
2163 // references into the collection set.
2164 _into_cset_dirty_card_queue_set.initialize(DirtyCardQ_CBL_mon,
2165 DirtyCardQ_FL_lock,
2166 -1, // never trigger processing
2167 -1, // no limit on length
2168 Shared_DirtyCardQ_lock,
2169 &JavaThread::dirty_card_queue_set());
2171 // In case we're keeping closure specialization stats, initialize those
2172 // counts and that mechanism.
2173 SpecializationStats::clear();
2175 _gc_alloc_region_list = NULL;
2177 // Do later initialization work for concurrent refinement.
2178 _cg1r->init();
2180 return JNI_OK;
2181 }
2183 void G1CollectedHeap::ref_processing_init() {
2184 // Reference processing in G1 currently works as follows:
2185 //
2186 // * There is only one reference processor instance that
2187 // 'spans' the entire heap. It is created by the code
2188 // below.
2189 // * Reference discovery is not enabled during an incremental
2190 // pause (see 6484982).
2191 // * Discoverered refs are not enqueued nor are they processed
2192 // during an incremental pause (see 6484982).
2193 // * Reference discovery is enabled at initial marking.
2194 // * Reference discovery is disabled and the discovered
2195 // references processed etc during remarking.
2196 // * Reference discovery is MT (see below).
2197 // * Reference discovery requires a barrier (see below).
2198 // * Reference processing is currently not MT (see 6608385).
2199 // * A full GC enables (non-MT) reference discovery and
2200 // processes any discovered references.
2202 SharedHeap::ref_processing_init();
2203 MemRegion mr = reserved_region();
2204 _ref_processor = ReferenceProcessor::create_ref_processor(
2205 mr, // span
2206 false, // Reference discovery is not atomic
2207 true, // mt_discovery
2208 &_is_alive_closure, // is alive closure
2209 // for efficiency
2210 ParallelGCThreads,
2211 ParallelRefProcEnabled,
2212 true); // Setting next fields of discovered
2213 // lists requires a barrier.
2214 }
2216 size_t G1CollectedHeap::capacity() const {
2217 return _g1_committed.byte_size();
2218 }
2220 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl,
2221 DirtyCardQueue* into_cset_dcq,
2222 bool concurrent,
2223 int worker_i) {
2224 // Clean cards in the hot card cache
2225 concurrent_g1_refine()->clean_up_cache(worker_i, g1_rem_set(), into_cset_dcq);
2227 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2228 int n_completed_buffers = 0;
2229 while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) {
2230 n_completed_buffers++;
2231 }
2232 g1_policy()->record_update_rs_processed_buffers(worker_i,
2233 (double) n_completed_buffers);
2234 dcqs.clear_n_completed_buffers();
2235 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!");
2236 }
2239 // Computes the sum of the storage used by the various regions.
2241 size_t G1CollectedHeap::used() const {
2242 assert(Heap_lock->owner() != NULL,
2243 "Should be owned on this thread's behalf.");
2244 size_t result = _summary_bytes_used;
2245 // Read only once in case it is set to NULL concurrently
2246 HeapRegion* hr = _cur_alloc_region;
2247 if (hr != NULL)
2248 result += hr->used();
2249 return result;
2250 }
2252 size_t G1CollectedHeap::used_unlocked() const {
2253 size_t result = _summary_bytes_used;
2254 return result;
2255 }
2257 class SumUsedClosure: public HeapRegionClosure {
2258 size_t _used;
2259 public:
2260 SumUsedClosure() : _used(0) {}
2261 bool doHeapRegion(HeapRegion* r) {
2262 if (!r->continuesHumongous()) {
2263 _used += r->used();
2264 }
2265 return false;
2266 }
2267 size_t result() { return _used; }
2268 };
2270 size_t G1CollectedHeap::recalculate_used() const {
2271 SumUsedClosure blk;
2272 _hrs->iterate(&blk);
2273 return blk.result();
2274 }
2276 #ifndef PRODUCT
2277 class SumUsedRegionsClosure: public HeapRegionClosure {
2278 size_t _num;
2279 public:
2280 SumUsedRegionsClosure() : _num(0) {}
2281 bool doHeapRegion(HeapRegion* r) {
2282 if (r->continuesHumongous() || r->used() > 0 || r->is_gc_alloc_region()) {
2283 _num += 1;
2284 }
2285 return false;
2286 }
2287 size_t result() { return _num; }
2288 };
2290 size_t G1CollectedHeap::recalculate_used_regions() const {
2291 SumUsedRegionsClosure blk;
2292 _hrs->iterate(&blk);
2293 return blk.result();
2294 }
2295 #endif // PRODUCT
2297 size_t G1CollectedHeap::unsafe_max_alloc() {
2298 if (free_regions() > 0) return HeapRegion::GrainBytes;
2299 // otherwise, is there space in the current allocation region?
2301 // We need to store the current allocation region in a local variable
2302 // here. The problem is that this method doesn't take any locks and
2303 // there may be other threads which overwrite the current allocation
2304 // region field. attempt_allocation(), for example, sets it to NULL
2305 // and this can happen *after* the NULL check here but before the call
2306 // to free(), resulting in a SIGSEGV. Note that this doesn't appear
2307 // to be a problem in the optimized build, since the two loads of the
2308 // current allocation region field are optimized away.
2309 HeapRegion* car = _cur_alloc_region;
2311 // FIXME: should iterate over all regions?
2312 if (car == NULL) {
2313 return 0;
2314 }
2315 return car->free();
2316 }
2318 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
2319 return
2320 ((cause == GCCause::_gc_locker && GCLockerInvokesConcurrent) ||
2321 (cause == GCCause::_java_lang_system_gc && ExplicitGCInvokesConcurrent));
2322 }
2324 void G1CollectedHeap::increment_full_collections_completed(bool concurrent) {
2325 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
2327 // We assume that if concurrent == true, then the caller is a
2328 // concurrent thread that was joined the Suspendible Thread
2329 // Set. If there's ever a cheap way to check this, we should add an
2330 // assert here.
2332 // We have already incremented _total_full_collections at the start
2333 // of the GC, so total_full_collections() represents how many full
2334 // collections have been started.
2335 unsigned int full_collections_started = total_full_collections();
2337 // Given that this method is called at the end of a Full GC or of a
2338 // concurrent cycle, and those can be nested (i.e., a Full GC can
2339 // interrupt a concurrent cycle), the number of full collections
2340 // completed should be either one (in the case where there was no
2341 // nesting) or two (when a Full GC interrupted a concurrent cycle)
2342 // behind the number of full collections started.
2344 // This is the case for the inner caller, i.e. a Full GC.
2345 assert(concurrent ||
2346 (full_collections_started == _full_collections_completed + 1) ||
2347 (full_collections_started == _full_collections_completed + 2),
2348 err_msg("for inner caller (Full GC): full_collections_started = %u "
2349 "is inconsistent with _full_collections_completed = %u",
2350 full_collections_started, _full_collections_completed));
2352 // This is the case for the outer caller, i.e. the concurrent cycle.
2353 assert(!concurrent ||
2354 (full_collections_started == _full_collections_completed + 1),
2355 err_msg("for outer caller (concurrent cycle): "
2356 "full_collections_started = %u "
2357 "is inconsistent with _full_collections_completed = %u",
2358 full_collections_started, _full_collections_completed));
2360 _full_collections_completed += 1;
2362 // We need to clear the "in_progress" flag in the CM thread before
2363 // we wake up any waiters (especially when ExplicitInvokesConcurrent
2364 // is set) so that if a waiter requests another System.gc() it doesn't
2365 // incorrectly see that a marking cyle is still in progress.
2366 if (concurrent) {
2367 _cmThread->clear_in_progress();
2368 }
2370 // This notify_all() will ensure that a thread that called
2371 // System.gc() with (with ExplicitGCInvokesConcurrent set or not)
2372 // and it's waiting for a full GC to finish will be woken up. It is
2373 // waiting in VM_G1IncCollectionPause::doit_epilogue().
2374 FullGCCount_lock->notify_all();
2375 }
2377 void G1CollectedHeap::collect_as_vm_thread(GCCause::Cause cause) {
2378 assert_at_safepoint(true /* should_be_vm_thread */);
2379 GCCauseSetter gcs(this, cause);
2380 switch (cause) {
2381 case GCCause::_heap_inspection:
2382 case GCCause::_heap_dump: {
2383 HandleMark hm;
2384 do_full_collection(false); // don't clear all soft refs
2385 break;
2386 }
2387 default: // XXX FIX ME
2388 ShouldNotReachHere(); // Unexpected use of this function
2389 }
2390 }
2392 void G1CollectedHeap::collect(GCCause::Cause cause) {
2393 // The caller doesn't have the Heap_lock
2394 assert(!Heap_lock->owned_by_self(), "this thread should not own the Heap_lock");
2396 unsigned int gc_count_before;
2397 unsigned int full_gc_count_before;
2398 {
2399 MutexLocker ml(Heap_lock);
2401 // Read the GC count while holding the Heap_lock
2402 gc_count_before = SharedHeap::heap()->total_collections();
2403 full_gc_count_before = SharedHeap::heap()->total_full_collections();
2404 }
2406 if (should_do_concurrent_full_gc(cause)) {
2407 // Schedule an initial-mark evacuation pause that will start a
2408 // concurrent cycle. We're setting word_size to 0 which means that
2409 // we are not requesting a post-GC allocation.
2410 VM_G1IncCollectionPause op(gc_count_before,
2411 0, /* word_size */
2412 true, /* should_initiate_conc_mark */
2413 g1_policy()->max_pause_time_ms(),
2414 cause);
2415 VMThread::execute(&op);
2416 } else {
2417 if (cause == GCCause::_gc_locker
2418 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2420 // Schedule a standard evacuation pause. We're setting word_size
2421 // to 0 which means that we are not requesting a post-GC allocation.
2422 VM_G1IncCollectionPause op(gc_count_before,
2423 0, /* word_size */
2424 false, /* should_initiate_conc_mark */
2425 g1_policy()->max_pause_time_ms(),
2426 cause);
2427 VMThread::execute(&op);
2428 } else {
2429 // Schedule a Full GC.
2430 VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause);
2431 VMThread::execute(&op);
2432 }
2433 }
2434 }
2436 bool G1CollectedHeap::is_in(const void* p) const {
2437 if (_g1_committed.contains(p)) {
2438 HeapRegion* hr = _hrs->addr_to_region(p);
2439 return hr->is_in(p);
2440 } else {
2441 return _perm_gen->as_gen()->is_in(p);
2442 }
2443 }
2445 // Iteration functions.
2447 // Iterates an OopClosure over all ref-containing fields of objects
2448 // within a HeapRegion.
2450 class IterateOopClosureRegionClosure: public HeapRegionClosure {
2451 MemRegion _mr;
2452 OopClosure* _cl;
2453 public:
2454 IterateOopClosureRegionClosure(MemRegion mr, OopClosure* cl)
2455 : _mr(mr), _cl(cl) {}
2456 bool doHeapRegion(HeapRegion* r) {
2457 if (! r->continuesHumongous()) {
2458 r->oop_iterate(_cl);
2459 }
2460 return false;
2461 }
2462 };
2464 void G1CollectedHeap::oop_iterate(OopClosure* cl, bool do_perm) {
2465 IterateOopClosureRegionClosure blk(_g1_committed, cl);
2466 _hrs->iterate(&blk);
2467 if (do_perm) {
2468 perm_gen()->oop_iterate(cl);
2469 }
2470 }
2472 void G1CollectedHeap::oop_iterate(MemRegion mr, OopClosure* cl, bool do_perm) {
2473 IterateOopClosureRegionClosure blk(mr, cl);
2474 _hrs->iterate(&blk);
2475 if (do_perm) {
2476 perm_gen()->oop_iterate(cl);
2477 }
2478 }
2480 // Iterates an ObjectClosure over all objects within a HeapRegion.
2482 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2483 ObjectClosure* _cl;
2484 public:
2485 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2486 bool doHeapRegion(HeapRegion* r) {
2487 if (! r->continuesHumongous()) {
2488 r->object_iterate(_cl);
2489 }
2490 return false;
2491 }
2492 };
2494 void G1CollectedHeap::object_iterate(ObjectClosure* cl, bool do_perm) {
2495 IterateObjectClosureRegionClosure blk(cl);
2496 _hrs->iterate(&blk);
2497 if (do_perm) {
2498 perm_gen()->object_iterate(cl);
2499 }
2500 }
2502 void G1CollectedHeap::object_iterate_since_last_GC(ObjectClosure* cl) {
2503 // FIXME: is this right?
2504 guarantee(false, "object_iterate_since_last_GC not supported by G1 heap");
2505 }
2507 // Calls a SpaceClosure on a HeapRegion.
2509 class SpaceClosureRegionClosure: public HeapRegionClosure {
2510 SpaceClosure* _cl;
2511 public:
2512 SpaceClosureRegionClosure(SpaceClosure* cl) : _cl(cl) {}
2513 bool doHeapRegion(HeapRegion* r) {
2514 _cl->do_space(r);
2515 return false;
2516 }
2517 };
2519 void G1CollectedHeap::space_iterate(SpaceClosure* cl) {
2520 SpaceClosureRegionClosure blk(cl);
2521 _hrs->iterate(&blk);
2522 }
2524 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) {
2525 _hrs->iterate(cl);
2526 }
2528 void G1CollectedHeap::heap_region_iterate_from(HeapRegion* r,
2529 HeapRegionClosure* cl) {
2530 _hrs->iterate_from(r, cl);
2531 }
2533 void
2534 G1CollectedHeap::heap_region_iterate_from(int idx, HeapRegionClosure* cl) {
2535 _hrs->iterate_from(idx, cl);
2536 }
2538 HeapRegion* G1CollectedHeap::region_at(size_t idx) { return _hrs->at(idx); }
2540 void
2541 G1CollectedHeap::heap_region_par_iterate_chunked(HeapRegionClosure* cl,
2542 int worker,
2543 jint claim_value) {
2544 const size_t regions = n_regions();
2545 const size_t worker_num = (G1CollectedHeap::use_parallel_gc_threads() ? ParallelGCThreads : 1);
2546 // try to spread out the starting points of the workers
2547 const size_t start_index = regions / worker_num * (size_t) worker;
2549 // each worker will actually look at all regions
2550 for (size_t count = 0; count < regions; ++count) {
2551 const size_t index = (start_index + count) % regions;
2552 assert(0 <= index && index < regions, "sanity");
2553 HeapRegion* r = region_at(index);
2554 // we'll ignore "continues humongous" regions (we'll process them
2555 // when we come across their corresponding "start humongous"
2556 // region) and regions already claimed
2557 if (r->claim_value() == claim_value || r->continuesHumongous()) {
2558 continue;
2559 }
2560 // OK, try to claim it
2561 if (r->claimHeapRegion(claim_value)) {
2562 // success!
2563 assert(!r->continuesHumongous(), "sanity");
2564 if (r->startsHumongous()) {
2565 // If the region is "starts humongous" we'll iterate over its
2566 // "continues humongous" first; in fact we'll do them
2567 // first. The order is important. In on case, calling the
2568 // closure on the "starts humongous" region might de-allocate
2569 // and clear all its "continues humongous" regions and, as a
2570 // result, we might end up processing them twice. So, we'll do
2571 // them first (notice: most closures will ignore them anyway) and
2572 // then we'll do the "starts humongous" region.
2573 for (size_t ch_index = index + 1; ch_index < regions; ++ch_index) {
2574 HeapRegion* chr = region_at(ch_index);
2576 // if the region has already been claimed or it's not
2577 // "continues humongous" we're done
2578 if (chr->claim_value() == claim_value ||
2579 !chr->continuesHumongous()) {
2580 break;
2581 }
2583 // Noone should have claimed it directly. We can given
2584 // that we claimed its "starts humongous" region.
2585 assert(chr->claim_value() != claim_value, "sanity");
2586 assert(chr->humongous_start_region() == r, "sanity");
2588 if (chr->claimHeapRegion(claim_value)) {
2589 // we should always be able to claim it; noone else should
2590 // be trying to claim this region
2592 bool res2 = cl->doHeapRegion(chr);
2593 assert(!res2, "Should not abort");
2595 // Right now, this holds (i.e., no closure that actually
2596 // does something with "continues humongous" regions
2597 // clears them). We might have to weaken it in the future,
2598 // but let's leave these two asserts here for extra safety.
2599 assert(chr->continuesHumongous(), "should still be the case");
2600 assert(chr->humongous_start_region() == r, "sanity");
2601 } else {
2602 guarantee(false, "we should not reach here");
2603 }
2604 }
2605 }
2607 assert(!r->continuesHumongous(), "sanity");
2608 bool res = cl->doHeapRegion(r);
2609 assert(!res, "Should not abort");
2610 }
2611 }
2612 }
2614 class ResetClaimValuesClosure: public HeapRegionClosure {
2615 public:
2616 bool doHeapRegion(HeapRegion* r) {
2617 r->set_claim_value(HeapRegion::InitialClaimValue);
2618 return false;
2619 }
2620 };
2622 void
2623 G1CollectedHeap::reset_heap_region_claim_values() {
2624 ResetClaimValuesClosure blk;
2625 heap_region_iterate(&blk);
2626 }
2628 #ifdef ASSERT
2629 // This checks whether all regions in the heap have the correct claim
2630 // value. I also piggy-backed on this a check to ensure that the
2631 // humongous_start_region() information on "continues humongous"
2632 // regions is correct.
2634 class CheckClaimValuesClosure : public HeapRegionClosure {
2635 private:
2636 jint _claim_value;
2637 size_t _failures;
2638 HeapRegion* _sh_region;
2639 public:
2640 CheckClaimValuesClosure(jint claim_value) :
2641 _claim_value(claim_value), _failures(0), _sh_region(NULL) { }
2642 bool doHeapRegion(HeapRegion* r) {
2643 if (r->claim_value() != _claim_value) {
2644 gclog_or_tty->print_cr("Region ["PTR_FORMAT","PTR_FORMAT"), "
2645 "claim value = %d, should be %d",
2646 r->bottom(), r->end(), r->claim_value(),
2647 _claim_value);
2648 ++_failures;
2649 }
2650 if (!r->isHumongous()) {
2651 _sh_region = NULL;
2652 } else if (r->startsHumongous()) {
2653 _sh_region = r;
2654 } else if (r->continuesHumongous()) {
2655 if (r->humongous_start_region() != _sh_region) {
2656 gclog_or_tty->print_cr("Region ["PTR_FORMAT","PTR_FORMAT"), "
2657 "HS = "PTR_FORMAT", should be "PTR_FORMAT,
2658 r->bottom(), r->end(),
2659 r->humongous_start_region(),
2660 _sh_region);
2661 ++_failures;
2662 }
2663 }
2664 return false;
2665 }
2666 size_t failures() {
2667 return _failures;
2668 }
2669 };
2671 bool G1CollectedHeap::check_heap_region_claim_values(jint claim_value) {
2672 CheckClaimValuesClosure cl(claim_value);
2673 heap_region_iterate(&cl);
2674 return cl.failures() == 0;
2675 }
2676 #endif // ASSERT
2678 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) {
2679 HeapRegion* r = g1_policy()->collection_set();
2680 while (r != NULL) {
2681 HeapRegion* next = r->next_in_collection_set();
2682 if (cl->doHeapRegion(r)) {
2683 cl->incomplete();
2684 return;
2685 }
2686 r = next;
2687 }
2688 }
2690 void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r,
2691 HeapRegionClosure *cl) {
2692 if (r == NULL) {
2693 // The CSet is empty so there's nothing to do.
2694 return;
2695 }
2697 assert(r->in_collection_set(),
2698 "Start region must be a member of the collection set.");
2699 HeapRegion* cur = r;
2700 while (cur != NULL) {
2701 HeapRegion* next = cur->next_in_collection_set();
2702 if (cl->doHeapRegion(cur) && false) {
2703 cl->incomplete();
2704 return;
2705 }
2706 cur = next;
2707 }
2708 cur = g1_policy()->collection_set();
2709 while (cur != r) {
2710 HeapRegion* next = cur->next_in_collection_set();
2711 if (cl->doHeapRegion(cur) && false) {
2712 cl->incomplete();
2713 return;
2714 }
2715 cur = next;
2716 }
2717 }
2719 CompactibleSpace* G1CollectedHeap::first_compactible_space() {
2720 return _hrs->length() > 0 ? _hrs->at(0) : NULL;
2721 }
2724 Space* G1CollectedHeap::space_containing(const void* addr) const {
2725 Space* res = heap_region_containing(addr);
2726 if (res == NULL)
2727 res = perm_gen()->space_containing(addr);
2728 return res;
2729 }
2731 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2732 Space* sp = space_containing(addr);
2733 if (sp != NULL) {
2734 return sp->block_start(addr);
2735 }
2736 return NULL;
2737 }
2739 size_t G1CollectedHeap::block_size(const HeapWord* addr) const {
2740 Space* sp = space_containing(addr);
2741 assert(sp != NULL, "block_size of address outside of heap");
2742 return sp->block_size(addr);
2743 }
2745 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2746 Space* sp = space_containing(addr);
2747 return sp->block_is_obj(addr);
2748 }
2750 bool G1CollectedHeap::supports_tlab_allocation() const {
2751 return true;
2752 }
2754 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
2755 return HeapRegion::GrainBytes;
2756 }
2758 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
2759 // Return the remaining space in the cur alloc region, but not less than
2760 // the min TLAB size.
2762 // Also, this value can be at most the humongous object threshold,
2763 // since we can't allow tlabs to grow big enough to accomodate
2764 // humongous objects.
2766 // We need to store the cur alloc region locally, since it might change
2767 // between when we test for NULL and when we use it later.
2768 ContiguousSpace* cur_alloc_space = _cur_alloc_region;
2769 size_t max_tlab_size = _humongous_object_threshold_in_words * wordSize;
2771 if (cur_alloc_space == NULL) {
2772 return max_tlab_size;
2773 } else {
2774 return MIN2(MAX2(cur_alloc_space->free(), (size_t)MinTLABSize),
2775 max_tlab_size);
2776 }
2777 }
2779 size_t G1CollectedHeap::large_typearray_limit() {
2780 // FIXME
2781 return HeapRegion::GrainBytes/HeapWordSize;
2782 }
2784 size_t G1CollectedHeap::max_capacity() const {
2785 return _g1_reserved.byte_size();
2786 }
2788 jlong G1CollectedHeap::millis_since_last_gc() {
2789 // assert(false, "NYI");
2790 return 0;
2791 }
2793 void G1CollectedHeap::prepare_for_verify() {
2794 if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) {
2795 ensure_parsability(false);
2796 }
2797 g1_rem_set()->prepare_for_verify();
2798 }
2800 class VerifyLivenessOopClosure: public OopClosure {
2801 G1CollectedHeap* g1h;
2802 public:
2803 VerifyLivenessOopClosure(G1CollectedHeap* _g1h) {
2804 g1h = _g1h;
2805 }
2806 void do_oop(narrowOop *p) { do_oop_work(p); }
2807 void do_oop( oop *p) { do_oop_work(p); }
2809 template <class T> void do_oop_work(T *p) {
2810 oop obj = oopDesc::load_decode_heap_oop(p);
2811 guarantee(obj == NULL || !g1h->is_obj_dead(obj),
2812 "Dead object referenced by a not dead object");
2813 }
2814 };
2816 class VerifyObjsInRegionClosure: public ObjectClosure {
2817 private:
2818 G1CollectedHeap* _g1h;
2819 size_t _live_bytes;
2820 HeapRegion *_hr;
2821 bool _use_prev_marking;
2822 public:
2823 // use_prev_marking == true -> use "prev" marking information,
2824 // use_prev_marking == false -> use "next" marking information
2825 VerifyObjsInRegionClosure(HeapRegion *hr, bool use_prev_marking)
2826 : _live_bytes(0), _hr(hr), _use_prev_marking(use_prev_marking) {
2827 _g1h = G1CollectedHeap::heap();
2828 }
2829 void do_object(oop o) {
2830 VerifyLivenessOopClosure isLive(_g1h);
2831 assert(o != NULL, "Huh?");
2832 if (!_g1h->is_obj_dead_cond(o, _use_prev_marking)) {
2833 o->oop_iterate(&isLive);
2834 if (!_hr->obj_allocated_since_prev_marking(o)) {
2835 size_t obj_size = o->size(); // Make sure we don't overflow
2836 _live_bytes += (obj_size * HeapWordSize);
2837 }
2838 }
2839 }
2840 size_t live_bytes() { return _live_bytes; }
2841 };
2843 class PrintObjsInRegionClosure : public ObjectClosure {
2844 HeapRegion *_hr;
2845 G1CollectedHeap *_g1;
2846 public:
2847 PrintObjsInRegionClosure(HeapRegion *hr) : _hr(hr) {
2848 _g1 = G1CollectedHeap::heap();
2849 };
2851 void do_object(oop o) {
2852 if (o != NULL) {
2853 HeapWord *start = (HeapWord *) o;
2854 size_t word_sz = o->size();
2855 gclog_or_tty->print("\nPrinting obj "PTR_FORMAT" of size " SIZE_FORMAT
2856 " isMarkedPrev %d isMarkedNext %d isAllocSince %d\n",
2857 (void*) o, word_sz,
2858 _g1->isMarkedPrev(o),
2859 _g1->isMarkedNext(o),
2860 _hr->obj_allocated_since_prev_marking(o));
2861 HeapWord *end = start + word_sz;
2862 HeapWord *cur;
2863 int *val;
2864 for (cur = start; cur < end; cur++) {
2865 val = (int *) cur;
2866 gclog_or_tty->print("\t "PTR_FORMAT":"PTR_FORMAT"\n", val, *val);
2867 }
2868 }
2869 }
2870 };
2872 class VerifyRegionClosure: public HeapRegionClosure {
2873 private:
2874 bool _allow_dirty;
2875 bool _par;
2876 bool _use_prev_marking;
2877 bool _failures;
2878 public:
2879 // use_prev_marking == true -> use "prev" marking information,
2880 // use_prev_marking == false -> use "next" marking information
2881 VerifyRegionClosure(bool allow_dirty, bool par, bool use_prev_marking)
2882 : _allow_dirty(allow_dirty),
2883 _par(par),
2884 _use_prev_marking(use_prev_marking),
2885 _failures(false) {}
2887 bool failures() {
2888 return _failures;
2889 }
2891 bool doHeapRegion(HeapRegion* r) {
2892 guarantee(_par || r->claim_value() == HeapRegion::InitialClaimValue,
2893 "Should be unclaimed at verify points.");
2894 if (!r->continuesHumongous()) {
2895 bool failures = false;
2896 r->verify(_allow_dirty, _use_prev_marking, &failures);
2897 if (failures) {
2898 _failures = true;
2899 } else {
2900 VerifyObjsInRegionClosure not_dead_yet_cl(r, _use_prev_marking);
2901 r->object_iterate(¬_dead_yet_cl);
2902 if (r->max_live_bytes() < not_dead_yet_cl.live_bytes()) {
2903 gclog_or_tty->print_cr("["PTR_FORMAT","PTR_FORMAT"] "
2904 "max_live_bytes "SIZE_FORMAT" "
2905 "< calculated "SIZE_FORMAT,
2906 r->bottom(), r->end(),
2907 r->max_live_bytes(),
2908 not_dead_yet_cl.live_bytes());
2909 _failures = true;
2910 }
2911 }
2912 }
2913 return false; // stop the region iteration if we hit a failure
2914 }
2915 };
2917 class VerifyRootsClosure: public OopsInGenClosure {
2918 private:
2919 G1CollectedHeap* _g1h;
2920 bool _use_prev_marking;
2921 bool _failures;
2922 public:
2923 // use_prev_marking == true -> use "prev" marking information,
2924 // use_prev_marking == false -> use "next" marking information
2925 VerifyRootsClosure(bool use_prev_marking) :
2926 _g1h(G1CollectedHeap::heap()),
2927 _use_prev_marking(use_prev_marking),
2928 _failures(false) { }
2930 bool failures() { return _failures; }
2932 template <class T> void do_oop_nv(T* p) {
2933 T heap_oop = oopDesc::load_heap_oop(p);
2934 if (!oopDesc::is_null(heap_oop)) {
2935 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
2936 if (_g1h->is_obj_dead_cond(obj, _use_prev_marking)) {
2937 gclog_or_tty->print_cr("Root location "PTR_FORMAT" "
2938 "points to dead obj "PTR_FORMAT, p, (void*) obj);
2939 obj->print_on(gclog_or_tty);
2940 _failures = true;
2941 }
2942 }
2943 }
2945 void do_oop(oop* p) { do_oop_nv(p); }
2946 void do_oop(narrowOop* p) { do_oop_nv(p); }
2947 };
2949 // This is the task used for parallel heap verification.
2951 class G1ParVerifyTask: public AbstractGangTask {
2952 private:
2953 G1CollectedHeap* _g1h;
2954 bool _allow_dirty;
2955 bool _use_prev_marking;
2956 bool _failures;
2958 public:
2959 // use_prev_marking == true -> use "prev" marking information,
2960 // use_prev_marking == false -> use "next" marking information
2961 G1ParVerifyTask(G1CollectedHeap* g1h, bool allow_dirty,
2962 bool use_prev_marking) :
2963 AbstractGangTask("Parallel verify task"),
2964 _g1h(g1h),
2965 _allow_dirty(allow_dirty),
2966 _use_prev_marking(use_prev_marking),
2967 _failures(false) { }
2969 bool failures() {
2970 return _failures;
2971 }
2973 void work(int worker_i) {
2974 HandleMark hm;
2975 VerifyRegionClosure blk(_allow_dirty, true, _use_prev_marking);
2976 _g1h->heap_region_par_iterate_chunked(&blk, worker_i,
2977 HeapRegion::ParVerifyClaimValue);
2978 if (blk.failures()) {
2979 _failures = true;
2980 }
2981 }
2982 };
2984 void G1CollectedHeap::verify(bool allow_dirty, bool silent) {
2985 verify(allow_dirty, silent, /* use_prev_marking */ true);
2986 }
2988 void G1CollectedHeap::verify(bool allow_dirty,
2989 bool silent,
2990 bool use_prev_marking) {
2991 if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) {
2992 if (!silent) { gclog_or_tty->print("roots "); }
2993 VerifyRootsClosure rootsCl(use_prev_marking);
2994 CodeBlobToOopClosure blobsCl(&rootsCl, /*do_marking=*/ false);
2995 process_strong_roots(true, // activate StrongRootsScope
2996 false,
2997 SharedHeap::SO_AllClasses,
2998 &rootsCl,
2999 &blobsCl,
3000 &rootsCl);
3001 bool failures = rootsCl.failures();
3002 rem_set()->invalidate(perm_gen()->used_region(), false);
3003 if (!silent) { gclog_or_tty->print("HeapRegionSets "); }
3004 verify_region_sets();
3005 if (!silent) { gclog_or_tty->print("HeapRegions "); }
3006 if (GCParallelVerificationEnabled && ParallelGCThreads > 1) {
3007 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3008 "sanity check");
3010 G1ParVerifyTask task(this, allow_dirty, use_prev_marking);
3011 int n_workers = workers()->total_workers();
3012 set_par_threads(n_workers);
3013 workers()->run_task(&task);
3014 set_par_threads(0);
3015 if (task.failures()) {
3016 failures = true;
3017 }
3019 assert(check_heap_region_claim_values(HeapRegion::ParVerifyClaimValue),
3020 "sanity check");
3022 reset_heap_region_claim_values();
3024 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3025 "sanity check");
3026 } else {
3027 VerifyRegionClosure blk(allow_dirty, false, use_prev_marking);
3028 _hrs->iterate(&blk);
3029 if (blk.failures()) {
3030 failures = true;
3031 }
3032 }
3033 if (!silent) gclog_or_tty->print("RemSet ");
3034 rem_set()->verify();
3036 if (failures) {
3037 gclog_or_tty->print_cr("Heap:");
3038 print_on(gclog_or_tty, true /* extended */);
3039 gclog_or_tty->print_cr("");
3040 #ifndef PRODUCT
3041 if (VerifyDuringGC && G1VerifyDuringGCPrintReachable) {
3042 concurrent_mark()->print_reachable("at-verification-failure",
3043 use_prev_marking, false /* all */);
3044 }
3045 #endif
3046 gclog_or_tty->flush();
3047 }
3048 guarantee(!failures, "there should not have been any failures");
3049 } else {
3050 if (!silent) gclog_or_tty->print("(SKIPPING roots, heapRegions, remset) ");
3051 }
3052 }
3054 class PrintRegionClosure: public HeapRegionClosure {
3055 outputStream* _st;
3056 public:
3057 PrintRegionClosure(outputStream* st) : _st(st) {}
3058 bool doHeapRegion(HeapRegion* r) {
3059 r->print_on(_st);
3060 return false;
3061 }
3062 };
3064 void G1CollectedHeap::print() const { print_on(tty); }
3066 void G1CollectedHeap::print_on(outputStream* st) const {
3067 print_on(st, PrintHeapAtGCExtended);
3068 }
3070 void G1CollectedHeap::print_on(outputStream* st, bool extended) const {
3071 st->print(" %-20s", "garbage-first heap");
3072 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
3073 capacity()/K, used_unlocked()/K);
3074 st->print(" [" INTPTR_FORMAT ", " INTPTR_FORMAT ", " INTPTR_FORMAT ")",
3075 _g1_storage.low_boundary(),
3076 _g1_storage.high(),
3077 _g1_storage.high_boundary());
3078 st->cr();
3079 st->print(" region size " SIZE_FORMAT "K, ",
3080 HeapRegion::GrainBytes/K);
3081 size_t young_regions = _young_list->length();
3082 st->print(SIZE_FORMAT " young (" SIZE_FORMAT "K), ",
3083 young_regions, young_regions * HeapRegion::GrainBytes / K);
3084 size_t survivor_regions = g1_policy()->recorded_survivor_regions();
3085 st->print(SIZE_FORMAT " survivors (" SIZE_FORMAT "K)",
3086 survivor_regions, survivor_regions * HeapRegion::GrainBytes / K);
3087 st->cr();
3088 perm()->as_gen()->print_on(st);
3089 if (extended) {
3090 st->cr();
3091 print_on_extended(st);
3092 }
3093 }
3095 void G1CollectedHeap::print_on_extended(outputStream* st) const {
3096 PrintRegionClosure blk(st);
3097 _hrs->iterate(&blk);
3098 }
3100 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
3101 if (G1CollectedHeap::use_parallel_gc_threads()) {
3102 workers()->print_worker_threads_on(st);
3103 }
3104 _cmThread->print_on(st);
3105 st->cr();
3106 _cm->print_worker_threads_on(st);
3107 _cg1r->print_worker_threads_on(st);
3108 st->cr();
3109 }
3111 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
3112 if (G1CollectedHeap::use_parallel_gc_threads()) {
3113 workers()->threads_do(tc);
3114 }
3115 tc->do_thread(_cmThread);
3116 _cg1r->threads_do(tc);
3117 }
3119 void G1CollectedHeap::print_tracing_info() const {
3120 // We'll overload this to mean "trace GC pause statistics."
3121 if (TraceGen0Time || TraceGen1Time) {
3122 // The "G1CollectorPolicy" is keeping track of these stats, so delegate
3123 // to that.
3124 g1_policy()->print_tracing_info();
3125 }
3126 if (G1SummarizeRSetStats) {
3127 g1_rem_set()->print_summary_info();
3128 }
3129 if (G1SummarizeConcMark) {
3130 concurrent_mark()->print_summary_info();
3131 }
3132 g1_policy()->print_yg_surv_rate_info();
3133 SpecializationStats::print();
3134 }
3136 int G1CollectedHeap::addr_to_arena_id(void* addr) const {
3137 HeapRegion* hr = heap_region_containing(addr);
3138 if (hr == NULL) {
3139 return 0;
3140 } else {
3141 return 1;
3142 }
3143 }
3145 G1CollectedHeap* G1CollectedHeap::heap() {
3146 assert(_sh->kind() == CollectedHeap::G1CollectedHeap,
3147 "not a garbage-first heap");
3148 return _g1h;
3149 }
3151 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) {
3152 // always_do_update_barrier = false;
3153 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
3154 // Call allocation profiler
3155 AllocationProfiler::iterate_since_last_gc();
3156 // Fill TLAB's and such
3157 ensure_parsability(true);
3158 }
3160 void G1CollectedHeap::gc_epilogue(bool full /* Ignored */) {
3161 // FIXME: what is this about?
3162 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
3163 // is set.
3164 COMPILER2_PRESENT(assert(DerivedPointerTable::is_empty(),
3165 "derived pointer present"));
3166 // always_do_update_barrier = true;
3167 }
3169 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
3170 unsigned int gc_count_before,
3171 bool* succeeded) {
3172 assert_heap_not_locked_and_not_at_safepoint();
3173 g1_policy()->record_stop_world_start();
3174 VM_G1IncCollectionPause op(gc_count_before,
3175 word_size,
3176 false, /* should_initiate_conc_mark */
3177 g1_policy()->max_pause_time_ms(),
3178 GCCause::_g1_inc_collection_pause);
3179 VMThread::execute(&op);
3181 HeapWord* result = op.result();
3182 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
3183 assert(result == NULL || ret_succeeded,
3184 "the result should be NULL if the VM did not succeed");
3185 *succeeded = ret_succeeded;
3187 assert_heap_not_locked();
3188 return result;
3189 }
3191 void
3192 G1CollectedHeap::doConcurrentMark() {
3193 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
3194 if (!_cmThread->in_progress()) {
3195 _cmThread->set_started();
3196 CGC_lock->notify();
3197 }
3198 }
3200 class VerifyMarkedObjsClosure: public ObjectClosure {
3201 G1CollectedHeap* _g1h;
3202 public:
3203 VerifyMarkedObjsClosure(G1CollectedHeap* g1h) : _g1h(g1h) {}
3204 void do_object(oop obj) {
3205 assert(obj->mark()->is_marked() ? !_g1h->is_obj_dead(obj) : true,
3206 "markandsweep mark should agree with concurrent deadness");
3207 }
3208 };
3210 void
3211 G1CollectedHeap::checkConcurrentMark() {
3212 VerifyMarkedObjsClosure verifycl(this);
3213 // MutexLockerEx x(getMarkBitMapLock(),
3214 // Mutex::_no_safepoint_check_flag);
3215 object_iterate(&verifycl, false);
3216 }
3218 void G1CollectedHeap::do_sync_mark() {
3219 _cm->checkpointRootsInitial();
3220 _cm->markFromRoots();
3221 _cm->checkpointRootsFinal(false);
3222 }
3224 // <NEW PREDICTION>
3226 double G1CollectedHeap::predict_region_elapsed_time_ms(HeapRegion *hr,
3227 bool young) {
3228 return _g1_policy->predict_region_elapsed_time_ms(hr, young);
3229 }
3231 void G1CollectedHeap::check_if_region_is_too_expensive(double
3232 predicted_time_ms) {
3233 _g1_policy->check_if_region_is_too_expensive(predicted_time_ms);
3234 }
3236 size_t G1CollectedHeap::pending_card_num() {
3237 size_t extra_cards = 0;
3238 JavaThread *curr = Threads::first();
3239 while (curr != NULL) {
3240 DirtyCardQueue& dcq = curr->dirty_card_queue();
3241 extra_cards += dcq.size();
3242 curr = curr->next();
3243 }
3244 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
3245 size_t buffer_size = dcqs.buffer_size();
3246 size_t buffer_num = dcqs.completed_buffers_num();
3247 return buffer_size * buffer_num + extra_cards;
3248 }
3250 size_t G1CollectedHeap::max_pending_card_num() {
3251 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
3252 size_t buffer_size = dcqs.buffer_size();
3253 size_t buffer_num = dcqs.completed_buffers_num();
3254 int thread_num = Threads::number_of_threads();
3255 return (buffer_num + thread_num) * buffer_size;
3256 }
3258 size_t G1CollectedHeap::cards_scanned() {
3259 return g1_rem_set()->cardsScanned();
3260 }
3262 void
3263 G1CollectedHeap::setup_surviving_young_words() {
3264 guarantee( _surviving_young_words == NULL, "pre-condition" );
3265 size_t array_length = g1_policy()->young_cset_length();
3266 _surviving_young_words = NEW_C_HEAP_ARRAY(size_t, array_length);
3267 if (_surviving_young_words == NULL) {
3268 vm_exit_out_of_memory(sizeof(size_t) * array_length,
3269 "Not enough space for young surv words summary.");
3270 }
3271 memset(_surviving_young_words, 0, array_length * sizeof(size_t));
3272 #ifdef ASSERT
3273 for (size_t i = 0; i < array_length; ++i) {
3274 assert( _surviving_young_words[i] == 0, "memset above" );
3275 }
3276 #endif // !ASSERT
3277 }
3279 void
3280 G1CollectedHeap::update_surviving_young_words(size_t* surv_young_words) {
3281 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
3282 size_t array_length = g1_policy()->young_cset_length();
3283 for (size_t i = 0; i < array_length; ++i)
3284 _surviving_young_words[i] += surv_young_words[i];
3285 }
3287 void
3288 G1CollectedHeap::cleanup_surviving_young_words() {
3289 guarantee( _surviving_young_words != NULL, "pre-condition" );
3290 FREE_C_HEAP_ARRAY(size_t, _surviving_young_words);
3291 _surviving_young_words = NULL;
3292 }
3294 // </NEW PREDICTION>
3296 struct PrepareForRSScanningClosure : public HeapRegionClosure {
3297 bool doHeapRegion(HeapRegion *r) {
3298 r->rem_set()->set_iter_claimed(0);
3299 return false;
3300 }
3301 };
3303 #if TASKQUEUE_STATS
3304 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
3305 st->print_raw_cr("GC Task Stats");
3306 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
3307 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
3308 }
3310 void G1CollectedHeap::print_taskqueue_stats(outputStream* const st) const {
3311 print_taskqueue_stats_hdr(st);
3313 TaskQueueStats totals;
3314 const int n = workers() != NULL ? workers()->total_workers() : 1;
3315 for (int i = 0; i < n; ++i) {
3316 st->print("%3d ", i); task_queue(i)->stats.print(st); st->cr();
3317 totals += task_queue(i)->stats;
3318 }
3319 st->print_raw("tot "); totals.print(st); st->cr();
3321 DEBUG_ONLY(totals.verify());
3322 }
3324 void G1CollectedHeap::reset_taskqueue_stats() {
3325 const int n = workers() != NULL ? workers()->total_workers() : 1;
3326 for (int i = 0; i < n; ++i) {
3327 task_queue(i)->stats.reset();
3328 }
3329 }
3330 #endif // TASKQUEUE_STATS
3332 bool
3333 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
3334 assert_at_safepoint(true /* should_be_vm_thread */);
3335 guarantee(!is_gc_active(), "collection is not reentrant");
3337 if (GC_locker::check_active_before_gc()) {
3338 return false;
3339 }
3341 SvcGCMarker sgcm(SvcGCMarker::MINOR);
3342 ResourceMark rm;
3344 if (PrintHeapAtGC) {
3345 Universe::print_heap_before_gc();
3346 }
3348 verify_region_sets_optional();
3350 {
3351 // This call will decide whether this pause is an initial-mark
3352 // pause. If it is, during_initial_mark_pause() will return true
3353 // for the duration of this pause.
3354 g1_policy()->decide_on_conc_mark_initiation();
3356 char verbose_str[128];
3357 sprintf(verbose_str, "GC pause ");
3358 if (g1_policy()->in_young_gc_mode()) {
3359 if (g1_policy()->full_young_gcs())
3360 strcat(verbose_str, "(young)");
3361 else
3362 strcat(verbose_str, "(partial)");
3363 }
3364 if (g1_policy()->during_initial_mark_pause()) {
3365 strcat(verbose_str, " (initial-mark)");
3366 // We are about to start a marking cycle, so we increment the
3367 // full collection counter.
3368 increment_total_full_collections();
3369 }
3371 // if PrintGCDetails is on, we'll print long statistics information
3372 // in the collector policy code, so let's not print this as the output
3373 // is messy if we do.
3374 gclog_or_tty->date_stamp(PrintGC && PrintGCDateStamps);
3375 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty);
3376 TraceTime t(verbose_str, PrintGC && !PrintGCDetails, true, gclog_or_tty);
3378 TraceMemoryManagerStats tms(false /* fullGC */);
3380 // If there are any free regions available on the secondary_free_list
3381 // make sure we append them to the free_list. However, we don't
3382 // have to wait for the rest of the cleanup operation to
3383 // finish. If it's still going on that's OK. If we run out of
3384 // regions, the region allocation code will check the
3385 // secondary_free_list and potentially wait if more free regions
3386 // are coming (see new_region_try_secondary_free_list()).
3387 if (!G1StressConcRegionFreeing) {
3388 append_secondary_free_list_if_not_empty();
3389 }
3391 increment_gc_time_stamp();
3393 if (g1_policy()->in_young_gc_mode()) {
3394 assert(check_young_list_well_formed(),
3395 "young list should be well formed");
3396 }
3398 { // Call to jvmpi::post_class_unload_events must occur outside of active GC
3399 IsGCActiveMark x;
3401 gc_prologue(false);
3402 increment_total_collections(false /* full gc */);
3404 #if G1_REM_SET_LOGGING
3405 gclog_or_tty->print_cr("\nJust chose CS, heap:");
3406 print();
3407 #endif
3409 if (VerifyBeforeGC && total_collections() >= VerifyGCStartAt) {
3410 HandleMark hm; // Discard invalid handles created during verification
3411 prepare_for_verify();
3412 gclog_or_tty->print(" VerifyBeforeGC:");
3413 Universe::verify(false);
3414 }
3416 COMPILER2_PRESENT(DerivedPointerTable::clear());
3418 // Please see comment in G1CollectedHeap::ref_processing_init()
3419 // to see how reference processing currently works in G1.
3420 //
3421 // We want to turn off ref discovery, if necessary, and turn it back on
3422 // on again later if we do. XXX Dubious: why is discovery disabled?
3423 bool was_enabled = ref_processor()->discovery_enabled();
3424 if (was_enabled) ref_processor()->disable_discovery();
3426 // Forget the current alloc region (we might even choose it to be part
3427 // of the collection set!).
3428 abandon_cur_alloc_region();
3430 // The elapsed time induced by the start time below deliberately elides
3431 // the possible verification above.
3432 double start_time_sec = os::elapsedTime();
3433 size_t start_used_bytes = used();
3435 #if YOUNG_LIST_VERBOSE
3436 gclog_or_tty->print_cr("\nBefore recording pause start.\nYoung_list:");
3437 _young_list->print();
3438 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3439 #endif // YOUNG_LIST_VERBOSE
3441 g1_policy()->record_collection_pause_start(start_time_sec,
3442 start_used_bytes);
3444 #if YOUNG_LIST_VERBOSE
3445 gclog_or_tty->print_cr("\nAfter recording pause start.\nYoung_list:");
3446 _young_list->print();
3447 #endif // YOUNG_LIST_VERBOSE
3449 if (g1_policy()->during_initial_mark_pause()) {
3450 concurrent_mark()->checkpointRootsInitialPre();
3451 }
3452 save_marks();
3454 // We must do this before any possible evacuation that should propagate
3455 // marks.
3456 if (mark_in_progress()) {
3457 double start_time_sec = os::elapsedTime();
3459 _cm->drainAllSATBBuffers();
3460 double finish_mark_ms = (os::elapsedTime() - start_time_sec) * 1000.0;
3461 g1_policy()->record_satb_drain_time(finish_mark_ms);
3462 }
3463 // Record the number of elements currently on the mark stack, so we
3464 // only iterate over these. (Since evacuation may add to the mark
3465 // stack, doing more exposes race conditions.) If no mark is in
3466 // progress, this will be zero.
3467 _cm->set_oops_do_bound();
3469 if (mark_in_progress())
3470 concurrent_mark()->newCSet();
3472 #if YOUNG_LIST_VERBOSE
3473 gclog_or_tty->print_cr("\nBefore choosing collection set.\nYoung_list:");
3474 _young_list->print();
3475 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3476 #endif // YOUNG_LIST_VERBOSE
3478 g1_policy()->choose_collection_set(target_pause_time_ms);
3480 // Nothing to do if we were unable to choose a collection set.
3481 #if G1_REM_SET_LOGGING
3482 gclog_or_tty->print_cr("\nAfter pause, heap:");
3483 print();
3484 #endif
3485 PrepareForRSScanningClosure prepare_for_rs_scan;
3486 collection_set_iterate(&prepare_for_rs_scan);
3488 setup_surviving_young_words();
3490 // Set up the gc allocation regions.
3491 get_gc_alloc_regions();
3493 // Actually do the work...
3494 evacuate_collection_set();
3496 free_collection_set(g1_policy()->collection_set());
3497 g1_policy()->clear_collection_set();
3499 cleanup_surviving_young_words();
3501 // Start a new incremental collection set for the next pause.
3502 g1_policy()->start_incremental_cset_building();
3504 // Clear the _cset_fast_test bitmap in anticipation of adding
3505 // regions to the incremental collection set for the next
3506 // evacuation pause.
3507 clear_cset_fast_test();
3509 if (g1_policy()->in_young_gc_mode()) {
3510 _young_list->reset_sampled_info();
3512 // Don't check the whole heap at this point as the
3513 // GC alloc regions from this pause have been tagged
3514 // as survivors and moved on to the survivor list.
3515 // Survivor regions will fail the !is_young() check.
3516 assert(check_young_list_empty(false /* check_heap */),
3517 "young list should be empty");
3519 #if YOUNG_LIST_VERBOSE
3520 gclog_or_tty->print_cr("Before recording survivors.\nYoung List:");
3521 _young_list->print();
3522 #endif // YOUNG_LIST_VERBOSE
3524 g1_policy()->record_survivor_regions(_young_list->survivor_length(),
3525 _young_list->first_survivor_region(),
3526 _young_list->last_survivor_region());
3528 _young_list->reset_auxilary_lists();
3529 }
3531 if (evacuation_failed()) {
3532 _summary_bytes_used = recalculate_used();
3533 } else {
3534 // The "used" of the the collection set have already been subtracted
3535 // when they were freed. Add in the bytes evacuated.
3536 _summary_bytes_used += g1_policy()->bytes_in_to_space();
3537 }
3539 if (g1_policy()->in_young_gc_mode() &&
3540 g1_policy()->during_initial_mark_pause()) {
3541 concurrent_mark()->checkpointRootsInitialPost();
3542 set_marking_started();
3543 // CAUTION: after the doConcurrentMark() call below,
3544 // the concurrent marking thread(s) could be running
3545 // concurrently with us. Make sure that anything after
3546 // this point does not assume that we are the only GC thread
3547 // running. Note: of course, the actual marking work will
3548 // not start until the safepoint itself is released in
3549 // ConcurrentGCThread::safepoint_desynchronize().
3550 doConcurrentMark();
3551 }
3553 #if YOUNG_LIST_VERBOSE
3554 gclog_or_tty->print_cr("\nEnd of the pause.\nYoung_list:");
3555 _young_list->print();
3556 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3557 #endif // YOUNG_LIST_VERBOSE
3559 double end_time_sec = os::elapsedTime();
3560 double pause_time_ms = (end_time_sec - start_time_sec) * MILLIUNITS;
3561 g1_policy()->record_pause_time_ms(pause_time_ms);
3562 g1_policy()->record_collection_pause_end();
3564 MemoryService::track_memory_usage();
3566 if (VerifyAfterGC && total_collections() >= VerifyGCStartAt) {
3567 HandleMark hm; // Discard invalid handles created during verification
3568 gclog_or_tty->print(" VerifyAfterGC:");
3569 prepare_for_verify();
3570 Universe::verify(false);
3571 }
3573 if (was_enabled) ref_processor()->enable_discovery();
3575 {
3576 size_t expand_bytes = g1_policy()->expansion_amount();
3577 if (expand_bytes > 0) {
3578 size_t bytes_before = capacity();
3579 if (!expand(expand_bytes)) {
3580 // We failed to expand the heap so let's verify that
3581 // committed/uncommitted amount match the backing store
3582 assert(capacity() == _g1_storage.committed_size(), "committed size mismatch");
3583 assert(max_capacity() == _g1_storage.reserved_size(), "reserved size mismatch");
3584 }
3585 }
3586 }
3588 if (mark_in_progress()) {
3589 concurrent_mark()->update_g1_committed();
3590 }
3592 #ifdef TRACESPINNING
3593 ParallelTaskTerminator::print_termination_counts();
3594 #endif
3596 gc_epilogue(false);
3597 }
3599 if (ExitAfterGCNum > 0 && total_collections() == ExitAfterGCNum) {
3600 gclog_or_tty->print_cr("Stopping after GC #%d", ExitAfterGCNum);
3601 print_tracing_info();
3602 vm_exit(-1);
3603 }
3604 }
3606 verify_region_sets_optional();
3608 TASKQUEUE_STATS_ONLY(if (ParallelGCVerbose) print_taskqueue_stats());
3609 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
3611 if (PrintHeapAtGC) {
3612 Universe::print_heap_after_gc();
3613 }
3614 if (G1SummarizeRSetStats &&
3615 (G1SummarizeRSetStatsPeriod > 0) &&
3616 (total_collections() % G1SummarizeRSetStatsPeriod == 0)) {
3617 g1_rem_set()->print_summary_info();
3618 }
3620 return true;
3621 }
3623 size_t G1CollectedHeap::desired_plab_sz(GCAllocPurpose purpose)
3624 {
3625 size_t gclab_word_size;
3626 switch (purpose) {
3627 case GCAllocForSurvived:
3628 gclab_word_size = YoungPLABSize;
3629 break;
3630 case GCAllocForTenured:
3631 gclab_word_size = OldPLABSize;
3632 break;
3633 default:
3634 assert(false, "unknown GCAllocPurpose");
3635 gclab_word_size = OldPLABSize;
3636 break;
3637 }
3638 return gclab_word_size;
3639 }
3642 void G1CollectedHeap::set_gc_alloc_region(int purpose, HeapRegion* r) {
3643 assert(purpose >= 0 && purpose < GCAllocPurposeCount, "invalid purpose");
3644 // make sure we don't call set_gc_alloc_region() multiple times on
3645 // the same region
3646 assert(r == NULL || !r->is_gc_alloc_region(),
3647 "shouldn't already be a GC alloc region");
3648 assert(r == NULL || !r->isHumongous(),
3649 "humongous regions shouldn't be used as GC alloc regions");
3651 HeapWord* original_top = NULL;
3652 if (r != NULL)
3653 original_top = r->top();
3655 // We will want to record the used space in r as being there before gc.
3656 // One we install it as a GC alloc region it's eligible for allocation.
3657 // So record it now and use it later.
3658 size_t r_used = 0;
3659 if (r != NULL) {
3660 r_used = r->used();
3662 if (G1CollectedHeap::use_parallel_gc_threads()) {
3663 // need to take the lock to guard against two threads calling
3664 // get_gc_alloc_region concurrently (very unlikely but...)
3665 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
3666 r->save_marks();
3667 }
3668 }
3669 HeapRegion* old_alloc_region = _gc_alloc_regions[purpose];
3670 _gc_alloc_regions[purpose] = r;
3671 if (old_alloc_region != NULL) {
3672 // Replace aliases too.
3673 for (int ap = 0; ap < GCAllocPurposeCount; ++ap) {
3674 if (_gc_alloc_regions[ap] == old_alloc_region) {
3675 _gc_alloc_regions[ap] = r;
3676 }
3677 }
3678 }
3679 if (r != NULL) {
3680 push_gc_alloc_region(r);
3681 if (mark_in_progress() && original_top != r->next_top_at_mark_start()) {
3682 // We are using a region as a GC alloc region after it has been used
3683 // as a mutator allocation region during the current marking cycle.
3684 // The mutator-allocated objects are currently implicitly marked, but
3685 // when we move hr->next_top_at_mark_start() forward at the the end
3686 // of the GC pause, they won't be. We therefore mark all objects in
3687 // the "gap". We do this object-by-object, since marking densely
3688 // does not currently work right with marking bitmap iteration. This
3689 // means we rely on TLAB filling at the start of pauses, and no
3690 // "resuscitation" of filled TLAB's. If we want to do this, we need
3691 // to fix the marking bitmap iteration.
3692 HeapWord* curhw = r->next_top_at_mark_start();
3693 HeapWord* t = original_top;
3695 while (curhw < t) {
3696 oop cur = (oop)curhw;
3697 // We'll assume parallel for generality. This is rare code.
3698 concurrent_mark()->markAndGrayObjectIfNecessary(cur); // can't we just mark them?
3699 curhw = curhw + cur->size();
3700 }
3701 assert(curhw == t, "Should have parsed correctly.");
3702 }
3703 if (G1PolicyVerbose > 1) {
3704 gclog_or_tty->print("New alloc region ["PTR_FORMAT", "PTR_FORMAT", " PTR_FORMAT") "
3705 "for survivors:", r->bottom(), original_top, r->end());
3706 r->print();
3707 }
3708 g1_policy()->record_before_bytes(r_used);
3709 }
3710 }
3712 void G1CollectedHeap::push_gc_alloc_region(HeapRegion* hr) {
3713 assert(Thread::current()->is_VM_thread() ||
3714 FreeList_lock->owned_by_self(), "Precondition");
3715 assert(!hr->is_gc_alloc_region() && !hr->in_collection_set(),
3716 "Precondition.");
3717 hr->set_is_gc_alloc_region(true);
3718 hr->set_next_gc_alloc_region(_gc_alloc_region_list);
3719 _gc_alloc_region_list = hr;
3720 }
3722 #ifdef G1_DEBUG
3723 class FindGCAllocRegion: public HeapRegionClosure {
3724 public:
3725 bool doHeapRegion(HeapRegion* r) {
3726 if (r->is_gc_alloc_region()) {
3727 gclog_or_tty->print_cr("Region %d ["PTR_FORMAT"...] is still a gc_alloc_region.",
3728 r->hrs_index(), r->bottom());
3729 }
3730 return false;
3731 }
3732 };
3733 #endif // G1_DEBUG
3735 void G1CollectedHeap::forget_alloc_region_list() {
3736 assert_at_safepoint(true /* should_be_vm_thread */);
3737 while (_gc_alloc_region_list != NULL) {
3738 HeapRegion* r = _gc_alloc_region_list;
3739 assert(r->is_gc_alloc_region(), "Invariant.");
3740 // We need HeapRegion::oops_on_card_seq_iterate_careful() to work on
3741 // newly allocated data in order to be able to apply deferred updates
3742 // before the GC is done for verification purposes (i.e to allow
3743 // G1HRRSFlushLogBuffersOnVerify). It's safe thing to do after the
3744 // collection.
3745 r->ContiguousSpace::set_saved_mark();
3746 _gc_alloc_region_list = r->next_gc_alloc_region();
3747 r->set_next_gc_alloc_region(NULL);
3748 r->set_is_gc_alloc_region(false);
3749 if (r->is_survivor()) {
3750 if (r->is_empty()) {
3751 r->set_not_young();
3752 } else {
3753 _young_list->add_survivor_region(r);
3754 }
3755 }
3756 }
3757 #ifdef G1_DEBUG
3758 FindGCAllocRegion fa;
3759 heap_region_iterate(&fa);
3760 #endif // G1_DEBUG
3761 }
3764 bool G1CollectedHeap::check_gc_alloc_regions() {
3765 // TODO: allocation regions check
3766 return true;
3767 }
3769 void G1CollectedHeap::get_gc_alloc_regions() {
3770 // First, let's check that the GC alloc region list is empty (it should)
3771 assert(_gc_alloc_region_list == NULL, "invariant");
3773 for (int ap = 0; ap < GCAllocPurposeCount; ++ap) {
3774 assert(_gc_alloc_regions[ap] == NULL, "invariant");
3775 assert(_gc_alloc_region_counts[ap] == 0, "invariant");
3777 // Create new GC alloc regions.
3778 HeapRegion* alloc_region = _retained_gc_alloc_regions[ap];
3779 _retained_gc_alloc_regions[ap] = NULL;
3781 if (alloc_region != NULL) {
3782 assert(_retain_gc_alloc_region[ap], "only way to retain a GC region");
3784 // let's make sure that the GC alloc region is not tagged as such
3785 // outside a GC operation
3786 assert(!alloc_region->is_gc_alloc_region(), "sanity");
3788 if (alloc_region->in_collection_set() ||
3789 alloc_region->top() == alloc_region->end() ||
3790 alloc_region->top() == alloc_region->bottom() ||
3791 alloc_region->isHumongous()) {
3792 // we will discard the current GC alloc region if
3793 // * it's in the collection set (it can happen!),
3794 // * it's already full (no point in using it),
3795 // * it's empty (this means that it was emptied during
3796 // a cleanup and it should be on the free list now), or
3797 // * it's humongous (this means that it was emptied
3798 // during a cleanup and was added to the free list, but
3799 // has been subseqently used to allocate a humongous
3800 // object that may be less than the region size).
3802 alloc_region = NULL;
3803 }
3804 }
3806 if (alloc_region == NULL) {
3807 // we will get a new GC alloc region
3808 alloc_region = new_gc_alloc_region(ap, HeapRegion::GrainWords);
3809 } else {
3810 // the region was retained from the last collection
3811 ++_gc_alloc_region_counts[ap];
3812 if (G1PrintHeapRegions) {
3813 gclog_or_tty->print_cr("new alloc region %d:["PTR_FORMAT", "PTR_FORMAT"], "
3814 "top "PTR_FORMAT,
3815 alloc_region->hrs_index(), alloc_region->bottom(), alloc_region->end(), alloc_region->top());
3816 }
3817 }
3819 if (alloc_region != NULL) {
3820 assert(_gc_alloc_regions[ap] == NULL, "pre-condition");
3821 set_gc_alloc_region(ap, alloc_region);
3822 }
3824 assert(_gc_alloc_regions[ap] == NULL ||
3825 _gc_alloc_regions[ap]->is_gc_alloc_region(),
3826 "the GC alloc region should be tagged as such");
3827 assert(_gc_alloc_regions[ap] == NULL ||
3828 _gc_alloc_regions[ap] == _gc_alloc_region_list,
3829 "the GC alloc region should be the same as the GC alloc list head");
3830 }
3831 // Set alternative regions for allocation purposes that have reached
3832 // their limit.
3833 for (int ap = 0; ap < GCAllocPurposeCount; ++ap) {
3834 GCAllocPurpose alt_purpose = g1_policy()->alternative_purpose(ap);
3835 if (_gc_alloc_regions[ap] == NULL && alt_purpose != ap) {
3836 _gc_alloc_regions[ap] = _gc_alloc_regions[alt_purpose];
3837 }
3838 }
3839 assert(check_gc_alloc_regions(), "alloc regions messed up");
3840 }
3842 void G1CollectedHeap::release_gc_alloc_regions(bool totally) {
3843 // We keep a separate list of all regions that have been alloc regions in
3844 // the current collection pause. Forget that now. This method will
3845 // untag the GC alloc regions and tear down the GC alloc region
3846 // list. It's desirable that no regions are tagged as GC alloc
3847 // outside GCs.
3849 forget_alloc_region_list();
3851 // The current alloc regions contain objs that have survived
3852 // collection. Make them no longer GC alloc regions.
3853 for (int ap = 0; ap < GCAllocPurposeCount; ++ap) {
3854 HeapRegion* r = _gc_alloc_regions[ap];
3855 _retained_gc_alloc_regions[ap] = NULL;
3856 _gc_alloc_region_counts[ap] = 0;
3858 if (r != NULL) {
3859 // we retain nothing on _gc_alloc_regions between GCs
3860 set_gc_alloc_region(ap, NULL);
3862 if (r->is_empty()) {
3863 // We didn't actually allocate anything in it; let's just put
3864 // it back on the free list.
3865 _free_list.add_as_tail(r);
3866 } else if (_retain_gc_alloc_region[ap] && !totally) {
3867 // retain it so that we can use it at the beginning of the next GC
3868 _retained_gc_alloc_regions[ap] = r;
3869 }
3870 }
3871 }
3872 }
3874 #ifndef PRODUCT
3875 // Useful for debugging
3877 void G1CollectedHeap::print_gc_alloc_regions() {
3878 gclog_or_tty->print_cr("GC alloc regions");
3879 for (int ap = 0; ap < GCAllocPurposeCount; ++ap) {
3880 HeapRegion* r = _gc_alloc_regions[ap];
3881 if (r == NULL) {
3882 gclog_or_tty->print_cr(" %2d : "PTR_FORMAT, ap, NULL);
3883 } else {
3884 gclog_or_tty->print_cr(" %2d : "PTR_FORMAT" "SIZE_FORMAT,
3885 ap, r->bottom(), r->used());
3886 }
3887 }
3888 }
3889 #endif // PRODUCT
3891 void G1CollectedHeap::init_for_evac_failure(OopsInHeapRegionClosure* cl) {
3892 _drain_in_progress = false;
3893 set_evac_failure_closure(cl);
3894 _evac_failure_scan_stack = new (ResourceObj::C_HEAP) GrowableArray<oop>(40, true);
3895 }
3897 void G1CollectedHeap::finalize_for_evac_failure() {
3898 assert(_evac_failure_scan_stack != NULL &&
3899 _evac_failure_scan_stack->length() == 0,
3900 "Postcondition");
3901 assert(!_drain_in_progress, "Postcondition");
3902 delete _evac_failure_scan_stack;
3903 _evac_failure_scan_stack = NULL;
3904 }
3908 // *** Sequential G1 Evacuation
3910 class G1IsAliveClosure: public BoolObjectClosure {
3911 G1CollectedHeap* _g1;
3912 public:
3913 G1IsAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
3914 void do_object(oop p) { assert(false, "Do not call."); }
3915 bool do_object_b(oop p) {
3916 // It is reachable if it is outside the collection set, or is inside
3917 // and forwarded.
3919 #ifdef G1_DEBUG
3920 gclog_or_tty->print_cr("is alive "PTR_FORMAT" in CS %d forwarded %d overall %d",
3921 (void*) p, _g1->obj_in_cs(p), p->is_forwarded(),
3922 !_g1->obj_in_cs(p) || p->is_forwarded());
3923 #endif // G1_DEBUG
3925 return !_g1->obj_in_cs(p) || p->is_forwarded();
3926 }
3927 };
3929 class G1KeepAliveClosure: public OopClosure {
3930 G1CollectedHeap* _g1;
3931 public:
3932 G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
3933 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
3934 void do_oop( oop* p) {
3935 oop obj = *p;
3936 #ifdef G1_DEBUG
3937 if (PrintGC && Verbose) {
3938 gclog_or_tty->print_cr("keep alive *"PTR_FORMAT" = "PTR_FORMAT" "PTR_FORMAT,
3939 p, (void*) obj, (void*) *p);
3940 }
3941 #endif // G1_DEBUG
3943 if (_g1->obj_in_cs(obj)) {
3944 assert( obj->is_forwarded(), "invariant" );
3945 *p = obj->forwardee();
3946 #ifdef G1_DEBUG
3947 gclog_or_tty->print_cr(" in CSet: moved "PTR_FORMAT" -> "PTR_FORMAT,
3948 (void*) obj, (void*) *p);
3949 #endif // G1_DEBUG
3950 }
3951 }
3952 };
3954 class UpdateRSetDeferred : public OopsInHeapRegionClosure {
3955 private:
3956 G1CollectedHeap* _g1;
3957 DirtyCardQueue *_dcq;
3958 CardTableModRefBS* _ct_bs;
3960 public:
3961 UpdateRSetDeferred(G1CollectedHeap* g1, DirtyCardQueue* dcq) :
3962 _g1(g1), _ct_bs((CardTableModRefBS*)_g1->barrier_set()), _dcq(dcq) {}
3964 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
3965 virtual void do_oop( oop* p) { do_oop_work(p); }
3966 template <class T> void do_oop_work(T* p) {
3967 assert(_from->is_in_reserved(p), "paranoia");
3968 if (!_from->is_in_reserved(oopDesc::load_decode_heap_oop(p)) &&
3969 !_from->is_survivor()) {
3970 size_t card_index = _ct_bs->index_for(p);
3971 if (_ct_bs->mark_card_deferred(card_index)) {
3972 _dcq->enqueue((jbyte*)_ct_bs->byte_for_index(card_index));
3973 }
3974 }
3975 }
3976 };
3978 class RemoveSelfPointerClosure: public ObjectClosure {
3979 private:
3980 G1CollectedHeap* _g1;
3981 ConcurrentMark* _cm;
3982 HeapRegion* _hr;
3983 size_t _prev_marked_bytes;
3984 size_t _next_marked_bytes;
3985 OopsInHeapRegionClosure *_cl;
3986 public:
3987 RemoveSelfPointerClosure(G1CollectedHeap* g1, HeapRegion* hr,
3988 OopsInHeapRegionClosure* cl) :
3989 _g1(g1), _hr(hr), _cm(_g1->concurrent_mark()), _prev_marked_bytes(0),
3990 _next_marked_bytes(0), _cl(cl) {}
3992 size_t prev_marked_bytes() { return _prev_marked_bytes; }
3993 size_t next_marked_bytes() { return _next_marked_bytes; }
3995 // <original comment>
3996 // The original idea here was to coalesce evacuated and dead objects.
3997 // However that caused complications with the block offset table (BOT).
3998 // In particular if there were two TLABs, one of them partially refined.
3999 // |----- TLAB_1--------|----TLAB_2-~~~(partially refined part)~~~|
4000 // The BOT entries of the unrefined part of TLAB_2 point to the start
4001 // of TLAB_2. If the last object of the TLAB_1 and the first object
4002 // of TLAB_2 are coalesced, then the cards of the unrefined part
4003 // would point into middle of the filler object.
4004 // The current approach is to not coalesce and leave the BOT contents intact.
4005 // </original comment>
4006 //
4007 // We now reset the BOT when we start the object iteration over the
4008 // region and refine its entries for every object we come across. So
4009 // the above comment is not really relevant and we should be able
4010 // to coalesce dead objects if we want to.
4011 void do_object(oop obj) {
4012 HeapWord* obj_addr = (HeapWord*) obj;
4013 assert(_hr->is_in(obj_addr), "sanity");
4014 size_t obj_size = obj->size();
4015 _hr->update_bot_for_object(obj_addr, obj_size);
4016 if (obj->is_forwarded() && obj->forwardee() == obj) {
4017 // The object failed to move.
4018 assert(!_g1->is_obj_dead(obj), "We should not be preserving dead objs.");
4019 _cm->markPrev(obj);
4020 assert(_cm->isPrevMarked(obj), "Should be marked!");
4021 _prev_marked_bytes += (obj_size * HeapWordSize);
4022 if (_g1->mark_in_progress() && !_g1->is_obj_ill(obj)) {
4023 _cm->markAndGrayObjectIfNecessary(obj);
4024 }
4025 obj->set_mark(markOopDesc::prototype());
4026 // While we were processing RSet buffers during the
4027 // collection, we actually didn't scan any cards on the
4028 // collection set, since we didn't want to update remebered
4029 // sets with entries that point into the collection set, given
4030 // that live objects fromthe collection set are about to move
4031 // and such entries will be stale very soon. This change also
4032 // dealt with a reliability issue which involved scanning a
4033 // card in the collection set and coming across an array that
4034 // was being chunked and looking malformed. The problem is
4035 // that, if evacuation fails, we might have remembered set
4036 // entries missing given that we skipped cards on the
4037 // collection set. So, we'll recreate such entries now.
4038 obj->oop_iterate(_cl);
4039 assert(_cm->isPrevMarked(obj), "Should be marked!");
4040 } else {
4041 // The object has been either evacuated or is dead. Fill it with a
4042 // dummy object.
4043 MemRegion mr((HeapWord*)obj, obj_size);
4044 CollectedHeap::fill_with_object(mr);
4045 _cm->clearRangeBothMaps(mr);
4046 }
4047 }
4048 };
4050 void G1CollectedHeap::remove_self_forwarding_pointers() {
4051 UpdateRSetImmediate immediate_update(_g1h->g1_rem_set());
4052 DirtyCardQueue dcq(&_g1h->dirty_card_queue_set());
4053 UpdateRSetDeferred deferred_update(_g1h, &dcq);
4054 OopsInHeapRegionClosure *cl;
4055 if (G1DeferredRSUpdate) {
4056 cl = &deferred_update;
4057 } else {
4058 cl = &immediate_update;
4059 }
4060 HeapRegion* cur = g1_policy()->collection_set();
4061 while (cur != NULL) {
4062 assert(g1_policy()->assertMarkedBytesDataOK(), "Should be!");
4063 assert(!cur->isHumongous(), "sanity");
4065 if (cur->evacuation_failed()) {
4066 assert(cur->in_collection_set(), "bad CS");
4067 RemoveSelfPointerClosure rspc(_g1h, cur, cl);
4069 cur->reset_bot();
4070 cl->set_region(cur);
4071 cur->object_iterate(&rspc);
4073 // A number of manipulations to make the TAMS be the current top,
4074 // and the marked bytes be the ones observed in the iteration.
4075 if (_g1h->concurrent_mark()->at_least_one_mark_complete()) {
4076 // The comments below are the postconditions achieved by the
4077 // calls. Note especially the last such condition, which says that
4078 // the count of marked bytes has been properly restored.
4079 cur->note_start_of_marking(false);
4080 // _next_top_at_mark_start == top, _next_marked_bytes == 0
4081 cur->add_to_marked_bytes(rspc.prev_marked_bytes());
4082 // _next_marked_bytes == prev_marked_bytes.
4083 cur->note_end_of_marking();
4084 // _prev_top_at_mark_start == top(),
4085 // _prev_marked_bytes == prev_marked_bytes
4086 }
4087 // If there is no mark in progress, we modified the _next variables
4088 // above needlessly, but harmlessly.
4089 if (_g1h->mark_in_progress()) {
4090 cur->note_start_of_marking(false);
4091 // _next_top_at_mark_start == top, _next_marked_bytes == 0
4092 // _next_marked_bytes == next_marked_bytes.
4093 }
4095 // Now make sure the region has the right index in the sorted array.
4096 g1_policy()->note_change_in_marked_bytes(cur);
4097 }
4098 cur = cur->next_in_collection_set();
4099 }
4100 assert(g1_policy()->assertMarkedBytesDataOK(), "Should be!");
4102 // Now restore saved marks, if any.
4103 if (_objs_with_preserved_marks != NULL) {
4104 assert(_preserved_marks_of_objs != NULL, "Both or none.");
4105 guarantee(_objs_with_preserved_marks->length() ==
4106 _preserved_marks_of_objs->length(), "Both or none.");
4107 for (int i = 0; i < _objs_with_preserved_marks->length(); i++) {
4108 oop obj = _objs_with_preserved_marks->at(i);
4109 markOop m = _preserved_marks_of_objs->at(i);
4110 obj->set_mark(m);
4111 }
4112 // Delete the preserved marks growable arrays (allocated on the C heap).
4113 delete _objs_with_preserved_marks;
4114 delete _preserved_marks_of_objs;
4115 _objs_with_preserved_marks = NULL;
4116 _preserved_marks_of_objs = NULL;
4117 }
4118 }
4120 void G1CollectedHeap::push_on_evac_failure_scan_stack(oop obj) {
4121 _evac_failure_scan_stack->push(obj);
4122 }
4124 void G1CollectedHeap::drain_evac_failure_scan_stack() {
4125 assert(_evac_failure_scan_stack != NULL, "precondition");
4127 while (_evac_failure_scan_stack->length() > 0) {
4128 oop obj = _evac_failure_scan_stack->pop();
4129 _evac_failure_closure->set_region(heap_region_containing(obj));
4130 obj->oop_iterate_backwards(_evac_failure_closure);
4131 }
4132 }
4134 oop
4135 G1CollectedHeap::handle_evacuation_failure_par(OopsInHeapRegionClosure* cl,
4136 oop old) {
4137 markOop m = old->mark();
4138 oop forward_ptr = old->forward_to_atomic(old);
4139 if (forward_ptr == NULL) {
4140 // Forward-to-self succeeded.
4141 if (_evac_failure_closure != cl) {
4142 MutexLockerEx x(EvacFailureStack_lock, Mutex::_no_safepoint_check_flag);
4143 assert(!_drain_in_progress,
4144 "Should only be true while someone holds the lock.");
4145 // Set the global evac-failure closure to the current thread's.
4146 assert(_evac_failure_closure == NULL, "Or locking has failed.");
4147 set_evac_failure_closure(cl);
4148 // Now do the common part.
4149 handle_evacuation_failure_common(old, m);
4150 // Reset to NULL.
4151 set_evac_failure_closure(NULL);
4152 } else {
4153 // The lock is already held, and this is recursive.
4154 assert(_drain_in_progress, "This should only be the recursive case.");
4155 handle_evacuation_failure_common(old, m);
4156 }
4157 return old;
4158 } else {
4159 // Someone else had a place to copy it.
4160 return forward_ptr;
4161 }
4162 }
4164 void G1CollectedHeap::handle_evacuation_failure_common(oop old, markOop m) {
4165 set_evacuation_failed(true);
4167 preserve_mark_if_necessary(old, m);
4169 HeapRegion* r = heap_region_containing(old);
4170 if (!r->evacuation_failed()) {
4171 r->set_evacuation_failed(true);
4172 if (G1PrintHeapRegions) {
4173 gclog_or_tty->print("overflow in heap region "PTR_FORMAT" "
4174 "["PTR_FORMAT","PTR_FORMAT")\n",
4175 r, r->bottom(), r->end());
4176 }
4177 }
4179 push_on_evac_failure_scan_stack(old);
4181 if (!_drain_in_progress) {
4182 // prevent recursion in copy_to_survivor_space()
4183 _drain_in_progress = true;
4184 drain_evac_failure_scan_stack();
4185 _drain_in_progress = false;
4186 }
4187 }
4189 void G1CollectedHeap::preserve_mark_if_necessary(oop obj, markOop m) {
4190 assert(evacuation_failed(), "Oversaving!");
4191 // We want to call the "for_promotion_failure" version only in the
4192 // case of a promotion failure.
4193 if (m->must_be_preserved_for_promotion_failure(obj)) {
4194 if (_objs_with_preserved_marks == NULL) {
4195 assert(_preserved_marks_of_objs == NULL, "Both or none.");
4196 _objs_with_preserved_marks =
4197 new (ResourceObj::C_HEAP) GrowableArray<oop>(40, true);
4198 _preserved_marks_of_objs =
4199 new (ResourceObj::C_HEAP) GrowableArray<markOop>(40, true);
4200 }
4201 _objs_with_preserved_marks->push(obj);
4202 _preserved_marks_of_objs->push(m);
4203 }
4204 }
4206 // *** Parallel G1 Evacuation
4208 HeapWord* G1CollectedHeap::par_allocate_during_gc(GCAllocPurpose purpose,
4209 size_t word_size) {
4210 assert(!isHumongous(word_size),
4211 err_msg("we should not be seeing humongous allocation requests "
4212 "during GC, word_size = "SIZE_FORMAT, word_size));
4214 HeapRegion* alloc_region = _gc_alloc_regions[purpose];
4215 // let the caller handle alloc failure
4216 if (alloc_region == NULL) return NULL;
4218 HeapWord* block = alloc_region->par_allocate(word_size);
4219 if (block == NULL) {
4220 block = allocate_during_gc_slow(purpose, alloc_region, true, word_size);
4221 }
4222 return block;
4223 }
4225 void G1CollectedHeap::retire_alloc_region(HeapRegion* alloc_region,
4226 bool par) {
4227 // Another thread might have obtained alloc_region for the given
4228 // purpose, and might be attempting to allocate in it, and might
4229 // succeed. Therefore, we can't do the "finalization" stuff on the
4230 // region below until we're sure the last allocation has happened.
4231 // We ensure this by allocating the remaining space with a garbage
4232 // object.
4233 if (par) par_allocate_remaining_space(alloc_region);
4234 // Now we can do the post-GC stuff on the region.
4235 alloc_region->note_end_of_copying();
4236 g1_policy()->record_after_bytes(alloc_region->used());
4237 }
4239 HeapWord*
4240 G1CollectedHeap::allocate_during_gc_slow(GCAllocPurpose purpose,
4241 HeapRegion* alloc_region,
4242 bool par,
4243 size_t word_size) {
4244 assert(!isHumongous(word_size),
4245 err_msg("we should not be seeing humongous allocation requests "
4246 "during GC, word_size = "SIZE_FORMAT, word_size));
4248 // We need to make sure we serialize calls to this method. Given
4249 // that the FreeList_lock guards accesses to the free_list anyway,
4250 // and we need to potentially remove a region from it, we'll use it
4251 // to protect the whole call.
4252 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
4254 HeapWord* block = NULL;
4255 // In the parallel case, a previous thread to obtain the lock may have
4256 // already assigned a new gc_alloc_region.
4257 if (alloc_region != _gc_alloc_regions[purpose]) {
4258 assert(par, "But should only happen in parallel case.");
4259 alloc_region = _gc_alloc_regions[purpose];
4260 if (alloc_region == NULL) return NULL;
4261 block = alloc_region->par_allocate(word_size);
4262 if (block != NULL) return block;
4263 // Otherwise, continue; this new region is empty, too.
4264 }
4265 assert(alloc_region != NULL, "We better have an allocation region");
4266 retire_alloc_region(alloc_region, par);
4268 if (_gc_alloc_region_counts[purpose] >= g1_policy()->max_regions(purpose)) {
4269 // Cannot allocate more regions for the given purpose.
4270 GCAllocPurpose alt_purpose = g1_policy()->alternative_purpose(purpose);
4271 // Is there an alternative?
4272 if (purpose != alt_purpose) {
4273 HeapRegion* alt_region = _gc_alloc_regions[alt_purpose];
4274 // Has not the alternative region been aliased?
4275 if (alloc_region != alt_region && alt_region != NULL) {
4276 // Try to allocate in the alternative region.
4277 if (par) {
4278 block = alt_region->par_allocate(word_size);
4279 } else {
4280 block = alt_region->allocate(word_size);
4281 }
4282 // Make an alias.
4283 _gc_alloc_regions[purpose] = _gc_alloc_regions[alt_purpose];
4284 if (block != NULL) {
4285 return block;
4286 }
4287 retire_alloc_region(alt_region, par);
4288 }
4289 // Both the allocation region and the alternative one are full
4290 // and aliased, replace them with a new allocation region.
4291 purpose = alt_purpose;
4292 } else {
4293 set_gc_alloc_region(purpose, NULL);
4294 return NULL;
4295 }
4296 }
4298 // Now allocate a new region for allocation.
4299 alloc_region = new_gc_alloc_region(purpose, word_size);
4301 // let the caller handle alloc failure
4302 if (alloc_region != NULL) {
4304 assert(check_gc_alloc_regions(), "alloc regions messed up");
4305 assert(alloc_region->saved_mark_at_top(),
4306 "Mark should have been saved already.");
4307 // This must be done last: once it's installed, other regions may
4308 // allocate in it (without holding the lock.)
4309 set_gc_alloc_region(purpose, alloc_region);
4311 if (par) {
4312 block = alloc_region->par_allocate(word_size);
4313 } else {
4314 block = alloc_region->allocate(word_size);
4315 }
4316 // Caller handles alloc failure.
4317 } else {
4318 // This sets other apis using the same old alloc region to NULL, also.
4319 set_gc_alloc_region(purpose, NULL);
4320 }
4321 return block; // May be NULL.
4322 }
4324 void G1CollectedHeap::par_allocate_remaining_space(HeapRegion* r) {
4325 HeapWord* block = NULL;
4326 size_t free_words;
4327 do {
4328 free_words = r->free()/HeapWordSize;
4329 // If there's too little space, no one can allocate, so we're done.
4330 if (free_words < CollectedHeap::min_fill_size()) return;
4331 // Otherwise, try to claim it.
4332 block = r->par_allocate(free_words);
4333 } while (block == NULL);
4334 fill_with_object(block, free_words);
4335 }
4337 #ifndef PRODUCT
4338 bool GCLabBitMapClosure::do_bit(size_t offset) {
4339 HeapWord* addr = _bitmap->offsetToHeapWord(offset);
4340 guarantee(_cm->isMarked(oop(addr)), "it should be!");
4341 return true;
4342 }
4343 #endif // PRODUCT
4345 G1ParScanThreadState::G1ParScanThreadState(G1CollectedHeap* g1h, int queue_num)
4346 : _g1h(g1h),
4347 _refs(g1h->task_queue(queue_num)),
4348 _dcq(&g1h->dirty_card_queue_set()),
4349 _ct_bs((CardTableModRefBS*)_g1h->barrier_set()),
4350 _g1_rem(g1h->g1_rem_set()),
4351 _hash_seed(17), _queue_num(queue_num),
4352 _term_attempts(0),
4353 _surviving_alloc_buffer(g1h->desired_plab_sz(GCAllocForSurvived)),
4354 _tenured_alloc_buffer(g1h->desired_plab_sz(GCAllocForTenured)),
4355 _age_table(false),
4356 _strong_roots_time(0), _term_time(0),
4357 _alloc_buffer_waste(0), _undo_waste(0)
4358 {
4359 // we allocate G1YoungSurvRateNumRegions plus one entries, since
4360 // we "sacrifice" entry 0 to keep track of surviving bytes for
4361 // non-young regions (where the age is -1)
4362 // We also add a few elements at the beginning and at the end in
4363 // an attempt to eliminate cache contention
4364 size_t real_length = 1 + _g1h->g1_policy()->young_cset_length();
4365 size_t array_length = PADDING_ELEM_NUM +
4366 real_length +
4367 PADDING_ELEM_NUM;
4368 _surviving_young_words_base = NEW_C_HEAP_ARRAY(size_t, array_length);
4369 if (_surviving_young_words_base == NULL)
4370 vm_exit_out_of_memory(array_length * sizeof(size_t),
4371 "Not enough space for young surv histo.");
4372 _surviving_young_words = _surviving_young_words_base + PADDING_ELEM_NUM;
4373 memset(_surviving_young_words, 0, real_length * sizeof(size_t));
4375 _alloc_buffers[GCAllocForSurvived] = &_surviving_alloc_buffer;
4376 _alloc_buffers[GCAllocForTenured] = &_tenured_alloc_buffer;
4378 _start = os::elapsedTime();
4379 }
4381 void
4382 G1ParScanThreadState::print_termination_stats_hdr(outputStream* const st)
4383 {
4384 st->print_raw_cr("GC Termination Stats");
4385 st->print_raw_cr(" elapsed --strong roots-- -------termination-------"
4386 " ------waste (KiB)------");
4387 st->print_raw_cr("thr ms ms % ms % attempts"
4388 " total alloc undo");
4389 st->print_raw_cr("--- --------- --------- ------ --------- ------ --------"
4390 " ------- ------- -------");
4391 }
4393 void
4394 G1ParScanThreadState::print_termination_stats(int i,
4395 outputStream* const st) const
4396 {
4397 const double elapsed_ms = elapsed_time() * 1000.0;
4398 const double s_roots_ms = strong_roots_time() * 1000.0;
4399 const double term_ms = term_time() * 1000.0;
4400 st->print_cr("%3d %9.2f %9.2f %6.2f "
4401 "%9.2f %6.2f " SIZE_FORMAT_W(8) " "
4402 SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7),
4403 i, elapsed_ms, s_roots_ms, s_roots_ms * 100 / elapsed_ms,
4404 term_ms, term_ms * 100 / elapsed_ms, term_attempts(),
4405 (alloc_buffer_waste() + undo_waste()) * HeapWordSize / K,
4406 alloc_buffer_waste() * HeapWordSize / K,
4407 undo_waste() * HeapWordSize / K);
4408 }
4410 #ifdef ASSERT
4411 bool G1ParScanThreadState::verify_ref(narrowOop* ref) const {
4412 assert(ref != NULL, "invariant");
4413 assert(UseCompressedOops, "sanity");
4414 assert(!has_partial_array_mask(ref), err_msg("ref=" PTR_FORMAT, ref));
4415 oop p = oopDesc::load_decode_heap_oop(ref);
4416 assert(_g1h->is_in_g1_reserved(p),
4417 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p)));
4418 return true;
4419 }
4421 bool G1ParScanThreadState::verify_ref(oop* ref) const {
4422 assert(ref != NULL, "invariant");
4423 if (has_partial_array_mask(ref)) {
4424 // Must be in the collection set--it's already been copied.
4425 oop p = clear_partial_array_mask(ref);
4426 assert(_g1h->obj_in_cs(p),
4427 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p)));
4428 } else {
4429 oop p = oopDesc::load_decode_heap_oop(ref);
4430 assert(_g1h->is_in_g1_reserved(p),
4431 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p)));
4432 }
4433 return true;
4434 }
4436 bool G1ParScanThreadState::verify_task(StarTask ref) const {
4437 if (ref.is_narrow()) {
4438 return verify_ref((narrowOop*) ref);
4439 } else {
4440 return verify_ref((oop*) ref);
4441 }
4442 }
4443 #endif // ASSERT
4445 void G1ParScanThreadState::trim_queue() {
4446 StarTask ref;
4447 do {
4448 // Drain the overflow stack first, so other threads can steal.
4449 while (refs()->pop_overflow(ref)) {
4450 deal_with_reference(ref);
4451 }
4452 while (refs()->pop_local(ref)) {
4453 deal_with_reference(ref);
4454 }
4455 } while (!refs()->is_empty());
4456 }
4458 G1ParClosureSuper::G1ParClosureSuper(G1CollectedHeap* g1, G1ParScanThreadState* par_scan_state) :
4459 _g1(g1), _g1_rem(_g1->g1_rem_set()), _cm(_g1->concurrent_mark()),
4460 _par_scan_state(par_scan_state) { }
4462 template <class T> void G1ParCopyHelper::mark_forwardee(T* p) {
4463 // This is called _after_ do_oop_work has been called, hence after
4464 // the object has been relocated to its new location and *p points
4465 // to its new location.
4467 T heap_oop = oopDesc::load_heap_oop(p);
4468 if (!oopDesc::is_null(heap_oop)) {
4469 oop obj = oopDesc::decode_heap_oop(heap_oop);
4470 assert((_g1->evacuation_failed()) || (!_g1->obj_in_cs(obj)),
4471 "shouldn't still be in the CSet if evacuation didn't fail.");
4472 HeapWord* addr = (HeapWord*)obj;
4473 if (_g1->is_in_g1_reserved(addr))
4474 _cm->grayRoot(oop(addr));
4475 }
4476 }
4478 oop G1ParCopyHelper::copy_to_survivor_space(oop old) {
4479 size_t word_sz = old->size();
4480 HeapRegion* from_region = _g1->heap_region_containing_raw(old);
4481 // +1 to make the -1 indexes valid...
4482 int young_index = from_region->young_index_in_cset()+1;
4483 assert( (from_region->is_young() && young_index > 0) ||
4484 (!from_region->is_young() && young_index == 0), "invariant" );
4485 G1CollectorPolicy* g1p = _g1->g1_policy();
4486 markOop m = old->mark();
4487 int age = m->has_displaced_mark_helper() ? m->displaced_mark_helper()->age()
4488 : m->age();
4489 GCAllocPurpose alloc_purpose = g1p->evacuation_destination(from_region, age,
4490 word_sz);
4491 HeapWord* obj_ptr = _par_scan_state->allocate(alloc_purpose, word_sz);
4492 oop obj = oop(obj_ptr);
4494 if (obj_ptr == NULL) {
4495 // This will either forward-to-self, or detect that someone else has
4496 // installed a forwarding pointer.
4497 OopsInHeapRegionClosure* cl = _par_scan_state->evac_failure_closure();
4498 return _g1->handle_evacuation_failure_par(cl, old);
4499 }
4501 // We're going to allocate linearly, so might as well prefetch ahead.
4502 Prefetch::write(obj_ptr, PrefetchCopyIntervalInBytes);
4504 oop forward_ptr = old->forward_to_atomic(obj);
4505 if (forward_ptr == NULL) {
4506 Copy::aligned_disjoint_words((HeapWord*) old, obj_ptr, word_sz);
4507 if (g1p->track_object_age(alloc_purpose)) {
4508 // We could simply do obj->incr_age(). However, this causes a
4509 // performance issue. obj->incr_age() will first check whether
4510 // the object has a displaced mark by checking its mark word;
4511 // getting the mark word from the new location of the object
4512 // stalls. So, given that we already have the mark word and we
4513 // are about to install it anyway, it's better to increase the
4514 // age on the mark word, when the object does not have a
4515 // displaced mark word. We're not expecting many objects to have
4516 // a displaced marked word, so that case is not optimized
4517 // further (it could be...) and we simply call obj->incr_age().
4519 if (m->has_displaced_mark_helper()) {
4520 // in this case, we have to install the mark word first,
4521 // otherwise obj looks to be forwarded (the old mark word,
4522 // which contains the forward pointer, was copied)
4523 obj->set_mark(m);
4524 obj->incr_age();
4525 } else {
4526 m = m->incr_age();
4527 obj->set_mark(m);
4528 }
4529 _par_scan_state->age_table()->add(obj, word_sz);
4530 } else {
4531 obj->set_mark(m);
4532 }
4534 // preserve "next" mark bit
4535 if (_g1->mark_in_progress() && !_g1->is_obj_ill(old)) {
4536 if (!use_local_bitmaps ||
4537 !_par_scan_state->alloc_buffer(alloc_purpose)->mark(obj_ptr)) {
4538 // if we couldn't mark it on the local bitmap (this happens when
4539 // the object was not allocated in the GCLab), we have to bite
4540 // the bullet and do the standard parallel mark
4541 _cm->markAndGrayObjectIfNecessary(obj);
4542 }
4543 #if 1
4544 if (_g1->isMarkedNext(old)) {
4545 _cm->nextMarkBitMap()->parClear((HeapWord*)old);
4546 }
4547 #endif
4548 }
4550 size_t* surv_young_words = _par_scan_state->surviving_young_words();
4551 surv_young_words[young_index] += word_sz;
4553 if (obj->is_objArray() && arrayOop(obj)->length() >= ParGCArrayScanChunk) {
4554 arrayOop(old)->set_length(0);
4555 oop* old_p = set_partial_array_mask(old);
4556 _par_scan_state->push_on_queue(old_p);
4557 } else {
4558 // No point in using the slower heap_region_containing() method,
4559 // given that we know obj is in the heap.
4560 _scanner->set_region(_g1->heap_region_containing_raw(obj));
4561 obj->oop_iterate_backwards(_scanner);
4562 }
4563 } else {
4564 _par_scan_state->undo_allocation(alloc_purpose, obj_ptr, word_sz);
4565 obj = forward_ptr;
4566 }
4567 return obj;
4568 }
4570 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_forwardee>
4571 template <class T>
4572 void G1ParCopyClosure <do_gen_barrier, barrier, do_mark_forwardee>
4573 ::do_oop_work(T* p) {
4574 oop obj = oopDesc::load_decode_heap_oop(p);
4575 assert(barrier != G1BarrierRS || obj != NULL,
4576 "Precondition: G1BarrierRS implies obj is nonNull");
4578 // here the null check is implicit in the cset_fast_test() test
4579 if (_g1->in_cset_fast_test(obj)) {
4580 #if G1_REM_SET_LOGGING
4581 gclog_or_tty->print_cr("Loc "PTR_FORMAT" contains pointer "PTR_FORMAT" "
4582 "into CS.", p, (void*) obj);
4583 #endif
4584 if (obj->is_forwarded()) {
4585 oopDesc::encode_store_heap_oop(p, obj->forwardee());
4586 } else {
4587 oop copy_oop = copy_to_survivor_space(obj);
4588 oopDesc::encode_store_heap_oop(p, copy_oop);
4589 }
4590 // When scanning the RS, we only care about objs in CS.
4591 if (barrier == G1BarrierRS) {
4592 _par_scan_state->update_rs(_from, p, _par_scan_state->queue_num());
4593 }
4594 }
4596 if (barrier == G1BarrierEvac && obj != NULL) {
4597 _par_scan_state->update_rs(_from, p, _par_scan_state->queue_num());
4598 }
4600 if (do_gen_barrier && obj != NULL) {
4601 par_do_barrier(p);
4602 }
4603 }
4605 template void G1ParCopyClosure<false, G1BarrierEvac, false>::do_oop_work(oop* p);
4606 template void G1ParCopyClosure<false, G1BarrierEvac, false>::do_oop_work(narrowOop* p);
4608 template <class T> void G1ParScanPartialArrayClosure::do_oop_nv(T* p) {
4609 assert(has_partial_array_mask(p), "invariant");
4610 oop old = clear_partial_array_mask(p);
4611 assert(old->is_objArray(), "must be obj array");
4612 assert(old->is_forwarded(), "must be forwarded");
4613 assert(Universe::heap()->is_in_reserved(old), "must be in heap.");
4615 objArrayOop obj = objArrayOop(old->forwardee());
4616 assert((void*)old != (void*)old->forwardee(), "self forwarding here?");
4617 // Process ParGCArrayScanChunk elements now
4618 // and push the remainder back onto queue
4619 int start = arrayOop(old)->length();
4620 int end = obj->length();
4621 int remainder = end - start;
4622 assert(start <= end, "just checking");
4623 if (remainder > 2 * ParGCArrayScanChunk) {
4624 // Test above combines last partial chunk with a full chunk
4625 end = start + ParGCArrayScanChunk;
4626 arrayOop(old)->set_length(end);
4627 // Push remainder.
4628 oop* old_p = set_partial_array_mask(old);
4629 assert(arrayOop(old)->length() < obj->length(), "Empty push?");
4630 _par_scan_state->push_on_queue(old_p);
4631 } else {
4632 // Restore length so that the heap remains parsable in
4633 // case of evacuation failure.
4634 arrayOop(old)->set_length(end);
4635 }
4636 _scanner.set_region(_g1->heap_region_containing_raw(obj));
4637 // process our set of indices (include header in first chunk)
4638 obj->oop_iterate_range(&_scanner, start, end);
4639 }
4641 class G1ParEvacuateFollowersClosure : public VoidClosure {
4642 protected:
4643 G1CollectedHeap* _g1h;
4644 G1ParScanThreadState* _par_scan_state;
4645 RefToScanQueueSet* _queues;
4646 ParallelTaskTerminator* _terminator;
4648 G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
4649 RefToScanQueueSet* queues() { return _queues; }
4650 ParallelTaskTerminator* terminator() { return _terminator; }
4652 public:
4653 G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h,
4654 G1ParScanThreadState* par_scan_state,
4655 RefToScanQueueSet* queues,
4656 ParallelTaskTerminator* terminator)
4657 : _g1h(g1h), _par_scan_state(par_scan_state),
4658 _queues(queues), _terminator(terminator) {}
4660 void do_void();
4662 private:
4663 inline bool offer_termination();
4664 };
4666 bool G1ParEvacuateFollowersClosure::offer_termination() {
4667 G1ParScanThreadState* const pss = par_scan_state();
4668 pss->start_term_time();
4669 const bool res = terminator()->offer_termination();
4670 pss->end_term_time();
4671 return res;
4672 }
4674 void G1ParEvacuateFollowersClosure::do_void() {
4675 StarTask stolen_task;
4676 G1ParScanThreadState* const pss = par_scan_state();
4677 pss->trim_queue();
4679 do {
4680 while (queues()->steal(pss->queue_num(), pss->hash_seed(), stolen_task)) {
4681 assert(pss->verify_task(stolen_task), "sanity");
4682 if (stolen_task.is_narrow()) {
4683 pss->deal_with_reference((narrowOop*) stolen_task);
4684 } else {
4685 pss->deal_with_reference((oop*) stolen_task);
4686 }
4688 // We've just processed a reference and we might have made
4689 // available new entries on the queues. So we have to make sure
4690 // we drain the queues as necessary.
4691 pss->trim_queue();
4692 }
4693 } while (!offer_termination());
4695 pss->retire_alloc_buffers();
4696 }
4698 class G1ParTask : public AbstractGangTask {
4699 protected:
4700 G1CollectedHeap* _g1h;
4701 RefToScanQueueSet *_queues;
4702 ParallelTaskTerminator _terminator;
4703 int _n_workers;
4705 Mutex _stats_lock;
4706 Mutex* stats_lock() { return &_stats_lock; }
4708 size_t getNCards() {
4709 return (_g1h->capacity() + G1BlockOffsetSharedArray::N_bytes - 1)
4710 / G1BlockOffsetSharedArray::N_bytes;
4711 }
4713 public:
4714 G1ParTask(G1CollectedHeap* g1h, int workers, RefToScanQueueSet *task_queues)
4715 : AbstractGangTask("G1 collection"),
4716 _g1h(g1h),
4717 _queues(task_queues),
4718 _terminator(workers, _queues),
4719 _stats_lock(Mutex::leaf, "parallel G1 stats lock", true),
4720 _n_workers(workers)
4721 {}
4723 RefToScanQueueSet* queues() { return _queues; }
4725 RefToScanQueue *work_queue(int i) {
4726 return queues()->queue(i);
4727 }
4729 void work(int i) {
4730 if (i >= _n_workers) return; // no work needed this round
4732 double start_time_ms = os::elapsedTime() * 1000.0;
4733 _g1h->g1_policy()->record_gc_worker_start_time(i, start_time_ms);
4735 ResourceMark rm;
4736 HandleMark hm;
4738 G1ParScanThreadState pss(_g1h, i);
4739 G1ParScanHeapEvacClosure scan_evac_cl(_g1h, &pss);
4740 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss);
4741 G1ParScanPartialArrayClosure partial_scan_cl(_g1h, &pss);
4743 pss.set_evac_closure(&scan_evac_cl);
4744 pss.set_evac_failure_closure(&evac_failure_cl);
4745 pss.set_partial_scan_closure(&partial_scan_cl);
4747 G1ParScanExtRootClosure only_scan_root_cl(_g1h, &pss);
4748 G1ParScanPermClosure only_scan_perm_cl(_g1h, &pss);
4749 G1ParScanHeapRSClosure only_scan_heap_rs_cl(_g1h, &pss);
4750 G1ParPushHeapRSClosure push_heap_rs_cl(_g1h, &pss);
4752 G1ParScanAndMarkExtRootClosure scan_mark_root_cl(_g1h, &pss);
4753 G1ParScanAndMarkPermClosure scan_mark_perm_cl(_g1h, &pss);
4754 G1ParScanAndMarkHeapRSClosure scan_mark_heap_rs_cl(_g1h, &pss);
4756 OopsInHeapRegionClosure *scan_root_cl;
4757 OopsInHeapRegionClosure *scan_perm_cl;
4759 if (_g1h->g1_policy()->during_initial_mark_pause()) {
4760 scan_root_cl = &scan_mark_root_cl;
4761 scan_perm_cl = &scan_mark_perm_cl;
4762 } else {
4763 scan_root_cl = &only_scan_root_cl;
4764 scan_perm_cl = &only_scan_perm_cl;
4765 }
4767 pss.start_strong_roots();
4768 _g1h->g1_process_strong_roots(/* not collecting perm */ false,
4769 SharedHeap::SO_AllClasses,
4770 scan_root_cl,
4771 &push_heap_rs_cl,
4772 scan_perm_cl,
4773 i);
4774 pss.end_strong_roots();
4775 {
4776 double start = os::elapsedTime();
4777 G1ParEvacuateFollowersClosure evac(_g1h, &pss, _queues, &_terminator);
4778 evac.do_void();
4779 double elapsed_ms = (os::elapsedTime()-start)*1000.0;
4780 double term_ms = pss.term_time()*1000.0;
4781 _g1h->g1_policy()->record_obj_copy_time(i, elapsed_ms-term_ms);
4782 _g1h->g1_policy()->record_termination(i, term_ms, pss.term_attempts());
4783 }
4784 _g1h->g1_policy()->record_thread_age_table(pss.age_table());
4785 _g1h->update_surviving_young_words(pss.surviving_young_words()+1);
4787 // Clean up any par-expanded rem sets.
4788 HeapRegionRemSet::par_cleanup();
4790 if (ParallelGCVerbose) {
4791 MutexLocker x(stats_lock());
4792 pss.print_termination_stats(i);
4793 }
4795 assert(pss.refs()->is_empty(), "should be empty");
4796 double end_time_ms = os::elapsedTime() * 1000.0;
4797 _g1h->g1_policy()->record_gc_worker_end_time(i, end_time_ms);
4798 }
4799 };
4801 // *** Common G1 Evacuation Stuff
4803 // This method is run in a GC worker.
4805 void
4806 G1CollectedHeap::
4807 g1_process_strong_roots(bool collecting_perm_gen,
4808 SharedHeap::ScanningOption so,
4809 OopClosure* scan_non_heap_roots,
4810 OopsInHeapRegionClosure* scan_rs,
4811 OopsInGenClosure* scan_perm,
4812 int worker_i) {
4813 // First scan the strong roots, including the perm gen.
4814 double ext_roots_start = os::elapsedTime();
4815 double closure_app_time_sec = 0.0;
4817 BufferingOopClosure buf_scan_non_heap_roots(scan_non_heap_roots);
4818 BufferingOopsInGenClosure buf_scan_perm(scan_perm);
4819 buf_scan_perm.set_generation(perm_gen());
4821 // Walk the code cache w/o buffering, because StarTask cannot handle
4822 // unaligned oop locations.
4823 CodeBlobToOopClosure eager_scan_code_roots(scan_non_heap_roots, /*do_marking=*/ true);
4825 process_strong_roots(false, // no scoping; this is parallel code
4826 collecting_perm_gen, so,
4827 &buf_scan_non_heap_roots,
4828 &eager_scan_code_roots,
4829 &buf_scan_perm);
4831 // Finish up any enqueued closure apps.
4832 buf_scan_non_heap_roots.done();
4833 buf_scan_perm.done();
4834 double ext_roots_end = os::elapsedTime();
4835 g1_policy()->reset_obj_copy_time(worker_i);
4836 double obj_copy_time_sec =
4837 buf_scan_non_heap_roots.closure_app_seconds() +
4838 buf_scan_perm.closure_app_seconds();
4839 g1_policy()->record_obj_copy_time(worker_i, obj_copy_time_sec * 1000.0);
4840 double ext_root_time_ms =
4841 ((ext_roots_end - ext_roots_start) - obj_copy_time_sec) * 1000.0;
4842 g1_policy()->record_ext_root_scan_time(worker_i, ext_root_time_ms);
4844 // Scan strong roots in mark stack.
4845 if (!_process_strong_tasks->is_task_claimed(G1H_PS_mark_stack_oops_do)) {
4846 concurrent_mark()->oops_do(scan_non_heap_roots);
4847 }
4848 double mark_stack_scan_ms = (os::elapsedTime() - ext_roots_end) * 1000.0;
4849 g1_policy()->record_mark_stack_scan_time(worker_i, mark_stack_scan_ms);
4851 // XXX What should this be doing in the parallel case?
4852 g1_policy()->record_collection_pause_end_CH_strong_roots();
4853 // Now scan the complement of the collection set.
4854 if (scan_rs != NULL) {
4855 g1_rem_set()->oops_into_collection_set_do(scan_rs, worker_i);
4856 }
4857 // Finish with the ref_processor roots.
4858 if (!_process_strong_tasks->is_task_claimed(G1H_PS_refProcessor_oops_do)) {
4859 // We need to treat the discovered reference lists as roots and
4860 // keep entries (which are added by the marking threads) on them
4861 // live until they can be processed at the end of marking.
4862 ref_processor()->weak_oops_do(scan_non_heap_roots);
4863 ref_processor()->oops_do(scan_non_heap_roots);
4864 }
4865 g1_policy()->record_collection_pause_end_G1_strong_roots();
4866 _process_strong_tasks->all_tasks_completed();
4867 }
4869 void
4870 G1CollectedHeap::g1_process_weak_roots(OopClosure* root_closure,
4871 OopClosure* non_root_closure) {
4872 CodeBlobToOopClosure roots_in_blobs(root_closure, /*do_marking=*/ false);
4873 SharedHeap::process_weak_roots(root_closure, &roots_in_blobs, non_root_closure);
4874 }
4877 class SaveMarksClosure: public HeapRegionClosure {
4878 public:
4879 bool doHeapRegion(HeapRegion* r) {
4880 r->save_marks();
4881 return false;
4882 }
4883 };
4885 void G1CollectedHeap::save_marks() {
4886 if (!CollectedHeap::use_parallel_gc_threads()) {
4887 SaveMarksClosure sm;
4888 heap_region_iterate(&sm);
4889 }
4890 // We do this even in the parallel case
4891 perm_gen()->save_marks();
4892 }
4894 void G1CollectedHeap::evacuate_collection_set() {
4895 set_evacuation_failed(false);
4897 g1_rem_set()->prepare_for_oops_into_collection_set_do();
4898 concurrent_g1_refine()->set_use_cache(false);
4899 concurrent_g1_refine()->clear_hot_cache_claimed_index();
4901 int n_workers = (ParallelGCThreads > 0 ? workers()->total_workers() : 1);
4902 set_par_threads(n_workers);
4903 G1ParTask g1_par_task(this, n_workers, _task_queues);
4905 init_for_evac_failure(NULL);
4907 rem_set()->prepare_for_younger_refs_iterate(true);
4909 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
4910 double start_par = os::elapsedTime();
4911 if (G1CollectedHeap::use_parallel_gc_threads()) {
4912 // The individual threads will set their evac-failure closures.
4913 StrongRootsScope srs(this);
4914 if (ParallelGCVerbose) G1ParScanThreadState::print_termination_stats_hdr();
4915 workers()->run_task(&g1_par_task);
4916 } else {
4917 StrongRootsScope srs(this);
4918 g1_par_task.work(0);
4919 }
4921 double par_time = (os::elapsedTime() - start_par) * 1000.0;
4922 g1_policy()->record_par_time(par_time);
4923 set_par_threads(0);
4924 // Is this the right thing to do here? We don't save marks
4925 // on individual heap regions when we allocate from
4926 // them in parallel, so this seems like the correct place for this.
4927 retire_all_alloc_regions();
4929 // Weak root processing.
4930 // Note: when JSR 292 is enabled and code blobs can contain
4931 // non-perm oops then we will need to process the code blobs
4932 // here too.
4933 {
4934 G1IsAliveClosure is_alive(this);
4935 G1KeepAliveClosure keep_alive(this);
4936 JNIHandles::weak_oops_do(&is_alive, &keep_alive);
4937 }
4938 release_gc_alloc_regions(false /* totally */);
4939 g1_rem_set()->cleanup_after_oops_into_collection_set_do();
4941 concurrent_g1_refine()->clear_hot_cache();
4942 concurrent_g1_refine()->set_use_cache(true);
4944 finalize_for_evac_failure();
4946 // Must do this before removing self-forwarding pointers, which clears
4947 // the per-region evac-failure flags.
4948 concurrent_mark()->complete_marking_in_collection_set();
4950 if (evacuation_failed()) {
4951 remove_self_forwarding_pointers();
4952 if (PrintGCDetails) {
4953 gclog_or_tty->print(" (to-space overflow)");
4954 } else if (PrintGC) {
4955 gclog_or_tty->print("--");
4956 }
4957 }
4959 if (G1DeferredRSUpdate) {
4960 RedirtyLoggedCardTableEntryFastClosure redirty;
4961 dirty_card_queue_set().set_closure(&redirty);
4962 dirty_card_queue_set().apply_closure_to_all_completed_buffers();
4964 DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set();
4965 dcq.merge_bufferlists(&dirty_card_queue_set());
4966 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
4967 }
4968 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
4969 }
4971 void G1CollectedHeap::free_region_if_empty(HeapRegion* hr,
4972 size_t* pre_used,
4973 FreeRegionList* free_list,
4974 HumongousRegionSet* humongous_proxy_set,
4975 HRRSCleanupTask* hrrs_cleanup_task,
4976 bool par) {
4977 if (hr->used() > 0 && hr->max_live_bytes() == 0 && !hr->is_young()) {
4978 if (hr->isHumongous()) {
4979 assert(hr->startsHumongous(), "we should only see starts humongous");
4980 free_humongous_region(hr, pre_used, free_list, humongous_proxy_set, par);
4981 } else {
4982 free_region(hr, pre_used, free_list, par);
4983 }
4984 } else {
4985 hr->rem_set()->do_cleanup_work(hrrs_cleanup_task);
4986 }
4987 }
4989 void G1CollectedHeap::free_region(HeapRegion* hr,
4990 size_t* pre_used,
4991 FreeRegionList* free_list,
4992 bool par) {
4993 assert(!hr->isHumongous(), "this is only for non-humongous regions");
4994 assert(!hr->is_empty(), "the region should not be empty");
4995 assert(free_list != NULL, "pre-condition");
4997 *pre_used += hr->used();
4998 hr->hr_clear(par, true /* clear_space */);
4999 free_list->add_as_tail(hr);
5000 }
5002 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
5003 size_t* pre_used,
5004 FreeRegionList* free_list,
5005 HumongousRegionSet* humongous_proxy_set,
5006 bool par) {
5007 assert(hr->startsHumongous(), "this is only for starts humongous regions");
5008 assert(free_list != NULL, "pre-condition");
5009 assert(humongous_proxy_set != NULL, "pre-condition");
5011 size_t hr_used = hr->used();
5012 size_t hr_capacity = hr->capacity();
5013 size_t hr_pre_used = 0;
5014 _humongous_set.remove_with_proxy(hr, humongous_proxy_set);
5015 hr->set_notHumongous();
5016 free_region(hr, &hr_pre_used, free_list, par);
5018 int i = hr->hrs_index() + 1;
5019 size_t num = 1;
5020 while ((size_t) i < n_regions()) {
5021 HeapRegion* curr_hr = _hrs->at(i);
5022 if (!curr_hr->continuesHumongous()) {
5023 break;
5024 }
5025 curr_hr->set_notHumongous();
5026 free_region(curr_hr, &hr_pre_used, free_list, par);
5027 num += 1;
5028 i += 1;
5029 }
5030 assert(hr_pre_used == hr_used,
5031 err_msg("hr_pre_used: "SIZE_FORMAT" and hr_used: "SIZE_FORMAT" "
5032 "should be the same", hr_pre_used, hr_used));
5033 *pre_used += hr_pre_used;
5034 }
5036 void G1CollectedHeap::update_sets_after_freeing_regions(size_t pre_used,
5037 FreeRegionList* free_list,
5038 HumongousRegionSet* humongous_proxy_set,
5039 bool par) {
5040 if (pre_used > 0) {
5041 Mutex* lock = (par) ? ParGCRareEvent_lock : NULL;
5042 MutexLockerEx x(lock, Mutex::_no_safepoint_check_flag);
5043 assert(_summary_bytes_used >= pre_used,
5044 err_msg("invariant: _summary_bytes_used: "SIZE_FORMAT" "
5045 "should be >= pre_used: "SIZE_FORMAT,
5046 _summary_bytes_used, pre_used));
5047 _summary_bytes_used -= pre_used;
5048 }
5049 if (free_list != NULL && !free_list->is_empty()) {
5050 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
5051 _free_list.add_as_tail(free_list);
5052 }
5053 if (humongous_proxy_set != NULL && !humongous_proxy_set->is_empty()) {
5054 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
5055 _humongous_set.update_from_proxy(humongous_proxy_set);
5056 }
5057 }
5059 void G1CollectedHeap::dirtyCardsForYoungRegions(CardTableModRefBS* ct_bs, HeapRegion* list) {
5060 while (list != NULL) {
5061 guarantee( list->is_young(), "invariant" );
5063 HeapWord* bottom = list->bottom();
5064 HeapWord* end = list->end();
5065 MemRegion mr(bottom, end);
5066 ct_bs->dirty(mr);
5068 list = list->get_next_young_region();
5069 }
5070 }
5073 class G1ParCleanupCTTask : public AbstractGangTask {
5074 CardTableModRefBS* _ct_bs;
5075 G1CollectedHeap* _g1h;
5076 HeapRegion* volatile _su_head;
5077 public:
5078 G1ParCleanupCTTask(CardTableModRefBS* ct_bs,
5079 G1CollectedHeap* g1h,
5080 HeapRegion* survivor_list) :
5081 AbstractGangTask("G1 Par Cleanup CT Task"),
5082 _ct_bs(ct_bs),
5083 _g1h(g1h),
5084 _su_head(survivor_list)
5085 { }
5087 void work(int i) {
5088 HeapRegion* r;
5089 while (r = _g1h->pop_dirty_cards_region()) {
5090 clear_cards(r);
5091 }
5092 // Redirty the cards of the survivor regions.
5093 dirty_list(&this->_su_head);
5094 }
5096 void clear_cards(HeapRegion* r) {
5097 // Cards for Survivor regions will be dirtied later.
5098 if (!r->is_survivor()) {
5099 _ct_bs->clear(MemRegion(r->bottom(), r->end()));
5100 }
5101 }
5103 void dirty_list(HeapRegion* volatile * head_ptr) {
5104 HeapRegion* head;
5105 do {
5106 // Pop region off the list.
5107 head = *head_ptr;
5108 if (head != NULL) {
5109 HeapRegion* r = (HeapRegion*)
5110 Atomic::cmpxchg_ptr(head->get_next_young_region(), head_ptr, head);
5111 if (r == head) {
5112 assert(!r->isHumongous(), "Humongous regions shouldn't be on survivor list");
5113 _ct_bs->dirty(MemRegion(r->bottom(), r->end()));
5114 }
5115 }
5116 } while (*head_ptr != NULL);
5117 }
5118 };
5121 #ifndef PRODUCT
5122 class G1VerifyCardTableCleanup: public HeapRegionClosure {
5123 CardTableModRefBS* _ct_bs;
5124 public:
5125 G1VerifyCardTableCleanup(CardTableModRefBS* ct_bs)
5126 : _ct_bs(ct_bs)
5127 { }
5128 virtual bool doHeapRegion(HeapRegion* r)
5129 {
5130 MemRegion mr(r->bottom(), r->end());
5131 if (r->is_survivor()) {
5132 _ct_bs->verify_dirty_region(mr);
5133 } else {
5134 _ct_bs->verify_clean_region(mr);
5135 }
5136 return false;
5137 }
5138 };
5139 #endif
5141 void G1CollectedHeap::cleanUpCardTable() {
5142 CardTableModRefBS* ct_bs = (CardTableModRefBS*) (barrier_set());
5143 double start = os::elapsedTime();
5145 // Iterate over the dirty cards region list.
5146 G1ParCleanupCTTask cleanup_task(ct_bs, this,
5147 _young_list->first_survivor_region());
5149 if (ParallelGCThreads > 0) {
5150 set_par_threads(workers()->total_workers());
5151 workers()->run_task(&cleanup_task);
5152 set_par_threads(0);
5153 } else {
5154 while (_dirty_cards_region_list) {
5155 HeapRegion* r = _dirty_cards_region_list;
5156 cleanup_task.clear_cards(r);
5157 _dirty_cards_region_list = r->get_next_dirty_cards_region();
5158 if (_dirty_cards_region_list == r) {
5159 // The last region.
5160 _dirty_cards_region_list = NULL;
5161 }
5162 r->set_next_dirty_cards_region(NULL);
5163 }
5164 // now, redirty the cards of the survivor regions
5165 // (it seemed faster to do it this way, instead of iterating over
5166 // all regions and then clearing / dirtying as appropriate)
5167 dirtyCardsForYoungRegions(ct_bs, _young_list->first_survivor_region());
5168 }
5170 double elapsed = os::elapsedTime() - start;
5171 g1_policy()->record_clear_ct_time( elapsed * 1000.0);
5172 #ifndef PRODUCT
5173 if (G1VerifyCTCleanup || VerifyAfterGC) {
5174 G1VerifyCardTableCleanup cleanup_verifier(ct_bs);
5175 heap_region_iterate(&cleanup_verifier);
5176 }
5177 #endif
5178 }
5180 void G1CollectedHeap::free_collection_set(HeapRegion* cs_head) {
5181 size_t pre_used = 0;
5182 FreeRegionList local_free_list("Local List for CSet Freeing");
5184 double young_time_ms = 0.0;
5185 double non_young_time_ms = 0.0;
5187 // Since the collection set is a superset of the the young list,
5188 // all we need to do to clear the young list is clear its
5189 // head and length, and unlink any young regions in the code below
5190 _young_list->clear();
5192 G1CollectorPolicy* policy = g1_policy();
5194 double start_sec = os::elapsedTime();
5195 bool non_young = true;
5197 HeapRegion* cur = cs_head;
5198 int age_bound = -1;
5199 size_t rs_lengths = 0;
5201 while (cur != NULL) {
5202 assert(!is_on_free_list(cur), "sanity");
5204 if (non_young) {
5205 if (cur->is_young()) {
5206 double end_sec = os::elapsedTime();
5207 double elapsed_ms = (end_sec - start_sec) * 1000.0;
5208 non_young_time_ms += elapsed_ms;
5210 start_sec = os::elapsedTime();
5211 non_young = false;
5212 }
5213 } else {
5214 double end_sec = os::elapsedTime();
5215 double elapsed_ms = (end_sec - start_sec) * 1000.0;
5216 young_time_ms += elapsed_ms;
5218 start_sec = os::elapsedTime();
5219 non_young = true;
5220 }
5222 rs_lengths += cur->rem_set()->occupied();
5224 HeapRegion* next = cur->next_in_collection_set();
5225 assert(cur->in_collection_set(), "bad CS");
5226 cur->set_next_in_collection_set(NULL);
5227 cur->set_in_collection_set(false);
5229 if (cur->is_young()) {
5230 int index = cur->young_index_in_cset();
5231 guarantee( index != -1, "invariant" );
5232 guarantee( (size_t)index < policy->young_cset_length(), "invariant" );
5233 size_t words_survived = _surviving_young_words[index];
5234 cur->record_surv_words_in_group(words_survived);
5236 // At this point the we have 'popped' cur from the collection set
5237 // (linked via next_in_collection_set()) but it is still in the
5238 // young list (linked via next_young_region()). Clear the
5239 // _next_young_region field.
5240 cur->set_next_young_region(NULL);
5241 } else {
5242 int index = cur->young_index_in_cset();
5243 guarantee( index == -1, "invariant" );
5244 }
5246 assert( (cur->is_young() && cur->young_index_in_cset() > -1) ||
5247 (!cur->is_young() && cur->young_index_in_cset() == -1),
5248 "invariant" );
5250 if (!cur->evacuation_failed()) {
5251 // And the region is empty.
5252 assert(!cur->is_empty(), "Should not have empty regions in a CS.");
5253 free_region(cur, &pre_used, &local_free_list, false /* par */);
5254 } else {
5255 cur->uninstall_surv_rate_group();
5256 if (cur->is_young())
5257 cur->set_young_index_in_cset(-1);
5258 cur->set_not_young();
5259 cur->set_evacuation_failed(false);
5260 }
5261 cur = next;
5262 }
5264 policy->record_max_rs_lengths(rs_lengths);
5265 policy->cset_regions_freed();
5267 double end_sec = os::elapsedTime();
5268 double elapsed_ms = (end_sec - start_sec) * 1000.0;
5269 if (non_young)
5270 non_young_time_ms += elapsed_ms;
5271 else
5272 young_time_ms += elapsed_ms;
5274 update_sets_after_freeing_regions(pre_used, &local_free_list,
5275 NULL /* humongous_proxy_set */,
5276 false /* par */);
5277 policy->record_young_free_cset_time_ms(young_time_ms);
5278 policy->record_non_young_free_cset_time_ms(non_young_time_ms);
5279 }
5281 // This routine is similar to the above but does not record
5282 // any policy statistics or update free lists; we are abandoning
5283 // the current incremental collection set in preparation of a
5284 // full collection. After the full GC we will start to build up
5285 // the incremental collection set again.
5286 // This is only called when we're doing a full collection
5287 // and is immediately followed by the tearing down of the young list.
5289 void G1CollectedHeap::abandon_collection_set(HeapRegion* cs_head) {
5290 HeapRegion* cur = cs_head;
5292 while (cur != NULL) {
5293 HeapRegion* next = cur->next_in_collection_set();
5294 assert(cur->in_collection_set(), "bad CS");
5295 cur->set_next_in_collection_set(NULL);
5296 cur->set_in_collection_set(false);
5297 cur->set_young_index_in_cset(-1);
5298 cur = next;
5299 }
5300 }
5302 void G1CollectedHeap::set_free_regions_coming() {
5303 if (G1ConcRegionFreeingVerbose) {
5304 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
5305 "setting free regions coming");
5306 }
5308 assert(!free_regions_coming(), "pre-condition");
5309 _free_regions_coming = true;
5310 }
5312 void G1CollectedHeap::reset_free_regions_coming() {
5313 {
5314 assert(free_regions_coming(), "pre-condition");
5315 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
5316 _free_regions_coming = false;
5317 SecondaryFreeList_lock->notify_all();
5318 }
5320 if (G1ConcRegionFreeingVerbose) {
5321 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
5322 "reset free regions coming");
5323 }
5324 }
5326 void G1CollectedHeap::wait_while_free_regions_coming() {
5327 // Most of the time we won't have to wait, so let's do a quick test
5328 // first before we take the lock.
5329 if (!free_regions_coming()) {
5330 return;
5331 }
5333 if (G1ConcRegionFreeingVerbose) {
5334 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
5335 "waiting for free regions");
5336 }
5338 {
5339 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
5340 while (free_regions_coming()) {
5341 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
5342 }
5343 }
5345 if (G1ConcRegionFreeingVerbose) {
5346 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
5347 "done waiting for free regions");
5348 }
5349 }
5351 size_t G1CollectedHeap::n_regions() {
5352 return _hrs->length();
5353 }
5355 size_t G1CollectedHeap::max_regions() {
5356 return
5357 (size_t)align_size_up(max_capacity(), HeapRegion::GrainBytes) /
5358 HeapRegion::GrainBytes;
5359 }
5361 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
5362 assert(heap_lock_held_for_gc(),
5363 "the heap lock should already be held by or for this thread");
5364 _young_list->push_region(hr);
5365 g1_policy()->set_region_short_lived(hr);
5366 }
5368 class NoYoungRegionsClosure: public HeapRegionClosure {
5369 private:
5370 bool _success;
5371 public:
5372 NoYoungRegionsClosure() : _success(true) { }
5373 bool doHeapRegion(HeapRegion* r) {
5374 if (r->is_young()) {
5375 gclog_or_tty->print_cr("Region ["PTR_FORMAT", "PTR_FORMAT") tagged as young",
5376 r->bottom(), r->end());
5377 _success = false;
5378 }
5379 return false;
5380 }
5381 bool success() { return _success; }
5382 };
5384 bool G1CollectedHeap::check_young_list_empty(bool check_heap, bool check_sample) {
5385 bool ret = _young_list->check_list_empty(check_sample);
5387 if (check_heap) {
5388 NoYoungRegionsClosure closure;
5389 heap_region_iterate(&closure);
5390 ret = ret && closure.success();
5391 }
5393 return ret;
5394 }
5396 void G1CollectedHeap::empty_young_list() {
5397 assert(heap_lock_held_for_gc(),
5398 "the heap lock should already be held by or for this thread");
5399 assert(g1_policy()->in_young_gc_mode(), "should be in young GC mode");
5401 _young_list->empty_list();
5402 }
5404 bool G1CollectedHeap::all_alloc_regions_no_allocs_since_save_marks() {
5405 bool no_allocs = true;
5406 for (int ap = 0; ap < GCAllocPurposeCount && no_allocs; ++ap) {
5407 HeapRegion* r = _gc_alloc_regions[ap];
5408 no_allocs = r == NULL || r->saved_mark_at_top();
5409 }
5410 return no_allocs;
5411 }
5413 void G1CollectedHeap::retire_all_alloc_regions() {
5414 for (int ap = 0; ap < GCAllocPurposeCount; ++ap) {
5415 HeapRegion* r = _gc_alloc_regions[ap];
5416 if (r != NULL) {
5417 // Check for aliases.
5418 bool has_processed_alias = false;
5419 for (int i = 0; i < ap; ++i) {
5420 if (_gc_alloc_regions[i] == r) {
5421 has_processed_alias = true;
5422 break;
5423 }
5424 }
5425 if (!has_processed_alias) {
5426 retire_alloc_region(r, false /* par */);
5427 }
5428 }
5429 }
5430 }
5432 // Done at the start of full GC.
5433 void G1CollectedHeap::tear_down_region_lists() {
5434 _free_list.remove_all();
5435 }
5437 class RegionResetter: public HeapRegionClosure {
5438 G1CollectedHeap* _g1h;
5439 FreeRegionList _local_free_list;
5441 public:
5442 RegionResetter() : _g1h(G1CollectedHeap::heap()),
5443 _local_free_list("Local Free List for RegionResetter") { }
5445 bool doHeapRegion(HeapRegion* r) {
5446 if (r->continuesHumongous()) return false;
5447 if (r->top() > r->bottom()) {
5448 if (r->top() < r->end()) {
5449 Copy::fill_to_words(r->top(),
5450 pointer_delta(r->end(), r->top()));
5451 }
5452 } else {
5453 assert(r->is_empty(), "tautology");
5454 _local_free_list.add_as_tail(r);
5455 }
5456 return false;
5457 }
5459 void update_free_lists() {
5460 _g1h->update_sets_after_freeing_regions(0, &_local_free_list, NULL,
5461 false /* par */);
5462 }
5463 };
5465 // Done at the end of full GC.
5466 void G1CollectedHeap::rebuild_region_lists() {
5467 // This needs to go at the end of the full GC.
5468 RegionResetter rs;
5469 heap_region_iterate(&rs);
5470 rs.update_free_lists();
5471 }
5473 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) {
5474 _refine_cte_cl->set_concurrent(concurrent);
5475 }
5477 #ifdef ASSERT
5479 bool G1CollectedHeap::is_in_closed_subset(const void* p) const {
5480 HeapRegion* hr = heap_region_containing(p);
5481 if (hr == NULL) {
5482 return is_in_permanent(p);
5483 } else {
5484 return hr->is_in(p);
5485 }
5486 }
5487 #endif // ASSERT
5489 class VerifyRegionListsClosure : public HeapRegionClosure {
5490 private:
5491 HumongousRegionSet* _humongous_set;
5492 FreeRegionList* _free_list;
5493 size_t _region_count;
5495 public:
5496 VerifyRegionListsClosure(HumongousRegionSet* humongous_set,
5497 FreeRegionList* free_list) :
5498 _humongous_set(humongous_set), _free_list(free_list),
5499 _region_count(0) { }
5501 size_t region_count() { return _region_count; }
5503 bool doHeapRegion(HeapRegion* hr) {
5504 _region_count += 1;
5506 if (hr->continuesHumongous()) {
5507 return false;
5508 }
5510 if (hr->is_young()) {
5511 // TODO
5512 } else if (hr->startsHumongous()) {
5513 _humongous_set->verify_next_region(hr);
5514 } else if (hr->is_empty()) {
5515 _free_list->verify_next_region(hr);
5516 }
5517 return false;
5518 }
5519 };
5521 void G1CollectedHeap::verify_region_sets() {
5522 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
5524 // First, check the explicit lists.
5525 _free_list.verify();
5526 {
5527 // Given that a concurrent operation might be adding regions to
5528 // the secondary free list we have to take the lock before
5529 // verifying it.
5530 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
5531 _secondary_free_list.verify();
5532 }
5533 _humongous_set.verify();
5535 // If a concurrent region freeing operation is in progress it will
5536 // be difficult to correctly attributed any free regions we come
5537 // across to the correct free list given that they might belong to
5538 // one of several (free_list, secondary_free_list, any local lists,
5539 // etc.). So, if that's the case we will skip the rest of the
5540 // verification operation. Alternatively, waiting for the concurrent
5541 // operation to complete will have a non-trivial effect on the GC's
5542 // operation (no concurrent operation will last longer than the
5543 // interval between two calls to verification) and it might hide
5544 // any issues that we would like to catch during testing.
5545 if (free_regions_coming()) {
5546 return;
5547 }
5549 {
5550 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
5551 // Make sure we append the secondary_free_list on the free_list so
5552 // that all free regions we will come across can be safely
5553 // attributed to the free_list.
5554 append_secondary_free_list();
5555 }
5557 // Finally, make sure that the region accounting in the lists is
5558 // consistent with what we see in the heap.
5559 _humongous_set.verify_start();
5560 _free_list.verify_start();
5562 VerifyRegionListsClosure cl(&_humongous_set, &_free_list);
5563 heap_region_iterate(&cl);
5565 _humongous_set.verify_end();
5566 _free_list.verify_end();
5567 }