Mon, 01 Dec 2014 15:24:56 +0100
8075210: Refactor strong root processing in order to allow G1 to evolve separately from GenCollectedHeap
Summary: Create a G1RootProcessor and move SharedHeap root processing to GenCollectedHeap
Reviewed-by: brutisso, tschatzl, ehelin
1 /*
2 * Copyright (c) 2001, 2014, 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 #if !defined(__clang_major__) && defined(__GNUC__)
26 #define ATTRIBUTE_PRINTF(x,y) // FIXME, formats are a mess.
27 #endif
29 #include "precompiled.hpp"
30 #include "classfile/metadataOnStackMark.hpp"
31 #include "code/codeCache.hpp"
32 #include "code/icBuffer.hpp"
33 #include "gc_implementation/g1/bufferingOopClosure.hpp"
34 #include "gc_implementation/g1/concurrentG1Refine.hpp"
35 #include "gc_implementation/g1/concurrentG1RefineThread.hpp"
36 #include "gc_implementation/g1/concurrentMarkThread.inline.hpp"
37 #include "gc_implementation/g1/g1AllocRegion.inline.hpp"
38 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
39 #include "gc_implementation/g1/g1CollectorPolicy.hpp"
40 #include "gc_implementation/g1/g1ErgoVerbose.hpp"
41 #include "gc_implementation/g1/g1EvacFailure.hpp"
42 #include "gc_implementation/g1/g1GCPhaseTimes.hpp"
43 #include "gc_implementation/g1/g1Log.hpp"
44 #include "gc_implementation/g1/g1MarkSweep.hpp"
45 #include "gc_implementation/g1/g1OopClosures.inline.hpp"
46 #include "gc_implementation/g1/g1ParScanThreadState.inline.hpp"
47 #include "gc_implementation/g1/g1RegionToSpaceMapper.hpp"
48 #include "gc_implementation/g1/g1RemSet.inline.hpp"
49 #include "gc_implementation/g1/g1RootProcessor.hpp"
50 #include "gc_implementation/g1/g1StringDedup.hpp"
51 #include "gc_implementation/g1/g1YCTypes.hpp"
52 #include "gc_implementation/g1/heapRegion.inline.hpp"
53 #include "gc_implementation/g1/heapRegionRemSet.hpp"
54 #include "gc_implementation/g1/heapRegionSet.inline.hpp"
55 #include "gc_implementation/g1/vm_operations_g1.hpp"
56 #include "gc_implementation/shared/gcHeapSummary.hpp"
57 #include "gc_implementation/shared/gcTimer.hpp"
58 #include "gc_implementation/shared/gcTrace.hpp"
59 #include "gc_implementation/shared/gcTraceTime.hpp"
60 #include "gc_implementation/shared/isGCActiveMark.hpp"
61 #include "memory/allocation.hpp"
62 #include "memory/gcLocker.inline.hpp"
63 #include "memory/generationSpec.hpp"
64 #include "memory/iterator.hpp"
65 #include "memory/referenceProcessor.hpp"
66 #include "oops/oop.inline.hpp"
67 #include "oops/oop.pcgc.inline.hpp"
68 #include "runtime/orderAccess.inline.hpp"
69 #include "runtime/vmThread.hpp"
71 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;
73 // turn it on so that the contents of the young list (scan-only /
74 // to-be-collected) are printed at "strategic" points before / during
75 // / after the collection --- this is useful for debugging
76 #define YOUNG_LIST_VERBOSE 0
77 // CURRENT STATUS
78 // This file is under construction. Search for "FIXME".
80 // INVARIANTS/NOTES
81 //
82 // All allocation activity covered by the G1CollectedHeap interface is
83 // serialized by acquiring the HeapLock. This happens in mem_allocate
84 // and allocate_new_tlab, which are the "entry" points to the
85 // allocation code from the rest of the JVM. (Note that this does not
86 // apply to TLAB allocation, which is not part of this interface: it
87 // is done by clients of this interface.)
89 // Local to this file.
91 class RefineCardTableEntryClosure: public CardTableEntryClosure {
92 bool _concurrent;
93 public:
94 RefineCardTableEntryClosure() : _concurrent(true) { }
96 bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
97 bool oops_into_cset = G1CollectedHeap::heap()->g1_rem_set()->refine_card(card_ptr, worker_i, false);
98 // This path is executed by the concurrent refine or mutator threads,
99 // concurrently, and so we do not care if card_ptr contains references
100 // that point into the collection set.
101 assert(!oops_into_cset, "should be");
103 if (_concurrent && SuspendibleThreadSet::should_yield()) {
104 // Caller will actually yield.
105 return false;
106 }
107 // Otherwise, we finished successfully; return true.
108 return true;
109 }
111 void set_concurrent(bool b) { _concurrent = b; }
112 };
115 class ClearLoggedCardTableEntryClosure: public CardTableEntryClosure {
116 size_t _num_processed;
117 CardTableModRefBS* _ctbs;
118 int _histo[256];
120 public:
121 ClearLoggedCardTableEntryClosure() :
122 _num_processed(0), _ctbs(G1CollectedHeap::heap()->g1_barrier_set())
123 {
124 for (int i = 0; i < 256; i++) _histo[i] = 0;
125 }
127 bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
128 unsigned char* ujb = (unsigned char*)card_ptr;
129 int ind = (int)(*ujb);
130 _histo[ind]++;
132 *card_ptr = (jbyte)CardTableModRefBS::clean_card_val();
133 _num_processed++;
135 return true;
136 }
138 size_t num_processed() { return _num_processed; }
140 void print_histo() {
141 gclog_or_tty->print_cr("Card table value histogram:");
142 for (int i = 0; i < 256; i++) {
143 if (_histo[i] != 0) {
144 gclog_or_tty->print_cr(" %d: %d", i, _histo[i]);
145 }
146 }
147 }
148 };
150 class RedirtyLoggedCardTableEntryClosure : public CardTableEntryClosure {
151 private:
152 size_t _num_processed;
154 public:
155 RedirtyLoggedCardTableEntryClosure() : CardTableEntryClosure(), _num_processed(0) { }
157 bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
158 *card_ptr = CardTableModRefBS::dirty_card_val();
159 _num_processed++;
160 return true;
161 }
163 size_t num_processed() const { return _num_processed; }
164 };
166 YoungList::YoungList(G1CollectedHeap* g1h) :
167 _g1h(g1h), _head(NULL), _length(0), _last_sampled_rs_lengths(0),
168 _survivor_head(NULL), _survivor_tail(NULL), _survivor_length(0) {
169 guarantee(check_list_empty(false), "just making sure...");
170 }
172 void YoungList::push_region(HeapRegion *hr) {
173 assert(!hr->is_young(), "should not already be young");
174 assert(hr->get_next_young_region() == NULL, "cause it should!");
176 hr->set_next_young_region(_head);
177 _head = hr;
179 _g1h->g1_policy()->set_region_eden(hr, (int) _length);
180 ++_length;
181 }
183 void YoungList::add_survivor_region(HeapRegion* hr) {
184 assert(hr->is_survivor(), "should be flagged as survivor region");
185 assert(hr->get_next_young_region() == NULL, "cause it should!");
187 hr->set_next_young_region(_survivor_head);
188 if (_survivor_head == NULL) {
189 _survivor_tail = hr;
190 }
191 _survivor_head = hr;
192 ++_survivor_length;
193 }
195 void YoungList::empty_list(HeapRegion* list) {
196 while (list != NULL) {
197 HeapRegion* next = list->get_next_young_region();
198 list->set_next_young_region(NULL);
199 list->uninstall_surv_rate_group();
200 // This is called before a Full GC and all the non-empty /
201 // non-humongous regions at the end of the Full GC will end up as
202 // old anyway.
203 list->set_old();
204 list = next;
205 }
206 }
208 void YoungList::empty_list() {
209 assert(check_list_well_formed(), "young list should be well formed");
211 empty_list(_head);
212 _head = NULL;
213 _length = 0;
215 empty_list(_survivor_head);
216 _survivor_head = NULL;
217 _survivor_tail = NULL;
218 _survivor_length = 0;
220 _last_sampled_rs_lengths = 0;
222 assert(check_list_empty(false), "just making sure...");
223 }
225 bool YoungList::check_list_well_formed() {
226 bool ret = true;
228 uint length = 0;
229 HeapRegion* curr = _head;
230 HeapRegion* last = NULL;
231 while (curr != NULL) {
232 if (!curr->is_young()) {
233 gclog_or_tty->print_cr("### YOUNG REGION "PTR_FORMAT"-"PTR_FORMAT" "
234 "incorrectly tagged (y: %d, surv: %d)",
235 curr->bottom(), curr->end(),
236 curr->is_young(), curr->is_survivor());
237 ret = false;
238 }
239 ++length;
240 last = curr;
241 curr = curr->get_next_young_region();
242 }
243 ret = ret && (length == _length);
245 if (!ret) {
246 gclog_or_tty->print_cr("### YOUNG LIST seems not well formed!");
247 gclog_or_tty->print_cr("### list has %u entries, _length is %u",
248 length, _length);
249 }
251 return ret;
252 }
254 bool YoungList::check_list_empty(bool check_sample) {
255 bool ret = true;
257 if (_length != 0) {
258 gclog_or_tty->print_cr("### YOUNG LIST should have 0 length, not %u",
259 _length);
260 ret = false;
261 }
262 if (check_sample && _last_sampled_rs_lengths != 0) {
263 gclog_or_tty->print_cr("### YOUNG LIST has non-zero last sampled RS lengths");
264 ret = false;
265 }
266 if (_head != NULL) {
267 gclog_or_tty->print_cr("### YOUNG LIST does not have a NULL head");
268 ret = false;
269 }
270 if (!ret) {
271 gclog_or_tty->print_cr("### YOUNG LIST does not seem empty");
272 }
274 return ret;
275 }
277 void
278 YoungList::rs_length_sampling_init() {
279 _sampled_rs_lengths = 0;
280 _curr = _head;
281 }
283 bool
284 YoungList::rs_length_sampling_more() {
285 return _curr != NULL;
286 }
288 void
289 YoungList::rs_length_sampling_next() {
290 assert( _curr != NULL, "invariant" );
291 size_t rs_length = _curr->rem_set()->occupied();
293 _sampled_rs_lengths += rs_length;
295 // The current region may not yet have been added to the
296 // incremental collection set (it gets added when it is
297 // retired as the current allocation region).
298 if (_curr->in_collection_set()) {
299 // Update the collection set policy information for this region
300 _g1h->g1_policy()->update_incremental_cset_info(_curr, rs_length);
301 }
303 _curr = _curr->get_next_young_region();
304 if (_curr == NULL) {
305 _last_sampled_rs_lengths = _sampled_rs_lengths;
306 // gclog_or_tty->print_cr("last sampled RS lengths = %d", _last_sampled_rs_lengths);
307 }
308 }
310 void
311 YoungList::reset_auxilary_lists() {
312 guarantee( is_empty(), "young list should be empty" );
313 assert(check_list_well_formed(), "young list should be well formed");
315 // Add survivor regions to SurvRateGroup.
316 _g1h->g1_policy()->note_start_adding_survivor_regions();
317 _g1h->g1_policy()->finished_recalculating_age_indexes(true /* is_survivors */);
319 int young_index_in_cset = 0;
320 for (HeapRegion* curr = _survivor_head;
321 curr != NULL;
322 curr = curr->get_next_young_region()) {
323 _g1h->g1_policy()->set_region_survivor(curr, young_index_in_cset);
325 // The region is a non-empty survivor so let's add it to
326 // the incremental collection set for the next evacuation
327 // pause.
328 _g1h->g1_policy()->add_region_to_incremental_cset_rhs(curr);
329 young_index_in_cset += 1;
330 }
331 assert((uint) young_index_in_cset == _survivor_length, "post-condition");
332 _g1h->g1_policy()->note_stop_adding_survivor_regions();
334 _head = _survivor_head;
335 _length = _survivor_length;
336 if (_survivor_head != NULL) {
337 assert(_survivor_tail != NULL, "cause it shouldn't be");
338 assert(_survivor_length > 0, "invariant");
339 _survivor_tail->set_next_young_region(NULL);
340 }
342 // Don't clear the survivor list handles until the start of
343 // the next evacuation pause - we need it in order to re-tag
344 // the survivor regions from this evacuation pause as 'young'
345 // at the start of the next.
347 _g1h->g1_policy()->finished_recalculating_age_indexes(false /* is_survivors */);
349 assert(check_list_well_formed(), "young list should be well formed");
350 }
352 void YoungList::print() {
353 HeapRegion* lists[] = {_head, _survivor_head};
354 const char* names[] = {"YOUNG", "SURVIVOR"};
356 for (unsigned int list = 0; list < ARRAY_SIZE(lists); ++list) {
357 gclog_or_tty->print_cr("%s LIST CONTENTS", names[list]);
358 HeapRegion *curr = lists[list];
359 if (curr == NULL)
360 gclog_or_tty->print_cr(" empty");
361 while (curr != NULL) {
362 gclog_or_tty->print_cr(" "HR_FORMAT", P: "PTR_FORMAT ", N: "PTR_FORMAT", age: %4d",
363 HR_FORMAT_PARAMS(curr),
364 curr->prev_top_at_mark_start(),
365 curr->next_top_at_mark_start(),
366 curr->age_in_surv_rate_group_cond());
367 curr = curr->get_next_young_region();
368 }
369 }
371 gclog_or_tty->cr();
372 }
374 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) {
375 OtherRegionsTable::invalidate(start_idx, num_regions);
376 }
378 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) {
379 // The from card cache is not the memory that is actually committed. So we cannot
380 // take advantage of the zero_filled parameter.
381 reset_from_card_cache(start_idx, num_regions);
382 }
384 void G1CollectedHeap::push_dirty_cards_region(HeapRegion* hr)
385 {
386 // Claim the right to put the region on the dirty cards region list
387 // by installing a self pointer.
388 HeapRegion* next = hr->get_next_dirty_cards_region();
389 if (next == NULL) {
390 HeapRegion* res = (HeapRegion*)
391 Atomic::cmpxchg_ptr(hr, hr->next_dirty_cards_region_addr(),
392 NULL);
393 if (res == NULL) {
394 HeapRegion* head;
395 do {
396 // Put the region to the dirty cards region list.
397 head = _dirty_cards_region_list;
398 next = (HeapRegion*)
399 Atomic::cmpxchg_ptr(hr, &_dirty_cards_region_list, head);
400 if (next == head) {
401 assert(hr->get_next_dirty_cards_region() == hr,
402 "hr->get_next_dirty_cards_region() != hr");
403 if (next == NULL) {
404 // The last region in the list points to itself.
405 hr->set_next_dirty_cards_region(hr);
406 } else {
407 hr->set_next_dirty_cards_region(next);
408 }
409 }
410 } while (next != head);
411 }
412 }
413 }
415 HeapRegion* G1CollectedHeap::pop_dirty_cards_region()
416 {
417 HeapRegion* head;
418 HeapRegion* hr;
419 do {
420 head = _dirty_cards_region_list;
421 if (head == NULL) {
422 return NULL;
423 }
424 HeapRegion* new_head = head->get_next_dirty_cards_region();
425 if (head == new_head) {
426 // The last region.
427 new_head = NULL;
428 }
429 hr = (HeapRegion*)Atomic::cmpxchg_ptr(new_head, &_dirty_cards_region_list,
430 head);
431 } while (hr != head);
432 assert(hr != NULL, "invariant");
433 hr->set_next_dirty_cards_region(NULL);
434 return hr;
435 }
437 #ifdef ASSERT
438 // A region is added to the collection set as it is retired
439 // so an address p can point to a region which will be in the
440 // collection set but has not yet been retired. This method
441 // therefore is only accurate during a GC pause after all
442 // regions have been retired. It is used for debugging
443 // to check if an nmethod has references to objects that can
444 // be move during a partial collection. Though it can be
445 // inaccurate, it is sufficient for G1 because the conservative
446 // implementation of is_scavengable() for G1 will indicate that
447 // all nmethods must be scanned during a partial collection.
448 bool G1CollectedHeap::is_in_partial_collection(const void* p) {
449 if (p == NULL) {
450 return false;
451 }
452 return heap_region_containing(p)->in_collection_set();
453 }
454 #endif
456 // Returns true if the reference points to an object that
457 // can move in an incremental collection.
458 bool G1CollectedHeap::is_scavengable(const void* p) {
459 HeapRegion* hr = heap_region_containing(p);
460 return !hr->isHumongous();
461 }
463 void G1CollectedHeap::check_ct_logs_at_safepoint() {
464 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
465 CardTableModRefBS* ct_bs = g1_barrier_set();
467 // Count the dirty cards at the start.
468 CountNonCleanMemRegionClosure count1(this);
469 ct_bs->mod_card_iterate(&count1);
470 int orig_count = count1.n();
472 // First clear the logged cards.
473 ClearLoggedCardTableEntryClosure clear;
474 dcqs.apply_closure_to_all_completed_buffers(&clear);
475 dcqs.iterate_closure_all_threads(&clear, false);
476 clear.print_histo();
478 // Now ensure that there's no dirty cards.
479 CountNonCleanMemRegionClosure count2(this);
480 ct_bs->mod_card_iterate(&count2);
481 if (count2.n() != 0) {
482 gclog_or_tty->print_cr("Card table has %d entries; %d originally",
483 count2.n(), orig_count);
484 }
485 guarantee(count2.n() == 0, "Card table should be clean.");
487 RedirtyLoggedCardTableEntryClosure redirty;
488 dcqs.apply_closure_to_all_completed_buffers(&redirty);
489 dcqs.iterate_closure_all_threads(&redirty, false);
490 gclog_or_tty->print_cr("Log entries = %d, dirty cards = %d.",
491 clear.num_processed(), orig_count);
492 guarantee(redirty.num_processed() == clear.num_processed(),
493 err_msg("Redirtied "SIZE_FORMAT" cards, bug cleared "SIZE_FORMAT,
494 redirty.num_processed(), clear.num_processed()));
496 CountNonCleanMemRegionClosure count3(this);
497 ct_bs->mod_card_iterate(&count3);
498 if (count3.n() != orig_count) {
499 gclog_or_tty->print_cr("Should have restored them all: orig = %d, final = %d.",
500 orig_count, count3.n());
501 guarantee(count3.n() >= orig_count, "Should have restored them all.");
502 }
503 }
505 // Private class members.
507 G1CollectedHeap* G1CollectedHeap::_g1h;
509 // Private methods.
511 HeapRegion*
512 G1CollectedHeap::new_region_try_secondary_free_list(bool is_old) {
513 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
514 while (!_secondary_free_list.is_empty() || free_regions_coming()) {
515 if (!_secondary_free_list.is_empty()) {
516 if (G1ConcRegionFreeingVerbose) {
517 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
518 "secondary_free_list has %u entries",
519 _secondary_free_list.length());
520 }
521 // It looks as if there are free regions available on the
522 // secondary_free_list. Let's move them to the free_list and try
523 // again to allocate from it.
524 append_secondary_free_list();
526 assert(_hrm.num_free_regions() > 0, "if the secondary_free_list was not "
527 "empty we should have moved at least one entry to the free_list");
528 HeapRegion* res = _hrm.allocate_free_region(is_old);
529 if (G1ConcRegionFreeingVerbose) {
530 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
531 "allocated "HR_FORMAT" from secondary_free_list",
532 HR_FORMAT_PARAMS(res));
533 }
534 return res;
535 }
537 // Wait here until we get notified either when (a) there are no
538 // more free regions coming or (b) some regions have been moved on
539 // the secondary_free_list.
540 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
541 }
543 if (G1ConcRegionFreeingVerbose) {
544 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
545 "could not allocate from secondary_free_list");
546 }
547 return NULL;
548 }
550 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) {
551 assert(!isHumongous(word_size) || word_size <= HeapRegion::GrainWords,
552 "the only time we use this to allocate a humongous region is "
553 "when we are allocating a single humongous region");
555 HeapRegion* res;
556 if (G1StressConcRegionFreeing) {
557 if (!_secondary_free_list.is_empty()) {
558 if (G1ConcRegionFreeingVerbose) {
559 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
560 "forced to look at the secondary_free_list");
561 }
562 res = new_region_try_secondary_free_list(is_old);
563 if (res != NULL) {
564 return res;
565 }
566 }
567 }
569 res = _hrm.allocate_free_region(is_old);
571 if (res == NULL) {
572 if (G1ConcRegionFreeingVerbose) {
573 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
574 "res == NULL, trying the secondary_free_list");
575 }
576 res = new_region_try_secondary_free_list(is_old);
577 }
578 if (res == NULL && do_expand && _expand_heap_after_alloc_failure) {
579 // Currently, only attempts to allocate GC alloc regions set
580 // do_expand to true. So, we should only reach here during a
581 // safepoint. If this assumption changes we might have to
582 // reconsider the use of _expand_heap_after_alloc_failure.
583 assert(SafepointSynchronize::is_at_safepoint(), "invariant");
585 ergo_verbose1(ErgoHeapSizing,
586 "attempt heap expansion",
587 ergo_format_reason("region allocation request failed")
588 ergo_format_byte("allocation request"),
589 word_size * HeapWordSize);
590 if (expand(word_size * HeapWordSize)) {
591 // Given that expand() succeeded in expanding the heap, and we
592 // always expand the heap by an amount aligned to the heap
593 // region size, the free list should in theory not be empty.
594 // In either case allocate_free_region() will check for NULL.
595 res = _hrm.allocate_free_region(is_old);
596 } else {
597 _expand_heap_after_alloc_failure = false;
598 }
599 }
600 return res;
601 }
603 HeapWord*
604 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first,
605 uint num_regions,
606 size_t word_size,
607 AllocationContext_t context) {
608 assert(first != G1_NO_HRM_INDEX, "pre-condition");
609 assert(isHumongous(word_size), "word_size should be humongous");
610 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
612 // Index of last region in the series + 1.
613 uint last = first + num_regions;
615 // We need to initialize the region(s) we just discovered. This is
616 // a bit tricky given that it can happen concurrently with
617 // refinement threads refining cards on these regions and
618 // potentially wanting to refine the BOT as they are scanning
619 // those cards (this can happen shortly after a cleanup; see CR
620 // 6991377). So we have to set up the region(s) carefully and in
621 // a specific order.
623 // The word size sum of all the regions we will allocate.
624 size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords;
625 assert(word_size <= word_size_sum, "sanity");
627 // This will be the "starts humongous" region.
628 HeapRegion* first_hr = region_at(first);
629 // The header of the new object will be placed at the bottom of
630 // the first region.
631 HeapWord* new_obj = first_hr->bottom();
632 // This will be the new end of the first region in the series that
633 // should also match the end of the last region in the series.
634 HeapWord* new_end = new_obj + word_size_sum;
635 // This will be the new top of the first region that will reflect
636 // this allocation.
637 HeapWord* new_top = new_obj + word_size;
639 // First, we need to zero the header of the space that we will be
640 // allocating. When we update top further down, some refinement
641 // threads might try to scan the region. By zeroing the header we
642 // ensure that any thread that will try to scan the region will
643 // come across the zero klass word and bail out.
644 //
645 // NOTE: It would not have been correct to have used
646 // CollectedHeap::fill_with_object() and make the space look like
647 // an int array. The thread that is doing the allocation will
648 // later update the object header to a potentially different array
649 // type and, for a very short period of time, the klass and length
650 // fields will be inconsistent. This could cause a refinement
651 // thread to calculate the object size incorrectly.
652 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
654 // We will set up the first region as "starts humongous". This
655 // will also update the BOT covering all the regions to reflect
656 // that there is a single object that starts at the bottom of the
657 // first region.
658 first_hr->set_startsHumongous(new_top, new_end);
659 first_hr->set_allocation_context(context);
660 // Then, if there are any, we will set up the "continues
661 // humongous" regions.
662 HeapRegion* hr = NULL;
663 for (uint i = first + 1; i < last; ++i) {
664 hr = region_at(i);
665 hr->set_continuesHumongous(first_hr);
666 hr->set_allocation_context(context);
667 }
668 // If we have "continues humongous" regions (hr != NULL), then the
669 // end of the last one should match new_end.
670 assert(hr == NULL || hr->end() == new_end, "sanity");
672 // Up to this point no concurrent thread would have been able to
673 // do any scanning on any region in this series. All the top
674 // fields still point to bottom, so the intersection between
675 // [bottom,top] and [card_start,card_end] will be empty. Before we
676 // update the top fields, we'll do a storestore to make sure that
677 // no thread sees the update to top before the zeroing of the
678 // object header and the BOT initialization.
679 OrderAccess::storestore();
681 // Now that the BOT and the object header have been initialized,
682 // we can update top of the "starts humongous" region.
683 assert(first_hr->bottom() < new_top && new_top <= first_hr->end(),
684 "new_top should be in this region");
685 first_hr->set_top(new_top);
686 if (_hr_printer.is_active()) {
687 HeapWord* bottom = first_hr->bottom();
688 HeapWord* end = first_hr->orig_end();
689 if ((first + 1) == last) {
690 // the series has a single humongous region
691 _hr_printer.alloc(G1HRPrinter::SingleHumongous, first_hr, new_top);
692 } else {
693 // the series has more than one humongous regions
694 _hr_printer.alloc(G1HRPrinter::StartsHumongous, first_hr, end);
695 }
696 }
698 // Now, we will update the top fields of the "continues humongous"
699 // regions. The reason we need to do this is that, otherwise,
700 // these regions would look empty and this will confuse parts of
701 // G1. For example, the code that looks for a consecutive number
702 // of empty regions will consider them empty and try to
703 // re-allocate them. We can extend is_empty() to also include
704 // !continuesHumongous(), but it is easier to just update the top
705 // fields here. The way we set top for all regions (i.e., top ==
706 // end for all regions but the last one, top == new_top for the
707 // last one) is actually used when we will free up the humongous
708 // region in free_humongous_region().
709 hr = NULL;
710 for (uint i = first + 1; i < last; ++i) {
711 hr = region_at(i);
712 if ((i + 1) == last) {
713 // last continues humongous region
714 assert(hr->bottom() < new_top && new_top <= hr->end(),
715 "new_top should fall on this region");
716 hr->set_top(new_top);
717 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, new_top);
718 } else {
719 // not last one
720 assert(new_top > hr->end(), "new_top should be above this region");
721 hr->set_top(hr->end());
722 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, hr->end());
723 }
724 }
725 // If we have continues humongous regions (hr != NULL), then the
726 // end of the last one should match new_end and its top should
727 // match new_top.
728 assert(hr == NULL ||
729 (hr->end() == new_end && hr->top() == new_top), "sanity");
730 check_bitmaps("Humongous Region Allocation", first_hr);
732 assert(first_hr->used() == word_size * HeapWordSize, "invariant");
733 _allocator->increase_used(first_hr->used());
734 _humongous_set.add(first_hr);
736 return new_obj;
737 }
739 // If could fit into free regions w/o expansion, try.
740 // Otherwise, if can expand, do so.
741 // Otherwise, if using ex regions might help, try with ex given back.
742 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size, AllocationContext_t context) {
743 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
745 verify_region_sets_optional();
747 uint first = G1_NO_HRM_INDEX;
748 uint obj_regions = (uint)(align_size_up_(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords);
750 if (obj_regions == 1) {
751 // Only one region to allocate, try to use a fast path by directly allocating
752 // from the free lists. Do not try to expand here, we will potentially do that
753 // later.
754 HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */);
755 if (hr != NULL) {
756 first = hr->hrm_index();
757 }
758 } else {
759 // We can't allocate humongous regions spanning more than one region while
760 // cleanupComplete() is running, since some of the regions we find to be
761 // empty might not yet be added to the free list. It is not straightforward
762 // to know in which list they are on so that we can remove them. We only
763 // need to do this if we need to allocate more than one region to satisfy the
764 // current humongous allocation request. If we are only allocating one region
765 // we use the one-region region allocation code (see above), that already
766 // potentially waits for regions from the secondary free list.
767 wait_while_free_regions_coming();
768 append_secondary_free_list_if_not_empty_with_lock();
770 // Policy: Try only empty regions (i.e. already committed first). Maybe we
771 // are lucky enough to find some.
772 first = _hrm.find_contiguous_only_empty(obj_regions);
773 if (first != G1_NO_HRM_INDEX) {
774 _hrm.allocate_free_regions_starting_at(first, obj_regions);
775 }
776 }
778 if (first == G1_NO_HRM_INDEX) {
779 // Policy: We could not find enough regions for the humongous object in the
780 // free list. Look through the heap to find a mix of free and uncommitted regions.
781 // If so, try expansion.
782 first = _hrm.find_contiguous_empty_or_unavailable(obj_regions);
783 if (first != G1_NO_HRM_INDEX) {
784 // We found something. Make sure these regions are committed, i.e. expand
785 // the heap. Alternatively we could do a defragmentation GC.
786 ergo_verbose1(ErgoHeapSizing,
787 "attempt heap expansion",
788 ergo_format_reason("humongous allocation request failed")
789 ergo_format_byte("allocation request"),
790 word_size * HeapWordSize);
792 _hrm.expand_at(first, obj_regions);
793 g1_policy()->record_new_heap_size(num_regions());
795 #ifdef ASSERT
796 for (uint i = first; i < first + obj_regions; ++i) {
797 HeapRegion* hr = region_at(i);
798 assert(hr->is_free(), "sanity");
799 assert(hr->is_empty(), "sanity");
800 assert(is_on_master_free_list(hr), "sanity");
801 }
802 #endif
803 _hrm.allocate_free_regions_starting_at(first, obj_regions);
804 } else {
805 // Policy: Potentially trigger a defragmentation GC.
806 }
807 }
809 HeapWord* result = NULL;
810 if (first != G1_NO_HRM_INDEX) {
811 result = humongous_obj_allocate_initialize_regions(first, obj_regions,
812 word_size, context);
813 assert(result != NULL, "it should always return a valid result");
815 // A successful humongous object allocation changes the used space
816 // information of the old generation so we need to recalculate the
817 // sizes and update the jstat counters here.
818 g1mm()->update_sizes();
819 }
821 verify_region_sets_optional();
823 return result;
824 }
826 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) {
827 assert_heap_not_locked_and_not_at_safepoint();
828 assert(!isHumongous(word_size), "we do not allow humongous TLABs");
830 unsigned int dummy_gc_count_before;
831 int dummy_gclocker_retry_count = 0;
832 return attempt_allocation(word_size, &dummy_gc_count_before, &dummy_gclocker_retry_count);
833 }
835 HeapWord*
836 G1CollectedHeap::mem_allocate(size_t word_size,
837 bool* gc_overhead_limit_was_exceeded) {
838 assert_heap_not_locked_and_not_at_safepoint();
840 // Loop until the allocation is satisfied, or unsatisfied after GC.
841 for (int try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
842 unsigned int gc_count_before;
844 HeapWord* result = NULL;
845 if (!isHumongous(word_size)) {
846 result = attempt_allocation(word_size, &gc_count_before, &gclocker_retry_count);
847 } else {
848 result = attempt_allocation_humongous(word_size, &gc_count_before, &gclocker_retry_count);
849 }
850 if (result != NULL) {
851 return result;
852 }
854 // Create the garbage collection operation...
855 VM_G1CollectForAllocation op(gc_count_before, word_size);
856 op.set_allocation_context(AllocationContext::current());
858 // ...and get the VM thread to execute it.
859 VMThread::execute(&op);
861 if (op.prologue_succeeded() && op.pause_succeeded()) {
862 // If the operation was successful we'll return the result even
863 // if it is NULL. If the allocation attempt failed immediately
864 // after a Full GC, it's unlikely we'll be able to allocate now.
865 HeapWord* result = op.result();
866 if (result != NULL && !isHumongous(word_size)) {
867 // Allocations that take place on VM operations do not do any
868 // card dirtying and we have to do it here. We only have to do
869 // this for non-humongous allocations, though.
870 dirty_young_block(result, word_size);
871 }
872 return result;
873 } else {
874 if (gclocker_retry_count > GCLockerRetryAllocationCount) {
875 return NULL;
876 }
877 assert(op.result() == NULL,
878 "the result should be NULL if the VM op did not succeed");
879 }
881 // Give a warning if we seem to be looping forever.
882 if ((QueuedAllocationWarningCount > 0) &&
883 (try_count % QueuedAllocationWarningCount == 0)) {
884 warning("G1CollectedHeap::mem_allocate retries %d times", try_count);
885 }
886 }
888 ShouldNotReachHere();
889 return NULL;
890 }
892 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size,
893 AllocationContext_t context,
894 unsigned int *gc_count_before_ret,
895 int* gclocker_retry_count_ret) {
896 // Make sure you read the note in attempt_allocation_humongous().
898 assert_heap_not_locked_and_not_at_safepoint();
899 assert(!isHumongous(word_size), "attempt_allocation_slow() should not "
900 "be called for humongous allocation requests");
902 // We should only get here after the first-level allocation attempt
903 // (attempt_allocation()) failed to allocate.
905 // We will loop until a) we manage to successfully perform the
906 // allocation or b) we successfully schedule a collection which
907 // fails to perform the allocation. b) is the only case when we'll
908 // return NULL.
909 HeapWord* result = NULL;
910 for (int try_count = 1; /* we'll return */; try_count += 1) {
911 bool should_try_gc;
912 unsigned int gc_count_before;
914 {
915 MutexLockerEx x(Heap_lock);
916 result = _allocator->mutator_alloc_region(context)->attempt_allocation_locked(word_size,
917 false /* bot_updates */);
918 if (result != NULL) {
919 return result;
920 }
922 // If we reach here, attempt_allocation_locked() above failed to
923 // allocate a new region. So the mutator alloc region should be NULL.
924 assert(_allocator->mutator_alloc_region(context)->get() == NULL, "only way to get here");
926 if (GC_locker::is_active_and_needs_gc()) {
927 if (g1_policy()->can_expand_young_list()) {
928 // No need for an ergo verbose message here,
929 // can_expand_young_list() does this when it returns true.
930 result = _allocator->mutator_alloc_region(context)->attempt_allocation_force(word_size,
931 false /* bot_updates */);
932 if (result != NULL) {
933 return result;
934 }
935 }
936 should_try_gc = false;
937 } else {
938 // The GCLocker may not be active but the GCLocker initiated
939 // GC may not yet have been performed (GCLocker::needs_gc()
940 // returns true). In this case we do not try this GC and
941 // wait until the GCLocker initiated GC is performed, and
942 // then retry the allocation.
943 if (GC_locker::needs_gc()) {
944 should_try_gc = false;
945 } else {
946 // Read the GC count while still holding the Heap_lock.
947 gc_count_before = total_collections();
948 should_try_gc = true;
949 }
950 }
951 }
953 if (should_try_gc) {
954 bool succeeded;
955 result = do_collection_pause(word_size, gc_count_before, &succeeded,
956 GCCause::_g1_inc_collection_pause);
957 if (result != NULL) {
958 assert(succeeded, "only way to get back a non-NULL result");
959 return result;
960 }
962 if (succeeded) {
963 // If we get here we successfully scheduled a collection which
964 // failed to allocate. No point in trying to allocate
965 // further. We'll just return NULL.
966 MutexLockerEx x(Heap_lock);
967 *gc_count_before_ret = total_collections();
968 return NULL;
969 }
970 } else {
971 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
972 MutexLockerEx x(Heap_lock);
973 *gc_count_before_ret = total_collections();
974 return NULL;
975 }
976 // The GCLocker is either active or the GCLocker initiated
977 // GC has not yet been performed. Stall until it is and
978 // then retry the allocation.
979 GC_locker::stall_until_clear();
980 (*gclocker_retry_count_ret) += 1;
981 }
983 // We can reach here if we were unsuccessful in scheduling a
984 // collection (because another thread beat us to it) or if we were
985 // stalled due to the GC locker. In either can we should retry the
986 // allocation attempt in case another thread successfully
987 // performed a collection and reclaimed enough space. We do the
988 // first attempt (without holding the Heap_lock) here and the
989 // follow-on attempt will be at the start of the next loop
990 // iteration (after taking the Heap_lock).
991 result = _allocator->mutator_alloc_region(context)->attempt_allocation(word_size,
992 false /* bot_updates */);
993 if (result != NULL) {
994 return result;
995 }
997 // Give a warning if we seem to be looping forever.
998 if ((QueuedAllocationWarningCount > 0) &&
999 (try_count % QueuedAllocationWarningCount == 0)) {
1000 warning("G1CollectedHeap::attempt_allocation_slow() "
1001 "retries %d times", try_count);
1002 }
1003 }
1005 ShouldNotReachHere();
1006 return NULL;
1007 }
1009 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size,
1010 unsigned int * gc_count_before_ret,
1011 int* gclocker_retry_count_ret) {
1012 // The structure of this method has a lot of similarities to
1013 // attempt_allocation_slow(). The reason these two were not merged
1014 // into a single one is that such a method would require several "if
1015 // allocation is not humongous do this, otherwise do that"
1016 // conditional paths which would obscure its flow. In fact, an early
1017 // version of this code did use a unified method which was harder to
1018 // follow and, as a result, it had subtle bugs that were hard to
1019 // track down. So keeping these two methods separate allows each to
1020 // be more readable. It will be good to keep these two in sync as
1021 // much as possible.
1023 assert_heap_not_locked_and_not_at_safepoint();
1024 assert(isHumongous(word_size), "attempt_allocation_humongous() "
1025 "should only be called for humongous allocations");
1027 // Humongous objects can exhaust the heap quickly, so we should check if we
1028 // need to start a marking cycle at each humongous object allocation. We do
1029 // the check before we do the actual allocation. The reason for doing it
1030 // before the allocation is that we avoid having to keep track of the newly
1031 // allocated memory while we do a GC.
1032 if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation",
1033 word_size)) {
1034 collect(GCCause::_g1_humongous_allocation);
1035 }
1037 // We will loop until a) we manage to successfully perform the
1038 // allocation or b) we successfully schedule a collection which
1039 // fails to perform the allocation. b) is the only case when we'll
1040 // return NULL.
1041 HeapWord* result = NULL;
1042 for (int try_count = 1; /* we'll return */; try_count += 1) {
1043 bool should_try_gc;
1044 unsigned int gc_count_before;
1046 {
1047 MutexLockerEx x(Heap_lock);
1049 // Given that humongous objects are not allocated in young
1050 // regions, we'll first try to do the allocation without doing a
1051 // collection hoping that there's enough space in the heap.
1052 result = humongous_obj_allocate(word_size, AllocationContext::current());
1053 if (result != NULL) {
1054 return result;
1055 }
1057 if (GC_locker::is_active_and_needs_gc()) {
1058 should_try_gc = false;
1059 } else {
1060 // The GCLocker may not be active but the GCLocker initiated
1061 // GC may not yet have been performed (GCLocker::needs_gc()
1062 // returns true). In this case we do not try this GC and
1063 // wait until the GCLocker initiated GC is performed, and
1064 // then retry the allocation.
1065 if (GC_locker::needs_gc()) {
1066 should_try_gc = false;
1067 } else {
1068 // Read the GC count while still holding the Heap_lock.
1069 gc_count_before = total_collections();
1070 should_try_gc = true;
1071 }
1072 }
1073 }
1075 if (should_try_gc) {
1076 // If we failed to allocate the humongous object, we should try to
1077 // do a collection pause (if we're allowed) in case it reclaims
1078 // enough space for the allocation to succeed after the pause.
1080 bool succeeded;
1081 result = do_collection_pause(word_size, gc_count_before, &succeeded,
1082 GCCause::_g1_humongous_allocation);
1083 if (result != NULL) {
1084 assert(succeeded, "only way to get back a non-NULL result");
1085 return result;
1086 }
1088 if (succeeded) {
1089 // If we get here we successfully scheduled a collection which
1090 // failed to allocate. No point in trying to allocate
1091 // further. We'll just return NULL.
1092 MutexLockerEx x(Heap_lock);
1093 *gc_count_before_ret = total_collections();
1094 return NULL;
1095 }
1096 } else {
1097 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
1098 MutexLockerEx x(Heap_lock);
1099 *gc_count_before_ret = total_collections();
1100 return NULL;
1101 }
1102 // The GCLocker is either active or the GCLocker initiated
1103 // GC has not yet been performed. Stall until it is and
1104 // then retry the allocation.
1105 GC_locker::stall_until_clear();
1106 (*gclocker_retry_count_ret) += 1;
1107 }
1109 // We can reach here if we were unsuccessful in scheduling a
1110 // collection (because another thread beat us to it) or if we were
1111 // stalled due to the GC locker. In either can we should retry the
1112 // allocation attempt in case another thread successfully
1113 // performed a collection and reclaimed enough space. Give a
1114 // warning if we seem to be looping forever.
1116 if ((QueuedAllocationWarningCount > 0) &&
1117 (try_count % QueuedAllocationWarningCount == 0)) {
1118 warning("G1CollectedHeap::attempt_allocation_humongous() "
1119 "retries %d times", try_count);
1120 }
1121 }
1123 ShouldNotReachHere();
1124 return NULL;
1125 }
1127 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
1128 AllocationContext_t context,
1129 bool expect_null_mutator_alloc_region) {
1130 assert_at_safepoint(true /* should_be_vm_thread */);
1131 assert(_allocator->mutator_alloc_region(context)->get() == NULL ||
1132 !expect_null_mutator_alloc_region,
1133 "the current alloc region was unexpectedly found to be non-NULL");
1135 if (!isHumongous(word_size)) {
1136 return _allocator->mutator_alloc_region(context)->attempt_allocation_locked(word_size,
1137 false /* bot_updates */);
1138 } else {
1139 HeapWord* result = humongous_obj_allocate(word_size, context);
1140 if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) {
1141 g1_policy()->set_initiate_conc_mark_if_possible();
1142 }
1143 return result;
1144 }
1146 ShouldNotReachHere();
1147 }
1149 class PostMCRemSetClearClosure: public HeapRegionClosure {
1150 G1CollectedHeap* _g1h;
1151 ModRefBarrierSet* _mr_bs;
1152 public:
1153 PostMCRemSetClearClosure(G1CollectedHeap* g1h, ModRefBarrierSet* mr_bs) :
1154 _g1h(g1h), _mr_bs(mr_bs) {}
1156 bool doHeapRegion(HeapRegion* r) {
1157 HeapRegionRemSet* hrrs = r->rem_set();
1159 if (r->continuesHumongous()) {
1160 // We'll assert that the strong code root list and RSet is empty
1161 assert(hrrs->strong_code_roots_list_length() == 0, "sanity");
1162 assert(hrrs->occupied() == 0, "RSet should be empty");
1163 return false;
1164 }
1166 _g1h->reset_gc_time_stamps(r);
1167 hrrs->clear();
1168 // You might think here that we could clear just the cards
1169 // corresponding to the used region. But no: if we leave a dirty card
1170 // in a region we might allocate into, then it would prevent that card
1171 // from being enqueued, and cause it to be missed.
1172 // Re: the performance cost: we shouldn't be doing full GC anyway!
1173 _mr_bs->clear(MemRegion(r->bottom(), r->end()));
1175 return false;
1176 }
1177 };
1179 void G1CollectedHeap::clear_rsets_post_compaction() {
1180 PostMCRemSetClearClosure rs_clear(this, g1_barrier_set());
1181 heap_region_iterate(&rs_clear);
1182 }
1184 class RebuildRSOutOfRegionClosure: public HeapRegionClosure {
1185 G1CollectedHeap* _g1h;
1186 UpdateRSOopClosure _cl;
1187 int _worker_i;
1188 public:
1189 RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, int worker_i = 0) :
1190 _cl(g1->g1_rem_set(), worker_i),
1191 _worker_i(worker_i),
1192 _g1h(g1)
1193 { }
1195 bool doHeapRegion(HeapRegion* r) {
1196 if (!r->continuesHumongous()) {
1197 _cl.set_from(r);
1198 r->oop_iterate(&_cl);
1199 }
1200 return false;
1201 }
1202 };
1204 class ParRebuildRSTask: public AbstractGangTask {
1205 G1CollectedHeap* _g1;
1206 public:
1207 ParRebuildRSTask(G1CollectedHeap* g1)
1208 : AbstractGangTask("ParRebuildRSTask"),
1209 _g1(g1)
1210 { }
1212 void work(uint worker_id) {
1213 RebuildRSOutOfRegionClosure rebuild_rs(_g1, worker_id);
1214 _g1->heap_region_par_iterate_chunked(&rebuild_rs, worker_id,
1215 _g1->workers()->active_workers(),
1216 HeapRegion::RebuildRSClaimValue);
1217 }
1218 };
1220 class PostCompactionPrinterClosure: public HeapRegionClosure {
1221 private:
1222 G1HRPrinter* _hr_printer;
1223 public:
1224 bool doHeapRegion(HeapRegion* hr) {
1225 assert(!hr->is_young(), "not expecting to find young regions");
1226 if (hr->is_free()) {
1227 // We only generate output for non-empty regions.
1228 } else if (hr->startsHumongous()) {
1229 if (hr->region_num() == 1) {
1230 // single humongous region
1231 _hr_printer->post_compaction(hr, G1HRPrinter::SingleHumongous);
1232 } else {
1233 _hr_printer->post_compaction(hr, G1HRPrinter::StartsHumongous);
1234 }
1235 } else if (hr->continuesHumongous()) {
1236 _hr_printer->post_compaction(hr, G1HRPrinter::ContinuesHumongous);
1237 } else if (hr->is_old()) {
1238 _hr_printer->post_compaction(hr, G1HRPrinter::Old);
1239 } else {
1240 ShouldNotReachHere();
1241 }
1242 return false;
1243 }
1245 PostCompactionPrinterClosure(G1HRPrinter* hr_printer)
1246 : _hr_printer(hr_printer) { }
1247 };
1249 void G1CollectedHeap::print_hrm_post_compaction() {
1250 PostCompactionPrinterClosure cl(hr_printer());
1251 heap_region_iterate(&cl);
1252 }
1254 bool G1CollectedHeap::do_collection(bool explicit_gc,
1255 bool clear_all_soft_refs,
1256 size_t word_size) {
1257 assert_at_safepoint(true /* should_be_vm_thread */);
1259 if (GC_locker::check_active_before_gc()) {
1260 return false;
1261 }
1263 STWGCTimer* gc_timer = G1MarkSweep::gc_timer();
1264 gc_timer->register_gc_start();
1266 SerialOldTracer* gc_tracer = G1MarkSweep::gc_tracer();
1267 gc_tracer->report_gc_start(gc_cause(), gc_timer->gc_start());
1269 SvcGCMarker sgcm(SvcGCMarker::FULL);
1270 ResourceMark rm;
1272 print_heap_before_gc();
1273 trace_heap_before_gc(gc_tracer);
1275 size_t metadata_prev_used = MetaspaceAux::used_bytes();
1277 verify_region_sets_optional();
1279 const bool do_clear_all_soft_refs = clear_all_soft_refs ||
1280 collector_policy()->should_clear_all_soft_refs();
1282 ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy());
1284 {
1285 IsGCActiveMark x;
1287 // Timing
1288 assert(gc_cause() != GCCause::_java_lang_system_gc || explicit_gc, "invariant");
1289 gclog_or_tty->date_stamp(G1Log::fine() && PrintGCDateStamps);
1290 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
1292 {
1293 GCTraceTime t(GCCauseString("Full GC", gc_cause()), G1Log::fine(), true, NULL, gc_tracer->gc_id());
1294 TraceCollectorStats tcs(g1mm()->full_collection_counters());
1295 TraceMemoryManagerStats tms(true /* fullGC */, gc_cause());
1297 double start = os::elapsedTime();
1298 g1_policy()->record_full_collection_start();
1300 // Note: When we have a more flexible GC logging framework that
1301 // allows us to add optional attributes to a GC log record we
1302 // could consider timing and reporting how long we wait in the
1303 // following two methods.
1304 wait_while_free_regions_coming();
1305 // If we start the compaction before the CM threads finish
1306 // scanning the root regions we might trip them over as we'll
1307 // be moving objects / updating references. So let's wait until
1308 // they are done. By telling them to abort, they should complete
1309 // early.
1310 _cm->root_regions()->abort();
1311 _cm->root_regions()->wait_until_scan_finished();
1312 append_secondary_free_list_if_not_empty_with_lock();
1314 gc_prologue(true);
1315 increment_total_collections(true /* full gc */);
1316 increment_old_marking_cycles_started();
1318 assert(used() == recalculate_used(), "Should be equal");
1320 verify_before_gc();
1322 check_bitmaps("Full GC Start");
1323 pre_full_gc_dump(gc_timer);
1325 COMPILER2_PRESENT(DerivedPointerTable::clear());
1327 // Disable discovery and empty the discovered lists
1328 // for the CM ref processor.
1329 ref_processor_cm()->disable_discovery();
1330 ref_processor_cm()->abandon_partial_discovery();
1331 ref_processor_cm()->verify_no_references_recorded();
1333 // Abandon current iterations of concurrent marking and concurrent
1334 // refinement, if any are in progress. We have to do this before
1335 // wait_until_scan_finished() below.
1336 concurrent_mark()->abort();
1338 // Make sure we'll choose a new allocation region afterwards.
1339 _allocator->release_mutator_alloc_region();
1340 _allocator->abandon_gc_alloc_regions();
1341 g1_rem_set()->cleanupHRRS();
1343 // We should call this after we retire any currently active alloc
1344 // regions so that all the ALLOC / RETIRE events are generated
1345 // before the start GC event.
1346 _hr_printer.start_gc(true /* full */, (size_t) total_collections());
1348 // We may have added regions to the current incremental collection
1349 // set between the last GC or pause and now. We need to clear the
1350 // incremental collection set and then start rebuilding it afresh
1351 // after this full GC.
1352 abandon_collection_set(g1_policy()->inc_cset_head());
1353 g1_policy()->clear_incremental_cset();
1354 g1_policy()->stop_incremental_cset_building();
1356 tear_down_region_sets(false /* free_list_only */);
1357 g1_policy()->set_gcs_are_young(true);
1359 // See the comments in g1CollectedHeap.hpp and
1360 // G1CollectedHeap::ref_processing_init() about
1361 // how reference processing currently works in G1.
1363 // Temporarily make discovery by the STW ref processor single threaded (non-MT).
1364 ReferenceProcessorMTDiscoveryMutator stw_rp_disc_ser(ref_processor_stw(), false);
1366 // Temporarily clear the STW ref processor's _is_alive_non_header field.
1367 ReferenceProcessorIsAliveMutator stw_rp_is_alive_null(ref_processor_stw(), NULL);
1369 ref_processor_stw()->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/);
1370 ref_processor_stw()->setup_policy(do_clear_all_soft_refs);
1372 // Do collection work
1373 {
1374 HandleMark hm; // Discard invalid handles created during gc
1375 G1MarkSweep::invoke_at_safepoint(ref_processor_stw(), do_clear_all_soft_refs);
1376 }
1378 assert(num_free_regions() == 0, "we should not have added any free regions");
1379 rebuild_region_sets(false /* free_list_only */);
1381 // Enqueue any discovered reference objects that have
1382 // not been removed from the discovered lists.
1383 ref_processor_stw()->enqueue_discovered_references();
1385 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
1387 MemoryService::track_memory_usage();
1389 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
1390 ref_processor_stw()->verify_no_references_recorded();
1392 // Delete metaspaces for unloaded class loaders and clean up loader_data graph
1393 ClassLoaderDataGraph::purge();
1394 MetaspaceAux::verify_metrics();
1396 // Note: since we've just done a full GC, concurrent
1397 // marking is no longer active. Therefore we need not
1398 // re-enable reference discovery for the CM ref processor.
1399 // That will be done at the start of the next marking cycle.
1400 assert(!ref_processor_cm()->discovery_enabled(), "Postcondition");
1401 ref_processor_cm()->verify_no_references_recorded();
1403 reset_gc_time_stamp();
1404 // Since everything potentially moved, we will clear all remembered
1405 // sets, and clear all cards. Later we will rebuild remembered
1406 // sets. We will also reset the GC time stamps of the regions.
1407 clear_rsets_post_compaction();
1408 check_gc_time_stamps();
1410 // Resize the heap if necessary.
1411 resize_if_necessary_after_full_collection(explicit_gc ? 0 : word_size);
1413 if (_hr_printer.is_active()) {
1414 // We should do this after we potentially resize the heap so
1415 // that all the COMMIT / UNCOMMIT events are generated before
1416 // the end GC event.
1418 print_hrm_post_compaction();
1419 _hr_printer.end_gc(true /* full */, (size_t) total_collections());
1420 }
1422 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
1423 if (hot_card_cache->use_cache()) {
1424 hot_card_cache->reset_card_counts();
1425 hot_card_cache->reset_hot_cache();
1426 }
1428 // Rebuild remembered sets of all regions.
1429 if (G1CollectedHeap::use_parallel_gc_threads()) {
1430 uint n_workers =
1431 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
1432 workers()->active_workers(),
1433 Threads::number_of_non_daemon_threads());
1434 assert(UseDynamicNumberOfGCThreads ||
1435 n_workers == workers()->total_workers(),
1436 "If not dynamic should be using all the workers");
1437 workers()->set_active_workers(n_workers);
1438 // Set parallel threads in the heap (_n_par_threads) only
1439 // before a parallel phase and always reset it to 0 after
1440 // the phase so that the number of parallel threads does
1441 // no get carried forward to a serial phase where there
1442 // may be code that is "possibly_parallel".
1443 set_par_threads(n_workers);
1445 ParRebuildRSTask rebuild_rs_task(this);
1446 assert(check_heap_region_claim_values(
1447 HeapRegion::InitialClaimValue), "sanity check");
1448 assert(UseDynamicNumberOfGCThreads ||
1449 workers()->active_workers() == workers()->total_workers(),
1450 "Unless dynamic should use total workers");
1451 // Use the most recent number of active workers
1452 assert(workers()->active_workers() > 0,
1453 "Active workers not properly set");
1454 set_par_threads(workers()->active_workers());
1455 workers()->run_task(&rebuild_rs_task);
1456 set_par_threads(0);
1457 assert(check_heap_region_claim_values(
1458 HeapRegion::RebuildRSClaimValue), "sanity check");
1459 reset_heap_region_claim_values();
1460 } else {
1461 RebuildRSOutOfRegionClosure rebuild_rs(this);
1462 heap_region_iterate(&rebuild_rs);
1463 }
1465 // Rebuild the strong code root lists for each region
1466 rebuild_strong_code_roots();
1468 if (true) { // FIXME
1469 MetaspaceGC::compute_new_size();
1470 }
1472 #ifdef TRACESPINNING
1473 ParallelTaskTerminator::print_termination_counts();
1474 #endif
1476 // Discard all rset updates
1477 JavaThread::dirty_card_queue_set().abandon_logs();
1478 assert(dirty_card_queue_set().completed_buffers_num() == 0, "DCQS should be empty");
1480 _young_list->reset_sampled_info();
1481 // At this point there should be no regions in the
1482 // entire heap tagged as young.
1483 assert(check_young_list_empty(true /* check_heap */),
1484 "young list should be empty at this point");
1486 // Update the number of full collections that have been completed.
1487 increment_old_marking_cycles_completed(false /* concurrent */);
1489 _hrm.verify_optional();
1490 verify_region_sets_optional();
1492 verify_after_gc();
1494 // Clear the previous marking bitmap, if needed for bitmap verification.
1495 // Note we cannot do this when we clear the next marking bitmap in
1496 // ConcurrentMark::abort() above since VerifyDuringGC verifies the
1497 // objects marked during a full GC against the previous bitmap.
1498 // But we need to clear it before calling check_bitmaps below since
1499 // the full GC has compacted objects and updated TAMS but not updated
1500 // the prev bitmap.
1501 if (G1VerifyBitmaps) {
1502 ((CMBitMap*) concurrent_mark()->prevMarkBitMap())->clearAll();
1503 }
1504 check_bitmaps("Full GC End");
1506 // Start a new incremental collection set for the next pause
1507 assert(g1_policy()->collection_set() == NULL, "must be");
1508 g1_policy()->start_incremental_cset_building();
1510 clear_cset_fast_test();
1512 _allocator->init_mutator_alloc_region();
1514 double end = os::elapsedTime();
1515 g1_policy()->record_full_collection_end();
1517 if (G1Log::fine()) {
1518 g1_policy()->print_heap_transition();
1519 }
1521 // We must call G1MonitoringSupport::update_sizes() in the same scoping level
1522 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
1523 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
1524 // before any GC notifications are raised.
1525 g1mm()->update_sizes();
1527 gc_epilogue(true);
1528 }
1530 if (G1Log::finer()) {
1531 g1_policy()->print_detailed_heap_transition(true /* full */);
1532 }
1534 print_heap_after_gc();
1535 trace_heap_after_gc(gc_tracer);
1537 post_full_gc_dump(gc_timer);
1539 gc_timer->register_gc_end();
1540 gc_tracer->report_gc_end(gc_timer->gc_end(), gc_timer->time_partitions());
1541 }
1543 return true;
1544 }
1546 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
1547 // do_collection() will return whether it succeeded in performing
1548 // the GC. Currently, there is no facility on the
1549 // do_full_collection() API to notify the caller than the collection
1550 // did not succeed (e.g., because it was locked out by the GC
1551 // locker). So, right now, we'll ignore the return value.
1552 bool dummy = do_collection(true, /* explicit_gc */
1553 clear_all_soft_refs,
1554 0 /* word_size */);
1555 }
1557 // This code is mostly copied from TenuredGeneration.
1558 void
1559 G1CollectedHeap::
1560 resize_if_necessary_after_full_collection(size_t word_size) {
1561 // Include the current allocation, if any, and bytes that will be
1562 // pre-allocated to support collections, as "used".
1563 const size_t used_after_gc = used();
1564 const size_t capacity_after_gc = capacity();
1565 const size_t free_after_gc = capacity_after_gc - used_after_gc;
1567 // This is enforced in arguments.cpp.
1568 assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
1569 "otherwise the code below doesn't make sense");
1571 // We don't have floating point command-line arguments
1572 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
1573 const double maximum_used_percentage = 1.0 - minimum_free_percentage;
1574 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
1575 const double minimum_used_percentage = 1.0 - maximum_free_percentage;
1577 const size_t min_heap_size = collector_policy()->min_heap_byte_size();
1578 const size_t max_heap_size = collector_policy()->max_heap_byte_size();
1580 // We have to be careful here as these two calculations can overflow
1581 // 32-bit size_t's.
1582 double used_after_gc_d = (double) used_after_gc;
1583 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
1584 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
1586 // Let's make sure that they are both under the max heap size, which
1587 // by default will make them fit into a size_t.
1588 double desired_capacity_upper_bound = (double) max_heap_size;
1589 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
1590 desired_capacity_upper_bound);
1591 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
1592 desired_capacity_upper_bound);
1594 // We can now safely turn them into size_t's.
1595 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
1596 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
1598 // This assert only makes sense here, before we adjust them
1599 // with respect to the min and max heap size.
1600 assert(minimum_desired_capacity <= maximum_desired_capacity,
1601 err_msg("minimum_desired_capacity = "SIZE_FORMAT", "
1602 "maximum_desired_capacity = "SIZE_FORMAT,
1603 minimum_desired_capacity, maximum_desired_capacity));
1605 // Should not be greater than the heap max size. No need to adjust
1606 // it with respect to the heap min size as it's a lower bound (i.e.,
1607 // we'll try to make the capacity larger than it, not smaller).
1608 minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size);
1609 // Should not be less than the heap min size. No need to adjust it
1610 // with respect to the heap max size as it's an upper bound (i.e.,
1611 // we'll try to make the capacity smaller than it, not greater).
1612 maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size);
1614 if (capacity_after_gc < minimum_desired_capacity) {
1615 // Don't expand unless it's significant
1616 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
1617 ergo_verbose4(ErgoHeapSizing,
1618 "attempt heap expansion",
1619 ergo_format_reason("capacity lower than "
1620 "min desired capacity after Full GC")
1621 ergo_format_byte("capacity")
1622 ergo_format_byte("occupancy")
1623 ergo_format_byte_perc("min desired capacity"),
1624 capacity_after_gc, used_after_gc,
1625 minimum_desired_capacity, (double) MinHeapFreeRatio);
1626 expand(expand_bytes);
1628 // No expansion, now see if we want to shrink
1629 } else if (capacity_after_gc > maximum_desired_capacity) {
1630 // Capacity too large, compute shrinking size
1631 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
1632 ergo_verbose4(ErgoHeapSizing,
1633 "attempt heap shrinking",
1634 ergo_format_reason("capacity higher than "
1635 "max desired capacity after Full GC")
1636 ergo_format_byte("capacity")
1637 ergo_format_byte("occupancy")
1638 ergo_format_byte_perc("max desired capacity"),
1639 capacity_after_gc, used_after_gc,
1640 maximum_desired_capacity, (double) MaxHeapFreeRatio);
1641 shrink(shrink_bytes);
1642 }
1643 }
1646 HeapWord*
1647 G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
1648 AllocationContext_t context,
1649 bool* succeeded) {
1650 assert_at_safepoint(true /* should_be_vm_thread */);
1652 *succeeded = true;
1653 // Let's attempt the allocation first.
1654 HeapWord* result =
1655 attempt_allocation_at_safepoint(word_size,
1656 context,
1657 false /* expect_null_mutator_alloc_region */);
1658 if (result != NULL) {
1659 assert(*succeeded, "sanity");
1660 return result;
1661 }
1663 // In a G1 heap, we're supposed to keep allocation from failing by
1664 // incremental pauses. Therefore, at least for now, we'll favor
1665 // expansion over collection. (This might change in the future if we can
1666 // do something smarter than full collection to satisfy a failed alloc.)
1667 result = expand_and_allocate(word_size, context);
1668 if (result != NULL) {
1669 assert(*succeeded, "sanity");
1670 return result;
1671 }
1673 // Expansion didn't work, we'll try to do a Full GC.
1674 bool gc_succeeded = do_collection(false, /* explicit_gc */
1675 false, /* clear_all_soft_refs */
1676 word_size);
1677 if (!gc_succeeded) {
1678 *succeeded = false;
1679 return NULL;
1680 }
1682 // Retry the allocation
1683 result = attempt_allocation_at_safepoint(word_size,
1684 context,
1685 true /* expect_null_mutator_alloc_region */);
1686 if (result != NULL) {
1687 assert(*succeeded, "sanity");
1688 return result;
1689 }
1691 // Then, try a Full GC that will collect all soft references.
1692 gc_succeeded = do_collection(false, /* explicit_gc */
1693 true, /* clear_all_soft_refs */
1694 word_size);
1695 if (!gc_succeeded) {
1696 *succeeded = false;
1697 return NULL;
1698 }
1700 // Retry the allocation once more
1701 result = attempt_allocation_at_safepoint(word_size,
1702 context,
1703 true /* expect_null_mutator_alloc_region */);
1704 if (result != NULL) {
1705 assert(*succeeded, "sanity");
1706 return result;
1707 }
1709 assert(!collector_policy()->should_clear_all_soft_refs(),
1710 "Flag should have been handled and cleared prior to this point");
1712 // What else? We might try synchronous finalization later. If the total
1713 // space available is large enough for the allocation, then a more
1714 // complete compaction phase than we've tried so far might be
1715 // appropriate.
1716 assert(*succeeded, "sanity");
1717 return NULL;
1718 }
1720 // Attempting to expand the heap sufficiently
1721 // to support an allocation of the given "word_size". If
1722 // successful, perform the allocation and return the address of the
1723 // allocated block, or else "NULL".
1725 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size, AllocationContext_t context) {
1726 assert_at_safepoint(true /* should_be_vm_thread */);
1728 verify_region_sets_optional();
1730 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
1731 ergo_verbose1(ErgoHeapSizing,
1732 "attempt heap expansion",
1733 ergo_format_reason("allocation request failed")
1734 ergo_format_byte("allocation request"),
1735 word_size * HeapWordSize);
1736 if (expand(expand_bytes)) {
1737 _hrm.verify_optional();
1738 verify_region_sets_optional();
1739 return attempt_allocation_at_safepoint(word_size,
1740 context,
1741 false /* expect_null_mutator_alloc_region */);
1742 }
1743 return NULL;
1744 }
1746 bool G1CollectedHeap::expand(size_t expand_bytes) {
1747 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
1748 aligned_expand_bytes = align_size_up(aligned_expand_bytes,
1749 HeapRegion::GrainBytes);
1750 ergo_verbose2(ErgoHeapSizing,
1751 "expand the heap",
1752 ergo_format_byte("requested expansion amount")
1753 ergo_format_byte("attempted expansion amount"),
1754 expand_bytes, aligned_expand_bytes);
1756 if (is_maximal_no_gc()) {
1757 ergo_verbose0(ErgoHeapSizing,
1758 "did not expand the heap",
1759 ergo_format_reason("heap already fully expanded"));
1760 return false;
1761 }
1763 uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes);
1764 assert(regions_to_expand > 0, "Must expand by at least one region");
1766 uint expanded_by = _hrm.expand_by(regions_to_expand);
1768 if (expanded_by > 0) {
1769 size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes;
1770 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
1771 g1_policy()->record_new_heap_size(num_regions());
1772 } else {
1773 ergo_verbose0(ErgoHeapSizing,
1774 "did not expand the heap",
1775 ergo_format_reason("heap expansion operation failed"));
1776 // The expansion of the virtual storage space was unsuccessful.
1777 // Let's see if it was because we ran out of swap.
1778 if (G1ExitOnExpansionFailure &&
1779 _hrm.available() >= regions_to_expand) {
1780 // We had head room...
1781 vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion");
1782 }
1783 }
1784 return regions_to_expand > 0;
1785 }
1787 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
1788 size_t aligned_shrink_bytes =
1789 ReservedSpace::page_align_size_down(shrink_bytes);
1790 aligned_shrink_bytes = align_size_down(aligned_shrink_bytes,
1791 HeapRegion::GrainBytes);
1792 uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes);
1794 uint num_regions_removed = _hrm.shrink_by(num_regions_to_remove);
1795 size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes;
1797 ergo_verbose3(ErgoHeapSizing,
1798 "shrink the heap",
1799 ergo_format_byte("requested shrinking amount")
1800 ergo_format_byte("aligned shrinking amount")
1801 ergo_format_byte("attempted shrinking amount"),
1802 shrink_bytes, aligned_shrink_bytes, shrunk_bytes);
1803 if (num_regions_removed > 0) {
1804 g1_policy()->record_new_heap_size(num_regions());
1805 } else {
1806 ergo_verbose0(ErgoHeapSizing,
1807 "did not shrink the heap",
1808 ergo_format_reason("heap shrinking operation failed"));
1809 }
1810 }
1812 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1813 verify_region_sets_optional();
1815 // We should only reach here at the end of a Full GC which means we
1816 // should not not be holding to any GC alloc regions. The method
1817 // below will make sure of that and do any remaining clean up.
1818 _allocator->abandon_gc_alloc_regions();
1820 // Instead of tearing down / rebuilding the free lists here, we
1821 // could instead use the remove_all_pending() method on free_list to
1822 // remove only the ones that we need to remove.
1823 tear_down_region_sets(true /* free_list_only */);
1824 shrink_helper(shrink_bytes);
1825 rebuild_region_sets(true /* free_list_only */);
1827 _hrm.verify_optional();
1828 verify_region_sets_optional();
1829 }
1831 // Public methods.
1833 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away
1834 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
1835 #endif // _MSC_VER
1838 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* policy_) :
1839 SharedHeap(policy_),
1840 _g1_policy(policy_),
1841 _dirty_card_queue_set(false),
1842 _into_cset_dirty_card_queue_set(false),
1843 _is_alive_closure_cm(this),
1844 _is_alive_closure_stw(this),
1845 _ref_processor_cm(NULL),
1846 _ref_processor_stw(NULL),
1847 _bot_shared(NULL),
1848 _evac_failure_scan_stack(NULL),
1849 _mark_in_progress(false),
1850 _cg1r(NULL),
1851 _g1mm(NULL),
1852 _refine_cte_cl(NULL),
1853 _full_collection(false),
1854 _secondary_free_list("Secondary Free List", new SecondaryFreeRegionListMtSafeChecker()),
1855 _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()),
1856 _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()),
1857 _humongous_is_live(),
1858 _has_humongous_reclaim_candidates(false),
1859 _free_regions_coming(false),
1860 _young_list(new YoungList(this)),
1861 _gc_time_stamp(0),
1862 _survivor_plab_stats(YoungPLABSize, PLABWeight),
1863 _old_plab_stats(OldPLABSize, PLABWeight),
1864 _expand_heap_after_alloc_failure(true),
1865 _surviving_young_words(NULL),
1866 _old_marking_cycles_started(0),
1867 _old_marking_cycles_completed(0),
1868 _concurrent_cycle_started(false),
1869 _in_cset_fast_test(),
1870 _dirty_cards_region_list(NULL),
1871 _worker_cset_start_region(NULL),
1872 _worker_cset_start_region_time_stamp(NULL),
1873 _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()),
1874 _gc_timer_cm(new (ResourceObj::C_HEAP, mtGC) ConcurrentGCTimer()),
1875 _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()),
1876 _gc_tracer_cm(new (ResourceObj::C_HEAP, mtGC) G1OldTracer()) {
1878 _g1h = this;
1880 _allocator = G1Allocator::create_allocator(_g1h);
1881 _humongous_object_threshold_in_words = HeapRegion::GrainWords / 2;
1883 int n_queues = MAX2((int)ParallelGCThreads, 1);
1884 _task_queues = new RefToScanQueueSet(n_queues);
1886 uint n_rem_sets = HeapRegionRemSet::num_par_rem_sets();
1887 assert(n_rem_sets > 0, "Invariant.");
1889 _worker_cset_start_region = NEW_C_HEAP_ARRAY(HeapRegion*, n_queues, mtGC);
1890 _worker_cset_start_region_time_stamp = NEW_C_HEAP_ARRAY(unsigned int, n_queues, mtGC);
1891 _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC);
1893 for (int i = 0; i < n_queues; i++) {
1894 RefToScanQueue* q = new RefToScanQueue();
1895 q->initialize();
1896 _task_queues->register_queue(i, q);
1897 ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo();
1898 }
1899 clear_cset_start_regions();
1901 // Initialize the G1EvacuationFailureALot counters and flags.
1902 NOT_PRODUCT(reset_evacuation_should_fail();)
1904 guarantee(_task_queues != NULL, "task_queues allocation failure.");
1905 }
1907 jint G1CollectedHeap::initialize() {
1908 CollectedHeap::pre_initialize();
1909 os::enable_vtime();
1911 G1Log::init();
1913 // Necessary to satisfy locking discipline assertions.
1915 MutexLocker x(Heap_lock);
1917 // We have to initialize the printer before committing the heap, as
1918 // it will be used then.
1919 _hr_printer.set_active(G1PrintHeapRegions);
1921 // While there are no constraints in the GC code that HeapWordSize
1922 // be any particular value, there are multiple other areas in the
1923 // system which believe this to be true (e.g. oop->object_size in some
1924 // cases incorrectly returns the size in wordSize units rather than
1925 // HeapWordSize).
1926 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
1928 size_t init_byte_size = collector_policy()->initial_heap_byte_size();
1929 size_t max_byte_size = collector_policy()->max_heap_byte_size();
1930 size_t heap_alignment = collector_policy()->heap_alignment();
1932 // Ensure that the sizes are properly aligned.
1933 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
1934 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
1935 Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap");
1937 _refine_cte_cl = new RefineCardTableEntryClosure();
1939 _cg1r = new ConcurrentG1Refine(this, _refine_cte_cl);
1941 // Reserve the maximum.
1943 // When compressed oops are enabled, the preferred heap base
1944 // is calculated by subtracting the requested size from the
1945 // 32Gb boundary and using the result as the base address for
1946 // heap reservation. If the requested size is not aligned to
1947 // HeapRegion::GrainBytes (i.e. the alignment that is passed
1948 // into the ReservedHeapSpace constructor) then the actual
1949 // base of the reserved heap may end up differing from the
1950 // address that was requested (i.e. the preferred heap base).
1951 // If this happens then we could end up using a non-optimal
1952 // compressed oops mode.
1954 ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size,
1955 heap_alignment);
1957 // It is important to do this in a way such that concurrent readers can't
1958 // temporarily think something is in the heap. (I've actually seen this
1959 // happen in asserts: DLD.)
1960 _reserved.set_word_size(0);
1961 _reserved.set_start((HeapWord*)heap_rs.base());
1962 _reserved.set_end((HeapWord*)(heap_rs.base() + heap_rs.size()));
1964 // Create the gen rem set (and barrier set) for the entire reserved region.
1965 _rem_set = collector_policy()->create_rem_set(_reserved, 2);
1966 set_barrier_set(rem_set()->bs());
1967 if (!barrier_set()->is_a(BarrierSet::G1SATBCTLogging)) {
1968 vm_exit_during_initialization("G1 requires a G1SATBLoggingCardTableModRefBS");
1969 return JNI_ENOMEM;
1970 }
1972 // Also create a G1 rem set.
1973 _g1_rem_set = new G1RemSet(this, g1_barrier_set());
1975 // Carve out the G1 part of the heap.
1977 ReservedSpace g1_rs = heap_rs.first_part(max_byte_size);
1978 G1RegionToSpaceMapper* heap_storage =
1979 G1RegionToSpaceMapper::create_mapper(g1_rs,
1980 UseLargePages ? os::large_page_size() : os::vm_page_size(),
1981 HeapRegion::GrainBytes,
1982 1,
1983 mtJavaHeap);
1984 heap_storage->set_mapping_changed_listener(&_listener);
1986 // Reserve space for the block offset table. We do not support automatic uncommit
1987 // for the card table at this time. BOT only.
1988 ReservedSpace bot_rs(G1BlockOffsetSharedArray::compute_size(g1_rs.size() / HeapWordSize));
1989 G1RegionToSpaceMapper* bot_storage =
1990 G1RegionToSpaceMapper::create_mapper(bot_rs,
1991 os::vm_page_size(),
1992 HeapRegion::GrainBytes,
1993 G1BlockOffsetSharedArray::N_bytes,
1994 mtGC);
1996 ReservedSpace cardtable_rs(G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize));
1997 G1RegionToSpaceMapper* cardtable_storage =
1998 G1RegionToSpaceMapper::create_mapper(cardtable_rs,
1999 os::vm_page_size(),
2000 HeapRegion::GrainBytes,
2001 G1BlockOffsetSharedArray::N_bytes,
2002 mtGC);
2004 // Reserve space for the card counts table.
2005 ReservedSpace card_counts_rs(G1BlockOffsetSharedArray::compute_size(g1_rs.size() / HeapWordSize));
2006 G1RegionToSpaceMapper* card_counts_storage =
2007 G1RegionToSpaceMapper::create_mapper(card_counts_rs,
2008 os::vm_page_size(),
2009 HeapRegion::GrainBytes,
2010 G1BlockOffsetSharedArray::N_bytes,
2011 mtGC);
2013 // Reserve space for prev and next bitmap.
2014 size_t bitmap_size = CMBitMap::compute_size(g1_rs.size());
2016 ReservedSpace prev_bitmap_rs(ReservedSpace::allocation_align_size_up(bitmap_size));
2017 G1RegionToSpaceMapper* prev_bitmap_storage =
2018 G1RegionToSpaceMapper::create_mapper(prev_bitmap_rs,
2019 os::vm_page_size(),
2020 HeapRegion::GrainBytes,
2021 CMBitMap::mark_distance(),
2022 mtGC);
2024 ReservedSpace next_bitmap_rs(ReservedSpace::allocation_align_size_up(bitmap_size));
2025 G1RegionToSpaceMapper* next_bitmap_storage =
2026 G1RegionToSpaceMapper::create_mapper(next_bitmap_rs,
2027 os::vm_page_size(),
2028 HeapRegion::GrainBytes,
2029 CMBitMap::mark_distance(),
2030 mtGC);
2032 _hrm.initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage);
2033 g1_barrier_set()->initialize(cardtable_storage);
2034 // Do later initialization work for concurrent refinement.
2035 _cg1r->init(card_counts_storage);
2037 // 6843694 - ensure that the maximum region index can fit
2038 // in the remembered set structures.
2039 const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
2040 guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
2042 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
2043 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
2044 guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
2045 "too many cards per region");
2047 FreeRegionList::set_unrealistically_long_length(max_regions() + 1);
2049 _bot_shared = new G1BlockOffsetSharedArray(_reserved, bot_storage);
2051 _g1h = this;
2053 _in_cset_fast_test.initialize(_hrm.reserved().start(), _hrm.reserved().end(), HeapRegion::GrainBytes);
2054 _humongous_is_live.initialize(_hrm.reserved().start(), _hrm.reserved().end(), HeapRegion::GrainBytes);
2056 // Create the ConcurrentMark data structure and thread.
2057 // (Must do this late, so that "max_regions" is defined.)
2058 _cm = new ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage);
2059 if (_cm == NULL || !_cm->completed_initialization()) {
2060 vm_shutdown_during_initialization("Could not create/initialize ConcurrentMark");
2061 return JNI_ENOMEM;
2062 }
2063 _cmThread = _cm->cmThread();
2065 // Initialize the from_card cache structure of HeapRegionRemSet.
2066 HeapRegionRemSet::init_heap(max_regions());
2068 // Now expand into the initial heap size.
2069 if (!expand(init_byte_size)) {
2070 vm_shutdown_during_initialization("Failed to allocate initial heap.");
2071 return JNI_ENOMEM;
2072 }
2074 // Perform any initialization actions delegated to the policy.
2075 g1_policy()->init();
2077 JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon,
2078 SATB_Q_FL_lock,
2079 G1SATBProcessCompletedThreshold,
2080 Shared_SATB_Q_lock);
2082 JavaThread::dirty_card_queue_set().initialize(_refine_cte_cl,
2083 DirtyCardQ_CBL_mon,
2084 DirtyCardQ_FL_lock,
2085 concurrent_g1_refine()->yellow_zone(),
2086 concurrent_g1_refine()->red_zone(),
2087 Shared_DirtyCardQ_lock);
2089 dirty_card_queue_set().initialize(NULL, // Should never be called by the Java code
2090 DirtyCardQ_CBL_mon,
2091 DirtyCardQ_FL_lock,
2092 -1, // never trigger processing
2093 -1, // no limit on length
2094 Shared_DirtyCardQ_lock,
2095 &JavaThread::dirty_card_queue_set());
2097 // Initialize the card queue set used to hold cards containing
2098 // references into the collection set.
2099 _into_cset_dirty_card_queue_set.initialize(NULL, // Should never be called by the Java code
2100 DirtyCardQ_CBL_mon,
2101 DirtyCardQ_FL_lock,
2102 -1, // never trigger processing
2103 -1, // no limit on length
2104 Shared_DirtyCardQ_lock,
2105 &JavaThread::dirty_card_queue_set());
2107 // In case we're keeping closure specialization stats, initialize those
2108 // counts and that mechanism.
2109 SpecializationStats::clear();
2111 // Here we allocate the dummy HeapRegion that is required by the
2112 // G1AllocRegion class.
2113 HeapRegion* dummy_region = _hrm.get_dummy_region();
2115 // We'll re-use the same region whether the alloc region will
2116 // require BOT updates or not and, if it doesn't, then a non-young
2117 // region will complain that it cannot support allocations without
2118 // BOT updates. So we'll tag the dummy region as eden to avoid that.
2119 dummy_region->set_eden();
2120 // Make sure it's full.
2121 dummy_region->set_top(dummy_region->end());
2122 G1AllocRegion::setup(this, dummy_region);
2124 _allocator->init_mutator_alloc_region();
2126 // Do create of the monitoring and management support so that
2127 // values in the heap have been properly initialized.
2128 _g1mm = new G1MonitoringSupport(this);
2130 G1StringDedup::initialize();
2132 return JNI_OK;
2133 }
2135 void G1CollectedHeap::stop() {
2136 // Stop all concurrent threads. We do this to make sure these threads
2137 // do not continue to execute and access resources (e.g. gclog_or_tty)
2138 // that are destroyed during shutdown.
2139 _cg1r->stop();
2140 _cmThread->stop();
2141 if (G1StringDedup::is_enabled()) {
2142 G1StringDedup::stop();
2143 }
2144 }
2146 void G1CollectedHeap::clear_humongous_is_live_table() {
2147 guarantee(G1ReclaimDeadHumongousObjectsAtYoungGC, "Should only be called if true");
2148 _humongous_is_live.clear();
2149 }
2151 size_t G1CollectedHeap::conservative_max_heap_alignment() {
2152 return HeapRegion::max_region_size();
2153 }
2155 void G1CollectedHeap::ref_processing_init() {
2156 // Reference processing in G1 currently works as follows:
2157 //
2158 // * There are two reference processor instances. One is
2159 // used to record and process discovered references
2160 // during concurrent marking; the other is used to
2161 // record and process references during STW pauses
2162 // (both full and incremental).
2163 // * Both ref processors need to 'span' the entire heap as
2164 // the regions in the collection set may be dotted around.
2165 //
2166 // * For the concurrent marking ref processor:
2167 // * Reference discovery is enabled at initial marking.
2168 // * Reference discovery is disabled and the discovered
2169 // references processed etc during remarking.
2170 // * Reference discovery is MT (see below).
2171 // * Reference discovery requires a barrier (see below).
2172 // * Reference processing may or may not be MT
2173 // (depending on the value of ParallelRefProcEnabled
2174 // and ParallelGCThreads).
2175 // * A full GC disables reference discovery by the CM
2176 // ref processor and abandons any entries on it's
2177 // discovered lists.
2178 //
2179 // * For the STW processor:
2180 // * Non MT discovery is enabled at the start of a full GC.
2181 // * Processing and enqueueing during a full GC is non-MT.
2182 // * During a full GC, references are processed after marking.
2183 //
2184 // * Discovery (may or may not be MT) is enabled at the start
2185 // of an incremental evacuation pause.
2186 // * References are processed near the end of a STW evacuation pause.
2187 // * For both types of GC:
2188 // * Discovery is atomic - i.e. not concurrent.
2189 // * Reference discovery will not need a barrier.
2191 SharedHeap::ref_processing_init();
2192 MemRegion mr = reserved_region();
2194 // Concurrent Mark ref processor
2195 _ref_processor_cm =
2196 new ReferenceProcessor(mr, // span
2197 ParallelRefProcEnabled && (ParallelGCThreads > 1),
2198 // mt processing
2199 (int) ParallelGCThreads,
2200 // degree of mt processing
2201 (ParallelGCThreads > 1) || (ConcGCThreads > 1),
2202 // mt discovery
2203 (int) MAX2(ParallelGCThreads, ConcGCThreads),
2204 // degree of mt discovery
2205 false,
2206 // Reference discovery is not atomic
2207 &_is_alive_closure_cm);
2208 // is alive closure
2209 // (for efficiency/performance)
2211 // STW ref processor
2212 _ref_processor_stw =
2213 new ReferenceProcessor(mr, // span
2214 ParallelRefProcEnabled && (ParallelGCThreads > 1),
2215 // mt processing
2216 MAX2((int)ParallelGCThreads, 1),
2217 // degree of mt processing
2218 (ParallelGCThreads > 1),
2219 // mt discovery
2220 MAX2((int)ParallelGCThreads, 1),
2221 // degree of mt discovery
2222 true,
2223 // Reference discovery is atomic
2224 &_is_alive_closure_stw);
2225 // is alive closure
2226 // (for efficiency/performance)
2227 }
2229 size_t G1CollectedHeap::capacity() const {
2230 return _hrm.length() * HeapRegion::GrainBytes;
2231 }
2233 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) {
2234 assert(!hr->continuesHumongous(), "pre-condition");
2235 hr->reset_gc_time_stamp();
2236 if (hr->startsHumongous()) {
2237 uint first_index = hr->hrm_index() + 1;
2238 uint last_index = hr->last_hc_index();
2239 for (uint i = first_index; i < last_index; i += 1) {
2240 HeapRegion* chr = region_at(i);
2241 assert(chr->continuesHumongous(), "sanity");
2242 chr->reset_gc_time_stamp();
2243 }
2244 }
2245 }
2247 #ifndef PRODUCT
2248 class CheckGCTimeStampsHRClosure : public HeapRegionClosure {
2249 private:
2250 unsigned _gc_time_stamp;
2251 bool _failures;
2253 public:
2254 CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) :
2255 _gc_time_stamp(gc_time_stamp), _failures(false) { }
2257 virtual bool doHeapRegion(HeapRegion* hr) {
2258 unsigned region_gc_time_stamp = hr->get_gc_time_stamp();
2259 if (_gc_time_stamp != region_gc_time_stamp) {
2260 gclog_or_tty->print_cr("Region "HR_FORMAT" has GC time stamp = %d, "
2261 "expected %d", HR_FORMAT_PARAMS(hr),
2262 region_gc_time_stamp, _gc_time_stamp);
2263 _failures = true;
2264 }
2265 return false;
2266 }
2268 bool failures() { return _failures; }
2269 };
2271 void G1CollectedHeap::check_gc_time_stamps() {
2272 CheckGCTimeStampsHRClosure cl(_gc_time_stamp);
2273 heap_region_iterate(&cl);
2274 guarantee(!cl.failures(), "all GC time stamps should have been reset");
2275 }
2276 #endif // PRODUCT
2278 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl,
2279 DirtyCardQueue* into_cset_dcq,
2280 bool concurrent,
2281 uint worker_i) {
2282 // Clean cards in the hot card cache
2283 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
2284 hot_card_cache->drain(worker_i, g1_rem_set(), into_cset_dcq);
2286 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2287 size_t n_completed_buffers = 0;
2288 while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) {
2289 n_completed_buffers++;
2290 }
2291 g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::UpdateRS, worker_i, n_completed_buffers);
2292 dcqs.clear_n_completed_buffers();
2293 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!");
2294 }
2297 // Computes the sum of the storage used by the various regions.
2298 size_t G1CollectedHeap::used() const {
2299 return _allocator->used();
2300 }
2302 size_t G1CollectedHeap::used_unlocked() const {
2303 return _allocator->used_unlocked();
2304 }
2306 class SumUsedClosure: public HeapRegionClosure {
2307 size_t _used;
2308 public:
2309 SumUsedClosure() : _used(0) {}
2310 bool doHeapRegion(HeapRegion* r) {
2311 if (!r->continuesHumongous()) {
2312 _used += r->used();
2313 }
2314 return false;
2315 }
2316 size_t result() { return _used; }
2317 };
2319 size_t G1CollectedHeap::recalculate_used() const {
2320 double recalculate_used_start = os::elapsedTime();
2322 SumUsedClosure blk;
2323 heap_region_iterate(&blk);
2325 g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0);
2326 return blk.result();
2327 }
2329 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
2330 switch (cause) {
2331 case GCCause::_gc_locker: return GCLockerInvokesConcurrent;
2332 case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent;
2333 case GCCause::_g1_humongous_allocation: return true;
2334 case GCCause::_update_allocation_context_stats_inc: return true;
2335 default: return false;
2336 }
2337 }
2339 #ifndef PRODUCT
2340 void G1CollectedHeap::allocate_dummy_regions() {
2341 // Let's fill up most of the region
2342 size_t word_size = HeapRegion::GrainWords - 1024;
2343 // And as a result the region we'll allocate will be humongous.
2344 guarantee(isHumongous(word_size), "sanity");
2346 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
2347 // Let's use the existing mechanism for the allocation
2348 HeapWord* dummy_obj = humongous_obj_allocate(word_size,
2349 AllocationContext::system());
2350 if (dummy_obj != NULL) {
2351 MemRegion mr(dummy_obj, word_size);
2352 CollectedHeap::fill_with_object(mr);
2353 } else {
2354 // If we can't allocate once, we probably cannot allocate
2355 // again. Let's get out of the loop.
2356 break;
2357 }
2358 }
2359 }
2360 #endif // !PRODUCT
2362 void G1CollectedHeap::increment_old_marking_cycles_started() {
2363 assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
2364 _old_marking_cycles_started == _old_marking_cycles_completed + 1,
2365 err_msg("Wrong marking cycle count (started: %d, completed: %d)",
2366 _old_marking_cycles_started, _old_marking_cycles_completed));
2368 _old_marking_cycles_started++;
2369 }
2371 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) {
2372 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
2374 // We assume that if concurrent == true, then the caller is a
2375 // concurrent thread that was joined the Suspendible Thread
2376 // Set. If there's ever a cheap way to check this, we should add an
2377 // assert here.
2379 // Given that this method is called at the end of a Full GC or of a
2380 // concurrent cycle, and those can be nested (i.e., a Full GC can
2381 // interrupt a concurrent cycle), the number of full collections
2382 // completed should be either one (in the case where there was no
2383 // nesting) or two (when a Full GC interrupted a concurrent cycle)
2384 // behind the number of full collections started.
2386 // This is the case for the inner caller, i.e. a Full GC.
2387 assert(concurrent ||
2388 (_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
2389 (_old_marking_cycles_started == _old_marking_cycles_completed + 2),
2390 err_msg("for inner caller (Full GC): _old_marking_cycles_started = %u "
2391 "is inconsistent with _old_marking_cycles_completed = %u",
2392 _old_marking_cycles_started, _old_marking_cycles_completed));
2394 // This is the case for the outer caller, i.e. the concurrent cycle.
2395 assert(!concurrent ||
2396 (_old_marking_cycles_started == _old_marking_cycles_completed + 1),
2397 err_msg("for outer caller (concurrent cycle): "
2398 "_old_marking_cycles_started = %u "
2399 "is inconsistent with _old_marking_cycles_completed = %u",
2400 _old_marking_cycles_started, _old_marking_cycles_completed));
2402 _old_marking_cycles_completed += 1;
2404 // We need to clear the "in_progress" flag in the CM thread before
2405 // we wake up any waiters (especially when ExplicitInvokesConcurrent
2406 // is set) so that if a waiter requests another System.gc() it doesn't
2407 // incorrectly see that a marking cycle is still in progress.
2408 if (concurrent) {
2409 _cmThread->clear_in_progress();
2410 }
2412 // This notify_all() will ensure that a thread that called
2413 // System.gc() with (with ExplicitGCInvokesConcurrent set or not)
2414 // and it's waiting for a full GC to finish will be woken up. It is
2415 // waiting in VM_G1IncCollectionPause::doit_epilogue().
2416 FullGCCount_lock->notify_all();
2417 }
2419 void G1CollectedHeap::register_concurrent_cycle_start(const Ticks& start_time) {
2420 _concurrent_cycle_started = true;
2421 _gc_timer_cm->register_gc_start(start_time);
2423 _gc_tracer_cm->report_gc_start(gc_cause(), _gc_timer_cm->gc_start());
2424 trace_heap_before_gc(_gc_tracer_cm);
2425 }
2427 void G1CollectedHeap::register_concurrent_cycle_end() {
2428 if (_concurrent_cycle_started) {
2429 if (_cm->has_aborted()) {
2430 _gc_tracer_cm->report_concurrent_mode_failure();
2431 }
2433 _gc_timer_cm->register_gc_end();
2434 _gc_tracer_cm->report_gc_end(_gc_timer_cm->gc_end(), _gc_timer_cm->time_partitions());
2436 _concurrent_cycle_started = false;
2437 }
2438 }
2440 void G1CollectedHeap::trace_heap_after_concurrent_cycle() {
2441 if (_concurrent_cycle_started) {
2442 trace_heap_after_gc(_gc_tracer_cm);
2443 }
2444 }
2446 G1YCType G1CollectedHeap::yc_type() {
2447 bool is_young = g1_policy()->gcs_are_young();
2448 bool is_initial_mark = g1_policy()->during_initial_mark_pause();
2449 bool is_during_mark = mark_in_progress();
2451 if (is_initial_mark) {
2452 return InitialMark;
2453 } else if (is_during_mark) {
2454 return DuringMark;
2455 } else if (is_young) {
2456 return Normal;
2457 } else {
2458 return Mixed;
2459 }
2460 }
2462 void G1CollectedHeap::collect(GCCause::Cause cause) {
2463 assert_heap_not_locked();
2465 unsigned int gc_count_before;
2466 unsigned int old_marking_count_before;
2467 unsigned int full_gc_count_before;
2468 bool retry_gc;
2470 do {
2471 retry_gc = false;
2473 {
2474 MutexLocker ml(Heap_lock);
2476 // Read the GC count while holding the Heap_lock
2477 gc_count_before = total_collections();
2478 full_gc_count_before = total_full_collections();
2479 old_marking_count_before = _old_marking_cycles_started;
2480 }
2482 if (should_do_concurrent_full_gc(cause)) {
2483 // Schedule an initial-mark evacuation pause that will start a
2484 // concurrent cycle. We're setting word_size to 0 which means that
2485 // we are not requesting a post-GC allocation.
2486 VM_G1IncCollectionPause op(gc_count_before,
2487 0, /* word_size */
2488 true, /* should_initiate_conc_mark */
2489 g1_policy()->max_pause_time_ms(),
2490 cause);
2491 op.set_allocation_context(AllocationContext::current());
2493 VMThread::execute(&op);
2494 if (!op.pause_succeeded()) {
2495 if (old_marking_count_before == _old_marking_cycles_started) {
2496 retry_gc = op.should_retry_gc();
2497 } else {
2498 // A Full GC happened while we were trying to schedule the
2499 // initial-mark GC. No point in starting a new cycle given
2500 // that the whole heap was collected anyway.
2501 }
2503 if (retry_gc) {
2504 if (GC_locker::is_active_and_needs_gc()) {
2505 GC_locker::stall_until_clear();
2506 }
2507 }
2508 }
2509 } else {
2510 if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc
2511 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2513 // Schedule a standard evacuation pause. We're setting word_size
2514 // to 0 which means that we are not requesting a post-GC allocation.
2515 VM_G1IncCollectionPause op(gc_count_before,
2516 0, /* word_size */
2517 false, /* should_initiate_conc_mark */
2518 g1_policy()->max_pause_time_ms(),
2519 cause);
2520 VMThread::execute(&op);
2521 } else {
2522 // Schedule a Full GC.
2523 VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause);
2524 VMThread::execute(&op);
2525 }
2526 }
2527 } while (retry_gc);
2528 }
2530 bool G1CollectedHeap::is_in(const void* p) const {
2531 if (_hrm.reserved().contains(p)) {
2532 // Given that we know that p is in the reserved space,
2533 // heap_region_containing_raw() should successfully
2534 // return the containing region.
2535 HeapRegion* hr = heap_region_containing_raw(p);
2536 return hr->is_in(p);
2537 } else {
2538 return false;
2539 }
2540 }
2542 #ifdef ASSERT
2543 bool G1CollectedHeap::is_in_exact(const void* p) const {
2544 bool contains = reserved_region().contains(p);
2545 bool available = _hrm.is_available(addr_to_region((HeapWord*)p));
2546 if (contains && available) {
2547 return true;
2548 } else {
2549 return false;
2550 }
2551 }
2552 #endif
2554 // Iteration functions.
2556 // Applies an ExtendedOopClosure onto all references of objects within a HeapRegion.
2558 class IterateOopClosureRegionClosure: public HeapRegionClosure {
2559 ExtendedOopClosure* _cl;
2560 public:
2561 IterateOopClosureRegionClosure(ExtendedOopClosure* cl) : _cl(cl) {}
2562 bool doHeapRegion(HeapRegion* r) {
2563 if (!r->continuesHumongous()) {
2564 r->oop_iterate(_cl);
2565 }
2566 return false;
2567 }
2568 };
2570 void G1CollectedHeap::oop_iterate(ExtendedOopClosure* cl) {
2571 IterateOopClosureRegionClosure blk(cl);
2572 heap_region_iterate(&blk);
2573 }
2575 // Iterates an ObjectClosure over all objects within a HeapRegion.
2577 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2578 ObjectClosure* _cl;
2579 public:
2580 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2581 bool doHeapRegion(HeapRegion* r) {
2582 if (! r->continuesHumongous()) {
2583 r->object_iterate(_cl);
2584 }
2585 return false;
2586 }
2587 };
2589 void G1CollectedHeap::object_iterate(ObjectClosure* cl) {
2590 IterateObjectClosureRegionClosure blk(cl);
2591 heap_region_iterate(&blk);
2592 }
2594 // Calls a SpaceClosure on a HeapRegion.
2596 class SpaceClosureRegionClosure: public HeapRegionClosure {
2597 SpaceClosure* _cl;
2598 public:
2599 SpaceClosureRegionClosure(SpaceClosure* cl) : _cl(cl) {}
2600 bool doHeapRegion(HeapRegion* r) {
2601 _cl->do_space(r);
2602 return false;
2603 }
2604 };
2606 void G1CollectedHeap::space_iterate(SpaceClosure* cl) {
2607 SpaceClosureRegionClosure blk(cl);
2608 heap_region_iterate(&blk);
2609 }
2611 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2612 _hrm.iterate(cl);
2613 }
2615 void
2616 G1CollectedHeap::heap_region_par_iterate_chunked(HeapRegionClosure* cl,
2617 uint worker_id,
2618 uint num_workers,
2619 jint claim_value) const {
2620 _hrm.par_iterate(cl, worker_id, num_workers, claim_value);
2621 }
2623 class ResetClaimValuesClosure: public HeapRegionClosure {
2624 public:
2625 bool doHeapRegion(HeapRegion* r) {
2626 r->set_claim_value(HeapRegion::InitialClaimValue);
2627 return false;
2628 }
2629 };
2631 void G1CollectedHeap::reset_heap_region_claim_values() {
2632 ResetClaimValuesClosure blk;
2633 heap_region_iterate(&blk);
2634 }
2636 void G1CollectedHeap::reset_cset_heap_region_claim_values() {
2637 ResetClaimValuesClosure blk;
2638 collection_set_iterate(&blk);
2639 }
2641 #ifdef ASSERT
2642 // This checks whether all regions in the heap have the correct claim
2643 // value. I also piggy-backed on this a check to ensure that the
2644 // humongous_start_region() information on "continues humongous"
2645 // regions is correct.
2647 class CheckClaimValuesClosure : public HeapRegionClosure {
2648 private:
2649 jint _claim_value;
2650 uint _failures;
2651 HeapRegion* _sh_region;
2653 public:
2654 CheckClaimValuesClosure(jint claim_value) :
2655 _claim_value(claim_value), _failures(0), _sh_region(NULL) { }
2656 bool doHeapRegion(HeapRegion* r) {
2657 if (r->claim_value() != _claim_value) {
2658 gclog_or_tty->print_cr("Region " HR_FORMAT ", "
2659 "claim value = %d, should be %d",
2660 HR_FORMAT_PARAMS(r),
2661 r->claim_value(), _claim_value);
2662 ++_failures;
2663 }
2664 if (!r->isHumongous()) {
2665 _sh_region = NULL;
2666 } else if (r->startsHumongous()) {
2667 _sh_region = r;
2668 } else if (r->continuesHumongous()) {
2669 if (r->humongous_start_region() != _sh_region) {
2670 gclog_or_tty->print_cr("Region " HR_FORMAT ", "
2671 "HS = "PTR_FORMAT", should be "PTR_FORMAT,
2672 HR_FORMAT_PARAMS(r),
2673 r->humongous_start_region(),
2674 _sh_region);
2675 ++_failures;
2676 }
2677 }
2678 return false;
2679 }
2680 uint failures() { return _failures; }
2681 };
2683 bool G1CollectedHeap::check_heap_region_claim_values(jint claim_value) {
2684 CheckClaimValuesClosure cl(claim_value);
2685 heap_region_iterate(&cl);
2686 return cl.failures() == 0;
2687 }
2689 class CheckClaimValuesInCSetHRClosure: public HeapRegionClosure {
2690 private:
2691 jint _claim_value;
2692 uint _failures;
2694 public:
2695 CheckClaimValuesInCSetHRClosure(jint claim_value) :
2696 _claim_value(claim_value), _failures(0) { }
2698 uint failures() { return _failures; }
2700 bool doHeapRegion(HeapRegion* hr) {
2701 assert(hr->in_collection_set(), "how?");
2702 assert(!hr->isHumongous(), "H-region in CSet");
2703 if (hr->claim_value() != _claim_value) {
2704 gclog_or_tty->print_cr("CSet Region " HR_FORMAT ", "
2705 "claim value = %d, should be %d",
2706 HR_FORMAT_PARAMS(hr),
2707 hr->claim_value(), _claim_value);
2708 _failures += 1;
2709 }
2710 return false;
2711 }
2712 };
2714 bool G1CollectedHeap::check_cset_heap_region_claim_values(jint claim_value) {
2715 CheckClaimValuesInCSetHRClosure cl(claim_value);
2716 collection_set_iterate(&cl);
2717 return cl.failures() == 0;
2718 }
2719 #endif // ASSERT
2721 // Clear the cached CSet starting regions and (more importantly)
2722 // the time stamps. Called when we reset the GC time stamp.
2723 void G1CollectedHeap::clear_cset_start_regions() {
2724 assert(_worker_cset_start_region != NULL, "sanity");
2725 assert(_worker_cset_start_region_time_stamp != NULL, "sanity");
2727 int n_queues = MAX2((int)ParallelGCThreads, 1);
2728 for (int i = 0; i < n_queues; i++) {
2729 _worker_cset_start_region[i] = NULL;
2730 _worker_cset_start_region_time_stamp[i] = 0;
2731 }
2732 }
2734 // Given the id of a worker, obtain or calculate a suitable
2735 // starting region for iterating over the current collection set.
2736 HeapRegion* G1CollectedHeap::start_cset_region_for_worker(uint worker_i) {
2737 assert(get_gc_time_stamp() > 0, "should have been updated by now");
2739 HeapRegion* result = NULL;
2740 unsigned gc_time_stamp = get_gc_time_stamp();
2742 if (_worker_cset_start_region_time_stamp[worker_i] == gc_time_stamp) {
2743 // Cached starting region for current worker was set
2744 // during the current pause - so it's valid.
2745 // Note: the cached starting heap region may be NULL
2746 // (when the collection set is empty).
2747 result = _worker_cset_start_region[worker_i];
2748 assert(result == NULL || result->in_collection_set(), "sanity");
2749 return result;
2750 }
2752 // The cached entry was not valid so let's calculate
2753 // a suitable starting heap region for this worker.
2755 // We want the parallel threads to start their collection
2756 // set iteration at different collection set regions to
2757 // avoid contention.
2758 // If we have:
2759 // n collection set regions
2760 // p threads
2761 // Then thread t will start at region floor ((t * n) / p)
2763 result = g1_policy()->collection_set();
2764 if (G1CollectedHeap::use_parallel_gc_threads()) {
2765 uint cs_size = g1_policy()->cset_region_length();
2766 uint active_workers = workers()->active_workers();
2767 assert(UseDynamicNumberOfGCThreads ||
2768 active_workers == workers()->total_workers(),
2769 "Unless dynamic should use total workers");
2771 uint end_ind = (cs_size * worker_i) / active_workers;
2772 uint start_ind = 0;
2774 if (worker_i > 0 &&
2775 _worker_cset_start_region_time_stamp[worker_i - 1] == gc_time_stamp) {
2776 // Previous workers starting region is valid
2777 // so let's iterate from there
2778 start_ind = (cs_size * (worker_i - 1)) / active_workers;
2779 result = _worker_cset_start_region[worker_i - 1];
2780 }
2782 for (uint i = start_ind; i < end_ind; i++) {
2783 result = result->next_in_collection_set();
2784 }
2785 }
2787 // Note: the calculated starting heap region may be NULL
2788 // (when the collection set is empty).
2789 assert(result == NULL || result->in_collection_set(), "sanity");
2790 assert(_worker_cset_start_region_time_stamp[worker_i] != gc_time_stamp,
2791 "should be updated only once per pause");
2792 _worker_cset_start_region[worker_i] = result;
2793 OrderAccess::storestore();
2794 _worker_cset_start_region_time_stamp[worker_i] = gc_time_stamp;
2795 return result;
2796 }
2798 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) {
2799 HeapRegion* r = g1_policy()->collection_set();
2800 while (r != NULL) {
2801 HeapRegion* next = r->next_in_collection_set();
2802 if (cl->doHeapRegion(r)) {
2803 cl->incomplete();
2804 return;
2805 }
2806 r = next;
2807 }
2808 }
2810 void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r,
2811 HeapRegionClosure *cl) {
2812 if (r == NULL) {
2813 // The CSet is empty so there's nothing to do.
2814 return;
2815 }
2817 assert(r->in_collection_set(),
2818 "Start region must be a member of the collection set.");
2819 HeapRegion* cur = r;
2820 while (cur != NULL) {
2821 HeapRegion* next = cur->next_in_collection_set();
2822 if (cl->doHeapRegion(cur) && false) {
2823 cl->incomplete();
2824 return;
2825 }
2826 cur = next;
2827 }
2828 cur = g1_policy()->collection_set();
2829 while (cur != r) {
2830 HeapRegion* next = cur->next_in_collection_set();
2831 if (cl->doHeapRegion(cur) && false) {
2832 cl->incomplete();
2833 return;
2834 }
2835 cur = next;
2836 }
2837 }
2839 HeapRegion* G1CollectedHeap::next_compaction_region(const HeapRegion* from) const {
2840 HeapRegion* result = _hrm.next_region_in_heap(from);
2841 while (result != NULL && result->isHumongous()) {
2842 result = _hrm.next_region_in_heap(result);
2843 }
2844 return result;
2845 }
2847 Space* G1CollectedHeap::space_containing(const void* addr) const {
2848 return heap_region_containing(addr);
2849 }
2851 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2852 Space* sp = space_containing(addr);
2853 return sp->block_start(addr);
2854 }
2856 size_t G1CollectedHeap::block_size(const HeapWord* addr) const {
2857 Space* sp = space_containing(addr);
2858 return sp->block_size(addr);
2859 }
2861 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2862 Space* sp = space_containing(addr);
2863 return sp->block_is_obj(addr);
2864 }
2866 bool G1CollectedHeap::supports_tlab_allocation() const {
2867 return true;
2868 }
2870 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
2871 return (_g1_policy->young_list_target_length() - young_list()->survivor_length()) * HeapRegion::GrainBytes;
2872 }
2874 size_t G1CollectedHeap::tlab_used(Thread* ignored) const {
2875 return young_list()->eden_used_bytes();
2876 }
2878 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size
2879 // must be smaller than the humongous object limit.
2880 size_t G1CollectedHeap::max_tlab_size() const {
2881 return align_size_down(_humongous_object_threshold_in_words - 1, MinObjAlignment);
2882 }
2884 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
2885 // Return the remaining space in the cur alloc region, but not less than
2886 // the min TLAB size.
2888 // Also, this value can be at most the humongous object threshold,
2889 // since we can't allow tlabs to grow big enough to accommodate
2890 // humongous objects.
2892 HeapRegion* hr = _allocator->mutator_alloc_region(AllocationContext::current())->get();
2893 size_t max_tlab = max_tlab_size() * wordSize;
2894 if (hr == NULL) {
2895 return max_tlab;
2896 } else {
2897 return MIN2(MAX2(hr->free(), (size_t) MinTLABSize), max_tlab);
2898 }
2899 }
2901 size_t G1CollectedHeap::max_capacity() const {
2902 return _hrm.reserved().byte_size();
2903 }
2905 jlong G1CollectedHeap::millis_since_last_gc() {
2906 // assert(false, "NYI");
2907 return 0;
2908 }
2910 void G1CollectedHeap::prepare_for_verify() {
2911 if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) {
2912 ensure_parsability(false);
2913 }
2914 g1_rem_set()->prepare_for_verify();
2915 }
2917 bool G1CollectedHeap::allocated_since_marking(oop obj, HeapRegion* hr,
2918 VerifyOption vo) {
2919 switch (vo) {
2920 case VerifyOption_G1UsePrevMarking:
2921 return hr->obj_allocated_since_prev_marking(obj);
2922 case VerifyOption_G1UseNextMarking:
2923 return hr->obj_allocated_since_next_marking(obj);
2924 case VerifyOption_G1UseMarkWord:
2925 return false;
2926 default:
2927 ShouldNotReachHere();
2928 }
2929 return false; // keep some compilers happy
2930 }
2932 HeapWord* G1CollectedHeap::top_at_mark_start(HeapRegion* hr, VerifyOption vo) {
2933 switch (vo) {
2934 case VerifyOption_G1UsePrevMarking: return hr->prev_top_at_mark_start();
2935 case VerifyOption_G1UseNextMarking: return hr->next_top_at_mark_start();
2936 case VerifyOption_G1UseMarkWord: return NULL;
2937 default: ShouldNotReachHere();
2938 }
2939 return NULL; // keep some compilers happy
2940 }
2942 bool G1CollectedHeap::is_marked(oop obj, VerifyOption vo) {
2943 switch (vo) {
2944 case VerifyOption_G1UsePrevMarking: return isMarkedPrev(obj);
2945 case VerifyOption_G1UseNextMarking: return isMarkedNext(obj);
2946 case VerifyOption_G1UseMarkWord: return obj->is_gc_marked();
2947 default: ShouldNotReachHere();
2948 }
2949 return false; // keep some compilers happy
2950 }
2952 const char* G1CollectedHeap::top_at_mark_start_str(VerifyOption vo) {
2953 switch (vo) {
2954 case VerifyOption_G1UsePrevMarking: return "PTAMS";
2955 case VerifyOption_G1UseNextMarking: return "NTAMS";
2956 case VerifyOption_G1UseMarkWord: return "NONE";
2957 default: ShouldNotReachHere();
2958 }
2959 return NULL; // keep some compilers happy
2960 }
2962 class VerifyRootsClosure: public OopClosure {
2963 private:
2964 G1CollectedHeap* _g1h;
2965 VerifyOption _vo;
2966 bool _failures;
2967 public:
2968 // _vo == UsePrevMarking -> use "prev" marking information,
2969 // _vo == UseNextMarking -> use "next" marking information,
2970 // _vo == UseMarkWord -> use mark word from object header.
2971 VerifyRootsClosure(VerifyOption vo) :
2972 _g1h(G1CollectedHeap::heap()),
2973 _vo(vo),
2974 _failures(false) { }
2976 bool failures() { return _failures; }
2978 template <class T> void do_oop_nv(T* p) {
2979 T heap_oop = oopDesc::load_heap_oop(p);
2980 if (!oopDesc::is_null(heap_oop)) {
2981 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
2982 if (_g1h->is_obj_dead_cond(obj, _vo)) {
2983 gclog_or_tty->print_cr("Root location "PTR_FORMAT" "
2984 "points to dead obj "PTR_FORMAT, p, (void*) obj);
2985 if (_vo == VerifyOption_G1UseMarkWord) {
2986 gclog_or_tty->print_cr(" Mark word: "PTR_FORMAT, (void*)(obj->mark()));
2987 }
2988 obj->print_on(gclog_or_tty);
2989 _failures = true;
2990 }
2991 }
2992 }
2994 void do_oop(oop* p) { do_oop_nv(p); }
2995 void do_oop(narrowOop* p) { do_oop_nv(p); }
2996 };
2998 class G1VerifyCodeRootOopClosure: public OopClosure {
2999 G1CollectedHeap* _g1h;
3000 OopClosure* _root_cl;
3001 nmethod* _nm;
3002 VerifyOption _vo;
3003 bool _failures;
3005 template <class T> void do_oop_work(T* p) {
3006 // First verify that this root is live
3007 _root_cl->do_oop(p);
3009 if (!G1VerifyHeapRegionCodeRoots) {
3010 // We're not verifying the code roots attached to heap region.
3011 return;
3012 }
3014 // Don't check the code roots during marking verification in a full GC
3015 if (_vo == VerifyOption_G1UseMarkWord) {
3016 return;
3017 }
3019 // Now verify that the current nmethod (which contains p) is
3020 // in the code root list of the heap region containing the
3021 // object referenced by p.
3023 T heap_oop = oopDesc::load_heap_oop(p);
3024 if (!oopDesc::is_null(heap_oop)) {
3025 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
3027 // Now fetch the region containing the object
3028 HeapRegion* hr = _g1h->heap_region_containing(obj);
3029 HeapRegionRemSet* hrrs = hr->rem_set();
3030 // Verify that the strong code root list for this region
3031 // contains the nmethod
3032 if (!hrrs->strong_code_roots_list_contains(_nm)) {
3033 gclog_or_tty->print_cr("Code root location "PTR_FORMAT" "
3034 "from nmethod "PTR_FORMAT" not in strong "
3035 "code roots for region ["PTR_FORMAT","PTR_FORMAT")",
3036 p, _nm, hr->bottom(), hr->end());
3037 _failures = true;
3038 }
3039 }
3040 }
3042 public:
3043 G1VerifyCodeRootOopClosure(G1CollectedHeap* g1h, OopClosure* root_cl, VerifyOption vo):
3044 _g1h(g1h), _root_cl(root_cl), _vo(vo), _nm(NULL), _failures(false) {}
3046 void do_oop(oop* p) { do_oop_work(p); }
3047 void do_oop(narrowOop* p) { do_oop_work(p); }
3049 void set_nmethod(nmethod* nm) { _nm = nm; }
3050 bool failures() { return _failures; }
3051 };
3053 class G1VerifyCodeRootBlobClosure: public CodeBlobClosure {
3054 G1VerifyCodeRootOopClosure* _oop_cl;
3056 public:
3057 G1VerifyCodeRootBlobClosure(G1VerifyCodeRootOopClosure* oop_cl):
3058 _oop_cl(oop_cl) {}
3060 void do_code_blob(CodeBlob* cb) {
3061 nmethod* nm = cb->as_nmethod_or_null();
3062 if (nm != NULL) {
3063 _oop_cl->set_nmethod(nm);
3064 nm->oops_do(_oop_cl);
3065 }
3066 }
3067 };
3069 class YoungRefCounterClosure : public OopClosure {
3070 G1CollectedHeap* _g1h;
3071 int _count;
3072 public:
3073 YoungRefCounterClosure(G1CollectedHeap* g1h) : _g1h(g1h), _count(0) {}
3074 void do_oop(oop* p) { if (_g1h->is_in_young(*p)) { _count++; } }
3075 void do_oop(narrowOop* p) { ShouldNotReachHere(); }
3077 int count() { return _count; }
3078 void reset_count() { _count = 0; };
3079 };
3081 class VerifyKlassClosure: public KlassClosure {
3082 YoungRefCounterClosure _young_ref_counter_closure;
3083 OopClosure *_oop_closure;
3084 public:
3085 VerifyKlassClosure(G1CollectedHeap* g1h, OopClosure* cl) : _young_ref_counter_closure(g1h), _oop_closure(cl) {}
3086 void do_klass(Klass* k) {
3087 k->oops_do(_oop_closure);
3089 _young_ref_counter_closure.reset_count();
3090 k->oops_do(&_young_ref_counter_closure);
3091 if (_young_ref_counter_closure.count() > 0) {
3092 guarantee(k->has_modified_oops(), err_msg("Klass %p, has young refs but is not dirty.", k));
3093 }
3094 }
3095 };
3097 class VerifyLivenessOopClosure: public OopClosure {
3098 G1CollectedHeap* _g1h;
3099 VerifyOption _vo;
3100 public:
3101 VerifyLivenessOopClosure(G1CollectedHeap* g1h, VerifyOption vo):
3102 _g1h(g1h), _vo(vo)
3103 { }
3104 void do_oop(narrowOop *p) { do_oop_work(p); }
3105 void do_oop( oop *p) { do_oop_work(p); }
3107 template <class T> void do_oop_work(T *p) {
3108 oop obj = oopDesc::load_decode_heap_oop(p);
3109 guarantee(obj == NULL || !_g1h->is_obj_dead_cond(obj, _vo),
3110 "Dead object referenced by a not dead object");
3111 }
3112 };
3114 class VerifyObjsInRegionClosure: public ObjectClosure {
3115 private:
3116 G1CollectedHeap* _g1h;
3117 size_t _live_bytes;
3118 HeapRegion *_hr;
3119 VerifyOption _vo;
3120 public:
3121 // _vo == UsePrevMarking -> use "prev" marking information,
3122 // _vo == UseNextMarking -> use "next" marking information,
3123 // _vo == UseMarkWord -> use mark word from object header.
3124 VerifyObjsInRegionClosure(HeapRegion *hr, VerifyOption vo)
3125 : _live_bytes(0), _hr(hr), _vo(vo) {
3126 _g1h = G1CollectedHeap::heap();
3127 }
3128 void do_object(oop o) {
3129 VerifyLivenessOopClosure isLive(_g1h, _vo);
3130 assert(o != NULL, "Huh?");
3131 if (!_g1h->is_obj_dead_cond(o, _vo)) {
3132 // If the object is alive according to the mark word,
3133 // then verify that the marking information agrees.
3134 // Note we can't verify the contra-positive of the
3135 // above: if the object is dead (according to the mark
3136 // word), it may not be marked, or may have been marked
3137 // but has since became dead, or may have been allocated
3138 // since the last marking.
3139 if (_vo == VerifyOption_G1UseMarkWord) {
3140 guarantee(!_g1h->is_obj_dead(o), "mark word and concurrent mark mismatch");
3141 }
3143 o->oop_iterate_no_header(&isLive);
3144 if (!_hr->obj_allocated_since_prev_marking(o)) {
3145 size_t obj_size = o->size(); // Make sure we don't overflow
3146 _live_bytes += (obj_size * HeapWordSize);
3147 }
3148 }
3149 }
3150 size_t live_bytes() { return _live_bytes; }
3151 };
3153 class PrintObjsInRegionClosure : public ObjectClosure {
3154 HeapRegion *_hr;
3155 G1CollectedHeap *_g1;
3156 public:
3157 PrintObjsInRegionClosure(HeapRegion *hr) : _hr(hr) {
3158 _g1 = G1CollectedHeap::heap();
3159 };
3161 void do_object(oop o) {
3162 if (o != NULL) {
3163 HeapWord *start = (HeapWord *) o;
3164 size_t word_sz = o->size();
3165 gclog_or_tty->print("\nPrinting obj "PTR_FORMAT" of size " SIZE_FORMAT
3166 " isMarkedPrev %d isMarkedNext %d isAllocSince %d\n",
3167 (void*) o, word_sz,
3168 _g1->isMarkedPrev(o),
3169 _g1->isMarkedNext(o),
3170 _hr->obj_allocated_since_prev_marking(o));
3171 HeapWord *end = start + word_sz;
3172 HeapWord *cur;
3173 int *val;
3174 for (cur = start; cur < end; cur++) {
3175 val = (int *) cur;
3176 gclog_or_tty->print("\t "PTR_FORMAT":"PTR_FORMAT"\n", val, *val);
3177 }
3178 }
3179 }
3180 };
3182 class VerifyRegionClosure: public HeapRegionClosure {
3183 private:
3184 bool _par;
3185 VerifyOption _vo;
3186 bool _failures;
3187 public:
3188 // _vo == UsePrevMarking -> use "prev" marking information,
3189 // _vo == UseNextMarking -> use "next" marking information,
3190 // _vo == UseMarkWord -> use mark word from object header.
3191 VerifyRegionClosure(bool par, VerifyOption vo)
3192 : _par(par),
3193 _vo(vo),
3194 _failures(false) {}
3196 bool failures() {
3197 return _failures;
3198 }
3200 bool doHeapRegion(HeapRegion* r) {
3201 if (!r->continuesHumongous()) {
3202 bool failures = false;
3203 r->verify(_vo, &failures);
3204 if (failures) {
3205 _failures = true;
3206 } else {
3207 VerifyObjsInRegionClosure not_dead_yet_cl(r, _vo);
3208 r->object_iterate(¬_dead_yet_cl);
3209 if (_vo != VerifyOption_G1UseNextMarking) {
3210 if (r->max_live_bytes() < not_dead_yet_cl.live_bytes()) {
3211 gclog_or_tty->print_cr("["PTR_FORMAT","PTR_FORMAT"] "
3212 "max_live_bytes "SIZE_FORMAT" "
3213 "< calculated "SIZE_FORMAT,
3214 r->bottom(), r->end(),
3215 r->max_live_bytes(),
3216 not_dead_yet_cl.live_bytes());
3217 _failures = true;
3218 }
3219 } else {
3220 // When vo == UseNextMarking we cannot currently do a sanity
3221 // check on the live bytes as the calculation has not been
3222 // finalized yet.
3223 }
3224 }
3225 }
3226 return false; // stop the region iteration if we hit a failure
3227 }
3228 };
3230 // This is the task used for parallel verification of the heap regions
3232 class G1ParVerifyTask: public AbstractGangTask {
3233 private:
3234 G1CollectedHeap* _g1h;
3235 VerifyOption _vo;
3236 bool _failures;
3238 public:
3239 // _vo == UsePrevMarking -> use "prev" marking information,
3240 // _vo == UseNextMarking -> use "next" marking information,
3241 // _vo == UseMarkWord -> use mark word from object header.
3242 G1ParVerifyTask(G1CollectedHeap* g1h, VerifyOption vo) :
3243 AbstractGangTask("Parallel verify task"),
3244 _g1h(g1h),
3245 _vo(vo),
3246 _failures(false) { }
3248 bool failures() {
3249 return _failures;
3250 }
3252 void work(uint worker_id) {
3253 HandleMark hm;
3254 VerifyRegionClosure blk(true, _vo);
3255 _g1h->heap_region_par_iterate_chunked(&blk, worker_id,
3256 _g1h->workers()->active_workers(),
3257 HeapRegion::ParVerifyClaimValue);
3258 if (blk.failures()) {
3259 _failures = true;
3260 }
3261 }
3262 };
3264 void G1CollectedHeap::verify(bool silent, VerifyOption vo) {
3265 if (SafepointSynchronize::is_at_safepoint()) {
3266 assert(Thread::current()->is_VM_thread(),
3267 "Expected to be executed serially by the VM thread at this point");
3269 if (!silent) { gclog_or_tty->print("Roots "); }
3270 VerifyRootsClosure rootsCl(vo);
3271 VerifyKlassClosure klassCl(this, &rootsCl);
3272 CLDToKlassAndOopClosure cldCl(&klassCl, &rootsCl, false);
3274 // We apply the relevant closures to all the oops in the
3275 // system dictionary, class loader data graph, the string table
3276 // and the nmethods in the code cache.
3277 G1VerifyCodeRootOopClosure codeRootsCl(this, &rootsCl, vo);
3278 G1VerifyCodeRootBlobClosure blobsCl(&codeRootsCl);
3280 {
3281 G1RootProcessor root_processor(this);
3282 root_processor.process_all_roots(&rootsCl,
3283 &cldCl,
3284 &blobsCl);
3285 }
3287 bool failures = rootsCl.failures() || codeRootsCl.failures();
3289 if (vo != VerifyOption_G1UseMarkWord) {
3290 // If we're verifying during a full GC then the region sets
3291 // will have been torn down at the start of the GC. Therefore
3292 // verifying the region sets will fail. So we only verify
3293 // the region sets when not in a full GC.
3294 if (!silent) { gclog_or_tty->print("HeapRegionSets "); }
3295 verify_region_sets();
3296 }
3298 if (!silent) { gclog_or_tty->print("HeapRegions "); }
3299 if (GCParallelVerificationEnabled && ParallelGCThreads > 1) {
3300 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3301 "sanity check");
3303 G1ParVerifyTask task(this, vo);
3304 assert(UseDynamicNumberOfGCThreads ||
3305 workers()->active_workers() == workers()->total_workers(),
3306 "If not dynamic should be using all the workers");
3307 int n_workers = workers()->active_workers();
3308 set_par_threads(n_workers);
3309 workers()->run_task(&task);
3310 set_par_threads(0);
3311 if (task.failures()) {
3312 failures = true;
3313 }
3315 // Checks that the expected amount of parallel work was done.
3316 // The implication is that n_workers is > 0.
3317 assert(check_heap_region_claim_values(HeapRegion::ParVerifyClaimValue),
3318 "sanity check");
3320 reset_heap_region_claim_values();
3322 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3323 "sanity check");
3324 } else {
3325 VerifyRegionClosure blk(false, vo);
3326 heap_region_iterate(&blk);
3327 if (blk.failures()) {
3328 failures = true;
3329 }
3330 }
3331 if (!silent) gclog_or_tty->print("RemSet ");
3332 rem_set()->verify();
3334 if (G1StringDedup::is_enabled()) {
3335 if (!silent) gclog_or_tty->print("StrDedup ");
3336 G1StringDedup::verify();
3337 }
3339 if (failures) {
3340 gclog_or_tty->print_cr("Heap:");
3341 // It helps to have the per-region information in the output to
3342 // help us track down what went wrong. This is why we call
3343 // print_extended_on() instead of print_on().
3344 print_extended_on(gclog_or_tty);
3345 gclog_or_tty->cr();
3346 #ifndef PRODUCT
3347 if (VerifyDuringGC && G1VerifyDuringGCPrintReachable) {
3348 concurrent_mark()->print_reachable("at-verification-failure",
3349 vo, false /* all */);
3350 }
3351 #endif
3352 gclog_or_tty->flush();
3353 }
3354 guarantee(!failures, "there should not have been any failures");
3355 } else {
3356 if (!silent) {
3357 gclog_or_tty->print("(SKIPPING Roots, HeapRegionSets, HeapRegions, RemSet");
3358 if (G1StringDedup::is_enabled()) {
3359 gclog_or_tty->print(", StrDedup");
3360 }
3361 gclog_or_tty->print(") ");
3362 }
3363 }
3364 }
3366 void G1CollectedHeap::verify(bool silent) {
3367 verify(silent, VerifyOption_G1UsePrevMarking);
3368 }
3370 double G1CollectedHeap::verify(bool guard, const char* msg) {
3371 double verify_time_ms = 0.0;
3373 if (guard && total_collections() >= VerifyGCStartAt) {
3374 double verify_start = os::elapsedTime();
3375 HandleMark hm; // Discard invalid handles created during verification
3376 prepare_for_verify();
3377 Universe::verify(VerifyOption_G1UsePrevMarking, msg);
3378 verify_time_ms = (os::elapsedTime() - verify_start) * 1000;
3379 }
3381 return verify_time_ms;
3382 }
3384 void G1CollectedHeap::verify_before_gc() {
3385 double verify_time_ms = verify(VerifyBeforeGC, " VerifyBeforeGC:");
3386 g1_policy()->phase_times()->record_verify_before_time_ms(verify_time_ms);
3387 }
3389 void G1CollectedHeap::verify_after_gc() {
3390 double verify_time_ms = verify(VerifyAfterGC, " VerifyAfterGC:");
3391 g1_policy()->phase_times()->record_verify_after_time_ms(verify_time_ms);
3392 }
3394 class PrintRegionClosure: public HeapRegionClosure {
3395 outputStream* _st;
3396 public:
3397 PrintRegionClosure(outputStream* st) : _st(st) {}
3398 bool doHeapRegion(HeapRegion* r) {
3399 r->print_on(_st);
3400 return false;
3401 }
3402 };
3404 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
3405 const HeapRegion* hr,
3406 const VerifyOption vo) const {
3407 switch (vo) {
3408 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr);
3409 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr);
3410 case VerifyOption_G1UseMarkWord: return !obj->is_gc_marked();
3411 default: ShouldNotReachHere();
3412 }
3413 return false; // keep some compilers happy
3414 }
3416 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
3417 const VerifyOption vo) const {
3418 switch (vo) {
3419 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj);
3420 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj);
3421 case VerifyOption_G1UseMarkWord: return !obj->is_gc_marked();
3422 default: ShouldNotReachHere();
3423 }
3424 return false; // keep some compilers happy
3425 }
3427 void G1CollectedHeap::print_on(outputStream* st) const {
3428 st->print(" %-20s", "garbage-first heap");
3429 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
3430 capacity()/K, used_unlocked()/K);
3431 st->print(" [" INTPTR_FORMAT ", " INTPTR_FORMAT ", " INTPTR_FORMAT ")",
3432 _hrm.reserved().start(),
3433 _hrm.reserved().start() + _hrm.length() + HeapRegion::GrainWords,
3434 _hrm.reserved().end());
3435 st->cr();
3436 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
3437 uint young_regions = _young_list->length();
3438 st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
3439 (size_t) young_regions * HeapRegion::GrainBytes / K);
3440 uint survivor_regions = g1_policy()->recorded_survivor_regions();
3441 st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
3442 (size_t) survivor_regions * HeapRegion::GrainBytes / K);
3443 st->cr();
3444 MetaspaceAux::print_on(st);
3445 }
3447 void G1CollectedHeap::print_extended_on(outputStream* st) const {
3448 print_on(st);
3450 // Print the per-region information.
3451 st->cr();
3452 st->print_cr("Heap Regions: (Y=young(eden), SU=young(survivor), "
3453 "HS=humongous(starts), HC=humongous(continues), "
3454 "CS=collection set, F=free, TS=gc time stamp, "
3455 "PTAMS=previous top-at-mark-start, "
3456 "NTAMS=next top-at-mark-start)");
3457 PrintRegionClosure blk(st);
3458 heap_region_iterate(&blk);
3459 }
3461 void G1CollectedHeap::print_on_error(outputStream* st) const {
3462 this->CollectedHeap::print_on_error(st);
3464 if (_cm != NULL) {
3465 st->cr();
3466 _cm->print_on_error(st);
3467 }
3468 }
3470 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
3471 if (G1CollectedHeap::use_parallel_gc_threads()) {
3472 workers()->print_worker_threads_on(st);
3473 }
3474 _cmThread->print_on(st);
3475 st->cr();
3476 _cm->print_worker_threads_on(st);
3477 _cg1r->print_worker_threads_on(st);
3478 if (G1StringDedup::is_enabled()) {
3479 G1StringDedup::print_worker_threads_on(st);
3480 }
3481 }
3483 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
3484 if (G1CollectedHeap::use_parallel_gc_threads()) {
3485 workers()->threads_do(tc);
3486 }
3487 tc->do_thread(_cmThread);
3488 _cg1r->threads_do(tc);
3489 if (G1StringDedup::is_enabled()) {
3490 G1StringDedup::threads_do(tc);
3491 }
3492 }
3494 void G1CollectedHeap::print_tracing_info() const {
3495 // We'll overload this to mean "trace GC pause statistics."
3496 if (TraceGen0Time || TraceGen1Time) {
3497 // The "G1CollectorPolicy" is keeping track of these stats, so delegate
3498 // to that.
3499 g1_policy()->print_tracing_info();
3500 }
3501 if (G1SummarizeRSetStats) {
3502 g1_rem_set()->print_summary_info();
3503 }
3504 if (G1SummarizeConcMark) {
3505 concurrent_mark()->print_summary_info();
3506 }
3507 g1_policy()->print_yg_surv_rate_info();
3508 SpecializationStats::print();
3509 }
3511 #ifndef PRODUCT
3512 // Helpful for debugging RSet issues.
3514 class PrintRSetsClosure : public HeapRegionClosure {
3515 private:
3516 const char* _msg;
3517 size_t _occupied_sum;
3519 public:
3520 bool doHeapRegion(HeapRegion* r) {
3521 HeapRegionRemSet* hrrs = r->rem_set();
3522 size_t occupied = hrrs->occupied();
3523 _occupied_sum += occupied;
3525 gclog_or_tty->print_cr("Printing RSet for region "HR_FORMAT,
3526 HR_FORMAT_PARAMS(r));
3527 if (occupied == 0) {
3528 gclog_or_tty->print_cr(" RSet is empty");
3529 } else {
3530 hrrs->print();
3531 }
3532 gclog_or_tty->print_cr("----------");
3533 return false;
3534 }
3536 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
3537 gclog_or_tty->cr();
3538 gclog_or_tty->print_cr("========================================");
3539 gclog_or_tty->print_cr("%s", msg);
3540 gclog_or_tty->cr();
3541 }
3543 ~PrintRSetsClosure() {
3544 gclog_or_tty->print_cr("Occupied Sum: "SIZE_FORMAT, _occupied_sum);
3545 gclog_or_tty->print_cr("========================================");
3546 gclog_or_tty->cr();
3547 }
3548 };
3550 void G1CollectedHeap::print_cset_rsets() {
3551 PrintRSetsClosure cl("Printing CSet RSets");
3552 collection_set_iterate(&cl);
3553 }
3555 void G1CollectedHeap::print_all_rsets() {
3556 PrintRSetsClosure cl("Printing All RSets");;
3557 heap_region_iterate(&cl);
3558 }
3559 #endif // PRODUCT
3561 G1CollectedHeap* G1CollectedHeap::heap() {
3562 assert(_sh->kind() == CollectedHeap::G1CollectedHeap,
3563 "not a garbage-first heap");
3564 return _g1h;
3565 }
3567 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) {
3568 // always_do_update_barrier = false;
3569 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
3570 // Fill TLAB's and such
3571 accumulate_statistics_all_tlabs();
3572 ensure_parsability(true);
3574 if (G1SummarizeRSetStats && (G1SummarizeRSetStatsPeriod > 0) &&
3575 (total_collections() % G1SummarizeRSetStatsPeriod == 0)) {
3576 g1_rem_set()->print_periodic_summary_info("Before GC RS summary");
3577 }
3578 }
3580 void G1CollectedHeap::gc_epilogue(bool full) {
3582 if (G1SummarizeRSetStats &&
3583 (G1SummarizeRSetStatsPeriod > 0) &&
3584 // we are at the end of the GC. Total collections has already been increased.
3585 ((total_collections() - 1) % G1SummarizeRSetStatsPeriod == 0)) {
3586 g1_rem_set()->print_periodic_summary_info("After GC RS summary");
3587 }
3589 // FIXME: what is this about?
3590 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
3591 // is set.
3592 COMPILER2_PRESENT(assert(DerivedPointerTable::is_empty(),
3593 "derived pointer present"));
3594 // always_do_update_barrier = true;
3596 resize_all_tlabs();
3597 allocation_context_stats().update(full);
3599 // We have just completed a GC. Update the soft reference
3600 // policy with the new heap occupancy
3601 Universe::update_heap_info_at_gc();
3602 }
3604 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
3605 unsigned int gc_count_before,
3606 bool* succeeded,
3607 GCCause::Cause gc_cause) {
3608 assert_heap_not_locked_and_not_at_safepoint();
3609 g1_policy()->record_stop_world_start();
3610 VM_G1IncCollectionPause op(gc_count_before,
3611 word_size,
3612 false, /* should_initiate_conc_mark */
3613 g1_policy()->max_pause_time_ms(),
3614 gc_cause);
3616 op.set_allocation_context(AllocationContext::current());
3617 VMThread::execute(&op);
3619 HeapWord* result = op.result();
3620 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
3621 assert(result == NULL || ret_succeeded,
3622 "the result should be NULL if the VM did not succeed");
3623 *succeeded = ret_succeeded;
3625 assert_heap_not_locked();
3626 return result;
3627 }
3629 void
3630 G1CollectedHeap::doConcurrentMark() {
3631 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
3632 if (!_cmThread->in_progress()) {
3633 _cmThread->set_started();
3634 CGC_lock->notify();
3635 }
3636 }
3638 size_t G1CollectedHeap::pending_card_num() {
3639 size_t extra_cards = 0;
3640 JavaThread *curr = Threads::first();
3641 while (curr != NULL) {
3642 DirtyCardQueue& dcq = curr->dirty_card_queue();
3643 extra_cards += dcq.size();
3644 curr = curr->next();
3645 }
3646 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
3647 size_t buffer_size = dcqs.buffer_size();
3648 size_t buffer_num = dcqs.completed_buffers_num();
3650 // PtrQueueSet::buffer_size() and PtrQueue:size() return sizes
3651 // in bytes - not the number of 'entries'. We need to convert
3652 // into a number of cards.
3653 return (buffer_size * buffer_num + extra_cards) / oopSize;
3654 }
3656 size_t G1CollectedHeap::cards_scanned() {
3657 return g1_rem_set()->cardsScanned();
3658 }
3660 bool G1CollectedHeap::humongous_region_is_always_live(uint index) {
3661 HeapRegion* region = region_at(index);
3662 assert(region->startsHumongous(), "Must start a humongous object");
3663 return oop(region->bottom())->is_objArray() || !region->rem_set()->is_empty();
3664 }
3666 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure {
3667 private:
3668 size_t _total_humongous;
3669 size_t _candidate_humongous;
3670 public:
3671 RegisterHumongousWithInCSetFastTestClosure() : _total_humongous(0), _candidate_humongous(0) {
3672 }
3674 virtual bool doHeapRegion(HeapRegion* r) {
3675 if (!r->startsHumongous()) {
3676 return false;
3677 }
3678 G1CollectedHeap* g1h = G1CollectedHeap::heap();
3680 uint region_idx = r->hrm_index();
3681 bool is_candidate = !g1h->humongous_region_is_always_live(region_idx);
3682 // Is_candidate already filters out humongous regions with some remembered set.
3683 // This will not lead to humongous object that we mistakenly keep alive because
3684 // during young collection the remembered sets will only be added to.
3685 if (is_candidate) {
3686 g1h->register_humongous_region_with_in_cset_fast_test(region_idx);
3687 _candidate_humongous++;
3688 }
3689 _total_humongous++;
3691 return false;
3692 }
3694 size_t total_humongous() const { return _total_humongous; }
3695 size_t candidate_humongous() const { return _candidate_humongous; }
3696 };
3698 void G1CollectedHeap::register_humongous_regions_with_in_cset_fast_test() {
3699 if (!G1ReclaimDeadHumongousObjectsAtYoungGC) {
3700 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0, 0);
3701 return;
3702 }
3704 RegisterHumongousWithInCSetFastTestClosure cl;
3705 heap_region_iterate(&cl);
3706 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(cl.total_humongous(),
3707 cl.candidate_humongous());
3708 _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0;
3710 if (_has_humongous_reclaim_candidates) {
3711 clear_humongous_is_live_table();
3712 }
3713 }
3715 void
3716 G1CollectedHeap::setup_surviving_young_words() {
3717 assert(_surviving_young_words == NULL, "pre-condition");
3718 uint array_length = g1_policy()->young_cset_region_length();
3719 _surviving_young_words = NEW_C_HEAP_ARRAY(size_t, (size_t) array_length, mtGC);
3720 if (_surviving_young_words == NULL) {
3721 vm_exit_out_of_memory(sizeof(size_t) * array_length, OOM_MALLOC_ERROR,
3722 "Not enough space for young surv words summary.");
3723 }
3724 memset(_surviving_young_words, 0, (size_t) array_length * sizeof(size_t));
3725 #ifdef ASSERT
3726 for (uint i = 0; i < array_length; ++i) {
3727 assert( _surviving_young_words[i] == 0, "memset above" );
3728 }
3729 #endif // !ASSERT
3730 }
3732 void
3733 G1CollectedHeap::update_surviving_young_words(size_t* surv_young_words) {
3734 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
3735 uint array_length = g1_policy()->young_cset_region_length();
3736 for (uint i = 0; i < array_length; ++i) {
3737 _surviving_young_words[i] += surv_young_words[i];
3738 }
3739 }
3741 void
3742 G1CollectedHeap::cleanup_surviving_young_words() {
3743 guarantee( _surviving_young_words != NULL, "pre-condition" );
3744 FREE_C_HEAP_ARRAY(size_t, _surviving_young_words, mtGC);
3745 _surviving_young_words = NULL;
3746 }
3748 #ifdef ASSERT
3749 class VerifyCSetClosure: public HeapRegionClosure {
3750 public:
3751 bool doHeapRegion(HeapRegion* hr) {
3752 // Here we check that the CSet region's RSet is ready for parallel
3753 // iteration. The fields that we'll verify are only manipulated
3754 // when the region is part of a CSet and is collected. Afterwards,
3755 // we reset these fields when we clear the region's RSet (when the
3756 // region is freed) so they are ready when the region is
3757 // re-allocated. The only exception to this is if there's an
3758 // evacuation failure and instead of freeing the region we leave
3759 // it in the heap. In that case, we reset these fields during
3760 // evacuation failure handling.
3761 guarantee(hr->rem_set()->verify_ready_for_par_iteration(), "verification");
3763 // Here's a good place to add any other checks we'd like to
3764 // perform on CSet regions.
3765 return false;
3766 }
3767 };
3768 #endif // ASSERT
3770 #if TASKQUEUE_STATS
3771 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
3772 st->print_raw_cr("GC Task Stats");
3773 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
3774 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
3775 }
3777 void G1CollectedHeap::print_taskqueue_stats(outputStream* const st) const {
3778 print_taskqueue_stats_hdr(st);
3780 TaskQueueStats totals;
3781 const int n = workers() != NULL ? workers()->total_workers() : 1;
3782 for (int i = 0; i < n; ++i) {
3783 st->print("%3d ", i); task_queue(i)->stats.print(st); st->cr();
3784 totals += task_queue(i)->stats;
3785 }
3786 st->print_raw("tot "); totals.print(st); st->cr();
3788 DEBUG_ONLY(totals.verify());
3789 }
3791 void G1CollectedHeap::reset_taskqueue_stats() {
3792 const int n = workers() != NULL ? workers()->total_workers() : 1;
3793 for (int i = 0; i < n; ++i) {
3794 task_queue(i)->stats.reset();
3795 }
3796 }
3797 #endif // TASKQUEUE_STATS
3799 void G1CollectedHeap::log_gc_header() {
3800 if (!G1Log::fine()) {
3801 return;
3802 }
3804 gclog_or_tty->gclog_stamp(_gc_tracer_stw->gc_id());
3806 GCCauseString gc_cause_str = GCCauseString("GC pause", gc_cause())
3807 .append(g1_policy()->gcs_are_young() ? "(young)" : "(mixed)")
3808 .append(g1_policy()->during_initial_mark_pause() ? " (initial-mark)" : "");
3810 gclog_or_tty->print("[%s", (const char*)gc_cause_str);
3811 }
3813 void G1CollectedHeap::log_gc_footer(double pause_time_sec) {
3814 if (!G1Log::fine()) {
3815 return;
3816 }
3818 if (G1Log::finer()) {
3819 if (evacuation_failed()) {
3820 gclog_or_tty->print(" (to-space exhausted)");
3821 }
3822 gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec);
3823 g1_policy()->phase_times()->note_gc_end();
3824 g1_policy()->phase_times()->print(pause_time_sec);
3825 g1_policy()->print_detailed_heap_transition();
3826 } else {
3827 if (evacuation_failed()) {
3828 gclog_or_tty->print("--");
3829 }
3830 g1_policy()->print_heap_transition();
3831 gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec);
3832 }
3833 gclog_or_tty->flush();
3834 }
3836 bool
3837 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
3838 assert_at_safepoint(true /* should_be_vm_thread */);
3839 guarantee(!is_gc_active(), "collection is not reentrant");
3841 if (GC_locker::check_active_before_gc()) {
3842 return false;
3843 }
3845 _gc_timer_stw->register_gc_start();
3847 _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start());
3849 SvcGCMarker sgcm(SvcGCMarker::MINOR);
3850 ResourceMark rm;
3852 print_heap_before_gc();
3853 trace_heap_before_gc(_gc_tracer_stw);
3855 verify_region_sets_optional();
3856 verify_dirty_young_regions();
3858 // This call will decide whether this pause is an initial-mark
3859 // pause. If it is, during_initial_mark_pause() will return true
3860 // for the duration of this pause.
3861 g1_policy()->decide_on_conc_mark_initiation();
3863 // We do not allow initial-mark to be piggy-backed on a mixed GC.
3864 assert(!g1_policy()->during_initial_mark_pause() ||
3865 g1_policy()->gcs_are_young(), "sanity");
3867 // We also do not allow mixed GCs during marking.
3868 assert(!mark_in_progress() || g1_policy()->gcs_are_young(), "sanity");
3870 // Record whether this pause is an initial mark. When the current
3871 // thread has completed its logging output and it's safe to signal
3872 // the CM thread, the flag's value in the policy has been reset.
3873 bool should_start_conc_mark = g1_policy()->during_initial_mark_pause();
3875 // Inner scope for scope based logging, timers, and stats collection
3876 {
3877 EvacuationInfo evacuation_info;
3879 if (g1_policy()->during_initial_mark_pause()) {
3880 // We are about to start a marking cycle, so we increment the
3881 // full collection counter.
3882 increment_old_marking_cycles_started();
3883 register_concurrent_cycle_start(_gc_timer_stw->gc_start());
3884 }
3886 _gc_tracer_stw->report_yc_type(yc_type());
3888 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
3890 uint active_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
3891 workers()->active_workers() : 1);
3892 double pause_start_sec = os::elapsedTime();
3893 g1_policy()->phase_times()->note_gc_start(active_workers, mark_in_progress());
3894 log_gc_header();
3896 TraceCollectorStats tcs(g1mm()->incremental_collection_counters());
3897 TraceMemoryManagerStats tms(false /* fullGC */, gc_cause());
3899 // If the secondary_free_list is not empty, append it to the
3900 // free_list. No need to wait for the cleanup operation to finish;
3901 // the region allocation code will check the secondary_free_list
3902 // and wait if necessary. If the G1StressConcRegionFreeing flag is
3903 // set, skip this step so that the region allocation code has to
3904 // get entries from the secondary_free_list.
3905 if (!G1StressConcRegionFreeing) {
3906 append_secondary_free_list_if_not_empty_with_lock();
3907 }
3909 assert(check_young_list_well_formed(), "young list should be well formed");
3910 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3911 "sanity check");
3913 // Don't dynamically change the number of GC threads this early. A value of
3914 // 0 is used to indicate serial work. When parallel work is done,
3915 // it will be set.
3917 { // Call to jvmpi::post_class_unload_events must occur outside of active GC
3918 IsGCActiveMark x;
3920 gc_prologue(false);
3921 increment_total_collections(false /* full gc */);
3922 increment_gc_time_stamp();
3924 verify_before_gc();
3925 check_bitmaps("GC Start");
3927 COMPILER2_PRESENT(DerivedPointerTable::clear());
3929 // Please see comment in g1CollectedHeap.hpp and
3930 // G1CollectedHeap::ref_processing_init() to see how
3931 // reference processing currently works in G1.
3933 // Enable discovery in the STW reference processor
3934 ref_processor_stw()->enable_discovery(true /*verify_disabled*/,
3935 true /*verify_no_refs*/);
3937 {
3938 // We want to temporarily turn off discovery by the
3939 // CM ref processor, if necessary, and turn it back on
3940 // on again later if we do. Using a scoped
3941 // NoRefDiscovery object will do this.
3942 NoRefDiscovery no_cm_discovery(ref_processor_cm());
3944 // Forget the current alloc region (we might even choose it to be part
3945 // of the collection set!).
3946 _allocator->release_mutator_alloc_region();
3948 // We should call this after we retire the mutator alloc
3949 // region(s) so that all the ALLOC / RETIRE events are generated
3950 // before the start GC event.
3951 _hr_printer.start_gc(false /* full */, (size_t) total_collections());
3953 // This timing is only used by the ergonomics to handle our pause target.
3954 // It is unclear why this should not include the full pause. We will
3955 // investigate this in CR 7178365.
3956 //
3957 // Preserving the old comment here if that helps the investigation:
3958 //
3959 // The elapsed time induced by the start time below deliberately elides
3960 // the possible verification above.
3961 double sample_start_time_sec = os::elapsedTime();
3963 #if YOUNG_LIST_VERBOSE
3964 gclog_or_tty->print_cr("\nBefore recording pause start.\nYoung_list:");
3965 _young_list->print();
3966 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3967 #endif // YOUNG_LIST_VERBOSE
3969 g1_policy()->record_collection_pause_start(sample_start_time_sec);
3971 double scan_wait_start = os::elapsedTime();
3972 // We have to wait until the CM threads finish scanning the
3973 // root regions as it's the only way to ensure that all the
3974 // objects on them have been correctly scanned before we start
3975 // moving them during the GC.
3976 bool waited = _cm->root_regions()->wait_until_scan_finished();
3977 double wait_time_ms = 0.0;
3978 if (waited) {
3979 double scan_wait_end = os::elapsedTime();
3980 wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
3981 }
3982 g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms);
3984 #if YOUNG_LIST_VERBOSE
3985 gclog_or_tty->print_cr("\nAfter recording pause start.\nYoung_list:");
3986 _young_list->print();
3987 #endif // YOUNG_LIST_VERBOSE
3989 if (g1_policy()->during_initial_mark_pause()) {
3990 concurrent_mark()->checkpointRootsInitialPre();
3991 }
3993 #if YOUNG_LIST_VERBOSE
3994 gclog_or_tty->print_cr("\nBefore choosing collection set.\nYoung_list:");
3995 _young_list->print();
3996 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3997 #endif // YOUNG_LIST_VERBOSE
3999 g1_policy()->finalize_cset(target_pause_time_ms, evacuation_info);
4001 register_humongous_regions_with_in_cset_fast_test();
4003 _cm->note_start_of_gc();
4004 // We should not verify the per-thread SATB buffers given that
4005 // we have not filtered them yet (we'll do so during the
4006 // GC). We also call this after finalize_cset() to
4007 // ensure that the CSet has been finalized.
4008 _cm->verify_no_cset_oops(true /* verify_stacks */,
4009 true /* verify_enqueued_buffers */,
4010 false /* verify_thread_buffers */,
4011 true /* verify_fingers */);
4013 if (_hr_printer.is_active()) {
4014 HeapRegion* hr = g1_policy()->collection_set();
4015 while (hr != NULL) {
4016 _hr_printer.cset(hr);
4017 hr = hr->next_in_collection_set();
4018 }
4019 }
4021 #ifdef ASSERT
4022 VerifyCSetClosure cl;
4023 collection_set_iterate(&cl);
4024 #endif // ASSERT
4026 setup_surviving_young_words();
4028 // Initialize the GC alloc regions.
4029 _allocator->init_gc_alloc_regions(evacuation_info);
4031 // Actually do the work...
4032 evacuate_collection_set(evacuation_info);
4034 // We do this to mainly verify the per-thread SATB buffers
4035 // (which have been filtered by now) since we didn't verify
4036 // them earlier. No point in re-checking the stacks / enqueued
4037 // buffers given that the CSet has not changed since last time
4038 // we checked.
4039 _cm->verify_no_cset_oops(false /* verify_stacks */,
4040 false /* verify_enqueued_buffers */,
4041 true /* verify_thread_buffers */,
4042 true /* verify_fingers */);
4044 free_collection_set(g1_policy()->collection_set(), evacuation_info);
4046 eagerly_reclaim_humongous_regions();
4048 g1_policy()->clear_collection_set();
4050 cleanup_surviving_young_words();
4052 // Start a new incremental collection set for the next pause.
4053 g1_policy()->start_incremental_cset_building();
4055 clear_cset_fast_test();
4057 _young_list->reset_sampled_info();
4059 // Don't check the whole heap at this point as the
4060 // GC alloc regions from this pause have been tagged
4061 // as survivors and moved on to the survivor list.
4062 // Survivor regions will fail the !is_young() check.
4063 assert(check_young_list_empty(false /* check_heap */),
4064 "young list should be empty");
4066 #if YOUNG_LIST_VERBOSE
4067 gclog_or_tty->print_cr("Before recording survivors.\nYoung List:");
4068 _young_list->print();
4069 #endif // YOUNG_LIST_VERBOSE
4071 g1_policy()->record_survivor_regions(_young_list->survivor_length(),
4072 _young_list->first_survivor_region(),
4073 _young_list->last_survivor_region());
4075 _young_list->reset_auxilary_lists();
4077 if (evacuation_failed()) {
4078 _allocator->set_used(recalculate_used());
4079 uint n_queues = MAX2((int)ParallelGCThreads, 1);
4080 for (uint i = 0; i < n_queues; i++) {
4081 if (_evacuation_failed_info_array[i].has_failed()) {
4082 _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]);
4083 }
4084 }
4085 } else {
4086 // The "used" of the the collection set have already been subtracted
4087 // when they were freed. Add in the bytes evacuated.
4088 _allocator->increase_used(g1_policy()->bytes_copied_during_gc());
4089 }
4091 if (g1_policy()->during_initial_mark_pause()) {
4092 // We have to do this before we notify the CM threads that
4093 // they can start working to make sure that all the
4094 // appropriate initialization is done on the CM object.
4095 concurrent_mark()->checkpointRootsInitialPost();
4096 set_marking_started();
4097 // Note that we don't actually trigger the CM thread at
4098 // this point. We do that later when we're sure that
4099 // the current thread has completed its logging output.
4100 }
4102 allocate_dummy_regions();
4104 #if YOUNG_LIST_VERBOSE
4105 gclog_or_tty->print_cr("\nEnd of the pause.\nYoung_list:");
4106 _young_list->print();
4107 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
4108 #endif // YOUNG_LIST_VERBOSE
4110 _allocator->init_mutator_alloc_region();
4112 {
4113 size_t expand_bytes = g1_policy()->expansion_amount();
4114 if (expand_bytes > 0) {
4115 size_t bytes_before = capacity();
4116 // No need for an ergo verbose message here,
4117 // expansion_amount() does this when it returns a value > 0.
4118 if (!expand(expand_bytes)) {
4119 // We failed to expand the heap. Cannot do anything about it.
4120 }
4121 }
4122 }
4124 // We redo the verification but now wrt to the new CSet which
4125 // has just got initialized after the previous CSet was freed.
4126 _cm->verify_no_cset_oops(true /* verify_stacks */,
4127 true /* verify_enqueued_buffers */,
4128 true /* verify_thread_buffers */,
4129 true /* verify_fingers */);
4130 _cm->note_end_of_gc();
4132 // This timing is only used by the ergonomics to handle our pause target.
4133 // It is unclear why this should not include the full pause. We will
4134 // investigate this in CR 7178365.
4135 double sample_end_time_sec = os::elapsedTime();
4136 double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
4137 g1_policy()->record_collection_pause_end(pause_time_ms, evacuation_info);
4139 MemoryService::track_memory_usage();
4141 // In prepare_for_verify() below we'll need to scan the deferred
4142 // update buffers to bring the RSets up-to-date if
4143 // G1HRRSFlushLogBuffersOnVerify has been set. While scanning
4144 // the update buffers we'll probably need to scan cards on the
4145 // regions we just allocated to (i.e., the GC alloc
4146 // regions). However, during the last GC we called
4147 // set_saved_mark() on all the GC alloc regions, so card
4148 // scanning might skip the [saved_mark_word()...top()] area of
4149 // those regions (i.e., the area we allocated objects into
4150 // during the last GC). But it shouldn't. Given that
4151 // saved_mark_word() is conditional on whether the GC time stamp
4152 // on the region is current or not, by incrementing the GC time
4153 // stamp here we invalidate all the GC time stamps on all the
4154 // regions and saved_mark_word() will simply return top() for
4155 // all the regions. This is a nicer way of ensuring this rather
4156 // than iterating over the regions and fixing them. In fact, the
4157 // GC time stamp increment here also ensures that
4158 // saved_mark_word() will return top() between pauses, i.e.,
4159 // during concurrent refinement. So we don't need the
4160 // is_gc_active() check to decided which top to use when
4161 // scanning cards (see CR 7039627).
4162 increment_gc_time_stamp();
4164 verify_after_gc();
4165 check_bitmaps("GC End");
4167 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
4168 ref_processor_stw()->verify_no_references_recorded();
4170 // CM reference discovery will be re-enabled if necessary.
4171 }
4173 // We should do this after we potentially expand the heap so
4174 // that all the COMMIT events are generated before the end GC
4175 // event, and after we retire the GC alloc regions so that all
4176 // RETIRE events are generated before the end GC event.
4177 _hr_printer.end_gc(false /* full */, (size_t) total_collections());
4179 #ifdef TRACESPINNING
4180 ParallelTaskTerminator::print_termination_counts();
4181 #endif
4183 gc_epilogue(false);
4184 }
4186 // Print the remainder of the GC log output.
4187 log_gc_footer(os::elapsedTime() - pause_start_sec);
4189 // It is not yet to safe to tell the concurrent mark to
4190 // start as we have some optional output below. We don't want the
4191 // output from the concurrent mark thread interfering with this
4192 // logging output either.
4194 _hrm.verify_optional();
4195 verify_region_sets_optional();
4197 TASKQUEUE_STATS_ONLY(if (ParallelGCVerbose) print_taskqueue_stats());
4198 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
4200 print_heap_after_gc();
4201 trace_heap_after_gc(_gc_tracer_stw);
4203 // We must call G1MonitoringSupport::update_sizes() in the same scoping level
4204 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
4205 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
4206 // before any GC notifications are raised.
4207 g1mm()->update_sizes();
4209 _gc_tracer_stw->report_evacuation_info(&evacuation_info);
4210 _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold());
4211 _gc_timer_stw->register_gc_end();
4212 _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions());
4213 }
4214 // It should now be safe to tell the concurrent mark thread to start
4215 // without its logging output interfering with the logging output
4216 // that came from the pause.
4218 if (should_start_conc_mark) {
4219 // CAUTION: after the doConcurrentMark() call below,
4220 // the concurrent marking thread(s) could be running
4221 // concurrently with us. Make sure that anything after
4222 // this point does not assume that we are the only GC thread
4223 // running. Note: of course, the actual marking work will
4224 // not start until the safepoint itself is released in
4225 // SuspendibleThreadSet::desynchronize().
4226 doConcurrentMark();
4227 }
4229 return true;
4230 }
4232 size_t G1CollectedHeap::desired_plab_sz(GCAllocPurpose purpose)
4233 {
4234 size_t gclab_word_size;
4235 switch (purpose) {
4236 case GCAllocForSurvived:
4237 gclab_word_size = _survivor_plab_stats.desired_plab_sz();
4238 break;
4239 case GCAllocForTenured:
4240 gclab_word_size = _old_plab_stats.desired_plab_sz();
4241 break;
4242 default:
4243 assert(false, "unknown GCAllocPurpose");
4244 gclab_word_size = _old_plab_stats.desired_plab_sz();
4245 break;
4246 }
4248 // Prevent humongous PLAB sizes for two reasons:
4249 // * PLABs are allocated using a similar paths as oops, but should
4250 // never be in a humongous region
4251 // * Allowing humongous PLABs needlessly churns the region free lists
4252 return MIN2(_humongous_object_threshold_in_words, gclab_word_size);
4253 }
4255 void G1CollectedHeap::init_for_evac_failure(OopsInHeapRegionClosure* cl) {
4256 _drain_in_progress = false;
4257 set_evac_failure_closure(cl);
4258 _evac_failure_scan_stack = new (ResourceObj::C_HEAP, mtGC) GrowableArray<oop>(40, true);
4259 }
4261 void G1CollectedHeap::finalize_for_evac_failure() {
4262 assert(_evac_failure_scan_stack != NULL &&
4263 _evac_failure_scan_stack->length() == 0,
4264 "Postcondition");
4265 assert(!_drain_in_progress, "Postcondition");
4266 delete _evac_failure_scan_stack;
4267 _evac_failure_scan_stack = NULL;
4268 }
4270 void G1CollectedHeap::remove_self_forwarding_pointers() {
4271 assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity");
4273 double remove_self_forwards_start = os::elapsedTime();
4275 G1ParRemoveSelfForwardPtrsTask rsfp_task(this);
4277 if (G1CollectedHeap::use_parallel_gc_threads()) {
4278 set_par_threads();
4279 workers()->run_task(&rsfp_task);
4280 set_par_threads(0);
4281 } else {
4282 rsfp_task.work(0);
4283 }
4285 assert(check_cset_heap_region_claim_values(HeapRegion::ParEvacFailureClaimValue), "sanity");
4287 // Reset the claim values in the regions in the collection set.
4288 reset_cset_heap_region_claim_values();
4290 assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity");
4292 // Now restore saved marks, if any.
4293 assert(_objs_with_preserved_marks.size() ==
4294 _preserved_marks_of_objs.size(), "Both or none.");
4295 while (!_objs_with_preserved_marks.is_empty()) {
4296 oop obj = _objs_with_preserved_marks.pop();
4297 markOop m = _preserved_marks_of_objs.pop();
4298 obj->set_mark(m);
4299 }
4300 _objs_with_preserved_marks.clear(true);
4301 _preserved_marks_of_objs.clear(true);
4303 g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0);
4304 }
4306 void G1CollectedHeap::push_on_evac_failure_scan_stack(oop obj) {
4307 _evac_failure_scan_stack->push(obj);
4308 }
4310 void G1CollectedHeap::drain_evac_failure_scan_stack() {
4311 assert(_evac_failure_scan_stack != NULL, "precondition");
4313 while (_evac_failure_scan_stack->length() > 0) {
4314 oop obj = _evac_failure_scan_stack->pop();
4315 _evac_failure_closure->set_region(heap_region_containing(obj));
4316 obj->oop_iterate_backwards(_evac_failure_closure);
4317 }
4318 }
4320 oop
4321 G1CollectedHeap::handle_evacuation_failure_par(G1ParScanThreadState* _par_scan_state,
4322 oop old) {
4323 assert(obj_in_cs(old),
4324 err_msg("obj: "PTR_FORMAT" should still be in the CSet",
4325 (HeapWord*) old));
4326 markOop m = old->mark();
4327 oop forward_ptr = old->forward_to_atomic(old);
4328 if (forward_ptr == NULL) {
4329 // Forward-to-self succeeded.
4330 assert(_par_scan_state != NULL, "par scan state");
4331 OopsInHeapRegionClosure* cl = _par_scan_state->evac_failure_closure();
4332 uint queue_num = _par_scan_state->queue_num();
4334 _evacuation_failed = true;
4335 _evacuation_failed_info_array[queue_num].register_copy_failure(old->size());
4336 if (_evac_failure_closure != cl) {
4337 MutexLockerEx x(EvacFailureStack_lock, Mutex::_no_safepoint_check_flag);
4338 assert(!_drain_in_progress,
4339 "Should only be true while someone holds the lock.");
4340 // Set the global evac-failure closure to the current thread's.
4341 assert(_evac_failure_closure == NULL, "Or locking has failed.");
4342 set_evac_failure_closure(cl);
4343 // Now do the common part.
4344 handle_evacuation_failure_common(old, m);
4345 // Reset to NULL.
4346 set_evac_failure_closure(NULL);
4347 } else {
4348 // The lock is already held, and this is recursive.
4349 assert(_drain_in_progress, "This should only be the recursive case.");
4350 handle_evacuation_failure_common(old, m);
4351 }
4352 return old;
4353 } else {
4354 // Forward-to-self failed. Either someone else managed to allocate
4355 // space for this object (old != forward_ptr) or they beat us in
4356 // self-forwarding it (old == forward_ptr).
4357 assert(old == forward_ptr || !obj_in_cs(forward_ptr),
4358 err_msg("obj: "PTR_FORMAT" forwarded to: "PTR_FORMAT" "
4359 "should not be in the CSet",
4360 (HeapWord*) old, (HeapWord*) forward_ptr));
4361 return forward_ptr;
4362 }
4363 }
4365 void G1CollectedHeap::handle_evacuation_failure_common(oop old, markOop m) {
4366 preserve_mark_if_necessary(old, m);
4368 HeapRegion* r = heap_region_containing(old);
4369 if (!r->evacuation_failed()) {
4370 r->set_evacuation_failed(true);
4371 _hr_printer.evac_failure(r);
4372 }
4374 push_on_evac_failure_scan_stack(old);
4376 if (!_drain_in_progress) {
4377 // prevent recursion in copy_to_survivor_space()
4378 _drain_in_progress = true;
4379 drain_evac_failure_scan_stack();
4380 _drain_in_progress = false;
4381 }
4382 }
4384 void G1CollectedHeap::preserve_mark_if_necessary(oop obj, markOop m) {
4385 assert(evacuation_failed(), "Oversaving!");
4386 // We want to call the "for_promotion_failure" version only in the
4387 // case of a promotion failure.
4388 if (m->must_be_preserved_for_promotion_failure(obj)) {
4389 _objs_with_preserved_marks.push(obj);
4390 _preserved_marks_of_objs.push(m);
4391 }
4392 }
4394 HeapWord* G1CollectedHeap::par_allocate_during_gc(GCAllocPurpose purpose,
4395 size_t word_size,
4396 AllocationContext_t context) {
4397 if (purpose == GCAllocForSurvived) {
4398 HeapWord* result = survivor_attempt_allocation(word_size, context);
4399 if (result != NULL) {
4400 return result;
4401 } else {
4402 // Let's try to allocate in the old gen in case we can fit the
4403 // object there.
4404 return old_attempt_allocation(word_size, context);
4405 }
4406 } else {
4407 assert(purpose == GCAllocForTenured, "sanity");
4408 HeapWord* result = old_attempt_allocation(word_size, context);
4409 if (result != NULL) {
4410 return result;
4411 } else {
4412 // Let's try to allocate in the survivors in case we can fit the
4413 // object there.
4414 return survivor_attempt_allocation(word_size, context);
4415 }
4416 }
4418 ShouldNotReachHere();
4419 // Trying to keep some compilers happy.
4420 return NULL;
4421 }
4423 void G1ParCopyHelper::mark_object(oop obj) {
4424 assert(!_g1->heap_region_containing(obj)->in_collection_set(), "should not mark objects in the CSet");
4426 // We know that the object is not moving so it's safe to read its size.
4427 _cm->grayRoot(obj, (size_t) obj->size(), _worker_id);
4428 }
4430 void G1ParCopyHelper::mark_forwarded_object(oop from_obj, oop to_obj) {
4431 assert(from_obj->is_forwarded(), "from obj should be forwarded");
4432 assert(from_obj->forwardee() == to_obj, "to obj should be the forwardee");
4433 assert(from_obj != to_obj, "should not be self-forwarded");
4435 assert(_g1->heap_region_containing(from_obj)->in_collection_set(), "from obj should be in the CSet");
4436 assert(!_g1->heap_region_containing(to_obj)->in_collection_set(), "should not mark objects in the CSet");
4438 // The object might be in the process of being copied by another
4439 // worker so we cannot trust that its to-space image is
4440 // well-formed. So we have to read its size from its from-space
4441 // image which we know should not be changing.
4442 _cm->grayRoot(to_obj, (size_t) from_obj->size(), _worker_id);
4443 }
4445 template <class T>
4446 void G1ParCopyHelper::do_klass_barrier(T* p, oop new_obj) {
4447 if (_g1->heap_region_containing_raw(new_obj)->is_young()) {
4448 _scanned_klass->record_modified_oops();
4449 }
4450 }
4452 template <G1Barrier barrier, G1Mark do_mark_object>
4453 template <class T>
4454 void G1ParCopyClosure<barrier, do_mark_object>::do_oop_work(T* p) {
4455 T heap_oop = oopDesc::load_heap_oop(p);
4457 if (oopDesc::is_null(heap_oop)) {
4458 return;
4459 }
4461 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
4463 assert(_worker_id == _par_scan_state->queue_num(), "sanity");
4465 G1CollectedHeap::in_cset_state_t state = _g1->in_cset_state(obj);
4467 if (state == G1CollectedHeap::InCSet) {
4468 oop forwardee;
4469 if (obj->is_forwarded()) {
4470 forwardee = obj->forwardee();
4471 } else {
4472 forwardee = _par_scan_state->copy_to_survivor_space(obj);
4473 }
4474 assert(forwardee != NULL, "forwardee should not be NULL");
4475 oopDesc::encode_store_heap_oop(p, forwardee);
4476 if (do_mark_object != G1MarkNone && forwardee != obj) {
4477 // If the object is self-forwarded we don't need to explicitly
4478 // mark it, the evacuation failure protocol will do so.
4479 mark_forwarded_object(obj, forwardee);
4480 }
4482 if (barrier == G1BarrierKlass) {
4483 do_klass_barrier(p, forwardee);
4484 }
4485 } else {
4486 if (state == G1CollectedHeap::IsHumongous) {
4487 _g1->set_humongous_is_live(obj);
4488 }
4489 // The object is not in collection set. If we're a root scanning
4490 // closure during an initial mark pause then attempt to mark the object.
4491 if (do_mark_object == G1MarkFromRoot) {
4492 mark_object(obj);
4493 }
4494 }
4496 if (barrier == G1BarrierEvac) {
4497 _par_scan_state->update_rs(_from, p, _worker_id);
4498 }
4499 }
4501 template void G1ParCopyClosure<G1BarrierEvac, G1MarkNone>::do_oop_work(oop* p);
4502 template void G1ParCopyClosure<G1BarrierEvac, G1MarkNone>::do_oop_work(narrowOop* p);
4504 class G1ParEvacuateFollowersClosure : public VoidClosure {
4505 protected:
4506 G1CollectedHeap* _g1h;
4507 G1ParScanThreadState* _par_scan_state;
4508 RefToScanQueueSet* _queues;
4509 ParallelTaskTerminator* _terminator;
4511 G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
4512 RefToScanQueueSet* queues() { return _queues; }
4513 ParallelTaskTerminator* terminator() { return _terminator; }
4515 public:
4516 G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h,
4517 G1ParScanThreadState* par_scan_state,
4518 RefToScanQueueSet* queues,
4519 ParallelTaskTerminator* terminator)
4520 : _g1h(g1h), _par_scan_state(par_scan_state),
4521 _queues(queues), _terminator(terminator) {}
4523 void do_void();
4525 private:
4526 inline bool offer_termination();
4527 };
4529 bool G1ParEvacuateFollowersClosure::offer_termination() {
4530 G1ParScanThreadState* const pss = par_scan_state();
4531 pss->start_term_time();
4532 const bool res = terminator()->offer_termination();
4533 pss->end_term_time();
4534 return res;
4535 }
4537 void G1ParEvacuateFollowersClosure::do_void() {
4538 G1ParScanThreadState* const pss = par_scan_state();
4539 pss->trim_queue();
4540 do {
4541 pss->steal_and_trim_queue(queues());
4542 } while (!offer_termination());
4543 }
4545 class G1KlassScanClosure : public KlassClosure {
4546 G1ParCopyHelper* _closure;
4547 bool _process_only_dirty;
4548 int _count;
4549 public:
4550 G1KlassScanClosure(G1ParCopyHelper* closure, bool process_only_dirty)
4551 : _process_only_dirty(process_only_dirty), _closure(closure), _count(0) {}
4552 void do_klass(Klass* klass) {
4553 // If the klass has not been dirtied we know that there's
4554 // no references into the young gen and we can skip it.
4555 if (!_process_only_dirty || klass->has_modified_oops()) {
4556 // Clean the klass since we're going to scavenge all the metadata.
4557 klass->clear_modified_oops();
4559 // Tell the closure that this klass is the Klass to scavenge
4560 // and is the one to dirty if oops are left pointing into the young gen.
4561 _closure->set_scanned_klass(klass);
4563 klass->oops_do(_closure);
4565 _closure->set_scanned_klass(NULL);
4566 }
4567 _count++;
4568 }
4569 };
4571 class G1ParTask : public AbstractGangTask {
4572 protected:
4573 G1CollectedHeap* _g1h;
4574 RefToScanQueueSet *_queues;
4575 G1RootProcessor* _root_processor;
4576 ParallelTaskTerminator _terminator;
4577 uint _n_workers;
4579 Mutex _stats_lock;
4580 Mutex* stats_lock() { return &_stats_lock; }
4582 public:
4583 G1ParTask(G1CollectedHeap* g1h, RefToScanQueueSet *task_queues, G1RootProcessor* root_processor)
4584 : AbstractGangTask("G1 collection"),
4585 _g1h(g1h),
4586 _queues(task_queues),
4587 _root_processor(root_processor),
4588 _terminator(0, _queues),
4589 _stats_lock(Mutex::leaf, "parallel G1 stats lock", true)
4590 {}
4592 RefToScanQueueSet* queues() { return _queues; }
4594 RefToScanQueue *work_queue(int i) {
4595 return queues()->queue(i);
4596 }
4598 ParallelTaskTerminator* terminator() { return &_terminator; }
4600 virtual void set_for_termination(int active_workers) {
4601 _root_processor->set_num_workers(active_workers);
4602 terminator()->reset_for_reuse(active_workers);
4603 _n_workers = active_workers;
4604 }
4606 // Helps out with CLD processing.
4607 //
4608 // During InitialMark we need to:
4609 // 1) Scavenge all CLDs for the young GC.
4610 // 2) Mark all objects directly reachable from strong CLDs.
4611 template <G1Mark do_mark_object>
4612 class G1CLDClosure : public CLDClosure {
4613 G1ParCopyClosure<G1BarrierNone, do_mark_object>* _oop_closure;
4614 G1ParCopyClosure<G1BarrierKlass, do_mark_object> _oop_in_klass_closure;
4615 G1KlassScanClosure _klass_in_cld_closure;
4616 bool _claim;
4618 public:
4619 G1CLDClosure(G1ParCopyClosure<G1BarrierNone, do_mark_object>* oop_closure,
4620 bool only_young, bool claim)
4621 : _oop_closure(oop_closure),
4622 _oop_in_klass_closure(oop_closure->g1(),
4623 oop_closure->pss(),
4624 oop_closure->rp()),
4625 _klass_in_cld_closure(&_oop_in_klass_closure, only_young),
4626 _claim(claim) {
4628 }
4630 void do_cld(ClassLoaderData* cld) {
4631 cld->oops_do(_oop_closure, &_klass_in_cld_closure, _claim);
4632 }
4633 };
4635 void work(uint worker_id) {
4636 if (worker_id >= _n_workers) return; // no work needed this round
4638 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerStart, worker_id, os::elapsedTime());
4640 {
4641 ResourceMark rm;
4642 HandleMark hm;
4644 ReferenceProcessor* rp = _g1h->ref_processor_stw();
4646 G1ParScanThreadState pss(_g1h, worker_id, rp);
4647 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, rp);
4649 pss.set_evac_failure_closure(&evac_failure_cl);
4651 bool only_young = _g1h->g1_policy()->gcs_are_young();
4653 // Non-IM young GC.
4654 G1ParCopyClosure<G1BarrierNone, G1MarkNone> scan_only_root_cl(_g1h, &pss, rp);
4655 G1CLDClosure<G1MarkNone> scan_only_cld_cl(&scan_only_root_cl,
4656 only_young, // Only process dirty klasses.
4657 false); // No need to claim CLDs.
4658 // IM young GC.
4659 // Strong roots closures.
4660 G1ParCopyClosure<G1BarrierNone, G1MarkFromRoot> scan_mark_root_cl(_g1h, &pss, rp);
4661 G1CLDClosure<G1MarkFromRoot> scan_mark_cld_cl(&scan_mark_root_cl,
4662 false, // Process all klasses.
4663 true); // Need to claim CLDs.
4664 // Weak roots closures.
4665 G1ParCopyClosure<G1BarrierNone, G1MarkPromotedFromRoot> scan_mark_weak_root_cl(_g1h, &pss, rp);
4666 G1CLDClosure<G1MarkPromotedFromRoot> scan_mark_weak_cld_cl(&scan_mark_weak_root_cl,
4667 false, // Process all klasses.
4668 true); // Need to claim CLDs.
4670 OopClosure* strong_root_cl;
4671 OopClosure* weak_root_cl;
4672 CLDClosure* strong_cld_cl;
4673 CLDClosure* weak_cld_cl;
4675 bool trace_metadata = false;
4677 if (_g1h->g1_policy()->during_initial_mark_pause()) {
4678 // We also need to mark copied objects.
4679 strong_root_cl = &scan_mark_root_cl;
4680 strong_cld_cl = &scan_mark_cld_cl;
4681 if (ClassUnloadingWithConcurrentMark) {
4682 weak_root_cl = &scan_mark_weak_root_cl;
4683 weak_cld_cl = &scan_mark_weak_cld_cl;
4684 trace_metadata = true;
4685 } else {
4686 weak_root_cl = &scan_mark_root_cl;
4687 weak_cld_cl = &scan_mark_cld_cl;
4688 }
4689 } else {
4690 strong_root_cl = &scan_only_root_cl;
4691 weak_root_cl = &scan_only_root_cl;
4692 strong_cld_cl = &scan_only_cld_cl;
4693 weak_cld_cl = &scan_only_cld_cl;
4694 }
4696 pss.start_strong_roots();
4698 _root_processor->evacuate_roots(strong_root_cl,
4699 weak_root_cl,
4700 strong_cld_cl,
4701 weak_cld_cl,
4702 trace_metadata,
4703 worker_id);
4705 G1ParPushHeapRSClosure push_heap_rs_cl(_g1h, &pss);
4706 _root_processor->scan_remembered_sets(&push_heap_rs_cl,
4707 weak_root_cl,
4708 worker_id);
4709 pss.end_strong_roots();
4711 {
4712 double start = os::elapsedTime();
4713 G1ParEvacuateFollowersClosure evac(_g1h, &pss, _queues, &_terminator);
4714 evac.do_void();
4715 double elapsed_sec = os::elapsedTime() - start;
4716 double term_sec = pss.term_time();
4717 _g1h->g1_policy()->phase_times()->add_time_secs(G1GCPhaseTimes::ObjCopy, worker_id, elapsed_sec - term_sec);
4718 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::Termination, worker_id, term_sec);
4719 _g1h->g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::Termination, worker_id, pss.term_attempts());
4720 }
4721 _g1h->g1_policy()->record_thread_age_table(pss.age_table());
4722 _g1h->update_surviving_young_words(pss.surviving_young_words()+1);
4724 if (ParallelGCVerbose) {
4725 MutexLocker x(stats_lock());
4726 pss.print_termination_stats(worker_id);
4727 }
4729 assert(pss.queue_is_empty(), "should be empty");
4731 // Close the inner scope so that the ResourceMark and HandleMark
4732 // destructors are executed here and are included as part of the
4733 // "GC Worker Time".
4734 }
4735 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerEnd, worker_id, os::elapsedTime());
4736 }
4737 };
4739 class G1StringSymbolTableUnlinkTask : public AbstractGangTask {
4740 private:
4741 BoolObjectClosure* _is_alive;
4742 int _initial_string_table_size;
4743 int _initial_symbol_table_size;
4745 bool _process_strings;
4746 int _strings_processed;
4747 int _strings_removed;
4749 bool _process_symbols;
4750 int _symbols_processed;
4751 int _symbols_removed;
4753 bool _do_in_parallel;
4754 public:
4755 G1StringSymbolTableUnlinkTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols) :
4756 AbstractGangTask("String/Symbol Unlinking"),
4757 _is_alive(is_alive),
4758 _do_in_parallel(G1CollectedHeap::use_parallel_gc_threads()),
4759 _process_strings(process_strings), _strings_processed(0), _strings_removed(0),
4760 _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0) {
4762 _initial_string_table_size = StringTable::the_table()->table_size();
4763 _initial_symbol_table_size = SymbolTable::the_table()->table_size();
4764 if (process_strings) {
4765 StringTable::clear_parallel_claimed_index();
4766 }
4767 if (process_symbols) {
4768 SymbolTable::clear_parallel_claimed_index();
4769 }
4770 }
4772 ~G1StringSymbolTableUnlinkTask() {
4773 guarantee(!_process_strings || !_do_in_parallel || StringTable::parallel_claimed_index() >= _initial_string_table_size,
4774 err_msg("claim value "INT32_FORMAT" after unlink less than initial string table size "INT32_FORMAT,
4775 StringTable::parallel_claimed_index(), _initial_string_table_size));
4776 guarantee(!_process_symbols || !_do_in_parallel || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size,
4777 err_msg("claim value "INT32_FORMAT" after unlink less than initial symbol table size "INT32_FORMAT,
4778 SymbolTable::parallel_claimed_index(), _initial_symbol_table_size));
4780 if (G1TraceStringSymbolTableScrubbing) {
4781 gclog_or_tty->print_cr("Cleaned string and symbol table, "
4782 "strings: "SIZE_FORMAT" processed, "SIZE_FORMAT" removed, "
4783 "symbols: "SIZE_FORMAT" processed, "SIZE_FORMAT" removed",
4784 strings_processed(), strings_removed(),
4785 symbols_processed(), symbols_removed());
4786 }
4787 }
4789 void work(uint worker_id) {
4790 if (_do_in_parallel) {
4791 int strings_processed = 0;
4792 int strings_removed = 0;
4793 int symbols_processed = 0;
4794 int symbols_removed = 0;
4795 if (_process_strings) {
4796 StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed);
4797 Atomic::add(strings_processed, &_strings_processed);
4798 Atomic::add(strings_removed, &_strings_removed);
4799 }
4800 if (_process_symbols) {
4801 SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed);
4802 Atomic::add(symbols_processed, &_symbols_processed);
4803 Atomic::add(symbols_removed, &_symbols_removed);
4804 }
4805 } else {
4806 if (_process_strings) {
4807 StringTable::unlink(_is_alive, &_strings_processed, &_strings_removed);
4808 }
4809 if (_process_symbols) {
4810 SymbolTable::unlink(&_symbols_processed, &_symbols_removed);
4811 }
4812 }
4813 }
4815 size_t strings_processed() const { return (size_t)_strings_processed; }
4816 size_t strings_removed() const { return (size_t)_strings_removed; }
4818 size_t symbols_processed() const { return (size_t)_symbols_processed; }
4819 size_t symbols_removed() const { return (size_t)_symbols_removed; }
4820 };
4822 class G1CodeCacheUnloadingTask VALUE_OBJ_CLASS_SPEC {
4823 private:
4824 static Monitor* _lock;
4826 BoolObjectClosure* const _is_alive;
4827 const bool _unloading_occurred;
4828 const uint _num_workers;
4830 // Variables used to claim nmethods.
4831 nmethod* _first_nmethod;
4832 volatile nmethod* _claimed_nmethod;
4834 // The list of nmethods that need to be processed by the second pass.
4835 volatile nmethod* _postponed_list;
4836 volatile uint _num_entered_barrier;
4838 public:
4839 G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) :
4840 _is_alive(is_alive),
4841 _unloading_occurred(unloading_occurred),
4842 _num_workers(num_workers),
4843 _first_nmethod(NULL),
4844 _claimed_nmethod(NULL),
4845 _postponed_list(NULL),
4846 _num_entered_barrier(0)
4847 {
4848 nmethod::increase_unloading_clock();
4849 _first_nmethod = CodeCache::alive_nmethod(CodeCache::first());
4850 _claimed_nmethod = (volatile nmethod*)_first_nmethod;
4851 }
4853 ~G1CodeCacheUnloadingTask() {
4854 CodeCache::verify_clean_inline_caches();
4856 CodeCache::set_needs_cache_clean(false);
4857 guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be");
4859 CodeCache::verify_icholder_relocations();
4860 }
4862 private:
4863 void add_to_postponed_list(nmethod* nm) {
4864 nmethod* old;
4865 do {
4866 old = (nmethod*)_postponed_list;
4867 nm->set_unloading_next(old);
4868 } while ((nmethod*)Atomic::cmpxchg_ptr(nm, &_postponed_list, old) != old);
4869 }
4871 void clean_nmethod(nmethod* nm) {
4872 bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred);
4874 if (postponed) {
4875 // This nmethod referred to an nmethod that has not been cleaned/unloaded yet.
4876 add_to_postponed_list(nm);
4877 }
4879 // Mark that this thread has been cleaned/unloaded.
4880 // After this call, it will be safe to ask if this nmethod was unloaded or not.
4881 nm->set_unloading_clock(nmethod::global_unloading_clock());
4882 }
4884 void clean_nmethod_postponed(nmethod* nm) {
4885 nm->do_unloading_parallel_postponed(_is_alive, _unloading_occurred);
4886 }
4888 static const int MaxClaimNmethods = 16;
4890 void claim_nmethods(nmethod** claimed_nmethods, int *num_claimed_nmethods) {
4891 nmethod* first;
4892 nmethod* last;
4894 do {
4895 *num_claimed_nmethods = 0;
4897 first = last = (nmethod*)_claimed_nmethod;
4899 if (first != NULL) {
4900 for (int i = 0; i < MaxClaimNmethods; i++) {
4901 last = CodeCache::alive_nmethod(CodeCache::next(last));
4903 if (last == NULL) {
4904 break;
4905 }
4907 claimed_nmethods[i] = last;
4908 (*num_claimed_nmethods)++;
4909 }
4910 }
4912 } while ((nmethod*)Atomic::cmpxchg_ptr(last, &_claimed_nmethod, first) != first);
4913 }
4915 nmethod* claim_postponed_nmethod() {
4916 nmethod* claim;
4917 nmethod* next;
4919 do {
4920 claim = (nmethod*)_postponed_list;
4921 if (claim == NULL) {
4922 return NULL;
4923 }
4925 next = claim->unloading_next();
4927 } while ((nmethod*)Atomic::cmpxchg_ptr(next, &_postponed_list, claim) != claim);
4929 return claim;
4930 }
4932 public:
4933 // Mark that we're done with the first pass of nmethod cleaning.
4934 void barrier_mark(uint worker_id) {
4935 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
4936 _num_entered_barrier++;
4937 if (_num_entered_barrier == _num_workers) {
4938 ml.notify_all();
4939 }
4940 }
4942 // See if we have to wait for the other workers to
4943 // finish their first-pass nmethod cleaning work.
4944 void barrier_wait(uint worker_id) {
4945 if (_num_entered_barrier < _num_workers) {
4946 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
4947 while (_num_entered_barrier < _num_workers) {
4948 ml.wait(Mutex::_no_safepoint_check_flag, 0, false);
4949 }
4950 }
4951 }
4953 // Cleaning and unloading of nmethods. Some work has to be postponed
4954 // to the second pass, when we know which nmethods survive.
4955 void work_first_pass(uint worker_id) {
4956 // The first nmethods is claimed by the first worker.
4957 if (worker_id == 0 && _first_nmethod != NULL) {
4958 clean_nmethod(_first_nmethod);
4959 _first_nmethod = NULL;
4960 }
4962 int num_claimed_nmethods;
4963 nmethod* claimed_nmethods[MaxClaimNmethods];
4965 while (true) {
4966 claim_nmethods(claimed_nmethods, &num_claimed_nmethods);
4968 if (num_claimed_nmethods == 0) {
4969 break;
4970 }
4972 for (int i = 0; i < num_claimed_nmethods; i++) {
4973 clean_nmethod(claimed_nmethods[i]);
4974 }
4975 }
4977 // The nmethod cleaning helps out and does the CodeCache part of MetadataOnStackMark.
4978 // Need to retire the buffers now that this thread has stopped cleaning nmethods.
4979 MetadataOnStackMark::retire_buffer_for_thread(Thread::current());
4980 }
4982 void work_second_pass(uint worker_id) {
4983 nmethod* nm;
4984 // Take care of postponed nmethods.
4985 while ((nm = claim_postponed_nmethod()) != NULL) {
4986 clean_nmethod_postponed(nm);
4987 }
4988 }
4989 };
4991 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock");
4993 class G1KlassCleaningTask : public StackObj {
4994 BoolObjectClosure* _is_alive;
4995 volatile jint _clean_klass_tree_claimed;
4996 ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator;
4998 public:
4999 G1KlassCleaningTask(BoolObjectClosure* is_alive) :
5000 _is_alive(is_alive),
5001 _clean_klass_tree_claimed(0),
5002 _klass_iterator() {
5003 }
5005 private:
5006 bool claim_clean_klass_tree_task() {
5007 if (_clean_klass_tree_claimed) {
5008 return false;
5009 }
5011 return Atomic::cmpxchg(1, (jint*)&_clean_klass_tree_claimed, 0) == 0;
5012 }
5014 InstanceKlass* claim_next_klass() {
5015 Klass* klass;
5016 do {
5017 klass =_klass_iterator.next_klass();
5018 } while (klass != NULL && !klass->oop_is_instance());
5020 return (InstanceKlass*)klass;
5021 }
5023 public:
5025 void clean_klass(InstanceKlass* ik) {
5026 ik->clean_implementors_list(_is_alive);
5027 ik->clean_method_data(_is_alive);
5029 // G1 specific cleanup work that has
5030 // been moved here to be done in parallel.
5031 ik->clean_dependent_nmethods();
5032 if (JvmtiExport::has_redefined_a_class()) {
5033 InstanceKlass::purge_previous_versions(ik);
5034 }
5035 }
5037 void work() {
5038 ResourceMark rm;
5040 // One worker will clean the subklass/sibling klass tree.
5041 if (claim_clean_klass_tree_task()) {
5042 Klass::clean_subklass_tree(_is_alive);
5043 }
5045 // All workers will help cleaning the classes,
5046 InstanceKlass* klass;
5047 while ((klass = claim_next_klass()) != NULL) {
5048 clean_klass(klass);
5049 }
5050 }
5051 };
5053 // To minimize the remark pause times, the tasks below are done in parallel.
5054 class G1ParallelCleaningTask : public AbstractGangTask {
5055 private:
5056 G1StringSymbolTableUnlinkTask _string_symbol_task;
5057 G1CodeCacheUnloadingTask _code_cache_task;
5058 G1KlassCleaningTask _klass_cleaning_task;
5060 public:
5061 // The constructor is run in the VMThread.
5062 G1ParallelCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, uint num_workers, bool unloading_occurred) :
5063 AbstractGangTask("Parallel Cleaning"),
5064 _string_symbol_task(is_alive, process_strings, process_symbols),
5065 _code_cache_task(num_workers, is_alive, unloading_occurred),
5066 _klass_cleaning_task(is_alive) {
5067 }
5069 void pre_work_verification() {
5070 // The VM Thread will have registered Metadata during the single-threaded phase of MetadataStackOnMark.
5071 assert(Thread::current()->is_VM_thread()
5072 || !MetadataOnStackMark::has_buffer_for_thread(Thread::current()), "Should be empty");
5073 }
5075 void post_work_verification() {
5076 assert(!MetadataOnStackMark::has_buffer_for_thread(Thread::current()), "Should be empty");
5077 }
5079 // The parallel work done by all worker threads.
5080 void work(uint worker_id) {
5081 pre_work_verification();
5083 // Do first pass of code cache cleaning.
5084 _code_cache_task.work_first_pass(worker_id);
5086 // Let the threads mark that the first pass is done.
5087 _code_cache_task.barrier_mark(worker_id);
5089 // Clean the Strings and Symbols.
5090 _string_symbol_task.work(worker_id);
5092 // Wait for all workers to finish the first code cache cleaning pass.
5093 _code_cache_task.barrier_wait(worker_id);
5095 // Do the second code cache cleaning work, which realize on
5096 // the liveness information gathered during the first pass.
5097 _code_cache_task.work_second_pass(worker_id);
5099 // Clean all klasses that were not unloaded.
5100 _klass_cleaning_task.work();
5102 post_work_verification();
5103 }
5104 };
5107 void G1CollectedHeap::parallel_cleaning(BoolObjectClosure* is_alive,
5108 bool process_strings,
5109 bool process_symbols,
5110 bool class_unloading_occurred) {
5111 uint n_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
5112 workers()->active_workers() : 1);
5114 G1ParallelCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols,
5115 n_workers, class_unloading_occurred);
5116 if (G1CollectedHeap::use_parallel_gc_threads()) {
5117 set_par_threads(n_workers);
5118 workers()->run_task(&g1_unlink_task);
5119 set_par_threads(0);
5120 } else {
5121 g1_unlink_task.work(0);
5122 }
5123 }
5125 void G1CollectedHeap::unlink_string_and_symbol_table(BoolObjectClosure* is_alive,
5126 bool process_strings, bool process_symbols) {
5127 {
5128 uint n_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
5129 _g1h->workers()->active_workers() : 1);
5130 G1StringSymbolTableUnlinkTask g1_unlink_task(is_alive, process_strings, process_symbols);
5131 if (G1CollectedHeap::use_parallel_gc_threads()) {
5132 set_par_threads(n_workers);
5133 workers()->run_task(&g1_unlink_task);
5134 set_par_threads(0);
5135 } else {
5136 g1_unlink_task.work(0);
5137 }
5138 }
5140 if (G1StringDedup::is_enabled()) {
5141 G1StringDedup::unlink(is_alive);
5142 }
5143 }
5145 class G1RedirtyLoggedCardsTask : public AbstractGangTask {
5146 private:
5147 DirtyCardQueueSet* _queue;
5148 public:
5149 G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue) : AbstractGangTask("Redirty Cards"), _queue(queue) { }
5151 virtual void work(uint worker_id) {
5152 G1GCPhaseTimes* phase_times = G1CollectedHeap::heap()->g1_policy()->phase_times();
5153 G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::RedirtyCards, worker_id);
5155 RedirtyLoggedCardTableEntryClosure cl;
5156 if (G1CollectedHeap::heap()->use_parallel_gc_threads()) {
5157 _queue->par_apply_closure_to_all_completed_buffers(&cl);
5158 } else {
5159 _queue->apply_closure_to_all_completed_buffers(&cl);
5160 }
5162 phase_times->record_thread_work_item(G1GCPhaseTimes::RedirtyCards, worker_id, cl.num_processed());
5163 }
5164 };
5166 void G1CollectedHeap::redirty_logged_cards() {
5167 double redirty_logged_cards_start = os::elapsedTime();
5169 uint n_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
5170 _g1h->workers()->active_workers() : 1);
5172 G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set());
5173 dirty_card_queue_set().reset_for_par_iteration();
5174 if (use_parallel_gc_threads()) {
5175 set_par_threads(n_workers);
5176 workers()->run_task(&redirty_task);
5177 set_par_threads(0);
5178 } else {
5179 redirty_task.work(0);
5180 }
5182 DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set();
5183 dcq.merge_bufferlists(&dirty_card_queue_set());
5184 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
5186 g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0);
5187 }
5189 // Weak Reference Processing support
5191 // An always "is_alive" closure that is used to preserve referents.
5192 // If the object is non-null then it's alive. Used in the preservation
5193 // of referent objects that are pointed to by reference objects
5194 // discovered by the CM ref processor.
5195 class G1AlwaysAliveClosure: public BoolObjectClosure {
5196 G1CollectedHeap* _g1;
5197 public:
5198 G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
5199 bool do_object_b(oop p) {
5200 if (p != NULL) {
5201 return true;
5202 }
5203 return false;
5204 }
5205 };
5207 bool G1STWIsAliveClosure::do_object_b(oop p) {
5208 // An object is reachable if it is outside the collection set,
5209 // or is inside and copied.
5210 return !_g1->obj_in_cs(p) || p->is_forwarded();
5211 }
5213 // Non Copying Keep Alive closure
5214 class G1KeepAliveClosure: public OopClosure {
5215 G1CollectedHeap* _g1;
5216 public:
5217 G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
5218 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
5219 void do_oop(oop* p) {
5220 oop obj = *p;
5221 assert(obj != NULL, "the caller should have filtered out NULL values");
5223 G1CollectedHeap::in_cset_state_t cset_state = _g1->in_cset_state(obj);
5224 if (cset_state == G1CollectedHeap::InNeither) {
5225 return;
5226 }
5227 if (cset_state == G1CollectedHeap::InCSet) {
5228 assert( obj->is_forwarded(), "invariant" );
5229 *p = obj->forwardee();
5230 } else {
5231 assert(!obj->is_forwarded(), "invariant" );
5232 assert(cset_state == G1CollectedHeap::IsHumongous,
5233 err_msg("Only allowed InCSet state is IsHumongous, but is %d", cset_state));
5234 _g1->set_humongous_is_live(obj);
5235 }
5236 }
5237 };
5239 // Copying Keep Alive closure - can be called from both
5240 // serial and parallel code as long as different worker
5241 // threads utilize different G1ParScanThreadState instances
5242 // and different queues.
5244 class G1CopyingKeepAliveClosure: public OopClosure {
5245 G1CollectedHeap* _g1h;
5246 OopClosure* _copy_non_heap_obj_cl;
5247 G1ParScanThreadState* _par_scan_state;
5249 public:
5250 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
5251 OopClosure* non_heap_obj_cl,
5252 G1ParScanThreadState* pss):
5253 _g1h(g1h),
5254 _copy_non_heap_obj_cl(non_heap_obj_cl),
5255 _par_scan_state(pss)
5256 {}
5258 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
5259 virtual void do_oop( oop* p) { do_oop_work(p); }
5261 template <class T> void do_oop_work(T* p) {
5262 oop obj = oopDesc::load_decode_heap_oop(p);
5264 if (_g1h->is_in_cset_or_humongous(obj)) {
5265 // If the referent object has been forwarded (either copied
5266 // to a new location or to itself in the event of an
5267 // evacuation failure) then we need to update the reference
5268 // field and, if both reference and referent are in the G1
5269 // heap, update the RSet for the referent.
5270 //
5271 // If the referent has not been forwarded then we have to keep
5272 // it alive by policy. Therefore we have copy the referent.
5273 //
5274 // If the reference field is in the G1 heap then we can push
5275 // on the PSS queue. When the queue is drained (after each
5276 // phase of reference processing) the object and it's followers
5277 // will be copied, the reference field set to point to the
5278 // new location, and the RSet updated. Otherwise we need to
5279 // use the the non-heap or metadata closures directly to copy
5280 // the referent object and update the pointer, while avoiding
5281 // updating the RSet.
5283 if (_g1h->is_in_g1_reserved(p)) {
5284 _par_scan_state->push_on_queue(p);
5285 } else {
5286 assert(!Metaspace::contains((const void*)p),
5287 err_msg("Unexpectedly found a pointer from metadata: "
5288 PTR_FORMAT, p));
5289 _copy_non_heap_obj_cl->do_oop(p);
5290 }
5291 }
5292 }
5293 };
5295 // Serial drain queue closure. Called as the 'complete_gc'
5296 // closure for each discovered list in some of the
5297 // reference processing phases.
5299 class G1STWDrainQueueClosure: public VoidClosure {
5300 protected:
5301 G1CollectedHeap* _g1h;
5302 G1ParScanThreadState* _par_scan_state;
5304 G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
5306 public:
5307 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
5308 _g1h(g1h),
5309 _par_scan_state(pss)
5310 { }
5312 void do_void() {
5313 G1ParScanThreadState* const pss = par_scan_state();
5314 pss->trim_queue();
5315 }
5316 };
5318 // Parallel Reference Processing closures
5320 // Implementation of AbstractRefProcTaskExecutor for parallel reference
5321 // processing during G1 evacuation pauses.
5323 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
5324 private:
5325 G1CollectedHeap* _g1h;
5326 RefToScanQueueSet* _queues;
5327 FlexibleWorkGang* _workers;
5328 int _active_workers;
5330 public:
5331 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
5332 FlexibleWorkGang* workers,
5333 RefToScanQueueSet *task_queues,
5334 int n_workers) :
5335 _g1h(g1h),
5336 _queues(task_queues),
5337 _workers(workers),
5338 _active_workers(n_workers)
5339 {
5340 assert(n_workers > 0, "shouldn't call this otherwise");
5341 }
5343 // Executes the given task using concurrent marking worker threads.
5344 virtual void execute(ProcessTask& task);
5345 virtual void execute(EnqueueTask& task);
5346 };
5348 // Gang task for possibly parallel reference processing
5350 class G1STWRefProcTaskProxy: public AbstractGangTask {
5351 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
5352 ProcessTask& _proc_task;
5353 G1CollectedHeap* _g1h;
5354 RefToScanQueueSet *_task_queues;
5355 ParallelTaskTerminator* _terminator;
5357 public:
5358 G1STWRefProcTaskProxy(ProcessTask& proc_task,
5359 G1CollectedHeap* g1h,
5360 RefToScanQueueSet *task_queues,
5361 ParallelTaskTerminator* terminator) :
5362 AbstractGangTask("Process reference objects in parallel"),
5363 _proc_task(proc_task),
5364 _g1h(g1h),
5365 _task_queues(task_queues),
5366 _terminator(terminator)
5367 {}
5369 virtual void work(uint worker_id) {
5370 // The reference processing task executed by a single worker.
5371 ResourceMark rm;
5372 HandleMark hm;
5374 G1STWIsAliveClosure is_alive(_g1h);
5376 G1ParScanThreadState pss(_g1h, worker_id, NULL);
5377 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5379 pss.set_evac_failure_closure(&evac_failure_cl);
5381 G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL);
5383 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5385 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5387 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5388 // We also need to mark copied objects.
5389 copy_non_heap_cl = ©_mark_non_heap_cl;
5390 }
5392 // Keep alive closure.
5393 G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, &pss);
5395 // Complete GC closure
5396 G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _task_queues, _terminator);
5398 // Call the reference processing task's work routine.
5399 _proc_task.work(worker_id, is_alive, keep_alive, drain_queue);
5401 // Note we cannot assert that the refs array is empty here as not all
5402 // of the processing tasks (specifically phase2 - pp2_work) execute
5403 // the complete_gc closure (which ordinarily would drain the queue) so
5404 // the queue may not be empty.
5405 }
5406 };
5408 // Driver routine for parallel reference processing.
5409 // Creates an instance of the ref processing gang
5410 // task and has the worker threads execute it.
5411 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) {
5412 assert(_workers != NULL, "Need parallel worker threads.");
5414 ParallelTaskTerminator terminator(_active_workers, _queues);
5415 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _queues, &terminator);
5417 _g1h->set_par_threads(_active_workers);
5418 _workers->run_task(&proc_task_proxy);
5419 _g1h->set_par_threads(0);
5420 }
5422 // Gang task for parallel reference enqueueing.
5424 class G1STWRefEnqueueTaskProxy: public AbstractGangTask {
5425 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
5426 EnqueueTask& _enq_task;
5428 public:
5429 G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) :
5430 AbstractGangTask("Enqueue reference objects in parallel"),
5431 _enq_task(enq_task)
5432 { }
5434 virtual void work(uint worker_id) {
5435 _enq_task.work(worker_id);
5436 }
5437 };
5439 // Driver routine for parallel reference enqueueing.
5440 // Creates an instance of the ref enqueueing gang
5441 // task and has the worker threads execute it.
5443 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
5444 assert(_workers != NULL, "Need parallel worker threads.");
5446 G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task);
5448 _g1h->set_par_threads(_active_workers);
5449 _workers->run_task(&enq_task_proxy);
5450 _g1h->set_par_threads(0);
5451 }
5453 // End of weak reference support closures
5455 // Abstract task used to preserve (i.e. copy) any referent objects
5456 // that are in the collection set and are pointed to by reference
5457 // objects discovered by the CM ref processor.
5459 class G1ParPreserveCMReferentsTask: public AbstractGangTask {
5460 protected:
5461 G1CollectedHeap* _g1h;
5462 RefToScanQueueSet *_queues;
5463 ParallelTaskTerminator _terminator;
5464 uint _n_workers;
5466 public:
5467 G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h,int workers, RefToScanQueueSet *task_queues) :
5468 AbstractGangTask("ParPreserveCMReferents"),
5469 _g1h(g1h),
5470 _queues(task_queues),
5471 _terminator(workers, _queues),
5472 _n_workers(workers)
5473 { }
5475 void work(uint worker_id) {
5476 ResourceMark rm;
5477 HandleMark hm;
5479 G1ParScanThreadState pss(_g1h, worker_id, NULL);
5480 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5482 pss.set_evac_failure_closure(&evac_failure_cl);
5484 assert(pss.queue_is_empty(), "both queue and overflow should be empty");
5486 G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL);
5488 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5490 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5492 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5493 // We also need to mark copied objects.
5494 copy_non_heap_cl = ©_mark_non_heap_cl;
5495 }
5497 // Is alive closure
5498 G1AlwaysAliveClosure always_alive(_g1h);
5500 // Copying keep alive closure. Applied to referent objects that need
5501 // to be copied.
5502 G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, &pss);
5504 ReferenceProcessor* rp = _g1h->ref_processor_cm();
5506 uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q();
5507 uint stride = MIN2(MAX2(_n_workers, 1U), limit);
5509 // limit is set using max_num_q() - which was set using ParallelGCThreads.
5510 // So this must be true - but assert just in case someone decides to
5511 // change the worker ids.
5512 assert(0 <= worker_id && worker_id < limit, "sanity");
5513 assert(!rp->discovery_is_atomic(), "check this code");
5515 // Select discovered lists [i, i+stride, i+2*stride,...,limit)
5516 for (uint idx = worker_id; idx < limit; idx += stride) {
5517 DiscoveredList& ref_list = rp->discovered_refs()[idx];
5519 DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive);
5520 while (iter.has_next()) {
5521 // Since discovery is not atomic for the CM ref processor, we
5522 // can see some null referent objects.
5523 iter.load_ptrs(DEBUG_ONLY(true));
5524 oop ref = iter.obj();
5526 // This will filter nulls.
5527 if (iter.is_referent_alive()) {
5528 iter.make_referent_alive();
5529 }
5530 iter.move_to_next();
5531 }
5532 }
5534 // Drain the queue - which may cause stealing
5535 G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _queues, &_terminator);
5536 drain_queue.do_void();
5537 // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure
5538 assert(pss.queue_is_empty(), "should be");
5539 }
5540 };
5542 // Weak Reference processing during an evacuation pause (part 1).
5543 void G1CollectedHeap::process_discovered_references(uint no_of_gc_workers) {
5544 double ref_proc_start = os::elapsedTime();
5546 ReferenceProcessor* rp = _ref_processor_stw;
5547 assert(rp->discovery_enabled(), "should have been enabled");
5549 // Any reference objects, in the collection set, that were 'discovered'
5550 // by the CM ref processor should have already been copied (either by
5551 // applying the external root copy closure to the discovered lists, or
5552 // by following an RSet entry).
5553 //
5554 // But some of the referents, that are in the collection set, that these
5555 // reference objects point to may not have been copied: the STW ref
5556 // processor would have seen that the reference object had already
5557 // been 'discovered' and would have skipped discovering the reference,
5558 // but would not have treated the reference object as a regular oop.
5559 // As a result the copy closure would not have been applied to the
5560 // referent object.
5561 //
5562 // We need to explicitly copy these referent objects - the references
5563 // will be processed at the end of remarking.
5564 //
5565 // We also need to do this copying before we process the reference
5566 // objects discovered by the STW ref processor in case one of these
5567 // referents points to another object which is also referenced by an
5568 // object discovered by the STW ref processor.
5570 assert(!G1CollectedHeap::use_parallel_gc_threads() ||
5571 no_of_gc_workers == workers()->active_workers(),
5572 "Need to reset active GC workers");
5574 set_par_threads(no_of_gc_workers);
5575 G1ParPreserveCMReferentsTask keep_cm_referents(this,
5576 no_of_gc_workers,
5577 _task_queues);
5579 if (G1CollectedHeap::use_parallel_gc_threads()) {
5580 workers()->run_task(&keep_cm_referents);
5581 } else {
5582 keep_cm_referents.work(0);
5583 }
5585 set_par_threads(0);
5587 // Closure to test whether a referent is alive.
5588 G1STWIsAliveClosure is_alive(this);
5590 // Even when parallel reference processing is enabled, the processing
5591 // of JNI refs is serial and performed serially by the current thread
5592 // rather than by a worker. The following PSS will be used for processing
5593 // JNI refs.
5595 // Use only a single queue for this PSS.
5596 G1ParScanThreadState pss(this, 0, NULL);
5598 // We do not embed a reference processor in the copying/scanning
5599 // closures while we're actually processing the discovered
5600 // reference objects.
5601 G1ParScanHeapEvacFailureClosure evac_failure_cl(this, &pss, NULL);
5603 pss.set_evac_failure_closure(&evac_failure_cl);
5605 assert(pss.queue_is_empty(), "pre-condition");
5607 G1ParScanExtRootClosure only_copy_non_heap_cl(this, &pss, NULL);
5609 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(this, &pss, NULL);
5611 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5613 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5614 // We also need to mark copied objects.
5615 copy_non_heap_cl = ©_mark_non_heap_cl;
5616 }
5618 // Keep alive closure.
5619 G1CopyingKeepAliveClosure keep_alive(this, copy_non_heap_cl, &pss);
5621 // Serial Complete GC closure
5622 G1STWDrainQueueClosure drain_queue(this, &pss);
5624 // Setup the soft refs policy...
5625 rp->setup_policy(false);
5627 ReferenceProcessorStats stats;
5628 if (!rp->processing_is_mt()) {
5629 // Serial reference processing...
5630 stats = rp->process_discovered_references(&is_alive,
5631 &keep_alive,
5632 &drain_queue,
5633 NULL,
5634 _gc_timer_stw,
5635 _gc_tracer_stw->gc_id());
5636 } else {
5637 // Parallel reference processing
5638 assert(rp->num_q() == no_of_gc_workers, "sanity");
5639 assert(no_of_gc_workers <= rp->max_num_q(), "sanity");
5641 G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers);
5642 stats = rp->process_discovered_references(&is_alive,
5643 &keep_alive,
5644 &drain_queue,
5645 &par_task_executor,
5646 _gc_timer_stw,
5647 _gc_tracer_stw->gc_id());
5648 }
5650 _gc_tracer_stw->report_gc_reference_stats(stats);
5652 // We have completed copying any necessary live referent objects.
5653 assert(pss.queue_is_empty(), "both queue and overflow should be empty");
5655 double ref_proc_time = os::elapsedTime() - ref_proc_start;
5656 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
5657 }
5659 // Weak Reference processing during an evacuation pause (part 2).
5660 void G1CollectedHeap::enqueue_discovered_references(uint no_of_gc_workers) {
5661 double ref_enq_start = os::elapsedTime();
5663 ReferenceProcessor* rp = _ref_processor_stw;
5664 assert(!rp->discovery_enabled(), "should have been disabled as part of processing");
5666 // Now enqueue any remaining on the discovered lists on to
5667 // the pending list.
5668 if (!rp->processing_is_mt()) {
5669 // Serial reference processing...
5670 rp->enqueue_discovered_references();
5671 } else {
5672 // Parallel reference enqueueing
5674 assert(no_of_gc_workers == workers()->active_workers(),
5675 "Need to reset active workers");
5676 assert(rp->num_q() == no_of_gc_workers, "sanity");
5677 assert(no_of_gc_workers <= rp->max_num_q(), "sanity");
5679 G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers);
5680 rp->enqueue_discovered_references(&par_task_executor);
5681 }
5683 rp->verify_no_references_recorded();
5684 assert(!rp->discovery_enabled(), "should have been disabled");
5686 // FIXME
5687 // CM's reference processing also cleans up the string and symbol tables.
5688 // Should we do that here also? We could, but it is a serial operation
5689 // and could significantly increase the pause time.
5691 double ref_enq_time = os::elapsedTime() - ref_enq_start;
5692 g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0);
5693 }
5695 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info) {
5696 _expand_heap_after_alloc_failure = true;
5697 _evacuation_failed = false;
5699 // Should G1EvacuationFailureALot be in effect for this GC?
5700 NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();)
5702 g1_rem_set()->prepare_for_oops_into_collection_set_do();
5704 // Disable the hot card cache.
5705 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
5706 hot_card_cache->reset_hot_cache_claimed_index();
5707 hot_card_cache->set_use_cache(false);
5709 uint n_workers;
5710 if (G1CollectedHeap::use_parallel_gc_threads()) {
5711 n_workers =
5712 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
5713 workers()->active_workers(),
5714 Threads::number_of_non_daemon_threads());
5715 assert(UseDynamicNumberOfGCThreads ||
5716 n_workers == workers()->total_workers(),
5717 "If not dynamic should be using all the workers");
5718 workers()->set_active_workers(n_workers);
5719 set_par_threads(n_workers);
5720 } else {
5721 assert(n_par_threads() == 0,
5722 "Should be the original non-parallel value");
5723 n_workers = 1;
5724 }
5727 init_for_evac_failure(NULL);
5729 rem_set()->prepare_for_younger_refs_iterate(true);
5731 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
5732 double start_par_time_sec = os::elapsedTime();
5733 double end_par_time_sec;
5735 {
5736 G1RootProcessor root_processor(this);
5737 G1ParTask g1_par_task(this, _task_queues, &root_processor);
5738 // InitialMark needs claim bits to keep track of the marked-through CLDs.
5739 if (g1_policy()->during_initial_mark_pause()) {
5740 ClassLoaderDataGraph::clear_claimed_marks();
5741 }
5743 if (G1CollectedHeap::use_parallel_gc_threads()) {
5744 // The individual threads will set their evac-failure closures.
5745 if (ParallelGCVerbose) G1ParScanThreadState::print_termination_stats_hdr();
5746 // These tasks use ShareHeap::_process_strong_tasks
5747 assert(UseDynamicNumberOfGCThreads ||
5748 workers()->active_workers() == workers()->total_workers(),
5749 "If not dynamic should be using all the workers");
5750 workers()->run_task(&g1_par_task);
5751 } else {
5752 g1_par_task.set_for_termination(n_workers);
5753 g1_par_task.work(0);
5754 }
5755 end_par_time_sec = os::elapsedTime();
5757 // Closing the inner scope will execute the destructor
5758 // for the G1RootProcessor object. We record the current
5759 // elapsed time before closing the scope so that time
5760 // taken for the destructor is NOT included in the
5761 // reported parallel time.
5762 }
5764 G1GCPhaseTimes* phase_times = g1_policy()->phase_times();
5766 double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0;
5767 phase_times->record_par_time(par_time_ms);
5769 double code_root_fixup_time_ms =
5770 (os::elapsedTime() - end_par_time_sec) * 1000.0;
5771 phase_times->record_code_root_fixup_time(code_root_fixup_time_ms);
5773 set_par_threads(0);
5775 // Process any discovered reference objects - we have
5776 // to do this _before_ we retire the GC alloc regions
5777 // as we may have to copy some 'reachable' referent
5778 // objects (and their reachable sub-graphs) that were
5779 // not copied during the pause.
5780 process_discovered_references(n_workers);
5782 if (G1StringDedup::is_enabled()) {
5783 double fixup_start = os::elapsedTime();
5785 G1STWIsAliveClosure is_alive(this);
5786 G1KeepAliveClosure keep_alive(this);
5787 G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive, true, phase_times);
5789 double fixup_time_ms = (os::elapsedTime() - fixup_start) * 1000.0;
5790 phase_times->record_string_dedup_fixup_time(fixup_time_ms);
5791 }
5793 _allocator->release_gc_alloc_regions(n_workers, evacuation_info);
5794 g1_rem_set()->cleanup_after_oops_into_collection_set_do();
5796 // Reset and re-enable the hot card cache.
5797 // Note the counts for the cards in the regions in the
5798 // collection set are reset when the collection set is freed.
5799 hot_card_cache->reset_hot_cache();
5800 hot_card_cache->set_use_cache(true);
5802 purge_code_root_memory();
5804 if (g1_policy()->during_initial_mark_pause()) {
5805 // Reset the claim values set during marking the strong code roots
5806 reset_heap_region_claim_values();
5807 }
5809 finalize_for_evac_failure();
5811 if (evacuation_failed()) {
5812 remove_self_forwarding_pointers();
5814 // Reset the G1EvacuationFailureALot counters and flags
5815 // Note: the values are reset only when an actual
5816 // evacuation failure occurs.
5817 NOT_PRODUCT(reset_evacuation_should_fail();)
5818 }
5820 // Enqueue any remaining references remaining on the STW
5821 // reference processor's discovered lists. We need to do
5822 // this after the card table is cleaned (and verified) as
5823 // the act of enqueueing entries on to the pending list
5824 // will log these updates (and dirty their associated
5825 // cards). We need these updates logged to update any
5826 // RSets.
5827 enqueue_discovered_references(n_workers);
5829 redirty_logged_cards();
5830 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
5831 }
5833 void G1CollectedHeap::free_region(HeapRegion* hr,
5834 FreeRegionList* free_list,
5835 bool par,
5836 bool locked) {
5837 assert(!hr->is_free(), "the region should not be free");
5838 assert(!hr->is_empty(), "the region should not be empty");
5839 assert(_hrm.is_available(hr->hrm_index()), "region should be committed");
5840 assert(free_list != NULL, "pre-condition");
5842 if (G1VerifyBitmaps) {
5843 MemRegion mr(hr->bottom(), hr->end());
5844 concurrent_mark()->clearRangePrevBitmap(mr);
5845 }
5847 // Clear the card counts for this region.
5848 // Note: we only need to do this if the region is not young
5849 // (since we don't refine cards in young regions).
5850 if (!hr->is_young()) {
5851 _cg1r->hot_card_cache()->reset_card_counts(hr);
5852 }
5853 hr->hr_clear(par, true /* clear_space */, locked /* locked */);
5854 free_list->add_ordered(hr);
5855 }
5857 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
5858 FreeRegionList* free_list,
5859 bool par) {
5860 assert(hr->startsHumongous(), "this is only for starts humongous regions");
5861 assert(free_list != NULL, "pre-condition");
5863 size_t hr_capacity = hr->capacity();
5864 // We need to read this before we make the region non-humongous,
5865 // otherwise the information will be gone.
5866 uint last_index = hr->last_hc_index();
5867 hr->clear_humongous();
5868 free_region(hr, free_list, par);
5870 uint i = hr->hrm_index() + 1;
5871 while (i < last_index) {
5872 HeapRegion* curr_hr = region_at(i);
5873 assert(curr_hr->continuesHumongous(), "invariant");
5874 curr_hr->clear_humongous();
5875 free_region(curr_hr, free_list, par);
5876 i += 1;
5877 }
5878 }
5880 void G1CollectedHeap::remove_from_old_sets(const HeapRegionSetCount& old_regions_removed,
5881 const HeapRegionSetCount& humongous_regions_removed) {
5882 if (old_regions_removed.length() > 0 || humongous_regions_removed.length() > 0) {
5883 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
5884 _old_set.bulk_remove(old_regions_removed);
5885 _humongous_set.bulk_remove(humongous_regions_removed);
5886 }
5888 }
5890 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) {
5891 assert(list != NULL, "list can't be null");
5892 if (!list->is_empty()) {
5893 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
5894 _hrm.insert_list_into_free_list(list);
5895 }
5896 }
5898 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) {
5899 _allocator->decrease_used(bytes);
5900 }
5902 class G1ParCleanupCTTask : public AbstractGangTask {
5903 G1SATBCardTableModRefBS* _ct_bs;
5904 G1CollectedHeap* _g1h;
5905 HeapRegion* volatile _su_head;
5906 public:
5907 G1ParCleanupCTTask(G1SATBCardTableModRefBS* ct_bs,
5908 G1CollectedHeap* g1h) :
5909 AbstractGangTask("G1 Par Cleanup CT Task"),
5910 _ct_bs(ct_bs), _g1h(g1h) { }
5912 void work(uint worker_id) {
5913 HeapRegion* r;
5914 while (r = _g1h->pop_dirty_cards_region()) {
5915 clear_cards(r);
5916 }
5917 }
5919 void clear_cards(HeapRegion* r) {
5920 // Cards of the survivors should have already been dirtied.
5921 if (!r->is_survivor()) {
5922 _ct_bs->clear(MemRegion(r->bottom(), r->end()));
5923 }
5924 }
5925 };
5927 #ifndef PRODUCT
5928 class G1VerifyCardTableCleanup: public HeapRegionClosure {
5929 G1CollectedHeap* _g1h;
5930 G1SATBCardTableModRefBS* _ct_bs;
5931 public:
5932 G1VerifyCardTableCleanup(G1CollectedHeap* g1h, G1SATBCardTableModRefBS* ct_bs)
5933 : _g1h(g1h), _ct_bs(ct_bs) { }
5934 virtual bool doHeapRegion(HeapRegion* r) {
5935 if (r->is_survivor()) {
5936 _g1h->verify_dirty_region(r);
5937 } else {
5938 _g1h->verify_not_dirty_region(r);
5939 }
5940 return false;
5941 }
5942 };
5944 void G1CollectedHeap::verify_not_dirty_region(HeapRegion* hr) {
5945 // All of the region should be clean.
5946 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
5947 MemRegion mr(hr->bottom(), hr->end());
5948 ct_bs->verify_not_dirty_region(mr);
5949 }
5951 void G1CollectedHeap::verify_dirty_region(HeapRegion* hr) {
5952 // We cannot guarantee that [bottom(),end()] is dirty. Threads
5953 // dirty allocated blocks as they allocate them. The thread that
5954 // retires each region and replaces it with a new one will do a
5955 // maximal allocation to fill in [pre_dummy_top(),end()] but will
5956 // not dirty that area (one less thing to have to do while holding
5957 // a lock). So we can only verify that [bottom(),pre_dummy_top()]
5958 // is dirty.
5959 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
5960 MemRegion mr(hr->bottom(), hr->pre_dummy_top());
5961 if (hr->is_young()) {
5962 ct_bs->verify_g1_young_region(mr);
5963 } else {
5964 ct_bs->verify_dirty_region(mr);
5965 }
5966 }
5968 void G1CollectedHeap::verify_dirty_young_list(HeapRegion* head) {
5969 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
5970 for (HeapRegion* hr = head; hr != NULL; hr = hr->get_next_young_region()) {
5971 verify_dirty_region(hr);
5972 }
5973 }
5975 void G1CollectedHeap::verify_dirty_young_regions() {
5976 verify_dirty_young_list(_young_list->first_region());
5977 }
5979 bool G1CollectedHeap::verify_no_bits_over_tams(const char* bitmap_name, CMBitMapRO* bitmap,
5980 HeapWord* tams, HeapWord* end) {
5981 guarantee(tams <= end,
5982 err_msg("tams: "PTR_FORMAT" end: "PTR_FORMAT, tams, end));
5983 HeapWord* result = bitmap->getNextMarkedWordAddress(tams, end);
5984 if (result < end) {
5985 gclog_or_tty->cr();
5986 gclog_or_tty->print_cr("## wrong marked address on %s bitmap: "PTR_FORMAT,
5987 bitmap_name, result);
5988 gclog_or_tty->print_cr("## %s tams: "PTR_FORMAT" end: "PTR_FORMAT,
5989 bitmap_name, tams, end);
5990 return false;
5991 }
5992 return true;
5993 }
5995 bool G1CollectedHeap::verify_bitmaps(const char* caller, HeapRegion* hr) {
5996 CMBitMapRO* prev_bitmap = concurrent_mark()->prevMarkBitMap();
5997 CMBitMapRO* next_bitmap = (CMBitMapRO*) concurrent_mark()->nextMarkBitMap();
5999 HeapWord* bottom = hr->bottom();
6000 HeapWord* ptams = hr->prev_top_at_mark_start();
6001 HeapWord* ntams = hr->next_top_at_mark_start();
6002 HeapWord* end = hr->end();
6004 bool res_p = verify_no_bits_over_tams("prev", prev_bitmap, ptams, end);
6006 bool res_n = true;
6007 // We reset mark_in_progress() before we reset _cmThread->in_progress() and in this window
6008 // we do the clearing of the next bitmap concurrently. Thus, we can not verify the bitmap
6009 // if we happen to be in that state.
6010 if (mark_in_progress() || !_cmThread->in_progress()) {
6011 res_n = verify_no_bits_over_tams("next", next_bitmap, ntams, end);
6012 }
6013 if (!res_p || !res_n) {
6014 gclog_or_tty->print_cr("#### Bitmap verification failed for "HR_FORMAT,
6015 HR_FORMAT_PARAMS(hr));
6016 gclog_or_tty->print_cr("#### Caller: %s", caller);
6017 return false;
6018 }
6019 return true;
6020 }
6022 void G1CollectedHeap::check_bitmaps(const char* caller, HeapRegion* hr) {
6023 if (!G1VerifyBitmaps) return;
6025 guarantee(verify_bitmaps(caller, hr), "bitmap verification");
6026 }
6028 class G1VerifyBitmapClosure : public HeapRegionClosure {
6029 private:
6030 const char* _caller;
6031 G1CollectedHeap* _g1h;
6032 bool _failures;
6034 public:
6035 G1VerifyBitmapClosure(const char* caller, G1CollectedHeap* g1h) :
6036 _caller(caller), _g1h(g1h), _failures(false) { }
6038 bool failures() { return _failures; }
6040 virtual bool doHeapRegion(HeapRegion* hr) {
6041 if (hr->continuesHumongous()) return false;
6043 bool result = _g1h->verify_bitmaps(_caller, hr);
6044 if (!result) {
6045 _failures = true;
6046 }
6047 return false;
6048 }
6049 };
6051 void G1CollectedHeap::check_bitmaps(const char* caller) {
6052 if (!G1VerifyBitmaps) return;
6054 G1VerifyBitmapClosure cl(caller, this);
6055 heap_region_iterate(&cl);
6056 guarantee(!cl.failures(), "bitmap verification");
6057 }
6058 #endif // PRODUCT
6060 void G1CollectedHeap::cleanUpCardTable() {
6061 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
6062 double start = os::elapsedTime();
6064 {
6065 // Iterate over the dirty cards region list.
6066 G1ParCleanupCTTask cleanup_task(ct_bs, this);
6068 if (G1CollectedHeap::use_parallel_gc_threads()) {
6069 set_par_threads();
6070 workers()->run_task(&cleanup_task);
6071 set_par_threads(0);
6072 } else {
6073 while (_dirty_cards_region_list) {
6074 HeapRegion* r = _dirty_cards_region_list;
6075 cleanup_task.clear_cards(r);
6076 _dirty_cards_region_list = r->get_next_dirty_cards_region();
6077 if (_dirty_cards_region_list == r) {
6078 // The last region.
6079 _dirty_cards_region_list = NULL;
6080 }
6081 r->set_next_dirty_cards_region(NULL);
6082 }
6083 }
6084 #ifndef PRODUCT
6085 if (G1VerifyCTCleanup || VerifyAfterGC) {
6086 G1VerifyCardTableCleanup cleanup_verifier(this, ct_bs);
6087 heap_region_iterate(&cleanup_verifier);
6088 }
6089 #endif
6090 }
6092 double elapsed = os::elapsedTime() - start;
6093 g1_policy()->phase_times()->record_clear_ct_time(elapsed * 1000.0);
6094 }
6096 void G1CollectedHeap::free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info) {
6097 size_t pre_used = 0;
6098 FreeRegionList local_free_list("Local List for CSet Freeing");
6100 double young_time_ms = 0.0;
6101 double non_young_time_ms = 0.0;
6103 // Since the collection set is a superset of the the young list,
6104 // all we need to do to clear the young list is clear its
6105 // head and length, and unlink any young regions in the code below
6106 _young_list->clear();
6108 G1CollectorPolicy* policy = g1_policy();
6110 double start_sec = os::elapsedTime();
6111 bool non_young = true;
6113 HeapRegion* cur = cs_head;
6114 int age_bound = -1;
6115 size_t rs_lengths = 0;
6117 while (cur != NULL) {
6118 assert(!is_on_master_free_list(cur), "sanity");
6119 if (non_young) {
6120 if (cur->is_young()) {
6121 double end_sec = os::elapsedTime();
6122 double elapsed_ms = (end_sec - start_sec) * 1000.0;
6123 non_young_time_ms += elapsed_ms;
6125 start_sec = os::elapsedTime();
6126 non_young = false;
6127 }
6128 } else {
6129 if (!cur->is_young()) {
6130 double end_sec = os::elapsedTime();
6131 double elapsed_ms = (end_sec - start_sec) * 1000.0;
6132 young_time_ms += elapsed_ms;
6134 start_sec = os::elapsedTime();
6135 non_young = true;
6136 }
6137 }
6139 rs_lengths += cur->rem_set()->occupied_locked();
6141 HeapRegion* next = cur->next_in_collection_set();
6142 assert(cur->in_collection_set(), "bad CS");
6143 cur->set_next_in_collection_set(NULL);
6144 cur->set_in_collection_set(false);
6146 if (cur->is_young()) {
6147 int index = cur->young_index_in_cset();
6148 assert(index != -1, "invariant");
6149 assert((uint) index < policy->young_cset_region_length(), "invariant");
6150 size_t words_survived = _surviving_young_words[index];
6151 cur->record_surv_words_in_group(words_survived);
6153 // At this point the we have 'popped' cur from the collection set
6154 // (linked via next_in_collection_set()) but it is still in the
6155 // young list (linked via next_young_region()). Clear the
6156 // _next_young_region field.
6157 cur->set_next_young_region(NULL);
6158 } else {
6159 int index = cur->young_index_in_cset();
6160 assert(index == -1, "invariant");
6161 }
6163 assert( (cur->is_young() && cur->young_index_in_cset() > -1) ||
6164 (!cur->is_young() && cur->young_index_in_cset() == -1),
6165 "invariant" );
6167 if (!cur->evacuation_failed()) {
6168 MemRegion used_mr = cur->used_region();
6170 // And the region is empty.
6171 assert(!used_mr.is_empty(), "Should not have empty regions in a CS.");
6172 pre_used += cur->used();
6173 free_region(cur, &local_free_list, false /* par */, true /* locked */);
6174 } else {
6175 cur->uninstall_surv_rate_group();
6176 if (cur->is_young()) {
6177 cur->set_young_index_in_cset(-1);
6178 }
6179 cur->set_evacuation_failed(false);
6180 // The region is now considered to be old.
6181 cur->set_old();
6182 _old_set.add(cur);
6183 evacuation_info.increment_collectionset_used_after(cur->used());
6184 }
6185 cur = next;
6186 }
6188 evacuation_info.set_regions_freed(local_free_list.length());
6189 policy->record_max_rs_lengths(rs_lengths);
6190 policy->cset_regions_freed();
6192 double end_sec = os::elapsedTime();
6193 double elapsed_ms = (end_sec - start_sec) * 1000.0;
6195 if (non_young) {
6196 non_young_time_ms += elapsed_ms;
6197 } else {
6198 young_time_ms += elapsed_ms;
6199 }
6201 prepend_to_freelist(&local_free_list);
6202 decrement_summary_bytes(pre_used);
6203 policy->phase_times()->record_young_free_cset_time_ms(young_time_ms);
6204 policy->phase_times()->record_non_young_free_cset_time_ms(non_young_time_ms);
6205 }
6207 class G1FreeHumongousRegionClosure : public HeapRegionClosure {
6208 private:
6209 FreeRegionList* _free_region_list;
6210 HeapRegionSet* _proxy_set;
6211 HeapRegionSetCount _humongous_regions_removed;
6212 size_t _freed_bytes;
6213 public:
6215 G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) :
6216 _free_region_list(free_region_list), _humongous_regions_removed(), _freed_bytes(0) {
6217 }
6219 virtual bool doHeapRegion(HeapRegion* r) {
6220 if (!r->startsHumongous()) {
6221 return false;
6222 }
6224 G1CollectedHeap* g1h = G1CollectedHeap::heap();
6226 oop obj = (oop)r->bottom();
6227 CMBitMap* next_bitmap = g1h->concurrent_mark()->nextMarkBitMap();
6229 // The following checks whether the humongous object is live are sufficient.
6230 // The main additional check (in addition to having a reference from the roots
6231 // or the young gen) is whether the humongous object has a remembered set entry.
6232 //
6233 // A humongous object cannot be live if there is no remembered set for it
6234 // because:
6235 // - there can be no references from within humongous starts regions referencing
6236 // the object because we never allocate other objects into them.
6237 // (I.e. there are no intra-region references that may be missed by the
6238 // remembered set)
6239 // - as soon there is a remembered set entry to the humongous starts region
6240 // (i.e. it has "escaped" to an old object) this remembered set entry will stay
6241 // until the end of a concurrent mark.
6242 //
6243 // It is not required to check whether the object has been found dead by marking
6244 // or not, in fact it would prevent reclamation within a concurrent cycle, as
6245 // all objects allocated during that time are considered live.
6246 // SATB marking is even more conservative than the remembered set.
6247 // So if at this point in the collection there is no remembered set entry,
6248 // nobody has a reference to it.
6249 // At the start of collection we flush all refinement logs, and remembered sets
6250 // are completely up-to-date wrt to references to the humongous object.
6251 //
6252 // Other implementation considerations:
6253 // - never consider object arrays: while they are a valid target, they have not
6254 // been observed to be used as temporary objects.
6255 // - they would also pose considerable effort for cleaning up the the remembered
6256 // sets.
6257 // While this cleanup is not strictly necessary to be done (or done instantly),
6258 // given that their occurrence is very low, this saves us this additional
6259 // complexity.
6260 uint region_idx = r->hrm_index();
6261 if (g1h->humongous_is_live(region_idx) ||
6262 g1h->humongous_region_is_always_live(region_idx)) {
6264 if (G1TraceReclaimDeadHumongousObjectsAtYoungGC) {
6265 gclog_or_tty->print_cr("Live humongous %d region %d with remset "SIZE_FORMAT" code roots "SIZE_FORMAT" is marked %d live-other %d obj array %d",
6266 r->isHumongous(),
6267 region_idx,
6268 r->rem_set()->occupied(),
6269 r->rem_set()->strong_code_roots_list_length(),
6270 next_bitmap->isMarked(r->bottom()),
6271 g1h->humongous_is_live(region_idx),
6272 obj->is_objArray()
6273 );
6274 }
6276 return false;
6277 }
6279 guarantee(!obj->is_objArray(),
6280 err_msg("Eagerly reclaiming object arrays is not supported, but the object "PTR_FORMAT" is.",
6281 r->bottom()));
6283 if (G1TraceReclaimDeadHumongousObjectsAtYoungGC) {
6284 gclog_or_tty->print_cr("Reclaim humongous region %d start "PTR_FORMAT" region %d length "UINT32_FORMAT" with remset "SIZE_FORMAT" code roots "SIZE_FORMAT" is marked %d live-other %d obj array %d",
6285 r->isHumongous(),
6286 r->bottom(),
6287 region_idx,
6288 r->region_num(),
6289 r->rem_set()->occupied(),
6290 r->rem_set()->strong_code_roots_list_length(),
6291 next_bitmap->isMarked(r->bottom()),
6292 g1h->humongous_is_live(region_idx),
6293 obj->is_objArray()
6294 );
6295 }
6296 // Need to clear mark bit of the humongous object if already set.
6297 if (next_bitmap->isMarked(r->bottom())) {
6298 next_bitmap->clear(r->bottom());
6299 }
6300 _freed_bytes += r->used();
6301 r->set_containing_set(NULL);
6302 _humongous_regions_removed.increment(1u, r->capacity());
6303 g1h->free_humongous_region(r, _free_region_list, false);
6305 return false;
6306 }
6308 HeapRegionSetCount& humongous_free_count() {
6309 return _humongous_regions_removed;
6310 }
6312 size_t bytes_freed() const {
6313 return _freed_bytes;
6314 }
6316 size_t humongous_reclaimed() const {
6317 return _humongous_regions_removed.length();
6318 }
6319 };
6321 void G1CollectedHeap::eagerly_reclaim_humongous_regions() {
6322 assert_at_safepoint(true);
6324 if (!G1ReclaimDeadHumongousObjectsAtYoungGC || !_has_humongous_reclaim_candidates) {
6325 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0);
6326 return;
6327 }
6329 double start_time = os::elapsedTime();
6331 FreeRegionList local_cleanup_list("Local Humongous Cleanup List");
6333 G1FreeHumongousRegionClosure cl(&local_cleanup_list);
6334 heap_region_iterate(&cl);
6336 HeapRegionSetCount empty_set;
6337 remove_from_old_sets(empty_set, cl.humongous_free_count());
6339 G1HRPrinter* hr_printer = _g1h->hr_printer();
6340 if (hr_printer->is_active()) {
6341 FreeRegionListIterator iter(&local_cleanup_list);
6342 while (iter.more_available()) {
6343 HeapRegion* hr = iter.get_next();
6344 hr_printer->cleanup(hr);
6345 }
6346 }
6348 prepend_to_freelist(&local_cleanup_list);
6349 decrement_summary_bytes(cl.bytes_freed());
6351 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0,
6352 cl.humongous_reclaimed());
6353 }
6355 // This routine is similar to the above but does not record
6356 // any policy statistics or update free lists; we are abandoning
6357 // the current incremental collection set in preparation of a
6358 // full collection. After the full GC we will start to build up
6359 // the incremental collection set again.
6360 // This is only called when we're doing a full collection
6361 // and is immediately followed by the tearing down of the young list.
6363 void G1CollectedHeap::abandon_collection_set(HeapRegion* cs_head) {
6364 HeapRegion* cur = cs_head;
6366 while (cur != NULL) {
6367 HeapRegion* next = cur->next_in_collection_set();
6368 assert(cur->in_collection_set(), "bad CS");
6369 cur->set_next_in_collection_set(NULL);
6370 cur->set_in_collection_set(false);
6371 cur->set_young_index_in_cset(-1);
6372 cur = next;
6373 }
6374 }
6376 void G1CollectedHeap::set_free_regions_coming() {
6377 if (G1ConcRegionFreeingVerbose) {
6378 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
6379 "setting free regions coming");
6380 }
6382 assert(!free_regions_coming(), "pre-condition");
6383 _free_regions_coming = true;
6384 }
6386 void G1CollectedHeap::reset_free_regions_coming() {
6387 assert(free_regions_coming(), "pre-condition");
6389 {
6390 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6391 _free_regions_coming = false;
6392 SecondaryFreeList_lock->notify_all();
6393 }
6395 if (G1ConcRegionFreeingVerbose) {
6396 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
6397 "reset free regions coming");
6398 }
6399 }
6401 void G1CollectedHeap::wait_while_free_regions_coming() {
6402 // Most of the time we won't have to wait, so let's do a quick test
6403 // first before we take the lock.
6404 if (!free_regions_coming()) {
6405 return;
6406 }
6408 if (G1ConcRegionFreeingVerbose) {
6409 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
6410 "waiting for free regions");
6411 }
6413 {
6414 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6415 while (free_regions_coming()) {
6416 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
6417 }
6418 }
6420 if (G1ConcRegionFreeingVerbose) {
6421 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
6422 "done waiting for free regions");
6423 }
6424 }
6426 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
6427 assert(heap_lock_held_for_gc(),
6428 "the heap lock should already be held by or for this thread");
6429 _young_list->push_region(hr);
6430 }
6432 class NoYoungRegionsClosure: public HeapRegionClosure {
6433 private:
6434 bool _success;
6435 public:
6436 NoYoungRegionsClosure() : _success(true) { }
6437 bool doHeapRegion(HeapRegion* r) {
6438 if (r->is_young()) {
6439 gclog_or_tty->print_cr("Region ["PTR_FORMAT", "PTR_FORMAT") tagged as young",
6440 r->bottom(), r->end());
6441 _success = false;
6442 }
6443 return false;
6444 }
6445 bool success() { return _success; }
6446 };
6448 bool G1CollectedHeap::check_young_list_empty(bool check_heap, bool check_sample) {
6449 bool ret = _young_list->check_list_empty(check_sample);
6451 if (check_heap) {
6452 NoYoungRegionsClosure closure;
6453 heap_region_iterate(&closure);
6454 ret = ret && closure.success();
6455 }
6457 return ret;
6458 }
6460 class TearDownRegionSetsClosure : public HeapRegionClosure {
6461 private:
6462 HeapRegionSet *_old_set;
6464 public:
6465 TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { }
6467 bool doHeapRegion(HeapRegion* r) {
6468 if (r->is_old()) {
6469 _old_set->remove(r);
6470 } else {
6471 // We ignore free regions, we'll empty the free list afterwards.
6472 // We ignore young regions, we'll empty the young list afterwards.
6473 // We ignore humongous regions, we're not tearing down the
6474 // humongous regions set.
6475 assert(r->is_free() || r->is_young() || r->isHumongous(),
6476 "it cannot be another type");
6477 }
6478 return false;
6479 }
6481 ~TearDownRegionSetsClosure() {
6482 assert(_old_set->is_empty(), "post-condition");
6483 }
6484 };
6486 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
6487 assert_at_safepoint(true /* should_be_vm_thread */);
6489 if (!free_list_only) {
6490 TearDownRegionSetsClosure cl(&_old_set);
6491 heap_region_iterate(&cl);
6493 // Note that emptying the _young_list is postponed and instead done as
6494 // the first step when rebuilding the regions sets again. The reason for
6495 // this is that during a full GC string deduplication needs to know if
6496 // a collected region was young or old when the full GC was initiated.
6497 }
6498 _hrm.remove_all_free_regions();
6499 }
6501 class RebuildRegionSetsClosure : public HeapRegionClosure {
6502 private:
6503 bool _free_list_only;
6504 HeapRegionSet* _old_set;
6505 HeapRegionManager* _hrm;
6506 size_t _total_used;
6508 public:
6509 RebuildRegionSetsClosure(bool free_list_only,
6510 HeapRegionSet* old_set, HeapRegionManager* hrm) :
6511 _free_list_only(free_list_only),
6512 _old_set(old_set), _hrm(hrm), _total_used(0) {
6513 assert(_hrm->num_free_regions() == 0, "pre-condition");
6514 if (!free_list_only) {
6515 assert(_old_set->is_empty(), "pre-condition");
6516 }
6517 }
6519 bool doHeapRegion(HeapRegion* r) {
6520 if (r->continuesHumongous()) {
6521 return false;
6522 }
6524 if (r->is_empty()) {
6525 // Add free regions to the free list
6526 r->set_free();
6527 r->set_allocation_context(AllocationContext::system());
6528 _hrm->insert_into_free_list(r);
6529 } else if (!_free_list_only) {
6530 assert(!r->is_young(), "we should not come across young regions");
6532 if (r->isHumongous()) {
6533 // We ignore humongous regions, we left the humongous set unchanged
6534 } else {
6535 // Objects that were compacted would have ended up on regions
6536 // that were previously old or free.
6537 assert(r->is_free() || r->is_old(), "invariant");
6538 // We now consider them old, so register as such.
6539 r->set_old();
6540 _old_set->add(r);
6541 }
6542 _total_used += r->used();
6543 }
6545 return false;
6546 }
6548 size_t total_used() {
6549 return _total_used;
6550 }
6551 };
6553 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
6554 assert_at_safepoint(true /* should_be_vm_thread */);
6556 if (!free_list_only) {
6557 _young_list->empty_list();
6558 }
6560 RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm);
6561 heap_region_iterate(&cl);
6563 if (!free_list_only) {
6564 _allocator->set_used(cl.total_used());
6565 }
6566 assert(_allocator->used_unlocked() == recalculate_used(),
6567 err_msg("inconsistent _allocator->used_unlocked(), "
6568 "value: "SIZE_FORMAT" recalculated: "SIZE_FORMAT,
6569 _allocator->used_unlocked(), recalculate_used()));
6570 }
6572 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) {
6573 _refine_cte_cl->set_concurrent(concurrent);
6574 }
6576 bool G1CollectedHeap::is_in_closed_subset(const void* p) const {
6577 HeapRegion* hr = heap_region_containing(p);
6578 return hr->is_in(p);
6579 }
6581 // Methods for the mutator alloc region
6583 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
6584 bool force) {
6585 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6586 assert(!force || g1_policy()->can_expand_young_list(),
6587 "if force is true we should be able to expand the young list");
6588 bool young_list_full = g1_policy()->is_young_list_full();
6589 if (force || !young_list_full) {
6590 HeapRegion* new_alloc_region = new_region(word_size,
6591 false /* is_old */,
6592 false /* do_expand */);
6593 if (new_alloc_region != NULL) {
6594 set_region_short_lived_locked(new_alloc_region);
6595 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Eden, young_list_full);
6596 check_bitmaps("Mutator Region Allocation", new_alloc_region);
6597 return new_alloc_region;
6598 }
6599 }
6600 return NULL;
6601 }
6603 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
6604 size_t allocated_bytes) {
6605 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6606 assert(alloc_region->is_eden(), "all mutator alloc regions should be eden");
6608 g1_policy()->add_region_to_incremental_cset_lhs(alloc_region);
6609 _allocator->increase_used(allocated_bytes);
6610 _hr_printer.retire(alloc_region);
6611 // We update the eden sizes here, when the region is retired,
6612 // instead of when it's allocated, since this is the point that its
6613 // used space has been recored in _summary_bytes_used.
6614 g1mm()->update_eden_size();
6615 }
6617 void G1CollectedHeap::set_par_threads() {
6618 // Don't change the number of workers. Use the value previously set
6619 // in the workgroup.
6620 assert(G1CollectedHeap::use_parallel_gc_threads(), "shouldn't be here otherwise");
6621 uint n_workers = workers()->active_workers();
6622 assert(UseDynamicNumberOfGCThreads ||
6623 n_workers == workers()->total_workers(),
6624 "Otherwise should be using the total number of workers");
6625 if (n_workers == 0) {
6626 assert(false, "Should have been set in prior evacuation pause.");
6627 n_workers = ParallelGCThreads;
6628 workers()->set_active_workers(n_workers);
6629 }
6630 set_par_threads(n_workers);
6631 }
6633 // Methods for the GC alloc regions
6635 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size,
6636 uint count,
6637 GCAllocPurpose ap) {
6638 assert(FreeList_lock->owned_by_self(), "pre-condition");
6640 if (count < g1_policy()->max_regions(ap)) {
6641 bool survivor = (ap == GCAllocForSurvived);
6642 HeapRegion* new_alloc_region = new_region(word_size,
6643 !survivor,
6644 true /* do_expand */);
6645 if (new_alloc_region != NULL) {
6646 // We really only need to do this for old regions given that we
6647 // should never scan survivors. But it doesn't hurt to do it
6648 // for survivors too.
6649 new_alloc_region->record_top_and_timestamp();
6650 if (survivor) {
6651 new_alloc_region->set_survivor();
6652 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Survivor);
6653 check_bitmaps("Survivor Region Allocation", new_alloc_region);
6654 } else {
6655 new_alloc_region->set_old();
6656 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Old);
6657 check_bitmaps("Old Region Allocation", new_alloc_region);
6658 }
6659 bool during_im = g1_policy()->during_initial_mark_pause();
6660 new_alloc_region->note_start_of_copying(during_im);
6661 return new_alloc_region;
6662 } else {
6663 g1_policy()->note_alloc_region_limit_reached(ap);
6664 }
6665 }
6666 return NULL;
6667 }
6669 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
6670 size_t allocated_bytes,
6671 GCAllocPurpose ap) {
6672 bool during_im = g1_policy()->during_initial_mark_pause();
6673 alloc_region->note_end_of_copying(during_im);
6674 g1_policy()->record_bytes_copied_during_gc(allocated_bytes);
6675 if (ap == GCAllocForSurvived) {
6676 young_list()->add_survivor_region(alloc_region);
6677 } else {
6678 _old_set.add(alloc_region);
6679 }
6680 _hr_printer.retire(alloc_region);
6681 }
6683 // Heap region set verification
6685 class VerifyRegionListsClosure : public HeapRegionClosure {
6686 private:
6687 HeapRegionSet* _old_set;
6688 HeapRegionSet* _humongous_set;
6689 HeapRegionManager* _hrm;
6691 public:
6692 HeapRegionSetCount _old_count;
6693 HeapRegionSetCount _humongous_count;
6694 HeapRegionSetCount _free_count;
6696 VerifyRegionListsClosure(HeapRegionSet* old_set,
6697 HeapRegionSet* humongous_set,
6698 HeapRegionManager* hrm) :
6699 _old_set(old_set), _humongous_set(humongous_set), _hrm(hrm),
6700 _old_count(), _humongous_count(), _free_count(){ }
6702 bool doHeapRegion(HeapRegion* hr) {
6703 if (hr->continuesHumongous()) {
6704 return false;
6705 }
6707 if (hr->is_young()) {
6708 // TODO
6709 } else if (hr->startsHumongous()) {
6710 assert(hr->containing_set() == _humongous_set, err_msg("Heap region %u is starts humongous but not in humongous set.", hr->hrm_index()));
6711 _humongous_count.increment(1u, hr->capacity());
6712 } else if (hr->is_empty()) {
6713 assert(_hrm->is_free(hr), err_msg("Heap region %u is empty but not on the free list.", hr->hrm_index()));
6714 _free_count.increment(1u, hr->capacity());
6715 } else if (hr->is_old()) {
6716 assert(hr->containing_set() == _old_set, err_msg("Heap region %u is old but not in the old set.", hr->hrm_index()));
6717 _old_count.increment(1u, hr->capacity());
6718 } else {
6719 ShouldNotReachHere();
6720 }
6721 return false;
6722 }
6724 void verify_counts(HeapRegionSet* old_set, HeapRegionSet* humongous_set, HeapRegionManager* free_list) {
6725 guarantee(old_set->length() == _old_count.length(), err_msg("Old set count mismatch. Expected %u, actual %u.", old_set->length(), _old_count.length()));
6726 guarantee(old_set->total_capacity_bytes() == _old_count.capacity(), err_msg("Old set capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
6727 old_set->total_capacity_bytes(), _old_count.capacity()));
6729 guarantee(humongous_set->length() == _humongous_count.length(), err_msg("Hum set count mismatch. Expected %u, actual %u.", humongous_set->length(), _humongous_count.length()));
6730 guarantee(humongous_set->total_capacity_bytes() == _humongous_count.capacity(), err_msg("Hum set capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
6731 humongous_set->total_capacity_bytes(), _humongous_count.capacity()));
6733 guarantee(free_list->num_free_regions() == _free_count.length(), err_msg("Free list count mismatch. Expected %u, actual %u.", free_list->num_free_regions(), _free_count.length()));
6734 guarantee(free_list->total_capacity_bytes() == _free_count.capacity(), err_msg("Free list capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
6735 free_list->total_capacity_bytes(), _free_count.capacity()));
6736 }
6737 };
6739 void G1CollectedHeap::verify_region_sets() {
6740 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6742 // First, check the explicit lists.
6743 _hrm.verify();
6744 {
6745 // Given that a concurrent operation might be adding regions to
6746 // the secondary free list we have to take the lock before
6747 // verifying it.
6748 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6749 _secondary_free_list.verify_list();
6750 }
6752 // If a concurrent region freeing operation is in progress it will
6753 // be difficult to correctly attributed any free regions we come
6754 // across to the correct free list given that they might belong to
6755 // one of several (free_list, secondary_free_list, any local lists,
6756 // etc.). So, if that's the case we will skip the rest of the
6757 // verification operation. Alternatively, waiting for the concurrent
6758 // operation to complete will have a non-trivial effect on the GC's
6759 // operation (no concurrent operation will last longer than the
6760 // interval between two calls to verification) and it might hide
6761 // any issues that we would like to catch during testing.
6762 if (free_regions_coming()) {
6763 return;
6764 }
6766 // Make sure we append the secondary_free_list on the free_list so
6767 // that all free regions we will come across can be safely
6768 // attributed to the free_list.
6769 append_secondary_free_list_if_not_empty_with_lock();
6771 // Finally, make sure that the region accounting in the lists is
6772 // consistent with what we see in the heap.
6774 VerifyRegionListsClosure cl(&_old_set, &_humongous_set, &_hrm);
6775 heap_region_iterate(&cl);
6776 cl.verify_counts(&_old_set, &_humongous_set, &_hrm);
6777 }
6779 // Optimized nmethod scanning
6781 class RegisterNMethodOopClosure: public OopClosure {
6782 G1CollectedHeap* _g1h;
6783 nmethod* _nm;
6785 template <class T> void do_oop_work(T* p) {
6786 T heap_oop = oopDesc::load_heap_oop(p);
6787 if (!oopDesc::is_null(heap_oop)) {
6788 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
6789 HeapRegion* hr = _g1h->heap_region_containing(obj);
6790 assert(!hr->continuesHumongous(),
6791 err_msg("trying to add code root "PTR_FORMAT" in continuation of humongous region "HR_FORMAT
6792 " starting at "HR_FORMAT,
6793 _nm, HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())));
6795 // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries.
6796 hr->add_strong_code_root_locked(_nm);
6797 }
6798 }
6800 public:
6801 RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
6802 _g1h(g1h), _nm(nm) {}
6804 void do_oop(oop* p) { do_oop_work(p); }
6805 void do_oop(narrowOop* p) { do_oop_work(p); }
6806 };
6808 class UnregisterNMethodOopClosure: public OopClosure {
6809 G1CollectedHeap* _g1h;
6810 nmethod* _nm;
6812 template <class T> void do_oop_work(T* p) {
6813 T heap_oop = oopDesc::load_heap_oop(p);
6814 if (!oopDesc::is_null(heap_oop)) {
6815 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
6816 HeapRegion* hr = _g1h->heap_region_containing(obj);
6817 assert(!hr->continuesHumongous(),
6818 err_msg("trying to remove code root "PTR_FORMAT" in continuation of humongous region "HR_FORMAT
6819 " starting at "HR_FORMAT,
6820 _nm, HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())));
6822 hr->remove_strong_code_root(_nm);
6823 }
6824 }
6826 public:
6827 UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
6828 _g1h(g1h), _nm(nm) {}
6830 void do_oop(oop* p) { do_oop_work(p); }
6831 void do_oop(narrowOop* p) { do_oop_work(p); }
6832 };
6834 void G1CollectedHeap::register_nmethod(nmethod* nm) {
6835 CollectedHeap::register_nmethod(nm);
6837 guarantee(nm != NULL, "sanity");
6838 RegisterNMethodOopClosure reg_cl(this, nm);
6839 nm->oops_do(®_cl);
6840 }
6842 void G1CollectedHeap::unregister_nmethod(nmethod* nm) {
6843 CollectedHeap::unregister_nmethod(nm);
6845 guarantee(nm != NULL, "sanity");
6846 UnregisterNMethodOopClosure reg_cl(this, nm);
6847 nm->oops_do(®_cl, true);
6848 }
6850 void G1CollectedHeap::purge_code_root_memory() {
6851 double purge_start = os::elapsedTime();
6852 G1CodeRootSet::purge();
6853 double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0;
6854 g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms);
6855 }
6857 class RebuildStrongCodeRootClosure: public CodeBlobClosure {
6858 G1CollectedHeap* _g1h;
6860 public:
6861 RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) :
6862 _g1h(g1h) {}
6864 void do_code_blob(CodeBlob* cb) {
6865 nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL;
6866 if (nm == NULL) {
6867 return;
6868 }
6870 if (ScavengeRootsInCode) {
6871 _g1h->register_nmethod(nm);
6872 }
6873 }
6874 };
6876 void G1CollectedHeap::rebuild_strong_code_roots() {
6877 RebuildStrongCodeRootClosure blob_cl(this);
6878 CodeCache::blobs_do(&blob_cl);
6879 }