Thu, 28 Aug 2014 17:05:41 +0200
8054808: Bitmap verification sometimes fails after Full GC aborts concurrent mark.
Summary: The verification code that checked whether no bitmap mark had been found re-read HeapRegion::end() after the check on the bitmap. Concurrent humongous object allocation could have changed HeapRegion::end() in the meantime. Fix this by using the actual end of the region instead of HeapRegion::end() for comparison.
Reviewed-by: brutisso, jmasa
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 "code/codeCache.hpp"
31 #include "code/icBuffer.hpp"
32 #include "gc_implementation/g1/bufferingOopClosure.hpp"
33 #include "gc_implementation/g1/concurrentG1Refine.hpp"
34 #include "gc_implementation/g1/concurrentG1RefineThread.hpp"
35 #include "gc_implementation/g1/concurrentMarkThread.inline.hpp"
36 #include "gc_implementation/g1/g1AllocRegion.inline.hpp"
37 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
38 #include "gc_implementation/g1/g1CollectorPolicy.hpp"
39 #include "gc_implementation/g1/g1ErgoVerbose.hpp"
40 #include "gc_implementation/g1/g1EvacFailure.hpp"
41 #include "gc_implementation/g1/g1GCPhaseTimes.hpp"
42 #include "gc_implementation/g1/g1Log.hpp"
43 #include "gc_implementation/g1/g1MarkSweep.hpp"
44 #include "gc_implementation/g1/g1OopClosures.inline.hpp"
45 #include "gc_implementation/g1/g1ParScanThreadState.inline.hpp"
46 #include "gc_implementation/g1/g1RegionToSpaceMapper.hpp"
47 #include "gc_implementation/g1/g1RemSet.inline.hpp"
48 #include "gc_implementation/g1/g1StringDedup.hpp"
49 #include "gc_implementation/g1/g1YCTypes.hpp"
50 #include "gc_implementation/g1/heapRegion.inline.hpp"
51 #include "gc_implementation/g1/heapRegionRemSet.hpp"
52 #include "gc_implementation/g1/heapRegionSet.inline.hpp"
53 #include "gc_implementation/g1/vm_operations_g1.hpp"
54 #include "gc_implementation/shared/gcHeapSummary.hpp"
55 #include "gc_implementation/shared/gcTimer.hpp"
56 #include "gc_implementation/shared/gcTrace.hpp"
57 #include "gc_implementation/shared/gcTraceTime.hpp"
58 #include "gc_implementation/shared/isGCActiveMark.hpp"
59 #include "memory/allocation.hpp"
60 #include "memory/gcLocker.inline.hpp"
61 #include "memory/generationSpec.hpp"
62 #include "memory/iterator.hpp"
63 #include "memory/referenceProcessor.hpp"
64 #include "oops/oop.inline.hpp"
65 #include "oops/oop.pcgc.inline.hpp"
66 #include "runtime/orderAccess.inline.hpp"
67 #include "runtime/vmThread.hpp"
69 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;
71 // turn it on so that the contents of the young list (scan-only /
72 // to-be-collected) are printed at "strategic" points before / during
73 // / after the collection --- this is useful for debugging
74 #define YOUNG_LIST_VERBOSE 0
75 // CURRENT STATUS
76 // This file is under construction. Search for "FIXME".
78 // INVARIANTS/NOTES
79 //
80 // All allocation activity covered by the G1CollectedHeap interface is
81 // serialized by acquiring the HeapLock. This happens in mem_allocate
82 // and allocate_new_tlab, which are the "entry" points to the
83 // allocation code from the rest of the JVM. (Note that this does not
84 // apply to TLAB allocation, which is not part of this interface: it
85 // is done by clients of this interface.)
87 // Notes on implementation of parallelism in different tasks.
88 //
89 // G1ParVerifyTask uses heap_region_par_iterate_chunked() for parallelism.
90 // The number of GC workers is passed to heap_region_par_iterate_chunked().
91 // It does use run_task() which sets _n_workers in the task.
92 // G1ParTask executes g1_process_roots() ->
93 // SharedHeap::process_roots() which calls eventually to
94 // CardTableModRefBS::par_non_clean_card_iterate_work() which uses
95 // SequentialSubTasksDone. SharedHeap::process_roots() also
96 // directly uses SubTasksDone (_process_strong_tasks field in SharedHeap).
97 //
99 // Local to this file.
101 class RefineCardTableEntryClosure: public CardTableEntryClosure {
102 bool _concurrent;
103 public:
104 RefineCardTableEntryClosure() : _concurrent(true) { }
106 bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
107 bool oops_into_cset = G1CollectedHeap::heap()->g1_rem_set()->refine_card(card_ptr, worker_i, false);
108 // This path is executed by the concurrent refine or mutator threads,
109 // concurrently, and so we do not care if card_ptr contains references
110 // that point into the collection set.
111 assert(!oops_into_cset, "should be");
113 if (_concurrent && SuspendibleThreadSet::should_yield()) {
114 // Caller will actually yield.
115 return false;
116 }
117 // Otherwise, we finished successfully; return true.
118 return true;
119 }
121 void set_concurrent(bool b) { _concurrent = b; }
122 };
125 class ClearLoggedCardTableEntryClosure: public CardTableEntryClosure {
126 size_t _num_processed;
127 CardTableModRefBS* _ctbs;
128 int _histo[256];
130 public:
131 ClearLoggedCardTableEntryClosure() :
132 _num_processed(0), _ctbs(G1CollectedHeap::heap()->g1_barrier_set())
133 {
134 for (int i = 0; i < 256; i++) _histo[i] = 0;
135 }
137 bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
138 unsigned char* ujb = (unsigned char*)card_ptr;
139 int ind = (int)(*ujb);
140 _histo[ind]++;
142 *card_ptr = (jbyte)CardTableModRefBS::clean_card_val();
143 _num_processed++;
145 return true;
146 }
148 size_t num_processed() { return _num_processed; }
150 void print_histo() {
151 gclog_or_tty->print_cr("Card table value histogram:");
152 for (int i = 0; i < 256; i++) {
153 if (_histo[i] != 0) {
154 gclog_or_tty->print_cr(" %d: %d", i, _histo[i]);
155 }
156 }
157 }
158 };
160 class RedirtyLoggedCardTableEntryClosure : public CardTableEntryClosure {
161 private:
162 size_t _num_processed;
164 public:
165 RedirtyLoggedCardTableEntryClosure() : CardTableEntryClosure(), _num_processed(0) { }
167 bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
168 *card_ptr = CardTableModRefBS::dirty_card_val();
169 _num_processed++;
170 return true;
171 }
173 size_t num_processed() const { return _num_processed; }
174 };
176 YoungList::YoungList(G1CollectedHeap* g1h) :
177 _g1h(g1h), _head(NULL), _length(0), _last_sampled_rs_lengths(0),
178 _survivor_head(NULL), _survivor_tail(NULL), _survivor_length(0) {
179 guarantee(check_list_empty(false), "just making sure...");
180 }
182 void YoungList::push_region(HeapRegion *hr) {
183 assert(!hr->is_young(), "should not already be young");
184 assert(hr->get_next_young_region() == NULL, "cause it should!");
186 hr->set_next_young_region(_head);
187 _head = hr;
189 _g1h->g1_policy()->set_region_eden(hr, (int) _length);
190 ++_length;
191 }
193 void YoungList::add_survivor_region(HeapRegion* hr) {
194 assert(hr->is_survivor(), "should be flagged as survivor region");
195 assert(hr->get_next_young_region() == NULL, "cause it should!");
197 hr->set_next_young_region(_survivor_head);
198 if (_survivor_head == NULL) {
199 _survivor_tail = hr;
200 }
201 _survivor_head = hr;
202 ++_survivor_length;
203 }
205 void YoungList::empty_list(HeapRegion* list) {
206 while (list != NULL) {
207 HeapRegion* next = list->get_next_young_region();
208 list->set_next_young_region(NULL);
209 list->uninstall_surv_rate_group();
210 list->set_not_young();
211 list = next;
212 }
213 }
215 void YoungList::empty_list() {
216 assert(check_list_well_formed(), "young list should be well formed");
218 empty_list(_head);
219 _head = NULL;
220 _length = 0;
222 empty_list(_survivor_head);
223 _survivor_head = NULL;
224 _survivor_tail = NULL;
225 _survivor_length = 0;
227 _last_sampled_rs_lengths = 0;
229 assert(check_list_empty(false), "just making sure...");
230 }
232 bool YoungList::check_list_well_formed() {
233 bool ret = true;
235 uint length = 0;
236 HeapRegion* curr = _head;
237 HeapRegion* last = NULL;
238 while (curr != NULL) {
239 if (!curr->is_young()) {
240 gclog_or_tty->print_cr("### YOUNG REGION "PTR_FORMAT"-"PTR_FORMAT" "
241 "incorrectly tagged (y: %d, surv: %d)",
242 curr->bottom(), curr->end(),
243 curr->is_young(), curr->is_survivor());
244 ret = false;
245 }
246 ++length;
247 last = curr;
248 curr = curr->get_next_young_region();
249 }
250 ret = ret && (length == _length);
252 if (!ret) {
253 gclog_or_tty->print_cr("### YOUNG LIST seems not well formed!");
254 gclog_or_tty->print_cr("### list has %u entries, _length is %u",
255 length, _length);
256 }
258 return ret;
259 }
261 bool YoungList::check_list_empty(bool check_sample) {
262 bool ret = true;
264 if (_length != 0) {
265 gclog_or_tty->print_cr("### YOUNG LIST should have 0 length, not %u",
266 _length);
267 ret = false;
268 }
269 if (check_sample && _last_sampled_rs_lengths != 0) {
270 gclog_or_tty->print_cr("### YOUNG LIST has non-zero last sampled RS lengths");
271 ret = false;
272 }
273 if (_head != NULL) {
274 gclog_or_tty->print_cr("### YOUNG LIST does not have a NULL head");
275 ret = false;
276 }
277 if (!ret) {
278 gclog_or_tty->print_cr("### YOUNG LIST does not seem empty");
279 }
281 return ret;
282 }
284 void
285 YoungList::rs_length_sampling_init() {
286 _sampled_rs_lengths = 0;
287 _curr = _head;
288 }
290 bool
291 YoungList::rs_length_sampling_more() {
292 return _curr != NULL;
293 }
295 void
296 YoungList::rs_length_sampling_next() {
297 assert( _curr != NULL, "invariant" );
298 size_t rs_length = _curr->rem_set()->occupied();
300 _sampled_rs_lengths += rs_length;
302 // The current region may not yet have been added to the
303 // incremental collection set (it gets added when it is
304 // retired as the current allocation region).
305 if (_curr->in_collection_set()) {
306 // Update the collection set policy information for this region
307 _g1h->g1_policy()->update_incremental_cset_info(_curr, rs_length);
308 }
310 _curr = _curr->get_next_young_region();
311 if (_curr == NULL) {
312 _last_sampled_rs_lengths = _sampled_rs_lengths;
313 // gclog_or_tty->print_cr("last sampled RS lengths = %d", _last_sampled_rs_lengths);
314 }
315 }
317 void
318 YoungList::reset_auxilary_lists() {
319 guarantee( is_empty(), "young list should be empty" );
320 assert(check_list_well_formed(), "young list should be well formed");
322 // Add survivor regions to SurvRateGroup.
323 _g1h->g1_policy()->note_start_adding_survivor_regions();
324 _g1h->g1_policy()->finished_recalculating_age_indexes(true /* is_survivors */);
326 int young_index_in_cset = 0;
327 for (HeapRegion* curr = _survivor_head;
328 curr != NULL;
329 curr = curr->get_next_young_region()) {
330 _g1h->g1_policy()->set_region_survivor(curr, young_index_in_cset);
332 // The region is a non-empty survivor so let's add it to
333 // the incremental collection set for the next evacuation
334 // pause.
335 _g1h->g1_policy()->add_region_to_incremental_cset_rhs(curr);
336 young_index_in_cset += 1;
337 }
338 assert((uint) young_index_in_cset == _survivor_length, "post-condition");
339 _g1h->g1_policy()->note_stop_adding_survivor_regions();
341 _head = _survivor_head;
342 _length = _survivor_length;
343 if (_survivor_head != NULL) {
344 assert(_survivor_tail != NULL, "cause it shouldn't be");
345 assert(_survivor_length > 0, "invariant");
346 _survivor_tail->set_next_young_region(NULL);
347 }
349 // Don't clear the survivor list handles until the start of
350 // the next evacuation pause - we need it in order to re-tag
351 // the survivor regions from this evacuation pause as 'young'
352 // at the start of the next.
354 _g1h->g1_policy()->finished_recalculating_age_indexes(false /* is_survivors */);
356 assert(check_list_well_formed(), "young list should be well formed");
357 }
359 void YoungList::print() {
360 HeapRegion* lists[] = {_head, _survivor_head};
361 const char* names[] = {"YOUNG", "SURVIVOR"};
363 for (unsigned int list = 0; list < ARRAY_SIZE(lists); ++list) {
364 gclog_or_tty->print_cr("%s LIST CONTENTS", names[list]);
365 HeapRegion *curr = lists[list];
366 if (curr == NULL)
367 gclog_or_tty->print_cr(" empty");
368 while (curr != NULL) {
369 gclog_or_tty->print_cr(" "HR_FORMAT", P: "PTR_FORMAT "N: "PTR_FORMAT", age: %4d",
370 HR_FORMAT_PARAMS(curr),
371 curr->prev_top_at_mark_start(),
372 curr->next_top_at_mark_start(),
373 curr->age_in_surv_rate_group_cond());
374 curr = curr->get_next_young_region();
375 }
376 }
378 gclog_or_tty->cr();
379 }
381 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) {
382 OtherRegionsTable::invalidate(start_idx, num_regions);
383 }
385 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions) {
386 reset_from_card_cache(start_idx, num_regions);
387 }
389 void G1CollectedHeap::push_dirty_cards_region(HeapRegion* hr)
390 {
391 // Claim the right to put the region on the dirty cards region list
392 // by installing a self pointer.
393 HeapRegion* next = hr->get_next_dirty_cards_region();
394 if (next == NULL) {
395 HeapRegion* res = (HeapRegion*)
396 Atomic::cmpxchg_ptr(hr, hr->next_dirty_cards_region_addr(),
397 NULL);
398 if (res == NULL) {
399 HeapRegion* head;
400 do {
401 // Put the region to the dirty cards region list.
402 head = _dirty_cards_region_list;
403 next = (HeapRegion*)
404 Atomic::cmpxchg_ptr(hr, &_dirty_cards_region_list, head);
405 if (next == head) {
406 assert(hr->get_next_dirty_cards_region() == hr,
407 "hr->get_next_dirty_cards_region() != hr");
408 if (next == NULL) {
409 // The last region in the list points to itself.
410 hr->set_next_dirty_cards_region(hr);
411 } else {
412 hr->set_next_dirty_cards_region(next);
413 }
414 }
415 } while (next != head);
416 }
417 }
418 }
420 HeapRegion* G1CollectedHeap::pop_dirty_cards_region()
421 {
422 HeapRegion* head;
423 HeapRegion* hr;
424 do {
425 head = _dirty_cards_region_list;
426 if (head == NULL) {
427 return NULL;
428 }
429 HeapRegion* new_head = head->get_next_dirty_cards_region();
430 if (head == new_head) {
431 // The last region.
432 new_head = NULL;
433 }
434 hr = (HeapRegion*)Atomic::cmpxchg_ptr(new_head, &_dirty_cards_region_list,
435 head);
436 } while (hr != head);
437 assert(hr != NULL, "invariant");
438 hr->set_next_dirty_cards_region(NULL);
439 return hr;
440 }
442 #ifdef ASSERT
443 // A region is added to the collection set as it is retired
444 // so an address p can point to a region which will be in the
445 // collection set but has not yet been retired. This method
446 // therefore is only accurate during a GC pause after all
447 // regions have been retired. It is used for debugging
448 // to check if an nmethod has references to objects that can
449 // be move during a partial collection. Though it can be
450 // inaccurate, it is sufficient for G1 because the conservative
451 // implementation of is_scavengable() for G1 will indicate that
452 // all nmethods must be scanned during a partial collection.
453 bool G1CollectedHeap::is_in_partial_collection(const void* p) {
454 if (p == NULL) {
455 return false;
456 }
457 return heap_region_containing(p)->in_collection_set();
458 }
459 #endif
461 // Returns true if the reference points to an object that
462 // can move in an incremental collection.
463 bool G1CollectedHeap::is_scavengable(const void* p) {
464 HeapRegion* hr = heap_region_containing(p);
465 return !hr->isHumongous();
466 }
468 void G1CollectedHeap::check_ct_logs_at_safepoint() {
469 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
470 CardTableModRefBS* ct_bs = g1_barrier_set();
472 // Count the dirty cards at the start.
473 CountNonCleanMemRegionClosure count1(this);
474 ct_bs->mod_card_iterate(&count1);
475 int orig_count = count1.n();
477 // First clear the logged cards.
478 ClearLoggedCardTableEntryClosure clear;
479 dcqs.apply_closure_to_all_completed_buffers(&clear);
480 dcqs.iterate_closure_all_threads(&clear, false);
481 clear.print_histo();
483 // Now ensure that there's no dirty cards.
484 CountNonCleanMemRegionClosure count2(this);
485 ct_bs->mod_card_iterate(&count2);
486 if (count2.n() != 0) {
487 gclog_or_tty->print_cr("Card table has %d entries; %d originally",
488 count2.n(), orig_count);
489 }
490 guarantee(count2.n() == 0, "Card table should be clean.");
492 RedirtyLoggedCardTableEntryClosure redirty;
493 dcqs.apply_closure_to_all_completed_buffers(&redirty);
494 dcqs.iterate_closure_all_threads(&redirty, false);
495 gclog_or_tty->print_cr("Log entries = %d, dirty cards = %d.",
496 clear.num_processed(), orig_count);
497 guarantee(redirty.num_processed() == clear.num_processed(),
498 err_msg("Redirtied "SIZE_FORMAT" cards, bug cleared "SIZE_FORMAT,
499 redirty.num_processed(), clear.num_processed()));
501 CountNonCleanMemRegionClosure count3(this);
502 ct_bs->mod_card_iterate(&count3);
503 if (count3.n() != orig_count) {
504 gclog_or_tty->print_cr("Should have restored them all: orig = %d, final = %d.",
505 orig_count, count3.n());
506 guarantee(count3.n() >= orig_count, "Should have restored them all.");
507 }
508 }
510 // Private class members.
512 G1CollectedHeap* G1CollectedHeap::_g1h;
514 // Private methods.
516 HeapRegion*
517 G1CollectedHeap::new_region_try_secondary_free_list(bool is_old) {
518 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
519 while (!_secondary_free_list.is_empty() || free_regions_coming()) {
520 if (!_secondary_free_list.is_empty()) {
521 if (G1ConcRegionFreeingVerbose) {
522 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
523 "secondary_free_list has %u entries",
524 _secondary_free_list.length());
525 }
526 // It looks as if there are free regions available on the
527 // secondary_free_list. Let's move them to the free_list and try
528 // again to allocate from it.
529 append_secondary_free_list();
531 assert(_hrm.num_free_regions() > 0, "if the secondary_free_list was not "
532 "empty we should have moved at least one entry to the free_list");
533 HeapRegion* res = _hrm.allocate_free_region(is_old);
534 if (G1ConcRegionFreeingVerbose) {
535 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
536 "allocated "HR_FORMAT" from secondary_free_list",
537 HR_FORMAT_PARAMS(res));
538 }
539 return res;
540 }
542 // Wait here until we get notified either when (a) there are no
543 // more free regions coming or (b) some regions have been moved on
544 // the secondary_free_list.
545 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
546 }
548 if (G1ConcRegionFreeingVerbose) {
549 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
550 "could not allocate from secondary_free_list");
551 }
552 return NULL;
553 }
555 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) {
556 assert(!isHumongous(word_size) || word_size <= HeapRegion::GrainWords,
557 "the only time we use this to allocate a humongous region is "
558 "when we are allocating a single humongous region");
560 HeapRegion* res;
561 if (G1StressConcRegionFreeing) {
562 if (!_secondary_free_list.is_empty()) {
563 if (G1ConcRegionFreeingVerbose) {
564 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
565 "forced to look at the secondary_free_list");
566 }
567 res = new_region_try_secondary_free_list(is_old);
568 if (res != NULL) {
569 return res;
570 }
571 }
572 }
574 res = _hrm.allocate_free_region(is_old);
576 if (res == NULL) {
577 if (G1ConcRegionFreeingVerbose) {
578 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
579 "res == NULL, trying the secondary_free_list");
580 }
581 res = new_region_try_secondary_free_list(is_old);
582 }
583 if (res == NULL && do_expand && _expand_heap_after_alloc_failure) {
584 // Currently, only attempts to allocate GC alloc regions set
585 // do_expand to true. So, we should only reach here during a
586 // safepoint. If this assumption changes we might have to
587 // reconsider the use of _expand_heap_after_alloc_failure.
588 assert(SafepointSynchronize::is_at_safepoint(), "invariant");
590 ergo_verbose1(ErgoHeapSizing,
591 "attempt heap expansion",
592 ergo_format_reason("region allocation request failed")
593 ergo_format_byte("allocation request"),
594 word_size * HeapWordSize);
595 if (expand(word_size * HeapWordSize)) {
596 // Given that expand() succeeded in expanding the heap, and we
597 // always expand the heap by an amount aligned to the heap
598 // region size, the free list should in theory not be empty.
599 // In either case allocate_free_region() will check for NULL.
600 res = _hrm.allocate_free_region(is_old);
601 } else {
602 _expand_heap_after_alloc_failure = false;
603 }
604 }
605 return res;
606 }
608 HeapWord*
609 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first,
610 uint num_regions,
611 size_t word_size) {
612 assert(first != G1_NO_HRM_INDEX, "pre-condition");
613 assert(isHumongous(word_size), "word_size should be humongous");
614 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
616 // Index of last region in the series + 1.
617 uint last = first + num_regions;
619 // We need to initialize the region(s) we just discovered. This is
620 // a bit tricky given that it can happen concurrently with
621 // refinement threads refining cards on these regions and
622 // potentially wanting to refine the BOT as they are scanning
623 // those cards (this can happen shortly after a cleanup; see CR
624 // 6991377). So we have to set up the region(s) carefully and in
625 // a specific order.
627 // The word size sum of all the regions we will allocate.
628 size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords;
629 assert(word_size <= word_size_sum, "sanity");
631 // This will be the "starts humongous" region.
632 HeapRegion* first_hr = region_at(first);
633 // The header of the new object will be placed at the bottom of
634 // the first region.
635 HeapWord* new_obj = first_hr->bottom();
636 // This will be the new end of the first region in the series that
637 // should also match the end of the last region in the series.
638 HeapWord* new_end = new_obj + word_size_sum;
639 // This will be the new top of the first region that will reflect
640 // this allocation.
641 HeapWord* new_top = new_obj + word_size;
643 // First, we need to zero the header of the space that we will be
644 // allocating. When we update top further down, some refinement
645 // threads might try to scan the region. By zeroing the header we
646 // ensure that any thread that will try to scan the region will
647 // come across the zero klass word and bail out.
648 //
649 // NOTE: It would not have been correct to have used
650 // CollectedHeap::fill_with_object() and make the space look like
651 // an int array. The thread that is doing the allocation will
652 // later update the object header to a potentially different array
653 // type and, for a very short period of time, the klass and length
654 // fields will be inconsistent. This could cause a refinement
655 // thread to calculate the object size incorrectly.
656 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
658 // We will set up the first region as "starts humongous". This
659 // will also update the BOT covering all the regions to reflect
660 // that there is a single object that starts at the bottom of the
661 // first region.
662 first_hr->set_startsHumongous(new_top, new_end);
664 // Then, if there are any, we will set up the "continues
665 // humongous" regions.
666 HeapRegion* hr = NULL;
667 for (uint i = first + 1; i < last; ++i) {
668 hr = region_at(i);
669 hr->set_continuesHumongous(first_hr);
670 }
671 // If we have "continues humongous" regions (hr != NULL), then the
672 // end of the last one should match new_end.
673 assert(hr == NULL || hr->end() == new_end, "sanity");
675 // Up to this point no concurrent thread would have been able to
676 // do any scanning on any region in this series. All the top
677 // fields still point to bottom, so the intersection between
678 // [bottom,top] and [card_start,card_end] will be empty. Before we
679 // update the top fields, we'll do a storestore to make sure that
680 // no thread sees the update to top before the zeroing of the
681 // object header and the BOT initialization.
682 OrderAccess::storestore();
684 // Now that the BOT and the object header have been initialized,
685 // we can update top of the "starts humongous" region.
686 assert(first_hr->bottom() < new_top && new_top <= first_hr->end(),
687 "new_top should be in this region");
688 first_hr->set_top(new_top);
689 if (_hr_printer.is_active()) {
690 HeapWord* bottom = first_hr->bottom();
691 HeapWord* end = first_hr->orig_end();
692 if ((first + 1) == last) {
693 // the series has a single humongous region
694 _hr_printer.alloc(G1HRPrinter::SingleHumongous, first_hr, new_top);
695 } else {
696 // the series has more than one humongous regions
697 _hr_printer.alloc(G1HRPrinter::StartsHumongous, first_hr, end);
698 }
699 }
701 // Now, we will update the top fields of the "continues humongous"
702 // regions. The reason we need to do this is that, otherwise,
703 // these regions would look empty and this will confuse parts of
704 // G1. For example, the code that looks for a consecutive number
705 // of empty regions will consider them empty and try to
706 // re-allocate them. We can extend is_empty() to also include
707 // !continuesHumongous(), but it is easier to just update the top
708 // fields here. The way we set top for all regions (i.e., top ==
709 // end for all regions but the last one, top == new_top for the
710 // last one) is actually used when we will free up the humongous
711 // region in free_humongous_region().
712 hr = NULL;
713 for (uint i = first + 1; i < last; ++i) {
714 hr = region_at(i);
715 if ((i + 1) == last) {
716 // last continues humongous region
717 assert(hr->bottom() < new_top && new_top <= hr->end(),
718 "new_top should fall on this region");
719 hr->set_top(new_top);
720 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, new_top);
721 } else {
722 // not last one
723 assert(new_top > hr->end(), "new_top should be above this region");
724 hr->set_top(hr->end());
725 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, hr->end());
726 }
727 }
728 // If we have continues humongous regions (hr != NULL), then the
729 // end of the last one should match new_end and its top should
730 // match new_top.
731 assert(hr == NULL ||
732 (hr->end() == new_end && hr->top() == new_top), "sanity");
733 check_bitmaps("Humongous Region Allocation", first_hr);
735 assert(first_hr->used() == word_size * HeapWordSize, "invariant");
736 _summary_bytes_used += first_hr->used();
737 _humongous_set.add(first_hr);
739 return new_obj;
740 }
742 // If could fit into free regions w/o expansion, try.
743 // Otherwise, if can expand, do so.
744 // Otherwise, if using ex regions might help, try with ex given back.
745 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size) {
746 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
748 verify_region_sets_optional();
750 uint first = G1_NO_HRM_INDEX;
751 uint obj_regions = (uint)(align_size_up_(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords);
753 if (obj_regions == 1) {
754 // Only one region to allocate, try to use a fast path by directly allocating
755 // from the free lists. Do not try to expand here, we will potentially do that
756 // later.
757 HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */);
758 if (hr != NULL) {
759 first = hr->hrm_index();
760 }
761 } else {
762 // We can't allocate humongous regions spanning more than one region while
763 // cleanupComplete() is running, since some of the regions we find to be
764 // empty might not yet be added to the free list. It is not straightforward
765 // to know in which list they are on so that we can remove them. We only
766 // need to do this if we need to allocate more than one region to satisfy the
767 // current humongous allocation request. If we are only allocating one region
768 // we use the one-region region allocation code (see above), that already
769 // potentially waits for regions from the secondary free list.
770 wait_while_free_regions_coming();
771 append_secondary_free_list_if_not_empty_with_lock();
773 // Policy: Try only empty regions (i.e. already committed first). Maybe we
774 // are lucky enough to find some.
775 first = _hrm.find_contiguous_only_empty(obj_regions);
776 if (first != G1_NO_HRM_INDEX) {
777 _hrm.allocate_free_regions_starting_at(first, obj_regions);
778 }
779 }
781 if (first == G1_NO_HRM_INDEX) {
782 // Policy: We could not find enough regions for the humongous object in the
783 // free list. Look through the heap to find a mix of free and uncommitted regions.
784 // If so, try expansion.
785 first = _hrm.find_contiguous_empty_or_unavailable(obj_regions);
786 if (first != G1_NO_HRM_INDEX) {
787 // We found something. Make sure these regions are committed, i.e. expand
788 // the heap. Alternatively we could do a defragmentation GC.
789 ergo_verbose1(ErgoHeapSizing,
790 "attempt heap expansion",
791 ergo_format_reason("humongous allocation request failed")
792 ergo_format_byte("allocation request"),
793 word_size * HeapWordSize);
795 _hrm.expand_at(first, obj_regions);
796 g1_policy()->record_new_heap_size(num_regions());
798 #ifdef ASSERT
799 for (uint i = first; i < first + obj_regions; ++i) {
800 HeapRegion* hr = region_at(i);
801 assert(hr->is_empty(), "sanity");
802 assert(is_on_master_free_list(hr), "sanity");
803 }
804 #endif
805 _hrm.allocate_free_regions_starting_at(first, obj_regions);
806 } else {
807 // Policy: Potentially trigger a defragmentation GC.
808 }
809 }
811 HeapWord* result = NULL;
812 if (first != G1_NO_HRM_INDEX) {
813 result = humongous_obj_allocate_initialize_regions(first, obj_regions, word_size);
814 assert(result != NULL, "it should always return a valid result");
816 // A successful humongous object allocation changes the used space
817 // information of the old generation so we need to recalculate the
818 // sizes and update the jstat counters here.
819 g1mm()->update_sizes();
820 }
822 verify_region_sets_optional();
824 return result;
825 }
827 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) {
828 assert_heap_not_locked_and_not_at_safepoint();
829 assert(!isHumongous(word_size), "we do not allow humongous TLABs");
831 unsigned int dummy_gc_count_before;
832 int dummy_gclocker_retry_count = 0;
833 return attempt_allocation(word_size, &dummy_gc_count_before, &dummy_gclocker_retry_count);
834 }
836 HeapWord*
837 G1CollectedHeap::mem_allocate(size_t word_size,
838 bool* gc_overhead_limit_was_exceeded) {
839 assert_heap_not_locked_and_not_at_safepoint();
841 // Loop until the allocation is satisfied, or unsatisfied after GC.
842 for (int try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
843 unsigned int gc_count_before;
845 HeapWord* result = NULL;
846 if (!isHumongous(word_size)) {
847 result = attempt_allocation(word_size, &gc_count_before, &gclocker_retry_count);
848 } else {
849 result = attempt_allocation_humongous(word_size, &gc_count_before, &gclocker_retry_count);
850 }
851 if (result != NULL) {
852 return result;
853 }
855 // Create the garbage collection operation...
856 VM_G1CollectForAllocation op(gc_count_before, word_size);
857 // ...and get the VM thread to execute it.
858 VMThread::execute(&op);
860 if (op.prologue_succeeded() && op.pause_succeeded()) {
861 // If the operation was successful we'll return the result even
862 // if it is NULL. If the allocation attempt failed immediately
863 // after a Full GC, it's unlikely we'll be able to allocate now.
864 HeapWord* result = op.result();
865 if (result != NULL && !isHumongous(word_size)) {
866 // Allocations that take place on VM operations do not do any
867 // card dirtying and we have to do it here. We only have to do
868 // this for non-humongous allocations, though.
869 dirty_young_block(result, word_size);
870 }
871 return result;
872 } else {
873 if (gclocker_retry_count > GCLockerRetryAllocationCount) {
874 return NULL;
875 }
876 assert(op.result() == NULL,
877 "the result should be NULL if the VM op did not succeed");
878 }
880 // Give a warning if we seem to be looping forever.
881 if ((QueuedAllocationWarningCount > 0) &&
882 (try_count % QueuedAllocationWarningCount == 0)) {
883 warning("G1CollectedHeap::mem_allocate retries %d times", try_count);
884 }
885 }
887 ShouldNotReachHere();
888 return NULL;
889 }
891 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size,
892 unsigned int *gc_count_before_ret,
893 int* gclocker_retry_count_ret) {
894 // Make sure you read the note in attempt_allocation_humongous().
896 assert_heap_not_locked_and_not_at_safepoint();
897 assert(!isHumongous(word_size), "attempt_allocation_slow() should not "
898 "be called for humongous allocation requests");
900 // We should only get here after the first-level allocation attempt
901 // (attempt_allocation()) failed to allocate.
903 // We will loop until a) we manage to successfully perform the
904 // allocation or b) we successfully schedule a collection which
905 // fails to perform the allocation. b) is the only case when we'll
906 // return NULL.
907 HeapWord* result = NULL;
908 for (int try_count = 1; /* we'll return */; try_count += 1) {
909 bool should_try_gc;
910 unsigned int gc_count_before;
912 {
913 MutexLockerEx x(Heap_lock);
915 result = _mutator_alloc_region.attempt_allocation_locked(word_size,
916 false /* bot_updates */);
917 if (result != NULL) {
918 return result;
919 }
921 // If we reach here, attempt_allocation_locked() above failed to
922 // allocate a new region. So the mutator alloc region should be NULL.
923 assert(_mutator_alloc_region.get() == NULL, "only way to get here");
925 if (GC_locker::is_active_and_needs_gc()) {
926 if (g1_policy()->can_expand_young_list()) {
927 // No need for an ergo verbose message here,
928 // can_expand_young_list() does this when it returns true.
929 result = _mutator_alloc_region.attempt_allocation_force(word_size,
930 false /* bot_updates */);
931 if (result != NULL) {
932 return result;
933 }
934 }
935 should_try_gc = false;
936 } else {
937 // The GCLocker may not be active but the GCLocker initiated
938 // GC may not yet have been performed (GCLocker::needs_gc()
939 // returns true). In this case we do not try this GC and
940 // wait until the GCLocker initiated GC is performed, and
941 // then retry the allocation.
942 if (GC_locker::needs_gc()) {
943 should_try_gc = false;
944 } else {
945 // Read the GC count while still holding the Heap_lock.
946 gc_count_before = total_collections();
947 should_try_gc = true;
948 }
949 }
950 }
952 if (should_try_gc) {
953 bool succeeded;
954 result = do_collection_pause(word_size, gc_count_before, &succeeded,
955 GCCause::_g1_inc_collection_pause);
956 if (result != NULL) {
957 assert(succeeded, "only way to get back a non-NULL result");
958 return result;
959 }
961 if (succeeded) {
962 // If we get here we successfully scheduled a collection which
963 // failed to allocate. No point in trying to allocate
964 // further. We'll just return NULL.
965 MutexLockerEx x(Heap_lock);
966 *gc_count_before_ret = total_collections();
967 return NULL;
968 }
969 } else {
970 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
971 MutexLockerEx x(Heap_lock);
972 *gc_count_before_ret = total_collections();
973 return NULL;
974 }
975 // The GCLocker is either active or the GCLocker initiated
976 // GC has not yet been performed. Stall until it is and
977 // then retry the allocation.
978 GC_locker::stall_until_clear();
979 (*gclocker_retry_count_ret) += 1;
980 }
982 // We can reach here if we were unsuccessful in scheduling a
983 // collection (because another thread beat us to it) or if we were
984 // stalled due to the GC locker. In either can we should retry the
985 // allocation attempt in case another thread successfully
986 // performed a collection and reclaimed enough space. We do the
987 // first attempt (without holding the Heap_lock) here and the
988 // follow-on attempt will be at the start of the next loop
989 // iteration (after taking the Heap_lock).
990 result = _mutator_alloc_region.attempt_allocation(word_size,
991 false /* bot_updates */);
992 if (result != NULL) {
993 return result;
994 }
996 // Give a warning if we seem to be looping forever.
997 if ((QueuedAllocationWarningCount > 0) &&
998 (try_count % QueuedAllocationWarningCount == 0)) {
999 warning("G1CollectedHeap::attempt_allocation_slow() "
1000 "retries %d times", try_count);
1001 }
1002 }
1004 ShouldNotReachHere();
1005 return NULL;
1006 }
1008 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size,
1009 unsigned int * gc_count_before_ret,
1010 int* gclocker_retry_count_ret) {
1011 // The structure of this method has a lot of similarities to
1012 // attempt_allocation_slow(). The reason these two were not merged
1013 // into a single one is that such a method would require several "if
1014 // allocation is not humongous do this, otherwise do that"
1015 // conditional paths which would obscure its flow. In fact, an early
1016 // version of this code did use a unified method which was harder to
1017 // follow and, as a result, it had subtle bugs that were hard to
1018 // track down. So keeping these two methods separate allows each to
1019 // be more readable. It will be good to keep these two in sync as
1020 // much as possible.
1022 assert_heap_not_locked_and_not_at_safepoint();
1023 assert(isHumongous(word_size), "attempt_allocation_humongous() "
1024 "should only be called for humongous allocations");
1026 // Humongous objects can exhaust the heap quickly, so we should check if we
1027 // need to start a marking cycle at each humongous object allocation. We do
1028 // the check before we do the actual allocation. The reason for doing it
1029 // before the allocation is that we avoid having to keep track of the newly
1030 // allocated memory while we do a GC.
1031 if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation",
1032 word_size)) {
1033 collect(GCCause::_g1_humongous_allocation);
1034 }
1036 // We will loop until a) we manage to successfully perform the
1037 // allocation or b) we successfully schedule a collection which
1038 // fails to perform the allocation. b) is the only case when we'll
1039 // return NULL.
1040 HeapWord* result = NULL;
1041 for (int try_count = 1; /* we'll return */; try_count += 1) {
1042 bool should_try_gc;
1043 unsigned int gc_count_before;
1045 {
1046 MutexLockerEx x(Heap_lock);
1048 // Given that humongous objects are not allocated in young
1049 // regions, we'll first try to do the allocation without doing a
1050 // collection hoping that there's enough space in the heap.
1051 result = humongous_obj_allocate(word_size);
1052 if (result != NULL) {
1053 return result;
1054 }
1056 if (GC_locker::is_active_and_needs_gc()) {
1057 should_try_gc = false;
1058 } else {
1059 // The GCLocker may not be active but the GCLocker initiated
1060 // GC may not yet have been performed (GCLocker::needs_gc()
1061 // returns true). In this case we do not try this GC and
1062 // wait until the GCLocker initiated GC is performed, and
1063 // then retry the allocation.
1064 if (GC_locker::needs_gc()) {
1065 should_try_gc = false;
1066 } else {
1067 // Read the GC count while still holding the Heap_lock.
1068 gc_count_before = total_collections();
1069 should_try_gc = true;
1070 }
1071 }
1072 }
1074 if (should_try_gc) {
1075 // If we failed to allocate the humongous object, we should try to
1076 // do a collection pause (if we're allowed) in case it reclaims
1077 // enough space for the allocation to succeed after the pause.
1079 bool succeeded;
1080 result = do_collection_pause(word_size, gc_count_before, &succeeded,
1081 GCCause::_g1_humongous_allocation);
1082 if (result != NULL) {
1083 assert(succeeded, "only way to get back a non-NULL result");
1084 return result;
1085 }
1087 if (succeeded) {
1088 // If we get here we successfully scheduled a collection which
1089 // failed to allocate. No point in trying to allocate
1090 // further. We'll just return NULL.
1091 MutexLockerEx x(Heap_lock);
1092 *gc_count_before_ret = total_collections();
1093 return NULL;
1094 }
1095 } else {
1096 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
1097 MutexLockerEx x(Heap_lock);
1098 *gc_count_before_ret = total_collections();
1099 return NULL;
1100 }
1101 // The GCLocker is either active or the GCLocker initiated
1102 // GC has not yet been performed. Stall until it is and
1103 // then retry the allocation.
1104 GC_locker::stall_until_clear();
1105 (*gclocker_retry_count_ret) += 1;
1106 }
1108 // We can reach here if we were unsuccessful in scheduling a
1109 // collection (because another thread beat us to it) or if we were
1110 // stalled due to the GC locker. In either can we should retry the
1111 // allocation attempt in case another thread successfully
1112 // performed a collection and reclaimed enough space. Give a
1113 // warning if we seem to be looping forever.
1115 if ((QueuedAllocationWarningCount > 0) &&
1116 (try_count % QueuedAllocationWarningCount == 0)) {
1117 warning("G1CollectedHeap::attempt_allocation_humongous() "
1118 "retries %d times", try_count);
1119 }
1120 }
1122 ShouldNotReachHere();
1123 return NULL;
1124 }
1126 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
1127 bool expect_null_mutator_alloc_region) {
1128 assert_at_safepoint(true /* should_be_vm_thread */);
1129 assert(_mutator_alloc_region.get() == NULL ||
1130 !expect_null_mutator_alloc_region,
1131 "the current alloc region was unexpectedly found to be non-NULL");
1133 if (!isHumongous(word_size)) {
1134 return _mutator_alloc_region.attempt_allocation_locked(word_size,
1135 false /* bot_updates */);
1136 } else {
1137 HeapWord* result = humongous_obj_allocate(word_size);
1138 if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) {
1139 g1_policy()->set_initiate_conc_mark_if_possible();
1140 }
1141 return result;
1142 }
1144 ShouldNotReachHere();
1145 }
1147 class PostMCRemSetClearClosure: public HeapRegionClosure {
1148 G1CollectedHeap* _g1h;
1149 ModRefBarrierSet* _mr_bs;
1150 public:
1151 PostMCRemSetClearClosure(G1CollectedHeap* g1h, ModRefBarrierSet* mr_bs) :
1152 _g1h(g1h), _mr_bs(mr_bs) {}
1154 bool doHeapRegion(HeapRegion* r) {
1155 HeapRegionRemSet* hrrs = r->rem_set();
1157 if (r->continuesHumongous()) {
1158 // We'll assert that the strong code root list and RSet is empty
1159 assert(hrrs->strong_code_roots_list_length() == 0, "sanity");
1160 assert(hrrs->occupied() == 0, "RSet should be empty");
1161 return false;
1162 }
1164 _g1h->reset_gc_time_stamps(r);
1165 hrrs->clear();
1166 // You might think here that we could clear just the cards
1167 // corresponding to the used region. But no: if we leave a dirty card
1168 // in a region we might allocate into, then it would prevent that card
1169 // from being enqueued, and cause it to be missed.
1170 // Re: the performance cost: we shouldn't be doing full GC anyway!
1171 _mr_bs->clear(MemRegion(r->bottom(), r->end()));
1173 return false;
1174 }
1175 };
1177 void G1CollectedHeap::clear_rsets_post_compaction() {
1178 PostMCRemSetClearClosure rs_clear(this, g1_barrier_set());
1179 heap_region_iterate(&rs_clear);
1180 }
1182 class RebuildRSOutOfRegionClosure: public HeapRegionClosure {
1183 G1CollectedHeap* _g1h;
1184 UpdateRSOopClosure _cl;
1185 int _worker_i;
1186 public:
1187 RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, int worker_i = 0) :
1188 _cl(g1->g1_rem_set(), worker_i),
1189 _worker_i(worker_i),
1190 _g1h(g1)
1191 { }
1193 bool doHeapRegion(HeapRegion* r) {
1194 if (!r->continuesHumongous()) {
1195 _cl.set_from(r);
1196 r->oop_iterate(&_cl);
1197 }
1198 return false;
1199 }
1200 };
1202 class ParRebuildRSTask: public AbstractGangTask {
1203 G1CollectedHeap* _g1;
1204 public:
1205 ParRebuildRSTask(G1CollectedHeap* g1)
1206 : AbstractGangTask("ParRebuildRSTask"),
1207 _g1(g1)
1208 { }
1210 void work(uint worker_id) {
1211 RebuildRSOutOfRegionClosure rebuild_rs(_g1, worker_id);
1212 _g1->heap_region_par_iterate_chunked(&rebuild_rs, worker_id,
1213 _g1->workers()->active_workers(),
1214 HeapRegion::RebuildRSClaimValue);
1215 }
1216 };
1218 class PostCompactionPrinterClosure: public HeapRegionClosure {
1219 private:
1220 G1HRPrinter* _hr_printer;
1221 public:
1222 bool doHeapRegion(HeapRegion* hr) {
1223 assert(!hr->is_young(), "not expecting to find young regions");
1224 // We only generate output for non-empty regions.
1225 if (!hr->is_empty()) {
1226 if (!hr->isHumongous()) {
1227 _hr_printer->post_compaction(hr, G1HRPrinter::Old);
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 {
1236 assert(hr->continuesHumongous(), "only way to get here");
1237 _hr_printer->post_compaction(hr, G1HRPrinter::ContinuesHumongous);
1238 }
1239 }
1240 return false;
1241 }
1243 PostCompactionPrinterClosure(G1HRPrinter* hr_printer)
1244 : _hr_printer(hr_printer) { }
1245 };
1247 void G1CollectedHeap::print_hrm_post_compaction() {
1248 PostCompactionPrinterClosure cl(hr_printer());
1249 heap_region_iterate(&cl);
1250 }
1252 bool G1CollectedHeap::do_collection(bool explicit_gc,
1253 bool clear_all_soft_refs,
1254 size_t word_size) {
1255 assert_at_safepoint(true /* should_be_vm_thread */);
1257 if (GC_locker::check_active_before_gc()) {
1258 return false;
1259 }
1261 STWGCTimer* gc_timer = G1MarkSweep::gc_timer();
1262 gc_timer->register_gc_start();
1264 SerialOldTracer* gc_tracer = G1MarkSweep::gc_tracer();
1265 gc_tracer->report_gc_start(gc_cause(), gc_timer->gc_start());
1267 SvcGCMarker sgcm(SvcGCMarker::FULL);
1268 ResourceMark rm;
1270 print_heap_before_gc();
1271 trace_heap_before_gc(gc_tracer);
1273 size_t metadata_prev_used = MetaspaceAux::used_bytes();
1275 verify_region_sets_optional();
1277 const bool do_clear_all_soft_refs = clear_all_soft_refs ||
1278 collector_policy()->should_clear_all_soft_refs();
1280 ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy());
1282 {
1283 IsGCActiveMark x;
1285 // Timing
1286 assert(gc_cause() != GCCause::_java_lang_system_gc || explicit_gc, "invariant");
1287 gclog_or_tty->date_stamp(G1Log::fine() && PrintGCDateStamps);
1288 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
1290 {
1291 GCTraceTime t(GCCauseString("Full GC", gc_cause()), G1Log::fine(), true, NULL, gc_tracer->gc_id());
1292 TraceCollectorStats tcs(g1mm()->full_collection_counters());
1293 TraceMemoryManagerStats tms(true /* fullGC */, gc_cause());
1295 double start = os::elapsedTime();
1296 g1_policy()->record_full_collection_start();
1298 // Note: When we have a more flexible GC logging framework that
1299 // allows us to add optional attributes to a GC log record we
1300 // could consider timing and reporting how long we wait in the
1301 // following two methods.
1302 wait_while_free_regions_coming();
1303 // If we start the compaction before the CM threads finish
1304 // scanning the root regions we might trip them over as we'll
1305 // be moving objects / updating references. So let's wait until
1306 // they are done. By telling them to abort, they should complete
1307 // early.
1308 _cm->root_regions()->abort();
1309 _cm->root_regions()->wait_until_scan_finished();
1310 append_secondary_free_list_if_not_empty_with_lock();
1312 gc_prologue(true);
1313 increment_total_collections(true /* full gc */);
1314 increment_old_marking_cycles_started();
1316 assert(used() == recalculate_used(), "Should be equal");
1318 verify_before_gc();
1320 check_bitmaps("Full GC Start");
1321 pre_full_gc_dump(gc_timer);
1323 COMPILER2_PRESENT(DerivedPointerTable::clear());
1325 // Disable discovery and empty the discovered lists
1326 // for the CM ref processor.
1327 ref_processor_cm()->disable_discovery();
1328 ref_processor_cm()->abandon_partial_discovery();
1329 ref_processor_cm()->verify_no_references_recorded();
1331 // Abandon current iterations of concurrent marking and concurrent
1332 // refinement, if any are in progress. We have to do this before
1333 // wait_until_scan_finished() below.
1334 concurrent_mark()->abort();
1336 // Make sure we'll choose a new allocation region afterwards.
1337 release_mutator_alloc_region();
1338 abandon_gc_alloc_regions();
1339 g1_rem_set()->cleanupHRRS();
1341 // We should call this after we retire any currently active alloc
1342 // regions so that all the ALLOC / RETIRE events are generated
1343 // before the start GC event.
1344 _hr_printer.start_gc(true /* full */, (size_t) total_collections());
1346 // We may have added regions to the current incremental collection
1347 // set between the last GC or pause and now. We need to clear the
1348 // incremental collection set and then start rebuilding it afresh
1349 // after this full GC.
1350 abandon_collection_set(g1_policy()->inc_cset_head());
1351 g1_policy()->clear_incremental_cset();
1352 g1_policy()->stop_incremental_cset_building();
1354 tear_down_region_sets(false /* free_list_only */);
1355 g1_policy()->set_gcs_are_young(true);
1357 // See the comments in g1CollectedHeap.hpp and
1358 // G1CollectedHeap::ref_processing_init() about
1359 // how reference processing currently works in G1.
1361 // Temporarily make discovery by the STW ref processor single threaded (non-MT).
1362 ReferenceProcessorMTDiscoveryMutator stw_rp_disc_ser(ref_processor_stw(), false);
1364 // Temporarily clear the STW ref processor's _is_alive_non_header field.
1365 ReferenceProcessorIsAliveMutator stw_rp_is_alive_null(ref_processor_stw(), NULL);
1367 ref_processor_stw()->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/);
1368 ref_processor_stw()->setup_policy(do_clear_all_soft_refs);
1370 // Do collection work
1371 {
1372 HandleMark hm; // Discard invalid handles created during gc
1373 G1MarkSweep::invoke_at_safepoint(ref_processor_stw(), do_clear_all_soft_refs);
1374 }
1376 assert(num_free_regions() == 0, "we should not have added any free regions");
1377 rebuild_region_sets(false /* free_list_only */);
1379 // Enqueue any discovered reference objects that have
1380 // not been removed from the discovered lists.
1381 ref_processor_stw()->enqueue_discovered_references();
1383 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
1385 MemoryService::track_memory_usage();
1387 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
1388 ref_processor_stw()->verify_no_references_recorded();
1390 // Delete metaspaces for unloaded class loaders and clean up loader_data graph
1391 ClassLoaderDataGraph::purge();
1392 MetaspaceAux::verify_metrics();
1394 // Note: since we've just done a full GC, concurrent
1395 // marking is no longer active. Therefore we need not
1396 // re-enable reference discovery for the CM ref processor.
1397 // That will be done at the start of the next marking cycle.
1398 assert(!ref_processor_cm()->discovery_enabled(), "Postcondition");
1399 ref_processor_cm()->verify_no_references_recorded();
1401 reset_gc_time_stamp();
1402 // Since everything potentially moved, we will clear all remembered
1403 // sets, and clear all cards. Later we will rebuild remembered
1404 // sets. We will also reset the GC time stamps of the regions.
1405 clear_rsets_post_compaction();
1406 check_gc_time_stamps();
1408 // Resize the heap if necessary.
1409 resize_if_necessary_after_full_collection(explicit_gc ? 0 : word_size);
1411 if (_hr_printer.is_active()) {
1412 // We should do this after we potentially resize the heap so
1413 // that all the COMMIT / UNCOMMIT events are generated before
1414 // the end GC event.
1416 print_hrm_post_compaction();
1417 _hr_printer.end_gc(true /* full */, (size_t) total_collections());
1418 }
1420 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
1421 if (hot_card_cache->use_cache()) {
1422 hot_card_cache->reset_card_counts();
1423 hot_card_cache->reset_hot_cache();
1424 }
1426 // Rebuild remembered sets of all regions.
1427 if (G1CollectedHeap::use_parallel_gc_threads()) {
1428 uint n_workers =
1429 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
1430 workers()->active_workers(),
1431 Threads::number_of_non_daemon_threads());
1432 assert(UseDynamicNumberOfGCThreads ||
1433 n_workers == workers()->total_workers(),
1434 "If not dynamic should be using all the workers");
1435 workers()->set_active_workers(n_workers);
1436 // Set parallel threads in the heap (_n_par_threads) only
1437 // before a parallel phase and always reset it to 0 after
1438 // the phase so that the number of parallel threads does
1439 // no get carried forward to a serial phase where there
1440 // may be code that is "possibly_parallel".
1441 set_par_threads(n_workers);
1443 ParRebuildRSTask rebuild_rs_task(this);
1444 assert(check_heap_region_claim_values(
1445 HeapRegion::InitialClaimValue), "sanity check");
1446 assert(UseDynamicNumberOfGCThreads ||
1447 workers()->active_workers() == workers()->total_workers(),
1448 "Unless dynamic should use total workers");
1449 // Use the most recent number of active workers
1450 assert(workers()->active_workers() > 0,
1451 "Active workers not properly set");
1452 set_par_threads(workers()->active_workers());
1453 workers()->run_task(&rebuild_rs_task);
1454 set_par_threads(0);
1455 assert(check_heap_region_claim_values(
1456 HeapRegion::RebuildRSClaimValue), "sanity check");
1457 reset_heap_region_claim_values();
1458 } else {
1459 RebuildRSOutOfRegionClosure rebuild_rs(this);
1460 heap_region_iterate(&rebuild_rs);
1461 }
1463 // Rebuild the strong code root lists for each region
1464 rebuild_strong_code_roots();
1466 if (true) { // FIXME
1467 MetaspaceGC::compute_new_size();
1468 }
1470 #ifdef TRACESPINNING
1471 ParallelTaskTerminator::print_termination_counts();
1472 #endif
1474 // Discard all rset updates
1475 JavaThread::dirty_card_queue_set().abandon_logs();
1476 assert(!G1DeferredRSUpdate
1477 || (G1DeferredRSUpdate &&
1478 (dirty_card_queue_set().completed_buffers_num() == 0)), "Should not be any");
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 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 bool* succeeded) {
1649 assert_at_safepoint(true /* should_be_vm_thread */);
1651 *succeeded = true;
1652 // Let's attempt the allocation first.
1653 HeapWord* result =
1654 attempt_allocation_at_safepoint(word_size,
1655 false /* expect_null_mutator_alloc_region */);
1656 if (result != NULL) {
1657 assert(*succeeded, "sanity");
1658 return result;
1659 }
1661 // In a G1 heap, we're supposed to keep allocation from failing by
1662 // incremental pauses. Therefore, at least for now, we'll favor
1663 // expansion over collection. (This might change in the future if we can
1664 // do something smarter than full collection to satisfy a failed alloc.)
1665 result = expand_and_allocate(word_size);
1666 if (result != NULL) {
1667 assert(*succeeded, "sanity");
1668 return result;
1669 }
1671 // Expansion didn't work, we'll try to do a Full GC.
1672 bool gc_succeeded = do_collection(false, /* explicit_gc */
1673 false, /* clear_all_soft_refs */
1674 word_size);
1675 if (!gc_succeeded) {
1676 *succeeded = false;
1677 return NULL;
1678 }
1680 // Retry the allocation
1681 result = attempt_allocation_at_safepoint(word_size,
1682 true /* expect_null_mutator_alloc_region */);
1683 if (result != NULL) {
1684 assert(*succeeded, "sanity");
1685 return result;
1686 }
1688 // Then, try a Full GC that will collect all soft references.
1689 gc_succeeded = do_collection(false, /* explicit_gc */
1690 true, /* clear_all_soft_refs */
1691 word_size);
1692 if (!gc_succeeded) {
1693 *succeeded = false;
1694 return NULL;
1695 }
1697 // Retry the allocation once more
1698 result = attempt_allocation_at_safepoint(word_size,
1699 true /* expect_null_mutator_alloc_region */);
1700 if (result != NULL) {
1701 assert(*succeeded, "sanity");
1702 return result;
1703 }
1705 assert(!collector_policy()->should_clear_all_soft_refs(),
1706 "Flag should have been handled and cleared prior to this point");
1708 // What else? We might try synchronous finalization later. If the total
1709 // space available is large enough for the allocation, then a more
1710 // complete compaction phase than we've tried so far might be
1711 // appropriate.
1712 assert(*succeeded, "sanity");
1713 return NULL;
1714 }
1716 // Attempting to expand the heap sufficiently
1717 // to support an allocation of the given "word_size". If
1718 // successful, perform the allocation and return the address of the
1719 // allocated block, or else "NULL".
1721 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size) {
1722 assert_at_safepoint(true /* should_be_vm_thread */);
1724 verify_region_sets_optional();
1726 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
1727 ergo_verbose1(ErgoHeapSizing,
1728 "attempt heap expansion",
1729 ergo_format_reason("allocation request failed")
1730 ergo_format_byte("allocation request"),
1731 word_size * HeapWordSize);
1732 if (expand(expand_bytes)) {
1733 _hrm.verify_optional();
1734 verify_region_sets_optional();
1735 return attempt_allocation_at_safepoint(word_size,
1736 false /* expect_null_mutator_alloc_region */);
1737 }
1738 return NULL;
1739 }
1741 bool G1CollectedHeap::expand(size_t expand_bytes) {
1742 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
1743 aligned_expand_bytes = align_size_up(aligned_expand_bytes,
1744 HeapRegion::GrainBytes);
1745 ergo_verbose2(ErgoHeapSizing,
1746 "expand the heap",
1747 ergo_format_byte("requested expansion amount")
1748 ergo_format_byte("attempted expansion amount"),
1749 expand_bytes, aligned_expand_bytes);
1751 if (is_maximal_no_gc()) {
1752 ergo_verbose0(ErgoHeapSizing,
1753 "did not expand the heap",
1754 ergo_format_reason("heap already fully expanded"));
1755 return false;
1756 }
1758 uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes);
1759 assert(regions_to_expand > 0, "Must expand by at least one region");
1761 uint expanded_by = _hrm.expand_by(regions_to_expand);
1763 if (expanded_by > 0) {
1764 size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes;
1765 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
1766 g1_policy()->record_new_heap_size(num_regions());
1767 } else {
1768 ergo_verbose0(ErgoHeapSizing,
1769 "did not expand the heap",
1770 ergo_format_reason("heap expansion operation failed"));
1771 // The expansion of the virtual storage space was unsuccessful.
1772 // Let's see if it was because we ran out of swap.
1773 if (G1ExitOnExpansionFailure &&
1774 _hrm.available() >= regions_to_expand) {
1775 // We had head room...
1776 vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion");
1777 }
1778 }
1779 return regions_to_expand > 0;
1780 }
1782 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
1783 size_t aligned_shrink_bytes =
1784 ReservedSpace::page_align_size_down(shrink_bytes);
1785 aligned_shrink_bytes = align_size_down(aligned_shrink_bytes,
1786 HeapRegion::GrainBytes);
1787 uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes);
1789 uint num_regions_removed = _hrm.shrink_by(num_regions_to_remove);
1790 size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes;
1792 ergo_verbose3(ErgoHeapSizing,
1793 "shrink the heap",
1794 ergo_format_byte("requested shrinking amount")
1795 ergo_format_byte("aligned shrinking amount")
1796 ergo_format_byte("attempted shrinking amount"),
1797 shrink_bytes, aligned_shrink_bytes, shrunk_bytes);
1798 if (num_regions_removed > 0) {
1799 g1_policy()->record_new_heap_size(num_regions());
1800 } else {
1801 ergo_verbose0(ErgoHeapSizing,
1802 "did not shrink the heap",
1803 ergo_format_reason("heap shrinking operation failed"));
1804 }
1805 }
1807 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1808 verify_region_sets_optional();
1810 // We should only reach here at the end of a Full GC which means we
1811 // should not not be holding to any GC alloc regions. The method
1812 // below will make sure of that and do any remaining clean up.
1813 abandon_gc_alloc_regions();
1815 // Instead of tearing down / rebuilding the free lists here, we
1816 // could instead use the remove_all_pending() method on free_list to
1817 // remove only the ones that we need to remove.
1818 tear_down_region_sets(true /* free_list_only */);
1819 shrink_helper(shrink_bytes);
1820 rebuild_region_sets(true /* free_list_only */);
1822 _hrm.verify_optional();
1823 verify_region_sets_optional();
1824 }
1826 // Public methods.
1828 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away
1829 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
1830 #endif // _MSC_VER
1833 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* policy_) :
1834 SharedHeap(policy_),
1835 _g1_policy(policy_),
1836 _dirty_card_queue_set(false),
1837 _into_cset_dirty_card_queue_set(false),
1838 _is_alive_closure_cm(this),
1839 _is_alive_closure_stw(this),
1840 _ref_processor_cm(NULL),
1841 _ref_processor_stw(NULL),
1842 _process_strong_tasks(new SubTasksDone(G1H_PS_NumElements)),
1843 _bot_shared(NULL),
1844 _evac_failure_scan_stack(NULL),
1845 _mark_in_progress(false),
1846 _cg1r(NULL), _summary_bytes_used(0),
1847 _g1mm(NULL),
1848 _refine_cte_cl(NULL),
1849 _full_collection(false),
1850 _secondary_free_list("Secondary Free List", new SecondaryFreeRegionListMtSafeChecker()),
1851 _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()),
1852 _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()),
1853 _humongous_is_live(),
1854 _has_humongous_reclaim_candidates(false),
1855 _free_regions_coming(false),
1856 _young_list(new YoungList(this)),
1857 _gc_time_stamp(0),
1858 _retained_old_gc_alloc_region(NULL),
1859 _survivor_plab_stats(YoungPLABSize, PLABWeight),
1860 _old_plab_stats(OldPLABSize, PLABWeight),
1861 _expand_heap_after_alloc_failure(true),
1862 _surviving_young_words(NULL),
1863 _old_marking_cycles_started(0),
1864 _old_marking_cycles_completed(0),
1865 _concurrent_cycle_started(false),
1866 _in_cset_fast_test(),
1867 _dirty_cards_region_list(NULL),
1868 _worker_cset_start_region(NULL),
1869 _worker_cset_start_region_time_stamp(NULL),
1870 _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()),
1871 _gc_timer_cm(new (ResourceObj::C_HEAP, mtGC) ConcurrentGCTimer()),
1872 _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()),
1873 _gc_tracer_cm(new (ResourceObj::C_HEAP, mtGC) G1OldTracer()) {
1875 _g1h = this;
1876 if (_process_strong_tasks == NULL || !_process_strong_tasks->valid()) {
1877 vm_exit_during_initialization("Failed necessary allocation.");
1878 }
1880 _humongous_object_threshold_in_words = HeapRegion::GrainWords / 2;
1882 int n_queues = MAX2((int)ParallelGCThreads, 1);
1883 _task_queues = new RefToScanQueueSet(n_queues);
1885 uint n_rem_sets = HeapRegionRemSet::num_par_rem_sets();
1886 assert(n_rem_sets > 0, "Invariant.");
1888 _worker_cset_start_region = NEW_C_HEAP_ARRAY(HeapRegion*, n_queues, mtGC);
1889 _worker_cset_start_region_time_stamp = NEW_C_HEAP_ARRAY(unsigned int, n_queues, mtGC);
1890 _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC);
1892 for (int i = 0; i < n_queues; i++) {
1893 RefToScanQueue* q = new RefToScanQueue();
1894 q->initialize();
1895 _task_queues->register_queue(i, q);
1896 ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo();
1897 }
1898 clear_cset_start_regions();
1900 // Initialize the G1EvacuationFailureALot counters and flags.
1901 NOT_PRODUCT(reset_evacuation_should_fail();)
1903 guarantee(_task_queues != NULL, "task_queues allocation failure.");
1904 }
1906 jint G1CollectedHeap::initialize() {
1907 CollectedHeap::pre_initialize();
1908 os::enable_vtime();
1910 G1Log::init();
1912 // Necessary to satisfy locking discipline assertions.
1914 MutexLocker x(Heap_lock);
1916 // We have to initialize the printer before committing the heap, as
1917 // it will be used then.
1918 _hr_printer.set_active(G1PrintHeapRegions);
1920 // While there are no constraints in the GC code that HeapWordSize
1921 // be any particular value, there are multiple other areas in the
1922 // system which believe this to be true (e.g. oop->object_size in some
1923 // cases incorrectly returns the size in wordSize units rather than
1924 // HeapWordSize).
1925 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
1927 size_t init_byte_size = collector_policy()->initial_heap_byte_size();
1928 size_t max_byte_size = collector_policy()->max_heap_byte_size();
1929 size_t heap_alignment = collector_policy()->heap_alignment();
1931 // Ensure that the sizes are properly aligned.
1932 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
1933 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
1934 Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap");
1936 _refine_cte_cl = new RefineCardTableEntryClosure();
1938 _cg1r = new ConcurrentG1Refine(this, _refine_cte_cl);
1940 // Reserve the maximum.
1942 // When compressed oops are enabled, the preferred heap base
1943 // is calculated by subtracting the requested size from the
1944 // 32Gb boundary and using the result as the base address for
1945 // heap reservation. If the requested size is not aligned to
1946 // HeapRegion::GrainBytes (i.e. the alignment that is passed
1947 // into the ReservedHeapSpace constructor) then the actual
1948 // base of the reserved heap may end up differing from the
1949 // address that was requested (i.e. the preferred heap base).
1950 // If this happens then we could end up using a non-optimal
1951 // compressed oops mode.
1953 ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size,
1954 heap_alignment);
1956 // It is important to do this in a way such that concurrent readers can't
1957 // temporarily think something is in the heap. (I've actually seen this
1958 // happen in asserts: DLD.)
1959 _reserved.set_word_size(0);
1960 _reserved.set_start((HeapWord*)heap_rs.base());
1961 _reserved.set_end((HeapWord*)(heap_rs.base() + heap_rs.size()));
1963 // Create the gen rem set (and barrier set) for the entire reserved region.
1964 _rem_set = collector_policy()->create_rem_set(_reserved, 2);
1965 set_barrier_set(rem_set()->bs());
1966 if (!barrier_set()->is_a(BarrierSet::G1SATBCTLogging)) {
1967 vm_exit_during_initialization("G1 requires a G1SATBLoggingCardTableModRefBS");
1968 return JNI_ENOMEM;
1969 }
1971 // Also create a G1 rem set.
1972 _g1_rem_set = new G1RemSet(this, g1_barrier_set());
1974 // Carve out the G1 part of the heap.
1976 ReservedSpace g1_rs = heap_rs.first_part(max_byte_size);
1977 G1RegionToSpaceMapper* heap_storage =
1978 G1RegionToSpaceMapper::create_mapper(g1_rs,
1979 UseLargePages ? os::large_page_size() : os::vm_page_size(),
1980 HeapRegion::GrainBytes,
1981 1,
1982 mtJavaHeap);
1983 heap_storage->set_mapping_changed_listener(&_listener);
1985 // Reserve space for the block offset table. We do not support automatic uncommit
1986 // for the card table at this time. BOT only.
1987 ReservedSpace bot_rs(G1BlockOffsetSharedArray::compute_size(g1_rs.size() / HeapWordSize));
1988 G1RegionToSpaceMapper* bot_storage =
1989 G1RegionToSpaceMapper::create_mapper(bot_rs,
1990 os::vm_page_size(),
1991 HeapRegion::GrainBytes,
1992 G1BlockOffsetSharedArray::N_bytes,
1993 mtGC);
1995 ReservedSpace cardtable_rs(G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize));
1996 G1RegionToSpaceMapper* cardtable_storage =
1997 G1RegionToSpaceMapper::create_mapper(cardtable_rs,
1998 os::vm_page_size(),
1999 HeapRegion::GrainBytes,
2000 G1BlockOffsetSharedArray::N_bytes,
2001 mtGC);
2003 // Reserve space for the card counts table.
2004 ReservedSpace card_counts_rs(G1BlockOffsetSharedArray::compute_size(g1_rs.size() / HeapWordSize));
2005 G1RegionToSpaceMapper* card_counts_storage =
2006 G1RegionToSpaceMapper::create_mapper(card_counts_rs,
2007 os::vm_page_size(),
2008 HeapRegion::GrainBytes,
2009 G1BlockOffsetSharedArray::N_bytes,
2010 mtGC);
2012 // Reserve space for prev and next bitmap.
2013 size_t bitmap_size = CMBitMap::compute_size(g1_rs.size());
2015 ReservedSpace prev_bitmap_rs(ReservedSpace::allocation_align_size_up(bitmap_size));
2016 G1RegionToSpaceMapper* prev_bitmap_storage =
2017 G1RegionToSpaceMapper::create_mapper(prev_bitmap_rs,
2018 os::vm_page_size(),
2019 HeapRegion::GrainBytes,
2020 CMBitMap::mark_distance(),
2021 mtGC);
2023 ReservedSpace next_bitmap_rs(ReservedSpace::allocation_align_size_up(bitmap_size));
2024 G1RegionToSpaceMapper* next_bitmap_storage =
2025 G1RegionToSpaceMapper::create_mapper(next_bitmap_rs,
2026 os::vm_page_size(),
2027 HeapRegion::GrainBytes,
2028 CMBitMap::mark_distance(),
2029 mtGC);
2031 _hrm.initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage);
2032 g1_barrier_set()->initialize(cardtable_storage);
2033 // Do later initialization work for concurrent refinement.
2034 _cg1r->init(card_counts_storage);
2036 // 6843694 - ensure that the maximum region index can fit
2037 // in the remembered set structures.
2038 const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
2039 guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
2041 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
2042 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
2043 guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
2044 "too many cards per region");
2046 FreeRegionList::set_unrealistically_long_length(max_regions() + 1);
2048 _bot_shared = new G1BlockOffsetSharedArray(_reserved, bot_storage);
2050 _g1h = this;
2052 _in_cset_fast_test.initialize(_hrm.reserved().start(), _hrm.reserved().end(), HeapRegion::GrainBytes);
2053 _humongous_is_live.initialize(_hrm.reserved().start(), _hrm.reserved().end(), HeapRegion::GrainBytes);
2055 // Create the ConcurrentMark data structure and thread.
2056 // (Must do this late, so that "max_regions" is defined.)
2057 _cm = new ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage);
2058 if (_cm == NULL || !_cm->completed_initialization()) {
2059 vm_shutdown_during_initialization("Could not create/initialize ConcurrentMark");
2060 return JNI_ENOMEM;
2061 }
2062 _cmThread = _cm->cmThread();
2064 // Initialize the from_card cache structure of HeapRegionRemSet.
2065 HeapRegionRemSet::init_heap(max_regions());
2067 // Now expand into the initial heap size.
2068 if (!expand(init_byte_size)) {
2069 vm_shutdown_during_initialization("Failed to allocate initial heap.");
2070 return JNI_ENOMEM;
2071 }
2073 // Perform any initialization actions delegated to the policy.
2074 g1_policy()->init();
2076 JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon,
2077 SATB_Q_FL_lock,
2078 G1SATBProcessCompletedThreshold,
2079 Shared_SATB_Q_lock);
2081 JavaThread::dirty_card_queue_set().initialize(_refine_cte_cl,
2082 DirtyCardQ_CBL_mon,
2083 DirtyCardQ_FL_lock,
2084 concurrent_g1_refine()->yellow_zone(),
2085 concurrent_g1_refine()->red_zone(),
2086 Shared_DirtyCardQ_lock);
2088 if (G1DeferredRSUpdate) {
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());
2096 }
2098 // Initialize the card queue set used to hold cards containing
2099 // references into the collection set.
2100 _into_cset_dirty_card_queue_set.initialize(NULL, // Should never be called by the Java code
2101 DirtyCardQ_CBL_mon,
2102 DirtyCardQ_FL_lock,
2103 -1, // never trigger processing
2104 -1, // no limit on length
2105 Shared_DirtyCardQ_lock,
2106 &JavaThread::dirty_card_queue_set());
2108 // In case we're keeping closure specialization stats, initialize those
2109 // counts and that mechanism.
2110 SpecializationStats::clear();
2112 // Here we allocate the dummy HeapRegion that is required by the
2113 // G1AllocRegion class.
2114 HeapRegion* dummy_region = _hrm.get_dummy_region();
2116 // We'll re-use the same region whether the alloc region will
2117 // require BOT updates or not and, if it doesn't, then a non-young
2118 // region will complain that it cannot support allocations without
2119 // BOT updates. So we'll tag the dummy region as young to avoid that.
2120 dummy_region->set_young();
2121 // Make sure it's full.
2122 dummy_region->set_top(dummy_region->end());
2123 G1AllocRegion::setup(this, dummy_region);
2125 init_mutator_alloc_region();
2127 // Do create of the monitoring and management support so that
2128 // values in the heap have been properly initialized.
2129 _g1mm = new G1MonitoringSupport(this);
2131 G1StringDedup::initialize();
2133 return JNI_OK;
2134 }
2136 void G1CollectedHeap::stop() {
2137 // Stop all concurrent threads. We do this to make sure these threads
2138 // do not continue to execute and access resources (e.g. gclog_or_tty)
2139 // that are destroyed during shutdown.
2140 _cg1r->stop();
2141 _cmThread->stop();
2142 if (G1StringDedup::is_enabled()) {
2143 G1StringDedup::stop();
2144 }
2145 }
2147 void G1CollectedHeap::clear_humongous_is_live_table() {
2148 guarantee(G1ReclaimDeadHumongousObjectsAtYoungGC, "Should only be called if true");
2149 _humongous_is_live.clear();
2150 }
2152 size_t G1CollectedHeap::conservative_max_heap_alignment() {
2153 return HeapRegion::max_region_size();
2154 }
2156 void G1CollectedHeap::ref_processing_init() {
2157 // Reference processing in G1 currently works as follows:
2158 //
2159 // * There are two reference processor instances. One is
2160 // used to record and process discovered references
2161 // during concurrent marking; the other is used to
2162 // record and process references during STW pauses
2163 // (both full and incremental).
2164 // * Both ref processors need to 'span' the entire heap as
2165 // the regions in the collection set may be dotted around.
2166 //
2167 // * For the concurrent marking ref processor:
2168 // * Reference discovery is enabled at initial marking.
2169 // * Reference discovery is disabled and the discovered
2170 // references processed etc during remarking.
2171 // * Reference discovery is MT (see below).
2172 // * Reference discovery requires a barrier (see below).
2173 // * Reference processing may or may not be MT
2174 // (depending on the value of ParallelRefProcEnabled
2175 // and ParallelGCThreads).
2176 // * A full GC disables reference discovery by the CM
2177 // ref processor and abandons any entries on it's
2178 // discovered lists.
2179 //
2180 // * For the STW processor:
2181 // * Non MT discovery is enabled at the start of a full GC.
2182 // * Processing and enqueueing during a full GC is non-MT.
2183 // * During a full GC, references are processed after marking.
2184 //
2185 // * Discovery (may or may not be MT) is enabled at the start
2186 // of an incremental evacuation pause.
2187 // * References are processed near the end of a STW evacuation pause.
2188 // * For both types of GC:
2189 // * Discovery is atomic - i.e. not concurrent.
2190 // * Reference discovery will not need a barrier.
2192 SharedHeap::ref_processing_init();
2193 MemRegion mr = reserved_region();
2195 // Concurrent Mark ref processor
2196 _ref_processor_cm =
2197 new ReferenceProcessor(mr, // span
2198 ParallelRefProcEnabled && (ParallelGCThreads > 1),
2199 // mt processing
2200 (int) ParallelGCThreads,
2201 // degree of mt processing
2202 (ParallelGCThreads > 1) || (ConcGCThreads > 1),
2203 // mt discovery
2204 (int) MAX2(ParallelGCThreads, ConcGCThreads),
2205 // degree of mt discovery
2206 false,
2207 // Reference discovery is not atomic
2208 &_is_alive_closure_cm);
2209 // is alive closure
2210 // (for efficiency/performance)
2212 // STW ref processor
2213 _ref_processor_stw =
2214 new ReferenceProcessor(mr, // span
2215 ParallelRefProcEnabled && (ParallelGCThreads > 1),
2216 // mt processing
2217 MAX2((int)ParallelGCThreads, 1),
2218 // degree of mt processing
2219 (ParallelGCThreads > 1),
2220 // mt discovery
2221 MAX2((int)ParallelGCThreads, 1),
2222 // degree of mt discovery
2223 true,
2224 // Reference discovery is atomic
2225 &_is_alive_closure_stw);
2226 // is alive closure
2227 // (for efficiency/performance)
2228 }
2230 size_t G1CollectedHeap::capacity() const {
2231 return _hrm.length() * HeapRegion::GrainBytes;
2232 }
2234 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) {
2235 assert(!hr->continuesHumongous(), "pre-condition");
2236 hr->reset_gc_time_stamp();
2237 if (hr->startsHumongous()) {
2238 uint first_index = hr->hrm_index() + 1;
2239 uint last_index = hr->last_hc_index();
2240 for (uint i = first_index; i < last_index; i += 1) {
2241 HeapRegion* chr = region_at(i);
2242 assert(chr->continuesHumongous(), "sanity");
2243 chr->reset_gc_time_stamp();
2244 }
2245 }
2246 }
2248 #ifndef PRODUCT
2249 class CheckGCTimeStampsHRClosure : public HeapRegionClosure {
2250 private:
2251 unsigned _gc_time_stamp;
2252 bool _failures;
2254 public:
2255 CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) :
2256 _gc_time_stamp(gc_time_stamp), _failures(false) { }
2258 virtual bool doHeapRegion(HeapRegion* hr) {
2259 unsigned region_gc_time_stamp = hr->get_gc_time_stamp();
2260 if (_gc_time_stamp != region_gc_time_stamp) {
2261 gclog_or_tty->print_cr("Region "HR_FORMAT" has GC time stamp = %d, "
2262 "expected %d", HR_FORMAT_PARAMS(hr),
2263 region_gc_time_stamp, _gc_time_stamp);
2264 _failures = true;
2265 }
2266 return false;
2267 }
2269 bool failures() { return _failures; }
2270 };
2272 void G1CollectedHeap::check_gc_time_stamps() {
2273 CheckGCTimeStampsHRClosure cl(_gc_time_stamp);
2274 heap_region_iterate(&cl);
2275 guarantee(!cl.failures(), "all GC time stamps should have been reset");
2276 }
2277 #endif // PRODUCT
2279 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl,
2280 DirtyCardQueue* into_cset_dcq,
2281 bool concurrent,
2282 uint worker_i) {
2283 // Clean cards in the hot card cache
2284 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
2285 hot_card_cache->drain(worker_i, g1_rem_set(), into_cset_dcq);
2287 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2288 int n_completed_buffers = 0;
2289 while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) {
2290 n_completed_buffers++;
2291 }
2292 g1_policy()->phase_times()->record_update_rs_processed_buffers(worker_i, n_completed_buffers);
2293 dcqs.clear_n_completed_buffers();
2294 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!");
2295 }
2298 // Computes the sum of the storage used by the various regions.
2300 size_t G1CollectedHeap::used() const {
2301 assert(Heap_lock->owner() != NULL,
2302 "Should be owned on this thread's behalf.");
2303 size_t result = _summary_bytes_used;
2304 // Read only once in case it is set to NULL concurrently
2305 HeapRegion* hr = _mutator_alloc_region.get();
2306 if (hr != NULL)
2307 result += hr->used();
2308 return result;
2309 }
2311 size_t G1CollectedHeap::used_unlocked() const {
2312 size_t result = _summary_bytes_used;
2313 return result;
2314 }
2316 class SumUsedClosure: public HeapRegionClosure {
2317 size_t _used;
2318 public:
2319 SumUsedClosure() : _used(0) {}
2320 bool doHeapRegion(HeapRegion* r) {
2321 if (!r->continuesHumongous()) {
2322 _used += r->used();
2323 }
2324 return false;
2325 }
2326 size_t result() { return _used; }
2327 };
2329 size_t G1CollectedHeap::recalculate_used() const {
2330 double recalculate_used_start = os::elapsedTime();
2332 SumUsedClosure blk;
2333 heap_region_iterate(&blk);
2335 g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0);
2336 return blk.result();
2337 }
2339 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
2340 switch (cause) {
2341 case GCCause::_gc_locker: return GCLockerInvokesConcurrent;
2342 case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent;
2343 case GCCause::_g1_humongous_allocation: return true;
2344 default: return false;
2345 }
2346 }
2348 #ifndef PRODUCT
2349 void G1CollectedHeap::allocate_dummy_regions() {
2350 // Let's fill up most of the region
2351 size_t word_size = HeapRegion::GrainWords - 1024;
2352 // And as a result the region we'll allocate will be humongous.
2353 guarantee(isHumongous(word_size), "sanity");
2355 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
2356 // Let's use the existing mechanism for the allocation
2357 HeapWord* dummy_obj = humongous_obj_allocate(word_size);
2358 if (dummy_obj != NULL) {
2359 MemRegion mr(dummy_obj, word_size);
2360 CollectedHeap::fill_with_object(mr);
2361 } else {
2362 // If we can't allocate once, we probably cannot allocate
2363 // again. Let's get out of the loop.
2364 break;
2365 }
2366 }
2367 }
2368 #endif // !PRODUCT
2370 void G1CollectedHeap::increment_old_marking_cycles_started() {
2371 assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
2372 _old_marking_cycles_started == _old_marking_cycles_completed + 1,
2373 err_msg("Wrong marking cycle count (started: %d, completed: %d)",
2374 _old_marking_cycles_started, _old_marking_cycles_completed));
2376 _old_marking_cycles_started++;
2377 }
2379 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) {
2380 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
2382 // We assume that if concurrent == true, then the caller is a
2383 // concurrent thread that was joined the Suspendible Thread
2384 // Set. If there's ever a cheap way to check this, we should add an
2385 // assert here.
2387 // Given that this method is called at the end of a Full GC or of a
2388 // concurrent cycle, and those can be nested (i.e., a Full GC can
2389 // interrupt a concurrent cycle), the number of full collections
2390 // completed should be either one (in the case where there was no
2391 // nesting) or two (when a Full GC interrupted a concurrent cycle)
2392 // behind the number of full collections started.
2394 // This is the case for the inner caller, i.e. a Full GC.
2395 assert(concurrent ||
2396 (_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
2397 (_old_marking_cycles_started == _old_marking_cycles_completed + 2),
2398 err_msg("for inner caller (Full GC): _old_marking_cycles_started = %u "
2399 "is inconsistent with _old_marking_cycles_completed = %u",
2400 _old_marking_cycles_started, _old_marking_cycles_completed));
2402 // This is the case for the outer caller, i.e. the concurrent cycle.
2403 assert(!concurrent ||
2404 (_old_marking_cycles_started == _old_marking_cycles_completed + 1),
2405 err_msg("for outer caller (concurrent cycle): "
2406 "_old_marking_cycles_started = %u "
2407 "is inconsistent with _old_marking_cycles_completed = %u",
2408 _old_marking_cycles_started, _old_marking_cycles_completed));
2410 _old_marking_cycles_completed += 1;
2412 // We need to clear the "in_progress" flag in the CM thread before
2413 // we wake up any waiters (especially when ExplicitInvokesConcurrent
2414 // is set) so that if a waiter requests another System.gc() it doesn't
2415 // incorrectly see that a marking cycle is still in progress.
2416 if (concurrent) {
2417 _cmThread->clear_in_progress();
2418 }
2420 // This notify_all() will ensure that a thread that called
2421 // System.gc() with (with ExplicitGCInvokesConcurrent set or not)
2422 // and it's waiting for a full GC to finish will be woken up. It is
2423 // waiting in VM_G1IncCollectionPause::doit_epilogue().
2424 FullGCCount_lock->notify_all();
2425 }
2427 void G1CollectedHeap::register_concurrent_cycle_start(const Ticks& start_time) {
2428 _concurrent_cycle_started = true;
2429 _gc_timer_cm->register_gc_start(start_time);
2431 _gc_tracer_cm->report_gc_start(gc_cause(), _gc_timer_cm->gc_start());
2432 trace_heap_before_gc(_gc_tracer_cm);
2433 }
2435 void G1CollectedHeap::register_concurrent_cycle_end() {
2436 if (_concurrent_cycle_started) {
2437 if (_cm->has_aborted()) {
2438 _gc_tracer_cm->report_concurrent_mode_failure();
2439 }
2441 _gc_timer_cm->register_gc_end();
2442 _gc_tracer_cm->report_gc_end(_gc_timer_cm->gc_end(), _gc_timer_cm->time_partitions());
2444 _concurrent_cycle_started = false;
2445 }
2446 }
2448 void G1CollectedHeap::trace_heap_after_concurrent_cycle() {
2449 if (_concurrent_cycle_started) {
2450 trace_heap_after_gc(_gc_tracer_cm);
2451 }
2452 }
2454 G1YCType G1CollectedHeap::yc_type() {
2455 bool is_young = g1_policy()->gcs_are_young();
2456 bool is_initial_mark = g1_policy()->during_initial_mark_pause();
2457 bool is_during_mark = mark_in_progress();
2459 if (is_initial_mark) {
2460 return InitialMark;
2461 } else if (is_during_mark) {
2462 return DuringMark;
2463 } else if (is_young) {
2464 return Normal;
2465 } else {
2466 return Mixed;
2467 }
2468 }
2470 void G1CollectedHeap::collect(GCCause::Cause cause) {
2471 assert_heap_not_locked();
2473 unsigned int gc_count_before;
2474 unsigned int old_marking_count_before;
2475 bool retry_gc;
2477 do {
2478 retry_gc = false;
2480 {
2481 MutexLocker ml(Heap_lock);
2483 // Read the GC count while holding the Heap_lock
2484 gc_count_before = total_collections();
2485 old_marking_count_before = _old_marking_cycles_started;
2486 }
2488 if (should_do_concurrent_full_gc(cause)) {
2489 // Schedule an initial-mark evacuation pause that will start a
2490 // concurrent cycle. We're setting word_size to 0 which means that
2491 // we are not requesting a post-GC allocation.
2492 VM_G1IncCollectionPause op(gc_count_before,
2493 0, /* word_size */
2494 true, /* should_initiate_conc_mark */
2495 g1_policy()->max_pause_time_ms(),
2496 cause);
2498 VMThread::execute(&op);
2499 if (!op.pause_succeeded()) {
2500 if (old_marking_count_before == _old_marking_cycles_started) {
2501 retry_gc = op.should_retry_gc();
2502 } else {
2503 // A Full GC happened while we were trying to schedule the
2504 // initial-mark GC. No point in starting a new cycle given
2505 // that the whole heap was collected anyway.
2506 }
2508 if (retry_gc) {
2509 if (GC_locker::is_active_and_needs_gc()) {
2510 GC_locker::stall_until_clear();
2511 }
2512 }
2513 }
2514 } else {
2515 if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc
2516 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2518 // Schedule a standard evacuation pause. We're setting word_size
2519 // to 0 which means that we are not requesting a post-GC allocation.
2520 VM_G1IncCollectionPause op(gc_count_before,
2521 0, /* word_size */
2522 false, /* should_initiate_conc_mark */
2523 g1_policy()->max_pause_time_ms(),
2524 cause);
2525 VMThread::execute(&op);
2526 } else {
2527 // Schedule a Full GC.
2528 VM_G1CollectFull op(gc_count_before, old_marking_count_before, cause);
2529 VMThread::execute(&op);
2530 }
2531 }
2532 } while (retry_gc);
2533 }
2535 bool G1CollectedHeap::is_in(const void* p) const {
2536 if (_hrm.reserved().contains(p)) {
2537 // Given that we know that p is in the reserved space,
2538 // heap_region_containing_raw() should successfully
2539 // return the containing region.
2540 HeapRegion* hr = heap_region_containing_raw(p);
2541 return hr->is_in(p);
2542 } else {
2543 return false;
2544 }
2545 }
2547 #ifdef ASSERT
2548 bool G1CollectedHeap::is_in_exact(const void* p) const {
2549 bool contains = reserved_region().contains(p);
2550 bool available = _hrm.is_available(addr_to_region((HeapWord*)p));
2551 if (contains && available) {
2552 return true;
2553 } else {
2554 return false;
2555 }
2556 }
2557 #endif
2559 // Iteration functions.
2561 // Applies an ExtendedOopClosure onto all references of objects within a HeapRegion.
2563 class IterateOopClosureRegionClosure: public HeapRegionClosure {
2564 ExtendedOopClosure* _cl;
2565 public:
2566 IterateOopClosureRegionClosure(ExtendedOopClosure* cl) : _cl(cl) {}
2567 bool doHeapRegion(HeapRegion* r) {
2568 if (!r->continuesHumongous()) {
2569 r->oop_iterate(_cl);
2570 }
2571 return false;
2572 }
2573 };
2575 void G1CollectedHeap::oop_iterate(ExtendedOopClosure* cl) {
2576 IterateOopClosureRegionClosure blk(cl);
2577 heap_region_iterate(&blk);
2578 }
2580 // Iterates an ObjectClosure over all objects within a HeapRegion.
2582 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2583 ObjectClosure* _cl;
2584 public:
2585 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2586 bool doHeapRegion(HeapRegion* r) {
2587 if (! r->continuesHumongous()) {
2588 r->object_iterate(_cl);
2589 }
2590 return false;
2591 }
2592 };
2594 void G1CollectedHeap::object_iterate(ObjectClosure* cl) {
2595 IterateObjectClosureRegionClosure blk(cl);
2596 heap_region_iterate(&blk);
2597 }
2599 // Calls a SpaceClosure on a HeapRegion.
2601 class SpaceClosureRegionClosure: public HeapRegionClosure {
2602 SpaceClosure* _cl;
2603 public:
2604 SpaceClosureRegionClosure(SpaceClosure* cl) : _cl(cl) {}
2605 bool doHeapRegion(HeapRegion* r) {
2606 _cl->do_space(r);
2607 return false;
2608 }
2609 };
2611 void G1CollectedHeap::space_iterate(SpaceClosure* cl) {
2612 SpaceClosureRegionClosure blk(cl);
2613 heap_region_iterate(&blk);
2614 }
2616 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2617 _hrm.iterate(cl);
2618 }
2620 void
2621 G1CollectedHeap::heap_region_par_iterate_chunked(HeapRegionClosure* cl,
2622 uint worker_id,
2623 uint num_workers,
2624 jint claim_value) const {
2625 _hrm.par_iterate(cl, worker_id, num_workers, claim_value);
2626 }
2628 class ResetClaimValuesClosure: public HeapRegionClosure {
2629 public:
2630 bool doHeapRegion(HeapRegion* r) {
2631 r->set_claim_value(HeapRegion::InitialClaimValue);
2632 return false;
2633 }
2634 };
2636 void G1CollectedHeap::reset_heap_region_claim_values() {
2637 ResetClaimValuesClosure blk;
2638 heap_region_iterate(&blk);
2639 }
2641 void G1CollectedHeap::reset_cset_heap_region_claim_values() {
2642 ResetClaimValuesClosure blk;
2643 collection_set_iterate(&blk);
2644 }
2646 #ifdef ASSERT
2647 // This checks whether all regions in the heap have the correct claim
2648 // value. I also piggy-backed on this a check to ensure that the
2649 // humongous_start_region() information on "continues humongous"
2650 // regions is correct.
2652 class CheckClaimValuesClosure : public HeapRegionClosure {
2653 private:
2654 jint _claim_value;
2655 uint _failures;
2656 HeapRegion* _sh_region;
2658 public:
2659 CheckClaimValuesClosure(jint claim_value) :
2660 _claim_value(claim_value), _failures(0), _sh_region(NULL) { }
2661 bool doHeapRegion(HeapRegion* r) {
2662 if (r->claim_value() != _claim_value) {
2663 gclog_or_tty->print_cr("Region " HR_FORMAT ", "
2664 "claim value = %d, should be %d",
2665 HR_FORMAT_PARAMS(r),
2666 r->claim_value(), _claim_value);
2667 ++_failures;
2668 }
2669 if (!r->isHumongous()) {
2670 _sh_region = NULL;
2671 } else if (r->startsHumongous()) {
2672 _sh_region = r;
2673 } else if (r->continuesHumongous()) {
2674 if (r->humongous_start_region() != _sh_region) {
2675 gclog_or_tty->print_cr("Region " HR_FORMAT ", "
2676 "HS = "PTR_FORMAT", should be "PTR_FORMAT,
2677 HR_FORMAT_PARAMS(r),
2678 r->humongous_start_region(),
2679 _sh_region);
2680 ++_failures;
2681 }
2682 }
2683 return false;
2684 }
2685 uint failures() { return _failures; }
2686 };
2688 bool G1CollectedHeap::check_heap_region_claim_values(jint claim_value) {
2689 CheckClaimValuesClosure cl(claim_value);
2690 heap_region_iterate(&cl);
2691 return cl.failures() == 0;
2692 }
2694 class CheckClaimValuesInCSetHRClosure: public HeapRegionClosure {
2695 private:
2696 jint _claim_value;
2697 uint _failures;
2699 public:
2700 CheckClaimValuesInCSetHRClosure(jint claim_value) :
2701 _claim_value(claim_value), _failures(0) { }
2703 uint failures() { return _failures; }
2705 bool doHeapRegion(HeapRegion* hr) {
2706 assert(hr->in_collection_set(), "how?");
2707 assert(!hr->isHumongous(), "H-region in CSet");
2708 if (hr->claim_value() != _claim_value) {
2709 gclog_or_tty->print_cr("CSet Region " HR_FORMAT ", "
2710 "claim value = %d, should be %d",
2711 HR_FORMAT_PARAMS(hr),
2712 hr->claim_value(), _claim_value);
2713 _failures += 1;
2714 }
2715 return false;
2716 }
2717 };
2719 bool G1CollectedHeap::check_cset_heap_region_claim_values(jint claim_value) {
2720 CheckClaimValuesInCSetHRClosure cl(claim_value);
2721 collection_set_iterate(&cl);
2722 return cl.failures() == 0;
2723 }
2724 #endif // ASSERT
2726 // Clear the cached CSet starting regions and (more importantly)
2727 // the time stamps. Called when we reset the GC time stamp.
2728 void G1CollectedHeap::clear_cset_start_regions() {
2729 assert(_worker_cset_start_region != NULL, "sanity");
2730 assert(_worker_cset_start_region_time_stamp != NULL, "sanity");
2732 int n_queues = MAX2((int)ParallelGCThreads, 1);
2733 for (int i = 0; i < n_queues; i++) {
2734 _worker_cset_start_region[i] = NULL;
2735 _worker_cset_start_region_time_stamp[i] = 0;
2736 }
2737 }
2739 // Given the id of a worker, obtain or calculate a suitable
2740 // starting region for iterating over the current collection set.
2741 HeapRegion* G1CollectedHeap::start_cset_region_for_worker(uint worker_i) {
2742 assert(get_gc_time_stamp() > 0, "should have been updated by now");
2744 HeapRegion* result = NULL;
2745 unsigned gc_time_stamp = get_gc_time_stamp();
2747 if (_worker_cset_start_region_time_stamp[worker_i] == gc_time_stamp) {
2748 // Cached starting region for current worker was set
2749 // during the current pause - so it's valid.
2750 // Note: the cached starting heap region may be NULL
2751 // (when the collection set is empty).
2752 result = _worker_cset_start_region[worker_i];
2753 assert(result == NULL || result->in_collection_set(), "sanity");
2754 return result;
2755 }
2757 // The cached entry was not valid so let's calculate
2758 // a suitable starting heap region for this worker.
2760 // We want the parallel threads to start their collection
2761 // set iteration at different collection set regions to
2762 // avoid contention.
2763 // If we have:
2764 // n collection set regions
2765 // p threads
2766 // Then thread t will start at region floor ((t * n) / p)
2768 result = g1_policy()->collection_set();
2769 if (G1CollectedHeap::use_parallel_gc_threads()) {
2770 uint cs_size = g1_policy()->cset_region_length();
2771 uint active_workers = workers()->active_workers();
2772 assert(UseDynamicNumberOfGCThreads ||
2773 active_workers == workers()->total_workers(),
2774 "Unless dynamic should use total workers");
2776 uint end_ind = (cs_size * worker_i) / active_workers;
2777 uint start_ind = 0;
2779 if (worker_i > 0 &&
2780 _worker_cset_start_region_time_stamp[worker_i - 1] == gc_time_stamp) {
2781 // Previous workers starting region is valid
2782 // so let's iterate from there
2783 start_ind = (cs_size * (worker_i - 1)) / active_workers;
2784 result = _worker_cset_start_region[worker_i - 1];
2785 }
2787 for (uint i = start_ind; i < end_ind; i++) {
2788 result = result->next_in_collection_set();
2789 }
2790 }
2792 // Note: the calculated starting heap region may be NULL
2793 // (when the collection set is empty).
2794 assert(result == NULL || result->in_collection_set(), "sanity");
2795 assert(_worker_cset_start_region_time_stamp[worker_i] != gc_time_stamp,
2796 "should be updated only once per pause");
2797 _worker_cset_start_region[worker_i] = result;
2798 OrderAccess::storestore();
2799 _worker_cset_start_region_time_stamp[worker_i] = gc_time_stamp;
2800 return result;
2801 }
2803 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) {
2804 HeapRegion* r = g1_policy()->collection_set();
2805 while (r != NULL) {
2806 HeapRegion* next = r->next_in_collection_set();
2807 if (cl->doHeapRegion(r)) {
2808 cl->incomplete();
2809 return;
2810 }
2811 r = next;
2812 }
2813 }
2815 void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r,
2816 HeapRegionClosure *cl) {
2817 if (r == NULL) {
2818 // The CSet is empty so there's nothing to do.
2819 return;
2820 }
2822 assert(r->in_collection_set(),
2823 "Start region must be a member of the collection set.");
2824 HeapRegion* cur = r;
2825 while (cur != NULL) {
2826 HeapRegion* next = cur->next_in_collection_set();
2827 if (cl->doHeapRegion(cur) && false) {
2828 cl->incomplete();
2829 return;
2830 }
2831 cur = next;
2832 }
2833 cur = g1_policy()->collection_set();
2834 while (cur != r) {
2835 HeapRegion* next = cur->next_in_collection_set();
2836 if (cl->doHeapRegion(cur) && false) {
2837 cl->incomplete();
2838 return;
2839 }
2840 cur = next;
2841 }
2842 }
2844 HeapRegion* G1CollectedHeap::next_compaction_region(const HeapRegion* from) const {
2845 HeapRegion* result = _hrm.next_region_in_heap(from);
2846 while (result != NULL && result->isHumongous()) {
2847 result = _hrm.next_region_in_heap(result);
2848 }
2849 return result;
2850 }
2852 Space* G1CollectedHeap::space_containing(const void* addr) const {
2853 return heap_region_containing(addr);
2854 }
2856 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2857 Space* sp = space_containing(addr);
2858 return sp->block_start(addr);
2859 }
2861 size_t G1CollectedHeap::block_size(const HeapWord* addr) const {
2862 Space* sp = space_containing(addr);
2863 return sp->block_size(addr);
2864 }
2866 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2867 Space* sp = space_containing(addr);
2868 return sp->block_is_obj(addr);
2869 }
2871 bool G1CollectedHeap::supports_tlab_allocation() const {
2872 return true;
2873 }
2875 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
2876 return (_g1_policy->young_list_target_length() - young_list()->survivor_length()) * HeapRegion::GrainBytes;
2877 }
2879 size_t G1CollectedHeap::tlab_used(Thread* ignored) const {
2880 return young_list()->eden_used_bytes();
2881 }
2883 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size
2884 // must be smaller than the humongous object limit.
2885 size_t G1CollectedHeap::max_tlab_size() const {
2886 return align_size_down(_humongous_object_threshold_in_words - 1, MinObjAlignment);
2887 }
2889 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
2890 // Return the remaining space in the cur alloc region, but not less than
2891 // the min TLAB size.
2893 // Also, this value can be at most the humongous object threshold,
2894 // since we can't allow tlabs to grow big enough to accommodate
2895 // humongous objects.
2897 HeapRegion* hr = _mutator_alloc_region.get();
2898 size_t max_tlab = max_tlab_size() * wordSize;
2899 if (hr == NULL) {
2900 return max_tlab;
2901 } else {
2902 return MIN2(MAX2(hr->free(), (size_t) MinTLABSize), max_tlab);
2903 }
2904 }
2906 size_t G1CollectedHeap::max_capacity() const {
2907 return _hrm.reserved().byte_size();
2908 }
2910 jlong G1CollectedHeap::millis_since_last_gc() {
2911 // assert(false, "NYI");
2912 return 0;
2913 }
2915 void G1CollectedHeap::prepare_for_verify() {
2916 if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) {
2917 ensure_parsability(false);
2918 }
2919 g1_rem_set()->prepare_for_verify();
2920 }
2922 bool G1CollectedHeap::allocated_since_marking(oop obj, HeapRegion* hr,
2923 VerifyOption vo) {
2924 switch (vo) {
2925 case VerifyOption_G1UsePrevMarking:
2926 return hr->obj_allocated_since_prev_marking(obj);
2927 case VerifyOption_G1UseNextMarking:
2928 return hr->obj_allocated_since_next_marking(obj);
2929 case VerifyOption_G1UseMarkWord:
2930 return false;
2931 default:
2932 ShouldNotReachHere();
2933 }
2934 return false; // keep some compilers happy
2935 }
2937 HeapWord* G1CollectedHeap::top_at_mark_start(HeapRegion* hr, VerifyOption vo) {
2938 switch (vo) {
2939 case VerifyOption_G1UsePrevMarking: return hr->prev_top_at_mark_start();
2940 case VerifyOption_G1UseNextMarking: return hr->next_top_at_mark_start();
2941 case VerifyOption_G1UseMarkWord: return NULL;
2942 default: ShouldNotReachHere();
2943 }
2944 return NULL; // keep some compilers happy
2945 }
2947 bool G1CollectedHeap::is_marked(oop obj, VerifyOption vo) {
2948 switch (vo) {
2949 case VerifyOption_G1UsePrevMarking: return isMarkedPrev(obj);
2950 case VerifyOption_G1UseNextMarking: return isMarkedNext(obj);
2951 case VerifyOption_G1UseMarkWord: return obj->is_gc_marked();
2952 default: ShouldNotReachHere();
2953 }
2954 return false; // keep some compilers happy
2955 }
2957 const char* G1CollectedHeap::top_at_mark_start_str(VerifyOption vo) {
2958 switch (vo) {
2959 case VerifyOption_G1UsePrevMarking: return "PTAMS";
2960 case VerifyOption_G1UseNextMarking: return "NTAMS";
2961 case VerifyOption_G1UseMarkWord: return "NONE";
2962 default: ShouldNotReachHere();
2963 }
2964 return NULL; // keep some compilers happy
2965 }
2967 class VerifyRootsClosure: public OopClosure {
2968 private:
2969 G1CollectedHeap* _g1h;
2970 VerifyOption _vo;
2971 bool _failures;
2972 public:
2973 // _vo == UsePrevMarking -> use "prev" marking information,
2974 // _vo == UseNextMarking -> use "next" marking information,
2975 // _vo == UseMarkWord -> use mark word from object header.
2976 VerifyRootsClosure(VerifyOption vo) :
2977 _g1h(G1CollectedHeap::heap()),
2978 _vo(vo),
2979 _failures(false) { }
2981 bool failures() { return _failures; }
2983 template <class T> void do_oop_nv(T* p) {
2984 T heap_oop = oopDesc::load_heap_oop(p);
2985 if (!oopDesc::is_null(heap_oop)) {
2986 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
2987 if (_g1h->is_obj_dead_cond(obj, _vo)) {
2988 gclog_or_tty->print_cr("Root location "PTR_FORMAT" "
2989 "points to dead obj "PTR_FORMAT, p, (void*) obj);
2990 if (_vo == VerifyOption_G1UseMarkWord) {
2991 gclog_or_tty->print_cr(" Mark word: "PTR_FORMAT, (void*)(obj->mark()));
2992 }
2993 obj->print_on(gclog_or_tty);
2994 _failures = true;
2995 }
2996 }
2997 }
2999 void do_oop(oop* p) { do_oop_nv(p); }
3000 void do_oop(narrowOop* p) { do_oop_nv(p); }
3001 };
3003 class G1VerifyCodeRootOopClosure: public OopClosure {
3004 G1CollectedHeap* _g1h;
3005 OopClosure* _root_cl;
3006 nmethod* _nm;
3007 VerifyOption _vo;
3008 bool _failures;
3010 template <class T> void do_oop_work(T* p) {
3011 // First verify that this root is live
3012 _root_cl->do_oop(p);
3014 if (!G1VerifyHeapRegionCodeRoots) {
3015 // We're not verifying the code roots attached to heap region.
3016 return;
3017 }
3019 // Don't check the code roots during marking verification in a full GC
3020 if (_vo == VerifyOption_G1UseMarkWord) {
3021 return;
3022 }
3024 // Now verify that the current nmethod (which contains p) is
3025 // in the code root list of the heap region containing the
3026 // object referenced by p.
3028 T heap_oop = oopDesc::load_heap_oop(p);
3029 if (!oopDesc::is_null(heap_oop)) {
3030 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
3032 // Now fetch the region containing the object
3033 HeapRegion* hr = _g1h->heap_region_containing(obj);
3034 HeapRegionRemSet* hrrs = hr->rem_set();
3035 // Verify that the strong code root list for this region
3036 // contains the nmethod
3037 if (!hrrs->strong_code_roots_list_contains(_nm)) {
3038 gclog_or_tty->print_cr("Code root location "PTR_FORMAT" "
3039 "from nmethod "PTR_FORMAT" not in strong "
3040 "code roots for region ["PTR_FORMAT","PTR_FORMAT")",
3041 p, _nm, hr->bottom(), hr->end());
3042 _failures = true;
3043 }
3044 }
3045 }
3047 public:
3048 G1VerifyCodeRootOopClosure(G1CollectedHeap* g1h, OopClosure* root_cl, VerifyOption vo):
3049 _g1h(g1h), _root_cl(root_cl), _vo(vo), _nm(NULL), _failures(false) {}
3051 void do_oop(oop* p) { do_oop_work(p); }
3052 void do_oop(narrowOop* p) { do_oop_work(p); }
3054 void set_nmethod(nmethod* nm) { _nm = nm; }
3055 bool failures() { return _failures; }
3056 };
3058 class G1VerifyCodeRootBlobClosure: public CodeBlobClosure {
3059 G1VerifyCodeRootOopClosure* _oop_cl;
3061 public:
3062 G1VerifyCodeRootBlobClosure(G1VerifyCodeRootOopClosure* oop_cl):
3063 _oop_cl(oop_cl) {}
3065 void do_code_blob(CodeBlob* cb) {
3066 nmethod* nm = cb->as_nmethod_or_null();
3067 if (nm != NULL) {
3068 _oop_cl->set_nmethod(nm);
3069 nm->oops_do(_oop_cl);
3070 }
3071 }
3072 };
3074 class YoungRefCounterClosure : public OopClosure {
3075 G1CollectedHeap* _g1h;
3076 int _count;
3077 public:
3078 YoungRefCounterClosure(G1CollectedHeap* g1h) : _g1h(g1h), _count(0) {}
3079 void do_oop(oop* p) { if (_g1h->is_in_young(*p)) { _count++; } }
3080 void do_oop(narrowOop* p) { ShouldNotReachHere(); }
3082 int count() { return _count; }
3083 void reset_count() { _count = 0; };
3084 };
3086 class VerifyKlassClosure: public KlassClosure {
3087 YoungRefCounterClosure _young_ref_counter_closure;
3088 OopClosure *_oop_closure;
3089 public:
3090 VerifyKlassClosure(G1CollectedHeap* g1h, OopClosure* cl) : _young_ref_counter_closure(g1h), _oop_closure(cl) {}
3091 void do_klass(Klass* k) {
3092 k->oops_do(_oop_closure);
3094 _young_ref_counter_closure.reset_count();
3095 k->oops_do(&_young_ref_counter_closure);
3096 if (_young_ref_counter_closure.count() > 0) {
3097 guarantee(k->has_modified_oops(), err_msg("Klass %p, has young refs but is not dirty.", k));
3098 }
3099 }
3100 };
3102 class VerifyLivenessOopClosure: public OopClosure {
3103 G1CollectedHeap* _g1h;
3104 VerifyOption _vo;
3105 public:
3106 VerifyLivenessOopClosure(G1CollectedHeap* g1h, VerifyOption vo):
3107 _g1h(g1h), _vo(vo)
3108 { }
3109 void do_oop(narrowOop *p) { do_oop_work(p); }
3110 void do_oop( oop *p) { do_oop_work(p); }
3112 template <class T> void do_oop_work(T *p) {
3113 oop obj = oopDesc::load_decode_heap_oop(p);
3114 guarantee(obj == NULL || !_g1h->is_obj_dead_cond(obj, _vo),
3115 "Dead object referenced by a not dead object");
3116 }
3117 };
3119 class VerifyObjsInRegionClosure: public ObjectClosure {
3120 private:
3121 G1CollectedHeap* _g1h;
3122 size_t _live_bytes;
3123 HeapRegion *_hr;
3124 VerifyOption _vo;
3125 public:
3126 // _vo == UsePrevMarking -> use "prev" marking information,
3127 // _vo == UseNextMarking -> use "next" marking information,
3128 // _vo == UseMarkWord -> use mark word from object header.
3129 VerifyObjsInRegionClosure(HeapRegion *hr, VerifyOption vo)
3130 : _live_bytes(0), _hr(hr), _vo(vo) {
3131 _g1h = G1CollectedHeap::heap();
3132 }
3133 void do_object(oop o) {
3134 VerifyLivenessOopClosure isLive(_g1h, _vo);
3135 assert(o != NULL, "Huh?");
3136 if (!_g1h->is_obj_dead_cond(o, _vo)) {
3137 // If the object is alive according to the mark word,
3138 // then verify that the marking information agrees.
3139 // Note we can't verify the contra-positive of the
3140 // above: if the object is dead (according to the mark
3141 // word), it may not be marked, or may have been marked
3142 // but has since became dead, or may have been allocated
3143 // since the last marking.
3144 if (_vo == VerifyOption_G1UseMarkWord) {
3145 guarantee(!_g1h->is_obj_dead(o), "mark word and concurrent mark mismatch");
3146 }
3148 o->oop_iterate_no_header(&isLive);
3149 if (!_hr->obj_allocated_since_prev_marking(o)) {
3150 size_t obj_size = o->size(); // Make sure we don't overflow
3151 _live_bytes += (obj_size * HeapWordSize);
3152 }
3153 }
3154 }
3155 size_t live_bytes() { return _live_bytes; }
3156 };
3158 class PrintObjsInRegionClosure : public ObjectClosure {
3159 HeapRegion *_hr;
3160 G1CollectedHeap *_g1;
3161 public:
3162 PrintObjsInRegionClosure(HeapRegion *hr) : _hr(hr) {
3163 _g1 = G1CollectedHeap::heap();
3164 };
3166 void do_object(oop o) {
3167 if (o != NULL) {
3168 HeapWord *start = (HeapWord *) o;
3169 size_t word_sz = o->size();
3170 gclog_or_tty->print("\nPrinting obj "PTR_FORMAT" of size " SIZE_FORMAT
3171 " isMarkedPrev %d isMarkedNext %d isAllocSince %d\n",
3172 (void*) o, word_sz,
3173 _g1->isMarkedPrev(o),
3174 _g1->isMarkedNext(o),
3175 _hr->obj_allocated_since_prev_marking(o));
3176 HeapWord *end = start + word_sz;
3177 HeapWord *cur;
3178 int *val;
3179 for (cur = start; cur < end; cur++) {
3180 val = (int *) cur;
3181 gclog_or_tty->print("\t "PTR_FORMAT":"PTR_FORMAT"\n", val, *val);
3182 }
3183 }
3184 }
3185 };
3187 class VerifyRegionClosure: public HeapRegionClosure {
3188 private:
3189 bool _par;
3190 VerifyOption _vo;
3191 bool _failures;
3192 public:
3193 // _vo == UsePrevMarking -> use "prev" marking information,
3194 // _vo == UseNextMarking -> use "next" marking information,
3195 // _vo == UseMarkWord -> use mark word from object header.
3196 VerifyRegionClosure(bool par, VerifyOption vo)
3197 : _par(par),
3198 _vo(vo),
3199 _failures(false) {}
3201 bool failures() {
3202 return _failures;
3203 }
3205 bool doHeapRegion(HeapRegion* r) {
3206 if (!r->continuesHumongous()) {
3207 bool failures = false;
3208 r->verify(_vo, &failures);
3209 if (failures) {
3210 _failures = true;
3211 } else {
3212 VerifyObjsInRegionClosure not_dead_yet_cl(r, _vo);
3213 r->object_iterate(¬_dead_yet_cl);
3214 if (_vo != VerifyOption_G1UseNextMarking) {
3215 if (r->max_live_bytes() < not_dead_yet_cl.live_bytes()) {
3216 gclog_or_tty->print_cr("["PTR_FORMAT","PTR_FORMAT"] "
3217 "max_live_bytes "SIZE_FORMAT" "
3218 "< calculated "SIZE_FORMAT,
3219 r->bottom(), r->end(),
3220 r->max_live_bytes(),
3221 not_dead_yet_cl.live_bytes());
3222 _failures = true;
3223 }
3224 } else {
3225 // When vo == UseNextMarking we cannot currently do a sanity
3226 // check on the live bytes as the calculation has not been
3227 // finalized yet.
3228 }
3229 }
3230 }
3231 return false; // stop the region iteration if we hit a failure
3232 }
3233 };
3235 // This is the task used for parallel verification of the heap regions
3237 class G1ParVerifyTask: public AbstractGangTask {
3238 private:
3239 G1CollectedHeap* _g1h;
3240 VerifyOption _vo;
3241 bool _failures;
3243 public:
3244 // _vo == UsePrevMarking -> use "prev" marking information,
3245 // _vo == UseNextMarking -> use "next" marking information,
3246 // _vo == UseMarkWord -> use mark word from object header.
3247 G1ParVerifyTask(G1CollectedHeap* g1h, VerifyOption vo) :
3248 AbstractGangTask("Parallel verify task"),
3249 _g1h(g1h),
3250 _vo(vo),
3251 _failures(false) { }
3253 bool failures() {
3254 return _failures;
3255 }
3257 void work(uint worker_id) {
3258 HandleMark hm;
3259 VerifyRegionClosure blk(true, _vo);
3260 _g1h->heap_region_par_iterate_chunked(&blk, worker_id,
3261 _g1h->workers()->active_workers(),
3262 HeapRegion::ParVerifyClaimValue);
3263 if (blk.failures()) {
3264 _failures = true;
3265 }
3266 }
3267 };
3269 void G1CollectedHeap::verify(bool silent, VerifyOption vo) {
3270 if (SafepointSynchronize::is_at_safepoint()) {
3271 assert(Thread::current()->is_VM_thread(),
3272 "Expected to be executed serially by the VM thread at this point");
3274 if (!silent) { gclog_or_tty->print("Roots "); }
3275 VerifyRootsClosure rootsCl(vo);
3276 VerifyKlassClosure klassCl(this, &rootsCl);
3277 CLDToKlassAndOopClosure cldCl(&klassCl, &rootsCl, false);
3279 // We apply the relevant closures to all the oops in the
3280 // system dictionary, class loader data graph, the string table
3281 // and the nmethods in the code cache.
3282 G1VerifyCodeRootOopClosure codeRootsCl(this, &rootsCl, vo);
3283 G1VerifyCodeRootBlobClosure blobsCl(&codeRootsCl);
3285 process_all_roots(true, // activate StrongRootsScope
3286 SO_AllCodeCache, // roots scanning options
3287 &rootsCl,
3288 &cldCl,
3289 &blobsCl);
3291 bool failures = rootsCl.failures() || codeRootsCl.failures();
3293 if (vo != VerifyOption_G1UseMarkWord) {
3294 // If we're verifying during a full GC then the region sets
3295 // will have been torn down at the start of the GC. Therefore
3296 // verifying the region sets will fail. So we only verify
3297 // the region sets when not in a full GC.
3298 if (!silent) { gclog_or_tty->print("HeapRegionSets "); }
3299 verify_region_sets();
3300 }
3302 if (!silent) { gclog_or_tty->print("HeapRegions "); }
3303 if (GCParallelVerificationEnabled && ParallelGCThreads > 1) {
3304 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3305 "sanity check");
3307 G1ParVerifyTask task(this, vo);
3308 assert(UseDynamicNumberOfGCThreads ||
3309 workers()->active_workers() == workers()->total_workers(),
3310 "If not dynamic should be using all the workers");
3311 int n_workers = workers()->active_workers();
3312 set_par_threads(n_workers);
3313 workers()->run_task(&task);
3314 set_par_threads(0);
3315 if (task.failures()) {
3316 failures = true;
3317 }
3319 // Checks that the expected amount of parallel work was done.
3320 // The implication is that n_workers is > 0.
3321 assert(check_heap_region_claim_values(HeapRegion::ParVerifyClaimValue),
3322 "sanity check");
3324 reset_heap_region_claim_values();
3326 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3327 "sanity check");
3328 } else {
3329 VerifyRegionClosure blk(false, vo);
3330 heap_region_iterate(&blk);
3331 if (blk.failures()) {
3332 failures = true;
3333 }
3334 }
3335 if (!silent) gclog_or_tty->print("RemSet ");
3336 rem_set()->verify();
3338 if (G1StringDedup::is_enabled()) {
3339 if (!silent) gclog_or_tty->print("StrDedup ");
3340 G1StringDedup::verify();
3341 }
3343 if (failures) {
3344 gclog_or_tty->print_cr("Heap:");
3345 // It helps to have the per-region information in the output to
3346 // help us track down what went wrong. This is why we call
3347 // print_extended_on() instead of print_on().
3348 print_extended_on(gclog_or_tty);
3349 gclog_or_tty->cr();
3350 #ifndef PRODUCT
3351 if (VerifyDuringGC && G1VerifyDuringGCPrintReachable) {
3352 concurrent_mark()->print_reachable("at-verification-failure",
3353 vo, false /* all */);
3354 }
3355 #endif
3356 gclog_or_tty->flush();
3357 }
3358 guarantee(!failures, "there should not have been any failures");
3359 } else {
3360 if (!silent) {
3361 gclog_or_tty->print("(SKIPPING Roots, HeapRegionSets, HeapRegions, RemSet");
3362 if (G1StringDedup::is_enabled()) {
3363 gclog_or_tty->print(", StrDedup");
3364 }
3365 gclog_or_tty->print(") ");
3366 }
3367 }
3368 }
3370 void G1CollectedHeap::verify(bool silent) {
3371 verify(silent, VerifyOption_G1UsePrevMarking);
3372 }
3374 double G1CollectedHeap::verify(bool guard, const char* msg) {
3375 double verify_time_ms = 0.0;
3377 if (guard && total_collections() >= VerifyGCStartAt) {
3378 double verify_start = os::elapsedTime();
3379 HandleMark hm; // Discard invalid handles created during verification
3380 prepare_for_verify();
3381 Universe::verify(VerifyOption_G1UsePrevMarking, msg);
3382 verify_time_ms = (os::elapsedTime() - verify_start) * 1000;
3383 }
3385 return verify_time_ms;
3386 }
3388 void G1CollectedHeap::verify_before_gc() {
3389 double verify_time_ms = verify(VerifyBeforeGC, " VerifyBeforeGC:");
3390 g1_policy()->phase_times()->record_verify_before_time_ms(verify_time_ms);
3391 }
3393 void G1CollectedHeap::verify_after_gc() {
3394 double verify_time_ms = verify(VerifyAfterGC, " VerifyAfterGC:");
3395 g1_policy()->phase_times()->record_verify_after_time_ms(verify_time_ms);
3396 }
3398 class PrintRegionClosure: public HeapRegionClosure {
3399 outputStream* _st;
3400 public:
3401 PrintRegionClosure(outputStream* st) : _st(st) {}
3402 bool doHeapRegion(HeapRegion* r) {
3403 r->print_on(_st);
3404 return false;
3405 }
3406 };
3408 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
3409 const HeapRegion* hr,
3410 const VerifyOption vo) const {
3411 switch (vo) {
3412 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr);
3413 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr);
3414 case VerifyOption_G1UseMarkWord: return !obj->is_gc_marked();
3415 default: ShouldNotReachHere();
3416 }
3417 return false; // keep some compilers happy
3418 }
3420 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
3421 const VerifyOption vo) const {
3422 switch (vo) {
3423 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj);
3424 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj);
3425 case VerifyOption_G1UseMarkWord: return !obj->is_gc_marked();
3426 default: ShouldNotReachHere();
3427 }
3428 return false; // keep some compilers happy
3429 }
3431 void G1CollectedHeap::print_on(outputStream* st) const {
3432 st->print(" %-20s", "garbage-first heap");
3433 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
3434 capacity()/K, used_unlocked()/K);
3435 st->print(" [" INTPTR_FORMAT ", " INTPTR_FORMAT ", " INTPTR_FORMAT ")",
3436 _hrm.reserved().start(),
3437 _hrm.reserved().start() + _hrm.length() + HeapRegion::GrainWords,
3438 _hrm.reserved().end());
3439 st->cr();
3440 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
3441 uint young_regions = _young_list->length();
3442 st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
3443 (size_t) young_regions * HeapRegion::GrainBytes / K);
3444 uint survivor_regions = g1_policy()->recorded_survivor_regions();
3445 st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
3446 (size_t) survivor_regions * HeapRegion::GrainBytes / K);
3447 st->cr();
3448 MetaspaceAux::print_on(st);
3449 }
3451 void G1CollectedHeap::print_extended_on(outputStream* st) const {
3452 print_on(st);
3454 // Print the per-region information.
3455 st->cr();
3456 st->print_cr("Heap Regions: (Y=young(eden), SU=young(survivor), "
3457 "HS=humongous(starts), HC=humongous(continues), "
3458 "CS=collection set, F=free, TS=gc time stamp, "
3459 "PTAMS=previous top-at-mark-start, "
3460 "NTAMS=next top-at-mark-start)");
3461 PrintRegionClosure blk(st);
3462 heap_region_iterate(&blk);
3463 }
3465 void G1CollectedHeap::print_on_error(outputStream* st) const {
3466 this->CollectedHeap::print_on_error(st);
3468 if (_cm != NULL) {
3469 st->cr();
3470 _cm->print_on_error(st);
3471 }
3472 }
3474 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
3475 if (G1CollectedHeap::use_parallel_gc_threads()) {
3476 workers()->print_worker_threads_on(st);
3477 }
3478 _cmThread->print_on(st);
3479 st->cr();
3480 _cm->print_worker_threads_on(st);
3481 _cg1r->print_worker_threads_on(st);
3482 if (G1StringDedup::is_enabled()) {
3483 G1StringDedup::print_worker_threads_on(st);
3484 }
3485 }
3487 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
3488 if (G1CollectedHeap::use_parallel_gc_threads()) {
3489 workers()->threads_do(tc);
3490 }
3491 tc->do_thread(_cmThread);
3492 _cg1r->threads_do(tc);
3493 if (G1StringDedup::is_enabled()) {
3494 G1StringDedup::threads_do(tc);
3495 }
3496 }
3498 void G1CollectedHeap::print_tracing_info() const {
3499 // We'll overload this to mean "trace GC pause statistics."
3500 if (TraceGen0Time || TraceGen1Time) {
3501 // The "G1CollectorPolicy" is keeping track of these stats, so delegate
3502 // to that.
3503 g1_policy()->print_tracing_info();
3504 }
3505 if (G1SummarizeRSetStats) {
3506 g1_rem_set()->print_summary_info();
3507 }
3508 if (G1SummarizeConcMark) {
3509 concurrent_mark()->print_summary_info();
3510 }
3511 g1_policy()->print_yg_surv_rate_info();
3512 SpecializationStats::print();
3513 }
3515 #ifndef PRODUCT
3516 // Helpful for debugging RSet issues.
3518 class PrintRSetsClosure : public HeapRegionClosure {
3519 private:
3520 const char* _msg;
3521 size_t _occupied_sum;
3523 public:
3524 bool doHeapRegion(HeapRegion* r) {
3525 HeapRegionRemSet* hrrs = r->rem_set();
3526 size_t occupied = hrrs->occupied();
3527 _occupied_sum += occupied;
3529 gclog_or_tty->print_cr("Printing RSet for region "HR_FORMAT,
3530 HR_FORMAT_PARAMS(r));
3531 if (occupied == 0) {
3532 gclog_or_tty->print_cr(" RSet is empty");
3533 } else {
3534 hrrs->print();
3535 }
3536 gclog_or_tty->print_cr("----------");
3537 return false;
3538 }
3540 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
3541 gclog_or_tty->cr();
3542 gclog_or_tty->print_cr("========================================");
3543 gclog_or_tty->print_cr("%s", msg);
3544 gclog_or_tty->cr();
3545 }
3547 ~PrintRSetsClosure() {
3548 gclog_or_tty->print_cr("Occupied Sum: "SIZE_FORMAT, _occupied_sum);
3549 gclog_or_tty->print_cr("========================================");
3550 gclog_or_tty->cr();
3551 }
3552 };
3554 void G1CollectedHeap::print_cset_rsets() {
3555 PrintRSetsClosure cl("Printing CSet RSets");
3556 collection_set_iterate(&cl);
3557 }
3559 void G1CollectedHeap::print_all_rsets() {
3560 PrintRSetsClosure cl("Printing All RSets");;
3561 heap_region_iterate(&cl);
3562 }
3563 #endif // PRODUCT
3565 G1CollectedHeap* G1CollectedHeap::heap() {
3566 assert(_sh->kind() == CollectedHeap::G1CollectedHeap,
3567 "not a garbage-first heap");
3568 return _g1h;
3569 }
3571 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) {
3572 // always_do_update_barrier = false;
3573 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
3574 // Fill TLAB's and such
3575 accumulate_statistics_all_tlabs();
3576 ensure_parsability(true);
3578 if (G1SummarizeRSetStats && (G1SummarizeRSetStatsPeriod > 0) &&
3579 (total_collections() % G1SummarizeRSetStatsPeriod == 0)) {
3580 g1_rem_set()->print_periodic_summary_info("Before GC RS summary");
3581 }
3582 }
3584 void G1CollectedHeap::gc_epilogue(bool full /* Ignored */) {
3586 if (G1SummarizeRSetStats &&
3587 (G1SummarizeRSetStatsPeriod > 0) &&
3588 // we are at the end of the GC. Total collections has already been increased.
3589 ((total_collections() - 1) % G1SummarizeRSetStatsPeriod == 0)) {
3590 g1_rem_set()->print_periodic_summary_info("After GC RS summary");
3591 }
3593 // FIXME: what is this about?
3594 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
3595 // is set.
3596 COMPILER2_PRESENT(assert(DerivedPointerTable::is_empty(),
3597 "derived pointer present"));
3598 // always_do_update_barrier = true;
3600 resize_all_tlabs();
3602 // We have just completed a GC. Update the soft reference
3603 // policy with the new heap occupancy
3604 Universe::update_heap_info_at_gc();
3605 }
3607 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
3608 unsigned int gc_count_before,
3609 bool* succeeded,
3610 GCCause::Cause gc_cause) {
3611 assert_heap_not_locked_and_not_at_safepoint();
3612 g1_policy()->record_stop_world_start();
3613 VM_G1IncCollectionPause op(gc_count_before,
3614 word_size,
3615 false, /* should_initiate_conc_mark */
3616 g1_policy()->max_pause_time_ms(),
3617 gc_cause);
3618 VMThread::execute(&op);
3620 HeapWord* result = op.result();
3621 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
3622 assert(result == NULL || ret_succeeded,
3623 "the result should be NULL if the VM did not succeed");
3624 *succeeded = ret_succeeded;
3626 assert_heap_not_locked();
3627 return result;
3628 }
3630 void
3631 G1CollectedHeap::doConcurrentMark() {
3632 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
3633 if (!_cmThread->in_progress()) {
3634 _cmThread->set_started();
3635 CGC_lock->notify();
3636 }
3637 }
3639 size_t G1CollectedHeap::pending_card_num() {
3640 size_t extra_cards = 0;
3641 JavaThread *curr = Threads::first();
3642 while (curr != NULL) {
3643 DirtyCardQueue& dcq = curr->dirty_card_queue();
3644 extra_cards += dcq.size();
3645 curr = curr->next();
3646 }
3647 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
3648 size_t buffer_size = dcqs.buffer_size();
3649 size_t buffer_num = dcqs.completed_buffers_num();
3651 // PtrQueueSet::buffer_size() and PtrQueue:size() return sizes
3652 // in bytes - not the number of 'entries'. We need to convert
3653 // into a number of cards.
3654 return (buffer_size * buffer_num + extra_cards) / oopSize;
3655 }
3657 size_t G1CollectedHeap::cards_scanned() {
3658 return g1_rem_set()->cardsScanned();
3659 }
3661 bool G1CollectedHeap::humongous_region_is_always_live(uint index) {
3662 HeapRegion* region = region_at(index);
3663 assert(region->startsHumongous(), "Must start a humongous object");
3664 return oop(region->bottom())->is_objArray() || !region->rem_set()->is_empty();
3665 }
3667 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure {
3668 private:
3669 size_t _total_humongous;
3670 size_t _candidate_humongous;
3671 public:
3672 RegisterHumongousWithInCSetFastTestClosure() : _total_humongous(0), _candidate_humongous(0) {
3673 }
3675 virtual bool doHeapRegion(HeapRegion* r) {
3676 if (!r->startsHumongous()) {
3677 return false;
3678 }
3679 G1CollectedHeap* g1h = G1CollectedHeap::heap();
3681 uint region_idx = r->hrm_index();
3682 bool is_candidate = !g1h->humongous_region_is_always_live(region_idx);
3683 // Is_candidate already filters out humongous regions with some remembered set.
3684 // This will not lead to humongous object that we mistakenly keep alive because
3685 // during young collection the remembered sets will only be added to.
3686 if (is_candidate) {
3687 g1h->register_humongous_region_with_in_cset_fast_test(region_idx);
3688 _candidate_humongous++;
3689 }
3690 _total_humongous++;
3692 return false;
3693 }
3695 size_t total_humongous() const { return _total_humongous; }
3696 size_t candidate_humongous() const { return _candidate_humongous; }
3697 };
3699 void G1CollectedHeap::register_humongous_regions_with_in_cset_fast_test() {
3700 if (!G1ReclaimDeadHumongousObjectsAtYoungGC) {
3701 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0, 0);
3702 return;
3703 }
3705 RegisterHumongousWithInCSetFastTestClosure cl;
3706 heap_region_iterate(&cl);
3707 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(cl.total_humongous(),
3708 cl.candidate_humongous());
3709 _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0;
3711 if (_has_humongous_reclaim_candidates) {
3712 clear_humongous_is_live_table();
3713 }
3714 }
3716 void
3717 G1CollectedHeap::setup_surviving_young_words() {
3718 assert(_surviving_young_words == NULL, "pre-condition");
3719 uint array_length = g1_policy()->young_cset_region_length();
3720 _surviving_young_words = NEW_C_HEAP_ARRAY(size_t, (size_t) array_length, mtGC);
3721 if (_surviving_young_words == NULL) {
3722 vm_exit_out_of_memory(sizeof(size_t) * array_length, OOM_MALLOC_ERROR,
3723 "Not enough space for young surv words summary.");
3724 }
3725 memset(_surviving_young_words, 0, (size_t) array_length * sizeof(size_t));
3726 #ifdef ASSERT
3727 for (uint i = 0; i < array_length; ++i) {
3728 assert( _surviving_young_words[i] == 0, "memset above" );
3729 }
3730 #endif // !ASSERT
3731 }
3733 void
3734 G1CollectedHeap::update_surviving_young_words(size_t* surv_young_words) {
3735 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
3736 uint array_length = g1_policy()->young_cset_region_length();
3737 for (uint i = 0; i < array_length; ++i) {
3738 _surviving_young_words[i] += surv_young_words[i];
3739 }
3740 }
3742 void
3743 G1CollectedHeap::cleanup_surviving_young_words() {
3744 guarantee( _surviving_young_words != NULL, "pre-condition" );
3745 FREE_C_HEAP_ARRAY(size_t, _surviving_young_words, mtGC);
3746 _surviving_young_words = NULL;
3747 }
3749 #ifdef ASSERT
3750 class VerifyCSetClosure: public HeapRegionClosure {
3751 public:
3752 bool doHeapRegion(HeapRegion* hr) {
3753 // Here we check that the CSet region's RSet is ready for parallel
3754 // iteration. The fields that we'll verify are only manipulated
3755 // when the region is part of a CSet and is collected. Afterwards,
3756 // we reset these fields when we clear the region's RSet (when the
3757 // region is freed) so they are ready when the region is
3758 // re-allocated. The only exception to this is if there's an
3759 // evacuation failure and instead of freeing the region we leave
3760 // it in the heap. In that case, we reset these fields during
3761 // evacuation failure handling.
3762 guarantee(hr->rem_set()->verify_ready_for_par_iteration(), "verification");
3764 // Here's a good place to add any other checks we'd like to
3765 // perform on CSet regions.
3766 return false;
3767 }
3768 };
3769 #endif // ASSERT
3771 #if TASKQUEUE_STATS
3772 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
3773 st->print_raw_cr("GC Task Stats");
3774 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
3775 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
3776 }
3778 void G1CollectedHeap::print_taskqueue_stats(outputStream* const st) const {
3779 print_taskqueue_stats_hdr(st);
3781 TaskQueueStats totals;
3782 const int n = workers() != NULL ? workers()->total_workers() : 1;
3783 for (int i = 0; i < n; ++i) {
3784 st->print("%3d ", i); task_queue(i)->stats.print(st); st->cr();
3785 totals += task_queue(i)->stats;
3786 }
3787 st->print_raw("tot "); totals.print(st); st->cr();
3789 DEBUG_ONLY(totals.verify());
3790 }
3792 void G1CollectedHeap::reset_taskqueue_stats() {
3793 const int n = workers() != NULL ? workers()->total_workers() : 1;
3794 for (int i = 0; i < n; ++i) {
3795 task_queue(i)->stats.reset();
3796 }
3797 }
3798 #endif // TASKQUEUE_STATS
3800 void G1CollectedHeap::log_gc_header() {
3801 if (!G1Log::fine()) {
3802 return;
3803 }
3805 gclog_or_tty->gclog_stamp(_gc_tracer_stw->gc_id());
3807 GCCauseString gc_cause_str = GCCauseString("GC pause", gc_cause())
3808 .append(g1_policy()->gcs_are_young() ? "(young)" : "(mixed)")
3809 .append(g1_policy()->during_initial_mark_pause() ? " (initial-mark)" : "");
3811 gclog_or_tty->print("[%s", (const char*)gc_cause_str);
3812 }
3814 void G1CollectedHeap::log_gc_footer(double pause_time_sec) {
3815 if (!G1Log::fine()) {
3816 return;
3817 }
3819 if (G1Log::finer()) {
3820 if (evacuation_failed()) {
3821 gclog_or_tty->print(" (to-space exhausted)");
3822 }
3823 gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec);
3824 g1_policy()->phase_times()->note_gc_end();
3825 g1_policy()->phase_times()->print(pause_time_sec);
3826 g1_policy()->print_detailed_heap_transition();
3827 } else {
3828 if (evacuation_failed()) {
3829 gclog_or_tty->print("--");
3830 }
3831 g1_policy()->print_heap_transition();
3832 gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec);
3833 }
3834 gclog_or_tty->flush();
3835 }
3837 bool
3838 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
3839 assert_at_safepoint(true /* should_be_vm_thread */);
3840 guarantee(!is_gc_active(), "collection is not reentrant");
3842 if (GC_locker::check_active_before_gc()) {
3843 return false;
3844 }
3846 _gc_timer_stw->register_gc_start();
3848 _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start());
3850 SvcGCMarker sgcm(SvcGCMarker::MINOR);
3851 ResourceMark rm;
3853 print_heap_before_gc();
3854 trace_heap_before_gc(_gc_tracer_stw);
3856 verify_region_sets_optional();
3857 verify_dirty_young_regions();
3859 // This call will decide whether this pause is an initial-mark
3860 // pause. If it is, during_initial_mark_pause() will return true
3861 // for the duration of this pause.
3862 g1_policy()->decide_on_conc_mark_initiation();
3864 // We do not allow initial-mark to be piggy-backed on a mixed GC.
3865 assert(!g1_policy()->during_initial_mark_pause() ||
3866 g1_policy()->gcs_are_young(), "sanity");
3868 // We also do not allow mixed GCs during marking.
3869 assert(!mark_in_progress() || g1_policy()->gcs_are_young(), "sanity");
3871 // Record whether this pause is an initial mark. When the current
3872 // thread has completed its logging output and it's safe to signal
3873 // the CM thread, the flag's value in the policy has been reset.
3874 bool should_start_conc_mark = g1_policy()->during_initial_mark_pause();
3876 // Inner scope for scope based logging, timers, and stats collection
3877 {
3878 EvacuationInfo evacuation_info;
3880 if (g1_policy()->during_initial_mark_pause()) {
3881 // We are about to start a marking cycle, so we increment the
3882 // full collection counter.
3883 increment_old_marking_cycles_started();
3884 register_concurrent_cycle_start(_gc_timer_stw->gc_start());
3885 }
3887 _gc_tracer_stw->report_yc_type(yc_type());
3889 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
3891 int active_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
3892 workers()->active_workers() : 1);
3893 double pause_start_sec = os::elapsedTime();
3894 g1_policy()->phase_times()->note_gc_start(active_workers);
3895 log_gc_header();
3897 TraceCollectorStats tcs(g1mm()->incremental_collection_counters());
3898 TraceMemoryManagerStats tms(false /* fullGC */, gc_cause());
3900 // If the secondary_free_list is not empty, append it to the
3901 // free_list. No need to wait for the cleanup operation to finish;
3902 // the region allocation code will check the secondary_free_list
3903 // and wait if necessary. If the G1StressConcRegionFreeing flag is
3904 // set, skip this step so that the region allocation code has to
3905 // get entries from the secondary_free_list.
3906 if (!G1StressConcRegionFreeing) {
3907 append_secondary_free_list_if_not_empty_with_lock();
3908 }
3910 assert(check_young_list_well_formed(), "young list should be well formed");
3911 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3912 "sanity check");
3914 // Don't dynamically change the number of GC threads this early. A value of
3915 // 0 is used to indicate serial work. When parallel work is done,
3916 // it will be set.
3918 { // Call to jvmpi::post_class_unload_events must occur outside of active GC
3919 IsGCActiveMark x;
3921 gc_prologue(false);
3922 increment_total_collections(false /* full gc */);
3923 increment_gc_time_stamp();
3925 verify_before_gc();
3926 check_bitmaps("GC Start");
3928 COMPILER2_PRESENT(DerivedPointerTable::clear());
3930 // Please see comment in g1CollectedHeap.hpp and
3931 // G1CollectedHeap::ref_processing_init() to see how
3932 // reference processing currently works in G1.
3934 // Enable discovery in the STW reference processor
3935 ref_processor_stw()->enable_discovery(true /*verify_disabled*/,
3936 true /*verify_no_refs*/);
3938 {
3939 // We want to temporarily turn off discovery by the
3940 // CM ref processor, if necessary, and turn it back on
3941 // on again later if we do. Using a scoped
3942 // NoRefDiscovery object will do this.
3943 NoRefDiscovery no_cm_discovery(ref_processor_cm());
3945 // Forget the current alloc region (we might even choose it to be part
3946 // of the collection set!).
3947 release_mutator_alloc_region();
3949 // We should call this after we retire the mutator alloc
3950 // region(s) so that all the ALLOC / RETIRE events are generated
3951 // before the start GC event.
3952 _hr_printer.start_gc(false /* full */, (size_t) total_collections());
3954 // This timing is only used by the ergonomics to handle our pause target.
3955 // It is unclear why this should not include the full pause. We will
3956 // investigate this in CR 7178365.
3957 //
3958 // Preserving the old comment here if that helps the investigation:
3959 //
3960 // The elapsed time induced by the start time below deliberately elides
3961 // the possible verification above.
3962 double sample_start_time_sec = os::elapsedTime();
3964 #if YOUNG_LIST_VERBOSE
3965 gclog_or_tty->print_cr("\nBefore recording pause start.\nYoung_list:");
3966 _young_list->print();
3967 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3968 #endif // YOUNG_LIST_VERBOSE
3970 g1_policy()->record_collection_pause_start(sample_start_time_sec);
3972 double scan_wait_start = os::elapsedTime();
3973 // We have to wait until the CM threads finish scanning the
3974 // root regions as it's the only way to ensure that all the
3975 // objects on them have been correctly scanned before we start
3976 // moving them during the GC.
3977 bool waited = _cm->root_regions()->wait_until_scan_finished();
3978 double wait_time_ms = 0.0;
3979 if (waited) {
3980 double scan_wait_end = os::elapsedTime();
3981 wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
3982 }
3983 g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms);
3985 #if YOUNG_LIST_VERBOSE
3986 gclog_or_tty->print_cr("\nAfter recording pause start.\nYoung_list:");
3987 _young_list->print();
3988 #endif // YOUNG_LIST_VERBOSE
3990 if (g1_policy()->during_initial_mark_pause()) {
3991 concurrent_mark()->checkpointRootsInitialPre();
3992 }
3994 #if YOUNG_LIST_VERBOSE
3995 gclog_or_tty->print_cr("\nBefore choosing collection set.\nYoung_list:");
3996 _young_list->print();
3997 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3998 #endif // YOUNG_LIST_VERBOSE
4000 g1_policy()->finalize_cset(target_pause_time_ms, evacuation_info);
4002 register_humongous_regions_with_in_cset_fast_test();
4004 _cm->note_start_of_gc();
4005 // We should not verify the per-thread SATB buffers given that
4006 // we have not filtered them yet (we'll do so during the
4007 // GC). We also call this after finalize_cset() to
4008 // ensure that the CSet has been finalized.
4009 _cm->verify_no_cset_oops(true /* verify_stacks */,
4010 true /* verify_enqueued_buffers */,
4011 false /* verify_thread_buffers */,
4012 true /* verify_fingers */);
4014 if (_hr_printer.is_active()) {
4015 HeapRegion* hr = g1_policy()->collection_set();
4016 while (hr != NULL) {
4017 G1HRPrinter::RegionType type;
4018 if (!hr->is_young()) {
4019 type = G1HRPrinter::Old;
4020 } else if (hr->is_survivor()) {
4021 type = G1HRPrinter::Survivor;
4022 } else {
4023 type = G1HRPrinter::Eden;
4024 }
4025 _hr_printer.cset(hr);
4026 hr = hr->next_in_collection_set();
4027 }
4028 }
4030 #ifdef ASSERT
4031 VerifyCSetClosure cl;
4032 collection_set_iterate(&cl);
4033 #endif // ASSERT
4035 setup_surviving_young_words();
4037 // Initialize the GC alloc regions.
4038 init_gc_alloc_regions(evacuation_info);
4040 // Actually do the work...
4041 evacuate_collection_set(evacuation_info);
4043 // We do this to mainly verify the per-thread SATB buffers
4044 // (which have been filtered by now) since we didn't verify
4045 // them earlier. No point in re-checking the stacks / enqueued
4046 // buffers given that the CSet has not changed since last time
4047 // we checked.
4048 _cm->verify_no_cset_oops(false /* verify_stacks */,
4049 false /* verify_enqueued_buffers */,
4050 true /* verify_thread_buffers */,
4051 true /* verify_fingers */);
4053 free_collection_set(g1_policy()->collection_set(), evacuation_info);
4055 eagerly_reclaim_humongous_regions();
4057 g1_policy()->clear_collection_set();
4059 cleanup_surviving_young_words();
4061 // Start a new incremental collection set for the next pause.
4062 g1_policy()->start_incremental_cset_building();
4064 clear_cset_fast_test();
4066 _young_list->reset_sampled_info();
4068 // Don't check the whole heap at this point as the
4069 // GC alloc regions from this pause have been tagged
4070 // as survivors and moved on to the survivor list.
4071 // Survivor regions will fail the !is_young() check.
4072 assert(check_young_list_empty(false /* check_heap */),
4073 "young list should be empty");
4075 #if YOUNG_LIST_VERBOSE
4076 gclog_or_tty->print_cr("Before recording survivors.\nYoung List:");
4077 _young_list->print();
4078 #endif // YOUNG_LIST_VERBOSE
4080 g1_policy()->record_survivor_regions(_young_list->survivor_length(),
4081 _young_list->first_survivor_region(),
4082 _young_list->last_survivor_region());
4084 _young_list->reset_auxilary_lists();
4086 if (evacuation_failed()) {
4087 _summary_bytes_used = recalculate_used();
4088 uint n_queues = MAX2((int)ParallelGCThreads, 1);
4089 for (uint i = 0; i < n_queues; i++) {
4090 if (_evacuation_failed_info_array[i].has_failed()) {
4091 _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]);
4092 }
4093 }
4094 } else {
4095 // The "used" of the the collection set have already been subtracted
4096 // when they were freed. Add in the bytes evacuated.
4097 _summary_bytes_used += g1_policy()->bytes_copied_during_gc();
4098 }
4100 if (g1_policy()->during_initial_mark_pause()) {
4101 // We have to do this before we notify the CM threads that
4102 // they can start working to make sure that all the
4103 // appropriate initialization is done on the CM object.
4104 concurrent_mark()->checkpointRootsInitialPost();
4105 set_marking_started();
4106 // Note that we don't actually trigger the CM thread at
4107 // this point. We do that later when we're sure that
4108 // the current thread has completed its logging output.
4109 }
4111 allocate_dummy_regions();
4113 #if YOUNG_LIST_VERBOSE
4114 gclog_or_tty->print_cr("\nEnd of the pause.\nYoung_list:");
4115 _young_list->print();
4116 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
4117 #endif // YOUNG_LIST_VERBOSE
4119 init_mutator_alloc_region();
4121 {
4122 size_t expand_bytes = g1_policy()->expansion_amount();
4123 if (expand_bytes > 0) {
4124 size_t bytes_before = capacity();
4125 // No need for an ergo verbose message here,
4126 // expansion_amount() does this when it returns a value > 0.
4127 if (!expand(expand_bytes)) {
4128 // We failed to expand the heap. Cannot do anything about it.
4129 }
4130 }
4131 }
4133 // We redo the verification but now wrt to the new CSet which
4134 // has just got initialized after the previous CSet was freed.
4135 _cm->verify_no_cset_oops(true /* verify_stacks */,
4136 true /* verify_enqueued_buffers */,
4137 true /* verify_thread_buffers */,
4138 true /* verify_fingers */);
4139 _cm->note_end_of_gc();
4141 // This timing is only used by the ergonomics to handle our pause target.
4142 // It is unclear why this should not include the full pause. We will
4143 // investigate this in CR 7178365.
4144 double sample_end_time_sec = os::elapsedTime();
4145 double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
4146 g1_policy()->record_collection_pause_end(pause_time_ms, evacuation_info);
4148 MemoryService::track_memory_usage();
4150 // In prepare_for_verify() below we'll need to scan the deferred
4151 // update buffers to bring the RSets up-to-date if
4152 // G1HRRSFlushLogBuffersOnVerify has been set. While scanning
4153 // the update buffers we'll probably need to scan cards on the
4154 // regions we just allocated to (i.e., the GC alloc
4155 // regions). However, during the last GC we called
4156 // set_saved_mark() on all the GC alloc regions, so card
4157 // scanning might skip the [saved_mark_word()...top()] area of
4158 // those regions (i.e., the area we allocated objects into
4159 // during the last GC). But it shouldn't. Given that
4160 // saved_mark_word() is conditional on whether the GC time stamp
4161 // on the region is current or not, by incrementing the GC time
4162 // stamp here we invalidate all the GC time stamps on all the
4163 // regions and saved_mark_word() will simply return top() for
4164 // all the regions. This is a nicer way of ensuring this rather
4165 // than iterating over the regions and fixing them. In fact, the
4166 // GC time stamp increment here also ensures that
4167 // saved_mark_word() will return top() between pauses, i.e.,
4168 // during concurrent refinement. So we don't need the
4169 // is_gc_active() check to decided which top to use when
4170 // scanning cards (see CR 7039627).
4171 increment_gc_time_stamp();
4173 verify_after_gc();
4174 check_bitmaps("GC End");
4176 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
4177 ref_processor_stw()->verify_no_references_recorded();
4179 // CM reference discovery will be re-enabled if necessary.
4180 }
4182 // We should do this after we potentially expand the heap so
4183 // that all the COMMIT events are generated before the end GC
4184 // event, and after we retire the GC alloc regions so that all
4185 // RETIRE events are generated before the end GC event.
4186 _hr_printer.end_gc(false /* full */, (size_t) total_collections());
4188 #ifdef TRACESPINNING
4189 ParallelTaskTerminator::print_termination_counts();
4190 #endif
4192 gc_epilogue(false);
4193 }
4195 // Print the remainder of the GC log output.
4196 log_gc_footer(os::elapsedTime() - pause_start_sec);
4198 // It is not yet to safe to tell the concurrent mark to
4199 // start as we have some optional output below. We don't want the
4200 // output from the concurrent mark thread interfering with this
4201 // logging output either.
4203 _hrm.verify_optional();
4204 verify_region_sets_optional();
4206 TASKQUEUE_STATS_ONLY(if (ParallelGCVerbose) print_taskqueue_stats());
4207 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
4209 print_heap_after_gc();
4210 trace_heap_after_gc(_gc_tracer_stw);
4212 // We must call G1MonitoringSupport::update_sizes() in the same scoping level
4213 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
4214 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
4215 // before any GC notifications are raised.
4216 g1mm()->update_sizes();
4218 _gc_tracer_stw->report_evacuation_info(&evacuation_info);
4219 _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold());
4220 _gc_timer_stw->register_gc_end();
4221 _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions());
4222 }
4223 // It should now be safe to tell the concurrent mark thread to start
4224 // without its logging output interfering with the logging output
4225 // that came from the pause.
4227 if (should_start_conc_mark) {
4228 // CAUTION: after the doConcurrentMark() call below,
4229 // the concurrent marking thread(s) could be running
4230 // concurrently with us. Make sure that anything after
4231 // this point does not assume that we are the only GC thread
4232 // running. Note: of course, the actual marking work will
4233 // not start until the safepoint itself is released in
4234 // SuspendibleThreadSet::desynchronize().
4235 doConcurrentMark();
4236 }
4238 return true;
4239 }
4241 size_t G1CollectedHeap::desired_plab_sz(GCAllocPurpose purpose)
4242 {
4243 size_t gclab_word_size;
4244 switch (purpose) {
4245 case GCAllocForSurvived:
4246 gclab_word_size = _survivor_plab_stats.desired_plab_sz();
4247 break;
4248 case GCAllocForTenured:
4249 gclab_word_size = _old_plab_stats.desired_plab_sz();
4250 break;
4251 default:
4252 assert(false, "unknown GCAllocPurpose");
4253 gclab_word_size = _old_plab_stats.desired_plab_sz();
4254 break;
4255 }
4257 // Prevent humongous PLAB sizes for two reasons:
4258 // * PLABs are allocated using a similar paths as oops, but should
4259 // never be in a humongous region
4260 // * Allowing humongous PLABs needlessly churns the region free lists
4261 return MIN2(_humongous_object_threshold_in_words, gclab_word_size);
4262 }
4264 void G1CollectedHeap::init_mutator_alloc_region() {
4265 assert(_mutator_alloc_region.get() == NULL, "pre-condition");
4266 _mutator_alloc_region.init();
4267 }
4269 void G1CollectedHeap::release_mutator_alloc_region() {
4270 _mutator_alloc_region.release();
4271 assert(_mutator_alloc_region.get() == NULL, "post-condition");
4272 }
4274 void G1CollectedHeap::use_retained_old_gc_alloc_region(EvacuationInfo& evacuation_info) {
4275 HeapRegion* retained_region = _retained_old_gc_alloc_region;
4276 _retained_old_gc_alloc_region = NULL;
4278 // We will discard the current GC alloc region if:
4279 // a) it's in the collection set (it can happen!),
4280 // b) it's already full (no point in using it),
4281 // c) it's empty (this means that it was emptied during
4282 // a cleanup and it should be on the free list now), or
4283 // d) it's humongous (this means that it was emptied
4284 // during a cleanup and was added to the free list, but
4285 // has been subsequently used to allocate a humongous
4286 // object that may be less than the region size).
4287 if (retained_region != NULL &&
4288 !retained_region->in_collection_set() &&
4289 !(retained_region->top() == retained_region->end()) &&
4290 !retained_region->is_empty() &&
4291 !retained_region->isHumongous()) {
4292 retained_region->record_top_and_timestamp();
4293 // The retained region was added to the old region set when it was
4294 // retired. We have to remove it now, since we don't allow regions
4295 // we allocate to in the region sets. We'll re-add it later, when
4296 // it's retired again.
4297 _old_set.remove(retained_region);
4298 bool during_im = g1_policy()->during_initial_mark_pause();
4299 retained_region->note_start_of_copying(during_im);
4300 _old_gc_alloc_region.set(retained_region);
4301 _hr_printer.reuse(retained_region);
4302 evacuation_info.set_alloc_regions_used_before(retained_region->used());
4303 }
4304 }
4306 void G1CollectedHeap::init_gc_alloc_regions(EvacuationInfo& evacuation_info) {
4307 assert_at_safepoint(true /* should_be_vm_thread */);
4309 _survivor_gc_alloc_region.init();
4310 _old_gc_alloc_region.init();
4312 use_retained_old_gc_alloc_region(evacuation_info);
4313 }
4315 void G1CollectedHeap::release_gc_alloc_regions(uint no_of_gc_workers, EvacuationInfo& evacuation_info) {
4316 evacuation_info.set_allocation_regions(_survivor_gc_alloc_region.count() +
4317 _old_gc_alloc_region.count());
4318 _survivor_gc_alloc_region.release();
4319 // If we have an old GC alloc region to release, we'll save it in
4320 // _retained_old_gc_alloc_region. If we don't
4321 // _retained_old_gc_alloc_region will become NULL. This is what we
4322 // want either way so no reason to check explicitly for either
4323 // condition.
4324 _retained_old_gc_alloc_region = _old_gc_alloc_region.release();
4326 if (ResizePLAB) {
4327 _survivor_plab_stats.adjust_desired_plab_sz(no_of_gc_workers);
4328 _old_plab_stats.adjust_desired_plab_sz(no_of_gc_workers);
4329 }
4330 }
4332 void G1CollectedHeap::abandon_gc_alloc_regions() {
4333 assert(_survivor_gc_alloc_region.get() == NULL, "pre-condition");
4334 assert(_old_gc_alloc_region.get() == NULL, "pre-condition");
4335 _retained_old_gc_alloc_region = NULL;
4336 }
4338 void G1CollectedHeap::init_for_evac_failure(OopsInHeapRegionClosure* cl) {
4339 _drain_in_progress = false;
4340 set_evac_failure_closure(cl);
4341 _evac_failure_scan_stack = new (ResourceObj::C_HEAP, mtGC) GrowableArray<oop>(40, true);
4342 }
4344 void G1CollectedHeap::finalize_for_evac_failure() {
4345 assert(_evac_failure_scan_stack != NULL &&
4346 _evac_failure_scan_stack->length() == 0,
4347 "Postcondition");
4348 assert(!_drain_in_progress, "Postcondition");
4349 delete _evac_failure_scan_stack;
4350 _evac_failure_scan_stack = NULL;
4351 }
4353 void G1CollectedHeap::remove_self_forwarding_pointers() {
4354 assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity");
4356 double remove_self_forwards_start = os::elapsedTime();
4358 G1ParRemoveSelfForwardPtrsTask rsfp_task(this);
4360 if (G1CollectedHeap::use_parallel_gc_threads()) {
4361 set_par_threads();
4362 workers()->run_task(&rsfp_task);
4363 set_par_threads(0);
4364 } else {
4365 rsfp_task.work(0);
4366 }
4368 assert(check_cset_heap_region_claim_values(HeapRegion::ParEvacFailureClaimValue), "sanity");
4370 // Reset the claim values in the regions in the collection set.
4371 reset_cset_heap_region_claim_values();
4373 assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity");
4375 // Now restore saved marks, if any.
4376 assert(_objs_with_preserved_marks.size() ==
4377 _preserved_marks_of_objs.size(), "Both or none.");
4378 while (!_objs_with_preserved_marks.is_empty()) {
4379 oop obj = _objs_with_preserved_marks.pop();
4380 markOop m = _preserved_marks_of_objs.pop();
4381 obj->set_mark(m);
4382 }
4383 _objs_with_preserved_marks.clear(true);
4384 _preserved_marks_of_objs.clear(true);
4386 g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0);
4387 }
4389 void G1CollectedHeap::push_on_evac_failure_scan_stack(oop obj) {
4390 _evac_failure_scan_stack->push(obj);
4391 }
4393 void G1CollectedHeap::drain_evac_failure_scan_stack() {
4394 assert(_evac_failure_scan_stack != NULL, "precondition");
4396 while (_evac_failure_scan_stack->length() > 0) {
4397 oop obj = _evac_failure_scan_stack->pop();
4398 _evac_failure_closure->set_region(heap_region_containing(obj));
4399 obj->oop_iterate_backwards(_evac_failure_closure);
4400 }
4401 }
4403 oop
4404 G1CollectedHeap::handle_evacuation_failure_par(G1ParScanThreadState* _par_scan_state,
4405 oop old) {
4406 assert(obj_in_cs(old),
4407 err_msg("obj: "PTR_FORMAT" should still be in the CSet",
4408 (HeapWord*) old));
4409 markOop m = old->mark();
4410 oop forward_ptr = old->forward_to_atomic(old);
4411 if (forward_ptr == NULL) {
4412 // Forward-to-self succeeded.
4413 assert(_par_scan_state != NULL, "par scan state");
4414 OopsInHeapRegionClosure* cl = _par_scan_state->evac_failure_closure();
4415 uint queue_num = _par_scan_state->queue_num();
4417 _evacuation_failed = true;
4418 _evacuation_failed_info_array[queue_num].register_copy_failure(old->size());
4419 if (_evac_failure_closure != cl) {
4420 MutexLockerEx x(EvacFailureStack_lock, Mutex::_no_safepoint_check_flag);
4421 assert(!_drain_in_progress,
4422 "Should only be true while someone holds the lock.");
4423 // Set the global evac-failure closure to the current thread's.
4424 assert(_evac_failure_closure == NULL, "Or locking has failed.");
4425 set_evac_failure_closure(cl);
4426 // Now do the common part.
4427 handle_evacuation_failure_common(old, m);
4428 // Reset to NULL.
4429 set_evac_failure_closure(NULL);
4430 } else {
4431 // The lock is already held, and this is recursive.
4432 assert(_drain_in_progress, "This should only be the recursive case.");
4433 handle_evacuation_failure_common(old, m);
4434 }
4435 return old;
4436 } else {
4437 // Forward-to-self failed. Either someone else managed to allocate
4438 // space for this object (old != forward_ptr) or they beat us in
4439 // self-forwarding it (old == forward_ptr).
4440 assert(old == forward_ptr || !obj_in_cs(forward_ptr),
4441 err_msg("obj: "PTR_FORMAT" forwarded to: "PTR_FORMAT" "
4442 "should not be in the CSet",
4443 (HeapWord*) old, (HeapWord*) forward_ptr));
4444 return forward_ptr;
4445 }
4446 }
4448 void G1CollectedHeap::handle_evacuation_failure_common(oop old, markOop m) {
4449 preserve_mark_if_necessary(old, m);
4451 HeapRegion* r = heap_region_containing(old);
4452 if (!r->evacuation_failed()) {
4453 r->set_evacuation_failed(true);
4454 _hr_printer.evac_failure(r);
4455 }
4457 push_on_evac_failure_scan_stack(old);
4459 if (!_drain_in_progress) {
4460 // prevent recursion in copy_to_survivor_space()
4461 _drain_in_progress = true;
4462 drain_evac_failure_scan_stack();
4463 _drain_in_progress = false;
4464 }
4465 }
4467 void G1CollectedHeap::preserve_mark_if_necessary(oop obj, markOop m) {
4468 assert(evacuation_failed(), "Oversaving!");
4469 // We want to call the "for_promotion_failure" version only in the
4470 // case of a promotion failure.
4471 if (m->must_be_preserved_for_promotion_failure(obj)) {
4472 _objs_with_preserved_marks.push(obj);
4473 _preserved_marks_of_objs.push(m);
4474 }
4475 }
4477 HeapWord* G1CollectedHeap::par_allocate_during_gc(GCAllocPurpose purpose,
4478 size_t word_size) {
4479 if (purpose == GCAllocForSurvived) {
4480 HeapWord* result = survivor_attempt_allocation(word_size);
4481 if (result != NULL) {
4482 return result;
4483 } else {
4484 // Let's try to allocate in the old gen in case we can fit the
4485 // object there.
4486 return old_attempt_allocation(word_size);
4487 }
4488 } else {
4489 assert(purpose == GCAllocForTenured, "sanity");
4490 HeapWord* result = old_attempt_allocation(word_size);
4491 if (result != NULL) {
4492 return result;
4493 } else {
4494 // Let's try to allocate in the survivors in case we can fit the
4495 // object there.
4496 return survivor_attempt_allocation(word_size);
4497 }
4498 }
4500 ShouldNotReachHere();
4501 // Trying to keep some compilers happy.
4502 return NULL;
4503 }
4505 G1ParGCAllocBuffer::G1ParGCAllocBuffer(size_t gclab_word_size) :
4506 ParGCAllocBuffer(gclab_word_size), _retired(true) { }
4508 void G1ParCopyHelper::mark_object(oop obj) {
4509 assert(!_g1->heap_region_containing(obj)->in_collection_set(), "should not mark objects in the CSet");
4511 // We know that the object is not moving so it's safe to read its size.
4512 _cm->grayRoot(obj, (size_t) obj->size(), _worker_id);
4513 }
4515 void G1ParCopyHelper::mark_forwarded_object(oop from_obj, oop to_obj) {
4516 assert(from_obj->is_forwarded(), "from obj should be forwarded");
4517 assert(from_obj->forwardee() == to_obj, "to obj should be the forwardee");
4518 assert(from_obj != to_obj, "should not be self-forwarded");
4520 assert(_g1->heap_region_containing(from_obj)->in_collection_set(), "from obj should be in the CSet");
4521 assert(!_g1->heap_region_containing(to_obj)->in_collection_set(), "should not mark objects in the CSet");
4523 // The object might be in the process of being copied by another
4524 // worker so we cannot trust that its to-space image is
4525 // well-formed. So we have to read its size from its from-space
4526 // image which we know should not be changing.
4527 _cm->grayRoot(to_obj, (size_t) from_obj->size(), _worker_id);
4528 }
4530 template <class T>
4531 void G1ParCopyHelper::do_klass_barrier(T* p, oop new_obj) {
4532 if (_g1->heap_region_containing_raw(new_obj)->is_young()) {
4533 _scanned_klass->record_modified_oops();
4534 }
4535 }
4537 template <G1Barrier barrier, G1Mark do_mark_object>
4538 template <class T>
4539 void G1ParCopyClosure<barrier, do_mark_object>::do_oop_work(T* p) {
4540 T heap_oop = oopDesc::load_heap_oop(p);
4542 if (oopDesc::is_null(heap_oop)) {
4543 return;
4544 }
4546 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
4548 assert(_worker_id == _par_scan_state->queue_num(), "sanity");
4550 G1CollectedHeap::in_cset_state_t state = _g1->in_cset_state(obj);
4552 if (state == G1CollectedHeap::InCSet) {
4553 oop forwardee;
4554 if (obj->is_forwarded()) {
4555 forwardee = obj->forwardee();
4556 } else {
4557 forwardee = _par_scan_state->copy_to_survivor_space(obj);
4558 }
4559 assert(forwardee != NULL, "forwardee should not be NULL");
4560 oopDesc::encode_store_heap_oop(p, forwardee);
4561 if (do_mark_object != G1MarkNone && forwardee != obj) {
4562 // If the object is self-forwarded we don't need to explicitly
4563 // mark it, the evacuation failure protocol will do so.
4564 mark_forwarded_object(obj, forwardee);
4565 }
4567 if (barrier == G1BarrierKlass) {
4568 do_klass_barrier(p, forwardee);
4569 }
4570 } else {
4571 if (state == G1CollectedHeap::IsHumongous) {
4572 _g1->set_humongous_is_live(obj);
4573 }
4574 // The object is not in collection set. If we're a root scanning
4575 // closure during an initial mark pause then attempt to mark the object.
4576 if (do_mark_object == G1MarkFromRoot) {
4577 mark_object(obj);
4578 }
4579 }
4581 if (barrier == G1BarrierEvac) {
4582 _par_scan_state->update_rs(_from, p, _worker_id);
4583 }
4584 }
4586 template void G1ParCopyClosure<G1BarrierEvac, G1MarkNone>::do_oop_work(oop* p);
4587 template void G1ParCopyClosure<G1BarrierEvac, G1MarkNone>::do_oop_work(narrowOop* p);
4589 class G1ParEvacuateFollowersClosure : public VoidClosure {
4590 protected:
4591 G1CollectedHeap* _g1h;
4592 G1ParScanThreadState* _par_scan_state;
4593 RefToScanQueueSet* _queues;
4594 ParallelTaskTerminator* _terminator;
4596 G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
4597 RefToScanQueueSet* queues() { return _queues; }
4598 ParallelTaskTerminator* terminator() { return _terminator; }
4600 public:
4601 G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h,
4602 G1ParScanThreadState* par_scan_state,
4603 RefToScanQueueSet* queues,
4604 ParallelTaskTerminator* terminator)
4605 : _g1h(g1h), _par_scan_state(par_scan_state),
4606 _queues(queues), _terminator(terminator) {}
4608 void do_void();
4610 private:
4611 inline bool offer_termination();
4612 };
4614 bool G1ParEvacuateFollowersClosure::offer_termination() {
4615 G1ParScanThreadState* const pss = par_scan_state();
4616 pss->start_term_time();
4617 const bool res = terminator()->offer_termination();
4618 pss->end_term_time();
4619 return res;
4620 }
4622 void G1ParEvacuateFollowersClosure::do_void() {
4623 G1ParScanThreadState* const pss = par_scan_state();
4624 pss->trim_queue();
4625 do {
4626 pss->steal_and_trim_queue(queues());
4627 } while (!offer_termination());
4628 }
4630 class G1KlassScanClosure : public KlassClosure {
4631 G1ParCopyHelper* _closure;
4632 bool _process_only_dirty;
4633 int _count;
4634 public:
4635 G1KlassScanClosure(G1ParCopyHelper* closure, bool process_only_dirty)
4636 : _process_only_dirty(process_only_dirty), _closure(closure), _count(0) {}
4637 void do_klass(Klass* klass) {
4638 // If the klass has not been dirtied we know that there's
4639 // no references into the young gen and we can skip it.
4640 if (!_process_only_dirty || klass->has_modified_oops()) {
4641 // Clean the klass since we're going to scavenge all the metadata.
4642 klass->clear_modified_oops();
4644 // Tell the closure that this klass is the Klass to scavenge
4645 // and is the one to dirty if oops are left pointing into the young gen.
4646 _closure->set_scanned_klass(klass);
4648 klass->oops_do(_closure);
4650 _closure->set_scanned_klass(NULL);
4651 }
4652 _count++;
4653 }
4654 };
4656 class G1ParTask : public AbstractGangTask {
4657 protected:
4658 G1CollectedHeap* _g1h;
4659 RefToScanQueueSet *_queues;
4660 ParallelTaskTerminator _terminator;
4661 uint _n_workers;
4663 Mutex _stats_lock;
4664 Mutex* stats_lock() { return &_stats_lock; }
4666 public:
4667 G1ParTask(G1CollectedHeap* g1h, RefToScanQueueSet *task_queues)
4668 : AbstractGangTask("G1 collection"),
4669 _g1h(g1h),
4670 _queues(task_queues),
4671 _terminator(0, _queues),
4672 _stats_lock(Mutex::leaf, "parallel G1 stats lock", true)
4673 {}
4675 RefToScanQueueSet* queues() { return _queues; }
4677 RefToScanQueue *work_queue(int i) {
4678 return queues()->queue(i);
4679 }
4681 ParallelTaskTerminator* terminator() { return &_terminator; }
4683 virtual void set_for_termination(int active_workers) {
4684 // This task calls set_n_termination() in par_non_clean_card_iterate_work()
4685 // in the young space (_par_seq_tasks) in the G1 heap
4686 // for SequentialSubTasksDone.
4687 // This task also uses SubTasksDone in SharedHeap and G1CollectedHeap
4688 // both of which need setting by set_n_termination().
4689 _g1h->SharedHeap::set_n_termination(active_workers);
4690 _g1h->set_n_termination(active_workers);
4691 terminator()->reset_for_reuse(active_workers);
4692 _n_workers = active_workers;
4693 }
4695 // Helps out with CLD processing.
4696 //
4697 // During InitialMark we need to:
4698 // 1) Scavenge all CLDs for the young GC.
4699 // 2) Mark all objects directly reachable from strong CLDs.
4700 template <G1Mark do_mark_object>
4701 class G1CLDClosure : public CLDClosure {
4702 G1ParCopyClosure<G1BarrierNone, do_mark_object>* _oop_closure;
4703 G1ParCopyClosure<G1BarrierKlass, do_mark_object> _oop_in_klass_closure;
4704 G1KlassScanClosure _klass_in_cld_closure;
4705 bool _claim;
4707 public:
4708 G1CLDClosure(G1ParCopyClosure<G1BarrierNone, do_mark_object>* oop_closure,
4709 bool only_young, bool claim)
4710 : _oop_closure(oop_closure),
4711 _oop_in_klass_closure(oop_closure->g1(),
4712 oop_closure->pss(),
4713 oop_closure->rp()),
4714 _klass_in_cld_closure(&_oop_in_klass_closure, only_young),
4715 _claim(claim) {
4717 }
4719 void do_cld(ClassLoaderData* cld) {
4720 cld->oops_do(_oop_closure, &_klass_in_cld_closure, _claim);
4721 }
4722 };
4724 class G1CodeBlobClosure: public CodeBlobClosure {
4725 OopClosure* _f;
4727 public:
4728 G1CodeBlobClosure(OopClosure* f) : _f(f) {}
4729 void do_code_blob(CodeBlob* blob) {
4730 nmethod* that = blob->as_nmethod_or_null();
4731 if (that != NULL) {
4732 if (!that->test_set_oops_do_mark()) {
4733 that->oops_do(_f);
4734 that->fix_oop_relocations();
4735 }
4736 }
4737 }
4738 };
4740 void work(uint worker_id) {
4741 if (worker_id >= _n_workers) return; // no work needed this round
4743 double start_time_ms = os::elapsedTime() * 1000.0;
4744 _g1h->g1_policy()->phase_times()->record_gc_worker_start_time(worker_id, start_time_ms);
4746 {
4747 ResourceMark rm;
4748 HandleMark hm;
4750 ReferenceProcessor* rp = _g1h->ref_processor_stw();
4752 G1ParScanThreadState pss(_g1h, worker_id, rp);
4753 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, rp);
4755 pss.set_evac_failure_closure(&evac_failure_cl);
4757 bool only_young = _g1h->g1_policy()->gcs_are_young();
4759 // Non-IM young GC.
4760 G1ParCopyClosure<G1BarrierNone, G1MarkNone> scan_only_root_cl(_g1h, &pss, rp);
4761 G1CLDClosure<G1MarkNone> scan_only_cld_cl(&scan_only_root_cl,
4762 only_young, // Only process dirty klasses.
4763 false); // No need to claim CLDs.
4764 // IM young GC.
4765 // Strong roots closures.
4766 G1ParCopyClosure<G1BarrierNone, G1MarkFromRoot> scan_mark_root_cl(_g1h, &pss, rp);
4767 G1CLDClosure<G1MarkFromRoot> scan_mark_cld_cl(&scan_mark_root_cl,
4768 false, // Process all klasses.
4769 true); // Need to claim CLDs.
4770 // Weak roots closures.
4771 G1ParCopyClosure<G1BarrierNone, G1MarkPromotedFromRoot> scan_mark_weak_root_cl(_g1h, &pss, rp);
4772 G1CLDClosure<G1MarkPromotedFromRoot> scan_mark_weak_cld_cl(&scan_mark_weak_root_cl,
4773 false, // Process all klasses.
4774 true); // Need to claim CLDs.
4776 G1CodeBlobClosure scan_only_code_cl(&scan_only_root_cl);
4777 G1CodeBlobClosure scan_mark_code_cl(&scan_mark_root_cl);
4778 // IM Weak code roots are handled later.
4780 OopClosure* strong_root_cl;
4781 OopClosure* weak_root_cl;
4782 CLDClosure* strong_cld_cl;
4783 CLDClosure* weak_cld_cl;
4784 CodeBlobClosure* strong_code_cl;
4786 if (_g1h->g1_policy()->during_initial_mark_pause()) {
4787 // We also need to mark copied objects.
4788 strong_root_cl = &scan_mark_root_cl;
4789 strong_cld_cl = &scan_mark_cld_cl;
4790 strong_code_cl = &scan_mark_code_cl;
4791 if (ClassUnloadingWithConcurrentMark) {
4792 weak_root_cl = &scan_mark_weak_root_cl;
4793 weak_cld_cl = &scan_mark_weak_cld_cl;
4794 } else {
4795 weak_root_cl = &scan_mark_root_cl;
4796 weak_cld_cl = &scan_mark_cld_cl;
4797 }
4798 } else {
4799 strong_root_cl = &scan_only_root_cl;
4800 weak_root_cl = &scan_only_root_cl;
4801 strong_cld_cl = &scan_only_cld_cl;
4802 weak_cld_cl = &scan_only_cld_cl;
4803 strong_code_cl = &scan_only_code_cl;
4804 }
4807 G1ParPushHeapRSClosure push_heap_rs_cl(_g1h, &pss);
4809 pss.start_strong_roots();
4810 _g1h->g1_process_roots(strong_root_cl,
4811 weak_root_cl,
4812 &push_heap_rs_cl,
4813 strong_cld_cl,
4814 weak_cld_cl,
4815 strong_code_cl,
4816 worker_id);
4818 pss.end_strong_roots();
4820 {
4821 double start = os::elapsedTime();
4822 G1ParEvacuateFollowersClosure evac(_g1h, &pss, _queues, &_terminator);
4823 evac.do_void();
4824 double elapsed_ms = (os::elapsedTime()-start)*1000.0;
4825 double term_ms = pss.term_time()*1000.0;
4826 _g1h->g1_policy()->phase_times()->add_obj_copy_time(worker_id, elapsed_ms-term_ms);
4827 _g1h->g1_policy()->phase_times()->record_termination(worker_id, term_ms, pss.term_attempts());
4828 }
4829 _g1h->g1_policy()->record_thread_age_table(pss.age_table());
4830 _g1h->update_surviving_young_words(pss.surviving_young_words()+1);
4832 if (ParallelGCVerbose) {
4833 MutexLocker x(stats_lock());
4834 pss.print_termination_stats(worker_id);
4835 }
4837 assert(pss.queue_is_empty(), "should be empty");
4839 // Close the inner scope so that the ResourceMark and HandleMark
4840 // destructors are executed here and are included as part of the
4841 // "GC Worker Time".
4842 }
4844 double end_time_ms = os::elapsedTime() * 1000.0;
4845 _g1h->g1_policy()->phase_times()->record_gc_worker_end_time(worker_id, end_time_ms);
4846 }
4847 };
4849 // *** Common G1 Evacuation Stuff
4851 // This method is run in a GC worker.
4853 void
4854 G1CollectedHeap::
4855 g1_process_roots(OopClosure* scan_non_heap_roots,
4856 OopClosure* scan_non_heap_weak_roots,
4857 OopsInHeapRegionClosure* scan_rs,
4858 CLDClosure* scan_strong_clds,
4859 CLDClosure* scan_weak_clds,
4860 CodeBlobClosure* scan_strong_code,
4861 uint worker_i) {
4863 // First scan the shared roots.
4864 double ext_roots_start = os::elapsedTime();
4865 double closure_app_time_sec = 0.0;
4867 bool during_im = _g1h->g1_policy()->during_initial_mark_pause();
4868 bool trace_metadata = during_im && ClassUnloadingWithConcurrentMark;
4870 BufferingOopClosure buf_scan_non_heap_roots(scan_non_heap_roots);
4871 BufferingOopClosure buf_scan_non_heap_weak_roots(scan_non_heap_weak_roots);
4873 process_roots(false, // no scoping; this is parallel code
4874 SharedHeap::SO_None,
4875 &buf_scan_non_heap_roots,
4876 &buf_scan_non_heap_weak_roots,
4877 scan_strong_clds,
4878 // Unloading Initial Marks handle the weak CLDs separately.
4879 (trace_metadata ? NULL : scan_weak_clds),
4880 scan_strong_code);
4882 // Now the CM ref_processor roots.
4883 if (!_process_strong_tasks->is_task_claimed(G1H_PS_refProcessor_oops_do)) {
4884 // We need to treat the discovered reference lists of the
4885 // concurrent mark ref processor as roots and keep entries
4886 // (which are added by the marking threads) on them live
4887 // until they can be processed at the end of marking.
4888 ref_processor_cm()->weak_oops_do(&buf_scan_non_heap_roots);
4889 }
4891 if (trace_metadata) {
4892 // Barrier to make sure all workers passed
4893 // the strong CLD and strong nmethods phases.
4894 active_strong_roots_scope()->wait_until_all_workers_done_with_threads(n_par_threads());
4896 // Now take the complement of the strong CLDs.
4897 ClassLoaderDataGraph::roots_cld_do(NULL, scan_weak_clds);
4898 }
4900 // Finish up any enqueued closure apps (attributed as object copy time).
4901 buf_scan_non_heap_roots.done();
4902 buf_scan_non_heap_weak_roots.done();
4904 double obj_copy_time_sec = buf_scan_non_heap_roots.closure_app_seconds()
4905 + buf_scan_non_heap_weak_roots.closure_app_seconds();
4907 g1_policy()->phase_times()->record_obj_copy_time(worker_i, obj_copy_time_sec * 1000.0);
4909 double ext_root_time_ms =
4910 ((os::elapsedTime() - ext_roots_start) - obj_copy_time_sec) * 1000.0;
4912 g1_policy()->phase_times()->record_ext_root_scan_time(worker_i, ext_root_time_ms);
4914 // During conc marking we have to filter the per-thread SATB buffers
4915 // to make sure we remove any oops into the CSet (which will show up
4916 // as implicitly live).
4917 double satb_filtering_ms = 0.0;
4918 if (!_process_strong_tasks->is_task_claimed(G1H_PS_filter_satb_buffers)) {
4919 if (mark_in_progress()) {
4920 double satb_filter_start = os::elapsedTime();
4922 JavaThread::satb_mark_queue_set().filter_thread_buffers();
4924 satb_filtering_ms = (os::elapsedTime() - satb_filter_start) * 1000.0;
4925 }
4926 }
4927 g1_policy()->phase_times()->record_satb_filtering_time(worker_i, satb_filtering_ms);
4929 // Now scan the complement of the collection set.
4930 MarkingCodeBlobClosure scavenge_cs_nmethods(scan_non_heap_weak_roots, CodeBlobToOopClosure::FixRelocations);
4932 g1_rem_set()->oops_into_collection_set_do(scan_rs, &scavenge_cs_nmethods, worker_i);
4934 _process_strong_tasks->all_tasks_completed();
4935 }
4937 class G1StringSymbolTableUnlinkTask : public AbstractGangTask {
4938 private:
4939 BoolObjectClosure* _is_alive;
4940 int _initial_string_table_size;
4941 int _initial_symbol_table_size;
4943 bool _process_strings;
4944 int _strings_processed;
4945 int _strings_removed;
4947 bool _process_symbols;
4948 int _symbols_processed;
4949 int _symbols_removed;
4951 bool _do_in_parallel;
4952 public:
4953 G1StringSymbolTableUnlinkTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols) :
4954 AbstractGangTask("String/Symbol Unlinking"),
4955 _is_alive(is_alive),
4956 _do_in_parallel(G1CollectedHeap::use_parallel_gc_threads()),
4957 _process_strings(process_strings), _strings_processed(0), _strings_removed(0),
4958 _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0) {
4960 _initial_string_table_size = StringTable::the_table()->table_size();
4961 _initial_symbol_table_size = SymbolTable::the_table()->table_size();
4962 if (process_strings) {
4963 StringTable::clear_parallel_claimed_index();
4964 }
4965 if (process_symbols) {
4966 SymbolTable::clear_parallel_claimed_index();
4967 }
4968 }
4970 ~G1StringSymbolTableUnlinkTask() {
4971 guarantee(!_process_strings || !_do_in_parallel || StringTable::parallel_claimed_index() >= _initial_string_table_size,
4972 err_msg("claim value "INT32_FORMAT" after unlink less than initial string table size "INT32_FORMAT,
4973 StringTable::parallel_claimed_index(), _initial_string_table_size));
4974 guarantee(!_process_symbols || !_do_in_parallel || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size,
4975 err_msg("claim value "INT32_FORMAT" after unlink less than initial symbol table size "INT32_FORMAT,
4976 SymbolTable::parallel_claimed_index(), _initial_symbol_table_size));
4978 if (G1TraceStringSymbolTableScrubbing) {
4979 gclog_or_tty->print_cr("Cleaned string and symbol table, "
4980 "strings: "SIZE_FORMAT" processed, "SIZE_FORMAT" removed, "
4981 "symbols: "SIZE_FORMAT" processed, "SIZE_FORMAT" removed",
4982 strings_processed(), strings_removed(),
4983 symbols_processed(), symbols_removed());
4984 }
4985 }
4987 void work(uint worker_id) {
4988 if (_do_in_parallel) {
4989 int strings_processed = 0;
4990 int strings_removed = 0;
4991 int symbols_processed = 0;
4992 int symbols_removed = 0;
4993 if (_process_strings) {
4994 StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed);
4995 Atomic::add(strings_processed, &_strings_processed);
4996 Atomic::add(strings_removed, &_strings_removed);
4997 }
4998 if (_process_symbols) {
4999 SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed);
5000 Atomic::add(symbols_processed, &_symbols_processed);
5001 Atomic::add(symbols_removed, &_symbols_removed);
5002 }
5003 } else {
5004 if (_process_strings) {
5005 StringTable::unlink(_is_alive, &_strings_processed, &_strings_removed);
5006 }
5007 if (_process_symbols) {
5008 SymbolTable::unlink(&_symbols_processed, &_symbols_removed);
5009 }
5010 }
5011 }
5013 size_t strings_processed() const { return (size_t)_strings_processed; }
5014 size_t strings_removed() const { return (size_t)_strings_removed; }
5016 size_t symbols_processed() const { return (size_t)_symbols_processed; }
5017 size_t symbols_removed() const { return (size_t)_symbols_removed; }
5018 };
5020 class G1CodeCacheUnloadingTask VALUE_OBJ_CLASS_SPEC {
5021 private:
5022 static Monitor* _lock;
5024 BoolObjectClosure* const _is_alive;
5025 const bool _unloading_occurred;
5026 const uint _num_workers;
5028 // Variables used to claim nmethods.
5029 nmethod* _first_nmethod;
5030 volatile nmethod* _claimed_nmethod;
5032 // The list of nmethods that need to be processed by the second pass.
5033 volatile nmethod* _postponed_list;
5034 volatile uint _num_entered_barrier;
5036 public:
5037 G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) :
5038 _is_alive(is_alive),
5039 _unloading_occurred(unloading_occurred),
5040 _num_workers(num_workers),
5041 _first_nmethod(NULL),
5042 _claimed_nmethod(NULL),
5043 _postponed_list(NULL),
5044 _num_entered_barrier(0)
5045 {
5046 nmethod::increase_unloading_clock();
5047 _first_nmethod = CodeCache::alive_nmethod(CodeCache::first());
5048 _claimed_nmethod = (volatile nmethod*)_first_nmethod;
5049 }
5051 ~G1CodeCacheUnloadingTask() {
5052 CodeCache::verify_clean_inline_caches();
5054 CodeCache::set_needs_cache_clean(false);
5055 guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be");
5057 CodeCache::verify_icholder_relocations();
5058 }
5060 private:
5061 void add_to_postponed_list(nmethod* nm) {
5062 nmethod* old;
5063 do {
5064 old = (nmethod*)_postponed_list;
5065 nm->set_unloading_next(old);
5066 } while ((nmethod*)Atomic::cmpxchg_ptr(nm, &_postponed_list, old) != old);
5067 }
5069 void clean_nmethod(nmethod* nm) {
5070 bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred);
5072 if (postponed) {
5073 // This nmethod referred to an nmethod that has not been cleaned/unloaded yet.
5074 add_to_postponed_list(nm);
5075 }
5077 // Mark that this thread has been cleaned/unloaded.
5078 // After this call, it will be safe to ask if this nmethod was unloaded or not.
5079 nm->set_unloading_clock(nmethod::global_unloading_clock());
5080 }
5082 void clean_nmethod_postponed(nmethod* nm) {
5083 nm->do_unloading_parallel_postponed(_is_alive, _unloading_occurred);
5084 }
5086 static const int MaxClaimNmethods = 16;
5088 void claim_nmethods(nmethod** claimed_nmethods, int *num_claimed_nmethods) {
5089 nmethod* first;
5090 nmethod* last;
5092 do {
5093 *num_claimed_nmethods = 0;
5095 first = last = (nmethod*)_claimed_nmethod;
5097 if (first != NULL) {
5098 for (int i = 0; i < MaxClaimNmethods; i++) {
5099 last = CodeCache::alive_nmethod(CodeCache::next(last));
5101 if (last == NULL) {
5102 break;
5103 }
5105 claimed_nmethods[i] = last;
5106 (*num_claimed_nmethods)++;
5107 }
5108 }
5110 } while ((nmethod*)Atomic::cmpxchg_ptr(last, &_claimed_nmethod, first) != first);
5111 }
5113 nmethod* claim_postponed_nmethod() {
5114 nmethod* claim;
5115 nmethod* next;
5117 do {
5118 claim = (nmethod*)_postponed_list;
5119 if (claim == NULL) {
5120 return NULL;
5121 }
5123 next = claim->unloading_next();
5125 } while ((nmethod*)Atomic::cmpxchg_ptr(next, &_postponed_list, claim) != claim);
5127 return claim;
5128 }
5130 public:
5131 // Mark that we're done with the first pass of nmethod cleaning.
5132 void barrier_mark(uint worker_id) {
5133 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
5134 _num_entered_barrier++;
5135 if (_num_entered_barrier == _num_workers) {
5136 ml.notify_all();
5137 }
5138 }
5140 // See if we have to wait for the other workers to
5141 // finish their first-pass nmethod cleaning work.
5142 void barrier_wait(uint worker_id) {
5143 if (_num_entered_barrier < _num_workers) {
5144 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
5145 while (_num_entered_barrier < _num_workers) {
5146 ml.wait(Mutex::_no_safepoint_check_flag, 0, false);
5147 }
5148 }
5149 }
5151 // Cleaning and unloading of nmethods. Some work has to be postponed
5152 // to the second pass, when we know which nmethods survive.
5153 void work_first_pass(uint worker_id) {
5154 // The first nmethods is claimed by the first worker.
5155 if (worker_id == 0 && _first_nmethod != NULL) {
5156 clean_nmethod(_first_nmethod);
5157 _first_nmethod = NULL;
5158 }
5160 int num_claimed_nmethods;
5161 nmethod* claimed_nmethods[MaxClaimNmethods];
5163 while (true) {
5164 claim_nmethods(claimed_nmethods, &num_claimed_nmethods);
5166 if (num_claimed_nmethods == 0) {
5167 break;
5168 }
5170 for (int i = 0; i < num_claimed_nmethods; i++) {
5171 clean_nmethod(claimed_nmethods[i]);
5172 }
5173 }
5174 }
5176 void work_second_pass(uint worker_id) {
5177 nmethod* nm;
5178 // Take care of postponed nmethods.
5179 while ((nm = claim_postponed_nmethod()) != NULL) {
5180 clean_nmethod_postponed(nm);
5181 }
5182 }
5183 };
5185 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock");
5187 class G1KlassCleaningTask : public StackObj {
5188 BoolObjectClosure* _is_alive;
5189 volatile jint _clean_klass_tree_claimed;
5190 ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator;
5192 public:
5193 G1KlassCleaningTask(BoolObjectClosure* is_alive) :
5194 _is_alive(is_alive),
5195 _clean_klass_tree_claimed(0),
5196 _klass_iterator() {
5197 }
5199 private:
5200 bool claim_clean_klass_tree_task() {
5201 if (_clean_klass_tree_claimed) {
5202 return false;
5203 }
5205 return Atomic::cmpxchg(1, (jint*)&_clean_klass_tree_claimed, 0) == 0;
5206 }
5208 InstanceKlass* claim_next_klass() {
5209 Klass* klass;
5210 do {
5211 klass =_klass_iterator.next_klass();
5212 } while (klass != NULL && !klass->oop_is_instance());
5214 return (InstanceKlass*)klass;
5215 }
5217 public:
5219 void clean_klass(InstanceKlass* ik) {
5220 ik->clean_implementors_list(_is_alive);
5221 ik->clean_method_data(_is_alive);
5223 // G1 specific cleanup work that has
5224 // been moved here to be done in parallel.
5225 ik->clean_dependent_nmethods();
5226 }
5228 void work() {
5229 ResourceMark rm;
5231 // One worker will clean the subklass/sibling klass tree.
5232 if (claim_clean_klass_tree_task()) {
5233 Klass::clean_subklass_tree(_is_alive);
5234 }
5236 // All workers will help cleaning the classes,
5237 InstanceKlass* klass;
5238 while ((klass = claim_next_klass()) != NULL) {
5239 clean_klass(klass);
5240 }
5241 }
5242 };
5244 // To minimize the remark pause times, the tasks below are done in parallel.
5245 class G1ParallelCleaningTask : public AbstractGangTask {
5246 private:
5247 G1StringSymbolTableUnlinkTask _string_symbol_task;
5248 G1CodeCacheUnloadingTask _code_cache_task;
5249 G1KlassCleaningTask _klass_cleaning_task;
5251 public:
5252 // The constructor is run in the VMThread.
5253 G1ParallelCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, uint num_workers, bool unloading_occurred) :
5254 AbstractGangTask("Parallel Cleaning"),
5255 _string_symbol_task(is_alive, process_strings, process_symbols),
5256 _code_cache_task(num_workers, is_alive, unloading_occurred),
5257 _klass_cleaning_task(is_alive) {
5258 }
5260 // The parallel work done by all worker threads.
5261 void work(uint worker_id) {
5262 // Do first pass of code cache cleaning.
5263 _code_cache_task.work_first_pass(worker_id);
5265 // Let the threads mark that the first pass is done.
5266 _code_cache_task.barrier_mark(worker_id);
5268 // Clean the Strings and Symbols.
5269 _string_symbol_task.work(worker_id);
5271 // Wait for all workers to finish the first code cache cleaning pass.
5272 _code_cache_task.barrier_wait(worker_id);
5274 // Do the second code cache cleaning work, which realize on
5275 // the liveness information gathered during the first pass.
5276 _code_cache_task.work_second_pass(worker_id);
5278 // Clean all klasses that were not unloaded.
5279 _klass_cleaning_task.work();
5280 }
5281 };
5284 void G1CollectedHeap::parallel_cleaning(BoolObjectClosure* is_alive,
5285 bool process_strings,
5286 bool process_symbols,
5287 bool class_unloading_occurred) {
5288 uint n_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
5289 workers()->active_workers() : 1);
5291 G1ParallelCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols,
5292 n_workers, class_unloading_occurred);
5293 if (G1CollectedHeap::use_parallel_gc_threads()) {
5294 set_par_threads(n_workers);
5295 workers()->run_task(&g1_unlink_task);
5296 set_par_threads(0);
5297 } else {
5298 g1_unlink_task.work(0);
5299 }
5300 }
5302 void G1CollectedHeap::unlink_string_and_symbol_table(BoolObjectClosure* is_alive,
5303 bool process_strings, bool process_symbols) {
5304 {
5305 uint n_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
5306 _g1h->workers()->active_workers() : 1);
5307 G1StringSymbolTableUnlinkTask g1_unlink_task(is_alive, process_strings, process_symbols);
5308 if (G1CollectedHeap::use_parallel_gc_threads()) {
5309 set_par_threads(n_workers);
5310 workers()->run_task(&g1_unlink_task);
5311 set_par_threads(0);
5312 } else {
5313 g1_unlink_task.work(0);
5314 }
5315 }
5317 if (G1StringDedup::is_enabled()) {
5318 G1StringDedup::unlink(is_alive);
5319 }
5320 }
5322 class G1RedirtyLoggedCardsTask : public AbstractGangTask {
5323 private:
5324 DirtyCardQueueSet* _queue;
5325 public:
5326 G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue) : AbstractGangTask("Redirty Cards"), _queue(queue) { }
5328 virtual void work(uint worker_id) {
5329 double start_time = os::elapsedTime();
5331 RedirtyLoggedCardTableEntryClosure cl;
5332 if (G1CollectedHeap::heap()->use_parallel_gc_threads()) {
5333 _queue->par_apply_closure_to_all_completed_buffers(&cl);
5334 } else {
5335 _queue->apply_closure_to_all_completed_buffers(&cl);
5336 }
5338 G1GCPhaseTimes* timer = G1CollectedHeap::heap()->g1_policy()->phase_times();
5339 timer->record_redirty_logged_cards_time_ms(worker_id, (os::elapsedTime() - start_time) * 1000.0);
5340 timer->record_redirty_logged_cards_processed_cards(worker_id, cl.num_processed());
5341 }
5342 };
5344 void G1CollectedHeap::redirty_logged_cards() {
5345 guarantee(G1DeferredRSUpdate, "Must only be called when using deferred RS updates.");
5346 double redirty_logged_cards_start = os::elapsedTime();
5348 uint n_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
5349 _g1h->workers()->active_workers() : 1);
5351 G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set());
5352 dirty_card_queue_set().reset_for_par_iteration();
5353 if (use_parallel_gc_threads()) {
5354 set_par_threads(n_workers);
5355 workers()->run_task(&redirty_task);
5356 set_par_threads(0);
5357 } else {
5358 redirty_task.work(0);
5359 }
5361 DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set();
5362 dcq.merge_bufferlists(&dirty_card_queue_set());
5363 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
5365 g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0);
5366 }
5368 // Weak Reference Processing support
5370 // An always "is_alive" closure that is used to preserve referents.
5371 // If the object is non-null then it's alive. Used in the preservation
5372 // of referent objects that are pointed to by reference objects
5373 // discovered by the CM ref processor.
5374 class G1AlwaysAliveClosure: public BoolObjectClosure {
5375 G1CollectedHeap* _g1;
5376 public:
5377 G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
5378 bool do_object_b(oop p) {
5379 if (p != NULL) {
5380 return true;
5381 }
5382 return false;
5383 }
5384 };
5386 bool G1STWIsAliveClosure::do_object_b(oop p) {
5387 // An object is reachable if it is outside the collection set,
5388 // or is inside and copied.
5389 return !_g1->obj_in_cs(p) || p->is_forwarded();
5390 }
5392 // Non Copying Keep Alive closure
5393 class G1KeepAliveClosure: public OopClosure {
5394 G1CollectedHeap* _g1;
5395 public:
5396 G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
5397 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
5398 void do_oop(oop* p) {
5399 oop obj = *p;
5401 G1CollectedHeap::in_cset_state_t cset_state = _g1->in_cset_state(obj);
5402 if (obj == NULL || cset_state == G1CollectedHeap::InNeither) {
5403 return;
5404 }
5405 if (cset_state == G1CollectedHeap::InCSet) {
5406 assert( obj->is_forwarded(), "invariant" );
5407 *p = obj->forwardee();
5408 } else {
5409 assert(!obj->is_forwarded(), "invariant" );
5410 assert(cset_state == G1CollectedHeap::IsHumongous,
5411 err_msg("Only allowed InCSet state is IsHumongous, but is %d", cset_state));
5412 _g1->set_humongous_is_live(obj);
5413 }
5414 }
5415 };
5417 // Copying Keep Alive closure - can be called from both
5418 // serial and parallel code as long as different worker
5419 // threads utilize different G1ParScanThreadState instances
5420 // and different queues.
5422 class G1CopyingKeepAliveClosure: public OopClosure {
5423 G1CollectedHeap* _g1h;
5424 OopClosure* _copy_non_heap_obj_cl;
5425 G1ParScanThreadState* _par_scan_state;
5427 public:
5428 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
5429 OopClosure* non_heap_obj_cl,
5430 G1ParScanThreadState* pss):
5431 _g1h(g1h),
5432 _copy_non_heap_obj_cl(non_heap_obj_cl),
5433 _par_scan_state(pss)
5434 {}
5436 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
5437 virtual void do_oop( oop* p) { do_oop_work(p); }
5439 template <class T> void do_oop_work(T* p) {
5440 oop obj = oopDesc::load_decode_heap_oop(p);
5442 if (_g1h->is_in_cset_or_humongous(obj)) {
5443 // If the referent object has been forwarded (either copied
5444 // to a new location or to itself in the event of an
5445 // evacuation failure) then we need to update the reference
5446 // field and, if both reference and referent are in the G1
5447 // heap, update the RSet for the referent.
5448 //
5449 // If the referent has not been forwarded then we have to keep
5450 // it alive by policy. Therefore we have copy the referent.
5451 //
5452 // If the reference field is in the G1 heap then we can push
5453 // on the PSS queue. When the queue is drained (after each
5454 // phase of reference processing) the object and it's followers
5455 // will be copied, the reference field set to point to the
5456 // new location, and the RSet updated. Otherwise we need to
5457 // use the the non-heap or metadata closures directly to copy
5458 // the referent object and update the pointer, while avoiding
5459 // updating the RSet.
5461 if (_g1h->is_in_g1_reserved(p)) {
5462 _par_scan_state->push_on_queue(p);
5463 } else {
5464 assert(!Metaspace::contains((const void*)p),
5465 err_msg("Unexpectedly found a pointer from metadata: "
5466 PTR_FORMAT, p));
5467 _copy_non_heap_obj_cl->do_oop(p);
5468 }
5469 }
5470 }
5471 };
5473 // Serial drain queue closure. Called as the 'complete_gc'
5474 // closure for each discovered list in some of the
5475 // reference processing phases.
5477 class G1STWDrainQueueClosure: public VoidClosure {
5478 protected:
5479 G1CollectedHeap* _g1h;
5480 G1ParScanThreadState* _par_scan_state;
5482 G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
5484 public:
5485 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
5486 _g1h(g1h),
5487 _par_scan_state(pss)
5488 { }
5490 void do_void() {
5491 G1ParScanThreadState* const pss = par_scan_state();
5492 pss->trim_queue();
5493 }
5494 };
5496 // Parallel Reference Processing closures
5498 // Implementation of AbstractRefProcTaskExecutor for parallel reference
5499 // processing during G1 evacuation pauses.
5501 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
5502 private:
5503 G1CollectedHeap* _g1h;
5504 RefToScanQueueSet* _queues;
5505 FlexibleWorkGang* _workers;
5506 int _active_workers;
5508 public:
5509 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
5510 FlexibleWorkGang* workers,
5511 RefToScanQueueSet *task_queues,
5512 int n_workers) :
5513 _g1h(g1h),
5514 _queues(task_queues),
5515 _workers(workers),
5516 _active_workers(n_workers)
5517 {
5518 assert(n_workers > 0, "shouldn't call this otherwise");
5519 }
5521 // Executes the given task using concurrent marking worker threads.
5522 virtual void execute(ProcessTask& task);
5523 virtual void execute(EnqueueTask& task);
5524 };
5526 // Gang task for possibly parallel reference processing
5528 class G1STWRefProcTaskProxy: public AbstractGangTask {
5529 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
5530 ProcessTask& _proc_task;
5531 G1CollectedHeap* _g1h;
5532 RefToScanQueueSet *_task_queues;
5533 ParallelTaskTerminator* _terminator;
5535 public:
5536 G1STWRefProcTaskProxy(ProcessTask& proc_task,
5537 G1CollectedHeap* g1h,
5538 RefToScanQueueSet *task_queues,
5539 ParallelTaskTerminator* terminator) :
5540 AbstractGangTask("Process reference objects in parallel"),
5541 _proc_task(proc_task),
5542 _g1h(g1h),
5543 _task_queues(task_queues),
5544 _terminator(terminator)
5545 {}
5547 virtual void work(uint worker_id) {
5548 // The reference processing task executed by a single worker.
5549 ResourceMark rm;
5550 HandleMark hm;
5552 G1STWIsAliveClosure is_alive(_g1h);
5554 G1ParScanThreadState pss(_g1h, worker_id, NULL);
5555 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5557 pss.set_evac_failure_closure(&evac_failure_cl);
5559 G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL);
5561 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5563 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5565 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5566 // We also need to mark copied objects.
5567 copy_non_heap_cl = ©_mark_non_heap_cl;
5568 }
5570 // Keep alive closure.
5571 G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, &pss);
5573 // Complete GC closure
5574 G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _task_queues, _terminator);
5576 // Call the reference processing task's work routine.
5577 _proc_task.work(worker_id, is_alive, keep_alive, drain_queue);
5579 // Note we cannot assert that the refs array is empty here as not all
5580 // of the processing tasks (specifically phase2 - pp2_work) execute
5581 // the complete_gc closure (which ordinarily would drain the queue) so
5582 // the queue may not be empty.
5583 }
5584 };
5586 // Driver routine for parallel reference processing.
5587 // Creates an instance of the ref processing gang
5588 // task and has the worker threads execute it.
5589 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) {
5590 assert(_workers != NULL, "Need parallel worker threads.");
5592 ParallelTaskTerminator terminator(_active_workers, _queues);
5593 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _queues, &terminator);
5595 _g1h->set_par_threads(_active_workers);
5596 _workers->run_task(&proc_task_proxy);
5597 _g1h->set_par_threads(0);
5598 }
5600 // Gang task for parallel reference enqueueing.
5602 class G1STWRefEnqueueTaskProxy: public AbstractGangTask {
5603 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
5604 EnqueueTask& _enq_task;
5606 public:
5607 G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) :
5608 AbstractGangTask("Enqueue reference objects in parallel"),
5609 _enq_task(enq_task)
5610 { }
5612 virtual void work(uint worker_id) {
5613 _enq_task.work(worker_id);
5614 }
5615 };
5617 // Driver routine for parallel reference enqueueing.
5618 // Creates an instance of the ref enqueueing gang
5619 // task and has the worker threads execute it.
5621 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
5622 assert(_workers != NULL, "Need parallel worker threads.");
5624 G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task);
5626 _g1h->set_par_threads(_active_workers);
5627 _workers->run_task(&enq_task_proxy);
5628 _g1h->set_par_threads(0);
5629 }
5631 // End of weak reference support closures
5633 // Abstract task used to preserve (i.e. copy) any referent objects
5634 // that are in the collection set and are pointed to by reference
5635 // objects discovered by the CM ref processor.
5637 class G1ParPreserveCMReferentsTask: public AbstractGangTask {
5638 protected:
5639 G1CollectedHeap* _g1h;
5640 RefToScanQueueSet *_queues;
5641 ParallelTaskTerminator _terminator;
5642 uint _n_workers;
5644 public:
5645 G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h,int workers, RefToScanQueueSet *task_queues) :
5646 AbstractGangTask("ParPreserveCMReferents"),
5647 _g1h(g1h),
5648 _queues(task_queues),
5649 _terminator(workers, _queues),
5650 _n_workers(workers)
5651 { }
5653 void work(uint worker_id) {
5654 ResourceMark rm;
5655 HandleMark hm;
5657 G1ParScanThreadState pss(_g1h, worker_id, NULL);
5658 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5660 pss.set_evac_failure_closure(&evac_failure_cl);
5662 assert(pss.queue_is_empty(), "both queue and overflow should be empty");
5664 G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL);
5666 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5668 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5670 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5671 // We also need to mark copied objects.
5672 copy_non_heap_cl = ©_mark_non_heap_cl;
5673 }
5675 // Is alive closure
5676 G1AlwaysAliveClosure always_alive(_g1h);
5678 // Copying keep alive closure. Applied to referent objects that need
5679 // to be copied.
5680 G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, &pss);
5682 ReferenceProcessor* rp = _g1h->ref_processor_cm();
5684 uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q();
5685 uint stride = MIN2(MAX2(_n_workers, 1U), limit);
5687 // limit is set using max_num_q() - which was set using ParallelGCThreads.
5688 // So this must be true - but assert just in case someone decides to
5689 // change the worker ids.
5690 assert(0 <= worker_id && worker_id < limit, "sanity");
5691 assert(!rp->discovery_is_atomic(), "check this code");
5693 // Select discovered lists [i, i+stride, i+2*stride,...,limit)
5694 for (uint idx = worker_id; idx < limit; idx += stride) {
5695 DiscoveredList& ref_list = rp->discovered_refs()[idx];
5697 DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive);
5698 while (iter.has_next()) {
5699 // Since discovery is not atomic for the CM ref processor, we
5700 // can see some null referent objects.
5701 iter.load_ptrs(DEBUG_ONLY(true));
5702 oop ref = iter.obj();
5704 // This will filter nulls.
5705 if (iter.is_referent_alive()) {
5706 iter.make_referent_alive();
5707 }
5708 iter.move_to_next();
5709 }
5710 }
5712 // Drain the queue - which may cause stealing
5713 G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _queues, &_terminator);
5714 drain_queue.do_void();
5715 // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure
5716 assert(pss.queue_is_empty(), "should be");
5717 }
5718 };
5720 // Weak Reference processing during an evacuation pause (part 1).
5721 void G1CollectedHeap::process_discovered_references(uint no_of_gc_workers) {
5722 double ref_proc_start = os::elapsedTime();
5724 ReferenceProcessor* rp = _ref_processor_stw;
5725 assert(rp->discovery_enabled(), "should have been enabled");
5727 // Any reference objects, in the collection set, that were 'discovered'
5728 // by the CM ref processor should have already been copied (either by
5729 // applying the external root copy closure to the discovered lists, or
5730 // by following an RSet entry).
5731 //
5732 // But some of the referents, that are in the collection set, that these
5733 // reference objects point to may not have been copied: the STW ref
5734 // processor would have seen that the reference object had already
5735 // been 'discovered' and would have skipped discovering the reference,
5736 // but would not have treated the reference object as a regular oop.
5737 // As a result the copy closure would not have been applied to the
5738 // referent object.
5739 //
5740 // We need to explicitly copy these referent objects - the references
5741 // will be processed at the end of remarking.
5742 //
5743 // We also need to do this copying before we process the reference
5744 // objects discovered by the STW ref processor in case one of these
5745 // referents points to another object which is also referenced by an
5746 // object discovered by the STW ref processor.
5748 assert(!G1CollectedHeap::use_parallel_gc_threads() ||
5749 no_of_gc_workers == workers()->active_workers(),
5750 "Need to reset active GC workers");
5752 set_par_threads(no_of_gc_workers);
5753 G1ParPreserveCMReferentsTask keep_cm_referents(this,
5754 no_of_gc_workers,
5755 _task_queues);
5757 if (G1CollectedHeap::use_parallel_gc_threads()) {
5758 workers()->run_task(&keep_cm_referents);
5759 } else {
5760 keep_cm_referents.work(0);
5761 }
5763 set_par_threads(0);
5765 // Closure to test whether a referent is alive.
5766 G1STWIsAliveClosure is_alive(this);
5768 // Even when parallel reference processing is enabled, the processing
5769 // of JNI refs is serial and performed serially by the current thread
5770 // rather than by a worker. The following PSS will be used for processing
5771 // JNI refs.
5773 // Use only a single queue for this PSS.
5774 G1ParScanThreadState pss(this, 0, NULL);
5776 // We do not embed a reference processor in the copying/scanning
5777 // closures while we're actually processing the discovered
5778 // reference objects.
5779 G1ParScanHeapEvacFailureClosure evac_failure_cl(this, &pss, NULL);
5781 pss.set_evac_failure_closure(&evac_failure_cl);
5783 assert(pss.queue_is_empty(), "pre-condition");
5785 G1ParScanExtRootClosure only_copy_non_heap_cl(this, &pss, NULL);
5787 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(this, &pss, NULL);
5789 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5791 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5792 // We also need to mark copied objects.
5793 copy_non_heap_cl = ©_mark_non_heap_cl;
5794 }
5796 // Keep alive closure.
5797 G1CopyingKeepAliveClosure keep_alive(this, copy_non_heap_cl, &pss);
5799 // Serial Complete GC closure
5800 G1STWDrainQueueClosure drain_queue(this, &pss);
5802 // Setup the soft refs policy...
5803 rp->setup_policy(false);
5805 ReferenceProcessorStats stats;
5806 if (!rp->processing_is_mt()) {
5807 // Serial reference processing...
5808 stats = rp->process_discovered_references(&is_alive,
5809 &keep_alive,
5810 &drain_queue,
5811 NULL,
5812 _gc_timer_stw,
5813 _gc_tracer_stw->gc_id());
5814 } else {
5815 // Parallel reference processing
5816 assert(rp->num_q() == no_of_gc_workers, "sanity");
5817 assert(no_of_gc_workers <= rp->max_num_q(), "sanity");
5819 G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers);
5820 stats = rp->process_discovered_references(&is_alive,
5821 &keep_alive,
5822 &drain_queue,
5823 &par_task_executor,
5824 _gc_timer_stw,
5825 _gc_tracer_stw->gc_id());
5826 }
5828 _gc_tracer_stw->report_gc_reference_stats(stats);
5830 // We have completed copying any necessary live referent objects.
5831 assert(pss.queue_is_empty(), "both queue and overflow should be empty");
5833 double ref_proc_time = os::elapsedTime() - ref_proc_start;
5834 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
5835 }
5837 // Weak Reference processing during an evacuation pause (part 2).
5838 void G1CollectedHeap::enqueue_discovered_references(uint no_of_gc_workers) {
5839 double ref_enq_start = os::elapsedTime();
5841 ReferenceProcessor* rp = _ref_processor_stw;
5842 assert(!rp->discovery_enabled(), "should have been disabled as part of processing");
5844 // Now enqueue any remaining on the discovered lists on to
5845 // the pending list.
5846 if (!rp->processing_is_mt()) {
5847 // Serial reference processing...
5848 rp->enqueue_discovered_references();
5849 } else {
5850 // Parallel reference enqueueing
5852 assert(no_of_gc_workers == workers()->active_workers(),
5853 "Need to reset active workers");
5854 assert(rp->num_q() == no_of_gc_workers, "sanity");
5855 assert(no_of_gc_workers <= rp->max_num_q(), "sanity");
5857 G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers);
5858 rp->enqueue_discovered_references(&par_task_executor);
5859 }
5861 rp->verify_no_references_recorded();
5862 assert(!rp->discovery_enabled(), "should have been disabled");
5864 // FIXME
5865 // CM's reference processing also cleans up the string and symbol tables.
5866 // Should we do that here also? We could, but it is a serial operation
5867 // and could significantly increase the pause time.
5869 double ref_enq_time = os::elapsedTime() - ref_enq_start;
5870 g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0);
5871 }
5873 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info) {
5874 _expand_heap_after_alloc_failure = true;
5875 _evacuation_failed = false;
5877 // Should G1EvacuationFailureALot be in effect for this GC?
5878 NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();)
5880 g1_rem_set()->prepare_for_oops_into_collection_set_do();
5882 // Disable the hot card cache.
5883 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
5884 hot_card_cache->reset_hot_cache_claimed_index();
5885 hot_card_cache->set_use_cache(false);
5887 uint n_workers;
5888 if (G1CollectedHeap::use_parallel_gc_threads()) {
5889 n_workers =
5890 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
5891 workers()->active_workers(),
5892 Threads::number_of_non_daemon_threads());
5893 assert(UseDynamicNumberOfGCThreads ||
5894 n_workers == workers()->total_workers(),
5895 "If not dynamic should be using all the workers");
5896 workers()->set_active_workers(n_workers);
5897 set_par_threads(n_workers);
5898 } else {
5899 assert(n_par_threads() == 0,
5900 "Should be the original non-parallel value");
5901 n_workers = 1;
5902 }
5904 G1ParTask g1_par_task(this, _task_queues);
5906 init_for_evac_failure(NULL);
5908 rem_set()->prepare_for_younger_refs_iterate(true);
5910 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
5911 double start_par_time_sec = os::elapsedTime();
5912 double end_par_time_sec;
5914 {
5915 StrongRootsScope srs(this);
5916 // InitialMark needs claim bits to keep track of the marked-through CLDs.
5917 if (g1_policy()->during_initial_mark_pause()) {
5918 ClassLoaderDataGraph::clear_claimed_marks();
5919 }
5921 if (G1CollectedHeap::use_parallel_gc_threads()) {
5922 // The individual threads will set their evac-failure closures.
5923 if (ParallelGCVerbose) G1ParScanThreadState::print_termination_stats_hdr();
5924 // These tasks use ShareHeap::_process_strong_tasks
5925 assert(UseDynamicNumberOfGCThreads ||
5926 workers()->active_workers() == workers()->total_workers(),
5927 "If not dynamic should be using all the workers");
5928 workers()->run_task(&g1_par_task);
5929 } else {
5930 g1_par_task.set_for_termination(n_workers);
5931 g1_par_task.work(0);
5932 }
5933 end_par_time_sec = os::elapsedTime();
5935 // Closing the inner scope will execute the destructor
5936 // for the StrongRootsScope object. We record the current
5937 // elapsed time before closing the scope so that time
5938 // taken for the SRS destructor is NOT included in the
5939 // reported parallel time.
5940 }
5942 double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0;
5943 g1_policy()->phase_times()->record_par_time(par_time_ms);
5945 double code_root_fixup_time_ms =
5946 (os::elapsedTime() - end_par_time_sec) * 1000.0;
5947 g1_policy()->phase_times()->record_code_root_fixup_time(code_root_fixup_time_ms);
5949 set_par_threads(0);
5951 // Process any discovered reference objects - we have
5952 // to do this _before_ we retire the GC alloc regions
5953 // as we may have to copy some 'reachable' referent
5954 // objects (and their reachable sub-graphs) that were
5955 // not copied during the pause.
5956 process_discovered_references(n_workers);
5958 // Weak root processing.
5959 {
5960 G1STWIsAliveClosure is_alive(this);
5961 G1KeepAliveClosure keep_alive(this);
5962 JNIHandles::weak_oops_do(&is_alive, &keep_alive);
5963 if (G1StringDedup::is_enabled()) {
5964 G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive);
5965 }
5966 }
5968 release_gc_alloc_regions(n_workers, evacuation_info);
5969 g1_rem_set()->cleanup_after_oops_into_collection_set_do();
5971 // Reset and re-enable the hot card cache.
5972 // Note the counts for the cards in the regions in the
5973 // collection set are reset when the collection set is freed.
5974 hot_card_cache->reset_hot_cache();
5975 hot_card_cache->set_use_cache(true);
5977 // Migrate the strong code roots attached to each region in
5978 // the collection set. Ideally we would like to do this
5979 // after we have finished the scanning/evacuation of the
5980 // strong code roots for a particular heap region.
5981 migrate_strong_code_roots();
5983 purge_code_root_memory();
5985 if (g1_policy()->during_initial_mark_pause()) {
5986 // Reset the claim values set during marking the strong code roots
5987 reset_heap_region_claim_values();
5988 }
5990 finalize_for_evac_failure();
5992 if (evacuation_failed()) {
5993 remove_self_forwarding_pointers();
5995 // Reset the G1EvacuationFailureALot counters and flags
5996 // Note: the values are reset only when an actual
5997 // evacuation failure occurs.
5998 NOT_PRODUCT(reset_evacuation_should_fail();)
5999 }
6001 // Enqueue any remaining references remaining on the STW
6002 // reference processor's discovered lists. We need to do
6003 // this after the card table is cleaned (and verified) as
6004 // the act of enqueueing entries on to the pending list
6005 // will log these updates (and dirty their associated
6006 // cards). We need these updates logged to update any
6007 // RSets.
6008 enqueue_discovered_references(n_workers);
6010 if (G1DeferredRSUpdate) {
6011 redirty_logged_cards();
6012 }
6013 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
6014 }
6016 void G1CollectedHeap::free_region(HeapRegion* hr,
6017 FreeRegionList* free_list,
6018 bool par,
6019 bool locked) {
6020 assert(!hr->isHumongous(), "this is only for non-humongous regions");
6021 assert(!hr->is_empty(), "the region should not be empty");
6022 assert(_hrm.is_available(hr->hrm_index()), "region should be committed");
6023 assert(free_list != NULL, "pre-condition");
6025 if (G1VerifyBitmaps) {
6026 MemRegion mr(hr->bottom(), hr->end());
6027 concurrent_mark()->clearRangePrevBitmap(mr);
6028 }
6030 // Clear the card counts for this region.
6031 // Note: we only need to do this if the region is not young
6032 // (since we don't refine cards in young regions).
6033 if (!hr->is_young()) {
6034 _cg1r->hot_card_cache()->reset_card_counts(hr);
6035 }
6036 hr->hr_clear(par, true /* clear_space */, locked /* locked */);
6037 free_list->add_ordered(hr);
6038 }
6040 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
6041 FreeRegionList* free_list,
6042 bool par) {
6043 assert(hr->startsHumongous(), "this is only for starts humongous regions");
6044 assert(free_list != NULL, "pre-condition");
6046 size_t hr_capacity = hr->capacity();
6047 // We need to read this before we make the region non-humongous,
6048 // otherwise the information will be gone.
6049 uint last_index = hr->last_hc_index();
6050 hr->set_notHumongous();
6051 free_region(hr, free_list, par);
6053 uint i = hr->hrm_index() + 1;
6054 while (i < last_index) {
6055 HeapRegion* curr_hr = region_at(i);
6056 assert(curr_hr->continuesHumongous(), "invariant");
6057 curr_hr->set_notHumongous();
6058 free_region(curr_hr, free_list, par);
6059 i += 1;
6060 }
6061 }
6063 void G1CollectedHeap::remove_from_old_sets(const HeapRegionSetCount& old_regions_removed,
6064 const HeapRegionSetCount& humongous_regions_removed) {
6065 if (old_regions_removed.length() > 0 || humongous_regions_removed.length() > 0) {
6066 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
6067 _old_set.bulk_remove(old_regions_removed);
6068 _humongous_set.bulk_remove(humongous_regions_removed);
6069 }
6071 }
6073 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) {
6074 assert(list != NULL, "list can't be null");
6075 if (!list->is_empty()) {
6076 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
6077 _hrm.insert_list_into_free_list(list);
6078 }
6079 }
6081 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) {
6082 assert(_summary_bytes_used >= bytes,
6083 err_msg("invariant: _summary_bytes_used: "SIZE_FORMAT" should be >= bytes: "SIZE_FORMAT,
6084 _summary_bytes_used, bytes));
6085 _summary_bytes_used -= bytes;
6086 }
6088 class G1ParCleanupCTTask : public AbstractGangTask {
6089 G1SATBCardTableModRefBS* _ct_bs;
6090 G1CollectedHeap* _g1h;
6091 HeapRegion* volatile _su_head;
6092 public:
6093 G1ParCleanupCTTask(G1SATBCardTableModRefBS* ct_bs,
6094 G1CollectedHeap* g1h) :
6095 AbstractGangTask("G1 Par Cleanup CT Task"),
6096 _ct_bs(ct_bs), _g1h(g1h) { }
6098 void work(uint worker_id) {
6099 HeapRegion* r;
6100 while (r = _g1h->pop_dirty_cards_region()) {
6101 clear_cards(r);
6102 }
6103 }
6105 void clear_cards(HeapRegion* r) {
6106 // Cards of the survivors should have already been dirtied.
6107 if (!r->is_survivor()) {
6108 _ct_bs->clear(MemRegion(r->bottom(), r->end()));
6109 }
6110 }
6111 };
6113 #ifndef PRODUCT
6114 class G1VerifyCardTableCleanup: public HeapRegionClosure {
6115 G1CollectedHeap* _g1h;
6116 G1SATBCardTableModRefBS* _ct_bs;
6117 public:
6118 G1VerifyCardTableCleanup(G1CollectedHeap* g1h, G1SATBCardTableModRefBS* ct_bs)
6119 : _g1h(g1h), _ct_bs(ct_bs) { }
6120 virtual bool doHeapRegion(HeapRegion* r) {
6121 if (r->is_survivor()) {
6122 _g1h->verify_dirty_region(r);
6123 } else {
6124 _g1h->verify_not_dirty_region(r);
6125 }
6126 return false;
6127 }
6128 };
6130 void G1CollectedHeap::verify_not_dirty_region(HeapRegion* hr) {
6131 // All of the region should be clean.
6132 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
6133 MemRegion mr(hr->bottom(), hr->end());
6134 ct_bs->verify_not_dirty_region(mr);
6135 }
6137 void G1CollectedHeap::verify_dirty_region(HeapRegion* hr) {
6138 // We cannot guarantee that [bottom(),end()] is dirty. Threads
6139 // dirty allocated blocks as they allocate them. The thread that
6140 // retires each region and replaces it with a new one will do a
6141 // maximal allocation to fill in [pre_dummy_top(),end()] but will
6142 // not dirty that area (one less thing to have to do while holding
6143 // a lock). So we can only verify that [bottom(),pre_dummy_top()]
6144 // is dirty.
6145 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
6146 MemRegion mr(hr->bottom(), hr->pre_dummy_top());
6147 if (hr->is_young()) {
6148 ct_bs->verify_g1_young_region(mr);
6149 } else {
6150 ct_bs->verify_dirty_region(mr);
6151 }
6152 }
6154 void G1CollectedHeap::verify_dirty_young_list(HeapRegion* head) {
6155 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
6156 for (HeapRegion* hr = head; hr != NULL; hr = hr->get_next_young_region()) {
6157 verify_dirty_region(hr);
6158 }
6159 }
6161 void G1CollectedHeap::verify_dirty_young_regions() {
6162 verify_dirty_young_list(_young_list->first_region());
6163 }
6165 bool G1CollectedHeap::verify_no_bits_over_tams(const char* bitmap_name, CMBitMapRO* bitmap,
6166 HeapWord* tams, HeapWord* end) {
6167 guarantee(tams <= end,
6168 err_msg("tams: "PTR_FORMAT" end: "PTR_FORMAT, tams, end));
6169 HeapWord* result = bitmap->getNextMarkedWordAddress(tams, end);
6170 if (result < end) {
6171 gclog_or_tty->cr();
6172 gclog_or_tty->print_cr("## wrong marked address on %s bitmap: "PTR_FORMAT,
6173 bitmap_name, result);
6174 gclog_or_tty->print_cr("## %s tams: "PTR_FORMAT" end: "PTR_FORMAT,
6175 bitmap_name, tams, end);
6176 return false;
6177 }
6178 return true;
6179 }
6181 bool G1CollectedHeap::verify_bitmaps(const char* caller, HeapRegion* hr) {
6182 CMBitMapRO* prev_bitmap = concurrent_mark()->prevMarkBitMap();
6183 CMBitMapRO* next_bitmap = (CMBitMapRO*) concurrent_mark()->nextMarkBitMap();
6185 HeapWord* bottom = hr->bottom();
6186 HeapWord* ptams = hr->prev_top_at_mark_start();
6187 HeapWord* ntams = hr->next_top_at_mark_start();
6188 HeapWord* end = hr->end();
6190 bool res_p = verify_no_bits_over_tams("prev", prev_bitmap, ptams, end);
6192 bool res_n = true;
6193 // We reset mark_in_progress() before we reset _cmThread->in_progress() and in this window
6194 // we do the clearing of the next bitmap concurrently. Thus, we can not verify the bitmap
6195 // if we happen to be in that state.
6196 if (mark_in_progress() || !_cmThread->in_progress()) {
6197 res_n = verify_no_bits_over_tams("next", next_bitmap, ntams, end);
6198 }
6199 if (!res_p || !res_n) {
6200 gclog_or_tty->print_cr("#### Bitmap verification failed for "HR_FORMAT,
6201 HR_FORMAT_PARAMS(hr));
6202 gclog_or_tty->print_cr("#### Caller: %s", caller);
6203 return false;
6204 }
6205 return true;
6206 }
6208 void G1CollectedHeap::check_bitmaps(const char* caller, HeapRegion* hr) {
6209 if (!G1VerifyBitmaps) return;
6211 guarantee(verify_bitmaps(caller, hr), "bitmap verification");
6212 }
6214 class G1VerifyBitmapClosure : public HeapRegionClosure {
6215 private:
6216 const char* _caller;
6217 G1CollectedHeap* _g1h;
6218 bool _failures;
6220 public:
6221 G1VerifyBitmapClosure(const char* caller, G1CollectedHeap* g1h) :
6222 _caller(caller), _g1h(g1h), _failures(false) { }
6224 bool failures() { return _failures; }
6226 virtual bool doHeapRegion(HeapRegion* hr) {
6227 if (hr->continuesHumongous()) return false;
6229 bool result = _g1h->verify_bitmaps(_caller, hr);
6230 if (!result) {
6231 _failures = true;
6232 }
6233 return false;
6234 }
6235 };
6237 void G1CollectedHeap::check_bitmaps(const char* caller) {
6238 if (!G1VerifyBitmaps) return;
6240 G1VerifyBitmapClosure cl(caller, this);
6241 heap_region_iterate(&cl);
6242 guarantee(!cl.failures(), "bitmap verification");
6243 }
6244 #endif // PRODUCT
6246 void G1CollectedHeap::cleanUpCardTable() {
6247 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
6248 double start = os::elapsedTime();
6250 {
6251 // Iterate over the dirty cards region list.
6252 G1ParCleanupCTTask cleanup_task(ct_bs, this);
6254 if (G1CollectedHeap::use_parallel_gc_threads()) {
6255 set_par_threads();
6256 workers()->run_task(&cleanup_task);
6257 set_par_threads(0);
6258 } else {
6259 while (_dirty_cards_region_list) {
6260 HeapRegion* r = _dirty_cards_region_list;
6261 cleanup_task.clear_cards(r);
6262 _dirty_cards_region_list = r->get_next_dirty_cards_region();
6263 if (_dirty_cards_region_list == r) {
6264 // The last region.
6265 _dirty_cards_region_list = NULL;
6266 }
6267 r->set_next_dirty_cards_region(NULL);
6268 }
6269 }
6270 #ifndef PRODUCT
6271 if (G1VerifyCTCleanup || VerifyAfterGC) {
6272 G1VerifyCardTableCleanup cleanup_verifier(this, ct_bs);
6273 heap_region_iterate(&cleanup_verifier);
6274 }
6275 #endif
6276 }
6278 double elapsed = os::elapsedTime() - start;
6279 g1_policy()->phase_times()->record_clear_ct_time(elapsed * 1000.0);
6280 }
6282 void G1CollectedHeap::free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info) {
6283 size_t pre_used = 0;
6284 FreeRegionList local_free_list("Local List for CSet Freeing");
6286 double young_time_ms = 0.0;
6287 double non_young_time_ms = 0.0;
6289 // Since the collection set is a superset of the the young list,
6290 // all we need to do to clear the young list is clear its
6291 // head and length, and unlink any young regions in the code below
6292 _young_list->clear();
6294 G1CollectorPolicy* policy = g1_policy();
6296 double start_sec = os::elapsedTime();
6297 bool non_young = true;
6299 HeapRegion* cur = cs_head;
6300 int age_bound = -1;
6301 size_t rs_lengths = 0;
6303 while (cur != NULL) {
6304 assert(!is_on_master_free_list(cur), "sanity");
6305 if (non_young) {
6306 if (cur->is_young()) {
6307 double end_sec = os::elapsedTime();
6308 double elapsed_ms = (end_sec - start_sec) * 1000.0;
6309 non_young_time_ms += elapsed_ms;
6311 start_sec = os::elapsedTime();
6312 non_young = false;
6313 }
6314 } else {
6315 if (!cur->is_young()) {
6316 double end_sec = os::elapsedTime();
6317 double elapsed_ms = (end_sec - start_sec) * 1000.0;
6318 young_time_ms += elapsed_ms;
6320 start_sec = os::elapsedTime();
6321 non_young = true;
6322 }
6323 }
6325 rs_lengths += cur->rem_set()->occupied_locked();
6327 HeapRegion* next = cur->next_in_collection_set();
6328 assert(cur->in_collection_set(), "bad CS");
6329 cur->set_next_in_collection_set(NULL);
6330 cur->set_in_collection_set(false);
6332 if (cur->is_young()) {
6333 int index = cur->young_index_in_cset();
6334 assert(index != -1, "invariant");
6335 assert((uint) index < policy->young_cset_region_length(), "invariant");
6336 size_t words_survived = _surviving_young_words[index];
6337 cur->record_surv_words_in_group(words_survived);
6339 // At this point the we have 'popped' cur from the collection set
6340 // (linked via next_in_collection_set()) but it is still in the
6341 // young list (linked via next_young_region()). Clear the
6342 // _next_young_region field.
6343 cur->set_next_young_region(NULL);
6344 } else {
6345 int index = cur->young_index_in_cset();
6346 assert(index == -1, "invariant");
6347 }
6349 assert( (cur->is_young() && cur->young_index_in_cset() > -1) ||
6350 (!cur->is_young() && cur->young_index_in_cset() == -1),
6351 "invariant" );
6353 if (!cur->evacuation_failed()) {
6354 MemRegion used_mr = cur->used_region();
6356 // And the region is empty.
6357 assert(!used_mr.is_empty(), "Should not have empty regions in a CS.");
6358 pre_used += cur->used();
6359 free_region(cur, &local_free_list, false /* par */, true /* locked */);
6360 } else {
6361 cur->uninstall_surv_rate_group();
6362 if (cur->is_young()) {
6363 cur->set_young_index_in_cset(-1);
6364 }
6365 cur->set_not_young();
6366 cur->set_evacuation_failed(false);
6367 // The region is now considered to be old.
6368 _old_set.add(cur);
6369 evacuation_info.increment_collectionset_used_after(cur->used());
6370 }
6371 cur = next;
6372 }
6374 evacuation_info.set_regions_freed(local_free_list.length());
6375 policy->record_max_rs_lengths(rs_lengths);
6376 policy->cset_regions_freed();
6378 double end_sec = os::elapsedTime();
6379 double elapsed_ms = (end_sec - start_sec) * 1000.0;
6381 if (non_young) {
6382 non_young_time_ms += elapsed_ms;
6383 } else {
6384 young_time_ms += elapsed_ms;
6385 }
6387 prepend_to_freelist(&local_free_list);
6388 decrement_summary_bytes(pre_used);
6389 policy->phase_times()->record_young_free_cset_time_ms(young_time_ms);
6390 policy->phase_times()->record_non_young_free_cset_time_ms(non_young_time_ms);
6391 }
6393 class G1FreeHumongousRegionClosure : public HeapRegionClosure {
6394 private:
6395 FreeRegionList* _free_region_list;
6396 HeapRegionSet* _proxy_set;
6397 HeapRegionSetCount _humongous_regions_removed;
6398 size_t _freed_bytes;
6399 public:
6401 G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) :
6402 _free_region_list(free_region_list), _humongous_regions_removed(), _freed_bytes(0) {
6403 }
6405 virtual bool doHeapRegion(HeapRegion* r) {
6406 if (!r->startsHumongous()) {
6407 return false;
6408 }
6410 G1CollectedHeap* g1h = G1CollectedHeap::heap();
6412 oop obj = (oop)r->bottom();
6413 CMBitMap* next_bitmap = g1h->concurrent_mark()->nextMarkBitMap();
6415 // The following checks whether the humongous object is live are sufficient.
6416 // The main additional check (in addition to having a reference from the roots
6417 // or the young gen) is whether the humongous object has a remembered set entry.
6418 //
6419 // A humongous object cannot be live if there is no remembered set for it
6420 // because:
6421 // - there can be no references from within humongous starts regions referencing
6422 // the object because we never allocate other objects into them.
6423 // (I.e. there are no intra-region references that may be missed by the
6424 // remembered set)
6425 // - as soon there is a remembered set entry to the humongous starts region
6426 // (i.e. it has "escaped" to an old object) this remembered set entry will stay
6427 // until the end of a concurrent mark.
6428 //
6429 // It is not required to check whether the object has been found dead by marking
6430 // or not, in fact it would prevent reclamation within a concurrent cycle, as
6431 // all objects allocated during that time are considered live.
6432 // SATB marking is even more conservative than the remembered set.
6433 // So if at this point in the collection there is no remembered set entry,
6434 // nobody has a reference to it.
6435 // At the start of collection we flush all refinement logs, and remembered sets
6436 // are completely up-to-date wrt to references to the humongous object.
6437 //
6438 // Other implementation considerations:
6439 // - never consider object arrays: while they are a valid target, they have not
6440 // been observed to be used as temporary objects.
6441 // - they would also pose considerable effort for cleaning up the the remembered
6442 // sets.
6443 // While this cleanup is not strictly necessary to be done (or done instantly),
6444 // given that their occurrence is very low, this saves us this additional
6445 // complexity.
6446 uint region_idx = r->hrm_index();
6447 if (g1h->humongous_is_live(region_idx) ||
6448 g1h->humongous_region_is_always_live(region_idx)) {
6450 if (G1TraceReclaimDeadHumongousObjectsAtYoungGC) {
6451 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",
6452 r->isHumongous(),
6453 region_idx,
6454 r->rem_set()->occupied(),
6455 r->rem_set()->strong_code_roots_list_length(),
6456 next_bitmap->isMarked(r->bottom()),
6457 g1h->humongous_is_live(region_idx),
6458 obj->is_objArray()
6459 );
6460 }
6462 return false;
6463 }
6465 guarantee(!obj->is_objArray(),
6466 err_msg("Eagerly reclaiming object arrays is not supported, but the object "PTR_FORMAT" is.",
6467 r->bottom()));
6469 if (G1TraceReclaimDeadHumongousObjectsAtYoungGC) {
6470 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",
6471 r->isHumongous(),
6472 r->bottom(),
6473 region_idx,
6474 r->region_num(),
6475 r->rem_set()->occupied(),
6476 r->rem_set()->strong_code_roots_list_length(),
6477 next_bitmap->isMarked(r->bottom()),
6478 g1h->humongous_is_live(region_idx),
6479 obj->is_objArray()
6480 );
6481 }
6482 // Need to clear mark bit of the humongous object if already set.
6483 if (next_bitmap->isMarked(r->bottom())) {
6484 next_bitmap->clear(r->bottom());
6485 }
6486 _freed_bytes += r->used();
6487 r->set_containing_set(NULL);
6488 _humongous_regions_removed.increment(1u, r->capacity());
6489 g1h->free_humongous_region(r, _free_region_list, false);
6491 return false;
6492 }
6494 HeapRegionSetCount& humongous_free_count() {
6495 return _humongous_regions_removed;
6496 }
6498 size_t bytes_freed() const {
6499 return _freed_bytes;
6500 }
6502 size_t humongous_reclaimed() const {
6503 return _humongous_regions_removed.length();
6504 }
6505 };
6507 void G1CollectedHeap::eagerly_reclaim_humongous_regions() {
6508 assert_at_safepoint(true);
6510 if (!G1ReclaimDeadHumongousObjectsAtYoungGC || !_has_humongous_reclaim_candidates) {
6511 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0);
6512 return;
6513 }
6515 double start_time = os::elapsedTime();
6517 FreeRegionList local_cleanup_list("Local Humongous Cleanup List");
6519 G1FreeHumongousRegionClosure cl(&local_cleanup_list);
6520 heap_region_iterate(&cl);
6522 HeapRegionSetCount empty_set;
6523 remove_from_old_sets(empty_set, cl.humongous_free_count());
6525 G1HRPrinter* hr_printer = _g1h->hr_printer();
6526 if (hr_printer->is_active()) {
6527 FreeRegionListIterator iter(&local_cleanup_list);
6528 while (iter.more_available()) {
6529 HeapRegion* hr = iter.get_next();
6530 hr_printer->cleanup(hr);
6531 }
6532 }
6534 prepend_to_freelist(&local_cleanup_list);
6535 decrement_summary_bytes(cl.bytes_freed());
6537 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0,
6538 cl.humongous_reclaimed());
6539 }
6541 // This routine is similar to the above but does not record
6542 // any policy statistics or update free lists; we are abandoning
6543 // the current incremental collection set in preparation of a
6544 // full collection. After the full GC we will start to build up
6545 // the incremental collection set again.
6546 // This is only called when we're doing a full collection
6547 // and is immediately followed by the tearing down of the young list.
6549 void G1CollectedHeap::abandon_collection_set(HeapRegion* cs_head) {
6550 HeapRegion* cur = cs_head;
6552 while (cur != NULL) {
6553 HeapRegion* next = cur->next_in_collection_set();
6554 assert(cur->in_collection_set(), "bad CS");
6555 cur->set_next_in_collection_set(NULL);
6556 cur->set_in_collection_set(false);
6557 cur->set_young_index_in_cset(-1);
6558 cur = next;
6559 }
6560 }
6562 void G1CollectedHeap::set_free_regions_coming() {
6563 if (G1ConcRegionFreeingVerbose) {
6564 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
6565 "setting free regions coming");
6566 }
6568 assert(!free_regions_coming(), "pre-condition");
6569 _free_regions_coming = true;
6570 }
6572 void G1CollectedHeap::reset_free_regions_coming() {
6573 assert(free_regions_coming(), "pre-condition");
6575 {
6576 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6577 _free_regions_coming = false;
6578 SecondaryFreeList_lock->notify_all();
6579 }
6581 if (G1ConcRegionFreeingVerbose) {
6582 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
6583 "reset free regions coming");
6584 }
6585 }
6587 void G1CollectedHeap::wait_while_free_regions_coming() {
6588 // Most of the time we won't have to wait, so let's do a quick test
6589 // first before we take the lock.
6590 if (!free_regions_coming()) {
6591 return;
6592 }
6594 if (G1ConcRegionFreeingVerbose) {
6595 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
6596 "waiting for free regions");
6597 }
6599 {
6600 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6601 while (free_regions_coming()) {
6602 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
6603 }
6604 }
6606 if (G1ConcRegionFreeingVerbose) {
6607 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
6608 "done waiting for free regions");
6609 }
6610 }
6612 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
6613 assert(heap_lock_held_for_gc(),
6614 "the heap lock should already be held by or for this thread");
6615 _young_list->push_region(hr);
6616 }
6618 class NoYoungRegionsClosure: public HeapRegionClosure {
6619 private:
6620 bool _success;
6621 public:
6622 NoYoungRegionsClosure() : _success(true) { }
6623 bool doHeapRegion(HeapRegion* r) {
6624 if (r->is_young()) {
6625 gclog_or_tty->print_cr("Region ["PTR_FORMAT", "PTR_FORMAT") tagged as young",
6626 r->bottom(), r->end());
6627 _success = false;
6628 }
6629 return false;
6630 }
6631 bool success() { return _success; }
6632 };
6634 bool G1CollectedHeap::check_young_list_empty(bool check_heap, bool check_sample) {
6635 bool ret = _young_list->check_list_empty(check_sample);
6637 if (check_heap) {
6638 NoYoungRegionsClosure closure;
6639 heap_region_iterate(&closure);
6640 ret = ret && closure.success();
6641 }
6643 return ret;
6644 }
6646 class TearDownRegionSetsClosure : public HeapRegionClosure {
6647 private:
6648 HeapRegionSet *_old_set;
6650 public:
6651 TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { }
6653 bool doHeapRegion(HeapRegion* r) {
6654 if (r->is_empty()) {
6655 // We ignore empty regions, we'll empty the free list afterwards
6656 } else if (r->is_young()) {
6657 // We ignore young regions, we'll empty the young list afterwards
6658 } else if (r->isHumongous()) {
6659 // We ignore humongous regions, we're not tearing down the
6660 // humongous region set
6661 } else {
6662 // The rest should be old
6663 _old_set->remove(r);
6664 }
6665 return false;
6666 }
6668 ~TearDownRegionSetsClosure() {
6669 assert(_old_set->is_empty(), "post-condition");
6670 }
6671 };
6673 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
6674 assert_at_safepoint(true /* should_be_vm_thread */);
6676 if (!free_list_only) {
6677 TearDownRegionSetsClosure cl(&_old_set);
6678 heap_region_iterate(&cl);
6680 // Note that emptying the _young_list is postponed and instead done as
6681 // the first step when rebuilding the regions sets again. The reason for
6682 // this is that during a full GC string deduplication needs to know if
6683 // a collected region was young or old when the full GC was initiated.
6684 }
6685 _hrm.remove_all_free_regions();
6686 }
6688 class RebuildRegionSetsClosure : public HeapRegionClosure {
6689 private:
6690 bool _free_list_only;
6691 HeapRegionSet* _old_set;
6692 HeapRegionManager* _hrm;
6693 size_t _total_used;
6695 public:
6696 RebuildRegionSetsClosure(bool free_list_only,
6697 HeapRegionSet* old_set, HeapRegionManager* hrm) :
6698 _free_list_only(free_list_only),
6699 _old_set(old_set), _hrm(hrm), _total_used(0) {
6700 assert(_hrm->num_free_regions() == 0, "pre-condition");
6701 if (!free_list_only) {
6702 assert(_old_set->is_empty(), "pre-condition");
6703 }
6704 }
6706 bool doHeapRegion(HeapRegion* r) {
6707 if (r->continuesHumongous()) {
6708 return false;
6709 }
6711 if (r->is_empty()) {
6712 // Add free regions to the free list
6713 _hrm->insert_into_free_list(r);
6714 } else if (!_free_list_only) {
6715 assert(!r->is_young(), "we should not come across young regions");
6717 if (r->isHumongous()) {
6718 // We ignore humongous regions, we left the humongous set unchanged
6719 } else {
6720 // The rest should be old, add them to the old set
6721 _old_set->add(r);
6722 }
6723 _total_used += r->used();
6724 }
6726 return false;
6727 }
6729 size_t total_used() {
6730 return _total_used;
6731 }
6732 };
6734 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
6735 assert_at_safepoint(true /* should_be_vm_thread */);
6737 if (!free_list_only) {
6738 _young_list->empty_list();
6739 }
6741 RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm);
6742 heap_region_iterate(&cl);
6744 if (!free_list_only) {
6745 _summary_bytes_used = cl.total_used();
6746 }
6747 assert(_summary_bytes_used == recalculate_used(),
6748 err_msg("inconsistent _summary_bytes_used, "
6749 "value: "SIZE_FORMAT" recalculated: "SIZE_FORMAT,
6750 _summary_bytes_used, recalculate_used()));
6751 }
6753 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) {
6754 _refine_cte_cl->set_concurrent(concurrent);
6755 }
6757 bool G1CollectedHeap::is_in_closed_subset(const void* p) const {
6758 HeapRegion* hr = heap_region_containing(p);
6759 return hr->is_in(p);
6760 }
6762 // Methods for the mutator alloc region
6764 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
6765 bool force) {
6766 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6767 assert(!force || g1_policy()->can_expand_young_list(),
6768 "if force is true we should be able to expand the young list");
6769 bool young_list_full = g1_policy()->is_young_list_full();
6770 if (force || !young_list_full) {
6771 HeapRegion* new_alloc_region = new_region(word_size,
6772 false /* is_old */,
6773 false /* do_expand */);
6774 if (new_alloc_region != NULL) {
6775 set_region_short_lived_locked(new_alloc_region);
6776 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Eden, young_list_full);
6777 check_bitmaps("Mutator Region Allocation", new_alloc_region);
6778 return new_alloc_region;
6779 }
6780 }
6781 return NULL;
6782 }
6784 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
6785 size_t allocated_bytes) {
6786 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6787 assert(alloc_region->is_young(), "all mutator alloc regions should be young");
6789 g1_policy()->add_region_to_incremental_cset_lhs(alloc_region);
6790 _summary_bytes_used += allocated_bytes;
6791 _hr_printer.retire(alloc_region);
6792 // We update the eden sizes here, when the region is retired,
6793 // instead of when it's allocated, since this is the point that its
6794 // used space has been recored in _summary_bytes_used.
6795 g1mm()->update_eden_size();
6796 }
6798 HeapRegion* MutatorAllocRegion::allocate_new_region(size_t word_size,
6799 bool force) {
6800 return _g1h->new_mutator_alloc_region(word_size, force);
6801 }
6803 void G1CollectedHeap::set_par_threads() {
6804 // Don't change the number of workers. Use the value previously set
6805 // in the workgroup.
6806 assert(G1CollectedHeap::use_parallel_gc_threads(), "shouldn't be here otherwise");
6807 uint n_workers = workers()->active_workers();
6808 assert(UseDynamicNumberOfGCThreads ||
6809 n_workers == workers()->total_workers(),
6810 "Otherwise should be using the total number of workers");
6811 if (n_workers == 0) {
6812 assert(false, "Should have been set in prior evacuation pause.");
6813 n_workers = ParallelGCThreads;
6814 workers()->set_active_workers(n_workers);
6815 }
6816 set_par_threads(n_workers);
6817 }
6819 void MutatorAllocRegion::retire_region(HeapRegion* alloc_region,
6820 size_t allocated_bytes) {
6821 _g1h->retire_mutator_alloc_region(alloc_region, allocated_bytes);
6822 }
6824 // Methods for the GC alloc regions
6826 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size,
6827 uint count,
6828 GCAllocPurpose ap) {
6829 assert(FreeList_lock->owned_by_self(), "pre-condition");
6831 if (count < g1_policy()->max_regions(ap)) {
6832 bool survivor = (ap == GCAllocForSurvived);
6833 HeapRegion* new_alloc_region = new_region(word_size,
6834 !survivor,
6835 true /* do_expand */);
6836 if (new_alloc_region != NULL) {
6837 // We really only need to do this for old regions given that we
6838 // should never scan survivors. But it doesn't hurt to do it
6839 // for survivors too.
6840 new_alloc_region->record_top_and_timestamp();
6841 if (survivor) {
6842 new_alloc_region->set_survivor();
6843 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Survivor);
6844 check_bitmaps("Survivor Region Allocation", new_alloc_region);
6845 } else {
6846 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Old);
6847 check_bitmaps("Old Region Allocation", new_alloc_region);
6848 }
6849 bool during_im = g1_policy()->during_initial_mark_pause();
6850 new_alloc_region->note_start_of_copying(during_im);
6851 return new_alloc_region;
6852 } else {
6853 g1_policy()->note_alloc_region_limit_reached(ap);
6854 }
6855 }
6856 return NULL;
6857 }
6859 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
6860 size_t allocated_bytes,
6861 GCAllocPurpose ap) {
6862 bool during_im = g1_policy()->during_initial_mark_pause();
6863 alloc_region->note_end_of_copying(during_im);
6864 g1_policy()->record_bytes_copied_during_gc(allocated_bytes);
6865 if (ap == GCAllocForSurvived) {
6866 young_list()->add_survivor_region(alloc_region);
6867 } else {
6868 _old_set.add(alloc_region);
6869 }
6870 _hr_printer.retire(alloc_region);
6871 }
6873 HeapRegion* SurvivorGCAllocRegion::allocate_new_region(size_t word_size,
6874 bool force) {
6875 assert(!force, "not supported for GC alloc regions");
6876 return _g1h->new_gc_alloc_region(word_size, count(), GCAllocForSurvived);
6877 }
6879 void SurvivorGCAllocRegion::retire_region(HeapRegion* alloc_region,
6880 size_t allocated_bytes) {
6881 _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes,
6882 GCAllocForSurvived);
6883 }
6885 HeapRegion* OldGCAllocRegion::allocate_new_region(size_t word_size,
6886 bool force) {
6887 assert(!force, "not supported for GC alloc regions");
6888 return _g1h->new_gc_alloc_region(word_size, count(), GCAllocForTenured);
6889 }
6891 void OldGCAllocRegion::retire_region(HeapRegion* alloc_region,
6892 size_t allocated_bytes) {
6893 _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes,
6894 GCAllocForTenured);
6895 }
6897 HeapRegion* OldGCAllocRegion::release() {
6898 HeapRegion* cur = get();
6899 if (cur != NULL) {
6900 // Determine how far we are from the next card boundary. If it is smaller than
6901 // the minimum object size we can allocate into, expand into the next card.
6902 HeapWord* top = cur->top();
6903 HeapWord* aligned_top = (HeapWord*)align_ptr_up(top, G1BlockOffsetSharedArray::N_bytes);
6905 size_t to_allocate_words = pointer_delta(aligned_top, top, HeapWordSize);
6907 if (to_allocate_words != 0) {
6908 // We are not at a card boundary. Fill up, possibly into the next, taking the
6909 // end of the region and the minimum object size into account.
6910 to_allocate_words = MIN2(pointer_delta(cur->end(), cur->top(), HeapWordSize),
6911 MAX2(to_allocate_words, G1CollectedHeap::min_fill_size()));
6913 // Skip allocation if there is not enough space to allocate even the smallest
6914 // possible object. In this case this region will not be retained, so the
6915 // original problem cannot occur.
6916 if (to_allocate_words >= G1CollectedHeap::min_fill_size()) {
6917 HeapWord* dummy = attempt_allocation(to_allocate_words, true /* bot_updates */);
6918 CollectedHeap::fill_with_object(dummy, to_allocate_words);
6919 }
6920 }
6921 }
6922 return G1AllocRegion::release();
6923 }
6925 // Heap region set verification
6927 class VerifyRegionListsClosure : public HeapRegionClosure {
6928 private:
6929 HeapRegionSet* _old_set;
6930 HeapRegionSet* _humongous_set;
6931 HeapRegionManager* _hrm;
6933 public:
6934 HeapRegionSetCount _old_count;
6935 HeapRegionSetCount _humongous_count;
6936 HeapRegionSetCount _free_count;
6938 VerifyRegionListsClosure(HeapRegionSet* old_set,
6939 HeapRegionSet* humongous_set,
6940 HeapRegionManager* hrm) :
6941 _old_set(old_set), _humongous_set(humongous_set), _hrm(hrm),
6942 _old_count(), _humongous_count(), _free_count(){ }
6944 bool doHeapRegion(HeapRegion* hr) {
6945 if (hr->continuesHumongous()) {
6946 return false;
6947 }
6949 if (hr->is_young()) {
6950 // TODO
6951 } else if (hr->startsHumongous()) {
6952 assert(hr->containing_set() == _humongous_set, err_msg("Heap region %u is starts humongous but not in humongous set.", hr->hrm_index()));
6953 _humongous_count.increment(1u, hr->capacity());
6954 } else if (hr->is_empty()) {
6955 assert(_hrm->is_free(hr), err_msg("Heap region %u is empty but not on the free list.", hr->hrm_index()));
6956 _free_count.increment(1u, hr->capacity());
6957 } else {
6958 assert(hr->containing_set() == _old_set, err_msg("Heap region %u is old but not in the old set.", hr->hrm_index()));
6959 _old_count.increment(1u, hr->capacity());
6960 }
6961 return false;
6962 }
6964 void verify_counts(HeapRegionSet* old_set, HeapRegionSet* humongous_set, HeapRegionManager* free_list) {
6965 guarantee(old_set->length() == _old_count.length(), err_msg("Old set count mismatch. Expected %u, actual %u.", old_set->length(), _old_count.length()));
6966 guarantee(old_set->total_capacity_bytes() == _old_count.capacity(), err_msg("Old set capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
6967 old_set->total_capacity_bytes(), _old_count.capacity()));
6969 guarantee(humongous_set->length() == _humongous_count.length(), err_msg("Hum set count mismatch. Expected %u, actual %u.", humongous_set->length(), _humongous_count.length()));
6970 guarantee(humongous_set->total_capacity_bytes() == _humongous_count.capacity(), err_msg("Hum set capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
6971 humongous_set->total_capacity_bytes(), _humongous_count.capacity()));
6973 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()));
6974 guarantee(free_list->total_capacity_bytes() == _free_count.capacity(), err_msg("Free list capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
6975 free_list->total_capacity_bytes(), _free_count.capacity()));
6976 }
6977 };
6979 void G1CollectedHeap::verify_region_sets() {
6980 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6982 // First, check the explicit lists.
6983 _hrm.verify();
6984 {
6985 // Given that a concurrent operation might be adding regions to
6986 // the secondary free list we have to take the lock before
6987 // verifying it.
6988 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6989 _secondary_free_list.verify_list();
6990 }
6992 // If a concurrent region freeing operation is in progress it will
6993 // be difficult to correctly attributed any free regions we come
6994 // across to the correct free list given that they might belong to
6995 // one of several (free_list, secondary_free_list, any local lists,
6996 // etc.). So, if that's the case we will skip the rest of the
6997 // verification operation. Alternatively, waiting for the concurrent
6998 // operation to complete will have a non-trivial effect on the GC's
6999 // operation (no concurrent operation will last longer than the
7000 // interval between two calls to verification) and it might hide
7001 // any issues that we would like to catch during testing.
7002 if (free_regions_coming()) {
7003 return;
7004 }
7006 // Make sure we append the secondary_free_list on the free_list so
7007 // that all free regions we will come across can be safely
7008 // attributed to the free_list.
7009 append_secondary_free_list_if_not_empty_with_lock();
7011 // Finally, make sure that the region accounting in the lists is
7012 // consistent with what we see in the heap.
7014 VerifyRegionListsClosure cl(&_old_set, &_humongous_set, &_hrm);
7015 heap_region_iterate(&cl);
7016 cl.verify_counts(&_old_set, &_humongous_set, &_hrm);
7017 }
7019 // Optimized nmethod scanning
7021 class RegisterNMethodOopClosure: public OopClosure {
7022 G1CollectedHeap* _g1h;
7023 nmethod* _nm;
7025 template <class T> void do_oop_work(T* p) {
7026 T heap_oop = oopDesc::load_heap_oop(p);
7027 if (!oopDesc::is_null(heap_oop)) {
7028 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
7029 HeapRegion* hr = _g1h->heap_region_containing(obj);
7030 assert(!hr->continuesHumongous(),
7031 err_msg("trying to add code root "PTR_FORMAT" in continuation of humongous region "HR_FORMAT
7032 " starting at "HR_FORMAT,
7033 _nm, HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())));
7035 // HeapRegion::add_strong_code_root() avoids adding duplicate
7036 // entries but having duplicates is OK since we "mark" nmethods
7037 // as visited when we scan the strong code root lists during the GC.
7038 hr->add_strong_code_root(_nm);
7039 assert(hr->rem_set()->strong_code_roots_list_contains(_nm),
7040 err_msg("failed to add code root "PTR_FORMAT" to remembered set of region "HR_FORMAT,
7041 _nm, HR_FORMAT_PARAMS(hr)));
7042 }
7043 }
7045 public:
7046 RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
7047 _g1h(g1h), _nm(nm) {}
7049 void do_oop(oop* p) { do_oop_work(p); }
7050 void do_oop(narrowOop* p) { do_oop_work(p); }
7051 };
7053 class UnregisterNMethodOopClosure: public OopClosure {
7054 G1CollectedHeap* _g1h;
7055 nmethod* _nm;
7057 template <class T> void do_oop_work(T* p) {
7058 T heap_oop = oopDesc::load_heap_oop(p);
7059 if (!oopDesc::is_null(heap_oop)) {
7060 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
7061 HeapRegion* hr = _g1h->heap_region_containing(obj);
7062 assert(!hr->continuesHumongous(),
7063 err_msg("trying to remove code root "PTR_FORMAT" in continuation of humongous region "HR_FORMAT
7064 " starting at "HR_FORMAT,
7065 _nm, HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())));
7067 hr->remove_strong_code_root(_nm);
7068 assert(!hr->rem_set()->strong_code_roots_list_contains(_nm),
7069 err_msg("failed to remove code root "PTR_FORMAT" of region "HR_FORMAT,
7070 _nm, HR_FORMAT_PARAMS(hr)));
7071 }
7072 }
7074 public:
7075 UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
7076 _g1h(g1h), _nm(nm) {}
7078 void do_oop(oop* p) { do_oop_work(p); }
7079 void do_oop(narrowOop* p) { do_oop_work(p); }
7080 };
7082 void G1CollectedHeap::register_nmethod(nmethod* nm) {
7083 CollectedHeap::register_nmethod(nm);
7085 guarantee(nm != NULL, "sanity");
7086 RegisterNMethodOopClosure reg_cl(this, nm);
7087 nm->oops_do(®_cl);
7088 }
7090 void G1CollectedHeap::unregister_nmethod(nmethod* nm) {
7091 CollectedHeap::unregister_nmethod(nm);
7093 guarantee(nm != NULL, "sanity");
7094 UnregisterNMethodOopClosure reg_cl(this, nm);
7095 nm->oops_do(®_cl, true);
7096 }
7098 class MigrateCodeRootsHeapRegionClosure: public HeapRegionClosure {
7099 public:
7100 bool doHeapRegion(HeapRegion *hr) {
7101 assert(!hr->isHumongous(),
7102 err_msg("humongous region "HR_FORMAT" should not have been added to collection set",
7103 HR_FORMAT_PARAMS(hr)));
7104 hr->migrate_strong_code_roots();
7105 return false;
7106 }
7107 };
7109 void G1CollectedHeap::migrate_strong_code_roots() {
7110 MigrateCodeRootsHeapRegionClosure cl;
7111 double migrate_start = os::elapsedTime();
7112 collection_set_iterate(&cl);
7113 double migration_time_ms = (os::elapsedTime() - migrate_start) * 1000.0;
7114 g1_policy()->phase_times()->record_strong_code_root_migration_time(migration_time_ms);
7115 }
7117 void G1CollectedHeap::purge_code_root_memory() {
7118 double purge_start = os::elapsedTime();
7119 G1CodeRootSet::purge_chunks(G1CodeRootsChunkCacheKeepPercent);
7120 double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0;
7121 g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms);
7122 }
7124 class RebuildStrongCodeRootClosure: public CodeBlobClosure {
7125 G1CollectedHeap* _g1h;
7127 public:
7128 RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) :
7129 _g1h(g1h) {}
7131 void do_code_blob(CodeBlob* cb) {
7132 nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL;
7133 if (nm == NULL) {
7134 return;
7135 }
7137 if (ScavengeRootsInCode) {
7138 _g1h->register_nmethod(nm);
7139 }
7140 }
7141 };
7143 void G1CollectedHeap::rebuild_strong_code_roots() {
7144 RebuildStrongCodeRootClosure blob_cl(this);
7145 CodeCache::blobs_do(&blob_cl);
7146 }