Thu, 23 Oct 2014 12:02:08 -0700
Merge
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 // This is called before a Full GC and all the non-empty /
211 // non-humongous regions at the end of the Full GC will end up as
212 // old anyway.
213 list->set_old();
214 list = next;
215 }
216 }
218 void YoungList::empty_list() {
219 assert(check_list_well_formed(), "young list should be well formed");
221 empty_list(_head);
222 _head = NULL;
223 _length = 0;
225 empty_list(_survivor_head);
226 _survivor_head = NULL;
227 _survivor_tail = NULL;
228 _survivor_length = 0;
230 _last_sampled_rs_lengths = 0;
232 assert(check_list_empty(false), "just making sure...");
233 }
235 bool YoungList::check_list_well_formed() {
236 bool ret = true;
238 uint length = 0;
239 HeapRegion* curr = _head;
240 HeapRegion* last = NULL;
241 while (curr != NULL) {
242 if (!curr->is_young()) {
243 gclog_or_tty->print_cr("### YOUNG REGION "PTR_FORMAT"-"PTR_FORMAT" "
244 "incorrectly tagged (y: %d, surv: %d)",
245 curr->bottom(), curr->end(),
246 curr->is_young(), curr->is_survivor());
247 ret = false;
248 }
249 ++length;
250 last = curr;
251 curr = curr->get_next_young_region();
252 }
253 ret = ret && (length == _length);
255 if (!ret) {
256 gclog_or_tty->print_cr("### YOUNG LIST seems not well formed!");
257 gclog_or_tty->print_cr("### list has %u entries, _length is %u",
258 length, _length);
259 }
261 return ret;
262 }
264 bool YoungList::check_list_empty(bool check_sample) {
265 bool ret = true;
267 if (_length != 0) {
268 gclog_or_tty->print_cr("### YOUNG LIST should have 0 length, not %u",
269 _length);
270 ret = false;
271 }
272 if (check_sample && _last_sampled_rs_lengths != 0) {
273 gclog_or_tty->print_cr("### YOUNG LIST has non-zero last sampled RS lengths");
274 ret = false;
275 }
276 if (_head != NULL) {
277 gclog_or_tty->print_cr("### YOUNG LIST does not have a NULL head");
278 ret = false;
279 }
280 if (!ret) {
281 gclog_or_tty->print_cr("### YOUNG LIST does not seem empty");
282 }
284 return ret;
285 }
287 void
288 YoungList::rs_length_sampling_init() {
289 _sampled_rs_lengths = 0;
290 _curr = _head;
291 }
293 bool
294 YoungList::rs_length_sampling_more() {
295 return _curr != NULL;
296 }
298 void
299 YoungList::rs_length_sampling_next() {
300 assert( _curr != NULL, "invariant" );
301 size_t rs_length = _curr->rem_set()->occupied();
303 _sampled_rs_lengths += rs_length;
305 // The current region may not yet have been added to the
306 // incremental collection set (it gets added when it is
307 // retired as the current allocation region).
308 if (_curr->in_collection_set()) {
309 // Update the collection set policy information for this region
310 _g1h->g1_policy()->update_incremental_cset_info(_curr, rs_length);
311 }
313 _curr = _curr->get_next_young_region();
314 if (_curr == NULL) {
315 _last_sampled_rs_lengths = _sampled_rs_lengths;
316 // gclog_or_tty->print_cr("last sampled RS lengths = %d", _last_sampled_rs_lengths);
317 }
318 }
320 void
321 YoungList::reset_auxilary_lists() {
322 guarantee( is_empty(), "young list should be empty" );
323 assert(check_list_well_formed(), "young list should be well formed");
325 // Add survivor regions to SurvRateGroup.
326 _g1h->g1_policy()->note_start_adding_survivor_regions();
327 _g1h->g1_policy()->finished_recalculating_age_indexes(true /* is_survivors */);
329 int young_index_in_cset = 0;
330 for (HeapRegion* curr = _survivor_head;
331 curr != NULL;
332 curr = curr->get_next_young_region()) {
333 _g1h->g1_policy()->set_region_survivor(curr, young_index_in_cset);
335 // The region is a non-empty survivor so let's add it to
336 // the incremental collection set for the next evacuation
337 // pause.
338 _g1h->g1_policy()->add_region_to_incremental_cset_rhs(curr);
339 young_index_in_cset += 1;
340 }
341 assert((uint) young_index_in_cset == _survivor_length, "post-condition");
342 _g1h->g1_policy()->note_stop_adding_survivor_regions();
344 _head = _survivor_head;
345 _length = _survivor_length;
346 if (_survivor_head != NULL) {
347 assert(_survivor_tail != NULL, "cause it shouldn't be");
348 assert(_survivor_length > 0, "invariant");
349 _survivor_tail->set_next_young_region(NULL);
350 }
352 // Don't clear the survivor list handles until the start of
353 // the next evacuation pause - we need it in order to re-tag
354 // the survivor regions from this evacuation pause as 'young'
355 // at the start of the next.
357 _g1h->g1_policy()->finished_recalculating_age_indexes(false /* is_survivors */);
359 assert(check_list_well_formed(), "young list should be well formed");
360 }
362 void YoungList::print() {
363 HeapRegion* lists[] = {_head, _survivor_head};
364 const char* names[] = {"YOUNG", "SURVIVOR"};
366 for (unsigned int list = 0; list < ARRAY_SIZE(lists); ++list) {
367 gclog_or_tty->print_cr("%s LIST CONTENTS", names[list]);
368 HeapRegion *curr = lists[list];
369 if (curr == NULL)
370 gclog_or_tty->print_cr(" empty");
371 while (curr != NULL) {
372 gclog_or_tty->print_cr(" "HR_FORMAT", P: "PTR_FORMAT ", N: "PTR_FORMAT", age: %4d",
373 HR_FORMAT_PARAMS(curr),
374 curr->prev_top_at_mark_start(),
375 curr->next_top_at_mark_start(),
376 curr->age_in_surv_rate_group_cond());
377 curr = curr->get_next_young_region();
378 }
379 }
381 gclog_or_tty->cr();
382 }
384 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) {
385 OtherRegionsTable::invalidate(start_idx, num_regions);
386 }
388 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) {
389 // The from card cache is not the memory that is actually committed. So we cannot
390 // take advantage of the zero_filled parameter.
391 reset_from_card_cache(start_idx, num_regions);
392 }
394 void G1CollectedHeap::push_dirty_cards_region(HeapRegion* hr)
395 {
396 // Claim the right to put the region on the dirty cards region list
397 // by installing a self pointer.
398 HeapRegion* next = hr->get_next_dirty_cards_region();
399 if (next == NULL) {
400 HeapRegion* res = (HeapRegion*)
401 Atomic::cmpxchg_ptr(hr, hr->next_dirty_cards_region_addr(),
402 NULL);
403 if (res == NULL) {
404 HeapRegion* head;
405 do {
406 // Put the region to the dirty cards region list.
407 head = _dirty_cards_region_list;
408 next = (HeapRegion*)
409 Atomic::cmpxchg_ptr(hr, &_dirty_cards_region_list, head);
410 if (next == head) {
411 assert(hr->get_next_dirty_cards_region() == hr,
412 "hr->get_next_dirty_cards_region() != hr");
413 if (next == NULL) {
414 // The last region in the list points to itself.
415 hr->set_next_dirty_cards_region(hr);
416 } else {
417 hr->set_next_dirty_cards_region(next);
418 }
419 }
420 } while (next != head);
421 }
422 }
423 }
425 HeapRegion* G1CollectedHeap::pop_dirty_cards_region()
426 {
427 HeapRegion* head;
428 HeapRegion* hr;
429 do {
430 head = _dirty_cards_region_list;
431 if (head == NULL) {
432 return NULL;
433 }
434 HeapRegion* new_head = head->get_next_dirty_cards_region();
435 if (head == new_head) {
436 // The last region.
437 new_head = NULL;
438 }
439 hr = (HeapRegion*)Atomic::cmpxchg_ptr(new_head, &_dirty_cards_region_list,
440 head);
441 } while (hr != head);
442 assert(hr != NULL, "invariant");
443 hr->set_next_dirty_cards_region(NULL);
444 return hr;
445 }
447 #ifdef ASSERT
448 // A region is added to the collection set as it is retired
449 // so an address p can point to a region which will be in the
450 // collection set but has not yet been retired. This method
451 // therefore is only accurate during a GC pause after all
452 // regions have been retired. It is used for debugging
453 // to check if an nmethod has references to objects that can
454 // be move during a partial collection. Though it can be
455 // inaccurate, it is sufficient for G1 because the conservative
456 // implementation of is_scavengable() for G1 will indicate that
457 // all nmethods must be scanned during a partial collection.
458 bool G1CollectedHeap::is_in_partial_collection(const void* p) {
459 if (p == NULL) {
460 return false;
461 }
462 return heap_region_containing(p)->in_collection_set();
463 }
464 #endif
466 // Returns true if the reference points to an object that
467 // can move in an incremental collection.
468 bool G1CollectedHeap::is_scavengable(const void* p) {
469 HeapRegion* hr = heap_region_containing(p);
470 return !hr->isHumongous();
471 }
473 void G1CollectedHeap::check_ct_logs_at_safepoint() {
474 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
475 CardTableModRefBS* ct_bs = g1_barrier_set();
477 // Count the dirty cards at the start.
478 CountNonCleanMemRegionClosure count1(this);
479 ct_bs->mod_card_iterate(&count1);
480 int orig_count = count1.n();
482 // First clear the logged cards.
483 ClearLoggedCardTableEntryClosure clear;
484 dcqs.apply_closure_to_all_completed_buffers(&clear);
485 dcqs.iterate_closure_all_threads(&clear, false);
486 clear.print_histo();
488 // Now ensure that there's no dirty cards.
489 CountNonCleanMemRegionClosure count2(this);
490 ct_bs->mod_card_iterate(&count2);
491 if (count2.n() != 0) {
492 gclog_or_tty->print_cr("Card table has %d entries; %d originally",
493 count2.n(), orig_count);
494 }
495 guarantee(count2.n() == 0, "Card table should be clean.");
497 RedirtyLoggedCardTableEntryClosure redirty;
498 dcqs.apply_closure_to_all_completed_buffers(&redirty);
499 dcqs.iterate_closure_all_threads(&redirty, false);
500 gclog_or_tty->print_cr("Log entries = %d, dirty cards = %d.",
501 clear.num_processed(), orig_count);
502 guarantee(redirty.num_processed() == clear.num_processed(),
503 err_msg("Redirtied "SIZE_FORMAT" cards, bug cleared "SIZE_FORMAT,
504 redirty.num_processed(), clear.num_processed()));
506 CountNonCleanMemRegionClosure count3(this);
507 ct_bs->mod_card_iterate(&count3);
508 if (count3.n() != orig_count) {
509 gclog_or_tty->print_cr("Should have restored them all: orig = %d, final = %d.",
510 orig_count, count3.n());
511 guarantee(count3.n() >= orig_count, "Should have restored them all.");
512 }
513 }
515 // Private class members.
517 G1CollectedHeap* G1CollectedHeap::_g1h;
519 // Private methods.
521 HeapRegion*
522 G1CollectedHeap::new_region_try_secondary_free_list(bool is_old) {
523 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
524 while (!_secondary_free_list.is_empty() || free_regions_coming()) {
525 if (!_secondary_free_list.is_empty()) {
526 if (G1ConcRegionFreeingVerbose) {
527 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
528 "secondary_free_list has %u entries",
529 _secondary_free_list.length());
530 }
531 // It looks as if there are free regions available on the
532 // secondary_free_list. Let's move them to the free_list and try
533 // again to allocate from it.
534 append_secondary_free_list();
536 assert(_hrm.num_free_regions() > 0, "if the secondary_free_list was not "
537 "empty we should have moved at least one entry to the free_list");
538 HeapRegion* res = _hrm.allocate_free_region(is_old);
539 if (G1ConcRegionFreeingVerbose) {
540 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
541 "allocated "HR_FORMAT" from secondary_free_list",
542 HR_FORMAT_PARAMS(res));
543 }
544 return res;
545 }
547 // Wait here until we get notified either when (a) there are no
548 // more free regions coming or (b) some regions have been moved on
549 // the secondary_free_list.
550 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
551 }
553 if (G1ConcRegionFreeingVerbose) {
554 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
555 "could not allocate from secondary_free_list");
556 }
557 return NULL;
558 }
560 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) {
561 assert(!isHumongous(word_size) || word_size <= HeapRegion::GrainWords,
562 "the only time we use this to allocate a humongous region is "
563 "when we are allocating a single humongous region");
565 HeapRegion* res;
566 if (G1StressConcRegionFreeing) {
567 if (!_secondary_free_list.is_empty()) {
568 if (G1ConcRegionFreeingVerbose) {
569 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
570 "forced to look at the secondary_free_list");
571 }
572 res = new_region_try_secondary_free_list(is_old);
573 if (res != NULL) {
574 return res;
575 }
576 }
577 }
579 res = _hrm.allocate_free_region(is_old);
581 if (res == NULL) {
582 if (G1ConcRegionFreeingVerbose) {
583 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
584 "res == NULL, trying the secondary_free_list");
585 }
586 res = new_region_try_secondary_free_list(is_old);
587 }
588 if (res == NULL && do_expand && _expand_heap_after_alloc_failure) {
589 // Currently, only attempts to allocate GC alloc regions set
590 // do_expand to true. So, we should only reach here during a
591 // safepoint. If this assumption changes we might have to
592 // reconsider the use of _expand_heap_after_alloc_failure.
593 assert(SafepointSynchronize::is_at_safepoint(), "invariant");
595 ergo_verbose1(ErgoHeapSizing,
596 "attempt heap expansion",
597 ergo_format_reason("region allocation request failed")
598 ergo_format_byte("allocation request"),
599 word_size * HeapWordSize);
600 if (expand(word_size * HeapWordSize)) {
601 // Given that expand() succeeded in expanding the heap, and we
602 // always expand the heap by an amount aligned to the heap
603 // region size, the free list should in theory not be empty.
604 // In either case allocate_free_region() will check for NULL.
605 res = _hrm.allocate_free_region(is_old);
606 } else {
607 _expand_heap_after_alloc_failure = false;
608 }
609 }
610 return res;
611 }
613 HeapWord*
614 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first,
615 uint num_regions,
616 size_t word_size,
617 AllocationContext_t context) {
618 assert(first != G1_NO_HRM_INDEX, "pre-condition");
619 assert(isHumongous(word_size), "word_size should be humongous");
620 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
622 // Index of last region in the series + 1.
623 uint last = first + num_regions;
625 // We need to initialize the region(s) we just discovered. This is
626 // a bit tricky given that it can happen concurrently with
627 // refinement threads refining cards on these regions and
628 // potentially wanting to refine the BOT as they are scanning
629 // those cards (this can happen shortly after a cleanup; see CR
630 // 6991377). So we have to set up the region(s) carefully and in
631 // a specific order.
633 // The word size sum of all the regions we will allocate.
634 size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords;
635 assert(word_size <= word_size_sum, "sanity");
637 // This will be the "starts humongous" region.
638 HeapRegion* first_hr = region_at(first);
639 // The header of the new object will be placed at the bottom of
640 // the first region.
641 HeapWord* new_obj = first_hr->bottom();
642 // This will be the new end of the first region in the series that
643 // should also match the end of the last region in the series.
644 HeapWord* new_end = new_obj + word_size_sum;
645 // This will be the new top of the first region that will reflect
646 // this allocation.
647 HeapWord* new_top = new_obj + word_size;
649 // First, we need to zero the header of the space that we will be
650 // allocating. When we update top further down, some refinement
651 // threads might try to scan the region. By zeroing the header we
652 // ensure that any thread that will try to scan the region will
653 // come across the zero klass word and bail out.
654 //
655 // NOTE: It would not have been correct to have used
656 // CollectedHeap::fill_with_object() and make the space look like
657 // an int array. The thread that is doing the allocation will
658 // later update the object header to a potentially different array
659 // type and, for a very short period of time, the klass and length
660 // fields will be inconsistent. This could cause a refinement
661 // thread to calculate the object size incorrectly.
662 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
664 // We will set up the first region as "starts humongous". This
665 // will also update the BOT covering all the regions to reflect
666 // that there is a single object that starts at the bottom of the
667 // first region.
668 first_hr->set_startsHumongous(new_top, new_end);
669 first_hr->set_allocation_context(context);
670 // Then, if there are any, we will set up the "continues
671 // humongous" regions.
672 HeapRegion* hr = NULL;
673 for (uint i = first + 1; i < last; ++i) {
674 hr = region_at(i);
675 hr->set_continuesHumongous(first_hr);
676 hr->set_allocation_context(context);
677 }
678 // If we have "continues humongous" regions (hr != NULL), then the
679 // end of the last one should match new_end.
680 assert(hr == NULL || hr->end() == new_end, "sanity");
682 // Up to this point no concurrent thread would have been able to
683 // do any scanning on any region in this series. All the top
684 // fields still point to bottom, so the intersection between
685 // [bottom,top] and [card_start,card_end] will be empty. Before we
686 // update the top fields, we'll do a storestore to make sure that
687 // no thread sees the update to top before the zeroing of the
688 // object header and the BOT initialization.
689 OrderAccess::storestore();
691 // Now that the BOT and the object header have been initialized,
692 // we can update top of the "starts humongous" region.
693 assert(first_hr->bottom() < new_top && new_top <= first_hr->end(),
694 "new_top should be in this region");
695 first_hr->set_top(new_top);
696 if (_hr_printer.is_active()) {
697 HeapWord* bottom = first_hr->bottom();
698 HeapWord* end = first_hr->orig_end();
699 if ((first + 1) == last) {
700 // the series has a single humongous region
701 _hr_printer.alloc(G1HRPrinter::SingleHumongous, first_hr, new_top);
702 } else {
703 // the series has more than one humongous regions
704 _hr_printer.alloc(G1HRPrinter::StartsHumongous, first_hr, end);
705 }
706 }
708 // Now, we will update the top fields of the "continues humongous"
709 // regions. The reason we need to do this is that, otherwise,
710 // these regions would look empty and this will confuse parts of
711 // G1. For example, the code that looks for a consecutive number
712 // of empty regions will consider them empty and try to
713 // re-allocate them. We can extend is_empty() to also include
714 // !continuesHumongous(), but it is easier to just update the top
715 // fields here. The way we set top for all regions (i.e., top ==
716 // end for all regions but the last one, top == new_top for the
717 // last one) is actually used when we will free up the humongous
718 // region in free_humongous_region().
719 hr = NULL;
720 for (uint i = first + 1; i < last; ++i) {
721 hr = region_at(i);
722 if ((i + 1) == last) {
723 // last continues humongous region
724 assert(hr->bottom() < new_top && new_top <= hr->end(),
725 "new_top should fall on this region");
726 hr->set_top(new_top);
727 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, new_top);
728 } else {
729 // not last one
730 assert(new_top > hr->end(), "new_top should be above this region");
731 hr->set_top(hr->end());
732 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, hr->end());
733 }
734 }
735 // If we have continues humongous regions (hr != NULL), then the
736 // end of the last one should match new_end and its top should
737 // match new_top.
738 assert(hr == NULL ||
739 (hr->end() == new_end && hr->top() == new_top), "sanity");
740 check_bitmaps("Humongous Region Allocation", first_hr);
742 assert(first_hr->used() == word_size * HeapWordSize, "invariant");
743 _allocator->increase_used(first_hr->used());
744 _humongous_set.add(first_hr);
746 return new_obj;
747 }
749 // If could fit into free regions w/o expansion, try.
750 // Otherwise, if can expand, do so.
751 // Otherwise, if using ex regions might help, try with ex given back.
752 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size, AllocationContext_t context) {
753 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
755 verify_region_sets_optional();
757 uint first = G1_NO_HRM_INDEX;
758 uint obj_regions = (uint)(align_size_up_(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords);
760 if (obj_regions == 1) {
761 // Only one region to allocate, try to use a fast path by directly allocating
762 // from the free lists. Do not try to expand here, we will potentially do that
763 // later.
764 HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */);
765 if (hr != NULL) {
766 first = hr->hrm_index();
767 }
768 } else {
769 // We can't allocate humongous regions spanning more than one region while
770 // cleanupComplete() is running, since some of the regions we find to be
771 // empty might not yet be added to the free list. It is not straightforward
772 // to know in which list they are on so that we can remove them. We only
773 // need to do this if we need to allocate more than one region to satisfy the
774 // current humongous allocation request. If we are only allocating one region
775 // we use the one-region region allocation code (see above), that already
776 // potentially waits for regions from the secondary free list.
777 wait_while_free_regions_coming();
778 append_secondary_free_list_if_not_empty_with_lock();
780 // Policy: Try only empty regions (i.e. already committed first). Maybe we
781 // are lucky enough to find some.
782 first = _hrm.find_contiguous_only_empty(obj_regions);
783 if (first != G1_NO_HRM_INDEX) {
784 _hrm.allocate_free_regions_starting_at(first, obj_regions);
785 }
786 }
788 if (first == G1_NO_HRM_INDEX) {
789 // Policy: We could not find enough regions for the humongous object in the
790 // free list. Look through the heap to find a mix of free and uncommitted regions.
791 // If so, try expansion.
792 first = _hrm.find_contiguous_empty_or_unavailable(obj_regions);
793 if (first != G1_NO_HRM_INDEX) {
794 // We found something. Make sure these regions are committed, i.e. expand
795 // the heap. Alternatively we could do a defragmentation GC.
796 ergo_verbose1(ErgoHeapSizing,
797 "attempt heap expansion",
798 ergo_format_reason("humongous allocation request failed")
799 ergo_format_byte("allocation request"),
800 word_size * HeapWordSize);
802 _hrm.expand_at(first, obj_regions);
803 g1_policy()->record_new_heap_size(num_regions());
805 #ifdef ASSERT
806 for (uint i = first; i < first + obj_regions; ++i) {
807 HeapRegion* hr = region_at(i);
808 assert(hr->is_free(), "sanity");
809 assert(hr->is_empty(), "sanity");
810 assert(is_on_master_free_list(hr), "sanity");
811 }
812 #endif
813 _hrm.allocate_free_regions_starting_at(first, obj_regions);
814 } else {
815 // Policy: Potentially trigger a defragmentation GC.
816 }
817 }
819 HeapWord* result = NULL;
820 if (first != G1_NO_HRM_INDEX) {
821 result = humongous_obj_allocate_initialize_regions(first, obj_regions,
822 word_size, context);
823 assert(result != NULL, "it should always return a valid result");
825 // A successful humongous object allocation changes the used space
826 // information of the old generation so we need to recalculate the
827 // sizes and update the jstat counters here.
828 g1mm()->update_sizes();
829 }
831 verify_region_sets_optional();
833 return result;
834 }
836 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) {
837 assert_heap_not_locked_and_not_at_safepoint();
838 assert(!isHumongous(word_size), "we do not allow humongous TLABs");
840 unsigned int dummy_gc_count_before;
841 int dummy_gclocker_retry_count = 0;
842 return attempt_allocation(word_size, &dummy_gc_count_before, &dummy_gclocker_retry_count);
843 }
845 HeapWord*
846 G1CollectedHeap::mem_allocate(size_t word_size,
847 bool* gc_overhead_limit_was_exceeded) {
848 assert_heap_not_locked_and_not_at_safepoint();
850 // Loop until the allocation is satisfied, or unsatisfied after GC.
851 for (int try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
852 unsigned int gc_count_before;
854 HeapWord* result = NULL;
855 if (!isHumongous(word_size)) {
856 result = attempt_allocation(word_size, &gc_count_before, &gclocker_retry_count);
857 } else {
858 result = attempt_allocation_humongous(word_size, &gc_count_before, &gclocker_retry_count);
859 }
860 if (result != NULL) {
861 return result;
862 }
864 // Create the garbage collection operation...
865 VM_G1CollectForAllocation op(gc_count_before, word_size);
866 op.set_allocation_context(AllocationContext::current());
868 // ...and get the VM thread to execute it.
869 VMThread::execute(&op);
871 if (op.prologue_succeeded() && op.pause_succeeded()) {
872 // If the operation was successful we'll return the result even
873 // if it is NULL. If the allocation attempt failed immediately
874 // after a Full GC, it's unlikely we'll be able to allocate now.
875 HeapWord* result = op.result();
876 if (result != NULL && !isHumongous(word_size)) {
877 // Allocations that take place on VM operations do not do any
878 // card dirtying and we have to do it here. We only have to do
879 // this for non-humongous allocations, though.
880 dirty_young_block(result, word_size);
881 }
882 return result;
883 } else {
884 if (gclocker_retry_count > GCLockerRetryAllocationCount) {
885 return NULL;
886 }
887 assert(op.result() == NULL,
888 "the result should be NULL if the VM op did not succeed");
889 }
891 // Give a warning if we seem to be looping forever.
892 if ((QueuedAllocationWarningCount > 0) &&
893 (try_count % QueuedAllocationWarningCount == 0)) {
894 warning("G1CollectedHeap::mem_allocate retries %d times", try_count);
895 }
896 }
898 ShouldNotReachHere();
899 return NULL;
900 }
902 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size,
903 AllocationContext_t context,
904 unsigned int *gc_count_before_ret,
905 int* gclocker_retry_count_ret) {
906 // Make sure you read the note in attempt_allocation_humongous().
908 assert_heap_not_locked_and_not_at_safepoint();
909 assert(!isHumongous(word_size), "attempt_allocation_slow() should not "
910 "be called for humongous allocation requests");
912 // We should only get here after the first-level allocation attempt
913 // (attempt_allocation()) failed to allocate.
915 // We will loop until a) we manage to successfully perform the
916 // allocation or b) we successfully schedule a collection which
917 // fails to perform the allocation. b) is the only case when we'll
918 // return NULL.
919 HeapWord* result = NULL;
920 for (int try_count = 1; /* we'll return */; try_count += 1) {
921 bool should_try_gc;
922 unsigned int gc_count_before;
924 {
925 MutexLockerEx x(Heap_lock);
926 result = _allocator->mutator_alloc_region(context)->attempt_allocation_locked(word_size,
927 false /* bot_updates */);
928 if (result != NULL) {
929 return result;
930 }
932 // If we reach here, attempt_allocation_locked() above failed to
933 // allocate a new region. So the mutator alloc region should be NULL.
934 assert(_allocator->mutator_alloc_region(context)->get() == NULL, "only way to get here");
936 if (GC_locker::is_active_and_needs_gc()) {
937 if (g1_policy()->can_expand_young_list()) {
938 // No need for an ergo verbose message here,
939 // can_expand_young_list() does this when it returns true.
940 result = _allocator->mutator_alloc_region(context)->attempt_allocation_force(word_size,
941 false /* bot_updates */);
942 if (result != NULL) {
943 return result;
944 }
945 }
946 should_try_gc = false;
947 } else {
948 // The GCLocker may not be active but the GCLocker initiated
949 // GC may not yet have been performed (GCLocker::needs_gc()
950 // returns true). In this case we do not try this GC and
951 // wait until the GCLocker initiated GC is performed, and
952 // then retry the allocation.
953 if (GC_locker::needs_gc()) {
954 should_try_gc = false;
955 } else {
956 // Read the GC count while still holding the Heap_lock.
957 gc_count_before = total_collections();
958 should_try_gc = true;
959 }
960 }
961 }
963 if (should_try_gc) {
964 bool succeeded;
965 result = do_collection_pause(word_size, gc_count_before, &succeeded,
966 GCCause::_g1_inc_collection_pause);
967 if (result != NULL) {
968 assert(succeeded, "only way to get back a non-NULL result");
969 return result;
970 }
972 if (succeeded) {
973 // If we get here we successfully scheduled a collection which
974 // failed to allocate. No point in trying to allocate
975 // further. We'll just return NULL.
976 MutexLockerEx x(Heap_lock);
977 *gc_count_before_ret = total_collections();
978 return NULL;
979 }
980 } else {
981 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
982 MutexLockerEx x(Heap_lock);
983 *gc_count_before_ret = total_collections();
984 return NULL;
985 }
986 // The GCLocker is either active or the GCLocker initiated
987 // GC has not yet been performed. Stall until it is and
988 // then retry the allocation.
989 GC_locker::stall_until_clear();
990 (*gclocker_retry_count_ret) += 1;
991 }
993 // We can reach here if we were unsuccessful in scheduling a
994 // collection (because another thread beat us to it) or if we were
995 // stalled due to the GC locker. In either can we should retry the
996 // allocation attempt in case another thread successfully
997 // performed a collection and reclaimed enough space. We do the
998 // first attempt (without holding the Heap_lock) here and the
999 // follow-on attempt will be at the start of the next loop
1000 // iteration (after taking the Heap_lock).
1001 result = _allocator->mutator_alloc_region(context)->attempt_allocation(word_size,
1002 false /* bot_updates */);
1003 if (result != NULL) {
1004 return result;
1005 }
1007 // Give a warning if we seem to be looping forever.
1008 if ((QueuedAllocationWarningCount > 0) &&
1009 (try_count % QueuedAllocationWarningCount == 0)) {
1010 warning("G1CollectedHeap::attempt_allocation_slow() "
1011 "retries %d times", try_count);
1012 }
1013 }
1015 ShouldNotReachHere();
1016 return NULL;
1017 }
1019 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size,
1020 unsigned int * gc_count_before_ret,
1021 int* gclocker_retry_count_ret) {
1022 // The structure of this method has a lot of similarities to
1023 // attempt_allocation_slow(). The reason these two were not merged
1024 // into a single one is that such a method would require several "if
1025 // allocation is not humongous do this, otherwise do that"
1026 // conditional paths which would obscure its flow. In fact, an early
1027 // version of this code did use a unified method which was harder to
1028 // follow and, as a result, it had subtle bugs that were hard to
1029 // track down. So keeping these two methods separate allows each to
1030 // be more readable. It will be good to keep these two in sync as
1031 // much as possible.
1033 assert_heap_not_locked_and_not_at_safepoint();
1034 assert(isHumongous(word_size), "attempt_allocation_humongous() "
1035 "should only be called for humongous allocations");
1037 // Humongous objects can exhaust the heap quickly, so we should check if we
1038 // need to start a marking cycle at each humongous object allocation. We do
1039 // the check before we do the actual allocation. The reason for doing it
1040 // before the allocation is that we avoid having to keep track of the newly
1041 // allocated memory while we do a GC.
1042 if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation",
1043 word_size)) {
1044 collect(GCCause::_g1_humongous_allocation);
1045 }
1047 // We will loop until a) we manage to successfully perform the
1048 // allocation or b) we successfully schedule a collection which
1049 // fails to perform the allocation. b) is the only case when we'll
1050 // return NULL.
1051 HeapWord* result = NULL;
1052 for (int try_count = 1; /* we'll return */; try_count += 1) {
1053 bool should_try_gc;
1054 unsigned int gc_count_before;
1056 {
1057 MutexLockerEx x(Heap_lock);
1059 // Given that humongous objects are not allocated in young
1060 // regions, we'll first try to do the allocation without doing a
1061 // collection hoping that there's enough space in the heap.
1062 result = humongous_obj_allocate(word_size, AllocationContext::current());
1063 if (result != NULL) {
1064 return result;
1065 }
1067 if (GC_locker::is_active_and_needs_gc()) {
1068 should_try_gc = false;
1069 } else {
1070 // The GCLocker may not be active but the GCLocker initiated
1071 // GC may not yet have been performed (GCLocker::needs_gc()
1072 // returns true). In this case we do not try this GC and
1073 // wait until the GCLocker initiated GC is performed, and
1074 // then retry the allocation.
1075 if (GC_locker::needs_gc()) {
1076 should_try_gc = false;
1077 } else {
1078 // Read the GC count while still holding the Heap_lock.
1079 gc_count_before = total_collections();
1080 should_try_gc = true;
1081 }
1082 }
1083 }
1085 if (should_try_gc) {
1086 // If we failed to allocate the humongous object, we should try to
1087 // do a collection pause (if we're allowed) in case it reclaims
1088 // enough space for the allocation to succeed after the pause.
1090 bool succeeded;
1091 result = do_collection_pause(word_size, gc_count_before, &succeeded,
1092 GCCause::_g1_humongous_allocation);
1093 if (result != NULL) {
1094 assert(succeeded, "only way to get back a non-NULL result");
1095 return result;
1096 }
1098 if (succeeded) {
1099 // If we get here we successfully scheduled a collection which
1100 // failed to allocate. No point in trying to allocate
1101 // further. We'll just return NULL.
1102 MutexLockerEx x(Heap_lock);
1103 *gc_count_before_ret = total_collections();
1104 return NULL;
1105 }
1106 } else {
1107 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
1108 MutexLockerEx x(Heap_lock);
1109 *gc_count_before_ret = total_collections();
1110 return NULL;
1111 }
1112 // The GCLocker is either active or the GCLocker initiated
1113 // GC has not yet been performed. Stall until it is and
1114 // then retry the allocation.
1115 GC_locker::stall_until_clear();
1116 (*gclocker_retry_count_ret) += 1;
1117 }
1119 // We can reach here if we were unsuccessful in scheduling a
1120 // collection (because another thread beat us to it) or if we were
1121 // stalled due to the GC locker. In either can we should retry the
1122 // allocation attempt in case another thread successfully
1123 // performed a collection and reclaimed enough space. Give a
1124 // warning if we seem to be looping forever.
1126 if ((QueuedAllocationWarningCount > 0) &&
1127 (try_count % QueuedAllocationWarningCount == 0)) {
1128 warning("G1CollectedHeap::attempt_allocation_humongous() "
1129 "retries %d times", try_count);
1130 }
1131 }
1133 ShouldNotReachHere();
1134 return NULL;
1135 }
1137 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
1138 AllocationContext_t context,
1139 bool expect_null_mutator_alloc_region) {
1140 assert_at_safepoint(true /* should_be_vm_thread */);
1141 assert(_allocator->mutator_alloc_region(context)->get() == NULL ||
1142 !expect_null_mutator_alloc_region,
1143 "the current alloc region was unexpectedly found to be non-NULL");
1145 if (!isHumongous(word_size)) {
1146 return _allocator->mutator_alloc_region(context)->attempt_allocation_locked(word_size,
1147 false /* bot_updates */);
1148 } else {
1149 HeapWord* result = humongous_obj_allocate(word_size, context);
1150 if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) {
1151 g1_policy()->set_initiate_conc_mark_if_possible();
1152 }
1153 return result;
1154 }
1156 ShouldNotReachHere();
1157 }
1159 class PostMCRemSetClearClosure: public HeapRegionClosure {
1160 G1CollectedHeap* _g1h;
1161 ModRefBarrierSet* _mr_bs;
1162 public:
1163 PostMCRemSetClearClosure(G1CollectedHeap* g1h, ModRefBarrierSet* mr_bs) :
1164 _g1h(g1h), _mr_bs(mr_bs) {}
1166 bool doHeapRegion(HeapRegion* r) {
1167 HeapRegionRemSet* hrrs = r->rem_set();
1169 if (r->continuesHumongous()) {
1170 // We'll assert that the strong code root list and RSet is empty
1171 assert(hrrs->strong_code_roots_list_length() == 0, "sanity");
1172 assert(hrrs->occupied() == 0, "RSet should be empty");
1173 return false;
1174 }
1176 _g1h->reset_gc_time_stamps(r);
1177 hrrs->clear();
1178 // You might think here that we could clear just the cards
1179 // corresponding to the used region. But no: if we leave a dirty card
1180 // in a region we might allocate into, then it would prevent that card
1181 // from being enqueued, and cause it to be missed.
1182 // Re: the performance cost: we shouldn't be doing full GC anyway!
1183 _mr_bs->clear(MemRegion(r->bottom(), r->end()));
1185 return false;
1186 }
1187 };
1189 void G1CollectedHeap::clear_rsets_post_compaction() {
1190 PostMCRemSetClearClosure rs_clear(this, g1_barrier_set());
1191 heap_region_iterate(&rs_clear);
1192 }
1194 class RebuildRSOutOfRegionClosure: public HeapRegionClosure {
1195 G1CollectedHeap* _g1h;
1196 UpdateRSOopClosure _cl;
1197 int _worker_i;
1198 public:
1199 RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, int worker_i = 0) :
1200 _cl(g1->g1_rem_set(), worker_i),
1201 _worker_i(worker_i),
1202 _g1h(g1)
1203 { }
1205 bool doHeapRegion(HeapRegion* r) {
1206 if (!r->continuesHumongous()) {
1207 _cl.set_from(r);
1208 r->oop_iterate(&_cl);
1209 }
1210 return false;
1211 }
1212 };
1214 class ParRebuildRSTask: public AbstractGangTask {
1215 G1CollectedHeap* _g1;
1216 public:
1217 ParRebuildRSTask(G1CollectedHeap* g1)
1218 : AbstractGangTask("ParRebuildRSTask"),
1219 _g1(g1)
1220 { }
1222 void work(uint worker_id) {
1223 RebuildRSOutOfRegionClosure rebuild_rs(_g1, worker_id);
1224 _g1->heap_region_par_iterate_chunked(&rebuild_rs, worker_id,
1225 _g1->workers()->active_workers(),
1226 HeapRegion::RebuildRSClaimValue);
1227 }
1228 };
1230 class PostCompactionPrinterClosure: public HeapRegionClosure {
1231 private:
1232 G1HRPrinter* _hr_printer;
1233 public:
1234 bool doHeapRegion(HeapRegion* hr) {
1235 assert(!hr->is_young(), "not expecting to find young regions");
1236 if (hr->is_free()) {
1237 // We only generate output for non-empty regions.
1238 } else if (hr->startsHumongous()) {
1239 if (hr->region_num() == 1) {
1240 // single humongous region
1241 _hr_printer->post_compaction(hr, G1HRPrinter::SingleHumongous);
1242 } else {
1243 _hr_printer->post_compaction(hr, G1HRPrinter::StartsHumongous);
1244 }
1245 } else if (hr->continuesHumongous()) {
1246 _hr_printer->post_compaction(hr, G1HRPrinter::ContinuesHumongous);
1247 } else if (hr->is_old()) {
1248 _hr_printer->post_compaction(hr, G1HRPrinter::Old);
1249 } else {
1250 ShouldNotReachHere();
1251 }
1252 return false;
1253 }
1255 PostCompactionPrinterClosure(G1HRPrinter* hr_printer)
1256 : _hr_printer(hr_printer) { }
1257 };
1259 void G1CollectedHeap::print_hrm_post_compaction() {
1260 PostCompactionPrinterClosure cl(hr_printer());
1261 heap_region_iterate(&cl);
1262 }
1264 bool G1CollectedHeap::do_collection(bool explicit_gc,
1265 bool clear_all_soft_refs,
1266 size_t word_size) {
1267 assert_at_safepoint(true /* should_be_vm_thread */);
1269 if (GC_locker::check_active_before_gc()) {
1270 return false;
1271 }
1273 STWGCTimer* gc_timer = G1MarkSweep::gc_timer();
1274 gc_timer->register_gc_start();
1276 SerialOldTracer* gc_tracer = G1MarkSweep::gc_tracer();
1277 gc_tracer->report_gc_start(gc_cause(), gc_timer->gc_start());
1279 SvcGCMarker sgcm(SvcGCMarker::FULL);
1280 ResourceMark rm;
1282 print_heap_before_gc();
1283 trace_heap_before_gc(gc_tracer);
1285 size_t metadata_prev_used = MetaspaceAux::used_bytes();
1287 verify_region_sets_optional();
1289 const bool do_clear_all_soft_refs = clear_all_soft_refs ||
1290 collector_policy()->should_clear_all_soft_refs();
1292 ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy());
1294 {
1295 IsGCActiveMark x;
1297 // Timing
1298 assert(gc_cause() != GCCause::_java_lang_system_gc || explicit_gc, "invariant");
1299 gclog_or_tty->date_stamp(G1Log::fine() && PrintGCDateStamps);
1300 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
1302 {
1303 GCTraceTime t(GCCauseString("Full GC", gc_cause()), G1Log::fine(), true, NULL, gc_tracer->gc_id());
1304 TraceCollectorStats tcs(g1mm()->full_collection_counters());
1305 TraceMemoryManagerStats tms(true /* fullGC */, gc_cause());
1307 double start = os::elapsedTime();
1308 g1_policy()->record_full_collection_start();
1310 // Note: When we have a more flexible GC logging framework that
1311 // allows us to add optional attributes to a GC log record we
1312 // could consider timing and reporting how long we wait in the
1313 // following two methods.
1314 wait_while_free_regions_coming();
1315 // If we start the compaction before the CM threads finish
1316 // scanning the root regions we might trip them over as we'll
1317 // be moving objects / updating references. So let's wait until
1318 // they are done. By telling them to abort, they should complete
1319 // early.
1320 _cm->root_regions()->abort();
1321 _cm->root_regions()->wait_until_scan_finished();
1322 append_secondary_free_list_if_not_empty_with_lock();
1324 gc_prologue(true);
1325 increment_total_collections(true /* full gc */);
1326 increment_old_marking_cycles_started();
1328 assert(used() == recalculate_used(), "Should be equal");
1330 verify_before_gc();
1332 check_bitmaps("Full GC Start");
1333 pre_full_gc_dump(gc_timer);
1335 COMPILER2_PRESENT(DerivedPointerTable::clear());
1337 // Disable discovery and empty the discovered lists
1338 // for the CM ref processor.
1339 ref_processor_cm()->disable_discovery();
1340 ref_processor_cm()->abandon_partial_discovery();
1341 ref_processor_cm()->verify_no_references_recorded();
1343 // Abandon current iterations of concurrent marking and concurrent
1344 // refinement, if any are in progress. We have to do this before
1345 // wait_until_scan_finished() below.
1346 concurrent_mark()->abort();
1348 // Make sure we'll choose a new allocation region afterwards.
1349 _allocator->release_mutator_alloc_region();
1350 _allocator->abandon_gc_alloc_regions();
1351 g1_rem_set()->cleanupHRRS();
1353 // We should call this after we retire any currently active alloc
1354 // regions so that all the ALLOC / RETIRE events are generated
1355 // before the start GC event.
1356 _hr_printer.start_gc(true /* full */, (size_t) total_collections());
1358 // We may have added regions to the current incremental collection
1359 // set between the last GC or pause and now. We need to clear the
1360 // incremental collection set and then start rebuilding it afresh
1361 // after this full GC.
1362 abandon_collection_set(g1_policy()->inc_cset_head());
1363 g1_policy()->clear_incremental_cset();
1364 g1_policy()->stop_incremental_cset_building();
1366 tear_down_region_sets(false /* free_list_only */);
1367 g1_policy()->set_gcs_are_young(true);
1369 // See the comments in g1CollectedHeap.hpp and
1370 // G1CollectedHeap::ref_processing_init() about
1371 // how reference processing currently works in G1.
1373 // Temporarily make discovery by the STW ref processor single threaded (non-MT).
1374 ReferenceProcessorMTDiscoveryMutator stw_rp_disc_ser(ref_processor_stw(), false);
1376 // Temporarily clear the STW ref processor's _is_alive_non_header field.
1377 ReferenceProcessorIsAliveMutator stw_rp_is_alive_null(ref_processor_stw(), NULL);
1379 ref_processor_stw()->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/);
1380 ref_processor_stw()->setup_policy(do_clear_all_soft_refs);
1382 // Do collection work
1383 {
1384 HandleMark hm; // Discard invalid handles created during gc
1385 G1MarkSweep::invoke_at_safepoint(ref_processor_stw(), do_clear_all_soft_refs);
1386 }
1388 assert(num_free_regions() == 0, "we should not have added any free regions");
1389 rebuild_region_sets(false /* free_list_only */);
1391 // Enqueue any discovered reference objects that have
1392 // not been removed from the discovered lists.
1393 ref_processor_stw()->enqueue_discovered_references();
1395 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
1397 MemoryService::track_memory_usage();
1399 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
1400 ref_processor_stw()->verify_no_references_recorded();
1402 // Delete metaspaces for unloaded class loaders and clean up loader_data graph
1403 ClassLoaderDataGraph::purge();
1404 MetaspaceAux::verify_metrics();
1406 // Note: since we've just done a full GC, concurrent
1407 // marking is no longer active. Therefore we need not
1408 // re-enable reference discovery for the CM ref processor.
1409 // That will be done at the start of the next marking cycle.
1410 assert(!ref_processor_cm()->discovery_enabled(), "Postcondition");
1411 ref_processor_cm()->verify_no_references_recorded();
1413 reset_gc_time_stamp();
1414 // Since everything potentially moved, we will clear all remembered
1415 // sets, and clear all cards. Later we will rebuild remembered
1416 // sets. We will also reset the GC time stamps of the regions.
1417 clear_rsets_post_compaction();
1418 check_gc_time_stamps();
1420 // Resize the heap if necessary.
1421 resize_if_necessary_after_full_collection(explicit_gc ? 0 : word_size);
1423 if (_hr_printer.is_active()) {
1424 // We should do this after we potentially resize the heap so
1425 // that all the COMMIT / UNCOMMIT events are generated before
1426 // the end GC event.
1428 print_hrm_post_compaction();
1429 _hr_printer.end_gc(true /* full */, (size_t) total_collections());
1430 }
1432 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
1433 if (hot_card_cache->use_cache()) {
1434 hot_card_cache->reset_card_counts();
1435 hot_card_cache->reset_hot_cache();
1436 }
1438 // Rebuild remembered sets of all regions.
1439 if (G1CollectedHeap::use_parallel_gc_threads()) {
1440 uint n_workers =
1441 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
1442 workers()->active_workers(),
1443 Threads::number_of_non_daemon_threads());
1444 assert(UseDynamicNumberOfGCThreads ||
1445 n_workers == workers()->total_workers(),
1446 "If not dynamic should be using all the workers");
1447 workers()->set_active_workers(n_workers);
1448 // Set parallel threads in the heap (_n_par_threads) only
1449 // before a parallel phase and always reset it to 0 after
1450 // the phase so that the number of parallel threads does
1451 // no get carried forward to a serial phase where there
1452 // may be code that is "possibly_parallel".
1453 set_par_threads(n_workers);
1455 ParRebuildRSTask rebuild_rs_task(this);
1456 assert(check_heap_region_claim_values(
1457 HeapRegion::InitialClaimValue), "sanity check");
1458 assert(UseDynamicNumberOfGCThreads ||
1459 workers()->active_workers() == workers()->total_workers(),
1460 "Unless dynamic should use total workers");
1461 // Use the most recent number of active workers
1462 assert(workers()->active_workers() > 0,
1463 "Active workers not properly set");
1464 set_par_threads(workers()->active_workers());
1465 workers()->run_task(&rebuild_rs_task);
1466 set_par_threads(0);
1467 assert(check_heap_region_claim_values(
1468 HeapRegion::RebuildRSClaimValue), "sanity check");
1469 reset_heap_region_claim_values();
1470 } else {
1471 RebuildRSOutOfRegionClosure rebuild_rs(this);
1472 heap_region_iterate(&rebuild_rs);
1473 }
1475 // Rebuild the strong code root lists for each region
1476 rebuild_strong_code_roots();
1478 if (true) { // FIXME
1479 MetaspaceGC::compute_new_size();
1480 }
1482 #ifdef TRACESPINNING
1483 ParallelTaskTerminator::print_termination_counts();
1484 #endif
1486 // Discard all rset updates
1487 JavaThread::dirty_card_queue_set().abandon_logs();
1488 assert(dirty_card_queue_set().completed_buffers_num() == 0, "DCQS should be empty");
1490 _young_list->reset_sampled_info();
1491 // At this point there should be no regions in the
1492 // entire heap tagged as young.
1493 assert(check_young_list_empty(true /* check_heap */),
1494 "young list should be empty at this point");
1496 // Update the number of full collections that have been completed.
1497 increment_old_marking_cycles_completed(false /* concurrent */);
1499 _hrm.verify_optional();
1500 verify_region_sets_optional();
1502 verify_after_gc();
1504 // Clear the previous marking bitmap, if needed for bitmap verification.
1505 // Note we cannot do this when we clear the next marking bitmap in
1506 // ConcurrentMark::abort() above since VerifyDuringGC verifies the
1507 // objects marked during a full GC against the previous bitmap.
1508 // But we need to clear it before calling check_bitmaps below since
1509 // the full GC has compacted objects and updated TAMS but not updated
1510 // the prev bitmap.
1511 if (G1VerifyBitmaps) {
1512 ((CMBitMap*) concurrent_mark()->prevMarkBitMap())->clearAll();
1513 }
1514 check_bitmaps("Full GC End");
1516 // Start a new incremental collection set for the next pause
1517 assert(g1_policy()->collection_set() == NULL, "must be");
1518 g1_policy()->start_incremental_cset_building();
1520 clear_cset_fast_test();
1522 _allocator->init_mutator_alloc_region();
1524 double end = os::elapsedTime();
1525 g1_policy()->record_full_collection_end();
1527 if (G1Log::fine()) {
1528 g1_policy()->print_heap_transition();
1529 }
1531 // We must call G1MonitoringSupport::update_sizes() in the same scoping level
1532 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
1533 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
1534 // before any GC notifications are raised.
1535 g1mm()->update_sizes();
1537 gc_epilogue(true);
1538 }
1540 if (G1Log::finer()) {
1541 g1_policy()->print_detailed_heap_transition(true /* full */);
1542 }
1544 print_heap_after_gc();
1545 trace_heap_after_gc(gc_tracer);
1547 post_full_gc_dump(gc_timer);
1549 gc_timer->register_gc_end();
1550 gc_tracer->report_gc_end(gc_timer->gc_end(), gc_timer->time_partitions());
1551 }
1553 return true;
1554 }
1556 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
1557 // do_collection() will return whether it succeeded in performing
1558 // the GC. Currently, there is no facility on the
1559 // do_full_collection() API to notify the caller than the collection
1560 // did not succeed (e.g., because it was locked out by the GC
1561 // locker). So, right now, we'll ignore the return value.
1562 bool dummy = do_collection(true, /* explicit_gc */
1563 clear_all_soft_refs,
1564 0 /* word_size */);
1565 }
1567 // This code is mostly copied from TenuredGeneration.
1568 void
1569 G1CollectedHeap::
1570 resize_if_necessary_after_full_collection(size_t word_size) {
1571 // Include the current allocation, if any, and bytes that will be
1572 // pre-allocated to support collections, as "used".
1573 const size_t used_after_gc = used();
1574 const size_t capacity_after_gc = capacity();
1575 const size_t free_after_gc = capacity_after_gc - used_after_gc;
1577 // This is enforced in arguments.cpp.
1578 assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
1579 "otherwise the code below doesn't make sense");
1581 // We don't have floating point command-line arguments
1582 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
1583 const double maximum_used_percentage = 1.0 - minimum_free_percentage;
1584 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
1585 const double minimum_used_percentage = 1.0 - maximum_free_percentage;
1587 const size_t min_heap_size = collector_policy()->min_heap_byte_size();
1588 const size_t max_heap_size = collector_policy()->max_heap_byte_size();
1590 // We have to be careful here as these two calculations can overflow
1591 // 32-bit size_t's.
1592 double used_after_gc_d = (double) used_after_gc;
1593 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
1594 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
1596 // Let's make sure that they are both under the max heap size, which
1597 // by default will make them fit into a size_t.
1598 double desired_capacity_upper_bound = (double) max_heap_size;
1599 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
1600 desired_capacity_upper_bound);
1601 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
1602 desired_capacity_upper_bound);
1604 // We can now safely turn them into size_t's.
1605 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
1606 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
1608 // This assert only makes sense here, before we adjust them
1609 // with respect to the min and max heap size.
1610 assert(minimum_desired_capacity <= maximum_desired_capacity,
1611 err_msg("minimum_desired_capacity = "SIZE_FORMAT", "
1612 "maximum_desired_capacity = "SIZE_FORMAT,
1613 minimum_desired_capacity, maximum_desired_capacity));
1615 // Should not be greater than the heap max size. No need to adjust
1616 // it with respect to the heap min size as it's a lower bound (i.e.,
1617 // we'll try to make the capacity larger than it, not smaller).
1618 minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size);
1619 // Should not be less than the heap min size. No need to adjust it
1620 // with respect to the heap max size as it's an upper bound (i.e.,
1621 // we'll try to make the capacity smaller than it, not greater).
1622 maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size);
1624 if (capacity_after_gc < minimum_desired_capacity) {
1625 // Don't expand unless it's significant
1626 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
1627 ergo_verbose4(ErgoHeapSizing,
1628 "attempt heap expansion",
1629 ergo_format_reason("capacity lower than "
1630 "min desired capacity after Full GC")
1631 ergo_format_byte("capacity")
1632 ergo_format_byte("occupancy")
1633 ergo_format_byte_perc("min desired capacity"),
1634 capacity_after_gc, used_after_gc,
1635 minimum_desired_capacity, (double) MinHeapFreeRatio);
1636 expand(expand_bytes);
1638 // No expansion, now see if we want to shrink
1639 } else if (capacity_after_gc > maximum_desired_capacity) {
1640 // Capacity too large, compute shrinking size
1641 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
1642 ergo_verbose4(ErgoHeapSizing,
1643 "attempt heap shrinking",
1644 ergo_format_reason("capacity higher than "
1645 "max desired capacity after Full GC")
1646 ergo_format_byte("capacity")
1647 ergo_format_byte("occupancy")
1648 ergo_format_byte_perc("max desired capacity"),
1649 capacity_after_gc, used_after_gc,
1650 maximum_desired_capacity, (double) MaxHeapFreeRatio);
1651 shrink(shrink_bytes);
1652 }
1653 }
1656 HeapWord*
1657 G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
1658 AllocationContext_t context,
1659 bool* succeeded) {
1660 assert_at_safepoint(true /* should_be_vm_thread */);
1662 *succeeded = true;
1663 // Let's attempt the allocation first.
1664 HeapWord* result =
1665 attempt_allocation_at_safepoint(word_size,
1666 context,
1667 false /* expect_null_mutator_alloc_region */);
1668 if (result != NULL) {
1669 assert(*succeeded, "sanity");
1670 return result;
1671 }
1673 // In a G1 heap, we're supposed to keep allocation from failing by
1674 // incremental pauses. Therefore, at least for now, we'll favor
1675 // expansion over collection. (This might change in the future if we can
1676 // do something smarter than full collection to satisfy a failed alloc.)
1677 result = expand_and_allocate(word_size, context);
1678 if (result != NULL) {
1679 assert(*succeeded, "sanity");
1680 return result;
1681 }
1683 // Expansion didn't work, we'll try to do a Full GC.
1684 bool gc_succeeded = do_collection(false, /* explicit_gc */
1685 false, /* clear_all_soft_refs */
1686 word_size);
1687 if (!gc_succeeded) {
1688 *succeeded = false;
1689 return NULL;
1690 }
1692 // Retry the allocation
1693 result = attempt_allocation_at_safepoint(word_size,
1694 context,
1695 true /* expect_null_mutator_alloc_region */);
1696 if (result != NULL) {
1697 assert(*succeeded, "sanity");
1698 return result;
1699 }
1701 // Then, try a Full GC that will collect all soft references.
1702 gc_succeeded = do_collection(false, /* explicit_gc */
1703 true, /* clear_all_soft_refs */
1704 word_size);
1705 if (!gc_succeeded) {
1706 *succeeded = false;
1707 return NULL;
1708 }
1710 // Retry the allocation once more
1711 result = attempt_allocation_at_safepoint(word_size,
1712 context,
1713 true /* expect_null_mutator_alloc_region */);
1714 if (result != NULL) {
1715 assert(*succeeded, "sanity");
1716 return result;
1717 }
1719 assert(!collector_policy()->should_clear_all_soft_refs(),
1720 "Flag should have been handled and cleared prior to this point");
1722 // What else? We might try synchronous finalization later. If the total
1723 // space available is large enough for the allocation, then a more
1724 // complete compaction phase than we've tried so far might be
1725 // appropriate.
1726 assert(*succeeded, "sanity");
1727 return NULL;
1728 }
1730 // Attempting to expand the heap sufficiently
1731 // to support an allocation of the given "word_size". If
1732 // successful, perform the allocation and return the address of the
1733 // allocated block, or else "NULL".
1735 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size, AllocationContext_t context) {
1736 assert_at_safepoint(true /* should_be_vm_thread */);
1738 verify_region_sets_optional();
1740 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
1741 ergo_verbose1(ErgoHeapSizing,
1742 "attempt heap expansion",
1743 ergo_format_reason("allocation request failed")
1744 ergo_format_byte("allocation request"),
1745 word_size * HeapWordSize);
1746 if (expand(expand_bytes)) {
1747 _hrm.verify_optional();
1748 verify_region_sets_optional();
1749 return attempt_allocation_at_safepoint(word_size,
1750 context,
1751 false /* expect_null_mutator_alloc_region */);
1752 }
1753 return NULL;
1754 }
1756 bool G1CollectedHeap::expand(size_t expand_bytes) {
1757 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
1758 aligned_expand_bytes = align_size_up(aligned_expand_bytes,
1759 HeapRegion::GrainBytes);
1760 ergo_verbose2(ErgoHeapSizing,
1761 "expand the heap",
1762 ergo_format_byte("requested expansion amount")
1763 ergo_format_byte("attempted expansion amount"),
1764 expand_bytes, aligned_expand_bytes);
1766 if (is_maximal_no_gc()) {
1767 ergo_verbose0(ErgoHeapSizing,
1768 "did not expand the heap",
1769 ergo_format_reason("heap already fully expanded"));
1770 return false;
1771 }
1773 uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes);
1774 assert(regions_to_expand > 0, "Must expand by at least one region");
1776 uint expanded_by = _hrm.expand_by(regions_to_expand);
1778 if (expanded_by > 0) {
1779 size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes;
1780 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
1781 g1_policy()->record_new_heap_size(num_regions());
1782 } else {
1783 ergo_verbose0(ErgoHeapSizing,
1784 "did not expand the heap",
1785 ergo_format_reason("heap expansion operation failed"));
1786 // The expansion of the virtual storage space was unsuccessful.
1787 // Let's see if it was because we ran out of swap.
1788 if (G1ExitOnExpansionFailure &&
1789 _hrm.available() >= regions_to_expand) {
1790 // We had head room...
1791 vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion");
1792 }
1793 }
1794 return regions_to_expand > 0;
1795 }
1797 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
1798 size_t aligned_shrink_bytes =
1799 ReservedSpace::page_align_size_down(shrink_bytes);
1800 aligned_shrink_bytes = align_size_down(aligned_shrink_bytes,
1801 HeapRegion::GrainBytes);
1802 uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes);
1804 uint num_regions_removed = _hrm.shrink_by(num_regions_to_remove);
1805 size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes;
1807 ergo_verbose3(ErgoHeapSizing,
1808 "shrink the heap",
1809 ergo_format_byte("requested shrinking amount")
1810 ergo_format_byte("aligned shrinking amount")
1811 ergo_format_byte("attempted shrinking amount"),
1812 shrink_bytes, aligned_shrink_bytes, shrunk_bytes);
1813 if (num_regions_removed > 0) {
1814 g1_policy()->record_new_heap_size(num_regions());
1815 } else {
1816 ergo_verbose0(ErgoHeapSizing,
1817 "did not shrink the heap",
1818 ergo_format_reason("heap shrinking operation failed"));
1819 }
1820 }
1822 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1823 verify_region_sets_optional();
1825 // We should only reach here at the end of a Full GC which means we
1826 // should not not be holding to any GC alloc regions. The method
1827 // below will make sure of that and do any remaining clean up.
1828 _allocator->abandon_gc_alloc_regions();
1830 // Instead of tearing down / rebuilding the free lists here, we
1831 // could instead use the remove_all_pending() method on free_list to
1832 // remove only the ones that we need to remove.
1833 tear_down_region_sets(true /* free_list_only */);
1834 shrink_helper(shrink_bytes);
1835 rebuild_region_sets(true /* free_list_only */);
1837 _hrm.verify_optional();
1838 verify_region_sets_optional();
1839 }
1841 // Public methods.
1843 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away
1844 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
1845 #endif // _MSC_VER
1848 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* policy_) :
1849 SharedHeap(policy_),
1850 _g1_policy(policy_),
1851 _dirty_card_queue_set(false),
1852 _into_cset_dirty_card_queue_set(false),
1853 _is_alive_closure_cm(this),
1854 _is_alive_closure_stw(this),
1855 _ref_processor_cm(NULL),
1856 _ref_processor_stw(NULL),
1857 _process_strong_tasks(new SubTasksDone(G1H_PS_NumElements)),
1858 _bot_shared(NULL),
1859 _evac_failure_scan_stack(NULL),
1860 _mark_in_progress(false),
1861 _cg1r(NULL),
1862 _g1mm(NULL),
1863 _refine_cte_cl(NULL),
1864 _full_collection(false),
1865 _secondary_free_list("Secondary Free List", new SecondaryFreeRegionListMtSafeChecker()),
1866 _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()),
1867 _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()),
1868 _humongous_is_live(),
1869 _has_humongous_reclaim_candidates(false),
1870 _free_regions_coming(false),
1871 _young_list(new YoungList(this)),
1872 _gc_time_stamp(0),
1873 _survivor_plab_stats(YoungPLABSize, PLABWeight),
1874 _old_plab_stats(OldPLABSize, PLABWeight),
1875 _expand_heap_after_alloc_failure(true),
1876 _surviving_young_words(NULL),
1877 _old_marking_cycles_started(0),
1878 _old_marking_cycles_completed(0),
1879 _concurrent_cycle_started(false),
1880 _in_cset_fast_test(),
1881 _dirty_cards_region_list(NULL),
1882 _worker_cset_start_region(NULL),
1883 _worker_cset_start_region_time_stamp(NULL),
1884 _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()),
1885 _gc_timer_cm(new (ResourceObj::C_HEAP, mtGC) ConcurrentGCTimer()),
1886 _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()),
1887 _gc_tracer_cm(new (ResourceObj::C_HEAP, mtGC) G1OldTracer()) {
1889 _g1h = this;
1890 if (_process_strong_tasks == NULL || !_process_strong_tasks->valid()) {
1891 vm_exit_during_initialization("Failed necessary allocation.");
1892 }
1894 _allocator = G1Allocator::create_allocator(_g1h);
1895 _humongous_object_threshold_in_words = HeapRegion::GrainWords / 2;
1897 int n_queues = MAX2((int)ParallelGCThreads, 1);
1898 _task_queues = new RefToScanQueueSet(n_queues);
1900 uint n_rem_sets = HeapRegionRemSet::num_par_rem_sets();
1901 assert(n_rem_sets > 0, "Invariant.");
1903 _worker_cset_start_region = NEW_C_HEAP_ARRAY(HeapRegion*, n_queues, mtGC);
1904 _worker_cset_start_region_time_stamp = NEW_C_HEAP_ARRAY(unsigned int, n_queues, mtGC);
1905 _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC);
1907 for (int i = 0; i < n_queues; i++) {
1908 RefToScanQueue* q = new RefToScanQueue();
1909 q->initialize();
1910 _task_queues->register_queue(i, q);
1911 ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo();
1912 }
1913 clear_cset_start_regions();
1915 // Initialize the G1EvacuationFailureALot counters and flags.
1916 NOT_PRODUCT(reset_evacuation_should_fail();)
1918 guarantee(_task_queues != NULL, "task_queues allocation failure.");
1919 }
1921 jint G1CollectedHeap::initialize() {
1922 CollectedHeap::pre_initialize();
1923 os::enable_vtime();
1925 G1Log::init();
1927 // Necessary to satisfy locking discipline assertions.
1929 MutexLocker x(Heap_lock);
1931 // We have to initialize the printer before committing the heap, as
1932 // it will be used then.
1933 _hr_printer.set_active(G1PrintHeapRegions);
1935 // While there are no constraints in the GC code that HeapWordSize
1936 // be any particular value, there are multiple other areas in the
1937 // system which believe this to be true (e.g. oop->object_size in some
1938 // cases incorrectly returns the size in wordSize units rather than
1939 // HeapWordSize).
1940 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
1942 size_t init_byte_size = collector_policy()->initial_heap_byte_size();
1943 size_t max_byte_size = collector_policy()->max_heap_byte_size();
1944 size_t heap_alignment = collector_policy()->heap_alignment();
1946 // Ensure that the sizes are properly aligned.
1947 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
1948 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
1949 Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap");
1951 _refine_cte_cl = new RefineCardTableEntryClosure();
1953 _cg1r = new ConcurrentG1Refine(this, _refine_cte_cl);
1955 // Reserve the maximum.
1957 // When compressed oops are enabled, the preferred heap base
1958 // is calculated by subtracting the requested size from the
1959 // 32Gb boundary and using the result as the base address for
1960 // heap reservation. If the requested size is not aligned to
1961 // HeapRegion::GrainBytes (i.e. the alignment that is passed
1962 // into the ReservedHeapSpace constructor) then the actual
1963 // base of the reserved heap may end up differing from the
1964 // address that was requested (i.e. the preferred heap base).
1965 // If this happens then we could end up using a non-optimal
1966 // compressed oops mode.
1968 ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size,
1969 heap_alignment);
1971 // It is important to do this in a way such that concurrent readers can't
1972 // temporarily think something is in the heap. (I've actually seen this
1973 // happen in asserts: DLD.)
1974 _reserved.set_word_size(0);
1975 _reserved.set_start((HeapWord*)heap_rs.base());
1976 _reserved.set_end((HeapWord*)(heap_rs.base() + heap_rs.size()));
1978 // Create the gen rem set (and barrier set) for the entire reserved region.
1979 _rem_set = collector_policy()->create_rem_set(_reserved, 2);
1980 set_barrier_set(rem_set()->bs());
1981 if (!barrier_set()->is_a(BarrierSet::G1SATBCTLogging)) {
1982 vm_exit_during_initialization("G1 requires a G1SATBLoggingCardTableModRefBS");
1983 return JNI_ENOMEM;
1984 }
1986 // Also create a G1 rem set.
1987 _g1_rem_set = new G1RemSet(this, g1_barrier_set());
1989 // Carve out the G1 part of the heap.
1991 ReservedSpace g1_rs = heap_rs.first_part(max_byte_size);
1992 G1RegionToSpaceMapper* heap_storage =
1993 G1RegionToSpaceMapper::create_mapper(g1_rs,
1994 UseLargePages ? os::large_page_size() : os::vm_page_size(),
1995 HeapRegion::GrainBytes,
1996 1,
1997 mtJavaHeap);
1998 heap_storage->set_mapping_changed_listener(&_listener);
2000 // Reserve space for the block offset table. We do not support automatic uncommit
2001 // for the card table at this time. BOT only.
2002 ReservedSpace bot_rs(G1BlockOffsetSharedArray::compute_size(g1_rs.size() / HeapWordSize));
2003 G1RegionToSpaceMapper* bot_storage =
2004 G1RegionToSpaceMapper::create_mapper(bot_rs,
2005 os::vm_page_size(),
2006 HeapRegion::GrainBytes,
2007 G1BlockOffsetSharedArray::N_bytes,
2008 mtGC);
2010 ReservedSpace cardtable_rs(G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize));
2011 G1RegionToSpaceMapper* cardtable_storage =
2012 G1RegionToSpaceMapper::create_mapper(cardtable_rs,
2013 os::vm_page_size(),
2014 HeapRegion::GrainBytes,
2015 G1BlockOffsetSharedArray::N_bytes,
2016 mtGC);
2018 // Reserve space for the card counts table.
2019 ReservedSpace card_counts_rs(G1BlockOffsetSharedArray::compute_size(g1_rs.size() / HeapWordSize));
2020 G1RegionToSpaceMapper* card_counts_storage =
2021 G1RegionToSpaceMapper::create_mapper(card_counts_rs,
2022 os::vm_page_size(),
2023 HeapRegion::GrainBytes,
2024 G1BlockOffsetSharedArray::N_bytes,
2025 mtGC);
2027 // Reserve space for prev and next bitmap.
2028 size_t bitmap_size = CMBitMap::compute_size(g1_rs.size());
2030 ReservedSpace prev_bitmap_rs(ReservedSpace::allocation_align_size_up(bitmap_size));
2031 G1RegionToSpaceMapper* prev_bitmap_storage =
2032 G1RegionToSpaceMapper::create_mapper(prev_bitmap_rs,
2033 os::vm_page_size(),
2034 HeapRegion::GrainBytes,
2035 CMBitMap::mark_distance(),
2036 mtGC);
2038 ReservedSpace next_bitmap_rs(ReservedSpace::allocation_align_size_up(bitmap_size));
2039 G1RegionToSpaceMapper* next_bitmap_storage =
2040 G1RegionToSpaceMapper::create_mapper(next_bitmap_rs,
2041 os::vm_page_size(),
2042 HeapRegion::GrainBytes,
2043 CMBitMap::mark_distance(),
2044 mtGC);
2046 _hrm.initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage);
2047 g1_barrier_set()->initialize(cardtable_storage);
2048 // Do later initialization work for concurrent refinement.
2049 _cg1r->init(card_counts_storage);
2051 // 6843694 - ensure that the maximum region index can fit
2052 // in the remembered set structures.
2053 const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
2054 guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
2056 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
2057 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
2058 guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
2059 "too many cards per region");
2061 FreeRegionList::set_unrealistically_long_length(max_regions() + 1);
2063 _bot_shared = new G1BlockOffsetSharedArray(_reserved, bot_storage);
2065 _g1h = this;
2067 _in_cset_fast_test.initialize(_hrm.reserved().start(), _hrm.reserved().end(), HeapRegion::GrainBytes);
2068 _humongous_is_live.initialize(_hrm.reserved().start(), _hrm.reserved().end(), HeapRegion::GrainBytes);
2070 // Create the ConcurrentMark data structure and thread.
2071 // (Must do this late, so that "max_regions" is defined.)
2072 _cm = new ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage);
2073 if (_cm == NULL || !_cm->completed_initialization()) {
2074 vm_shutdown_during_initialization("Could not create/initialize ConcurrentMark");
2075 return JNI_ENOMEM;
2076 }
2077 _cmThread = _cm->cmThread();
2079 // Initialize the from_card cache structure of HeapRegionRemSet.
2080 HeapRegionRemSet::init_heap(max_regions());
2082 // Now expand into the initial heap size.
2083 if (!expand(init_byte_size)) {
2084 vm_shutdown_during_initialization("Failed to allocate initial heap.");
2085 return JNI_ENOMEM;
2086 }
2088 // Perform any initialization actions delegated to the policy.
2089 g1_policy()->init();
2091 JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon,
2092 SATB_Q_FL_lock,
2093 G1SATBProcessCompletedThreshold,
2094 Shared_SATB_Q_lock);
2096 JavaThread::dirty_card_queue_set().initialize(_refine_cte_cl,
2097 DirtyCardQ_CBL_mon,
2098 DirtyCardQ_FL_lock,
2099 concurrent_g1_refine()->yellow_zone(),
2100 concurrent_g1_refine()->red_zone(),
2101 Shared_DirtyCardQ_lock);
2103 dirty_card_queue_set().initialize(NULL, // Should never be called by the Java code
2104 DirtyCardQ_CBL_mon,
2105 DirtyCardQ_FL_lock,
2106 -1, // never trigger processing
2107 -1, // no limit on length
2108 Shared_DirtyCardQ_lock,
2109 &JavaThread::dirty_card_queue_set());
2111 // Initialize the card queue set used to hold cards containing
2112 // references into the collection set.
2113 _into_cset_dirty_card_queue_set.initialize(NULL, // Should never be called by the Java code
2114 DirtyCardQ_CBL_mon,
2115 DirtyCardQ_FL_lock,
2116 -1, // never trigger processing
2117 -1, // no limit on length
2118 Shared_DirtyCardQ_lock,
2119 &JavaThread::dirty_card_queue_set());
2121 // In case we're keeping closure specialization stats, initialize those
2122 // counts and that mechanism.
2123 SpecializationStats::clear();
2125 // Here we allocate the dummy HeapRegion that is required by the
2126 // G1AllocRegion class.
2127 HeapRegion* dummy_region = _hrm.get_dummy_region();
2129 // We'll re-use the same region whether the alloc region will
2130 // require BOT updates or not and, if it doesn't, then a non-young
2131 // region will complain that it cannot support allocations without
2132 // BOT updates. So we'll tag the dummy region as eden to avoid that.
2133 dummy_region->set_eden();
2134 // Make sure it's full.
2135 dummy_region->set_top(dummy_region->end());
2136 G1AllocRegion::setup(this, dummy_region);
2138 _allocator->init_mutator_alloc_region();
2140 // Do create of the monitoring and management support so that
2141 // values in the heap have been properly initialized.
2142 _g1mm = new G1MonitoringSupport(this);
2144 G1StringDedup::initialize();
2146 return JNI_OK;
2147 }
2149 void G1CollectedHeap::stop() {
2150 // Stop all concurrent threads. We do this to make sure these threads
2151 // do not continue to execute and access resources (e.g. gclog_or_tty)
2152 // that are destroyed during shutdown.
2153 _cg1r->stop();
2154 _cmThread->stop();
2155 if (G1StringDedup::is_enabled()) {
2156 G1StringDedup::stop();
2157 }
2158 }
2160 void G1CollectedHeap::clear_humongous_is_live_table() {
2161 guarantee(G1ReclaimDeadHumongousObjectsAtYoungGC, "Should only be called if true");
2162 _humongous_is_live.clear();
2163 }
2165 size_t G1CollectedHeap::conservative_max_heap_alignment() {
2166 return HeapRegion::max_region_size();
2167 }
2169 void G1CollectedHeap::ref_processing_init() {
2170 // Reference processing in G1 currently works as follows:
2171 //
2172 // * There are two reference processor instances. One is
2173 // used to record and process discovered references
2174 // during concurrent marking; the other is used to
2175 // record and process references during STW pauses
2176 // (both full and incremental).
2177 // * Both ref processors need to 'span' the entire heap as
2178 // the regions in the collection set may be dotted around.
2179 //
2180 // * For the concurrent marking ref processor:
2181 // * Reference discovery is enabled at initial marking.
2182 // * Reference discovery is disabled and the discovered
2183 // references processed etc during remarking.
2184 // * Reference discovery is MT (see below).
2185 // * Reference discovery requires a barrier (see below).
2186 // * Reference processing may or may not be MT
2187 // (depending on the value of ParallelRefProcEnabled
2188 // and ParallelGCThreads).
2189 // * A full GC disables reference discovery by the CM
2190 // ref processor and abandons any entries on it's
2191 // discovered lists.
2192 //
2193 // * For the STW processor:
2194 // * Non MT discovery is enabled at the start of a full GC.
2195 // * Processing and enqueueing during a full GC is non-MT.
2196 // * During a full GC, references are processed after marking.
2197 //
2198 // * Discovery (may or may not be MT) is enabled at the start
2199 // of an incremental evacuation pause.
2200 // * References are processed near the end of a STW evacuation pause.
2201 // * For both types of GC:
2202 // * Discovery is atomic - i.e. not concurrent.
2203 // * Reference discovery will not need a barrier.
2205 SharedHeap::ref_processing_init();
2206 MemRegion mr = reserved_region();
2208 // Concurrent Mark ref processor
2209 _ref_processor_cm =
2210 new ReferenceProcessor(mr, // span
2211 ParallelRefProcEnabled && (ParallelGCThreads > 1),
2212 // mt processing
2213 (int) ParallelGCThreads,
2214 // degree of mt processing
2215 (ParallelGCThreads > 1) || (ConcGCThreads > 1),
2216 // mt discovery
2217 (int) MAX2(ParallelGCThreads, ConcGCThreads),
2218 // degree of mt discovery
2219 false,
2220 // Reference discovery is not atomic
2221 &_is_alive_closure_cm);
2222 // is alive closure
2223 // (for efficiency/performance)
2225 // STW ref processor
2226 _ref_processor_stw =
2227 new ReferenceProcessor(mr, // span
2228 ParallelRefProcEnabled && (ParallelGCThreads > 1),
2229 // mt processing
2230 MAX2((int)ParallelGCThreads, 1),
2231 // degree of mt processing
2232 (ParallelGCThreads > 1),
2233 // mt discovery
2234 MAX2((int)ParallelGCThreads, 1),
2235 // degree of mt discovery
2236 true,
2237 // Reference discovery is atomic
2238 &_is_alive_closure_stw);
2239 // is alive closure
2240 // (for efficiency/performance)
2241 }
2243 size_t G1CollectedHeap::capacity() const {
2244 return _hrm.length() * HeapRegion::GrainBytes;
2245 }
2247 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) {
2248 assert(!hr->continuesHumongous(), "pre-condition");
2249 hr->reset_gc_time_stamp();
2250 if (hr->startsHumongous()) {
2251 uint first_index = hr->hrm_index() + 1;
2252 uint last_index = hr->last_hc_index();
2253 for (uint i = first_index; i < last_index; i += 1) {
2254 HeapRegion* chr = region_at(i);
2255 assert(chr->continuesHumongous(), "sanity");
2256 chr->reset_gc_time_stamp();
2257 }
2258 }
2259 }
2261 #ifndef PRODUCT
2262 class CheckGCTimeStampsHRClosure : public HeapRegionClosure {
2263 private:
2264 unsigned _gc_time_stamp;
2265 bool _failures;
2267 public:
2268 CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) :
2269 _gc_time_stamp(gc_time_stamp), _failures(false) { }
2271 virtual bool doHeapRegion(HeapRegion* hr) {
2272 unsigned region_gc_time_stamp = hr->get_gc_time_stamp();
2273 if (_gc_time_stamp != region_gc_time_stamp) {
2274 gclog_or_tty->print_cr("Region "HR_FORMAT" has GC time stamp = %d, "
2275 "expected %d", HR_FORMAT_PARAMS(hr),
2276 region_gc_time_stamp, _gc_time_stamp);
2277 _failures = true;
2278 }
2279 return false;
2280 }
2282 bool failures() { return _failures; }
2283 };
2285 void G1CollectedHeap::check_gc_time_stamps() {
2286 CheckGCTimeStampsHRClosure cl(_gc_time_stamp);
2287 heap_region_iterate(&cl);
2288 guarantee(!cl.failures(), "all GC time stamps should have been reset");
2289 }
2290 #endif // PRODUCT
2292 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl,
2293 DirtyCardQueue* into_cset_dcq,
2294 bool concurrent,
2295 uint worker_i) {
2296 // Clean cards in the hot card cache
2297 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
2298 hot_card_cache->drain(worker_i, g1_rem_set(), into_cset_dcq);
2300 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2301 int n_completed_buffers = 0;
2302 while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) {
2303 n_completed_buffers++;
2304 }
2305 g1_policy()->phase_times()->record_update_rs_processed_buffers(worker_i, n_completed_buffers);
2306 dcqs.clear_n_completed_buffers();
2307 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!");
2308 }
2311 // Computes the sum of the storage used by the various regions.
2312 size_t G1CollectedHeap::used() const {
2313 return _allocator->used();
2314 }
2316 size_t G1CollectedHeap::used_unlocked() const {
2317 return _allocator->used_unlocked();
2318 }
2320 class SumUsedClosure: public HeapRegionClosure {
2321 size_t _used;
2322 public:
2323 SumUsedClosure() : _used(0) {}
2324 bool doHeapRegion(HeapRegion* r) {
2325 if (!r->continuesHumongous()) {
2326 _used += r->used();
2327 }
2328 return false;
2329 }
2330 size_t result() { return _used; }
2331 };
2333 size_t G1CollectedHeap::recalculate_used() const {
2334 double recalculate_used_start = os::elapsedTime();
2336 SumUsedClosure blk;
2337 heap_region_iterate(&blk);
2339 g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0);
2340 return blk.result();
2341 }
2343 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
2344 switch (cause) {
2345 case GCCause::_gc_locker: return GCLockerInvokesConcurrent;
2346 case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent;
2347 case GCCause::_g1_humongous_allocation: return true;
2348 case GCCause::_update_allocation_context_stats_inc: return true;
2349 default: return false;
2350 }
2351 }
2353 #ifndef PRODUCT
2354 void G1CollectedHeap::allocate_dummy_regions() {
2355 // Let's fill up most of the region
2356 size_t word_size = HeapRegion::GrainWords - 1024;
2357 // And as a result the region we'll allocate will be humongous.
2358 guarantee(isHumongous(word_size), "sanity");
2360 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
2361 // Let's use the existing mechanism for the allocation
2362 HeapWord* dummy_obj = humongous_obj_allocate(word_size,
2363 AllocationContext::system());
2364 if (dummy_obj != NULL) {
2365 MemRegion mr(dummy_obj, word_size);
2366 CollectedHeap::fill_with_object(mr);
2367 } else {
2368 // If we can't allocate once, we probably cannot allocate
2369 // again. Let's get out of the loop.
2370 break;
2371 }
2372 }
2373 }
2374 #endif // !PRODUCT
2376 void G1CollectedHeap::increment_old_marking_cycles_started() {
2377 assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
2378 _old_marking_cycles_started == _old_marking_cycles_completed + 1,
2379 err_msg("Wrong marking cycle count (started: %d, completed: %d)",
2380 _old_marking_cycles_started, _old_marking_cycles_completed));
2382 _old_marking_cycles_started++;
2383 }
2385 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) {
2386 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
2388 // We assume that if concurrent == true, then the caller is a
2389 // concurrent thread that was joined the Suspendible Thread
2390 // Set. If there's ever a cheap way to check this, we should add an
2391 // assert here.
2393 // Given that this method is called at the end of a Full GC or of a
2394 // concurrent cycle, and those can be nested (i.e., a Full GC can
2395 // interrupt a concurrent cycle), the number of full collections
2396 // completed should be either one (in the case where there was no
2397 // nesting) or two (when a Full GC interrupted a concurrent cycle)
2398 // behind the number of full collections started.
2400 // This is the case for the inner caller, i.e. a Full GC.
2401 assert(concurrent ||
2402 (_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
2403 (_old_marking_cycles_started == _old_marking_cycles_completed + 2),
2404 err_msg("for inner caller (Full GC): _old_marking_cycles_started = %u "
2405 "is inconsistent with _old_marking_cycles_completed = %u",
2406 _old_marking_cycles_started, _old_marking_cycles_completed));
2408 // This is the case for the outer caller, i.e. the concurrent cycle.
2409 assert(!concurrent ||
2410 (_old_marking_cycles_started == _old_marking_cycles_completed + 1),
2411 err_msg("for outer caller (concurrent cycle): "
2412 "_old_marking_cycles_started = %u "
2413 "is inconsistent with _old_marking_cycles_completed = %u",
2414 _old_marking_cycles_started, _old_marking_cycles_completed));
2416 _old_marking_cycles_completed += 1;
2418 // We need to clear the "in_progress" flag in the CM thread before
2419 // we wake up any waiters (especially when ExplicitInvokesConcurrent
2420 // is set) so that if a waiter requests another System.gc() it doesn't
2421 // incorrectly see that a marking cycle is still in progress.
2422 if (concurrent) {
2423 _cmThread->clear_in_progress();
2424 }
2426 // This notify_all() will ensure that a thread that called
2427 // System.gc() with (with ExplicitGCInvokesConcurrent set or not)
2428 // and it's waiting for a full GC to finish will be woken up. It is
2429 // waiting in VM_G1IncCollectionPause::doit_epilogue().
2430 FullGCCount_lock->notify_all();
2431 }
2433 void G1CollectedHeap::register_concurrent_cycle_start(const Ticks& start_time) {
2434 _concurrent_cycle_started = true;
2435 _gc_timer_cm->register_gc_start(start_time);
2437 _gc_tracer_cm->report_gc_start(gc_cause(), _gc_timer_cm->gc_start());
2438 trace_heap_before_gc(_gc_tracer_cm);
2439 }
2441 void G1CollectedHeap::register_concurrent_cycle_end() {
2442 if (_concurrent_cycle_started) {
2443 if (_cm->has_aborted()) {
2444 _gc_tracer_cm->report_concurrent_mode_failure();
2445 }
2447 _gc_timer_cm->register_gc_end();
2448 _gc_tracer_cm->report_gc_end(_gc_timer_cm->gc_end(), _gc_timer_cm->time_partitions());
2450 _concurrent_cycle_started = false;
2451 }
2452 }
2454 void G1CollectedHeap::trace_heap_after_concurrent_cycle() {
2455 if (_concurrent_cycle_started) {
2456 trace_heap_after_gc(_gc_tracer_cm);
2457 }
2458 }
2460 G1YCType G1CollectedHeap::yc_type() {
2461 bool is_young = g1_policy()->gcs_are_young();
2462 bool is_initial_mark = g1_policy()->during_initial_mark_pause();
2463 bool is_during_mark = mark_in_progress();
2465 if (is_initial_mark) {
2466 return InitialMark;
2467 } else if (is_during_mark) {
2468 return DuringMark;
2469 } else if (is_young) {
2470 return Normal;
2471 } else {
2472 return Mixed;
2473 }
2474 }
2476 void G1CollectedHeap::collect(GCCause::Cause cause) {
2477 assert_heap_not_locked();
2479 unsigned int gc_count_before;
2480 unsigned int old_marking_count_before;
2481 bool retry_gc;
2483 do {
2484 retry_gc = false;
2486 {
2487 MutexLocker ml(Heap_lock);
2489 // Read the GC count while holding the Heap_lock
2490 gc_count_before = total_collections();
2491 old_marking_count_before = _old_marking_cycles_started;
2492 }
2494 if (should_do_concurrent_full_gc(cause)) {
2495 // Schedule an initial-mark evacuation pause that will start a
2496 // concurrent cycle. We're setting word_size to 0 which means that
2497 // we are not requesting a post-GC allocation.
2498 VM_G1IncCollectionPause op(gc_count_before,
2499 0, /* word_size */
2500 true, /* should_initiate_conc_mark */
2501 g1_policy()->max_pause_time_ms(),
2502 cause);
2503 op.set_allocation_context(AllocationContext::current());
2505 VMThread::execute(&op);
2506 if (!op.pause_succeeded()) {
2507 if (old_marking_count_before == _old_marking_cycles_started) {
2508 retry_gc = op.should_retry_gc();
2509 } else {
2510 // A Full GC happened while we were trying to schedule the
2511 // initial-mark GC. No point in starting a new cycle given
2512 // that the whole heap was collected anyway.
2513 }
2515 if (retry_gc) {
2516 if (GC_locker::is_active_and_needs_gc()) {
2517 GC_locker::stall_until_clear();
2518 }
2519 }
2520 }
2521 } else {
2522 if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc
2523 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2525 // Schedule a standard evacuation pause. We're setting word_size
2526 // to 0 which means that we are not requesting a post-GC allocation.
2527 VM_G1IncCollectionPause op(gc_count_before,
2528 0, /* word_size */
2529 false, /* should_initiate_conc_mark */
2530 g1_policy()->max_pause_time_ms(),
2531 cause);
2532 VMThread::execute(&op);
2533 } else {
2534 // Schedule a Full GC.
2535 VM_G1CollectFull op(gc_count_before, old_marking_count_before, cause);
2536 VMThread::execute(&op);
2537 }
2538 }
2539 } while (retry_gc);
2540 }
2542 bool G1CollectedHeap::is_in(const void* p) const {
2543 if (_hrm.reserved().contains(p)) {
2544 // Given that we know that p is in the reserved space,
2545 // heap_region_containing_raw() should successfully
2546 // return the containing region.
2547 HeapRegion* hr = heap_region_containing_raw(p);
2548 return hr->is_in(p);
2549 } else {
2550 return false;
2551 }
2552 }
2554 #ifdef ASSERT
2555 bool G1CollectedHeap::is_in_exact(const void* p) const {
2556 bool contains = reserved_region().contains(p);
2557 bool available = _hrm.is_available(addr_to_region((HeapWord*)p));
2558 if (contains && available) {
2559 return true;
2560 } else {
2561 return false;
2562 }
2563 }
2564 #endif
2566 // Iteration functions.
2568 // Applies an ExtendedOopClosure onto all references of objects within a HeapRegion.
2570 class IterateOopClosureRegionClosure: public HeapRegionClosure {
2571 ExtendedOopClosure* _cl;
2572 public:
2573 IterateOopClosureRegionClosure(ExtendedOopClosure* cl) : _cl(cl) {}
2574 bool doHeapRegion(HeapRegion* r) {
2575 if (!r->continuesHumongous()) {
2576 r->oop_iterate(_cl);
2577 }
2578 return false;
2579 }
2580 };
2582 void G1CollectedHeap::oop_iterate(ExtendedOopClosure* cl) {
2583 IterateOopClosureRegionClosure blk(cl);
2584 heap_region_iterate(&blk);
2585 }
2587 // Iterates an ObjectClosure over all objects within a HeapRegion.
2589 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2590 ObjectClosure* _cl;
2591 public:
2592 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2593 bool doHeapRegion(HeapRegion* r) {
2594 if (! r->continuesHumongous()) {
2595 r->object_iterate(_cl);
2596 }
2597 return false;
2598 }
2599 };
2601 void G1CollectedHeap::object_iterate(ObjectClosure* cl) {
2602 IterateObjectClosureRegionClosure blk(cl);
2603 heap_region_iterate(&blk);
2604 }
2606 // Calls a SpaceClosure on a HeapRegion.
2608 class SpaceClosureRegionClosure: public HeapRegionClosure {
2609 SpaceClosure* _cl;
2610 public:
2611 SpaceClosureRegionClosure(SpaceClosure* cl) : _cl(cl) {}
2612 bool doHeapRegion(HeapRegion* r) {
2613 _cl->do_space(r);
2614 return false;
2615 }
2616 };
2618 void G1CollectedHeap::space_iterate(SpaceClosure* cl) {
2619 SpaceClosureRegionClosure blk(cl);
2620 heap_region_iterate(&blk);
2621 }
2623 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2624 _hrm.iterate(cl);
2625 }
2627 void
2628 G1CollectedHeap::heap_region_par_iterate_chunked(HeapRegionClosure* cl,
2629 uint worker_id,
2630 uint num_workers,
2631 jint claim_value) const {
2632 _hrm.par_iterate(cl, worker_id, num_workers, claim_value);
2633 }
2635 class ResetClaimValuesClosure: public HeapRegionClosure {
2636 public:
2637 bool doHeapRegion(HeapRegion* r) {
2638 r->set_claim_value(HeapRegion::InitialClaimValue);
2639 return false;
2640 }
2641 };
2643 void G1CollectedHeap::reset_heap_region_claim_values() {
2644 ResetClaimValuesClosure blk;
2645 heap_region_iterate(&blk);
2646 }
2648 void G1CollectedHeap::reset_cset_heap_region_claim_values() {
2649 ResetClaimValuesClosure blk;
2650 collection_set_iterate(&blk);
2651 }
2653 #ifdef ASSERT
2654 // This checks whether all regions in the heap have the correct claim
2655 // value. I also piggy-backed on this a check to ensure that the
2656 // humongous_start_region() information on "continues humongous"
2657 // regions is correct.
2659 class CheckClaimValuesClosure : public HeapRegionClosure {
2660 private:
2661 jint _claim_value;
2662 uint _failures;
2663 HeapRegion* _sh_region;
2665 public:
2666 CheckClaimValuesClosure(jint claim_value) :
2667 _claim_value(claim_value), _failures(0), _sh_region(NULL) { }
2668 bool doHeapRegion(HeapRegion* r) {
2669 if (r->claim_value() != _claim_value) {
2670 gclog_or_tty->print_cr("Region " HR_FORMAT ", "
2671 "claim value = %d, should be %d",
2672 HR_FORMAT_PARAMS(r),
2673 r->claim_value(), _claim_value);
2674 ++_failures;
2675 }
2676 if (!r->isHumongous()) {
2677 _sh_region = NULL;
2678 } else if (r->startsHumongous()) {
2679 _sh_region = r;
2680 } else if (r->continuesHumongous()) {
2681 if (r->humongous_start_region() != _sh_region) {
2682 gclog_or_tty->print_cr("Region " HR_FORMAT ", "
2683 "HS = "PTR_FORMAT", should be "PTR_FORMAT,
2684 HR_FORMAT_PARAMS(r),
2685 r->humongous_start_region(),
2686 _sh_region);
2687 ++_failures;
2688 }
2689 }
2690 return false;
2691 }
2692 uint failures() { return _failures; }
2693 };
2695 bool G1CollectedHeap::check_heap_region_claim_values(jint claim_value) {
2696 CheckClaimValuesClosure cl(claim_value);
2697 heap_region_iterate(&cl);
2698 return cl.failures() == 0;
2699 }
2701 class CheckClaimValuesInCSetHRClosure: public HeapRegionClosure {
2702 private:
2703 jint _claim_value;
2704 uint _failures;
2706 public:
2707 CheckClaimValuesInCSetHRClosure(jint claim_value) :
2708 _claim_value(claim_value), _failures(0) { }
2710 uint failures() { return _failures; }
2712 bool doHeapRegion(HeapRegion* hr) {
2713 assert(hr->in_collection_set(), "how?");
2714 assert(!hr->isHumongous(), "H-region in CSet");
2715 if (hr->claim_value() != _claim_value) {
2716 gclog_or_tty->print_cr("CSet Region " HR_FORMAT ", "
2717 "claim value = %d, should be %d",
2718 HR_FORMAT_PARAMS(hr),
2719 hr->claim_value(), _claim_value);
2720 _failures += 1;
2721 }
2722 return false;
2723 }
2724 };
2726 bool G1CollectedHeap::check_cset_heap_region_claim_values(jint claim_value) {
2727 CheckClaimValuesInCSetHRClosure cl(claim_value);
2728 collection_set_iterate(&cl);
2729 return cl.failures() == 0;
2730 }
2731 #endif // ASSERT
2733 // Clear the cached CSet starting regions and (more importantly)
2734 // the time stamps. Called when we reset the GC time stamp.
2735 void G1CollectedHeap::clear_cset_start_regions() {
2736 assert(_worker_cset_start_region != NULL, "sanity");
2737 assert(_worker_cset_start_region_time_stamp != NULL, "sanity");
2739 int n_queues = MAX2((int)ParallelGCThreads, 1);
2740 for (int i = 0; i < n_queues; i++) {
2741 _worker_cset_start_region[i] = NULL;
2742 _worker_cset_start_region_time_stamp[i] = 0;
2743 }
2744 }
2746 // Given the id of a worker, obtain or calculate a suitable
2747 // starting region for iterating over the current collection set.
2748 HeapRegion* G1CollectedHeap::start_cset_region_for_worker(uint worker_i) {
2749 assert(get_gc_time_stamp() > 0, "should have been updated by now");
2751 HeapRegion* result = NULL;
2752 unsigned gc_time_stamp = get_gc_time_stamp();
2754 if (_worker_cset_start_region_time_stamp[worker_i] == gc_time_stamp) {
2755 // Cached starting region for current worker was set
2756 // during the current pause - so it's valid.
2757 // Note: the cached starting heap region may be NULL
2758 // (when the collection set is empty).
2759 result = _worker_cset_start_region[worker_i];
2760 assert(result == NULL || result->in_collection_set(), "sanity");
2761 return result;
2762 }
2764 // The cached entry was not valid so let's calculate
2765 // a suitable starting heap region for this worker.
2767 // We want the parallel threads to start their collection
2768 // set iteration at different collection set regions to
2769 // avoid contention.
2770 // If we have:
2771 // n collection set regions
2772 // p threads
2773 // Then thread t will start at region floor ((t * n) / p)
2775 result = g1_policy()->collection_set();
2776 if (G1CollectedHeap::use_parallel_gc_threads()) {
2777 uint cs_size = g1_policy()->cset_region_length();
2778 uint active_workers = workers()->active_workers();
2779 assert(UseDynamicNumberOfGCThreads ||
2780 active_workers == workers()->total_workers(),
2781 "Unless dynamic should use total workers");
2783 uint end_ind = (cs_size * worker_i) / active_workers;
2784 uint start_ind = 0;
2786 if (worker_i > 0 &&
2787 _worker_cset_start_region_time_stamp[worker_i - 1] == gc_time_stamp) {
2788 // Previous workers starting region is valid
2789 // so let's iterate from there
2790 start_ind = (cs_size * (worker_i - 1)) / active_workers;
2791 result = _worker_cset_start_region[worker_i - 1];
2792 }
2794 for (uint i = start_ind; i < end_ind; i++) {
2795 result = result->next_in_collection_set();
2796 }
2797 }
2799 // Note: the calculated starting heap region may be NULL
2800 // (when the collection set is empty).
2801 assert(result == NULL || result->in_collection_set(), "sanity");
2802 assert(_worker_cset_start_region_time_stamp[worker_i] != gc_time_stamp,
2803 "should be updated only once per pause");
2804 _worker_cset_start_region[worker_i] = result;
2805 OrderAccess::storestore();
2806 _worker_cset_start_region_time_stamp[worker_i] = gc_time_stamp;
2807 return result;
2808 }
2810 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) {
2811 HeapRegion* r = g1_policy()->collection_set();
2812 while (r != NULL) {
2813 HeapRegion* next = r->next_in_collection_set();
2814 if (cl->doHeapRegion(r)) {
2815 cl->incomplete();
2816 return;
2817 }
2818 r = next;
2819 }
2820 }
2822 void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r,
2823 HeapRegionClosure *cl) {
2824 if (r == NULL) {
2825 // The CSet is empty so there's nothing to do.
2826 return;
2827 }
2829 assert(r->in_collection_set(),
2830 "Start region must be a member of the collection set.");
2831 HeapRegion* cur = r;
2832 while (cur != NULL) {
2833 HeapRegion* next = cur->next_in_collection_set();
2834 if (cl->doHeapRegion(cur) && false) {
2835 cl->incomplete();
2836 return;
2837 }
2838 cur = next;
2839 }
2840 cur = g1_policy()->collection_set();
2841 while (cur != r) {
2842 HeapRegion* next = cur->next_in_collection_set();
2843 if (cl->doHeapRegion(cur) && false) {
2844 cl->incomplete();
2845 return;
2846 }
2847 cur = next;
2848 }
2849 }
2851 HeapRegion* G1CollectedHeap::next_compaction_region(const HeapRegion* from) const {
2852 HeapRegion* result = _hrm.next_region_in_heap(from);
2853 while (result != NULL && result->isHumongous()) {
2854 result = _hrm.next_region_in_heap(result);
2855 }
2856 return result;
2857 }
2859 Space* G1CollectedHeap::space_containing(const void* addr) const {
2860 return heap_region_containing(addr);
2861 }
2863 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2864 Space* sp = space_containing(addr);
2865 return sp->block_start(addr);
2866 }
2868 size_t G1CollectedHeap::block_size(const HeapWord* addr) const {
2869 Space* sp = space_containing(addr);
2870 return sp->block_size(addr);
2871 }
2873 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2874 Space* sp = space_containing(addr);
2875 return sp->block_is_obj(addr);
2876 }
2878 bool G1CollectedHeap::supports_tlab_allocation() const {
2879 return true;
2880 }
2882 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
2883 return (_g1_policy->young_list_target_length() - young_list()->survivor_length()) * HeapRegion::GrainBytes;
2884 }
2886 size_t G1CollectedHeap::tlab_used(Thread* ignored) const {
2887 return young_list()->eden_used_bytes();
2888 }
2890 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size
2891 // must be smaller than the humongous object limit.
2892 size_t G1CollectedHeap::max_tlab_size() const {
2893 return align_size_down(_humongous_object_threshold_in_words - 1, MinObjAlignment);
2894 }
2896 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
2897 // Return the remaining space in the cur alloc region, but not less than
2898 // the min TLAB size.
2900 // Also, this value can be at most the humongous object threshold,
2901 // since we can't allow tlabs to grow big enough to accommodate
2902 // humongous objects.
2904 HeapRegion* hr = _allocator->mutator_alloc_region(AllocationContext::current())->get();
2905 size_t max_tlab = max_tlab_size() * wordSize;
2906 if (hr == NULL) {
2907 return max_tlab;
2908 } else {
2909 return MIN2(MAX2(hr->free(), (size_t) MinTLABSize), max_tlab);
2910 }
2911 }
2913 size_t G1CollectedHeap::max_capacity() const {
2914 return _hrm.reserved().byte_size();
2915 }
2917 jlong G1CollectedHeap::millis_since_last_gc() {
2918 // assert(false, "NYI");
2919 return 0;
2920 }
2922 void G1CollectedHeap::prepare_for_verify() {
2923 if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) {
2924 ensure_parsability(false);
2925 }
2926 g1_rem_set()->prepare_for_verify();
2927 }
2929 bool G1CollectedHeap::allocated_since_marking(oop obj, HeapRegion* hr,
2930 VerifyOption vo) {
2931 switch (vo) {
2932 case VerifyOption_G1UsePrevMarking:
2933 return hr->obj_allocated_since_prev_marking(obj);
2934 case VerifyOption_G1UseNextMarking:
2935 return hr->obj_allocated_since_next_marking(obj);
2936 case VerifyOption_G1UseMarkWord:
2937 return false;
2938 default:
2939 ShouldNotReachHere();
2940 }
2941 return false; // keep some compilers happy
2942 }
2944 HeapWord* G1CollectedHeap::top_at_mark_start(HeapRegion* hr, VerifyOption vo) {
2945 switch (vo) {
2946 case VerifyOption_G1UsePrevMarking: return hr->prev_top_at_mark_start();
2947 case VerifyOption_G1UseNextMarking: return hr->next_top_at_mark_start();
2948 case VerifyOption_G1UseMarkWord: return NULL;
2949 default: ShouldNotReachHere();
2950 }
2951 return NULL; // keep some compilers happy
2952 }
2954 bool G1CollectedHeap::is_marked(oop obj, VerifyOption vo) {
2955 switch (vo) {
2956 case VerifyOption_G1UsePrevMarking: return isMarkedPrev(obj);
2957 case VerifyOption_G1UseNextMarking: return isMarkedNext(obj);
2958 case VerifyOption_G1UseMarkWord: return obj->is_gc_marked();
2959 default: ShouldNotReachHere();
2960 }
2961 return false; // keep some compilers happy
2962 }
2964 const char* G1CollectedHeap::top_at_mark_start_str(VerifyOption vo) {
2965 switch (vo) {
2966 case VerifyOption_G1UsePrevMarking: return "PTAMS";
2967 case VerifyOption_G1UseNextMarking: return "NTAMS";
2968 case VerifyOption_G1UseMarkWord: return "NONE";
2969 default: ShouldNotReachHere();
2970 }
2971 return NULL; // keep some compilers happy
2972 }
2974 class VerifyRootsClosure: public OopClosure {
2975 private:
2976 G1CollectedHeap* _g1h;
2977 VerifyOption _vo;
2978 bool _failures;
2979 public:
2980 // _vo == UsePrevMarking -> use "prev" marking information,
2981 // _vo == UseNextMarking -> use "next" marking information,
2982 // _vo == UseMarkWord -> use mark word from object header.
2983 VerifyRootsClosure(VerifyOption vo) :
2984 _g1h(G1CollectedHeap::heap()),
2985 _vo(vo),
2986 _failures(false) { }
2988 bool failures() { return _failures; }
2990 template <class T> void do_oop_nv(T* p) {
2991 T heap_oop = oopDesc::load_heap_oop(p);
2992 if (!oopDesc::is_null(heap_oop)) {
2993 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
2994 if (_g1h->is_obj_dead_cond(obj, _vo)) {
2995 gclog_or_tty->print_cr("Root location "PTR_FORMAT" "
2996 "points to dead obj "PTR_FORMAT, p, (void*) obj);
2997 if (_vo == VerifyOption_G1UseMarkWord) {
2998 gclog_or_tty->print_cr(" Mark word: "PTR_FORMAT, (void*)(obj->mark()));
2999 }
3000 obj->print_on(gclog_or_tty);
3001 _failures = true;
3002 }
3003 }
3004 }
3006 void do_oop(oop* p) { do_oop_nv(p); }
3007 void do_oop(narrowOop* p) { do_oop_nv(p); }
3008 };
3010 class G1VerifyCodeRootOopClosure: public OopClosure {
3011 G1CollectedHeap* _g1h;
3012 OopClosure* _root_cl;
3013 nmethod* _nm;
3014 VerifyOption _vo;
3015 bool _failures;
3017 template <class T> void do_oop_work(T* p) {
3018 // First verify that this root is live
3019 _root_cl->do_oop(p);
3021 if (!G1VerifyHeapRegionCodeRoots) {
3022 // We're not verifying the code roots attached to heap region.
3023 return;
3024 }
3026 // Don't check the code roots during marking verification in a full GC
3027 if (_vo == VerifyOption_G1UseMarkWord) {
3028 return;
3029 }
3031 // Now verify that the current nmethod (which contains p) is
3032 // in the code root list of the heap region containing the
3033 // object referenced by p.
3035 T heap_oop = oopDesc::load_heap_oop(p);
3036 if (!oopDesc::is_null(heap_oop)) {
3037 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
3039 // Now fetch the region containing the object
3040 HeapRegion* hr = _g1h->heap_region_containing(obj);
3041 HeapRegionRemSet* hrrs = hr->rem_set();
3042 // Verify that the strong code root list for this region
3043 // contains the nmethod
3044 if (!hrrs->strong_code_roots_list_contains(_nm)) {
3045 gclog_or_tty->print_cr("Code root location "PTR_FORMAT" "
3046 "from nmethod "PTR_FORMAT" not in strong "
3047 "code roots for region ["PTR_FORMAT","PTR_FORMAT")",
3048 p, _nm, hr->bottom(), hr->end());
3049 _failures = true;
3050 }
3051 }
3052 }
3054 public:
3055 G1VerifyCodeRootOopClosure(G1CollectedHeap* g1h, OopClosure* root_cl, VerifyOption vo):
3056 _g1h(g1h), _root_cl(root_cl), _vo(vo), _nm(NULL), _failures(false) {}
3058 void do_oop(oop* p) { do_oop_work(p); }
3059 void do_oop(narrowOop* p) { do_oop_work(p); }
3061 void set_nmethod(nmethod* nm) { _nm = nm; }
3062 bool failures() { return _failures; }
3063 };
3065 class G1VerifyCodeRootBlobClosure: public CodeBlobClosure {
3066 G1VerifyCodeRootOopClosure* _oop_cl;
3068 public:
3069 G1VerifyCodeRootBlobClosure(G1VerifyCodeRootOopClosure* oop_cl):
3070 _oop_cl(oop_cl) {}
3072 void do_code_blob(CodeBlob* cb) {
3073 nmethod* nm = cb->as_nmethod_or_null();
3074 if (nm != NULL) {
3075 _oop_cl->set_nmethod(nm);
3076 nm->oops_do(_oop_cl);
3077 }
3078 }
3079 };
3081 class YoungRefCounterClosure : public OopClosure {
3082 G1CollectedHeap* _g1h;
3083 int _count;
3084 public:
3085 YoungRefCounterClosure(G1CollectedHeap* g1h) : _g1h(g1h), _count(0) {}
3086 void do_oop(oop* p) { if (_g1h->is_in_young(*p)) { _count++; } }
3087 void do_oop(narrowOop* p) { ShouldNotReachHere(); }
3089 int count() { return _count; }
3090 void reset_count() { _count = 0; };
3091 };
3093 class VerifyKlassClosure: public KlassClosure {
3094 YoungRefCounterClosure _young_ref_counter_closure;
3095 OopClosure *_oop_closure;
3096 public:
3097 VerifyKlassClosure(G1CollectedHeap* g1h, OopClosure* cl) : _young_ref_counter_closure(g1h), _oop_closure(cl) {}
3098 void do_klass(Klass* k) {
3099 k->oops_do(_oop_closure);
3101 _young_ref_counter_closure.reset_count();
3102 k->oops_do(&_young_ref_counter_closure);
3103 if (_young_ref_counter_closure.count() > 0) {
3104 guarantee(k->has_modified_oops(), err_msg("Klass %p, has young refs but is not dirty.", k));
3105 }
3106 }
3107 };
3109 class VerifyLivenessOopClosure: public OopClosure {
3110 G1CollectedHeap* _g1h;
3111 VerifyOption _vo;
3112 public:
3113 VerifyLivenessOopClosure(G1CollectedHeap* g1h, VerifyOption vo):
3114 _g1h(g1h), _vo(vo)
3115 { }
3116 void do_oop(narrowOop *p) { do_oop_work(p); }
3117 void do_oop( oop *p) { do_oop_work(p); }
3119 template <class T> void do_oop_work(T *p) {
3120 oop obj = oopDesc::load_decode_heap_oop(p);
3121 guarantee(obj == NULL || !_g1h->is_obj_dead_cond(obj, _vo),
3122 "Dead object referenced by a not dead object");
3123 }
3124 };
3126 class VerifyObjsInRegionClosure: public ObjectClosure {
3127 private:
3128 G1CollectedHeap* _g1h;
3129 size_t _live_bytes;
3130 HeapRegion *_hr;
3131 VerifyOption _vo;
3132 public:
3133 // _vo == UsePrevMarking -> use "prev" marking information,
3134 // _vo == UseNextMarking -> use "next" marking information,
3135 // _vo == UseMarkWord -> use mark word from object header.
3136 VerifyObjsInRegionClosure(HeapRegion *hr, VerifyOption vo)
3137 : _live_bytes(0), _hr(hr), _vo(vo) {
3138 _g1h = G1CollectedHeap::heap();
3139 }
3140 void do_object(oop o) {
3141 VerifyLivenessOopClosure isLive(_g1h, _vo);
3142 assert(o != NULL, "Huh?");
3143 if (!_g1h->is_obj_dead_cond(o, _vo)) {
3144 // If the object is alive according to the mark word,
3145 // then verify that the marking information agrees.
3146 // Note we can't verify the contra-positive of the
3147 // above: if the object is dead (according to the mark
3148 // word), it may not be marked, or may have been marked
3149 // but has since became dead, or may have been allocated
3150 // since the last marking.
3151 if (_vo == VerifyOption_G1UseMarkWord) {
3152 guarantee(!_g1h->is_obj_dead(o), "mark word and concurrent mark mismatch");
3153 }
3155 o->oop_iterate_no_header(&isLive);
3156 if (!_hr->obj_allocated_since_prev_marking(o)) {
3157 size_t obj_size = o->size(); // Make sure we don't overflow
3158 _live_bytes += (obj_size * HeapWordSize);
3159 }
3160 }
3161 }
3162 size_t live_bytes() { return _live_bytes; }
3163 };
3165 class PrintObjsInRegionClosure : public ObjectClosure {
3166 HeapRegion *_hr;
3167 G1CollectedHeap *_g1;
3168 public:
3169 PrintObjsInRegionClosure(HeapRegion *hr) : _hr(hr) {
3170 _g1 = G1CollectedHeap::heap();
3171 };
3173 void do_object(oop o) {
3174 if (o != NULL) {
3175 HeapWord *start = (HeapWord *) o;
3176 size_t word_sz = o->size();
3177 gclog_or_tty->print("\nPrinting obj "PTR_FORMAT" of size " SIZE_FORMAT
3178 " isMarkedPrev %d isMarkedNext %d isAllocSince %d\n",
3179 (void*) o, word_sz,
3180 _g1->isMarkedPrev(o),
3181 _g1->isMarkedNext(o),
3182 _hr->obj_allocated_since_prev_marking(o));
3183 HeapWord *end = start + word_sz;
3184 HeapWord *cur;
3185 int *val;
3186 for (cur = start; cur < end; cur++) {
3187 val = (int *) cur;
3188 gclog_or_tty->print("\t "PTR_FORMAT":"PTR_FORMAT"\n", val, *val);
3189 }
3190 }
3191 }
3192 };
3194 class VerifyRegionClosure: public HeapRegionClosure {
3195 private:
3196 bool _par;
3197 VerifyOption _vo;
3198 bool _failures;
3199 public:
3200 // _vo == UsePrevMarking -> use "prev" marking information,
3201 // _vo == UseNextMarking -> use "next" marking information,
3202 // _vo == UseMarkWord -> use mark word from object header.
3203 VerifyRegionClosure(bool par, VerifyOption vo)
3204 : _par(par),
3205 _vo(vo),
3206 _failures(false) {}
3208 bool failures() {
3209 return _failures;
3210 }
3212 bool doHeapRegion(HeapRegion* r) {
3213 if (!r->continuesHumongous()) {
3214 bool failures = false;
3215 r->verify(_vo, &failures);
3216 if (failures) {
3217 _failures = true;
3218 } else {
3219 VerifyObjsInRegionClosure not_dead_yet_cl(r, _vo);
3220 r->object_iterate(¬_dead_yet_cl);
3221 if (_vo != VerifyOption_G1UseNextMarking) {
3222 if (r->max_live_bytes() < not_dead_yet_cl.live_bytes()) {
3223 gclog_or_tty->print_cr("["PTR_FORMAT","PTR_FORMAT"] "
3224 "max_live_bytes "SIZE_FORMAT" "
3225 "< calculated "SIZE_FORMAT,
3226 r->bottom(), r->end(),
3227 r->max_live_bytes(),
3228 not_dead_yet_cl.live_bytes());
3229 _failures = true;
3230 }
3231 } else {
3232 // When vo == UseNextMarking we cannot currently do a sanity
3233 // check on the live bytes as the calculation has not been
3234 // finalized yet.
3235 }
3236 }
3237 }
3238 return false; // stop the region iteration if we hit a failure
3239 }
3240 };
3242 // This is the task used for parallel verification of the heap regions
3244 class G1ParVerifyTask: public AbstractGangTask {
3245 private:
3246 G1CollectedHeap* _g1h;
3247 VerifyOption _vo;
3248 bool _failures;
3250 public:
3251 // _vo == UsePrevMarking -> use "prev" marking information,
3252 // _vo == UseNextMarking -> use "next" marking information,
3253 // _vo == UseMarkWord -> use mark word from object header.
3254 G1ParVerifyTask(G1CollectedHeap* g1h, VerifyOption vo) :
3255 AbstractGangTask("Parallel verify task"),
3256 _g1h(g1h),
3257 _vo(vo),
3258 _failures(false) { }
3260 bool failures() {
3261 return _failures;
3262 }
3264 void work(uint worker_id) {
3265 HandleMark hm;
3266 VerifyRegionClosure blk(true, _vo);
3267 _g1h->heap_region_par_iterate_chunked(&blk, worker_id,
3268 _g1h->workers()->active_workers(),
3269 HeapRegion::ParVerifyClaimValue);
3270 if (blk.failures()) {
3271 _failures = true;
3272 }
3273 }
3274 };
3276 void G1CollectedHeap::verify(bool silent, VerifyOption vo) {
3277 if (SafepointSynchronize::is_at_safepoint()) {
3278 assert(Thread::current()->is_VM_thread(),
3279 "Expected to be executed serially by the VM thread at this point");
3281 if (!silent) { gclog_or_tty->print("Roots "); }
3282 VerifyRootsClosure rootsCl(vo);
3283 VerifyKlassClosure klassCl(this, &rootsCl);
3284 CLDToKlassAndOopClosure cldCl(&klassCl, &rootsCl, false);
3286 // We apply the relevant closures to all the oops in the
3287 // system dictionary, class loader data graph, the string table
3288 // and the nmethods in the code cache.
3289 G1VerifyCodeRootOopClosure codeRootsCl(this, &rootsCl, vo);
3290 G1VerifyCodeRootBlobClosure blobsCl(&codeRootsCl);
3292 process_all_roots(true, // activate StrongRootsScope
3293 SO_AllCodeCache, // roots scanning options
3294 &rootsCl,
3295 &cldCl,
3296 &blobsCl);
3298 bool failures = rootsCl.failures() || codeRootsCl.failures();
3300 if (vo != VerifyOption_G1UseMarkWord) {
3301 // If we're verifying during a full GC then the region sets
3302 // will have been torn down at the start of the GC. Therefore
3303 // verifying the region sets will fail. So we only verify
3304 // the region sets when not in a full GC.
3305 if (!silent) { gclog_or_tty->print("HeapRegionSets "); }
3306 verify_region_sets();
3307 }
3309 if (!silent) { gclog_or_tty->print("HeapRegions "); }
3310 if (GCParallelVerificationEnabled && ParallelGCThreads > 1) {
3311 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3312 "sanity check");
3314 G1ParVerifyTask task(this, vo);
3315 assert(UseDynamicNumberOfGCThreads ||
3316 workers()->active_workers() == workers()->total_workers(),
3317 "If not dynamic should be using all the workers");
3318 int n_workers = workers()->active_workers();
3319 set_par_threads(n_workers);
3320 workers()->run_task(&task);
3321 set_par_threads(0);
3322 if (task.failures()) {
3323 failures = true;
3324 }
3326 // Checks that the expected amount of parallel work was done.
3327 // The implication is that n_workers is > 0.
3328 assert(check_heap_region_claim_values(HeapRegion::ParVerifyClaimValue),
3329 "sanity check");
3331 reset_heap_region_claim_values();
3333 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3334 "sanity check");
3335 } else {
3336 VerifyRegionClosure blk(false, vo);
3337 heap_region_iterate(&blk);
3338 if (blk.failures()) {
3339 failures = true;
3340 }
3341 }
3342 if (!silent) gclog_or_tty->print("RemSet ");
3343 rem_set()->verify();
3345 if (G1StringDedup::is_enabled()) {
3346 if (!silent) gclog_or_tty->print("StrDedup ");
3347 G1StringDedup::verify();
3348 }
3350 if (failures) {
3351 gclog_or_tty->print_cr("Heap:");
3352 // It helps to have the per-region information in the output to
3353 // help us track down what went wrong. This is why we call
3354 // print_extended_on() instead of print_on().
3355 print_extended_on(gclog_or_tty);
3356 gclog_or_tty->cr();
3357 #ifndef PRODUCT
3358 if (VerifyDuringGC && G1VerifyDuringGCPrintReachable) {
3359 concurrent_mark()->print_reachable("at-verification-failure",
3360 vo, false /* all */);
3361 }
3362 #endif
3363 gclog_or_tty->flush();
3364 }
3365 guarantee(!failures, "there should not have been any failures");
3366 } else {
3367 if (!silent) {
3368 gclog_or_tty->print("(SKIPPING Roots, HeapRegionSets, HeapRegions, RemSet");
3369 if (G1StringDedup::is_enabled()) {
3370 gclog_or_tty->print(", StrDedup");
3371 }
3372 gclog_or_tty->print(") ");
3373 }
3374 }
3375 }
3377 void G1CollectedHeap::verify(bool silent) {
3378 verify(silent, VerifyOption_G1UsePrevMarking);
3379 }
3381 double G1CollectedHeap::verify(bool guard, const char* msg) {
3382 double verify_time_ms = 0.0;
3384 if (guard && total_collections() >= VerifyGCStartAt) {
3385 double verify_start = os::elapsedTime();
3386 HandleMark hm; // Discard invalid handles created during verification
3387 prepare_for_verify();
3388 Universe::verify(VerifyOption_G1UsePrevMarking, msg);
3389 verify_time_ms = (os::elapsedTime() - verify_start) * 1000;
3390 }
3392 return verify_time_ms;
3393 }
3395 void G1CollectedHeap::verify_before_gc() {
3396 double verify_time_ms = verify(VerifyBeforeGC, " VerifyBeforeGC:");
3397 g1_policy()->phase_times()->record_verify_before_time_ms(verify_time_ms);
3398 }
3400 void G1CollectedHeap::verify_after_gc() {
3401 double verify_time_ms = verify(VerifyAfterGC, " VerifyAfterGC:");
3402 g1_policy()->phase_times()->record_verify_after_time_ms(verify_time_ms);
3403 }
3405 class PrintRegionClosure: public HeapRegionClosure {
3406 outputStream* _st;
3407 public:
3408 PrintRegionClosure(outputStream* st) : _st(st) {}
3409 bool doHeapRegion(HeapRegion* r) {
3410 r->print_on(_st);
3411 return false;
3412 }
3413 };
3415 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
3416 const HeapRegion* hr,
3417 const VerifyOption vo) const {
3418 switch (vo) {
3419 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr);
3420 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr);
3421 case VerifyOption_G1UseMarkWord: return !obj->is_gc_marked();
3422 default: ShouldNotReachHere();
3423 }
3424 return false; // keep some compilers happy
3425 }
3427 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
3428 const VerifyOption vo) const {
3429 switch (vo) {
3430 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj);
3431 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj);
3432 case VerifyOption_G1UseMarkWord: return !obj->is_gc_marked();
3433 default: ShouldNotReachHere();
3434 }
3435 return false; // keep some compilers happy
3436 }
3438 void G1CollectedHeap::print_on(outputStream* st) const {
3439 st->print(" %-20s", "garbage-first heap");
3440 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
3441 capacity()/K, used_unlocked()/K);
3442 st->print(" [" INTPTR_FORMAT ", " INTPTR_FORMAT ", " INTPTR_FORMAT ")",
3443 _hrm.reserved().start(),
3444 _hrm.reserved().start() + _hrm.length() + HeapRegion::GrainWords,
3445 _hrm.reserved().end());
3446 st->cr();
3447 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
3448 uint young_regions = _young_list->length();
3449 st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
3450 (size_t) young_regions * HeapRegion::GrainBytes / K);
3451 uint survivor_regions = g1_policy()->recorded_survivor_regions();
3452 st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
3453 (size_t) survivor_regions * HeapRegion::GrainBytes / K);
3454 st->cr();
3455 MetaspaceAux::print_on(st);
3456 }
3458 void G1CollectedHeap::print_extended_on(outputStream* st) const {
3459 print_on(st);
3461 // Print the per-region information.
3462 st->cr();
3463 st->print_cr("Heap Regions: (Y=young(eden), SU=young(survivor), "
3464 "HS=humongous(starts), HC=humongous(continues), "
3465 "CS=collection set, F=free, TS=gc time stamp, "
3466 "PTAMS=previous top-at-mark-start, "
3467 "NTAMS=next top-at-mark-start)");
3468 PrintRegionClosure blk(st);
3469 heap_region_iterate(&blk);
3470 }
3472 void G1CollectedHeap::print_on_error(outputStream* st) const {
3473 this->CollectedHeap::print_on_error(st);
3475 if (_cm != NULL) {
3476 st->cr();
3477 _cm->print_on_error(st);
3478 }
3479 }
3481 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
3482 if (G1CollectedHeap::use_parallel_gc_threads()) {
3483 workers()->print_worker_threads_on(st);
3484 }
3485 _cmThread->print_on(st);
3486 st->cr();
3487 _cm->print_worker_threads_on(st);
3488 _cg1r->print_worker_threads_on(st);
3489 if (G1StringDedup::is_enabled()) {
3490 G1StringDedup::print_worker_threads_on(st);
3491 }
3492 }
3494 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
3495 if (G1CollectedHeap::use_parallel_gc_threads()) {
3496 workers()->threads_do(tc);
3497 }
3498 tc->do_thread(_cmThread);
3499 _cg1r->threads_do(tc);
3500 if (G1StringDedup::is_enabled()) {
3501 G1StringDedup::threads_do(tc);
3502 }
3503 }
3505 void G1CollectedHeap::print_tracing_info() const {
3506 // We'll overload this to mean "trace GC pause statistics."
3507 if (TraceGen0Time || TraceGen1Time) {
3508 // The "G1CollectorPolicy" is keeping track of these stats, so delegate
3509 // to that.
3510 g1_policy()->print_tracing_info();
3511 }
3512 if (G1SummarizeRSetStats) {
3513 g1_rem_set()->print_summary_info();
3514 }
3515 if (G1SummarizeConcMark) {
3516 concurrent_mark()->print_summary_info();
3517 }
3518 g1_policy()->print_yg_surv_rate_info();
3519 SpecializationStats::print();
3520 }
3522 #ifndef PRODUCT
3523 // Helpful for debugging RSet issues.
3525 class PrintRSetsClosure : public HeapRegionClosure {
3526 private:
3527 const char* _msg;
3528 size_t _occupied_sum;
3530 public:
3531 bool doHeapRegion(HeapRegion* r) {
3532 HeapRegionRemSet* hrrs = r->rem_set();
3533 size_t occupied = hrrs->occupied();
3534 _occupied_sum += occupied;
3536 gclog_or_tty->print_cr("Printing RSet for region "HR_FORMAT,
3537 HR_FORMAT_PARAMS(r));
3538 if (occupied == 0) {
3539 gclog_or_tty->print_cr(" RSet is empty");
3540 } else {
3541 hrrs->print();
3542 }
3543 gclog_or_tty->print_cr("----------");
3544 return false;
3545 }
3547 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
3548 gclog_or_tty->cr();
3549 gclog_or_tty->print_cr("========================================");
3550 gclog_or_tty->print_cr("%s", msg);
3551 gclog_or_tty->cr();
3552 }
3554 ~PrintRSetsClosure() {
3555 gclog_or_tty->print_cr("Occupied Sum: "SIZE_FORMAT, _occupied_sum);
3556 gclog_or_tty->print_cr("========================================");
3557 gclog_or_tty->cr();
3558 }
3559 };
3561 void G1CollectedHeap::print_cset_rsets() {
3562 PrintRSetsClosure cl("Printing CSet RSets");
3563 collection_set_iterate(&cl);
3564 }
3566 void G1CollectedHeap::print_all_rsets() {
3567 PrintRSetsClosure cl("Printing All RSets");;
3568 heap_region_iterate(&cl);
3569 }
3570 #endif // PRODUCT
3572 G1CollectedHeap* G1CollectedHeap::heap() {
3573 assert(_sh->kind() == CollectedHeap::G1CollectedHeap,
3574 "not a garbage-first heap");
3575 return _g1h;
3576 }
3578 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) {
3579 // always_do_update_barrier = false;
3580 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
3581 // Fill TLAB's and such
3582 accumulate_statistics_all_tlabs();
3583 ensure_parsability(true);
3585 if (G1SummarizeRSetStats && (G1SummarizeRSetStatsPeriod > 0) &&
3586 (total_collections() % G1SummarizeRSetStatsPeriod == 0)) {
3587 g1_rem_set()->print_periodic_summary_info("Before GC RS summary");
3588 }
3589 }
3591 void G1CollectedHeap::gc_epilogue(bool full) {
3593 if (G1SummarizeRSetStats &&
3594 (G1SummarizeRSetStatsPeriod > 0) &&
3595 // we are at the end of the GC. Total collections has already been increased.
3596 ((total_collections() - 1) % G1SummarizeRSetStatsPeriod == 0)) {
3597 g1_rem_set()->print_periodic_summary_info("After GC RS summary");
3598 }
3600 // FIXME: what is this about?
3601 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
3602 // is set.
3603 COMPILER2_PRESENT(assert(DerivedPointerTable::is_empty(),
3604 "derived pointer present"));
3605 // always_do_update_barrier = true;
3607 resize_all_tlabs();
3608 allocation_context_stats().update(full);
3610 // We have just completed a GC. Update the soft reference
3611 // policy with the new heap occupancy
3612 Universe::update_heap_info_at_gc();
3613 }
3615 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
3616 unsigned int gc_count_before,
3617 bool* succeeded,
3618 GCCause::Cause gc_cause) {
3619 assert_heap_not_locked_and_not_at_safepoint();
3620 g1_policy()->record_stop_world_start();
3621 VM_G1IncCollectionPause op(gc_count_before,
3622 word_size,
3623 false, /* should_initiate_conc_mark */
3624 g1_policy()->max_pause_time_ms(),
3625 gc_cause);
3627 op.set_allocation_context(AllocationContext::current());
3628 VMThread::execute(&op);
3630 HeapWord* result = op.result();
3631 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
3632 assert(result == NULL || ret_succeeded,
3633 "the result should be NULL if the VM did not succeed");
3634 *succeeded = ret_succeeded;
3636 assert_heap_not_locked();
3637 return result;
3638 }
3640 void
3641 G1CollectedHeap::doConcurrentMark() {
3642 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
3643 if (!_cmThread->in_progress()) {
3644 _cmThread->set_started();
3645 CGC_lock->notify();
3646 }
3647 }
3649 size_t G1CollectedHeap::pending_card_num() {
3650 size_t extra_cards = 0;
3651 JavaThread *curr = Threads::first();
3652 while (curr != NULL) {
3653 DirtyCardQueue& dcq = curr->dirty_card_queue();
3654 extra_cards += dcq.size();
3655 curr = curr->next();
3656 }
3657 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
3658 size_t buffer_size = dcqs.buffer_size();
3659 size_t buffer_num = dcqs.completed_buffers_num();
3661 // PtrQueueSet::buffer_size() and PtrQueue:size() return sizes
3662 // in bytes - not the number of 'entries'. We need to convert
3663 // into a number of cards.
3664 return (buffer_size * buffer_num + extra_cards) / oopSize;
3665 }
3667 size_t G1CollectedHeap::cards_scanned() {
3668 return g1_rem_set()->cardsScanned();
3669 }
3671 bool G1CollectedHeap::humongous_region_is_always_live(uint index) {
3672 HeapRegion* region = region_at(index);
3673 assert(region->startsHumongous(), "Must start a humongous object");
3674 return oop(region->bottom())->is_objArray() || !region->rem_set()->is_empty();
3675 }
3677 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure {
3678 private:
3679 size_t _total_humongous;
3680 size_t _candidate_humongous;
3681 public:
3682 RegisterHumongousWithInCSetFastTestClosure() : _total_humongous(0), _candidate_humongous(0) {
3683 }
3685 virtual bool doHeapRegion(HeapRegion* r) {
3686 if (!r->startsHumongous()) {
3687 return false;
3688 }
3689 G1CollectedHeap* g1h = G1CollectedHeap::heap();
3691 uint region_idx = r->hrm_index();
3692 bool is_candidate = !g1h->humongous_region_is_always_live(region_idx);
3693 // Is_candidate already filters out humongous regions with some remembered set.
3694 // This will not lead to humongous object that we mistakenly keep alive because
3695 // during young collection the remembered sets will only be added to.
3696 if (is_candidate) {
3697 g1h->register_humongous_region_with_in_cset_fast_test(region_idx);
3698 _candidate_humongous++;
3699 }
3700 _total_humongous++;
3702 return false;
3703 }
3705 size_t total_humongous() const { return _total_humongous; }
3706 size_t candidate_humongous() const { return _candidate_humongous; }
3707 };
3709 void G1CollectedHeap::register_humongous_regions_with_in_cset_fast_test() {
3710 if (!G1ReclaimDeadHumongousObjectsAtYoungGC) {
3711 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0, 0);
3712 return;
3713 }
3715 RegisterHumongousWithInCSetFastTestClosure cl;
3716 heap_region_iterate(&cl);
3717 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(cl.total_humongous(),
3718 cl.candidate_humongous());
3719 _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0;
3721 if (_has_humongous_reclaim_candidates) {
3722 clear_humongous_is_live_table();
3723 }
3724 }
3726 void
3727 G1CollectedHeap::setup_surviving_young_words() {
3728 assert(_surviving_young_words == NULL, "pre-condition");
3729 uint array_length = g1_policy()->young_cset_region_length();
3730 _surviving_young_words = NEW_C_HEAP_ARRAY(size_t, (size_t) array_length, mtGC);
3731 if (_surviving_young_words == NULL) {
3732 vm_exit_out_of_memory(sizeof(size_t) * array_length, OOM_MALLOC_ERROR,
3733 "Not enough space for young surv words summary.");
3734 }
3735 memset(_surviving_young_words, 0, (size_t) array_length * sizeof(size_t));
3736 #ifdef ASSERT
3737 for (uint i = 0; i < array_length; ++i) {
3738 assert( _surviving_young_words[i] == 0, "memset above" );
3739 }
3740 #endif // !ASSERT
3741 }
3743 void
3744 G1CollectedHeap::update_surviving_young_words(size_t* surv_young_words) {
3745 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
3746 uint array_length = g1_policy()->young_cset_region_length();
3747 for (uint i = 0; i < array_length; ++i) {
3748 _surviving_young_words[i] += surv_young_words[i];
3749 }
3750 }
3752 void
3753 G1CollectedHeap::cleanup_surviving_young_words() {
3754 guarantee( _surviving_young_words != NULL, "pre-condition" );
3755 FREE_C_HEAP_ARRAY(size_t, _surviving_young_words, mtGC);
3756 _surviving_young_words = NULL;
3757 }
3759 #ifdef ASSERT
3760 class VerifyCSetClosure: public HeapRegionClosure {
3761 public:
3762 bool doHeapRegion(HeapRegion* hr) {
3763 // Here we check that the CSet region's RSet is ready for parallel
3764 // iteration. The fields that we'll verify are only manipulated
3765 // when the region is part of a CSet and is collected. Afterwards,
3766 // we reset these fields when we clear the region's RSet (when the
3767 // region is freed) so they are ready when the region is
3768 // re-allocated. The only exception to this is if there's an
3769 // evacuation failure and instead of freeing the region we leave
3770 // it in the heap. In that case, we reset these fields during
3771 // evacuation failure handling.
3772 guarantee(hr->rem_set()->verify_ready_for_par_iteration(), "verification");
3774 // Here's a good place to add any other checks we'd like to
3775 // perform on CSet regions.
3776 return false;
3777 }
3778 };
3779 #endif // ASSERT
3781 #if TASKQUEUE_STATS
3782 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
3783 st->print_raw_cr("GC Task Stats");
3784 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
3785 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
3786 }
3788 void G1CollectedHeap::print_taskqueue_stats(outputStream* const st) const {
3789 print_taskqueue_stats_hdr(st);
3791 TaskQueueStats totals;
3792 const int n = workers() != NULL ? workers()->total_workers() : 1;
3793 for (int i = 0; i < n; ++i) {
3794 st->print("%3d ", i); task_queue(i)->stats.print(st); st->cr();
3795 totals += task_queue(i)->stats;
3796 }
3797 st->print_raw("tot "); totals.print(st); st->cr();
3799 DEBUG_ONLY(totals.verify());
3800 }
3802 void G1CollectedHeap::reset_taskqueue_stats() {
3803 const int n = workers() != NULL ? workers()->total_workers() : 1;
3804 for (int i = 0; i < n; ++i) {
3805 task_queue(i)->stats.reset();
3806 }
3807 }
3808 #endif // TASKQUEUE_STATS
3810 void G1CollectedHeap::log_gc_header() {
3811 if (!G1Log::fine()) {
3812 return;
3813 }
3815 gclog_or_tty->gclog_stamp(_gc_tracer_stw->gc_id());
3817 GCCauseString gc_cause_str = GCCauseString("GC pause", gc_cause())
3818 .append(g1_policy()->gcs_are_young() ? "(young)" : "(mixed)")
3819 .append(g1_policy()->during_initial_mark_pause() ? " (initial-mark)" : "");
3821 gclog_or_tty->print("[%s", (const char*)gc_cause_str);
3822 }
3824 void G1CollectedHeap::log_gc_footer(double pause_time_sec) {
3825 if (!G1Log::fine()) {
3826 return;
3827 }
3829 if (G1Log::finer()) {
3830 if (evacuation_failed()) {
3831 gclog_or_tty->print(" (to-space exhausted)");
3832 }
3833 gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec);
3834 g1_policy()->phase_times()->note_gc_end();
3835 g1_policy()->phase_times()->print(pause_time_sec);
3836 g1_policy()->print_detailed_heap_transition();
3837 } else {
3838 if (evacuation_failed()) {
3839 gclog_or_tty->print("--");
3840 }
3841 g1_policy()->print_heap_transition();
3842 gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec);
3843 }
3844 gclog_or_tty->flush();
3845 }
3847 bool
3848 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
3849 assert_at_safepoint(true /* should_be_vm_thread */);
3850 guarantee(!is_gc_active(), "collection is not reentrant");
3852 if (GC_locker::check_active_before_gc()) {
3853 return false;
3854 }
3856 _gc_timer_stw->register_gc_start();
3858 _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start());
3860 SvcGCMarker sgcm(SvcGCMarker::MINOR);
3861 ResourceMark rm;
3863 print_heap_before_gc();
3864 trace_heap_before_gc(_gc_tracer_stw);
3866 verify_region_sets_optional();
3867 verify_dirty_young_regions();
3869 // This call will decide whether this pause is an initial-mark
3870 // pause. If it is, during_initial_mark_pause() will return true
3871 // for the duration of this pause.
3872 g1_policy()->decide_on_conc_mark_initiation();
3874 // We do not allow initial-mark to be piggy-backed on a mixed GC.
3875 assert(!g1_policy()->during_initial_mark_pause() ||
3876 g1_policy()->gcs_are_young(), "sanity");
3878 // We also do not allow mixed GCs during marking.
3879 assert(!mark_in_progress() || g1_policy()->gcs_are_young(), "sanity");
3881 // Record whether this pause is an initial mark. When the current
3882 // thread has completed its logging output and it's safe to signal
3883 // the CM thread, the flag's value in the policy has been reset.
3884 bool should_start_conc_mark = g1_policy()->during_initial_mark_pause();
3886 // Inner scope for scope based logging, timers, and stats collection
3887 {
3888 EvacuationInfo evacuation_info;
3890 if (g1_policy()->during_initial_mark_pause()) {
3891 // We are about to start a marking cycle, so we increment the
3892 // full collection counter.
3893 increment_old_marking_cycles_started();
3894 register_concurrent_cycle_start(_gc_timer_stw->gc_start());
3895 }
3897 _gc_tracer_stw->report_yc_type(yc_type());
3899 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
3901 int active_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
3902 workers()->active_workers() : 1);
3903 double pause_start_sec = os::elapsedTime();
3904 g1_policy()->phase_times()->note_gc_start(active_workers);
3905 log_gc_header();
3907 TraceCollectorStats tcs(g1mm()->incremental_collection_counters());
3908 TraceMemoryManagerStats tms(false /* fullGC */, gc_cause());
3910 // If the secondary_free_list is not empty, append it to the
3911 // free_list. No need to wait for the cleanup operation to finish;
3912 // the region allocation code will check the secondary_free_list
3913 // and wait if necessary. If the G1StressConcRegionFreeing flag is
3914 // set, skip this step so that the region allocation code has to
3915 // get entries from the secondary_free_list.
3916 if (!G1StressConcRegionFreeing) {
3917 append_secondary_free_list_if_not_empty_with_lock();
3918 }
3920 assert(check_young_list_well_formed(), "young list should be well formed");
3921 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3922 "sanity check");
3924 // Don't dynamically change the number of GC threads this early. A value of
3925 // 0 is used to indicate serial work. When parallel work is done,
3926 // it will be set.
3928 { // Call to jvmpi::post_class_unload_events must occur outside of active GC
3929 IsGCActiveMark x;
3931 gc_prologue(false);
3932 increment_total_collections(false /* full gc */);
3933 increment_gc_time_stamp();
3935 verify_before_gc();
3936 check_bitmaps("GC Start");
3938 COMPILER2_PRESENT(DerivedPointerTable::clear());
3940 // Please see comment in g1CollectedHeap.hpp and
3941 // G1CollectedHeap::ref_processing_init() to see how
3942 // reference processing currently works in G1.
3944 // Enable discovery in the STW reference processor
3945 ref_processor_stw()->enable_discovery(true /*verify_disabled*/,
3946 true /*verify_no_refs*/);
3948 {
3949 // We want to temporarily turn off discovery by the
3950 // CM ref processor, if necessary, and turn it back on
3951 // on again later if we do. Using a scoped
3952 // NoRefDiscovery object will do this.
3953 NoRefDiscovery no_cm_discovery(ref_processor_cm());
3955 // Forget the current alloc region (we might even choose it to be part
3956 // of the collection set!).
3957 _allocator->release_mutator_alloc_region();
3959 // We should call this after we retire the mutator alloc
3960 // region(s) so that all the ALLOC / RETIRE events are generated
3961 // before the start GC event.
3962 _hr_printer.start_gc(false /* full */, (size_t) total_collections());
3964 // This timing is only used by the ergonomics to handle our pause target.
3965 // It is unclear why this should not include the full pause. We will
3966 // investigate this in CR 7178365.
3967 //
3968 // Preserving the old comment here if that helps the investigation:
3969 //
3970 // The elapsed time induced by the start time below deliberately elides
3971 // the possible verification above.
3972 double sample_start_time_sec = os::elapsedTime();
3974 #if YOUNG_LIST_VERBOSE
3975 gclog_or_tty->print_cr("\nBefore recording pause start.\nYoung_list:");
3976 _young_list->print();
3977 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3978 #endif // YOUNG_LIST_VERBOSE
3980 g1_policy()->record_collection_pause_start(sample_start_time_sec);
3982 double scan_wait_start = os::elapsedTime();
3983 // We have to wait until the CM threads finish scanning the
3984 // root regions as it's the only way to ensure that all the
3985 // objects on them have been correctly scanned before we start
3986 // moving them during the GC.
3987 bool waited = _cm->root_regions()->wait_until_scan_finished();
3988 double wait_time_ms = 0.0;
3989 if (waited) {
3990 double scan_wait_end = os::elapsedTime();
3991 wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
3992 }
3993 g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms);
3995 #if YOUNG_LIST_VERBOSE
3996 gclog_or_tty->print_cr("\nAfter recording pause start.\nYoung_list:");
3997 _young_list->print();
3998 #endif // YOUNG_LIST_VERBOSE
4000 if (g1_policy()->during_initial_mark_pause()) {
4001 concurrent_mark()->checkpointRootsInitialPre();
4002 }
4004 #if YOUNG_LIST_VERBOSE
4005 gclog_or_tty->print_cr("\nBefore choosing collection set.\nYoung_list:");
4006 _young_list->print();
4007 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
4008 #endif // YOUNG_LIST_VERBOSE
4010 g1_policy()->finalize_cset(target_pause_time_ms, evacuation_info);
4012 register_humongous_regions_with_in_cset_fast_test();
4014 _cm->note_start_of_gc();
4015 // We should not verify the per-thread SATB buffers given that
4016 // we have not filtered them yet (we'll do so during the
4017 // GC). We also call this after finalize_cset() to
4018 // ensure that the CSet has been finalized.
4019 _cm->verify_no_cset_oops(true /* verify_stacks */,
4020 true /* verify_enqueued_buffers */,
4021 false /* verify_thread_buffers */,
4022 true /* verify_fingers */);
4024 if (_hr_printer.is_active()) {
4025 HeapRegion* hr = g1_policy()->collection_set();
4026 while (hr != NULL) {
4027 _hr_printer.cset(hr);
4028 hr = hr->next_in_collection_set();
4029 }
4030 }
4032 #ifdef ASSERT
4033 VerifyCSetClosure cl;
4034 collection_set_iterate(&cl);
4035 #endif // ASSERT
4037 setup_surviving_young_words();
4039 // Initialize the GC alloc regions.
4040 _allocator->init_gc_alloc_regions(evacuation_info);
4042 // Actually do the work...
4043 evacuate_collection_set(evacuation_info);
4045 // We do this to mainly verify the per-thread SATB buffers
4046 // (which have been filtered by now) since we didn't verify
4047 // them earlier. No point in re-checking the stacks / enqueued
4048 // buffers given that the CSet has not changed since last time
4049 // we checked.
4050 _cm->verify_no_cset_oops(false /* verify_stacks */,
4051 false /* verify_enqueued_buffers */,
4052 true /* verify_thread_buffers */,
4053 true /* verify_fingers */);
4055 free_collection_set(g1_policy()->collection_set(), evacuation_info);
4057 eagerly_reclaim_humongous_regions();
4059 g1_policy()->clear_collection_set();
4061 cleanup_surviving_young_words();
4063 // Start a new incremental collection set for the next pause.
4064 g1_policy()->start_incremental_cset_building();
4066 clear_cset_fast_test();
4068 _young_list->reset_sampled_info();
4070 // Don't check the whole heap at this point as the
4071 // GC alloc regions from this pause have been tagged
4072 // as survivors and moved on to the survivor list.
4073 // Survivor regions will fail the !is_young() check.
4074 assert(check_young_list_empty(false /* check_heap */),
4075 "young list should be empty");
4077 #if YOUNG_LIST_VERBOSE
4078 gclog_or_tty->print_cr("Before recording survivors.\nYoung List:");
4079 _young_list->print();
4080 #endif // YOUNG_LIST_VERBOSE
4082 g1_policy()->record_survivor_regions(_young_list->survivor_length(),
4083 _young_list->first_survivor_region(),
4084 _young_list->last_survivor_region());
4086 _young_list->reset_auxilary_lists();
4088 if (evacuation_failed()) {
4089 _allocator->set_used(recalculate_used());
4090 uint n_queues = MAX2((int)ParallelGCThreads, 1);
4091 for (uint i = 0; i < n_queues; i++) {
4092 if (_evacuation_failed_info_array[i].has_failed()) {
4093 _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]);
4094 }
4095 }
4096 } else {
4097 // The "used" of the the collection set have already been subtracted
4098 // when they were freed. Add in the bytes evacuated.
4099 _allocator->increase_used(g1_policy()->bytes_copied_during_gc());
4100 }
4102 if (g1_policy()->during_initial_mark_pause()) {
4103 // We have to do this before we notify the CM threads that
4104 // they can start working to make sure that all the
4105 // appropriate initialization is done on the CM object.
4106 concurrent_mark()->checkpointRootsInitialPost();
4107 set_marking_started();
4108 // Note that we don't actually trigger the CM thread at
4109 // this point. We do that later when we're sure that
4110 // the current thread has completed its logging output.
4111 }
4113 allocate_dummy_regions();
4115 #if YOUNG_LIST_VERBOSE
4116 gclog_or_tty->print_cr("\nEnd of the pause.\nYoung_list:");
4117 _young_list->print();
4118 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
4119 #endif // YOUNG_LIST_VERBOSE
4121 _allocator->init_mutator_alloc_region();
4123 {
4124 size_t expand_bytes = g1_policy()->expansion_amount();
4125 if (expand_bytes > 0) {
4126 size_t bytes_before = capacity();
4127 // No need for an ergo verbose message here,
4128 // expansion_amount() does this when it returns a value > 0.
4129 if (!expand(expand_bytes)) {
4130 // We failed to expand the heap. Cannot do anything about it.
4131 }
4132 }
4133 }
4135 // We redo the verification but now wrt to the new CSet which
4136 // has just got initialized after the previous CSet was freed.
4137 _cm->verify_no_cset_oops(true /* verify_stacks */,
4138 true /* verify_enqueued_buffers */,
4139 true /* verify_thread_buffers */,
4140 true /* verify_fingers */);
4141 _cm->note_end_of_gc();
4143 // This timing is only used by the ergonomics to handle our pause target.
4144 // It is unclear why this should not include the full pause. We will
4145 // investigate this in CR 7178365.
4146 double sample_end_time_sec = os::elapsedTime();
4147 double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
4148 g1_policy()->record_collection_pause_end(pause_time_ms, evacuation_info);
4150 MemoryService::track_memory_usage();
4152 // In prepare_for_verify() below we'll need to scan the deferred
4153 // update buffers to bring the RSets up-to-date if
4154 // G1HRRSFlushLogBuffersOnVerify has been set. While scanning
4155 // the update buffers we'll probably need to scan cards on the
4156 // regions we just allocated to (i.e., the GC alloc
4157 // regions). However, during the last GC we called
4158 // set_saved_mark() on all the GC alloc regions, so card
4159 // scanning might skip the [saved_mark_word()...top()] area of
4160 // those regions (i.e., the area we allocated objects into
4161 // during the last GC). But it shouldn't. Given that
4162 // saved_mark_word() is conditional on whether the GC time stamp
4163 // on the region is current or not, by incrementing the GC time
4164 // stamp here we invalidate all the GC time stamps on all the
4165 // regions and saved_mark_word() will simply return top() for
4166 // all the regions. This is a nicer way of ensuring this rather
4167 // than iterating over the regions and fixing them. In fact, the
4168 // GC time stamp increment here also ensures that
4169 // saved_mark_word() will return top() between pauses, i.e.,
4170 // during concurrent refinement. So we don't need the
4171 // is_gc_active() check to decided which top to use when
4172 // scanning cards (see CR 7039627).
4173 increment_gc_time_stamp();
4175 verify_after_gc();
4176 check_bitmaps("GC End");
4178 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
4179 ref_processor_stw()->verify_no_references_recorded();
4181 // CM reference discovery will be re-enabled if necessary.
4182 }
4184 // We should do this after we potentially expand the heap so
4185 // that all the COMMIT events are generated before the end GC
4186 // event, and after we retire the GC alloc regions so that all
4187 // RETIRE events are generated before the end GC event.
4188 _hr_printer.end_gc(false /* full */, (size_t) total_collections());
4190 #ifdef TRACESPINNING
4191 ParallelTaskTerminator::print_termination_counts();
4192 #endif
4194 gc_epilogue(false);
4195 }
4197 // Print the remainder of the GC log output.
4198 log_gc_footer(os::elapsedTime() - pause_start_sec);
4200 // It is not yet to safe to tell the concurrent mark to
4201 // start as we have some optional output below. We don't want the
4202 // output from the concurrent mark thread interfering with this
4203 // logging output either.
4205 _hrm.verify_optional();
4206 verify_region_sets_optional();
4208 TASKQUEUE_STATS_ONLY(if (ParallelGCVerbose) print_taskqueue_stats());
4209 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
4211 print_heap_after_gc();
4212 trace_heap_after_gc(_gc_tracer_stw);
4214 // We must call G1MonitoringSupport::update_sizes() in the same scoping level
4215 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
4216 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
4217 // before any GC notifications are raised.
4218 g1mm()->update_sizes();
4220 _gc_tracer_stw->report_evacuation_info(&evacuation_info);
4221 _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold());
4222 _gc_timer_stw->register_gc_end();
4223 _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions());
4224 }
4225 // It should now be safe to tell the concurrent mark thread to start
4226 // without its logging output interfering with the logging output
4227 // that came from the pause.
4229 if (should_start_conc_mark) {
4230 // CAUTION: after the doConcurrentMark() call below,
4231 // the concurrent marking thread(s) could be running
4232 // concurrently with us. Make sure that anything after
4233 // this point does not assume that we are the only GC thread
4234 // running. Note: of course, the actual marking work will
4235 // not start until the safepoint itself is released in
4236 // SuspendibleThreadSet::desynchronize().
4237 doConcurrentMark();
4238 }
4240 return true;
4241 }
4243 size_t G1CollectedHeap::desired_plab_sz(GCAllocPurpose purpose)
4244 {
4245 size_t gclab_word_size;
4246 switch (purpose) {
4247 case GCAllocForSurvived:
4248 gclab_word_size = _survivor_plab_stats.desired_plab_sz();
4249 break;
4250 case GCAllocForTenured:
4251 gclab_word_size = _old_plab_stats.desired_plab_sz();
4252 break;
4253 default:
4254 assert(false, "unknown GCAllocPurpose");
4255 gclab_word_size = _old_plab_stats.desired_plab_sz();
4256 break;
4257 }
4259 // Prevent humongous PLAB sizes for two reasons:
4260 // * PLABs are allocated using a similar paths as oops, but should
4261 // never be in a humongous region
4262 // * Allowing humongous PLABs needlessly churns the region free lists
4263 return MIN2(_humongous_object_threshold_in_words, gclab_word_size);
4264 }
4266 void G1CollectedHeap::init_for_evac_failure(OopsInHeapRegionClosure* cl) {
4267 _drain_in_progress = false;
4268 set_evac_failure_closure(cl);
4269 _evac_failure_scan_stack = new (ResourceObj::C_HEAP, mtGC) GrowableArray<oop>(40, true);
4270 }
4272 void G1CollectedHeap::finalize_for_evac_failure() {
4273 assert(_evac_failure_scan_stack != NULL &&
4274 _evac_failure_scan_stack->length() == 0,
4275 "Postcondition");
4276 assert(!_drain_in_progress, "Postcondition");
4277 delete _evac_failure_scan_stack;
4278 _evac_failure_scan_stack = NULL;
4279 }
4281 void G1CollectedHeap::remove_self_forwarding_pointers() {
4282 assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity");
4284 double remove_self_forwards_start = os::elapsedTime();
4286 G1ParRemoveSelfForwardPtrsTask rsfp_task(this);
4288 if (G1CollectedHeap::use_parallel_gc_threads()) {
4289 set_par_threads();
4290 workers()->run_task(&rsfp_task);
4291 set_par_threads(0);
4292 } else {
4293 rsfp_task.work(0);
4294 }
4296 assert(check_cset_heap_region_claim_values(HeapRegion::ParEvacFailureClaimValue), "sanity");
4298 // Reset the claim values in the regions in the collection set.
4299 reset_cset_heap_region_claim_values();
4301 assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity");
4303 // Now restore saved marks, if any.
4304 assert(_objs_with_preserved_marks.size() ==
4305 _preserved_marks_of_objs.size(), "Both or none.");
4306 while (!_objs_with_preserved_marks.is_empty()) {
4307 oop obj = _objs_with_preserved_marks.pop();
4308 markOop m = _preserved_marks_of_objs.pop();
4309 obj->set_mark(m);
4310 }
4311 _objs_with_preserved_marks.clear(true);
4312 _preserved_marks_of_objs.clear(true);
4314 g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0);
4315 }
4317 void G1CollectedHeap::push_on_evac_failure_scan_stack(oop obj) {
4318 _evac_failure_scan_stack->push(obj);
4319 }
4321 void G1CollectedHeap::drain_evac_failure_scan_stack() {
4322 assert(_evac_failure_scan_stack != NULL, "precondition");
4324 while (_evac_failure_scan_stack->length() > 0) {
4325 oop obj = _evac_failure_scan_stack->pop();
4326 _evac_failure_closure->set_region(heap_region_containing(obj));
4327 obj->oop_iterate_backwards(_evac_failure_closure);
4328 }
4329 }
4331 oop
4332 G1CollectedHeap::handle_evacuation_failure_par(G1ParScanThreadState* _par_scan_state,
4333 oop old) {
4334 assert(obj_in_cs(old),
4335 err_msg("obj: "PTR_FORMAT" should still be in the CSet",
4336 (HeapWord*) old));
4337 markOop m = old->mark();
4338 oop forward_ptr = old->forward_to_atomic(old);
4339 if (forward_ptr == NULL) {
4340 // Forward-to-self succeeded.
4341 assert(_par_scan_state != NULL, "par scan state");
4342 OopsInHeapRegionClosure* cl = _par_scan_state->evac_failure_closure();
4343 uint queue_num = _par_scan_state->queue_num();
4345 _evacuation_failed = true;
4346 _evacuation_failed_info_array[queue_num].register_copy_failure(old->size());
4347 if (_evac_failure_closure != cl) {
4348 MutexLockerEx x(EvacFailureStack_lock, Mutex::_no_safepoint_check_flag);
4349 assert(!_drain_in_progress,
4350 "Should only be true while someone holds the lock.");
4351 // Set the global evac-failure closure to the current thread's.
4352 assert(_evac_failure_closure == NULL, "Or locking has failed.");
4353 set_evac_failure_closure(cl);
4354 // Now do the common part.
4355 handle_evacuation_failure_common(old, m);
4356 // Reset to NULL.
4357 set_evac_failure_closure(NULL);
4358 } else {
4359 // The lock is already held, and this is recursive.
4360 assert(_drain_in_progress, "This should only be the recursive case.");
4361 handle_evacuation_failure_common(old, m);
4362 }
4363 return old;
4364 } else {
4365 // Forward-to-self failed. Either someone else managed to allocate
4366 // space for this object (old != forward_ptr) or they beat us in
4367 // self-forwarding it (old == forward_ptr).
4368 assert(old == forward_ptr || !obj_in_cs(forward_ptr),
4369 err_msg("obj: "PTR_FORMAT" forwarded to: "PTR_FORMAT" "
4370 "should not be in the CSet",
4371 (HeapWord*) old, (HeapWord*) forward_ptr));
4372 return forward_ptr;
4373 }
4374 }
4376 void G1CollectedHeap::handle_evacuation_failure_common(oop old, markOop m) {
4377 preserve_mark_if_necessary(old, m);
4379 HeapRegion* r = heap_region_containing(old);
4380 if (!r->evacuation_failed()) {
4381 r->set_evacuation_failed(true);
4382 _hr_printer.evac_failure(r);
4383 }
4385 push_on_evac_failure_scan_stack(old);
4387 if (!_drain_in_progress) {
4388 // prevent recursion in copy_to_survivor_space()
4389 _drain_in_progress = true;
4390 drain_evac_failure_scan_stack();
4391 _drain_in_progress = false;
4392 }
4393 }
4395 void G1CollectedHeap::preserve_mark_if_necessary(oop obj, markOop m) {
4396 assert(evacuation_failed(), "Oversaving!");
4397 // We want to call the "for_promotion_failure" version only in the
4398 // case of a promotion failure.
4399 if (m->must_be_preserved_for_promotion_failure(obj)) {
4400 _objs_with_preserved_marks.push(obj);
4401 _preserved_marks_of_objs.push(m);
4402 }
4403 }
4405 HeapWord* G1CollectedHeap::par_allocate_during_gc(GCAllocPurpose purpose,
4406 size_t word_size,
4407 AllocationContext_t context) {
4408 if (purpose == GCAllocForSurvived) {
4409 HeapWord* result = survivor_attempt_allocation(word_size, context);
4410 if (result != NULL) {
4411 return result;
4412 } else {
4413 // Let's try to allocate in the old gen in case we can fit the
4414 // object there.
4415 return old_attempt_allocation(word_size, context);
4416 }
4417 } else {
4418 assert(purpose == GCAllocForTenured, "sanity");
4419 HeapWord* result = old_attempt_allocation(word_size, context);
4420 if (result != NULL) {
4421 return result;
4422 } else {
4423 // Let's try to allocate in the survivors in case we can fit the
4424 // object there.
4425 return survivor_attempt_allocation(word_size, context);
4426 }
4427 }
4429 ShouldNotReachHere();
4430 // Trying to keep some compilers happy.
4431 return NULL;
4432 }
4434 void G1ParCopyHelper::mark_object(oop obj) {
4435 assert(!_g1->heap_region_containing(obj)->in_collection_set(), "should not mark objects in the CSet");
4437 // We know that the object is not moving so it's safe to read its size.
4438 _cm->grayRoot(obj, (size_t) obj->size(), _worker_id);
4439 }
4441 void G1ParCopyHelper::mark_forwarded_object(oop from_obj, oop to_obj) {
4442 assert(from_obj->is_forwarded(), "from obj should be forwarded");
4443 assert(from_obj->forwardee() == to_obj, "to obj should be the forwardee");
4444 assert(from_obj != to_obj, "should not be self-forwarded");
4446 assert(_g1->heap_region_containing(from_obj)->in_collection_set(), "from obj should be in the CSet");
4447 assert(!_g1->heap_region_containing(to_obj)->in_collection_set(), "should not mark objects in the CSet");
4449 // The object might be in the process of being copied by another
4450 // worker so we cannot trust that its to-space image is
4451 // well-formed. So we have to read its size from its from-space
4452 // image which we know should not be changing.
4453 _cm->grayRoot(to_obj, (size_t) from_obj->size(), _worker_id);
4454 }
4456 template <class T>
4457 void G1ParCopyHelper::do_klass_barrier(T* p, oop new_obj) {
4458 if (_g1->heap_region_containing_raw(new_obj)->is_young()) {
4459 _scanned_klass->record_modified_oops();
4460 }
4461 }
4463 template <G1Barrier barrier, G1Mark do_mark_object>
4464 template <class T>
4465 void G1ParCopyClosure<barrier, do_mark_object>::do_oop_work(T* p) {
4466 T heap_oop = oopDesc::load_heap_oop(p);
4468 if (oopDesc::is_null(heap_oop)) {
4469 return;
4470 }
4472 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
4474 assert(_worker_id == _par_scan_state->queue_num(), "sanity");
4476 G1CollectedHeap::in_cset_state_t state = _g1->in_cset_state(obj);
4478 if (state == G1CollectedHeap::InCSet) {
4479 oop forwardee;
4480 if (obj->is_forwarded()) {
4481 forwardee = obj->forwardee();
4482 } else {
4483 forwardee = _par_scan_state->copy_to_survivor_space(obj);
4484 }
4485 assert(forwardee != NULL, "forwardee should not be NULL");
4486 oopDesc::encode_store_heap_oop(p, forwardee);
4487 if (do_mark_object != G1MarkNone && forwardee != obj) {
4488 // If the object is self-forwarded we don't need to explicitly
4489 // mark it, the evacuation failure protocol will do so.
4490 mark_forwarded_object(obj, forwardee);
4491 }
4493 if (barrier == G1BarrierKlass) {
4494 do_klass_barrier(p, forwardee);
4495 }
4496 } else {
4497 if (state == G1CollectedHeap::IsHumongous) {
4498 _g1->set_humongous_is_live(obj);
4499 }
4500 // The object is not in collection set. If we're a root scanning
4501 // closure during an initial mark pause then attempt to mark the object.
4502 if (do_mark_object == G1MarkFromRoot) {
4503 mark_object(obj);
4504 }
4505 }
4507 if (barrier == G1BarrierEvac) {
4508 _par_scan_state->update_rs(_from, p, _worker_id);
4509 }
4510 }
4512 template void G1ParCopyClosure<G1BarrierEvac, G1MarkNone>::do_oop_work(oop* p);
4513 template void G1ParCopyClosure<G1BarrierEvac, G1MarkNone>::do_oop_work(narrowOop* p);
4515 class G1ParEvacuateFollowersClosure : public VoidClosure {
4516 protected:
4517 G1CollectedHeap* _g1h;
4518 G1ParScanThreadState* _par_scan_state;
4519 RefToScanQueueSet* _queues;
4520 ParallelTaskTerminator* _terminator;
4522 G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
4523 RefToScanQueueSet* queues() { return _queues; }
4524 ParallelTaskTerminator* terminator() { return _terminator; }
4526 public:
4527 G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h,
4528 G1ParScanThreadState* par_scan_state,
4529 RefToScanQueueSet* queues,
4530 ParallelTaskTerminator* terminator)
4531 : _g1h(g1h), _par_scan_state(par_scan_state),
4532 _queues(queues), _terminator(terminator) {}
4534 void do_void();
4536 private:
4537 inline bool offer_termination();
4538 };
4540 bool G1ParEvacuateFollowersClosure::offer_termination() {
4541 G1ParScanThreadState* const pss = par_scan_state();
4542 pss->start_term_time();
4543 const bool res = terminator()->offer_termination();
4544 pss->end_term_time();
4545 return res;
4546 }
4548 void G1ParEvacuateFollowersClosure::do_void() {
4549 G1ParScanThreadState* const pss = par_scan_state();
4550 pss->trim_queue();
4551 do {
4552 pss->steal_and_trim_queue(queues());
4553 } while (!offer_termination());
4554 }
4556 class G1KlassScanClosure : public KlassClosure {
4557 G1ParCopyHelper* _closure;
4558 bool _process_only_dirty;
4559 int _count;
4560 public:
4561 G1KlassScanClosure(G1ParCopyHelper* closure, bool process_only_dirty)
4562 : _process_only_dirty(process_only_dirty), _closure(closure), _count(0) {}
4563 void do_klass(Klass* klass) {
4564 // If the klass has not been dirtied we know that there's
4565 // no references into the young gen and we can skip it.
4566 if (!_process_only_dirty || klass->has_modified_oops()) {
4567 // Clean the klass since we're going to scavenge all the metadata.
4568 klass->clear_modified_oops();
4570 // Tell the closure that this klass is the Klass to scavenge
4571 // and is the one to dirty if oops are left pointing into the young gen.
4572 _closure->set_scanned_klass(klass);
4574 klass->oops_do(_closure);
4576 _closure->set_scanned_klass(NULL);
4577 }
4578 _count++;
4579 }
4580 };
4582 class G1CodeBlobClosure : public CodeBlobClosure {
4583 class HeapRegionGatheringOopClosure : public OopClosure {
4584 G1CollectedHeap* _g1h;
4585 OopClosure* _work;
4586 nmethod* _nm;
4588 template <typename T>
4589 void do_oop_work(T* p) {
4590 _work->do_oop(p);
4591 T oop_or_narrowoop = oopDesc::load_heap_oop(p);
4592 if (!oopDesc::is_null(oop_or_narrowoop)) {
4593 oop o = oopDesc::decode_heap_oop_not_null(oop_or_narrowoop);
4594 HeapRegion* hr = _g1h->heap_region_containing_raw(o);
4595 assert(!_g1h->obj_in_cs(o) || hr->rem_set()->strong_code_roots_list_contains(_nm), "if o still in CS then evacuation failed and nm must already be in the remset");
4596 hr->add_strong_code_root(_nm);
4597 }
4598 }
4600 public:
4601 HeapRegionGatheringOopClosure(OopClosure* oc) : _g1h(G1CollectedHeap::heap()), _work(oc), _nm(NULL) {}
4603 void do_oop(oop* o) {
4604 do_oop_work(o);
4605 }
4607 void do_oop(narrowOop* o) {
4608 do_oop_work(o);
4609 }
4611 void set_nm(nmethod* nm) {
4612 _nm = nm;
4613 }
4614 };
4616 HeapRegionGatheringOopClosure _oc;
4617 public:
4618 G1CodeBlobClosure(OopClosure* oc) : _oc(oc) {}
4620 void do_code_blob(CodeBlob* cb) {
4621 nmethod* nm = cb->as_nmethod_or_null();
4622 if (nm != NULL) {
4623 if (!nm->test_set_oops_do_mark()) {
4624 _oc.set_nm(nm);
4625 nm->oops_do(&_oc);
4626 nm->fix_oop_relocations();
4627 }
4628 }
4629 }
4630 };
4632 class G1ParTask : public AbstractGangTask {
4633 protected:
4634 G1CollectedHeap* _g1h;
4635 RefToScanQueueSet *_queues;
4636 ParallelTaskTerminator _terminator;
4637 uint _n_workers;
4639 Mutex _stats_lock;
4640 Mutex* stats_lock() { return &_stats_lock; }
4642 public:
4643 G1ParTask(G1CollectedHeap* g1h, RefToScanQueueSet *task_queues)
4644 : AbstractGangTask("G1 collection"),
4645 _g1h(g1h),
4646 _queues(task_queues),
4647 _terminator(0, _queues),
4648 _stats_lock(Mutex::leaf, "parallel G1 stats lock", true)
4649 {}
4651 RefToScanQueueSet* queues() { return _queues; }
4653 RefToScanQueue *work_queue(int i) {
4654 return queues()->queue(i);
4655 }
4657 ParallelTaskTerminator* terminator() { return &_terminator; }
4659 virtual void set_for_termination(int active_workers) {
4660 // This task calls set_n_termination() in par_non_clean_card_iterate_work()
4661 // in the young space (_par_seq_tasks) in the G1 heap
4662 // for SequentialSubTasksDone.
4663 // This task also uses SubTasksDone in SharedHeap and G1CollectedHeap
4664 // both of which need setting by set_n_termination().
4665 _g1h->SharedHeap::set_n_termination(active_workers);
4666 _g1h->set_n_termination(active_workers);
4667 terminator()->reset_for_reuse(active_workers);
4668 _n_workers = active_workers;
4669 }
4671 // Helps out with CLD processing.
4672 //
4673 // During InitialMark we need to:
4674 // 1) Scavenge all CLDs for the young GC.
4675 // 2) Mark all objects directly reachable from strong CLDs.
4676 template <G1Mark do_mark_object>
4677 class G1CLDClosure : public CLDClosure {
4678 G1ParCopyClosure<G1BarrierNone, do_mark_object>* _oop_closure;
4679 G1ParCopyClosure<G1BarrierKlass, do_mark_object> _oop_in_klass_closure;
4680 G1KlassScanClosure _klass_in_cld_closure;
4681 bool _claim;
4683 public:
4684 G1CLDClosure(G1ParCopyClosure<G1BarrierNone, do_mark_object>* oop_closure,
4685 bool only_young, bool claim)
4686 : _oop_closure(oop_closure),
4687 _oop_in_klass_closure(oop_closure->g1(),
4688 oop_closure->pss(),
4689 oop_closure->rp()),
4690 _klass_in_cld_closure(&_oop_in_klass_closure, only_young),
4691 _claim(claim) {
4693 }
4695 void do_cld(ClassLoaderData* cld) {
4696 cld->oops_do(_oop_closure, &_klass_in_cld_closure, _claim);
4697 }
4698 };
4700 void work(uint worker_id) {
4701 if (worker_id >= _n_workers) return; // no work needed this round
4703 double start_time_ms = os::elapsedTime() * 1000.0;
4704 _g1h->g1_policy()->phase_times()->record_gc_worker_start_time(worker_id, start_time_ms);
4706 {
4707 ResourceMark rm;
4708 HandleMark hm;
4710 ReferenceProcessor* rp = _g1h->ref_processor_stw();
4712 G1ParScanThreadState pss(_g1h, worker_id, rp);
4713 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, rp);
4715 pss.set_evac_failure_closure(&evac_failure_cl);
4717 bool only_young = _g1h->g1_policy()->gcs_are_young();
4719 // Non-IM young GC.
4720 G1ParCopyClosure<G1BarrierNone, G1MarkNone> scan_only_root_cl(_g1h, &pss, rp);
4721 G1CLDClosure<G1MarkNone> scan_only_cld_cl(&scan_only_root_cl,
4722 only_young, // Only process dirty klasses.
4723 false); // No need to claim CLDs.
4724 // IM young GC.
4725 // Strong roots closures.
4726 G1ParCopyClosure<G1BarrierNone, G1MarkFromRoot> scan_mark_root_cl(_g1h, &pss, rp);
4727 G1CLDClosure<G1MarkFromRoot> scan_mark_cld_cl(&scan_mark_root_cl,
4728 false, // Process all klasses.
4729 true); // Need to claim CLDs.
4730 // Weak roots closures.
4731 G1ParCopyClosure<G1BarrierNone, G1MarkPromotedFromRoot> scan_mark_weak_root_cl(_g1h, &pss, rp);
4732 G1CLDClosure<G1MarkPromotedFromRoot> scan_mark_weak_cld_cl(&scan_mark_weak_root_cl,
4733 false, // Process all klasses.
4734 true); // Need to claim CLDs.
4736 G1CodeBlobClosure scan_only_code_cl(&scan_only_root_cl);
4737 G1CodeBlobClosure scan_mark_code_cl(&scan_mark_root_cl);
4738 // IM Weak code roots are handled later.
4740 OopClosure* strong_root_cl;
4741 OopClosure* weak_root_cl;
4742 CLDClosure* strong_cld_cl;
4743 CLDClosure* weak_cld_cl;
4744 CodeBlobClosure* strong_code_cl;
4746 if (_g1h->g1_policy()->during_initial_mark_pause()) {
4747 // We also need to mark copied objects.
4748 strong_root_cl = &scan_mark_root_cl;
4749 strong_cld_cl = &scan_mark_cld_cl;
4750 strong_code_cl = &scan_mark_code_cl;
4751 if (ClassUnloadingWithConcurrentMark) {
4752 weak_root_cl = &scan_mark_weak_root_cl;
4753 weak_cld_cl = &scan_mark_weak_cld_cl;
4754 } else {
4755 weak_root_cl = &scan_mark_root_cl;
4756 weak_cld_cl = &scan_mark_cld_cl;
4757 }
4758 } else {
4759 strong_root_cl = &scan_only_root_cl;
4760 weak_root_cl = &scan_only_root_cl;
4761 strong_cld_cl = &scan_only_cld_cl;
4762 weak_cld_cl = &scan_only_cld_cl;
4763 strong_code_cl = &scan_only_code_cl;
4764 }
4767 G1ParPushHeapRSClosure push_heap_rs_cl(_g1h, &pss);
4769 pss.start_strong_roots();
4770 _g1h->g1_process_roots(strong_root_cl,
4771 weak_root_cl,
4772 &push_heap_rs_cl,
4773 strong_cld_cl,
4774 weak_cld_cl,
4775 strong_code_cl,
4776 worker_id);
4778 pss.end_strong_roots();
4780 {
4781 double start = os::elapsedTime();
4782 G1ParEvacuateFollowersClosure evac(_g1h, &pss, _queues, &_terminator);
4783 evac.do_void();
4784 double elapsed_ms = (os::elapsedTime()-start)*1000.0;
4785 double term_ms = pss.term_time()*1000.0;
4786 _g1h->g1_policy()->phase_times()->add_obj_copy_time(worker_id, elapsed_ms-term_ms);
4787 _g1h->g1_policy()->phase_times()->record_termination(worker_id, term_ms, pss.term_attempts());
4788 }
4789 _g1h->g1_policy()->record_thread_age_table(pss.age_table());
4790 _g1h->update_surviving_young_words(pss.surviving_young_words()+1);
4792 if (ParallelGCVerbose) {
4793 MutexLocker x(stats_lock());
4794 pss.print_termination_stats(worker_id);
4795 }
4797 assert(pss.queue_is_empty(), "should be empty");
4799 // Close the inner scope so that the ResourceMark and HandleMark
4800 // destructors are executed here and are included as part of the
4801 // "GC Worker Time".
4802 }
4804 double end_time_ms = os::elapsedTime() * 1000.0;
4805 _g1h->g1_policy()->phase_times()->record_gc_worker_end_time(worker_id, end_time_ms);
4806 }
4807 };
4809 // *** Common G1 Evacuation Stuff
4811 // This method is run in a GC worker.
4813 void
4814 G1CollectedHeap::
4815 g1_process_roots(OopClosure* scan_non_heap_roots,
4816 OopClosure* scan_non_heap_weak_roots,
4817 OopsInHeapRegionClosure* scan_rs,
4818 CLDClosure* scan_strong_clds,
4819 CLDClosure* scan_weak_clds,
4820 CodeBlobClosure* scan_strong_code,
4821 uint worker_i) {
4823 // First scan the shared roots.
4824 double ext_roots_start = os::elapsedTime();
4825 double closure_app_time_sec = 0.0;
4827 bool during_im = _g1h->g1_policy()->during_initial_mark_pause();
4828 bool trace_metadata = during_im && ClassUnloadingWithConcurrentMark;
4830 BufferingOopClosure buf_scan_non_heap_roots(scan_non_heap_roots);
4831 BufferingOopClosure buf_scan_non_heap_weak_roots(scan_non_heap_weak_roots);
4833 process_roots(false, // no scoping; this is parallel code
4834 SharedHeap::SO_None,
4835 &buf_scan_non_heap_roots,
4836 &buf_scan_non_heap_weak_roots,
4837 scan_strong_clds,
4838 // Unloading Initial Marks handle the weak CLDs separately.
4839 (trace_metadata ? NULL : scan_weak_clds),
4840 scan_strong_code);
4842 // Now the CM ref_processor roots.
4843 if (!_process_strong_tasks->is_task_claimed(G1H_PS_refProcessor_oops_do)) {
4844 // We need to treat the discovered reference lists of the
4845 // concurrent mark ref processor as roots and keep entries
4846 // (which are added by the marking threads) on them live
4847 // until they can be processed at the end of marking.
4848 ref_processor_cm()->weak_oops_do(&buf_scan_non_heap_roots);
4849 }
4851 if (trace_metadata) {
4852 // Barrier to make sure all workers passed
4853 // the strong CLD and strong nmethods phases.
4854 active_strong_roots_scope()->wait_until_all_workers_done_with_threads(n_par_threads());
4856 // Now take the complement of the strong CLDs.
4857 ClassLoaderDataGraph::roots_cld_do(NULL, scan_weak_clds);
4858 }
4860 // Finish up any enqueued closure apps (attributed as object copy time).
4861 buf_scan_non_heap_roots.done();
4862 buf_scan_non_heap_weak_roots.done();
4864 double obj_copy_time_sec = buf_scan_non_heap_roots.closure_app_seconds()
4865 + buf_scan_non_heap_weak_roots.closure_app_seconds();
4867 g1_policy()->phase_times()->record_obj_copy_time(worker_i, obj_copy_time_sec * 1000.0);
4869 double ext_root_time_ms =
4870 ((os::elapsedTime() - ext_roots_start) - obj_copy_time_sec) * 1000.0;
4872 g1_policy()->phase_times()->record_ext_root_scan_time(worker_i, ext_root_time_ms);
4874 // During conc marking we have to filter the per-thread SATB buffers
4875 // to make sure we remove any oops into the CSet (which will show up
4876 // as implicitly live).
4877 double satb_filtering_ms = 0.0;
4878 if (!_process_strong_tasks->is_task_claimed(G1H_PS_filter_satb_buffers)) {
4879 if (mark_in_progress()) {
4880 double satb_filter_start = os::elapsedTime();
4882 JavaThread::satb_mark_queue_set().filter_thread_buffers();
4884 satb_filtering_ms = (os::elapsedTime() - satb_filter_start) * 1000.0;
4885 }
4886 }
4887 g1_policy()->phase_times()->record_satb_filtering_time(worker_i, satb_filtering_ms);
4889 // Now scan the complement of the collection set.
4890 G1CodeBlobClosure scavenge_cs_nmethods(scan_non_heap_weak_roots);
4892 g1_rem_set()->oops_into_collection_set_do(scan_rs, &scavenge_cs_nmethods, worker_i);
4894 _process_strong_tasks->all_tasks_completed();
4895 }
4897 class G1StringSymbolTableUnlinkTask : public AbstractGangTask {
4898 private:
4899 BoolObjectClosure* _is_alive;
4900 int _initial_string_table_size;
4901 int _initial_symbol_table_size;
4903 bool _process_strings;
4904 int _strings_processed;
4905 int _strings_removed;
4907 bool _process_symbols;
4908 int _symbols_processed;
4909 int _symbols_removed;
4911 bool _do_in_parallel;
4912 public:
4913 G1StringSymbolTableUnlinkTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols) :
4914 AbstractGangTask("String/Symbol Unlinking"),
4915 _is_alive(is_alive),
4916 _do_in_parallel(G1CollectedHeap::use_parallel_gc_threads()),
4917 _process_strings(process_strings), _strings_processed(0), _strings_removed(0),
4918 _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0) {
4920 _initial_string_table_size = StringTable::the_table()->table_size();
4921 _initial_symbol_table_size = SymbolTable::the_table()->table_size();
4922 if (process_strings) {
4923 StringTable::clear_parallel_claimed_index();
4924 }
4925 if (process_symbols) {
4926 SymbolTable::clear_parallel_claimed_index();
4927 }
4928 }
4930 ~G1StringSymbolTableUnlinkTask() {
4931 guarantee(!_process_strings || !_do_in_parallel || StringTable::parallel_claimed_index() >= _initial_string_table_size,
4932 err_msg("claim value "INT32_FORMAT" after unlink less than initial string table size "INT32_FORMAT,
4933 StringTable::parallel_claimed_index(), _initial_string_table_size));
4934 guarantee(!_process_symbols || !_do_in_parallel || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size,
4935 err_msg("claim value "INT32_FORMAT" after unlink less than initial symbol table size "INT32_FORMAT,
4936 SymbolTable::parallel_claimed_index(), _initial_symbol_table_size));
4938 if (G1TraceStringSymbolTableScrubbing) {
4939 gclog_or_tty->print_cr("Cleaned string and symbol table, "
4940 "strings: "SIZE_FORMAT" processed, "SIZE_FORMAT" removed, "
4941 "symbols: "SIZE_FORMAT" processed, "SIZE_FORMAT" removed",
4942 strings_processed(), strings_removed(),
4943 symbols_processed(), symbols_removed());
4944 }
4945 }
4947 void work(uint worker_id) {
4948 if (_do_in_parallel) {
4949 int strings_processed = 0;
4950 int strings_removed = 0;
4951 int symbols_processed = 0;
4952 int symbols_removed = 0;
4953 if (_process_strings) {
4954 StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed);
4955 Atomic::add(strings_processed, &_strings_processed);
4956 Atomic::add(strings_removed, &_strings_removed);
4957 }
4958 if (_process_symbols) {
4959 SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed);
4960 Atomic::add(symbols_processed, &_symbols_processed);
4961 Atomic::add(symbols_removed, &_symbols_removed);
4962 }
4963 } else {
4964 if (_process_strings) {
4965 StringTable::unlink(_is_alive, &_strings_processed, &_strings_removed);
4966 }
4967 if (_process_symbols) {
4968 SymbolTable::unlink(&_symbols_processed, &_symbols_removed);
4969 }
4970 }
4971 }
4973 size_t strings_processed() const { return (size_t)_strings_processed; }
4974 size_t strings_removed() const { return (size_t)_strings_removed; }
4976 size_t symbols_processed() const { return (size_t)_symbols_processed; }
4977 size_t symbols_removed() const { return (size_t)_symbols_removed; }
4978 };
4980 class G1CodeCacheUnloadingTask VALUE_OBJ_CLASS_SPEC {
4981 private:
4982 static Monitor* _lock;
4984 BoolObjectClosure* const _is_alive;
4985 const bool _unloading_occurred;
4986 const uint _num_workers;
4988 // Variables used to claim nmethods.
4989 nmethod* _first_nmethod;
4990 volatile nmethod* _claimed_nmethod;
4992 // The list of nmethods that need to be processed by the second pass.
4993 volatile nmethod* _postponed_list;
4994 volatile uint _num_entered_barrier;
4996 public:
4997 G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) :
4998 _is_alive(is_alive),
4999 _unloading_occurred(unloading_occurred),
5000 _num_workers(num_workers),
5001 _first_nmethod(NULL),
5002 _claimed_nmethod(NULL),
5003 _postponed_list(NULL),
5004 _num_entered_barrier(0)
5005 {
5006 nmethod::increase_unloading_clock();
5007 _first_nmethod = CodeCache::alive_nmethod(CodeCache::first());
5008 _claimed_nmethod = (volatile nmethod*)_first_nmethod;
5009 }
5011 ~G1CodeCacheUnloadingTask() {
5012 CodeCache::verify_clean_inline_caches();
5014 CodeCache::set_needs_cache_clean(false);
5015 guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be");
5017 CodeCache::verify_icholder_relocations();
5018 }
5020 private:
5021 void add_to_postponed_list(nmethod* nm) {
5022 nmethod* old;
5023 do {
5024 old = (nmethod*)_postponed_list;
5025 nm->set_unloading_next(old);
5026 } while ((nmethod*)Atomic::cmpxchg_ptr(nm, &_postponed_list, old) != old);
5027 }
5029 void clean_nmethod(nmethod* nm) {
5030 bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred);
5032 if (postponed) {
5033 // This nmethod referred to an nmethod that has not been cleaned/unloaded yet.
5034 add_to_postponed_list(nm);
5035 }
5037 // Mark that this thread has been cleaned/unloaded.
5038 // After this call, it will be safe to ask if this nmethod was unloaded or not.
5039 nm->set_unloading_clock(nmethod::global_unloading_clock());
5040 }
5042 void clean_nmethod_postponed(nmethod* nm) {
5043 nm->do_unloading_parallel_postponed(_is_alive, _unloading_occurred);
5044 }
5046 static const int MaxClaimNmethods = 16;
5048 void claim_nmethods(nmethod** claimed_nmethods, int *num_claimed_nmethods) {
5049 nmethod* first;
5050 nmethod* last;
5052 do {
5053 *num_claimed_nmethods = 0;
5055 first = last = (nmethod*)_claimed_nmethod;
5057 if (first != NULL) {
5058 for (int i = 0; i < MaxClaimNmethods; i++) {
5059 last = CodeCache::alive_nmethod(CodeCache::next(last));
5061 if (last == NULL) {
5062 break;
5063 }
5065 claimed_nmethods[i] = last;
5066 (*num_claimed_nmethods)++;
5067 }
5068 }
5070 } while ((nmethod*)Atomic::cmpxchg_ptr(last, &_claimed_nmethod, first) != first);
5071 }
5073 nmethod* claim_postponed_nmethod() {
5074 nmethod* claim;
5075 nmethod* next;
5077 do {
5078 claim = (nmethod*)_postponed_list;
5079 if (claim == NULL) {
5080 return NULL;
5081 }
5083 next = claim->unloading_next();
5085 } while ((nmethod*)Atomic::cmpxchg_ptr(next, &_postponed_list, claim) != claim);
5087 return claim;
5088 }
5090 public:
5091 // Mark that we're done with the first pass of nmethod cleaning.
5092 void barrier_mark(uint worker_id) {
5093 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
5094 _num_entered_barrier++;
5095 if (_num_entered_barrier == _num_workers) {
5096 ml.notify_all();
5097 }
5098 }
5100 // See if we have to wait for the other workers to
5101 // finish their first-pass nmethod cleaning work.
5102 void barrier_wait(uint worker_id) {
5103 if (_num_entered_barrier < _num_workers) {
5104 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
5105 while (_num_entered_barrier < _num_workers) {
5106 ml.wait(Mutex::_no_safepoint_check_flag, 0, false);
5107 }
5108 }
5109 }
5111 // Cleaning and unloading of nmethods. Some work has to be postponed
5112 // to the second pass, when we know which nmethods survive.
5113 void work_first_pass(uint worker_id) {
5114 // The first nmethods is claimed by the first worker.
5115 if (worker_id == 0 && _first_nmethod != NULL) {
5116 clean_nmethod(_first_nmethod);
5117 _first_nmethod = NULL;
5118 }
5120 int num_claimed_nmethods;
5121 nmethod* claimed_nmethods[MaxClaimNmethods];
5123 while (true) {
5124 claim_nmethods(claimed_nmethods, &num_claimed_nmethods);
5126 if (num_claimed_nmethods == 0) {
5127 break;
5128 }
5130 for (int i = 0; i < num_claimed_nmethods; i++) {
5131 clean_nmethod(claimed_nmethods[i]);
5132 }
5133 }
5134 }
5136 void work_second_pass(uint worker_id) {
5137 nmethod* nm;
5138 // Take care of postponed nmethods.
5139 while ((nm = claim_postponed_nmethod()) != NULL) {
5140 clean_nmethod_postponed(nm);
5141 }
5142 }
5143 };
5145 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock");
5147 class G1KlassCleaningTask : public StackObj {
5148 BoolObjectClosure* _is_alive;
5149 volatile jint _clean_klass_tree_claimed;
5150 ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator;
5152 public:
5153 G1KlassCleaningTask(BoolObjectClosure* is_alive) :
5154 _is_alive(is_alive),
5155 _clean_klass_tree_claimed(0),
5156 _klass_iterator() {
5157 }
5159 private:
5160 bool claim_clean_klass_tree_task() {
5161 if (_clean_klass_tree_claimed) {
5162 return false;
5163 }
5165 return Atomic::cmpxchg(1, (jint*)&_clean_klass_tree_claimed, 0) == 0;
5166 }
5168 InstanceKlass* claim_next_klass() {
5169 Klass* klass;
5170 do {
5171 klass =_klass_iterator.next_klass();
5172 } while (klass != NULL && !klass->oop_is_instance());
5174 return (InstanceKlass*)klass;
5175 }
5177 public:
5179 void clean_klass(InstanceKlass* ik) {
5180 ik->clean_implementors_list(_is_alive);
5181 ik->clean_method_data(_is_alive);
5183 // G1 specific cleanup work that has
5184 // been moved here to be done in parallel.
5185 ik->clean_dependent_nmethods();
5186 }
5188 void work() {
5189 ResourceMark rm;
5191 // One worker will clean the subklass/sibling klass tree.
5192 if (claim_clean_klass_tree_task()) {
5193 Klass::clean_subklass_tree(_is_alive);
5194 }
5196 // All workers will help cleaning the classes,
5197 InstanceKlass* klass;
5198 while ((klass = claim_next_klass()) != NULL) {
5199 clean_klass(klass);
5200 }
5201 }
5202 };
5204 // To minimize the remark pause times, the tasks below are done in parallel.
5205 class G1ParallelCleaningTask : public AbstractGangTask {
5206 private:
5207 G1StringSymbolTableUnlinkTask _string_symbol_task;
5208 G1CodeCacheUnloadingTask _code_cache_task;
5209 G1KlassCleaningTask _klass_cleaning_task;
5211 public:
5212 // The constructor is run in the VMThread.
5213 G1ParallelCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, uint num_workers, bool unloading_occurred) :
5214 AbstractGangTask("Parallel Cleaning"),
5215 _string_symbol_task(is_alive, process_strings, process_symbols),
5216 _code_cache_task(num_workers, is_alive, unloading_occurred),
5217 _klass_cleaning_task(is_alive) {
5218 }
5220 // The parallel work done by all worker threads.
5221 void work(uint worker_id) {
5222 // Do first pass of code cache cleaning.
5223 _code_cache_task.work_first_pass(worker_id);
5225 // Let the threads mark that the first pass is done.
5226 _code_cache_task.barrier_mark(worker_id);
5228 // Clean the Strings and Symbols.
5229 _string_symbol_task.work(worker_id);
5231 // Wait for all workers to finish the first code cache cleaning pass.
5232 _code_cache_task.barrier_wait(worker_id);
5234 // Do the second code cache cleaning work, which realize on
5235 // the liveness information gathered during the first pass.
5236 _code_cache_task.work_second_pass(worker_id);
5238 // Clean all klasses that were not unloaded.
5239 _klass_cleaning_task.work();
5240 }
5241 };
5244 void G1CollectedHeap::parallel_cleaning(BoolObjectClosure* is_alive,
5245 bool process_strings,
5246 bool process_symbols,
5247 bool class_unloading_occurred) {
5248 uint n_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
5249 workers()->active_workers() : 1);
5251 G1ParallelCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols,
5252 n_workers, class_unloading_occurred);
5253 if (G1CollectedHeap::use_parallel_gc_threads()) {
5254 set_par_threads(n_workers);
5255 workers()->run_task(&g1_unlink_task);
5256 set_par_threads(0);
5257 } else {
5258 g1_unlink_task.work(0);
5259 }
5260 }
5262 void G1CollectedHeap::unlink_string_and_symbol_table(BoolObjectClosure* is_alive,
5263 bool process_strings, bool process_symbols) {
5264 {
5265 uint n_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
5266 _g1h->workers()->active_workers() : 1);
5267 G1StringSymbolTableUnlinkTask g1_unlink_task(is_alive, process_strings, process_symbols);
5268 if (G1CollectedHeap::use_parallel_gc_threads()) {
5269 set_par_threads(n_workers);
5270 workers()->run_task(&g1_unlink_task);
5271 set_par_threads(0);
5272 } else {
5273 g1_unlink_task.work(0);
5274 }
5275 }
5277 if (G1StringDedup::is_enabled()) {
5278 G1StringDedup::unlink(is_alive);
5279 }
5280 }
5282 class G1RedirtyLoggedCardsTask : public AbstractGangTask {
5283 private:
5284 DirtyCardQueueSet* _queue;
5285 public:
5286 G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue) : AbstractGangTask("Redirty Cards"), _queue(queue) { }
5288 virtual void work(uint worker_id) {
5289 double start_time = os::elapsedTime();
5291 RedirtyLoggedCardTableEntryClosure cl;
5292 if (G1CollectedHeap::heap()->use_parallel_gc_threads()) {
5293 _queue->par_apply_closure_to_all_completed_buffers(&cl);
5294 } else {
5295 _queue->apply_closure_to_all_completed_buffers(&cl);
5296 }
5298 G1GCPhaseTimes* timer = G1CollectedHeap::heap()->g1_policy()->phase_times();
5299 timer->record_redirty_logged_cards_time_ms(worker_id, (os::elapsedTime() - start_time) * 1000.0);
5300 timer->record_redirty_logged_cards_processed_cards(worker_id, cl.num_processed());
5301 }
5302 };
5304 void G1CollectedHeap::redirty_logged_cards() {
5305 double redirty_logged_cards_start = os::elapsedTime();
5307 uint n_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
5308 _g1h->workers()->active_workers() : 1);
5310 G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set());
5311 dirty_card_queue_set().reset_for_par_iteration();
5312 if (use_parallel_gc_threads()) {
5313 set_par_threads(n_workers);
5314 workers()->run_task(&redirty_task);
5315 set_par_threads(0);
5316 } else {
5317 redirty_task.work(0);
5318 }
5320 DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set();
5321 dcq.merge_bufferlists(&dirty_card_queue_set());
5322 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
5324 g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0);
5325 }
5327 // Weak Reference Processing support
5329 // An always "is_alive" closure that is used to preserve referents.
5330 // If the object is non-null then it's alive. Used in the preservation
5331 // of referent objects that are pointed to by reference objects
5332 // discovered by the CM ref processor.
5333 class G1AlwaysAliveClosure: public BoolObjectClosure {
5334 G1CollectedHeap* _g1;
5335 public:
5336 G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
5337 bool do_object_b(oop p) {
5338 if (p != NULL) {
5339 return true;
5340 }
5341 return false;
5342 }
5343 };
5345 bool G1STWIsAliveClosure::do_object_b(oop p) {
5346 // An object is reachable if it is outside the collection set,
5347 // or is inside and copied.
5348 return !_g1->obj_in_cs(p) || p->is_forwarded();
5349 }
5351 // Non Copying Keep Alive closure
5352 class G1KeepAliveClosure: public OopClosure {
5353 G1CollectedHeap* _g1;
5354 public:
5355 G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
5356 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
5357 void do_oop(oop* p) {
5358 oop obj = *p;
5359 assert(obj != NULL, "the caller should have filtered out NULL values");
5361 G1CollectedHeap::in_cset_state_t cset_state = _g1->in_cset_state(obj);
5362 if (cset_state == G1CollectedHeap::InNeither) {
5363 return;
5364 }
5365 if (cset_state == G1CollectedHeap::InCSet) {
5366 assert( obj->is_forwarded(), "invariant" );
5367 *p = obj->forwardee();
5368 } else {
5369 assert(!obj->is_forwarded(), "invariant" );
5370 assert(cset_state == G1CollectedHeap::IsHumongous,
5371 err_msg("Only allowed InCSet state is IsHumongous, but is %d", cset_state));
5372 _g1->set_humongous_is_live(obj);
5373 }
5374 }
5375 };
5377 // Copying Keep Alive closure - can be called from both
5378 // serial and parallel code as long as different worker
5379 // threads utilize different G1ParScanThreadState instances
5380 // and different queues.
5382 class G1CopyingKeepAliveClosure: public OopClosure {
5383 G1CollectedHeap* _g1h;
5384 OopClosure* _copy_non_heap_obj_cl;
5385 G1ParScanThreadState* _par_scan_state;
5387 public:
5388 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
5389 OopClosure* non_heap_obj_cl,
5390 G1ParScanThreadState* pss):
5391 _g1h(g1h),
5392 _copy_non_heap_obj_cl(non_heap_obj_cl),
5393 _par_scan_state(pss)
5394 {}
5396 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
5397 virtual void do_oop( oop* p) { do_oop_work(p); }
5399 template <class T> void do_oop_work(T* p) {
5400 oop obj = oopDesc::load_decode_heap_oop(p);
5402 if (_g1h->is_in_cset_or_humongous(obj)) {
5403 // If the referent object has been forwarded (either copied
5404 // to a new location or to itself in the event of an
5405 // evacuation failure) then we need to update the reference
5406 // field and, if both reference and referent are in the G1
5407 // heap, update the RSet for the referent.
5408 //
5409 // If the referent has not been forwarded then we have to keep
5410 // it alive by policy. Therefore we have copy the referent.
5411 //
5412 // If the reference field is in the G1 heap then we can push
5413 // on the PSS queue. When the queue is drained (after each
5414 // phase of reference processing) the object and it's followers
5415 // will be copied, the reference field set to point to the
5416 // new location, and the RSet updated. Otherwise we need to
5417 // use the the non-heap or metadata closures directly to copy
5418 // the referent object and update the pointer, while avoiding
5419 // updating the RSet.
5421 if (_g1h->is_in_g1_reserved(p)) {
5422 _par_scan_state->push_on_queue(p);
5423 } else {
5424 assert(!Metaspace::contains((const void*)p),
5425 err_msg("Unexpectedly found a pointer from metadata: "
5426 PTR_FORMAT, p));
5427 _copy_non_heap_obj_cl->do_oop(p);
5428 }
5429 }
5430 }
5431 };
5433 // Serial drain queue closure. Called as the 'complete_gc'
5434 // closure for each discovered list in some of the
5435 // reference processing phases.
5437 class G1STWDrainQueueClosure: public VoidClosure {
5438 protected:
5439 G1CollectedHeap* _g1h;
5440 G1ParScanThreadState* _par_scan_state;
5442 G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
5444 public:
5445 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
5446 _g1h(g1h),
5447 _par_scan_state(pss)
5448 { }
5450 void do_void() {
5451 G1ParScanThreadState* const pss = par_scan_state();
5452 pss->trim_queue();
5453 }
5454 };
5456 // Parallel Reference Processing closures
5458 // Implementation of AbstractRefProcTaskExecutor for parallel reference
5459 // processing during G1 evacuation pauses.
5461 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
5462 private:
5463 G1CollectedHeap* _g1h;
5464 RefToScanQueueSet* _queues;
5465 FlexibleWorkGang* _workers;
5466 int _active_workers;
5468 public:
5469 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
5470 FlexibleWorkGang* workers,
5471 RefToScanQueueSet *task_queues,
5472 int n_workers) :
5473 _g1h(g1h),
5474 _queues(task_queues),
5475 _workers(workers),
5476 _active_workers(n_workers)
5477 {
5478 assert(n_workers > 0, "shouldn't call this otherwise");
5479 }
5481 // Executes the given task using concurrent marking worker threads.
5482 virtual void execute(ProcessTask& task);
5483 virtual void execute(EnqueueTask& task);
5484 };
5486 // Gang task for possibly parallel reference processing
5488 class G1STWRefProcTaskProxy: public AbstractGangTask {
5489 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
5490 ProcessTask& _proc_task;
5491 G1CollectedHeap* _g1h;
5492 RefToScanQueueSet *_task_queues;
5493 ParallelTaskTerminator* _terminator;
5495 public:
5496 G1STWRefProcTaskProxy(ProcessTask& proc_task,
5497 G1CollectedHeap* g1h,
5498 RefToScanQueueSet *task_queues,
5499 ParallelTaskTerminator* terminator) :
5500 AbstractGangTask("Process reference objects in parallel"),
5501 _proc_task(proc_task),
5502 _g1h(g1h),
5503 _task_queues(task_queues),
5504 _terminator(terminator)
5505 {}
5507 virtual void work(uint worker_id) {
5508 // The reference processing task executed by a single worker.
5509 ResourceMark rm;
5510 HandleMark hm;
5512 G1STWIsAliveClosure is_alive(_g1h);
5514 G1ParScanThreadState pss(_g1h, worker_id, NULL);
5515 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5517 pss.set_evac_failure_closure(&evac_failure_cl);
5519 G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL);
5521 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5523 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5525 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5526 // We also need to mark copied objects.
5527 copy_non_heap_cl = ©_mark_non_heap_cl;
5528 }
5530 // Keep alive closure.
5531 G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, &pss);
5533 // Complete GC closure
5534 G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _task_queues, _terminator);
5536 // Call the reference processing task's work routine.
5537 _proc_task.work(worker_id, is_alive, keep_alive, drain_queue);
5539 // Note we cannot assert that the refs array is empty here as not all
5540 // of the processing tasks (specifically phase2 - pp2_work) execute
5541 // the complete_gc closure (which ordinarily would drain the queue) so
5542 // the queue may not be empty.
5543 }
5544 };
5546 // Driver routine for parallel reference processing.
5547 // Creates an instance of the ref processing gang
5548 // task and has the worker threads execute it.
5549 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) {
5550 assert(_workers != NULL, "Need parallel worker threads.");
5552 ParallelTaskTerminator terminator(_active_workers, _queues);
5553 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _queues, &terminator);
5555 _g1h->set_par_threads(_active_workers);
5556 _workers->run_task(&proc_task_proxy);
5557 _g1h->set_par_threads(0);
5558 }
5560 // Gang task for parallel reference enqueueing.
5562 class G1STWRefEnqueueTaskProxy: public AbstractGangTask {
5563 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
5564 EnqueueTask& _enq_task;
5566 public:
5567 G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) :
5568 AbstractGangTask("Enqueue reference objects in parallel"),
5569 _enq_task(enq_task)
5570 { }
5572 virtual void work(uint worker_id) {
5573 _enq_task.work(worker_id);
5574 }
5575 };
5577 // Driver routine for parallel reference enqueueing.
5578 // Creates an instance of the ref enqueueing gang
5579 // task and has the worker threads execute it.
5581 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
5582 assert(_workers != NULL, "Need parallel worker threads.");
5584 G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task);
5586 _g1h->set_par_threads(_active_workers);
5587 _workers->run_task(&enq_task_proxy);
5588 _g1h->set_par_threads(0);
5589 }
5591 // End of weak reference support closures
5593 // Abstract task used to preserve (i.e. copy) any referent objects
5594 // that are in the collection set and are pointed to by reference
5595 // objects discovered by the CM ref processor.
5597 class G1ParPreserveCMReferentsTask: public AbstractGangTask {
5598 protected:
5599 G1CollectedHeap* _g1h;
5600 RefToScanQueueSet *_queues;
5601 ParallelTaskTerminator _terminator;
5602 uint _n_workers;
5604 public:
5605 G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h,int workers, RefToScanQueueSet *task_queues) :
5606 AbstractGangTask("ParPreserveCMReferents"),
5607 _g1h(g1h),
5608 _queues(task_queues),
5609 _terminator(workers, _queues),
5610 _n_workers(workers)
5611 { }
5613 void work(uint worker_id) {
5614 ResourceMark rm;
5615 HandleMark hm;
5617 G1ParScanThreadState pss(_g1h, worker_id, NULL);
5618 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5620 pss.set_evac_failure_closure(&evac_failure_cl);
5622 assert(pss.queue_is_empty(), "both queue and overflow should be empty");
5624 G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL);
5626 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5628 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5630 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5631 // We also need to mark copied objects.
5632 copy_non_heap_cl = ©_mark_non_heap_cl;
5633 }
5635 // Is alive closure
5636 G1AlwaysAliveClosure always_alive(_g1h);
5638 // Copying keep alive closure. Applied to referent objects that need
5639 // to be copied.
5640 G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, &pss);
5642 ReferenceProcessor* rp = _g1h->ref_processor_cm();
5644 uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q();
5645 uint stride = MIN2(MAX2(_n_workers, 1U), limit);
5647 // limit is set using max_num_q() - which was set using ParallelGCThreads.
5648 // So this must be true - but assert just in case someone decides to
5649 // change the worker ids.
5650 assert(0 <= worker_id && worker_id < limit, "sanity");
5651 assert(!rp->discovery_is_atomic(), "check this code");
5653 // Select discovered lists [i, i+stride, i+2*stride,...,limit)
5654 for (uint idx = worker_id; idx < limit; idx += stride) {
5655 DiscoveredList& ref_list = rp->discovered_refs()[idx];
5657 DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive);
5658 while (iter.has_next()) {
5659 // Since discovery is not atomic for the CM ref processor, we
5660 // can see some null referent objects.
5661 iter.load_ptrs(DEBUG_ONLY(true));
5662 oop ref = iter.obj();
5664 // This will filter nulls.
5665 if (iter.is_referent_alive()) {
5666 iter.make_referent_alive();
5667 }
5668 iter.move_to_next();
5669 }
5670 }
5672 // Drain the queue - which may cause stealing
5673 G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _queues, &_terminator);
5674 drain_queue.do_void();
5675 // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure
5676 assert(pss.queue_is_empty(), "should be");
5677 }
5678 };
5680 // Weak Reference processing during an evacuation pause (part 1).
5681 void G1CollectedHeap::process_discovered_references(uint no_of_gc_workers) {
5682 double ref_proc_start = os::elapsedTime();
5684 ReferenceProcessor* rp = _ref_processor_stw;
5685 assert(rp->discovery_enabled(), "should have been enabled");
5687 // Any reference objects, in the collection set, that were 'discovered'
5688 // by the CM ref processor should have already been copied (either by
5689 // applying the external root copy closure to the discovered lists, or
5690 // by following an RSet entry).
5691 //
5692 // But some of the referents, that are in the collection set, that these
5693 // reference objects point to may not have been copied: the STW ref
5694 // processor would have seen that the reference object had already
5695 // been 'discovered' and would have skipped discovering the reference,
5696 // but would not have treated the reference object as a regular oop.
5697 // As a result the copy closure would not have been applied to the
5698 // referent object.
5699 //
5700 // We need to explicitly copy these referent objects - the references
5701 // will be processed at the end of remarking.
5702 //
5703 // We also need to do this copying before we process the reference
5704 // objects discovered by the STW ref processor in case one of these
5705 // referents points to another object which is also referenced by an
5706 // object discovered by the STW ref processor.
5708 assert(!G1CollectedHeap::use_parallel_gc_threads() ||
5709 no_of_gc_workers == workers()->active_workers(),
5710 "Need to reset active GC workers");
5712 set_par_threads(no_of_gc_workers);
5713 G1ParPreserveCMReferentsTask keep_cm_referents(this,
5714 no_of_gc_workers,
5715 _task_queues);
5717 if (G1CollectedHeap::use_parallel_gc_threads()) {
5718 workers()->run_task(&keep_cm_referents);
5719 } else {
5720 keep_cm_referents.work(0);
5721 }
5723 set_par_threads(0);
5725 // Closure to test whether a referent is alive.
5726 G1STWIsAliveClosure is_alive(this);
5728 // Even when parallel reference processing is enabled, the processing
5729 // of JNI refs is serial and performed serially by the current thread
5730 // rather than by a worker. The following PSS will be used for processing
5731 // JNI refs.
5733 // Use only a single queue for this PSS.
5734 G1ParScanThreadState pss(this, 0, NULL);
5736 // We do not embed a reference processor in the copying/scanning
5737 // closures while we're actually processing the discovered
5738 // reference objects.
5739 G1ParScanHeapEvacFailureClosure evac_failure_cl(this, &pss, NULL);
5741 pss.set_evac_failure_closure(&evac_failure_cl);
5743 assert(pss.queue_is_empty(), "pre-condition");
5745 G1ParScanExtRootClosure only_copy_non_heap_cl(this, &pss, NULL);
5747 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(this, &pss, NULL);
5749 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5751 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5752 // We also need to mark copied objects.
5753 copy_non_heap_cl = ©_mark_non_heap_cl;
5754 }
5756 // Keep alive closure.
5757 G1CopyingKeepAliveClosure keep_alive(this, copy_non_heap_cl, &pss);
5759 // Serial Complete GC closure
5760 G1STWDrainQueueClosure drain_queue(this, &pss);
5762 // Setup the soft refs policy...
5763 rp->setup_policy(false);
5765 ReferenceProcessorStats stats;
5766 if (!rp->processing_is_mt()) {
5767 // Serial reference processing...
5768 stats = rp->process_discovered_references(&is_alive,
5769 &keep_alive,
5770 &drain_queue,
5771 NULL,
5772 _gc_timer_stw,
5773 _gc_tracer_stw->gc_id());
5774 } else {
5775 // Parallel reference processing
5776 assert(rp->num_q() == no_of_gc_workers, "sanity");
5777 assert(no_of_gc_workers <= rp->max_num_q(), "sanity");
5779 G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers);
5780 stats = rp->process_discovered_references(&is_alive,
5781 &keep_alive,
5782 &drain_queue,
5783 &par_task_executor,
5784 _gc_timer_stw,
5785 _gc_tracer_stw->gc_id());
5786 }
5788 _gc_tracer_stw->report_gc_reference_stats(stats);
5790 // We have completed copying any necessary live referent objects.
5791 assert(pss.queue_is_empty(), "both queue and overflow should be empty");
5793 double ref_proc_time = os::elapsedTime() - ref_proc_start;
5794 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
5795 }
5797 // Weak Reference processing during an evacuation pause (part 2).
5798 void G1CollectedHeap::enqueue_discovered_references(uint no_of_gc_workers) {
5799 double ref_enq_start = os::elapsedTime();
5801 ReferenceProcessor* rp = _ref_processor_stw;
5802 assert(!rp->discovery_enabled(), "should have been disabled as part of processing");
5804 // Now enqueue any remaining on the discovered lists on to
5805 // the pending list.
5806 if (!rp->processing_is_mt()) {
5807 // Serial reference processing...
5808 rp->enqueue_discovered_references();
5809 } else {
5810 // Parallel reference enqueueing
5812 assert(no_of_gc_workers == workers()->active_workers(),
5813 "Need to reset active workers");
5814 assert(rp->num_q() == no_of_gc_workers, "sanity");
5815 assert(no_of_gc_workers <= rp->max_num_q(), "sanity");
5817 G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers);
5818 rp->enqueue_discovered_references(&par_task_executor);
5819 }
5821 rp->verify_no_references_recorded();
5822 assert(!rp->discovery_enabled(), "should have been disabled");
5824 // FIXME
5825 // CM's reference processing also cleans up the string and symbol tables.
5826 // Should we do that here also? We could, but it is a serial operation
5827 // and could significantly increase the pause time.
5829 double ref_enq_time = os::elapsedTime() - ref_enq_start;
5830 g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0);
5831 }
5833 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info) {
5834 _expand_heap_after_alloc_failure = true;
5835 _evacuation_failed = false;
5837 // Should G1EvacuationFailureALot be in effect for this GC?
5838 NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();)
5840 g1_rem_set()->prepare_for_oops_into_collection_set_do();
5842 // Disable the hot card cache.
5843 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
5844 hot_card_cache->reset_hot_cache_claimed_index();
5845 hot_card_cache->set_use_cache(false);
5847 uint n_workers;
5848 if (G1CollectedHeap::use_parallel_gc_threads()) {
5849 n_workers =
5850 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
5851 workers()->active_workers(),
5852 Threads::number_of_non_daemon_threads());
5853 assert(UseDynamicNumberOfGCThreads ||
5854 n_workers == workers()->total_workers(),
5855 "If not dynamic should be using all the workers");
5856 workers()->set_active_workers(n_workers);
5857 set_par_threads(n_workers);
5858 } else {
5859 assert(n_par_threads() == 0,
5860 "Should be the original non-parallel value");
5861 n_workers = 1;
5862 }
5864 G1ParTask g1_par_task(this, _task_queues);
5866 init_for_evac_failure(NULL);
5868 rem_set()->prepare_for_younger_refs_iterate(true);
5870 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
5871 double start_par_time_sec = os::elapsedTime();
5872 double end_par_time_sec;
5874 {
5875 StrongRootsScope srs(this);
5876 // InitialMark needs claim bits to keep track of the marked-through CLDs.
5877 if (g1_policy()->during_initial_mark_pause()) {
5878 ClassLoaderDataGraph::clear_claimed_marks();
5879 }
5881 if (G1CollectedHeap::use_parallel_gc_threads()) {
5882 // The individual threads will set their evac-failure closures.
5883 if (ParallelGCVerbose) G1ParScanThreadState::print_termination_stats_hdr();
5884 // These tasks use ShareHeap::_process_strong_tasks
5885 assert(UseDynamicNumberOfGCThreads ||
5886 workers()->active_workers() == workers()->total_workers(),
5887 "If not dynamic should be using all the workers");
5888 workers()->run_task(&g1_par_task);
5889 } else {
5890 g1_par_task.set_for_termination(n_workers);
5891 g1_par_task.work(0);
5892 }
5893 end_par_time_sec = os::elapsedTime();
5895 // Closing the inner scope will execute the destructor
5896 // for the StrongRootsScope object. We record the current
5897 // elapsed time before closing the scope so that time
5898 // taken for the SRS destructor is NOT included in the
5899 // reported parallel time.
5900 }
5902 double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0;
5903 g1_policy()->phase_times()->record_par_time(par_time_ms);
5905 double code_root_fixup_time_ms =
5906 (os::elapsedTime() - end_par_time_sec) * 1000.0;
5907 g1_policy()->phase_times()->record_code_root_fixup_time(code_root_fixup_time_ms);
5909 set_par_threads(0);
5911 // Process any discovered reference objects - we have
5912 // to do this _before_ we retire the GC alloc regions
5913 // as we may have to copy some 'reachable' referent
5914 // objects (and their reachable sub-graphs) that were
5915 // not copied during the pause.
5916 process_discovered_references(n_workers);
5918 // Weak root processing.
5919 {
5920 G1STWIsAliveClosure is_alive(this);
5921 G1KeepAliveClosure keep_alive(this);
5922 JNIHandles::weak_oops_do(&is_alive, &keep_alive);
5923 if (G1StringDedup::is_enabled()) {
5924 G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive);
5925 }
5926 }
5928 _allocator->release_gc_alloc_regions(n_workers, evacuation_info);
5929 g1_rem_set()->cleanup_after_oops_into_collection_set_do();
5931 // Reset and re-enable the hot card cache.
5932 // Note the counts for the cards in the regions in the
5933 // collection set are reset when the collection set is freed.
5934 hot_card_cache->reset_hot_cache();
5935 hot_card_cache->set_use_cache(true);
5937 purge_code_root_memory();
5939 if (g1_policy()->during_initial_mark_pause()) {
5940 // Reset the claim values set during marking the strong code roots
5941 reset_heap_region_claim_values();
5942 }
5944 finalize_for_evac_failure();
5946 if (evacuation_failed()) {
5947 remove_self_forwarding_pointers();
5949 // Reset the G1EvacuationFailureALot counters and flags
5950 // Note: the values are reset only when an actual
5951 // evacuation failure occurs.
5952 NOT_PRODUCT(reset_evacuation_should_fail();)
5953 }
5955 // Enqueue any remaining references remaining on the STW
5956 // reference processor's discovered lists. We need to do
5957 // this after the card table is cleaned (and verified) as
5958 // the act of enqueueing entries on to the pending list
5959 // will log these updates (and dirty their associated
5960 // cards). We need these updates logged to update any
5961 // RSets.
5962 enqueue_discovered_references(n_workers);
5964 redirty_logged_cards();
5965 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
5966 }
5968 void G1CollectedHeap::free_region(HeapRegion* hr,
5969 FreeRegionList* free_list,
5970 bool par,
5971 bool locked) {
5972 assert(!hr->is_free(), "the region should not be free");
5973 assert(!hr->is_empty(), "the region should not be empty");
5974 assert(_hrm.is_available(hr->hrm_index()), "region should be committed");
5975 assert(free_list != NULL, "pre-condition");
5977 if (G1VerifyBitmaps) {
5978 MemRegion mr(hr->bottom(), hr->end());
5979 concurrent_mark()->clearRangePrevBitmap(mr);
5980 }
5982 // Clear the card counts for this region.
5983 // Note: we only need to do this if the region is not young
5984 // (since we don't refine cards in young regions).
5985 if (!hr->is_young()) {
5986 _cg1r->hot_card_cache()->reset_card_counts(hr);
5987 }
5988 hr->hr_clear(par, true /* clear_space */, locked /* locked */);
5989 free_list->add_ordered(hr);
5990 }
5992 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
5993 FreeRegionList* free_list,
5994 bool par) {
5995 assert(hr->startsHumongous(), "this is only for starts humongous regions");
5996 assert(free_list != NULL, "pre-condition");
5998 size_t hr_capacity = hr->capacity();
5999 // We need to read this before we make the region non-humongous,
6000 // otherwise the information will be gone.
6001 uint last_index = hr->last_hc_index();
6002 hr->clear_humongous();
6003 free_region(hr, free_list, par);
6005 uint i = hr->hrm_index() + 1;
6006 while (i < last_index) {
6007 HeapRegion* curr_hr = region_at(i);
6008 assert(curr_hr->continuesHumongous(), "invariant");
6009 curr_hr->clear_humongous();
6010 free_region(curr_hr, free_list, par);
6011 i += 1;
6012 }
6013 }
6015 void G1CollectedHeap::remove_from_old_sets(const HeapRegionSetCount& old_regions_removed,
6016 const HeapRegionSetCount& humongous_regions_removed) {
6017 if (old_regions_removed.length() > 0 || humongous_regions_removed.length() > 0) {
6018 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
6019 _old_set.bulk_remove(old_regions_removed);
6020 _humongous_set.bulk_remove(humongous_regions_removed);
6021 }
6023 }
6025 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) {
6026 assert(list != NULL, "list can't be null");
6027 if (!list->is_empty()) {
6028 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
6029 _hrm.insert_list_into_free_list(list);
6030 }
6031 }
6033 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) {
6034 _allocator->decrease_used(bytes);
6035 }
6037 class G1ParCleanupCTTask : public AbstractGangTask {
6038 G1SATBCardTableModRefBS* _ct_bs;
6039 G1CollectedHeap* _g1h;
6040 HeapRegion* volatile _su_head;
6041 public:
6042 G1ParCleanupCTTask(G1SATBCardTableModRefBS* ct_bs,
6043 G1CollectedHeap* g1h) :
6044 AbstractGangTask("G1 Par Cleanup CT Task"),
6045 _ct_bs(ct_bs), _g1h(g1h) { }
6047 void work(uint worker_id) {
6048 HeapRegion* r;
6049 while (r = _g1h->pop_dirty_cards_region()) {
6050 clear_cards(r);
6051 }
6052 }
6054 void clear_cards(HeapRegion* r) {
6055 // Cards of the survivors should have already been dirtied.
6056 if (!r->is_survivor()) {
6057 _ct_bs->clear(MemRegion(r->bottom(), r->end()));
6058 }
6059 }
6060 };
6062 #ifndef PRODUCT
6063 class G1VerifyCardTableCleanup: public HeapRegionClosure {
6064 G1CollectedHeap* _g1h;
6065 G1SATBCardTableModRefBS* _ct_bs;
6066 public:
6067 G1VerifyCardTableCleanup(G1CollectedHeap* g1h, G1SATBCardTableModRefBS* ct_bs)
6068 : _g1h(g1h), _ct_bs(ct_bs) { }
6069 virtual bool doHeapRegion(HeapRegion* r) {
6070 if (r->is_survivor()) {
6071 _g1h->verify_dirty_region(r);
6072 } else {
6073 _g1h->verify_not_dirty_region(r);
6074 }
6075 return false;
6076 }
6077 };
6079 void G1CollectedHeap::verify_not_dirty_region(HeapRegion* hr) {
6080 // All of the region should be clean.
6081 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
6082 MemRegion mr(hr->bottom(), hr->end());
6083 ct_bs->verify_not_dirty_region(mr);
6084 }
6086 void G1CollectedHeap::verify_dirty_region(HeapRegion* hr) {
6087 // We cannot guarantee that [bottom(),end()] is dirty. Threads
6088 // dirty allocated blocks as they allocate them. The thread that
6089 // retires each region and replaces it with a new one will do a
6090 // maximal allocation to fill in [pre_dummy_top(),end()] but will
6091 // not dirty that area (one less thing to have to do while holding
6092 // a lock). So we can only verify that [bottom(),pre_dummy_top()]
6093 // is dirty.
6094 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
6095 MemRegion mr(hr->bottom(), hr->pre_dummy_top());
6096 if (hr->is_young()) {
6097 ct_bs->verify_g1_young_region(mr);
6098 } else {
6099 ct_bs->verify_dirty_region(mr);
6100 }
6101 }
6103 void G1CollectedHeap::verify_dirty_young_list(HeapRegion* head) {
6104 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
6105 for (HeapRegion* hr = head; hr != NULL; hr = hr->get_next_young_region()) {
6106 verify_dirty_region(hr);
6107 }
6108 }
6110 void G1CollectedHeap::verify_dirty_young_regions() {
6111 verify_dirty_young_list(_young_list->first_region());
6112 }
6114 bool G1CollectedHeap::verify_no_bits_over_tams(const char* bitmap_name, CMBitMapRO* bitmap,
6115 HeapWord* tams, HeapWord* end) {
6116 guarantee(tams <= end,
6117 err_msg("tams: "PTR_FORMAT" end: "PTR_FORMAT, tams, end));
6118 HeapWord* result = bitmap->getNextMarkedWordAddress(tams, end);
6119 if (result < end) {
6120 gclog_or_tty->cr();
6121 gclog_or_tty->print_cr("## wrong marked address on %s bitmap: "PTR_FORMAT,
6122 bitmap_name, result);
6123 gclog_or_tty->print_cr("## %s tams: "PTR_FORMAT" end: "PTR_FORMAT,
6124 bitmap_name, tams, end);
6125 return false;
6126 }
6127 return true;
6128 }
6130 bool G1CollectedHeap::verify_bitmaps(const char* caller, HeapRegion* hr) {
6131 CMBitMapRO* prev_bitmap = concurrent_mark()->prevMarkBitMap();
6132 CMBitMapRO* next_bitmap = (CMBitMapRO*) concurrent_mark()->nextMarkBitMap();
6134 HeapWord* bottom = hr->bottom();
6135 HeapWord* ptams = hr->prev_top_at_mark_start();
6136 HeapWord* ntams = hr->next_top_at_mark_start();
6137 HeapWord* end = hr->end();
6139 bool res_p = verify_no_bits_over_tams("prev", prev_bitmap, ptams, end);
6141 bool res_n = true;
6142 // We reset mark_in_progress() before we reset _cmThread->in_progress() and in this window
6143 // we do the clearing of the next bitmap concurrently. Thus, we can not verify the bitmap
6144 // if we happen to be in that state.
6145 if (mark_in_progress() || !_cmThread->in_progress()) {
6146 res_n = verify_no_bits_over_tams("next", next_bitmap, ntams, end);
6147 }
6148 if (!res_p || !res_n) {
6149 gclog_or_tty->print_cr("#### Bitmap verification failed for "HR_FORMAT,
6150 HR_FORMAT_PARAMS(hr));
6151 gclog_or_tty->print_cr("#### Caller: %s", caller);
6152 return false;
6153 }
6154 return true;
6155 }
6157 void G1CollectedHeap::check_bitmaps(const char* caller, HeapRegion* hr) {
6158 if (!G1VerifyBitmaps) return;
6160 guarantee(verify_bitmaps(caller, hr), "bitmap verification");
6161 }
6163 class G1VerifyBitmapClosure : public HeapRegionClosure {
6164 private:
6165 const char* _caller;
6166 G1CollectedHeap* _g1h;
6167 bool _failures;
6169 public:
6170 G1VerifyBitmapClosure(const char* caller, G1CollectedHeap* g1h) :
6171 _caller(caller), _g1h(g1h), _failures(false) { }
6173 bool failures() { return _failures; }
6175 virtual bool doHeapRegion(HeapRegion* hr) {
6176 if (hr->continuesHumongous()) return false;
6178 bool result = _g1h->verify_bitmaps(_caller, hr);
6179 if (!result) {
6180 _failures = true;
6181 }
6182 return false;
6183 }
6184 };
6186 void G1CollectedHeap::check_bitmaps(const char* caller) {
6187 if (!G1VerifyBitmaps) return;
6189 G1VerifyBitmapClosure cl(caller, this);
6190 heap_region_iterate(&cl);
6191 guarantee(!cl.failures(), "bitmap verification");
6192 }
6193 #endif // PRODUCT
6195 void G1CollectedHeap::cleanUpCardTable() {
6196 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
6197 double start = os::elapsedTime();
6199 {
6200 // Iterate over the dirty cards region list.
6201 G1ParCleanupCTTask cleanup_task(ct_bs, this);
6203 if (G1CollectedHeap::use_parallel_gc_threads()) {
6204 set_par_threads();
6205 workers()->run_task(&cleanup_task);
6206 set_par_threads(0);
6207 } else {
6208 while (_dirty_cards_region_list) {
6209 HeapRegion* r = _dirty_cards_region_list;
6210 cleanup_task.clear_cards(r);
6211 _dirty_cards_region_list = r->get_next_dirty_cards_region();
6212 if (_dirty_cards_region_list == r) {
6213 // The last region.
6214 _dirty_cards_region_list = NULL;
6215 }
6216 r->set_next_dirty_cards_region(NULL);
6217 }
6218 }
6219 #ifndef PRODUCT
6220 if (G1VerifyCTCleanup || VerifyAfterGC) {
6221 G1VerifyCardTableCleanup cleanup_verifier(this, ct_bs);
6222 heap_region_iterate(&cleanup_verifier);
6223 }
6224 #endif
6225 }
6227 double elapsed = os::elapsedTime() - start;
6228 g1_policy()->phase_times()->record_clear_ct_time(elapsed * 1000.0);
6229 }
6231 void G1CollectedHeap::free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info) {
6232 size_t pre_used = 0;
6233 FreeRegionList local_free_list("Local List for CSet Freeing");
6235 double young_time_ms = 0.0;
6236 double non_young_time_ms = 0.0;
6238 // Since the collection set is a superset of the the young list,
6239 // all we need to do to clear the young list is clear its
6240 // head and length, and unlink any young regions in the code below
6241 _young_list->clear();
6243 G1CollectorPolicy* policy = g1_policy();
6245 double start_sec = os::elapsedTime();
6246 bool non_young = true;
6248 HeapRegion* cur = cs_head;
6249 int age_bound = -1;
6250 size_t rs_lengths = 0;
6252 while (cur != NULL) {
6253 assert(!is_on_master_free_list(cur), "sanity");
6254 if (non_young) {
6255 if (cur->is_young()) {
6256 double end_sec = os::elapsedTime();
6257 double elapsed_ms = (end_sec - start_sec) * 1000.0;
6258 non_young_time_ms += elapsed_ms;
6260 start_sec = os::elapsedTime();
6261 non_young = false;
6262 }
6263 } else {
6264 if (!cur->is_young()) {
6265 double end_sec = os::elapsedTime();
6266 double elapsed_ms = (end_sec - start_sec) * 1000.0;
6267 young_time_ms += elapsed_ms;
6269 start_sec = os::elapsedTime();
6270 non_young = true;
6271 }
6272 }
6274 rs_lengths += cur->rem_set()->occupied_locked();
6276 HeapRegion* next = cur->next_in_collection_set();
6277 assert(cur->in_collection_set(), "bad CS");
6278 cur->set_next_in_collection_set(NULL);
6279 cur->set_in_collection_set(false);
6281 if (cur->is_young()) {
6282 int index = cur->young_index_in_cset();
6283 assert(index != -1, "invariant");
6284 assert((uint) index < policy->young_cset_region_length(), "invariant");
6285 size_t words_survived = _surviving_young_words[index];
6286 cur->record_surv_words_in_group(words_survived);
6288 // At this point the we have 'popped' cur from the collection set
6289 // (linked via next_in_collection_set()) but it is still in the
6290 // young list (linked via next_young_region()). Clear the
6291 // _next_young_region field.
6292 cur->set_next_young_region(NULL);
6293 } else {
6294 int index = cur->young_index_in_cset();
6295 assert(index == -1, "invariant");
6296 }
6298 assert( (cur->is_young() && cur->young_index_in_cset() > -1) ||
6299 (!cur->is_young() && cur->young_index_in_cset() == -1),
6300 "invariant" );
6302 if (!cur->evacuation_failed()) {
6303 MemRegion used_mr = cur->used_region();
6305 // And the region is empty.
6306 assert(!used_mr.is_empty(), "Should not have empty regions in a CS.");
6307 pre_used += cur->used();
6308 free_region(cur, &local_free_list, false /* par */, true /* locked */);
6309 } else {
6310 cur->uninstall_surv_rate_group();
6311 if (cur->is_young()) {
6312 cur->set_young_index_in_cset(-1);
6313 }
6314 cur->set_evacuation_failed(false);
6315 // The region is now considered to be old.
6316 cur->set_old();
6317 _old_set.add(cur);
6318 evacuation_info.increment_collectionset_used_after(cur->used());
6319 }
6320 cur = next;
6321 }
6323 evacuation_info.set_regions_freed(local_free_list.length());
6324 policy->record_max_rs_lengths(rs_lengths);
6325 policy->cset_regions_freed();
6327 double end_sec = os::elapsedTime();
6328 double elapsed_ms = (end_sec - start_sec) * 1000.0;
6330 if (non_young) {
6331 non_young_time_ms += elapsed_ms;
6332 } else {
6333 young_time_ms += elapsed_ms;
6334 }
6336 prepend_to_freelist(&local_free_list);
6337 decrement_summary_bytes(pre_used);
6338 policy->phase_times()->record_young_free_cset_time_ms(young_time_ms);
6339 policy->phase_times()->record_non_young_free_cset_time_ms(non_young_time_ms);
6340 }
6342 class G1FreeHumongousRegionClosure : public HeapRegionClosure {
6343 private:
6344 FreeRegionList* _free_region_list;
6345 HeapRegionSet* _proxy_set;
6346 HeapRegionSetCount _humongous_regions_removed;
6347 size_t _freed_bytes;
6348 public:
6350 G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) :
6351 _free_region_list(free_region_list), _humongous_regions_removed(), _freed_bytes(0) {
6352 }
6354 virtual bool doHeapRegion(HeapRegion* r) {
6355 if (!r->startsHumongous()) {
6356 return false;
6357 }
6359 G1CollectedHeap* g1h = G1CollectedHeap::heap();
6361 oop obj = (oop)r->bottom();
6362 CMBitMap* next_bitmap = g1h->concurrent_mark()->nextMarkBitMap();
6364 // The following checks whether the humongous object is live are sufficient.
6365 // The main additional check (in addition to having a reference from the roots
6366 // or the young gen) is whether the humongous object has a remembered set entry.
6367 //
6368 // A humongous object cannot be live if there is no remembered set for it
6369 // because:
6370 // - there can be no references from within humongous starts regions referencing
6371 // the object because we never allocate other objects into them.
6372 // (I.e. there are no intra-region references that may be missed by the
6373 // remembered set)
6374 // - as soon there is a remembered set entry to the humongous starts region
6375 // (i.e. it has "escaped" to an old object) this remembered set entry will stay
6376 // until the end of a concurrent mark.
6377 //
6378 // It is not required to check whether the object has been found dead by marking
6379 // or not, in fact it would prevent reclamation within a concurrent cycle, as
6380 // all objects allocated during that time are considered live.
6381 // SATB marking is even more conservative than the remembered set.
6382 // So if at this point in the collection there is no remembered set entry,
6383 // nobody has a reference to it.
6384 // At the start of collection we flush all refinement logs, and remembered sets
6385 // are completely up-to-date wrt to references to the humongous object.
6386 //
6387 // Other implementation considerations:
6388 // - never consider object arrays: while they are a valid target, they have not
6389 // been observed to be used as temporary objects.
6390 // - they would also pose considerable effort for cleaning up the the remembered
6391 // sets.
6392 // While this cleanup is not strictly necessary to be done (or done instantly),
6393 // given that their occurrence is very low, this saves us this additional
6394 // complexity.
6395 uint region_idx = r->hrm_index();
6396 if (g1h->humongous_is_live(region_idx) ||
6397 g1h->humongous_region_is_always_live(region_idx)) {
6399 if (G1TraceReclaimDeadHumongousObjectsAtYoungGC) {
6400 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",
6401 r->isHumongous(),
6402 region_idx,
6403 r->rem_set()->occupied(),
6404 r->rem_set()->strong_code_roots_list_length(),
6405 next_bitmap->isMarked(r->bottom()),
6406 g1h->humongous_is_live(region_idx),
6407 obj->is_objArray()
6408 );
6409 }
6411 return false;
6412 }
6414 guarantee(!obj->is_objArray(),
6415 err_msg("Eagerly reclaiming object arrays is not supported, but the object "PTR_FORMAT" is.",
6416 r->bottom()));
6418 if (G1TraceReclaimDeadHumongousObjectsAtYoungGC) {
6419 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",
6420 r->isHumongous(),
6421 r->bottom(),
6422 region_idx,
6423 r->region_num(),
6424 r->rem_set()->occupied(),
6425 r->rem_set()->strong_code_roots_list_length(),
6426 next_bitmap->isMarked(r->bottom()),
6427 g1h->humongous_is_live(region_idx),
6428 obj->is_objArray()
6429 );
6430 }
6431 // Need to clear mark bit of the humongous object if already set.
6432 if (next_bitmap->isMarked(r->bottom())) {
6433 next_bitmap->clear(r->bottom());
6434 }
6435 _freed_bytes += r->used();
6436 r->set_containing_set(NULL);
6437 _humongous_regions_removed.increment(1u, r->capacity());
6438 g1h->free_humongous_region(r, _free_region_list, false);
6440 return false;
6441 }
6443 HeapRegionSetCount& humongous_free_count() {
6444 return _humongous_regions_removed;
6445 }
6447 size_t bytes_freed() const {
6448 return _freed_bytes;
6449 }
6451 size_t humongous_reclaimed() const {
6452 return _humongous_regions_removed.length();
6453 }
6454 };
6456 void G1CollectedHeap::eagerly_reclaim_humongous_regions() {
6457 assert_at_safepoint(true);
6459 if (!G1ReclaimDeadHumongousObjectsAtYoungGC || !_has_humongous_reclaim_candidates) {
6460 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0);
6461 return;
6462 }
6464 double start_time = os::elapsedTime();
6466 FreeRegionList local_cleanup_list("Local Humongous Cleanup List");
6468 G1FreeHumongousRegionClosure cl(&local_cleanup_list);
6469 heap_region_iterate(&cl);
6471 HeapRegionSetCount empty_set;
6472 remove_from_old_sets(empty_set, cl.humongous_free_count());
6474 G1HRPrinter* hr_printer = _g1h->hr_printer();
6475 if (hr_printer->is_active()) {
6476 FreeRegionListIterator iter(&local_cleanup_list);
6477 while (iter.more_available()) {
6478 HeapRegion* hr = iter.get_next();
6479 hr_printer->cleanup(hr);
6480 }
6481 }
6483 prepend_to_freelist(&local_cleanup_list);
6484 decrement_summary_bytes(cl.bytes_freed());
6486 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0,
6487 cl.humongous_reclaimed());
6488 }
6490 // This routine is similar to the above but does not record
6491 // any policy statistics or update free lists; we are abandoning
6492 // the current incremental collection set in preparation of a
6493 // full collection. After the full GC we will start to build up
6494 // the incremental collection set again.
6495 // This is only called when we're doing a full collection
6496 // and is immediately followed by the tearing down of the young list.
6498 void G1CollectedHeap::abandon_collection_set(HeapRegion* cs_head) {
6499 HeapRegion* cur = cs_head;
6501 while (cur != NULL) {
6502 HeapRegion* next = cur->next_in_collection_set();
6503 assert(cur->in_collection_set(), "bad CS");
6504 cur->set_next_in_collection_set(NULL);
6505 cur->set_in_collection_set(false);
6506 cur->set_young_index_in_cset(-1);
6507 cur = next;
6508 }
6509 }
6511 void G1CollectedHeap::set_free_regions_coming() {
6512 if (G1ConcRegionFreeingVerbose) {
6513 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
6514 "setting free regions coming");
6515 }
6517 assert(!free_regions_coming(), "pre-condition");
6518 _free_regions_coming = true;
6519 }
6521 void G1CollectedHeap::reset_free_regions_coming() {
6522 assert(free_regions_coming(), "pre-condition");
6524 {
6525 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6526 _free_regions_coming = false;
6527 SecondaryFreeList_lock->notify_all();
6528 }
6530 if (G1ConcRegionFreeingVerbose) {
6531 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
6532 "reset free regions coming");
6533 }
6534 }
6536 void G1CollectedHeap::wait_while_free_regions_coming() {
6537 // Most of the time we won't have to wait, so let's do a quick test
6538 // first before we take the lock.
6539 if (!free_regions_coming()) {
6540 return;
6541 }
6543 if (G1ConcRegionFreeingVerbose) {
6544 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
6545 "waiting for free regions");
6546 }
6548 {
6549 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6550 while (free_regions_coming()) {
6551 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
6552 }
6553 }
6555 if (G1ConcRegionFreeingVerbose) {
6556 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
6557 "done waiting for free regions");
6558 }
6559 }
6561 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
6562 assert(heap_lock_held_for_gc(),
6563 "the heap lock should already be held by or for this thread");
6564 _young_list->push_region(hr);
6565 }
6567 class NoYoungRegionsClosure: public HeapRegionClosure {
6568 private:
6569 bool _success;
6570 public:
6571 NoYoungRegionsClosure() : _success(true) { }
6572 bool doHeapRegion(HeapRegion* r) {
6573 if (r->is_young()) {
6574 gclog_or_tty->print_cr("Region ["PTR_FORMAT", "PTR_FORMAT") tagged as young",
6575 r->bottom(), r->end());
6576 _success = false;
6577 }
6578 return false;
6579 }
6580 bool success() { return _success; }
6581 };
6583 bool G1CollectedHeap::check_young_list_empty(bool check_heap, bool check_sample) {
6584 bool ret = _young_list->check_list_empty(check_sample);
6586 if (check_heap) {
6587 NoYoungRegionsClosure closure;
6588 heap_region_iterate(&closure);
6589 ret = ret && closure.success();
6590 }
6592 return ret;
6593 }
6595 class TearDownRegionSetsClosure : public HeapRegionClosure {
6596 private:
6597 HeapRegionSet *_old_set;
6599 public:
6600 TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { }
6602 bool doHeapRegion(HeapRegion* r) {
6603 if (r->is_old()) {
6604 _old_set->remove(r);
6605 } else {
6606 // We ignore free regions, we'll empty the free list afterwards.
6607 // We ignore young regions, we'll empty the young list afterwards.
6608 // We ignore humongous regions, we're not tearing down the
6609 // humongous regions set.
6610 assert(r->is_free() || r->is_young() || r->isHumongous(),
6611 "it cannot be another type");
6612 }
6613 return false;
6614 }
6616 ~TearDownRegionSetsClosure() {
6617 assert(_old_set->is_empty(), "post-condition");
6618 }
6619 };
6621 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
6622 assert_at_safepoint(true /* should_be_vm_thread */);
6624 if (!free_list_only) {
6625 TearDownRegionSetsClosure cl(&_old_set);
6626 heap_region_iterate(&cl);
6628 // Note that emptying the _young_list is postponed and instead done as
6629 // the first step when rebuilding the regions sets again. The reason for
6630 // this is that during a full GC string deduplication needs to know if
6631 // a collected region was young or old when the full GC was initiated.
6632 }
6633 _hrm.remove_all_free_regions();
6634 }
6636 class RebuildRegionSetsClosure : public HeapRegionClosure {
6637 private:
6638 bool _free_list_only;
6639 HeapRegionSet* _old_set;
6640 HeapRegionManager* _hrm;
6641 size_t _total_used;
6643 public:
6644 RebuildRegionSetsClosure(bool free_list_only,
6645 HeapRegionSet* old_set, HeapRegionManager* hrm) :
6646 _free_list_only(free_list_only),
6647 _old_set(old_set), _hrm(hrm), _total_used(0) {
6648 assert(_hrm->num_free_regions() == 0, "pre-condition");
6649 if (!free_list_only) {
6650 assert(_old_set->is_empty(), "pre-condition");
6651 }
6652 }
6654 bool doHeapRegion(HeapRegion* r) {
6655 if (r->continuesHumongous()) {
6656 return false;
6657 }
6659 if (r->is_empty()) {
6660 // Add free regions to the free list
6661 r->set_free();
6662 r->set_allocation_context(AllocationContext::system());
6663 _hrm->insert_into_free_list(r);
6664 } else if (!_free_list_only) {
6665 assert(!r->is_young(), "we should not come across young regions");
6667 if (r->isHumongous()) {
6668 // We ignore humongous regions, we left the humongous set unchanged
6669 } else {
6670 // Objects that were compacted would have ended up on regions
6671 // that were previously old or free.
6672 assert(r->is_free() || r->is_old(), "invariant");
6673 // We now consider them old, so register as such.
6674 r->set_old();
6675 _old_set->add(r);
6676 }
6677 _total_used += r->used();
6678 }
6680 return false;
6681 }
6683 size_t total_used() {
6684 return _total_used;
6685 }
6686 };
6688 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
6689 assert_at_safepoint(true /* should_be_vm_thread */);
6691 if (!free_list_only) {
6692 _young_list->empty_list();
6693 }
6695 RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm);
6696 heap_region_iterate(&cl);
6698 if (!free_list_only) {
6699 _allocator->set_used(cl.total_used());
6700 }
6701 assert(_allocator->used_unlocked() == recalculate_used(),
6702 err_msg("inconsistent _allocator->used_unlocked(), "
6703 "value: "SIZE_FORMAT" recalculated: "SIZE_FORMAT,
6704 _allocator->used_unlocked(), recalculate_used()));
6705 }
6707 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) {
6708 _refine_cte_cl->set_concurrent(concurrent);
6709 }
6711 bool G1CollectedHeap::is_in_closed_subset(const void* p) const {
6712 HeapRegion* hr = heap_region_containing(p);
6713 return hr->is_in(p);
6714 }
6716 // Methods for the mutator alloc region
6718 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
6719 bool force) {
6720 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6721 assert(!force || g1_policy()->can_expand_young_list(),
6722 "if force is true we should be able to expand the young list");
6723 bool young_list_full = g1_policy()->is_young_list_full();
6724 if (force || !young_list_full) {
6725 HeapRegion* new_alloc_region = new_region(word_size,
6726 false /* is_old */,
6727 false /* do_expand */);
6728 if (new_alloc_region != NULL) {
6729 set_region_short_lived_locked(new_alloc_region);
6730 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Eden, young_list_full);
6731 check_bitmaps("Mutator Region Allocation", new_alloc_region);
6732 return new_alloc_region;
6733 }
6734 }
6735 return NULL;
6736 }
6738 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
6739 size_t allocated_bytes) {
6740 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6741 assert(alloc_region->is_eden(), "all mutator alloc regions should be eden");
6743 g1_policy()->add_region_to_incremental_cset_lhs(alloc_region);
6744 _allocator->increase_used(allocated_bytes);
6745 _hr_printer.retire(alloc_region);
6746 // We update the eden sizes here, when the region is retired,
6747 // instead of when it's allocated, since this is the point that its
6748 // used space has been recored in _summary_bytes_used.
6749 g1mm()->update_eden_size();
6750 }
6752 void G1CollectedHeap::set_par_threads() {
6753 // Don't change the number of workers. Use the value previously set
6754 // in the workgroup.
6755 assert(G1CollectedHeap::use_parallel_gc_threads(), "shouldn't be here otherwise");
6756 uint n_workers = workers()->active_workers();
6757 assert(UseDynamicNumberOfGCThreads ||
6758 n_workers == workers()->total_workers(),
6759 "Otherwise should be using the total number of workers");
6760 if (n_workers == 0) {
6761 assert(false, "Should have been set in prior evacuation pause.");
6762 n_workers = ParallelGCThreads;
6763 workers()->set_active_workers(n_workers);
6764 }
6765 set_par_threads(n_workers);
6766 }
6768 // Methods for the GC alloc regions
6770 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size,
6771 uint count,
6772 GCAllocPurpose ap) {
6773 assert(FreeList_lock->owned_by_self(), "pre-condition");
6775 if (count < g1_policy()->max_regions(ap)) {
6776 bool survivor = (ap == GCAllocForSurvived);
6777 HeapRegion* new_alloc_region = new_region(word_size,
6778 !survivor,
6779 true /* do_expand */);
6780 if (new_alloc_region != NULL) {
6781 // We really only need to do this for old regions given that we
6782 // should never scan survivors. But it doesn't hurt to do it
6783 // for survivors too.
6784 new_alloc_region->record_top_and_timestamp();
6785 if (survivor) {
6786 new_alloc_region->set_survivor();
6787 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Survivor);
6788 check_bitmaps("Survivor Region Allocation", new_alloc_region);
6789 } else {
6790 new_alloc_region->set_old();
6791 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Old);
6792 check_bitmaps("Old Region Allocation", new_alloc_region);
6793 }
6794 bool during_im = g1_policy()->during_initial_mark_pause();
6795 new_alloc_region->note_start_of_copying(during_im);
6796 return new_alloc_region;
6797 } else {
6798 g1_policy()->note_alloc_region_limit_reached(ap);
6799 }
6800 }
6801 return NULL;
6802 }
6804 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
6805 size_t allocated_bytes,
6806 GCAllocPurpose ap) {
6807 bool during_im = g1_policy()->during_initial_mark_pause();
6808 alloc_region->note_end_of_copying(during_im);
6809 g1_policy()->record_bytes_copied_during_gc(allocated_bytes);
6810 if (ap == GCAllocForSurvived) {
6811 young_list()->add_survivor_region(alloc_region);
6812 } else {
6813 _old_set.add(alloc_region);
6814 }
6815 _hr_printer.retire(alloc_region);
6816 }
6818 // Heap region set verification
6820 class VerifyRegionListsClosure : public HeapRegionClosure {
6821 private:
6822 HeapRegionSet* _old_set;
6823 HeapRegionSet* _humongous_set;
6824 HeapRegionManager* _hrm;
6826 public:
6827 HeapRegionSetCount _old_count;
6828 HeapRegionSetCount _humongous_count;
6829 HeapRegionSetCount _free_count;
6831 VerifyRegionListsClosure(HeapRegionSet* old_set,
6832 HeapRegionSet* humongous_set,
6833 HeapRegionManager* hrm) :
6834 _old_set(old_set), _humongous_set(humongous_set), _hrm(hrm),
6835 _old_count(), _humongous_count(), _free_count(){ }
6837 bool doHeapRegion(HeapRegion* hr) {
6838 if (hr->continuesHumongous()) {
6839 return false;
6840 }
6842 if (hr->is_young()) {
6843 // TODO
6844 } else if (hr->startsHumongous()) {
6845 assert(hr->containing_set() == _humongous_set, err_msg("Heap region %u is starts humongous but not in humongous set.", hr->hrm_index()));
6846 _humongous_count.increment(1u, hr->capacity());
6847 } else if (hr->is_empty()) {
6848 assert(_hrm->is_free(hr), err_msg("Heap region %u is empty but not on the free list.", hr->hrm_index()));
6849 _free_count.increment(1u, hr->capacity());
6850 } else if (hr->is_old()) {
6851 assert(hr->containing_set() == _old_set, err_msg("Heap region %u is old but not in the old set.", hr->hrm_index()));
6852 _old_count.increment(1u, hr->capacity());
6853 } else {
6854 ShouldNotReachHere();
6855 }
6856 return false;
6857 }
6859 void verify_counts(HeapRegionSet* old_set, HeapRegionSet* humongous_set, HeapRegionManager* free_list) {
6860 guarantee(old_set->length() == _old_count.length(), err_msg("Old set count mismatch. Expected %u, actual %u.", old_set->length(), _old_count.length()));
6861 guarantee(old_set->total_capacity_bytes() == _old_count.capacity(), err_msg("Old set capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
6862 old_set->total_capacity_bytes(), _old_count.capacity()));
6864 guarantee(humongous_set->length() == _humongous_count.length(), err_msg("Hum set count mismatch. Expected %u, actual %u.", humongous_set->length(), _humongous_count.length()));
6865 guarantee(humongous_set->total_capacity_bytes() == _humongous_count.capacity(), err_msg("Hum set capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
6866 humongous_set->total_capacity_bytes(), _humongous_count.capacity()));
6868 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()));
6869 guarantee(free_list->total_capacity_bytes() == _free_count.capacity(), err_msg("Free list capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
6870 free_list->total_capacity_bytes(), _free_count.capacity()));
6871 }
6872 };
6874 void G1CollectedHeap::verify_region_sets() {
6875 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6877 // First, check the explicit lists.
6878 _hrm.verify();
6879 {
6880 // Given that a concurrent operation might be adding regions to
6881 // the secondary free list we have to take the lock before
6882 // verifying it.
6883 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6884 _secondary_free_list.verify_list();
6885 }
6887 // If a concurrent region freeing operation is in progress it will
6888 // be difficult to correctly attributed any free regions we come
6889 // across to the correct free list given that they might belong to
6890 // one of several (free_list, secondary_free_list, any local lists,
6891 // etc.). So, if that's the case we will skip the rest of the
6892 // verification operation. Alternatively, waiting for the concurrent
6893 // operation to complete will have a non-trivial effect on the GC's
6894 // operation (no concurrent operation will last longer than the
6895 // interval between two calls to verification) and it might hide
6896 // any issues that we would like to catch during testing.
6897 if (free_regions_coming()) {
6898 return;
6899 }
6901 // Make sure we append the secondary_free_list on the free_list so
6902 // that all free regions we will come across can be safely
6903 // attributed to the free_list.
6904 append_secondary_free_list_if_not_empty_with_lock();
6906 // Finally, make sure that the region accounting in the lists is
6907 // consistent with what we see in the heap.
6909 VerifyRegionListsClosure cl(&_old_set, &_humongous_set, &_hrm);
6910 heap_region_iterate(&cl);
6911 cl.verify_counts(&_old_set, &_humongous_set, &_hrm);
6912 }
6914 // Optimized nmethod scanning
6916 class RegisterNMethodOopClosure: public OopClosure {
6917 G1CollectedHeap* _g1h;
6918 nmethod* _nm;
6920 template <class T> void do_oop_work(T* p) {
6921 T heap_oop = oopDesc::load_heap_oop(p);
6922 if (!oopDesc::is_null(heap_oop)) {
6923 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
6924 HeapRegion* hr = _g1h->heap_region_containing(obj);
6925 assert(!hr->continuesHumongous(),
6926 err_msg("trying to add code root "PTR_FORMAT" in continuation of humongous region "HR_FORMAT
6927 " starting at "HR_FORMAT,
6928 _nm, HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())));
6930 // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries.
6931 hr->add_strong_code_root_locked(_nm);
6932 }
6933 }
6935 public:
6936 RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
6937 _g1h(g1h), _nm(nm) {}
6939 void do_oop(oop* p) { do_oop_work(p); }
6940 void do_oop(narrowOop* p) { do_oop_work(p); }
6941 };
6943 class UnregisterNMethodOopClosure: public OopClosure {
6944 G1CollectedHeap* _g1h;
6945 nmethod* _nm;
6947 template <class T> void do_oop_work(T* p) {
6948 T heap_oop = oopDesc::load_heap_oop(p);
6949 if (!oopDesc::is_null(heap_oop)) {
6950 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
6951 HeapRegion* hr = _g1h->heap_region_containing(obj);
6952 assert(!hr->continuesHumongous(),
6953 err_msg("trying to remove code root "PTR_FORMAT" in continuation of humongous region "HR_FORMAT
6954 " starting at "HR_FORMAT,
6955 _nm, HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())));
6957 hr->remove_strong_code_root(_nm);
6958 }
6959 }
6961 public:
6962 UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
6963 _g1h(g1h), _nm(nm) {}
6965 void do_oop(oop* p) { do_oop_work(p); }
6966 void do_oop(narrowOop* p) { do_oop_work(p); }
6967 };
6969 void G1CollectedHeap::register_nmethod(nmethod* nm) {
6970 CollectedHeap::register_nmethod(nm);
6972 guarantee(nm != NULL, "sanity");
6973 RegisterNMethodOopClosure reg_cl(this, nm);
6974 nm->oops_do(®_cl);
6975 }
6977 void G1CollectedHeap::unregister_nmethod(nmethod* nm) {
6978 CollectedHeap::unregister_nmethod(nm);
6980 guarantee(nm != NULL, "sanity");
6981 UnregisterNMethodOopClosure reg_cl(this, nm);
6982 nm->oops_do(®_cl, true);
6983 }
6985 void G1CollectedHeap::purge_code_root_memory() {
6986 double purge_start = os::elapsedTime();
6987 G1CodeRootSet::purge();
6988 double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0;
6989 g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms);
6990 }
6992 class RebuildStrongCodeRootClosure: public CodeBlobClosure {
6993 G1CollectedHeap* _g1h;
6995 public:
6996 RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) :
6997 _g1h(g1h) {}
6999 void do_code_blob(CodeBlob* cb) {
7000 nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL;
7001 if (nm == NULL) {
7002 return;
7003 }
7005 if (ScavengeRootsInCode) {
7006 _g1h->register_nmethod(nm);
7007 }
7008 }
7009 };
7011 void G1CollectedHeap::rebuild_strong_code_roots() {
7012 RebuildStrongCodeRootClosure blob_cl(this);
7013 CodeCache::blobs_do(&blob_cl);
7014 }