Mon, 20 Oct 2014 10:18:17 +0200
8058568: GC cleanup phase can cause G1 skipping a System.gc()
Summary: Marking G1 FullGC as a _full collection and passing down the correct before count.
Reviewed-by: brutisso, mgerdin
1 /*
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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5 * This code is free software; you can redistribute it and/or modify it
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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 unsigned int full_gc_count_before;
2482 bool retry_gc;
2484 do {
2485 retry_gc = false;
2487 {
2488 MutexLocker ml(Heap_lock);
2490 // Read the GC count while holding the Heap_lock
2491 gc_count_before = total_collections();
2492 full_gc_count_before = total_full_collections();
2493 old_marking_count_before = _old_marking_cycles_started;
2494 }
2496 if (should_do_concurrent_full_gc(cause)) {
2497 // Schedule an initial-mark evacuation pause that will start a
2498 // concurrent cycle. We're setting word_size to 0 which means that
2499 // we are not requesting a post-GC allocation.
2500 VM_G1IncCollectionPause op(gc_count_before,
2501 0, /* word_size */
2502 true, /* should_initiate_conc_mark */
2503 g1_policy()->max_pause_time_ms(),
2504 cause);
2505 op.set_allocation_context(AllocationContext::current());
2507 VMThread::execute(&op);
2508 if (!op.pause_succeeded()) {
2509 if (old_marking_count_before == _old_marking_cycles_started) {
2510 retry_gc = op.should_retry_gc();
2511 } else {
2512 // A Full GC happened while we were trying to schedule the
2513 // initial-mark GC. No point in starting a new cycle given
2514 // that the whole heap was collected anyway.
2515 }
2517 if (retry_gc) {
2518 if (GC_locker::is_active_and_needs_gc()) {
2519 GC_locker::stall_until_clear();
2520 }
2521 }
2522 }
2523 } else {
2524 if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc
2525 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2527 // Schedule a standard evacuation pause. We're setting word_size
2528 // to 0 which means that we are not requesting a post-GC allocation.
2529 VM_G1IncCollectionPause op(gc_count_before,
2530 0, /* word_size */
2531 false, /* should_initiate_conc_mark */
2532 g1_policy()->max_pause_time_ms(),
2533 cause);
2534 VMThread::execute(&op);
2535 } else {
2536 // Schedule a Full GC.
2537 VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause);
2538 VMThread::execute(&op);
2539 }
2540 }
2541 } while (retry_gc);
2542 }
2544 bool G1CollectedHeap::is_in(const void* p) const {
2545 if (_hrm.reserved().contains(p)) {
2546 // Given that we know that p is in the reserved space,
2547 // heap_region_containing_raw() should successfully
2548 // return the containing region.
2549 HeapRegion* hr = heap_region_containing_raw(p);
2550 return hr->is_in(p);
2551 } else {
2552 return false;
2553 }
2554 }
2556 #ifdef ASSERT
2557 bool G1CollectedHeap::is_in_exact(const void* p) const {
2558 bool contains = reserved_region().contains(p);
2559 bool available = _hrm.is_available(addr_to_region((HeapWord*)p));
2560 if (contains && available) {
2561 return true;
2562 } else {
2563 return false;
2564 }
2565 }
2566 #endif
2568 // Iteration functions.
2570 // Applies an ExtendedOopClosure onto all references of objects within a HeapRegion.
2572 class IterateOopClosureRegionClosure: public HeapRegionClosure {
2573 ExtendedOopClosure* _cl;
2574 public:
2575 IterateOopClosureRegionClosure(ExtendedOopClosure* cl) : _cl(cl) {}
2576 bool doHeapRegion(HeapRegion* r) {
2577 if (!r->continuesHumongous()) {
2578 r->oop_iterate(_cl);
2579 }
2580 return false;
2581 }
2582 };
2584 void G1CollectedHeap::oop_iterate(ExtendedOopClosure* cl) {
2585 IterateOopClosureRegionClosure blk(cl);
2586 heap_region_iterate(&blk);
2587 }
2589 // Iterates an ObjectClosure over all objects within a HeapRegion.
2591 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2592 ObjectClosure* _cl;
2593 public:
2594 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2595 bool doHeapRegion(HeapRegion* r) {
2596 if (! r->continuesHumongous()) {
2597 r->object_iterate(_cl);
2598 }
2599 return false;
2600 }
2601 };
2603 void G1CollectedHeap::object_iterate(ObjectClosure* cl) {
2604 IterateObjectClosureRegionClosure blk(cl);
2605 heap_region_iterate(&blk);
2606 }
2608 // Calls a SpaceClosure on a HeapRegion.
2610 class SpaceClosureRegionClosure: public HeapRegionClosure {
2611 SpaceClosure* _cl;
2612 public:
2613 SpaceClosureRegionClosure(SpaceClosure* cl) : _cl(cl) {}
2614 bool doHeapRegion(HeapRegion* r) {
2615 _cl->do_space(r);
2616 return false;
2617 }
2618 };
2620 void G1CollectedHeap::space_iterate(SpaceClosure* cl) {
2621 SpaceClosureRegionClosure blk(cl);
2622 heap_region_iterate(&blk);
2623 }
2625 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2626 _hrm.iterate(cl);
2627 }
2629 void
2630 G1CollectedHeap::heap_region_par_iterate_chunked(HeapRegionClosure* cl,
2631 uint worker_id,
2632 uint num_workers,
2633 jint claim_value) const {
2634 _hrm.par_iterate(cl, worker_id, num_workers, claim_value);
2635 }
2637 class ResetClaimValuesClosure: public HeapRegionClosure {
2638 public:
2639 bool doHeapRegion(HeapRegion* r) {
2640 r->set_claim_value(HeapRegion::InitialClaimValue);
2641 return false;
2642 }
2643 };
2645 void G1CollectedHeap::reset_heap_region_claim_values() {
2646 ResetClaimValuesClosure blk;
2647 heap_region_iterate(&blk);
2648 }
2650 void G1CollectedHeap::reset_cset_heap_region_claim_values() {
2651 ResetClaimValuesClosure blk;
2652 collection_set_iterate(&blk);
2653 }
2655 #ifdef ASSERT
2656 // This checks whether all regions in the heap have the correct claim
2657 // value. I also piggy-backed on this a check to ensure that the
2658 // humongous_start_region() information on "continues humongous"
2659 // regions is correct.
2661 class CheckClaimValuesClosure : public HeapRegionClosure {
2662 private:
2663 jint _claim_value;
2664 uint _failures;
2665 HeapRegion* _sh_region;
2667 public:
2668 CheckClaimValuesClosure(jint claim_value) :
2669 _claim_value(claim_value), _failures(0), _sh_region(NULL) { }
2670 bool doHeapRegion(HeapRegion* r) {
2671 if (r->claim_value() != _claim_value) {
2672 gclog_or_tty->print_cr("Region " HR_FORMAT ", "
2673 "claim value = %d, should be %d",
2674 HR_FORMAT_PARAMS(r),
2675 r->claim_value(), _claim_value);
2676 ++_failures;
2677 }
2678 if (!r->isHumongous()) {
2679 _sh_region = NULL;
2680 } else if (r->startsHumongous()) {
2681 _sh_region = r;
2682 } else if (r->continuesHumongous()) {
2683 if (r->humongous_start_region() != _sh_region) {
2684 gclog_or_tty->print_cr("Region " HR_FORMAT ", "
2685 "HS = "PTR_FORMAT", should be "PTR_FORMAT,
2686 HR_FORMAT_PARAMS(r),
2687 r->humongous_start_region(),
2688 _sh_region);
2689 ++_failures;
2690 }
2691 }
2692 return false;
2693 }
2694 uint failures() { return _failures; }
2695 };
2697 bool G1CollectedHeap::check_heap_region_claim_values(jint claim_value) {
2698 CheckClaimValuesClosure cl(claim_value);
2699 heap_region_iterate(&cl);
2700 return cl.failures() == 0;
2701 }
2703 class CheckClaimValuesInCSetHRClosure: public HeapRegionClosure {
2704 private:
2705 jint _claim_value;
2706 uint _failures;
2708 public:
2709 CheckClaimValuesInCSetHRClosure(jint claim_value) :
2710 _claim_value(claim_value), _failures(0) { }
2712 uint failures() { return _failures; }
2714 bool doHeapRegion(HeapRegion* hr) {
2715 assert(hr->in_collection_set(), "how?");
2716 assert(!hr->isHumongous(), "H-region in CSet");
2717 if (hr->claim_value() != _claim_value) {
2718 gclog_or_tty->print_cr("CSet Region " HR_FORMAT ", "
2719 "claim value = %d, should be %d",
2720 HR_FORMAT_PARAMS(hr),
2721 hr->claim_value(), _claim_value);
2722 _failures += 1;
2723 }
2724 return false;
2725 }
2726 };
2728 bool G1CollectedHeap::check_cset_heap_region_claim_values(jint claim_value) {
2729 CheckClaimValuesInCSetHRClosure cl(claim_value);
2730 collection_set_iterate(&cl);
2731 return cl.failures() == 0;
2732 }
2733 #endif // ASSERT
2735 // Clear the cached CSet starting regions and (more importantly)
2736 // the time stamps. Called when we reset the GC time stamp.
2737 void G1CollectedHeap::clear_cset_start_regions() {
2738 assert(_worker_cset_start_region != NULL, "sanity");
2739 assert(_worker_cset_start_region_time_stamp != NULL, "sanity");
2741 int n_queues = MAX2((int)ParallelGCThreads, 1);
2742 for (int i = 0; i < n_queues; i++) {
2743 _worker_cset_start_region[i] = NULL;
2744 _worker_cset_start_region_time_stamp[i] = 0;
2745 }
2746 }
2748 // Given the id of a worker, obtain or calculate a suitable
2749 // starting region for iterating over the current collection set.
2750 HeapRegion* G1CollectedHeap::start_cset_region_for_worker(uint worker_i) {
2751 assert(get_gc_time_stamp() > 0, "should have been updated by now");
2753 HeapRegion* result = NULL;
2754 unsigned gc_time_stamp = get_gc_time_stamp();
2756 if (_worker_cset_start_region_time_stamp[worker_i] == gc_time_stamp) {
2757 // Cached starting region for current worker was set
2758 // during the current pause - so it's valid.
2759 // Note: the cached starting heap region may be NULL
2760 // (when the collection set is empty).
2761 result = _worker_cset_start_region[worker_i];
2762 assert(result == NULL || result->in_collection_set(), "sanity");
2763 return result;
2764 }
2766 // The cached entry was not valid so let's calculate
2767 // a suitable starting heap region for this worker.
2769 // We want the parallel threads to start their collection
2770 // set iteration at different collection set regions to
2771 // avoid contention.
2772 // If we have:
2773 // n collection set regions
2774 // p threads
2775 // Then thread t will start at region floor ((t * n) / p)
2777 result = g1_policy()->collection_set();
2778 if (G1CollectedHeap::use_parallel_gc_threads()) {
2779 uint cs_size = g1_policy()->cset_region_length();
2780 uint active_workers = workers()->active_workers();
2781 assert(UseDynamicNumberOfGCThreads ||
2782 active_workers == workers()->total_workers(),
2783 "Unless dynamic should use total workers");
2785 uint end_ind = (cs_size * worker_i) / active_workers;
2786 uint start_ind = 0;
2788 if (worker_i > 0 &&
2789 _worker_cset_start_region_time_stamp[worker_i - 1] == gc_time_stamp) {
2790 // Previous workers starting region is valid
2791 // so let's iterate from there
2792 start_ind = (cs_size * (worker_i - 1)) / active_workers;
2793 result = _worker_cset_start_region[worker_i - 1];
2794 }
2796 for (uint i = start_ind; i < end_ind; i++) {
2797 result = result->next_in_collection_set();
2798 }
2799 }
2801 // Note: the calculated starting heap region may be NULL
2802 // (when the collection set is empty).
2803 assert(result == NULL || result->in_collection_set(), "sanity");
2804 assert(_worker_cset_start_region_time_stamp[worker_i] != gc_time_stamp,
2805 "should be updated only once per pause");
2806 _worker_cset_start_region[worker_i] = result;
2807 OrderAccess::storestore();
2808 _worker_cset_start_region_time_stamp[worker_i] = gc_time_stamp;
2809 return result;
2810 }
2812 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) {
2813 HeapRegion* r = g1_policy()->collection_set();
2814 while (r != NULL) {
2815 HeapRegion* next = r->next_in_collection_set();
2816 if (cl->doHeapRegion(r)) {
2817 cl->incomplete();
2818 return;
2819 }
2820 r = next;
2821 }
2822 }
2824 void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r,
2825 HeapRegionClosure *cl) {
2826 if (r == NULL) {
2827 // The CSet is empty so there's nothing to do.
2828 return;
2829 }
2831 assert(r->in_collection_set(),
2832 "Start region must be a member of the collection set.");
2833 HeapRegion* cur = r;
2834 while (cur != NULL) {
2835 HeapRegion* next = cur->next_in_collection_set();
2836 if (cl->doHeapRegion(cur) && false) {
2837 cl->incomplete();
2838 return;
2839 }
2840 cur = next;
2841 }
2842 cur = g1_policy()->collection_set();
2843 while (cur != r) {
2844 HeapRegion* next = cur->next_in_collection_set();
2845 if (cl->doHeapRegion(cur) && false) {
2846 cl->incomplete();
2847 return;
2848 }
2849 cur = next;
2850 }
2851 }
2853 HeapRegion* G1CollectedHeap::next_compaction_region(const HeapRegion* from) const {
2854 HeapRegion* result = _hrm.next_region_in_heap(from);
2855 while (result != NULL && result->isHumongous()) {
2856 result = _hrm.next_region_in_heap(result);
2857 }
2858 return result;
2859 }
2861 Space* G1CollectedHeap::space_containing(const void* addr) const {
2862 return heap_region_containing(addr);
2863 }
2865 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2866 Space* sp = space_containing(addr);
2867 return sp->block_start(addr);
2868 }
2870 size_t G1CollectedHeap::block_size(const HeapWord* addr) const {
2871 Space* sp = space_containing(addr);
2872 return sp->block_size(addr);
2873 }
2875 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2876 Space* sp = space_containing(addr);
2877 return sp->block_is_obj(addr);
2878 }
2880 bool G1CollectedHeap::supports_tlab_allocation() const {
2881 return true;
2882 }
2884 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
2885 return (_g1_policy->young_list_target_length() - young_list()->survivor_length()) * HeapRegion::GrainBytes;
2886 }
2888 size_t G1CollectedHeap::tlab_used(Thread* ignored) const {
2889 return young_list()->eden_used_bytes();
2890 }
2892 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size
2893 // must be smaller than the humongous object limit.
2894 size_t G1CollectedHeap::max_tlab_size() const {
2895 return align_size_down(_humongous_object_threshold_in_words - 1, MinObjAlignment);
2896 }
2898 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
2899 // Return the remaining space in the cur alloc region, but not less than
2900 // the min TLAB size.
2902 // Also, this value can be at most the humongous object threshold,
2903 // since we can't allow tlabs to grow big enough to accommodate
2904 // humongous objects.
2906 HeapRegion* hr = _allocator->mutator_alloc_region(AllocationContext::current())->get();
2907 size_t max_tlab = max_tlab_size() * wordSize;
2908 if (hr == NULL) {
2909 return max_tlab;
2910 } else {
2911 return MIN2(MAX2(hr->free(), (size_t) MinTLABSize), max_tlab);
2912 }
2913 }
2915 size_t G1CollectedHeap::max_capacity() const {
2916 return _hrm.reserved().byte_size();
2917 }
2919 jlong G1CollectedHeap::millis_since_last_gc() {
2920 // assert(false, "NYI");
2921 return 0;
2922 }
2924 void G1CollectedHeap::prepare_for_verify() {
2925 if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) {
2926 ensure_parsability(false);
2927 }
2928 g1_rem_set()->prepare_for_verify();
2929 }
2931 bool G1CollectedHeap::allocated_since_marking(oop obj, HeapRegion* hr,
2932 VerifyOption vo) {
2933 switch (vo) {
2934 case VerifyOption_G1UsePrevMarking:
2935 return hr->obj_allocated_since_prev_marking(obj);
2936 case VerifyOption_G1UseNextMarking:
2937 return hr->obj_allocated_since_next_marking(obj);
2938 case VerifyOption_G1UseMarkWord:
2939 return false;
2940 default:
2941 ShouldNotReachHere();
2942 }
2943 return false; // keep some compilers happy
2944 }
2946 HeapWord* G1CollectedHeap::top_at_mark_start(HeapRegion* hr, VerifyOption vo) {
2947 switch (vo) {
2948 case VerifyOption_G1UsePrevMarking: return hr->prev_top_at_mark_start();
2949 case VerifyOption_G1UseNextMarking: return hr->next_top_at_mark_start();
2950 case VerifyOption_G1UseMarkWord: return NULL;
2951 default: ShouldNotReachHere();
2952 }
2953 return NULL; // keep some compilers happy
2954 }
2956 bool G1CollectedHeap::is_marked(oop obj, VerifyOption vo) {
2957 switch (vo) {
2958 case VerifyOption_G1UsePrevMarking: return isMarkedPrev(obj);
2959 case VerifyOption_G1UseNextMarking: return isMarkedNext(obj);
2960 case VerifyOption_G1UseMarkWord: return obj->is_gc_marked();
2961 default: ShouldNotReachHere();
2962 }
2963 return false; // keep some compilers happy
2964 }
2966 const char* G1CollectedHeap::top_at_mark_start_str(VerifyOption vo) {
2967 switch (vo) {
2968 case VerifyOption_G1UsePrevMarking: return "PTAMS";
2969 case VerifyOption_G1UseNextMarking: return "NTAMS";
2970 case VerifyOption_G1UseMarkWord: return "NONE";
2971 default: ShouldNotReachHere();
2972 }
2973 return NULL; // keep some compilers happy
2974 }
2976 class VerifyRootsClosure: public OopClosure {
2977 private:
2978 G1CollectedHeap* _g1h;
2979 VerifyOption _vo;
2980 bool _failures;
2981 public:
2982 // _vo == UsePrevMarking -> use "prev" marking information,
2983 // _vo == UseNextMarking -> use "next" marking information,
2984 // _vo == UseMarkWord -> use mark word from object header.
2985 VerifyRootsClosure(VerifyOption vo) :
2986 _g1h(G1CollectedHeap::heap()),
2987 _vo(vo),
2988 _failures(false) { }
2990 bool failures() { return _failures; }
2992 template <class T> void do_oop_nv(T* p) {
2993 T heap_oop = oopDesc::load_heap_oop(p);
2994 if (!oopDesc::is_null(heap_oop)) {
2995 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
2996 if (_g1h->is_obj_dead_cond(obj, _vo)) {
2997 gclog_or_tty->print_cr("Root location "PTR_FORMAT" "
2998 "points to dead obj "PTR_FORMAT, p, (void*) obj);
2999 if (_vo == VerifyOption_G1UseMarkWord) {
3000 gclog_or_tty->print_cr(" Mark word: "PTR_FORMAT, (void*)(obj->mark()));
3001 }
3002 obj->print_on(gclog_or_tty);
3003 _failures = true;
3004 }
3005 }
3006 }
3008 void do_oop(oop* p) { do_oop_nv(p); }
3009 void do_oop(narrowOop* p) { do_oop_nv(p); }
3010 };
3012 class G1VerifyCodeRootOopClosure: public OopClosure {
3013 G1CollectedHeap* _g1h;
3014 OopClosure* _root_cl;
3015 nmethod* _nm;
3016 VerifyOption _vo;
3017 bool _failures;
3019 template <class T> void do_oop_work(T* p) {
3020 // First verify that this root is live
3021 _root_cl->do_oop(p);
3023 if (!G1VerifyHeapRegionCodeRoots) {
3024 // We're not verifying the code roots attached to heap region.
3025 return;
3026 }
3028 // Don't check the code roots during marking verification in a full GC
3029 if (_vo == VerifyOption_G1UseMarkWord) {
3030 return;
3031 }
3033 // Now verify that the current nmethod (which contains p) is
3034 // in the code root list of the heap region containing the
3035 // object referenced by p.
3037 T heap_oop = oopDesc::load_heap_oop(p);
3038 if (!oopDesc::is_null(heap_oop)) {
3039 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
3041 // Now fetch the region containing the object
3042 HeapRegion* hr = _g1h->heap_region_containing(obj);
3043 HeapRegionRemSet* hrrs = hr->rem_set();
3044 // Verify that the strong code root list for this region
3045 // contains the nmethod
3046 if (!hrrs->strong_code_roots_list_contains(_nm)) {
3047 gclog_or_tty->print_cr("Code root location "PTR_FORMAT" "
3048 "from nmethod "PTR_FORMAT" not in strong "
3049 "code roots for region ["PTR_FORMAT","PTR_FORMAT")",
3050 p, _nm, hr->bottom(), hr->end());
3051 _failures = true;
3052 }
3053 }
3054 }
3056 public:
3057 G1VerifyCodeRootOopClosure(G1CollectedHeap* g1h, OopClosure* root_cl, VerifyOption vo):
3058 _g1h(g1h), _root_cl(root_cl), _vo(vo), _nm(NULL), _failures(false) {}
3060 void do_oop(oop* p) { do_oop_work(p); }
3061 void do_oop(narrowOop* p) { do_oop_work(p); }
3063 void set_nmethod(nmethod* nm) { _nm = nm; }
3064 bool failures() { return _failures; }
3065 };
3067 class G1VerifyCodeRootBlobClosure: public CodeBlobClosure {
3068 G1VerifyCodeRootOopClosure* _oop_cl;
3070 public:
3071 G1VerifyCodeRootBlobClosure(G1VerifyCodeRootOopClosure* oop_cl):
3072 _oop_cl(oop_cl) {}
3074 void do_code_blob(CodeBlob* cb) {
3075 nmethod* nm = cb->as_nmethod_or_null();
3076 if (nm != NULL) {
3077 _oop_cl->set_nmethod(nm);
3078 nm->oops_do(_oop_cl);
3079 }
3080 }
3081 };
3083 class YoungRefCounterClosure : public OopClosure {
3084 G1CollectedHeap* _g1h;
3085 int _count;
3086 public:
3087 YoungRefCounterClosure(G1CollectedHeap* g1h) : _g1h(g1h), _count(0) {}
3088 void do_oop(oop* p) { if (_g1h->is_in_young(*p)) { _count++; } }
3089 void do_oop(narrowOop* p) { ShouldNotReachHere(); }
3091 int count() { return _count; }
3092 void reset_count() { _count = 0; };
3093 };
3095 class VerifyKlassClosure: public KlassClosure {
3096 YoungRefCounterClosure _young_ref_counter_closure;
3097 OopClosure *_oop_closure;
3098 public:
3099 VerifyKlassClosure(G1CollectedHeap* g1h, OopClosure* cl) : _young_ref_counter_closure(g1h), _oop_closure(cl) {}
3100 void do_klass(Klass* k) {
3101 k->oops_do(_oop_closure);
3103 _young_ref_counter_closure.reset_count();
3104 k->oops_do(&_young_ref_counter_closure);
3105 if (_young_ref_counter_closure.count() > 0) {
3106 guarantee(k->has_modified_oops(), err_msg("Klass %p, has young refs but is not dirty.", k));
3107 }
3108 }
3109 };
3111 class VerifyLivenessOopClosure: public OopClosure {
3112 G1CollectedHeap* _g1h;
3113 VerifyOption _vo;
3114 public:
3115 VerifyLivenessOopClosure(G1CollectedHeap* g1h, VerifyOption vo):
3116 _g1h(g1h), _vo(vo)
3117 { }
3118 void do_oop(narrowOop *p) { do_oop_work(p); }
3119 void do_oop( oop *p) { do_oop_work(p); }
3121 template <class T> void do_oop_work(T *p) {
3122 oop obj = oopDesc::load_decode_heap_oop(p);
3123 guarantee(obj == NULL || !_g1h->is_obj_dead_cond(obj, _vo),
3124 "Dead object referenced by a not dead object");
3125 }
3126 };
3128 class VerifyObjsInRegionClosure: public ObjectClosure {
3129 private:
3130 G1CollectedHeap* _g1h;
3131 size_t _live_bytes;
3132 HeapRegion *_hr;
3133 VerifyOption _vo;
3134 public:
3135 // _vo == UsePrevMarking -> use "prev" marking information,
3136 // _vo == UseNextMarking -> use "next" marking information,
3137 // _vo == UseMarkWord -> use mark word from object header.
3138 VerifyObjsInRegionClosure(HeapRegion *hr, VerifyOption vo)
3139 : _live_bytes(0), _hr(hr), _vo(vo) {
3140 _g1h = G1CollectedHeap::heap();
3141 }
3142 void do_object(oop o) {
3143 VerifyLivenessOopClosure isLive(_g1h, _vo);
3144 assert(o != NULL, "Huh?");
3145 if (!_g1h->is_obj_dead_cond(o, _vo)) {
3146 // If the object is alive according to the mark word,
3147 // then verify that the marking information agrees.
3148 // Note we can't verify the contra-positive of the
3149 // above: if the object is dead (according to the mark
3150 // word), it may not be marked, or may have been marked
3151 // but has since became dead, or may have been allocated
3152 // since the last marking.
3153 if (_vo == VerifyOption_G1UseMarkWord) {
3154 guarantee(!_g1h->is_obj_dead(o), "mark word and concurrent mark mismatch");
3155 }
3157 o->oop_iterate_no_header(&isLive);
3158 if (!_hr->obj_allocated_since_prev_marking(o)) {
3159 size_t obj_size = o->size(); // Make sure we don't overflow
3160 _live_bytes += (obj_size * HeapWordSize);
3161 }
3162 }
3163 }
3164 size_t live_bytes() { return _live_bytes; }
3165 };
3167 class PrintObjsInRegionClosure : public ObjectClosure {
3168 HeapRegion *_hr;
3169 G1CollectedHeap *_g1;
3170 public:
3171 PrintObjsInRegionClosure(HeapRegion *hr) : _hr(hr) {
3172 _g1 = G1CollectedHeap::heap();
3173 };
3175 void do_object(oop o) {
3176 if (o != NULL) {
3177 HeapWord *start = (HeapWord *) o;
3178 size_t word_sz = o->size();
3179 gclog_or_tty->print("\nPrinting obj "PTR_FORMAT" of size " SIZE_FORMAT
3180 " isMarkedPrev %d isMarkedNext %d isAllocSince %d\n",
3181 (void*) o, word_sz,
3182 _g1->isMarkedPrev(o),
3183 _g1->isMarkedNext(o),
3184 _hr->obj_allocated_since_prev_marking(o));
3185 HeapWord *end = start + word_sz;
3186 HeapWord *cur;
3187 int *val;
3188 for (cur = start; cur < end; cur++) {
3189 val = (int *) cur;
3190 gclog_or_tty->print("\t "PTR_FORMAT":"PTR_FORMAT"\n", val, *val);
3191 }
3192 }
3193 }
3194 };
3196 class VerifyRegionClosure: public HeapRegionClosure {
3197 private:
3198 bool _par;
3199 VerifyOption _vo;
3200 bool _failures;
3201 public:
3202 // _vo == UsePrevMarking -> use "prev" marking information,
3203 // _vo == UseNextMarking -> use "next" marking information,
3204 // _vo == UseMarkWord -> use mark word from object header.
3205 VerifyRegionClosure(bool par, VerifyOption vo)
3206 : _par(par),
3207 _vo(vo),
3208 _failures(false) {}
3210 bool failures() {
3211 return _failures;
3212 }
3214 bool doHeapRegion(HeapRegion* r) {
3215 if (!r->continuesHumongous()) {
3216 bool failures = false;
3217 r->verify(_vo, &failures);
3218 if (failures) {
3219 _failures = true;
3220 } else {
3221 VerifyObjsInRegionClosure not_dead_yet_cl(r, _vo);
3222 r->object_iterate(¬_dead_yet_cl);
3223 if (_vo != VerifyOption_G1UseNextMarking) {
3224 if (r->max_live_bytes() < not_dead_yet_cl.live_bytes()) {
3225 gclog_or_tty->print_cr("["PTR_FORMAT","PTR_FORMAT"] "
3226 "max_live_bytes "SIZE_FORMAT" "
3227 "< calculated "SIZE_FORMAT,
3228 r->bottom(), r->end(),
3229 r->max_live_bytes(),
3230 not_dead_yet_cl.live_bytes());
3231 _failures = true;
3232 }
3233 } else {
3234 // When vo == UseNextMarking we cannot currently do a sanity
3235 // check on the live bytes as the calculation has not been
3236 // finalized yet.
3237 }
3238 }
3239 }
3240 return false; // stop the region iteration if we hit a failure
3241 }
3242 };
3244 // This is the task used for parallel verification of the heap regions
3246 class G1ParVerifyTask: public AbstractGangTask {
3247 private:
3248 G1CollectedHeap* _g1h;
3249 VerifyOption _vo;
3250 bool _failures;
3252 public:
3253 // _vo == UsePrevMarking -> use "prev" marking information,
3254 // _vo == UseNextMarking -> use "next" marking information,
3255 // _vo == UseMarkWord -> use mark word from object header.
3256 G1ParVerifyTask(G1CollectedHeap* g1h, VerifyOption vo) :
3257 AbstractGangTask("Parallel verify task"),
3258 _g1h(g1h),
3259 _vo(vo),
3260 _failures(false) { }
3262 bool failures() {
3263 return _failures;
3264 }
3266 void work(uint worker_id) {
3267 HandleMark hm;
3268 VerifyRegionClosure blk(true, _vo);
3269 _g1h->heap_region_par_iterate_chunked(&blk, worker_id,
3270 _g1h->workers()->active_workers(),
3271 HeapRegion::ParVerifyClaimValue);
3272 if (blk.failures()) {
3273 _failures = true;
3274 }
3275 }
3276 };
3278 void G1CollectedHeap::verify(bool silent, VerifyOption vo) {
3279 if (SafepointSynchronize::is_at_safepoint()) {
3280 assert(Thread::current()->is_VM_thread(),
3281 "Expected to be executed serially by the VM thread at this point");
3283 if (!silent) { gclog_or_tty->print("Roots "); }
3284 VerifyRootsClosure rootsCl(vo);
3285 VerifyKlassClosure klassCl(this, &rootsCl);
3286 CLDToKlassAndOopClosure cldCl(&klassCl, &rootsCl, false);
3288 // We apply the relevant closures to all the oops in the
3289 // system dictionary, class loader data graph, the string table
3290 // and the nmethods in the code cache.
3291 G1VerifyCodeRootOopClosure codeRootsCl(this, &rootsCl, vo);
3292 G1VerifyCodeRootBlobClosure blobsCl(&codeRootsCl);
3294 process_all_roots(true, // activate StrongRootsScope
3295 SO_AllCodeCache, // roots scanning options
3296 &rootsCl,
3297 &cldCl,
3298 &blobsCl);
3300 bool failures = rootsCl.failures() || codeRootsCl.failures();
3302 if (vo != VerifyOption_G1UseMarkWord) {
3303 // If we're verifying during a full GC then the region sets
3304 // will have been torn down at the start of the GC. Therefore
3305 // verifying the region sets will fail. So we only verify
3306 // the region sets when not in a full GC.
3307 if (!silent) { gclog_or_tty->print("HeapRegionSets "); }
3308 verify_region_sets();
3309 }
3311 if (!silent) { gclog_or_tty->print("HeapRegions "); }
3312 if (GCParallelVerificationEnabled && ParallelGCThreads > 1) {
3313 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3314 "sanity check");
3316 G1ParVerifyTask task(this, vo);
3317 assert(UseDynamicNumberOfGCThreads ||
3318 workers()->active_workers() == workers()->total_workers(),
3319 "If not dynamic should be using all the workers");
3320 int n_workers = workers()->active_workers();
3321 set_par_threads(n_workers);
3322 workers()->run_task(&task);
3323 set_par_threads(0);
3324 if (task.failures()) {
3325 failures = true;
3326 }
3328 // Checks that the expected amount of parallel work was done.
3329 // The implication is that n_workers is > 0.
3330 assert(check_heap_region_claim_values(HeapRegion::ParVerifyClaimValue),
3331 "sanity check");
3333 reset_heap_region_claim_values();
3335 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3336 "sanity check");
3337 } else {
3338 VerifyRegionClosure blk(false, vo);
3339 heap_region_iterate(&blk);
3340 if (blk.failures()) {
3341 failures = true;
3342 }
3343 }
3344 if (!silent) gclog_or_tty->print("RemSet ");
3345 rem_set()->verify();
3347 if (G1StringDedup::is_enabled()) {
3348 if (!silent) gclog_or_tty->print("StrDedup ");
3349 G1StringDedup::verify();
3350 }
3352 if (failures) {
3353 gclog_or_tty->print_cr("Heap:");
3354 // It helps to have the per-region information in the output to
3355 // help us track down what went wrong. This is why we call
3356 // print_extended_on() instead of print_on().
3357 print_extended_on(gclog_or_tty);
3358 gclog_or_tty->cr();
3359 #ifndef PRODUCT
3360 if (VerifyDuringGC && G1VerifyDuringGCPrintReachable) {
3361 concurrent_mark()->print_reachable("at-verification-failure",
3362 vo, false /* all */);
3363 }
3364 #endif
3365 gclog_or_tty->flush();
3366 }
3367 guarantee(!failures, "there should not have been any failures");
3368 } else {
3369 if (!silent) {
3370 gclog_or_tty->print("(SKIPPING Roots, HeapRegionSets, HeapRegions, RemSet");
3371 if (G1StringDedup::is_enabled()) {
3372 gclog_or_tty->print(", StrDedup");
3373 }
3374 gclog_or_tty->print(") ");
3375 }
3376 }
3377 }
3379 void G1CollectedHeap::verify(bool silent) {
3380 verify(silent, VerifyOption_G1UsePrevMarking);
3381 }
3383 double G1CollectedHeap::verify(bool guard, const char* msg) {
3384 double verify_time_ms = 0.0;
3386 if (guard && total_collections() >= VerifyGCStartAt) {
3387 double verify_start = os::elapsedTime();
3388 HandleMark hm; // Discard invalid handles created during verification
3389 prepare_for_verify();
3390 Universe::verify(VerifyOption_G1UsePrevMarking, msg);
3391 verify_time_ms = (os::elapsedTime() - verify_start) * 1000;
3392 }
3394 return verify_time_ms;
3395 }
3397 void G1CollectedHeap::verify_before_gc() {
3398 double verify_time_ms = verify(VerifyBeforeGC, " VerifyBeforeGC:");
3399 g1_policy()->phase_times()->record_verify_before_time_ms(verify_time_ms);
3400 }
3402 void G1CollectedHeap::verify_after_gc() {
3403 double verify_time_ms = verify(VerifyAfterGC, " VerifyAfterGC:");
3404 g1_policy()->phase_times()->record_verify_after_time_ms(verify_time_ms);
3405 }
3407 class PrintRegionClosure: public HeapRegionClosure {
3408 outputStream* _st;
3409 public:
3410 PrintRegionClosure(outputStream* st) : _st(st) {}
3411 bool doHeapRegion(HeapRegion* r) {
3412 r->print_on(_st);
3413 return false;
3414 }
3415 };
3417 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
3418 const HeapRegion* hr,
3419 const VerifyOption vo) const {
3420 switch (vo) {
3421 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr);
3422 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr);
3423 case VerifyOption_G1UseMarkWord: return !obj->is_gc_marked();
3424 default: ShouldNotReachHere();
3425 }
3426 return false; // keep some compilers happy
3427 }
3429 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
3430 const VerifyOption vo) const {
3431 switch (vo) {
3432 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj);
3433 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj);
3434 case VerifyOption_G1UseMarkWord: return !obj->is_gc_marked();
3435 default: ShouldNotReachHere();
3436 }
3437 return false; // keep some compilers happy
3438 }
3440 void G1CollectedHeap::print_on(outputStream* st) const {
3441 st->print(" %-20s", "garbage-first heap");
3442 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
3443 capacity()/K, used_unlocked()/K);
3444 st->print(" [" INTPTR_FORMAT ", " INTPTR_FORMAT ", " INTPTR_FORMAT ")",
3445 _hrm.reserved().start(),
3446 _hrm.reserved().start() + _hrm.length() + HeapRegion::GrainWords,
3447 _hrm.reserved().end());
3448 st->cr();
3449 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
3450 uint young_regions = _young_list->length();
3451 st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
3452 (size_t) young_regions * HeapRegion::GrainBytes / K);
3453 uint survivor_regions = g1_policy()->recorded_survivor_regions();
3454 st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
3455 (size_t) survivor_regions * HeapRegion::GrainBytes / K);
3456 st->cr();
3457 MetaspaceAux::print_on(st);
3458 }
3460 void G1CollectedHeap::print_extended_on(outputStream* st) const {
3461 print_on(st);
3463 // Print the per-region information.
3464 st->cr();
3465 st->print_cr("Heap Regions: (Y=young(eden), SU=young(survivor), "
3466 "HS=humongous(starts), HC=humongous(continues), "
3467 "CS=collection set, F=free, TS=gc time stamp, "
3468 "PTAMS=previous top-at-mark-start, "
3469 "NTAMS=next top-at-mark-start)");
3470 PrintRegionClosure blk(st);
3471 heap_region_iterate(&blk);
3472 }
3474 void G1CollectedHeap::print_on_error(outputStream* st) const {
3475 this->CollectedHeap::print_on_error(st);
3477 if (_cm != NULL) {
3478 st->cr();
3479 _cm->print_on_error(st);
3480 }
3481 }
3483 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
3484 if (G1CollectedHeap::use_parallel_gc_threads()) {
3485 workers()->print_worker_threads_on(st);
3486 }
3487 _cmThread->print_on(st);
3488 st->cr();
3489 _cm->print_worker_threads_on(st);
3490 _cg1r->print_worker_threads_on(st);
3491 if (G1StringDedup::is_enabled()) {
3492 G1StringDedup::print_worker_threads_on(st);
3493 }
3494 }
3496 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
3497 if (G1CollectedHeap::use_parallel_gc_threads()) {
3498 workers()->threads_do(tc);
3499 }
3500 tc->do_thread(_cmThread);
3501 _cg1r->threads_do(tc);
3502 if (G1StringDedup::is_enabled()) {
3503 G1StringDedup::threads_do(tc);
3504 }
3505 }
3507 void G1CollectedHeap::print_tracing_info() const {
3508 // We'll overload this to mean "trace GC pause statistics."
3509 if (TraceGen0Time || TraceGen1Time) {
3510 // The "G1CollectorPolicy" is keeping track of these stats, so delegate
3511 // to that.
3512 g1_policy()->print_tracing_info();
3513 }
3514 if (G1SummarizeRSetStats) {
3515 g1_rem_set()->print_summary_info();
3516 }
3517 if (G1SummarizeConcMark) {
3518 concurrent_mark()->print_summary_info();
3519 }
3520 g1_policy()->print_yg_surv_rate_info();
3521 SpecializationStats::print();
3522 }
3524 #ifndef PRODUCT
3525 // Helpful for debugging RSet issues.
3527 class PrintRSetsClosure : public HeapRegionClosure {
3528 private:
3529 const char* _msg;
3530 size_t _occupied_sum;
3532 public:
3533 bool doHeapRegion(HeapRegion* r) {
3534 HeapRegionRemSet* hrrs = r->rem_set();
3535 size_t occupied = hrrs->occupied();
3536 _occupied_sum += occupied;
3538 gclog_or_tty->print_cr("Printing RSet for region "HR_FORMAT,
3539 HR_FORMAT_PARAMS(r));
3540 if (occupied == 0) {
3541 gclog_or_tty->print_cr(" RSet is empty");
3542 } else {
3543 hrrs->print();
3544 }
3545 gclog_or_tty->print_cr("----------");
3546 return false;
3547 }
3549 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
3550 gclog_or_tty->cr();
3551 gclog_or_tty->print_cr("========================================");
3552 gclog_or_tty->print_cr("%s", msg);
3553 gclog_or_tty->cr();
3554 }
3556 ~PrintRSetsClosure() {
3557 gclog_or_tty->print_cr("Occupied Sum: "SIZE_FORMAT, _occupied_sum);
3558 gclog_or_tty->print_cr("========================================");
3559 gclog_or_tty->cr();
3560 }
3561 };
3563 void G1CollectedHeap::print_cset_rsets() {
3564 PrintRSetsClosure cl("Printing CSet RSets");
3565 collection_set_iterate(&cl);
3566 }
3568 void G1CollectedHeap::print_all_rsets() {
3569 PrintRSetsClosure cl("Printing All RSets");;
3570 heap_region_iterate(&cl);
3571 }
3572 #endif // PRODUCT
3574 G1CollectedHeap* G1CollectedHeap::heap() {
3575 assert(_sh->kind() == CollectedHeap::G1CollectedHeap,
3576 "not a garbage-first heap");
3577 return _g1h;
3578 }
3580 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) {
3581 // always_do_update_barrier = false;
3582 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
3583 // Fill TLAB's and such
3584 accumulate_statistics_all_tlabs();
3585 ensure_parsability(true);
3587 if (G1SummarizeRSetStats && (G1SummarizeRSetStatsPeriod > 0) &&
3588 (total_collections() % G1SummarizeRSetStatsPeriod == 0)) {
3589 g1_rem_set()->print_periodic_summary_info("Before GC RS summary");
3590 }
3591 }
3593 void G1CollectedHeap::gc_epilogue(bool full) {
3595 if (G1SummarizeRSetStats &&
3596 (G1SummarizeRSetStatsPeriod > 0) &&
3597 // we are at the end of the GC. Total collections has already been increased.
3598 ((total_collections() - 1) % G1SummarizeRSetStatsPeriod == 0)) {
3599 g1_rem_set()->print_periodic_summary_info("After GC RS summary");
3600 }
3602 // FIXME: what is this about?
3603 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
3604 // is set.
3605 COMPILER2_PRESENT(assert(DerivedPointerTable::is_empty(),
3606 "derived pointer present"));
3607 // always_do_update_barrier = true;
3609 resize_all_tlabs();
3610 allocation_context_stats().update(full);
3612 // We have just completed a GC. Update the soft reference
3613 // policy with the new heap occupancy
3614 Universe::update_heap_info_at_gc();
3615 }
3617 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
3618 unsigned int gc_count_before,
3619 bool* succeeded,
3620 GCCause::Cause gc_cause) {
3621 assert_heap_not_locked_and_not_at_safepoint();
3622 g1_policy()->record_stop_world_start();
3623 VM_G1IncCollectionPause op(gc_count_before,
3624 word_size,
3625 false, /* should_initiate_conc_mark */
3626 g1_policy()->max_pause_time_ms(),
3627 gc_cause);
3629 op.set_allocation_context(AllocationContext::current());
3630 VMThread::execute(&op);
3632 HeapWord* result = op.result();
3633 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
3634 assert(result == NULL || ret_succeeded,
3635 "the result should be NULL if the VM did not succeed");
3636 *succeeded = ret_succeeded;
3638 assert_heap_not_locked();
3639 return result;
3640 }
3642 void
3643 G1CollectedHeap::doConcurrentMark() {
3644 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
3645 if (!_cmThread->in_progress()) {
3646 _cmThread->set_started();
3647 CGC_lock->notify();
3648 }
3649 }
3651 size_t G1CollectedHeap::pending_card_num() {
3652 size_t extra_cards = 0;
3653 JavaThread *curr = Threads::first();
3654 while (curr != NULL) {
3655 DirtyCardQueue& dcq = curr->dirty_card_queue();
3656 extra_cards += dcq.size();
3657 curr = curr->next();
3658 }
3659 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
3660 size_t buffer_size = dcqs.buffer_size();
3661 size_t buffer_num = dcqs.completed_buffers_num();
3663 // PtrQueueSet::buffer_size() and PtrQueue:size() return sizes
3664 // in bytes - not the number of 'entries'. We need to convert
3665 // into a number of cards.
3666 return (buffer_size * buffer_num + extra_cards) / oopSize;
3667 }
3669 size_t G1CollectedHeap::cards_scanned() {
3670 return g1_rem_set()->cardsScanned();
3671 }
3673 bool G1CollectedHeap::humongous_region_is_always_live(uint index) {
3674 HeapRegion* region = region_at(index);
3675 assert(region->startsHumongous(), "Must start a humongous object");
3676 return oop(region->bottom())->is_objArray() || !region->rem_set()->is_empty();
3677 }
3679 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure {
3680 private:
3681 size_t _total_humongous;
3682 size_t _candidate_humongous;
3683 public:
3684 RegisterHumongousWithInCSetFastTestClosure() : _total_humongous(0), _candidate_humongous(0) {
3685 }
3687 virtual bool doHeapRegion(HeapRegion* r) {
3688 if (!r->startsHumongous()) {
3689 return false;
3690 }
3691 G1CollectedHeap* g1h = G1CollectedHeap::heap();
3693 uint region_idx = r->hrm_index();
3694 bool is_candidate = !g1h->humongous_region_is_always_live(region_idx);
3695 // Is_candidate already filters out humongous regions with some remembered set.
3696 // This will not lead to humongous object that we mistakenly keep alive because
3697 // during young collection the remembered sets will only be added to.
3698 if (is_candidate) {
3699 g1h->register_humongous_region_with_in_cset_fast_test(region_idx);
3700 _candidate_humongous++;
3701 }
3702 _total_humongous++;
3704 return false;
3705 }
3707 size_t total_humongous() const { return _total_humongous; }
3708 size_t candidate_humongous() const { return _candidate_humongous; }
3709 };
3711 void G1CollectedHeap::register_humongous_regions_with_in_cset_fast_test() {
3712 if (!G1ReclaimDeadHumongousObjectsAtYoungGC) {
3713 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0, 0);
3714 return;
3715 }
3717 RegisterHumongousWithInCSetFastTestClosure cl;
3718 heap_region_iterate(&cl);
3719 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(cl.total_humongous(),
3720 cl.candidate_humongous());
3721 _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0;
3723 if (_has_humongous_reclaim_candidates) {
3724 clear_humongous_is_live_table();
3725 }
3726 }
3728 void
3729 G1CollectedHeap::setup_surviving_young_words() {
3730 assert(_surviving_young_words == NULL, "pre-condition");
3731 uint array_length = g1_policy()->young_cset_region_length();
3732 _surviving_young_words = NEW_C_HEAP_ARRAY(size_t, (size_t) array_length, mtGC);
3733 if (_surviving_young_words == NULL) {
3734 vm_exit_out_of_memory(sizeof(size_t) * array_length, OOM_MALLOC_ERROR,
3735 "Not enough space for young surv words summary.");
3736 }
3737 memset(_surviving_young_words, 0, (size_t) array_length * sizeof(size_t));
3738 #ifdef ASSERT
3739 for (uint i = 0; i < array_length; ++i) {
3740 assert( _surviving_young_words[i] == 0, "memset above" );
3741 }
3742 #endif // !ASSERT
3743 }
3745 void
3746 G1CollectedHeap::update_surviving_young_words(size_t* surv_young_words) {
3747 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
3748 uint array_length = g1_policy()->young_cset_region_length();
3749 for (uint i = 0; i < array_length; ++i) {
3750 _surviving_young_words[i] += surv_young_words[i];
3751 }
3752 }
3754 void
3755 G1CollectedHeap::cleanup_surviving_young_words() {
3756 guarantee( _surviving_young_words != NULL, "pre-condition" );
3757 FREE_C_HEAP_ARRAY(size_t, _surviving_young_words, mtGC);
3758 _surviving_young_words = NULL;
3759 }
3761 #ifdef ASSERT
3762 class VerifyCSetClosure: public HeapRegionClosure {
3763 public:
3764 bool doHeapRegion(HeapRegion* hr) {
3765 // Here we check that the CSet region's RSet is ready for parallel
3766 // iteration. The fields that we'll verify are only manipulated
3767 // when the region is part of a CSet and is collected. Afterwards,
3768 // we reset these fields when we clear the region's RSet (when the
3769 // region is freed) so they are ready when the region is
3770 // re-allocated. The only exception to this is if there's an
3771 // evacuation failure and instead of freeing the region we leave
3772 // it in the heap. In that case, we reset these fields during
3773 // evacuation failure handling.
3774 guarantee(hr->rem_set()->verify_ready_for_par_iteration(), "verification");
3776 // Here's a good place to add any other checks we'd like to
3777 // perform on CSet regions.
3778 return false;
3779 }
3780 };
3781 #endif // ASSERT
3783 #if TASKQUEUE_STATS
3784 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
3785 st->print_raw_cr("GC Task Stats");
3786 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
3787 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
3788 }
3790 void G1CollectedHeap::print_taskqueue_stats(outputStream* const st) const {
3791 print_taskqueue_stats_hdr(st);
3793 TaskQueueStats totals;
3794 const int n = workers() != NULL ? workers()->total_workers() : 1;
3795 for (int i = 0; i < n; ++i) {
3796 st->print("%3d ", i); task_queue(i)->stats.print(st); st->cr();
3797 totals += task_queue(i)->stats;
3798 }
3799 st->print_raw("tot "); totals.print(st); st->cr();
3801 DEBUG_ONLY(totals.verify());
3802 }
3804 void G1CollectedHeap::reset_taskqueue_stats() {
3805 const int n = workers() != NULL ? workers()->total_workers() : 1;
3806 for (int i = 0; i < n; ++i) {
3807 task_queue(i)->stats.reset();
3808 }
3809 }
3810 #endif // TASKQUEUE_STATS
3812 void G1CollectedHeap::log_gc_header() {
3813 if (!G1Log::fine()) {
3814 return;
3815 }
3817 gclog_or_tty->gclog_stamp(_gc_tracer_stw->gc_id());
3819 GCCauseString gc_cause_str = GCCauseString("GC pause", gc_cause())
3820 .append(g1_policy()->gcs_are_young() ? "(young)" : "(mixed)")
3821 .append(g1_policy()->during_initial_mark_pause() ? " (initial-mark)" : "");
3823 gclog_or_tty->print("[%s", (const char*)gc_cause_str);
3824 }
3826 void G1CollectedHeap::log_gc_footer(double pause_time_sec) {
3827 if (!G1Log::fine()) {
3828 return;
3829 }
3831 if (G1Log::finer()) {
3832 if (evacuation_failed()) {
3833 gclog_or_tty->print(" (to-space exhausted)");
3834 }
3835 gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec);
3836 g1_policy()->phase_times()->note_gc_end();
3837 g1_policy()->phase_times()->print(pause_time_sec);
3838 g1_policy()->print_detailed_heap_transition();
3839 } else {
3840 if (evacuation_failed()) {
3841 gclog_or_tty->print("--");
3842 }
3843 g1_policy()->print_heap_transition();
3844 gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec);
3845 }
3846 gclog_or_tty->flush();
3847 }
3849 bool
3850 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
3851 assert_at_safepoint(true /* should_be_vm_thread */);
3852 guarantee(!is_gc_active(), "collection is not reentrant");
3854 if (GC_locker::check_active_before_gc()) {
3855 return false;
3856 }
3858 _gc_timer_stw->register_gc_start();
3860 _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start());
3862 SvcGCMarker sgcm(SvcGCMarker::MINOR);
3863 ResourceMark rm;
3865 print_heap_before_gc();
3866 trace_heap_before_gc(_gc_tracer_stw);
3868 verify_region_sets_optional();
3869 verify_dirty_young_regions();
3871 // This call will decide whether this pause is an initial-mark
3872 // pause. If it is, during_initial_mark_pause() will return true
3873 // for the duration of this pause.
3874 g1_policy()->decide_on_conc_mark_initiation();
3876 // We do not allow initial-mark to be piggy-backed on a mixed GC.
3877 assert(!g1_policy()->during_initial_mark_pause() ||
3878 g1_policy()->gcs_are_young(), "sanity");
3880 // We also do not allow mixed GCs during marking.
3881 assert(!mark_in_progress() || g1_policy()->gcs_are_young(), "sanity");
3883 // Record whether this pause is an initial mark. When the current
3884 // thread has completed its logging output and it's safe to signal
3885 // the CM thread, the flag's value in the policy has been reset.
3886 bool should_start_conc_mark = g1_policy()->during_initial_mark_pause();
3888 // Inner scope for scope based logging, timers, and stats collection
3889 {
3890 EvacuationInfo evacuation_info;
3892 if (g1_policy()->during_initial_mark_pause()) {
3893 // We are about to start a marking cycle, so we increment the
3894 // full collection counter.
3895 increment_old_marking_cycles_started();
3896 register_concurrent_cycle_start(_gc_timer_stw->gc_start());
3897 }
3899 _gc_tracer_stw->report_yc_type(yc_type());
3901 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
3903 int active_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
3904 workers()->active_workers() : 1);
3905 double pause_start_sec = os::elapsedTime();
3906 g1_policy()->phase_times()->note_gc_start(active_workers);
3907 log_gc_header();
3909 TraceCollectorStats tcs(g1mm()->incremental_collection_counters());
3910 TraceMemoryManagerStats tms(false /* fullGC */, gc_cause());
3912 // If the secondary_free_list is not empty, append it to the
3913 // free_list. No need to wait for the cleanup operation to finish;
3914 // the region allocation code will check the secondary_free_list
3915 // and wait if necessary. If the G1StressConcRegionFreeing flag is
3916 // set, skip this step so that the region allocation code has to
3917 // get entries from the secondary_free_list.
3918 if (!G1StressConcRegionFreeing) {
3919 append_secondary_free_list_if_not_empty_with_lock();
3920 }
3922 assert(check_young_list_well_formed(), "young list should be well formed");
3923 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3924 "sanity check");
3926 // Don't dynamically change the number of GC threads this early. A value of
3927 // 0 is used to indicate serial work. When parallel work is done,
3928 // it will be set.
3930 { // Call to jvmpi::post_class_unload_events must occur outside of active GC
3931 IsGCActiveMark x;
3933 gc_prologue(false);
3934 increment_total_collections(false /* full gc */);
3935 increment_gc_time_stamp();
3937 verify_before_gc();
3938 check_bitmaps("GC Start");
3940 COMPILER2_PRESENT(DerivedPointerTable::clear());
3942 // Please see comment in g1CollectedHeap.hpp and
3943 // G1CollectedHeap::ref_processing_init() to see how
3944 // reference processing currently works in G1.
3946 // Enable discovery in the STW reference processor
3947 ref_processor_stw()->enable_discovery(true /*verify_disabled*/,
3948 true /*verify_no_refs*/);
3950 {
3951 // We want to temporarily turn off discovery by the
3952 // CM ref processor, if necessary, and turn it back on
3953 // on again later if we do. Using a scoped
3954 // NoRefDiscovery object will do this.
3955 NoRefDiscovery no_cm_discovery(ref_processor_cm());
3957 // Forget the current alloc region (we might even choose it to be part
3958 // of the collection set!).
3959 _allocator->release_mutator_alloc_region();
3961 // We should call this after we retire the mutator alloc
3962 // region(s) so that all the ALLOC / RETIRE events are generated
3963 // before the start GC event.
3964 _hr_printer.start_gc(false /* full */, (size_t) total_collections());
3966 // This timing is only used by the ergonomics to handle our pause target.
3967 // It is unclear why this should not include the full pause. We will
3968 // investigate this in CR 7178365.
3969 //
3970 // Preserving the old comment here if that helps the investigation:
3971 //
3972 // The elapsed time induced by the start time below deliberately elides
3973 // the possible verification above.
3974 double sample_start_time_sec = os::elapsedTime();
3976 #if YOUNG_LIST_VERBOSE
3977 gclog_or_tty->print_cr("\nBefore recording pause start.\nYoung_list:");
3978 _young_list->print();
3979 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3980 #endif // YOUNG_LIST_VERBOSE
3982 g1_policy()->record_collection_pause_start(sample_start_time_sec);
3984 double scan_wait_start = os::elapsedTime();
3985 // We have to wait until the CM threads finish scanning the
3986 // root regions as it's the only way to ensure that all the
3987 // objects on them have been correctly scanned before we start
3988 // moving them during the GC.
3989 bool waited = _cm->root_regions()->wait_until_scan_finished();
3990 double wait_time_ms = 0.0;
3991 if (waited) {
3992 double scan_wait_end = os::elapsedTime();
3993 wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
3994 }
3995 g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms);
3997 #if YOUNG_LIST_VERBOSE
3998 gclog_or_tty->print_cr("\nAfter recording pause start.\nYoung_list:");
3999 _young_list->print();
4000 #endif // YOUNG_LIST_VERBOSE
4002 if (g1_policy()->during_initial_mark_pause()) {
4003 concurrent_mark()->checkpointRootsInitialPre();
4004 }
4006 #if YOUNG_LIST_VERBOSE
4007 gclog_or_tty->print_cr("\nBefore choosing collection set.\nYoung_list:");
4008 _young_list->print();
4009 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
4010 #endif // YOUNG_LIST_VERBOSE
4012 g1_policy()->finalize_cset(target_pause_time_ms, evacuation_info);
4014 register_humongous_regions_with_in_cset_fast_test();
4016 _cm->note_start_of_gc();
4017 // We should not verify the per-thread SATB buffers given that
4018 // we have not filtered them yet (we'll do so during the
4019 // GC). We also call this after finalize_cset() to
4020 // ensure that the CSet has been finalized.
4021 _cm->verify_no_cset_oops(true /* verify_stacks */,
4022 true /* verify_enqueued_buffers */,
4023 false /* verify_thread_buffers */,
4024 true /* verify_fingers */);
4026 if (_hr_printer.is_active()) {
4027 HeapRegion* hr = g1_policy()->collection_set();
4028 while (hr != NULL) {
4029 _hr_printer.cset(hr);
4030 hr = hr->next_in_collection_set();
4031 }
4032 }
4034 #ifdef ASSERT
4035 VerifyCSetClosure cl;
4036 collection_set_iterate(&cl);
4037 #endif // ASSERT
4039 setup_surviving_young_words();
4041 // Initialize the GC alloc regions.
4042 _allocator->init_gc_alloc_regions(evacuation_info);
4044 // Actually do the work...
4045 evacuate_collection_set(evacuation_info);
4047 // We do this to mainly verify the per-thread SATB buffers
4048 // (which have been filtered by now) since we didn't verify
4049 // them earlier. No point in re-checking the stacks / enqueued
4050 // buffers given that the CSet has not changed since last time
4051 // we checked.
4052 _cm->verify_no_cset_oops(false /* verify_stacks */,
4053 false /* verify_enqueued_buffers */,
4054 true /* verify_thread_buffers */,
4055 true /* verify_fingers */);
4057 free_collection_set(g1_policy()->collection_set(), evacuation_info);
4059 eagerly_reclaim_humongous_regions();
4061 g1_policy()->clear_collection_set();
4063 cleanup_surviving_young_words();
4065 // Start a new incremental collection set for the next pause.
4066 g1_policy()->start_incremental_cset_building();
4068 clear_cset_fast_test();
4070 _young_list->reset_sampled_info();
4072 // Don't check the whole heap at this point as the
4073 // GC alloc regions from this pause have been tagged
4074 // as survivors and moved on to the survivor list.
4075 // Survivor regions will fail the !is_young() check.
4076 assert(check_young_list_empty(false /* check_heap */),
4077 "young list should be empty");
4079 #if YOUNG_LIST_VERBOSE
4080 gclog_or_tty->print_cr("Before recording survivors.\nYoung List:");
4081 _young_list->print();
4082 #endif // YOUNG_LIST_VERBOSE
4084 g1_policy()->record_survivor_regions(_young_list->survivor_length(),
4085 _young_list->first_survivor_region(),
4086 _young_list->last_survivor_region());
4088 _young_list->reset_auxilary_lists();
4090 if (evacuation_failed()) {
4091 _allocator->set_used(recalculate_used());
4092 uint n_queues = MAX2((int)ParallelGCThreads, 1);
4093 for (uint i = 0; i < n_queues; i++) {
4094 if (_evacuation_failed_info_array[i].has_failed()) {
4095 _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]);
4096 }
4097 }
4098 } else {
4099 // The "used" of the the collection set have already been subtracted
4100 // when they were freed. Add in the bytes evacuated.
4101 _allocator->increase_used(g1_policy()->bytes_copied_during_gc());
4102 }
4104 if (g1_policy()->during_initial_mark_pause()) {
4105 // We have to do this before we notify the CM threads that
4106 // they can start working to make sure that all the
4107 // appropriate initialization is done on the CM object.
4108 concurrent_mark()->checkpointRootsInitialPost();
4109 set_marking_started();
4110 // Note that we don't actually trigger the CM thread at
4111 // this point. We do that later when we're sure that
4112 // the current thread has completed its logging output.
4113 }
4115 allocate_dummy_regions();
4117 #if YOUNG_LIST_VERBOSE
4118 gclog_or_tty->print_cr("\nEnd of the pause.\nYoung_list:");
4119 _young_list->print();
4120 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
4121 #endif // YOUNG_LIST_VERBOSE
4123 _allocator->init_mutator_alloc_region();
4125 {
4126 size_t expand_bytes = g1_policy()->expansion_amount();
4127 if (expand_bytes > 0) {
4128 size_t bytes_before = capacity();
4129 // No need for an ergo verbose message here,
4130 // expansion_amount() does this when it returns a value > 0.
4131 if (!expand(expand_bytes)) {
4132 // We failed to expand the heap. Cannot do anything about it.
4133 }
4134 }
4135 }
4137 // We redo the verification but now wrt to the new CSet which
4138 // has just got initialized after the previous CSet was freed.
4139 _cm->verify_no_cset_oops(true /* verify_stacks */,
4140 true /* verify_enqueued_buffers */,
4141 true /* verify_thread_buffers */,
4142 true /* verify_fingers */);
4143 _cm->note_end_of_gc();
4145 // This timing is only used by the ergonomics to handle our pause target.
4146 // It is unclear why this should not include the full pause. We will
4147 // investigate this in CR 7178365.
4148 double sample_end_time_sec = os::elapsedTime();
4149 double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
4150 g1_policy()->record_collection_pause_end(pause_time_ms, evacuation_info);
4152 MemoryService::track_memory_usage();
4154 // In prepare_for_verify() below we'll need to scan the deferred
4155 // update buffers to bring the RSets up-to-date if
4156 // G1HRRSFlushLogBuffersOnVerify has been set. While scanning
4157 // the update buffers we'll probably need to scan cards on the
4158 // regions we just allocated to (i.e., the GC alloc
4159 // regions). However, during the last GC we called
4160 // set_saved_mark() on all the GC alloc regions, so card
4161 // scanning might skip the [saved_mark_word()...top()] area of
4162 // those regions (i.e., the area we allocated objects into
4163 // during the last GC). But it shouldn't. Given that
4164 // saved_mark_word() is conditional on whether the GC time stamp
4165 // on the region is current or not, by incrementing the GC time
4166 // stamp here we invalidate all the GC time stamps on all the
4167 // regions and saved_mark_word() will simply return top() for
4168 // all the regions. This is a nicer way of ensuring this rather
4169 // than iterating over the regions and fixing them. In fact, the
4170 // GC time stamp increment here also ensures that
4171 // saved_mark_word() will return top() between pauses, i.e.,
4172 // during concurrent refinement. So we don't need the
4173 // is_gc_active() check to decided which top to use when
4174 // scanning cards (see CR 7039627).
4175 increment_gc_time_stamp();
4177 verify_after_gc();
4178 check_bitmaps("GC End");
4180 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
4181 ref_processor_stw()->verify_no_references_recorded();
4183 // CM reference discovery will be re-enabled if necessary.
4184 }
4186 // We should do this after we potentially expand the heap so
4187 // that all the COMMIT events are generated before the end GC
4188 // event, and after we retire the GC alloc regions so that all
4189 // RETIRE events are generated before the end GC event.
4190 _hr_printer.end_gc(false /* full */, (size_t) total_collections());
4192 #ifdef TRACESPINNING
4193 ParallelTaskTerminator::print_termination_counts();
4194 #endif
4196 gc_epilogue(false);
4197 }
4199 // Print the remainder of the GC log output.
4200 log_gc_footer(os::elapsedTime() - pause_start_sec);
4202 // It is not yet to safe to tell the concurrent mark to
4203 // start as we have some optional output below. We don't want the
4204 // output from the concurrent mark thread interfering with this
4205 // logging output either.
4207 _hrm.verify_optional();
4208 verify_region_sets_optional();
4210 TASKQUEUE_STATS_ONLY(if (ParallelGCVerbose) print_taskqueue_stats());
4211 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
4213 print_heap_after_gc();
4214 trace_heap_after_gc(_gc_tracer_stw);
4216 // We must call G1MonitoringSupport::update_sizes() in the same scoping level
4217 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
4218 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
4219 // before any GC notifications are raised.
4220 g1mm()->update_sizes();
4222 _gc_tracer_stw->report_evacuation_info(&evacuation_info);
4223 _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold());
4224 _gc_timer_stw->register_gc_end();
4225 _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions());
4226 }
4227 // It should now be safe to tell the concurrent mark thread to start
4228 // without its logging output interfering with the logging output
4229 // that came from the pause.
4231 if (should_start_conc_mark) {
4232 // CAUTION: after the doConcurrentMark() call below,
4233 // the concurrent marking thread(s) could be running
4234 // concurrently with us. Make sure that anything after
4235 // this point does not assume that we are the only GC thread
4236 // running. Note: of course, the actual marking work will
4237 // not start until the safepoint itself is released in
4238 // SuspendibleThreadSet::desynchronize().
4239 doConcurrentMark();
4240 }
4242 return true;
4243 }
4245 size_t G1CollectedHeap::desired_plab_sz(GCAllocPurpose purpose)
4246 {
4247 size_t gclab_word_size;
4248 switch (purpose) {
4249 case GCAllocForSurvived:
4250 gclab_word_size = _survivor_plab_stats.desired_plab_sz();
4251 break;
4252 case GCAllocForTenured:
4253 gclab_word_size = _old_plab_stats.desired_plab_sz();
4254 break;
4255 default:
4256 assert(false, "unknown GCAllocPurpose");
4257 gclab_word_size = _old_plab_stats.desired_plab_sz();
4258 break;
4259 }
4261 // Prevent humongous PLAB sizes for two reasons:
4262 // * PLABs are allocated using a similar paths as oops, but should
4263 // never be in a humongous region
4264 // * Allowing humongous PLABs needlessly churns the region free lists
4265 return MIN2(_humongous_object_threshold_in_words, gclab_word_size);
4266 }
4268 void G1CollectedHeap::init_for_evac_failure(OopsInHeapRegionClosure* cl) {
4269 _drain_in_progress = false;
4270 set_evac_failure_closure(cl);
4271 _evac_failure_scan_stack = new (ResourceObj::C_HEAP, mtGC) GrowableArray<oop>(40, true);
4272 }
4274 void G1CollectedHeap::finalize_for_evac_failure() {
4275 assert(_evac_failure_scan_stack != NULL &&
4276 _evac_failure_scan_stack->length() == 0,
4277 "Postcondition");
4278 assert(!_drain_in_progress, "Postcondition");
4279 delete _evac_failure_scan_stack;
4280 _evac_failure_scan_stack = NULL;
4281 }
4283 void G1CollectedHeap::remove_self_forwarding_pointers() {
4284 assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity");
4286 double remove_self_forwards_start = os::elapsedTime();
4288 G1ParRemoveSelfForwardPtrsTask rsfp_task(this);
4290 if (G1CollectedHeap::use_parallel_gc_threads()) {
4291 set_par_threads();
4292 workers()->run_task(&rsfp_task);
4293 set_par_threads(0);
4294 } else {
4295 rsfp_task.work(0);
4296 }
4298 assert(check_cset_heap_region_claim_values(HeapRegion::ParEvacFailureClaimValue), "sanity");
4300 // Reset the claim values in the regions in the collection set.
4301 reset_cset_heap_region_claim_values();
4303 assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity");
4305 // Now restore saved marks, if any.
4306 assert(_objs_with_preserved_marks.size() ==
4307 _preserved_marks_of_objs.size(), "Both or none.");
4308 while (!_objs_with_preserved_marks.is_empty()) {
4309 oop obj = _objs_with_preserved_marks.pop();
4310 markOop m = _preserved_marks_of_objs.pop();
4311 obj->set_mark(m);
4312 }
4313 _objs_with_preserved_marks.clear(true);
4314 _preserved_marks_of_objs.clear(true);
4316 g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0);
4317 }
4319 void G1CollectedHeap::push_on_evac_failure_scan_stack(oop obj) {
4320 _evac_failure_scan_stack->push(obj);
4321 }
4323 void G1CollectedHeap::drain_evac_failure_scan_stack() {
4324 assert(_evac_failure_scan_stack != NULL, "precondition");
4326 while (_evac_failure_scan_stack->length() > 0) {
4327 oop obj = _evac_failure_scan_stack->pop();
4328 _evac_failure_closure->set_region(heap_region_containing(obj));
4329 obj->oop_iterate_backwards(_evac_failure_closure);
4330 }
4331 }
4333 oop
4334 G1CollectedHeap::handle_evacuation_failure_par(G1ParScanThreadState* _par_scan_state,
4335 oop old) {
4336 assert(obj_in_cs(old),
4337 err_msg("obj: "PTR_FORMAT" should still be in the CSet",
4338 (HeapWord*) old));
4339 markOop m = old->mark();
4340 oop forward_ptr = old->forward_to_atomic(old);
4341 if (forward_ptr == NULL) {
4342 // Forward-to-self succeeded.
4343 assert(_par_scan_state != NULL, "par scan state");
4344 OopsInHeapRegionClosure* cl = _par_scan_state->evac_failure_closure();
4345 uint queue_num = _par_scan_state->queue_num();
4347 _evacuation_failed = true;
4348 _evacuation_failed_info_array[queue_num].register_copy_failure(old->size());
4349 if (_evac_failure_closure != cl) {
4350 MutexLockerEx x(EvacFailureStack_lock, Mutex::_no_safepoint_check_flag);
4351 assert(!_drain_in_progress,
4352 "Should only be true while someone holds the lock.");
4353 // Set the global evac-failure closure to the current thread's.
4354 assert(_evac_failure_closure == NULL, "Or locking has failed.");
4355 set_evac_failure_closure(cl);
4356 // Now do the common part.
4357 handle_evacuation_failure_common(old, m);
4358 // Reset to NULL.
4359 set_evac_failure_closure(NULL);
4360 } else {
4361 // The lock is already held, and this is recursive.
4362 assert(_drain_in_progress, "This should only be the recursive case.");
4363 handle_evacuation_failure_common(old, m);
4364 }
4365 return old;
4366 } else {
4367 // Forward-to-self failed. Either someone else managed to allocate
4368 // space for this object (old != forward_ptr) or they beat us in
4369 // self-forwarding it (old == forward_ptr).
4370 assert(old == forward_ptr || !obj_in_cs(forward_ptr),
4371 err_msg("obj: "PTR_FORMAT" forwarded to: "PTR_FORMAT" "
4372 "should not be in the CSet",
4373 (HeapWord*) old, (HeapWord*) forward_ptr));
4374 return forward_ptr;
4375 }
4376 }
4378 void G1CollectedHeap::handle_evacuation_failure_common(oop old, markOop m) {
4379 preserve_mark_if_necessary(old, m);
4381 HeapRegion* r = heap_region_containing(old);
4382 if (!r->evacuation_failed()) {
4383 r->set_evacuation_failed(true);
4384 _hr_printer.evac_failure(r);
4385 }
4387 push_on_evac_failure_scan_stack(old);
4389 if (!_drain_in_progress) {
4390 // prevent recursion in copy_to_survivor_space()
4391 _drain_in_progress = true;
4392 drain_evac_failure_scan_stack();
4393 _drain_in_progress = false;
4394 }
4395 }
4397 void G1CollectedHeap::preserve_mark_if_necessary(oop obj, markOop m) {
4398 assert(evacuation_failed(), "Oversaving!");
4399 // We want to call the "for_promotion_failure" version only in the
4400 // case of a promotion failure.
4401 if (m->must_be_preserved_for_promotion_failure(obj)) {
4402 _objs_with_preserved_marks.push(obj);
4403 _preserved_marks_of_objs.push(m);
4404 }
4405 }
4407 HeapWord* G1CollectedHeap::par_allocate_during_gc(GCAllocPurpose purpose,
4408 size_t word_size,
4409 AllocationContext_t context) {
4410 if (purpose == GCAllocForSurvived) {
4411 HeapWord* result = survivor_attempt_allocation(word_size, context);
4412 if (result != NULL) {
4413 return result;
4414 } else {
4415 // Let's try to allocate in the old gen in case we can fit the
4416 // object there.
4417 return old_attempt_allocation(word_size, context);
4418 }
4419 } else {
4420 assert(purpose == GCAllocForTenured, "sanity");
4421 HeapWord* result = old_attempt_allocation(word_size, context);
4422 if (result != NULL) {
4423 return result;
4424 } else {
4425 // Let's try to allocate in the survivors in case we can fit the
4426 // object there.
4427 return survivor_attempt_allocation(word_size, context);
4428 }
4429 }
4431 ShouldNotReachHere();
4432 // Trying to keep some compilers happy.
4433 return NULL;
4434 }
4436 void G1ParCopyHelper::mark_object(oop obj) {
4437 assert(!_g1->heap_region_containing(obj)->in_collection_set(), "should not mark objects in the CSet");
4439 // We know that the object is not moving so it's safe to read its size.
4440 _cm->grayRoot(obj, (size_t) obj->size(), _worker_id);
4441 }
4443 void G1ParCopyHelper::mark_forwarded_object(oop from_obj, oop to_obj) {
4444 assert(from_obj->is_forwarded(), "from obj should be forwarded");
4445 assert(from_obj->forwardee() == to_obj, "to obj should be the forwardee");
4446 assert(from_obj != to_obj, "should not be self-forwarded");
4448 assert(_g1->heap_region_containing(from_obj)->in_collection_set(), "from obj should be in the CSet");
4449 assert(!_g1->heap_region_containing(to_obj)->in_collection_set(), "should not mark objects in the CSet");
4451 // The object might be in the process of being copied by another
4452 // worker so we cannot trust that its to-space image is
4453 // well-formed. So we have to read its size from its from-space
4454 // image which we know should not be changing.
4455 _cm->grayRoot(to_obj, (size_t) from_obj->size(), _worker_id);
4456 }
4458 template <class T>
4459 void G1ParCopyHelper::do_klass_barrier(T* p, oop new_obj) {
4460 if (_g1->heap_region_containing_raw(new_obj)->is_young()) {
4461 _scanned_klass->record_modified_oops();
4462 }
4463 }
4465 template <G1Barrier barrier, G1Mark do_mark_object>
4466 template <class T>
4467 void G1ParCopyClosure<barrier, do_mark_object>::do_oop_work(T* p) {
4468 T heap_oop = oopDesc::load_heap_oop(p);
4470 if (oopDesc::is_null(heap_oop)) {
4471 return;
4472 }
4474 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
4476 assert(_worker_id == _par_scan_state->queue_num(), "sanity");
4478 G1CollectedHeap::in_cset_state_t state = _g1->in_cset_state(obj);
4480 if (state == G1CollectedHeap::InCSet) {
4481 oop forwardee;
4482 if (obj->is_forwarded()) {
4483 forwardee = obj->forwardee();
4484 } else {
4485 forwardee = _par_scan_state->copy_to_survivor_space(obj);
4486 }
4487 assert(forwardee != NULL, "forwardee should not be NULL");
4488 oopDesc::encode_store_heap_oop(p, forwardee);
4489 if (do_mark_object != G1MarkNone && forwardee != obj) {
4490 // If the object is self-forwarded we don't need to explicitly
4491 // mark it, the evacuation failure protocol will do so.
4492 mark_forwarded_object(obj, forwardee);
4493 }
4495 if (barrier == G1BarrierKlass) {
4496 do_klass_barrier(p, forwardee);
4497 }
4498 } else {
4499 if (state == G1CollectedHeap::IsHumongous) {
4500 _g1->set_humongous_is_live(obj);
4501 }
4502 // The object is not in collection set. If we're a root scanning
4503 // closure during an initial mark pause then attempt to mark the object.
4504 if (do_mark_object == G1MarkFromRoot) {
4505 mark_object(obj);
4506 }
4507 }
4509 if (barrier == G1BarrierEvac) {
4510 _par_scan_state->update_rs(_from, p, _worker_id);
4511 }
4512 }
4514 template void G1ParCopyClosure<G1BarrierEvac, G1MarkNone>::do_oop_work(oop* p);
4515 template void G1ParCopyClosure<G1BarrierEvac, G1MarkNone>::do_oop_work(narrowOop* p);
4517 class G1ParEvacuateFollowersClosure : public VoidClosure {
4518 protected:
4519 G1CollectedHeap* _g1h;
4520 G1ParScanThreadState* _par_scan_state;
4521 RefToScanQueueSet* _queues;
4522 ParallelTaskTerminator* _terminator;
4524 G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
4525 RefToScanQueueSet* queues() { return _queues; }
4526 ParallelTaskTerminator* terminator() { return _terminator; }
4528 public:
4529 G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h,
4530 G1ParScanThreadState* par_scan_state,
4531 RefToScanQueueSet* queues,
4532 ParallelTaskTerminator* terminator)
4533 : _g1h(g1h), _par_scan_state(par_scan_state),
4534 _queues(queues), _terminator(terminator) {}
4536 void do_void();
4538 private:
4539 inline bool offer_termination();
4540 };
4542 bool G1ParEvacuateFollowersClosure::offer_termination() {
4543 G1ParScanThreadState* const pss = par_scan_state();
4544 pss->start_term_time();
4545 const bool res = terminator()->offer_termination();
4546 pss->end_term_time();
4547 return res;
4548 }
4550 void G1ParEvacuateFollowersClosure::do_void() {
4551 G1ParScanThreadState* const pss = par_scan_state();
4552 pss->trim_queue();
4553 do {
4554 pss->steal_and_trim_queue(queues());
4555 } while (!offer_termination());
4556 }
4558 class G1KlassScanClosure : public KlassClosure {
4559 G1ParCopyHelper* _closure;
4560 bool _process_only_dirty;
4561 int _count;
4562 public:
4563 G1KlassScanClosure(G1ParCopyHelper* closure, bool process_only_dirty)
4564 : _process_only_dirty(process_only_dirty), _closure(closure), _count(0) {}
4565 void do_klass(Klass* klass) {
4566 // If the klass has not been dirtied we know that there's
4567 // no references into the young gen and we can skip it.
4568 if (!_process_only_dirty || klass->has_modified_oops()) {
4569 // Clean the klass since we're going to scavenge all the metadata.
4570 klass->clear_modified_oops();
4572 // Tell the closure that this klass is the Klass to scavenge
4573 // and is the one to dirty if oops are left pointing into the young gen.
4574 _closure->set_scanned_klass(klass);
4576 klass->oops_do(_closure);
4578 _closure->set_scanned_klass(NULL);
4579 }
4580 _count++;
4581 }
4582 };
4584 class G1CodeBlobClosure : public CodeBlobClosure {
4585 class HeapRegionGatheringOopClosure : public OopClosure {
4586 G1CollectedHeap* _g1h;
4587 OopClosure* _work;
4588 nmethod* _nm;
4590 template <typename T>
4591 void do_oop_work(T* p) {
4592 _work->do_oop(p);
4593 T oop_or_narrowoop = oopDesc::load_heap_oop(p);
4594 if (!oopDesc::is_null(oop_or_narrowoop)) {
4595 oop o = oopDesc::decode_heap_oop_not_null(oop_or_narrowoop);
4596 HeapRegion* hr = _g1h->heap_region_containing_raw(o);
4597 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");
4598 hr->add_strong_code_root(_nm);
4599 }
4600 }
4602 public:
4603 HeapRegionGatheringOopClosure(OopClosure* oc) : _g1h(G1CollectedHeap::heap()), _work(oc), _nm(NULL) {}
4605 void do_oop(oop* o) {
4606 do_oop_work(o);
4607 }
4609 void do_oop(narrowOop* o) {
4610 do_oop_work(o);
4611 }
4613 void set_nm(nmethod* nm) {
4614 _nm = nm;
4615 }
4616 };
4618 HeapRegionGatheringOopClosure _oc;
4619 public:
4620 G1CodeBlobClosure(OopClosure* oc) : _oc(oc) {}
4622 void do_code_blob(CodeBlob* cb) {
4623 nmethod* nm = cb->as_nmethod_or_null();
4624 if (nm != NULL) {
4625 if (!nm->test_set_oops_do_mark()) {
4626 _oc.set_nm(nm);
4627 nm->oops_do(&_oc);
4628 nm->fix_oop_relocations();
4629 }
4630 }
4631 }
4632 };
4634 class G1ParTask : public AbstractGangTask {
4635 protected:
4636 G1CollectedHeap* _g1h;
4637 RefToScanQueueSet *_queues;
4638 ParallelTaskTerminator _terminator;
4639 uint _n_workers;
4641 Mutex _stats_lock;
4642 Mutex* stats_lock() { return &_stats_lock; }
4644 public:
4645 G1ParTask(G1CollectedHeap* g1h, RefToScanQueueSet *task_queues)
4646 : AbstractGangTask("G1 collection"),
4647 _g1h(g1h),
4648 _queues(task_queues),
4649 _terminator(0, _queues),
4650 _stats_lock(Mutex::leaf, "parallel G1 stats lock", true)
4651 {}
4653 RefToScanQueueSet* queues() { return _queues; }
4655 RefToScanQueue *work_queue(int i) {
4656 return queues()->queue(i);
4657 }
4659 ParallelTaskTerminator* terminator() { return &_terminator; }
4661 virtual void set_for_termination(int active_workers) {
4662 // This task calls set_n_termination() in par_non_clean_card_iterate_work()
4663 // in the young space (_par_seq_tasks) in the G1 heap
4664 // for SequentialSubTasksDone.
4665 // This task also uses SubTasksDone in SharedHeap and G1CollectedHeap
4666 // both of which need setting by set_n_termination().
4667 _g1h->SharedHeap::set_n_termination(active_workers);
4668 _g1h->set_n_termination(active_workers);
4669 terminator()->reset_for_reuse(active_workers);
4670 _n_workers = active_workers;
4671 }
4673 // Helps out with CLD processing.
4674 //
4675 // During InitialMark we need to:
4676 // 1) Scavenge all CLDs for the young GC.
4677 // 2) Mark all objects directly reachable from strong CLDs.
4678 template <G1Mark do_mark_object>
4679 class G1CLDClosure : public CLDClosure {
4680 G1ParCopyClosure<G1BarrierNone, do_mark_object>* _oop_closure;
4681 G1ParCopyClosure<G1BarrierKlass, do_mark_object> _oop_in_klass_closure;
4682 G1KlassScanClosure _klass_in_cld_closure;
4683 bool _claim;
4685 public:
4686 G1CLDClosure(G1ParCopyClosure<G1BarrierNone, do_mark_object>* oop_closure,
4687 bool only_young, bool claim)
4688 : _oop_closure(oop_closure),
4689 _oop_in_klass_closure(oop_closure->g1(),
4690 oop_closure->pss(),
4691 oop_closure->rp()),
4692 _klass_in_cld_closure(&_oop_in_klass_closure, only_young),
4693 _claim(claim) {
4695 }
4697 void do_cld(ClassLoaderData* cld) {
4698 cld->oops_do(_oop_closure, &_klass_in_cld_closure, _claim);
4699 }
4700 };
4702 void work(uint worker_id) {
4703 if (worker_id >= _n_workers) return; // no work needed this round
4705 double start_time_ms = os::elapsedTime() * 1000.0;
4706 _g1h->g1_policy()->phase_times()->record_gc_worker_start_time(worker_id, start_time_ms);
4708 {
4709 ResourceMark rm;
4710 HandleMark hm;
4712 ReferenceProcessor* rp = _g1h->ref_processor_stw();
4714 G1ParScanThreadState pss(_g1h, worker_id, rp);
4715 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, rp);
4717 pss.set_evac_failure_closure(&evac_failure_cl);
4719 bool only_young = _g1h->g1_policy()->gcs_are_young();
4721 // Non-IM young GC.
4722 G1ParCopyClosure<G1BarrierNone, G1MarkNone> scan_only_root_cl(_g1h, &pss, rp);
4723 G1CLDClosure<G1MarkNone> scan_only_cld_cl(&scan_only_root_cl,
4724 only_young, // Only process dirty klasses.
4725 false); // No need to claim CLDs.
4726 // IM young GC.
4727 // Strong roots closures.
4728 G1ParCopyClosure<G1BarrierNone, G1MarkFromRoot> scan_mark_root_cl(_g1h, &pss, rp);
4729 G1CLDClosure<G1MarkFromRoot> scan_mark_cld_cl(&scan_mark_root_cl,
4730 false, // Process all klasses.
4731 true); // Need to claim CLDs.
4732 // Weak roots closures.
4733 G1ParCopyClosure<G1BarrierNone, G1MarkPromotedFromRoot> scan_mark_weak_root_cl(_g1h, &pss, rp);
4734 G1CLDClosure<G1MarkPromotedFromRoot> scan_mark_weak_cld_cl(&scan_mark_weak_root_cl,
4735 false, // Process all klasses.
4736 true); // Need to claim CLDs.
4738 G1CodeBlobClosure scan_only_code_cl(&scan_only_root_cl);
4739 G1CodeBlobClosure scan_mark_code_cl(&scan_mark_root_cl);
4740 // IM Weak code roots are handled later.
4742 OopClosure* strong_root_cl;
4743 OopClosure* weak_root_cl;
4744 CLDClosure* strong_cld_cl;
4745 CLDClosure* weak_cld_cl;
4746 CodeBlobClosure* strong_code_cl;
4748 if (_g1h->g1_policy()->during_initial_mark_pause()) {
4749 // We also need to mark copied objects.
4750 strong_root_cl = &scan_mark_root_cl;
4751 strong_cld_cl = &scan_mark_cld_cl;
4752 strong_code_cl = &scan_mark_code_cl;
4753 if (ClassUnloadingWithConcurrentMark) {
4754 weak_root_cl = &scan_mark_weak_root_cl;
4755 weak_cld_cl = &scan_mark_weak_cld_cl;
4756 } else {
4757 weak_root_cl = &scan_mark_root_cl;
4758 weak_cld_cl = &scan_mark_cld_cl;
4759 }
4760 } else {
4761 strong_root_cl = &scan_only_root_cl;
4762 weak_root_cl = &scan_only_root_cl;
4763 strong_cld_cl = &scan_only_cld_cl;
4764 weak_cld_cl = &scan_only_cld_cl;
4765 strong_code_cl = &scan_only_code_cl;
4766 }
4769 G1ParPushHeapRSClosure push_heap_rs_cl(_g1h, &pss);
4771 pss.start_strong_roots();
4772 _g1h->g1_process_roots(strong_root_cl,
4773 weak_root_cl,
4774 &push_heap_rs_cl,
4775 strong_cld_cl,
4776 weak_cld_cl,
4777 strong_code_cl,
4778 worker_id);
4780 pss.end_strong_roots();
4782 {
4783 double start = os::elapsedTime();
4784 G1ParEvacuateFollowersClosure evac(_g1h, &pss, _queues, &_terminator);
4785 evac.do_void();
4786 double elapsed_ms = (os::elapsedTime()-start)*1000.0;
4787 double term_ms = pss.term_time()*1000.0;
4788 _g1h->g1_policy()->phase_times()->add_obj_copy_time(worker_id, elapsed_ms-term_ms);
4789 _g1h->g1_policy()->phase_times()->record_termination(worker_id, term_ms, pss.term_attempts());
4790 }
4791 _g1h->g1_policy()->record_thread_age_table(pss.age_table());
4792 _g1h->update_surviving_young_words(pss.surviving_young_words()+1);
4794 if (ParallelGCVerbose) {
4795 MutexLocker x(stats_lock());
4796 pss.print_termination_stats(worker_id);
4797 }
4799 assert(pss.queue_is_empty(), "should be empty");
4801 // Close the inner scope so that the ResourceMark and HandleMark
4802 // destructors are executed here and are included as part of the
4803 // "GC Worker Time".
4804 }
4806 double end_time_ms = os::elapsedTime() * 1000.0;
4807 _g1h->g1_policy()->phase_times()->record_gc_worker_end_time(worker_id, end_time_ms);
4808 }
4809 };
4811 // *** Common G1 Evacuation Stuff
4813 // This method is run in a GC worker.
4815 void
4816 G1CollectedHeap::
4817 g1_process_roots(OopClosure* scan_non_heap_roots,
4818 OopClosure* scan_non_heap_weak_roots,
4819 OopsInHeapRegionClosure* scan_rs,
4820 CLDClosure* scan_strong_clds,
4821 CLDClosure* scan_weak_clds,
4822 CodeBlobClosure* scan_strong_code,
4823 uint worker_i) {
4825 // First scan the shared roots.
4826 double ext_roots_start = os::elapsedTime();
4827 double closure_app_time_sec = 0.0;
4829 bool during_im = _g1h->g1_policy()->during_initial_mark_pause();
4830 bool trace_metadata = during_im && ClassUnloadingWithConcurrentMark;
4832 BufferingOopClosure buf_scan_non_heap_roots(scan_non_heap_roots);
4833 BufferingOopClosure buf_scan_non_heap_weak_roots(scan_non_heap_weak_roots);
4835 process_roots(false, // no scoping; this is parallel code
4836 SharedHeap::SO_None,
4837 &buf_scan_non_heap_roots,
4838 &buf_scan_non_heap_weak_roots,
4839 scan_strong_clds,
4840 // Unloading Initial Marks handle the weak CLDs separately.
4841 (trace_metadata ? NULL : scan_weak_clds),
4842 scan_strong_code);
4844 // Now the CM ref_processor roots.
4845 if (!_process_strong_tasks->is_task_claimed(G1H_PS_refProcessor_oops_do)) {
4846 // We need to treat the discovered reference lists of the
4847 // concurrent mark ref processor as roots and keep entries
4848 // (which are added by the marking threads) on them live
4849 // until they can be processed at the end of marking.
4850 ref_processor_cm()->weak_oops_do(&buf_scan_non_heap_roots);
4851 }
4853 if (trace_metadata) {
4854 // Barrier to make sure all workers passed
4855 // the strong CLD and strong nmethods phases.
4856 active_strong_roots_scope()->wait_until_all_workers_done_with_threads(n_par_threads());
4858 // Now take the complement of the strong CLDs.
4859 ClassLoaderDataGraph::roots_cld_do(NULL, scan_weak_clds);
4860 }
4862 // Finish up any enqueued closure apps (attributed as object copy time).
4863 buf_scan_non_heap_roots.done();
4864 buf_scan_non_heap_weak_roots.done();
4866 double obj_copy_time_sec = buf_scan_non_heap_roots.closure_app_seconds()
4867 + buf_scan_non_heap_weak_roots.closure_app_seconds();
4869 g1_policy()->phase_times()->record_obj_copy_time(worker_i, obj_copy_time_sec * 1000.0);
4871 double ext_root_time_ms =
4872 ((os::elapsedTime() - ext_roots_start) - obj_copy_time_sec) * 1000.0;
4874 g1_policy()->phase_times()->record_ext_root_scan_time(worker_i, ext_root_time_ms);
4876 // During conc marking we have to filter the per-thread SATB buffers
4877 // to make sure we remove any oops into the CSet (which will show up
4878 // as implicitly live).
4879 double satb_filtering_ms = 0.0;
4880 if (!_process_strong_tasks->is_task_claimed(G1H_PS_filter_satb_buffers)) {
4881 if (mark_in_progress()) {
4882 double satb_filter_start = os::elapsedTime();
4884 JavaThread::satb_mark_queue_set().filter_thread_buffers();
4886 satb_filtering_ms = (os::elapsedTime() - satb_filter_start) * 1000.0;
4887 }
4888 }
4889 g1_policy()->phase_times()->record_satb_filtering_time(worker_i, satb_filtering_ms);
4891 // Now scan the complement of the collection set.
4892 G1CodeBlobClosure scavenge_cs_nmethods(scan_non_heap_weak_roots);
4894 g1_rem_set()->oops_into_collection_set_do(scan_rs, &scavenge_cs_nmethods, worker_i);
4896 _process_strong_tasks->all_tasks_completed();
4897 }
4899 class G1StringSymbolTableUnlinkTask : public AbstractGangTask {
4900 private:
4901 BoolObjectClosure* _is_alive;
4902 int _initial_string_table_size;
4903 int _initial_symbol_table_size;
4905 bool _process_strings;
4906 int _strings_processed;
4907 int _strings_removed;
4909 bool _process_symbols;
4910 int _symbols_processed;
4911 int _symbols_removed;
4913 bool _do_in_parallel;
4914 public:
4915 G1StringSymbolTableUnlinkTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols) :
4916 AbstractGangTask("String/Symbol Unlinking"),
4917 _is_alive(is_alive),
4918 _do_in_parallel(G1CollectedHeap::use_parallel_gc_threads()),
4919 _process_strings(process_strings), _strings_processed(0), _strings_removed(0),
4920 _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0) {
4922 _initial_string_table_size = StringTable::the_table()->table_size();
4923 _initial_symbol_table_size = SymbolTable::the_table()->table_size();
4924 if (process_strings) {
4925 StringTable::clear_parallel_claimed_index();
4926 }
4927 if (process_symbols) {
4928 SymbolTable::clear_parallel_claimed_index();
4929 }
4930 }
4932 ~G1StringSymbolTableUnlinkTask() {
4933 guarantee(!_process_strings || !_do_in_parallel || StringTable::parallel_claimed_index() >= _initial_string_table_size,
4934 err_msg("claim value "INT32_FORMAT" after unlink less than initial string table size "INT32_FORMAT,
4935 StringTable::parallel_claimed_index(), _initial_string_table_size));
4936 guarantee(!_process_symbols || !_do_in_parallel || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size,
4937 err_msg("claim value "INT32_FORMAT" after unlink less than initial symbol table size "INT32_FORMAT,
4938 SymbolTable::parallel_claimed_index(), _initial_symbol_table_size));
4940 if (G1TraceStringSymbolTableScrubbing) {
4941 gclog_or_tty->print_cr("Cleaned string and symbol table, "
4942 "strings: "SIZE_FORMAT" processed, "SIZE_FORMAT" removed, "
4943 "symbols: "SIZE_FORMAT" processed, "SIZE_FORMAT" removed",
4944 strings_processed(), strings_removed(),
4945 symbols_processed(), symbols_removed());
4946 }
4947 }
4949 void work(uint worker_id) {
4950 if (_do_in_parallel) {
4951 int strings_processed = 0;
4952 int strings_removed = 0;
4953 int symbols_processed = 0;
4954 int symbols_removed = 0;
4955 if (_process_strings) {
4956 StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed);
4957 Atomic::add(strings_processed, &_strings_processed);
4958 Atomic::add(strings_removed, &_strings_removed);
4959 }
4960 if (_process_symbols) {
4961 SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed);
4962 Atomic::add(symbols_processed, &_symbols_processed);
4963 Atomic::add(symbols_removed, &_symbols_removed);
4964 }
4965 } else {
4966 if (_process_strings) {
4967 StringTable::unlink(_is_alive, &_strings_processed, &_strings_removed);
4968 }
4969 if (_process_symbols) {
4970 SymbolTable::unlink(&_symbols_processed, &_symbols_removed);
4971 }
4972 }
4973 }
4975 size_t strings_processed() const { return (size_t)_strings_processed; }
4976 size_t strings_removed() const { return (size_t)_strings_removed; }
4978 size_t symbols_processed() const { return (size_t)_symbols_processed; }
4979 size_t symbols_removed() const { return (size_t)_symbols_removed; }
4980 };
4982 class G1CodeCacheUnloadingTask VALUE_OBJ_CLASS_SPEC {
4983 private:
4984 static Monitor* _lock;
4986 BoolObjectClosure* const _is_alive;
4987 const bool _unloading_occurred;
4988 const uint _num_workers;
4990 // Variables used to claim nmethods.
4991 nmethod* _first_nmethod;
4992 volatile nmethod* _claimed_nmethod;
4994 // The list of nmethods that need to be processed by the second pass.
4995 volatile nmethod* _postponed_list;
4996 volatile uint _num_entered_barrier;
4998 public:
4999 G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) :
5000 _is_alive(is_alive),
5001 _unloading_occurred(unloading_occurred),
5002 _num_workers(num_workers),
5003 _first_nmethod(NULL),
5004 _claimed_nmethod(NULL),
5005 _postponed_list(NULL),
5006 _num_entered_barrier(0)
5007 {
5008 nmethod::increase_unloading_clock();
5009 _first_nmethod = CodeCache::alive_nmethod(CodeCache::first());
5010 _claimed_nmethod = (volatile nmethod*)_first_nmethod;
5011 }
5013 ~G1CodeCacheUnloadingTask() {
5014 CodeCache::verify_clean_inline_caches();
5016 CodeCache::set_needs_cache_clean(false);
5017 guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be");
5019 CodeCache::verify_icholder_relocations();
5020 }
5022 private:
5023 void add_to_postponed_list(nmethod* nm) {
5024 nmethod* old;
5025 do {
5026 old = (nmethod*)_postponed_list;
5027 nm->set_unloading_next(old);
5028 } while ((nmethod*)Atomic::cmpxchg_ptr(nm, &_postponed_list, old) != old);
5029 }
5031 void clean_nmethod(nmethod* nm) {
5032 bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred);
5034 if (postponed) {
5035 // This nmethod referred to an nmethod that has not been cleaned/unloaded yet.
5036 add_to_postponed_list(nm);
5037 }
5039 // Mark that this thread has been cleaned/unloaded.
5040 // After this call, it will be safe to ask if this nmethod was unloaded or not.
5041 nm->set_unloading_clock(nmethod::global_unloading_clock());
5042 }
5044 void clean_nmethod_postponed(nmethod* nm) {
5045 nm->do_unloading_parallel_postponed(_is_alive, _unloading_occurred);
5046 }
5048 static const int MaxClaimNmethods = 16;
5050 void claim_nmethods(nmethod** claimed_nmethods, int *num_claimed_nmethods) {
5051 nmethod* first;
5052 nmethod* last;
5054 do {
5055 *num_claimed_nmethods = 0;
5057 first = last = (nmethod*)_claimed_nmethod;
5059 if (first != NULL) {
5060 for (int i = 0; i < MaxClaimNmethods; i++) {
5061 last = CodeCache::alive_nmethod(CodeCache::next(last));
5063 if (last == NULL) {
5064 break;
5065 }
5067 claimed_nmethods[i] = last;
5068 (*num_claimed_nmethods)++;
5069 }
5070 }
5072 } while ((nmethod*)Atomic::cmpxchg_ptr(last, &_claimed_nmethod, first) != first);
5073 }
5075 nmethod* claim_postponed_nmethod() {
5076 nmethod* claim;
5077 nmethod* next;
5079 do {
5080 claim = (nmethod*)_postponed_list;
5081 if (claim == NULL) {
5082 return NULL;
5083 }
5085 next = claim->unloading_next();
5087 } while ((nmethod*)Atomic::cmpxchg_ptr(next, &_postponed_list, claim) != claim);
5089 return claim;
5090 }
5092 public:
5093 // Mark that we're done with the first pass of nmethod cleaning.
5094 void barrier_mark(uint worker_id) {
5095 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
5096 _num_entered_barrier++;
5097 if (_num_entered_barrier == _num_workers) {
5098 ml.notify_all();
5099 }
5100 }
5102 // See if we have to wait for the other workers to
5103 // finish their first-pass nmethod cleaning work.
5104 void barrier_wait(uint worker_id) {
5105 if (_num_entered_barrier < _num_workers) {
5106 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
5107 while (_num_entered_barrier < _num_workers) {
5108 ml.wait(Mutex::_no_safepoint_check_flag, 0, false);
5109 }
5110 }
5111 }
5113 // Cleaning and unloading of nmethods. Some work has to be postponed
5114 // to the second pass, when we know which nmethods survive.
5115 void work_first_pass(uint worker_id) {
5116 // The first nmethods is claimed by the first worker.
5117 if (worker_id == 0 && _first_nmethod != NULL) {
5118 clean_nmethod(_first_nmethod);
5119 _first_nmethod = NULL;
5120 }
5122 int num_claimed_nmethods;
5123 nmethod* claimed_nmethods[MaxClaimNmethods];
5125 while (true) {
5126 claim_nmethods(claimed_nmethods, &num_claimed_nmethods);
5128 if (num_claimed_nmethods == 0) {
5129 break;
5130 }
5132 for (int i = 0; i < num_claimed_nmethods; i++) {
5133 clean_nmethod(claimed_nmethods[i]);
5134 }
5135 }
5136 }
5138 void work_second_pass(uint worker_id) {
5139 nmethod* nm;
5140 // Take care of postponed nmethods.
5141 while ((nm = claim_postponed_nmethod()) != NULL) {
5142 clean_nmethod_postponed(nm);
5143 }
5144 }
5145 };
5147 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock");
5149 class G1KlassCleaningTask : public StackObj {
5150 BoolObjectClosure* _is_alive;
5151 volatile jint _clean_klass_tree_claimed;
5152 ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator;
5154 public:
5155 G1KlassCleaningTask(BoolObjectClosure* is_alive) :
5156 _is_alive(is_alive),
5157 _clean_klass_tree_claimed(0),
5158 _klass_iterator() {
5159 }
5161 private:
5162 bool claim_clean_klass_tree_task() {
5163 if (_clean_klass_tree_claimed) {
5164 return false;
5165 }
5167 return Atomic::cmpxchg(1, (jint*)&_clean_klass_tree_claimed, 0) == 0;
5168 }
5170 InstanceKlass* claim_next_klass() {
5171 Klass* klass;
5172 do {
5173 klass =_klass_iterator.next_klass();
5174 } while (klass != NULL && !klass->oop_is_instance());
5176 return (InstanceKlass*)klass;
5177 }
5179 public:
5181 void clean_klass(InstanceKlass* ik) {
5182 ik->clean_implementors_list(_is_alive);
5183 ik->clean_method_data(_is_alive);
5185 // G1 specific cleanup work that has
5186 // been moved here to be done in parallel.
5187 ik->clean_dependent_nmethods();
5188 }
5190 void work() {
5191 ResourceMark rm;
5193 // One worker will clean the subklass/sibling klass tree.
5194 if (claim_clean_klass_tree_task()) {
5195 Klass::clean_subklass_tree(_is_alive);
5196 }
5198 // All workers will help cleaning the classes,
5199 InstanceKlass* klass;
5200 while ((klass = claim_next_klass()) != NULL) {
5201 clean_klass(klass);
5202 }
5203 }
5204 };
5206 // To minimize the remark pause times, the tasks below are done in parallel.
5207 class G1ParallelCleaningTask : public AbstractGangTask {
5208 private:
5209 G1StringSymbolTableUnlinkTask _string_symbol_task;
5210 G1CodeCacheUnloadingTask _code_cache_task;
5211 G1KlassCleaningTask _klass_cleaning_task;
5213 public:
5214 // The constructor is run in the VMThread.
5215 G1ParallelCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, uint num_workers, bool unloading_occurred) :
5216 AbstractGangTask("Parallel Cleaning"),
5217 _string_symbol_task(is_alive, process_strings, process_symbols),
5218 _code_cache_task(num_workers, is_alive, unloading_occurred),
5219 _klass_cleaning_task(is_alive) {
5220 }
5222 // The parallel work done by all worker threads.
5223 void work(uint worker_id) {
5224 // Do first pass of code cache cleaning.
5225 _code_cache_task.work_first_pass(worker_id);
5227 // Let the threads mark that the first pass is done.
5228 _code_cache_task.barrier_mark(worker_id);
5230 // Clean the Strings and Symbols.
5231 _string_symbol_task.work(worker_id);
5233 // Wait for all workers to finish the first code cache cleaning pass.
5234 _code_cache_task.barrier_wait(worker_id);
5236 // Do the second code cache cleaning work, which realize on
5237 // the liveness information gathered during the first pass.
5238 _code_cache_task.work_second_pass(worker_id);
5240 // Clean all klasses that were not unloaded.
5241 _klass_cleaning_task.work();
5242 }
5243 };
5246 void G1CollectedHeap::parallel_cleaning(BoolObjectClosure* is_alive,
5247 bool process_strings,
5248 bool process_symbols,
5249 bool class_unloading_occurred) {
5250 uint n_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
5251 workers()->active_workers() : 1);
5253 G1ParallelCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols,
5254 n_workers, class_unloading_occurred);
5255 if (G1CollectedHeap::use_parallel_gc_threads()) {
5256 set_par_threads(n_workers);
5257 workers()->run_task(&g1_unlink_task);
5258 set_par_threads(0);
5259 } else {
5260 g1_unlink_task.work(0);
5261 }
5262 }
5264 void G1CollectedHeap::unlink_string_and_symbol_table(BoolObjectClosure* is_alive,
5265 bool process_strings, bool process_symbols) {
5266 {
5267 uint n_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
5268 _g1h->workers()->active_workers() : 1);
5269 G1StringSymbolTableUnlinkTask g1_unlink_task(is_alive, process_strings, process_symbols);
5270 if (G1CollectedHeap::use_parallel_gc_threads()) {
5271 set_par_threads(n_workers);
5272 workers()->run_task(&g1_unlink_task);
5273 set_par_threads(0);
5274 } else {
5275 g1_unlink_task.work(0);
5276 }
5277 }
5279 if (G1StringDedup::is_enabled()) {
5280 G1StringDedup::unlink(is_alive);
5281 }
5282 }
5284 class G1RedirtyLoggedCardsTask : public AbstractGangTask {
5285 private:
5286 DirtyCardQueueSet* _queue;
5287 public:
5288 G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue) : AbstractGangTask("Redirty Cards"), _queue(queue) { }
5290 virtual void work(uint worker_id) {
5291 double start_time = os::elapsedTime();
5293 RedirtyLoggedCardTableEntryClosure cl;
5294 if (G1CollectedHeap::heap()->use_parallel_gc_threads()) {
5295 _queue->par_apply_closure_to_all_completed_buffers(&cl);
5296 } else {
5297 _queue->apply_closure_to_all_completed_buffers(&cl);
5298 }
5300 G1GCPhaseTimes* timer = G1CollectedHeap::heap()->g1_policy()->phase_times();
5301 timer->record_redirty_logged_cards_time_ms(worker_id, (os::elapsedTime() - start_time) * 1000.0);
5302 timer->record_redirty_logged_cards_processed_cards(worker_id, cl.num_processed());
5303 }
5304 };
5306 void G1CollectedHeap::redirty_logged_cards() {
5307 double redirty_logged_cards_start = os::elapsedTime();
5309 uint n_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
5310 _g1h->workers()->active_workers() : 1);
5312 G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set());
5313 dirty_card_queue_set().reset_for_par_iteration();
5314 if (use_parallel_gc_threads()) {
5315 set_par_threads(n_workers);
5316 workers()->run_task(&redirty_task);
5317 set_par_threads(0);
5318 } else {
5319 redirty_task.work(0);
5320 }
5322 DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set();
5323 dcq.merge_bufferlists(&dirty_card_queue_set());
5324 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
5326 g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0);
5327 }
5329 // Weak Reference Processing support
5331 // An always "is_alive" closure that is used to preserve referents.
5332 // If the object is non-null then it's alive. Used in the preservation
5333 // of referent objects that are pointed to by reference objects
5334 // discovered by the CM ref processor.
5335 class G1AlwaysAliveClosure: public BoolObjectClosure {
5336 G1CollectedHeap* _g1;
5337 public:
5338 G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
5339 bool do_object_b(oop p) {
5340 if (p != NULL) {
5341 return true;
5342 }
5343 return false;
5344 }
5345 };
5347 bool G1STWIsAliveClosure::do_object_b(oop p) {
5348 // An object is reachable if it is outside the collection set,
5349 // or is inside and copied.
5350 return !_g1->obj_in_cs(p) || p->is_forwarded();
5351 }
5353 // Non Copying Keep Alive closure
5354 class G1KeepAliveClosure: public OopClosure {
5355 G1CollectedHeap* _g1;
5356 public:
5357 G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
5358 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
5359 void do_oop(oop* p) {
5360 oop obj = *p;
5361 assert(obj != NULL, "the caller should have filtered out NULL values");
5363 G1CollectedHeap::in_cset_state_t cset_state = _g1->in_cset_state(obj);
5364 if (cset_state == G1CollectedHeap::InNeither) {
5365 return;
5366 }
5367 if (cset_state == G1CollectedHeap::InCSet) {
5368 assert( obj->is_forwarded(), "invariant" );
5369 *p = obj->forwardee();
5370 } else {
5371 assert(!obj->is_forwarded(), "invariant" );
5372 assert(cset_state == G1CollectedHeap::IsHumongous,
5373 err_msg("Only allowed InCSet state is IsHumongous, but is %d", cset_state));
5374 _g1->set_humongous_is_live(obj);
5375 }
5376 }
5377 };
5379 // Copying Keep Alive closure - can be called from both
5380 // serial and parallel code as long as different worker
5381 // threads utilize different G1ParScanThreadState instances
5382 // and different queues.
5384 class G1CopyingKeepAliveClosure: public OopClosure {
5385 G1CollectedHeap* _g1h;
5386 OopClosure* _copy_non_heap_obj_cl;
5387 G1ParScanThreadState* _par_scan_state;
5389 public:
5390 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
5391 OopClosure* non_heap_obj_cl,
5392 G1ParScanThreadState* pss):
5393 _g1h(g1h),
5394 _copy_non_heap_obj_cl(non_heap_obj_cl),
5395 _par_scan_state(pss)
5396 {}
5398 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
5399 virtual void do_oop( oop* p) { do_oop_work(p); }
5401 template <class T> void do_oop_work(T* p) {
5402 oop obj = oopDesc::load_decode_heap_oop(p);
5404 if (_g1h->is_in_cset_or_humongous(obj)) {
5405 // If the referent object has been forwarded (either copied
5406 // to a new location or to itself in the event of an
5407 // evacuation failure) then we need to update the reference
5408 // field and, if both reference and referent are in the G1
5409 // heap, update the RSet for the referent.
5410 //
5411 // If the referent has not been forwarded then we have to keep
5412 // it alive by policy. Therefore we have copy the referent.
5413 //
5414 // If the reference field is in the G1 heap then we can push
5415 // on the PSS queue. When the queue is drained (after each
5416 // phase of reference processing) the object and it's followers
5417 // will be copied, the reference field set to point to the
5418 // new location, and the RSet updated. Otherwise we need to
5419 // use the the non-heap or metadata closures directly to copy
5420 // the referent object and update the pointer, while avoiding
5421 // updating the RSet.
5423 if (_g1h->is_in_g1_reserved(p)) {
5424 _par_scan_state->push_on_queue(p);
5425 } else {
5426 assert(!Metaspace::contains((const void*)p),
5427 err_msg("Unexpectedly found a pointer from metadata: "
5428 PTR_FORMAT, p));
5429 _copy_non_heap_obj_cl->do_oop(p);
5430 }
5431 }
5432 }
5433 };
5435 // Serial drain queue closure. Called as the 'complete_gc'
5436 // closure for each discovered list in some of the
5437 // reference processing phases.
5439 class G1STWDrainQueueClosure: public VoidClosure {
5440 protected:
5441 G1CollectedHeap* _g1h;
5442 G1ParScanThreadState* _par_scan_state;
5444 G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
5446 public:
5447 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
5448 _g1h(g1h),
5449 _par_scan_state(pss)
5450 { }
5452 void do_void() {
5453 G1ParScanThreadState* const pss = par_scan_state();
5454 pss->trim_queue();
5455 }
5456 };
5458 // Parallel Reference Processing closures
5460 // Implementation of AbstractRefProcTaskExecutor for parallel reference
5461 // processing during G1 evacuation pauses.
5463 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
5464 private:
5465 G1CollectedHeap* _g1h;
5466 RefToScanQueueSet* _queues;
5467 FlexibleWorkGang* _workers;
5468 int _active_workers;
5470 public:
5471 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
5472 FlexibleWorkGang* workers,
5473 RefToScanQueueSet *task_queues,
5474 int n_workers) :
5475 _g1h(g1h),
5476 _queues(task_queues),
5477 _workers(workers),
5478 _active_workers(n_workers)
5479 {
5480 assert(n_workers > 0, "shouldn't call this otherwise");
5481 }
5483 // Executes the given task using concurrent marking worker threads.
5484 virtual void execute(ProcessTask& task);
5485 virtual void execute(EnqueueTask& task);
5486 };
5488 // Gang task for possibly parallel reference processing
5490 class G1STWRefProcTaskProxy: public AbstractGangTask {
5491 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
5492 ProcessTask& _proc_task;
5493 G1CollectedHeap* _g1h;
5494 RefToScanQueueSet *_task_queues;
5495 ParallelTaskTerminator* _terminator;
5497 public:
5498 G1STWRefProcTaskProxy(ProcessTask& proc_task,
5499 G1CollectedHeap* g1h,
5500 RefToScanQueueSet *task_queues,
5501 ParallelTaskTerminator* terminator) :
5502 AbstractGangTask("Process reference objects in parallel"),
5503 _proc_task(proc_task),
5504 _g1h(g1h),
5505 _task_queues(task_queues),
5506 _terminator(terminator)
5507 {}
5509 virtual void work(uint worker_id) {
5510 // The reference processing task executed by a single worker.
5511 ResourceMark rm;
5512 HandleMark hm;
5514 G1STWIsAliveClosure is_alive(_g1h);
5516 G1ParScanThreadState pss(_g1h, worker_id, NULL);
5517 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5519 pss.set_evac_failure_closure(&evac_failure_cl);
5521 G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL);
5523 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5525 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5527 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5528 // We also need to mark copied objects.
5529 copy_non_heap_cl = ©_mark_non_heap_cl;
5530 }
5532 // Keep alive closure.
5533 G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, &pss);
5535 // Complete GC closure
5536 G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _task_queues, _terminator);
5538 // Call the reference processing task's work routine.
5539 _proc_task.work(worker_id, is_alive, keep_alive, drain_queue);
5541 // Note we cannot assert that the refs array is empty here as not all
5542 // of the processing tasks (specifically phase2 - pp2_work) execute
5543 // the complete_gc closure (which ordinarily would drain the queue) so
5544 // the queue may not be empty.
5545 }
5546 };
5548 // Driver routine for parallel reference processing.
5549 // Creates an instance of the ref processing gang
5550 // task and has the worker threads execute it.
5551 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) {
5552 assert(_workers != NULL, "Need parallel worker threads.");
5554 ParallelTaskTerminator terminator(_active_workers, _queues);
5555 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _queues, &terminator);
5557 _g1h->set_par_threads(_active_workers);
5558 _workers->run_task(&proc_task_proxy);
5559 _g1h->set_par_threads(0);
5560 }
5562 // Gang task for parallel reference enqueueing.
5564 class G1STWRefEnqueueTaskProxy: public AbstractGangTask {
5565 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
5566 EnqueueTask& _enq_task;
5568 public:
5569 G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) :
5570 AbstractGangTask("Enqueue reference objects in parallel"),
5571 _enq_task(enq_task)
5572 { }
5574 virtual void work(uint worker_id) {
5575 _enq_task.work(worker_id);
5576 }
5577 };
5579 // Driver routine for parallel reference enqueueing.
5580 // Creates an instance of the ref enqueueing gang
5581 // task and has the worker threads execute it.
5583 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
5584 assert(_workers != NULL, "Need parallel worker threads.");
5586 G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task);
5588 _g1h->set_par_threads(_active_workers);
5589 _workers->run_task(&enq_task_proxy);
5590 _g1h->set_par_threads(0);
5591 }
5593 // End of weak reference support closures
5595 // Abstract task used to preserve (i.e. copy) any referent objects
5596 // that are in the collection set and are pointed to by reference
5597 // objects discovered by the CM ref processor.
5599 class G1ParPreserveCMReferentsTask: public AbstractGangTask {
5600 protected:
5601 G1CollectedHeap* _g1h;
5602 RefToScanQueueSet *_queues;
5603 ParallelTaskTerminator _terminator;
5604 uint _n_workers;
5606 public:
5607 G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h,int workers, RefToScanQueueSet *task_queues) :
5608 AbstractGangTask("ParPreserveCMReferents"),
5609 _g1h(g1h),
5610 _queues(task_queues),
5611 _terminator(workers, _queues),
5612 _n_workers(workers)
5613 { }
5615 void work(uint worker_id) {
5616 ResourceMark rm;
5617 HandleMark hm;
5619 G1ParScanThreadState pss(_g1h, worker_id, NULL);
5620 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5622 pss.set_evac_failure_closure(&evac_failure_cl);
5624 assert(pss.queue_is_empty(), "both queue and overflow should be empty");
5626 G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL);
5628 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5630 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5632 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5633 // We also need to mark copied objects.
5634 copy_non_heap_cl = ©_mark_non_heap_cl;
5635 }
5637 // Is alive closure
5638 G1AlwaysAliveClosure always_alive(_g1h);
5640 // Copying keep alive closure. Applied to referent objects that need
5641 // to be copied.
5642 G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, &pss);
5644 ReferenceProcessor* rp = _g1h->ref_processor_cm();
5646 uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q();
5647 uint stride = MIN2(MAX2(_n_workers, 1U), limit);
5649 // limit is set using max_num_q() - which was set using ParallelGCThreads.
5650 // So this must be true - but assert just in case someone decides to
5651 // change the worker ids.
5652 assert(0 <= worker_id && worker_id < limit, "sanity");
5653 assert(!rp->discovery_is_atomic(), "check this code");
5655 // Select discovered lists [i, i+stride, i+2*stride,...,limit)
5656 for (uint idx = worker_id; idx < limit; idx += stride) {
5657 DiscoveredList& ref_list = rp->discovered_refs()[idx];
5659 DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive);
5660 while (iter.has_next()) {
5661 // Since discovery is not atomic for the CM ref processor, we
5662 // can see some null referent objects.
5663 iter.load_ptrs(DEBUG_ONLY(true));
5664 oop ref = iter.obj();
5666 // This will filter nulls.
5667 if (iter.is_referent_alive()) {
5668 iter.make_referent_alive();
5669 }
5670 iter.move_to_next();
5671 }
5672 }
5674 // Drain the queue - which may cause stealing
5675 G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _queues, &_terminator);
5676 drain_queue.do_void();
5677 // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure
5678 assert(pss.queue_is_empty(), "should be");
5679 }
5680 };
5682 // Weak Reference processing during an evacuation pause (part 1).
5683 void G1CollectedHeap::process_discovered_references(uint no_of_gc_workers) {
5684 double ref_proc_start = os::elapsedTime();
5686 ReferenceProcessor* rp = _ref_processor_stw;
5687 assert(rp->discovery_enabled(), "should have been enabled");
5689 // Any reference objects, in the collection set, that were 'discovered'
5690 // by the CM ref processor should have already been copied (either by
5691 // applying the external root copy closure to the discovered lists, or
5692 // by following an RSet entry).
5693 //
5694 // But some of the referents, that are in the collection set, that these
5695 // reference objects point to may not have been copied: the STW ref
5696 // processor would have seen that the reference object had already
5697 // been 'discovered' and would have skipped discovering the reference,
5698 // but would not have treated the reference object as a regular oop.
5699 // As a result the copy closure would not have been applied to the
5700 // referent object.
5701 //
5702 // We need to explicitly copy these referent objects - the references
5703 // will be processed at the end of remarking.
5704 //
5705 // We also need to do this copying before we process the reference
5706 // objects discovered by the STW ref processor in case one of these
5707 // referents points to another object which is also referenced by an
5708 // object discovered by the STW ref processor.
5710 assert(!G1CollectedHeap::use_parallel_gc_threads() ||
5711 no_of_gc_workers == workers()->active_workers(),
5712 "Need to reset active GC workers");
5714 set_par_threads(no_of_gc_workers);
5715 G1ParPreserveCMReferentsTask keep_cm_referents(this,
5716 no_of_gc_workers,
5717 _task_queues);
5719 if (G1CollectedHeap::use_parallel_gc_threads()) {
5720 workers()->run_task(&keep_cm_referents);
5721 } else {
5722 keep_cm_referents.work(0);
5723 }
5725 set_par_threads(0);
5727 // Closure to test whether a referent is alive.
5728 G1STWIsAliveClosure is_alive(this);
5730 // Even when parallel reference processing is enabled, the processing
5731 // of JNI refs is serial and performed serially by the current thread
5732 // rather than by a worker. The following PSS will be used for processing
5733 // JNI refs.
5735 // Use only a single queue for this PSS.
5736 G1ParScanThreadState pss(this, 0, NULL);
5738 // We do not embed a reference processor in the copying/scanning
5739 // closures while we're actually processing the discovered
5740 // reference objects.
5741 G1ParScanHeapEvacFailureClosure evac_failure_cl(this, &pss, NULL);
5743 pss.set_evac_failure_closure(&evac_failure_cl);
5745 assert(pss.queue_is_empty(), "pre-condition");
5747 G1ParScanExtRootClosure only_copy_non_heap_cl(this, &pss, NULL);
5749 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(this, &pss, NULL);
5751 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5753 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5754 // We also need to mark copied objects.
5755 copy_non_heap_cl = ©_mark_non_heap_cl;
5756 }
5758 // Keep alive closure.
5759 G1CopyingKeepAliveClosure keep_alive(this, copy_non_heap_cl, &pss);
5761 // Serial Complete GC closure
5762 G1STWDrainQueueClosure drain_queue(this, &pss);
5764 // Setup the soft refs policy...
5765 rp->setup_policy(false);
5767 ReferenceProcessorStats stats;
5768 if (!rp->processing_is_mt()) {
5769 // Serial reference processing...
5770 stats = rp->process_discovered_references(&is_alive,
5771 &keep_alive,
5772 &drain_queue,
5773 NULL,
5774 _gc_timer_stw,
5775 _gc_tracer_stw->gc_id());
5776 } else {
5777 // Parallel reference processing
5778 assert(rp->num_q() == no_of_gc_workers, "sanity");
5779 assert(no_of_gc_workers <= rp->max_num_q(), "sanity");
5781 G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers);
5782 stats = rp->process_discovered_references(&is_alive,
5783 &keep_alive,
5784 &drain_queue,
5785 &par_task_executor,
5786 _gc_timer_stw,
5787 _gc_tracer_stw->gc_id());
5788 }
5790 _gc_tracer_stw->report_gc_reference_stats(stats);
5792 // We have completed copying any necessary live referent objects.
5793 assert(pss.queue_is_empty(), "both queue and overflow should be empty");
5795 double ref_proc_time = os::elapsedTime() - ref_proc_start;
5796 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
5797 }
5799 // Weak Reference processing during an evacuation pause (part 2).
5800 void G1CollectedHeap::enqueue_discovered_references(uint no_of_gc_workers) {
5801 double ref_enq_start = os::elapsedTime();
5803 ReferenceProcessor* rp = _ref_processor_stw;
5804 assert(!rp->discovery_enabled(), "should have been disabled as part of processing");
5806 // Now enqueue any remaining on the discovered lists on to
5807 // the pending list.
5808 if (!rp->processing_is_mt()) {
5809 // Serial reference processing...
5810 rp->enqueue_discovered_references();
5811 } else {
5812 // Parallel reference enqueueing
5814 assert(no_of_gc_workers == workers()->active_workers(),
5815 "Need to reset active workers");
5816 assert(rp->num_q() == no_of_gc_workers, "sanity");
5817 assert(no_of_gc_workers <= rp->max_num_q(), "sanity");
5819 G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers);
5820 rp->enqueue_discovered_references(&par_task_executor);
5821 }
5823 rp->verify_no_references_recorded();
5824 assert(!rp->discovery_enabled(), "should have been disabled");
5826 // FIXME
5827 // CM's reference processing also cleans up the string and symbol tables.
5828 // Should we do that here also? We could, but it is a serial operation
5829 // and could significantly increase the pause time.
5831 double ref_enq_time = os::elapsedTime() - ref_enq_start;
5832 g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0);
5833 }
5835 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info) {
5836 _expand_heap_after_alloc_failure = true;
5837 _evacuation_failed = false;
5839 // Should G1EvacuationFailureALot be in effect for this GC?
5840 NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();)
5842 g1_rem_set()->prepare_for_oops_into_collection_set_do();
5844 // Disable the hot card cache.
5845 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
5846 hot_card_cache->reset_hot_cache_claimed_index();
5847 hot_card_cache->set_use_cache(false);
5849 uint n_workers;
5850 if (G1CollectedHeap::use_parallel_gc_threads()) {
5851 n_workers =
5852 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
5853 workers()->active_workers(),
5854 Threads::number_of_non_daemon_threads());
5855 assert(UseDynamicNumberOfGCThreads ||
5856 n_workers == workers()->total_workers(),
5857 "If not dynamic should be using all the workers");
5858 workers()->set_active_workers(n_workers);
5859 set_par_threads(n_workers);
5860 } else {
5861 assert(n_par_threads() == 0,
5862 "Should be the original non-parallel value");
5863 n_workers = 1;
5864 }
5866 G1ParTask g1_par_task(this, _task_queues);
5868 init_for_evac_failure(NULL);
5870 rem_set()->prepare_for_younger_refs_iterate(true);
5872 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
5873 double start_par_time_sec = os::elapsedTime();
5874 double end_par_time_sec;
5876 {
5877 StrongRootsScope srs(this);
5878 // InitialMark needs claim bits to keep track of the marked-through CLDs.
5879 if (g1_policy()->during_initial_mark_pause()) {
5880 ClassLoaderDataGraph::clear_claimed_marks();
5881 }
5883 if (G1CollectedHeap::use_parallel_gc_threads()) {
5884 // The individual threads will set their evac-failure closures.
5885 if (ParallelGCVerbose) G1ParScanThreadState::print_termination_stats_hdr();
5886 // These tasks use ShareHeap::_process_strong_tasks
5887 assert(UseDynamicNumberOfGCThreads ||
5888 workers()->active_workers() == workers()->total_workers(),
5889 "If not dynamic should be using all the workers");
5890 workers()->run_task(&g1_par_task);
5891 } else {
5892 g1_par_task.set_for_termination(n_workers);
5893 g1_par_task.work(0);
5894 }
5895 end_par_time_sec = os::elapsedTime();
5897 // Closing the inner scope will execute the destructor
5898 // for the StrongRootsScope object. We record the current
5899 // elapsed time before closing the scope so that time
5900 // taken for the SRS destructor is NOT included in the
5901 // reported parallel time.
5902 }
5904 double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0;
5905 g1_policy()->phase_times()->record_par_time(par_time_ms);
5907 double code_root_fixup_time_ms =
5908 (os::elapsedTime() - end_par_time_sec) * 1000.0;
5909 g1_policy()->phase_times()->record_code_root_fixup_time(code_root_fixup_time_ms);
5911 set_par_threads(0);
5913 // Process any discovered reference objects - we have
5914 // to do this _before_ we retire the GC alloc regions
5915 // as we may have to copy some 'reachable' referent
5916 // objects (and their reachable sub-graphs) that were
5917 // not copied during the pause.
5918 process_discovered_references(n_workers);
5920 // Weak root processing.
5921 {
5922 G1STWIsAliveClosure is_alive(this);
5923 G1KeepAliveClosure keep_alive(this);
5924 JNIHandles::weak_oops_do(&is_alive, &keep_alive);
5925 if (G1StringDedup::is_enabled()) {
5926 G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive);
5927 }
5928 }
5930 _allocator->release_gc_alloc_regions(n_workers, evacuation_info);
5931 g1_rem_set()->cleanup_after_oops_into_collection_set_do();
5933 // Reset and re-enable the hot card cache.
5934 // Note the counts for the cards in the regions in the
5935 // collection set are reset when the collection set is freed.
5936 hot_card_cache->reset_hot_cache();
5937 hot_card_cache->set_use_cache(true);
5939 purge_code_root_memory();
5941 if (g1_policy()->during_initial_mark_pause()) {
5942 // Reset the claim values set during marking the strong code roots
5943 reset_heap_region_claim_values();
5944 }
5946 finalize_for_evac_failure();
5948 if (evacuation_failed()) {
5949 remove_self_forwarding_pointers();
5951 // Reset the G1EvacuationFailureALot counters and flags
5952 // Note: the values are reset only when an actual
5953 // evacuation failure occurs.
5954 NOT_PRODUCT(reset_evacuation_should_fail();)
5955 }
5957 // Enqueue any remaining references remaining on the STW
5958 // reference processor's discovered lists. We need to do
5959 // this after the card table is cleaned (and verified) as
5960 // the act of enqueueing entries on to the pending list
5961 // will log these updates (and dirty their associated
5962 // cards). We need these updates logged to update any
5963 // RSets.
5964 enqueue_discovered_references(n_workers);
5966 redirty_logged_cards();
5967 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
5968 }
5970 void G1CollectedHeap::free_region(HeapRegion* hr,
5971 FreeRegionList* free_list,
5972 bool par,
5973 bool locked) {
5974 assert(!hr->is_free(), "the region should not be free");
5975 assert(!hr->is_empty(), "the region should not be empty");
5976 assert(_hrm.is_available(hr->hrm_index()), "region should be committed");
5977 assert(free_list != NULL, "pre-condition");
5979 if (G1VerifyBitmaps) {
5980 MemRegion mr(hr->bottom(), hr->end());
5981 concurrent_mark()->clearRangePrevBitmap(mr);
5982 }
5984 // Clear the card counts for this region.
5985 // Note: we only need to do this if the region is not young
5986 // (since we don't refine cards in young regions).
5987 if (!hr->is_young()) {
5988 _cg1r->hot_card_cache()->reset_card_counts(hr);
5989 }
5990 hr->hr_clear(par, true /* clear_space */, locked /* locked */);
5991 free_list->add_ordered(hr);
5992 }
5994 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
5995 FreeRegionList* free_list,
5996 bool par) {
5997 assert(hr->startsHumongous(), "this is only for starts humongous regions");
5998 assert(free_list != NULL, "pre-condition");
6000 size_t hr_capacity = hr->capacity();
6001 // We need to read this before we make the region non-humongous,
6002 // otherwise the information will be gone.
6003 uint last_index = hr->last_hc_index();
6004 hr->clear_humongous();
6005 free_region(hr, free_list, par);
6007 uint i = hr->hrm_index() + 1;
6008 while (i < last_index) {
6009 HeapRegion* curr_hr = region_at(i);
6010 assert(curr_hr->continuesHumongous(), "invariant");
6011 curr_hr->clear_humongous();
6012 free_region(curr_hr, free_list, par);
6013 i += 1;
6014 }
6015 }
6017 void G1CollectedHeap::remove_from_old_sets(const HeapRegionSetCount& old_regions_removed,
6018 const HeapRegionSetCount& humongous_regions_removed) {
6019 if (old_regions_removed.length() > 0 || humongous_regions_removed.length() > 0) {
6020 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
6021 _old_set.bulk_remove(old_regions_removed);
6022 _humongous_set.bulk_remove(humongous_regions_removed);
6023 }
6025 }
6027 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) {
6028 assert(list != NULL, "list can't be null");
6029 if (!list->is_empty()) {
6030 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
6031 _hrm.insert_list_into_free_list(list);
6032 }
6033 }
6035 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) {
6036 _allocator->decrease_used(bytes);
6037 }
6039 class G1ParCleanupCTTask : public AbstractGangTask {
6040 G1SATBCardTableModRefBS* _ct_bs;
6041 G1CollectedHeap* _g1h;
6042 HeapRegion* volatile _su_head;
6043 public:
6044 G1ParCleanupCTTask(G1SATBCardTableModRefBS* ct_bs,
6045 G1CollectedHeap* g1h) :
6046 AbstractGangTask("G1 Par Cleanup CT Task"),
6047 _ct_bs(ct_bs), _g1h(g1h) { }
6049 void work(uint worker_id) {
6050 HeapRegion* r;
6051 while (r = _g1h->pop_dirty_cards_region()) {
6052 clear_cards(r);
6053 }
6054 }
6056 void clear_cards(HeapRegion* r) {
6057 // Cards of the survivors should have already been dirtied.
6058 if (!r->is_survivor()) {
6059 _ct_bs->clear(MemRegion(r->bottom(), r->end()));
6060 }
6061 }
6062 };
6064 #ifndef PRODUCT
6065 class G1VerifyCardTableCleanup: public HeapRegionClosure {
6066 G1CollectedHeap* _g1h;
6067 G1SATBCardTableModRefBS* _ct_bs;
6068 public:
6069 G1VerifyCardTableCleanup(G1CollectedHeap* g1h, G1SATBCardTableModRefBS* ct_bs)
6070 : _g1h(g1h), _ct_bs(ct_bs) { }
6071 virtual bool doHeapRegion(HeapRegion* r) {
6072 if (r->is_survivor()) {
6073 _g1h->verify_dirty_region(r);
6074 } else {
6075 _g1h->verify_not_dirty_region(r);
6076 }
6077 return false;
6078 }
6079 };
6081 void G1CollectedHeap::verify_not_dirty_region(HeapRegion* hr) {
6082 // All of the region should be clean.
6083 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
6084 MemRegion mr(hr->bottom(), hr->end());
6085 ct_bs->verify_not_dirty_region(mr);
6086 }
6088 void G1CollectedHeap::verify_dirty_region(HeapRegion* hr) {
6089 // We cannot guarantee that [bottom(),end()] is dirty. Threads
6090 // dirty allocated blocks as they allocate them. The thread that
6091 // retires each region and replaces it with a new one will do a
6092 // maximal allocation to fill in [pre_dummy_top(),end()] but will
6093 // not dirty that area (one less thing to have to do while holding
6094 // a lock). So we can only verify that [bottom(),pre_dummy_top()]
6095 // is dirty.
6096 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
6097 MemRegion mr(hr->bottom(), hr->pre_dummy_top());
6098 if (hr->is_young()) {
6099 ct_bs->verify_g1_young_region(mr);
6100 } else {
6101 ct_bs->verify_dirty_region(mr);
6102 }
6103 }
6105 void G1CollectedHeap::verify_dirty_young_list(HeapRegion* head) {
6106 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
6107 for (HeapRegion* hr = head; hr != NULL; hr = hr->get_next_young_region()) {
6108 verify_dirty_region(hr);
6109 }
6110 }
6112 void G1CollectedHeap::verify_dirty_young_regions() {
6113 verify_dirty_young_list(_young_list->first_region());
6114 }
6116 bool G1CollectedHeap::verify_no_bits_over_tams(const char* bitmap_name, CMBitMapRO* bitmap,
6117 HeapWord* tams, HeapWord* end) {
6118 guarantee(tams <= end,
6119 err_msg("tams: "PTR_FORMAT" end: "PTR_FORMAT, tams, end));
6120 HeapWord* result = bitmap->getNextMarkedWordAddress(tams, end);
6121 if (result < end) {
6122 gclog_or_tty->cr();
6123 gclog_or_tty->print_cr("## wrong marked address on %s bitmap: "PTR_FORMAT,
6124 bitmap_name, result);
6125 gclog_or_tty->print_cr("## %s tams: "PTR_FORMAT" end: "PTR_FORMAT,
6126 bitmap_name, tams, end);
6127 return false;
6128 }
6129 return true;
6130 }
6132 bool G1CollectedHeap::verify_bitmaps(const char* caller, HeapRegion* hr) {
6133 CMBitMapRO* prev_bitmap = concurrent_mark()->prevMarkBitMap();
6134 CMBitMapRO* next_bitmap = (CMBitMapRO*) concurrent_mark()->nextMarkBitMap();
6136 HeapWord* bottom = hr->bottom();
6137 HeapWord* ptams = hr->prev_top_at_mark_start();
6138 HeapWord* ntams = hr->next_top_at_mark_start();
6139 HeapWord* end = hr->end();
6141 bool res_p = verify_no_bits_over_tams("prev", prev_bitmap, ptams, end);
6143 bool res_n = true;
6144 // We reset mark_in_progress() before we reset _cmThread->in_progress() and in this window
6145 // we do the clearing of the next bitmap concurrently. Thus, we can not verify the bitmap
6146 // if we happen to be in that state.
6147 if (mark_in_progress() || !_cmThread->in_progress()) {
6148 res_n = verify_no_bits_over_tams("next", next_bitmap, ntams, end);
6149 }
6150 if (!res_p || !res_n) {
6151 gclog_or_tty->print_cr("#### Bitmap verification failed for "HR_FORMAT,
6152 HR_FORMAT_PARAMS(hr));
6153 gclog_or_tty->print_cr("#### Caller: %s", caller);
6154 return false;
6155 }
6156 return true;
6157 }
6159 void G1CollectedHeap::check_bitmaps(const char* caller, HeapRegion* hr) {
6160 if (!G1VerifyBitmaps) return;
6162 guarantee(verify_bitmaps(caller, hr), "bitmap verification");
6163 }
6165 class G1VerifyBitmapClosure : public HeapRegionClosure {
6166 private:
6167 const char* _caller;
6168 G1CollectedHeap* _g1h;
6169 bool _failures;
6171 public:
6172 G1VerifyBitmapClosure(const char* caller, G1CollectedHeap* g1h) :
6173 _caller(caller), _g1h(g1h), _failures(false) { }
6175 bool failures() { return _failures; }
6177 virtual bool doHeapRegion(HeapRegion* hr) {
6178 if (hr->continuesHumongous()) return false;
6180 bool result = _g1h->verify_bitmaps(_caller, hr);
6181 if (!result) {
6182 _failures = true;
6183 }
6184 return false;
6185 }
6186 };
6188 void G1CollectedHeap::check_bitmaps(const char* caller) {
6189 if (!G1VerifyBitmaps) return;
6191 G1VerifyBitmapClosure cl(caller, this);
6192 heap_region_iterate(&cl);
6193 guarantee(!cl.failures(), "bitmap verification");
6194 }
6195 #endif // PRODUCT
6197 void G1CollectedHeap::cleanUpCardTable() {
6198 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
6199 double start = os::elapsedTime();
6201 {
6202 // Iterate over the dirty cards region list.
6203 G1ParCleanupCTTask cleanup_task(ct_bs, this);
6205 if (G1CollectedHeap::use_parallel_gc_threads()) {
6206 set_par_threads();
6207 workers()->run_task(&cleanup_task);
6208 set_par_threads(0);
6209 } else {
6210 while (_dirty_cards_region_list) {
6211 HeapRegion* r = _dirty_cards_region_list;
6212 cleanup_task.clear_cards(r);
6213 _dirty_cards_region_list = r->get_next_dirty_cards_region();
6214 if (_dirty_cards_region_list == r) {
6215 // The last region.
6216 _dirty_cards_region_list = NULL;
6217 }
6218 r->set_next_dirty_cards_region(NULL);
6219 }
6220 }
6221 #ifndef PRODUCT
6222 if (G1VerifyCTCleanup || VerifyAfterGC) {
6223 G1VerifyCardTableCleanup cleanup_verifier(this, ct_bs);
6224 heap_region_iterate(&cleanup_verifier);
6225 }
6226 #endif
6227 }
6229 double elapsed = os::elapsedTime() - start;
6230 g1_policy()->phase_times()->record_clear_ct_time(elapsed * 1000.0);
6231 }
6233 void G1CollectedHeap::free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info) {
6234 size_t pre_used = 0;
6235 FreeRegionList local_free_list("Local List for CSet Freeing");
6237 double young_time_ms = 0.0;
6238 double non_young_time_ms = 0.0;
6240 // Since the collection set is a superset of the the young list,
6241 // all we need to do to clear the young list is clear its
6242 // head and length, and unlink any young regions in the code below
6243 _young_list->clear();
6245 G1CollectorPolicy* policy = g1_policy();
6247 double start_sec = os::elapsedTime();
6248 bool non_young = true;
6250 HeapRegion* cur = cs_head;
6251 int age_bound = -1;
6252 size_t rs_lengths = 0;
6254 while (cur != NULL) {
6255 assert(!is_on_master_free_list(cur), "sanity");
6256 if (non_young) {
6257 if (cur->is_young()) {
6258 double end_sec = os::elapsedTime();
6259 double elapsed_ms = (end_sec - start_sec) * 1000.0;
6260 non_young_time_ms += elapsed_ms;
6262 start_sec = os::elapsedTime();
6263 non_young = false;
6264 }
6265 } else {
6266 if (!cur->is_young()) {
6267 double end_sec = os::elapsedTime();
6268 double elapsed_ms = (end_sec - start_sec) * 1000.0;
6269 young_time_ms += elapsed_ms;
6271 start_sec = os::elapsedTime();
6272 non_young = true;
6273 }
6274 }
6276 rs_lengths += cur->rem_set()->occupied_locked();
6278 HeapRegion* next = cur->next_in_collection_set();
6279 assert(cur->in_collection_set(), "bad CS");
6280 cur->set_next_in_collection_set(NULL);
6281 cur->set_in_collection_set(false);
6283 if (cur->is_young()) {
6284 int index = cur->young_index_in_cset();
6285 assert(index != -1, "invariant");
6286 assert((uint) index < policy->young_cset_region_length(), "invariant");
6287 size_t words_survived = _surviving_young_words[index];
6288 cur->record_surv_words_in_group(words_survived);
6290 // At this point the we have 'popped' cur from the collection set
6291 // (linked via next_in_collection_set()) but it is still in the
6292 // young list (linked via next_young_region()). Clear the
6293 // _next_young_region field.
6294 cur->set_next_young_region(NULL);
6295 } else {
6296 int index = cur->young_index_in_cset();
6297 assert(index == -1, "invariant");
6298 }
6300 assert( (cur->is_young() && cur->young_index_in_cset() > -1) ||
6301 (!cur->is_young() && cur->young_index_in_cset() == -1),
6302 "invariant" );
6304 if (!cur->evacuation_failed()) {
6305 MemRegion used_mr = cur->used_region();
6307 // And the region is empty.
6308 assert(!used_mr.is_empty(), "Should not have empty regions in a CS.");
6309 pre_used += cur->used();
6310 free_region(cur, &local_free_list, false /* par */, true /* locked */);
6311 } else {
6312 cur->uninstall_surv_rate_group();
6313 if (cur->is_young()) {
6314 cur->set_young_index_in_cset(-1);
6315 }
6316 cur->set_evacuation_failed(false);
6317 // The region is now considered to be old.
6318 cur->set_old();
6319 _old_set.add(cur);
6320 evacuation_info.increment_collectionset_used_after(cur->used());
6321 }
6322 cur = next;
6323 }
6325 evacuation_info.set_regions_freed(local_free_list.length());
6326 policy->record_max_rs_lengths(rs_lengths);
6327 policy->cset_regions_freed();
6329 double end_sec = os::elapsedTime();
6330 double elapsed_ms = (end_sec - start_sec) * 1000.0;
6332 if (non_young) {
6333 non_young_time_ms += elapsed_ms;
6334 } else {
6335 young_time_ms += elapsed_ms;
6336 }
6338 prepend_to_freelist(&local_free_list);
6339 decrement_summary_bytes(pre_used);
6340 policy->phase_times()->record_young_free_cset_time_ms(young_time_ms);
6341 policy->phase_times()->record_non_young_free_cset_time_ms(non_young_time_ms);
6342 }
6344 class G1FreeHumongousRegionClosure : public HeapRegionClosure {
6345 private:
6346 FreeRegionList* _free_region_list;
6347 HeapRegionSet* _proxy_set;
6348 HeapRegionSetCount _humongous_regions_removed;
6349 size_t _freed_bytes;
6350 public:
6352 G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) :
6353 _free_region_list(free_region_list), _humongous_regions_removed(), _freed_bytes(0) {
6354 }
6356 virtual bool doHeapRegion(HeapRegion* r) {
6357 if (!r->startsHumongous()) {
6358 return false;
6359 }
6361 G1CollectedHeap* g1h = G1CollectedHeap::heap();
6363 oop obj = (oop)r->bottom();
6364 CMBitMap* next_bitmap = g1h->concurrent_mark()->nextMarkBitMap();
6366 // The following checks whether the humongous object is live are sufficient.
6367 // The main additional check (in addition to having a reference from the roots
6368 // or the young gen) is whether the humongous object has a remembered set entry.
6369 //
6370 // A humongous object cannot be live if there is no remembered set for it
6371 // because:
6372 // - there can be no references from within humongous starts regions referencing
6373 // the object because we never allocate other objects into them.
6374 // (I.e. there are no intra-region references that may be missed by the
6375 // remembered set)
6376 // - as soon there is a remembered set entry to the humongous starts region
6377 // (i.e. it has "escaped" to an old object) this remembered set entry will stay
6378 // until the end of a concurrent mark.
6379 //
6380 // It is not required to check whether the object has been found dead by marking
6381 // or not, in fact it would prevent reclamation within a concurrent cycle, as
6382 // all objects allocated during that time are considered live.
6383 // SATB marking is even more conservative than the remembered set.
6384 // So if at this point in the collection there is no remembered set entry,
6385 // nobody has a reference to it.
6386 // At the start of collection we flush all refinement logs, and remembered sets
6387 // are completely up-to-date wrt to references to the humongous object.
6388 //
6389 // Other implementation considerations:
6390 // - never consider object arrays: while they are a valid target, they have not
6391 // been observed to be used as temporary objects.
6392 // - they would also pose considerable effort for cleaning up the the remembered
6393 // sets.
6394 // While this cleanup is not strictly necessary to be done (or done instantly),
6395 // given that their occurrence is very low, this saves us this additional
6396 // complexity.
6397 uint region_idx = r->hrm_index();
6398 if (g1h->humongous_is_live(region_idx) ||
6399 g1h->humongous_region_is_always_live(region_idx)) {
6401 if (G1TraceReclaimDeadHumongousObjectsAtYoungGC) {
6402 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",
6403 r->isHumongous(),
6404 region_idx,
6405 r->rem_set()->occupied(),
6406 r->rem_set()->strong_code_roots_list_length(),
6407 next_bitmap->isMarked(r->bottom()),
6408 g1h->humongous_is_live(region_idx),
6409 obj->is_objArray()
6410 );
6411 }
6413 return false;
6414 }
6416 guarantee(!obj->is_objArray(),
6417 err_msg("Eagerly reclaiming object arrays is not supported, but the object "PTR_FORMAT" is.",
6418 r->bottom()));
6420 if (G1TraceReclaimDeadHumongousObjectsAtYoungGC) {
6421 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",
6422 r->isHumongous(),
6423 r->bottom(),
6424 region_idx,
6425 r->region_num(),
6426 r->rem_set()->occupied(),
6427 r->rem_set()->strong_code_roots_list_length(),
6428 next_bitmap->isMarked(r->bottom()),
6429 g1h->humongous_is_live(region_idx),
6430 obj->is_objArray()
6431 );
6432 }
6433 // Need to clear mark bit of the humongous object if already set.
6434 if (next_bitmap->isMarked(r->bottom())) {
6435 next_bitmap->clear(r->bottom());
6436 }
6437 _freed_bytes += r->used();
6438 r->set_containing_set(NULL);
6439 _humongous_regions_removed.increment(1u, r->capacity());
6440 g1h->free_humongous_region(r, _free_region_list, false);
6442 return false;
6443 }
6445 HeapRegionSetCount& humongous_free_count() {
6446 return _humongous_regions_removed;
6447 }
6449 size_t bytes_freed() const {
6450 return _freed_bytes;
6451 }
6453 size_t humongous_reclaimed() const {
6454 return _humongous_regions_removed.length();
6455 }
6456 };
6458 void G1CollectedHeap::eagerly_reclaim_humongous_regions() {
6459 assert_at_safepoint(true);
6461 if (!G1ReclaimDeadHumongousObjectsAtYoungGC || !_has_humongous_reclaim_candidates) {
6462 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0);
6463 return;
6464 }
6466 double start_time = os::elapsedTime();
6468 FreeRegionList local_cleanup_list("Local Humongous Cleanup List");
6470 G1FreeHumongousRegionClosure cl(&local_cleanup_list);
6471 heap_region_iterate(&cl);
6473 HeapRegionSetCount empty_set;
6474 remove_from_old_sets(empty_set, cl.humongous_free_count());
6476 G1HRPrinter* hr_printer = _g1h->hr_printer();
6477 if (hr_printer->is_active()) {
6478 FreeRegionListIterator iter(&local_cleanup_list);
6479 while (iter.more_available()) {
6480 HeapRegion* hr = iter.get_next();
6481 hr_printer->cleanup(hr);
6482 }
6483 }
6485 prepend_to_freelist(&local_cleanup_list);
6486 decrement_summary_bytes(cl.bytes_freed());
6488 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0,
6489 cl.humongous_reclaimed());
6490 }
6492 // This routine is similar to the above but does not record
6493 // any policy statistics or update free lists; we are abandoning
6494 // the current incremental collection set in preparation of a
6495 // full collection. After the full GC we will start to build up
6496 // the incremental collection set again.
6497 // This is only called when we're doing a full collection
6498 // and is immediately followed by the tearing down of the young list.
6500 void G1CollectedHeap::abandon_collection_set(HeapRegion* cs_head) {
6501 HeapRegion* cur = cs_head;
6503 while (cur != NULL) {
6504 HeapRegion* next = cur->next_in_collection_set();
6505 assert(cur->in_collection_set(), "bad CS");
6506 cur->set_next_in_collection_set(NULL);
6507 cur->set_in_collection_set(false);
6508 cur->set_young_index_in_cset(-1);
6509 cur = next;
6510 }
6511 }
6513 void G1CollectedHeap::set_free_regions_coming() {
6514 if (G1ConcRegionFreeingVerbose) {
6515 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
6516 "setting free regions coming");
6517 }
6519 assert(!free_regions_coming(), "pre-condition");
6520 _free_regions_coming = true;
6521 }
6523 void G1CollectedHeap::reset_free_regions_coming() {
6524 assert(free_regions_coming(), "pre-condition");
6526 {
6527 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6528 _free_regions_coming = false;
6529 SecondaryFreeList_lock->notify_all();
6530 }
6532 if (G1ConcRegionFreeingVerbose) {
6533 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
6534 "reset free regions coming");
6535 }
6536 }
6538 void G1CollectedHeap::wait_while_free_regions_coming() {
6539 // Most of the time we won't have to wait, so let's do a quick test
6540 // first before we take the lock.
6541 if (!free_regions_coming()) {
6542 return;
6543 }
6545 if (G1ConcRegionFreeingVerbose) {
6546 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
6547 "waiting for free regions");
6548 }
6550 {
6551 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6552 while (free_regions_coming()) {
6553 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
6554 }
6555 }
6557 if (G1ConcRegionFreeingVerbose) {
6558 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
6559 "done waiting for free regions");
6560 }
6561 }
6563 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
6564 assert(heap_lock_held_for_gc(),
6565 "the heap lock should already be held by or for this thread");
6566 _young_list->push_region(hr);
6567 }
6569 class NoYoungRegionsClosure: public HeapRegionClosure {
6570 private:
6571 bool _success;
6572 public:
6573 NoYoungRegionsClosure() : _success(true) { }
6574 bool doHeapRegion(HeapRegion* r) {
6575 if (r->is_young()) {
6576 gclog_or_tty->print_cr("Region ["PTR_FORMAT", "PTR_FORMAT") tagged as young",
6577 r->bottom(), r->end());
6578 _success = false;
6579 }
6580 return false;
6581 }
6582 bool success() { return _success; }
6583 };
6585 bool G1CollectedHeap::check_young_list_empty(bool check_heap, bool check_sample) {
6586 bool ret = _young_list->check_list_empty(check_sample);
6588 if (check_heap) {
6589 NoYoungRegionsClosure closure;
6590 heap_region_iterate(&closure);
6591 ret = ret && closure.success();
6592 }
6594 return ret;
6595 }
6597 class TearDownRegionSetsClosure : public HeapRegionClosure {
6598 private:
6599 HeapRegionSet *_old_set;
6601 public:
6602 TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { }
6604 bool doHeapRegion(HeapRegion* r) {
6605 if (r->is_old()) {
6606 _old_set->remove(r);
6607 } else {
6608 // We ignore free regions, we'll empty the free list afterwards.
6609 // We ignore young regions, we'll empty the young list afterwards.
6610 // We ignore humongous regions, we're not tearing down the
6611 // humongous regions set.
6612 assert(r->is_free() || r->is_young() || r->isHumongous(),
6613 "it cannot be another type");
6614 }
6615 return false;
6616 }
6618 ~TearDownRegionSetsClosure() {
6619 assert(_old_set->is_empty(), "post-condition");
6620 }
6621 };
6623 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
6624 assert_at_safepoint(true /* should_be_vm_thread */);
6626 if (!free_list_only) {
6627 TearDownRegionSetsClosure cl(&_old_set);
6628 heap_region_iterate(&cl);
6630 // Note that emptying the _young_list is postponed and instead done as
6631 // the first step when rebuilding the regions sets again. The reason for
6632 // this is that during a full GC string deduplication needs to know if
6633 // a collected region was young or old when the full GC was initiated.
6634 }
6635 _hrm.remove_all_free_regions();
6636 }
6638 class RebuildRegionSetsClosure : public HeapRegionClosure {
6639 private:
6640 bool _free_list_only;
6641 HeapRegionSet* _old_set;
6642 HeapRegionManager* _hrm;
6643 size_t _total_used;
6645 public:
6646 RebuildRegionSetsClosure(bool free_list_only,
6647 HeapRegionSet* old_set, HeapRegionManager* hrm) :
6648 _free_list_only(free_list_only),
6649 _old_set(old_set), _hrm(hrm), _total_used(0) {
6650 assert(_hrm->num_free_regions() == 0, "pre-condition");
6651 if (!free_list_only) {
6652 assert(_old_set->is_empty(), "pre-condition");
6653 }
6654 }
6656 bool doHeapRegion(HeapRegion* r) {
6657 if (r->continuesHumongous()) {
6658 return false;
6659 }
6661 if (r->is_empty()) {
6662 // Add free regions to the free list
6663 r->set_free();
6664 r->set_allocation_context(AllocationContext::system());
6665 _hrm->insert_into_free_list(r);
6666 } else if (!_free_list_only) {
6667 assert(!r->is_young(), "we should not come across young regions");
6669 if (r->isHumongous()) {
6670 // We ignore humongous regions, we left the humongous set unchanged
6671 } else {
6672 // Objects that were compacted would have ended up on regions
6673 // that were previously old or free.
6674 assert(r->is_free() || r->is_old(), "invariant");
6675 // We now consider them old, so register as such.
6676 r->set_old();
6677 _old_set->add(r);
6678 }
6679 _total_used += r->used();
6680 }
6682 return false;
6683 }
6685 size_t total_used() {
6686 return _total_used;
6687 }
6688 };
6690 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
6691 assert_at_safepoint(true /* should_be_vm_thread */);
6693 if (!free_list_only) {
6694 _young_list->empty_list();
6695 }
6697 RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm);
6698 heap_region_iterate(&cl);
6700 if (!free_list_only) {
6701 _allocator->set_used(cl.total_used());
6702 }
6703 assert(_allocator->used_unlocked() == recalculate_used(),
6704 err_msg("inconsistent _allocator->used_unlocked(), "
6705 "value: "SIZE_FORMAT" recalculated: "SIZE_FORMAT,
6706 _allocator->used_unlocked(), recalculate_used()));
6707 }
6709 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) {
6710 _refine_cte_cl->set_concurrent(concurrent);
6711 }
6713 bool G1CollectedHeap::is_in_closed_subset(const void* p) const {
6714 HeapRegion* hr = heap_region_containing(p);
6715 return hr->is_in(p);
6716 }
6718 // Methods for the mutator alloc region
6720 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
6721 bool force) {
6722 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6723 assert(!force || g1_policy()->can_expand_young_list(),
6724 "if force is true we should be able to expand the young list");
6725 bool young_list_full = g1_policy()->is_young_list_full();
6726 if (force || !young_list_full) {
6727 HeapRegion* new_alloc_region = new_region(word_size,
6728 false /* is_old */,
6729 false /* do_expand */);
6730 if (new_alloc_region != NULL) {
6731 set_region_short_lived_locked(new_alloc_region);
6732 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Eden, young_list_full);
6733 check_bitmaps("Mutator Region Allocation", new_alloc_region);
6734 return new_alloc_region;
6735 }
6736 }
6737 return NULL;
6738 }
6740 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
6741 size_t allocated_bytes) {
6742 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6743 assert(alloc_region->is_eden(), "all mutator alloc regions should be eden");
6745 g1_policy()->add_region_to_incremental_cset_lhs(alloc_region);
6746 _allocator->increase_used(allocated_bytes);
6747 _hr_printer.retire(alloc_region);
6748 // We update the eden sizes here, when the region is retired,
6749 // instead of when it's allocated, since this is the point that its
6750 // used space has been recored in _summary_bytes_used.
6751 g1mm()->update_eden_size();
6752 }
6754 void G1CollectedHeap::set_par_threads() {
6755 // Don't change the number of workers. Use the value previously set
6756 // in the workgroup.
6757 assert(G1CollectedHeap::use_parallel_gc_threads(), "shouldn't be here otherwise");
6758 uint n_workers = workers()->active_workers();
6759 assert(UseDynamicNumberOfGCThreads ||
6760 n_workers == workers()->total_workers(),
6761 "Otherwise should be using the total number of workers");
6762 if (n_workers == 0) {
6763 assert(false, "Should have been set in prior evacuation pause.");
6764 n_workers = ParallelGCThreads;
6765 workers()->set_active_workers(n_workers);
6766 }
6767 set_par_threads(n_workers);
6768 }
6770 // Methods for the GC alloc regions
6772 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size,
6773 uint count,
6774 GCAllocPurpose ap) {
6775 assert(FreeList_lock->owned_by_self(), "pre-condition");
6777 if (count < g1_policy()->max_regions(ap)) {
6778 bool survivor = (ap == GCAllocForSurvived);
6779 HeapRegion* new_alloc_region = new_region(word_size,
6780 !survivor,
6781 true /* do_expand */);
6782 if (new_alloc_region != NULL) {
6783 // We really only need to do this for old regions given that we
6784 // should never scan survivors. But it doesn't hurt to do it
6785 // for survivors too.
6786 new_alloc_region->record_top_and_timestamp();
6787 if (survivor) {
6788 new_alloc_region->set_survivor();
6789 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Survivor);
6790 check_bitmaps("Survivor Region Allocation", new_alloc_region);
6791 } else {
6792 new_alloc_region->set_old();
6793 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Old);
6794 check_bitmaps("Old Region Allocation", new_alloc_region);
6795 }
6796 bool during_im = g1_policy()->during_initial_mark_pause();
6797 new_alloc_region->note_start_of_copying(during_im);
6798 return new_alloc_region;
6799 } else {
6800 g1_policy()->note_alloc_region_limit_reached(ap);
6801 }
6802 }
6803 return NULL;
6804 }
6806 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
6807 size_t allocated_bytes,
6808 GCAllocPurpose ap) {
6809 bool during_im = g1_policy()->during_initial_mark_pause();
6810 alloc_region->note_end_of_copying(during_im);
6811 g1_policy()->record_bytes_copied_during_gc(allocated_bytes);
6812 if (ap == GCAllocForSurvived) {
6813 young_list()->add_survivor_region(alloc_region);
6814 } else {
6815 _old_set.add(alloc_region);
6816 }
6817 _hr_printer.retire(alloc_region);
6818 }
6820 // Heap region set verification
6822 class VerifyRegionListsClosure : public HeapRegionClosure {
6823 private:
6824 HeapRegionSet* _old_set;
6825 HeapRegionSet* _humongous_set;
6826 HeapRegionManager* _hrm;
6828 public:
6829 HeapRegionSetCount _old_count;
6830 HeapRegionSetCount _humongous_count;
6831 HeapRegionSetCount _free_count;
6833 VerifyRegionListsClosure(HeapRegionSet* old_set,
6834 HeapRegionSet* humongous_set,
6835 HeapRegionManager* hrm) :
6836 _old_set(old_set), _humongous_set(humongous_set), _hrm(hrm),
6837 _old_count(), _humongous_count(), _free_count(){ }
6839 bool doHeapRegion(HeapRegion* hr) {
6840 if (hr->continuesHumongous()) {
6841 return false;
6842 }
6844 if (hr->is_young()) {
6845 // TODO
6846 } else if (hr->startsHumongous()) {
6847 assert(hr->containing_set() == _humongous_set, err_msg("Heap region %u is starts humongous but not in humongous set.", hr->hrm_index()));
6848 _humongous_count.increment(1u, hr->capacity());
6849 } else if (hr->is_empty()) {
6850 assert(_hrm->is_free(hr), err_msg("Heap region %u is empty but not on the free list.", hr->hrm_index()));
6851 _free_count.increment(1u, hr->capacity());
6852 } else if (hr->is_old()) {
6853 assert(hr->containing_set() == _old_set, err_msg("Heap region %u is old but not in the old set.", hr->hrm_index()));
6854 _old_count.increment(1u, hr->capacity());
6855 } else {
6856 ShouldNotReachHere();
6857 }
6858 return false;
6859 }
6861 void verify_counts(HeapRegionSet* old_set, HeapRegionSet* humongous_set, HeapRegionManager* free_list) {
6862 guarantee(old_set->length() == _old_count.length(), err_msg("Old set count mismatch. Expected %u, actual %u.", old_set->length(), _old_count.length()));
6863 guarantee(old_set->total_capacity_bytes() == _old_count.capacity(), err_msg("Old set capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
6864 old_set->total_capacity_bytes(), _old_count.capacity()));
6866 guarantee(humongous_set->length() == _humongous_count.length(), err_msg("Hum set count mismatch. Expected %u, actual %u.", humongous_set->length(), _humongous_count.length()));
6867 guarantee(humongous_set->total_capacity_bytes() == _humongous_count.capacity(), err_msg("Hum set capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
6868 humongous_set->total_capacity_bytes(), _humongous_count.capacity()));
6870 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()));
6871 guarantee(free_list->total_capacity_bytes() == _free_count.capacity(), err_msg("Free list capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
6872 free_list->total_capacity_bytes(), _free_count.capacity()));
6873 }
6874 };
6876 void G1CollectedHeap::verify_region_sets() {
6877 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6879 // First, check the explicit lists.
6880 _hrm.verify();
6881 {
6882 // Given that a concurrent operation might be adding regions to
6883 // the secondary free list we have to take the lock before
6884 // verifying it.
6885 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6886 _secondary_free_list.verify_list();
6887 }
6889 // If a concurrent region freeing operation is in progress it will
6890 // be difficult to correctly attributed any free regions we come
6891 // across to the correct free list given that they might belong to
6892 // one of several (free_list, secondary_free_list, any local lists,
6893 // etc.). So, if that's the case we will skip the rest of the
6894 // verification operation. Alternatively, waiting for the concurrent
6895 // operation to complete will have a non-trivial effect on the GC's
6896 // operation (no concurrent operation will last longer than the
6897 // interval between two calls to verification) and it might hide
6898 // any issues that we would like to catch during testing.
6899 if (free_regions_coming()) {
6900 return;
6901 }
6903 // Make sure we append the secondary_free_list on the free_list so
6904 // that all free regions we will come across can be safely
6905 // attributed to the free_list.
6906 append_secondary_free_list_if_not_empty_with_lock();
6908 // Finally, make sure that the region accounting in the lists is
6909 // consistent with what we see in the heap.
6911 VerifyRegionListsClosure cl(&_old_set, &_humongous_set, &_hrm);
6912 heap_region_iterate(&cl);
6913 cl.verify_counts(&_old_set, &_humongous_set, &_hrm);
6914 }
6916 // Optimized nmethod scanning
6918 class RegisterNMethodOopClosure: public OopClosure {
6919 G1CollectedHeap* _g1h;
6920 nmethod* _nm;
6922 template <class T> void do_oop_work(T* p) {
6923 T heap_oop = oopDesc::load_heap_oop(p);
6924 if (!oopDesc::is_null(heap_oop)) {
6925 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
6926 HeapRegion* hr = _g1h->heap_region_containing(obj);
6927 assert(!hr->continuesHumongous(),
6928 err_msg("trying to add code root "PTR_FORMAT" in continuation of humongous region "HR_FORMAT
6929 " starting at "HR_FORMAT,
6930 _nm, HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())));
6932 // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries.
6933 hr->add_strong_code_root_locked(_nm);
6934 }
6935 }
6937 public:
6938 RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
6939 _g1h(g1h), _nm(nm) {}
6941 void do_oop(oop* p) { do_oop_work(p); }
6942 void do_oop(narrowOop* p) { do_oop_work(p); }
6943 };
6945 class UnregisterNMethodOopClosure: public OopClosure {
6946 G1CollectedHeap* _g1h;
6947 nmethod* _nm;
6949 template <class T> void do_oop_work(T* p) {
6950 T heap_oop = oopDesc::load_heap_oop(p);
6951 if (!oopDesc::is_null(heap_oop)) {
6952 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
6953 HeapRegion* hr = _g1h->heap_region_containing(obj);
6954 assert(!hr->continuesHumongous(),
6955 err_msg("trying to remove code root "PTR_FORMAT" in continuation of humongous region "HR_FORMAT
6956 " starting at "HR_FORMAT,
6957 _nm, HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())));
6959 hr->remove_strong_code_root(_nm);
6960 }
6961 }
6963 public:
6964 UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
6965 _g1h(g1h), _nm(nm) {}
6967 void do_oop(oop* p) { do_oop_work(p); }
6968 void do_oop(narrowOop* p) { do_oop_work(p); }
6969 };
6971 void G1CollectedHeap::register_nmethod(nmethod* nm) {
6972 CollectedHeap::register_nmethod(nm);
6974 guarantee(nm != NULL, "sanity");
6975 RegisterNMethodOopClosure reg_cl(this, nm);
6976 nm->oops_do(®_cl);
6977 }
6979 void G1CollectedHeap::unregister_nmethod(nmethod* nm) {
6980 CollectedHeap::unregister_nmethod(nm);
6982 guarantee(nm != NULL, "sanity");
6983 UnregisterNMethodOopClosure reg_cl(this, nm);
6984 nm->oops_do(®_cl, true);
6985 }
6987 void G1CollectedHeap::purge_code_root_memory() {
6988 double purge_start = os::elapsedTime();
6989 G1CodeRootSet::purge();
6990 double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0;
6991 g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms);
6992 }
6994 class RebuildStrongCodeRootClosure: public CodeBlobClosure {
6995 G1CollectedHeap* _g1h;
6997 public:
6998 RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) :
6999 _g1h(g1h) {}
7001 void do_code_blob(CodeBlob* cb) {
7002 nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL;
7003 if (nm == NULL) {
7004 return;
7005 }
7007 if (ScavengeRootsInCode) {
7008 _g1h->register_nmethod(nm);
7009 }
7010 }
7011 };
7013 void G1CollectedHeap::rebuild_strong_code_roots() {
7014 RebuildStrongCodeRootClosure blob_cl(this);
7015 CodeCache::blobs_do(&blob_cl);
7016 }