Fri, 05 Sep 2014 09:49:19 +0200
8057536: Refactor G1 to allow context specific allocations
Summary: Splitting out a g1 allocator class to simply specialized allocators which can associate each allocation with a given context.
Reviewed-by: mgerdin, brutisso
1 /*
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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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 list->set_not_young();
211 list = next;
212 }
213 }
215 void YoungList::empty_list() {
216 assert(check_list_well_formed(), "young list should be well formed");
218 empty_list(_head);
219 _head = NULL;
220 _length = 0;
222 empty_list(_survivor_head);
223 _survivor_head = NULL;
224 _survivor_tail = NULL;
225 _survivor_length = 0;
227 _last_sampled_rs_lengths = 0;
229 assert(check_list_empty(false), "just making sure...");
230 }
232 bool YoungList::check_list_well_formed() {
233 bool ret = true;
235 uint length = 0;
236 HeapRegion* curr = _head;
237 HeapRegion* last = NULL;
238 while (curr != NULL) {
239 if (!curr->is_young()) {
240 gclog_or_tty->print_cr("### YOUNG REGION "PTR_FORMAT"-"PTR_FORMAT" "
241 "incorrectly tagged (y: %d, surv: %d)",
242 curr->bottom(), curr->end(),
243 curr->is_young(), curr->is_survivor());
244 ret = false;
245 }
246 ++length;
247 last = curr;
248 curr = curr->get_next_young_region();
249 }
250 ret = ret && (length == _length);
252 if (!ret) {
253 gclog_or_tty->print_cr("### YOUNG LIST seems not well formed!");
254 gclog_or_tty->print_cr("### list has %u entries, _length is %u",
255 length, _length);
256 }
258 return ret;
259 }
261 bool YoungList::check_list_empty(bool check_sample) {
262 bool ret = true;
264 if (_length != 0) {
265 gclog_or_tty->print_cr("### YOUNG LIST should have 0 length, not %u",
266 _length);
267 ret = false;
268 }
269 if (check_sample && _last_sampled_rs_lengths != 0) {
270 gclog_or_tty->print_cr("### YOUNG LIST has non-zero last sampled RS lengths");
271 ret = false;
272 }
273 if (_head != NULL) {
274 gclog_or_tty->print_cr("### YOUNG LIST does not have a NULL head");
275 ret = false;
276 }
277 if (!ret) {
278 gclog_or_tty->print_cr("### YOUNG LIST does not seem empty");
279 }
281 return ret;
282 }
284 void
285 YoungList::rs_length_sampling_init() {
286 _sampled_rs_lengths = 0;
287 _curr = _head;
288 }
290 bool
291 YoungList::rs_length_sampling_more() {
292 return _curr != NULL;
293 }
295 void
296 YoungList::rs_length_sampling_next() {
297 assert( _curr != NULL, "invariant" );
298 size_t rs_length = _curr->rem_set()->occupied();
300 _sampled_rs_lengths += rs_length;
302 // The current region may not yet have been added to the
303 // incremental collection set (it gets added when it is
304 // retired as the current allocation region).
305 if (_curr->in_collection_set()) {
306 // Update the collection set policy information for this region
307 _g1h->g1_policy()->update_incremental_cset_info(_curr, rs_length);
308 }
310 _curr = _curr->get_next_young_region();
311 if (_curr == NULL) {
312 _last_sampled_rs_lengths = _sampled_rs_lengths;
313 // gclog_or_tty->print_cr("last sampled RS lengths = %d", _last_sampled_rs_lengths);
314 }
315 }
317 void
318 YoungList::reset_auxilary_lists() {
319 guarantee( is_empty(), "young list should be empty" );
320 assert(check_list_well_formed(), "young list should be well formed");
322 // Add survivor regions to SurvRateGroup.
323 _g1h->g1_policy()->note_start_adding_survivor_regions();
324 _g1h->g1_policy()->finished_recalculating_age_indexes(true /* is_survivors */);
326 int young_index_in_cset = 0;
327 for (HeapRegion* curr = _survivor_head;
328 curr != NULL;
329 curr = curr->get_next_young_region()) {
330 _g1h->g1_policy()->set_region_survivor(curr, young_index_in_cset);
332 // The region is a non-empty survivor so let's add it to
333 // the incremental collection set for the next evacuation
334 // pause.
335 _g1h->g1_policy()->add_region_to_incremental_cset_rhs(curr);
336 young_index_in_cset += 1;
337 }
338 assert((uint) young_index_in_cset == _survivor_length, "post-condition");
339 _g1h->g1_policy()->note_stop_adding_survivor_regions();
341 _head = _survivor_head;
342 _length = _survivor_length;
343 if (_survivor_head != NULL) {
344 assert(_survivor_tail != NULL, "cause it shouldn't be");
345 assert(_survivor_length > 0, "invariant");
346 _survivor_tail->set_next_young_region(NULL);
347 }
349 // Don't clear the survivor list handles until the start of
350 // the next evacuation pause - we need it in order to re-tag
351 // the survivor regions from this evacuation pause as 'young'
352 // at the start of the next.
354 _g1h->g1_policy()->finished_recalculating_age_indexes(false /* is_survivors */);
356 assert(check_list_well_formed(), "young list should be well formed");
357 }
359 void YoungList::print() {
360 HeapRegion* lists[] = {_head, _survivor_head};
361 const char* names[] = {"YOUNG", "SURVIVOR"};
363 for (unsigned int list = 0; list < ARRAY_SIZE(lists); ++list) {
364 gclog_or_tty->print_cr("%s LIST CONTENTS", names[list]);
365 HeapRegion *curr = lists[list];
366 if (curr == NULL)
367 gclog_or_tty->print_cr(" empty");
368 while (curr != NULL) {
369 gclog_or_tty->print_cr(" "HR_FORMAT", P: "PTR_FORMAT "N: "PTR_FORMAT", age: %4d",
370 HR_FORMAT_PARAMS(curr),
371 curr->prev_top_at_mark_start(),
372 curr->next_top_at_mark_start(),
373 curr->age_in_surv_rate_group_cond());
374 curr = curr->get_next_young_region();
375 }
376 }
378 gclog_or_tty->cr();
379 }
381 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) {
382 OtherRegionsTable::invalidate(start_idx, num_regions);
383 }
385 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions) {
386 reset_from_card_cache(start_idx, num_regions);
387 }
389 void G1CollectedHeap::push_dirty_cards_region(HeapRegion* hr)
390 {
391 // Claim the right to put the region on the dirty cards region list
392 // by installing a self pointer.
393 HeapRegion* next = hr->get_next_dirty_cards_region();
394 if (next == NULL) {
395 HeapRegion* res = (HeapRegion*)
396 Atomic::cmpxchg_ptr(hr, hr->next_dirty_cards_region_addr(),
397 NULL);
398 if (res == NULL) {
399 HeapRegion* head;
400 do {
401 // Put the region to the dirty cards region list.
402 head = _dirty_cards_region_list;
403 next = (HeapRegion*)
404 Atomic::cmpxchg_ptr(hr, &_dirty_cards_region_list, head);
405 if (next == head) {
406 assert(hr->get_next_dirty_cards_region() == hr,
407 "hr->get_next_dirty_cards_region() != hr");
408 if (next == NULL) {
409 // The last region in the list points to itself.
410 hr->set_next_dirty_cards_region(hr);
411 } else {
412 hr->set_next_dirty_cards_region(next);
413 }
414 }
415 } while (next != head);
416 }
417 }
418 }
420 HeapRegion* G1CollectedHeap::pop_dirty_cards_region()
421 {
422 HeapRegion* head;
423 HeapRegion* hr;
424 do {
425 head = _dirty_cards_region_list;
426 if (head == NULL) {
427 return NULL;
428 }
429 HeapRegion* new_head = head->get_next_dirty_cards_region();
430 if (head == new_head) {
431 // The last region.
432 new_head = NULL;
433 }
434 hr = (HeapRegion*)Atomic::cmpxchg_ptr(new_head, &_dirty_cards_region_list,
435 head);
436 } while (hr != head);
437 assert(hr != NULL, "invariant");
438 hr->set_next_dirty_cards_region(NULL);
439 return hr;
440 }
442 #ifdef ASSERT
443 // A region is added to the collection set as it is retired
444 // so an address p can point to a region which will be in the
445 // collection set but has not yet been retired. This method
446 // therefore is only accurate during a GC pause after all
447 // regions have been retired. It is used for debugging
448 // to check if an nmethod has references to objects that can
449 // be move during a partial collection. Though it can be
450 // inaccurate, it is sufficient for G1 because the conservative
451 // implementation of is_scavengable() for G1 will indicate that
452 // all nmethods must be scanned during a partial collection.
453 bool G1CollectedHeap::is_in_partial_collection(const void* p) {
454 if (p == NULL) {
455 return false;
456 }
457 return heap_region_containing(p)->in_collection_set();
458 }
459 #endif
461 // Returns true if the reference points to an object that
462 // can move in an incremental collection.
463 bool G1CollectedHeap::is_scavengable(const void* p) {
464 HeapRegion* hr = heap_region_containing(p);
465 return !hr->isHumongous();
466 }
468 void G1CollectedHeap::check_ct_logs_at_safepoint() {
469 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
470 CardTableModRefBS* ct_bs = g1_barrier_set();
472 // Count the dirty cards at the start.
473 CountNonCleanMemRegionClosure count1(this);
474 ct_bs->mod_card_iterate(&count1);
475 int orig_count = count1.n();
477 // First clear the logged cards.
478 ClearLoggedCardTableEntryClosure clear;
479 dcqs.apply_closure_to_all_completed_buffers(&clear);
480 dcqs.iterate_closure_all_threads(&clear, false);
481 clear.print_histo();
483 // Now ensure that there's no dirty cards.
484 CountNonCleanMemRegionClosure count2(this);
485 ct_bs->mod_card_iterate(&count2);
486 if (count2.n() != 0) {
487 gclog_or_tty->print_cr("Card table has %d entries; %d originally",
488 count2.n(), orig_count);
489 }
490 guarantee(count2.n() == 0, "Card table should be clean.");
492 RedirtyLoggedCardTableEntryClosure redirty;
493 dcqs.apply_closure_to_all_completed_buffers(&redirty);
494 dcqs.iterate_closure_all_threads(&redirty, false);
495 gclog_or_tty->print_cr("Log entries = %d, dirty cards = %d.",
496 clear.num_processed(), orig_count);
497 guarantee(redirty.num_processed() == clear.num_processed(),
498 err_msg("Redirtied "SIZE_FORMAT" cards, bug cleared "SIZE_FORMAT,
499 redirty.num_processed(), clear.num_processed()));
501 CountNonCleanMemRegionClosure count3(this);
502 ct_bs->mod_card_iterate(&count3);
503 if (count3.n() != orig_count) {
504 gclog_or_tty->print_cr("Should have restored them all: orig = %d, final = %d.",
505 orig_count, count3.n());
506 guarantee(count3.n() >= orig_count, "Should have restored them all.");
507 }
508 }
510 // Private class members.
512 G1CollectedHeap* G1CollectedHeap::_g1h;
514 // Private methods.
516 HeapRegion*
517 G1CollectedHeap::new_region_try_secondary_free_list(bool is_old) {
518 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
519 while (!_secondary_free_list.is_empty() || free_regions_coming()) {
520 if (!_secondary_free_list.is_empty()) {
521 if (G1ConcRegionFreeingVerbose) {
522 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
523 "secondary_free_list has %u entries",
524 _secondary_free_list.length());
525 }
526 // It looks as if there are free regions available on the
527 // secondary_free_list. Let's move them to the free_list and try
528 // again to allocate from it.
529 append_secondary_free_list();
531 assert(_hrm.num_free_regions() > 0, "if the secondary_free_list was not "
532 "empty we should have moved at least one entry to the free_list");
533 HeapRegion* res = _hrm.allocate_free_region(is_old);
534 if (G1ConcRegionFreeingVerbose) {
535 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
536 "allocated "HR_FORMAT" from secondary_free_list",
537 HR_FORMAT_PARAMS(res));
538 }
539 return res;
540 }
542 // Wait here until we get notified either when (a) there are no
543 // more free regions coming or (b) some regions have been moved on
544 // the secondary_free_list.
545 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
546 }
548 if (G1ConcRegionFreeingVerbose) {
549 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
550 "could not allocate from secondary_free_list");
551 }
552 return NULL;
553 }
555 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) {
556 assert(!isHumongous(word_size) || word_size <= HeapRegion::GrainWords,
557 "the only time we use this to allocate a humongous region is "
558 "when we are allocating a single humongous region");
560 HeapRegion* res;
561 if (G1StressConcRegionFreeing) {
562 if (!_secondary_free_list.is_empty()) {
563 if (G1ConcRegionFreeingVerbose) {
564 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
565 "forced to look at the secondary_free_list");
566 }
567 res = new_region_try_secondary_free_list(is_old);
568 if (res != NULL) {
569 return res;
570 }
571 }
572 }
574 res = _hrm.allocate_free_region(is_old);
576 if (res == NULL) {
577 if (G1ConcRegionFreeingVerbose) {
578 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
579 "res == NULL, trying the secondary_free_list");
580 }
581 res = new_region_try_secondary_free_list(is_old);
582 }
583 if (res == NULL && do_expand && _expand_heap_after_alloc_failure) {
584 // Currently, only attempts to allocate GC alloc regions set
585 // do_expand to true. So, we should only reach here during a
586 // safepoint. If this assumption changes we might have to
587 // reconsider the use of _expand_heap_after_alloc_failure.
588 assert(SafepointSynchronize::is_at_safepoint(), "invariant");
590 ergo_verbose1(ErgoHeapSizing,
591 "attempt heap expansion",
592 ergo_format_reason("region allocation request failed")
593 ergo_format_byte("allocation request"),
594 word_size * HeapWordSize);
595 if (expand(word_size * HeapWordSize)) {
596 // Given that expand() succeeded in expanding the heap, and we
597 // always expand the heap by an amount aligned to the heap
598 // region size, the free list should in theory not be empty.
599 // In either case allocate_free_region() will check for NULL.
600 res = _hrm.allocate_free_region(is_old);
601 } else {
602 _expand_heap_after_alloc_failure = false;
603 }
604 }
605 return res;
606 }
608 HeapWord*
609 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first,
610 uint num_regions,
611 size_t word_size,
612 AllocationContext_t context) {
613 assert(first != G1_NO_HRM_INDEX, "pre-condition");
614 assert(isHumongous(word_size), "word_size should be humongous");
615 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
617 // Index of last region in the series + 1.
618 uint last = first + num_regions;
620 // We need to initialize the region(s) we just discovered. This is
621 // a bit tricky given that it can happen concurrently with
622 // refinement threads refining cards on these regions and
623 // potentially wanting to refine the BOT as they are scanning
624 // those cards (this can happen shortly after a cleanup; see CR
625 // 6991377). So we have to set up the region(s) carefully and in
626 // a specific order.
628 // The word size sum of all the regions we will allocate.
629 size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords;
630 assert(word_size <= word_size_sum, "sanity");
632 // This will be the "starts humongous" region.
633 HeapRegion* first_hr = region_at(first);
634 // The header of the new object will be placed at the bottom of
635 // the first region.
636 HeapWord* new_obj = first_hr->bottom();
637 // This will be the new end of the first region in the series that
638 // should also match the end of the last region in the series.
639 HeapWord* new_end = new_obj + word_size_sum;
640 // This will be the new top of the first region that will reflect
641 // this allocation.
642 HeapWord* new_top = new_obj + word_size;
644 // First, we need to zero the header of the space that we will be
645 // allocating. When we update top further down, some refinement
646 // threads might try to scan the region. By zeroing the header we
647 // ensure that any thread that will try to scan the region will
648 // come across the zero klass word and bail out.
649 //
650 // NOTE: It would not have been correct to have used
651 // CollectedHeap::fill_with_object() and make the space look like
652 // an int array. The thread that is doing the allocation will
653 // later update the object header to a potentially different array
654 // type and, for a very short period of time, the klass and length
655 // fields will be inconsistent. This could cause a refinement
656 // thread to calculate the object size incorrectly.
657 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
659 // We will set up the first region as "starts humongous". This
660 // will also update the BOT covering all the regions to reflect
661 // that there is a single object that starts at the bottom of the
662 // first region.
663 first_hr->set_startsHumongous(new_top, new_end);
664 first_hr->set_allocation_context(context);
665 // Then, if there are any, we will set up the "continues
666 // humongous" regions.
667 HeapRegion* hr = NULL;
668 for (uint i = first + 1; i < last; ++i) {
669 hr = region_at(i);
670 hr->set_continuesHumongous(first_hr);
671 hr->set_allocation_context(context);
672 }
673 // If we have "continues humongous" regions (hr != NULL), then the
674 // end of the last one should match new_end.
675 assert(hr == NULL || hr->end() == new_end, "sanity");
677 // Up to this point no concurrent thread would have been able to
678 // do any scanning on any region in this series. All the top
679 // fields still point to bottom, so the intersection between
680 // [bottom,top] and [card_start,card_end] will be empty. Before we
681 // update the top fields, we'll do a storestore to make sure that
682 // no thread sees the update to top before the zeroing of the
683 // object header and the BOT initialization.
684 OrderAccess::storestore();
686 // Now that the BOT and the object header have been initialized,
687 // we can update top of the "starts humongous" region.
688 assert(first_hr->bottom() < new_top && new_top <= first_hr->end(),
689 "new_top should be in this region");
690 first_hr->set_top(new_top);
691 if (_hr_printer.is_active()) {
692 HeapWord* bottom = first_hr->bottom();
693 HeapWord* end = first_hr->orig_end();
694 if ((first + 1) == last) {
695 // the series has a single humongous region
696 _hr_printer.alloc(G1HRPrinter::SingleHumongous, first_hr, new_top);
697 } else {
698 // the series has more than one humongous regions
699 _hr_printer.alloc(G1HRPrinter::StartsHumongous, first_hr, end);
700 }
701 }
703 // Now, we will update the top fields of the "continues humongous"
704 // regions. The reason we need to do this is that, otherwise,
705 // these regions would look empty and this will confuse parts of
706 // G1. For example, the code that looks for a consecutive number
707 // of empty regions will consider them empty and try to
708 // re-allocate them. We can extend is_empty() to also include
709 // !continuesHumongous(), but it is easier to just update the top
710 // fields here. The way we set top for all regions (i.e., top ==
711 // end for all regions but the last one, top == new_top for the
712 // last one) is actually used when we will free up the humongous
713 // region in free_humongous_region().
714 hr = NULL;
715 for (uint i = first + 1; i < last; ++i) {
716 hr = region_at(i);
717 if ((i + 1) == last) {
718 // last continues humongous region
719 assert(hr->bottom() < new_top && new_top <= hr->end(),
720 "new_top should fall on this region");
721 hr->set_top(new_top);
722 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, new_top);
723 } else {
724 // not last one
725 assert(new_top > hr->end(), "new_top should be above this region");
726 hr->set_top(hr->end());
727 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, hr->end());
728 }
729 }
730 // If we have continues humongous regions (hr != NULL), then the
731 // end of the last one should match new_end and its top should
732 // match new_top.
733 assert(hr == NULL ||
734 (hr->end() == new_end && hr->top() == new_top), "sanity");
735 check_bitmaps("Humongous Region Allocation", first_hr);
737 assert(first_hr->used() == word_size * HeapWordSize, "invariant");
738 _allocator->increase_used(first_hr->used());
739 _humongous_set.add(first_hr);
741 return new_obj;
742 }
744 // If could fit into free regions w/o expansion, try.
745 // Otherwise, if can expand, do so.
746 // Otherwise, if using ex regions might help, try with ex given back.
747 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size, AllocationContext_t context) {
748 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
750 verify_region_sets_optional();
752 uint first = G1_NO_HRM_INDEX;
753 uint obj_regions = (uint)(align_size_up_(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords);
755 if (obj_regions == 1) {
756 // Only one region to allocate, try to use a fast path by directly allocating
757 // from the free lists. Do not try to expand here, we will potentially do that
758 // later.
759 HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */);
760 if (hr != NULL) {
761 first = hr->hrm_index();
762 }
763 } else {
764 // We can't allocate humongous regions spanning more than one region while
765 // cleanupComplete() is running, since some of the regions we find to be
766 // empty might not yet be added to the free list. It is not straightforward
767 // to know in which list they are on so that we can remove them. We only
768 // need to do this if we need to allocate more than one region to satisfy the
769 // current humongous allocation request. If we are only allocating one region
770 // we use the one-region region allocation code (see above), that already
771 // potentially waits for regions from the secondary free list.
772 wait_while_free_regions_coming();
773 append_secondary_free_list_if_not_empty_with_lock();
775 // Policy: Try only empty regions (i.e. already committed first). Maybe we
776 // are lucky enough to find some.
777 first = _hrm.find_contiguous_only_empty(obj_regions);
778 if (first != G1_NO_HRM_INDEX) {
779 _hrm.allocate_free_regions_starting_at(first, obj_regions);
780 }
781 }
783 if (first == G1_NO_HRM_INDEX) {
784 // Policy: We could not find enough regions for the humongous object in the
785 // free list. Look through the heap to find a mix of free and uncommitted regions.
786 // If so, try expansion.
787 first = _hrm.find_contiguous_empty_or_unavailable(obj_regions);
788 if (first != G1_NO_HRM_INDEX) {
789 // We found something. Make sure these regions are committed, i.e. expand
790 // the heap. Alternatively we could do a defragmentation GC.
791 ergo_verbose1(ErgoHeapSizing,
792 "attempt heap expansion",
793 ergo_format_reason("humongous allocation request failed")
794 ergo_format_byte("allocation request"),
795 word_size * HeapWordSize);
797 _hrm.expand_at(first, obj_regions);
798 g1_policy()->record_new_heap_size(num_regions());
800 #ifdef ASSERT
801 for (uint i = first; i < first + obj_regions; ++i) {
802 HeapRegion* hr = region_at(i);
803 assert(hr->is_empty(), "sanity");
804 assert(is_on_master_free_list(hr), "sanity");
805 }
806 #endif
807 _hrm.allocate_free_regions_starting_at(first, obj_regions);
808 } else {
809 // Policy: Potentially trigger a defragmentation GC.
810 }
811 }
813 HeapWord* result = NULL;
814 if (first != G1_NO_HRM_INDEX) {
815 result = humongous_obj_allocate_initialize_regions(first, obj_regions,
816 word_size, context);
817 assert(result != NULL, "it should always return a valid result");
819 // A successful humongous object allocation changes the used space
820 // information of the old generation so we need to recalculate the
821 // sizes and update the jstat counters here.
822 g1mm()->update_sizes();
823 }
825 verify_region_sets_optional();
827 return result;
828 }
830 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) {
831 assert_heap_not_locked_and_not_at_safepoint();
832 assert(!isHumongous(word_size), "we do not allow humongous TLABs");
834 unsigned int dummy_gc_count_before;
835 int dummy_gclocker_retry_count = 0;
836 return attempt_allocation(word_size, &dummy_gc_count_before, &dummy_gclocker_retry_count);
837 }
839 HeapWord*
840 G1CollectedHeap::mem_allocate(size_t word_size,
841 bool* gc_overhead_limit_was_exceeded) {
842 assert_heap_not_locked_and_not_at_safepoint();
844 // Loop until the allocation is satisfied, or unsatisfied after GC.
845 for (int try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
846 unsigned int gc_count_before;
848 HeapWord* result = NULL;
849 if (!isHumongous(word_size)) {
850 result = attempt_allocation(word_size, &gc_count_before, &gclocker_retry_count);
851 } else {
852 result = attempt_allocation_humongous(word_size, &gc_count_before, &gclocker_retry_count);
853 }
854 if (result != NULL) {
855 return result;
856 }
858 // Create the garbage collection operation...
859 VM_G1CollectForAllocation op(gc_count_before, word_size);
860 op.set_allocation_context(AllocationContext::current());
862 // ...and get the VM thread to execute it.
863 VMThread::execute(&op);
865 if (op.prologue_succeeded() && op.pause_succeeded()) {
866 // If the operation was successful we'll return the result even
867 // if it is NULL. If the allocation attempt failed immediately
868 // after a Full GC, it's unlikely we'll be able to allocate now.
869 HeapWord* result = op.result();
870 if (result != NULL && !isHumongous(word_size)) {
871 // Allocations that take place on VM operations do not do any
872 // card dirtying and we have to do it here. We only have to do
873 // this for non-humongous allocations, though.
874 dirty_young_block(result, word_size);
875 }
876 return result;
877 } else {
878 if (gclocker_retry_count > GCLockerRetryAllocationCount) {
879 return NULL;
880 }
881 assert(op.result() == NULL,
882 "the result should be NULL if the VM op did not succeed");
883 }
885 // Give a warning if we seem to be looping forever.
886 if ((QueuedAllocationWarningCount > 0) &&
887 (try_count % QueuedAllocationWarningCount == 0)) {
888 warning("G1CollectedHeap::mem_allocate retries %d times", try_count);
889 }
890 }
892 ShouldNotReachHere();
893 return NULL;
894 }
896 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size,
897 AllocationContext_t context,
898 unsigned int *gc_count_before_ret,
899 int* gclocker_retry_count_ret) {
900 // Make sure you read the note in attempt_allocation_humongous().
902 assert_heap_not_locked_and_not_at_safepoint();
903 assert(!isHumongous(word_size), "attempt_allocation_slow() should not "
904 "be called for humongous allocation requests");
906 // We should only get here after the first-level allocation attempt
907 // (attempt_allocation()) failed to allocate.
909 // We will loop until a) we manage to successfully perform the
910 // allocation or b) we successfully schedule a collection which
911 // fails to perform the allocation. b) is the only case when we'll
912 // return NULL.
913 HeapWord* result = NULL;
914 for (int try_count = 1; /* we'll return */; try_count += 1) {
915 bool should_try_gc;
916 unsigned int gc_count_before;
918 {
919 MutexLockerEx x(Heap_lock);
920 result = _allocator->mutator_alloc_region(context)->attempt_allocation_locked(word_size,
921 false /* bot_updates */);
922 if (result != NULL) {
923 return result;
924 }
926 // If we reach here, attempt_allocation_locked() above failed to
927 // allocate a new region. So the mutator alloc region should be NULL.
928 assert(_allocator->mutator_alloc_region(context)->get() == NULL, "only way to get here");
930 if (GC_locker::is_active_and_needs_gc()) {
931 if (g1_policy()->can_expand_young_list()) {
932 // No need for an ergo verbose message here,
933 // can_expand_young_list() does this when it returns true.
934 result = _allocator->mutator_alloc_region(context)->attempt_allocation_force(word_size,
935 false /* bot_updates */);
936 if (result != NULL) {
937 return result;
938 }
939 }
940 should_try_gc = false;
941 } else {
942 // The GCLocker may not be active but the GCLocker initiated
943 // GC may not yet have been performed (GCLocker::needs_gc()
944 // returns true). In this case we do not try this GC and
945 // wait until the GCLocker initiated GC is performed, and
946 // then retry the allocation.
947 if (GC_locker::needs_gc()) {
948 should_try_gc = false;
949 } else {
950 // Read the GC count while still holding the Heap_lock.
951 gc_count_before = total_collections();
952 should_try_gc = true;
953 }
954 }
955 }
957 if (should_try_gc) {
958 bool succeeded;
959 result = do_collection_pause(word_size, gc_count_before, &succeeded,
960 GCCause::_g1_inc_collection_pause);
961 if (result != NULL) {
962 assert(succeeded, "only way to get back a non-NULL result");
963 return result;
964 }
966 if (succeeded) {
967 // If we get here we successfully scheduled a collection which
968 // failed to allocate. No point in trying to allocate
969 // further. We'll just return NULL.
970 MutexLockerEx x(Heap_lock);
971 *gc_count_before_ret = total_collections();
972 return NULL;
973 }
974 } else {
975 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
976 MutexLockerEx x(Heap_lock);
977 *gc_count_before_ret = total_collections();
978 return NULL;
979 }
980 // The GCLocker is either active or the GCLocker initiated
981 // GC has not yet been performed. Stall until it is and
982 // then retry the allocation.
983 GC_locker::stall_until_clear();
984 (*gclocker_retry_count_ret) += 1;
985 }
987 // We can reach here if we were unsuccessful in scheduling a
988 // collection (because another thread beat us to it) or if we were
989 // stalled due to the GC locker. In either can we should retry the
990 // allocation attempt in case another thread successfully
991 // performed a collection and reclaimed enough space. We do the
992 // first attempt (without holding the Heap_lock) here and the
993 // follow-on attempt will be at the start of the next loop
994 // iteration (after taking the Heap_lock).
995 result = _allocator->mutator_alloc_region(context)->attempt_allocation(word_size,
996 false /* bot_updates */);
997 if (result != NULL) {
998 return result;
999 }
1001 // Give a warning if we seem to be looping forever.
1002 if ((QueuedAllocationWarningCount > 0) &&
1003 (try_count % QueuedAllocationWarningCount == 0)) {
1004 warning("G1CollectedHeap::attempt_allocation_slow() "
1005 "retries %d times", try_count);
1006 }
1007 }
1009 ShouldNotReachHere();
1010 return NULL;
1011 }
1013 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size,
1014 unsigned int * gc_count_before_ret,
1015 int* gclocker_retry_count_ret) {
1016 // The structure of this method has a lot of similarities to
1017 // attempt_allocation_slow(). The reason these two were not merged
1018 // into a single one is that such a method would require several "if
1019 // allocation is not humongous do this, otherwise do that"
1020 // conditional paths which would obscure its flow. In fact, an early
1021 // version of this code did use a unified method which was harder to
1022 // follow and, as a result, it had subtle bugs that were hard to
1023 // track down. So keeping these two methods separate allows each to
1024 // be more readable. It will be good to keep these two in sync as
1025 // much as possible.
1027 assert_heap_not_locked_and_not_at_safepoint();
1028 assert(isHumongous(word_size), "attempt_allocation_humongous() "
1029 "should only be called for humongous allocations");
1031 // Humongous objects can exhaust the heap quickly, so we should check if we
1032 // need to start a marking cycle at each humongous object allocation. We do
1033 // the check before we do the actual allocation. The reason for doing it
1034 // before the allocation is that we avoid having to keep track of the newly
1035 // allocated memory while we do a GC.
1036 if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation",
1037 word_size)) {
1038 collect(GCCause::_g1_humongous_allocation);
1039 }
1041 // We will loop until a) we manage to successfully perform the
1042 // allocation or b) we successfully schedule a collection which
1043 // fails to perform the allocation. b) is the only case when we'll
1044 // return NULL.
1045 HeapWord* result = NULL;
1046 for (int try_count = 1; /* we'll return */; try_count += 1) {
1047 bool should_try_gc;
1048 unsigned int gc_count_before;
1050 {
1051 MutexLockerEx x(Heap_lock);
1053 // Given that humongous objects are not allocated in young
1054 // regions, we'll first try to do the allocation without doing a
1055 // collection hoping that there's enough space in the heap.
1056 result = humongous_obj_allocate(word_size, AllocationContext::current());
1057 if (result != NULL) {
1058 return result;
1059 }
1061 if (GC_locker::is_active_and_needs_gc()) {
1062 should_try_gc = false;
1063 } else {
1064 // The GCLocker may not be active but the GCLocker initiated
1065 // GC may not yet have been performed (GCLocker::needs_gc()
1066 // returns true). In this case we do not try this GC and
1067 // wait until the GCLocker initiated GC is performed, and
1068 // then retry the allocation.
1069 if (GC_locker::needs_gc()) {
1070 should_try_gc = false;
1071 } else {
1072 // Read the GC count while still holding the Heap_lock.
1073 gc_count_before = total_collections();
1074 should_try_gc = true;
1075 }
1076 }
1077 }
1079 if (should_try_gc) {
1080 // If we failed to allocate the humongous object, we should try to
1081 // do a collection pause (if we're allowed) in case it reclaims
1082 // enough space for the allocation to succeed after the pause.
1084 bool succeeded;
1085 result = do_collection_pause(word_size, gc_count_before, &succeeded,
1086 GCCause::_g1_humongous_allocation);
1087 if (result != NULL) {
1088 assert(succeeded, "only way to get back a non-NULL result");
1089 return result;
1090 }
1092 if (succeeded) {
1093 // If we get here we successfully scheduled a collection which
1094 // failed to allocate. No point in trying to allocate
1095 // further. We'll just return NULL.
1096 MutexLockerEx x(Heap_lock);
1097 *gc_count_before_ret = total_collections();
1098 return NULL;
1099 }
1100 } else {
1101 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
1102 MutexLockerEx x(Heap_lock);
1103 *gc_count_before_ret = total_collections();
1104 return NULL;
1105 }
1106 // The GCLocker is either active or the GCLocker initiated
1107 // GC has not yet been performed. Stall until it is and
1108 // then retry the allocation.
1109 GC_locker::stall_until_clear();
1110 (*gclocker_retry_count_ret) += 1;
1111 }
1113 // We can reach here if we were unsuccessful in scheduling a
1114 // collection (because another thread beat us to it) or if we were
1115 // stalled due to the GC locker. In either can we should retry the
1116 // allocation attempt in case another thread successfully
1117 // performed a collection and reclaimed enough space. Give a
1118 // warning if we seem to be looping forever.
1120 if ((QueuedAllocationWarningCount > 0) &&
1121 (try_count % QueuedAllocationWarningCount == 0)) {
1122 warning("G1CollectedHeap::attempt_allocation_humongous() "
1123 "retries %d times", try_count);
1124 }
1125 }
1127 ShouldNotReachHere();
1128 return NULL;
1129 }
1131 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
1132 AllocationContext_t context,
1133 bool expect_null_mutator_alloc_region) {
1134 assert_at_safepoint(true /* should_be_vm_thread */);
1135 assert(_allocator->mutator_alloc_region(context)->get() == NULL ||
1136 !expect_null_mutator_alloc_region,
1137 "the current alloc region was unexpectedly found to be non-NULL");
1139 if (!isHumongous(word_size)) {
1140 return _allocator->mutator_alloc_region(context)->attempt_allocation_locked(word_size,
1141 false /* bot_updates */);
1142 } else {
1143 HeapWord* result = humongous_obj_allocate(word_size, context);
1144 if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) {
1145 g1_policy()->set_initiate_conc_mark_if_possible();
1146 }
1147 return result;
1148 }
1150 ShouldNotReachHere();
1151 }
1153 class PostMCRemSetClearClosure: public HeapRegionClosure {
1154 G1CollectedHeap* _g1h;
1155 ModRefBarrierSet* _mr_bs;
1156 public:
1157 PostMCRemSetClearClosure(G1CollectedHeap* g1h, ModRefBarrierSet* mr_bs) :
1158 _g1h(g1h), _mr_bs(mr_bs) {}
1160 bool doHeapRegion(HeapRegion* r) {
1161 HeapRegionRemSet* hrrs = r->rem_set();
1163 if (r->continuesHumongous()) {
1164 // We'll assert that the strong code root list and RSet is empty
1165 assert(hrrs->strong_code_roots_list_length() == 0, "sanity");
1166 assert(hrrs->occupied() == 0, "RSet should be empty");
1167 return false;
1168 }
1170 _g1h->reset_gc_time_stamps(r);
1171 hrrs->clear();
1172 // You might think here that we could clear just the cards
1173 // corresponding to the used region. But no: if we leave a dirty card
1174 // in a region we might allocate into, then it would prevent that card
1175 // from being enqueued, and cause it to be missed.
1176 // Re: the performance cost: we shouldn't be doing full GC anyway!
1177 _mr_bs->clear(MemRegion(r->bottom(), r->end()));
1179 return false;
1180 }
1181 };
1183 void G1CollectedHeap::clear_rsets_post_compaction() {
1184 PostMCRemSetClearClosure rs_clear(this, g1_barrier_set());
1185 heap_region_iterate(&rs_clear);
1186 }
1188 class RebuildRSOutOfRegionClosure: public HeapRegionClosure {
1189 G1CollectedHeap* _g1h;
1190 UpdateRSOopClosure _cl;
1191 int _worker_i;
1192 public:
1193 RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, int worker_i = 0) :
1194 _cl(g1->g1_rem_set(), worker_i),
1195 _worker_i(worker_i),
1196 _g1h(g1)
1197 { }
1199 bool doHeapRegion(HeapRegion* r) {
1200 if (!r->continuesHumongous()) {
1201 _cl.set_from(r);
1202 r->oop_iterate(&_cl);
1203 }
1204 return false;
1205 }
1206 };
1208 class ParRebuildRSTask: public AbstractGangTask {
1209 G1CollectedHeap* _g1;
1210 public:
1211 ParRebuildRSTask(G1CollectedHeap* g1)
1212 : AbstractGangTask("ParRebuildRSTask"),
1213 _g1(g1)
1214 { }
1216 void work(uint worker_id) {
1217 RebuildRSOutOfRegionClosure rebuild_rs(_g1, worker_id);
1218 _g1->heap_region_par_iterate_chunked(&rebuild_rs, worker_id,
1219 _g1->workers()->active_workers(),
1220 HeapRegion::RebuildRSClaimValue);
1221 }
1222 };
1224 class PostCompactionPrinterClosure: public HeapRegionClosure {
1225 private:
1226 G1HRPrinter* _hr_printer;
1227 public:
1228 bool doHeapRegion(HeapRegion* hr) {
1229 assert(!hr->is_young(), "not expecting to find young regions");
1230 // We only generate output for non-empty regions.
1231 if (!hr->is_empty()) {
1232 if (!hr->isHumongous()) {
1233 _hr_printer->post_compaction(hr, G1HRPrinter::Old);
1234 } else if (hr->startsHumongous()) {
1235 if (hr->region_num() == 1) {
1236 // single humongous region
1237 _hr_printer->post_compaction(hr, G1HRPrinter::SingleHumongous);
1238 } else {
1239 _hr_printer->post_compaction(hr, G1HRPrinter::StartsHumongous);
1240 }
1241 } else {
1242 assert(hr->continuesHumongous(), "only way to get here");
1243 _hr_printer->post_compaction(hr, G1HRPrinter::ContinuesHumongous);
1244 }
1245 }
1246 return false;
1247 }
1249 PostCompactionPrinterClosure(G1HRPrinter* hr_printer)
1250 : _hr_printer(hr_printer) { }
1251 };
1253 void G1CollectedHeap::print_hrm_post_compaction() {
1254 PostCompactionPrinterClosure cl(hr_printer());
1255 heap_region_iterate(&cl);
1256 }
1258 bool G1CollectedHeap::do_collection(bool explicit_gc,
1259 bool clear_all_soft_refs,
1260 size_t word_size) {
1261 assert_at_safepoint(true /* should_be_vm_thread */);
1263 if (GC_locker::check_active_before_gc()) {
1264 return false;
1265 }
1267 STWGCTimer* gc_timer = G1MarkSweep::gc_timer();
1268 gc_timer->register_gc_start();
1270 SerialOldTracer* gc_tracer = G1MarkSweep::gc_tracer();
1271 gc_tracer->report_gc_start(gc_cause(), gc_timer->gc_start());
1273 SvcGCMarker sgcm(SvcGCMarker::FULL);
1274 ResourceMark rm;
1276 print_heap_before_gc();
1277 trace_heap_before_gc(gc_tracer);
1279 size_t metadata_prev_used = MetaspaceAux::used_bytes();
1281 verify_region_sets_optional();
1283 const bool do_clear_all_soft_refs = clear_all_soft_refs ||
1284 collector_policy()->should_clear_all_soft_refs();
1286 ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy());
1288 {
1289 IsGCActiveMark x;
1291 // Timing
1292 assert(gc_cause() != GCCause::_java_lang_system_gc || explicit_gc, "invariant");
1293 gclog_or_tty->date_stamp(G1Log::fine() && PrintGCDateStamps);
1294 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
1296 {
1297 GCTraceTime t(GCCauseString("Full GC", gc_cause()), G1Log::fine(), true, NULL, gc_tracer->gc_id());
1298 TraceCollectorStats tcs(g1mm()->full_collection_counters());
1299 TraceMemoryManagerStats tms(true /* fullGC */, gc_cause());
1301 double start = os::elapsedTime();
1302 g1_policy()->record_full_collection_start();
1304 // Note: When we have a more flexible GC logging framework that
1305 // allows us to add optional attributes to a GC log record we
1306 // could consider timing and reporting how long we wait in the
1307 // following two methods.
1308 wait_while_free_regions_coming();
1309 // If we start the compaction before the CM threads finish
1310 // scanning the root regions we might trip them over as we'll
1311 // be moving objects / updating references. So let's wait until
1312 // they are done. By telling them to abort, they should complete
1313 // early.
1314 _cm->root_regions()->abort();
1315 _cm->root_regions()->wait_until_scan_finished();
1316 append_secondary_free_list_if_not_empty_with_lock();
1318 gc_prologue(true);
1319 increment_total_collections(true /* full gc */);
1320 increment_old_marking_cycles_started();
1322 assert(used() == recalculate_used(), "Should be equal");
1324 verify_before_gc();
1326 check_bitmaps("Full GC Start");
1327 pre_full_gc_dump(gc_timer);
1329 COMPILER2_PRESENT(DerivedPointerTable::clear());
1331 // Disable discovery and empty the discovered lists
1332 // for the CM ref processor.
1333 ref_processor_cm()->disable_discovery();
1334 ref_processor_cm()->abandon_partial_discovery();
1335 ref_processor_cm()->verify_no_references_recorded();
1337 // Abandon current iterations of concurrent marking and concurrent
1338 // refinement, if any are in progress. We have to do this before
1339 // wait_until_scan_finished() below.
1340 concurrent_mark()->abort();
1342 // Make sure we'll choose a new allocation region afterwards.
1343 _allocator->release_mutator_alloc_region();
1344 _allocator->abandon_gc_alloc_regions();
1345 g1_rem_set()->cleanupHRRS();
1347 // We should call this after we retire any currently active alloc
1348 // regions so that all the ALLOC / RETIRE events are generated
1349 // before the start GC event.
1350 _hr_printer.start_gc(true /* full */, (size_t) total_collections());
1352 // We may have added regions to the current incremental collection
1353 // set between the last GC or pause and now. We need to clear the
1354 // incremental collection set and then start rebuilding it afresh
1355 // after this full GC.
1356 abandon_collection_set(g1_policy()->inc_cset_head());
1357 g1_policy()->clear_incremental_cset();
1358 g1_policy()->stop_incremental_cset_building();
1360 tear_down_region_sets(false /* free_list_only */);
1361 g1_policy()->set_gcs_are_young(true);
1363 // See the comments in g1CollectedHeap.hpp and
1364 // G1CollectedHeap::ref_processing_init() about
1365 // how reference processing currently works in G1.
1367 // Temporarily make discovery by the STW ref processor single threaded (non-MT).
1368 ReferenceProcessorMTDiscoveryMutator stw_rp_disc_ser(ref_processor_stw(), false);
1370 // Temporarily clear the STW ref processor's _is_alive_non_header field.
1371 ReferenceProcessorIsAliveMutator stw_rp_is_alive_null(ref_processor_stw(), NULL);
1373 ref_processor_stw()->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/);
1374 ref_processor_stw()->setup_policy(do_clear_all_soft_refs);
1376 // Do collection work
1377 {
1378 HandleMark hm; // Discard invalid handles created during gc
1379 G1MarkSweep::invoke_at_safepoint(ref_processor_stw(), do_clear_all_soft_refs);
1380 }
1382 assert(num_free_regions() == 0, "we should not have added any free regions");
1383 rebuild_region_sets(false /* free_list_only */);
1385 // Enqueue any discovered reference objects that have
1386 // not been removed from the discovered lists.
1387 ref_processor_stw()->enqueue_discovered_references();
1389 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
1391 MemoryService::track_memory_usage();
1393 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
1394 ref_processor_stw()->verify_no_references_recorded();
1396 // Delete metaspaces for unloaded class loaders and clean up loader_data graph
1397 ClassLoaderDataGraph::purge();
1398 MetaspaceAux::verify_metrics();
1400 // Note: since we've just done a full GC, concurrent
1401 // marking is no longer active. Therefore we need not
1402 // re-enable reference discovery for the CM ref processor.
1403 // That will be done at the start of the next marking cycle.
1404 assert(!ref_processor_cm()->discovery_enabled(), "Postcondition");
1405 ref_processor_cm()->verify_no_references_recorded();
1407 reset_gc_time_stamp();
1408 // Since everything potentially moved, we will clear all remembered
1409 // sets, and clear all cards. Later we will rebuild remembered
1410 // sets. We will also reset the GC time stamps of the regions.
1411 clear_rsets_post_compaction();
1412 check_gc_time_stamps();
1414 // Resize the heap if necessary.
1415 resize_if_necessary_after_full_collection(explicit_gc ? 0 : word_size);
1417 if (_hr_printer.is_active()) {
1418 // We should do this after we potentially resize the heap so
1419 // that all the COMMIT / UNCOMMIT events are generated before
1420 // the end GC event.
1422 print_hrm_post_compaction();
1423 _hr_printer.end_gc(true /* full */, (size_t) total_collections());
1424 }
1426 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
1427 if (hot_card_cache->use_cache()) {
1428 hot_card_cache->reset_card_counts();
1429 hot_card_cache->reset_hot_cache();
1430 }
1432 // Rebuild remembered sets of all regions.
1433 if (G1CollectedHeap::use_parallel_gc_threads()) {
1434 uint n_workers =
1435 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
1436 workers()->active_workers(),
1437 Threads::number_of_non_daemon_threads());
1438 assert(UseDynamicNumberOfGCThreads ||
1439 n_workers == workers()->total_workers(),
1440 "If not dynamic should be using all the workers");
1441 workers()->set_active_workers(n_workers);
1442 // Set parallel threads in the heap (_n_par_threads) only
1443 // before a parallel phase and always reset it to 0 after
1444 // the phase so that the number of parallel threads does
1445 // no get carried forward to a serial phase where there
1446 // may be code that is "possibly_parallel".
1447 set_par_threads(n_workers);
1449 ParRebuildRSTask rebuild_rs_task(this);
1450 assert(check_heap_region_claim_values(
1451 HeapRegion::InitialClaimValue), "sanity check");
1452 assert(UseDynamicNumberOfGCThreads ||
1453 workers()->active_workers() == workers()->total_workers(),
1454 "Unless dynamic should use total workers");
1455 // Use the most recent number of active workers
1456 assert(workers()->active_workers() > 0,
1457 "Active workers not properly set");
1458 set_par_threads(workers()->active_workers());
1459 workers()->run_task(&rebuild_rs_task);
1460 set_par_threads(0);
1461 assert(check_heap_region_claim_values(
1462 HeapRegion::RebuildRSClaimValue), "sanity check");
1463 reset_heap_region_claim_values();
1464 } else {
1465 RebuildRSOutOfRegionClosure rebuild_rs(this);
1466 heap_region_iterate(&rebuild_rs);
1467 }
1469 // Rebuild the strong code root lists for each region
1470 rebuild_strong_code_roots();
1472 if (true) { // FIXME
1473 MetaspaceGC::compute_new_size();
1474 }
1476 #ifdef TRACESPINNING
1477 ParallelTaskTerminator::print_termination_counts();
1478 #endif
1480 // Discard all rset updates
1481 JavaThread::dirty_card_queue_set().abandon_logs();
1482 assert(!G1DeferredRSUpdate
1483 || (G1DeferredRSUpdate &&
1484 (dirty_card_queue_set().completed_buffers_num() == 0)), "Should not be any");
1486 _young_list->reset_sampled_info();
1487 // At this point there should be no regions in the
1488 // entire heap tagged as young.
1489 assert(check_young_list_empty(true /* check_heap */),
1490 "young list should be empty at this point");
1492 // Update the number of full collections that have been completed.
1493 increment_old_marking_cycles_completed(false /* concurrent */);
1495 _hrm.verify_optional();
1496 verify_region_sets_optional();
1498 verify_after_gc();
1500 // Clear the previous marking bitmap, if needed for bitmap verification.
1501 // Note we cannot do this when we clear the next marking bitmap in
1502 // ConcurrentMark::abort() above since VerifyDuringGC verifies the
1503 // objects marked during a full GC against the previous bitmap.
1504 // But we need to clear it before calling check_bitmaps below since
1505 // the full GC has compacted objects and updated TAMS but not updated
1506 // the prev bitmap.
1507 if (G1VerifyBitmaps) {
1508 ((CMBitMap*) concurrent_mark()->prevMarkBitMap())->clearAll();
1509 }
1510 check_bitmaps("Full GC End");
1512 // Start a new incremental collection set for the next pause
1513 assert(g1_policy()->collection_set() == NULL, "must be");
1514 g1_policy()->start_incremental_cset_building();
1516 clear_cset_fast_test();
1518 _allocator->init_mutator_alloc_region();
1520 double end = os::elapsedTime();
1521 g1_policy()->record_full_collection_end();
1523 if (G1Log::fine()) {
1524 g1_policy()->print_heap_transition();
1525 }
1527 // We must call G1MonitoringSupport::update_sizes() in the same scoping level
1528 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
1529 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
1530 // before any GC notifications are raised.
1531 g1mm()->update_sizes();
1533 gc_epilogue(true);
1534 }
1536 if (G1Log::finer()) {
1537 g1_policy()->print_detailed_heap_transition(true /* full */);
1538 }
1540 print_heap_after_gc();
1541 trace_heap_after_gc(gc_tracer);
1543 post_full_gc_dump(gc_timer);
1545 gc_timer->register_gc_end();
1546 gc_tracer->report_gc_end(gc_timer->gc_end(), gc_timer->time_partitions());
1547 }
1549 return true;
1550 }
1552 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
1553 // do_collection() will return whether it succeeded in performing
1554 // the GC. Currently, there is no facility on the
1555 // do_full_collection() API to notify the caller than the collection
1556 // did not succeed (e.g., because it was locked out by the GC
1557 // locker). So, right now, we'll ignore the return value.
1558 bool dummy = do_collection(true, /* explicit_gc */
1559 clear_all_soft_refs,
1560 0 /* word_size */);
1561 }
1563 // This code is mostly copied from TenuredGeneration.
1564 void
1565 G1CollectedHeap::
1566 resize_if_necessary_after_full_collection(size_t word_size) {
1567 // Include the current allocation, if any, and bytes that will be
1568 // pre-allocated to support collections, as "used".
1569 const size_t used_after_gc = used();
1570 const size_t capacity_after_gc = capacity();
1571 const size_t free_after_gc = capacity_after_gc - used_after_gc;
1573 // This is enforced in arguments.cpp.
1574 assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
1575 "otherwise the code below doesn't make sense");
1577 // We don't have floating point command-line arguments
1578 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
1579 const double maximum_used_percentage = 1.0 - minimum_free_percentage;
1580 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
1581 const double minimum_used_percentage = 1.0 - maximum_free_percentage;
1583 const size_t min_heap_size = collector_policy()->min_heap_byte_size();
1584 const size_t max_heap_size = collector_policy()->max_heap_byte_size();
1586 // We have to be careful here as these two calculations can overflow
1587 // 32-bit size_t's.
1588 double used_after_gc_d = (double) used_after_gc;
1589 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
1590 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
1592 // Let's make sure that they are both under the max heap size, which
1593 // by default will make them fit into a size_t.
1594 double desired_capacity_upper_bound = (double) max_heap_size;
1595 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
1596 desired_capacity_upper_bound);
1597 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
1598 desired_capacity_upper_bound);
1600 // We can now safely turn them into size_t's.
1601 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
1602 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
1604 // This assert only makes sense here, before we adjust them
1605 // with respect to the min and max heap size.
1606 assert(minimum_desired_capacity <= maximum_desired_capacity,
1607 err_msg("minimum_desired_capacity = "SIZE_FORMAT", "
1608 "maximum_desired_capacity = "SIZE_FORMAT,
1609 minimum_desired_capacity, maximum_desired_capacity));
1611 // Should not be greater than the heap max size. No need to adjust
1612 // it with respect to the heap min size as it's a lower bound (i.e.,
1613 // we'll try to make the capacity larger than it, not smaller).
1614 minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size);
1615 // Should not be less than the heap min size. No need to adjust it
1616 // with respect to the heap max size as it's an upper bound (i.e.,
1617 // we'll try to make the capacity smaller than it, not greater).
1618 maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size);
1620 if (capacity_after_gc < minimum_desired_capacity) {
1621 // Don't expand unless it's significant
1622 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
1623 ergo_verbose4(ErgoHeapSizing,
1624 "attempt heap expansion",
1625 ergo_format_reason("capacity lower than "
1626 "min desired capacity after Full GC")
1627 ergo_format_byte("capacity")
1628 ergo_format_byte("occupancy")
1629 ergo_format_byte_perc("min desired capacity"),
1630 capacity_after_gc, used_after_gc,
1631 minimum_desired_capacity, (double) MinHeapFreeRatio);
1632 expand(expand_bytes);
1634 // No expansion, now see if we want to shrink
1635 } else if (capacity_after_gc > maximum_desired_capacity) {
1636 // Capacity too large, compute shrinking size
1637 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
1638 ergo_verbose4(ErgoHeapSizing,
1639 "attempt heap shrinking",
1640 ergo_format_reason("capacity higher than "
1641 "max desired capacity after Full GC")
1642 ergo_format_byte("capacity")
1643 ergo_format_byte("occupancy")
1644 ergo_format_byte_perc("max desired capacity"),
1645 capacity_after_gc, used_after_gc,
1646 maximum_desired_capacity, (double) MaxHeapFreeRatio);
1647 shrink(shrink_bytes);
1648 }
1649 }
1652 HeapWord*
1653 G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
1654 AllocationContext_t context,
1655 bool* succeeded) {
1656 assert_at_safepoint(true /* should_be_vm_thread */);
1658 *succeeded = true;
1659 // Let's attempt the allocation first.
1660 HeapWord* result =
1661 attempt_allocation_at_safepoint(word_size,
1662 context,
1663 false /* expect_null_mutator_alloc_region */);
1664 if (result != NULL) {
1665 assert(*succeeded, "sanity");
1666 return result;
1667 }
1669 // In a G1 heap, we're supposed to keep allocation from failing by
1670 // incremental pauses. Therefore, at least for now, we'll favor
1671 // expansion over collection. (This might change in the future if we can
1672 // do something smarter than full collection to satisfy a failed alloc.)
1673 result = expand_and_allocate(word_size, context);
1674 if (result != NULL) {
1675 assert(*succeeded, "sanity");
1676 return result;
1677 }
1679 // Expansion didn't work, we'll try to do a Full GC.
1680 bool gc_succeeded = do_collection(false, /* explicit_gc */
1681 false, /* clear_all_soft_refs */
1682 word_size);
1683 if (!gc_succeeded) {
1684 *succeeded = false;
1685 return NULL;
1686 }
1688 // Retry the allocation
1689 result = attempt_allocation_at_safepoint(word_size,
1690 context,
1691 true /* expect_null_mutator_alloc_region */);
1692 if (result != NULL) {
1693 assert(*succeeded, "sanity");
1694 return result;
1695 }
1697 // Then, try a Full GC that will collect all soft references.
1698 gc_succeeded = do_collection(false, /* explicit_gc */
1699 true, /* clear_all_soft_refs */
1700 word_size);
1701 if (!gc_succeeded) {
1702 *succeeded = false;
1703 return NULL;
1704 }
1706 // Retry the allocation once more
1707 result = attempt_allocation_at_safepoint(word_size,
1708 context,
1709 true /* expect_null_mutator_alloc_region */);
1710 if (result != NULL) {
1711 assert(*succeeded, "sanity");
1712 return result;
1713 }
1715 assert(!collector_policy()->should_clear_all_soft_refs(),
1716 "Flag should have been handled and cleared prior to this point");
1718 // What else? We might try synchronous finalization later. If the total
1719 // space available is large enough for the allocation, then a more
1720 // complete compaction phase than we've tried so far might be
1721 // appropriate.
1722 assert(*succeeded, "sanity");
1723 return NULL;
1724 }
1726 // Attempting to expand the heap sufficiently
1727 // to support an allocation of the given "word_size". If
1728 // successful, perform the allocation and return the address of the
1729 // allocated block, or else "NULL".
1731 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size, AllocationContext_t context) {
1732 assert_at_safepoint(true /* should_be_vm_thread */);
1734 verify_region_sets_optional();
1736 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
1737 ergo_verbose1(ErgoHeapSizing,
1738 "attempt heap expansion",
1739 ergo_format_reason("allocation request failed")
1740 ergo_format_byte("allocation request"),
1741 word_size * HeapWordSize);
1742 if (expand(expand_bytes)) {
1743 _hrm.verify_optional();
1744 verify_region_sets_optional();
1745 return attempt_allocation_at_safepoint(word_size,
1746 context,
1747 false /* expect_null_mutator_alloc_region */);
1748 }
1749 return NULL;
1750 }
1752 bool G1CollectedHeap::expand(size_t expand_bytes) {
1753 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
1754 aligned_expand_bytes = align_size_up(aligned_expand_bytes,
1755 HeapRegion::GrainBytes);
1756 ergo_verbose2(ErgoHeapSizing,
1757 "expand the heap",
1758 ergo_format_byte("requested expansion amount")
1759 ergo_format_byte("attempted expansion amount"),
1760 expand_bytes, aligned_expand_bytes);
1762 if (is_maximal_no_gc()) {
1763 ergo_verbose0(ErgoHeapSizing,
1764 "did not expand the heap",
1765 ergo_format_reason("heap already fully expanded"));
1766 return false;
1767 }
1769 uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes);
1770 assert(regions_to_expand > 0, "Must expand by at least one region");
1772 uint expanded_by = _hrm.expand_by(regions_to_expand);
1774 if (expanded_by > 0) {
1775 size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes;
1776 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
1777 g1_policy()->record_new_heap_size(num_regions());
1778 } else {
1779 ergo_verbose0(ErgoHeapSizing,
1780 "did not expand the heap",
1781 ergo_format_reason("heap expansion operation failed"));
1782 // The expansion of the virtual storage space was unsuccessful.
1783 // Let's see if it was because we ran out of swap.
1784 if (G1ExitOnExpansionFailure &&
1785 _hrm.available() >= regions_to_expand) {
1786 // We had head room...
1787 vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion");
1788 }
1789 }
1790 return regions_to_expand > 0;
1791 }
1793 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
1794 size_t aligned_shrink_bytes =
1795 ReservedSpace::page_align_size_down(shrink_bytes);
1796 aligned_shrink_bytes = align_size_down(aligned_shrink_bytes,
1797 HeapRegion::GrainBytes);
1798 uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes);
1800 uint num_regions_removed = _hrm.shrink_by(num_regions_to_remove);
1801 size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes;
1803 ergo_verbose3(ErgoHeapSizing,
1804 "shrink the heap",
1805 ergo_format_byte("requested shrinking amount")
1806 ergo_format_byte("aligned shrinking amount")
1807 ergo_format_byte("attempted shrinking amount"),
1808 shrink_bytes, aligned_shrink_bytes, shrunk_bytes);
1809 if (num_regions_removed > 0) {
1810 g1_policy()->record_new_heap_size(num_regions());
1811 } else {
1812 ergo_verbose0(ErgoHeapSizing,
1813 "did not shrink the heap",
1814 ergo_format_reason("heap shrinking operation failed"));
1815 }
1816 }
1818 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1819 verify_region_sets_optional();
1821 // We should only reach here at the end of a Full GC which means we
1822 // should not not be holding to any GC alloc regions. The method
1823 // below will make sure of that and do any remaining clean up.
1824 _allocator->abandon_gc_alloc_regions();
1826 // Instead of tearing down / rebuilding the free lists here, we
1827 // could instead use the remove_all_pending() method on free_list to
1828 // remove only the ones that we need to remove.
1829 tear_down_region_sets(true /* free_list_only */);
1830 shrink_helper(shrink_bytes);
1831 rebuild_region_sets(true /* free_list_only */);
1833 _hrm.verify_optional();
1834 verify_region_sets_optional();
1835 }
1837 // Public methods.
1839 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away
1840 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
1841 #endif // _MSC_VER
1844 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* policy_) :
1845 SharedHeap(policy_),
1846 _g1_policy(policy_),
1847 _dirty_card_queue_set(false),
1848 _into_cset_dirty_card_queue_set(false),
1849 _is_alive_closure_cm(this),
1850 _is_alive_closure_stw(this),
1851 _ref_processor_cm(NULL),
1852 _ref_processor_stw(NULL),
1853 _process_strong_tasks(new SubTasksDone(G1H_PS_NumElements)),
1854 _bot_shared(NULL),
1855 _evac_failure_scan_stack(NULL),
1856 _mark_in_progress(false),
1857 _cg1r(NULL),
1858 _g1mm(NULL),
1859 _refine_cte_cl(NULL),
1860 _full_collection(false),
1861 _secondary_free_list("Secondary Free List", new SecondaryFreeRegionListMtSafeChecker()),
1862 _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()),
1863 _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()),
1864 _humongous_is_live(),
1865 _has_humongous_reclaim_candidates(false),
1866 _free_regions_coming(false),
1867 _young_list(new YoungList(this)),
1868 _gc_time_stamp(0),
1869 _survivor_plab_stats(YoungPLABSize, PLABWeight),
1870 _old_plab_stats(OldPLABSize, PLABWeight),
1871 _expand_heap_after_alloc_failure(true),
1872 _surviving_young_words(NULL),
1873 _old_marking_cycles_started(0),
1874 _old_marking_cycles_completed(0),
1875 _concurrent_cycle_started(false),
1876 _in_cset_fast_test(),
1877 _dirty_cards_region_list(NULL),
1878 _worker_cset_start_region(NULL),
1879 _worker_cset_start_region_time_stamp(NULL),
1880 _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()),
1881 _gc_timer_cm(new (ResourceObj::C_HEAP, mtGC) ConcurrentGCTimer()),
1882 _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()),
1883 _gc_tracer_cm(new (ResourceObj::C_HEAP, mtGC) G1OldTracer()) {
1885 _g1h = this;
1886 if (_process_strong_tasks == NULL || !_process_strong_tasks->valid()) {
1887 vm_exit_during_initialization("Failed necessary allocation.");
1888 }
1890 _allocator = G1Allocator::create_allocator(_g1h);
1891 _humongous_object_threshold_in_words = HeapRegion::GrainWords / 2;
1893 int n_queues = MAX2((int)ParallelGCThreads, 1);
1894 _task_queues = new RefToScanQueueSet(n_queues);
1896 uint n_rem_sets = HeapRegionRemSet::num_par_rem_sets();
1897 assert(n_rem_sets > 0, "Invariant.");
1899 _worker_cset_start_region = NEW_C_HEAP_ARRAY(HeapRegion*, n_queues, mtGC);
1900 _worker_cset_start_region_time_stamp = NEW_C_HEAP_ARRAY(unsigned int, n_queues, mtGC);
1901 _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC);
1903 for (int i = 0; i < n_queues; i++) {
1904 RefToScanQueue* q = new RefToScanQueue();
1905 q->initialize();
1906 _task_queues->register_queue(i, q);
1907 ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo();
1908 }
1909 clear_cset_start_regions();
1911 // Initialize the G1EvacuationFailureALot counters and flags.
1912 NOT_PRODUCT(reset_evacuation_should_fail();)
1914 guarantee(_task_queues != NULL, "task_queues allocation failure.");
1915 }
1917 jint G1CollectedHeap::initialize() {
1918 CollectedHeap::pre_initialize();
1919 os::enable_vtime();
1921 G1Log::init();
1923 // Necessary to satisfy locking discipline assertions.
1925 MutexLocker x(Heap_lock);
1927 // We have to initialize the printer before committing the heap, as
1928 // it will be used then.
1929 _hr_printer.set_active(G1PrintHeapRegions);
1931 // While there are no constraints in the GC code that HeapWordSize
1932 // be any particular value, there are multiple other areas in the
1933 // system which believe this to be true (e.g. oop->object_size in some
1934 // cases incorrectly returns the size in wordSize units rather than
1935 // HeapWordSize).
1936 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
1938 size_t init_byte_size = collector_policy()->initial_heap_byte_size();
1939 size_t max_byte_size = collector_policy()->max_heap_byte_size();
1940 size_t heap_alignment = collector_policy()->heap_alignment();
1942 // Ensure that the sizes are properly aligned.
1943 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
1944 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
1945 Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap");
1947 _refine_cte_cl = new RefineCardTableEntryClosure();
1949 _cg1r = new ConcurrentG1Refine(this, _refine_cte_cl);
1951 // Reserve the maximum.
1953 // When compressed oops are enabled, the preferred heap base
1954 // is calculated by subtracting the requested size from the
1955 // 32Gb boundary and using the result as the base address for
1956 // heap reservation. If the requested size is not aligned to
1957 // HeapRegion::GrainBytes (i.e. the alignment that is passed
1958 // into the ReservedHeapSpace constructor) then the actual
1959 // base of the reserved heap may end up differing from the
1960 // address that was requested (i.e. the preferred heap base).
1961 // If this happens then we could end up using a non-optimal
1962 // compressed oops mode.
1964 ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size,
1965 heap_alignment);
1967 // It is important to do this in a way such that concurrent readers can't
1968 // temporarily think something is in the heap. (I've actually seen this
1969 // happen in asserts: DLD.)
1970 _reserved.set_word_size(0);
1971 _reserved.set_start((HeapWord*)heap_rs.base());
1972 _reserved.set_end((HeapWord*)(heap_rs.base() + heap_rs.size()));
1974 // Create the gen rem set (and barrier set) for the entire reserved region.
1975 _rem_set = collector_policy()->create_rem_set(_reserved, 2);
1976 set_barrier_set(rem_set()->bs());
1977 if (!barrier_set()->is_a(BarrierSet::G1SATBCTLogging)) {
1978 vm_exit_during_initialization("G1 requires a G1SATBLoggingCardTableModRefBS");
1979 return JNI_ENOMEM;
1980 }
1982 // Also create a G1 rem set.
1983 _g1_rem_set = new G1RemSet(this, g1_barrier_set());
1985 // Carve out the G1 part of the heap.
1987 ReservedSpace g1_rs = heap_rs.first_part(max_byte_size);
1988 G1RegionToSpaceMapper* heap_storage =
1989 G1RegionToSpaceMapper::create_mapper(g1_rs,
1990 UseLargePages ? os::large_page_size() : os::vm_page_size(),
1991 HeapRegion::GrainBytes,
1992 1,
1993 mtJavaHeap);
1994 heap_storage->set_mapping_changed_listener(&_listener);
1996 // Reserve space for the block offset table. We do not support automatic uncommit
1997 // for the card table at this time. BOT only.
1998 ReservedSpace bot_rs(G1BlockOffsetSharedArray::compute_size(g1_rs.size() / HeapWordSize));
1999 G1RegionToSpaceMapper* bot_storage =
2000 G1RegionToSpaceMapper::create_mapper(bot_rs,
2001 os::vm_page_size(),
2002 HeapRegion::GrainBytes,
2003 G1BlockOffsetSharedArray::N_bytes,
2004 mtGC);
2006 ReservedSpace cardtable_rs(G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize));
2007 G1RegionToSpaceMapper* cardtable_storage =
2008 G1RegionToSpaceMapper::create_mapper(cardtable_rs,
2009 os::vm_page_size(),
2010 HeapRegion::GrainBytes,
2011 G1BlockOffsetSharedArray::N_bytes,
2012 mtGC);
2014 // Reserve space for the card counts table.
2015 ReservedSpace card_counts_rs(G1BlockOffsetSharedArray::compute_size(g1_rs.size() / HeapWordSize));
2016 G1RegionToSpaceMapper* card_counts_storage =
2017 G1RegionToSpaceMapper::create_mapper(card_counts_rs,
2018 os::vm_page_size(),
2019 HeapRegion::GrainBytes,
2020 G1BlockOffsetSharedArray::N_bytes,
2021 mtGC);
2023 // Reserve space for prev and next bitmap.
2024 size_t bitmap_size = CMBitMap::compute_size(g1_rs.size());
2026 ReservedSpace prev_bitmap_rs(ReservedSpace::allocation_align_size_up(bitmap_size));
2027 G1RegionToSpaceMapper* prev_bitmap_storage =
2028 G1RegionToSpaceMapper::create_mapper(prev_bitmap_rs,
2029 os::vm_page_size(),
2030 HeapRegion::GrainBytes,
2031 CMBitMap::mark_distance(),
2032 mtGC);
2034 ReservedSpace next_bitmap_rs(ReservedSpace::allocation_align_size_up(bitmap_size));
2035 G1RegionToSpaceMapper* next_bitmap_storage =
2036 G1RegionToSpaceMapper::create_mapper(next_bitmap_rs,
2037 os::vm_page_size(),
2038 HeapRegion::GrainBytes,
2039 CMBitMap::mark_distance(),
2040 mtGC);
2042 _hrm.initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage);
2043 g1_barrier_set()->initialize(cardtable_storage);
2044 // Do later initialization work for concurrent refinement.
2045 _cg1r->init(card_counts_storage);
2047 // 6843694 - ensure that the maximum region index can fit
2048 // in the remembered set structures.
2049 const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
2050 guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
2052 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
2053 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
2054 guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
2055 "too many cards per region");
2057 FreeRegionList::set_unrealistically_long_length(max_regions() + 1);
2059 _bot_shared = new G1BlockOffsetSharedArray(_reserved, bot_storage);
2061 _g1h = this;
2063 _in_cset_fast_test.initialize(_hrm.reserved().start(), _hrm.reserved().end(), HeapRegion::GrainBytes);
2064 _humongous_is_live.initialize(_hrm.reserved().start(), _hrm.reserved().end(), HeapRegion::GrainBytes);
2066 // Create the ConcurrentMark data structure and thread.
2067 // (Must do this late, so that "max_regions" is defined.)
2068 _cm = new ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage);
2069 if (_cm == NULL || !_cm->completed_initialization()) {
2070 vm_shutdown_during_initialization("Could not create/initialize ConcurrentMark");
2071 return JNI_ENOMEM;
2072 }
2073 _cmThread = _cm->cmThread();
2075 // Initialize the from_card cache structure of HeapRegionRemSet.
2076 HeapRegionRemSet::init_heap(max_regions());
2078 // Now expand into the initial heap size.
2079 if (!expand(init_byte_size)) {
2080 vm_shutdown_during_initialization("Failed to allocate initial heap.");
2081 return JNI_ENOMEM;
2082 }
2084 // Perform any initialization actions delegated to the policy.
2085 g1_policy()->init();
2087 JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon,
2088 SATB_Q_FL_lock,
2089 G1SATBProcessCompletedThreshold,
2090 Shared_SATB_Q_lock);
2092 JavaThread::dirty_card_queue_set().initialize(_refine_cte_cl,
2093 DirtyCardQ_CBL_mon,
2094 DirtyCardQ_FL_lock,
2095 concurrent_g1_refine()->yellow_zone(),
2096 concurrent_g1_refine()->red_zone(),
2097 Shared_DirtyCardQ_lock);
2099 if (G1DeferredRSUpdate) {
2100 dirty_card_queue_set().initialize(NULL, // Should never be called by the Java code
2101 DirtyCardQ_CBL_mon,
2102 DirtyCardQ_FL_lock,
2103 -1, // never trigger processing
2104 -1, // no limit on length
2105 Shared_DirtyCardQ_lock,
2106 &JavaThread::dirty_card_queue_set());
2107 }
2109 // Initialize the card queue set used to hold cards containing
2110 // references into the collection set.
2111 _into_cset_dirty_card_queue_set.initialize(NULL, // Should never be called by the Java code
2112 DirtyCardQ_CBL_mon,
2113 DirtyCardQ_FL_lock,
2114 -1, // never trigger processing
2115 -1, // no limit on length
2116 Shared_DirtyCardQ_lock,
2117 &JavaThread::dirty_card_queue_set());
2119 // In case we're keeping closure specialization stats, initialize those
2120 // counts and that mechanism.
2121 SpecializationStats::clear();
2123 // Here we allocate the dummy HeapRegion that is required by the
2124 // G1AllocRegion class.
2125 HeapRegion* dummy_region = _hrm.get_dummy_region();
2127 // We'll re-use the same region whether the alloc region will
2128 // require BOT updates or not and, if it doesn't, then a non-young
2129 // region will complain that it cannot support allocations without
2130 // BOT updates. So we'll tag the dummy region as young to avoid that.
2131 dummy_region->set_young();
2132 // Make sure it's full.
2133 dummy_region->set_top(dummy_region->end());
2134 G1AllocRegion::setup(this, dummy_region);
2136 _allocator->init_mutator_alloc_region();
2138 // Do create of the monitoring and management support so that
2139 // values in the heap have been properly initialized.
2140 _g1mm = new G1MonitoringSupport(this);
2142 G1StringDedup::initialize();
2144 return JNI_OK;
2145 }
2147 void G1CollectedHeap::stop() {
2148 // Stop all concurrent threads. We do this to make sure these threads
2149 // do not continue to execute and access resources (e.g. gclog_or_tty)
2150 // that are destroyed during shutdown.
2151 _cg1r->stop();
2152 _cmThread->stop();
2153 if (G1StringDedup::is_enabled()) {
2154 G1StringDedup::stop();
2155 }
2156 }
2158 void G1CollectedHeap::clear_humongous_is_live_table() {
2159 guarantee(G1ReclaimDeadHumongousObjectsAtYoungGC, "Should only be called if true");
2160 _humongous_is_live.clear();
2161 }
2163 size_t G1CollectedHeap::conservative_max_heap_alignment() {
2164 return HeapRegion::max_region_size();
2165 }
2167 void G1CollectedHeap::ref_processing_init() {
2168 // Reference processing in G1 currently works as follows:
2169 //
2170 // * There are two reference processor instances. One is
2171 // used to record and process discovered references
2172 // during concurrent marking; the other is used to
2173 // record and process references during STW pauses
2174 // (both full and incremental).
2175 // * Both ref processors need to 'span' the entire heap as
2176 // the regions in the collection set may be dotted around.
2177 //
2178 // * For the concurrent marking ref processor:
2179 // * Reference discovery is enabled at initial marking.
2180 // * Reference discovery is disabled and the discovered
2181 // references processed etc during remarking.
2182 // * Reference discovery is MT (see below).
2183 // * Reference discovery requires a barrier (see below).
2184 // * Reference processing may or may not be MT
2185 // (depending on the value of ParallelRefProcEnabled
2186 // and ParallelGCThreads).
2187 // * A full GC disables reference discovery by the CM
2188 // ref processor and abandons any entries on it's
2189 // discovered lists.
2190 //
2191 // * For the STW processor:
2192 // * Non MT discovery is enabled at the start of a full GC.
2193 // * Processing and enqueueing during a full GC is non-MT.
2194 // * During a full GC, references are processed after marking.
2195 //
2196 // * Discovery (may or may not be MT) is enabled at the start
2197 // of an incremental evacuation pause.
2198 // * References are processed near the end of a STW evacuation pause.
2199 // * For both types of GC:
2200 // * Discovery is atomic - i.e. not concurrent.
2201 // * Reference discovery will not need a barrier.
2203 SharedHeap::ref_processing_init();
2204 MemRegion mr = reserved_region();
2206 // Concurrent Mark ref processor
2207 _ref_processor_cm =
2208 new ReferenceProcessor(mr, // span
2209 ParallelRefProcEnabled && (ParallelGCThreads > 1),
2210 // mt processing
2211 (int) ParallelGCThreads,
2212 // degree of mt processing
2213 (ParallelGCThreads > 1) || (ConcGCThreads > 1),
2214 // mt discovery
2215 (int) MAX2(ParallelGCThreads, ConcGCThreads),
2216 // degree of mt discovery
2217 false,
2218 // Reference discovery is not atomic
2219 &_is_alive_closure_cm);
2220 // is alive closure
2221 // (for efficiency/performance)
2223 // STW ref processor
2224 _ref_processor_stw =
2225 new ReferenceProcessor(mr, // span
2226 ParallelRefProcEnabled && (ParallelGCThreads > 1),
2227 // mt processing
2228 MAX2((int)ParallelGCThreads, 1),
2229 // degree of mt processing
2230 (ParallelGCThreads > 1),
2231 // mt discovery
2232 MAX2((int)ParallelGCThreads, 1),
2233 // degree of mt discovery
2234 true,
2235 // Reference discovery is atomic
2236 &_is_alive_closure_stw);
2237 // is alive closure
2238 // (for efficiency/performance)
2239 }
2241 size_t G1CollectedHeap::capacity() const {
2242 return _hrm.length() * HeapRegion::GrainBytes;
2243 }
2245 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) {
2246 assert(!hr->continuesHumongous(), "pre-condition");
2247 hr->reset_gc_time_stamp();
2248 if (hr->startsHumongous()) {
2249 uint first_index = hr->hrm_index() + 1;
2250 uint last_index = hr->last_hc_index();
2251 for (uint i = first_index; i < last_index; i += 1) {
2252 HeapRegion* chr = region_at(i);
2253 assert(chr->continuesHumongous(), "sanity");
2254 chr->reset_gc_time_stamp();
2255 }
2256 }
2257 }
2259 #ifndef PRODUCT
2260 class CheckGCTimeStampsHRClosure : public HeapRegionClosure {
2261 private:
2262 unsigned _gc_time_stamp;
2263 bool _failures;
2265 public:
2266 CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) :
2267 _gc_time_stamp(gc_time_stamp), _failures(false) { }
2269 virtual bool doHeapRegion(HeapRegion* hr) {
2270 unsigned region_gc_time_stamp = hr->get_gc_time_stamp();
2271 if (_gc_time_stamp != region_gc_time_stamp) {
2272 gclog_or_tty->print_cr("Region "HR_FORMAT" has GC time stamp = %d, "
2273 "expected %d", HR_FORMAT_PARAMS(hr),
2274 region_gc_time_stamp, _gc_time_stamp);
2275 _failures = true;
2276 }
2277 return false;
2278 }
2280 bool failures() { return _failures; }
2281 };
2283 void G1CollectedHeap::check_gc_time_stamps() {
2284 CheckGCTimeStampsHRClosure cl(_gc_time_stamp);
2285 heap_region_iterate(&cl);
2286 guarantee(!cl.failures(), "all GC time stamps should have been reset");
2287 }
2288 #endif // PRODUCT
2290 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl,
2291 DirtyCardQueue* into_cset_dcq,
2292 bool concurrent,
2293 uint worker_i) {
2294 // Clean cards in the hot card cache
2295 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
2296 hot_card_cache->drain(worker_i, g1_rem_set(), into_cset_dcq);
2298 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2299 int n_completed_buffers = 0;
2300 while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) {
2301 n_completed_buffers++;
2302 }
2303 g1_policy()->phase_times()->record_update_rs_processed_buffers(worker_i, n_completed_buffers);
2304 dcqs.clear_n_completed_buffers();
2305 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!");
2306 }
2309 // Computes the sum of the storage used by the various regions.
2310 size_t G1CollectedHeap::used() const {
2311 return _allocator->used();
2312 }
2314 size_t G1CollectedHeap::used_unlocked() const {
2315 return _allocator->used_unlocked();
2316 }
2318 class SumUsedClosure: public HeapRegionClosure {
2319 size_t _used;
2320 public:
2321 SumUsedClosure() : _used(0) {}
2322 bool doHeapRegion(HeapRegion* r) {
2323 if (!r->continuesHumongous()) {
2324 _used += r->used();
2325 }
2326 return false;
2327 }
2328 size_t result() { return _used; }
2329 };
2331 size_t G1CollectedHeap::recalculate_used() const {
2332 double recalculate_used_start = os::elapsedTime();
2334 SumUsedClosure blk;
2335 heap_region_iterate(&blk);
2337 g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0);
2338 return blk.result();
2339 }
2341 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
2342 switch (cause) {
2343 case GCCause::_gc_locker: return GCLockerInvokesConcurrent;
2344 case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent;
2345 case GCCause::_g1_humongous_allocation: return true;
2346 default: return false;
2347 }
2348 }
2350 #ifndef PRODUCT
2351 void G1CollectedHeap::allocate_dummy_regions() {
2352 // Let's fill up most of the region
2353 size_t word_size = HeapRegion::GrainWords - 1024;
2354 // And as a result the region we'll allocate will be humongous.
2355 guarantee(isHumongous(word_size), "sanity");
2357 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
2358 // Let's use the existing mechanism for the allocation
2359 HeapWord* dummy_obj = humongous_obj_allocate(word_size,
2360 AllocationContext::system());
2361 if (dummy_obj != NULL) {
2362 MemRegion mr(dummy_obj, word_size);
2363 CollectedHeap::fill_with_object(mr);
2364 } else {
2365 // If we can't allocate once, we probably cannot allocate
2366 // again. Let's get out of the loop.
2367 break;
2368 }
2369 }
2370 }
2371 #endif // !PRODUCT
2373 void G1CollectedHeap::increment_old_marking_cycles_started() {
2374 assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
2375 _old_marking_cycles_started == _old_marking_cycles_completed + 1,
2376 err_msg("Wrong marking cycle count (started: %d, completed: %d)",
2377 _old_marking_cycles_started, _old_marking_cycles_completed));
2379 _old_marking_cycles_started++;
2380 }
2382 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) {
2383 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
2385 // We assume that if concurrent == true, then the caller is a
2386 // concurrent thread that was joined the Suspendible Thread
2387 // Set. If there's ever a cheap way to check this, we should add an
2388 // assert here.
2390 // Given that this method is called at the end of a Full GC or of a
2391 // concurrent cycle, and those can be nested (i.e., a Full GC can
2392 // interrupt a concurrent cycle), the number of full collections
2393 // completed should be either one (in the case where there was no
2394 // nesting) or two (when a Full GC interrupted a concurrent cycle)
2395 // behind the number of full collections started.
2397 // This is the case for the inner caller, i.e. a Full GC.
2398 assert(concurrent ||
2399 (_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
2400 (_old_marking_cycles_started == _old_marking_cycles_completed + 2),
2401 err_msg("for inner caller (Full GC): _old_marking_cycles_started = %u "
2402 "is inconsistent with _old_marking_cycles_completed = %u",
2403 _old_marking_cycles_started, _old_marking_cycles_completed));
2405 // This is the case for the outer caller, i.e. the concurrent cycle.
2406 assert(!concurrent ||
2407 (_old_marking_cycles_started == _old_marking_cycles_completed + 1),
2408 err_msg("for outer caller (concurrent cycle): "
2409 "_old_marking_cycles_started = %u "
2410 "is inconsistent with _old_marking_cycles_completed = %u",
2411 _old_marking_cycles_started, _old_marking_cycles_completed));
2413 _old_marking_cycles_completed += 1;
2415 // We need to clear the "in_progress" flag in the CM thread before
2416 // we wake up any waiters (especially when ExplicitInvokesConcurrent
2417 // is set) so that if a waiter requests another System.gc() it doesn't
2418 // incorrectly see that a marking cycle is still in progress.
2419 if (concurrent) {
2420 _cmThread->clear_in_progress();
2421 }
2423 // This notify_all() will ensure that a thread that called
2424 // System.gc() with (with ExplicitGCInvokesConcurrent set or not)
2425 // and it's waiting for a full GC to finish will be woken up. It is
2426 // waiting in VM_G1IncCollectionPause::doit_epilogue().
2427 FullGCCount_lock->notify_all();
2428 }
2430 void G1CollectedHeap::register_concurrent_cycle_start(const Ticks& start_time) {
2431 _concurrent_cycle_started = true;
2432 _gc_timer_cm->register_gc_start(start_time);
2434 _gc_tracer_cm->report_gc_start(gc_cause(), _gc_timer_cm->gc_start());
2435 trace_heap_before_gc(_gc_tracer_cm);
2436 }
2438 void G1CollectedHeap::register_concurrent_cycle_end() {
2439 if (_concurrent_cycle_started) {
2440 if (_cm->has_aborted()) {
2441 _gc_tracer_cm->report_concurrent_mode_failure();
2442 }
2444 _gc_timer_cm->register_gc_end();
2445 _gc_tracer_cm->report_gc_end(_gc_timer_cm->gc_end(), _gc_timer_cm->time_partitions());
2447 _concurrent_cycle_started = false;
2448 }
2449 }
2451 void G1CollectedHeap::trace_heap_after_concurrent_cycle() {
2452 if (_concurrent_cycle_started) {
2453 trace_heap_after_gc(_gc_tracer_cm);
2454 }
2455 }
2457 G1YCType G1CollectedHeap::yc_type() {
2458 bool is_young = g1_policy()->gcs_are_young();
2459 bool is_initial_mark = g1_policy()->during_initial_mark_pause();
2460 bool is_during_mark = mark_in_progress();
2462 if (is_initial_mark) {
2463 return InitialMark;
2464 } else if (is_during_mark) {
2465 return DuringMark;
2466 } else if (is_young) {
2467 return Normal;
2468 } else {
2469 return Mixed;
2470 }
2471 }
2473 void G1CollectedHeap::collect(GCCause::Cause cause) {
2474 assert_heap_not_locked();
2476 unsigned int gc_count_before;
2477 unsigned int old_marking_count_before;
2478 bool retry_gc;
2480 do {
2481 retry_gc = false;
2483 {
2484 MutexLocker ml(Heap_lock);
2486 // Read the GC count while holding the Heap_lock
2487 gc_count_before = total_collections();
2488 old_marking_count_before = _old_marking_cycles_started;
2489 }
2491 if (should_do_concurrent_full_gc(cause)) {
2492 // Schedule an initial-mark evacuation pause that will start a
2493 // concurrent cycle. We're setting word_size to 0 which means that
2494 // we are not requesting a post-GC allocation.
2495 VM_G1IncCollectionPause op(gc_count_before,
2496 0, /* word_size */
2497 true, /* should_initiate_conc_mark */
2498 g1_policy()->max_pause_time_ms(),
2499 cause);
2500 op.set_allocation_context(AllocationContext::current());
2502 VMThread::execute(&op);
2503 if (!op.pause_succeeded()) {
2504 if (old_marking_count_before == _old_marking_cycles_started) {
2505 retry_gc = op.should_retry_gc();
2506 } else {
2507 // A Full GC happened while we were trying to schedule the
2508 // initial-mark GC. No point in starting a new cycle given
2509 // that the whole heap was collected anyway.
2510 }
2512 if (retry_gc) {
2513 if (GC_locker::is_active_and_needs_gc()) {
2514 GC_locker::stall_until_clear();
2515 }
2516 }
2517 }
2518 } else {
2519 if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc
2520 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2522 // Schedule a standard evacuation pause. We're setting word_size
2523 // to 0 which means that we are not requesting a post-GC allocation.
2524 VM_G1IncCollectionPause op(gc_count_before,
2525 0, /* word_size */
2526 false, /* should_initiate_conc_mark */
2527 g1_policy()->max_pause_time_ms(),
2528 cause);
2529 VMThread::execute(&op);
2530 } else {
2531 // Schedule a Full GC.
2532 VM_G1CollectFull op(gc_count_before, old_marking_count_before, cause);
2533 VMThread::execute(&op);
2534 }
2535 }
2536 } while (retry_gc);
2537 }
2539 bool G1CollectedHeap::is_in(const void* p) const {
2540 if (_hrm.reserved().contains(p)) {
2541 // Given that we know that p is in the reserved space,
2542 // heap_region_containing_raw() should successfully
2543 // return the containing region.
2544 HeapRegion* hr = heap_region_containing_raw(p);
2545 return hr->is_in(p);
2546 } else {
2547 return false;
2548 }
2549 }
2551 #ifdef ASSERT
2552 bool G1CollectedHeap::is_in_exact(const void* p) const {
2553 bool contains = reserved_region().contains(p);
2554 bool available = _hrm.is_available(addr_to_region((HeapWord*)p));
2555 if (contains && available) {
2556 return true;
2557 } else {
2558 return false;
2559 }
2560 }
2561 #endif
2563 // Iteration functions.
2565 // Applies an ExtendedOopClosure onto all references of objects within a HeapRegion.
2567 class IterateOopClosureRegionClosure: public HeapRegionClosure {
2568 ExtendedOopClosure* _cl;
2569 public:
2570 IterateOopClosureRegionClosure(ExtendedOopClosure* cl) : _cl(cl) {}
2571 bool doHeapRegion(HeapRegion* r) {
2572 if (!r->continuesHumongous()) {
2573 r->oop_iterate(_cl);
2574 }
2575 return false;
2576 }
2577 };
2579 void G1CollectedHeap::oop_iterate(ExtendedOopClosure* cl) {
2580 IterateOopClosureRegionClosure blk(cl);
2581 heap_region_iterate(&blk);
2582 }
2584 // Iterates an ObjectClosure over all objects within a HeapRegion.
2586 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2587 ObjectClosure* _cl;
2588 public:
2589 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2590 bool doHeapRegion(HeapRegion* r) {
2591 if (! r->continuesHumongous()) {
2592 r->object_iterate(_cl);
2593 }
2594 return false;
2595 }
2596 };
2598 void G1CollectedHeap::object_iterate(ObjectClosure* cl) {
2599 IterateObjectClosureRegionClosure blk(cl);
2600 heap_region_iterate(&blk);
2601 }
2603 // Calls a SpaceClosure on a HeapRegion.
2605 class SpaceClosureRegionClosure: public HeapRegionClosure {
2606 SpaceClosure* _cl;
2607 public:
2608 SpaceClosureRegionClosure(SpaceClosure* cl) : _cl(cl) {}
2609 bool doHeapRegion(HeapRegion* r) {
2610 _cl->do_space(r);
2611 return false;
2612 }
2613 };
2615 void G1CollectedHeap::space_iterate(SpaceClosure* cl) {
2616 SpaceClosureRegionClosure blk(cl);
2617 heap_region_iterate(&blk);
2618 }
2620 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2621 _hrm.iterate(cl);
2622 }
2624 void
2625 G1CollectedHeap::heap_region_par_iterate_chunked(HeapRegionClosure* cl,
2626 uint worker_id,
2627 uint num_workers,
2628 jint claim_value) const {
2629 _hrm.par_iterate(cl, worker_id, num_workers, claim_value);
2630 }
2632 class ResetClaimValuesClosure: public HeapRegionClosure {
2633 public:
2634 bool doHeapRegion(HeapRegion* r) {
2635 r->set_claim_value(HeapRegion::InitialClaimValue);
2636 return false;
2637 }
2638 };
2640 void G1CollectedHeap::reset_heap_region_claim_values() {
2641 ResetClaimValuesClosure blk;
2642 heap_region_iterate(&blk);
2643 }
2645 void G1CollectedHeap::reset_cset_heap_region_claim_values() {
2646 ResetClaimValuesClosure blk;
2647 collection_set_iterate(&blk);
2648 }
2650 #ifdef ASSERT
2651 // This checks whether all regions in the heap have the correct claim
2652 // value. I also piggy-backed on this a check to ensure that the
2653 // humongous_start_region() information on "continues humongous"
2654 // regions is correct.
2656 class CheckClaimValuesClosure : public HeapRegionClosure {
2657 private:
2658 jint _claim_value;
2659 uint _failures;
2660 HeapRegion* _sh_region;
2662 public:
2663 CheckClaimValuesClosure(jint claim_value) :
2664 _claim_value(claim_value), _failures(0), _sh_region(NULL) { }
2665 bool doHeapRegion(HeapRegion* r) {
2666 if (r->claim_value() != _claim_value) {
2667 gclog_or_tty->print_cr("Region " HR_FORMAT ", "
2668 "claim value = %d, should be %d",
2669 HR_FORMAT_PARAMS(r),
2670 r->claim_value(), _claim_value);
2671 ++_failures;
2672 }
2673 if (!r->isHumongous()) {
2674 _sh_region = NULL;
2675 } else if (r->startsHumongous()) {
2676 _sh_region = r;
2677 } else if (r->continuesHumongous()) {
2678 if (r->humongous_start_region() != _sh_region) {
2679 gclog_or_tty->print_cr("Region " HR_FORMAT ", "
2680 "HS = "PTR_FORMAT", should be "PTR_FORMAT,
2681 HR_FORMAT_PARAMS(r),
2682 r->humongous_start_region(),
2683 _sh_region);
2684 ++_failures;
2685 }
2686 }
2687 return false;
2688 }
2689 uint failures() { return _failures; }
2690 };
2692 bool G1CollectedHeap::check_heap_region_claim_values(jint claim_value) {
2693 CheckClaimValuesClosure cl(claim_value);
2694 heap_region_iterate(&cl);
2695 return cl.failures() == 0;
2696 }
2698 class CheckClaimValuesInCSetHRClosure: public HeapRegionClosure {
2699 private:
2700 jint _claim_value;
2701 uint _failures;
2703 public:
2704 CheckClaimValuesInCSetHRClosure(jint claim_value) :
2705 _claim_value(claim_value), _failures(0) { }
2707 uint failures() { return _failures; }
2709 bool doHeapRegion(HeapRegion* hr) {
2710 assert(hr->in_collection_set(), "how?");
2711 assert(!hr->isHumongous(), "H-region in CSet");
2712 if (hr->claim_value() != _claim_value) {
2713 gclog_or_tty->print_cr("CSet Region " HR_FORMAT ", "
2714 "claim value = %d, should be %d",
2715 HR_FORMAT_PARAMS(hr),
2716 hr->claim_value(), _claim_value);
2717 _failures += 1;
2718 }
2719 return false;
2720 }
2721 };
2723 bool G1CollectedHeap::check_cset_heap_region_claim_values(jint claim_value) {
2724 CheckClaimValuesInCSetHRClosure cl(claim_value);
2725 collection_set_iterate(&cl);
2726 return cl.failures() == 0;
2727 }
2728 #endif // ASSERT
2730 // Clear the cached CSet starting regions and (more importantly)
2731 // the time stamps. Called when we reset the GC time stamp.
2732 void G1CollectedHeap::clear_cset_start_regions() {
2733 assert(_worker_cset_start_region != NULL, "sanity");
2734 assert(_worker_cset_start_region_time_stamp != NULL, "sanity");
2736 int n_queues = MAX2((int)ParallelGCThreads, 1);
2737 for (int i = 0; i < n_queues; i++) {
2738 _worker_cset_start_region[i] = NULL;
2739 _worker_cset_start_region_time_stamp[i] = 0;
2740 }
2741 }
2743 // Given the id of a worker, obtain or calculate a suitable
2744 // starting region for iterating over the current collection set.
2745 HeapRegion* G1CollectedHeap::start_cset_region_for_worker(uint worker_i) {
2746 assert(get_gc_time_stamp() > 0, "should have been updated by now");
2748 HeapRegion* result = NULL;
2749 unsigned gc_time_stamp = get_gc_time_stamp();
2751 if (_worker_cset_start_region_time_stamp[worker_i] == gc_time_stamp) {
2752 // Cached starting region for current worker was set
2753 // during the current pause - so it's valid.
2754 // Note: the cached starting heap region may be NULL
2755 // (when the collection set is empty).
2756 result = _worker_cset_start_region[worker_i];
2757 assert(result == NULL || result->in_collection_set(), "sanity");
2758 return result;
2759 }
2761 // The cached entry was not valid so let's calculate
2762 // a suitable starting heap region for this worker.
2764 // We want the parallel threads to start their collection
2765 // set iteration at different collection set regions to
2766 // avoid contention.
2767 // If we have:
2768 // n collection set regions
2769 // p threads
2770 // Then thread t will start at region floor ((t * n) / p)
2772 result = g1_policy()->collection_set();
2773 if (G1CollectedHeap::use_parallel_gc_threads()) {
2774 uint cs_size = g1_policy()->cset_region_length();
2775 uint active_workers = workers()->active_workers();
2776 assert(UseDynamicNumberOfGCThreads ||
2777 active_workers == workers()->total_workers(),
2778 "Unless dynamic should use total workers");
2780 uint end_ind = (cs_size * worker_i) / active_workers;
2781 uint start_ind = 0;
2783 if (worker_i > 0 &&
2784 _worker_cset_start_region_time_stamp[worker_i - 1] == gc_time_stamp) {
2785 // Previous workers starting region is valid
2786 // so let's iterate from there
2787 start_ind = (cs_size * (worker_i - 1)) / active_workers;
2788 result = _worker_cset_start_region[worker_i - 1];
2789 }
2791 for (uint i = start_ind; i < end_ind; i++) {
2792 result = result->next_in_collection_set();
2793 }
2794 }
2796 // Note: the calculated starting heap region may be NULL
2797 // (when the collection set is empty).
2798 assert(result == NULL || result->in_collection_set(), "sanity");
2799 assert(_worker_cset_start_region_time_stamp[worker_i] != gc_time_stamp,
2800 "should be updated only once per pause");
2801 _worker_cset_start_region[worker_i] = result;
2802 OrderAccess::storestore();
2803 _worker_cset_start_region_time_stamp[worker_i] = gc_time_stamp;
2804 return result;
2805 }
2807 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) {
2808 HeapRegion* r = g1_policy()->collection_set();
2809 while (r != NULL) {
2810 HeapRegion* next = r->next_in_collection_set();
2811 if (cl->doHeapRegion(r)) {
2812 cl->incomplete();
2813 return;
2814 }
2815 r = next;
2816 }
2817 }
2819 void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r,
2820 HeapRegionClosure *cl) {
2821 if (r == NULL) {
2822 // The CSet is empty so there's nothing to do.
2823 return;
2824 }
2826 assert(r->in_collection_set(),
2827 "Start region must be a member of the collection set.");
2828 HeapRegion* cur = r;
2829 while (cur != NULL) {
2830 HeapRegion* next = cur->next_in_collection_set();
2831 if (cl->doHeapRegion(cur) && false) {
2832 cl->incomplete();
2833 return;
2834 }
2835 cur = next;
2836 }
2837 cur = g1_policy()->collection_set();
2838 while (cur != r) {
2839 HeapRegion* next = cur->next_in_collection_set();
2840 if (cl->doHeapRegion(cur) && false) {
2841 cl->incomplete();
2842 return;
2843 }
2844 cur = next;
2845 }
2846 }
2848 HeapRegion* G1CollectedHeap::next_compaction_region(const HeapRegion* from) const {
2849 HeapRegion* result = _hrm.next_region_in_heap(from);
2850 while (result != NULL && result->isHumongous()) {
2851 result = _hrm.next_region_in_heap(result);
2852 }
2853 return result;
2854 }
2856 Space* G1CollectedHeap::space_containing(const void* addr) const {
2857 return heap_region_containing(addr);
2858 }
2860 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2861 Space* sp = space_containing(addr);
2862 return sp->block_start(addr);
2863 }
2865 size_t G1CollectedHeap::block_size(const HeapWord* addr) const {
2866 Space* sp = space_containing(addr);
2867 return sp->block_size(addr);
2868 }
2870 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2871 Space* sp = space_containing(addr);
2872 return sp->block_is_obj(addr);
2873 }
2875 bool G1CollectedHeap::supports_tlab_allocation() const {
2876 return true;
2877 }
2879 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
2880 return (_g1_policy->young_list_target_length() - young_list()->survivor_length()) * HeapRegion::GrainBytes;
2881 }
2883 size_t G1CollectedHeap::tlab_used(Thread* ignored) const {
2884 return young_list()->eden_used_bytes();
2885 }
2887 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size
2888 // must be smaller than the humongous object limit.
2889 size_t G1CollectedHeap::max_tlab_size() const {
2890 return align_size_down(_humongous_object_threshold_in_words - 1, MinObjAlignment);
2891 }
2893 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
2894 // Return the remaining space in the cur alloc region, but not less than
2895 // the min TLAB size.
2897 // Also, this value can be at most the humongous object threshold,
2898 // since we can't allow tlabs to grow big enough to accommodate
2899 // humongous objects.
2901 HeapRegion* hr = _allocator->mutator_alloc_region(AllocationContext::current())->get();
2902 size_t max_tlab = max_tlab_size() * wordSize;
2903 if (hr == NULL) {
2904 return max_tlab;
2905 } else {
2906 return MIN2(MAX2(hr->free(), (size_t) MinTLABSize), max_tlab);
2907 }
2908 }
2910 size_t G1CollectedHeap::max_capacity() const {
2911 return _hrm.reserved().byte_size();
2912 }
2914 jlong G1CollectedHeap::millis_since_last_gc() {
2915 // assert(false, "NYI");
2916 return 0;
2917 }
2919 void G1CollectedHeap::prepare_for_verify() {
2920 if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) {
2921 ensure_parsability(false);
2922 }
2923 g1_rem_set()->prepare_for_verify();
2924 }
2926 bool G1CollectedHeap::allocated_since_marking(oop obj, HeapRegion* hr,
2927 VerifyOption vo) {
2928 switch (vo) {
2929 case VerifyOption_G1UsePrevMarking:
2930 return hr->obj_allocated_since_prev_marking(obj);
2931 case VerifyOption_G1UseNextMarking:
2932 return hr->obj_allocated_since_next_marking(obj);
2933 case VerifyOption_G1UseMarkWord:
2934 return false;
2935 default:
2936 ShouldNotReachHere();
2937 }
2938 return false; // keep some compilers happy
2939 }
2941 HeapWord* G1CollectedHeap::top_at_mark_start(HeapRegion* hr, VerifyOption vo) {
2942 switch (vo) {
2943 case VerifyOption_G1UsePrevMarking: return hr->prev_top_at_mark_start();
2944 case VerifyOption_G1UseNextMarking: return hr->next_top_at_mark_start();
2945 case VerifyOption_G1UseMarkWord: return NULL;
2946 default: ShouldNotReachHere();
2947 }
2948 return NULL; // keep some compilers happy
2949 }
2951 bool G1CollectedHeap::is_marked(oop obj, VerifyOption vo) {
2952 switch (vo) {
2953 case VerifyOption_G1UsePrevMarking: return isMarkedPrev(obj);
2954 case VerifyOption_G1UseNextMarking: return isMarkedNext(obj);
2955 case VerifyOption_G1UseMarkWord: return obj->is_gc_marked();
2956 default: ShouldNotReachHere();
2957 }
2958 return false; // keep some compilers happy
2959 }
2961 const char* G1CollectedHeap::top_at_mark_start_str(VerifyOption vo) {
2962 switch (vo) {
2963 case VerifyOption_G1UsePrevMarking: return "PTAMS";
2964 case VerifyOption_G1UseNextMarking: return "NTAMS";
2965 case VerifyOption_G1UseMarkWord: return "NONE";
2966 default: ShouldNotReachHere();
2967 }
2968 return NULL; // keep some compilers happy
2969 }
2971 class VerifyRootsClosure: public OopClosure {
2972 private:
2973 G1CollectedHeap* _g1h;
2974 VerifyOption _vo;
2975 bool _failures;
2976 public:
2977 // _vo == UsePrevMarking -> use "prev" marking information,
2978 // _vo == UseNextMarking -> use "next" marking information,
2979 // _vo == UseMarkWord -> use mark word from object header.
2980 VerifyRootsClosure(VerifyOption vo) :
2981 _g1h(G1CollectedHeap::heap()),
2982 _vo(vo),
2983 _failures(false) { }
2985 bool failures() { return _failures; }
2987 template <class T> void do_oop_nv(T* p) {
2988 T heap_oop = oopDesc::load_heap_oop(p);
2989 if (!oopDesc::is_null(heap_oop)) {
2990 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
2991 if (_g1h->is_obj_dead_cond(obj, _vo)) {
2992 gclog_or_tty->print_cr("Root location "PTR_FORMAT" "
2993 "points to dead obj "PTR_FORMAT, p, (void*) obj);
2994 if (_vo == VerifyOption_G1UseMarkWord) {
2995 gclog_or_tty->print_cr(" Mark word: "PTR_FORMAT, (void*)(obj->mark()));
2996 }
2997 obj->print_on(gclog_or_tty);
2998 _failures = true;
2999 }
3000 }
3001 }
3003 void do_oop(oop* p) { do_oop_nv(p); }
3004 void do_oop(narrowOop* p) { do_oop_nv(p); }
3005 };
3007 class G1VerifyCodeRootOopClosure: public OopClosure {
3008 G1CollectedHeap* _g1h;
3009 OopClosure* _root_cl;
3010 nmethod* _nm;
3011 VerifyOption _vo;
3012 bool _failures;
3014 template <class T> void do_oop_work(T* p) {
3015 // First verify that this root is live
3016 _root_cl->do_oop(p);
3018 if (!G1VerifyHeapRegionCodeRoots) {
3019 // We're not verifying the code roots attached to heap region.
3020 return;
3021 }
3023 // Don't check the code roots during marking verification in a full GC
3024 if (_vo == VerifyOption_G1UseMarkWord) {
3025 return;
3026 }
3028 // Now verify that the current nmethod (which contains p) is
3029 // in the code root list of the heap region containing the
3030 // object referenced by p.
3032 T heap_oop = oopDesc::load_heap_oop(p);
3033 if (!oopDesc::is_null(heap_oop)) {
3034 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
3036 // Now fetch the region containing the object
3037 HeapRegion* hr = _g1h->heap_region_containing(obj);
3038 HeapRegionRemSet* hrrs = hr->rem_set();
3039 // Verify that the strong code root list for this region
3040 // contains the nmethod
3041 if (!hrrs->strong_code_roots_list_contains(_nm)) {
3042 gclog_or_tty->print_cr("Code root location "PTR_FORMAT" "
3043 "from nmethod "PTR_FORMAT" not in strong "
3044 "code roots for region ["PTR_FORMAT","PTR_FORMAT")",
3045 p, _nm, hr->bottom(), hr->end());
3046 _failures = true;
3047 }
3048 }
3049 }
3051 public:
3052 G1VerifyCodeRootOopClosure(G1CollectedHeap* g1h, OopClosure* root_cl, VerifyOption vo):
3053 _g1h(g1h), _root_cl(root_cl), _vo(vo), _nm(NULL), _failures(false) {}
3055 void do_oop(oop* p) { do_oop_work(p); }
3056 void do_oop(narrowOop* p) { do_oop_work(p); }
3058 void set_nmethod(nmethod* nm) { _nm = nm; }
3059 bool failures() { return _failures; }
3060 };
3062 class G1VerifyCodeRootBlobClosure: public CodeBlobClosure {
3063 G1VerifyCodeRootOopClosure* _oop_cl;
3065 public:
3066 G1VerifyCodeRootBlobClosure(G1VerifyCodeRootOopClosure* oop_cl):
3067 _oop_cl(oop_cl) {}
3069 void do_code_blob(CodeBlob* cb) {
3070 nmethod* nm = cb->as_nmethod_or_null();
3071 if (nm != NULL) {
3072 _oop_cl->set_nmethod(nm);
3073 nm->oops_do(_oop_cl);
3074 }
3075 }
3076 };
3078 class YoungRefCounterClosure : public OopClosure {
3079 G1CollectedHeap* _g1h;
3080 int _count;
3081 public:
3082 YoungRefCounterClosure(G1CollectedHeap* g1h) : _g1h(g1h), _count(0) {}
3083 void do_oop(oop* p) { if (_g1h->is_in_young(*p)) { _count++; } }
3084 void do_oop(narrowOop* p) { ShouldNotReachHere(); }
3086 int count() { return _count; }
3087 void reset_count() { _count = 0; };
3088 };
3090 class VerifyKlassClosure: public KlassClosure {
3091 YoungRefCounterClosure _young_ref_counter_closure;
3092 OopClosure *_oop_closure;
3093 public:
3094 VerifyKlassClosure(G1CollectedHeap* g1h, OopClosure* cl) : _young_ref_counter_closure(g1h), _oop_closure(cl) {}
3095 void do_klass(Klass* k) {
3096 k->oops_do(_oop_closure);
3098 _young_ref_counter_closure.reset_count();
3099 k->oops_do(&_young_ref_counter_closure);
3100 if (_young_ref_counter_closure.count() > 0) {
3101 guarantee(k->has_modified_oops(), err_msg("Klass %p, has young refs but is not dirty.", k));
3102 }
3103 }
3104 };
3106 class VerifyLivenessOopClosure: public OopClosure {
3107 G1CollectedHeap* _g1h;
3108 VerifyOption _vo;
3109 public:
3110 VerifyLivenessOopClosure(G1CollectedHeap* g1h, VerifyOption vo):
3111 _g1h(g1h), _vo(vo)
3112 { }
3113 void do_oop(narrowOop *p) { do_oop_work(p); }
3114 void do_oop( oop *p) { do_oop_work(p); }
3116 template <class T> void do_oop_work(T *p) {
3117 oop obj = oopDesc::load_decode_heap_oop(p);
3118 guarantee(obj == NULL || !_g1h->is_obj_dead_cond(obj, _vo),
3119 "Dead object referenced by a not dead object");
3120 }
3121 };
3123 class VerifyObjsInRegionClosure: public ObjectClosure {
3124 private:
3125 G1CollectedHeap* _g1h;
3126 size_t _live_bytes;
3127 HeapRegion *_hr;
3128 VerifyOption _vo;
3129 public:
3130 // _vo == UsePrevMarking -> use "prev" marking information,
3131 // _vo == UseNextMarking -> use "next" marking information,
3132 // _vo == UseMarkWord -> use mark word from object header.
3133 VerifyObjsInRegionClosure(HeapRegion *hr, VerifyOption vo)
3134 : _live_bytes(0), _hr(hr), _vo(vo) {
3135 _g1h = G1CollectedHeap::heap();
3136 }
3137 void do_object(oop o) {
3138 VerifyLivenessOopClosure isLive(_g1h, _vo);
3139 assert(o != NULL, "Huh?");
3140 if (!_g1h->is_obj_dead_cond(o, _vo)) {
3141 // If the object is alive according to the mark word,
3142 // then verify that the marking information agrees.
3143 // Note we can't verify the contra-positive of the
3144 // above: if the object is dead (according to the mark
3145 // word), it may not be marked, or may have been marked
3146 // but has since became dead, or may have been allocated
3147 // since the last marking.
3148 if (_vo == VerifyOption_G1UseMarkWord) {
3149 guarantee(!_g1h->is_obj_dead(o), "mark word and concurrent mark mismatch");
3150 }
3152 o->oop_iterate_no_header(&isLive);
3153 if (!_hr->obj_allocated_since_prev_marking(o)) {
3154 size_t obj_size = o->size(); // Make sure we don't overflow
3155 _live_bytes += (obj_size * HeapWordSize);
3156 }
3157 }
3158 }
3159 size_t live_bytes() { return _live_bytes; }
3160 };
3162 class PrintObjsInRegionClosure : public ObjectClosure {
3163 HeapRegion *_hr;
3164 G1CollectedHeap *_g1;
3165 public:
3166 PrintObjsInRegionClosure(HeapRegion *hr) : _hr(hr) {
3167 _g1 = G1CollectedHeap::heap();
3168 };
3170 void do_object(oop o) {
3171 if (o != NULL) {
3172 HeapWord *start = (HeapWord *) o;
3173 size_t word_sz = o->size();
3174 gclog_or_tty->print("\nPrinting obj "PTR_FORMAT" of size " SIZE_FORMAT
3175 " isMarkedPrev %d isMarkedNext %d isAllocSince %d\n",
3176 (void*) o, word_sz,
3177 _g1->isMarkedPrev(o),
3178 _g1->isMarkedNext(o),
3179 _hr->obj_allocated_since_prev_marking(o));
3180 HeapWord *end = start + word_sz;
3181 HeapWord *cur;
3182 int *val;
3183 for (cur = start; cur < end; cur++) {
3184 val = (int *) cur;
3185 gclog_or_tty->print("\t "PTR_FORMAT":"PTR_FORMAT"\n", val, *val);
3186 }
3187 }
3188 }
3189 };
3191 class VerifyRegionClosure: public HeapRegionClosure {
3192 private:
3193 bool _par;
3194 VerifyOption _vo;
3195 bool _failures;
3196 public:
3197 // _vo == UsePrevMarking -> use "prev" marking information,
3198 // _vo == UseNextMarking -> use "next" marking information,
3199 // _vo == UseMarkWord -> use mark word from object header.
3200 VerifyRegionClosure(bool par, VerifyOption vo)
3201 : _par(par),
3202 _vo(vo),
3203 _failures(false) {}
3205 bool failures() {
3206 return _failures;
3207 }
3209 bool doHeapRegion(HeapRegion* r) {
3210 if (!r->continuesHumongous()) {
3211 bool failures = false;
3212 r->verify(_vo, &failures);
3213 if (failures) {
3214 _failures = true;
3215 } else {
3216 VerifyObjsInRegionClosure not_dead_yet_cl(r, _vo);
3217 r->object_iterate(¬_dead_yet_cl);
3218 if (_vo != VerifyOption_G1UseNextMarking) {
3219 if (r->max_live_bytes() < not_dead_yet_cl.live_bytes()) {
3220 gclog_or_tty->print_cr("["PTR_FORMAT","PTR_FORMAT"] "
3221 "max_live_bytes "SIZE_FORMAT" "
3222 "< calculated "SIZE_FORMAT,
3223 r->bottom(), r->end(),
3224 r->max_live_bytes(),
3225 not_dead_yet_cl.live_bytes());
3226 _failures = true;
3227 }
3228 } else {
3229 // When vo == UseNextMarking we cannot currently do a sanity
3230 // check on the live bytes as the calculation has not been
3231 // finalized yet.
3232 }
3233 }
3234 }
3235 return false; // stop the region iteration if we hit a failure
3236 }
3237 };
3239 // This is the task used for parallel verification of the heap regions
3241 class G1ParVerifyTask: public AbstractGangTask {
3242 private:
3243 G1CollectedHeap* _g1h;
3244 VerifyOption _vo;
3245 bool _failures;
3247 public:
3248 // _vo == UsePrevMarking -> use "prev" marking information,
3249 // _vo == UseNextMarking -> use "next" marking information,
3250 // _vo == UseMarkWord -> use mark word from object header.
3251 G1ParVerifyTask(G1CollectedHeap* g1h, VerifyOption vo) :
3252 AbstractGangTask("Parallel verify task"),
3253 _g1h(g1h),
3254 _vo(vo),
3255 _failures(false) { }
3257 bool failures() {
3258 return _failures;
3259 }
3261 void work(uint worker_id) {
3262 HandleMark hm;
3263 VerifyRegionClosure blk(true, _vo);
3264 _g1h->heap_region_par_iterate_chunked(&blk, worker_id,
3265 _g1h->workers()->active_workers(),
3266 HeapRegion::ParVerifyClaimValue);
3267 if (blk.failures()) {
3268 _failures = true;
3269 }
3270 }
3271 };
3273 void G1CollectedHeap::verify(bool silent, VerifyOption vo) {
3274 if (SafepointSynchronize::is_at_safepoint()) {
3275 assert(Thread::current()->is_VM_thread(),
3276 "Expected to be executed serially by the VM thread at this point");
3278 if (!silent) { gclog_or_tty->print("Roots "); }
3279 VerifyRootsClosure rootsCl(vo);
3280 VerifyKlassClosure klassCl(this, &rootsCl);
3281 CLDToKlassAndOopClosure cldCl(&klassCl, &rootsCl, false);
3283 // We apply the relevant closures to all the oops in the
3284 // system dictionary, class loader data graph, the string table
3285 // and the nmethods in the code cache.
3286 G1VerifyCodeRootOopClosure codeRootsCl(this, &rootsCl, vo);
3287 G1VerifyCodeRootBlobClosure blobsCl(&codeRootsCl);
3289 process_all_roots(true, // activate StrongRootsScope
3290 SO_AllCodeCache, // roots scanning options
3291 &rootsCl,
3292 &cldCl,
3293 &blobsCl);
3295 bool failures = rootsCl.failures() || codeRootsCl.failures();
3297 if (vo != VerifyOption_G1UseMarkWord) {
3298 // If we're verifying during a full GC then the region sets
3299 // will have been torn down at the start of the GC. Therefore
3300 // verifying the region sets will fail. So we only verify
3301 // the region sets when not in a full GC.
3302 if (!silent) { gclog_or_tty->print("HeapRegionSets "); }
3303 verify_region_sets();
3304 }
3306 if (!silent) { gclog_or_tty->print("HeapRegions "); }
3307 if (GCParallelVerificationEnabled && ParallelGCThreads > 1) {
3308 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3309 "sanity check");
3311 G1ParVerifyTask task(this, vo);
3312 assert(UseDynamicNumberOfGCThreads ||
3313 workers()->active_workers() == workers()->total_workers(),
3314 "If not dynamic should be using all the workers");
3315 int n_workers = workers()->active_workers();
3316 set_par_threads(n_workers);
3317 workers()->run_task(&task);
3318 set_par_threads(0);
3319 if (task.failures()) {
3320 failures = true;
3321 }
3323 // Checks that the expected amount of parallel work was done.
3324 // The implication is that n_workers is > 0.
3325 assert(check_heap_region_claim_values(HeapRegion::ParVerifyClaimValue),
3326 "sanity check");
3328 reset_heap_region_claim_values();
3330 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3331 "sanity check");
3332 } else {
3333 VerifyRegionClosure blk(false, vo);
3334 heap_region_iterate(&blk);
3335 if (blk.failures()) {
3336 failures = true;
3337 }
3338 }
3339 if (!silent) gclog_or_tty->print("RemSet ");
3340 rem_set()->verify();
3342 if (G1StringDedup::is_enabled()) {
3343 if (!silent) gclog_or_tty->print("StrDedup ");
3344 G1StringDedup::verify();
3345 }
3347 if (failures) {
3348 gclog_or_tty->print_cr("Heap:");
3349 // It helps to have the per-region information in the output to
3350 // help us track down what went wrong. This is why we call
3351 // print_extended_on() instead of print_on().
3352 print_extended_on(gclog_or_tty);
3353 gclog_or_tty->cr();
3354 #ifndef PRODUCT
3355 if (VerifyDuringGC && G1VerifyDuringGCPrintReachable) {
3356 concurrent_mark()->print_reachable("at-verification-failure",
3357 vo, false /* all */);
3358 }
3359 #endif
3360 gclog_or_tty->flush();
3361 }
3362 guarantee(!failures, "there should not have been any failures");
3363 } else {
3364 if (!silent) {
3365 gclog_or_tty->print("(SKIPPING Roots, HeapRegionSets, HeapRegions, RemSet");
3366 if (G1StringDedup::is_enabled()) {
3367 gclog_or_tty->print(", StrDedup");
3368 }
3369 gclog_or_tty->print(") ");
3370 }
3371 }
3372 }
3374 void G1CollectedHeap::verify(bool silent) {
3375 verify(silent, VerifyOption_G1UsePrevMarking);
3376 }
3378 double G1CollectedHeap::verify(bool guard, const char* msg) {
3379 double verify_time_ms = 0.0;
3381 if (guard && total_collections() >= VerifyGCStartAt) {
3382 double verify_start = os::elapsedTime();
3383 HandleMark hm; // Discard invalid handles created during verification
3384 prepare_for_verify();
3385 Universe::verify(VerifyOption_G1UsePrevMarking, msg);
3386 verify_time_ms = (os::elapsedTime() - verify_start) * 1000;
3387 }
3389 return verify_time_ms;
3390 }
3392 void G1CollectedHeap::verify_before_gc() {
3393 double verify_time_ms = verify(VerifyBeforeGC, " VerifyBeforeGC:");
3394 g1_policy()->phase_times()->record_verify_before_time_ms(verify_time_ms);
3395 }
3397 void G1CollectedHeap::verify_after_gc() {
3398 double verify_time_ms = verify(VerifyAfterGC, " VerifyAfterGC:");
3399 g1_policy()->phase_times()->record_verify_after_time_ms(verify_time_ms);
3400 }
3402 class PrintRegionClosure: public HeapRegionClosure {
3403 outputStream* _st;
3404 public:
3405 PrintRegionClosure(outputStream* st) : _st(st) {}
3406 bool doHeapRegion(HeapRegion* r) {
3407 r->print_on(_st);
3408 return false;
3409 }
3410 };
3412 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
3413 const HeapRegion* hr,
3414 const VerifyOption vo) const {
3415 switch (vo) {
3416 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr);
3417 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr);
3418 case VerifyOption_G1UseMarkWord: return !obj->is_gc_marked();
3419 default: ShouldNotReachHere();
3420 }
3421 return false; // keep some compilers happy
3422 }
3424 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
3425 const VerifyOption vo) const {
3426 switch (vo) {
3427 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj);
3428 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj);
3429 case VerifyOption_G1UseMarkWord: return !obj->is_gc_marked();
3430 default: ShouldNotReachHere();
3431 }
3432 return false; // keep some compilers happy
3433 }
3435 void G1CollectedHeap::print_on(outputStream* st) const {
3436 st->print(" %-20s", "garbage-first heap");
3437 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
3438 capacity()/K, used_unlocked()/K);
3439 st->print(" [" INTPTR_FORMAT ", " INTPTR_FORMAT ", " INTPTR_FORMAT ")",
3440 _hrm.reserved().start(),
3441 _hrm.reserved().start() + _hrm.length() + HeapRegion::GrainWords,
3442 _hrm.reserved().end());
3443 st->cr();
3444 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
3445 uint young_regions = _young_list->length();
3446 st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
3447 (size_t) young_regions * HeapRegion::GrainBytes / K);
3448 uint survivor_regions = g1_policy()->recorded_survivor_regions();
3449 st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
3450 (size_t) survivor_regions * HeapRegion::GrainBytes / K);
3451 st->cr();
3452 MetaspaceAux::print_on(st);
3453 }
3455 void G1CollectedHeap::print_extended_on(outputStream* st) const {
3456 print_on(st);
3458 // Print the per-region information.
3459 st->cr();
3460 st->print_cr("Heap Regions: (Y=young(eden), SU=young(survivor), "
3461 "HS=humongous(starts), HC=humongous(continues), "
3462 "CS=collection set, F=free, TS=gc time stamp, "
3463 "PTAMS=previous top-at-mark-start, "
3464 "NTAMS=next top-at-mark-start)");
3465 PrintRegionClosure blk(st);
3466 heap_region_iterate(&blk);
3467 }
3469 void G1CollectedHeap::print_on_error(outputStream* st) const {
3470 this->CollectedHeap::print_on_error(st);
3472 if (_cm != NULL) {
3473 st->cr();
3474 _cm->print_on_error(st);
3475 }
3476 }
3478 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
3479 if (G1CollectedHeap::use_parallel_gc_threads()) {
3480 workers()->print_worker_threads_on(st);
3481 }
3482 _cmThread->print_on(st);
3483 st->cr();
3484 _cm->print_worker_threads_on(st);
3485 _cg1r->print_worker_threads_on(st);
3486 if (G1StringDedup::is_enabled()) {
3487 G1StringDedup::print_worker_threads_on(st);
3488 }
3489 }
3491 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
3492 if (G1CollectedHeap::use_parallel_gc_threads()) {
3493 workers()->threads_do(tc);
3494 }
3495 tc->do_thread(_cmThread);
3496 _cg1r->threads_do(tc);
3497 if (G1StringDedup::is_enabled()) {
3498 G1StringDedup::threads_do(tc);
3499 }
3500 }
3502 void G1CollectedHeap::print_tracing_info() const {
3503 // We'll overload this to mean "trace GC pause statistics."
3504 if (TraceGen0Time || TraceGen1Time) {
3505 // The "G1CollectorPolicy" is keeping track of these stats, so delegate
3506 // to that.
3507 g1_policy()->print_tracing_info();
3508 }
3509 if (G1SummarizeRSetStats) {
3510 g1_rem_set()->print_summary_info();
3511 }
3512 if (G1SummarizeConcMark) {
3513 concurrent_mark()->print_summary_info();
3514 }
3515 g1_policy()->print_yg_surv_rate_info();
3516 SpecializationStats::print();
3517 }
3519 #ifndef PRODUCT
3520 // Helpful for debugging RSet issues.
3522 class PrintRSetsClosure : public HeapRegionClosure {
3523 private:
3524 const char* _msg;
3525 size_t _occupied_sum;
3527 public:
3528 bool doHeapRegion(HeapRegion* r) {
3529 HeapRegionRemSet* hrrs = r->rem_set();
3530 size_t occupied = hrrs->occupied();
3531 _occupied_sum += occupied;
3533 gclog_or_tty->print_cr("Printing RSet for region "HR_FORMAT,
3534 HR_FORMAT_PARAMS(r));
3535 if (occupied == 0) {
3536 gclog_or_tty->print_cr(" RSet is empty");
3537 } else {
3538 hrrs->print();
3539 }
3540 gclog_or_tty->print_cr("----------");
3541 return false;
3542 }
3544 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
3545 gclog_or_tty->cr();
3546 gclog_or_tty->print_cr("========================================");
3547 gclog_or_tty->print_cr("%s", msg);
3548 gclog_or_tty->cr();
3549 }
3551 ~PrintRSetsClosure() {
3552 gclog_or_tty->print_cr("Occupied Sum: "SIZE_FORMAT, _occupied_sum);
3553 gclog_or_tty->print_cr("========================================");
3554 gclog_or_tty->cr();
3555 }
3556 };
3558 void G1CollectedHeap::print_cset_rsets() {
3559 PrintRSetsClosure cl("Printing CSet RSets");
3560 collection_set_iterate(&cl);
3561 }
3563 void G1CollectedHeap::print_all_rsets() {
3564 PrintRSetsClosure cl("Printing All RSets");;
3565 heap_region_iterate(&cl);
3566 }
3567 #endif // PRODUCT
3569 G1CollectedHeap* G1CollectedHeap::heap() {
3570 assert(_sh->kind() == CollectedHeap::G1CollectedHeap,
3571 "not a garbage-first heap");
3572 return _g1h;
3573 }
3575 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) {
3576 // always_do_update_barrier = false;
3577 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
3578 // Fill TLAB's and such
3579 accumulate_statistics_all_tlabs();
3580 ensure_parsability(true);
3582 if (G1SummarizeRSetStats && (G1SummarizeRSetStatsPeriod > 0) &&
3583 (total_collections() % G1SummarizeRSetStatsPeriod == 0)) {
3584 g1_rem_set()->print_periodic_summary_info("Before GC RS summary");
3585 }
3586 }
3588 void G1CollectedHeap::gc_epilogue(bool full /* Ignored */) {
3590 if (G1SummarizeRSetStats &&
3591 (G1SummarizeRSetStatsPeriod > 0) &&
3592 // we are at the end of the GC. Total collections has already been increased.
3593 ((total_collections() - 1) % G1SummarizeRSetStatsPeriod == 0)) {
3594 g1_rem_set()->print_periodic_summary_info("After GC RS summary");
3595 }
3597 // FIXME: what is this about?
3598 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
3599 // is set.
3600 COMPILER2_PRESENT(assert(DerivedPointerTable::is_empty(),
3601 "derived pointer present"));
3602 // always_do_update_barrier = true;
3604 resize_all_tlabs();
3606 // We have just completed a GC. Update the soft reference
3607 // policy with the new heap occupancy
3608 Universe::update_heap_info_at_gc();
3609 }
3611 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
3612 unsigned int gc_count_before,
3613 bool* succeeded,
3614 GCCause::Cause gc_cause) {
3615 assert_heap_not_locked_and_not_at_safepoint();
3616 g1_policy()->record_stop_world_start();
3617 VM_G1IncCollectionPause op(gc_count_before,
3618 word_size,
3619 false, /* should_initiate_conc_mark */
3620 g1_policy()->max_pause_time_ms(),
3621 gc_cause);
3623 op.set_allocation_context(AllocationContext::current());
3624 VMThread::execute(&op);
3626 HeapWord* result = op.result();
3627 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
3628 assert(result == NULL || ret_succeeded,
3629 "the result should be NULL if the VM did not succeed");
3630 *succeeded = ret_succeeded;
3632 assert_heap_not_locked();
3633 return result;
3634 }
3636 void
3637 G1CollectedHeap::doConcurrentMark() {
3638 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
3639 if (!_cmThread->in_progress()) {
3640 _cmThread->set_started();
3641 CGC_lock->notify();
3642 }
3643 }
3645 size_t G1CollectedHeap::pending_card_num() {
3646 size_t extra_cards = 0;
3647 JavaThread *curr = Threads::first();
3648 while (curr != NULL) {
3649 DirtyCardQueue& dcq = curr->dirty_card_queue();
3650 extra_cards += dcq.size();
3651 curr = curr->next();
3652 }
3653 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
3654 size_t buffer_size = dcqs.buffer_size();
3655 size_t buffer_num = dcqs.completed_buffers_num();
3657 // PtrQueueSet::buffer_size() and PtrQueue:size() return sizes
3658 // in bytes - not the number of 'entries'. We need to convert
3659 // into a number of cards.
3660 return (buffer_size * buffer_num + extra_cards) / oopSize;
3661 }
3663 size_t G1CollectedHeap::cards_scanned() {
3664 return g1_rem_set()->cardsScanned();
3665 }
3667 bool G1CollectedHeap::humongous_region_is_always_live(uint index) {
3668 HeapRegion* region = region_at(index);
3669 assert(region->startsHumongous(), "Must start a humongous object");
3670 return oop(region->bottom())->is_objArray() || !region->rem_set()->is_empty();
3671 }
3673 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure {
3674 private:
3675 size_t _total_humongous;
3676 size_t _candidate_humongous;
3677 public:
3678 RegisterHumongousWithInCSetFastTestClosure() : _total_humongous(0), _candidate_humongous(0) {
3679 }
3681 virtual bool doHeapRegion(HeapRegion* r) {
3682 if (!r->startsHumongous()) {
3683 return false;
3684 }
3685 G1CollectedHeap* g1h = G1CollectedHeap::heap();
3687 uint region_idx = r->hrm_index();
3688 bool is_candidate = !g1h->humongous_region_is_always_live(region_idx);
3689 // Is_candidate already filters out humongous regions with some remembered set.
3690 // This will not lead to humongous object that we mistakenly keep alive because
3691 // during young collection the remembered sets will only be added to.
3692 if (is_candidate) {
3693 g1h->register_humongous_region_with_in_cset_fast_test(region_idx);
3694 _candidate_humongous++;
3695 }
3696 _total_humongous++;
3698 return false;
3699 }
3701 size_t total_humongous() const { return _total_humongous; }
3702 size_t candidate_humongous() const { return _candidate_humongous; }
3703 };
3705 void G1CollectedHeap::register_humongous_regions_with_in_cset_fast_test() {
3706 if (!G1ReclaimDeadHumongousObjectsAtYoungGC) {
3707 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0, 0);
3708 return;
3709 }
3711 RegisterHumongousWithInCSetFastTestClosure cl;
3712 heap_region_iterate(&cl);
3713 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(cl.total_humongous(),
3714 cl.candidate_humongous());
3715 _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0;
3717 if (_has_humongous_reclaim_candidates) {
3718 clear_humongous_is_live_table();
3719 }
3720 }
3722 void
3723 G1CollectedHeap::setup_surviving_young_words() {
3724 assert(_surviving_young_words == NULL, "pre-condition");
3725 uint array_length = g1_policy()->young_cset_region_length();
3726 _surviving_young_words = NEW_C_HEAP_ARRAY(size_t, (size_t) array_length, mtGC);
3727 if (_surviving_young_words == NULL) {
3728 vm_exit_out_of_memory(sizeof(size_t) * array_length, OOM_MALLOC_ERROR,
3729 "Not enough space for young surv words summary.");
3730 }
3731 memset(_surviving_young_words, 0, (size_t) array_length * sizeof(size_t));
3732 #ifdef ASSERT
3733 for (uint i = 0; i < array_length; ++i) {
3734 assert( _surviving_young_words[i] == 0, "memset above" );
3735 }
3736 #endif // !ASSERT
3737 }
3739 void
3740 G1CollectedHeap::update_surviving_young_words(size_t* surv_young_words) {
3741 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
3742 uint array_length = g1_policy()->young_cset_region_length();
3743 for (uint i = 0; i < array_length; ++i) {
3744 _surviving_young_words[i] += surv_young_words[i];
3745 }
3746 }
3748 void
3749 G1CollectedHeap::cleanup_surviving_young_words() {
3750 guarantee( _surviving_young_words != NULL, "pre-condition" );
3751 FREE_C_HEAP_ARRAY(size_t, _surviving_young_words, mtGC);
3752 _surviving_young_words = NULL;
3753 }
3755 #ifdef ASSERT
3756 class VerifyCSetClosure: public HeapRegionClosure {
3757 public:
3758 bool doHeapRegion(HeapRegion* hr) {
3759 // Here we check that the CSet region's RSet is ready for parallel
3760 // iteration. The fields that we'll verify are only manipulated
3761 // when the region is part of a CSet and is collected. Afterwards,
3762 // we reset these fields when we clear the region's RSet (when the
3763 // region is freed) so they are ready when the region is
3764 // re-allocated. The only exception to this is if there's an
3765 // evacuation failure and instead of freeing the region we leave
3766 // it in the heap. In that case, we reset these fields during
3767 // evacuation failure handling.
3768 guarantee(hr->rem_set()->verify_ready_for_par_iteration(), "verification");
3770 // Here's a good place to add any other checks we'd like to
3771 // perform on CSet regions.
3772 return false;
3773 }
3774 };
3775 #endif // ASSERT
3777 #if TASKQUEUE_STATS
3778 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
3779 st->print_raw_cr("GC Task Stats");
3780 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
3781 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
3782 }
3784 void G1CollectedHeap::print_taskqueue_stats(outputStream* const st) const {
3785 print_taskqueue_stats_hdr(st);
3787 TaskQueueStats totals;
3788 const int n = workers() != NULL ? workers()->total_workers() : 1;
3789 for (int i = 0; i < n; ++i) {
3790 st->print("%3d ", i); task_queue(i)->stats.print(st); st->cr();
3791 totals += task_queue(i)->stats;
3792 }
3793 st->print_raw("tot "); totals.print(st); st->cr();
3795 DEBUG_ONLY(totals.verify());
3796 }
3798 void G1CollectedHeap::reset_taskqueue_stats() {
3799 const int n = workers() != NULL ? workers()->total_workers() : 1;
3800 for (int i = 0; i < n; ++i) {
3801 task_queue(i)->stats.reset();
3802 }
3803 }
3804 #endif // TASKQUEUE_STATS
3806 void G1CollectedHeap::log_gc_header() {
3807 if (!G1Log::fine()) {
3808 return;
3809 }
3811 gclog_or_tty->gclog_stamp(_gc_tracer_stw->gc_id());
3813 GCCauseString gc_cause_str = GCCauseString("GC pause", gc_cause())
3814 .append(g1_policy()->gcs_are_young() ? "(young)" : "(mixed)")
3815 .append(g1_policy()->during_initial_mark_pause() ? " (initial-mark)" : "");
3817 gclog_or_tty->print("[%s", (const char*)gc_cause_str);
3818 }
3820 void G1CollectedHeap::log_gc_footer(double pause_time_sec) {
3821 if (!G1Log::fine()) {
3822 return;
3823 }
3825 if (G1Log::finer()) {
3826 if (evacuation_failed()) {
3827 gclog_or_tty->print(" (to-space exhausted)");
3828 }
3829 gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec);
3830 g1_policy()->phase_times()->note_gc_end();
3831 g1_policy()->phase_times()->print(pause_time_sec);
3832 g1_policy()->print_detailed_heap_transition();
3833 } else {
3834 if (evacuation_failed()) {
3835 gclog_or_tty->print("--");
3836 }
3837 g1_policy()->print_heap_transition();
3838 gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec);
3839 }
3840 gclog_or_tty->flush();
3841 }
3843 bool
3844 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
3845 assert_at_safepoint(true /* should_be_vm_thread */);
3846 guarantee(!is_gc_active(), "collection is not reentrant");
3848 if (GC_locker::check_active_before_gc()) {
3849 return false;
3850 }
3852 _gc_timer_stw->register_gc_start();
3854 _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start());
3856 SvcGCMarker sgcm(SvcGCMarker::MINOR);
3857 ResourceMark rm;
3859 print_heap_before_gc();
3860 trace_heap_before_gc(_gc_tracer_stw);
3862 verify_region_sets_optional();
3863 verify_dirty_young_regions();
3865 // This call will decide whether this pause is an initial-mark
3866 // pause. If it is, during_initial_mark_pause() will return true
3867 // for the duration of this pause.
3868 g1_policy()->decide_on_conc_mark_initiation();
3870 // We do not allow initial-mark to be piggy-backed on a mixed GC.
3871 assert(!g1_policy()->during_initial_mark_pause() ||
3872 g1_policy()->gcs_are_young(), "sanity");
3874 // We also do not allow mixed GCs during marking.
3875 assert(!mark_in_progress() || g1_policy()->gcs_are_young(), "sanity");
3877 // Record whether this pause is an initial mark. When the current
3878 // thread has completed its logging output and it's safe to signal
3879 // the CM thread, the flag's value in the policy has been reset.
3880 bool should_start_conc_mark = g1_policy()->during_initial_mark_pause();
3882 // Inner scope for scope based logging, timers, and stats collection
3883 {
3884 EvacuationInfo evacuation_info;
3886 if (g1_policy()->during_initial_mark_pause()) {
3887 // We are about to start a marking cycle, so we increment the
3888 // full collection counter.
3889 increment_old_marking_cycles_started();
3890 register_concurrent_cycle_start(_gc_timer_stw->gc_start());
3891 }
3893 _gc_tracer_stw->report_yc_type(yc_type());
3895 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
3897 int active_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
3898 workers()->active_workers() : 1);
3899 double pause_start_sec = os::elapsedTime();
3900 g1_policy()->phase_times()->note_gc_start(active_workers);
3901 log_gc_header();
3903 TraceCollectorStats tcs(g1mm()->incremental_collection_counters());
3904 TraceMemoryManagerStats tms(false /* fullGC */, gc_cause());
3906 // If the secondary_free_list is not empty, append it to the
3907 // free_list. No need to wait for the cleanup operation to finish;
3908 // the region allocation code will check the secondary_free_list
3909 // and wait if necessary. If the G1StressConcRegionFreeing flag is
3910 // set, skip this step so that the region allocation code has to
3911 // get entries from the secondary_free_list.
3912 if (!G1StressConcRegionFreeing) {
3913 append_secondary_free_list_if_not_empty_with_lock();
3914 }
3916 assert(check_young_list_well_formed(), "young list should be well formed");
3917 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3918 "sanity check");
3920 // Don't dynamically change the number of GC threads this early. A value of
3921 // 0 is used to indicate serial work. When parallel work is done,
3922 // it will be set.
3924 { // Call to jvmpi::post_class_unload_events must occur outside of active GC
3925 IsGCActiveMark x;
3927 gc_prologue(false);
3928 increment_total_collections(false /* full gc */);
3929 increment_gc_time_stamp();
3931 verify_before_gc();
3932 check_bitmaps("GC Start");
3934 COMPILER2_PRESENT(DerivedPointerTable::clear());
3936 // Please see comment in g1CollectedHeap.hpp and
3937 // G1CollectedHeap::ref_processing_init() to see how
3938 // reference processing currently works in G1.
3940 // Enable discovery in the STW reference processor
3941 ref_processor_stw()->enable_discovery(true /*verify_disabled*/,
3942 true /*verify_no_refs*/);
3944 {
3945 // We want to temporarily turn off discovery by the
3946 // CM ref processor, if necessary, and turn it back on
3947 // on again later if we do. Using a scoped
3948 // NoRefDiscovery object will do this.
3949 NoRefDiscovery no_cm_discovery(ref_processor_cm());
3951 // Forget the current alloc region (we might even choose it to be part
3952 // of the collection set!).
3953 _allocator->release_mutator_alloc_region();
3955 // We should call this after we retire the mutator alloc
3956 // region(s) so that all the ALLOC / RETIRE events are generated
3957 // before the start GC event.
3958 _hr_printer.start_gc(false /* full */, (size_t) total_collections());
3960 // This timing is only used by the ergonomics to handle our pause target.
3961 // It is unclear why this should not include the full pause. We will
3962 // investigate this in CR 7178365.
3963 //
3964 // Preserving the old comment here if that helps the investigation:
3965 //
3966 // The elapsed time induced by the start time below deliberately elides
3967 // the possible verification above.
3968 double sample_start_time_sec = os::elapsedTime();
3970 #if YOUNG_LIST_VERBOSE
3971 gclog_or_tty->print_cr("\nBefore recording pause start.\nYoung_list:");
3972 _young_list->print();
3973 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3974 #endif // YOUNG_LIST_VERBOSE
3976 g1_policy()->record_collection_pause_start(sample_start_time_sec);
3978 double scan_wait_start = os::elapsedTime();
3979 // We have to wait until the CM threads finish scanning the
3980 // root regions as it's the only way to ensure that all the
3981 // objects on them have been correctly scanned before we start
3982 // moving them during the GC.
3983 bool waited = _cm->root_regions()->wait_until_scan_finished();
3984 double wait_time_ms = 0.0;
3985 if (waited) {
3986 double scan_wait_end = os::elapsedTime();
3987 wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
3988 }
3989 g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms);
3991 #if YOUNG_LIST_VERBOSE
3992 gclog_or_tty->print_cr("\nAfter recording pause start.\nYoung_list:");
3993 _young_list->print();
3994 #endif // YOUNG_LIST_VERBOSE
3996 if (g1_policy()->during_initial_mark_pause()) {
3997 concurrent_mark()->checkpointRootsInitialPre();
3998 }
4000 #if YOUNG_LIST_VERBOSE
4001 gclog_or_tty->print_cr("\nBefore choosing collection set.\nYoung_list:");
4002 _young_list->print();
4003 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
4004 #endif // YOUNG_LIST_VERBOSE
4006 g1_policy()->finalize_cset(target_pause_time_ms, evacuation_info);
4008 register_humongous_regions_with_in_cset_fast_test();
4010 _cm->note_start_of_gc();
4011 // We should not verify the per-thread SATB buffers given that
4012 // we have not filtered them yet (we'll do so during the
4013 // GC). We also call this after finalize_cset() to
4014 // ensure that the CSet has been finalized.
4015 _cm->verify_no_cset_oops(true /* verify_stacks */,
4016 true /* verify_enqueued_buffers */,
4017 false /* verify_thread_buffers */,
4018 true /* verify_fingers */);
4020 if (_hr_printer.is_active()) {
4021 HeapRegion* hr = g1_policy()->collection_set();
4022 while (hr != NULL) {
4023 G1HRPrinter::RegionType type;
4024 if (!hr->is_young()) {
4025 type = G1HRPrinter::Old;
4026 } else if (hr->is_survivor()) {
4027 type = G1HRPrinter::Survivor;
4028 } else {
4029 type = G1HRPrinter::Eden;
4030 }
4031 _hr_printer.cset(hr);
4032 hr = hr->next_in_collection_set();
4033 }
4034 }
4036 #ifdef ASSERT
4037 VerifyCSetClosure cl;
4038 collection_set_iterate(&cl);
4039 #endif // ASSERT
4041 setup_surviving_young_words();
4043 // Initialize the GC alloc regions.
4044 _allocator->init_gc_alloc_regions(evacuation_info);
4046 // Actually do the work...
4047 evacuate_collection_set(evacuation_info);
4049 // We do this to mainly verify the per-thread SATB buffers
4050 // (which have been filtered by now) since we didn't verify
4051 // them earlier. No point in re-checking the stacks / enqueued
4052 // buffers given that the CSet has not changed since last time
4053 // we checked.
4054 _cm->verify_no_cset_oops(false /* verify_stacks */,
4055 false /* verify_enqueued_buffers */,
4056 true /* verify_thread_buffers */,
4057 true /* verify_fingers */);
4059 free_collection_set(g1_policy()->collection_set(), evacuation_info);
4061 eagerly_reclaim_humongous_regions();
4063 g1_policy()->clear_collection_set();
4065 cleanup_surviving_young_words();
4067 // Start a new incremental collection set for the next pause.
4068 g1_policy()->start_incremental_cset_building();
4070 clear_cset_fast_test();
4072 _young_list->reset_sampled_info();
4074 // Don't check the whole heap at this point as the
4075 // GC alloc regions from this pause have been tagged
4076 // as survivors and moved on to the survivor list.
4077 // Survivor regions will fail the !is_young() check.
4078 assert(check_young_list_empty(false /* check_heap */),
4079 "young list should be empty");
4081 #if YOUNG_LIST_VERBOSE
4082 gclog_or_tty->print_cr("Before recording survivors.\nYoung List:");
4083 _young_list->print();
4084 #endif // YOUNG_LIST_VERBOSE
4086 g1_policy()->record_survivor_regions(_young_list->survivor_length(),
4087 _young_list->first_survivor_region(),
4088 _young_list->last_survivor_region());
4090 _young_list->reset_auxilary_lists();
4092 if (evacuation_failed()) {
4093 _allocator->set_used(recalculate_used());
4094 uint n_queues = MAX2((int)ParallelGCThreads, 1);
4095 for (uint i = 0; i < n_queues; i++) {
4096 if (_evacuation_failed_info_array[i].has_failed()) {
4097 _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]);
4098 }
4099 }
4100 } else {
4101 // The "used" of the the collection set have already been subtracted
4102 // when they were freed. Add in the bytes evacuated.
4103 _allocator->increase_used(g1_policy()->bytes_copied_during_gc());
4104 }
4106 if (g1_policy()->during_initial_mark_pause()) {
4107 // We have to do this before we notify the CM threads that
4108 // they can start working to make sure that all the
4109 // appropriate initialization is done on the CM object.
4110 concurrent_mark()->checkpointRootsInitialPost();
4111 set_marking_started();
4112 // Note that we don't actually trigger the CM thread at
4113 // this point. We do that later when we're sure that
4114 // the current thread has completed its logging output.
4115 }
4117 allocate_dummy_regions();
4119 #if YOUNG_LIST_VERBOSE
4120 gclog_or_tty->print_cr("\nEnd of the pause.\nYoung_list:");
4121 _young_list->print();
4122 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
4123 #endif // YOUNG_LIST_VERBOSE
4125 _allocator->init_mutator_alloc_region();
4127 {
4128 size_t expand_bytes = g1_policy()->expansion_amount();
4129 if (expand_bytes > 0) {
4130 size_t bytes_before = capacity();
4131 // No need for an ergo verbose message here,
4132 // expansion_amount() does this when it returns a value > 0.
4133 if (!expand(expand_bytes)) {
4134 // We failed to expand the heap. Cannot do anything about it.
4135 }
4136 }
4137 }
4139 // We redo the verification but now wrt to the new CSet which
4140 // has just got initialized after the previous CSet was freed.
4141 _cm->verify_no_cset_oops(true /* verify_stacks */,
4142 true /* verify_enqueued_buffers */,
4143 true /* verify_thread_buffers */,
4144 true /* verify_fingers */);
4145 _cm->note_end_of_gc();
4147 // This timing is only used by the ergonomics to handle our pause target.
4148 // It is unclear why this should not include the full pause. We will
4149 // investigate this in CR 7178365.
4150 double sample_end_time_sec = os::elapsedTime();
4151 double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
4152 g1_policy()->record_collection_pause_end(pause_time_ms, evacuation_info);
4154 MemoryService::track_memory_usage();
4156 // In prepare_for_verify() below we'll need to scan the deferred
4157 // update buffers to bring the RSets up-to-date if
4158 // G1HRRSFlushLogBuffersOnVerify has been set. While scanning
4159 // the update buffers we'll probably need to scan cards on the
4160 // regions we just allocated to (i.e., the GC alloc
4161 // regions). However, during the last GC we called
4162 // set_saved_mark() on all the GC alloc regions, so card
4163 // scanning might skip the [saved_mark_word()...top()] area of
4164 // those regions (i.e., the area we allocated objects into
4165 // during the last GC). But it shouldn't. Given that
4166 // saved_mark_word() is conditional on whether the GC time stamp
4167 // on the region is current or not, by incrementing the GC time
4168 // stamp here we invalidate all the GC time stamps on all the
4169 // regions and saved_mark_word() will simply return top() for
4170 // all the regions. This is a nicer way of ensuring this rather
4171 // than iterating over the regions and fixing them. In fact, the
4172 // GC time stamp increment here also ensures that
4173 // saved_mark_word() will return top() between pauses, i.e.,
4174 // during concurrent refinement. So we don't need the
4175 // is_gc_active() check to decided which top to use when
4176 // scanning cards (see CR 7039627).
4177 increment_gc_time_stamp();
4179 verify_after_gc();
4180 check_bitmaps("GC End");
4182 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
4183 ref_processor_stw()->verify_no_references_recorded();
4185 // CM reference discovery will be re-enabled if necessary.
4186 }
4188 // We should do this after we potentially expand the heap so
4189 // that all the COMMIT events are generated before the end GC
4190 // event, and after we retire the GC alloc regions so that all
4191 // RETIRE events are generated before the end GC event.
4192 _hr_printer.end_gc(false /* full */, (size_t) total_collections());
4194 #ifdef TRACESPINNING
4195 ParallelTaskTerminator::print_termination_counts();
4196 #endif
4198 gc_epilogue(false);
4199 }
4201 // Print the remainder of the GC log output.
4202 log_gc_footer(os::elapsedTime() - pause_start_sec);
4204 // It is not yet to safe to tell the concurrent mark to
4205 // start as we have some optional output below. We don't want the
4206 // output from the concurrent mark thread interfering with this
4207 // logging output either.
4209 _hrm.verify_optional();
4210 verify_region_sets_optional();
4212 TASKQUEUE_STATS_ONLY(if (ParallelGCVerbose) print_taskqueue_stats());
4213 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
4215 print_heap_after_gc();
4216 trace_heap_after_gc(_gc_tracer_stw);
4218 // We must call G1MonitoringSupport::update_sizes() in the same scoping level
4219 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
4220 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
4221 // before any GC notifications are raised.
4222 g1mm()->update_sizes();
4224 _gc_tracer_stw->report_evacuation_info(&evacuation_info);
4225 _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold());
4226 _gc_timer_stw->register_gc_end();
4227 _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions());
4228 }
4229 // It should now be safe to tell the concurrent mark thread to start
4230 // without its logging output interfering with the logging output
4231 // that came from the pause.
4233 if (should_start_conc_mark) {
4234 // CAUTION: after the doConcurrentMark() call below,
4235 // the concurrent marking thread(s) could be running
4236 // concurrently with us. Make sure that anything after
4237 // this point does not assume that we are the only GC thread
4238 // running. Note: of course, the actual marking work will
4239 // not start until the safepoint itself is released in
4240 // SuspendibleThreadSet::desynchronize().
4241 doConcurrentMark();
4242 }
4244 return true;
4245 }
4247 size_t G1CollectedHeap::desired_plab_sz(GCAllocPurpose purpose)
4248 {
4249 size_t gclab_word_size;
4250 switch (purpose) {
4251 case GCAllocForSurvived:
4252 gclab_word_size = _survivor_plab_stats.desired_plab_sz();
4253 break;
4254 case GCAllocForTenured:
4255 gclab_word_size = _old_plab_stats.desired_plab_sz();
4256 break;
4257 default:
4258 assert(false, "unknown GCAllocPurpose");
4259 gclab_word_size = _old_plab_stats.desired_plab_sz();
4260 break;
4261 }
4263 // Prevent humongous PLAB sizes for two reasons:
4264 // * PLABs are allocated using a similar paths as oops, but should
4265 // never be in a humongous region
4266 // * Allowing humongous PLABs needlessly churns the region free lists
4267 return MIN2(_humongous_object_threshold_in_words, gclab_word_size);
4268 }
4270 void G1CollectedHeap::init_for_evac_failure(OopsInHeapRegionClosure* cl) {
4271 _drain_in_progress = false;
4272 set_evac_failure_closure(cl);
4273 _evac_failure_scan_stack = new (ResourceObj::C_HEAP, mtGC) GrowableArray<oop>(40, true);
4274 }
4276 void G1CollectedHeap::finalize_for_evac_failure() {
4277 assert(_evac_failure_scan_stack != NULL &&
4278 _evac_failure_scan_stack->length() == 0,
4279 "Postcondition");
4280 assert(!_drain_in_progress, "Postcondition");
4281 delete _evac_failure_scan_stack;
4282 _evac_failure_scan_stack = NULL;
4283 }
4285 void G1CollectedHeap::remove_self_forwarding_pointers() {
4286 assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity");
4288 double remove_self_forwards_start = os::elapsedTime();
4290 G1ParRemoveSelfForwardPtrsTask rsfp_task(this);
4292 if (G1CollectedHeap::use_parallel_gc_threads()) {
4293 set_par_threads();
4294 workers()->run_task(&rsfp_task);
4295 set_par_threads(0);
4296 } else {
4297 rsfp_task.work(0);
4298 }
4300 assert(check_cset_heap_region_claim_values(HeapRegion::ParEvacFailureClaimValue), "sanity");
4302 // Reset the claim values in the regions in the collection set.
4303 reset_cset_heap_region_claim_values();
4305 assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity");
4307 // Now restore saved marks, if any.
4308 assert(_objs_with_preserved_marks.size() ==
4309 _preserved_marks_of_objs.size(), "Both or none.");
4310 while (!_objs_with_preserved_marks.is_empty()) {
4311 oop obj = _objs_with_preserved_marks.pop();
4312 markOop m = _preserved_marks_of_objs.pop();
4313 obj->set_mark(m);
4314 }
4315 _objs_with_preserved_marks.clear(true);
4316 _preserved_marks_of_objs.clear(true);
4318 g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0);
4319 }
4321 void G1CollectedHeap::push_on_evac_failure_scan_stack(oop obj) {
4322 _evac_failure_scan_stack->push(obj);
4323 }
4325 void G1CollectedHeap::drain_evac_failure_scan_stack() {
4326 assert(_evac_failure_scan_stack != NULL, "precondition");
4328 while (_evac_failure_scan_stack->length() > 0) {
4329 oop obj = _evac_failure_scan_stack->pop();
4330 _evac_failure_closure->set_region(heap_region_containing(obj));
4331 obj->oop_iterate_backwards(_evac_failure_closure);
4332 }
4333 }
4335 oop
4336 G1CollectedHeap::handle_evacuation_failure_par(G1ParScanThreadState* _par_scan_state,
4337 oop old) {
4338 assert(obj_in_cs(old),
4339 err_msg("obj: "PTR_FORMAT" should still be in the CSet",
4340 (HeapWord*) old));
4341 markOop m = old->mark();
4342 oop forward_ptr = old->forward_to_atomic(old);
4343 if (forward_ptr == NULL) {
4344 // Forward-to-self succeeded.
4345 assert(_par_scan_state != NULL, "par scan state");
4346 OopsInHeapRegionClosure* cl = _par_scan_state->evac_failure_closure();
4347 uint queue_num = _par_scan_state->queue_num();
4349 _evacuation_failed = true;
4350 _evacuation_failed_info_array[queue_num].register_copy_failure(old->size());
4351 if (_evac_failure_closure != cl) {
4352 MutexLockerEx x(EvacFailureStack_lock, Mutex::_no_safepoint_check_flag);
4353 assert(!_drain_in_progress,
4354 "Should only be true while someone holds the lock.");
4355 // Set the global evac-failure closure to the current thread's.
4356 assert(_evac_failure_closure == NULL, "Or locking has failed.");
4357 set_evac_failure_closure(cl);
4358 // Now do the common part.
4359 handle_evacuation_failure_common(old, m);
4360 // Reset to NULL.
4361 set_evac_failure_closure(NULL);
4362 } else {
4363 // The lock is already held, and this is recursive.
4364 assert(_drain_in_progress, "This should only be the recursive case.");
4365 handle_evacuation_failure_common(old, m);
4366 }
4367 return old;
4368 } else {
4369 // Forward-to-self failed. Either someone else managed to allocate
4370 // space for this object (old != forward_ptr) or they beat us in
4371 // self-forwarding it (old == forward_ptr).
4372 assert(old == forward_ptr || !obj_in_cs(forward_ptr),
4373 err_msg("obj: "PTR_FORMAT" forwarded to: "PTR_FORMAT" "
4374 "should not be in the CSet",
4375 (HeapWord*) old, (HeapWord*) forward_ptr));
4376 return forward_ptr;
4377 }
4378 }
4380 void G1CollectedHeap::handle_evacuation_failure_common(oop old, markOop m) {
4381 preserve_mark_if_necessary(old, m);
4383 HeapRegion* r = heap_region_containing(old);
4384 if (!r->evacuation_failed()) {
4385 r->set_evacuation_failed(true);
4386 _hr_printer.evac_failure(r);
4387 }
4389 push_on_evac_failure_scan_stack(old);
4391 if (!_drain_in_progress) {
4392 // prevent recursion in copy_to_survivor_space()
4393 _drain_in_progress = true;
4394 drain_evac_failure_scan_stack();
4395 _drain_in_progress = false;
4396 }
4397 }
4399 void G1CollectedHeap::preserve_mark_if_necessary(oop obj, markOop m) {
4400 assert(evacuation_failed(), "Oversaving!");
4401 // We want to call the "for_promotion_failure" version only in the
4402 // case of a promotion failure.
4403 if (m->must_be_preserved_for_promotion_failure(obj)) {
4404 _objs_with_preserved_marks.push(obj);
4405 _preserved_marks_of_objs.push(m);
4406 }
4407 }
4409 HeapWord* G1CollectedHeap::par_allocate_during_gc(GCAllocPurpose purpose,
4410 size_t word_size,
4411 AllocationContext_t context) {
4412 if (purpose == GCAllocForSurvived) {
4413 HeapWord* result = survivor_attempt_allocation(word_size, context);
4414 if (result != NULL) {
4415 return result;
4416 } else {
4417 // Let's try to allocate in the old gen in case we can fit the
4418 // object there.
4419 return old_attempt_allocation(word_size, context);
4420 }
4421 } else {
4422 assert(purpose == GCAllocForTenured, "sanity");
4423 HeapWord* result = old_attempt_allocation(word_size, context);
4424 if (result != NULL) {
4425 return result;
4426 } else {
4427 // Let's try to allocate in the survivors in case we can fit the
4428 // object there.
4429 return survivor_attempt_allocation(word_size, context);
4430 }
4431 }
4433 ShouldNotReachHere();
4434 // Trying to keep some compilers happy.
4435 return NULL;
4436 }
4438 void G1ParCopyHelper::mark_object(oop obj) {
4439 assert(!_g1->heap_region_containing(obj)->in_collection_set(), "should not mark objects in the CSet");
4441 // We know that the object is not moving so it's safe to read its size.
4442 _cm->grayRoot(obj, (size_t) obj->size(), _worker_id);
4443 }
4445 void G1ParCopyHelper::mark_forwarded_object(oop from_obj, oop to_obj) {
4446 assert(from_obj->is_forwarded(), "from obj should be forwarded");
4447 assert(from_obj->forwardee() == to_obj, "to obj should be the forwardee");
4448 assert(from_obj != to_obj, "should not be self-forwarded");
4450 assert(_g1->heap_region_containing(from_obj)->in_collection_set(), "from obj should be in the CSet");
4451 assert(!_g1->heap_region_containing(to_obj)->in_collection_set(), "should not mark objects in the CSet");
4453 // The object might be in the process of being copied by another
4454 // worker so we cannot trust that its to-space image is
4455 // well-formed. So we have to read its size from its from-space
4456 // image which we know should not be changing.
4457 _cm->grayRoot(to_obj, (size_t) from_obj->size(), _worker_id);
4458 }
4460 template <class T>
4461 void G1ParCopyHelper::do_klass_barrier(T* p, oop new_obj) {
4462 if (_g1->heap_region_containing_raw(new_obj)->is_young()) {
4463 _scanned_klass->record_modified_oops();
4464 }
4465 }
4467 template <G1Barrier barrier, G1Mark do_mark_object>
4468 template <class T>
4469 void G1ParCopyClosure<barrier, do_mark_object>::do_oop_work(T* p) {
4470 T heap_oop = oopDesc::load_heap_oop(p);
4472 if (oopDesc::is_null(heap_oop)) {
4473 return;
4474 }
4476 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
4478 assert(_worker_id == _par_scan_state->queue_num(), "sanity");
4480 G1CollectedHeap::in_cset_state_t state = _g1->in_cset_state(obj);
4482 if (state == G1CollectedHeap::InCSet) {
4483 oop forwardee;
4484 if (obj->is_forwarded()) {
4485 forwardee = obj->forwardee();
4486 } else {
4487 forwardee = _par_scan_state->copy_to_survivor_space(obj);
4488 }
4489 assert(forwardee != NULL, "forwardee should not be NULL");
4490 oopDesc::encode_store_heap_oop(p, forwardee);
4491 if (do_mark_object != G1MarkNone && forwardee != obj) {
4492 // If the object is self-forwarded we don't need to explicitly
4493 // mark it, the evacuation failure protocol will do so.
4494 mark_forwarded_object(obj, forwardee);
4495 }
4497 if (barrier == G1BarrierKlass) {
4498 do_klass_barrier(p, forwardee);
4499 }
4500 } else {
4501 if (state == G1CollectedHeap::IsHumongous) {
4502 _g1->set_humongous_is_live(obj);
4503 }
4504 // The object is not in collection set. If we're a root scanning
4505 // closure during an initial mark pause then attempt to mark the object.
4506 if (do_mark_object == G1MarkFromRoot) {
4507 mark_object(obj);
4508 }
4509 }
4511 if (barrier == G1BarrierEvac) {
4512 _par_scan_state->update_rs(_from, p, _worker_id);
4513 }
4514 }
4516 template void G1ParCopyClosure<G1BarrierEvac, G1MarkNone>::do_oop_work(oop* p);
4517 template void G1ParCopyClosure<G1BarrierEvac, G1MarkNone>::do_oop_work(narrowOop* p);
4519 class G1ParEvacuateFollowersClosure : public VoidClosure {
4520 protected:
4521 G1CollectedHeap* _g1h;
4522 G1ParScanThreadState* _par_scan_state;
4523 RefToScanQueueSet* _queues;
4524 ParallelTaskTerminator* _terminator;
4526 G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
4527 RefToScanQueueSet* queues() { return _queues; }
4528 ParallelTaskTerminator* terminator() { return _terminator; }
4530 public:
4531 G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h,
4532 G1ParScanThreadState* par_scan_state,
4533 RefToScanQueueSet* queues,
4534 ParallelTaskTerminator* terminator)
4535 : _g1h(g1h), _par_scan_state(par_scan_state),
4536 _queues(queues), _terminator(terminator) {}
4538 void do_void();
4540 private:
4541 inline bool offer_termination();
4542 };
4544 bool G1ParEvacuateFollowersClosure::offer_termination() {
4545 G1ParScanThreadState* const pss = par_scan_state();
4546 pss->start_term_time();
4547 const bool res = terminator()->offer_termination();
4548 pss->end_term_time();
4549 return res;
4550 }
4552 void G1ParEvacuateFollowersClosure::do_void() {
4553 G1ParScanThreadState* const pss = par_scan_state();
4554 pss->trim_queue();
4555 do {
4556 pss->steal_and_trim_queue(queues());
4557 } while (!offer_termination());
4558 }
4560 class G1KlassScanClosure : public KlassClosure {
4561 G1ParCopyHelper* _closure;
4562 bool _process_only_dirty;
4563 int _count;
4564 public:
4565 G1KlassScanClosure(G1ParCopyHelper* closure, bool process_only_dirty)
4566 : _process_only_dirty(process_only_dirty), _closure(closure), _count(0) {}
4567 void do_klass(Klass* klass) {
4568 // If the klass has not been dirtied we know that there's
4569 // no references into the young gen and we can skip it.
4570 if (!_process_only_dirty || klass->has_modified_oops()) {
4571 // Clean the klass since we're going to scavenge all the metadata.
4572 klass->clear_modified_oops();
4574 // Tell the closure that this klass is the Klass to scavenge
4575 // and is the one to dirty if oops are left pointing into the young gen.
4576 _closure->set_scanned_klass(klass);
4578 klass->oops_do(_closure);
4580 _closure->set_scanned_klass(NULL);
4581 }
4582 _count++;
4583 }
4584 };
4586 class G1ParTask : public AbstractGangTask {
4587 protected:
4588 G1CollectedHeap* _g1h;
4589 RefToScanQueueSet *_queues;
4590 ParallelTaskTerminator _terminator;
4591 uint _n_workers;
4593 Mutex _stats_lock;
4594 Mutex* stats_lock() { return &_stats_lock; }
4596 public:
4597 G1ParTask(G1CollectedHeap* g1h, RefToScanQueueSet *task_queues)
4598 : AbstractGangTask("G1 collection"),
4599 _g1h(g1h),
4600 _queues(task_queues),
4601 _terminator(0, _queues),
4602 _stats_lock(Mutex::leaf, "parallel G1 stats lock", true)
4603 {}
4605 RefToScanQueueSet* queues() { return _queues; }
4607 RefToScanQueue *work_queue(int i) {
4608 return queues()->queue(i);
4609 }
4611 ParallelTaskTerminator* terminator() { return &_terminator; }
4613 virtual void set_for_termination(int active_workers) {
4614 // This task calls set_n_termination() in par_non_clean_card_iterate_work()
4615 // in the young space (_par_seq_tasks) in the G1 heap
4616 // for SequentialSubTasksDone.
4617 // This task also uses SubTasksDone in SharedHeap and G1CollectedHeap
4618 // both of which need setting by set_n_termination().
4619 _g1h->SharedHeap::set_n_termination(active_workers);
4620 _g1h->set_n_termination(active_workers);
4621 terminator()->reset_for_reuse(active_workers);
4622 _n_workers = active_workers;
4623 }
4625 // Helps out with CLD processing.
4626 //
4627 // During InitialMark we need to:
4628 // 1) Scavenge all CLDs for the young GC.
4629 // 2) Mark all objects directly reachable from strong CLDs.
4630 template <G1Mark do_mark_object>
4631 class G1CLDClosure : public CLDClosure {
4632 G1ParCopyClosure<G1BarrierNone, do_mark_object>* _oop_closure;
4633 G1ParCopyClosure<G1BarrierKlass, do_mark_object> _oop_in_klass_closure;
4634 G1KlassScanClosure _klass_in_cld_closure;
4635 bool _claim;
4637 public:
4638 G1CLDClosure(G1ParCopyClosure<G1BarrierNone, do_mark_object>* oop_closure,
4639 bool only_young, bool claim)
4640 : _oop_closure(oop_closure),
4641 _oop_in_klass_closure(oop_closure->g1(),
4642 oop_closure->pss(),
4643 oop_closure->rp()),
4644 _klass_in_cld_closure(&_oop_in_klass_closure, only_young),
4645 _claim(claim) {
4647 }
4649 void do_cld(ClassLoaderData* cld) {
4650 cld->oops_do(_oop_closure, &_klass_in_cld_closure, _claim);
4651 }
4652 };
4654 class G1CodeBlobClosure: public CodeBlobClosure {
4655 OopClosure* _f;
4657 public:
4658 G1CodeBlobClosure(OopClosure* f) : _f(f) {}
4659 void do_code_blob(CodeBlob* blob) {
4660 nmethod* that = blob->as_nmethod_or_null();
4661 if (that != NULL) {
4662 if (!that->test_set_oops_do_mark()) {
4663 that->oops_do(_f);
4664 that->fix_oop_relocations();
4665 }
4666 }
4667 }
4668 };
4670 void work(uint worker_id) {
4671 if (worker_id >= _n_workers) return; // no work needed this round
4673 double start_time_ms = os::elapsedTime() * 1000.0;
4674 _g1h->g1_policy()->phase_times()->record_gc_worker_start_time(worker_id, start_time_ms);
4676 {
4677 ResourceMark rm;
4678 HandleMark hm;
4680 ReferenceProcessor* rp = _g1h->ref_processor_stw();
4682 G1ParScanThreadState pss(_g1h, worker_id, rp);
4683 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, rp);
4685 pss.set_evac_failure_closure(&evac_failure_cl);
4687 bool only_young = _g1h->g1_policy()->gcs_are_young();
4689 // Non-IM young GC.
4690 G1ParCopyClosure<G1BarrierNone, G1MarkNone> scan_only_root_cl(_g1h, &pss, rp);
4691 G1CLDClosure<G1MarkNone> scan_only_cld_cl(&scan_only_root_cl,
4692 only_young, // Only process dirty klasses.
4693 false); // No need to claim CLDs.
4694 // IM young GC.
4695 // Strong roots closures.
4696 G1ParCopyClosure<G1BarrierNone, G1MarkFromRoot> scan_mark_root_cl(_g1h, &pss, rp);
4697 G1CLDClosure<G1MarkFromRoot> scan_mark_cld_cl(&scan_mark_root_cl,
4698 false, // Process all klasses.
4699 true); // Need to claim CLDs.
4700 // Weak roots closures.
4701 G1ParCopyClosure<G1BarrierNone, G1MarkPromotedFromRoot> scan_mark_weak_root_cl(_g1h, &pss, rp);
4702 G1CLDClosure<G1MarkPromotedFromRoot> scan_mark_weak_cld_cl(&scan_mark_weak_root_cl,
4703 false, // Process all klasses.
4704 true); // Need to claim CLDs.
4706 G1CodeBlobClosure scan_only_code_cl(&scan_only_root_cl);
4707 G1CodeBlobClosure scan_mark_code_cl(&scan_mark_root_cl);
4708 // IM Weak code roots are handled later.
4710 OopClosure* strong_root_cl;
4711 OopClosure* weak_root_cl;
4712 CLDClosure* strong_cld_cl;
4713 CLDClosure* weak_cld_cl;
4714 CodeBlobClosure* strong_code_cl;
4716 if (_g1h->g1_policy()->during_initial_mark_pause()) {
4717 // We also need to mark copied objects.
4718 strong_root_cl = &scan_mark_root_cl;
4719 strong_cld_cl = &scan_mark_cld_cl;
4720 strong_code_cl = &scan_mark_code_cl;
4721 if (ClassUnloadingWithConcurrentMark) {
4722 weak_root_cl = &scan_mark_weak_root_cl;
4723 weak_cld_cl = &scan_mark_weak_cld_cl;
4724 } else {
4725 weak_root_cl = &scan_mark_root_cl;
4726 weak_cld_cl = &scan_mark_cld_cl;
4727 }
4728 } else {
4729 strong_root_cl = &scan_only_root_cl;
4730 weak_root_cl = &scan_only_root_cl;
4731 strong_cld_cl = &scan_only_cld_cl;
4732 weak_cld_cl = &scan_only_cld_cl;
4733 strong_code_cl = &scan_only_code_cl;
4734 }
4737 G1ParPushHeapRSClosure push_heap_rs_cl(_g1h, &pss);
4739 pss.start_strong_roots();
4740 _g1h->g1_process_roots(strong_root_cl,
4741 weak_root_cl,
4742 &push_heap_rs_cl,
4743 strong_cld_cl,
4744 weak_cld_cl,
4745 strong_code_cl,
4746 worker_id);
4748 pss.end_strong_roots();
4750 {
4751 double start = os::elapsedTime();
4752 G1ParEvacuateFollowersClosure evac(_g1h, &pss, _queues, &_terminator);
4753 evac.do_void();
4754 double elapsed_ms = (os::elapsedTime()-start)*1000.0;
4755 double term_ms = pss.term_time()*1000.0;
4756 _g1h->g1_policy()->phase_times()->add_obj_copy_time(worker_id, elapsed_ms-term_ms);
4757 _g1h->g1_policy()->phase_times()->record_termination(worker_id, term_ms, pss.term_attempts());
4758 }
4759 _g1h->g1_policy()->record_thread_age_table(pss.age_table());
4760 _g1h->update_surviving_young_words(pss.surviving_young_words()+1);
4762 if (ParallelGCVerbose) {
4763 MutexLocker x(stats_lock());
4764 pss.print_termination_stats(worker_id);
4765 }
4767 assert(pss.queue_is_empty(), "should be empty");
4769 // Close the inner scope so that the ResourceMark and HandleMark
4770 // destructors are executed here and are included as part of the
4771 // "GC Worker Time".
4772 }
4774 double end_time_ms = os::elapsedTime() * 1000.0;
4775 _g1h->g1_policy()->phase_times()->record_gc_worker_end_time(worker_id, end_time_ms);
4776 }
4777 };
4779 // *** Common G1 Evacuation Stuff
4781 // This method is run in a GC worker.
4783 void
4784 G1CollectedHeap::
4785 g1_process_roots(OopClosure* scan_non_heap_roots,
4786 OopClosure* scan_non_heap_weak_roots,
4787 OopsInHeapRegionClosure* scan_rs,
4788 CLDClosure* scan_strong_clds,
4789 CLDClosure* scan_weak_clds,
4790 CodeBlobClosure* scan_strong_code,
4791 uint worker_i) {
4793 // First scan the shared roots.
4794 double ext_roots_start = os::elapsedTime();
4795 double closure_app_time_sec = 0.0;
4797 bool during_im = _g1h->g1_policy()->during_initial_mark_pause();
4798 bool trace_metadata = during_im && ClassUnloadingWithConcurrentMark;
4800 BufferingOopClosure buf_scan_non_heap_roots(scan_non_heap_roots);
4801 BufferingOopClosure buf_scan_non_heap_weak_roots(scan_non_heap_weak_roots);
4803 process_roots(false, // no scoping; this is parallel code
4804 SharedHeap::SO_None,
4805 &buf_scan_non_heap_roots,
4806 &buf_scan_non_heap_weak_roots,
4807 scan_strong_clds,
4808 // Unloading Initial Marks handle the weak CLDs separately.
4809 (trace_metadata ? NULL : scan_weak_clds),
4810 scan_strong_code);
4812 // Now the CM ref_processor roots.
4813 if (!_process_strong_tasks->is_task_claimed(G1H_PS_refProcessor_oops_do)) {
4814 // We need to treat the discovered reference lists of the
4815 // concurrent mark ref processor as roots and keep entries
4816 // (which are added by the marking threads) on them live
4817 // until they can be processed at the end of marking.
4818 ref_processor_cm()->weak_oops_do(&buf_scan_non_heap_roots);
4819 }
4821 if (trace_metadata) {
4822 // Barrier to make sure all workers passed
4823 // the strong CLD and strong nmethods phases.
4824 active_strong_roots_scope()->wait_until_all_workers_done_with_threads(n_par_threads());
4826 // Now take the complement of the strong CLDs.
4827 ClassLoaderDataGraph::roots_cld_do(NULL, scan_weak_clds);
4828 }
4830 // Finish up any enqueued closure apps (attributed as object copy time).
4831 buf_scan_non_heap_roots.done();
4832 buf_scan_non_heap_weak_roots.done();
4834 double obj_copy_time_sec = buf_scan_non_heap_roots.closure_app_seconds()
4835 + buf_scan_non_heap_weak_roots.closure_app_seconds();
4837 g1_policy()->phase_times()->record_obj_copy_time(worker_i, obj_copy_time_sec * 1000.0);
4839 double ext_root_time_ms =
4840 ((os::elapsedTime() - ext_roots_start) - obj_copy_time_sec) * 1000.0;
4842 g1_policy()->phase_times()->record_ext_root_scan_time(worker_i, ext_root_time_ms);
4844 // During conc marking we have to filter the per-thread SATB buffers
4845 // to make sure we remove any oops into the CSet (which will show up
4846 // as implicitly live).
4847 double satb_filtering_ms = 0.0;
4848 if (!_process_strong_tasks->is_task_claimed(G1H_PS_filter_satb_buffers)) {
4849 if (mark_in_progress()) {
4850 double satb_filter_start = os::elapsedTime();
4852 JavaThread::satb_mark_queue_set().filter_thread_buffers();
4854 satb_filtering_ms = (os::elapsedTime() - satb_filter_start) * 1000.0;
4855 }
4856 }
4857 g1_policy()->phase_times()->record_satb_filtering_time(worker_i, satb_filtering_ms);
4859 // Now scan the complement of the collection set.
4860 MarkingCodeBlobClosure scavenge_cs_nmethods(scan_non_heap_weak_roots, CodeBlobToOopClosure::FixRelocations);
4862 g1_rem_set()->oops_into_collection_set_do(scan_rs, &scavenge_cs_nmethods, worker_i);
4864 _process_strong_tasks->all_tasks_completed();
4865 }
4867 class G1StringSymbolTableUnlinkTask : public AbstractGangTask {
4868 private:
4869 BoolObjectClosure* _is_alive;
4870 int _initial_string_table_size;
4871 int _initial_symbol_table_size;
4873 bool _process_strings;
4874 int _strings_processed;
4875 int _strings_removed;
4877 bool _process_symbols;
4878 int _symbols_processed;
4879 int _symbols_removed;
4881 bool _do_in_parallel;
4882 public:
4883 G1StringSymbolTableUnlinkTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols) :
4884 AbstractGangTask("String/Symbol Unlinking"),
4885 _is_alive(is_alive),
4886 _do_in_parallel(G1CollectedHeap::use_parallel_gc_threads()),
4887 _process_strings(process_strings), _strings_processed(0), _strings_removed(0),
4888 _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0) {
4890 _initial_string_table_size = StringTable::the_table()->table_size();
4891 _initial_symbol_table_size = SymbolTable::the_table()->table_size();
4892 if (process_strings) {
4893 StringTable::clear_parallel_claimed_index();
4894 }
4895 if (process_symbols) {
4896 SymbolTable::clear_parallel_claimed_index();
4897 }
4898 }
4900 ~G1StringSymbolTableUnlinkTask() {
4901 guarantee(!_process_strings || !_do_in_parallel || StringTable::parallel_claimed_index() >= _initial_string_table_size,
4902 err_msg("claim value "INT32_FORMAT" after unlink less than initial string table size "INT32_FORMAT,
4903 StringTable::parallel_claimed_index(), _initial_string_table_size));
4904 guarantee(!_process_symbols || !_do_in_parallel || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size,
4905 err_msg("claim value "INT32_FORMAT" after unlink less than initial symbol table size "INT32_FORMAT,
4906 SymbolTable::parallel_claimed_index(), _initial_symbol_table_size));
4908 if (G1TraceStringSymbolTableScrubbing) {
4909 gclog_or_tty->print_cr("Cleaned string and symbol table, "
4910 "strings: "SIZE_FORMAT" processed, "SIZE_FORMAT" removed, "
4911 "symbols: "SIZE_FORMAT" processed, "SIZE_FORMAT" removed",
4912 strings_processed(), strings_removed(),
4913 symbols_processed(), symbols_removed());
4914 }
4915 }
4917 void work(uint worker_id) {
4918 if (_do_in_parallel) {
4919 int strings_processed = 0;
4920 int strings_removed = 0;
4921 int symbols_processed = 0;
4922 int symbols_removed = 0;
4923 if (_process_strings) {
4924 StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed);
4925 Atomic::add(strings_processed, &_strings_processed);
4926 Atomic::add(strings_removed, &_strings_removed);
4927 }
4928 if (_process_symbols) {
4929 SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed);
4930 Atomic::add(symbols_processed, &_symbols_processed);
4931 Atomic::add(symbols_removed, &_symbols_removed);
4932 }
4933 } else {
4934 if (_process_strings) {
4935 StringTable::unlink(_is_alive, &_strings_processed, &_strings_removed);
4936 }
4937 if (_process_symbols) {
4938 SymbolTable::unlink(&_symbols_processed, &_symbols_removed);
4939 }
4940 }
4941 }
4943 size_t strings_processed() const { return (size_t)_strings_processed; }
4944 size_t strings_removed() const { return (size_t)_strings_removed; }
4946 size_t symbols_processed() const { return (size_t)_symbols_processed; }
4947 size_t symbols_removed() const { return (size_t)_symbols_removed; }
4948 };
4950 class G1CodeCacheUnloadingTask VALUE_OBJ_CLASS_SPEC {
4951 private:
4952 static Monitor* _lock;
4954 BoolObjectClosure* const _is_alive;
4955 const bool _unloading_occurred;
4956 const uint _num_workers;
4958 // Variables used to claim nmethods.
4959 nmethod* _first_nmethod;
4960 volatile nmethod* _claimed_nmethod;
4962 // The list of nmethods that need to be processed by the second pass.
4963 volatile nmethod* _postponed_list;
4964 volatile uint _num_entered_barrier;
4966 public:
4967 G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) :
4968 _is_alive(is_alive),
4969 _unloading_occurred(unloading_occurred),
4970 _num_workers(num_workers),
4971 _first_nmethod(NULL),
4972 _claimed_nmethod(NULL),
4973 _postponed_list(NULL),
4974 _num_entered_barrier(0)
4975 {
4976 nmethod::increase_unloading_clock();
4977 _first_nmethod = CodeCache::alive_nmethod(CodeCache::first());
4978 _claimed_nmethod = (volatile nmethod*)_first_nmethod;
4979 }
4981 ~G1CodeCacheUnloadingTask() {
4982 CodeCache::verify_clean_inline_caches();
4984 CodeCache::set_needs_cache_clean(false);
4985 guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be");
4987 CodeCache::verify_icholder_relocations();
4988 }
4990 private:
4991 void add_to_postponed_list(nmethod* nm) {
4992 nmethod* old;
4993 do {
4994 old = (nmethod*)_postponed_list;
4995 nm->set_unloading_next(old);
4996 } while ((nmethod*)Atomic::cmpxchg_ptr(nm, &_postponed_list, old) != old);
4997 }
4999 void clean_nmethod(nmethod* nm) {
5000 bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred);
5002 if (postponed) {
5003 // This nmethod referred to an nmethod that has not been cleaned/unloaded yet.
5004 add_to_postponed_list(nm);
5005 }
5007 // Mark that this thread has been cleaned/unloaded.
5008 // After this call, it will be safe to ask if this nmethod was unloaded or not.
5009 nm->set_unloading_clock(nmethod::global_unloading_clock());
5010 }
5012 void clean_nmethod_postponed(nmethod* nm) {
5013 nm->do_unloading_parallel_postponed(_is_alive, _unloading_occurred);
5014 }
5016 static const int MaxClaimNmethods = 16;
5018 void claim_nmethods(nmethod** claimed_nmethods, int *num_claimed_nmethods) {
5019 nmethod* first;
5020 nmethod* last;
5022 do {
5023 *num_claimed_nmethods = 0;
5025 first = last = (nmethod*)_claimed_nmethod;
5027 if (first != NULL) {
5028 for (int i = 0; i < MaxClaimNmethods; i++) {
5029 last = CodeCache::alive_nmethod(CodeCache::next(last));
5031 if (last == NULL) {
5032 break;
5033 }
5035 claimed_nmethods[i] = last;
5036 (*num_claimed_nmethods)++;
5037 }
5038 }
5040 } while ((nmethod*)Atomic::cmpxchg_ptr(last, &_claimed_nmethod, first) != first);
5041 }
5043 nmethod* claim_postponed_nmethod() {
5044 nmethod* claim;
5045 nmethod* next;
5047 do {
5048 claim = (nmethod*)_postponed_list;
5049 if (claim == NULL) {
5050 return NULL;
5051 }
5053 next = claim->unloading_next();
5055 } while ((nmethod*)Atomic::cmpxchg_ptr(next, &_postponed_list, claim) != claim);
5057 return claim;
5058 }
5060 public:
5061 // Mark that we're done with the first pass of nmethod cleaning.
5062 void barrier_mark(uint worker_id) {
5063 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
5064 _num_entered_barrier++;
5065 if (_num_entered_barrier == _num_workers) {
5066 ml.notify_all();
5067 }
5068 }
5070 // See if we have to wait for the other workers to
5071 // finish their first-pass nmethod cleaning work.
5072 void barrier_wait(uint worker_id) {
5073 if (_num_entered_barrier < _num_workers) {
5074 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
5075 while (_num_entered_barrier < _num_workers) {
5076 ml.wait(Mutex::_no_safepoint_check_flag, 0, false);
5077 }
5078 }
5079 }
5081 // Cleaning and unloading of nmethods. Some work has to be postponed
5082 // to the second pass, when we know which nmethods survive.
5083 void work_first_pass(uint worker_id) {
5084 // The first nmethods is claimed by the first worker.
5085 if (worker_id == 0 && _first_nmethod != NULL) {
5086 clean_nmethod(_first_nmethod);
5087 _first_nmethod = NULL;
5088 }
5090 int num_claimed_nmethods;
5091 nmethod* claimed_nmethods[MaxClaimNmethods];
5093 while (true) {
5094 claim_nmethods(claimed_nmethods, &num_claimed_nmethods);
5096 if (num_claimed_nmethods == 0) {
5097 break;
5098 }
5100 for (int i = 0; i < num_claimed_nmethods; i++) {
5101 clean_nmethod(claimed_nmethods[i]);
5102 }
5103 }
5104 }
5106 void work_second_pass(uint worker_id) {
5107 nmethod* nm;
5108 // Take care of postponed nmethods.
5109 while ((nm = claim_postponed_nmethod()) != NULL) {
5110 clean_nmethod_postponed(nm);
5111 }
5112 }
5113 };
5115 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock");
5117 class G1KlassCleaningTask : public StackObj {
5118 BoolObjectClosure* _is_alive;
5119 volatile jint _clean_klass_tree_claimed;
5120 ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator;
5122 public:
5123 G1KlassCleaningTask(BoolObjectClosure* is_alive) :
5124 _is_alive(is_alive),
5125 _clean_klass_tree_claimed(0),
5126 _klass_iterator() {
5127 }
5129 private:
5130 bool claim_clean_klass_tree_task() {
5131 if (_clean_klass_tree_claimed) {
5132 return false;
5133 }
5135 return Atomic::cmpxchg(1, (jint*)&_clean_klass_tree_claimed, 0) == 0;
5136 }
5138 InstanceKlass* claim_next_klass() {
5139 Klass* klass;
5140 do {
5141 klass =_klass_iterator.next_klass();
5142 } while (klass != NULL && !klass->oop_is_instance());
5144 return (InstanceKlass*)klass;
5145 }
5147 public:
5149 void clean_klass(InstanceKlass* ik) {
5150 ik->clean_implementors_list(_is_alive);
5151 ik->clean_method_data(_is_alive);
5153 // G1 specific cleanup work that has
5154 // been moved here to be done in parallel.
5155 ik->clean_dependent_nmethods();
5156 }
5158 void work() {
5159 ResourceMark rm;
5161 // One worker will clean the subklass/sibling klass tree.
5162 if (claim_clean_klass_tree_task()) {
5163 Klass::clean_subklass_tree(_is_alive);
5164 }
5166 // All workers will help cleaning the classes,
5167 InstanceKlass* klass;
5168 while ((klass = claim_next_klass()) != NULL) {
5169 clean_klass(klass);
5170 }
5171 }
5172 };
5174 // To minimize the remark pause times, the tasks below are done in parallel.
5175 class G1ParallelCleaningTask : public AbstractGangTask {
5176 private:
5177 G1StringSymbolTableUnlinkTask _string_symbol_task;
5178 G1CodeCacheUnloadingTask _code_cache_task;
5179 G1KlassCleaningTask _klass_cleaning_task;
5181 public:
5182 // The constructor is run in the VMThread.
5183 G1ParallelCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, uint num_workers, bool unloading_occurred) :
5184 AbstractGangTask("Parallel Cleaning"),
5185 _string_symbol_task(is_alive, process_strings, process_symbols),
5186 _code_cache_task(num_workers, is_alive, unloading_occurred),
5187 _klass_cleaning_task(is_alive) {
5188 }
5190 // The parallel work done by all worker threads.
5191 void work(uint worker_id) {
5192 // Do first pass of code cache cleaning.
5193 _code_cache_task.work_first_pass(worker_id);
5195 // Let the threads mark that the first pass is done.
5196 _code_cache_task.barrier_mark(worker_id);
5198 // Clean the Strings and Symbols.
5199 _string_symbol_task.work(worker_id);
5201 // Wait for all workers to finish the first code cache cleaning pass.
5202 _code_cache_task.barrier_wait(worker_id);
5204 // Do the second code cache cleaning work, which realize on
5205 // the liveness information gathered during the first pass.
5206 _code_cache_task.work_second_pass(worker_id);
5208 // Clean all klasses that were not unloaded.
5209 _klass_cleaning_task.work();
5210 }
5211 };
5214 void G1CollectedHeap::parallel_cleaning(BoolObjectClosure* is_alive,
5215 bool process_strings,
5216 bool process_symbols,
5217 bool class_unloading_occurred) {
5218 uint n_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
5219 workers()->active_workers() : 1);
5221 G1ParallelCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols,
5222 n_workers, class_unloading_occurred);
5223 if (G1CollectedHeap::use_parallel_gc_threads()) {
5224 set_par_threads(n_workers);
5225 workers()->run_task(&g1_unlink_task);
5226 set_par_threads(0);
5227 } else {
5228 g1_unlink_task.work(0);
5229 }
5230 }
5232 void G1CollectedHeap::unlink_string_and_symbol_table(BoolObjectClosure* is_alive,
5233 bool process_strings, bool process_symbols) {
5234 {
5235 uint n_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
5236 _g1h->workers()->active_workers() : 1);
5237 G1StringSymbolTableUnlinkTask g1_unlink_task(is_alive, process_strings, process_symbols);
5238 if (G1CollectedHeap::use_parallel_gc_threads()) {
5239 set_par_threads(n_workers);
5240 workers()->run_task(&g1_unlink_task);
5241 set_par_threads(0);
5242 } else {
5243 g1_unlink_task.work(0);
5244 }
5245 }
5247 if (G1StringDedup::is_enabled()) {
5248 G1StringDedup::unlink(is_alive);
5249 }
5250 }
5252 class G1RedirtyLoggedCardsTask : public AbstractGangTask {
5253 private:
5254 DirtyCardQueueSet* _queue;
5255 public:
5256 G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue) : AbstractGangTask("Redirty Cards"), _queue(queue) { }
5258 virtual void work(uint worker_id) {
5259 double start_time = os::elapsedTime();
5261 RedirtyLoggedCardTableEntryClosure cl;
5262 if (G1CollectedHeap::heap()->use_parallel_gc_threads()) {
5263 _queue->par_apply_closure_to_all_completed_buffers(&cl);
5264 } else {
5265 _queue->apply_closure_to_all_completed_buffers(&cl);
5266 }
5268 G1GCPhaseTimes* timer = G1CollectedHeap::heap()->g1_policy()->phase_times();
5269 timer->record_redirty_logged_cards_time_ms(worker_id, (os::elapsedTime() - start_time) * 1000.0);
5270 timer->record_redirty_logged_cards_processed_cards(worker_id, cl.num_processed());
5271 }
5272 };
5274 void G1CollectedHeap::redirty_logged_cards() {
5275 guarantee(G1DeferredRSUpdate, "Must only be called when using deferred RS updates.");
5276 double redirty_logged_cards_start = os::elapsedTime();
5278 uint n_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
5279 _g1h->workers()->active_workers() : 1);
5281 G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set());
5282 dirty_card_queue_set().reset_for_par_iteration();
5283 if (use_parallel_gc_threads()) {
5284 set_par_threads(n_workers);
5285 workers()->run_task(&redirty_task);
5286 set_par_threads(0);
5287 } else {
5288 redirty_task.work(0);
5289 }
5291 DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set();
5292 dcq.merge_bufferlists(&dirty_card_queue_set());
5293 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
5295 g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0);
5296 }
5298 // Weak Reference Processing support
5300 // An always "is_alive" closure that is used to preserve referents.
5301 // If the object is non-null then it's alive. Used in the preservation
5302 // of referent objects that are pointed to by reference objects
5303 // discovered by the CM ref processor.
5304 class G1AlwaysAliveClosure: public BoolObjectClosure {
5305 G1CollectedHeap* _g1;
5306 public:
5307 G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
5308 bool do_object_b(oop p) {
5309 if (p != NULL) {
5310 return true;
5311 }
5312 return false;
5313 }
5314 };
5316 bool G1STWIsAliveClosure::do_object_b(oop p) {
5317 // An object is reachable if it is outside the collection set,
5318 // or is inside and copied.
5319 return !_g1->obj_in_cs(p) || p->is_forwarded();
5320 }
5322 // Non Copying Keep Alive closure
5323 class G1KeepAliveClosure: public OopClosure {
5324 G1CollectedHeap* _g1;
5325 public:
5326 G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
5327 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
5328 void do_oop(oop* p) {
5329 oop obj = *p;
5331 G1CollectedHeap::in_cset_state_t cset_state = _g1->in_cset_state(obj);
5332 if (obj == NULL || cset_state == G1CollectedHeap::InNeither) {
5333 return;
5334 }
5335 if (cset_state == G1CollectedHeap::InCSet) {
5336 assert( obj->is_forwarded(), "invariant" );
5337 *p = obj->forwardee();
5338 } else {
5339 assert(!obj->is_forwarded(), "invariant" );
5340 assert(cset_state == G1CollectedHeap::IsHumongous,
5341 err_msg("Only allowed InCSet state is IsHumongous, but is %d", cset_state));
5342 _g1->set_humongous_is_live(obj);
5343 }
5344 }
5345 };
5347 // Copying Keep Alive closure - can be called from both
5348 // serial and parallel code as long as different worker
5349 // threads utilize different G1ParScanThreadState instances
5350 // and different queues.
5352 class G1CopyingKeepAliveClosure: public OopClosure {
5353 G1CollectedHeap* _g1h;
5354 OopClosure* _copy_non_heap_obj_cl;
5355 G1ParScanThreadState* _par_scan_state;
5357 public:
5358 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
5359 OopClosure* non_heap_obj_cl,
5360 G1ParScanThreadState* pss):
5361 _g1h(g1h),
5362 _copy_non_heap_obj_cl(non_heap_obj_cl),
5363 _par_scan_state(pss)
5364 {}
5366 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
5367 virtual void do_oop( oop* p) { do_oop_work(p); }
5369 template <class T> void do_oop_work(T* p) {
5370 oop obj = oopDesc::load_decode_heap_oop(p);
5372 if (_g1h->is_in_cset_or_humongous(obj)) {
5373 // If the referent object has been forwarded (either copied
5374 // to a new location or to itself in the event of an
5375 // evacuation failure) then we need to update the reference
5376 // field and, if both reference and referent are in the G1
5377 // heap, update the RSet for the referent.
5378 //
5379 // If the referent has not been forwarded then we have to keep
5380 // it alive by policy. Therefore we have copy the referent.
5381 //
5382 // If the reference field is in the G1 heap then we can push
5383 // on the PSS queue. When the queue is drained (after each
5384 // phase of reference processing) the object and it's followers
5385 // will be copied, the reference field set to point to the
5386 // new location, and the RSet updated. Otherwise we need to
5387 // use the the non-heap or metadata closures directly to copy
5388 // the referent object and update the pointer, while avoiding
5389 // updating the RSet.
5391 if (_g1h->is_in_g1_reserved(p)) {
5392 _par_scan_state->push_on_queue(p);
5393 } else {
5394 assert(!Metaspace::contains((const void*)p),
5395 err_msg("Unexpectedly found a pointer from metadata: "
5396 PTR_FORMAT, p));
5397 _copy_non_heap_obj_cl->do_oop(p);
5398 }
5399 }
5400 }
5401 };
5403 // Serial drain queue closure. Called as the 'complete_gc'
5404 // closure for each discovered list in some of the
5405 // reference processing phases.
5407 class G1STWDrainQueueClosure: public VoidClosure {
5408 protected:
5409 G1CollectedHeap* _g1h;
5410 G1ParScanThreadState* _par_scan_state;
5412 G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
5414 public:
5415 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
5416 _g1h(g1h),
5417 _par_scan_state(pss)
5418 { }
5420 void do_void() {
5421 G1ParScanThreadState* const pss = par_scan_state();
5422 pss->trim_queue();
5423 }
5424 };
5426 // Parallel Reference Processing closures
5428 // Implementation of AbstractRefProcTaskExecutor for parallel reference
5429 // processing during G1 evacuation pauses.
5431 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
5432 private:
5433 G1CollectedHeap* _g1h;
5434 RefToScanQueueSet* _queues;
5435 FlexibleWorkGang* _workers;
5436 int _active_workers;
5438 public:
5439 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
5440 FlexibleWorkGang* workers,
5441 RefToScanQueueSet *task_queues,
5442 int n_workers) :
5443 _g1h(g1h),
5444 _queues(task_queues),
5445 _workers(workers),
5446 _active_workers(n_workers)
5447 {
5448 assert(n_workers > 0, "shouldn't call this otherwise");
5449 }
5451 // Executes the given task using concurrent marking worker threads.
5452 virtual void execute(ProcessTask& task);
5453 virtual void execute(EnqueueTask& task);
5454 };
5456 // Gang task for possibly parallel reference processing
5458 class G1STWRefProcTaskProxy: public AbstractGangTask {
5459 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
5460 ProcessTask& _proc_task;
5461 G1CollectedHeap* _g1h;
5462 RefToScanQueueSet *_task_queues;
5463 ParallelTaskTerminator* _terminator;
5465 public:
5466 G1STWRefProcTaskProxy(ProcessTask& proc_task,
5467 G1CollectedHeap* g1h,
5468 RefToScanQueueSet *task_queues,
5469 ParallelTaskTerminator* terminator) :
5470 AbstractGangTask("Process reference objects in parallel"),
5471 _proc_task(proc_task),
5472 _g1h(g1h),
5473 _task_queues(task_queues),
5474 _terminator(terminator)
5475 {}
5477 virtual void work(uint worker_id) {
5478 // The reference processing task executed by a single worker.
5479 ResourceMark rm;
5480 HandleMark hm;
5482 G1STWIsAliveClosure is_alive(_g1h);
5484 G1ParScanThreadState pss(_g1h, worker_id, NULL);
5485 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5487 pss.set_evac_failure_closure(&evac_failure_cl);
5489 G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL);
5491 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5493 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5495 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5496 // We also need to mark copied objects.
5497 copy_non_heap_cl = ©_mark_non_heap_cl;
5498 }
5500 // Keep alive closure.
5501 G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, &pss);
5503 // Complete GC closure
5504 G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _task_queues, _terminator);
5506 // Call the reference processing task's work routine.
5507 _proc_task.work(worker_id, is_alive, keep_alive, drain_queue);
5509 // Note we cannot assert that the refs array is empty here as not all
5510 // of the processing tasks (specifically phase2 - pp2_work) execute
5511 // the complete_gc closure (which ordinarily would drain the queue) so
5512 // the queue may not be empty.
5513 }
5514 };
5516 // Driver routine for parallel reference processing.
5517 // Creates an instance of the ref processing gang
5518 // task and has the worker threads execute it.
5519 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) {
5520 assert(_workers != NULL, "Need parallel worker threads.");
5522 ParallelTaskTerminator terminator(_active_workers, _queues);
5523 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _queues, &terminator);
5525 _g1h->set_par_threads(_active_workers);
5526 _workers->run_task(&proc_task_proxy);
5527 _g1h->set_par_threads(0);
5528 }
5530 // Gang task for parallel reference enqueueing.
5532 class G1STWRefEnqueueTaskProxy: public AbstractGangTask {
5533 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
5534 EnqueueTask& _enq_task;
5536 public:
5537 G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) :
5538 AbstractGangTask("Enqueue reference objects in parallel"),
5539 _enq_task(enq_task)
5540 { }
5542 virtual void work(uint worker_id) {
5543 _enq_task.work(worker_id);
5544 }
5545 };
5547 // Driver routine for parallel reference enqueueing.
5548 // Creates an instance of the ref enqueueing gang
5549 // task and has the worker threads execute it.
5551 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
5552 assert(_workers != NULL, "Need parallel worker threads.");
5554 G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task);
5556 _g1h->set_par_threads(_active_workers);
5557 _workers->run_task(&enq_task_proxy);
5558 _g1h->set_par_threads(0);
5559 }
5561 // End of weak reference support closures
5563 // Abstract task used to preserve (i.e. copy) any referent objects
5564 // that are in the collection set and are pointed to by reference
5565 // objects discovered by the CM ref processor.
5567 class G1ParPreserveCMReferentsTask: public AbstractGangTask {
5568 protected:
5569 G1CollectedHeap* _g1h;
5570 RefToScanQueueSet *_queues;
5571 ParallelTaskTerminator _terminator;
5572 uint _n_workers;
5574 public:
5575 G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h,int workers, RefToScanQueueSet *task_queues) :
5576 AbstractGangTask("ParPreserveCMReferents"),
5577 _g1h(g1h),
5578 _queues(task_queues),
5579 _terminator(workers, _queues),
5580 _n_workers(workers)
5581 { }
5583 void work(uint worker_id) {
5584 ResourceMark rm;
5585 HandleMark hm;
5587 G1ParScanThreadState pss(_g1h, worker_id, NULL);
5588 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5590 pss.set_evac_failure_closure(&evac_failure_cl);
5592 assert(pss.queue_is_empty(), "both queue and overflow should be empty");
5594 G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL);
5596 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5598 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5600 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5601 // We also need to mark copied objects.
5602 copy_non_heap_cl = ©_mark_non_heap_cl;
5603 }
5605 // Is alive closure
5606 G1AlwaysAliveClosure always_alive(_g1h);
5608 // Copying keep alive closure. Applied to referent objects that need
5609 // to be copied.
5610 G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, &pss);
5612 ReferenceProcessor* rp = _g1h->ref_processor_cm();
5614 uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q();
5615 uint stride = MIN2(MAX2(_n_workers, 1U), limit);
5617 // limit is set using max_num_q() - which was set using ParallelGCThreads.
5618 // So this must be true - but assert just in case someone decides to
5619 // change the worker ids.
5620 assert(0 <= worker_id && worker_id < limit, "sanity");
5621 assert(!rp->discovery_is_atomic(), "check this code");
5623 // Select discovered lists [i, i+stride, i+2*stride,...,limit)
5624 for (uint idx = worker_id; idx < limit; idx += stride) {
5625 DiscoveredList& ref_list = rp->discovered_refs()[idx];
5627 DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive);
5628 while (iter.has_next()) {
5629 // Since discovery is not atomic for the CM ref processor, we
5630 // can see some null referent objects.
5631 iter.load_ptrs(DEBUG_ONLY(true));
5632 oop ref = iter.obj();
5634 // This will filter nulls.
5635 if (iter.is_referent_alive()) {
5636 iter.make_referent_alive();
5637 }
5638 iter.move_to_next();
5639 }
5640 }
5642 // Drain the queue - which may cause stealing
5643 G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _queues, &_terminator);
5644 drain_queue.do_void();
5645 // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure
5646 assert(pss.queue_is_empty(), "should be");
5647 }
5648 };
5650 // Weak Reference processing during an evacuation pause (part 1).
5651 void G1CollectedHeap::process_discovered_references(uint no_of_gc_workers) {
5652 double ref_proc_start = os::elapsedTime();
5654 ReferenceProcessor* rp = _ref_processor_stw;
5655 assert(rp->discovery_enabled(), "should have been enabled");
5657 // Any reference objects, in the collection set, that were 'discovered'
5658 // by the CM ref processor should have already been copied (either by
5659 // applying the external root copy closure to the discovered lists, or
5660 // by following an RSet entry).
5661 //
5662 // But some of the referents, that are in the collection set, that these
5663 // reference objects point to may not have been copied: the STW ref
5664 // processor would have seen that the reference object had already
5665 // been 'discovered' and would have skipped discovering the reference,
5666 // but would not have treated the reference object as a regular oop.
5667 // As a result the copy closure would not have been applied to the
5668 // referent object.
5669 //
5670 // We need to explicitly copy these referent objects - the references
5671 // will be processed at the end of remarking.
5672 //
5673 // We also need to do this copying before we process the reference
5674 // objects discovered by the STW ref processor in case one of these
5675 // referents points to another object which is also referenced by an
5676 // object discovered by the STW ref processor.
5678 assert(!G1CollectedHeap::use_parallel_gc_threads() ||
5679 no_of_gc_workers == workers()->active_workers(),
5680 "Need to reset active GC workers");
5682 set_par_threads(no_of_gc_workers);
5683 G1ParPreserveCMReferentsTask keep_cm_referents(this,
5684 no_of_gc_workers,
5685 _task_queues);
5687 if (G1CollectedHeap::use_parallel_gc_threads()) {
5688 workers()->run_task(&keep_cm_referents);
5689 } else {
5690 keep_cm_referents.work(0);
5691 }
5693 set_par_threads(0);
5695 // Closure to test whether a referent is alive.
5696 G1STWIsAliveClosure is_alive(this);
5698 // Even when parallel reference processing is enabled, the processing
5699 // of JNI refs is serial and performed serially by the current thread
5700 // rather than by a worker. The following PSS will be used for processing
5701 // JNI refs.
5703 // Use only a single queue for this PSS.
5704 G1ParScanThreadState pss(this, 0, NULL);
5706 // We do not embed a reference processor in the copying/scanning
5707 // closures while we're actually processing the discovered
5708 // reference objects.
5709 G1ParScanHeapEvacFailureClosure evac_failure_cl(this, &pss, NULL);
5711 pss.set_evac_failure_closure(&evac_failure_cl);
5713 assert(pss.queue_is_empty(), "pre-condition");
5715 G1ParScanExtRootClosure only_copy_non_heap_cl(this, &pss, NULL);
5717 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(this, &pss, NULL);
5719 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5721 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5722 // We also need to mark copied objects.
5723 copy_non_heap_cl = ©_mark_non_heap_cl;
5724 }
5726 // Keep alive closure.
5727 G1CopyingKeepAliveClosure keep_alive(this, copy_non_heap_cl, &pss);
5729 // Serial Complete GC closure
5730 G1STWDrainQueueClosure drain_queue(this, &pss);
5732 // Setup the soft refs policy...
5733 rp->setup_policy(false);
5735 ReferenceProcessorStats stats;
5736 if (!rp->processing_is_mt()) {
5737 // Serial reference processing...
5738 stats = rp->process_discovered_references(&is_alive,
5739 &keep_alive,
5740 &drain_queue,
5741 NULL,
5742 _gc_timer_stw,
5743 _gc_tracer_stw->gc_id());
5744 } else {
5745 // Parallel reference processing
5746 assert(rp->num_q() == no_of_gc_workers, "sanity");
5747 assert(no_of_gc_workers <= rp->max_num_q(), "sanity");
5749 G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers);
5750 stats = rp->process_discovered_references(&is_alive,
5751 &keep_alive,
5752 &drain_queue,
5753 &par_task_executor,
5754 _gc_timer_stw,
5755 _gc_tracer_stw->gc_id());
5756 }
5758 _gc_tracer_stw->report_gc_reference_stats(stats);
5760 // We have completed copying any necessary live referent objects.
5761 assert(pss.queue_is_empty(), "both queue and overflow should be empty");
5763 double ref_proc_time = os::elapsedTime() - ref_proc_start;
5764 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
5765 }
5767 // Weak Reference processing during an evacuation pause (part 2).
5768 void G1CollectedHeap::enqueue_discovered_references(uint no_of_gc_workers) {
5769 double ref_enq_start = os::elapsedTime();
5771 ReferenceProcessor* rp = _ref_processor_stw;
5772 assert(!rp->discovery_enabled(), "should have been disabled as part of processing");
5774 // Now enqueue any remaining on the discovered lists on to
5775 // the pending list.
5776 if (!rp->processing_is_mt()) {
5777 // Serial reference processing...
5778 rp->enqueue_discovered_references();
5779 } else {
5780 // Parallel reference enqueueing
5782 assert(no_of_gc_workers == workers()->active_workers(),
5783 "Need to reset active workers");
5784 assert(rp->num_q() == no_of_gc_workers, "sanity");
5785 assert(no_of_gc_workers <= rp->max_num_q(), "sanity");
5787 G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers);
5788 rp->enqueue_discovered_references(&par_task_executor);
5789 }
5791 rp->verify_no_references_recorded();
5792 assert(!rp->discovery_enabled(), "should have been disabled");
5794 // FIXME
5795 // CM's reference processing also cleans up the string and symbol tables.
5796 // Should we do that here also? We could, but it is a serial operation
5797 // and could significantly increase the pause time.
5799 double ref_enq_time = os::elapsedTime() - ref_enq_start;
5800 g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0);
5801 }
5803 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info) {
5804 _expand_heap_after_alloc_failure = true;
5805 _evacuation_failed = false;
5807 // Should G1EvacuationFailureALot be in effect for this GC?
5808 NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();)
5810 g1_rem_set()->prepare_for_oops_into_collection_set_do();
5812 // Disable the hot card cache.
5813 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
5814 hot_card_cache->reset_hot_cache_claimed_index();
5815 hot_card_cache->set_use_cache(false);
5817 uint n_workers;
5818 if (G1CollectedHeap::use_parallel_gc_threads()) {
5819 n_workers =
5820 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
5821 workers()->active_workers(),
5822 Threads::number_of_non_daemon_threads());
5823 assert(UseDynamicNumberOfGCThreads ||
5824 n_workers == workers()->total_workers(),
5825 "If not dynamic should be using all the workers");
5826 workers()->set_active_workers(n_workers);
5827 set_par_threads(n_workers);
5828 } else {
5829 assert(n_par_threads() == 0,
5830 "Should be the original non-parallel value");
5831 n_workers = 1;
5832 }
5834 G1ParTask g1_par_task(this, _task_queues);
5836 init_for_evac_failure(NULL);
5838 rem_set()->prepare_for_younger_refs_iterate(true);
5840 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
5841 double start_par_time_sec = os::elapsedTime();
5842 double end_par_time_sec;
5844 {
5845 StrongRootsScope srs(this);
5846 // InitialMark needs claim bits to keep track of the marked-through CLDs.
5847 if (g1_policy()->during_initial_mark_pause()) {
5848 ClassLoaderDataGraph::clear_claimed_marks();
5849 }
5851 if (G1CollectedHeap::use_parallel_gc_threads()) {
5852 // The individual threads will set their evac-failure closures.
5853 if (ParallelGCVerbose) G1ParScanThreadState::print_termination_stats_hdr();
5854 // These tasks use ShareHeap::_process_strong_tasks
5855 assert(UseDynamicNumberOfGCThreads ||
5856 workers()->active_workers() == workers()->total_workers(),
5857 "If not dynamic should be using all the workers");
5858 workers()->run_task(&g1_par_task);
5859 } else {
5860 g1_par_task.set_for_termination(n_workers);
5861 g1_par_task.work(0);
5862 }
5863 end_par_time_sec = os::elapsedTime();
5865 // Closing the inner scope will execute the destructor
5866 // for the StrongRootsScope object. We record the current
5867 // elapsed time before closing the scope so that time
5868 // taken for the SRS destructor is NOT included in the
5869 // reported parallel time.
5870 }
5872 double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0;
5873 g1_policy()->phase_times()->record_par_time(par_time_ms);
5875 double code_root_fixup_time_ms =
5876 (os::elapsedTime() - end_par_time_sec) * 1000.0;
5877 g1_policy()->phase_times()->record_code_root_fixup_time(code_root_fixup_time_ms);
5879 set_par_threads(0);
5881 // Process any discovered reference objects - we have
5882 // to do this _before_ we retire the GC alloc regions
5883 // as we may have to copy some 'reachable' referent
5884 // objects (and their reachable sub-graphs) that were
5885 // not copied during the pause.
5886 process_discovered_references(n_workers);
5888 // Weak root processing.
5889 {
5890 G1STWIsAliveClosure is_alive(this);
5891 G1KeepAliveClosure keep_alive(this);
5892 JNIHandles::weak_oops_do(&is_alive, &keep_alive);
5893 if (G1StringDedup::is_enabled()) {
5894 G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive);
5895 }
5896 }
5898 _allocator->release_gc_alloc_regions(n_workers, evacuation_info);
5899 g1_rem_set()->cleanup_after_oops_into_collection_set_do();
5901 // Reset and re-enable the hot card cache.
5902 // Note the counts for the cards in the regions in the
5903 // collection set are reset when the collection set is freed.
5904 hot_card_cache->reset_hot_cache();
5905 hot_card_cache->set_use_cache(true);
5907 // Migrate the strong code roots attached to each region in
5908 // the collection set. Ideally we would like to do this
5909 // after we have finished the scanning/evacuation of the
5910 // strong code roots for a particular heap region.
5911 migrate_strong_code_roots();
5913 purge_code_root_memory();
5915 if (g1_policy()->during_initial_mark_pause()) {
5916 // Reset the claim values set during marking the strong code roots
5917 reset_heap_region_claim_values();
5918 }
5920 finalize_for_evac_failure();
5922 if (evacuation_failed()) {
5923 remove_self_forwarding_pointers();
5925 // Reset the G1EvacuationFailureALot counters and flags
5926 // Note: the values are reset only when an actual
5927 // evacuation failure occurs.
5928 NOT_PRODUCT(reset_evacuation_should_fail();)
5929 }
5931 // Enqueue any remaining references remaining on the STW
5932 // reference processor's discovered lists. We need to do
5933 // this after the card table is cleaned (and verified) as
5934 // the act of enqueueing entries on to the pending list
5935 // will log these updates (and dirty their associated
5936 // cards). We need these updates logged to update any
5937 // RSets.
5938 enqueue_discovered_references(n_workers);
5940 if (G1DeferredRSUpdate) {
5941 redirty_logged_cards();
5942 }
5943 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
5944 }
5946 void G1CollectedHeap::free_region(HeapRegion* hr,
5947 FreeRegionList* free_list,
5948 bool par,
5949 bool locked) {
5950 assert(!hr->isHumongous(), "this is only for non-humongous regions");
5951 assert(!hr->is_empty(), "the region should not be empty");
5952 assert(_hrm.is_available(hr->hrm_index()), "region should be committed");
5953 assert(free_list != NULL, "pre-condition");
5955 if (G1VerifyBitmaps) {
5956 MemRegion mr(hr->bottom(), hr->end());
5957 concurrent_mark()->clearRangePrevBitmap(mr);
5958 }
5960 // Clear the card counts for this region.
5961 // Note: we only need to do this if the region is not young
5962 // (since we don't refine cards in young regions).
5963 if (!hr->is_young()) {
5964 _cg1r->hot_card_cache()->reset_card_counts(hr);
5965 }
5966 hr->hr_clear(par, true /* clear_space */, locked /* locked */);
5967 free_list->add_ordered(hr);
5968 }
5970 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
5971 FreeRegionList* free_list,
5972 bool par) {
5973 assert(hr->startsHumongous(), "this is only for starts humongous regions");
5974 assert(free_list != NULL, "pre-condition");
5976 size_t hr_capacity = hr->capacity();
5977 // We need to read this before we make the region non-humongous,
5978 // otherwise the information will be gone.
5979 uint last_index = hr->last_hc_index();
5980 hr->set_notHumongous();
5981 free_region(hr, free_list, par);
5983 uint i = hr->hrm_index() + 1;
5984 while (i < last_index) {
5985 HeapRegion* curr_hr = region_at(i);
5986 assert(curr_hr->continuesHumongous(), "invariant");
5987 curr_hr->set_notHumongous();
5988 free_region(curr_hr, free_list, par);
5989 i += 1;
5990 }
5991 }
5993 void G1CollectedHeap::remove_from_old_sets(const HeapRegionSetCount& old_regions_removed,
5994 const HeapRegionSetCount& humongous_regions_removed) {
5995 if (old_regions_removed.length() > 0 || humongous_regions_removed.length() > 0) {
5996 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
5997 _old_set.bulk_remove(old_regions_removed);
5998 _humongous_set.bulk_remove(humongous_regions_removed);
5999 }
6001 }
6003 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) {
6004 assert(list != NULL, "list can't be null");
6005 if (!list->is_empty()) {
6006 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
6007 _hrm.insert_list_into_free_list(list);
6008 }
6009 }
6011 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) {
6012 _allocator->decrease_used(bytes);
6013 }
6015 class G1ParCleanupCTTask : public AbstractGangTask {
6016 G1SATBCardTableModRefBS* _ct_bs;
6017 G1CollectedHeap* _g1h;
6018 HeapRegion* volatile _su_head;
6019 public:
6020 G1ParCleanupCTTask(G1SATBCardTableModRefBS* ct_bs,
6021 G1CollectedHeap* g1h) :
6022 AbstractGangTask("G1 Par Cleanup CT Task"),
6023 _ct_bs(ct_bs), _g1h(g1h) { }
6025 void work(uint worker_id) {
6026 HeapRegion* r;
6027 while (r = _g1h->pop_dirty_cards_region()) {
6028 clear_cards(r);
6029 }
6030 }
6032 void clear_cards(HeapRegion* r) {
6033 // Cards of the survivors should have already been dirtied.
6034 if (!r->is_survivor()) {
6035 _ct_bs->clear(MemRegion(r->bottom(), r->end()));
6036 }
6037 }
6038 };
6040 #ifndef PRODUCT
6041 class G1VerifyCardTableCleanup: public HeapRegionClosure {
6042 G1CollectedHeap* _g1h;
6043 G1SATBCardTableModRefBS* _ct_bs;
6044 public:
6045 G1VerifyCardTableCleanup(G1CollectedHeap* g1h, G1SATBCardTableModRefBS* ct_bs)
6046 : _g1h(g1h), _ct_bs(ct_bs) { }
6047 virtual bool doHeapRegion(HeapRegion* r) {
6048 if (r->is_survivor()) {
6049 _g1h->verify_dirty_region(r);
6050 } else {
6051 _g1h->verify_not_dirty_region(r);
6052 }
6053 return false;
6054 }
6055 };
6057 void G1CollectedHeap::verify_not_dirty_region(HeapRegion* hr) {
6058 // All of the region should be clean.
6059 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
6060 MemRegion mr(hr->bottom(), hr->end());
6061 ct_bs->verify_not_dirty_region(mr);
6062 }
6064 void G1CollectedHeap::verify_dirty_region(HeapRegion* hr) {
6065 // We cannot guarantee that [bottom(),end()] is dirty. Threads
6066 // dirty allocated blocks as they allocate them. The thread that
6067 // retires each region and replaces it with a new one will do a
6068 // maximal allocation to fill in [pre_dummy_top(),end()] but will
6069 // not dirty that area (one less thing to have to do while holding
6070 // a lock). So we can only verify that [bottom(),pre_dummy_top()]
6071 // is dirty.
6072 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
6073 MemRegion mr(hr->bottom(), hr->pre_dummy_top());
6074 if (hr->is_young()) {
6075 ct_bs->verify_g1_young_region(mr);
6076 } else {
6077 ct_bs->verify_dirty_region(mr);
6078 }
6079 }
6081 void G1CollectedHeap::verify_dirty_young_list(HeapRegion* head) {
6082 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
6083 for (HeapRegion* hr = head; hr != NULL; hr = hr->get_next_young_region()) {
6084 verify_dirty_region(hr);
6085 }
6086 }
6088 void G1CollectedHeap::verify_dirty_young_regions() {
6089 verify_dirty_young_list(_young_list->first_region());
6090 }
6092 bool G1CollectedHeap::verify_no_bits_over_tams(const char* bitmap_name, CMBitMapRO* bitmap,
6093 HeapWord* tams, HeapWord* end) {
6094 guarantee(tams <= end,
6095 err_msg("tams: "PTR_FORMAT" end: "PTR_FORMAT, tams, end));
6096 HeapWord* result = bitmap->getNextMarkedWordAddress(tams, end);
6097 if (result < end) {
6098 gclog_or_tty->cr();
6099 gclog_or_tty->print_cr("## wrong marked address on %s bitmap: "PTR_FORMAT,
6100 bitmap_name, result);
6101 gclog_or_tty->print_cr("## %s tams: "PTR_FORMAT" end: "PTR_FORMAT,
6102 bitmap_name, tams, end);
6103 return false;
6104 }
6105 return true;
6106 }
6108 bool G1CollectedHeap::verify_bitmaps(const char* caller, HeapRegion* hr) {
6109 CMBitMapRO* prev_bitmap = concurrent_mark()->prevMarkBitMap();
6110 CMBitMapRO* next_bitmap = (CMBitMapRO*) concurrent_mark()->nextMarkBitMap();
6112 HeapWord* bottom = hr->bottom();
6113 HeapWord* ptams = hr->prev_top_at_mark_start();
6114 HeapWord* ntams = hr->next_top_at_mark_start();
6115 HeapWord* end = hr->end();
6117 bool res_p = verify_no_bits_over_tams("prev", prev_bitmap, ptams, end);
6119 bool res_n = true;
6120 // We reset mark_in_progress() before we reset _cmThread->in_progress() and in this window
6121 // we do the clearing of the next bitmap concurrently. Thus, we can not verify the bitmap
6122 // if we happen to be in that state.
6123 if (mark_in_progress() || !_cmThread->in_progress()) {
6124 res_n = verify_no_bits_over_tams("next", next_bitmap, ntams, end);
6125 }
6126 if (!res_p || !res_n) {
6127 gclog_or_tty->print_cr("#### Bitmap verification failed for "HR_FORMAT,
6128 HR_FORMAT_PARAMS(hr));
6129 gclog_or_tty->print_cr("#### Caller: %s", caller);
6130 return false;
6131 }
6132 return true;
6133 }
6135 void G1CollectedHeap::check_bitmaps(const char* caller, HeapRegion* hr) {
6136 if (!G1VerifyBitmaps) return;
6138 guarantee(verify_bitmaps(caller, hr), "bitmap verification");
6139 }
6141 class G1VerifyBitmapClosure : public HeapRegionClosure {
6142 private:
6143 const char* _caller;
6144 G1CollectedHeap* _g1h;
6145 bool _failures;
6147 public:
6148 G1VerifyBitmapClosure(const char* caller, G1CollectedHeap* g1h) :
6149 _caller(caller), _g1h(g1h), _failures(false) { }
6151 bool failures() { return _failures; }
6153 virtual bool doHeapRegion(HeapRegion* hr) {
6154 if (hr->continuesHumongous()) return false;
6156 bool result = _g1h->verify_bitmaps(_caller, hr);
6157 if (!result) {
6158 _failures = true;
6159 }
6160 return false;
6161 }
6162 };
6164 void G1CollectedHeap::check_bitmaps(const char* caller) {
6165 if (!G1VerifyBitmaps) return;
6167 G1VerifyBitmapClosure cl(caller, this);
6168 heap_region_iterate(&cl);
6169 guarantee(!cl.failures(), "bitmap verification");
6170 }
6171 #endif // PRODUCT
6173 void G1CollectedHeap::cleanUpCardTable() {
6174 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
6175 double start = os::elapsedTime();
6177 {
6178 // Iterate over the dirty cards region list.
6179 G1ParCleanupCTTask cleanup_task(ct_bs, this);
6181 if (G1CollectedHeap::use_parallel_gc_threads()) {
6182 set_par_threads();
6183 workers()->run_task(&cleanup_task);
6184 set_par_threads(0);
6185 } else {
6186 while (_dirty_cards_region_list) {
6187 HeapRegion* r = _dirty_cards_region_list;
6188 cleanup_task.clear_cards(r);
6189 _dirty_cards_region_list = r->get_next_dirty_cards_region();
6190 if (_dirty_cards_region_list == r) {
6191 // The last region.
6192 _dirty_cards_region_list = NULL;
6193 }
6194 r->set_next_dirty_cards_region(NULL);
6195 }
6196 }
6197 #ifndef PRODUCT
6198 if (G1VerifyCTCleanup || VerifyAfterGC) {
6199 G1VerifyCardTableCleanup cleanup_verifier(this, ct_bs);
6200 heap_region_iterate(&cleanup_verifier);
6201 }
6202 #endif
6203 }
6205 double elapsed = os::elapsedTime() - start;
6206 g1_policy()->phase_times()->record_clear_ct_time(elapsed * 1000.0);
6207 }
6209 void G1CollectedHeap::free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info) {
6210 size_t pre_used = 0;
6211 FreeRegionList local_free_list("Local List for CSet Freeing");
6213 double young_time_ms = 0.0;
6214 double non_young_time_ms = 0.0;
6216 // Since the collection set is a superset of the the young list,
6217 // all we need to do to clear the young list is clear its
6218 // head and length, and unlink any young regions in the code below
6219 _young_list->clear();
6221 G1CollectorPolicy* policy = g1_policy();
6223 double start_sec = os::elapsedTime();
6224 bool non_young = true;
6226 HeapRegion* cur = cs_head;
6227 int age_bound = -1;
6228 size_t rs_lengths = 0;
6230 while (cur != NULL) {
6231 assert(!is_on_master_free_list(cur), "sanity");
6232 if (non_young) {
6233 if (cur->is_young()) {
6234 double end_sec = os::elapsedTime();
6235 double elapsed_ms = (end_sec - start_sec) * 1000.0;
6236 non_young_time_ms += elapsed_ms;
6238 start_sec = os::elapsedTime();
6239 non_young = false;
6240 }
6241 } else {
6242 if (!cur->is_young()) {
6243 double end_sec = os::elapsedTime();
6244 double elapsed_ms = (end_sec - start_sec) * 1000.0;
6245 young_time_ms += elapsed_ms;
6247 start_sec = os::elapsedTime();
6248 non_young = true;
6249 }
6250 }
6252 rs_lengths += cur->rem_set()->occupied_locked();
6254 HeapRegion* next = cur->next_in_collection_set();
6255 assert(cur->in_collection_set(), "bad CS");
6256 cur->set_next_in_collection_set(NULL);
6257 cur->set_in_collection_set(false);
6259 if (cur->is_young()) {
6260 int index = cur->young_index_in_cset();
6261 assert(index != -1, "invariant");
6262 assert((uint) index < policy->young_cset_region_length(), "invariant");
6263 size_t words_survived = _surviving_young_words[index];
6264 cur->record_surv_words_in_group(words_survived);
6266 // At this point the we have 'popped' cur from the collection set
6267 // (linked via next_in_collection_set()) but it is still in the
6268 // young list (linked via next_young_region()). Clear the
6269 // _next_young_region field.
6270 cur->set_next_young_region(NULL);
6271 } else {
6272 int index = cur->young_index_in_cset();
6273 assert(index == -1, "invariant");
6274 }
6276 assert( (cur->is_young() && cur->young_index_in_cset() > -1) ||
6277 (!cur->is_young() && cur->young_index_in_cset() == -1),
6278 "invariant" );
6280 if (!cur->evacuation_failed()) {
6281 MemRegion used_mr = cur->used_region();
6283 // And the region is empty.
6284 assert(!used_mr.is_empty(), "Should not have empty regions in a CS.");
6285 pre_used += cur->used();
6286 free_region(cur, &local_free_list, false /* par */, true /* locked */);
6287 } else {
6288 cur->uninstall_surv_rate_group();
6289 if (cur->is_young()) {
6290 cur->set_young_index_in_cset(-1);
6291 }
6292 cur->set_not_young();
6293 cur->set_evacuation_failed(false);
6294 // The region is now considered to be old.
6295 _old_set.add(cur);
6296 evacuation_info.increment_collectionset_used_after(cur->used());
6297 }
6298 cur = next;
6299 }
6301 evacuation_info.set_regions_freed(local_free_list.length());
6302 policy->record_max_rs_lengths(rs_lengths);
6303 policy->cset_regions_freed();
6305 double end_sec = os::elapsedTime();
6306 double elapsed_ms = (end_sec - start_sec) * 1000.0;
6308 if (non_young) {
6309 non_young_time_ms += elapsed_ms;
6310 } else {
6311 young_time_ms += elapsed_ms;
6312 }
6314 prepend_to_freelist(&local_free_list);
6315 decrement_summary_bytes(pre_used);
6316 policy->phase_times()->record_young_free_cset_time_ms(young_time_ms);
6317 policy->phase_times()->record_non_young_free_cset_time_ms(non_young_time_ms);
6318 }
6320 class G1FreeHumongousRegionClosure : public HeapRegionClosure {
6321 private:
6322 FreeRegionList* _free_region_list;
6323 HeapRegionSet* _proxy_set;
6324 HeapRegionSetCount _humongous_regions_removed;
6325 size_t _freed_bytes;
6326 public:
6328 G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) :
6329 _free_region_list(free_region_list), _humongous_regions_removed(), _freed_bytes(0) {
6330 }
6332 virtual bool doHeapRegion(HeapRegion* r) {
6333 if (!r->startsHumongous()) {
6334 return false;
6335 }
6337 G1CollectedHeap* g1h = G1CollectedHeap::heap();
6339 oop obj = (oop)r->bottom();
6340 CMBitMap* next_bitmap = g1h->concurrent_mark()->nextMarkBitMap();
6342 // The following checks whether the humongous object is live are sufficient.
6343 // The main additional check (in addition to having a reference from the roots
6344 // or the young gen) is whether the humongous object has a remembered set entry.
6345 //
6346 // A humongous object cannot be live if there is no remembered set for it
6347 // because:
6348 // - there can be no references from within humongous starts regions referencing
6349 // the object because we never allocate other objects into them.
6350 // (I.e. there are no intra-region references that may be missed by the
6351 // remembered set)
6352 // - as soon there is a remembered set entry to the humongous starts region
6353 // (i.e. it has "escaped" to an old object) this remembered set entry will stay
6354 // until the end of a concurrent mark.
6355 //
6356 // It is not required to check whether the object has been found dead by marking
6357 // or not, in fact it would prevent reclamation within a concurrent cycle, as
6358 // all objects allocated during that time are considered live.
6359 // SATB marking is even more conservative than the remembered set.
6360 // So if at this point in the collection there is no remembered set entry,
6361 // nobody has a reference to it.
6362 // At the start of collection we flush all refinement logs, and remembered sets
6363 // are completely up-to-date wrt to references to the humongous object.
6364 //
6365 // Other implementation considerations:
6366 // - never consider object arrays: while they are a valid target, they have not
6367 // been observed to be used as temporary objects.
6368 // - they would also pose considerable effort for cleaning up the the remembered
6369 // sets.
6370 // While this cleanup is not strictly necessary to be done (or done instantly),
6371 // given that their occurrence is very low, this saves us this additional
6372 // complexity.
6373 uint region_idx = r->hrm_index();
6374 if (g1h->humongous_is_live(region_idx) ||
6375 g1h->humongous_region_is_always_live(region_idx)) {
6377 if (G1TraceReclaimDeadHumongousObjectsAtYoungGC) {
6378 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",
6379 r->isHumongous(),
6380 region_idx,
6381 r->rem_set()->occupied(),
6382 r->rem_set()->strong_code_roots_list_length(),
6383 next_bitmap->isMarked(r->bottom()),
6384 g1h->humongous_is_live(region_idx),
6385 obj->is_objArray()
6386 );
6387 }
6389 return false;
6390 }
6392 guarantee(!obj->is_objArray(),
6393 err_msg("Eagerly reclaiming object arrays is not supported, but the object "PTR_FORMAT" is.",
6394 r->bottom()));
6396 if (G1TraceReclaimDeadHumongousObjectsAtYoungGC) {
6397 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",
6398 r->isHumongous(),
6399 r->bottom(),
6400 region_idx,
6401 r->region_num(),
6402 r->rem_set()->occupied(),
6403 r->rem_set()->strong_code_roots_list_length(),
6404 next_bitmap->isMarked(r->bottom()),
6405 g1h->humongous_is_live(region_idx),
6406 obj->is_objArray()
6407 );
6408 }
6409 // Need to clear mark bit of the humongous object if already set.
6410 if (next_bitmap->isMarked(r->bottom())) {
6411 next_bitmap->clear(r->bottom());
6412 }
6413 _freed_bytes += r->used();
6414 r->set_containing_set(NULL);
6415 _humongous_regions_removed.increment(1u, r->capacity());
6416 g1h->free_humongous_region(r, _free_region_list, false);
6418 return false;
6419 }
6421 HeapRegionSetCount& humongous_free_count() {
6422 return _humongous_regions_removed;
6423 }
6425 size_t bytes_freed() const {
6426 return _freed_bytes;
6427 }
6429 size_t humongous_reclaimed() const {
6430 return _humongous_regions_removed.length();
6431 }
6432 };
6434 void G1CollectedHeap::eagerly_reclaim_humongous_regions() {
6435 assert_at_safepoint(true);
6437 if (!G1ReclaimDeadHumongousObjectsAtYoungGC || !_has_humongous_reclaim_candidates) {
6438 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0);
6439 return;
6440 }
6442 double start_time = os::elapsedTime();
6444 FreeRegionList local_cleanup_list("Local Humongous Cleanup List");
6446 G1FreeHumongousRegionClosure cl(&local_cleanup_list);
6447 heap_region_iterate(&cl);
6449 HeapRegionSetCount empty_set;
6450 remove_from_old_sets(empty_set, cl.humongous_free_count());
6452 G1HRPrinter* hr_printer = _g1h->hr_printer();
6453 if (hr_printer->is_active()) {
6454 FreeRegionListIterator iter(&local_cleanup_list);
6455 while (iter.more_available()) {
6456 HeapRegion* hr = iter.get_next();
6457 hr_printer->cleanup(hr);
6458 }
6459 }
6461 prepend_to_freelist(&local_cleanup_list);
6462 decrement_summary_bytes(cl.bytes_freed());
6464 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0,
6465 cl.humongous_reclaimed());
6466 }
6468 // This routine is similar to the above but does not record
6469 // any policy statistics or update free lists; we are abandoning
6470 // the current incremental collection set in preparation of a
6471 // full collection. After the full GC we will start to build up
6472 // the incremental collection set again.
6473 // This is only called when we're doing a full collection
6474 // and is immediately followed by the tearing down of the young list.
6476 void G1CollectedHeap::abandon_collection_set(HeapRegion* cs_head) {
6477 HeapRegion* cur = cs_head;
6479 while (cur != NULL) {
6480 HeapRegion* next = cur->next_in_collection_set();
6481 assert(cur->in_collection_set(), "bad CS");
6482 cur->set_next_in_collection_set(NULL);
6483 cur->set_in_collection_set(false);
6484 cur->set_young_index_in_cset(-1);
6485 cur = next;
6486 }
6487 }
6489 void G1CollectedHeap::set_free_regions_coming() {
6490 if (G1ConcRegionFreeingVerbose) {
6491 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
6492 "setting free regions coming");
6493 }
6495 assert(!free_regions_coming(), "pre-condition");
6496 _free_regions_coming = true;
6497 }
6499 void G1CollectedHeap::reset_free_regions_coming() {
6500 assert(free_regions_coming(), "pre-condition");
6502 {
6503 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6504 _free_regions_coming = false;
6505 SecondaryFreeList_lock->notify_all();
6506 }
6508 if (G1ConcRegionFreeingVerbose) {
6509 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
6510 "reset free regions coming");
6511 }
6512 }
6514 void G1CollectedHeap::wait_while_free_regions_coming() {
6515 // Most of the time we won't have to wait, so let's do a quick test
6516 // first before we take the lock.
6517 if (!free_regions_coming()) {
6518 return;
6519 }
6521 if (G1ConcRegionFreeingVerbose) {
6522 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
6523 "waiting for free regions");
6524 }
6526 {
6527 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6528 while (free_regions_coming()) {
6529 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
6530 }
6531 }
6533 if (G1ConcRegionFreeingVerbose) {
6534 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
6535 "done waiting for free regions");
6536 }
6537 }
6539 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
6540 assert(heap_lock_held_for_gc(),
6541 "the heap lock should already be held by or for this thread");
6542 _young_list->push_region(hr);
6543 }
6545 class NoYoungRegionsClosure: public HeapRegionClosure {
6546 private:
6547 bool _success;
6548 public:
6549 NoYoungRegionsClosure() : _success(true) { }
6550 bool doHeapRegion(HeapRegion* r) {
6551 if (r->is_young()) {
6552 gclog_or_tty->print_cr("Region ["PTR_FORMAT", "PTR_FORMAT") tagged as young",
6553 r->bottom(), r->end());
6554 _success = false;
6555 }
6556 return false;
6557 }
6558 bool success() { return _success; }
6559 };
6561 bool G1CollectedHeap::check_young_list_empty(bool check_heap, bool check_sample) {
6562 bool ret = _young_list->check_list_empty(check_sample);
6564 if (check_heap) {
6565 NoYoungRegionsClosure closure;
6566 heap_region_iterate(&closure);
6567 ret = ret && closure.success();
6568 }
6570 return ret;
6571 }
6573 class TearDownRegionSetsClosure : public HeapRegionClosure {
6574 private:
6575 HeapRegionSet *_old_set;
6577 public:
6578 TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { }
6580 bool doHeapRegion(HeapRegion* r) {
6581 if (r->is_empty()) {
6582 // We ignore empty regions, we'll empty the free list afterwards
6583 } else if (r->is_young()) {
6584 // We ignore young regions, we'll empty the young list afterwards
6585 } else if (r->isHumongous()) {
6586 // We ignore humongous regions, we're not tearing down the
6587 // humongous region set
6588 } else {
6589 // The rest should be old
6590 _old_set->remove(r);
6591 }
6592 return false;
6593 }
6595 ~TearDownRegionSetsClosure() {
6596 assert(_old_set->is_empty(), "post-condition");
6597 }
6598 };
6600 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
6601 assert_at_safepoint(true /* should_be_vm_thread */);
6603 if (!free_list_only) {
6604 TearDownRegionSetsClosure cl(&_old_set);
6605 heap_region_iterate(&cl);
6607 // Note that emptying the _young_list is postponed and instead done as
6608 // the first step when rebuilding the regions sets again. The reason for
6609 // this is that during a full GC string deduplication needs to know if
6610 // a collected region was young or old when the full GC was initiated.
6611 }
6612 _hrm.remove_all_free_regions();
6613 }
6615 class RebuildRegionSetsClosure : public HeapRegionClosure {
6616 private:
6617 bool _free_list_only;
6618 HeapRegionSet* _old_set;
6619 HeapRegionManager* _hrm;
6620 size_t _total_used;
6622 public:
6623 RebuildRegionSetsClosure(bool free_list_only,
6624 HeapRegionSet* old_set, HeapRegionManager* hrm) :
6625 _free_list_only(free_list_only),
6626 _old_set(old_set), _hrm(hrm), _total_used(0) {
6627 assert(_hrm->num_free_regions() == 0, "pre-condition");
6628 if (!free_list_only) {
6629 assert(_old_set->is_empty(), "pre-condition");
6630 }
6631 }
6633 bool doHeapRegion(HeapRegion* r) {
6634 if (r->continuesHumongous()) {
6635 return false;
6636 }
6638 if (r->is_empty()) {
6639 // Add free regions to the free list
6640 r->set_allocation_context(AllocationContext::system());
6641 _hrm->insert_into_free_list(r);
6642 } else if (!_free_list_only) {
6643 assert(!r->is_young(), "we should not come across young regions");
6645 if (r->isHumongous()) {
6646 // We ignore humongous regions, we left the humongous set unchanged
6647 } else {
6648 // The rest should be old, add them to the old set
6649 _old_set->add(r);
6650 }
6651 _total_used += r->used();
6652 }
6654 return false;
6655 }
6657 size_t total_used() {
6658 return _total_used;
6659 }
6660 };
6662 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
6663 assert_at_safepoint(true /* should_be_vm_thread */);
6665 if (!free_list_only) {
6666 _young_list->empty_list();
6667 }
6669 RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm);
6670 heap_region_iterate(&cl);
6672 if (!free_list_only) {
6673 _allocator->set_used(cl.total_used());
6674 }
6675 assert(_allocator->used_unlocked() == recalculate_used(),
6676 err_msg("inconsistent _allocator->used_unlocked(), "
6677 "value: "SIZE_FORMAT" recalculated: "SIZE_FORMAT,
6678 _allocator->used_unlocked(), recalculate_used()));
6679 }
6681 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) {
6682 _refine_cte_cl->set_concurrent(concurrent);
6683 }
6685 bool G1CollectedHeap::is_in_closed_subset(const void* p) const {
6686 HeapRegion* hr = heap_region_containing(p);
6687 return hr->is_in(p);
6688 }
6690 // Methods for the mutator alloc region
6692 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
6693 bool force) {
6694 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6695 assert(!force || g1_policy()->can_expand_young_list(),
6696 "if force is true we should be able to expand the young list");
6697 bool young_list_full = g1_policy()->is_young_list_full();
6698 if (force || !young_list_full) {
6699 HeapRegion* new_alloc_region = new_region(word_size,
6700 false /* is_old */,
6701 false /* do_expand */);
6702 if (new_alloc_region != NULL) {
6703 set_region_short_lived_locked(new_alloc_region);
6704 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Eden, young_list_full);
6705 check_bitmaps("Mutator Region Allocation", new_alloc_region);
6706 return new_alloc_region;
6707 }
6708 }
6709 return NULL;
6710 }
6712 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
6713 size_t allocated_bytes) {
6714 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6715 assert(alloc_region->is_young(), "all mutator alloc regions should be young");
6717 g1_policy()->add_region_to_incremental_cset_lhs(alloc_region);
6718 _allocator->increase_used(allocated_bytes);
6719 _hr_printer.retire(alloc_region);
6720 // We update the eden sizes here, when the region is retired,
6721 // instead of when it's allocated, since this is the point that its
6722 // used space has been recored in _summary_bytes_used.
6723 g1mm()->update_eden_size();
6724 }
6726 void G1CollectedHeap::set_par_threads() {
6727 // Don't change the number of workers. Use the value previously set
6728 // in the workgroup.
6729 assert(G1CollectedHeap::use_parallel_gc_threads(), "shouldn't be here otherwise");
6730 uint n_workers = workers()->active_workers();
6731 assert(UseDynamicNumberOfGCThreads ||
6732 n_workers == workers()->total_workers(),
6733 "Otherwise should be using the total number of workers");
6734 if (n_workers == 0) {
6735 assert(false, "Should have been set in prior evacuation pause.");
6736 n_workers = ParallelGCThreads;
6737 workers()->set_active_workers(n_workers);
6738 }
6739 set_par_threads(n_workers);
6740 }
6742 // Methods for the GC alloc regions
6744 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size,
6745 uint count,
6746 GCAllocPurpose ap) {
6747 assert(FreeList_lock->owned_by_self(), "pre-condition");
6749 if (count < g1_policy()->max_regions(ap)) {
6750 bool survivor = (ap == GCAllocForSurvived);
6751 HeapRegion* new_alloc_region = new_region(word_size,
6752 !survivor,
6753 true /* do_expand */);
6754 if (new_alloc_region != NULL) {
6755 // We really only need to do this for old regions given that we
6756 // should never scan survivors. But it doesn't hurt to do it
6757 // for survivors too.
6758 new_alloc_region->record_top_and_timestamp();
6759 if (survivor) {
6760 new_alloc_region->set_survivor();
6761 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Survivor);
6762 check_bitmaps("Survivor Region Allocation", new_alloc_region);
6763 } else {
6764 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Old);
6765 check_bitmaps("Old Region Allocation", new_alloc_region);
6766 }
6767 bool during_im = g1_policy()->during_initial_mark_pause();
6768 new_alloc_region->note_start_of_copying(during_im);
6769 return new_alloc_region;
6770 } else {
6771 g1_policy()->note_alloc_region_limit_reached(ap);
6772 }
6773 }
6774 return NULL;
6775 }
6777 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
6778 size_t allocated_bytes,
6779 GCAllocPurpose ap) {
6780 bool during_im = g1_policy()->during_initial_mark_pause();
6781 alloc_region->note_end_of_copying(during_im);
6782 g1_policy()->record_bytes_copied_during_gc(allocated_bytes);
6783 if (ap == GCAllocForSurvived) {
6784 young_list()->add_survivor_region(alloc_region);
6785 } else {
6786 _old_set.add(alloc_region);
6787 }
6788 _hr_printer.retire(alloc_region);
6789 }
6791 // Heap region set verification
6793 class VerifyRegionListsClosure : public HeapRegionClosure {
6794 private:
6795 HeapRegionSet* _old_set;
6796 HeapRegionSet* _humongous_set;
6797 HeapRegionManager* _hrm;
6799 public:
6800 HeapRegionSetCount _old_count;
6801 HeapRegionSetCount _humongous_count;
6802 HeapRegionSetCount _free_count;
6804 VerifyRegionListsClosure(HeapRegionSet* old_set,
6805 HeapRegionSet* humongous_set,
6806 HeapRegionManager* hrm) :
6807 _old_set(old_set), _humongous_set(humongous_set), _hrm(hrm),
6808 _old_count(), _humongous_count(), _free_count(){ }
6810 bool doHeapRegion(HeapRegion* hr) {
6811 if (hr->continuesHumongous()) {
6812 return false;
6813 }
6815 if (hr->is_young()) {
6816 // TODO
6817 } else if (hr->startsHumongous()) {
6818 assert(hr->containing_set() == _humongous_set, err_msg("Heap region %u is starts humongous but not in humongous set.", hr->hrm_index()));
6819 _humongous_count.increment(1u, hr->capacity());
6820 } else if (hr->is_empty()) {
6821 assert(_hrm->is_free(hr), err_msg("Heap region %u is empty but not on the free list.", hr->hrm_index()));
6822 _free_count.increment(1u, hr->capacity());
6823 } else {
6824 assert(hr->containing_set() == _old_set, err_msg("Heap region %u is old but not in the old set.", hr->hrm_index()));
6825 _old_count.increment(1u, hr->capacity());
6826 }
6827 return false;
6828 }
6830 void verify_counts(HeapRegionSet* old_set, HeapRegionSet* humongous_set, HeapRegionManager* free_list) {
6831 guarantee(old_set->length() == _old_count.length(), err_msg("Old set count mismatch. Expected %u, actual %u.", old_set->length(), _old_count.length()));
6832 guarantee(old_set->total_capacity_bytes() == _old_count.capacity(), err_msg("Old set capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
6833 old_set->total_capacity_bytes(), _old_count.capacity()));
6835 guarantee(humongous_set->length() == _humongous_count.length(), err_msg("Hum set count mismatch. Expected %u, actual %u.", humongous_set->length(), _humongous_count.length()));
6836 guarantee(humongous_set->total_capacity_bytes() == _humongous_count.capacity(), err_msg("Hum set capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
6837 humongous_set->total_capacity_bytes(), _humongous_count.capacity()));
6839 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()));
6840 guarantee(free_list->total_capacity_bytes() == _free_count.capacity(), err_msg("Free list capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
6841 free_list->total_capacity_bytes(), _free_count.capacity()));
6842 }
6843 };
6845 void G1CollectedHeap::verify_region_sets() {
6846 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6848 // First, check the explicit lists.
6849 _hrm.verify();
6850 {
6851 // Given that a concurrent operation might be adding regions to
6852 // the secondary free list we have to take the lock before
6853 // verifying it.
6854 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6855 _secondary_free_list.verify_list();
6856 }
6858 // If a concurrent region freeing operation is in progress it will
6859 // be difficult to correctly attributed any free regions we come
6860 // across to the correct free list given that they might belong to
6861 // one of several (free_list, secondary_free_list, any local lists,
6862 // etc.). So, if that's the case we will skip the rest of the
6863 // verification operation. Alternatively, waiting for the concurrent
6864 // operation to complete will have a non-trivial effect on the GC's
6865 // operation (no concurrent operation will last longer than the
6866 // interval between two calls to verification) and it might hide
6867 // any issues that we would like to catch during testing.
6868 if (free_regions_coming()) {
6869 return;
6870 }
6872 // Make sure we append the secondary_free_list on the free_list so
6873 // that all free regions we will come across can be safely
6874 // attributed to the free_list.
6875 append_secondary_free_list_if_not_empty_with_lock();
6877 // Finally, make sure that the region accounting in the lists is
6878 // consistent with what we see in the heap.
6880 VerifyRegionListsClosure cl(&_old_set, &_humongous_set, &_hrm);
6881 heap_region_iterate(&cl);
6882 cl.verify_counts(&_old_set, &_humongous_set, &_hrm);
6883 }
6885 // Optimized nmethod scanning
6887 class RegisterNMethodOopClosure: public OopClosure {
6888 G1CollectedHeap* _g1h;
6889 nmethod* _nm;
6891 template <class T> void do_oop_work(T* p) {
6892 T heap_oop = oopDesc::load_heap_oop(p);
6893 if (!oopDesc::is_null(heap_oop)) {
6894 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
6895 HeapRegion* hr = _g1h->heap_region_containing(obj);
6896 assert(!hr->continuesHumongous(),
6897 err_msg("trying to add code root "PTR_FORMAT" in continuation of humongous region "HR_FORMAT
6898 " starting at "HR_FORMAT,
6899 _nm, HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())));
6901 // HeapRegion::add_strong_code_root() avoids adding duplicate
6902 // entries but having duplicates is OK since we "mark" nmethods
6903 // as visited when we scan the strong code root lists during the GC.
6904 hr->add_strong_code_root(_nm);
6905 assert(hr->rem_set()->strong_code_roots_list_contains(_nm),
6906 err_msg("failed to add code root "PTR_FORMAT" to remembered set of region "HR_FORMAT,
6907 _nm, HR_FORMAT_PARAMS(hr)));
6908 }
6909 }
6911 public:
6912 RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
6913 _g1h(g1h), _nm(nm) {}
6915 void do_oop(oop* p) { do_oop_work(p); }
6916 void do_oop(narrowOop* p) { do_oop_work(p); }
6917 };
6919 class UnregisterNMethodOopClosure: public OopClosure {
6920 G1CollectedHeap* _g1h;
6921 nmethod* _nm;
6923 template <class T> void do_oop_work(T* p) {
6924 T heap_oop = oopDesc::load_heap_oop(p);
6925 if (!oopDesc::is_null(heap_oop)) {
6926 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
6927 HeapRegion* hr = _g1h->heap_region_containing(obj);
6928 assert(!hr->continuesHumongous(),
6929 err_msg("trying to remove code root "PTR_FORMAT" in continuation of humongous region "HR_FORMAT
6930 " starting at "HR_FORMAT,
6931 _nm, HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())));
6933 hr->remove_strong_code_root(_nm);
6934 assert(!hr->rem_set()->strong_code_roots_list_contains(_nm),
6935 err_msg("failed to remove code root "PTR_FORMAT" of region "HR_FORMAT,
6936 _nm, HR_FORMAT_PARAMS(hr)));
6937 }
6938 }
6940 public:
6941 UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
6942 _g1h(g1h), _nm(nm) {}
6944 void do_oop(oop* p) { do_oop_work(p); }
6945 void do_oop(narrowOop* p) { do_oop_work(p); }
6946 };
6948 void G1CollectedHeap::register_nmethod(nmethod* nm) {
6949 CollectedHeap::register_nmethod(nm);
6951 guarantee(nm != NULL, "sanity");
6952 RegisterNMethodOopClosure reg_cl(this, nm);
6953 nm->oops_do(®_cl);
6954 }
6956 void G1CollectedHeap::unregister_nmethod(nmethod* nm) {
6957 CollectedHeap::unregister_nmethod(nm);
6959 guarantee(nm != NULL, "sanity");
6960 UnregisterNMethodOopClosure reg_cl(this, nm);
6961 nm->oops_do(®_cl, true);
6962 }
6964 class MigrateCodeRootsHeapRegionClosure: public HeapRegionClosure {
6965 public:
6966 bool doHeapRegion(HeapRegion *hr) {
6967 assert(!hr->isHumongous(),
6968 err_msg("humongous region "HR_FORMAT" should not have been added to collection set",
6969 HR_FORMAT_PARAMS(hr)));
6970 hr->migrate_strong_code_roots();
6971 return false;
6972 }
6973 };
6975 void G1CollectedHeap::migrate_strong_code_roots() {
6976 MigrateCodeRootsHeapRegionClosure cl;
6977 double migrate_start = os::elapsedTime();
6978 collection_set_iterate(&cl);
6979 double migration_time_ms = (os::elapsedTime() - migrate_start) * 1000.0;
6980 g1_policy()->phase_times()->record_strong_code_root_migration_time(migration_time_ms);
6981 }
6983 void G1CollectedHeap::purge_code_root_memory() {
6984 double purge_start = os::elapsedTime();
6985 G1CodeRootSet::purge_chunks(G1CodeRootsChunkCacheKeepPercent);
6986 double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0;
6987 g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms);
6988 }
6990 class RebuildStrongCodeRootClosure: public CodeBlobClosure {
6991 G1CollectedHeap* _g1h;
6993 public:
6994 RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) :
6995 _g1h(g1h) {}
6997 void do_code_blob(CodeBlob* cb) {
6998 nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL;
6999 if (nm == NULL) {
7000 return;
7001 }
7003 if (ScavengeRootsInCode) {
7004 _g1h->register_nmethod(nm);
7005 }
7006 }
7007 };
7009 void G1CollectedHeap::rebuild_strong_code_roots() {
7010 RebuildStrongCodeRootClosure blob_cl(this);
7011 CodeCache::blobs_do(&blob_cl);
7012 }