Fri, 20 Jan 2012 18:01:32 +0100
7131791: G1: Asserts in nightly testing due to 6976060
Summary: Create a handle and fake an object to make sure that we don't loose the memory we just allocated
Reviewed-by: tonyp, stefank
1 /*
2 * Copyright (c) 2001, 2012, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
25 #include "precompiled.hpp"
26 #include "code/icBuffer.hpp"
27 #include "gc_implementation/g1/bufferingOopClosure.hpp"
28 #include "gc_implementation/g1/concurrentG1Refine.hpp"
29 #include "gc_implementation/g1/concurrentG1RefineThread.hpp"
30 #include "gc_implementation/g1/concurrentMarkThread.inline.hpp"
31 #include "gc_implementation/g1/g1AllocRegion.inline.hpp"
32 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
33 #include "gc_implementation/g1/g1CollectorPolicy.hpp"
34 #include "gc_implementation/g1/g1ErgoVerbose.hpp"
35 #include "gc_implementation/g1/g1EvacFailure.hpp"
36 #include "gc_implementation/g1/g1MarkSweep.hpp"
37 #include "gc_implementation/g1/g1OopClosures.inline.hpp"
38 #include "gc_implementation/g1/g1RemSet.inline.hpp"
39 #include "gc_implementation/g1/heapRegion.inline.hpp"
40 #include "gc_implementation/g1/heapRegionRemSet.hpp"
41 #include "gc_implementation/g1/heapRegionSeq.inline.hpp"
42 #include "gc_implementation/g1/vm_operations_g1.hpp"
43 #include "gc_implementation/shared/isGCActiveMark.hpp"
44 #include "memory/gcLocker.inline.hpp"
45 #include "memory/genOopClosures.inline.hpp"
46 #include "memory/generationSpec.hpp"
47 #include "memory/referenceProcessor.hpp"
48 #include "oops/oop.inline.hpp"
49 #include "oops/oop.pcgc.inline.hpp"
50 #include "runtime/aprofiler.hpp"
51 #include "runtime/vmThread.hpp"
53 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;
55 // turn it on so that the contents of the young list (scan-only /
56 // to-be-collected) are printed at "strategic" points before / during
57 // / after the collection --- this is useful for debugging
58 #define YOUNG_LIST_VERBOSE 0
59 // CURRENT STATUS
60 // This file is under construction. Search for "FIXME".
62 // INVARIANTS/NOTES
63 //
64 // All allocation activity covered by the G1CollectedHeap interface is
65 // serialized by acquiring the HeapLock. This happens in mem_allocate
66 // and allocate_new_tlab, which are the "entry" points to the
67 // allocation code from the rest of the JVM. (Note that this does not
68 // apply to TLAB allocation, which is not part of this interface: it
69 // is done by clients of this interface.)
71 // Notes on implementation of parallelism in different tasks.
72 //
73 // G1ParVerifyTask uses heap_region_par_iterate_chunked() for parallelism.
74 // The number of GC workers is passed to heap_region_par_iterate_chunked().
75 // It does use run_task() which sets _n_workers in the task.
76 // G1ParTask executes g1_process_strong_roots() ->
77 // SharedHeap::process_strong_roots() which calls eventuall to
78 // CardTableModRefBS::par_non_clean_card_iterate_work() which uses
79 // SequentialSubTasksDone. SharedHeap::process_strong_roots() also
80 // directly uses SubTasksDone (_process_strong_tasks field in SharedHeap).
81 //
83 // Local to this file.
85 class RefineCardTableEntryClosure: public CardTableEntryClosure {
86 SuspendibleThreadSet* _sts;
87 G1RemSet* _g1rs;
88 ConcurrentG1Refine* _cg1r;
89 bool _concurrent;
90 public:
91 RefineCardTableEntryClosure(SuspendibleThreadSet* sts,
92 G1RemSet* g1rs,
93 ConcurrentG1Refine* cg1r) :
94 _sts(sts), _g1rs(g1rs), _cg1r(cg1r), _concurrent(true)
95 {}
96 bool do_card_ptr(jbyte* card_ptr, int worker_i) {
97 bool oops_into_cset = _g1rs->concurrentRefineOneCard(card_ptr, worker_i, false);
98 // This path is executed by the concurrent refine or mutator threads,
99 // concurrently, and so we do not care if card_ptr contains references
100 // that point into the collection set.
101 assert(!oops_into_cset, "should be");
103 if (_concurrent && _sts->should_yield()) {
104 // Caller will actually yield.
105 return false;
106 }
107 // Otherwise, we finished successfully; return true.
108 return true;
109 }
110 void set_concurrent(bool b) { _concurrent = b; }
111 };
114 class ClearLoggedCardTableEntryClosure: public CardTableEntryClosure {
115 int _calls;
116 G1CollectedHeap* _g1h;
117 CardTableModRefBS* _ctbs;
118 int _histo[256];
119 public:
120 ClearLoggedCardTableEntryClosure() :
121 _calls(0)
122 {
123 _g1h = G1CollectedHeap::heap();
124 _ctbs = (CardTableModRefBS*)_g1h->barrier_set();
125 for (int i = 0; i < 256; i++) _histo[i] = 0;
126 }
127 bool do_card_ptr(jbyte* card_ptr, int worker_i) {
128 if (_g1h->is_in_reserved(_ctbs->addr_for(card_ptr))) {
129 _calls++;
130 unsigned char* ujb = (unsigned char*)card_ptr;
131 int ind = (int)(*ujb);
132 _histo[ind]++;
133 *card_ptr = -1;
134 }
135 return true;
136 }
137 int calls() { return _calls; }
138 void print_histo() {
139 gclog_or_tty->print_cr("Card table value histogram:");
140 for (int i = 0; i < 256; i++) {
141 if (_histo[i] != 0) {
142 gclog_or_tty->print_cr(" %d: %d", i, _histo[i]);
143 }
144 }
145 }
146 };
148 class RedirtyLoggedCardTableEntryClosure: public CardTableEntryClosure {
149 int _calls;
150 G1CollectedHeap* _g1h;
151 CardTableModRefBS* _ctbs;
152 public:
153 RedirtyLoggedCardTableEntryClosure() :
154 _calls(0)
155 {
156 _g1h = G1CollectedHeap::heap();
157 _ctbs = (CardTableModRefBS*)_g1h->barrier_set();
158 }
159 bool do_card_ptr(jbyte* card_ptr, int worker_i) {
160 if (_g1h->is_in_reserved(_ctbs->addr_for(card_ptr))) {
161 _calls++;
162 *card_ptr = 0;
163 }
164 return true;
165 }
166 int calls() { return _calls; }
167 };
169 class RedirtyLoggedCardTableEntryFastClosure : public CardTableEntryClosure {
170 public:
171 bool do_card_ptr(jbyte* card_ptr, int worker_i) {
172 *card_ptr = CardTableModRefBS::dirty_card_val();
173 return true;
174 }
175 };
177 YoungList::YoungList(G1CollectedHeap* g1h)
178 : _g1h(g1h), _head(NULL),
179 _length(0),
180 _last_sampled_rs_lengths(0),
181 _survivor_head(NULL), _survivor_tail(NULL), _survivor_length(0)
182 {
183 guarantee( check_list_empty(false), "just making sure..." );
184 }
186 void YoungList::push_region(HeapRegion *hr) {
187 assert(!hr->is_young(), "should not already be young");
188 assert(hr->get_next_young_region() == NULL, "cause it should!");
190 hr->set_next_young_region(_head);
191 _head = hr;
193 _g1h->g1_policy()->set_region_eden(hr, (int) _length);
194 ++_length;
195 }
197 void YoungList::add_survivor_region(HeapRegion* hr) {
198 assert(hr->is_survivor(), "should be flagged as survivor region");
199 assert(hr->get_next_young_region() == NULL, "cause it should!");
201 hr->set_next_young_region(_survivor_head);
202 if (_survivor_head == NULL) {
203 _survivor_tail = hr;
204 }
205 _survivor_head = hr;
206 ++_survivor_length;
207 }
209 void YoungList::empty_list(HeapRegion* list) {
210 while (list != NULL) {
211 HeapRegion* next = list->get_next_young_region();
212 list->set_next_young_region(NULL);
213 list->uninstall_surv_rate_group();
214 list->set_not_young();
215 list = next;
216 }
217 }
219 void YoungList::empty_list() {
220 assert(check_list_well_formed(), "young list should be well formed");
222 empty_list(_head);
223 _head = NULL;
224 _length = 0;
226 empty_list(_survivor_head);
227 _survivor_head = NULL;
228 _survivor_tail = NULL;
229 _survivor_length = 0;
231 _last_sampled_rs_lengths = 0;
233 assert(check_list_empty(false), "just making sure...");
234 }
236 bool YoungList::check_list_well_formed() {
237 bool ret = true;
239 size_t length = 0;
240 HeapRegion* curr = _head;
241 HeapRegion* last = NULL;
242 while (curr != NULL) {
243 if (!curr->is_young()) {
244 gclog_or_tty->print_cr("### YOUNG REGION "PTR_FORMAT"-"PTR_FORMAT" "
245 "incorrectly tagged (y: %d, surv: %d)",
246 curr->bottom(), curr->end(),
247 curr->is_young(), curr->is_survivor());
248 ret = false;
249 }
250 ++length;
251 last = curr;
252 curr = curr->get_next_young_region();
253 }
254 ret = ret && (length == _length);
256 if (!ret) {
257 gclog_or_tty->print_cr("### YOUNG LIST seems not well formed!");
258 gclog_or_tty->print_cr("### list has %d entries, _length is %d",
259 length, _length);
260 }
262 return ret;
263 }
265 bool YoungList::check_list_empty(bool check_sample) {
266 bool ret = true;
268 if (_length != 0) {
269 gclog_or_tty->print_cr("### YOUNG LIST should have 0 length, not %d",
270 _length);
271 ret = false;
272 }
273 if (check_sample && _last_sampled_rs_lengths != 0) {
274 gclog_or_tty->print_cr("### YOUNG LIST has non-zero last sampled RS lengths");
275 ret = false;
276 }
277 if (_head != NULL) {
278 gclog_or_tty->print_cr("### YOUNG LIST does not have a NULL head");
279 ret = false;
280 }
281 if (!ret) {
282 gclog_or_tty->print_cr("### YOUNG LIST does not seem empty");
283 }
285 return ret;
286 }
288 void
289 YoungList::rs_length_sampling_init() {
290 _sampled_rs_lengths = 0;
291 _curr = _head;
292 }
294 bool
295 YoungList::rs_length_sampling_more() {
296 return _curr != NULL;
297 }
299 void
300 YoungList::rs_length_sampling_next() {
301 assert( _curr != NULL, "invariant" );
302 size_t rs_length = _curr->rem_set()->occupied();
304 _sampled_rs_lengths += rs_length;
306 // The current region may not yet have been added to the
307 // incremental collection set (it gets added when it is
308 // retired as the current allocation region).
309 if (_curr->in_collection_set()) {
310 // Update the collection set policy information for this region
311 _g1h->g1_policy()->update_incremental_cset_info(_curr, rs_length);
312 }
314 _curr = _curr->get_next_young_region();
315 if (_curr == NULL) {
316 _last_sampled_rs_lengths = _sampled_rs_lengths;
317 // gclog_or_tty->print_cr("last sampled RS lengths = %d", _last_sampled_rs_lengths);
318 }
319 }
321 void
322 YoungList::reset_auxilary_lists() {
323 guarantee( is_empty(), "young list should be empty" );
324 assert(check_list_well_formed(), "young list should be well formed");
326 // Add survivor regions to SurvRateGroup.
327 _g1h->g1_policy()->note_start_adding_survivor_regions();
328 _g1h->g1_policy()->finished_recalculating_age_indexes(true /* is_survivors */);
330 int young_index_in_cset = 0;
331 for (HeapRegion* curr = _survivor_head;
332 curr != NULL;
333 curr = curr->get_next_young_region()) {
334 _g1h->g1_policy()->set_region_survivor(curr, young_index_in_cset);
336 // The region is a non-empty survivor so let's add it to
337 // the incremental collection set for the next evacuation
338 // pause.
339 _g1h->g1_policy()->add_region_to_incremental_cset_rhs(curr);
340 young_index_in_cset += 1;
341 }
342 assert((size_t) young_index_in_cset == _survivor_length,
343 "post-condition");
344 _g1h->g1_policy()->note_stop_adding_survivor_regions();
346 _head = _survivor_head;
347 _length = _survivor_length;
348 if (_survivor_head != NULL) {
349 assert(_survivor_tail != NULL, "cause it shouldn't be");
350 assert(_survivor_length > 0, "invariant");
351 _survivor_tail->set_next_young_region(NULL);
352 }
354 // Don't clear the survivor list handles until the start of
355 // the next evacuation pause - we need it in order to re-tag
356 // the survivor regions from this evacuation pause as 'young'
357 // at the start of the next.
359 _g1h->g1_policy()->finished_recalculating_age_indexes(false /* is_survivors */);
361 assert(check_list_well_formed(), "young list should be well formed");
362 }
364 void YoungList::print() {
365 HeapRegion* lists[] = {_head, _survivor_head};
366 const char* names[] = {"YOUNG", "SURVIVOR"};
368 for (unsigned int list = 0; list < ARRAY_SIZE(lists); ++list) {
369 gclog_or_tty->print_cr("%s LIST CONTENTS", names[list]);
370 HeapRegion *curr = lists[list];
371 if (curr == NULL)
372 gclog_or_tty->print_cr(" empty");
373 while (curr != NULL) {
374 gclog_or_tty->print_cr(" [%08x-%08x], t: %08x, P: %08x, N: %08x, C: %08x, "
375 "age: %4d, y: %d, surv: %d",
376 curr->bottom(), curr->end(),
377 curr->top(),
378 curr->prev_top_at_mark_start(),
379 curr->next_top_at_mark_start(),
380 curr->top_at_conc_mark_count(),
381 curr->age_in_surv_rate_group_cond(),
382 curr->is_young(),
383 curr->is_survivor());
384 curr = curr->get_next_young_region();
385 }
386 }
388 gclog_or_tty->print_cr("");
389 }
391 void G1CollectedHeap::push_dirty_cards_region(HeapRegion* hr)
392 {
393 // Claim the right to put the region on the dirty cards region list
394 // by installing a self pointer.
395 HeapRegion* next = hr->get_next_dirty_cards_region();
396 if (next == NULL) {
397 HeapRegion* res = (HeapRegion*)
398 Atomic::cmpxchg_ptr(hr, hr->next_dirty_cards_region_addr(),
399 NULL);
400 if (res == NULL) {
401 HeapRegion* head;
402 do {
403 // Put the region to the dirty cards region list.
404 head = _dirty_cards_region_list;
405 next = (HeapRegion*)
406 Atomic::cmpxchg_ptr(hr, &_dirty_cards_region_list, head);
407 if (next == head) {
408 assert(hr->get_next_dirty_cards_region() == hr,
409 "hr->get_next_dirty_cards_region() != hr");
410 if (next == NULL) {
411 // The last region in the list points to itself.
412 hr->set_next_dirty_cards_region(hr);
413 } else {
414 hr->set_next_dirty_cards_region(next);
415 }
416 }
417 } while (next != head);
418 }
419 }
420 }
422 HeapRegion* G1CollectedHeap::pop_dirty_cards_region()
423 {
424 HeapRegion* head;
425 HeapRegion* hr;
426 do {
427 head = _dirty_cards_region_list;
428 if (head == NULL) {
429 return NULL;
430 }
431 HeapRegion* new_head = head->get_next_dirty_cards_region();
432 if (head == new_head) {
433 // The last region.
434 new_head = NULL;
435 }
436 hr = (HeapRegion*)Atomic::cmpxchg_ptr(new_head, &_dirty_cards_region_list,
437 head);
438 } while (hr != head);
439 assert(hr != NULL, "invariant");
440 hr->set_next_dirty_cards_region(NULL);
441 return hr;
442 }
444 void G1CollectedHeap::stop_conc_gc_threads() {
445 _cg1r->stop();
446 _cmThread->stop();
447 }
449 #ifdef ASSERT
450 // A region is added to the collection set as it is retired
451 // so an address p can point to a region which will be in the
452 // collection set but has not yet been retired. This method
453 // therefore is only accurate during a GC pause after all
454 // regions have been retired. It is used for debugging
455 // to check if an nmethod has references to objects that can
456 // be move during a partial collection. Though it can be
457 // inaccurate, it is sufficient for G1 because the conservative
458 // implementation of is_scavengable() for G1 will indicate that
459 // all nmethods must be scanned during a partial collection.
460 bool G1CollectedHeap::is_in_partial_collection(const void* p) {
461 HeapRegion* hr = heap_region_containing(p);
462 return hr != NULL && hr->in_collection_set();
463 }
464 #endif
466 // Returns true if the reference points to an object that
467 // can move in an incremental collecction.
468 bool G1CollectedHeap::is_scavengable(const void* p) {
469 G1CollectedHeap* g1h = G1CollectedHeap::heap();
470 G1CollectorPolicy* g1p = g1h->g1_policy();
471 HeapRegion* hr = heap_region_containing(p);
472 if (hr == NULL) {
473 // perm gen (or null)
474 return false;
475 } else {
476 return !hr->isHumongous();
477 }
478 }
480 void G1CollectedHeap::check_ct_logs_at_safepoint() {
481 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
482 CardTableModRefBS* ct_bs = (CardTableModRefBS*)barrier_set();
484 // Count the dirty cards at the start.
485 CountNonCleanMemRegionClosure count1(this);
486 ct_bs->mod_card_iterate(&count1);
487 int orig_count = count1.n();
489 // First clear the logged cards.
490 ClearLoggedCardTableEntryClosure clear;
491 dcqs.set_closure(&clear);
492 dcqs.apply_closure_to_all_completed_buffers();
493 dcqs.iterate_closure_all_threads(false);
494 clear.print_histo();
496 // Now ensure that there's no dirty cards.
497 CountNonCleanMemRegionClosure count2(this);
498 ct_bs->mod_card_iterate(&count2);
499 if (count2.n() != 0) {
500 gclog_or_tty->print_cr("Card table has %d entries; %d originally",
501 count2.n(), orig_count);
502 }
503 guarantee(count2.n() == 0, "Card table should be clean.");
505 RedirtyLoggedCardTableEntryClosure redirty;
506 JavaThread::dirty_card_queue_set().set_closure(&redirty);
507 dcqs.apply_closure_to_all_completed_buffers();
508 dcqs.iterate_closure_all_threads(false);
509 gclog_or_tty->print_cr("Log entries = %d, dirty cards = %d.",
510 clear.calls(), orig_count);
511 guarantee(redirty.calls() == clear.calls(),
512 "Or else mechanism is broken.");
514 CountNonCleanMemRegionClosure count3(this);
515 ct_bs->mod_card_iterate(&count3);
516 if (count3.n() != orig_count) {
517 gclog_or_tty->print_cr("Should have restored them all: orig = %d, final = %d.",
518 orig_count, count3.n());
519 guarantee(count3.n() >= orig_count, "Should have restored them all.");
520 }
522 JavaThread::dirty_card_queue_set().set_closure(_refine_cte_cl);
523 }
525 // Private class members.
527 G1CollectedHeap* G1CollectedHeap::_g1h;
529 // Private methods.
531 HeapRegion*
532 G1CollectedHeap::new_region_try_secondary_free_list() {
533 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
534 while (!_secondary_free_list.is_empty() || free_regions_coming()) {
535 if (!_secondary_free_list.is_empty()) {
536 if (G1ConcRegionFreeingVerbose) {
537 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
538 "secondary_free_list has "SIZE_FORMAT" entries",
539 _secondary_free_list.length());
540 }
541 // It looks as if there are free regions available on the
542 // secondary_free_list. Let's move them to the free_list and try
543 // again to allocate from it.
544 append_secondary_free_list();
546 assert(!_free_list.is_empty(), "if the secondary_free_list was not "
547 "empty we should have moved at least one entry to the free_list");
548 HeapRegion* res = _free_list.remove_head();
549 if (G1ConcRegionFreeingVerbose) {
550 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
551 "allocated "HR_FORMAT" from secondary_free_list",
552 HR_FORMAT_PARAMS(res));
553 }
554 return res;
555 }
557 // Wait here until we get notifed either when (a) there are no
558 // more free regions coming or (b) some regions have been moved on
559 // the secondary_free_list.
560 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
561 }
563 if (G1ConcRegionFreeingVerbose) {
564 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
565 "could not allocate from secondary_free_list");
566 }
567 return NULL;
568 }
570 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool do_expand) {
571 assert(!isHumongous(word_size) || word_size <= HeapRegion::GrainWords,
572 "the only time we use this to allocate a humongous region is "
573 "when we are allocating a single humongous region");
575 HeapRegion* res;
576 if (G1StressConcRegionFreeing) {
577 if (!_secondary_free_list.is_empty()) {
578 if (G1ConcRegionFreeingVerbose) {
579 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
580 "forced to look at the secondary_free_list");
581 }
582 res = new_region_try_secondary_free_list();
583 if (res != NULL) {
584 return res;
585 }
586 }
587 }
588 res = _free_list.remove_head_or_null();
589 if (res == NULL) {
590 if (G1ConcRegionFreeingVerbose) {
591 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
592 "res == NULL, trying the secondary_free_list");
593 }
594 res = new_region_try_secondary_free_list();
595 }
596 if (res == NULL && do_expand && _expand_heap_after_alloc_failure) {
597 // Currently, only attempts to allocate GC alloc regions set
598 // do_expand to true. So, we should only reach here during a
599 // safepoint. If this assumption changes we might have to
600 // reconsider the use of _expand_heap_after_alloc_failure.
601 assert(SafepointSynchronize::is_at_safepoint(), "invariant");
603 ergo_verbose1(ErgoHeapSizing,
604 "attempt heap expansion",
605 ergo_format_reason("region allocation request failed")
606 ergo_format_byte("allocation request"),
607 word_size * HeapWordSize);
608 if (expand(word_size * HeapWordSize)) {
609 // Given that expand() succeeded in expanding the heap, and we
610 // always expand the heap by an amount aligned to the heap
611 // region size, the free list should in theory not be empty. So
612 // it would probably be OK to use remove_head(). But the extra
613 // check for NULL is unlikely to be a performance issue here (we
614 // just expanded the heap!) so let's just be conservative and
615 // use remove_head_or_null().
616 res = _free_list.remove_head_or_null();
617 } else {
618 _expand_heap_after_alloc_failure = false;
619 }
620 }
621 return res;
622 }
624 size_t G1CollectedHeap::humongous_obj_allocate_find_first(size_t num_regions,
625 size_t word_size) {
626 assert(isHumongous(word_size), "word_size should be humongous");
627 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
629 size_t first = G1_NULL_HRS_INDEX;
630 if (num_regions == 1) {
631 // Only one region to allocate, no need to go through the slower
632 // path. The caller will attempt the expasion if this fails, so
633 // let's not try to expand here too.
634 HeapRegion* hr = new_region(word_size, false /* do_expand */);
635 if (hr != NULL) {
636 first = hr->hrs_index();
637 } else {
638 first = G1_NULL_HRS_INDEX;
639 }
640 } else {
641 // We can't allocate humongous regions while cleanupComplete() is
642 // running, since some of the regions we find to be empty might not
643 // yet be added to the free list and it is not straightforward to
644 // know which list they are on so that we can remove them. Note
645 // that we only need to do this if we need to allocate more than
646 // one region to satisfy the current humongous allocation
647 // request. If we are only allocating one region we use the common
648 // region allocation code (see above).
649 wait_while_free_regions_coming();
650 append_secondary_free_list_if_not_empty_with_lock();
652 if (free_regions() >= num_regions) {
653 first = _hrs.find_contiguous(num_regions);
654 if (first != G1_NULL_HRS_INDEX) {
655 for (size_t i = first; i < first + num_regions; ++i) {
656 HeapRegion* hr = region_at(i);
657 assert(hr->is_empty(), "sanity");
658 assert(is_on_master_free_list(hr), "sanity");
659 hr->set_pending_removal(true);
660 }
661 _free_list.remove_all_pending(num_regions);
662 }
663 }
664 }
665 return first;
666 }
668 HeapWord*
669 G1CollectedHeap::humongous_obj_allocate_initialize_regions(size_t first,
670 size_t num_regions,
671 size_t word_size) {
672 assert(first != G1_NULL_HRS_INDEX, "pre-condition");
673 assert(isHumongous(word_size), "word_size should be humongous");
674 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
676 // Index of last region in the series + 1.
677 size_t last = first + num_regions;
679 // We need to initialize the region(s) we just discovered. This is
680 // a bit tricky given that it can happen concurrently with
681 // refinement threads refining cards on these regions and
682 // potentially wanting to refine the BOT as they are scanning
683 // those cards (this can happen shortly after a cleanup; see CR
684 // 6991377). So we have to set up the region(s) carefully and in
685 // a specific order.
687 // The word size sum of all the regions we will allocate.
688 size_t word_size_sum = num_regions * HeapRegion::GrainWords;
689 assert(word_size <= word_size_sum, "sanity");
691 // This will be the "starts humongous" region.
692 HeapRegion* first_hr = region_at(first);
693 // The header of the new object will be placed at the bottom of
694 // the first region.
695 HeapWord* new_obj = first_hr->bottom();
696 // This will be the new end of the first region in the series that
697 // should also match the end of the last region in the seriers.
698 HeapWord* new_end = new_obj + word_size_sum;
699 // This will be the new top of the first region that will reflect
700 // this allocation.
701 HeapWord* new_top = new_obj + word_size;
703 // First, we need to zero the header of the space that we will be
704 // allocating. When we update top further down, some refinement
705 // threads might try to scan the region. By zeroing the header we
706 // ensure that any thread that will try to scan the region will
707 // come across the zero klass word and bail out.
708 //
709 // NOTE: It would not have been correct to have used
710 // CollectedHeap::fill_with_object() and make the space look like
711 // an int array. The thread that is doing the allocation will
712 // later update the object header to a potentially different array
713 // type and, for a very short period of time, the klass and length
714 // fields will be inconsistent. This could cause a refinement
715 // thread to calculate the object size incorrectly.
716 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
718 // We will set up the first region as "starts humongous". This
719 // will also update the BOT covering all the regions to reflect
720 // that there is a single object that starts at the bottom of the
721 // first region.
722 first_hr->set_startsHumongous(new_top, new_end);
724 // Then, if there are any, we will set up the "continues
725 // humongous" regions.
726 HeapRegion* hr = NULL;
727 for (size_t i = first + 1; i < last; ++i) {
728 hr = region_at(i);
729 hr->set_continuesHumongous(first_hr);
730 }
731 // If we have "continues humongous" regions (hr != NULL), then the
732 // end of the last one should match new_end.
733 assert(hr == NULL || hr->end() == new_end, "sanity");
735 // Up to this point no concurrent thread would have been able to
736 // do any scanning on any region in this series. All the top
737 // fields still point to bottom, so the intersection between
738 // [bottom,top] and [card_start,card_end] will be empty. Before we
739 // update the top fields, we'll do a storestore to make sure that
740 // no thread sees the update to top before the zeroing of the
741 // object header and the BOT initialization.
742 OrderAccess::storestore();
744 // Now that the BOT and the object header have been initialized,
745 // we can update top of the "starts humongous" region.
746 assert(first_hr->bottom() < new_top && new_top <= first_hr->end(),
747 "new_top should be in this region");
748 first_hr->set_top(new_top);
749 if (_hr_printer.is_active()) {
750 HeapWord* bottom = first_hr->bottom();
751 HeapWord* end = first_hr->orig_end();
752 if ((first + 1) == last) {
753 // the series has a single humongous region
754 _hr_printer.alloc(G1HRPrinter::SingleHumongous, first_hr, new_top);
755 } else {
756 // the series has more than one humongous regions
757 _hr_printer.alloc(G1HRPrinter::StartsHumongous, first_hr, end);
758 }
759 }
761 // Now, we will update the top fields of the "continues humongous"
762 // regions. The reason we need to do this is that, otherwise,
763 // these regions would look empty and this will confuse parts of
764 // G1. For example, the code that looks for a consecutive number
765 // of empty regions will consider them empty and try to
766 // re-allocate them. We can extend is_empty() to also include
767 // !continuesHumongous(), but it is easier to just update the top
768 // fields here. The way we set top for all regions (i.e., top ==
769 // end for all regions but the last one, top == new_top for the
770 // last one) is actually used when we will free up the humongous
771 // region in free_humongous_region().
772 hr = NULL;
773 for (size_t i = first + 1; i < last; ++i) {
774 hr = region_at(i);
775 if ((i + 1) == last) {
776 // last continues humongous region
777 assert(hr->bottom() < new_top && new_top <= hr->end(),
778 "new_top should fall on this region");
779 hr->set_top(new_top);
780 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, new_top);
781 } else {
782 // not last one
783 assert(new_top > hr->end(), "new_top should be above this region");
784 hr->set_top(hr->end());
785 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, hr->end());
786 }
787 }
788 // If we have continues humongous regions (hr != NULL), then the
789 // end of the last one should match new_end and its top should
790 // match new_top.
791 assert(hr == NULL ||
792 (hr->end() == new_end && hr->top() == new_top), "sanity");
794 assert(first_hr->used() == word_size * HeapWordSize, "invariant");
795 _summary_bytes_used += first_hr->used();
796 _humongous_set.add(first_hr);
798 return new_obj;
799 }
801 // If could fit into free regions w/o expansion, try.
802 // Otherwise, if can expand, do so.
803 // Otherwise, if using ex regions might help, try with ex given back.
804 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size) {
805 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
807 verify_region_sets_optional();
809 size_t num_regions =
810 round_to(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords;
811 size_t x_size = expansion_regions();
812 size_t fs = _hrs.free_suffix();
813 size_t first = humongous_obj_allocate_find_first(num_regions, word_size);
814 if (first == G1_NULL_HRS_INDEX) {
815 // The only thing we can do now is attempt expansion.
816 if (fs + x_size >= num_regions) {
817 // If the number of regions we're trying to allocate for this
818 // object is at most the number of regions in the free suffix,
819 // then the call to humongous_obj_allocate_find_first() above
820 // should have succeeded and we wouldn't be here.
821 //
822 // We should only be trying to expand when the free suffix is
823 // not sufficient for the object _and_ we have some expansion
824 // room available.
825 assert(num_regions > fs, "earlier allocation should have succeeded");
827 ergo_verbose1(ErgoHeapSizing,
828 "attempt heap expansion",
829 ergo_format_reason("humongous allocation request failed")
830 ergo_format_byte("allocation request"),
831 word_size * HeapWordSize);
832 if (expand((num_regions - fs) * HeapRegion::GrainBytes)) {
833 // Even though the heap was expanded, it might not have
834 // reached the desired size. So, we cannot assume that the
835 // allocation will succeed.
836 first = humongous_obj_allocate_find_first(num_regions, word_size);
837 }
838 }
839 }
841 HeapWord* result = NULL;
842 if (first != G1_NULL_HRS_INDEX) {
843 result =
844 humongous_obj_allocate_initialize_regions(first, num_regions, word_size);
845 assert(result != NULL, "it should always return a valid result");
847 // A successful humongous object allocation changes the used space
848 // information of the old generation so we need to recalculate the
849 // sizes and update the jstat counters here.
850 g1mm()->update_sizes();
851 }
853 verify_region_sets_optional();
855 return result;
856 }
858 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) {
859 assert_heap_not_locked_and_not_at_safepoint();
860 assert(!isHumongous(word_size), "we do not allow humongous TLABs");
862 unsigned int dummy_gc_count_before;
863 return attempt_allocation(word_size, &dummy_gc_count_before);
864 }
866 HeapWord*
867 G1CollectedHeap::mem_allocate(size_t word_size,
868 bool* gc_overhead_limit_was_exceeded) {
869 assert_heap_not_locked_and_not_at_safepoint();
871 // Loop until the allocation is satisified, or unsatisfied after GC.
872 for (int try_count = 1; /* we'll return */; try_count += 1) {
873 unsigned int gc_count_before;
875 HeapWord* result = NULL;
876 if (!isHumongous(word_size)) {
877 result = attempt_allocation(word_size, &gc_count_before);
878 } else {
879 result = attempt_allocation_humongous(word_size, &gc_count_before);
880 }
881 if (result != NULL) {
882 return result;
883 }
885 // Create the garbage collection operation...
886 VM_G1CollectForAllocation op(gc_count_before, word_size);
887 // ...and get the VM thread to execute it.
888 VMThread::execute(&op);
890 if (op.prologue_succeeded() && op.pause_succeeded()) {
891 // If the operation was successful we'll return the result even
892 // if it is NULL. If the allocation attempt failed immediately
893 // after a Full GC, it's unlikely we'll be able to allocate now.
894 HeapWord* result = op.result();
895 if (result != NULL && !isHumongous(word_size)) {
896 // Allocations that take place on VM operations do not do any
897 // card dirtying and we have to do it here. We only have to do
898 // this for non-humongous allocations, though.
899 dirty_young_block(result, word_size);
900 }
901 return result;
902 } else {
903 assert(op.result() == NULL,
904 "the result should be NULL if the VM op did not succeed");
905 }
907 // Give a warning if we seem to be looping forever.
908 if ((QueuedAllocationWarningCount > 0) &&
909 (try_count % QueuedAllocationWarningCount == 0)) {
910 warning("G1CollectedHeap::mem_allocate retries %d times", try_count);
911 }
912 }
914 ShouldNotReachHere();
915 return NULL;
916 }
918 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size,
919 unsigned int *gc_count_before_ret) {
920 // Make sure you read the note in attempt_allocation_humongous().
922 assert_heap_not_locked_and_not_at_safepoint();
923 assert(!isHumongous(word_size), "attempt_allocation_slow() should not "
924 "be called for humongous allocation requests");
926 // We should only get here after the first-level allocation attempt
927 // (attempt_allocation()) failed to allocate.
929 // We will loop until a) we manage to successfully perform the
930 // allocation or b) we successfully schedule a collection which
931 // fails to perform the allocation. b) is the only case when we'll
932 // return NULL.
933 HeapWord* result = NULL;
934 for (int try_count = 1; /* we'll return */; try_count += 1) {
935 bool should_try_gc;
936 unsigned int gc_count_before;
938 {
939 MutexLockerEx x(Heap_lock);
941 result = _mutator_alloc_region.attempt_allocation_locked(word_size,
942 false /* bot_updates */);
943 if (result != NULL) {
944 return result;
945 }
947 // If we reach here, attempt_allocation_locked() above failed to
948 // allocate a new region. So the mutator alloc region should be NULL.
949 assert(_mutator_alloc_region.get() == NULL, "only way to get here");
951 if (GC_locker::is_active_and_needs_gc()) {
952 if (g1_policy()->can_expand_young_list()) {
953 // No need for an ergo verbose message here,
954 // can_expand_young_list() does this when it returns true.
955 result = _mutator_alloc_region.attempt_allocation_force(word_size,
956 false /* bot_updates */);
957 if (result != NULL) {
958 return result;
959 }
960 }
961 should_try_gc = false;
962 } else {
963 // Read the GC count while still holding the Heap_lock.
964 gc_count_before = SharedHeap::heap()->total_collections();
965 should_try_gc = true;
966 }
967 }
969 if (should_try_gc) {
970 bool succeeded;
971 result = do_collection_pause(word_size, gc_count_before, &succeeded);
972 if (result != NULL) {
973 assert(succeeded, "only way to get back a non-NULL result");
974 return result;
975 }
977 if (succeeded) {
978 // If we get here we successfully scheduled a collection which
979 // failed to allocate. No point in trying to allocate
980 // further. We'll just return NULL.
981 MutexLockerEx x(Heap_lock);
982 *gc_count_before_ret = SharedHeap::heap()->total_collections();
983 return NULL;
984 }
985 } else {
986 GC_locker::stall_until_clear();
987 }
989 // We can reach here if we were unsuccessul in scheduling a
990 // collection (because another thread beat us to it) or if we were
991 // stalled due to the GC locker. In either can we should retry the
992 // allocation attempt in case another thread successfully
993 // performed a collection and reclaimed enough space. We do the
994 // first attempt (without holding the Heap_lock) here and the
995 // follow-on attempt will be at the start of the next loop
996 // iteration (after taking the Heap_lock).
997 result = _mutator_alloc_region.attempt_allocation(word_size,
998 false /* bot_updates */);
999 if (result != NULL ){
1000 return result;
1001 }
1003 // Give a warning if we seem to be looping forever.
1004 if ((QueuedAllocationWarningCount > 0) &&
1005 (try_count % QueuedAllocationWarningCount == 0)) {
1006 warning("G1CollectedHeap::attempt_allocation_slow() "
1007 "retries %d times", try_count);
1008 }
1009 }
1011 ShouldNotReachHere();
1012 return NULL;
1013 }
1015 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size,
1016 unsigned int * gc_count_before_ret) {
1017 // The structure of this method has a lot of similarities to
1018 // attempt_allocation_slow(). The reason these two were not merged
1019 // into a single one is that such a method would require several "if
1020 // allocation is not humongous do this, otherwise do that"
1021 // conditional paths which would obscure its flow. In fact, an early
1022 // version of this code did use a unified method which was harder to
1023 // follow and, as a result, it had subtle bugs that were hard to
1024 // track down. So keeping these two methods separate allows each to
1025 // be more readable. It will be good to keep these two in sync as
1026 // much as possible.
1028 assert_heap_not_locked_and_not_at_safepoint();
1029 assert(isHumongous(word_size), "attempt_allocation_humongous() "
1030 "should only be called for humongous allocations");
1032 // We will loop until a) we manage to successfully perform the
1033 // allocation or b) we successfully schedule a collection which
1034 // fails to perform the allocation. b) is the only case when we'll
1035 // return NULL.
1036 HeapWord* result = NULL;
1037 for (int try_count = 1; /* we'll return */; try_count += 1) {
1038 bool should_try_gc;
1039 unsigned int gc_count_before;
1041 {
1042 MutexLockerEx x(Heap_lock);
1044 // Given that humongous objects are not allocated in young
1045 // regions, we'll first try to do the allocation without doing a
1046 // collection hoping that there's enough space in the heap.
1047 result = humongous_obj_allocate(word_size);
1049 if (result == NULL) {
1050 if (GC_locker::is_active_and_needs_gc()) {
1051 should_try_gc = false;
1052 } else {
1053 // Read the GC count while still holding the Heap_lock.
1054 gc_count_before = SharedHeap::heap()->total_collections();
1055 should_try_gc = true;
1056 }
1057 }
1058 }
1060 if (result != NULL) {
1061 if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation")) {
1062 // We need to release the Heap_lock before we try to call collect().
1063 // The result will not be stored in any object before this method
1064 // returns, so the GC might miss it. Thus, we create a handle to the result
1065 // and fake an object at that place.
1066 CollectedHeap::fill_with_object(result, word_size, false);
1067 Handle h((oop)result);
1068 collect(GCCause::_g1_humongous_allocation);
1069 assert(result == (HeapWord*)h(), "Humongous objects should not be moved by collections");
1070 }
1071 return result;
1072 }
1074 if (should_try_gc) {
1075 // If we failed to allocate the humongous object, we should try to
1076 // do a collection pause (if we're allowed) in case it reclaims
1077 // enough space for the allocation to succeed after the pause.
1079 bool succeeded;
1080 result = do_collection_pause(word_size, gc_count_before, &succeeded);
1081 if (result != NULL) {
1082 assert(succeeded, "only way to get back a non-NULL result");
1083 return result;
1084 }
1086 if (succeeded) {
1087 // If we get here we successfully scheduled a collection which
1088 // failed to allocate. No point in trying to allocate
1089 // further. We'll just return NULL.
1090 MutexLockerEx x(Heap_lock);
1091 *gc_count_before_ret = SharedHeap::heap()->total_collections();
1092 return NULL;
1093 }
1094 } else {
1095 GC_locker::stall_until_clear();
1096 }
1098 // We can reach here if we were unsuccessul in scheduling a
1099 // collection (because another thread beat us to it) or if we were
1100 // stalled due to the GC locker. In either can we should retry the
1101 // allocation attempt in case another thread successfully
1102 // performed a collection and reclaimed enough space. Give a
1103 // warning if we seem to be looping forever.
1105 if ((QueuedAllocationWarningCount > 0) &&
1106 (try_count % QueuedAllocationWarningCount == 0)) {
1107 warning("G1CollectedHeap::attempt_allocation_humongous() "
1108 "retries %d times", try_count);
1109 }
1110 }
1112 ShouldNotReachHere();
1113 return NULL;
1114 }
1116 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
1117 bool expect_null_mutator_alloc_region) {
1118 assert_at_safepoint(true /* should_be_vm_thread */);
1119 assert(_mutator_alloc_region.get() == NULL ||
1120 !expect_null_mutator_alloc_region,
1121 "the current alloc region was unexpectedly found to be non-NULL");
1123 if (!isHumongous(word_size)) {
1124 return _mutator_alloc_region.attempt_allocation_locked(word_size,
1125 false /* bot_updates */);
1126 } else {
1127 HeapWord* result = humongous_obj_allocate(word_size);
1128 if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) {
1129 g1_policy()->set_initiate_conc_mark_if_possible();
1130 }
1131 return result;
1132 }
1134 ShouldNotReachHere();
1135 }
1137 class PostMCRemSetClearClosure: public HeapRegionClosure {
1138 ModRefBarrierSet* _mr_bs;
1139 public:
1140 PostMCRemSetClearClosure(ModRefBarrierSet* mr_bs) : _mr_bs(mr_bs) {}
1141 bool doHeapRegion(HeapRegion* r) {
1142 r->reset_gc_time_stamp();
1143 if (r->continuesHumongous())
1144 return false;
1145 HeapRegionRemSet* hrrs = r->rem_set();
1146 if (hrrs != NULL) hrrs->clear();
1147 // You might think here that we could clear just the cards
1148 // corresponding to the used region. But no: if we leave a dirty card
1149 // in a region we might allocate into, then it would prevent that card
1150 // from being enqueued, and cause it to be missed.
1151 // Re: the performance cost: we shouldn't be doing full GC anyway!
1152 _mr_bs->clear(MemRegion(r->bottom(), r->end()));
1153 return false;
1154 }
1155 };
1158 class PostMCRemSetInvalidateClosure: public HeapRegionClosure {
1159 ModRefBarrierSet* _mr_bs;
1160 public:
1161 PostMCRemSetInvalidateClosure(ModRefBarrierSet* mr_bs) : _mr_bs(mr_bs) {}
1162 bool doHeapRegion(HeapRegion* r) {
1163 if (r->continuesHumongous()) return false;
1164 if (r->used_region().word_size() != 0) {
1165 _mr_bs->invalidate(r->used_region(), true /*whole heap*/);
1166 }
1167 return false;
1168 }
1169 };
1171 class RebuildRSOutOfRegionClosure: public HeapRegionClosure {
1172 G1CollectedHeap* _g1h;
1173 UpdateRSOopClosure _cl;
1174 int _worker_i;
1175 public:
1176 RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, int worker_i = 0) :
1177 _cl(g1->g1_rem_set(), worker_i),
1178 _worker_i(worker_i),
1179 _g1h(g1)
1180 { }
1182 bool doHeapRegion(HeapRegion* r) {
1183 if (!r->continuesHumongous()) {
1184 _cl.set_from(r);
1185 r->oop_iterate(&_cl);
1186 }
1187 return false;
1188 }
1189 };
1191 class ParRebuildRSTask: public AbstractGangTask {
1192 G1CollectedHeap* _g1;
1193 public:
1194 ParRebuildRSTask(G1CollectedHeap* g1)
1195 : AbstractGangTask("ParRebuildRSTask"),
1196 _g1(g1)
1197 { }
1199 void work(uint worker_id) {
1200 RebuildRSOutOfRegionClosure rebuild_rs(_g1, worker_id);
1201 _g1->heap_region_par_iterate_chunked(&rebuild_rs, worker_id,
1202 _g1->workers()->active_workers(),
1203 HeapRegion::RebuildRSClaimValue);
1204 }
1205 };
1207 class PostCompactionPrinterClosure: public HeapRegionClosure {
1208 private:
1209 G1HRPrinter* _hr_printer;
1210 public:
1211 bool doHeapRegion(HeapRegion* hr) {
1212 assert(!hr->is_young(), "not expecting to find young regions");
1213 // We only generate output for non-empty regions.
1214 if (!hr->is_empty()) {
1215 if (!hr->isHumongous()) {
1216 _hr_printer->post_compaction(hr, G1HRPrinter::Old);
1217 } else if (hr->startsHumongous()) {
1218 if (hr->capacity() == HeapRegion::GrainBytes) {
1219 // single humongous region
1220 _hr_printer->post_compaction(hr, G1HRPrinter::SingleHumongous);
1221 } else {
1222 _hr_printer->post_compaction(hr, G1HRPrinter::StartsHumongous);
1223 }
1224 } else {
1225 assert(hr->continuesHumongous(), "only way to get here");
1226 _hr_printer->post_compaction(hr, G1HRPrinter::ContinuesHumongous);
1227 }
1228 }
1229 return false;
1230 }
1232 PostCompactionPrinterClosure(G1HRPrinter* hr_printer)
1233 : _hr_printer(hr_printer) { }
1234 };
1236 bool G1CollectedHeap::do_collection(bool explicit_gc,
1237 bool clear_all_soft_refs,
1238 size_t word_size) {
1239 assert_at_safepoint(true /* should_be_vm_thread */);
1241 if (GC_locker::check_active_before_gc()) {
1242 return false;
1243 }
1245 SvcGCMarker sgcm(SvcGCMarker::FULL);
1246 ResourceMark rm;
1248 if (PrintHeapAtGC) {
1249 Universe::print_heap_before_gc();
1250 }
1252 HRSPhaseSetter x(HRSPhaseFullGC);
1253 verify_region_sets_optional();
1255 const bool do_clear_all_soft_refs = clear_all_soft_refs ||
1256 collector_policy()->should_clear_all_soft_refs();
1258 ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy());
1260 {
1261 IsGCActiveMark x;
1263 // Timing
1264 bool system_gc = (gc_cause() == GCCause::_java_lang_system_gc);
1265 assert(!system_gc || explicit_gc, "invariant");
1266 gclog_or_tty->date_stamp(PrintGC && PrintGCDateStamps);
1267 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty);
1268 TraceTime t(system_gc ? "Full GC (System.gc())" : "Full GC",
1269 PrintGC, true, gclog_or_tty);
1271 TraceCollectorStats tcs(g1mm()->full_collection_counters());
1272 TraceMemoryManagerStats tms(true /* fullGC */, gc_cause());
1274 double start = os::elapsedTime();
1275 g1_policy()->record_full_collection_start();
1277 wait_while_free_regions_coming();
1278 append_secondary_free_list_if_not_empty_with_lock();
1280 gc_prologue(true);
1281 increment_total_collections(true /* full gc */);
1283 size_t g1h_prev_used = used();
1284 assert(used() == recalculate_used(), "Should be equal");
1286 if (VerifyBeforeGC && total_collections() >= VerifyGCStartAt) {
1287 HandleMark hm; // Discard invalid handles created during verification
1288 gclog_or_tty->print(" VerifyBeforeGC:");
1289 prepare_for_verify();
1290 Universe::verify(/* allow dirty */ true,
1291 /* silent */ false,
1292 /* option */ VerifyOption_G1UsePrevMarking);
1294 }
1295 pre_full_gc_dump();
1297 COMPILER2_PRESENT(DerivedPointerTable::clear());
1299 // Disable discovery and empty the discovered lists
1300 // for the CM ref processor.
1301 ref_processor_cm()->disable_discovery();
1302 ref_processor_cm()->abandon_partial_discovery();
1303 ref_processor_cm()->verify_no_references_recorded();
1305 // Abandon current iterations of concurrent marking and concurrent
1306 // refinement, if any are in progress.
1307 concurrent_mark()->abort();
1309 // Make sure we'll choose a new allocation region afterwards.
1310 release_mutator_alloc_region();
1311 abandon_gc_alloc_regions();
1312 g1_rem_set()->cleanupHRRS();
1314 // We should call this after we retire any currently active alloc
1315 // regions so that all the ALLOC / RETIRE events are generated
1316 // before the start GC event.
1317 _hr_printer.start_gc(true /* full */, (size_t) total_collections());
1319 // We may have added regions to the current incremental collection
1320 // set between the last GC or pause and now. We need to clear the
1321 // incremental collection set and then start rebuilding it afresh
1322 // after this full GC.
1323 abandon_collection_set(g1_policy()->inc_cset_head());
1324 g1_policy()->clear_incremental_cset();
1325 g1_policy()->stop_incremental_cset_building();
1327 tear_down_region_sets(false /* free_list_only */);
1328 g1_policy()->set_gcs_are_young(true);
1330 // See the comments in g1CollectedHeap.hpp and
1331 // G1CollectedHeap::ref_processing_init() about
1332 // how reference processing currently works in G1.
1334 // Temporarily make discovery by the STW ref processor single threaded (non-MT).
1335 ReferenceProcessorMTDiscoveryMutator stw_rp_disc_ser(ref_processor_stw(), false);
1337 // Temporarily clear the STW ref processor's _is_alive_non_header field.
1338 ReferenceProcessorIsAliveMutator stw_rp_is_alive_null(ref_processor_stw(), NULL);
1340 ref_processor_stw()->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/);
1341 ref_processor_stw()->setup_policy(do_clear_all_soft_refs);
1343 // Do collection work
1344 {
1345 HandleMark hm; // Discard invalid handles created during gc
1346 G1MarkSweep::invoke_at_safepoint(ref_processor_stw(), do_clear_all_soft_refs);
1347 }
1349 assert(free_regions() == 0, "we should not have added any free regions");
1350 rebuild_region_sets(false /* free_list_only */);
1352 // Enqueue any discovered reference objects that have
1353 // not been removed from the discovered lists.
1354 ref_processor_stw()->enqueue_discovered_references();
1356 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
1358 MemoryService::track_memory_usage();
1360 if (VerifyAfterGC && total_collections() >= VerifyGCStartAt) {
1361 HandleMark hm; // Discard invalid handles created during verification
1362 gclog_or_tty->print(" VerifyAfterGC:");
1363 prepare_for_verify();
1364 Universe::verify(/* allow dirty */ false,
1365 /* silent */ false,
1366 /* option */ VerifyOption_G1UsePrevMarking);
1368 }
1370 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
1371 ref_processor_stw()->verify_no_references_recorded();
1373 // Note: since we've just done a full GC, concurrent
1374 // marking is no longer active. Therefore we need not
1375 // re-enable reference discovery for the CM ref processor.
1376 // That will be done at the start of the next marking cycle.
1377 assert(!ref_processor_cm()->discovery_enabled(), "Postcondition");
1378 ref_processor_cm()->verify_no_references_recorded();
1380 reset_gc_time_stamp();
1381 // Since everything potentially moved, we will clear all remembered
1382 // sets, and clear all cards. Later we will rebuild remebered
1383 // sets. We will also reset the GC time stamps of the regions.
1384 PostMCRemSetClearClosure rs_clear(mr_bs());
1385 heap_region_iterate(&rs_clear);
1387 // Resize the heap if necessary.
1388 resize_if_necessary_after_full_collection(explicit_gc ? 0 : word_size);
1390 if (_hr_printer.is_active()) {
1391 // We should do this after we potentially resize the heap so
1392 // that all the COMMIT / UNCOMMIT events are generated before
1393 // the end GC event.
1395 PostCompactionPrinterClosure cl(hr_printer());
1396 heap_region_iterate(&cl);
1398 _hr_printer.end_gc(true /* full */, (size_t) total_collections());
1399 }
1401 if (_cg1r->use_cache()) {
1402 _cg1r->clear_and_record_card_counts();
1403 _cg1r->clear_hot_cache();
1404 }
1406 // Rebuild remembered sets of all regions.
1407 if (G1CollectedHeap::use_parallel_gc_threads()) {
1408 uint n_workers =
1409 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
1410 workers()->active_workers(),
1411 Threads::number_of_non_daemon_threads());
1412 assert(UseDynamicNumberOfGCThreads ||
1413 n_workers == workers()->total_workers(),
1414 "If not dynamic should be using all the workers");
1415 workers()->set_active_workers(n_workers);
1416 // Set parallel threads in the heap (_n_par_threads) only
1417 // before a parallel phase and always reset it to 0 after
1418 // the phase so that the number of parallel threads does
1419 // no get carried forward to a serial phase where there
1420 // may be code that is "possibly_parallel".
1421 set_par_threads(n_workers);
1423 ParRebuildRSTask rebuild_rs_task(this);
1424 assert(check_heap_region_claim_values(
1425 HeapRegion::InitialClaimValue), "sanity check");
1426 assert(UseDynamicNumberOfGCThreads ||
1427 workers()->active_workers() == workers()->total_workers(),
1428 "Unless dynamic should use total workers");
1429 // Use the most recent number of active workers
1430 assert(workers()->active_workers() > 0,
1431 "Active workers not properly set");
1432 set_par_threads(workers()->active_workers());
1433 workers()->run_task(&rebuild_rs_task);
1434 set_par_threads(0);
1435 assert(check_heap_region_claim_values(
1436 HeapRegion::RebuildRSClaimValue), "sanity check");
1437 reset_heap_region_claim_values();
1438 } else {
1439 RebuildRSOutOfRegionClosure rebuild_rs(this);
1440 heap_region_iterate(&rebuild_rs);
1441 }
1443 if (PrintGC) {
1444 print_size_transition(gclog_or_tty, g1h_prev_used, used(), capacity());
1445 }
1447 if (true) { // FIXME
1448 // Ask the permanent generation to adjust size for full collections
1449 perm()->compute_new_size();
1450 }
1452 // Start a new incremental collection set for the next pause
1453 assert(g1_policy()->collection_set() == NULL, "must be");
1454 g1_policy()->start_incremental_cset_building();
1456 // Clear the _cset_fast_test bitmap in anticipation of adding
1457 // regions to the incremental collection set for the next
1458 // evacuation pause.
1459 clear_cset_fast_test();
1461 init_mutator_alloc_region();
1463 double end = os::elapsedTime();
1464 g1_policy()->record_full_collection_end();
1466 #ifdef TRACESPINNING
1467 ParallelTaskTerminator::print_termination_counts();
1468 #endif
1470 gc_epilogue(true);
1472 // Discard all rset updates
1473 JavaThread::dirty_card_queue_set().abandon_logs();
1474 assert(!G1DeferredRSUpdate
1475 || (G1DeferredRSUpdate && (dirty_card_queue_set().completed_buffers_num() == 0)), "Should not be any");
1476 }
1478 _young_list->reset_sampled_info();
1479 // At this point there should be no regions in the
1480 // entire heap tagged as young.
1481 assert( check_young_list_empty(true /* check_heap */),
1482 "young list should be empty at this point");
1484 // Update the number of full collections that have been completed.
1485 increment_full_collections_completed(false /* concurrent */);
1487 _hrs.verify_optional();
1488 verify_region_sets_optional();
1490 if (PrintHeapAtGC) {
1491 Universe::print_heap_after_gc();
1492 }
1493 g1mm()->update_sizes();
1494 post_full_gc_dump();
1496 return true;
1497 }
1499 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
1500 // do_collection() will return whether it succeeded in performing
1501 // the GC. Currently, there is no facility on the
1502 // do_full_collection() API to notify the caller than the collection
1503 // did not succeed (e.g., because it was locked out by the GC
1504 // locker). So, right now, we'll ignore the return value.
1505 bool dummy = do_collection(true, /* explicit_gc */
1506 clear_all_soft_refs,
1507 0 /* word_size */);
1508 }
1510 // This code is mostly copied from TenuredGeneration.
1511 void
1512 G1CollectedHeap::
1513 resize_if_necessary_after_full_collection(size_t word_size) {
1514 assert(MinHeapFreeRatio <= MaxHeapFreeRatio, "sanity check");
1516 // Include the current allocation, if any, and bytes that will be
1517 // pre-allocated to support collections, as "used".
1518 const size_t used_after_gc = used();
1519 const size_t capacity_after_gc = capacity();
1520 const size_t free_after_gc = capacity_after_gc - used_after_gc;
1522 // This is enforced in arguments.cpp.
1523 assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
1524 "otherwise the code below doesn't make sense");
1526 // We don't have floating point command-line arguments
1527 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
1528 const double maximum_used_percentage = 1.0 - minimum_free_percentage;
1529 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
1530 const double minimum_used_percentage = 1.0 - maximum_free_percentage;
1532 const size_t min_heap_size = collector_policy()->min_heap_byte_size();
1533 const size_t max_heap_size = collector_policy()->max_heap_byte_size();
1535 // We have to be careful here as these two calculations can overflow
1536 // 32-bit size_t's.
1537 double used_after_gc_d = (double) used_after_gc;
1538 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
1539 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
1541 // Let's make sure that they are both under the max heap size, which
1542 // by default will make them fit into a size_t.
1543 double desired_capacity_upper_bound = (double) max_heap_size;
1544 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
1545 desired_capacity_upper_bound);
1546 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
1547 desired_capacity_upper_bound);
1549 // We can now safely turn them into size_t's.
1550 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
1551 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
1553 // This assert only makes sense here, before we adjust them
1554 // with respect to the min and max heap size.
1555 assert(minimum_desired_capacity <= maximum_desired_capacity,
1556 err_msg("minimum_desired_capacity = "SIZE_FORMAT", "
1557 "maximum_desired_capacity = "SIZE_FORMAT,
1558 minimum_desired_capacity, maximum_desired_capacity));
1560 // Should not be greater than the heap max size. No need to adjust
1561 // it with respect to the heap min size as it's a lower bound (i.e.,
1562 // we'll try to make the capacity larger than it, not smaller).
1563 minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size);
1564 // Should not be less than the heap min size. No need to adjust it
1565 // with respect to the heap max size as it's an upper bound (i.e.,
1566 // we'll try to make the capacity smaller than it, not greater).
1567 maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size);
1569 if (capacity_after_gc < minimum_desired_capacity) {
1570 // Don't expand unless it's significant
1571 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
1572 ergo_verbose4(ErgoHeapSizing,
1573 "attempt heap expansion",
1574 ergo_format_reason("capacity lower than "
1575 "min desired capacity after Full GC")
1576 ergo_format_byte("capacity")
1577 ergo_format_byte("occupancy")
1578 ergo_format_byte_perc("min desired capacity"),
1579 capacity_after_gc, used_after_gc,
1580 minimum_desired_capacity, (double) MinHeapFreeRatio);
1581 expand(expand_bytes);
1583 // No expansion, now see if we want to shrink
1584 } else if (capacity_after_gc > maximum_desired_capacity) {
1585 // Capacity too large, compute shrinking size
1586 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
1587 ergo_verbose4(ErgoHeapSizing,
1588 "attempt heap shrinking",
1589 ergo_format_reason("capacity higher than "
1590 "max desired capacity after Full GC")
1591 ergo_format_byte("capacity")
1592 ergo_format_byte("occupancy")
1593 ergo_format_byte_perc("max desired capacity"),
1594 capacity_after_gc, used_after_gc,
1595 maximum_desired_capacity, (double) MaxHeapFreeRatio);
1596 shrink(shrink_bytes);
1597 }
1598 }
1601 HeapWord*
1602 G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
1603 bool* succeeded) {
1604 assert_at_safepoint(true /* should_be_vm_thread */);
1606 *succeeded = true;
1607 // Let's attempt the allocation first.
1608 HeapWord* result =
1609 attempt_allocation_at_safepoint(word_size,
1610 false /* expect_null_mutator_alloc_region */);
1611 if (result != NULL) {
1612 assert(*succeeded, "sanity");
1613 return result;
1614 }
1616 // In a G1 heap, we're supposed to keep allocation from failing by
1617 // incremental pauses. Therefore, at least for now, we'll favor
1618 // expansion over collection. (This might change in the future if we can
1619 // do something smarter than full collection to satisfy a failed alloc.)
1620 result = expand_and_allocate(word_size);
1621 if (result != NULL) {
1622 assert(*succeeded, "sanity");
1623 return result;
1624 }
1626 // Expansion didn't work, we'll try to do a Full GC.
1627 bool gc_succeeded = do_collection(false, /* explicit_gc */
1628 false, /* clear_all_soft_refs */
1629 word_size);
1630 if (!gc_succeeded) {
1631 *succeeded = false;
1632 return NULL;
1633 }
1635 // Retry the allocation
1636 result = attempt_allocation_at_safepoint(word_size,
1637 true /* expect_null_mutator_alloc_region */);
1638 if (result != NULL) {
1639 assert(*succeeded, "sanity");
1640 return result;
1641 }
1643 // Then, try a Full GC that will collect all soft references.
1644 gc_succeeded = do_collection(false, /* explicit_gc */
1645 true, /* clear_all_soft_refs */
1646 word_size);
1647 if (!gc_succeeded) {
1648 *succeeded = false;
1649 return NULL;
1650 }
1652 // Retry the allocation once more
1653 result = attempt_allocation_at_safepoint(word_size,
1654 true /* expect_null_mutator_alloc_region */);
1655 if (result != NULL) {
1656 assert(*succeeded, "sanity");
1657 return result;
1658 }
1660 assert(!collector_policy()->should_clear_all_soft_refs(),
1661 "Flag should have been handled and cleared prior to this point");
1663 // What else? We might try synchronous finalization later. If the total
1664 // space available is large enough for the allocation, then a more
1665 // complete compaction phase than we've tried so far might be
1666 // appropriate.
1667 assert(*succeeded, "sanity");
1668 return NULL;
1669 }
1671 // Attempting to expand the heap sufficiently
1672 // to support an allocation of the given "word_size". If
1673 // successful, perform the allocation and return the address of the
1674 // allocated block, or else "NULL".
1676 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size) {
1677 assert_at_safepoint(true /* should_be_vm_thread */);
1679 verify_region_sets_optional();
1681 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
1682 ergo_verbose1(ErgoHeapSizing,
1683 "attempt heap expansion",
1684 ergo_format_reason("allocation request failed")
1685 ergo_format_byte("allocation request"),
1686 word_size * HeapWordSize);
1687 if (expand(expand_bytes)) {
1688 _hrs.verify_optional();
1689 verify_region_sets_optional();
1690 return attempt_allocation_at_safepoint(word_size,
1691 false /* expect_null_mutator_alloc_region */);
1692 }
1693 return NULL;
1694 }
1696 void G1CollectedHeap::update_committed_space(HeapWord* old_end,
1697 HeapWord* new_end) {
1698 assert(old_end != new_end, "don't call this otherwise");
1699 assert((HeapWord*) _g1_storage.high() == new_end, "invariant");
1701 // Update the committed mem region.
1702 _g1_committed.set_end(new_end);
1703 // Tell the card table about the update.
1704 Universe::heap()->barrier_set()->resize_covered_region(_g1_committed);
1705 // Tell the BOT about the update.
1706 _bot_shared->resize(_g1_committed.word_size());
1707 }
1709 bool G1CollectedHeap::expand(size_t expand_bytes) {
1710 size_t old_mem_size = _g1_storage.committed_size();
1711 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
1712 aligned_expand_bytes = align_size_up(aligned_expand_bytes,
1713 HeapRegion::GrainBytes);
1714 ergo_verbose2(ErgoHeapSizing,
1715 "expand the heap",
1716 ergo_format_byte("requested expansion amount")
1717 ergo_format_byte("attempted expansion amount"),
1718 expand_bytes, aligned_expand_bytes);
1720 // First commit the memory.
1721 HeapWord* old_end = (HeapWord*) _g1_storage.high();
1722 bool successful = _g1_storage.expand_by(aligned_expand_bytes);
1723 if (successful) {
1724 // Then propagate this update to the necessary data structures.
1725 HeapWord* new_end = (HeapWord*) _g1_storage.high();
1726 update_committed_space(old_end, new_end);
1728 FreeRegionList expansion_list("Local Expansion List");
1729 MemRegion mr = _hrs.expand_by(old_end, new_end, &expansion_list);
1730 assert(mr.start() == old_end, "post-condition");
1731 // mr might be a smaller region than what was requested if
1732 // expand_by() was unable to allocate the HeapRegion instances
1733 assert(mr.end() <= new_end, "post-condition");
1735 size_t actual_expand_bytes = mr.byte_size();
1736 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
1737 assert(actual_expand_bytes == expansion_list.total_capacity_bytes(),
1738 "post-condition");
1739 if (actual_expand_bytes < aligned_expand_bytes) {
1740 // We could not expand _hrs to the desired size. In this case we
1741 // need to shrink the committed space accordingly.
1742 assert(mr.end() < new_end, "invariant");
1744 size_t diff_bytes = aligned_expand_bytes - actual_expand_bytes;
1745 // First uncommit the memory.
1746 _g1_storage.shrink_by(diff_bytes);
1747 // Then propagate this update to the necessary data structures.
1748 update_committed_space(new_end, mr.end());
1749 }
1750 _free_list.add_as_tail(&expansion_list);
1752 if (_hr_printer.is_active()) {
1753 HeapWord* curr = mr.start();
1754 while (curr < mr.end()) {
1755 HeapWord* curr_end = curr + HeapRegion::GrainWords;
1756 _hr_printer.commit(curr, curr_end);
1757 curr = curr_end;
1758 }
1759 assert(curr == mr.end(), "post-condition");
1760 }
1761 g1_policy()->record_new_heap_size(n_regions());
1762 } else {
1763 ergo_verbose0(ErgoHeapSizing,
1764 "did not expand the heap",
1765 ergo_format_reason("heap expansion operation failed"));
1766 // The expansion of the virtual storage space was unsuccessful.
1767 // Let's see if it was because we ran out of swap.
1768 if (G1ExitOnExpansionFailure &&
1769 _g1_storage.uncommitted_size() >= aligned_expand_bytes) {
1770 // We had head room...
1771 vm_exit_out_of_memory(aligned_expand_bytes, "G1 heap expansion");
1772 }
1773 }
1774 return successful;
1775 }
1777 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
1778 size_t old_mem_size = _g1_storage.committed_size();
1779 size_t aligned_shrink_bytes =
1780 ReservedSpace::page_align_size_down(shrink_bytes);
1781 aligned_shrink_bytes = align_size_down(aligned_shrink_bytes,
1782 HeapRegion::GrainBytes);
1783 size_t num_regions_deleted = 0;
1784 MemRegion mr = _hrs.shrink_by(aligned_shrink_bytes, &num_regions_deleted);
1785 HeapWord* old_end = (HeapWord*) _g1_storage.high();
1786 assert(mr.end() == old_end, "post-condition");
1788 ergo_verbose3(ErgoHeapSizing,
1789 "shrink the heap",
1790 ergo_format_byte("requested shrinking amount")
1791 ergo_format_byte("aligned shrinking amount")
1792 ergo_format_byte("attempted shrinking amount"),
1793 shrink_bytes, aligned_shrink_bytes, mr.byte_size());
1794 if (mr.byte_size() > 0) {
1795 if (_hr_printer.is_active()) {
1796 HeapWord* curr = mr.end();
1797 while (curr > mr.start()) {
1798 HeapWord* curr_end = curr;
1799 curr -= HeapRegion::GrainWords;
1800 _hr_printer.uncommit(curr, curr_end);
1801 }
1802 assert(curr == mr.start(), "post-condition");
1803 }
1805 _g1_storage.shrink_by(mr.byte_size());
1806 HeapWord* new_end = (HeapWord*) _g1_storage.high();
1807 assert(mr.start() == new_end, "post-condition");
1809 _expansion_regions += num_regions_deleted;
1810 update_committed_space(old_end, new_end);
1811 HeapRegionRemSet::shrink_heap(n_regions());
1812 g1_policy()->record_new_heap_size(n_regions());
1813 } else {
1814 ergo_verbose0(ErgoHeapSizing,
1815 "did not shrink the heap",
1816 ergo_format_reason("heap shrinking operation failed"));
1817 }
1818 }
1820 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1821 verify_region_sets_optional();
1823 // We should only reach here at the end of a Full GC which means we
1824 // should not not be holding to any GC alloc regions. The method
1825 // below will make sure of that and do any remaining clean up.
1826 abandon_gc_alloc_regions();
1828 // Instead of tearing down / rebuilding the free lists here, we
1829 // could instead use the remove_all_pending() method on free_list to
1830 // remove only the ones that we need to remove.
1831 tear_down_region_sets(true /* free_list_only */);
1832 shrink_helper(shrink_bytes);
1833 rebuild_region_sets(true /* free_list_only */);
1835 _hrs.verify_optional();
1836 verify_region_sets_optional();
1837 }
1839 // Public methods.
1841 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away
1842 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
1843 #endif // _MSC_VER
1846 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* policy_) :
1847 SharedHeap(policy_),
1848 _g1_policy(policy_),
1849 _dirty_card_queue_set(false),
1850 _into_cset_dirty_card_queue_set(false),
1851 _is_alive_closure_cm(this),
1852 _is_alive_closure_stw(this),
1853 _ref_processor_cm(NULL),
1854 _ref_processor_stw(NULL),
1855 _process_strong_tasks(new SubTasksDone(G1H_PS_NumElements)),
1856 _bot_shared(NULL),
1857 _objs_with_preserved_marks(NULL), _preserved_marks_of_objs(NULL),
1858 _evac_failure_scan_stack(NULL) ,
1859 _mark_in_progress(false),
1860 _cg1r(NULL), _summary_bytes_used(0),
1861 _g1mm(NULL),
1862 _refine_cte_cl(NULL),
1863 _full_collection(false),
1864 _free_list("Master Free List"),
1865 _secondary_free_list("Secondary Free List"),
1866 _old_set("Old Set"),
1867 _humongous_set("Master Humongous Set"),
1868 _free_regions_coming(false),
1869 _young_list(new YoungList(this)),
1870 _gc_time_stamp(0),
1871 _retained_old_gc_alloc_region(NULL),
1872 _expand_heap_after_alloc_failure(true),
1873 _surviving_young_words(NULL),
1874 _full_collections_completed(0),
1875 _in_cset_fast_test(NULL),
1876 _in_cset_fast_test_base(NULL),
1877 _dirty_cards_region_list(NULL),
1878 _worker_cset_start_region(NULL),
1879 _worker_cset_start_region_time_stamp(NULL) {
1880 _g1h = this; // To catch bugs.
1881 if (_process_strong_tasks == NULL || !_process_strong_tasks->valid()) {
1882 vm_exit_during_initialization("Failed necessary allocation.");
1883 }
1885 _humongous_object_threshold_in_words = HeapRegion::GrainWords / 2;
1887 int n_queues = MAX2((int)ParallelGCThreads, 1);
1888 _task_queues = new RefToScanQueueSet(n_queues);
1890 int n_rem_sets = HeapRegionRemSet::num_par_rem_sets();
1891 assert(n_rem_sets > 0, "Invariant.");
1893 HeapRegionRemSetIterator** iter_arr =
1894 NEW_C_HEAP_ARRAY(HeapRegionRemSetIterator*, n_queues);
1895 for (int i = 0; i < n_queues; i++) {
1896 iter_arr[i] = new HeapRegionRemSetIterator();
1897 }
1898 _rem_set_iterator = iter_arr;
1900 _worker_cset_start_region = NEW_C_HEAP_ARRAY(HeapRegion*, n_queues);
1901 _worker_cset_start_region_time_stamp = NEW_C_HEAP_ARRAY(unsigned int, n_queues);
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 }
1909 clear_cset_start_regions();
1911 guarantee(_task_queues != NULL, "task_queues allocation failure.");
1912 }
1914 jint G1CollectedHeap::initialize() {
1915 CollectedHeap::pre_initialize();
1916 os::enable_vtime();
1918 // Necessary to satisfy locking discipline assertions.
1920 MutexLocker x(Heap_lock);
1922 // We have to initialize the printer before committing the heap, as
1923 // it will be used then.
1924 _hr_printer.set_active(G1PrintHeapRegions);
1926 // While there are no constraints in the GC code that HeapWordSize
1927 // be any particular value, there are multiple other areas in the
1928 // system which believe this to be true (e.g. oop->object_size in some
1929 // cases incorrectly returns the size in wordSize units rather than
1930 // HeapWordSize).
1931 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
1933 size_t init_byte_size = collector_policy()->initial_heap_byte_size();
1934 size_t max_byte_size = collector_policy()->max_heap_byte_size();
1936 // Ensure that the sizes are properly aligned.
1937 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
1938 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
1940 _cg1r = new ConcurrentG1Refine();
1942 // Reserve the maximum.
1943 PermanentGenerationSpec* pgs = collector_policy()->permanent_generation();
1944 // Includes the perm-gen.
1946 // When compressed oops are enabled, the preferred heap base
1947 // is calculated by subtracting the requested size from the
1948 // 32Gb boundary and using the result as the base address for
1949 // heap reservation. If the requested size is not aligned to
1950 // HeapRegion::GrainBytes (i.e. the alignment that is passed
1951 // into the ReservedHeapSpace constructor) then the actual
1952 // base of the reserved heap may end up differing from the
1953 // address that was requested (i.e. the preferred heap base).
1954 // If this happens then we could end up using a non-optimal
1955 // compressed oops mode.
1957 // Since max_byte_size is aligned to the size of a heap region (checked
1958 // above), we also need to align the perm gen size as it might not be.
1959 const size_t total_reserved = max_byte_size +
1960 align_size_up(pgs->max_size(), HeapRegion::GrainBytes);
1961 Universe::check_alignment(total_reserved, HeapRegion::GrainBytes, "g1 heap and perm");
1963 char* addr = Universe::preferred_heap_base(total_reserved, Universe::UnscaledNarrowOop);
1965 ReservedHeapSpace heap_rs(total_reserved, HeapRegion::GrainBytes,
1966 UseLargePages, addr);
1968 if (UseCompressedOops) {
1969 if (addr != NULL && !heap_rs.is_reserved()) {
1970 // Failed to reserve at specified address - the requested memory
1971 // region is taken already, for example, by 'java' launcher.
1972 // Try again to reserver heap higher.
1973 addr = Universe::preferred_heap_base(total_reserved, Universe::ZeroBasedNarrowOop);
1975 ReservedHeapSpace heap_rs0(total_reserved, HeapRegion::GrainBytes,
1976 UseLargePages, addr);
1978 if (addr != NULL && !heap_rs0.is_reserved()) {
1979 // Failed to reserve at specified address again - give up.
1980 addr = Universe::preferred_heap_base(total_reserved, Universe::HeapBasedNarrowOop);
1981 assert(addr == NULL, "");
1983 ReservedHeapSpace heap_rs1(total_reserved, HeapRegion::GrainBytes,
1984 UseLargePages, addr);
1985 heap_rs = heap_rs1;
1986 } else {
1987 heap_rs = heap_rs0;
1988 }
1989 }
1990 }
1992 if (!heap_rs.is_reserved()) {
1993 vm_exit_during_initialization("Could not reserve enough space for object heap");
1994 return JNI_ENOMEM;
1995 }
1997 // It is important to do this in a way such that concurrent readers can't
1998 // temporarily think somethings in the heap. (I've actually seen this
1999 // happen in asserts: DLD.)
2000 _reserved.set_word_size(0);
2001 _reserved.set_start((HeapWord*)heap_rs.base());
2002 _reserved.set_end((HeapWord*)(heap_rs.base() + heap_rs.size()));
2004 _expansion_regions = max_byte_size/HeapRegion::GrainBytes;
2006 // Create the gen rem set (and barrier set) for the entire reserved region.
2007 _rem_set = collector_policy()->create_rem_set(_reserved, 2);
2008 set_barrier_set(rem_set()->bs());
2009 if (barrier_set()->is_a(BarrierSet::ModRef)) {
2010 _mr_bs = (ModRefBarrierSet*)_barrier_set;
2011 } else {
2012 vm_exit_during_initialization("G1 requires a mod ref bs.");
2013 return JNI_ENOMEM;
2014 }
2016 // Also create a G1 rem set.
2017 if (mr_bs()->is_a(BarrierSet::CardTableModRef)) {
2018 _g1_rem_set = new G1RemSet(this, (CardTableModRefBS*)mr_bs());
2019 } else {
2020 vm_exit_during_initialization("G1 requires a cardtable mod ref bs.");
2021 return JNI_ENOMEM;
2022 }
2024 // Carve out the G1 part of the heap.
2026 ReservedSpace g1_rs = heap_rs.first_part(max_byte_size);
2027 _g1_reserved = MemRegion((HeapWord*)g1_rs.base(),
2028 g1_rs.size()/HeapWordSize);
2029 ReservedSpace perm_gen_rs = heap_rs.last_part(max_byte_size);
2031 _perm_gen = pgs->init(perm_gen_rs, pgs->init_size(), rem_set());
2033 _g1_storage.initialize(g1_rs, 0);
2034 _g1_committed = MemRegion((HeapWord*)_g1_storage.low(), (size_t) 0);
2035 _hrs.initialize((HeapWord*) _g1_reserved.start(),
2036 (HeapWord*) _g1_reserved.end(),
2037 _expansion_regions);
2039 // 6843694 - ensure that the maximum region index can fit
2040 // in the remembered set structures.
2041 const size_t max_region_idx = ((size_t)1 << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
2042 guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
2044 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
2045 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
2046 guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
2047 "too many cards per region");
2049 HeapRegionSet::set_unrealistically_long_length(max_regions() + 1);
2051 _bot_shared = new G1BlockOffsetSharedArray(_reserved,
2052 heap_word_size(init_byte_size));
2054 _g1h = this;
2056 _in_cset_fast_test_length = max_regions();
2057 _in_cset_fast_test_base = NEW_C_HEAP_ARRAY(bool, _in_cset_fast_test_length);
2059 // We're biasing _in_cset_fast_test to avoid subtracting the
2060 // beginning of the heap every time we want to index; basically
2061 // it's the same with what we do with the card table.
2062 _in_cset_fast_test = _in_cset_fast_test_base -
2063 ((size_t) _g1_reserved.start() >> HeapRegion::LogOfHRGrainBytes);
2065 // Clear the _cset_fast_test bitmap in anticipation of adding
2066 // regions to the incremental collection set for the first
2067 // evacuation pause.
2068 clear_cset_fast_test();
2070 // Create the ConcurrentMark data structure and thread.
2071 // (Must do this late, so that "max_regions" is defined.)
2072 _cm = new ConcurrentMark(heap_rs, (int) max_regions());
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_exit_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 _refine_cte_cl =
2088 new RefineCardTableEntryClosure(ConcurrentG1RefineThread::sts(),
2089 g1_rem_set(),
2090 concurrent_g1_refine());
2091 JavaThread::dirty_card_queue_set().set_closure(_refine_cte_cl);
2093 JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon,
2094 SATB_Q_FL_lock,
2095 G1SATBProcessCompletedThreshold,
2096 Shared_SATB_Q_lock);
2098 JavaThread::dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
2099 DirtyCardQ_FL_lock,
2100 concurrent_g1_refine()->yellow_zone(),
2101 concurrent_g1_refine()->red_zone(),
2102 Shared_DirtyCardQ_lock);
2104 if (G1DeferredRSUpdate) {
2105 dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
2106 DirtyCardQ_FL_lock,
2107 -1, // never trigger processing
2108 -1, // no limit on length
2109 Shared_DirtyCardQ_lock,
2110 &JavaThread::dirty_card_queue_set());
2111 }
2113 // Initialize the card queue set used to hold cards containing
2114 // references into the collection set.
2115 _into_cset_dirty_card_queue_set.initialize(DirtyCardQ_CBL_mon,
2116 DirtyCardQ_FL_lock,
2117 -1, // never trigger processing
2118 -1, // no limit on length
2119 Shared_DirtyCardQ_lock,
2120 &JavaThread::dirty_card_queue_set());
2122 // In case we're keeping closure specialization stats, initialize those
2123 // counts and that mechanism.
2124 SpecializationStats::clear();
2126 // Do later initialization work for concurrent refinement.
2127 _cg1r->init();
2129 // Here we allocate the dummy full region that is required by the
2130 // G1AllocRegion class. If we don't pass an address in the reserved
2131 // space here, lots of asserts fire.
2133 HeapRegion* dummy_region = new_heap_region(0 /* index of bottom region */,
2134 _g1_reserved.start());
2135 // We'll re-use the same region whether the alloc region will
2136 // require BOT updates or not and, if it doesn't, then a non-young
2137 // region will complain that it cannot support allocations without
2138 // BOT updates. So we'll tag the dummy region as young to avoid that.
2139 dummy_region->set_young();
2140 // Make sure it's full.
2141 dummy_region->set_top(dummy_region->end());
2142 G1AllocRegion::setup(this, dummy_region);
2144 init_mutator_alloc_region();
2146 // Do create of the monitoring and management support so that
2147 // values in the heap have been properly initialized.
2148 _g1mm = new G1MonitoringSupport(this);
2150 return JNI_OK;
2151 }
2153 void G1CollectedHeap::ref_processing_init() {
2154 // Reference processing in G1 currently works as follows:
2155 //
2156 // * There are two reference processor instances. One is
2157 // used to record and process discovered references
2158 // during concurrent marking; the other is used to
2159 // record and process references during STW pauses
2160 // (both full and incremental).
2161 // * Both ref processors need to 'span' the entire heap as
2162 // the regions in the collection set may be dotted around.
2163 //
2164 // * For the concurrent marking ref processor:
2165 // * Reference discovery is enabled at initial marking.
2166 // * Reference discovery is disabled and the discovered
2167 // references processed etc during remarking.
2168 // * Reference discovery is MT (see below).
2169 // * Reference discovery requires a barrier (see below).
2170 // * Reference processing may or may not be MT
2171 // (depending on the value of ParallelRefProcEnabled
2172 // and ParallelGCThreads).
2173 // * A full GC disables reference discovery by the CM
2174 // ref processor and abandons any entries on it's
2175 // discovered lists.
2176 //
2177 // * For the STW processor:
2178 // * Non MT discovery is enabled at the start of a full GC.
2179 // * Processing and enqueueing during a full GC is non-MT.
2180 // * During a full GC, references are processed after marking.
2181 //
2182 // * Discovery (may or may not be MT) is enabled at the start
2183 // of an incremental evacuation pause.
2184 // * References are processed near the end of a STW evacuation pause.
2185 // * For both types of GC:
2186 // * Discovery is atomic - i.e. not concurrent.
2187 // * Reference discovery will not need a barrier.
2189 SharedHeap::ref_processing_init();
2190 MemRegion mr = reserved_region();
2192 // Concurrent Mark ref processor
2193 _ref_processor_cm =
2194 new ReferenceProcessor(mr, // span
2195 ParallelRefProcEnabled && (ParallelGCThreads > 1),
2196 // mt processing
2197 (int) ParallelGCThreads,
2198 // degree of mt processing
2199 (ParallelGCThreads > 1) || (ConcGCThreads > 1),
2200 // mt discovery
2201 (int) MAX2(ParallelGCThreads, ConcGCThreads),
2202 // degree of mt discovery
2203 false,
2204 // Reference discovery is not atomic
2205 &_is_alive_closure_cm,
2206 // is alive closure
2207 // (for efficiency/performance)
2208 true);
2209 // Setting next fields of discovered
2210 // lists requires a barrier.
2212 // STW ref processor
2213 _ref_processor_stw =
2214 new ReferenceProcessor(mr, // span
2215 ParallelRefProcEnabled && (ParallelGCThreads > 1),
2216 // mt processing
2217 MAX2((int)ParallelGCThreads, 1),
2218 // degree of mt processing
2219 (ParallelGCThreads > 1),
2220 // mt discovery
2221 MAX2((int)ParallelGCThreads, 1),
2222 // degree of mt discovery
2223 true,
2224 // Reference discovery is atomic
2225 &_is_alive_closure_stw,
2226 // is alive closure
2227 // (for efficiency/performance)
2228 false);
2229 // Setting next fields of discovered
2230 // lists requires a barrier.
2231 }
2233 size_t G1CollectedHeap::capacity() const {
2234 return _g1_committed.byte_size();
2235 }
2237 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl,
2238 DirtyCardQueue* into_cset_dcq,
2239 bool concurrent,
2240 int worker_i) {
2241 // Clean cards in the hot card cache
2242 concurrent_g1_refine()->clean_up_cache(worker_i, g1_rem_set(), into_cset_dcq);
2244 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2245 int n_completed_buffers = 0;
2246 while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) {
2247 n_completed_buffers++;
2248 }
2249 g1_policy()->record_update_rs_processed_buffers(worker_i,
2250 (double) n_completed_buffers);
2251 dcqs.clear_n_completed_buffers();
2252 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!");
2253 }
2256 // Computes the sum of the storage used by the various regions.
2258 size_t G1CollectedHeap::used() const {
2259 assert(Heap_lock->owner() != NULL,
2260 "Should be owned on this thread's behalf.");
2261 size_t result = _summary_bytes_used;
2262 // Read only once in case it is set to NULL concurrently
2263 HeapRegion* hr = _mutator_alloc_region.get();
2264 if (hr != NULL)
2265 result += hr->used();
2266 return result;
2267 }
2269 size_t G1CollectedHeap::used_unlocked() const {
2270 size_t result = _summary_bytes_used;
2271 return result;
2272 }
2274 class SumUsedClosure: public HeapRegionClosure {
2275 size_t _used;
2276 public:
2277 SumUsedClosure() : _used(0) {}
2278 bool doHeapRegion(HeapRegion* r) {
2279 if (!r->continuesHumongous()) {
2280 _used += r->used();
2281 }
2282 return false;
2283 }
2284 size_t result() { return _used; }
2285 };
2287 size_t G1CollectedHeap::recalculate_used() const {
2288 SumUsedClosure blk;
2289 heap_region_iterate(&blk);
2290 return blk.result();
2291 }
2293 size_t G1CollectedHeap::unsafe_max_alloc() {
2294 if (free_regions() > 0) return HeapRegion::GrainBytes;
2295 // otherwise, is there space in the current allocation region?
2297 // We need to store the current allocation region in a local variable
2298 // here. The problem is that this method doesn't take any locks and
2299 // there may be other threads which overwrite the current allocation
2300 // region field. attempt_allocation(), for example, sets it to NULL
2301 // and this can happen *after* the NULL check here but before the call
2302 // to free(), resulting in a SIGSEGV. Note that this doesn't appear
2303 // to be a problem in the optimized build, since the two loads of the
2304 // current allocation region field are optimized away.
2305 HeapRegion* hr = _mutator_alloc_region.get();
2306 if (hr == NULL) {
2307 return 0;
2308 }
2309 return hr->free();
2310 }
2312 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
2313 return
2314 ((cause == GCCause::_gc_locker && GCLockerInvokesConcurrent) ||
2315 (cause == GCCause::_java_lang_system_gc && ExplicitGCInvokesConcurrent) ||
2316 cause == GCCause::_g1_humongous_allocation);
2317 }
2319 #ifndef PRODUCT
2320 void G1CollectedHeap::allocate_dummy_regions() {
2321 // Let's fill up most of the region
2322 size_t word_size = HeapRegion::GrainWords - 1024;
2323 // And as a result the region we'll allocate will be humongous.
2324 guarantee(isHumongous(word_size), "sanity");
2326 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
2327 // Let's use the existing mechanism for the allocation
2328 HeapWord* dummy_obj = humongous_obj_allocate(word_size);
2329 if (dummy_obj != NULL) {
2330 MemRegion mr(dummy_obj, word_size);
2331 CollectedHeap::fill_with_object(mr);
2332 } else {
2333 // If we can't allocate once, we probably cannot allocate
2334 // again. Let's get out of the loop.
2335 break;
2336 }
2337 }
2338 }
2339 #endif // !PRODUCT
2341 void G1CollectedHeap::increment_full_collections_completed(bool concurrent) {
2342 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
2344 // We assume that if concurrent == true, then the caller is a
2345 // concurrent thread that was joined the Suspendible Thread
2346 // Set. If there's ever a cheap way to check this, we should add an
2347 // assert here.
2349 // We have already incremented _total_full_collections at the start
2350 // of the GC, so total_full_collections() represents how many full
2351 // collections have been started.
2352 unsigned int full_collections_started = total_full_collections();
2354 // Given that this method is called at the end of a Full GC or of a
2355 // concurrent cycle, and those can be nested (i.e., a Full GC can
2356 // interrupt a concurrent cycle), the number of full collections
2357 // completed should be either one (in the case where there was no
2358 // nesting) or two (when a Full GC interrupted a concurrent cycle)
2359 // behind the number of full collections started.
2361 // This is the case for the inner caller, i.e. a Full GC.
2362 assert(concurrent ||
2363 (full_collections_started == _full_collections_completed + 1) ||
2364 (full_collections_started == _full_collections_completed + 2),
2365 err_msg("for inner caller (Full GC): full_collections_started = %u "
2366 "is inconsistent with _full_collections_completed = %u",
2367 full_collections_started, _full_collections_completed));
2369 // This is the case for the outer caller, i.e. the concurrent cycle.
2370 assert(!concurrent ||
2371 (full_collections_started == _full_collections_completed + 1),
2372 err_msg("for outer caller (concurrent cycle): "
2373 "full_collections_started = %u "
2374 "is inconsistent with _full_collections_completed = %u",
2375 full_collections_started, _full_collections_completed));
2377 _full_collections_completed += 1;
2379 // We need to clear the "in_progress" flag in the CM thread before
2380 // we wake up any waiters (especially when ExplicitInvokesConcurrent
2381 // is set) so that if a waiter requests another System.gc() it doesn't
2382 // incorrectly see that a marking cyle is still in progress.
2383 if (concurrent) {
2384 _cmThread->clear_in_progress();
2385 }
2387 // This notify_all() will ensure that a thread that called
2388 // System.gc() with (with ExplicitGCInvokesConcurrent set or not)
2389 // and it's waiting for a full GC to finish will be woken up. It is
2390 // waiting in VM_G1IncCollectionPause::doit_epilogue().
2391 FullGCCount_lock->notify_all();
2392 }
2394 void G1CollectedHeap::collect_as_vm_thread(GCCause::Cause cause) {
2395 assert_at_safepoint(true /* should_be_vm_thread */);
2396 GCCauseSetter gcs(this, cause);
2397 switch (cause) {
2398 case GCCause::_heap_inspection:
2399 case GCCause::_heap_dump: {
2400 HandleMark hm;
2401 do_full_collection(false); // don't clear all soft refs
2402 break;
2403 }
2404 default: // XXX FIX ME
2405 ShouldNotReachHere(); // Unexpected use of this function
2406 }
2407 }
2409 void G1CollectedHeap::collect(GCCause::Cause cause) {
2410 // The caller doesn't have the Heap_lock
2411 assert(!Heap_lock->owned_by_self(), "this thread should not own the Heap_lock");
2413 unsigned int gc_count_before;
2414 unsigned int full_gc_count_before;
2415 {
2416 MutexLocker ml(Heap_lock);
2418 // Read the GC count while holding the Heap_lock
2419 gc_count_before = SharedHeap::heap()->total_collections();
2420 full_gc_count_before = SharedHeap::heap()->total_full_collections();
2421 }
2423 if (should_do_concurrent_full_gc(cause)) {
2424 // Schedule an initial-mark evacuation pause that will start a
2425 // concurrent cycle. We're setting word_size to 0 which means that
2426 // we are not requesting a post-GC allocation.
2427 VM_G1IncCollectionPause op(gc_count_before,
2428 0, /* word_size */
2429 true, /* should_initiate_conc_mark */
2430 g1_policy()->max_pause_time_ms(),
2431 cause);
2432 VMThread::execute(&op);
2433 } else {
2434 if (cause == GCCause::_gc_locker
2435 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2437 // Schedule a standard evacuation pause. We're setting word_size
2438 // to 0 which means that we are not requesting a post-GC allocation.
2439 VM_G1IncCollectionPause op(gc_count_before,
2440 0, /* word_size */
2441 false, /* should_initiate_conc_mark */
2442 g1_policy()->max_pause_time_ms(),
2443 cause);
2444 VMThread::execute(&op);
2445 } else {
2446 // Schedule a Full GC.
2447 VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause);
2448 VMThread::execute(&op);
2449 }
2450 }
2451 }
2453 bool G1CollectedHeap::is_in(const void* p) const {
2454 if (_g1_committed.contains(p)) {
2455 // Given that we know that p is in the committed space,
2456 // heap_region_containing_raw() should successfully
2457 // return the containing region.
2458 HeapRegion* hr = heap_region_containing_raw(p);
2459 return hr->is_in(p);
2460 } else {
2461 return _perm_gen->as_gen()->is_in(p);
2462 }
2463 }
2465 // Iteration functions.
2467 // Iterates an OopClosure over all ref-containing fields of objects
2468 // within a HeapRegion.
2470 class IterateOopClosureRegionClosure: public HeapRegionClosure {
2471 MemRegion _mr;
2472 OopClosure* _cl;
2473 public:
2474 IterateOopClosureRegionClosure(MemRegion mr, OopClosure* cl)
2475 : _mr(mr), _cl(cl) {}
2476 bool doHeapRegion(HeapRegion* r) {
2477 if (! r->continuesHumongous()) {
2478 r->oop_iterate(_cl);
2479 }
2480 return false;
2481 }
2482 };
2484 void G1CollectedHeap::oop_iterate(OopClosure* cl, bool do_perm) {
2485 IterateOopClosureRegionClosure blk(_g1_committed, cl);
2486 heap_region_iterate(&blk);
2487 if (do_perm) {
2488 perm_gen()->oop_iterate(cl);
2489 }
2490 }
2492 void G1CollectedHeap::oop_iterate(MemRegion mr, OopClosure* cl, bool do_perm) {
2493 IterateOopClosureRegionClosure blk(mr, cl);
2494 heap_region_iterate(&blk);
2495 if (do_perm) {
2496 perm_gen()->oop_iterate(cl);
2497 }
2498 }
2500 // Iterates an ObjectClosure over all objects within a HeapRegion.
2502 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2503 ObjectClosure* _cl;
2504 public:
2505 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2506 bool doHeapRegion(HeapRegion* r) {
2507 if (! r->continuesHumongous()) {
2508 r->object_iterate(_cl);
2509 }
2510 return false;
2511 }
2512 };
2514 void G1CollectedHeap::object_iterate(ObjectClosure* cl, bool do_perm) {
2515 IterateObjectClosureRegionClosure blk(cl);
2516 heap_region_iterate(&blk);
2517 if (do_perm) {
2518 perm_gen()->object_iterate(cl);
2519 }
2520 }
2522 void G1CollectedHeap::object_iterate_since_last_GC(ObjectClosure* cl) {
2523 // FIXME: is this right?
2524 guarantee(false, "object_iterate_since_last_GC not supported by G1 heap");
2525 }
2527 // Calls a SpaceClosure on a HeapRegion.
2529 class SpaceClosureRegionClosure: public HeapRegionClosure {
2530 SpaceClosure* _cl;
2531 public:
2532 SpaceClosureRegionClosure(SpaceClosure* cl) : _cl(cl) {}
2533 bool doHeapRegion(HeapRegion* r) {
2534 _cl->do_space(r);
2535 return false;
2536 }
2537 };
2539 void G1CollectedHeap::space_iterate(SpaceClosure* cl) {
2540 SpaceClosureRegionClosure blk(cl);
2541 heap_region_iterate(&blk);
2542 }
2544 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2545 _hrs.iterate(cl);
2546 }
2548 void G1CollectedHeap::heap_region_iterate_from(HeapRegion* r,
2549 HeapRegionClosure* cl) const {
2550 _hrs.iterate_from(r, cl);
2551 }
2553 void
2554 G1CollectedHeap::heap_region_par_iterate_chunked(HeapRegionClosure* cl,
2555 uint worker,
2556 uint no_of_par_workers,
2557 jint claim_value) {
2558 const size_t regions = n_regions();
2559 const uint max_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
2560 no_of_par_workers :
2561 1);
2562 assert(UseDynamicNumberOfGCThreads ||
2563 no_of_par_workers == workers()->total_workers(),
2564 "Non dynamic should use fixed number of workers");
2565 // try to spread out the starting points of the workers
2566 const size_t start_index = regions / max_workers * (size_t) worker;
2568 // each worker will actually look at all regions
2569 for (size_t count = 0; count < regions; ++count) {
2570 const size_t index = (start_index + count) % regions;
2571 assert(0 <= index && index < regions, "sanity");
2572 HeapRegion* r = region_at(index);
2573 // we'll ignore "continues humongous" regions (we'll process them
2574 // when we come across their corresponding "start humongous"
2575 // region) and regions already claimed
2576 if (r->claim_value() == claim_value || r->continuesHumongous()) {
2577 continue;
2578 }
2579 // OK, try to claim it
2580 if (r->claimHeapRegion(claim_value)) {
2581 // success!
2582 assert(!r->continuesHumongous(), "sanity");
2583 if (r->startsHumongous()) {
2584 // If the region is "starts humongous" we'll iterate over its
2585 // "continues humongous" first; in fact we'll do them
2586 // first. The order is important. In on case, calling the
2587 // closure on the "starts humongous" region might de-allocate
2588 // and clear all its "continues humongous" regions and, as a
2589 // result, we might end up processing them twice. So, we'll do
2590 // them first (notice: most closures will ignore them anyway) and
2591 // then we'll do the "starts humongous" region.
2592 for (size_t ch_index = index + 1; ch_index < regions; ++ch_index) {
2593 HeapRegion* chr = region_at(ch_index);
2595 // if the region has already been claimed or it's not
2596 // "continues humongous" we're done
2597 if (chr->claim_value() == claim_value ||
2598 !chr->continuesHumongous()) {
2599 break;
2600 }
2602 // Noone should have claimed it directly. We can given
2603 // that we claimed its "starts humongous" region.
2604 assert(chr->claim_value() != claim_value, "sanity");
2605 assert(chr->humongous_start_region() == r, "sanity");
2607 if (chr->claimHeapRegion(claim_value)) {
2608 // we should always be able to claim it; noone else should
2609 // be trying to claim this region
2611 bool res2 = cl->doHeapRegion(chr);
2612 assert(!res2, "Should not abort");
2614 // Right now, this holds (i.e., no closure that actually
2615 // does something with "continues humongous" regions
2616 // clears them). We might have to weaken it in the future,
2617 // but let's leave these two asserts here for extra safety.
2618 assert(chr->continuesHumongous(), "should still be the case");
2619 assert(chr->humongous_start_region() == r, "sanity");
2620 } else {
2621 guarantee(false, "we should not reach here");
2622 }
2623 }
2624 }
2626 assert(!r->continuesHumongous(), "sanity");
2627 bool res = cl->doHeapRegion(r);
2628 assert(!res, "Should not abort");
2629 }
2630 }
2631 }
2633 class ResetClaimValuesClosure: public HeapRegionClosure {
2634 public:
2635 bool doHeapRegion(HeapRegion* r) {
2636 r->set_claim_value(HeapRegion::InitialClaimValue);
2637 return false;
2638 }
2639 };
2641 void G1CollectedHeap::reset_heap_region_claim_values() {
2642 ResetClaimValuesClosure blk;
2643 heap_region_iterate(&blk);
2644 }
2646 void G1CollectedHeap::reset_cset_heap_region_claim_values() {
2647 ResetClaimValuesClosure blk;
2648 collection_set_iterate(&blk);
2649 }
2651 #ifdef ASSERT
2652 // This checks whether all regions in the heap have the correct claim
2653 // value. I also piggy-backed on this a check to ensure that the
2654 // humongous_start_region() information on "continues humongous"
2655 // regions is correct.
2657 class CheckClaimValuesClosure : public HeapRegionClosure {
2658 private:
2659 jint _claim_value;
2660 size_t _failures;
2661 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 size_t failures() {
2690 return _failures;
2691 }
2692 };
2694 bool G1CollectedHeap::check_heap_region_claim_values(jint claim_value) {
2695 CheckClaimValuesClosure cl(claim_value);
2696 heap_region_iterate(&cl);
2697 return cl.failures() == 0;
2698 }
2700 class CheckClaimValuesInCSetHRClosure: public HeapRegionClosure {
2701 jint _claim_value;
2702 size_t _failures;
2704 public:
2705 CheckClaimValuesInCSetHRClosure(jint claim_value) :
2706 _claim_value(claim_value),
2707 _failures(0) { }
2709 size_t failures() {
2710 return _failures;
2711 }
2713 bool doHeapRegion(HeapRegion* hr) {
2714 assert(hr->in_collection_set(), "how?");
2715 assert(!hr->isHumongous(), "H-region in CSet");
2716 if (hr->claim_value() != _claim_value) {
2717 gclog_or_tty->print_cr("CSet Region " HR_FORMAT ", "
2718 "claim value = %d, should be %d",
2719 HR_FORMAT_PARAMS(hr),
2720 hr->claim_value(), _claim_value);
2721 _failures += 1;
2722 }
2723 return false;
2724 }
2725 };
2727 bool G1CollectedHeap::check_cset_heap_region_claim_values(jint claim_value) {
2728 CheckClaimValuesInCSetHRClosure cl(claim_value);
2729 collection_set_iterate(&cl);
2730 return cl.failures() == 0;
2731 }
2732 #endif // ASSERT
2734 // Clear the cached CSet starting regions and (more importantly)
2735 // the time stamps. Called when we reset the GC time stamp.
2736 void G1CollectedHeap::clear_cset_start_regions() {
2737 assert(_worker_cset_start_region != NULL, "sanity");
2738 assert(_worker_cset_start_region_time_stamp != NULL, "sanity");
2740 int n_queues = MAX2((int)ParallelGCThreads, 1);
2741 for (int i = 0; i < n_queues; i++) {
2742 _worker_cset_start_region[i] = NULL;
2743 _worker_cset_start_region_time_stamp[i] = 0;
2744 }
2745 }
2747 // Given the id of a worker, obtain or calculate a suitable
2748 // starting region for iterating over the current collection set.
2749 HeapRegion* G1CollectedHeap::start_cset_region_for_worker(int worker_i) {
2750 assert(get_gc_time_stamp() > 0, "should have been updated by now");
2752 HeapRegion* result = NULL;
2753 unsigned gc_time_stamp = get_gc_time_stamp();
2755 if (_worker_cset_start_region_time_stamp[worker_i] == gc_time_stamp) {
2756 // Cached starting region for current worker was set
2757 // during the current pause - so it's valid.
2758 // Note: the cached starting heap region may be NULL
2759 // (when the collection set is empty).
2760 result = _worker_cset_start_region[worker_i];
2761 assert(result == NULL || result->in_collection_set(), "sanity");
2762 return result;
2763 }
2765 // The cached entry was not valid so let's calculate
2766 // a suitable starting heap region for this worker.
2768 // We want the parallel threads to start their collection
2769 // set iteration at different collection set regions to
2770 // avoid contention.
2771 // If we have:
2772 // n collection set regions
2773 // p threads
2774 // Then thread t will start at region floor ((t * n) / p)
2776 result = g1_policy()->collection_set();
2777 if (G1CollectedHeap::use_parallel_gc_threads()) {
2778 size_t cs_size = g1_policy()->cset_region_length();
2779 uint active_workers = workers()->active_workers();
2780 assert(UseDynamicNumberOfGCThreads ||
2781 active_workers == workers()->total_workers(),
2782 "Unless dynamic should use total workers");
2784 size_t end_ind = (cs_size * worker_i) / active_workers;
2785 size_t start_ind = 0;
2787 if (worker_i > 0 &&
2788 _worker_cset_start_region_time_stamp[worker_i - 1] == gc_time_stamp) {
2789 // Previous workers starting region is valid
2790 // so let's iterate from there
2791 start_ind = (cs_size * (worker_i - 1)) / active_workers;
2792 result = _worker_cset_start_region[worker_i - 1];
2793 }
2795 for (size_t i = start_ind; i < end_ind; i++) {
2796 result = result->next_in_collection_set();
2797 }
2798 }
2800 // Note: the calculated starting heap region may be NULL
2801 // (when the collection set is empty).
2802 assert(result == NULL || result->in_collection_set(), "sanity");
2803 assert(_worker_cset_start_region_time_stamp[worker_i] != gc_time_stamp,
2804 "should be updated only once per pause");
2805 _worker_cset_start_region[worker_i] = result;
2806 OrderAccess::storestore();
2807 _worker_cset_start_region_time_stamp[worker_i] = gc_time_stamp;
2808 return result;
2809 }
2811 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) {
2812 HeapRegion* r = g1_policy()->collection_set();
2813 while (r != NULL) {
2814 HeapRegion* next = r->next_in_collection_set();
2815 if (cl->doHeapRegion(r)) {
2816 cl->incomplete();
2817 return;
2818 }
2819 r = next;
2820 }
2821 }
2823 void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r,
2824 HeapRegionClosure *cl) {
2825 if (r == NULL) {
2826 // The CSet is empty so there's nothing to do.
2827 return;
2828 }
2830 assert(r->in_collection_set(),
2831 "Start region must be a member of the collection set.");
2832 HeapRegion* cur = r;
2833 while (cur != NULL) {
2834 HeapRegion* next = cur->next_in_collection_set();
2835 if (cl->doHeapRegion(cur) && false) {
2836 cl->incomplete();
2837 return;
2838 }
2839 cur = next;
2840 }
2841 cur = g1_policy()->collection_set();
2842 while (cur != r) {
2843 HeapRegion* next = cur->next_in_collection_set();
2844 if (cl->doHeapRegion(cur) && false) {
2845 cl->incomplete();
2846 return;
2847 }
2848 cur = next;
2849 }
2850 }
2852 CompactibleSpace* G1CollectedHeap::first_compactible_space() {
2853 return n_regions() > 0 ? region_at(0) : NULL;
2854 }
2857 Space* G1CollectedHeap::space_containing(const void* addr) const {
2858 Space* res = heap_region_containing(addr);
2859 if (res == NULL)
2860 res = perm_gen()->space_containing(addr);
2861 return res;
2862 }
2864 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2865 Space* sp = space_containing(addr);
2866 if (sp != NULL) {
2867 return sp->block_start(addr);
2868 }
2869 return NULL;
2870 }
2872 size_t G1CollectedHeap::block_size(const HeapWord* addr) const {
2873 Space* sp = space_containing(addr);
2874 assert(sp != NULL, "block_size of address outside of heap");
2875 return sp->block_size(addr);
2876 }
2878 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2879 Space* sp = space_containing(addr);
2880 return sp->block_is_obj(addr);
2881 }
2883 bool G1CollectedHeap::supports_tlab_allocation() const {
2884 return true;
2885 }
2887 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
2888 return HeapRegion::GrainBytes;
2889 }
2891 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
2892 // Return the remaining space in the cur alloc region, but not less than
2893 // the min TLAB size.
2895 // Also, this value can be at most the humongous object threshold,
2896 // since we can't allow tlabs to grow big enough to accomodate
2897 // humongous objects.
2899 HeapRegion* hr = _mutator_alloc_region.get();
2900 size_t max_tlab_size = _humongous_object_threshold_in_words * wordSize;
2901 if (hr == NULL) {
2902 return max_tlab_size;
2903 } else {
2904 return MIN2(MAX2(hr->free(), (size_t) MinTLABSize), max_tlab_size);
2905 }
2906 }
2908 size_t G1CollectedHeap::max_capacity() const {
2909 return _g1_reserved.byte_size();
2910 }
2912 jlong G1CollectedHeap::millis_since_last_gc() {
2913 // assert(false, "NYI");
2914 return 0;
2915 }
2917 void G1CollectedHeap::prepare_for_verify() {
2918 if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) {
2919 ensure_parsability(false);
2920 }
2921 g1_rem_set()->prepare_for_verify();
2922 }
2924 class VerifyLivenessOopClosure: public OopClosure {
2925 G1CollectedHeap* _g1h;
2926 VerifyOption _vo;
2927 public:
2928 VerifyLivenessOopClosure(G1CollectedHeap* g1h, VerifyOption vo):
2929 _g1h(g1h), _vo(vo)
2930 { }
2931 void do_oop(narrowOop *p) { do_oop_work(p); }
2932 void do_oop( oop *p) { do_oop_work(p); }
2934 template <class T> void do_oop_work(T *p) {
2935 oop obj = oopDesc::load_decode_heap_oop(p);
2936 guarantee(obj == NULL || !_g1h->is_obj_dead_cond(obj, _vo),
2937 "Dead object referenced by a not dead object");
2938 }
2939 };
2941 class VerifyObjsInRegionClosure: public ObjectClosure {
2942 private:
2943 G1CollectedHeap* _g1h;
2944 size_t _live_bytes;
2945 HeapRegion *_hr;
2946 VerifyOption _vo;
2947 public:
2948 // _vo == UsePrevMarking -> use "prev" marking information,
2949 // _vo == UseNextMarking -> use "next" marking information,
2950 // _vo == UseMarkWord -> use mark word from object header.
2951 VerifyObjsInRegionClosure(HeapRegion *hr, VerifyOption vo)
2952 : _live_bytes(0), _hr(hr), _vo(vo) {
2953 _g1h = G1CollectedHeap::heap();
2954 }
2955 void do_object(oop o) {
2956 VerifyLivenessOopClosure isLive(_g1h, _vo);
2957 assert(o != NULL, "Huh?");
2958 if (!_g1h->is_obj_dead_cond(o, _vo)) {
2959 // If the object is alive according to the mark word,
2960 // then verify that the marking information agrees.
2961 // Note we can't verify the contra-positive of the
2962 // above: if the object is dead (according to the mark
2963 // word), it may not be marked, or may have been marked
2964 // but has since became dead, or may have been allocated
2965 // since the last marking.
2966 if (_vo == VerifyOption_G1UseMarkWord) {
2967 guarantee(!_g1h->is_obj_dead(o), "mark word and concurrent mark mismatch");
2968 }
2970 o->oop_iterate(&isLive);
2971 if (!_hr->obj_allocated_since_prev_marking(o)) {
2972 size_t obj_size = o->size(); // Make sure we don't overflow
2973 _live_bytes += (obj_size * HeapWordSize);
2974 }
2975 }
2976 }
2977 size_t live_bytes() { return _live_bytes; }
2978 };
2980 class PrintObjsInRegionClosure : public ObjectClosure {
2981 HeapRegion *_hr;
2982 G1CollectedHeap *_g1;
2983 public:
2984 PrintObjsInRegionClosure(HeapRegion *hr) : _hr(hr) {
2985 _g1 = G1CollectedHeap::heap();
2986 };
2988 void do_object(oop o) {
2989 if (o != NULL) {
2990 HeapWord *start = (HeapWord *) o;
2991 size_t word_sz = o->size();
2992 gclog_or_tty->print("\nPrinting obj "PTR_FORMAT" of size " SIZE_FORMAT
2993 " isMarkedPrev %d isMarkedNext %d isAllocSince %d\n",
2994 (void*) o, word_sz,
2995 _g1->isMarkedPrev(o),
2996 _g1->isMarkedNext(o),
2997 _hr->obj_allocated_since_prev_marking(o));
2998 HeapWord *end = start + word_sz;
2999 HeapWord *cur;
3000 int *val;
3001 for (cur = start; cur < end; cur++) {
3002 val = (int *) cur;
3003 gclog_or_tty->print("\t "PTR_FORMAT":"PTR_FORMAT"\n", val, *val);
3004 }
3005 }
3006 }
3007 };
3009 class VerifyRegionClosure: public HeapRegionClosure {
3010 private:
3011 bool _allow_dirty;
3012 bool _par;
3013 VerifyOption _vo;
3014 bool _failures;
3015 public:
3016 // _vo == UsePrevMarking -> use "prev" marking information,
3017 // _vo == UseNextMarking -> use "next" marking information,
3018 // _vo == UseMarkWord -> use mark word from object header.
3019 VerifyRegionClosure(bool allow_dirty, bool par, VerifyOption vo)
3020 : _allow_dirty(allow_dirty),
3021 _par(par),
3022 _vo(vo),
3023 _failures(false) {}
3025 bool failures() {
3026 return _failures;
3027 }
3029 bool doHeapRegion(HeapRegion* r) {
3030 guarantee(_par || r->claim_value() == HeapRegion::InitialClaimValue,
3031 "Should be unclaimed at verify points.");
3032 if (!r->continuesHumongous()) {
3033 bool failures = false;
3034 r->verify(_allow_dirty, _vo, &failures);
3035 if (failures) {
3036 _failures = true;
3037 } else {
3038 VerifyObjsInRegionClosure not_dead_yet_cl(r, _vo);
3039 r->object_iterate(¬_dead_yet_cl);
3040 if (_vo != VerifyOption_G1UseNextMarking) {
3041 if (r->max_live_bytes() < not_dead_yet_cl.live_bytes()) {
3042 gclog_or_tty->print_cr("["PTR_FORMAT","PTR_FORMAT"] "
3043 "max_live_bytes "SIZE_FORMAT" "
3044 "< calculated "SIZE_FORMAT,
3045 r->bottom(), r->end(),
3046 r->max_live_bytes(),
3047 not_dead_yet_cl.live_bytes());
3048 _failures = true;
3049 }
3050 } else {
3051 // When vo == UseNextMarking we cannot currently do a sanity
3052 // check on the live bytes as the calculation has not been
3053 // finalized yet.
3054 }
3055 }
3056 }
3057 return false; // stop the region iteration if we hit a failure
3058 }
3059 };
3061 class VerifyRootsClosure: public OopsInGenClosure {
3062 private:
3063 G1CollectedHeap* _g1h;
3064 VerifyOption _vo;
3065 bool _failures;
3066 public:
3067 // _vo == UsePrevMarking -> use "prev" marking information,
3068 // _vo == UseNextMarking -> use "next" marking information,
3069 // _vo == UseMarkWord -> use mark word from object header.
3070 VerifyRootsClosure(VerifyOption vo) :
3071 _g1h(G1CollectedHeap::heap()),
3072 _vo(vo),
3073 _failures(false) { }
3075 bool failures() { return _failures; }
3077 template <class T> void do_oop_nv(T* p) {
3078 T heap_oop = oopDesc::load_heap_oop(p);
3079 if (!oopDesc::is_null(heap_oop)) {
3080 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
3081 if (_g1h->is_obj_dead_cond(obj, _vo)) {
3082 gclog_or_tty->print_cr("Root location "PTR_FORMAT" "
3083 "points to dead obj "PTR_FORMAT, p, (void*) obj);
3084 if (_vo == VerifyOption_G1UseMarkWord) {
3085 gclog_or_tty->print_cr(" Mark word: "PTR_FORMAT, (void*)(obj->mark()));
3086 }
3087 obj->print_on(gclog_or_tty);
3088 _failures = true;
3089 }
3090 }
3091 }
3093 void do_oop(oop* p) { do_oop_nv(p); }
3094 void do_oop(narrowOop* p) { do_oop_nv(p); }
3095 };
3097 // This is the task used for parallel heap verification.
3099 class G1ParVerifyTask: public AbstractGangTask {
3100 private:
3101 G1CollectedHeap* _g1h;
3102 bool _allow_dirty;
3103 VerifyOption _vo;
3104 bool _failures;
3106 public:
3107 // _vo == UsePrevMarking -> use "prev" marking information,
3108 // _vo == UseNextMarking -> use "next" marking information,
3109 // _vo == UseMarkWord -> use mark word from object header.
3110 G1ParVerifyTask(G1CollectedHeap* g1h, bool allow_dirty, VerifyOption vo) :
3111 AbstractGangTask("Parallel verify task"),
3112 _g1h(g1h),
3113 _allow_dirty(allow_dirty),
3114 _vo(vo),
3115 _failures(false) { }
3117 bool failures() {
3118 return _failures;
3119 }
3121 void work(uint worker_id) {
3122 HandleMark hm;
3123 VerifyRegionClosure blk(_allow_dirty, true, _vo);
3124 _g1h->heap_region_par_iterate_chunked(&blk, worker_id,
3125 _g1h->workers()->active_workers(),
3126 HeapRegion::ParVerifyClaimValue);
3127 if (blk.failures()) {
3128 _failures = true;
3129 }
3130 }
3131 };
3133 void G1CollectedHeap::verify(bool allow_dirty, bool silent) {
3134 verify(allow_dirty, silent, VerifyOption_G1UsePrevMarking);
3135 }
3137 void G1CollectedHeap::verify(bool allow_dirty,
3138 bool silent,
3139 VerifyOption vo) {
3140 if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) {
3141 if (!silent) { gclog_or_tty->print("Roots (excluding permgen) "); }
3142 VerifyRootsClosure rootsCl(vo);
3144 assert(Thread::current()->is_VM_thread(),
3145 "Expected to be executed serially by the VM thread at this point");
3147 CodeBlobToOopClosure blobsCl(&rootsCl, /*do_marking=*/ false);
3149 // We apply the relevant closures to all the oops in the
3150 // system dictionary, the string table and the code cache.
3151 const int so = SharedHeap::SO_AllClasses | SharedHeap::SO_Strings | SharedHeap::SO_CodeCache;
3153 process_strong_roots(true, // activate StrongRootsScope
3154 true, // we set "collecting perm gen" to true,
3155 // so we don't reset the dirty cards in the perm gen.
3156 SharedHeap::ScanningOption(so), // roots scanning options
3157 &rootsCl,
3158 &blobsCl,
3159 &rootsCl);
3161 // If we're verifying after the marking phase of a Full GC then we can't
3162 // treat the perm gen as roots into the G1 heap. Some of the objects in
3163 // the perm gen may be dead and hence not marked. If one of these dead
3164 // objects is considered to be a root then we may end up with a false
3165 // "Root location <x> points to dead ob <y>" failure.
3166 if (vo != VerifyOption_G1UseMarkWord) {
3167 // Since we used "collecting_perm_gen" == true above, we will not have
3168 // checked the refs from perm into the G1-collected heap. We check those
3169 // references explicitly below. Whether the relevant cards are dirty
3170 // is checked further below in the rem set verification.
3171 if (!silent) { gclog_or_tty->print("Permgen roots "); }
3172 perm_gen()->oop_iterate(&rootsCl);
3173 }
3174 bool failures = rootsCl.failures();
3176 if (vo != VerifyOption_G1UseMarkWord) {
3177 // If we're verifying during a full GC then the region sets
3178 // will have been torn down at the start of the GC. Therefore
3179 // verifying the region sets will fail. So we only verify
3180 // the region sets when not in a full GC.
3181 if (!silent) { gclog_or_tty->print("HeapRegionSets "); }
3182 verify_region_sets();
3183 }
3185 if (!silent) { gclog_or_tty->print("HeapRegions "); }
3186 if (GCParallelVerificationEnabled && ParallelGCThreads > 1) {
3187 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3188 "sanity check");
3190 G1ParVerifyTask task(this, allow_dirty, vo);
3191 assert(UseDynamicNumberOfGCThreads ||
3192 workers()->active_workers() == workers()->total_workers(),
3193 "If not dynamic should be using all the workers");
3194 int n_workers = workers()->active_workers();
3195 set_par_threads(n_workers);
3196 workers()->run_task(&task);
3197 set_par_threads(0);
3198 if (task.failures()) {
3199 failures = true;
3200 }
3202 // Checks that the expected amount of parallel work was done.
3203 // The implication is that n_workers is > 0.
3204 assert(check_heap_region_claim_values(HeapRegion::ParVerifyClaimValue),
3205 "sanity check");
3207 reset_heap_region_claim_values();
3209 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3210 "sanity check");
3211 } else {
3212 VerifyRegionClosure blk(allow_dirty, false, vo);
3213 heap_region_iterate(&blk);
3214 if (blk.failures()) {
3215 failures = true;
3216 }
3217 }
3218 if (!silent) gclog_or_tty->print("RemSet ");
3219 rem_set()->verify();
3221 if (failures) {
3222 gclog_or_tty->print_cr("Heap:");
3223 // It helps to have the per-region information in the output to
3224 // help us track down what went wrong. This is why we call
3225 // print_extended_on() instead of print_on().
3226 print_extended_on(gclog_or_tty);
3227 gclog_or_tty->print_cr("");
3228 #ifndef PRODUCT
3229 if (VerifyDuringGC && G1VerifyDuringGCPrintReachable) {
3230 concurrent_mark()->print_reachable("at-verification-failure",
3231 vo, false /* all */);
3232 }
3233 #endif
3234 gclog_or_tty->flush();
3235 }
3236 guarantee(!failures, "there should not have been any failures");
3237 } else {
3238 if (!silent) gclog_or_tty->print("(SKIPPING roots, heapRegions, remset) ");
3239 }
3240 }
3242 class PrintRegionClosure: public HeapRegionClosure {
3243 outputStream* _st;
3244 public:
3245 PrintRegionClosure(outputStream* st) : _st(st) {}
3246 bool doHeapRegion(HeapRegion* r) {
3247 r->print_on(_st);
3248 return false;
3249 }
3250 };
3252 void G1CollectedHeap::print_on(outputStream* st) const {
3253 st->print(" %-20s", "garbage-first heap");
3254 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
3255 capacity()/K, used_unlocked()/K);
3256 st->print(" [" INTPTR_FORMAT ", " INTPTR_FORMAT ", " INTPTR_FORMAT ")",
3257 _g1_storage.low_boundary(),
3258 _g1_storage.high(),
3259 _g1_storage.high_boundary());
3260 st->cr();
3261 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
3262 size_t young_regions = _young_list->length();
3263 st->print(SIZE_FORMAT " young (" SIZE_FORMAT "K), ",
3264 young_regions, young_regions * HeapRegion::GrainBytes / K);
3265 size_t survivor_regions = g1_policy()->recorded_survivor_regions();
3266 st->print(SIZE_FORMAT " survivors (" SIZE_FORMAT "K)",
3267 survivor_regions, survivor_regions * HeapRegion::GrainBytes / K);
3268 st->cr();
3269 perm()->as_gen()->print_on(st);
3270 }
3272 void G1CollectedHeap::print_extended_on(outputStream* st) const {
3273 print_on(st);
3275 // Print the per-region information.
3276 st->cr();
3277 st->print_cr("Heap Regions: (Y=young(eden), SU=young(survivor), HS=humongous(starts), HC=humongous(continues), CS=collection set, F=free, TS=gc time stamp, PTAMS=previous top-at-mark-start, NTAMS=next top-at-mark-start)");
3278 PrintRegionClosure blk(st);
3279 heap_region_iterate(&blk);
3280 }
3282 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
3283 if (G1CollectedHeap::use_parallel_gc_threads()) {
3284 workers()->print_worker_threads_on(st);
3285 }
3286 _cmThread->print_on(st);
3287 st->cr();
3288 _cm->print_worker_threads_on(st);
3289 _cg1r->print_worker_threads_on(st);
3290 st->cr();
3291 }
3293 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
3294 if (G1CollectedHeap::use_parallel_gc_threads()) {
3295 workers()->threads_do(tc);
3296 }
3297 tc->do_thread(_cmThread);
3298 _cg1r->threads_do(tc);
3299 }
3301 void G1CollectedHeap::print_tracing_info() const {
3302 // We'll overload this to mean "trace GC pause statistics."
3303 if (TraceGen0Time || TraceGen1Time) {
3304 // The "G1CollectorPolicy" is keeping track of these stats, so delegate
3305 // to that.
3306 g1_policy()->print_tracing_info();
3307 }
3308 if (G1SummarizeRSetStats) {
3309 g1_rem_set()->print_summary_info();
3310 }
3311 if (G1SummarizeConcMark) {
3312 concurrent_mark()->print_summary_info();
3313 }
3314 g1_policy()->print_yg_surv_rate_info();
3315 SpecializationStats::print();
3316 }
3318 #ifndef PRODUCT
3319 // Helpful for debugging RSet issues.
3321 class PrintRSetsClosure : public HeapRegionClosure {
3322 private:
3323 const char* _msg;
3324 size_t _occupied_sum;
3326 public:
3327 bool doHeapRegion(HeapRegion* r) {
3328 HeapRegionRemSet* hrrs = r->rem_set();
3329 size_t occupied = hrrs->occupied();
3330 _occupied_sum += occupied;
3332 gclog_or_tty->print_cr("Printing RSet for region "HR_FORMAT,
3333 HR_FORMAT_PARAMS(r));
3334 if (occupied == 0) {
3335 gclog_or_tty->print_cr(" RSet is empty");
3336 } else {
3337 hrrs->print();
3338 }
3339 gclog_or_tty->print_cr("----------");
3340 return false;
3341 }
3343 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
3344 gclog_or_tty->cr();
3345 gclog_or_tty->print_cr("========================================");
3346 gclog_or_tty->print_cr(msg);
3347 gclog_or_tty->cr();
3348 }
3350 ~PrintRSetsClosure() {
3351 gclog_or_tty->print_cr("Occupied Sum: "SIZE_FORMAT, _occupied_sum);
3352 gclog_or_tty->print_cr("========================================");
3353 gclog_or_tty->cr();
3354 }
3355 };
3357 void G1CollectedHeap::print_cset_rsets() {
3358 PrintRSetsClosure cl("Printing CSet RSets");
3359 collection_set_iterate(&cl);
3360 }
3362 void G1CollectedHeap::print_all_rsets() {
3363 PrintRSetsClosure cl("Printing All RSets");;
3364 heap_region_iterate(&cl);
3365 }
3366 #endif // PRODUCT
3368 G1CollectedHeap* G1CollectedHeap::heap() {
3369 assert(_sh->kind() == CollectedHeap::G1CollectedHeap,
3370 "not a garbage-first heap");
3371 return _g1h;
3372 }
3374 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) {
3375 // always_do_update_barrier = false;
3376 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
3377 // Call allocation profiler
3378 AllocationProfiler::iterate_since_last_gc();
3379 // Fill TLAB's and such
3380 ensure_parsability(true);
3381 }
3383 void G1CollectedHeap::gc_epilogue(bool full /* Ignored */) {
3384 // FIXME: what is this about?
3385 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
3386 // is set.
3387 COMPILER2_PRESENT(assert(DerivedPointerTable::is_empty(),
3388 "derived pointer present"));
3389 // always_do_update_barrier = true;
3391 // We have just completed a GC. Update the soft reference
3392 // policy with the new heap occupancy
3393 Universe::update_heap_info_at_gc();
3394 }
3396 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
3397 unsigned int gc_count_before,
3398 bool* succeeded) {
3399 assert_heap_not_locked_and_not_at_safepoint();
3400 g1_policy()->record_stop_world_start();
3401 VM_G1IncCollectionPause op(gc_count_before,
3402 word_size,
3403 false, /* should_initiate_conc_mark */
3404 g1_policy()->max_pause_time_ms(),
3405 GCCause::_g1_inc_collection_pause);
3406 VMThread::execute(&op);
3408 HeapWord* result = op.result();
3409 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
3410 assert(result == NULL || ret_succeeded,
3411 "the result should be NULL if the VM did not succeed");
3412 *succeeded = ret_succeeded;
3414 assert_heap_not_locked();
3415 return result;
3416 }
3418 void
3419 G1CollectedHeap::doConcurrentMark() {
3420 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
3421 if (!_cmThread->in_progress()) {
3422 _cmThread->set_started();
3423 CGC_lock->notify();
3424 }
3425 }
3427 double G1CollectedHeap::predict_region_elapsed_time_ms(HeapRegion *hr,
3428 bool young) {
3429 return _g1_policy->predict_region_elapsed_time_ms(hr, young);
3430 }
3432 void G1CollectedHeap::check_if_region_is_too_expensive(double
3433 predicted_time_ms) {
3434 _g1_policy->check_if_region_is_too_expensive(predicted_time_ms);
3435 }
3437 size_t G1CollectedHeap::pending_card_num() {
3438 size_t extra_cards = 0;
3439 JavaThread *curr = Threads::first();
3440 while (curr != NULL) {
3441 DirtyCardQueue& dcq = curr->dirty_card_queue();
3442 extra_cards += dcq.size();
3443 curr = curr->next();
3444 }
3445 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
3446 size_t buffer_size = dcqs.buffer_size();
3447 size_t buffer_num = dcqs.completed_buffers_num();
3448 return buffer_size * buffer_num + extra_cards;
3449 }
3451 size_t G1CollectedHeap::max_pending_card_num() {
3452 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
3453 size_t buffer_size = dcqs.buffer_size();
3454 size_t buffer_num = dcqs.completed_buffers_num();
3455 int thread_num = Threads::number_of_threads();
3456 return (buffer_num + thread_num) * buffer_size;
3457 }
3459 size_t G1CollectedHeap::cards_scanned() {
3460 return g1_rem_set()->cardsScanned();
3461 }
3463 void
3464 G1CollectedHeap::setup_surviving_young_words() {
3465 guarantee( _surviving_young_words == NULL, "pre-condition" );
3466 size_t array_length = g1_policy()->young_cset_region_length();
3467 _surviving_young_words = NEW_C_HEAP_ARRAY(size_t, array_length);
3468 if (_surviving_young_words == NULL) {
3469 vm_exit_out_of_memory(sizeof(size_t) * array_length,
3470 "Not enough space for young surv words summary.");
3471 }
3472 memset(_surviving_young_words, 0, array_length * sizeof(size_t));
3473 #ifdef ASSERT
3474 for (size_t i = 0; i < array_length; ++i) {
3475 assert( _surviving_young_words[i] == 0, "memset above" );
3476 }
3477 #endif // !ASSERT
3478 }
3480 void
3481 G1CollectedHeap::update_surviving_young_words(size_t* surv_young_words) {
3482 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
3483 size_t array_length = g1_policy()->young_cset_region_length();
3484 for (size_t i = 0; i < array_length; ++i)
3485 _surviving_young_words[i] += surv_young_words[i];
3486 }
3488 void
3489 G1CollectedHeap::cleanup_surviving_young_words() {
3490 guarantee( _surviving_young_words != NULL, "pre-condition" );
3491 FREE_C_HEAP_ARRAY(size_t, _surviving_young_words);
3492 _surviving_young_words = NULL;
3493 }
3495 #ifdef ASSERT
3496 class VerifyCSetClosure: public HeapRegionClosure {
3497 public:
3498 bool doHeapRegion(HeapRegion* hr) {
3499 // Here we check that the CSet region's RSet is ready for parallel
3500 // iteration. The fields that we'll verify are only manipulated
3501 // when the region is part of a CSet and is collected. Afterwards,
3502 // we reset these fields when we clear the region's RSet (when the
3503 // region is freed) so they are ready when the region is
3504 // re-allocated. The only exception to this is if there's an
3505 // evacuation failure and instead of freeing the region we leave
3506 // it in the heap. In that case, we reset these fields during
3507 // evacuation failure handling.
3508 guarantee(hr->rem_set()->verify_ready_for_par_iteration(), "verification");
3510 // Here's a good place to add any other checks we'd like to
3511 // perform on CSet regions.
3512 return false;
3513 }
3514 };
3515 #endif // ASSERT
3517 #if TASKQUEUE_STATS
3518 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
3519 st->print_raw_cr("GC Task Stats");
3520 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
3521 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
3522 }
3524 void G1CollectedHeap::print_taskqueue_stats(outputStream* const st) const {
3525 print_taskqueue_stats_hdr(st);
3527 TaskQueueStats totals;
3528 const int n = workers() != NULL ? workers()->total_workers() : 1;
3529 for (int i = 0; i < n; ++i) {
3530 st->print("%3d ", i); task_queue(i)->stats.print(st); st->cr();
3531 totals += task_queue(i)->stats;
3532 }
3533 st->print_raw("tot "); totals.print(st); st->cr();
3535 DEBUG_ONLY(totals.verify());
3536 }
3538 void G1CollectedHeap::reset_taskqueue_stats() {
3539 const int n = workers() != NULL ? workers()->total_workers() : 1;
3540 for (int i = 0; i < n; ++i) {
3541 task_queue(i)->stats.reset();
3542 }
3543 }
3544 #endif // TASKQUEUE_STATS
3546 bool
3547 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
3548 assert_at_safepoint(true /* should_be_vm_thread */);
3549 guarantee(!is_gc_active(), "collection is not reentrant");
3551 if (GC_locker::check_active_before_gc()) {
3552 return false;
3553 }
3555 SvcGCMarker sgcm(SvcGCMarker::MINOR);
3556 ResourceMark rm;
3558 if (PrintHeapAtGC) {
3559 Universe::print_heap_before_gc();
3560 }
3562 HRSPhaseSetter x(HRSPhaseEvacuation);
3563 verify_region_sets_optional();
3564 verify_dirty_young_regions();
3566 // This call will decide whether this pause is an initial-mark
3567 // pause. If it is, during_initial_mark_pause() will return true
3568 // for the duration of this pause.
3569 g1_policy()->decide_on_conc_mark_initiation();
3571 // We do not allow initial-mark to be piggy-backed on a mixed GC.
3572 assert(!g1_policy()->during_initial_mark_pause() ||
3573 g1_policy()->gcs_are_young(), "sanity");
3575 // We also do not allow mixed GCs during marking.
3576 assert(!mark_in_progress() || g1_policy()->gcs_are_young(), "sanity");
3578 // Record whether this pause is an initial mark. When the current
3579 // thread has completed its logging output and it's safe to signal
3580 // the CM thread, the flag's value in the policy has been reset.
3581 bool should_start_conc_mark = g1_policy()->during_initial_mark_pause();
3583 // Inner scope for scope based logging, timers, and stats collection
3584 {
3585 char verbose_str[128];
3586 sprintf(verbose_str, "GC pause ");
3587 if (g1_policy()->gcs_are_young()) {
3588 strcat(verbose_str, "(young)");
3589 } else {
3590 strcat(verbose_str, "(mixed)");
3591 }
3592 if (g1_policy()->during_initial_mark_pause()) {
3593 strcat(verbose_str, " (initial-mark)");
3594 // We are about to start a marking cycle, so we increment the
3595 // full collection counter.
3596 increment_total_full_collections();
3597 }
3599 // if PrintGCDetails is on, we'll print long statistics information
3600 // in the collector policy code, so let's not print this as the output
3601 // is messy if we do.
3602 gclog_or_tty->date_stamp(PrintGC && PrintGCDateStamps);
3603 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty);
3604 TraceTime t(verbose_str, PrintGC && !PrintGCDetails, true, gclog_or_tty);
3606 TraceCollectorStats tcs(g1mm()->incremental_collection_counters());
3607 TraceMemoryManagerStats tms(false /* fullGC */, gc_cause());
3609 // If the secondary_free_list is not empty, append it to the
3610 // free_list. No need to wait for the cleanup operation to finish;
3611 // the region allocation code will check the secondary_free_list
3612 // and wait if necessary. If the G1StressConcRegionFreeing flag is
3613 // set, skip this step so that the region allocation code has to
3614 // get entries from the secondary_free_list.
3615 if (!G1StressConcRegionFreeing) {
3616 append_secondary_free_list_if_not_empty_with_lock();
3617 }
3619 assert(check_young_list_well_formed(),
3620 "young list should be well formed");
3622 // Don't dynamically change the number of GC threads this early. A value of
3623 // 0 is used to indicate serial work. When parallel work is done,
3624 // it will be set.
3626 { // Call to jvmpi::post_class_unload_events must occur outside of active GC
3627 IsGCActiveMark x;
3629 gc_prologue(false);
3630 increment_total_collections(false /* full gc */);
3631 increment_gc_time_stamp();
3633 if (VerifyBeforeGC && total_collections() >= VerifyGCStartAt) {
3634 HandleMark hm; // Discard invalid handles created during verification
3635 gclog_or_tty->print(" VerifyBeforeGC:");
3636 prepare_for_verify();
3637 Universe::verify(/* allow dirty */ false,
3638 /* silent */ false,
3639 /* option */ VerifyOption_G1UsePrevMarking);
3640 }
3642 COMPILER2_PRESENT(DerivedPointerTable::clear());
3644 // Please see comment in g1CollectedHeap.hpp and
3645 // G1CollectedHeap::ref_processing_init() to see how
3646 // reference processing currently works in G1.
3648 // Enable discovery in the STW reference processor
3649 ref_processor_stw()->enable_discovery(true /*verify_disabled*/,
3650 true /*verify_no_refs*/);
3652 {
3653 // We want to temporarily turn off discovery by the
3654 // CM ref processor, if necessary, and turn it back on
3655 // on again later if we do. Using a scoped
3656 // NoRefDiscovery object will do this.
3657 NoRefDiscovery no_cm_discovery(ref_processor_cm());
3659 // Forget the current alloc region (we might even choose it to be part
3660 // of the collection set!).
3661 release_mutator_alloc_region();
3663 // We should call this after we retire the mutator alloc
3664 // region(s) so that all the ALLOC / RETIRE events are generated
3665 // before the start GC event.
3666 _hr_printer.start_gc(false /* full */, (size_t) total_collections());
3668 // The elapsed time induced by the start time below deliberately elides
3669 // the possible verification above.
3670 double start_time_sec = os::elapsedTime();
3671 size_t start_used_bytes = used();
3673 #if YOUNG_LIST_VERBOSE
3674 gclog_or_tty->print_cr("\nBefore recording pause start.\nYoung_list:");
3675 _young_list->print();
3676 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3677 #endif // YOUNG_LIST_VERBOSE
3679 g1_policy()->record_collection_pause_start(start_time_sec,
3680 start_used_bytes);
3682 #if YOUNG_LIST_VERBOSE
3683 gclog_or_tty->print_cr("\nAfter recording pause start.\nYoung_list:");
3684 _young_list->print();
3685 #endif // YOUNG_LIST_VERBOSE
3687 if (g1_policy()->during_initial_mark_pause()) {
3688 concurrent_mark()->checkpointRootsInitialPre();
3689 }
3690 perm_gen()->save_marks();
3692 #if YOUNG_LIST_VERBOSE
3693 gclog_or_tty->print_cr("\nBefore choosing collection set.\nYoung_list:");
3694 _young_list->print();
3695 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3696 #endif // YOUNG_LIST_VERBOSE
3698 g1_policy()->choose_collection_set(target_pause_time_ms);
3700 _cm->note_start_of_gc();
3701 // We should not verify the per-thread SATB buffers given that
3702 // we have not filtered them yet (we'll do so during the
3703 // GC). We also call this after choose_collection_set() to
3704 // ensure that the CSet has been finalized.
3705 _cm->verify_no_cset_oops(true /* verify_stacks */,
3706 true /* verify_enqueued_buffers */,
3707 false /* verify_thread_buffers */,
3708 true /* verify_fingers */);
3710 if (_hr_printer.is_active()) {
3711 HeapRegion* hr = g1_policy()->collection_set();
3712 while (hr != NULL) {
3713 G1HRPrinter::RegionType type;
3714 if (!hr->is_young()) {
3715 type = G1HRPrinter::Old;
3716 } else if (hr->is_survivor()) {
3717 type = G1HRPrinter::Survivor;
3718 } else {
3719 type = G1HRPrinter::Eden;
3720 }
3721 _hr_printer.cset(hr);
3722 hr = hr->next_in_collection_set();
3723 }
3724 }
3726 #ifdef ASSERT
3727 VerifyCSetClosure cl;
3728 collection_set_iterate(&cl);
3729 #endif // ASSERT
3731 setup_surviving_young_words();
3733 // Initialize the GC alloc regions.
3734 init_gc_alloc_regions();
3736 // Actually do the work...
3737 evacuate_collection_set();
3739 // We do this to mainly verify the per-thread SATB buffers
3740 // (which have been filtered by now) since we didn't verify
3741 // them earlier. No point in re-checking the stacks / enqueued
3742 // buffers given that the CSet has not changed since last time
3743 // we checked.
3744 _cm->verify_no_cset_oops(false /* verify_stacks */,
3745 false /* verify_enqueued_buffers */,
3746 true /* verify_thread_buffers */,
3747 true /* verify_fingers */);
3749 free_collection_set(g1_policy()->collection_set());
3750 g1_policy()->clear_collection_set();
3752 cleanup_surviving_young_words();
3754 // Start a new incremental collection set for the next pause.
3755 g1_policy()->start_incremental_cset_building();
3757 // Clear the _cset_fast_test bitmap in anticipation of adding
3758 // regions to the incremental collection set for the next
3759 // evacuation pause.
3760 clear_cset_fast_test();
3762 _young_list->reset_sampled_info();
3764 // Don't check the whole heap at this point as the
3765 // GC alloc regions from this pause have been tagged
3766 // as survivors and moved on to the survivor list.
3767 // Survivor regions will fail the !is_young() check.
3768 assert(check_young_list_empty(false /* check_heap */),
3769 "young list should be empty");
3771 #if YOUNG_LIST_VERBOSE
3772 gclog_or_tty->print_cr("Before recording survivors.\nYoung List:");
3773 _young_list->print();
3774 #endif // YOUNG_LIST_VERBOSE
3776 g1_policy()->record_survivor_regions(_young_list->survivor_length(),
3777 _young_list->first_survivor_region(),
3778 _young_list->last_survivor_region());
3780 _young_list->reset_auxilary_lists();
3782 if (evacuation_failed()) {
3783 _summary_bytes_used = recalculate_used();
3784 } else {
3785 // The "used" of the the collection set have already been subtracted
3786 // when they were freed. Add in the bytes evacuated.
3787 _summary_bytes_used += g1_policy()->bytes_copied_during_gc();
3788 }
3790 if (g1_policy()->during_initial_mark_pause()) {
3791 concurrent_mark()->checkpointRootsInitialPost();
3792 set_marking_started();
3793 // Note that we don't actually trigger the CM thread at
3794 // this point. We do that later when we're sure that
3795 // the current thread has completed its logging output.
3796 }
3798 allocate_dummy_regions();
3800 #if YOUNG_LIST_VERBOSE
3801 gclog_or_tty->print_cr("\nEnd of the pause.\nYoung_list:");
3802 _young_list->print();
3803 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3804 #endif // YOUNG_LIST_VERBOSE
3806 init_mutator_alloc_region();
3808 {
3809 size_t expand_bytes = g1_policy()->expansion_amount();
3810 if (expand_bytes > 0) {
3811 size_t bytes_before = capacity();
3812 // No need for an ergo verbose message here,
3813 // expansion_amount() does this when it returns a value > 0.
3814 if (!expand(expand_bytes)) {
3815 // We failed to expand the heap so let's verify that
3816 // committed/uncommitted amount match the backing store
3817 assert(capacity() == _g1_storage.committed_size(), "committed size mismatch");
3818 assert(max_capacity() == _g1_storage.reserved_size(), "reserved size mismatch");
3819 }
3820 }
3821 }
3823 // We redo the verificaiton but now wrt to the new CSet which
3824 // has just got initialized after the previous CSet was freed.
3825 _cm->verify_no_cset_oops(true /* verify_stacks */,
3826 true /* verify_enqueued_buffers */,
3827 true /* verify_thread_buffers */,
3828 true /* verify_fingers */);
3829 _cm->note_end_of_gc();
3831 double end_time_sec = os::elapsedTime();
3832 double pause_time_ms = (end_time_sec - start_time_sec) * MILLIUNITS;
3833 g1_policy()->record_pause_time_ms(pause_time_ms);
3834 int active_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
3835 workers()->active_workers() : 1);
3836 g1_policy()->record_collection_pause_end(active_workers);
3838 MemoryService::track_memory_usage();
3840 // In prepare_for_verify() below we'll need to scan the deferred
3841 // update buffers to bring the RSets up-to-date if
3842 // G1HRRSFlushLogBuffersOnVerify has been set. While scanning
3843 // the update buffers we'll probably need to scan cards on the
3844 // regions we just allocated to (i.e., the GC alloc
3845 // regions). However, during the last GC we called
3846 // set_saved_mark() on all the GC alloc regions, so card
3847 // scanning might skip the [saved_mark_word()...top()] area of
3848 // those regions (i.e., the area we allocated objects into
3849 // during the last GC). But it shouldn't. Given that
3850 // saved_mark_word() is conditional on whether the GC time stamp
3851 // on the region is current or not, by incrementing the GC time
3852 // stamp here we invalidate all the GC time stamps on all the
3853 // regions and saved_mark_word() will simply return top() for
3854 // all the regions. This is a nicer way of ensuring this rather
3855 // than iterating over the regions and fixing them. In fact, the
3856 // GC time stamp increment here also ensures that
3857 // saved_mark_word() will return top() between pauses, i.e.,
3858 // during concurrent refinement. So we don't need the
3859 // is_gc_active() check to decided which top to use when
3860 // scanning cards (see CR 7039627).
3861 increment_gc_time_stamp();
3863 if (VerifyAfterGC && total_collections() >= VerifyGCStartAt) {
3864 HandleMark hm; // Discard invalid handles created during verification
3865 gclog_or_tty->print(" VerifyAfterGC:");
3866 prepare_for_verify();
3867 Universe::verify(/* allow dirty */ true,
3868 /* silent */ false,
3869 /* option */ VerifyOption_G1UsePrevMarking);
3870 }
3872 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
3873 ref_processor_stw()->verify_no_references_recorded();
3875 // CM reference discovery will be re-enabled if necessary.
3876 }
3878 // We should do this after we potentially expand the heap so
3879 // that all the COMMIT events are generated before the end GC
3880 // event, and after we retire the GC alloc regions so that all
3881 // RETIRE events are generated before the end GC event.
3882 _hr_printer.end_gc(false /* full */, (size_t) total_collections());
3884 // We have to do this after we decide whether to expand the heap or not.
3885 g1_policy()->print_heap_transition();
3887 if (mark_in_progress()) {
3888 concurrent_mark()->update_g1_committed();
3889 }
3891 #ifdef TRACESPINNING
3892 ParallelTaskTerminator::print_termination_counts();
3893 #endif
3895 gc_epilogue(false);
3896 }
3898 if (ExitAfterGCNum > 0 && total_collections() == ExitAfterGCNum) {
3899 gclog_or_tty->print_cr("Stopping after GC #%d", ExitAfterGCNum);
3900 print_tracing_info();
3901 vm_exit(-1);
3902 }
3903 }
3905 // The closing of the inner scope, immediately above, will complete
3906 // the PrintGC logging output. The record_collection_pause_end() call
3907 // above will complete the logging output of PrintGCDetails.
3908 //
3909 // It is not yet to safe, however, to tell the concurrent mark to
3910 // start as we have some optional output below. We don't want the
3911 // output from the concurrent mark thread interfering with this
3912 // logging output either.
3914 _hrs.verify_optional();
3915 verify_region_sets_optional();
3917 TASKQUEUE_STATS_ONLY(if (ParallelGCVerbose) print_taskqueue_stats());
3918 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
3920 if (PrintHeapAtGC) {
3921 Universe::print_heap_after_gc();
3922 }
3923 g1mm()->update_sizes();
3925 if (G1SummarizeRSetStats &&
3926 (G1SummarizeRSetStatsPeriod > 0) &&
3927 (total_collections() % G1SummarizeRSetStatsPeriod == 0)) {
3928 g1_rem_set()->print_summary_info();
3929 }
3931 // It should now be safe to tell the concurrent mark thread to start
3932 // without its logging output interfering with the logging output
3933 // that came from the pause.
3935 if (should_start_conc_mark) {
3936 // CAUTION: after the doConcurrentMark() call below,
3937 // the concurrent marking thread(s) could be running
3938 // concurrently with us. Make sure that anything after
3939 // this point does not assume that we are the only GC thread
3940 // running. Note: of course, the actual marking work will
3941 // not start until the safepoint itself is released in
3942 // ConcurrentGCThread::safepoint_desynchronize().
3943 doConcurrentMark();
3944 }
3946 return true;
3947 }
3949 size_t G1CollectedHeap::desired_plab_sz(GCAllocPurpose purpose)
3950 {
3951 size_t gclab_word_size;
3952 switch (purpose) {
3953 case GCAllocForSurvived:
3954 gclab_word_size = YoungPLABSize;
3955 break;
3956 case GCAllocForTenured:
3957 gclab_word_size = OldPLABSize;
3958 break;
3959 default:
3960 assert(false, "unknown GCAllocPurpose");
3961 gclab_word_size = OldPLABSize;
3962 break;
3963 }
3964 return gclab_word_size;
3965 }
3967 void G1CollectedHeap::init_mutator_alloc_region() {
3968 assert(_mutator_alloc_region.get() == NULL, "pre-condition");
3969 _mutator_alloc_region.init();
3970 }
3972 void G1CollectedHeap::release_mutator_alloc_region() {
3973 _mutator_alloc_region.release();
3974 assert(_mutator_alloc_region.get() == NULL, "post-condition");
3975 }
3977 void G1CollectedHeap::init_gc_alloc_regions() {
3978 assert_at_safepoint(true /* should_be_vm_thread */);
3980 _survivor_gc_alloc_region.init();
3981 _old_gc_alloc_region.init();
3982 HeapRegion* retained_region = _retained_old_gc_alloc_region;
3983 _retained_old_gc_alloc_region = NULL;
3985 // We will discard the current GC alloc region if:
3986 // a) it's in the collection set (it can happen!),
3987 // b) it's already full (no point in using it),
3988 // c) it's empty (this means that it was emptied during
3989 // a cleanup and it should be on the free list now), or
3990 // d) it's humongous (this means that it was emptied
3991 // during a cleanup and was added to the free list, but
3992 // has been subseqently used to allocate a humongous
3993 // object that may be less than the region size).
3994 if (retained_region != NULL &&
3995 !retained_region->in_collection_set() &&
3996 !(retained_region->top() == retained_region->end()) &&
3997 !retained_region->is_empty() &&
3998 !retained_region->isHumongous()) {
3999 retained_region->set_saved_mark();
4000 // The retained region was added to the old region set when it was
4001 // retired. We have to remove it now, since we don't allow regions
4002 // we allocate to in the region sets. We'll re-add it later, when
4003 // it's retired again.
4004 _old_set.remove(retained_region);
4005 bool during_im = g1_policy()->during_initial_mark_pause();
4006 retained_region->note_start_of_copying(during_im);
4007 _old_gc_alloc_region.set(retained_region);
4008 _hr_printer.reuse(retained_region);
4009 }
4010 }
4012 void G1CollectedHeap::release_gc_alloc_regions() {
4013 _survivor_gc_alloc_region.release();
4014 // If we have an old GC alloc region to release, we'll save it in
4015 // _retained_old_gc_alloc_region. If we don't
4016 // _retained_old_gc_alloc_region will become NULL. This is what we
4017 // want either way so no reason to check explicitly for either
4018 // condition.
4019 _retained_old_gc_alloc_region = _old_gc_alloc_region.release();
4020 }
4022 void G1CollectedHeap::abandon_gc_alloc_regions() {
4023 assert(_survivor_gc_alloc_region.get() == NULL, "pre-condition");
4024 assert(_old_gc_alloc_region.get() == NULL, "pre-condition");
4025 _retained_old_gc_alloc_region = NULL;
4026 }
4028 void G1CollectedHeap::init_for_evac_failure(OopsInHeapRegionClosure* cl) {
4029 _drain_in_progress = false;
4030 set_evac_failure_closure(cl);
4031 _evac_failure_scan_stack = new (ResourceObj::C_HEAP) GrowableArray<oop>(40, true);
4032 }
4034 void G1CollectedHeap::finalize_for_evac_failure() {
4035 assert(_evac_failure_scan_stack != NULL &&
4036 _evac_failure_scan_stack->length() == 0,
4037 "Postcondition");
4038 assert(!_drain_in_progress, "Postcondition");
4039 delete _evac_failure_scan_stack;
4040 _evac_failure_scan_stack = NULL;
4041 }
4043 void G1CollectedHeap::remove_self_forwarding_pointers() {
4044 assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity");
4045 assert(g1_policy()->assertMarkedBytesDataOK(), "Should be!");
4047 G1ParRemoveSelfForwardPtrsTask rsfp_task(this);
4049 if (G1CollectedHeap::use_parallel_gc_threads()) {
4050 set_par_threads();
4051 workers()->run_task(&rsfp_task);
4052 set_par_threads(0);
4053 } else {
4054 rsfp_task.work(0);
4055 }
4057 assert(check_cset_heap_region_claim_values(HeapRegion::ParEvacFailureClaimValue), "sanity");
4059 // Reset the claim values in the regions in the collection set.
4060 reset_cset_heap_region_claim_values();
4062 assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity");
4063 assert(g1_policy()->assertMarkedBytesDataOK(), "Should be!");
4065 // Now restore saved marks, if any.
4066 if (_objs_with_preserved_marks != NULL) {
4067 assert(_preserved_marks_of_objs != NULL, "Both or none.");
4068 guarantee(_objs_with_preserved_marks->length() ==
4069 _preserved_marks_of_objs->length(), "Both or none.");
4070 for (int i = 0; i < _objs_with_preserved_marks->length(); i++) {
4071 oop obj = _objs_with_preserved_marks->at(i);
4072 markOop m = _preserved_marks_of_objs->at(i);
4073 obj->set_mark(m);
4074 }
4076 // Delete the preserved marks growable arrays (allocated on the C heap).
4077 delete _objs_with_preserved_marks;
4078 delete _preserved_marks_of_objs;
4079 _objs_with_preserved_marks = NULL;
4080 _preserved_marks_of_objs = NULL;
4081 }
4082 }
4084 void G1CollectedHeap::push_on_evac_failure_scan_stack(oop obj) {
4085 _evac_failure_scan_stack->push(obj);
4086 }
4088 void G1CollectedHeap::drain_evac_failure_scan_stack() {
4089 assert(_evac_failure_scan_stack != NULL, "precondition");
4091 while (_evac_failure_scan_stack->length() > 0) {
4092 oop obj = _evac_failure_scan_stack->pop();
4093 _evac_failure_closure->set_region(heap_region_containing(obj));
4094 obj->oop_iterate_backwards(_evac_failure_closure);
4095 }
4096 }
4098 oop
4099 G1CollectedHeap::handle_evacuation_failure_par(OopsInHeapRegionClosure* cl,
4100 oop old) {
4101 assert(obj_in_cs(old),
4102 err_msg("obj: "PTR_FORMAT" should still be in the CSet",
4103 (HeapWord*) old));
4104 markOop m = old->mark();
4105 oop forward_ptr = old->forward_to_atomic(old);
4106 if (forward_ptr == NULL) {
4107 // Forward-to-self succeeded.
4109 if (_evac_failure_closure != cl) {
4110 MutexLockerEx x(EvacFailureStack_lock, Mutex::_no_safepoint_check_flag);
4111 assert(!_drain_in_progress,
4112 "Should only be true while someone holds the lock.");
4113 // Set the global evac-failure closure to the current thread's.
4114 assert(_evac_failure_closure == NULL, "Or locking has failed.");
4115 set_evac_failure_closure(cl);
4116 // Now do the common part.
4117 handle_evacuation_failure_common(old, m);
4118 // Reset to NULL.
4119 set_evac_failure_closure(NULL);
4120 } else {
4121 // The lock is already held, and this is recursive.
4122 assert(_drain_in_progress, "This should only be the recursive case.");
4123 handle_evacuation_failure_common(old, m);
4124 }
4125 return old;
4126 } else {
4127 // Forward-to-self failed. Either someone else managed to allocate
4128 // space for this object (old != forward_ptr) or they beat us in
4129 // self-forwarding it (old == forward_ptr).
4130 assert(old == forward_ptr || !obj_in_cs(forward_ptr),
4131 err_msg("obj: "PTR_FORMAT" forwarded to: "PTR_FORMAT" "
4132 "should not be in the CSet",
4133 (HeapWord*) old, (HeapWord*) forward_ptr));
4134 return forward_ptr;
4135 }
4136 }
4138 void G1CollectedHeap::handle_evacuation_failure_common(oop old, markOop m) {
4139 set_evacuation_failed(true);
4141 preserve_mark_if_necessary(old, m);
4143 HeapRegion* r = heap_region_containing(old);
4144 if (!r->evacuation_failed()) {
4145 r->set_evacuation_failed(true);
4146 _hr_printer.evac_failure(r);
4147 }
4149 push_on_evac_failure_scan_stack(old);
4151 if (!_drain_in_progress) {
4152 // prevent recursion in copy_to_survivor_space()
4153 _drain_in_progress = true;
4154 drain_evac_failure_scan_stack();
4155 _drain_in_progress = false;
4156 }
4157 }
4159 void G1CollectedHeap::preserve_mark_if_necessary(oop obj, markOop m) {
4160 assert(evacuation_failed(), "Oversaving!");
4161 // We want to call the "for_promotion_failure" version only in the
4162 // case of a promotion failure.
4163 if (m->must_be_preserved_for_promotion_failure(obj)) {
4164 if (_objs_with_preserved_marks == NULL) {
4165 assert(_preserved_marks_of_objs == NULL, "Both or none.");
4166 _objs_with_preserved_marks =
4167 new (ResourceObj::C_HEAP) GrowableArray<oop>(40, true);
4168 _preserved_marks_of_objs =
4169 new (ResourceObj::C_HEAP) GrowableArray<markOop>(40, true);
4170 }
4171 _objs_with_preserved_marks->push(obj);
4172 _preserved_marks_of_objs->push(m);
4173 }
4174 }
4176 HeapWord* G1CollectedHeap::par_allocate_during_gc(GCAllocPurpose purpose,
4177 size_t word_size) {
4178 if (purpose == GCAllocForSurvived) {
4179 HeapWord* result = survivor_attempt_allocation(word_size);
4180 if (result != NULL) {
4181 return result;
4182 } else {
4183 // Let's try to allocate in the old gen in case we can fit the
4184 // object there.
4185 return old_attempt_allocation(word_size);
4186 }
4187 } else {
4188 assert(purpose == GCAllocForTenured, "sanity");
4189 HeapWord* result = old_attempt_allocation(word_size);
4190 if (result != NULL) {
4191 return result;
4192 } else {
4193 // Let's try to allocate in the survivors in case we can fit the
4194 // object there.
4195 return survivor_attempt_allocation(word_size);
4196 }
4197 }
4199 ShouldNotReachHere();
4200 // Trying to keep some compilers happy.
4201 return NULL;
4202 }
4204 G1ParGCAllocBuffer::G1ParGCAllocBuffer(size_t gclab_word_size) :
4205 ParGCAllocBuffer(gclab_word_size), _retired(false) { }
4207 G1ParScanThreadState::G1ParScanThreadState(G1CollectedHeap* g1h, int queue_num)
4208 : _g1h(g1h),
4209 _refs(g1h->task_queue(queue_num)),
4210 _dcq(&g1h->dirty_card_queue_set()),
4211 _ct_bs((CardTableModRefBS*)_g1h->barrier_set()),
4212 _g1_rem(g1h->g1_rem_set()),
4213 _hash_seed(17), _queue_num(queue_num),
4214 _term_attempts(0),
4215 _surviving_alloc_buffer(g1h->desired_plab_sz(GCAllocForSurvived)),
4216 _tenured_alloc_buffer(g1h->desired_plab_sz(GCAllocForTenured)),
4217 _age_table(false),
4218 _strong_roots_time(0), _term_time(0),
4219 _alloc_buffer_waste(0), _undo_waste(0) {
4220 // we allocate G1YoungSurvRateNumRegions plus one entries, since
4221 // we "sacrifice" entry 0 to keep track of surviving bytes for
4222 // non-young regions (where the age is -1)
4223 // We also add a few elements at the beginning and at the end in
4224 // an attempt to eliminate cache contention
4225 size_t real_length = 1 + _g1h->g1_policy()->young_cset_region_length();
4226 size_t array_length = PADDING_ELEM_NUM +
4227 real_length +
4228 PADDING_ELEM_NUM;
4229 _surviving_young_words_base = NEW_C_HEAP_ARRAY(size_t, array_length);
4230 if (_surviving_young_words_base == NULL)
4231 vm_exit_out_of_memory(array_length * sizeof(size_t),
4232 "Not enough space for young surv histo.");
4233 _surviving_young_words = _surviving_young_words_base + PADDING_ELEM_NUM;
4234 memset(_surviving_young_words, 0, real_length * sizeof(size_t));
4236 _alloc_buffers[GCAllocForSurvived] = &_surviving_alloc_buffer;
4237 _alloc_buffers[GCAllocForTenured] = &_tenured_alloc_buffer;
4239 _start = os::elapsedTime();
4240 }
4242 void
4243 G1ParScanThreadState::print_termination_stats_hdr(outputStream* const st)
4244 {
4245 st->print_raw_cr("GC Termination Stats");
4246 st->print_raw_cr(" elapsed --strong roots-- -------termination-------"
4247 " ------waste (KiB)------");
4248 st->print_raw_cr("thr ms ms % ms % attempts"
4249 " total alloc undo");
4250 st->print_raw_cr("--- --------- --------- ------ --------- ------ --------"
4251 " ------- ------- -------");
4252 }
4254 void
4255 G1ParScanThreadState::print_termination_stats(int i,
4256 outputStream* const st) const
4257 {
4258 const double elapsed_ms = elapsed_time() * 1000.0;
4259 const double s_roots_ms = strong_roots_time() * 1000.0;
4260 const double term_ms = term_time() * 1000.0;
4261 st->print_cr("%3d %9.2f %9.2f %6.2f "
4262 "%9.2f %6.2f " SIZE_FORMAT_W(8) " "
4263 SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7),
4264 i, elapsed_ms, s_roots_ms, s_roots_ms * 100 / elapsed_ms,
4265 term_ms, term_ms * 100 / elapsed_ms, term_attempts(),
4266 (alloc_buffer_waste() + undo_waste()) * HeapWordSize / K,
4267 alloc_buffer_waste() * HeapWordSize / K,
4268 undo_waste() * HeapWordSize / K);
4269 }
4271 #ifdef ASSERT
4272 bool G1ParScanThreadState::verify_ref(narrowOop* ref) const {
4273 assert(ref != NULL, "invariant");
4274 assert(UseCompressedOops, "sanity");
4275 assert(!has_partial_array_mask(ref), err_msg("ref=" PTR_FORMAT, ref));
4276 oop p = oopDesc::load_decode_heap_oop(ref);
4277 assert(_g1h->is_in_g1_reserved(p),
4278 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p)));
4279 return true;
4280 }
4282 bool G1ParScanThreadState::verify_ref(oop* ref) const {
4283 assert(ref != NULL, "invariant");
4284 if (has_partial_array_mask(ref)) {
4285 // Must be in the collection set--it's already been copied.
4286 oop p = clear_partial_array_mask(ref);
4287 assert(_g1h->obj_in_cs(p),
4288 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p)));
4289 } else {
4290 oop p = oopDesc::load_decode_heap_oop(ref);
4291 assert(_g1h->is_in_g1_reserved(p),
4292 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p)));
4293 }
4294 return true;
4295 }
4297 bool G1ParScanThreadState::verify_task(StarTask ref) const {
4298 if (ref.is_narrow()) {
4299 return verify_ref((narrowOop*) ref);
4300 } else {
4301 return verify_ref((oop*) ref);
4302 }
4303 }
4304 #endif // ASSERT
4306 void G1ParScanThreadState::trim_queue() {
4307 assert(_evac_cl != NULL, "not set");
4308 assert(_evac_failure_cl != NULL, "not set");
4309 assert(_partial_scan_cl != NULL, "not set");
4311 StarTask ref;
4312 do {
4313 // Drain the overflow stack first, so other threads can steal.
4314 while (refs()->pop_overflow(ref)) {
4315 deal_with_reference(ref);
4316 }
4318 while (refs()->pop_local(ref)) {
4319 deal_with_reference(ref);
4320 }
4321 } while (!refs()->is_empty());
4322 }
4324 G1ParClosureSuper::G1ParClosureSuper(G1CollectedHeap* g1,
4325 G1ParScanThreadState* par_scan_state) :
4326 _g1(g1), _g1_rem(_g1->g1_rem_set()), _cm(_g1->concurrent_mark()),
4327 _par_scan_state(par_scan_state),
4328 _during_initial_mark(_g1->g1_policy()->during_initial_mark_pause()),
4329 _mark_in_progress(_g1->mark_in_progress()) { }
4331 void G1ParCopyHelper::mark_object(oop obj) {
4332 #ifdef ASSERT
4333 HeapRegion* hr = _g1->heap_region_containing(obj);
4334 assert(hr != NULL, "sanity");
4335 assert(!hr->in_collection_set(), "should not mark objects in the CSet");
4336 #endif // ASSERT
4338 // We know that the object is not moving so it's safe to read its size.
4339 _cm->grayRoot(obj, (size_t) obj->size());
4340 }
4342 void G1ParCopyHelper::mark_forwarded_object(oop from_obj, oop to_obj) {
4343 #ifdef ASSERT
4344 assert(from_obj->is_forwarded(), "from obj should be forwarded");
4345 assert(from_obj->forwardee() == to_obj, "to obj should be the forwardee");
4346 assert(from_obj != to_obj, "should not be self-forwarded");
4348 HeapRegion* from_hr = _g1->heap_region_containing(from_obj);
4349 assert(from_hr != NULL, "sanity");
4350 assert(from_hr->in_collection_set(), "from obj should be in the CSet");
4352 HeapRegion* to_hr = _g1->heap_region_containing(to_obj);
4353 assert(to_hr != NULL, "sanity");
4354 assert(!to_hr->in_collection_set(), "should not mark objects in the CSet");
4355 #endif // ASSERT
4357 // The object might be in the process of being copied by another
4358 // worker so we cannot trust that its to-space image is
4359 // well-formed. So we have to read its size from its from-space
4360 // image which we know should not be changing.
4361 _cm->grayRoot(to_obj, (size_t) from_obj->size());
4362 }
4364 oop G1ParCopyHelper::copy_to_survivor_space(oop old) {
4365 size_t word_sz = old->size();
4366 HeapRegion* from_region = _g1->heap_region_containing_raw(old);
4367 // +1 to make the -1 indexes valid...
4368 int young_index = from_region->young_index_in_cset()+1;
4369 assert( (from_region->is_young() && young_index > 0) ||
4370 (!from_region->is_young() && young_index == 0), "invariant" );
4371 G1CollectorPolicy* g1p = _g1->g1_policy();
4372 markOop m = old->mark();
4373 int age = m->has_displaced_mark_helper() ? m->displaced_mark_helper()->age()
4374 : m->age();
4375 GCAllocPurpose alloc_purpose = g1p->evacuation_destination(from_region, age,
4376 word_sz);
4377 HeapWord* obj_ptr = _par_scan_state->allocate(alloc_purpose, word_sz);
4378 oop obj = oop(obj_ptr);
4380 if (obj_ptr == NULL) {
4381 // This will either forward-to-self, or detect that someone else has
4382 // installed a forwarding pointer.
4383 OopsInHeapRegionClosure* cl = _par_scan_state->evac_failure_closure();
4384 return _g1->handle_evacuation_failure_par(cl, old);
4385 }
4387 // We're going to allocate linearly, so might as well prefetch ahead.
4388 Prefetch::write(obj_ptr, PrefetchCopyIntervalInBytes);
4390 oop forward_ptr = old->forward_to_atomic(obj);
4391 if (forward_ptr == NULL) {
4392 Copy::aligned_disjoint_words((HeapWord*) old, obj_ptr, word_sz);
4393 if (g1p->track_object_age(alloc_purpose)) {
4394 // We could simply do obj->incr_age(). However, this causes a
4395 // performance issue. obj->incr_age() will first check whether
4396 // the object has a displaced mark by checking its mark word;
4397 // getting the mark word from the new location of the object
4398 // stalls. So, given that we already have the mark word and we
4399 // are about to install it anyway, it's better to increase the
4400 // age on the mark word, when the object does not have a
4401 // displaced mark word. We're not expecting many objects to have
4402 // a displaced marked word, so that case is not optimized
4403 // further (it could be...) and we simply call obj->incr_age().
4405 if (m->has_displaced_mark_helper()) {
4406 // in this case, we have to install the mark word first,
4407 // otherwise obj looks to be forwarded (the old mark word,
4408 // which contains the forward pointer, was copied)
4409 obj->set_mark(m);
4410 obj->incr_age();
4411 } else {
4412 m = m->incr_age();
4413 obj->set_mark(m);
4414 }
4415 _par_scan_state->age_table()->add(obj, word_sz);
4416 } else {
4417 obj->set_mark(m);
4418 }
4420 size_t* surv_young_words = _par_scan_state->surviving_young_words();
4421 surv_young_words[young_index] += word_sz;
4423 if (obj->is_objArray() && arrayOop(obj)->length() >= ParGCArrayScanChunk) {
4424 // We keep track of the next start index in the length field of
4425 // the to-space object. The actual length can be found in the
4426 // length field of the from-space object.
4427 arrayOop(obj)->set_length(0);
4428 oop* old_p = set_partial_array_mask(old);
4429 _par_scan_state->push_on_queue(old_p);
4430 } else {
4431 // No point in using the slower heap_region_containing() method,
4432 // given that we know obj is in the heap.
4433 _scanner->set_region(_g1->heap_region_containing_raw(obj));
4434 obj->oop_iterate_backwards(_scanner);
4435 }
4436 } else {
4437 _par_scan_state->undo_allocation(alloc_purpose, obj_ptr, word_sz);
4438 obj = forward_ptr;
4439 }
4440 return obj;
4441 }
4443 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object>
4444 template <class T>
4445 void G1ParCopyClosure<do_gen_barrier, barrier, do_mark_object>
4446 ::do_oop_work(T* p) {
4447 oop obj = oopDesc::load_decode_heap_oop(p);
4448 assert(barrier != G1BarrierRS || obj != NULL,
4449 "Precondition: G1BarrierRS implies obj is non-NULL");
4451 // here the null check is implicit in the cset_fast_test() test
4452 if (_g1->in_cset_fast_test(obj)) {
4453 oop forwardee;
4454 if (obj->is_forwarded()) {
4455 forwardee = obj->forwardee();
4456 } else {
4457 forwardee = copy_to_survivor_space(obj);
4458 }
4459 assert(forwardee != NULL, "forwardee should not be NULL");
4460 oopDesc::encode_store_heap_oop(p, forwardee);
4461 if (do_mark_object && forwardee != obj) {
4462 // If the object is self-forwarded we don't need to explicitly
4463 // mark it, the evacuation failure protocol will do so.
4464 mark_forwarded_object(obj, forwardee);
4465 }
4467 // When scanning the RS, we only care about objs in CS.
4468 if (barrier == G1BarrierRS) {
4469 _par_scan_state->update_rs(_from, p, _par_scan_state->queue_num());
4470 }
4471 } else {
4472 // The object is not in collection set. If we're a root scanning
4473 // closure during an initial mark pause (i.e. do_mark_object will
4474 // be true) then attempt to mark the object.
4475 if (do_mark_object && _g1->is_in_g1_reserved(obj)) {
4476 mark_object(obj);
4477 }
4478 }
4480 if (barrier == G1BarrierEvac && obj != NULL) {
4481 _par_scan_state->update_rs(_from, p, _par_scan_state->queue_num());
4482 }
4484 if (do_gen_barrier && obj != NULL) {
4485 par_do_barrier(p);
4486 }
4487 }
4489 template void G1ParCopyClosure<false, G1BarrierEvac, false>::do_oop_work(oop* p);
4490 template void G1ParCopyClosure<false, G1BarrierEvac, false>::do_oop_work(narrowOop* p);
4492 template <class T> void G1ParScanPartialArrayClosure::do_oop_nv(T* p) {
4493 assert(has_partial_array_mask(p), "invariant");
4494 oop from_obj = clear_partial_array_mask(p);
4496 assert(Universe::heap()->is_in_reserved(from_obj), "must be in heap.");
4497 assert(from_obj->is_objArray(), "must be obj array");
4498 objArrayOop from_obj_array = objArrayOop(from_obj);
4499 // The from-space object contains the real length.
4500 int length = from_obj_array->length();
4502 assert(from_obj->is_forwarded(), "must be forwarded");
4503 oop to_obj = from_obj->forwardee();
4504 assert(from_obj != to_obj, "should not be chunking self-forwarded objects");
4505 objArrayOop to_obj_array = objArrayOop(to_obj);
4506 // We keep track of the next start index in the length field of the
4507 // to-space object.
4508 int next_index = to_obj_array->length();
4509 assert(0 <= next_index && next_index < length,
4510 err_msg("invariant, next index: %d, length: %d", next_index, length));
4512 int start = next_index;
4513 int end = length;
4514 int remainder = end - start;
4515 // We'll try not to push a range that's smaller than ParGCArrayScanChunk.
4516 if (remainder > 2 * ParGCArrayScanChunk) {
4517 end = start + ParGCArrayScanChunk;
4518 to_obj_array->set_length(end);
4519 // Push the remainder before we process the range in case another
4520 // worker has run out of things to do and can steal it.
4521 oop* from_obj_p = set_partial_array_mask(from_obj);
4522 _par_scan_state->push_on_queue(from_obj_p);
4523 } else {
4524 assert(length == end, "sanity");
4525 // We'll process the final range for this object. Restore the length
4526 // so that the heap remains parsable in case of evacuation failure.
4527 to_obj_array->set_length(end);
4528 }
4529 _scanner.set_region(_g1->heap_region_containing_raw(to_obj));
4530 // Process indexes [start,end). It will also process the header
4531 // along with the first chunk (i.e., the chunk with start == 0).
4532 // Note that at this point the length field of to_obj_array is not
4533 // correct given that we are using it to keep track of the next
4534 // start index. oop_iterate_range() (thankfully!) ignores the length
4535 // field and only relies on the start / end parameters. It does
4536 // however return the size of the object which will be incorrect. So
4537 // we have to ignore it even if we wanted to use it.
4538 to_obj_array->oop_iterate_range(&_scanner, start, end);
4539 }
4541 class G1ParEvacuateFollowersClosure : public VoidClosure {
4542 protected:
4543 G1CollectedHeap* _g1h;
4544 G1ParScanThreadState* _par_scan_state;
4545 RefToScanQueueSet* _queues;
4546 ParallelTaskTerminator* _terminator;
4548 G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
4549 RefToScanQueueSet* queues() { return _queues; }
4550 ParallelTaskTerminator* terminator() { return _terminator; }
4552 public:
4553 G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h,
4554 G1ParScanThreadState* par_scan_state,
4555 RefToScanQueueSet* queues,
4556 ParallelTaskTerminator* terminator)
4557 : _g1h(g1h), _par_scan_state(par_scan_state),
4558 _queues(queues), _terminator(terminator) {}
4560 void do_void();
4562 private:
4563 inline bool offer_termination();
4564 };
4566 bool G1ParEvacuateFollowersClosure::offer_termination() {
4567 G1ParScanThreadState* const pss = par_scan_state();
4568 pss->start_term_time();
4569 const bool res = terminator()->offer_termination();
4570 pss->end_term_time();
4571 return res;
4572 }
4574 void G1ParEvacuateFollowersClosure::do_void() {
4575 StarTask stolen_task;
4576 G1ParScanThreadState* const pss = par_scan_state();
4577 pss->trim_queue();
4579 do {
4580 while (queues()->steal(pss->queue_num(), pss->hash_seed(), stolen_task)) {
4581 assert(pss->verify_task(stolen_task), "sanity");
4582 if (stolen_task.is_narrow()) {
4583 pss->deal_with_reference((narrowOop*) stolen_task);
4584 } else {
4585 pss->deal_with_reference((oop*) stolen_task);
4586 }
4588 // We've just processed a reference and we might have made
4589 // available new entries on the queues. So we have to make sure
4590 // we drain the queues as necessary.
4591 pss->trim_queue();
4592 }
4593 } while (!offer_termination());
4595 pss->retire_alloc_buffers();
4596 }
4598 class G1ParTask : public AbstractGangTask {
4599 protected:
4600 G1CollectedHeap* _g1h;
4601 RefToScanQueueSet *_queues;
4602 ParallelTaskTerminator _terminator;
4603 uint _n_workers;
4605 Mutex _stats_lock;
4606 Mutex* stats_lock() { return &_stats_lock; }
4608 size_t getNCards() {
4609 return (_g1h->capacity() + G1BlockOffsetSharedArray::N_bytes - 1)
4610 / G1BlockOffsetSharedArray::N_bytes;
4611 }
4613 public:
4614 G1ParTask(G1CollectedHeap* g1h,
4615 RefToScanQueueSet *task_queues)
4616 : AbstractGangTask("G1 collection"),
4617 _g1h(g1h),
4618 _queues(task_queues),
4619 _terminator(0, _queues),
4620 _stats_lock(Mutex::leaf, "parallel G1 stats lock", true)
4621 {}
4623 RefToScanQueueSet* queues() { return _queues; }
4625 RefToScanQueue *work_queue(int i) {
4626 return queues()->queue(i);
4627 }
4629 ParallelTaskTerminator* terminator() { return &_terminator; }
4631 virtual void set_for_termination(int active_workers) {
4632 // This task calls set_n_termination() in par_non_clean_card_iterate_work()
4633 // in the young space (_par_seq_tasks) in the G1 heap
4634 // for SequentialSubTasksDone.
4635 // This task also uses SubTasksDone in SharedHeap and G1CollectedHeap
4636 // both of which need setting by set_n_termination().
4637 _g1h->SharedHeap::set_n_termination(active_workers);
4638 _g1h->set_n_termination(active_workers);
4639 terminator()->reset_for_reuse(active_workers);
4640 _n_workers = active_workers;
4641 }
4643 void work(uint worker_id) {
4644 if (worker_id >= _n_workers) return; // no work needed this round
4646 double start_time_ms = os::elapsedTime() * 1000.0;
4647 _g1h->g1_policy()->record_gc_worker_start_time(worker_id, start_time_ms);
4649 ResourceMark rm;
4650 HandleMark hm;
4652 ReferenceProcessor* rp = _g1h->ref_processor_stw();
4654 G1ParScanThreadState pss(_g1h, worker_id);
4655 G1ParScanHeapEvacClosure scan_evac_cl(_g1h, &pss, rp);
4656 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, rp);
4657 G1ParScanPartialArrayClosure partial_scan_cl(_g1h, &pss, rp);
4659 pss.set_evac_closure(&scan_evac_cl);
4660 pss.set_evac_failure_closure(&evac_failure_cl);
4661 pss.set_partial_scan_closure(&partial_scan_cl);
4663 G1ParScanExtRootClosure only_scan_root_cl(_g1h, &pss, rp);
4664 G1ParScanPermClosure only_scan_perm_cl(_g1h, &pss, rp);
4666 G1ParScanAndMarkExtRootClosure scan_mark_root_cl(_g1h, &pss, rp);
4667 G1ParScanAndMarkPermClosure scan_mark_perm_cl(_g1h, &pss, rp);
4669 OopClosure* scan_root_cl = &only_scan_root_cl;
4670 OopsInHeapRegionClosure* scan_perm_cl = &only_scan_perm_cl;
4672 if (_g1h->g1_policy()->during_initial_mark_pause()) {
4673 // We also need to mark copied objects.
4674 scan_root_cl = &scan_mark_root_cl;
4675 scan_perm_cl = &scan_mark_perm_cl;
4676 }
4678 G1ParPushHeapRSClosure push_heap_rs_cl(_g1h, &pss);
4680 pss.start_strong_roots();
4681 _g1h->g1_process_strong_roots(/* not collecting perm */ false,
4682 SharedHeap::SO_AllClasses,
4683 scan_root_cl,
4684 &push_heap_rs_cl,
4685 scan_perm_cl,
4686 worker_id);
4687 pss.end_strong_roots();
4689 {
4690 double start = os::elapsedTime();
4691 G1ParEvacuateFollowersClosure evac(_g1h, &pss, _queues, &_terminator);
4692 evac.do_void();
4693 double elapsed_ms = (os::elapsedTime()-start)*1000.0;
4694 double term_ms = pss.term_time()*1000.0;
4695 _g1h->g1_policy()->record_obj_copy_time(worker_id, elapsed_ms-term_ms);
4696 _g1h->g1_policy()->record_termination(worker_id, term_ms, pss.term_attempts());
4697 }
4698 _g1h->g1_policy()->record_thread_age_table(pss.age_table());
4699 _g1h->update_surviving_young_words(pss.surviving_young_words()+1);
4701 // Clean up any par-expanded rem sets.
4702 HeapRegionRemSet::par_cleanup();
4704 if (ParallelGCVerbose) {
4705 MutexLocker x(stats_lock());
4706 pss.print_termination_stats(worker_id);
4707 }
4709 assert(pss.refs()->is_empty(), "should be empty");
4710 double end_time_ms = os::elapsedTime() * 1000.0;
4711 _g1h->g1_policy()->record_gc_worker_end_time(worker_id, end_time_ms);
4712 }
4713 };
4715 // *** Common G1 Evacuation Stuff
4717 // This method is run in a GC worker.
4719 void
4720 G1CollectedHeap::
4721 g1_process_strong_roots(bool collecting_perm_gen,
4722 SharedHeap::ScanningOption so,
4723 OopClosure* scan_non_heap_roots,
4724 OopsInHeapRegionClosure* scan_rs,
4725 OopsInGenClosure* scan_perm,
4726 int worker_i) {
4728 // First scan the strong roots, including the perm gen.
4729 double ext_roots_start = os::elapsedTime();
4730 double closure_app_time_sec = 0.0;
4732 BufferingOopClosure buf_scan_non_heap_roots(scan_non_heap_roots);
4733 BufferingOopsInGenClosure buf_scan_perm(scan_perm);
4734 buf_scan_perm.set_generation(perm_gen());
4736 // Walk the code cache w/o buffering, because StarTask cannot handle
4737 // unaligned oop locations.
4738 CodeBlobToOopClosure eager_scan_code_roots(scan_non_heap_roots, /*do_marking=*/ true);
4740 process_strong_roots(false, // no scoping; this is parallel code
4741 collecting_perm_gen, so,
4742 &buf_scan_non_heap_roots,
4743 &eager_scan_code_roots,
4744 &buf_scan_perm);
4746 // Now the CM ref_processor roots.
4747 if (!_process_strong_tasks->is_task_claimed(G1H_PS_refProcessor_oops_do)) {
4748 // We need to treat the discovered reference lists of the
4749 // concurrent mark ref processor as roots and keep entries
4750 // (which are added by the marking threads) on them live
4751 // until they can be processed at the end of marking.
4752 ref_processor_cm()->weak_oops_do(&buf_scan_non_heap_roots);
4753 }
4755 // Finish up any enqueued closure apps (attributed as object copy time).
4756 buf_scan_non_heap_roots.done();
4757 buf_scan_perm.done();
4759 double ext_roots_end = os::elapsedTime();
4761 g1_policy()->reset_obj_copy_time(worker_i);
4762 double obj_copy_time_sec = buf_scan_perm.closure_app_seconds() +
4763 buf_scan_non_heap_roots.closure_app_seconds();
4764 g1_policy()->record_obj_copy_time(worker_i, obj_copy_time_sec * 1000.0);
4766 double ext_root_time_ms =
4767 ((ext_roots_end - ext_roots_start) - obj_copy_time_sec) * 1000.0;
4769 g1_policy()->record_ext_root_scan_time(worker_i, ext_root_time_ms);
4771 // During conc marking we have to filter the per-thread SATB buffers
4772 // to make sure we remove any oops into the CSet (which will show up
4773 // as implicitly live).
4774 if (!_process_strong_tasks->is_task_claimed(G1H_PS_filter_satb_buffers)) {
4775 if (mark_in_progress()) {
4776 JavaThread::satb_mark_queue_set().filter_thread_buffers();
4777 }
4778 }
4779 double satb_filtering_ms = (os::elapsedTime() - ext_roots_end) * 1000.0;
4780 g1_policy()->record_satb_filtering_time(worker_i, satb_filtering_ms);
4782 // Now scan the complement of the collection set.
4783 if (scan_rs != NULL) {
4784 g1_rem_set()->oops_into_collection_set_do(scan_rs, worker_i);
4785 }
4787 _process_strong_tasks->all_tasks_completed();
4788 }
4790 void
4791 G1CollectedHeap::g1_process_weak_roots(OopClosure* root_closure,
4792 OopClosure* non_root_closure) {
4793 CodeBlobToOopClosure roots_in_blobs(root_closure, /*do_marking=*/ false);
4794 SharedHeap::process_weak_roots(root_closure, &roots_in_blobs, non_root_closure);
4795 }
4797 // Weak Reference Processing support
4799 // An always "is_alive" closure that is used to preserve referents.
4800 // If the object is non-null then it's alive. Used in the preservation
4801 // of referent objects that are pointed to by reference objects
4802 // discovered by the CM ref processor.
4803 class G1AlwaysAliveClosure: public BoolObjectClosure {
4804 G1CollectedHeap* _g1;
4805 public:
4806 G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
4807 void do_object(oop p) { assert(false, "Do not call."); }
4808 bool do_object_b(oop p) {
4809 if (p != NULL) {
4810 return true;
4811 }
4812 return false;
4813 }
4814 };
4816 bool G1STWIsAliveClosure::do_object_b(oop p) {
4817 // An object is reachable if it is outside the collection set,
4818 // or is inside and copied.
4819 return !_g1->obj_in_cs(p) || p->is_forwarded();
4820 }
4822 // Non Copying Keep Alive closure
4823 class G1KeepAliveClosure: public OopClosure {
4824 G1CollectedHeap* _g1;
4825 public:
4826 G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
4827 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
4828 void do_oop( oop* p) {
4829 oop obj = *p;
4831 if (_g1->obj_in_cs(obj)) {
4832 assert( obj->is_forwarded(), "invariant" );
4833 *p = obj->forwardee();
4834 }
4835 }
4836 };
4838 // Copying Keep Alive closure - can be called from both
4839 // serial and parallel code as long as different worker
4840 // threads utilize different G1ParScanThreadState instances
4841 // and different queues.
4843 class G1CopyingKeepAliveClosure: public OopClosure {
4844 G1CollectedHeap* _g1h;
4845 OopClosure* _copy_non_heap_obj_cl;
4846 OopsInHeapRegionClosure* _copy_perm_obj_cl;
4847 G1ParScanThreadState* _par_scan_state;
4849 public:
4850 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
4851 OopClosure* non_heap_obj_cl,
4852 OopsInHeapRegionClosure* perm_obj_cl,
4853 G1ParScanThreadState* pss):
4854 _g1h(g1h),
4855 _copy_non_heap_obj_cl(non_heap_obj_cl),
4856 _copy_perm_obj_cl(perm_obj_cl),
4857 _par_scan_state(pss)
4858 {}
4860 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
4861 virtual void do_oop( oop* p) { do_oop_work(p); }
4863 template <class T> void do_oop_work(T* p) {
4864 oop obj = oopDesc::load_decode_heap_oop(p);
4866 if (_g1h->obj_in_cs(obj)) {
4867 // If the referent object has been forwarded (either copied
4868 // to a new location or to itself in the event of an
4869 // evacuation failure) then we need to update the reference
4870 // field and, if both reference and referent are in the G1
4871 // heap, update the RSet for the referent.
4872 //
4873 // If the referent has not been forwarded then we have to keep
4874 // it alive by policy. Therefore we have copy the referent.
4875 //
4876 // If the reference field is in the G1 heap then we can push
4877 // on the PSS queue. When the queue is drained (after each
4878 // phase of reference processing) the object and it's followers
4879 // will be copied, the reference field set to point to the
4880 // new location, and the RSet updated. Otherwise we need to
4881 // use the the non-heap or perm closures directly to copy
4882 // the refernt object and update the pointer, while avoiding
4883 // updating the RSet.
4885 if (_g1h->is_in_g1_reserved(p)) {
4886 _par_scan_state->push_on_queue(p);
4887 } else {
4888 // The reference field is not in the G1 heap.
4889 if (_g1h->perm_gen()->is_in(p)) {
4890 _copy_perm_obj_cl->do_oop(p);
4891 } else {
4892 _copy_non_heap_obj_cl->do_oop(p);
4893 }
4894 }
4895 }
4896 }
4897 };
4899 // Serial drain queue closure. Called as the 'complete_gc'
4900 // closure for each discovered list in some of the
4901 // reference processing phases.
4903 class G1STWDrainQueueClosure: public VoidClosure {
4904 protected:
4905 G1CollectedHeap* _g1h;
4906 G1ParScanThreadState* _par_scan_state;
4908 G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
4910 public:
4911 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
4912 _g1h(g1h),
4913 _par_scan_state(pss)
4914 { }
4916 void do_void() {
4917 G1ParScanThreadState* const pss = par_scan_state();
4918 pss->trim_queue();
4919 }
4920 };
4922 // Parallel Reference Processing closures
4924 // Implementation of AbstractRefProcTaskExecutor for parallel reference
4925 // processing during G1 evacuation pauses.
4927 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
4928 private:
4929 G1CollectedHeap* _g1h;
4930 RefToScanQueueSet* _queues;
4931 FlexibleWorkGang* _workers;
4932 int _active_workers;
4934 public:
4935 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
4936 FlexibleWorkGang* workers,
4937 RefToScanQueueSet *task_queues,
4938 int n_workers) :
4939 _g1h(g1h),
4940 _queues(task_queues),
4941 _workers(workers),
4942 _active_workers(n_workers)
4943 {
4944 assert(n_workers > 0, "shouldn't call this otherwise");
4945 }
4947 // Executes the given task using concurrent marking worker threads.
4948 virtual void execute(ProcessTask& task);
4949 virtual void execute(EnqueueTask& task);
4950 };
4952 // Gang task for possibly parallel reference processing
4954 class G1STWRefProcTaskProxy: public AbstractGangTask {
4955 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
4956 ProcessTask& _proc_task;
4957 G1CollectedHeap* _g1h;
4958 RefToScanQueueSet *_task_queues;
4959 ParallelTaskTerminator* _terminator;
4961 public:
4962 G1STWRefProcTaskProxy(ProcessTask& proc_task,
4963 G1CollectedHeap* g1h,
4964 RefToScanQueueSet *task_queues,
4965 ParallelTaskTerminator* terminator) :
4966 AbstractGangTask("Process reference objects in parallel"),
4967 _proc_task(proc_task),
4968 _g1h(g1h),
4969 _task_queues(task_queues),
4970 _terminator(terminator)
4971 {}
4973 virtual void work(uint worker_id) {
4974 // The reference processing task executed by a single worker.
4975 ResourceMark rm;
4976 HandleMark hm;
4978 G1STWIsAliveClosure is_alive(_g1h);
4980 G1ParScanThreadState pss(_g1h, worker_id);
4982 G1ParScanHeapEvacClosure scan_evac_cl(_g1h, &pss, NULL);
4983 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
4984 G1ParScanPartialArrayClosure partial_scan_cl(_g1h, &pss, NULL);
4986 pss.set_evac_closure(&scan_evac_cl);
4987 pss.set_evac_failure_closure(&evac_failure_cl);
4988 pss.set_partial_scan_closure(&partial_scan_cl);
4990 G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL);
4991 G1ParScanPermClosure only_copy_perm_cl(_g1h, &pss, NULL);
4993 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
4994 G1ParScanAndMarkPermClosure copy_mark_perm_cl(_g1h, &pss, NULL);
4996 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
4997 OopsInHeapRegionClosure* copy_perm_cl = &only_copy_perm_cl;
4999 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5000 // We also need to mark copied objects.
5001 copy_non_heap_cl = ©_mark_non_heap_cl;
5002 copy_perm_cl = ©_mark_perm_cl;
5003 }
5005 // Keep alive closure.
5006 G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, copy_perm_cl, &pss);
5008 // Complete GC closure
5009 G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _task_queues, _terminator);
5011 // Call the reference processing task's work routine.
5012 _proc_task.work(worker_id, is_alive, keep_alive, drain_queue);
5014 // Note we cannot assert that the refs array is empty here as not all
5015 // of the processing tasks (specifically phase2 - pp2_work) execute
5016 // the complete_gc closure (which ordinarily would drain the queue) so
5017 // the queue may not be empty.
5018 }
5019 };
5021 // Driver routine for parallel reference processing.
5022 // Creates an instance of the ref processing gang
5023 // task and has the worker threads execute it.
5024 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) {
5025 assert(_workers != NULL, "Need parallel worker threads.");
5027 ParallelTaskTerminator terminator(_active_workers, _queues);
5028 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _queues, &terminator);
5030 _g1h->set_par_threads(_active_workers);
5031 _workers->run_task(&proc_task_proxy);
5032 _g1h->set_par_threads(0);
5033 }
5035 // Gang task for parallel reference enqueueing.
5037 class G1STWRefEnqueueTaskProxy: public AbstractGangTask {
5038 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
5039 EnqueueTask& _enq_task;
5041 public:
5042 G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) :
5043 AbstractGangTask("Enqueue reference objects in parallel"),
5044 _enq_task(enq_task)
5045 { }
5047 virtual void work(uint worker_id) {
5048 _enq_task.work(worker_id);
5049 }
5050 };
5052 // Driver routine for parallel reference enqueing.
5053 // Creates an instance of the ref enqueueing gang
5054 // task and has the worker threads execute it.
5056 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
5057 assert(_workers != NULL, "Need parallel worker threads.");
5059 G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task);
5061 _g1h->set_par_threads(_active_workers);
5062 _workers->run_task(&enq_task_proxy);
5063 _g1h->set_par_threads(0);
5064 }
5066 // End of weak reference support closures
5068 // Abstract task used to preserve (i.e. copy) any referent objects
5069 // that are in the collection set and are pointed to by reference
5070 // objects discovered by the CM ref processor.
5072 class G1ParPreserveCMReferentsTask: public AbstractGangTask {
5073 protected:
5074 G1CollectedHeap* _g1h;
5075 RefToScanQueueSet *_queues;
5076 ParallelTaskTerminator _terminator;
5077 uint _n_workers;
5079 public:
5080 G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h,int workers, RefToScanQueueSet *task_queues) :
5081 AbstractGangTask("ParPreserveCMReferents"),
5082 _g1h(g1h),
5083 _queues(task_queues),
5084 _terminator(workers, _queues),
5085 _n_workers(workers)
5086 { }
5088 void work(uint worker_id) {
5089 ResourceMark rm;
5090 HandleMark hm;
5092 G1ParScanThreadState pss(_g1h, worker_id);
5093 G1ParScanHeapEvacClosure scan_evac_cl(_g1h, &pss, NULL);
5094 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5095 G1ParScanPartialArrayClosure partial_scan_cl(_g1h, &pss, NULL);
5097 pss.set_evac_closure(&scan_evac_cl);
5098 pss.set_evac_failure_closure(&evac_failure_cl);
5099 pss.set_partial_scan_closure(&partial_scan_cl);
5101 assert(pss.refs()->is_empty(), "both queue and overflow should be empty");
5104 G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL);
5105 G1ParScanPermClosure only_copy_perm_cl(_g1h, &pss, NULL);
5107 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5108 G1ParScanAndMarkPermClosure copy_mark_perm_cl(_g1h, &pss, NULL);
5110 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5111 OopsInHeapRegionClosure* copy_perm_cl = &only_copy_perm_cl;
5113 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5114 // We also need to mark copied objects.
5115 copy_non_heap_cl = ©_mark_non_heap_cl;
5116 copy_perm_cl = ©_mark_perm_cl;
5117 }
5119 // Is alive closure
5120 G1AlwaysAliveClosure always_alive(_g1h);
5122 // Copying keep alive closure. Applied to referent objects that need
5123 // to be copied.
5124 G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, copy_perm_cl, &pss);
5126 ReferenceProcessor* rp = _g1h->ref_processor_cm();
5128 uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q();
5129 uint stride = MIN2(MAX2(_n_workers, 1U), limit);
5131 // limit is set using max_num_q() - which was set using ParallelGCThreads.
5132 // So this must be true - but assert just in case someone decides to
5133 // change the worker ids.
5134 assert(0 <= worker_id && worker_id < limit, "sanity");
5135 assert(!rp->discovery_is_atomic(), "check this code");
5137 // Select discovered lists [i, i+stride, i+2*stride,...,limit)
5138 for (uint idx = worker_id; idx < limit; idx += stride) {
5139 DiscoveredList& ref_list = rp->discovered_refs()[idx];
5141 DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive);
5142 while (iter.has_next()) {
5143 // Since discovery is not atomic for the CM ref processor, we
5144 // can see some null referent objects.
5145 iter.load_ptrs(DEBUG_ONLY(true));
5146 oop ref = iter.obj();
5148 // This will filter nulls.
5149 if (iter.is_referent_alive()) {
5150 iter.make_referent_alive();
5151 }
5152 iter.move_to_next();
5153 }
5154 }
5156 // Drain the queue - which may cause stealing
5157 G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _queues, &_terminator);
5158 drain_queue.do_void();
5159 // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure
5160 assert(pss.refs()->is_empty(), "should be");
5161 }
5162 };
5164 // Weak Reference processing during an evacuation pause (part 1).
5165 void G1CollectedHeap::process_discovered_references() {
5166 double ref_proc_start = os::elapsedTime();
5168 ReferenceProcessor* rp = _ref_processor_stw;
5169 assert(rp->discovery_enabled(), "should have been enabled");
5171 // Any reference objects, in the collection set, that were 'discovered'
5172 // by the CM ref processor should have already been copied (either by
5173 // applying the external root copy closure to the discovered lists, or
5174 // by following an RSet entry).
5175 //
5176 // But some of the referents, that are in the collection set, that these
5177 // reference objects point to may not have been copied: the STW ref
5178 // processor would have seen that the reference object had already
5179 // been 'discovered' and would have skipped discovering the reference,
5180 // but would not have treated the reference object as a regular oop.
5181 // As a reult the copy closure would not have been applied to the
5182 // referent object.
5183 //
5184 // We need to explicitly copy these referent objects - the references
5185 // will be processed at the end of remarking.
5186 //
5187 // We also need to do this copying before we process the reference
5188 // objects discovered by the STW ref processor in case one of these
5189 // referents points to another object which is also referenced by an
5190 // object discovered by the STW ref processor.
5192 uint active_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
5193 workers()->active_workers() : 1);
5195 assert(!G1CollectedHeap::use_parallel_gc_threads() ||
5196 active_workers == workers()->active_workers(),
5197 "Need to reset active_workers");
5199 set_par_threads(active_workers);
5200 G1ParPreserveCMReferentsTask keep_cm_referents(this, active_workers, _task_queues);
5202 if (G1CollectedHeap::use_parallel_gc_threads()) {
5203 workers()->run_task(&keep_cm_referents);
5204 } else {
5205 keep_cm_referents.work(0);
5206 }
5208 set_par_threads(0);
5210 // Closure to test whether a referent is alive.
5211 G1STWIsAliveClosure is_alive(this);
5213 // Even when parallel reference processing is enabled, the processing
5214 // of JNI refs is serial and performed serially by the current thread
5215 // rather than by a worker. The following PSS will be used for processing
5216 // JNI refs.
5218 // Use only a single queue for this PSS.
5219 G1ParScanThreadState pss(this, 0);
5221 // We do not embed a reference processor in the copying/scanning
5222 // closures while we're actually processing the discovered
5223 // reference objects.
5224 G1ParScanHeapEvacClosure scan_evac_cl(this, &pss, NULL);
5225 G1ParScanHeapEvacFailureClosure evac_failure_cl(this, &pss, NULL);
5226 G1ParScanPartialArrayClosure partial_scan_cl(this, &pss, NULL);
5228 pss.set_evac_closure(&scan_evac_cl);
5229 pss.set_evac_failure_closure(&evac_failure_cl);
5230 pss.set_partial_scan_closure(&partial_scan_cl);
5232 assert(pss.refs()->is_empty(), "pre-condition");
5234 G1ParScanExtRootClosure only_copy_non_heap_cl(this, &pss, NULL);
5235 G1ParScanPermClosure only_copy_perm_cl(this, &pss, NULL);
5237 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(this, &pss, NULL);
5238 G1ParScanAndMarkPermClosure copy_mark_perm_cl(this, &pss, NULL);
5240 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5241 OopsInHeapRegionClosure* copy_perm_cl = &only_copy_perm_cl;
5243 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5244 // We also need to mark copied objects.
5245 copy_non_heap_cl = ©_mark_non_heap_cl;
5246 copy_perm_cl = ©_mark_perm_cl;
5247 }
5249 // Keep alive closure.
5250 G1CopyingKeepAliveClosure keep_alive(this, copy_non_heap_cl, copy_perm_cl, &pss);
5252 // Serial Complete GC closure
5253 G1STWDrainQueueClosure drain_queue(this, &pss);
5255 // Setup the soft refs policy...
5256 rp->setup_policy(false);
5258 if (!rp->processing_is_mt()) {
5259 // Serial reference processing...
5260 rp->process_discovered_references(&is_alive,
5261 &keep_alive,
5262 &drain_queue,
5263 NULL);
5264 } else {
5265 // Parallel reference processing
5266 assert(rp->num_q() == active_workers, "sanity");
5267 assert(active_workers <= rp->max_num_q(), "sanity");
5269 G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, active_workers);
5270 rp->process_discovered_references(&is_alive, &keep_alive, &drain_queue, &par_task_executor);
5271 }
5273 // We have completed copying any necessary live referent objects
5274 // (that were not copied during the actual pause) so we can
5275 // retire any active alloc buffers
5276 pss.retire_alloc_buffers();
5277 assert(pss.refs()->is_empty(), "both queue and overflow should be empty");
5279 double ref_proc_time = os::elapsedTime() - ref_proc_start;
5280 g1_policy()->record_ref_proc_time(ref_proc_time * 1000.0);
5281 }
5283 // Weak Reference processing during an evacuation pause (part 2).
5284 void G1CollectedHeap::enqueue_discovered_references() {
5285 double ref_enq_start = os::elapsedTime();
5287 ReferenceProcessor* rp = _ref_processor_stw;
5288 assert(!rp->discovery_enabled(), "should have been disabled as part of processing");
5290 // Now enqueue any remaining on the discovered lists on to
5291 // the pending list.
5292 if (!rp->processing_is_mt()) {
5293 // Serial reference processing...
5294 rp->enqueue_discovered_references();
5295 } else {
5296 // Parallel reference enqueuing
5298 uint active_workers = (ParallelGCThreads > 0 ? workers()->active_workers() : 1);
5299 assert(active_workers == workers()->active_workers(),
5300 "Need to reset active_workers");
5301 assert(rp->num_q() == active_workers, "sanity");
5302 assert(active_workers <= rp->max_num_q(), "sanity");
5304 G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, active_workers);
5305 rp->enqueue_discovered_references(&par_task_executor);
5306 }
5308 rp->verify_no_references_recorded();
5309 assert(!rp->discovery_enabled(), "should have been disabled");
5311 // FIXME
5312 // CM's reference processing also cleans up the string and symbol tables.
5313 // Should we do that here also? We could, but it is a serial operation
5314 // and could signicantly increase the pause time.
5316 double ref_enq_time = os::elapsedTime() - ref_enq_start;
5317 g1_policy()->record_ref_enq_time(ref_enq_time * 1000.0);
5318 }
5320 void G1CollectedHeap::evacuate_collection_set() {
5321 _expand_heap_after_alloc_failure = true;
5322 set_evacuation_failed(false);
5324 g1_rem_set()->prepare_for_oops_into_collection_set_do();
5325 concurrent_g1_refine()->set_use_cache(false);
5326 concurrent_g1_refine()->clear_hot_cache_claimed_index();
5328 uint n_workers;
5329 if (G1CollectedHeap::use_parallel_gc_threads()) {
5330 n_workers =
5331 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
5332 workers()->active_workers(),
5333 Threads::number_of_non_daemon_threads());
5334 assert(UseDynamicNumberOfGCThreads ||
5335 n_workers == workers()->total_workers(),
5336 "If not dynamic should be using all the workers");
5337 workers()->set_active_workers(n_workers);
5338 set_par_threads(n_workers);
5339 } else {
5340 assert(n_par_threads() == 0,
5341 "Should be the original non-parallel value");
5342 n_workers = 1;
5343 }
5345 G1ParTask g1_par_task(this, _task_queues);
5347 init_for_evac_failure(NULL);
5349 rem_set()->prepare_for_younger_refs_iterate(true);
5351 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
5352 double start_par = os::elapsedTime();
5354 if (G1CollectedHeap::use_parallel_gc_threads()) {
5355 // The individual threads will set their evac-failure closures.
5356 StrongRootsScope srs(this);
5357 if (ParallelGCVerbose) G1ParScanThreadState::print_termination_stats_hdr();
5358 // These tasks use ShareHeap::_process_strong_tasks
5359 assert(UseDynamicNumberOfGCThreads ||
5360 workers()->active_workers() == workers()->total_workers(),
5361 "If not dynamic should be using all the workers");
5362 workers()->run_task(&g1_par_task);
5363 } else {
5364 StrongRootsScope srs(this);
5365 g1_par_task.set_for_termination(n_workers);
5366 g1_par_task.work(0);
5367 }
5369 double par_time = (os::elapsedTime() - start_par) * 1000.0;
5370 g1_policy()->record_par_time(par_time);
5372 set_par_threads(0);
5374 // Process any discovered reference objects - we have
5375 // to do this _before_ we retire the GC alloc regions
5376 // as we may have to copy some 'reachable' referent
5377 // objects (and their reachable sub-graphs) that were
5378 // not copied during the pause.
5379 process_discovered_references();
5381 // Weak root processing.
5382 // Note: when JSR 292 is enabled and code blobs can contain
5383 // non-perm oops then we will need to process the code blobs
5384 // here too.
5385 {
5386 G1STWIsAliveClosure is_alive(this);
5387 G1KeepAliveClosure keep_alive(this);
5388 JNIHandles::weak_oops_do(&is_alive, &keep_alive);
5389 }
5391 release_gc_alloc_regions();
5392 g1_rem_set()->cleanup_after_oops_into_collection_set_do();
5394 concurrent_g1_refine()->clear_hot_cache();
5395 concurrent_g1_refine()->set_use_cache(true);
5397 finalize_for_evac_failure();
5399 if (evacuation_failed()) {
5400 remove_self_forwarding_pointers();
5401 if (PrintGCDetails) {
5402 gclog_or_tty->print(" (to-space overflow)");
5403 } else if (PrintGC) {
5404 gclog_or_tty->print("--");
5405 }
5406 }
5408 // Enqueue any remaining references remaining on the STW
5409 // reference processor's discovered lists. We need to do
5410 // this after the card table is cleaned (and verified) as
5411 // the act of enqueuing entries on to the pending list
5412 // will log these updates (and dirty their associated
5413 // cards). We need these updates logged to update any
5414 // RSets.
5415 enqueue_discovered_references();
5417 if (G1DeferredRSUpdate) {
5418 RedirtyLoggedCardTableEntryFastClosure redirty;
5419 dirty_card_queue_set().set_closure(&redirty);
5420 dirty_card_queue_set().apply_closure_to_all_completed_buffers();
5422 DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set();
5423 dcq.merge_bufferlists(&dirty_card_queue_set());
5424 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
5425 }
5426 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
5427 }
5429 void G1CollectedHeap::free_region_if_empty(HeapRegion* hr,
5430 size_t* pre_used,
5431 FreeRegionList* free_list,
5432 OldRegionSet* old_proxy_set,
5433 HumongousRegionSet* humongous_proxy_set,
5434 HRRSCleanupTask* hrrs_cleanup_task,
5435 bool par) {
5436 if (hr->used() > 0 && hr->max_live_bytes() == 0 && !hr->is_young()) {
5437 if (hr->isHumongous()) {
5438 assert(hr->startsHumongous(), "we should only see starts humongous");
5439 free_humongous_region(hr, pre_used, free_list, humongous_proxy_set, par);
5440 } else {
5441 _old_set.remove_with_proxy(hr, old_proxy_set);
5442 free_region(hr, pre_used, free_list, par);
5443 }
5444 } else {
5445 hr->rem_set()->do_cleanup_work(hrrs_cleanup_task);
5446 }
5447 }
5449 void G1CollectedHeap::free_region(HeapRegion* hr,
5450 size_t* pre_used,
5451 FreeRegionList* free_list,
5452 bool par) {
5453 assert(!hr->isHumongous(), "this is only for non-humongous regions");
5454 assert(!hr->is_empty(), "the region should not be empty");
5455 assert(free_list != NULL, "pre-condition");
5457 *pre_used += hr->used();
5458 hr->hr_clear(par, true /* clear_space */);
5459 free_list->add_as_head(hr);
5460 }
5462 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
5463 size_t* pre_used,
5464 FreeRegionList* free_list,
5465 HumongousRegionSet* humongous_proxy_set,
5466 bool par) {
5467 assert(hr->startsHumongous(), "this is only for starts humongous regions");
5468 assert(free_list != NULL, "pre-condition");
5469 assert(humongous_proxy_set != NULL, "pre-condition");
5471 size_t hr_used = hr->used();
5472 size_t hr_capacity = hr->capacity();
5473 size_t hr_pre_used = 0;
5474 _humongous_set.remove_with_proxy(hr, humongous_proxy_set);
5475 hr->set_notHumongous();
5476 free_region(hr, &hr_pre_used, free_list, par);
5478 size_t i = hr->hrs_index() + 1;
5479 size_t num = 1;
5480 while (i < n_regions()) {
5481 HeapRegion* curr_hr = region_at(i);
5482 if (!curr_hr->continuesHumongous()) {
5483 break;
5484 }
5485 curr_hr->set_notHumongous();
5486 free_region(curr_hr, &hr_pre_used, free_list, par);
5487 num += 1;
5488 i += 1;
5489 }
5490 assert(hr_pre_used == hr_used,
5491 err_msg("hr_pre_used: "SIZE_FORMAT" and hr_used: "SIZE_FORMAT" "
5492 "should be the same", hr_pre_used, hr_used));
5493 *pre_used += hr_pre_used;
5494 }
5496 void G1CollectedHeap::update_sets_after_freeing_regions(size_t pre_used,
5497 FreeRegionList* free_list,
5498 OldRegionSet* old_proxy_set,
5499 HumongousRegionSet* humongous_proxy_set,
5500 bool par) {
5501 if (pre_used > 0) {
5502 Mutex* lock = (par) ? ParGCRareEvent_lock : NULL;
5503 MutexLockerEx x(lock, Mutex::_no_safepoint_check_flag);
5504 assert(_summary_bytes_used >= pre_used,
5505 err_msg("invariant: _summary_bytes_used: "SIZE_FORMAT" "
5506 "should be >= pre_used: "SIZE_FORMAT,
5507 _summary_bytes_used, pre_used));
5508 _summary_bytes_used -= pre_used;
5509 }
5510 if (free_list != NULL && !free_list->is_empty()) {
5511 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
5512 _free_list.add_as_head(free_list);
5513 }
5514 if (old_proxy_set != NULL && !old_proxy_set->is_empty()) {
5515 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
5516 _old_set.update_from_proxy(old_proxy_set);
5517 }
5518 if (humongous_proxy_set != NULL && !humongous_proxy_set->is_empty()) {
5519 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
5520 _humongous_set.update_from_proxy(humongous_proxy_set);
5521 }
5522 }
5524 class G1ParCleanupCTTask : public AbstractGangTask {
5525 CardTableModRefBS* _ct_bs;
5526 G1CollectedHeap* _g1h;
5527 HeapRegion* volatile _su_head;
5528 public:
5529 G1ParCleanupCTTask(CardTableModRefBS* ct_bs,
5530 G1CollectedHeap* g1h) :
5531 AbstractGangTask("G1 Par Cleanup CT Task"),
5532 _ct_bs(ct_bs), _g1h(g1h) { }
5534 void work(uint worker_id) {
5535 HeapRegion* r;
5536 while (r = _g1h->pop_dirty_cards_region()) {
5537 clear_cards(r);
5538 }
5539 }
5541 void clear_cards(HeapRegion* r) {
5542 // Cards of the survivors should have already been dirtied.
5543 if (!r->is_survivor()) {
5544 _ct_bs->clear(MemRegion(r->bottom(), r->end()));
5545 }
5546 }
5547 };
5549 #ifndef PRODUCT
5550 class G1VerifyCardTableCleanup: public HeapRegionClosure {
5551 G1CollectedHeap* _g1h;
5552 CardTableModRefBS* _ct_bs;
5553 public:
5554 G1VerifyCardTableCleanup(G1CollectedHeap* g1h, CardTableModRefBS* ct_bs)
5555 : _g1h(g1h), _ct_bs(ct_bs) { }
5556 virtual bool doHeapRegion(HeapRegion* r) {
5557 if (r->is_survivor()) {
5558 _g1h->verify_dirty_region(r);
5559 } else {
5560 _g1h->verify_not_dirty_region(r);
5561 }
5562 return false;
5563 }
5564 };
5566 void G1CollectedHeap::verify_not_dirty_region(HeapRegion* hr) {
5567 // All of the region should be clean.
5568 CardTableModRefBS* ct_bs = (CardTableModRefBS*)barrier_set();
5569 MemRegion mr(hr->bottom(), hr->end());
5570 ct_bs->verify_not_dirty_region(mr);
5571 }
5573 void G1CollectedHeap::verify_dirty_region(HeapRegion* hr) {
5574 // We cannot guarantee that [bottom(),end()] is dirty. Threads
5575 // dirty allocated blocks as they allocate them. The thread that
5576 // retires each region and replaces it with a new one will do a
5577 // maximal allocation to fill in [pre_dummy_top(),end()] but will
5578 // not dirty that area (one less thing to have to do while holding
5579 // a lock). So we can only verify that [bottom(),pre_dummy_top()]
5580 // is dirty.
5581 CardTableModRefBS* ct_bs = (CardTableModRefBS*) barrier_set();
5582 MemRegion mr(hr->bottom(), hr->pre_dummy_top());
5583 ct_bs->verify_dirty_region(mr);
5584 }
5586 void G1CollectedHeap::verify_dirty_young_list(HeapRegion* head) {
5587 CardTableModRefBS* ct_bs = (CardTableModRefBS*) barrier_set();
5588 for (HeapRegion* hr = head; hr != NULL; hr = hr->get_next_young_region()) {
5589 verify_dirty_region(hr);
5590 }
5591 }
5593 void G1CollectedHeap::verify_dirty_young_regions() {
5594 verify_dirty_young_list(_young_list->first_region());
5595 verify_dirty_young_list(_young_list->first_survivor_region());
5596 }
5597 #endif
5599 void G1CollectedHeap::cleanUpCardTable() {
5600 CardTableModRefBS* ct_bs = (CardTableModRefBS*) (barrier_set());
5601 double start = os::elapsedTime();
5603 {
5604 // Iterate over the dirty cards region list.
5605 G1ParCleanupCTTask cleanup_task(ct_bs, this);
5607 if (G1CollectedHeap::use_parallel_gc_threads()) {
5608 set_par_threads();
5609 workers()->run_task(&cleanup_task);
5610 set_par_threads(0);
5611 } else {
5612 while (_dirty_cards_region_list) {
5613 HeapRegion* r = _dirty_cards_region_list;
5614 cleanup_task.clear_cards(r);
5615 _dirty_cards_region_list = r->get_next_dirty_cards_region();
5616 if (_dirty_cards_region_list == r) {
5617 // The last region.
5618 _dirty_cards_region_list = NULL;
5619 }
5620 r->set_next_dirty_cards_region(NULL);
5621 }
5622 }
5623 #ifndef PRODUCT
5624 if (G1VerifyCTCleanup || VerifyAfterGC) {
5625 G1VerifyCardTableCleanup cleanup_verifier(this, ct_bs);
5626 heap_region_iterate(&cleanup_verifier);
5627 }
5628 #endif
5629 }
5631 double elapsed = os::elapsedTime() - start;
5632 g1_policy()->record_clear_ct_time(elapsed * 1000.0);
5633 }
5635 void G1CollectedHeap::free_collection_set(HeapRegion* cs_head) {
5636 size_t pre_used = 0;
5637 FreeRegionList local_free_list("Local List for CSet Freeing");
5639 double young_time_ms = 0.0;
5640 double non_young_time_ms = 0.0;
5642 // Since the collection set is a superset of the the young list,
5643 // all we need to do to clear the young list is clear its
5644 // head and length, and unlink any young regions in the code below
5645 _young_list->clear();
5647 G1CollectorPolicy* policy = g1_policy();
5649 double start_sec = os::elapsedTime();
5650 bool non_young = true;
5652 HeapRegion* cur = cs_head;
5653 int age_bound = -1;
5654 size_t rs_lengths = 0;
5656 while (cur != NULL) {
5657 assert(!is_on_master_free_list(cur), "sanity");
5658 if (non_young) {
5659 if (cur->is_young()) {
5660 double end_sec = os::elapsedTime();
5661 double elapsed_ms = (end_sec - start_sec) * 1000.0;
5662 non_young_time_ms += elapsed_ms;
5664 start_sec = os::elapsedTime();
5665 non_young = false;
5666 }
5667 } else {
5668 if (!cur->is_young()) {
5669 double end_sec = os::elapsedTime();
5670 double elapsed_ms = (end_sec - start_sec) * 1000.0;
5671 young_time_ms += elapsed_ms;
5673 start_sec = os::elapsedTime();
5674 non_young = true;
5675 }
5676 }
5678 rs_lengths += cur->rem_set()->occupied();
5680 HeapRegion* next = cur->next_in_collection_set();
5681 assert(cur->in_collection_set(), "bad CS");
5682 cur->set_next_in_collection_set(NULL);
5683 cur->set_in_collection_set(false);
5685 if (cur->is_young()) {
5686 int index = cur->young_index_in_cset();
5687 assert(index != -1, "invariant");
5688 assert((size_t) index < policy->young_cset_region_length(), "invariant");
5689 size_t words_survived = _surviving_young_words[index];
5690 cur->record_surv_words_in_group(words_survived);
5692 // At this point the we have 'popped' cur from the collection set
5693 // (linked via next_in_collection_set()) but it is still in the
5694 // young list (linked via next_young_region()). Clear the
5695 // _next_young_region field.
5696 cur->set_next_young_region(NULL);
5697 } else {
5698 int index = cur->young_index_in_cset();
5699 assert(index == -1, "invariant");
5700 }
5702 assert( (cur->is_young() && cur->young_index_in_cset() > -1) ||
5703 (!cur->is_young() && cur->young_index_in_cset() == -1),
5704 "invariant" );
5706 if (!cur->evacuation_failed()) {
5707 MemRegion used_mr = cur->used_region();
5709 // And the region is empty.
5710 assert(!used_mr.is_empty(), "Should not have empty regions in a CS.");
5712 // If marking is in progress then clear any objects marked in
5713 // the current region. Note mark_in_progress() returns false,
5714 // even during an initial mark pause, until the set_marking_started()
5715 // call which takes place later in the pause.
5716 if (mark_in_progress()) {
5717 assert(!g1_policy()->during_initial_mark_pause(), "sanity");
5718 _cm->nextMarkBitMap()->clearRange(used_mr);
5719 }
5721 free_region(cur, &pre_used, &local_free_list, false /* par */);
5722 } else {
5723 cur->uninstall_surv_rate_group();
5724 if (cur->is_young()) {
5725 cur->set_young_index_in_cset(-1);
5726 }
5727 cur->set_not_young();
5728 cur->set_evacuation_failed(false);
5729 // The region is now considered to be old.
5730 _old_set.add(cur);
5731 }
5732 cur = next;
5733 }
5735 policy->record_max_rs_lengths(rs_lengths);
5736 policy->cset_regions_freed();
5738 double end_sec = os::elapsedTime();
5739 double elapsed_ms = (end_sec - start_sec) * 1000.0;
5741 if (non_young) {
5742 non_young_time_ms += elapsed_ms;
5743 } else {
5744 young_time_ms += elapsed_ms;
5745 }
5747 update_sets_after_freeing_regions(pre_used, &local_free_list,
5748 NULL /* old_proxy_set */,
5749 NULL /* humongous_proxy_set */,
5750 false /* par */);
5751 policy->record_young_free_cset_time_ms(young_time_ms);
5752 policy->record_non_young_free_cset_time_ms(non_young_time_ms);
5753 }
5755 // This routine is similar to the above but does not record
5756 // any policy statistics or update free lists; we are abandoning
5757 // the current incremental collection set in preparation of a
5758 // full collection. After the full GC we will start to build up
5759 // the incremental collection set again.
5760 // This is only called when we're doing a full collection
5761 // and is immediately followed by the tearing down of the young list.
5763 void G1CollectedHeap::abandon_collection_set(HeapRegion* cs_head) {
5764 HeapRegion* cur = cs_head;
5766 while (cur != NULL) {
5767 HeapRegion* next = cur->next_in_collection_set();
5768 assert(cur->in_collection_set(), "bad CS");
5769 cur->set_next_in_collection_set(NULL);
5770 cur->set_in_collection_set(false);
5771 cur->set_young_index_in_cset(-1);
5772 cur = next;
5773 }
5774 }
5776 void G1CollectedHeap::set_free_regions_coming() {
5777 if (G1ConcRegionFreeingVerbose) {
5778 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
5779 "setting free regions coming");
5780 }
5782 assert(!free_regions_coming(), "pre-condition");
5783 _free_regions_coming = true;
5784 }
5786 void G1CollectedHeap::reset_free_regions_coming() {
5787 {
5788 assert(free_regions_coming(), "pre-condition");
5789 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
5790 _free_regions_coming = false;
5791 SecondaryFreeList_lock->notify_all();
5792 }
5794 if (G1ConcRegionFreeingVerbose) {
5795 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
5796 "reset free regions coming");
5797 }
5798 }
5800 void G1CollectedHeap::wait_while_free_regions_coming() {
5801 // Most of the time we won't have to wait, so let's do a quick test
5802 // first before we take the lock.
5803 if (!free_regions_coming()) {
5804 return;
5805 }
5807 if (G1ConcRegionFreeingVerbose) {
5808 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
5809 "waiting for free regions");
5810 }
5812 {
5813 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
5814 while (free_regions_coming()) {
5815 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
5816 }
5817 }
5819 if (G1ConcRegionFreeingVerbose) {
5820 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
5821 "done waiting for free regions");
5822 }
5823 }
5825 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
5826 assert(heap_lock_held_for_gc(),
5827 "the heap lock should already be held by or for this thread");
5828 _young_list->push_region(hr);
5829 }
5831 class NoYoungRegionsClosure: public HeapRegionClosure {
5832 private:
5833 bool _success;
5834 public:
5835 NoYoungRegionsClosure() : _success(true) { }
5836 bool doHeapRegion(HeapRegion* r) {
5837 if (r->is_young()) {
5838 gclog_or_tty->print_cr("Region ["PTR_FORMAT", "PTR_FORMAT") tagged as young",
5839 r->bottom(), r->end());
5840 _success = false;
5841 }
5842 return false;
5843 }
5844 bool success() { return _success; }
5845 };
5847 bool G1CollectedHeap::check_young_list_empty(bool check_heap, bool check_sample) {
5848 bool ret = _young_list->check_list_empty(check_sample);
5850 if (check_heap) {
5851 NoYoungRegionsClosure closure;
5852 heap_region_iterate(&closure);
5853 ret = ret && closure.success();
5854 }
5856 return ret;
5857 }
5859 class TearDownRegionSetsClosure : public HeapRegionClosure {
5860 private:
5861 OldRegionSet *_old_set;
5863 public:
5864 TearDownRegionSetsClosure(OldRegionSet* old_set) : _old_set(old_set) { }
5866 bool doHeapRegion(HeapRegion* r) {
5867 if (r->is_empty()) {
5868 // We ignore empty regions, we'll empty the free list afterwards
5869 } else if (r->is_young()) {
5870 // We ignore young regions, we'll empty the young list afterwards
5871 } else if (r->isHumongous()) {
5872 // We ignore humongous regions, we're not tearing down the
5873 // humongous region set
5874 } else {
5875 // The rest should be old
5876 _old_set->remove(r);
5877 }
5878 return false;
5879 }
5881 ~TearDownRegionSetsClosure() {
5882 assert(_old_set->is_empty(), "post-condition");
5883 }
5884 };
5886 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
5887 assert_at_safepoint(true /* should_be_vm_thread */);
5889 if (!free_list_only) {
5890 TearDownRegionSetsClosure cl(&_old_set);
5891 heap_region_iterate(&cl);
5893 // Need to do this after the heap iteration to be able to
5894 // recognize the young regions and ignore them during the iteration.
5895 _young_list->empty_list();
5896 }
5897 _free_list.remove_all();
5898 }
5900 class RebuildRegionSetsClosure : public HeapRegionClosure {
5901 private:
5902 bool _free_list_only;
5903 OldRegionSet* _old_set;
5904 FreeRegionList* _free_list;
5905 size_t _total_used;
5907 public:
5908 RebuildRegionSetsClosure(bool free_list_only,
5909 OldRegionSet* old_set, FreeRegionList* free_list) :
5910 _free_list_only(free_list_only),
5911 _old_set(old_set), _free_list(free_list), _total_used(0) {
5912 assert(_free_list->is_empty(), "pre-condition");
5913 if (!free_list_only) {
5914 assert(_old_set->is_empty(), "pre-condition");
5915 }
5916 }
5918 bool doHeapRegion(HeapRegion* r) {
5919 if (r->continuesHumongous()) {
5920 return false;
5921 }
5923 if (r->is_empty()) {
5924 // Add free regions to the free list
5925 _free_list->add_as_tail(r);
5926 } else if (!_free_list_only) {
5927 assert(!r->is_young(), "we should not come across young regions");
5929 if (r->isHumongous()) {
5930 // We ignore humongous regions, we left the humongous set unchanged
5931 } else {
5932 // The rest should be old, add them to the old set
5933 _old_set->add(r);
5934 }
5935 _total_used += r->used();
5936 }
5938 return false;
5939 }
5941 size_t total_used() {
5942 return _total_used;
5943 }
5944 };
5946 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
5947 assert_at_safepoint(true /* should_be_vm_thread */);
5949 RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_free_list);
5950 heap_region_iterate(&cl);
5952 if (!free_list_only) {
5953 _summary_bytes_used = cl.total_used();
5954 }
5955 assert(_summary_bytes_used == recalculate_used(),
5956 err_msg("inconsistent _summary_bytes_used, "
5957 "value: "SIZE_FORMAT" recalculated: "SIZE_FORMAT,
5958 _summary_bytes_used, recalculate_used()));
5959 }
5961 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) {
5962 _refine_cte_cl->set_concurrent(concurrent);
5963 }
5965 bool G1CollectedHeap::is_in_closed_subset(const void* p) const {
5966 HeapRegion* hr = heap_region_containing(p);
5967 if (hr == NULL) {
5968 return is_in_permanent(p);
5969 } else {
5970 return hr->is_in(p);
5971 }
5972 }
5974 // Methods for the mutator alloc region
5976 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
5977 bool force) {
5978 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
5979 assert(!force || g1_policy()->can_expand_young_list(),
5980 "if force is true we should be able to expand the young list");
5981 bool young_list_full = g1_policy()->is_young_list_full();
5982 if (force || !young_list_full) {
5983 HeapRegion* new_alloc_region = new_region(word_size,
5984 false /* do_expand */);
5985 if (new_alloc_region != NULL) {
5986 set_region_short_lived_locked(new_alloc_region);
5987 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Eden, young_list_full);
5988 return new_alloc_region;
5989 }
5990 }
5991 return NULL;
5992 }
5994 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
5995 size_t allocated_bytes) {
5996 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
5997 assert(alloc_region->is_young(), "all mutator alloc regions should be young");
5999 g1_policy()->add_region_to_incremental_cset_lhs(alloc_region);
6000 _summary_bytes_used += allocated_bytes;
6001 _hr_printer.retire(alloc_region);
6002 // We update the eden sizes here, when the region is retired,
6003 // instead of when it's allocated, since this is the point that its
6004 // used space has been recored in _summary_bytes_used.
6005 g1mm()->update_eden_size();
6006 }
6008 HeapRegion* MutatorAllocRegion::allocate_new_region(size_t word_size,
6009 bool force) {
6010 return _g1h->new_mutator_alloc_region(word_size, force);
6011 }
6013 void G1CollectedHeap::set_par_threads() {
6014 // Don't change the number of workers. Use the value previously set
6015 // in the workgroup.
6016 assert(G1CollectedHeap::use_parallel_gc_threads(), "shouldn't be here otherwise");
6017 uint n_workers = workers()->active_workers();
6018 assert(UseDynamicNumberOfGCThreads ||
6019 n_workers == workers()->total_workers(),
6020 "Otherwise should be using the total number of workers");
6021 if (n_workers == 0) {
6022 assert(false, "Should have been set in prior evacuation pause.");
6023 n_workers = ParallelGCThreads;
6024 workers()->set_active_workers(n_workers);
6025 }
6026 set_par_threads(n_workers);
6027 }
6029 void MutatorAllocRegion::retire_region(HeapRegion* alloc_region,
6030 size_t allocated_bytes) {
6031 _g1h->retire_mutator_alloc_region(alloc_region, allocated_bytes);
6032 }
6034 // Methods for the GC alloc regions
6036 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size,
6037 size_t count,
6038 GCAllocPurpose ap) {
6039 assert(FreeList_lock->owned_by_self(), "pre-condition");
6041 if (count < g1_policy()->max_regions(ap)) {
6042 HeapRegion* new_alloc_region = new_region(word_size,
6043 true /* do_expand */);
6044 if (new_alloc_region != NULL) {
6045 // We really only need to do this for old regions given that we
6046 // should never scan survivors. But it doesn't hurt to do it
6047 // for survivors too.
6048 new_alloc_region->set_saved_mark();
6049 if (ap == GCAllocForSurvived) {
6050 new_alloc_region->set_survivor();
6051 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Survivor);
6052 } else {
6053 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Old);
6054 }
6055 bool during_im = g1_policy()->during_initial_mark_pause();
6056 new_alloc_region->note_start_of_copying(during_im);
6057 return new_alloc_region;
6058 } else {
6059 g1_policy()->note_alloc_region_limit_reached(ap);
6060 }
6061 }
6062 return NULL;
6063 }
6065 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
6066 size_t allocated_bytes,
6067 GCAllocPurpose ap) {
6068 bool during_im = g1_policy()->during_initial_mark_pause();
6069 alloc_region->note_end_of_copying(during_im);
6070 g1_policy()->record_bytes_copied_during_gc(allocated_bytes);
6071 if (ap == GCAllocForSurvived) {
6072 young_list()->add_survivor_region(alloc_region);
6073 } else {
6074 _old_set.add(alloc_region);
6075 }
6076 _hr_printer.retire(alloc_region);
6077 }
6079 HeapRegion* SurvivorGCAllocRegion::allocate_new_region(size_t word_size,
6080 bool force) {
6081 assert(!force, "not supported for GC alloc regions");
6082 return _g1h->new_gc_alloc_region(word_size, count(), GCAllocForSurvived);
6083 }
6085 void SurvivorGCAllocRegion::retire_region(HeapRegion* alloc_region,
6086 size_t allocated_bytes) {
6087 _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes,
6088 GCAllocForSurvived);
6089 }
6091 HeapRegion* OldGCAllocRegion::allocate_new_region(size_t word_size,
6092 bool force) {
6093 assert(!force, "not supported for GC alloc regions");
6094 return _g1h->new_gc_alloc_region(word_size, count(), GCAllocForTenured);
6095 }
6097 void OldGCAllocRegion::retire_region(HeapRegion* alloc_region,
6098 size_t allocated_bytes) {
6099 _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes,
6100 GCAllocForTenured);
6101 }
6102 // Heap region set verification
6104 class VerifyRegionListsClosure : public HeapRegionClosure {
6105 private:
6106 FreeRegionList* _free_list;
6107 OldRegionSet* _old_set;
6108 HumongousRegionSet* _humongous_set;
6109 size_t _region_count;
6111 public:
6112 VerifyRegionListsClosure(OldRegionSet* old_set,
6113 HumongousRegionSet* humongous_set,
6114 FreeRegionList* free_list) :
6115 _old_set(old_set), _humongous_set(humongous_set),
6116 _free_list(free_list), _region_count(0) { }
6118 size_t region_count() { return _region_count; }
6120 bool doHeapRegion(HeapRegion* hr) {
6121 _region_count += 1;
6123 if (hr->continuesHumongous()) {
6124 return false;
6125 }
6127 if (hr->is_young()) {
6128 // TODO
6129 } else if (hr->startsHumongous()) {
6130 _humongous_set->verify_next_region(hr);
6131 } else if (hr->is_empty()) {
6132 _free_list->verify_next_region(hr);
6133 } else {
6134 _old_set->verify_next_region(hr);
6135 }
6136 return false;
6137 }
6138 };
6140 HeapRegion* G1CollectedHeap::new_heap_region(size_t hrs_index,
6141 HeapWord* bottom) {
6142 HeapWord* end = bottom + HeapRegion::GrainWords;
6143 MemRegion mr(bottom, end);
6144 assert(_g1_reserved.contains(mr), "invariant");
6145 // This might return NULL if the allocation fails
6146 return new HeapRegion(hrs_index, _bot_shared, mr, true /* is_zeroed */);
6147 }
6149 void G1CollectedHeap::verify_region_sets() {
6150 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6152 // First, check the explicit lists.
6153 _free_list.verify();
6154 {
6155 // Given that a concurrent operation might be adding regions to
6156 // the secondary free list we have to take the lock before
6157 // verifying it.
6158 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6159 _secondary_free_list.verify();
6160 }
6161 _old_set.verify();
6162 _humongous_set.verify();
6164 // If a concurrent region freeing operation is in progress it will
6165 // be difficult to correctly attributed any free regions we come
6166 // across to the correct free list given that they might belong to
6167 // one of several (free_list, secondary_free_list, any local lists,
6168 // etc.). So, if that's the case we will skip the rest of the
6169 // verification operation. Alternatively, waiting for the concurrent
6170 // operation to complete will have a non-trivial effect on the GC's
6171 // operation (no concurrent operation will last longer than the
6172 // interval between two calls to verification) and it might hide
6173 // any issues that we would like to catch during testing.
6174 if (free_regions_coming()) {
6175 return;
6176 }
6178 // Make sure we append the secondary_free_list on the free_list so
6179 // that all free regions we will come across can be safely
6180 // attributed to the free_list.
6181 append_secondary_free_list_if_not_empty_with_lock();
6183 // Finally, make sure that the region accounting in the lists is
6184 // consistent with what we see in the heap.
6185 _old_set.verify_start();
6186 _humongous_set.verify_start();
6187 _free_list.verify_start();
6189 VerifyRegionListsClosure cl(&_old_set, &_humongous_set, &_free_list);
6190 heap_region_iterate(&cl);
6192 _old_set.verify_end();
6193 _humongous_set.verify_end();
6194 _free_list.verify_end();
6195 }